Raising your AQ IQ - OLI Support Center - Process ...support.olisystems.com/Documents/Manuals/AQ-IQFullPrint07-26-2004… · Chapter 1 Raising your AQ IQ 1 ... Using the OLI/StreamAnalyzer

Raising your

AQ IQ

OLI Systems, Inc.

Copyrights, 2004 OLI Systems, Inc. All rights reserved. The enclosed materials are provided to the lessees, selected individuals and agents of OLI Systems, Inc. The material may not be duplicated or otherwise provided to any entity with out the expressed permission of OLI Systems, Inc.

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www.olisystems.com

Contents

Chapter 1 Raising your AQ IQ 1 New Software Tools To Solve Chemical Process And Corrosion Problems .....1

Examples of OLI Electrolyte Applications..................................................................4 OLI Real World Solutions...........................................................................................4

AQ IQ Example Problems .........................................................................................................6

Chapter 2 Calculating pH for Aqueous Solutions 7 What you see is not what you get! .............................................................................................7 Complex Salt Solutions .............................................................................................................8 Using the OLI/StreamAnalyzer .................................................................................................8 What’s the bottom line?...........................................................................................................19 Advanced Problems .................................................................................................................19

Chapter 3 Neutralized an Acid 21 How to avoid accidental hazardous waste generation! ............................................................21

Hydrofluoric Acid Stream .........................................................................................21 Neutralizing Stream...................................................................................................22 Using the StreamAnalyzer™.....................................................................................22 Mixing the HF Acid with the CaCl2 stream...............................................................28 Analysis of the Chemistry .........................................................................................31 Conclusion.................................................................................................................34

Advanced Problems .................................................................................................................35

Chapter 4 Water Treatment 37 You can’t get there from here!................................................................................................. 37

Let’s get started ... .....................................................................................................37 What is the pH? .........................................................................................................39 Now, What About the Contaminated Waste?............................................................48 Conclusion.................................................................................................................52


Chapter 5 Sour Gas Treatment 55 A little bit of water can go a long way (in creating a Big Process Problem) ...........................55

Scope .........................................................................................................................55 Purpose ......................................................................................................................56 Objectives..................................................................................................................56

Start the tour ............................................................................................................................57 Let’s get started ... .....................................................................................................57 The Corrosion Rate at the Dew Point ........................................................................63 Adding the rates calculation. .....................................................................................63 Mitigation ..................................................................................................................68 Adjusting the solution chemistry. ..............................................................................69

ii Raising your AQ IQ

Alloys ........................................................................................................................74 Save ...........................................................................................................................74


Chapter 6 Chlorine Scrubbing 77 If 10 percent is good, 20 has to be better…? ...........................................................................77

Let’s get started ... .....................................................................................................78 Stream Review ..........................................................................................................80 Adding a Mixed Stream.............................................................................................81 Why does adding base remove Chlorine? .................................................................89 What happens if you use more concentrated solutions? ............................................91 Conclusion.................................................................................................................93


Chapter 7 Gypsum Solubility 97 Getting an edge on the competition. ........................................................................................97

Let’s get started ... .....................................................................................................97 What is a precipitation point calculation? ............................................................... 105 Back to the application… ........................................................................................ 109 Adding sodium chloride .......................................................................................... 113 Save your work........................................................................................................ 122 Conclusion............................................................................................................... 123

Advanced Problems ............................................................................................................... 124

Chapter 8 H2S-CO2 Injection 125 Out of Sight – Out of Mind?.................................................................................................. 125

Let’s get started ... ................................................................................................... 125 Reconciling Electroneutrality .................................................................................. 132 Back to the reconciliation........................................................................................ 137 Converting an Analysis into a stream...................................................................... 139 Simulations at reservoir conditions ......................................................................... 141 Adding the waste gas............................................................................................... 143 Reviewing the results .............................................................................................. 147 What does this all mean?......................................................................................... 151 Save your file........................................................................................................... 151 Conclusion............................................................................................................... 151


Chapter 9 Organic Acid Removal 153 When Henry’s Law Constants don’t really help you ............................................................. 153

Let’s get started ... ................................................................................................... 153 Solution pH.............................................................................................................. 159 Washing the acids out of the aqueous phase. .......................................................... 161 Removing the organic acids from the 2nd liquid phase ............................................ 163 Save, save, and save again....................................................................................... 165 Conclusion............................................................................................................... 165


Appendix A OLI Company Profile 167

OLI Software Simulation Tools ... Providing Real World Answers ........................................................................................................................... 167

Appendix B References 171

Appendix C Product Description Sheets 173 Overview ............................................................................................................................... 173 Environmental Simulation Program (ESP) ............................................................................ 175

FEATURES............................................................................................................. 175 APPLICATIONS..................................................................................................... 175 CAPABILITIES ...................................................................................................... 176 RELATED PRODUCTS......................................................................................... 176

Corrosion Analyzer................................................................................................................ 177 FEATURES............................................................................................................. 177 APPLICATIONS..................................................................................................... 177 CAPABILITIES ...................................................................................................... 178 RELATED PRODUCTS......................................................................................... 178

Stream Analyzer and Lab Analyzer ....................................................................................... 179 FEATURES............................................................................................................. 179 APPLICATIONS..................................................................................................... 180 CAPABILITIES ...................................................................................................... 180

ScaleChem............................................................................................................................. 181 FEATURES............................................................................................................. 181 CAPABILITIES ...................................................................................................... 182 SCALECHEM V3.1 ................................................................................................ 182

HYSYS™ Electrolytes OLI (HEO)....................................................................................... 183 FEATURES............................................................................................................. 183 APPLICATIONS..................................................................................................... 183 CAPABILITIES ...................................................................................................... 184

Aspen OLI ............................................................................................................................. 185 FEATURES............................................................................................................. 185 CONTACT US........................................................................................................ 186

iv Raising your AQ IQ

Raising your AQ IQ Chapter 1 Raising your AQ IQ • 1

Chapter 1 Raising your AQ IQ

New Software Tools To Solve Chemical Process And Corrosion Problems

Aqueous electrolytes are everywhere – and ignoring electrolytes doesn’t make your problems go away. You can spend a lot of time and money doing laboratory and plant testing, or conventional process simulation, and still be plagued by persistent scale, corrosion, pH control, conversion efficiency, process upsets, environmental contamination, water and offgas treatment, and countless other problems – All because you haven’t properly accounted for electrolytes. And what’s more, predicting the behavior of chemicals in water for realistic industrial conditions has never been easy or intuitive. What are electrolytes? Simply put, electrolytes are chemicals that break down, recombine, and react in water or other solvents. When this happens in the real world, the result is a complex mixture that is very difficult to predict and control. The result in your operations is pH control problems, unwanted scale and solids formation, corrosion, water and gas effluent emissions and permit violations, process upsets, and a host of other problems.

What is Your AQ IQ?

By that we mean: How well do you understand aqueous chemistry and apply it routinely to solving real-world problems in your operations?

How do you manage process upsets, water treatment, scale, corrosion, and other aqueous electrolyte related operating problems today?

This seminar will provide you with insights and methods to address these and many other common industry applications.

2 • Chapter 1 Raising your AQ IQ Raising your AQ IQ

Prediction of phase equilibria for electrolyte systems is complicated by virtue of the fact that chemical reaction equilibrium and phase equilibrium must be considered simultaneously. The phase equilibrium methods commonly taught as part of a university chemical thermodynamics curriculum are applicable for hydrocarbons and other non-aqueous systems, but not aqueous electrolyte systems. Furthermore, to predict the behavior of real-world aqueous systems, all of the species that can form, including aqueous complexes and solids, and their non-ideal behavior in real solutions, must be accounted for. OLI refers to “real solutions” as those containing multiple components at ionic strengths where the common simplified methods and ideal solution assumptions are invalid. Electrolyte Technology And Applications A great many industrial processes cannot be designed and operated effectively without comprehensively and accurately addressing electrolyte chemistry and phenomena. The same statement can be made with regard to many oil and gas production and environmental problems as well. Electrolyte chemistry plays an important role in many chemical operations, including:

• Aqueous chemical and separations processes • pH neutralization, Ion exchange, Desalination • Chemical conversion and reactors • Corrosion and scaling of equipment in chemical

plants, refineries, gas plants, pipelines, oil and gas wells, tanks

• Reactive separations including acid gas treatment • Water treatment including heavy metals removal • Environmental behavior of wastes, discharges, and

accidental releases • Pharmaceutical and specialty chemical

manufacturing • Solution crystallization • Electrochemical processes

Real-World Risk. Electrolyte chemistry is particularly complex and challenging to understand and predict, especially for real industrial systems containing many components and operating over broad ranges of temperature, pressure, and concentration. Simplified aqueous modeling and computational approaches using approximation methods are usually useless, or worse yet, dangerously misleading, when applied to real-world electrolyte applications. Aqueous electrolyte systems often behave in complex and counter-intuitive ways, introducing great risk into plant design and operation if not properly understood and accounted for. For example, when solids form at the wrong place at the wrong time, the results can be catastrophic. On the other hand, reliable electrolyte models make possible tremendous insight, process alternatives, and efficiencies in plant design, trouble-shooting, and optimization. Modeling Electrolyte Chemistry. The first key to predicting the behavior of aqueous electrolyte systems is to account for all of the species that can form in the system. For example, sodium chloride in water forms 5 species: H2O, H+, OH-, Na+, and Cl-. But ferric chloride in water can form over 15 species because of the tendency of iron to complex with hydroxide and chloride in the aqueous phase, and because of the possibility of solids to form and precipitate under some conditions. A solution such as a brine with only 5 cations and 5


anions can have well over 200 species. All of these must be properly accounted for in order to accurately predict pH, reaction and phase equilibria, and solids formation. The next key is to have a proper framework to model the standard state properties over a broad range of conditions. Next, a robust activity coefficient model must be used in order to account for species-species interactions and non-ideal behavior of real systems. These must all be supported by a complete database of regressed and estimated parameters based on high quality experimental data. Finally, the complete system of equilibrium and mass balance equations must be rigorously and efficiently solved. The OLI electrolyte approach is based on and distinguished by the following unique elements:

• Complete speciation. The OLI model predicts and considers all of the true species in solution, and accounts for these in the computations.

• Robust standard state framework. Based on the Helgeson equation of state and parameter regression and proprietary estimation techniques, the OLI model provides accurate equilibrium constants and other standard state properties over the broadest possible aqueous range of conditions.

• Activity coefficients for complex, high ionic strength systems. Based on the combined work of Bromley, Zemaitis, Meissner, Pitzer, and OLI technologists, OLI models can predict behavior under real world conditions.

• Comprehensive databank. The OLI Databank covers over 80 inorganic elements and their associated compounds and complexes, and over 3000 organic chemicals. OLI Data Service provides customized coverage of clients’ chemistry in the form of private databanks.

• Thermo-physical properties. OLI has developed unique chemical-physical based models to compute thermodynamic and transport properties for complex aqueous mixtures.

All of this know-how, methods, and data taken together make up the OLI Engine. The OLI Engine is at the heart of every OLI software product. It is applicable over the range of conditions of -50 to 300 °C, 0 to 1500 bar, and up to 30 molal ionic strength. OLI Engine provides all the required facilities “out of the box.” This enables a user to avoid all of the complexities associated with aqueous electrolyte systems. This means that the user never has to:

• Write an equilibrium reaction • Define true species in the aqueous phase (the user only

provides the customary molecular chemical components) • Deal with any complexities associated with solving for the

occurrence of other physical phases in addition to the aqueous phase

• Carry out any data regressions to develop model coefficients (these are all provided by the in-place OLI databank)

The OLI Engine provides comprehensive and accurate simulation and prediction of the behavior of complex electrolyte systems. OLI clients have used this unique and powerful electrolyte capability to provide hundreds of millions of dollars benefit through a host of applications in the oil and gas, chemicals, government research, paper, metals and mining, pharmaceutical, petroleum, and energy industries.

This seminar covers some of the basics of aqueous electrolyte chemistry and applications. For further information, the reader is referred to OLI’s Resource Center on the OLI website (www.olisystems.com) which contains many technical papers and articles on these and related topics.


Examples of OLI Electrolyte Applications • Emergency Chlorine

Scrubber • Caustic Wash Tower • Acid Stream Neutralization • Manufacture of KF • Dynamic pH Control • Removal of Fluoride Ions

from Waste Water • Scrubbing Refinery

Process Streams with DEA

• Chlor-Alkali Brine Treatment

• Ahlstron NSSC “Stora” Process

• Tower Scale Control

• Foul Feed Stripper • Multi-Effect Evaporator • Cooling Tower

• Coke Oven Gas

• Ammonia Still

• Organic Acid Removal in Brines

• BTEX Stripper • MSF Desalination Plant • Removal of

Chlorobenzene with Biological Treatment

• Dregs Washer and Clarifier

• CO2 Corrosion • Corrosion Rates in Acids

• Inhibitor Squeeze in Oil/Gas Reservoirs

• Corrosion in LiBr Refrigeration Brines

• Thermodynamic Analysis of Corrosion Inhibitors

• Electrostatic Precipitator Separation

• H2S/CO2 Corrosion Products under Gas Pipeline Conditions

• Hazardous Waste Deep well Disposal

• Contaminated Groundwater Management

OLI Real World Solutions

In the Plant: o Optimized the design of a pH-control neutralization system saving more than $3MM o Identified the cause (elemental sulfur corrosion) and modified process conditions for the

absorber and regenerator of a desulfurization process. Identified the cause (ammonium bisulfide precipitation and corrosion) and appropriate materials for an ammonia separation process

o Identified the conditions for de-alloying of a copper/nickel alloy, defined the precise conditions for nickel dissolution in the process, and defined process modifications to eliminate the corrosion problem.

o Predicted scaling indices in process streams and, therefore, their effects on process equipment, minimizing costly upsets and downtime

o Evaluated process changes to minimize corrosion in units, reducing downtime and equipment replacement

o Predicted the onset and effects of CaCO3 scaling so stream conditions could be altered to avoid a problem.

In the Laboratory:

o Evaluated and selected inorganic corrosion inhibitors for Lithium Bromide chiller systems, reducing costly laboratory evaluations

o Minimized lab time and expense to find operating conditions for producing ceramic materials of the highest purity

o Identified laboratory analysis errors, preventing costly errors in the diagnosis and correction of a plant problem.


In the Environment: o Optimized conditions for the removal of trace metals from wastewaters, allowing regulatory

permit limits to be met. o Developed a sound scientific basis for a successful technical defense in a law suit involving

more than $100MM. o Saved more than $20MM by devising a more effective remedy to protect groundwater from

heavy metals, which was then accepted by the US EPA.Identified the cause and effective corrective action for the buildup of materials in a biotreatment unit, avoiding a costly unit shutdown and clean-out.

In the Oilfield: o Predicted the severity of halite scale formation at the early design stage of a deep well

project, and then used the results to design a water treatment plant, chokes, subsea production template.

o Determined the prospective costs for an oilfield lease purchase where the redevelopment plan calls for completing deeper zones and water flooding other zones with co-mingling of brines.

o Diagnosed the cause of calcium fluoride and lead (Pb) sulfide scale formation in a deep sour well, and used the results to design a scale management strategy.

o Determined the relative likelihood of halite formation problems (rather than calcite or iron sulfide) in an old oilfield redevelopment to support the choice of remedy (fresh water injection versus inhibitor squeeze) that saved money and increased production time.


AQ IQ Example Problems Basic electrolytes What you see is NOT what you get

Study of different salts in water, pH, speciation, solids and hydrates

Effluent discharge How to avoid accidental hazardous waste generation

Study of mixing waste streams with hydrofluoric acid (HF) stream and CaCl2

Discharge limits You can't get there from here

Study of reagents and techniques for reducing the soluble nickel to 0.1 mg/L in a discharge stream

Sour gas A little bit of water can go a long way (in creating process problems)

Study of an alkanolamine gas sweetening plant with scale and corrosion in the condensed overhead gas

Chlorine scrubbing If 10% is good, is 20% better?

Problems with emergency release of chlorine gas from a process

Gypsum solubility Getting an edge on the competition

Modern gypsum (CaSO4.2H2O) production involving recovery of sulfur waste products. Study to find the optimum conditions to recover a pollutant and use it for commercial purposes

Sulfur removal Out of sight - out of mind?

Study of ratios of H2S mixed with produced water re-injecting into the formation a possible H2S disposal method. The issue is the possibility of plugging the reservoir with unexpected solids.

Organic acid removal When Henry's Law Constants don't really help you

Study of organic acids in produced waters from oil and gas production, with methods for analysis and removal from the oil - and from the produced water.

Raising your AQ IQ Chapter 2 Calculating pH for Aqueous Solutions • 7

Chapter 2 Calculating pH for Aqueous Solutions

What you see is not what you get! • The behavior of aqueous electrolytes solutions is more complicated that most

people would like to admit.

• Even simple single salt systems may yield many new complexes in aqueous solution.

• Accurate calculation of pH depends on accounting for all of the molecules, ions, complexes, and other species that can exist in the system (i.e., complete “speciation”)

Let’s look at a simple salt solution; sodium chloride in water. How many species are there in this solution?

NaCl + H2O → Na+ + Cl- + H+ + OH- + H2O

Water appears on both sides of the reaction since it does not fully dissociate. This gives us five aqueous species.

What would the pH be of a 1 molal1 solution of sodium chloride at 25 oC and 1 atmosphere?

Sodium chloride essentially dissociates in water to give us equal moles of sodium ion and chloride ion. Because of its tendency to completely dissociate in water, sodium chloride is referred to as a “strong electrolyte.” The water dissociates according to the dissociation constant for water. At 25 the dissociation constant for water is approximately:

Kw = [H+][OH-] = 10-14

1 The unit molal is moles of solute per kilogram of solvent. In aqueous systems is moles/Kg H2O.

8 • Chapter 2 Calculating pH for Aqueous Solutions Raising your AQ IQ

This results in an aqueous concentration for hydrogen of 10-7 moles/Kg H2O. So the final concentrations are:

[Na+] = 1.0 moles/Kg H2O

[Cl-] = 1.0 moles/Kg H2O

[H+] = 10-7 moles/Kg H2O

[OH-] = 10-7 moles/Kg H2O

H2O = 1.0 Kg/H2O

The definition of pH is:

pH = - Log [H+]

Thus the pH of this solution is:

pH = - Log (10-7) = -(-7) = 7

Complex Salt Solutions Now let’s look at a more complicated solution. What is the pH of a 1.0 molal Iron (III) Chloride solution at 25 oC and 1 atmosphere?

Let’s use the simple salt approach first.

FeCl3 + H2O → Fe3+ + 3Cl- + H+ + OH- + H2O

The final concentrations would be:

[Fe3+] = 1.0 mole/KgH2O

[Cl-] = 3.0 mole/KgH2O

[H+] = 10-7 moles/Kg H2O

[OH-] = 10-7 moles/Kg H2O

H2O = 1.0 Kg/H2O

The pH would then be:

pH = - Log [H+] = - Log (10-7) = -(-7) = 7

The experimentally measured pH is approximately 2.2. The simple salt approach does not seem to work for this salt.

Using the OLI/StreamAnalyzer We will now use the OLI/StreamAnalyzer™ to look at the chemistry of the iron chloride system.

We will first start the StreamAnalyzer™.

Locate the StreamAnalyzer icon on your desktop or find it via the start button.

Figure 2-1 The OLI StreamAnalyzer Icon for version 1.3

Is it possible to accurately predict pH for chemicals that react and form complexes in water? What are the keys to getting the right answer?


This will display the main StreamAnalyzer Window.

Figure 2-2 The StreamAnalyzer Splash Screen.

This splash window shows what version and build number is being used (in this case it is version 1.3 build 23). The window will disappear in a few moments.

The main StreamAnalyzer window will then appear.

Figure 2-3 The StreamAnalyzer main window


Figure 2-4 The main Stream Analyzer Window

Click on the “Add New Stream” icon.

The program will automatically create a new stream with a default name. We will then be positioned on a data entry dialog named “Definition”.

This window is the explorer view. Normally we start by clicking on Add New Stream

This window is the tree view. A list of currently defined objects is displayed here.


Figure 2-5 Adding a single point calculation

A new object, a Stream, has appeared in the tree-view.


Figure 2-6 Entering Stream Information

The shaded areas of the stream definition are required by the program. By default, we will start at 25 degrees centigrade, 1 atmosphere and 55.508 moles of water. This amount of water is 1 kilogram of water. This effectively makes any component concentration a molal concentration. We enter the chemical formula of FeCl3 in the inflow grid and then enter a value of 1.0. You may use the mouse or tabs keys to move around the grid. The concept employed here is that the user will define a stream (or import it from another program or process) whose values will propagate throughout all subsequent calculations.

Enter the chemical formula FeCl3 and then enter a value of 1.0 in mole units. Click on the Add Single Point button when finished.

The yellow areas are required. We enter the data in the white spaces in the grid. The component iron (III) Chloride is entered here as FeCL3

Click on the Add Single Point button to start a calculation.

If a red X appears next to the name you entered, then the program does not recognize the name. Please check to see if the spelling is correct. More about entering user data later in this course.


Figure 2-7 Starting the calculation.

We are now ready to start the calculations but let us review some options on this screen.

The tree view expands to show the new calculation.


Figure 2-8 Entering the conditions of the calculation.

The data in the Definition grid has been propagated from the stream that we just previously entered. You may change the values or add to the list of species. This does not affect the original stream definition.

Please note: The names that you enter in the grid may be different from what is displayed depending on settings in the Tools menu. This will be discussed later. We will leave the values as is, click the Type of Calculation button.

Figure 2-9 Single Point Calculation Types

There are several types of calculations that can be performed. We will use the default calculation type of Isothermal for this demonstrations. Each type of calculation is defined as:

What to do next? Click this button to find out!

We can select from several types of calculations. The summary box indicates the current status of the calculation.

Green means GO! Click here to start


Isothermal A constant temperature and pressure calculation.

Isenthalpic A constant heat loss/gain is applied to the calculation and a temperature or pressure can be adjusted to meet this new heat content.

Bubble Point The temperature or pressure is adjusted to reach a condition where a small amount of vapor begins to appear.

Dew Point The temperature or pressure is adjusted to reach a condition where a small amount of aqueous liquid appears.

Vapor Amount The temperature or pressure is adjusted to produce a specified amount of vapor.

Vapor Fraction The temperature or pressure is adjusted to produce a specified amount of vapor as a fraction of the total quantity.

Set pH The pH of the solution can be specified by adjusting the flowrate of a species.

Precipitation Point The amount of a solid (solubility point) may be specified by adjusting the flowrate of a species.

Composition Point The aqueous concentration of a species may specified by adjusting the flowrate of a species

Custom Combinations of the above calculations can be created.

Select Isothermal calculations.


Figure 2-10 Let's GO! Click the Calculate button!

Click the green calculate button

The program will now start the calculation. After a moment, an “Orbit” will appear illustrating that the calculation is proceeding. For long-time users of the OLI Software message will appear that might seem familiar.

Figure 2-11 The OLI Orbit

The calculation will continue for several moments. When it is done, you will be returned to the same Definition screen.

We’re already to go, click the green calculate button!

Cancel will end the calculation. Close removes the Orbit

The current operation is displayed as well as the current calculation point.


Click on the Report tab.

Scroll down to find the Stream Parameters section.

Figure 2-12 The Stream Parameter

The answer to our question is that the pH of the solution is approximately 2.2. This is fairly acidic and a good question to ask is why is it so acidic? Scroll down the report to see the list of species.

Scroll up or down to see the list of species

Figure 2-13 Species in solution.

Why is the pH so low? The aqueous iron species complex the hydroxide ion which shifts the water dissociation in the direction to replenish the hydroxide ions2. This also produces hydrogen ions which do not have a corresponding place to go and therefore remain free, lowering the pH.

This equilibrium is always present:

H2O = H+ + OH-

2 Le Châtelier’s principle. P.W.Atkins. Physical Chemistry. W.H.Freeman and Company, San Francisco (1982) p 269.

Here is our Answer, the pH is 2.22. We also report some additional information. We can scroll down to see more information or use the Customize button to tailor our report. We can use the Windows Print commands to print this information.

Simple salts in solution can create many species which were not deemed important. The concentration of many of the iron hydroxide species appear to be small but have a great effect on the pH. For example, the concentration of [FeOH+] = 5.2x10-3 moles/Kg H2O which is sufficient to remove the equivalent amount of hydroxide ions. The water equilibrium must shift to replace these ions and produces some additional hydrogen ion.


Getting the Chemistry Right To control and troubleshoot your process, you must start by getting the chemistry right. For aqueous systems, that means two essential considerations:

• Comprehensively taking into account the presence of all of the species that can form in the system (“complete speciation”)

• Rigorously taking into account the non-ideal behavior resulting from the interactions of charged species (ions) and molecules in solution. This is especially important as concentrations get above very dilute levels as typically is the case for most real world systems. (Discussed in a later chapter)

Regarding speciation, OLI software automatically accounts for all of the species that can form from the inflows that you specify. Furthermore, the OLI Databank contains all of the physical properties data and parameters needed to complete the calculations. The user does not need to supply data or regress parameters. The OLI software is ready to use out-of-the-box. The curve above is taken from a StreamAnalyzer survey. You will learn to generate these curves in a later chapter. The curves above plot the predominant species in the ferric chloride – water system. You can see that along with the Fe+3 and Cl-1 ions that might be suspected, the predominant iron species is actually the iron hydroxide complex FeOH+2. As explained in the text, the formation of this complex is the reason that the H+ ion concentration is elevated above neutral (between 0.001 and 0.01 on the plot compared to 10-7 for a neutral solution), yielding a pH of 2.2.


What’s the bottom line? Simple approaches to even simple salts solutions can lead to serious errors in pH and concentration. The rigorous calculation of solution concentrations are necessary to make good engineering decisions.

Advanced Problems

1. How many kilograms of sodium chloride (NaCl) will dissolve into 1 kilogram of water at 50 oC and 1 atmosphere pressure?

2. How many kilograms NaCl will dissolve into 0.9 kilograms of water with 0.100 Kg of methanol at 50 oC and 1 Atmosphere?


Raising your AQ IQ Chapter 3 Neutralized an Acid • 21

Chapter 3 Neutralized an Acid

How to avoid accidental hazardous waste generation! • Effluent discharge costs and regulations encourage consideration of novel recycle

options.

• Blending plant streams can often lead to unwanted, and perhaps costly results.

• The formation of solids and aqueous complexes greatly influences the pH of a mixture. Acid or base neutralization can be readily calculated, but only when all species are accounted for.

A waste stream containing small amounts of HF had a pH that was low enough to be borderline RCRA1 hazardous (acidity). An attempt to “neutralize the stream using another plant stream of neutral pH gave an unexpected and potentially costly result.

Hydrofluoric Acid Stream The hydrofluoric acid (HF) stream was to be at 25 centigrade, 1 atmosphere and a concentration of 0.1 moles HF/Kg H2O. This is often referred to as the molal concentration scale. What would the pH be of this stream? We can estimate the pH from the know dissociation constant for the acid.

The pKa for HF at the stated conditions is 3.21. This is an equilibrium constant of

Ka = 6.1673 x 10 –4. To estimate the pH we use the following simple assumptions.

( )−+ += FHHF AQ

1 RCRA is the Resource Conservation and Recovery Act. 42 U.S.C. s/s 6901 et seq. (1976). RCRA (pronounced "rick-rah") gave EPA the authority to control hazardous waste from the "cradle-to-grave." This includes the generation, transportation, treatment, storage, and disposal of hazardous waste. RCRA also set forth a framework for the management of non-hazardous wastes.

22 • Chapter 3 Neutralized an Acid Raising your AQ IQ

If we start with 0.1 molal HF, at equilibrium we have the following condition

HF(aq) = H+ + F-

(0.1 – X) (X) (X)

42

101673.6)1.0(

−=−

= xX

XK

Assuming that X is much less than 0.1, the value for X = 7.85x10-3. Since this is a

value for H+, the concentration of the hydrogen ion is 7.85x10-3 molal. Since

[ ]+−= HLogpH

The pH = 2.10

This is fairly acid by RCRA standards.

Neutralizing Stream We will use calcium chloride (CaCl2) to neutralize the HF stream. We will use the same concentration of 0.1 molal and the same temperature and pressure. CaCl2 dissociates in water according to:

−+ +→ ClCaCaCl 222

The corresponding acid for this reaction is HCl which also strongly dissociates. The corresponding base is Ca(OH)2 which also strongly dissociates. The expectant pH of a solution which is the product of a strong acid and a strong base is approximately 7.0.

Using the StreamAnalyzer™ We will now start the StreamAnalyzer™ to see how close are estimates are to the actual rigorous calculations.

Start the StreamAnalyzer and use the File/Open menu item to locate a pre-loaded file. This file should be located in the following folder:

\My Documents\My OLI Cases\Analyzer 1.3\Samples

and has the name:

Hazardous Waste.sta2

The file contains two stream that have been previous defined.

2 The file extension may not be displayed depending on your folder option settings.


Figure 3-1 Preloaded file

Just how good was our prediction for the pH of the hydrofluoric acid stream? To find out, we will need to perform some calculations.

Double-click on the HF Acid icon either in the tree view on the left or in the Explorer view on the right.


Figure 3-2 Stream Definition for the HF stream

We have defined the HF stream to be at 25 oC, 1 Atmosphere pressure, 55.508 moles of water3, and 0.1 moles of HF.

Click the Add Single Point button in the upper right-hand corner.

3 55.508 moles of H2O is exactly equal to 1000 grams of water, or 1 Kg. This makes any concentration in this stream effectively a molal concentration value.


Figure 3-3 Adding an isothermal single point calculation.

As you can see, we have added a dependant object to the HF Acid object in the tree view. This indicates that much of the information in this calculation was derived from the parent Stream.

Click the Calculate button to find the pH.

When the program finishes, look in the Summary box.


Figure 3-4 pH = 2.12

The calculated pH is 2.114. The estimated pH is 2.10. This is very good agreement. It would tend to imply that the acid HF did not dissociate to a large degree.

Now what about the pH of the calcium chloride stream?

Double-Click the CaCl2 stream object in the tree-view.

Figure 3-5 Click the CaCl2 object

4 This value may be different that what you actually observed due to small improvements in the data base.

Double-click this object


Figure 3-6 Entering the CaCl2 stream

The conditions for the calcium chloride stream are similar except that we are using a 0.1 molal solution of CaCl2.

Double-click the Add Single Point button.

As before, we now have an input grid for the calculation.

Figure 3-7 Click on Calculate

Click on the Calculate button to find the pH

As before, the calculated pH can be found in the Summary box.


Figure 3-8 the pH is 6.91

The calculated pH is 6.9 which is somewhat lower than the predicted pH of 7.0. This probably due to some complexing of calcium and hydroxide ions in solution. Our estimate is still not too bad a number.

Mixing the HF Acid with the CaCl2 stream. What would happen if we mixed the two stream. After all, that is the purpose of the experiment. The HF stream is nearly too acidic to discharge to the environment. Neutralization could be obtained by the more basic CaCl2 stream.

Since the volumes of the two streams are nearly the same, we could average the pH’s to see the neutralized pH.

Average pH = (2.11 + 6.9)/2 = 4.5

This would be an allowable discharge pH according to RCRA.

What is the actual calculated pH?

Figure 3-9 Selecting Streams from the menu

Select Streams from the menu items.

Figure 3-10 Selecting mixed streams

Select Add Mixed Stream from the menu


This will display the Mix Stream Calculation. Many streams may be mixed at isothermal conditions, or at other varying conditions. We will mix the stream isothermally.

Figure 3-11 Available streams for the mix calculation.

Select each Stream and click the right-double-arrow (>>) to select it.

Figure 3-12 Both streams selected.

The two streams have been selected. You can see a new object has appeared in the tree-view. This is the mixed stream object.


Figure 3-13 A new object appears

The name of the object is automatically created. The number is automatically updated (in this case MixedStream6). You will probably have a different number.

Click the Calculate button.

After a few moments, the pH will be returned in the Summary box.

Figure 3-14 The pH is 1.4

The calculated pH is 1.44!!! Can this be correct? We have taken an acid and neutralized it with a more basic solution. The pH decreased. Something else besides acid and base chemistry must be taking place.


Analysis of the Chemistry

Figure 3-15 The input grid

Click on the Report tab and scroll down to the species section.

Figure 3-16 Scrolled down to find the True Species output. Focused on CaF2

The circle above is focused on a solid species, CaF2. This solid is formed when the calcium ion “Sees” two fluoride ions according to this equation:

−+ +← FCaCaF s 22)(2

The solid is very insoluble and forms rather easily. There was an initial amount of 0.1 moles of HF that we entered. Almost 0.047 moles of CaF2

were formed. Since


there are 2 moles of fluoride ion per mole of calcium fluoride, this accounts for 0.094 moles of fluoride ion. Only 0.006 moles of fluoride ion remain in solution.

This means that we have taken the equilibrium:

( )−+ += FHHF AQ

and placed it under stress. In the mixing operation we have removed fluoride ions from aqueous solution. Le Chatlier’s principle states that if we disturb an equilibrium, the equilibrium will shift to restore itself. In this case, the undissociated HF will dissociate to produce more fluoride ions. This also produces additional hydrogen ions.

Double-click the original HF Stream and then the Single Point Calculation beneath it.

Click the Report tab and scroll down to the Species report. Locate the H+1 row.

Figure 3-17 The H+1 amount for the HF Stream

In the initial HF stream, the pH was equal to 2.11. This corresponds to 8.3883 x 10-3 moles of H+ ion per Kilogram of water5.

Now double-click the Mixed Stream object and go back to the Species report.

Figure 3-18 Back to the Mixed Stream Species Report

5 The relationship of the hydrogen ion to pH is actually pH = -log(aH) where aH is the activity of the hydrogen ion (a = γ[H+]). You need the activity coefficient of the hydrogen ion (which is reported lower in the report) to make an exact conversion)


We have produced a total of 0.0941 mole of hydrogen ion, an additional 0.086 moles of H+ from further dissociation of HF. But this is in approximately 2 Kg of water. The real concentration is .047 moles of hydrogen ion per Kg H2O with a pH of approximately 1.4

Generating Titration Curves The graph above illustrates an interesting titration curve resulting from the neutralization of HF using calcium phosphate. Once again, solids are formed during the process. This results in several inflection points in the titration curve. The neutralization of the HF waste stream with a calcium chloride waste stream was performed using the Mixed Stream Single Point calculation feature. Titration curves like the one above can be readily performed using the Mixed Stream, ratio, volume or proportion features in StreamAnalyzer.


Partial Pressure of Gases (Full OLI Model)

0.01

0.1

1

10

100

1000

10000

100000

0.01 0.1 1 10 100 1000 10000 100000

Experimental

Calc

ulat

ed CO2 (60 C)H2S (60 C)NH3 (60 C)CO2 (20 C)H2S (20 C)NH3 (20 C)Diagonal

Partial Pressures of Gases (VLE only)

0.010.1

1

10100

100010000

100000

0.01 0.1 1 10 100 1000 10000 100000

Experimental

Calc

ulat

ed

CO2 (60 C)H2S (60 C)NH3 (60 C)CO2 (20 C)H2S (20 C)NH3 (20 C)Diagonal

Partial Pressure of Gases (Full OLI Model)

0.01

0.1

1

10

100

1000

10000

100000

0.01 0.1 1 10 100 1000 10000 100000

Experimental

Calc

ulat

ed CO2 (60 C)H2S (60 C)NH3 (60 C)CO2 (20 C)H2S (20 C)NH3 (20 C)Diagonal

Partial Pressures of Gases (VLE only)

0.010.1

1

10100

100010000

100000

0.01 0.1 1 10 100 1000 10000 100000

Experimental

Calc

ulat

ed

CO2 (60 C)H2S (60 C)NH3 (60 C)CO2 (20 C)H2S (20 C)NH3 (20 C)Diagonal

Vapor Liquid Equilibrium (VLE) Accurate vapor liquid equilibrium for multi-component aqueous electrolytes systems also requires accounting for all possible species (“complete speciation”). In this case, solids may or may not form. Either way, it is impossible to accurately determine the phase equilibria and the aqueous phase pH unless all of the reactions in the aqueous phase are considered. An important industry application is sour gas scrubbing. The graph on the left illustrates the results of calculating the phase equilibrium considering VLE only, and ignoring the aqueous phase reactions. An example of this approach would be using Henry’s Law constants from a Table, or using an equation of state such as SRK or Peng-Robinson. Such approaches may provide an approximate solution for just binary systems (e.g. CO2 –H2O, H2S – H2O, or NH3 – H2O). But when more than one compound is present with water, reactions in the aqueous phase lead to aqueous complexes that significantly reduce the partitioning of the acid gases to the vapor phase. The graph on the right shows that the OLI models, which take into account the aqueous phase complexes, accurately predict the chemistry and phase partitioning for acid gas systems.

Conclusion The pH’s of the individual streams were based on simple chemistry and therefore the pH’s were easily estimated. The mixed stream involved more complicated chemistry and our simple estimate was not even close.

A statement can be made that we can not reliably predict mixed pH’s knowing the pH’s of the individual stream.

As an aside, it seems that the following is also true “The resultant pH of a mixed stream of a weak acid and a strong base will have a pH lower than that of the acid providing that a component leaves the solution via a phase change” The weak acid in this case is HF and the strong base is Ca(OH)2 with the fluoride ion leaving solution as CaF2.


Advanced Problems 1. How many moles of ammonia (NH3) will it take to dissolve 0.1 moles

of copper hydroxide (Cu(OH)2) in 55.508 moles of water at 25 oC and 1 atmosphere pressure?


Raising your AQ IQ Chapter 4 Water Treatment • 37

Chapter 4 Water Treatment

You can’t get there from here! • Metals are often removed from water by precipitation processes.

• Careful control of the pH of the precipitation process is necessary in order to achieve the best possible metal removal.

• The presence of other species in a waste stream can significantly affect the removal levels that can be achieved.

• A thorough understanding of the chemistry is needed to design effective water treatment polishing processes such as ion exchange.

The Application ... The city of Clearwater, Florida has a discharge limit for nickel of 0.1 mg/L1.

In this application, a user is discharging a wastewater that contains nickel ion at a concentration of 0.002 moles/Kg H2O. The existing treatment strategy is to precipitate the nickel ion as Nickel Hydroxide - Ni(OH)2 – prior to discharge into the municipal sewage system. The soluble nickel remaining after precipitation is less than 0.1 mg/L which is a design specification.

During the course the plant operation, some cyanide ion is inadvertently added to the waste stream. The soluble nickel is now many times in excess of 0.1ppm.

Let’s get started ... We begin by starting the OLI/StreamAnalyzer Program. This may be accomplished by clicking the StreamAnalyzer icon or by using the Start button and finding the StreamAnalyzer under Program.

Once started, the OLI Splash screen will display.

1 See http://www.clearwater-fl.com

38 • Chapter 4 Water Treatment Raising your AQ IQ

Figure 4-1 The OLI Splash Screen

After a few moments, the main OLI/StreamAnalyzer welcome screen will display.

Figure 4-2 The StreamAnalyzer Welcome Screen

Use File/Open menu item to locate a pre-loaded file.

This file should be located in the following folder:


and has the name:


Nickel Removal.sta2

Figure 4-3 The pre-loaded file

The pre-loaded file has a stream that contains only the 0.002 mole/Kg H2O Nickel concentration and the a stream contaminated with cyanide.

What is the pH? Let’s review the stream definition.

Double-click the stream “Nickel Stream”.

Figure 4-4 The tree view

This will display the Definition window.




Figure 4-5 the definition grid

You can see that we have already added 0.002 moles of Ni(OH)2 to the sample. Water is also entered at 55.508 moles. The amount of water is one kilogram of water which makes the nickel hydroxide concentration effectively a molal concentration unit.

Normally we would either add a single point calculation or a survey at this time. These have already been done for you.

We would like to see the natural pH of the solution.

Click on the “pH” object.

Figure 4-6 Click on pH

There are several calculation types from which we could select. We use the default type of Isothermal.


When the program is completed (the wave is gone) we are ready to review the results. This may be done in several ways. This tour will examine several of the methods.

Click on the Advanced button.

Figure 4-7 the advanced button



We want to display the calculated state and additional stream parameters. The Update button can be used to update new values found in the stream to this calculation.

Select the Calculated State radio button.

Click Additional Stream Parameters.

Click OK

The grid will now change to blue to indicate that these are calculated values. The pH can be found in the grid.

Figure 4-8 the results, the pH is 8.4

Our primary interest in this application is finding the optimum pH for nickel removal. To create a plot of the data, we will need to make a survey.

Adding a pH Survey There are many ways to move around in the StreamAnalyzer. We will constantly highlight them as we move around in the tours. Remember that there are frequently more than one method to achieve a desired result.

Click on the pH Survey icon in the tree view on the left-hand side of the window.

The results are displayed in blue. The resultant pH is approximately 8.37. This number may be different from your value because the database is constantly updated.


Figure 4-9 click on pH Survey

Figure 4-10 The pH Survey Definition Tab.

The calculate button light is grayed out which indicates that the calculation is not yet ready to proceed. The Summary box indicates that we require additional information.



Figure 4-11 The summary box, an acid and a base need to be selected

The acid titrant and the base titrant need to be defined. For this tour, these will be hydrochloric acid (HCl) and sodium hydroxide (NaOH).

Add the component inflows HCl and NaOH to the grid. Do not add any values for them.

Figure 4-12 Added new component inflows.

Click the Specs… button


Figure 4-13 pH Survey Options

Select HCl from the Acid column and NaOH from the Base column.

Click on OK.

We are now ready to begin the calculations.


The program will run for a short time. When the orbit disappears, check the summary box to see if the calculation is complete. In the tree-view, you can expand the survey to see if all the points converged.

A small calculation result window may appear. If it does, simply close it.

Figure 4-14 Calculation result windows. Click the X to close it.

Obtaining results We can now obtain some graphical results.

Click on the Plot tab.

Click this X to close the box


Figure 4-15 the default plot

For many calculations, the values on the plot extend over a very large range of numbers. The default linear axis may not capture all the details we require.

Right-Click anywhere in the plot window and select Toggle Y-axis Log

Figure 4-16 the plot right-click

The display will now change.


Figure 4-17 log axis plot

Although this plot tells us a great deal, we require more specific information about nickel species. Remember, there is a limit to the amount of soluble nickel that can be discharged. We need to clean this diagram up.

Click the Customize button.

Figure 4-18 The customize plot dialog

The Dominant Aqueous variable in the Y-Axis box should be displayed. Select it and then click the left double-arrow (<<) button which will remove it from the plot.

Scroll down the left-hand window to find MBG Aqueous Totals.

You can select and drag the legend to comfortable positions.

Scroll down this list to find more variables


Figure 4-19 Selecting more variables

MGB is an abbreviation for Material Balance Groups

The grid updates to show the material balance totals available to display. In this case we desire the Nickel (+2) species. The variable displayed will be the sum of all nickel containing species in the aqueous phase.

Double-Click the NI(+2) item or select it and use the >> button.

Click the OK button

Figure 4-20 The results of the pH survey.

The material balance group variable is a sum of all the species for that material in the phase requested. For example, in this case all the NI(+2) –Aq variable is a sum of all nickel containing ions in solution. Any solids are excluded.

This is the 0.1mg/L limit for Nickel.


You can see that a minimum in aqueous solubility seems to occur in the pH=10 range. This is the result of nickel solids forming and leaving the aqueous phase.

The limit of 0.1 ppm for Ni+2 is approximately 2 x 10-6 moles. At a pH=10, we are several orders of magnitude below this limit.

What else is important in this solution.

Click the Customize button and add the following species to the plot (you may need to scroll up or down to find all the species).

Aqueous:

Ni(OH)2

NiOH+1

Ni+2

Ni(OH)3-1

Solids:

Ni(OH)2

Figure 4-21 Important nickel species

You can see that the soluble nickel (Ni(+2)-Aq) is a summation of the other species. The large drop in the value is because most of the nickel leaves the aqueous solution as Ni(OH)2-Solid at pH’s greater than 7.0 with a maximum near pH=10.

Now, What About the Contaminated Waste?

The real importance of aqueous speciation modeling of this treatment is only really appreciated if we introduce the cyanides which brings us to the real waste treatment problem.


Please follow these steps for this next scenario. Please note: we will only show the screens that are substantially different from those that you have scene.

What is the pH of the Cyanide contaminated stream? Click the Contaminated Stream in the tree view in the left-hand window.

Figure 4-22Click on the Contaminated object

This will display the stream view in the right-hand window.

Figure 4-23 The input grid

As you can see, 0.01 moles of hydrogen cyanide have been added to the solution. As before, we have already partially added a single point calculation and a survey.

Click the “pH” object under the Contaminated object.

Figure 4-24Click the pH object

The grid should now look like this:




Figure 4-25 Adding HCN

When the Calculate Button light turns green, click the button.

Getting results of the Single Point Calculation. There are several method for reviewing the results of a calculation. Scenario 1 showed how the advanced button can reveal additional information. In this scenario we will use a different technique.

Right-Click anywhere in the grid

The following pop-up menu will appear.

Figure 4-26 Right-clicking on the grid

Select Show Calculated

Right-Click again and select Additional Stream Parameters

The resultant pH should be approximately 4.04

Run the pH survey. Click the “pH Survey” Object stream in the tree view in the left-hand window.


This will display the grid view in the right-hand window.

We have already added the HCl and NaOH to the grid since we already know that they will be the pH titrants. The titrants have already been selected. All we have to do is:

Click the Calculate Button.

Reviewing results. When the program has finished calculating:


Figure 4-27 Nickel Waste Stream with HCN added

We have provided you with a partial list of species to plot. We now want you to add two additional variables:

0.1mg/L limit



Click on the Customize button and add:

NI(+2) MBG Aqueous Totals

NiNi(CN)4 Solid

The results have changed very dramatically. The new optimum pH for Ni removal is around 4.0, rather than 10.0. The lowest total Ni remaining in solution is now on the order of 10-5 which is actually well over 0.1 mg/L.

The culprit is the Ni(CN)-2 complex of nickel and cyanide. Basically, the plot of the total Ni in solution and the Ni(CN)-2 complex overlap over the interval pH=5 to 12. This means that virtually all nickel in solution is in the form of this complex.

This complex thus holds the Ni in solution and does not allow the nickel hydroxide to even form. Instead, a much weaker precipitate, the NiNi(CN)4 salt forms over a narrow range of pH with 4.0 being the optimum.

The nickel can no longer be discharged into the municipal sewage system. Alternative forms of removal must now be considered

.

Conclusion Water treatment processes can be optimized and effectively managed when the chemistry is thoroughly understood. Trace species can have a significant effect on the performance and compliance of these processes.

The StreamAnalyzer survey feature makes it easy for you to perform sensitivity studies to determine how the key variables in your process affect the outcome. For example, the surveys you performed could be repeated at different temperatures to see if there is a significant effect. The plot on the left shows that as the temperature is varied and there is no cyanide ion present, the total nickel concentration remaining in the aqueous phase is about the same, but the pH at which the minimum occurs varies over a range from about 9 to 11. The right plot shows that when the cyanide ion is present, the chemistry is relatively insensitive to temperature over a range of 15 to 45 °C. The survey feature can help guide and save you lab time and cost. One option to remove the nickel when cyanide is present could be ion exchange. Although is might be assumed that a cationic resin would be needed to remove the nickel, the OLI software shows that the important species to remove is actually the nickel cyanide complex which is a negatively (-2) charged species. The correct alternative would be an anionic exchange resin.


Advanced Problems 1. Could 0.01 moles/Kg H2O sodium sulfide be used to react with the

cyanide contaminated stream to remove the nickel?

2. Would lowering the operating pH to 2 improve the nickel removal?


Raising your AQ IQ Chapter 5 Sour Gas Treatment • 55

Chapter 5 Sour Gas Treatment

A little bit of water can go a long way (in creating a Big Process Problem)

• Whenever water is present in a process, there is the possibility of condensation of a liquid phase that can lead to solids deposition and/or corrosion.

• Real world systems are often complicated by the presence of a second liquid phase, making phase equilibrium prediction challenging.

• Conventional process simulation cannot readily address these kinds of situations. They can be addressed by importing “streams” into the OLI Analyzers.

Scope An alkanolamine gas sweetening plant has scaling and corrosion problems in the condensed overhead gas.

56 • Chapter 5 Sour Gas Treatment Raising your AQ IQ

Figure 5-1 An Alkanolamine gas sweetening plant (diagram from HYSYS 3.1)

Purpose Diethanolamine is used to neutralize an acid gas containing carbon dioxide and hydrogen sulfide. The Diethanolamine is regenerated and the acid gases are driven off in a stripper. The off gas from this stripper is saturated with water vapor. As these gases cool, they will condense. This condensate can be very corrosive. The service life of the plant can be shortened considerably due to these condensed acid gases.

Objectives

1. Determine the dew point temperature of the acid gas 2. To remove the condensed aqueous phase and perform

corrosion rate calculations. 3. To consider mitigation strategies for the pipes.


Start the tour










and has the name:

Sour Gas.sta1

This file was saved with the CorrosionAnalyzer Plug-In enabled. A warning message will appear.



Figure 5-4 Corrosion Analyzer Plug-In warning.

Clicking on the OK button will launch the program but any CorrosionAnalyzer related objects will be disabled.

Figure 5-5 StreamAnalyzer with disabled rates calculation

The Analyzers™ allow you to “Plug-In” other analyzers into each other. For example, we can plug-in the CorrosionAnalyzer™ into the StreamAnalyzer™. The files created are still StreamAnalyzer files.

Select Tools from the menu item.


Figure 5-6 Selecting Tools

This will display a menu.

Figure 5-7 The tools menu

Select Options…from the list.

Figure 5-8 the Options Dialog.

There are many things that can be modified with this dialog. The look and feel for the software as well as default locations can be specified.

Click on the Plug-Ins line in the Category Tree-view.


Figure 5-9 The plug-ins dialog

Several OLI programs are available here.

Check the CorrosionAnalyzer box.

Figure 5-10 Selecting the corrosion Analyzer.

Click on the OK button.

You will now be required to close and restart the program.

Close the program without saving the file.

Restart the program opening the same file Sour Gas.STA


The stream has the following composition. We have already added the stream for you in this example.

Table 1 Gas Concentration

Species Concentration (mole %)

H2O 5.42

CO2 77.4

N2 0.02

H2S 16.6

CH4 0.50

C2H6 0.03

C3H8 0.03

Temperature 38 oC

Pressure 1.2 Atmospheres

Stream Amount 100 moles

You will notice that the value for water is in yellow. This value will be automatically calculated from the sum of the other inflow components. Error message may occur if you have concentrations that require the mole percentages of water to be negative.


The Corrosion Rate at the Dew Point We now want to determine the corrosion rate at the dew point temperature for this gas. The dew point is the temperature where the first amount of aqueous liquid will condense. We have already added a corrosion rates calculation to the stream.

Figure 5-11

Adding the rates calculation. This will display a default view of the rates of corrosion. We have already filled out the grid for you. If you are working from scratch we did the following:

We will now change the Types of Rates Calculation and the Flow Conditions.

Figure 5-12 Default conditions.

Change the type of calculation to Single Point Rate and the flow conditions to Pipe Flow and use the default values.

Figure 5-13

The contact surface should be set to

Carbon steel G10100 (generic)

What’s all this about corrosion rates? OLI Systems, Inc. is also a world leader in providing simulation tools for corrosion scientists and engineers. OLI holds a separate course called the “Corrosion Teach-In.” It is held at several locations world wide each year. Contact OLI for more information.


Figure 5-14

We now will add the dew point calculation on top of the corrosion rates calculation.

Click the Specs… button.

Figure 5-15 The specs… button.

Now select the Calculation Type line.

Figure 5-16 The calculation type dialog

Click the Type of Calculation button and select Dew Point.


Figure 5-17 Selecting dew point

Figure 5-18 Temperature selected.

We want to calculate the corrosion rate at the dew point temperature.

Click the Temperature radio button and then click OK

We now have a screen that should look like this:


Figure 5-19 The completely filled out grid.


When the program finishes, we would like to see the rate of corrosion of the steel.

Click the Point 1 of 1 mini-tab at the bottom of the grid.


Figure 5-20 The output grid

Right-click anywhere on the grid to display a pop-up menu.

Figure 5-21 The pop-up grid menu


Select Corrosion Values from the menu

Figure 5-22 Selecting Corrosion Values.

This will display the overall corrosion information for this stream.

Figure 5-23 The corrosion information

The corrosion rate is approximately 0.7 mm/yr. The dew point is approximately a temperature of 37.6 oC. The value is in green to note that it was a secondary calculation.

Click on the Report Tab and scroll down to the Stream Parameters.

Figure 5-24 The stream parameters

The pH is nearly 3.9 of the condensed vapor.

Mitigation There are several solutions for mitigating the corrosion problem. A simple solution is to add insulation to prevent temperature drops. The dew point is very close to the overhead gas temperature so this may not be a suitable option. Adding heat to keep the temperature above the dew point is usually considered along with insulation.

Changing the chemistry to change the partial oxidation and reduction processes is also an option. Finally, changing alloys could mitigate the corrosion problem.

What are all those other tabs? It is beyond the scope of this course to explain those tabs. OLI’s Corrosion Teach-In course explains these diagrams in great detail.


Adjusting the solution chemistry.

In this section, we will add sodium hydroxide to raise the pH to 8.0

Click on the original stream in the tree view.

The original stream should be the first stream in the list.

Figure 5-25 Selecting the first stream.

This stream contains the original input information.

Click the Add Single Point button.

Select Set pH.

When setting the pH, you must specify a titrant. There are several methods of selecting titrants.


Figure 5-26

Figure 5-27

The desired titrant, sodium hydroxide (NaOH), is not on the list. We can add it by entering a new inflow species.

Click the New Inflow button.


Figure 5-28

You can search for any component in an OLI database. If the species has stored synonyms and / or structures, they will be displayed.

Enter the species name NAOH in the Component box.

Figure 5-29


As you can see, synonyms are filled out as well as the internal OLI name (OLI Tag), molecular weights and the chemical abstract service number.

Click the Add to Stream button.

Click the Close button.

The Select titrant window will be updated with a new species.

Figure 5-30

Select NaOH and then click OK.

The input window will now be updated with a grid entry for NaOH and a target pH value initially set to 0.0.


Figure 5-31

Enter a target pH of 8.0

The program is now set up to adjust the amount of NaOH to match a target value of pH = 8.0.

Figure 5-32


Look at the summary box when the calculation is complete.

New species, NaOH with zero concentration

Initial target pH is 0.0, it must be changed to 8.0


Figure 5-33

The pH is indeed set to 8.0 and the concentration of NaOH is approximately 42 mole percent in the aqueous phase. Also notice that in the Phase Amount section, there is some solid material.


Scroll down to the Species Output (True Species) section.

Figure 5-34

This section of the report shows the detailed speciation for this point. At a pH of 8.0, this gas stream will form 72.4 moles of sodium bicarbonate (NaHCO3) for every 100 moles of gas (the initial amount).

Using sodium hydroxide is probably a bad choice for mitigating the corrosion since a scale of NaHCO3 would likely form and plug the process equipment. Metal hydroxides are very good at scrubbing carbon dioxide from gas streams.


Alloys Since treating the acid gas with a base is probably not a good idea for metal hydroxides, perhaps we can change the alloy.

We will go back to the condensate stream (the second stream on the tree view) and add a new corrosion rates calculation.

Figure 5-35

Click on the Sour Gas stream.

Click on the Add Corrosion Rates button.

Change the Contact Surface to 13%Cr stainless steel

We will now change the Types of Rates Calculation and the Flow Conditions.

Change the type of calculation to Single Point Rate and the flow conditions to Pipe Flow and use the default values.

Click the Specs… button and select Calculation Type and then Select Dew Point Temperature.


Click on the Report Tab and scroll down to the Calculated Rates section.

Figure 5-36

The calculated corrosion rate is 0.06 mm/yr. A little more than one order of magnitude decrease over carbon steel

Save This would be a good time to save your work.


Conclusion. Whenever water is present in a process, there is the possibility of condensation of a liquid phase that can lead to solids deposition and/or corrosion. Real world systems are often complicated by the presence of a second liquid phase, making phase equilibrium prediction challenging. Conventional process simulation cannot readily address these kinds of situations. They can be addressed by importing “streams” into the OLI Analyzers. The Analyzers can perform pH adjustment, dew point and bubble point, precipitation point, and corrosion rate calculations for streams that you define or import from a conventional simulator.

This example showed how the addition of a reagent used to raise the pH led to the formation of potentially problematic solids. In real world applications such as upstream oil and gas, it is possible to have situations where gas, aqueous liquid (brine), second liquid (oil), and solids co-exist. For example in this case CO2 may partition between the gas, oil, brine, and solids (as a solid carbonate for example). Accurate simulation of this situation requires accounting for the equilibrium in all four phases at once, the so called four phase flash. This can be a difficult situation for conventional simulators to handle. The OLI software is designed to make it easy to perform four phase flash calculations, and then plot the results as a function of variables that you select. The OLI software can even import streams from a conventional simulator so that corrosion, solids scaling, and other process conditions or options can be evaluated. Below is an excerpt from a StreamAnalyzer report illustrating the calculated results for a four phase flash calculation. Note that the true species composition, in this case reported as moles, is reported by phase. Note also that CO2 does in fact partition to all four phases (to the solid phase in the form of calcium carbonate). Species Output (True Species) Total Aqueous Vapor Solid 2nd Liquid mol mol mol mol mol Water 54.901 54.877 0.019027 0.0 4.9505e-3 Carbon dioxide 0.37944 0.014427 0.29040 0.0 0.074610 Hydrogen sulfide 0.66117 0.059542 0.30722 0.0 0.29441 Ammonia 0.012101 0.011817 1.2379e-4 0.0 1.6083e-4 Dodecane 10.000 2.6265e-8 1.1282e-4 0.0 9.9999 Calcium chloride 6.1070e-28 6.1070e-28 0.0 0.0 0.0 Calcium carbonate (calcite) 9.9504e-3 5.7152e-6 0.0 9.9447e-3 0.0 Hydrogen chloride 2.6357e-16 1.5178e-16 1.1179e-16 0.0 0.0 Ammonium ion(+1) 0.97447 0.97447 0.0 0.0 0.0 Bicarbonate ion(-1) 0.59204 0.59204 0.0 0.0 0.0 Calcium bicarbonate ion(+1) 2.5321e-5 2.5321e-5 0.0 0.0 0.0 Calcium hydroxide ion(+1) 5.7940e-11 5.7940e-11 0.0 0.0 0.0 Calcium ion(+2) 2.4286e-5 2.4286e-5 0.0 0.0 0.0 Calcium monochloride ion(+1) 2.6160e-12 2.6160e-12 0.0 0.0 0.0 Carbamate ion(-1) 0.013435 0.013435 0.0 0.0 0.0 Carbonate ion(-2) 5.1132e-3 5.1132e-3 0.0 0.0 0.0 Chloride ion(-1) 0.020000 0.020000 0.0 0.0 0.0 Hydrogen ion(+1) 3.2786e-8 3.2786e-8 0.0 0.0 0.0 Hydrogen sulfide ion (-1) 0.33882 0.33882 0.0 0.0 0.0 Hydroxide ion(-1) 6.1638e-7 6.1638e-7 0.0 0.0 0.0 Sulfide ion(-2) 1.1942e-5 1.1942e-5 0.0 0.0 0.0 Total (by phase) 67.907 56.907 0.61688 9.9447e-3 10.374


Advanced Problems 1. As we saw in the example, using sodium hydroxide to adjust the pH

caused unwanted solids to form. Using ammonia (NH3), recalculate the pH calculation to see if solids form.

2. Are there any other titrants that would raise the pH but not cause solids to form?

Raising your AQ IQ Chapter 6 Chlorine Scrubbing • 77

Chapter 6 Chlorine Scrubbing

If 10 percent is good, 20 has to be better…? An emergency scrubber is to be designed to handle the emergency release of chlorine gas from a process. The gas stream contains chlorine, carbon dioxide and nitrogen. Caustic (NaOH) is to be the scrubbing liquid.

The design specification is to remove 90 % of the total chlorine. There is a concern that due to the presence of CO2 that carbonate solids may form and plug the scrubber.

FC

Emergency Chlorine Scrubber

Caustic25 oC

1 Atm

1000g/hr total

10 wt% NaOH

Waste Gas25oC

1 Atm

Cl2 5.8 mol/hr

CO2 52 mol/hr

N2 58 mol/hr

Overhead

Bottoms

3 Stages

25 oC

1 Atm

Figure 6-1 Schematic of the scrubber

The scrubber (also referred to as an absorber) contains a feed back controller to control the amount of caustic used to neutralize the chlorine. The flow rate of the

78 • Chapter 6 Chlorine Scrubbing Raising your AQ IQ

caustic stream is an initial guess and may be larger or smaller when the program finishes.

It is sometimes useful to perform a simple one stage calculation prior to performing a multistage calculation. In this case a simple one stage equilibrium calculation was performed using survey feature of the OLI/StreamAnalyzer. Although this is not a true scrubber, in that only one stage will be simulated, it does provide some insight into the chemistry taking place inside.










and has the name:

Chlorine Removal.sta1



Figure 6-4 the partially filled out file

We have provided you with a chlorine stream (Cl2) and two sodium hydroxide streams. One at ten weight percent (10 % NaOH) and the other at twenty weight percent (20 % NaOH). We will use both of these streams to remove chlorine.

Stream Review We should take a brief look at each of the streams to determine if they are correct. The following figures display the Stream Description tab for each stream.

Figure 6-5 Chlorine Stream


Figure 6-6 10 weight percent NaOH Stream

Figure 6-7 20 weight percent Stream

Now that we have reviewed our streams. Let us mix the streams together. The StreamAnalyzer has the ability to perform a titration. To start this will need to add a new type of stream, the Mixed Stream.

Adding a Mixed Stream Locate the Streams menu item.

Figure 6-8 The streams menu item.

Select Add Mixed Stream from the pull down menu.

Figure 6-9 The pull down menu.

This will display the mixed stream dialog.


Figure 6-10 Adding Mixed Streams

The Available Streams window displays what streams are ready to use for mixing calculations.

Figure 6-11 Available streams.

We can highlight the stream (or streams) that we need and then double-click the right arrow button.

Figure 6-12 Multiple selections are allowed.

Click this button after making your selection.


Figure 6-13 Selected streams

If you want to remove a stream (or streams) you can highlight them in the Selected window and use the left double-arrow.

Once we have selected the streams we now need to set up the calculation. We have two streams with which can be varied in proportion to each other. We want to keep the flow of the chlorine gas constant and vary the flow of the 10 % NaOH stream.

Figure 6-14 The action items for the calculation.

We need to change the Type of survey button to a ratio calculation.

The menu will display as follows:

Figure 6-15 Survey menu options.

Single Point Mix The streams are mixed according to the proportions specified in the grid.

Volume The volume of the target stream is mixed according to the specs… button. The reported volume is for the total system

Ratio The amount of one stream is adjusted while the other is held constant. The report is in terms of the adjusted stream only

Proportion The flow of one stream is increased while the flow of the remaining streams are decreased to maintain a constant proportion.

For our purposes, select the Ratio menu item.

We want to calculate each point at isothermal conditions (as not to add another degree of freedom to our calculations, we can study heating effects later if we wish). We now need to tell the program to vary a stream and by how much

Click on the Specs… button.

Click this button to make your selection.


Figure 6-16 The specs... dialog

The variable which is highlighted is the ratio variable. We will adjust one stream from a flow rate of zero to a flow that is 10 times the initial flow of the stream. In this case, we are adjusting the 10 % NaOH stream which has a mass flow rate of approximately 1 Kg/hr. The flow will be adjusted from 0 to 10 Kg/hr.

We do need to specify which stream is to be adjusted.

Highlight the General item in the tree-view:

Figure 6-17 Highlight the General item.

The streams to be considered are displayed next to the tree view.


Figure 6-18 Chlorine is selected.

If the chlorine stream is highlighted, we will have to change it to the 10 % NaOH stream.

Click on the “10 % NaOH” stream.

Figure 6-19 Selecting the correct stream.

Click back on the Variable-Ratio item in the tree view.

If chlorine is highlighted, change the focus to 10 % NaOH


Figure 6-20 back to the ranges

Change the increment value from 1.0 to 0.25.

Figure 6-21 Change the increment.

This provides for a smoother looking curve.

Click the OK button.

You are now ready to calculate.


When the calculation has completed, click on the Plot tab.


Figure 6-22 The default plot

We will need to change the plot to see how much chlorine was removed.


Figure 6-23 The customize plot button.

We need to find the amount of chlorine vapor that is remaining in the gas phase.

Double-click the “Dominant Aqueous” item in the Y-Axis window.


Scroll up or down to find the Vapor section and select Cl2 by double-clicking it in the left window.

Figure 6-24 Selecting chlorine vapor

Click on the OK button.

Figure 6-25 Chlorine in the vapor phase.

We initially had 5.8 moles of chlorine. Thus at 0.58 moles of chlorine in the vapor corresponds to 10 % remaining or 90% removed. You can mouse-over the points to find a value near 0.58 moles of chlorine.

This is approximately 0.58 moles of Cl2(VAP).


This corresponds to a ratio of the 10 % NaOH stream of 3.5. That implies that we need about 3.5 Kg/hr of the base stream to remove the desired chlorine. The chlorine stream is approximately 4.3 Kg/hr so the ratio we want is 4.3/3.5 or 1.23

Why does adding base remove Chlorine? The absorption of chlorine gas follows these equilibria:

Cl2(vap) = Cl2(aq)

Cl2(aq) + H2O = H+ + Cl- + HClOo(aq)

HClOo(aq) = H+ + ClO-

Adding a base, such as sodium hydroxide, increases the pH. pH is defined by

pH = - Log10[H+]

Thus if the pH increases, the concentration of hydrogen ion must decrease. As the hydrogen ion decreases, the equilibria above have to shift to restore the equilibrium.

Let’s look at each equilibrium individually:

HClOo(aq) = H+ + ClO-

As the hydrogen ion concentration decreases, this equilibrium will dissociate more to replace the hydrogen ion. We can say that they hypochlorous acid concentration will also decrease as the hydrogen ion decreases.

Cl2(aq) + H2O = H+ + Cl- + HClOo(aq)

This equilibrium is more complicated. It too will shift to the right (decreasing the chlorine concentration and the water concentration) as the hydrogen ion concentration decreases. A double effect occurs because the hypochlorous acid is also decreasing.

Cl2(vap) = Cl2(aq)

As the aqueous chlorine concentration decreases, the amount of vapor chlorine must also decrease. This is why basic scrubbing of an acid gas works. For this case, a mole of sodium hydroxide should remove two moles of chlorine gas. The slope of the line should be straight.

This brings up the question, why did the curve for the chlorine remove level off at a non-zero value?

To review, look a the plot once again:


Figure 6-26 Reviewing chlorine removal

Something else must be occurring. Perhaps solids are appearing.

Click the Customize button. Scroll down to find the Solids section and select Dominant Solids. Click OK when done.

Figure 6-27 Same figure with solids added


The dominant solid on the plot is sodium bicarbonate (NaHCO3). It seems to appear above a ratio of 4.8.

Why does the formation of the sodium bicarbonate solid prevent any more chlorine from being absorbed? Let’s start with some basic equilibria:

When the solid sodium bicarbonate is forming, this equilibrium exists:

NaHCO3(s) = Na+ + HCO3-

As long as the solid sodium bicarbonate is forming, the amounts of the sodium ion and bicarbonate ion remain constant.

The bicarbonate ion dissociates:

HCO3- = H+ + CO3

2-

Since the bicarbonate ion is constant, so is the hydrogen ion and the carbonate ion.

Since the hydrogen ion concentration is essentially fixed by the formation of the sodium bicarbonate, the chlorine hydrolysis (the second reaction) is fixed. This fixes the VLE equilibrium in the first equation. The hypochlorous acid species can not dissociate further since it is also fixed by the constant hydrogen ion.

All this is acceptable since our design specification was to remove 90 % of the vapor chlorine using 10 weight percent sodium hydroxide.

What happens if you use more concentrated solutions? In actual practice, a user used twenty weight percent instead of ten weight percent. The ratio of the flows (1.23 chlorine/base) was still maintained. We are going to repeat the steps above except we will use the 20 % NaOH stream instead.

Please follow these steps.

Locate the Streams menu item.

Select Add Mixed Stream from the pull down menu.

The Available Streams window displays what streams are ready to use for mixing calculations. Select the Cl2 and the 20% NaOH streams

Change the Type of survey button to a ratio calculation.

The menu will display as follows:

Select the Ratio menu item.

Click on the Specs… button.

Highlight the General item in the tree-view:

Click on the “10 % NaOH” stream.

Click back on the Variable-Ratio item in the tree view.

Change the increment value from 1.0 to 0.25.



When the calculation has completed, click on the Plot tab.




Double-click the “Dominant Aqueous” item in the Y-Axis window.

Scroll up or down to find the Vapor section and select Cl2 by double-clicking it in the left window.

Scroll up or down to fine the Solid section and select Dominant Solids


Figure 6-29 20 % NaOH

We initially had 5.8 moles of chlorine. Thus at 0.58 moles of chlorine in the vapor corresponds to 10 % remaining or 90% removed. You can mouse-over the points to find a value near 0.58 moles of chlorine.

This corresponds to a ratio of the 20 % NaOH stream of 3.5. That implies that we need about 3.5 Kg/hr of the base stream to remove the desired chlorine. The chlorine stream is approximately 4.3 Kg/hr so the ratio we want is 4.3/3.5 or 1.23

So what is different here? In this case you will notice that the line corresponding the solid NaHCO3 is non-zero at our operating point. This means that solids will form if we want to get to our desired set point.

Solid formation in a scrubber can be bad news. Solids plug process equipment, trays and packing. Pressure drops and unexpected heat profiles may occur. Shortened equipment life is expected and frequent maintenance is required.

Conclusion Good results were obtained with only 10 % NaOH. Using the more concentrated solution under the idea that more is better was certainly a bad idea.

This is approximately 0.58 moles of Cl2(VAP). The original set point


Reliable prediction of solids precipitation from aqueous solutions can be challenging. Recall from a previous discussion, the two essential considerations for modeling aqueous systems:

• Comprehensively taking into account the presence of all of the species that can form in the system (“complete speciation”)

• Rigorously taking into account the non-ideal behavior resulting from the interactions of charged species (ions) and molecules in solution. This is especially important as concentrations get above very dilute levels as typically is the case for most real world systems. (Discussed in a later chapter)

Often at higher concentrations, there is a significant departure from ideal solution behavior. OLI captures this behavior through a combination of robust standard states thermodynamic model and activity coefficients models. The solid-liquid equilibrium behavior is also modeled as a function of temperature. The result is unsurpassed solid prediction capability for aqueous solutions.

The solubility of a salt in water varies with temperature, usually increasing with increasing temperature. However some salts exhibit inverse solubility behavior over a given temperature range. An example of this is sodium sulfate shown on the right. This type of behavior can lead to unexpected plugging of pipes, heat exchangers, and towers as the fluid temperature changes through the system. OLI software can predict this kind of behavior for real solutions to help you avoid these problems.


Tower separations are a common industrial unit operation. OLI has developed an aqueous flowsheet simulator called ESP that is designed specifically to simulate aqueous electrolytes processes. One of the unique features of this product is the ability to include heat and mass transfer as well as chemical reactions and reaction rate constants in the tower separations simulations. This feature provides the most realistic simulation possible for electrolyte separations. Contact OLI for more details on the ESP product.


Advanced Problems Using sodium hydroxide (caustic) can be expensive. Cheaper bases such as lime or quick lime (Ca(OH)2) are frequently used.

1. How much calcium hydroxide is required to remove 90 % of the chlorine from the vapor?

2. Are there any additional solids that are produced.

3. Can you determine another reagent that may be cheaper and better than sodium hydroxide?

Raising your AQ IQ Chapter 7 Gypsum Solubility • 97

Chapter 7 Gypsum Solubility

Getting an edge on the competition. • Reliable simulation of complex processes can provide insights for process

optimization and reduced operating costs.

• The solubility of salts is significantly effected by the presence of other salts.

Modern gypsum (CaSO4•2H2O) production frequently involves recovering sulfur waste products from the off gas of power plants. This gas is scrubbed with a lime (CaO) solution which can form gypsum. This impure solid is re-dissolved and purified to make commercial wallboard.

There are many advantages to this process, notably the ability to recover a pollutant and use it for commercial purposes (reducing the cost of scrubbing) and reducing the need to mine a mineral.

In this application we will see that there is a region where we can optimize the solubility of gypsum in the re-dissolving process.



98 • Chapter 7 Gypsum Solubility Raising your AQ IQ




We will build this file from scratch.

Click the Add New Stream Icon.

Figure 7-3 Add a new stream

Our first goal is to determine the solubility of calcium sulfate (CaSO4) as a function of temperature. The input grid should look like the following:


Figure 7-4 Standard input grid

Enter CaSO4 into the Inflow section.

Figure 7-5 Entering CaSO4

If the display is not in formula view, use the menu item Tools and Select Names Manager. Select Formula from the list. If formulas are displayed, skip down to Resuming the application

Selecting Formula View

Figure 7-6 Select Tools


Figure 7-7 Select Names Manager

Figure 7-8 Select Formula and then click OK

Resuming the application Click the Add Survey button.

Figure 7-9 Click Add Survey

Our input screen should look like the following:


Figure 7-10 Survey Input grid

We would like to work in weight fraction units.

Select Tools from the menu line.


Select Units Manager from the menu.

Figure 7-12 Select Units Manager


Figure 7-13 The Units Manager Dialog

Click the Custom radio button.

Figure 7-14 Use the drop down arrow to find Mass Fraction.


We have now set up our units for mass fraction. As you can see the input grid is now set to 100 mass% water. The default survey is temperature, which we want. However we only want to go to 30 oC while saturating the solution with CaSO4. The solid phase that should appear is CaSO4•2H2O (gypsum).

By default, a temperature survey will only vary the temperature in the range specified. We will need to instruct the simulation to adjust our inflow to maintain saturation as well.


Click the Custom Radio Button


Figure 7-15 the specs... button.

Change the Start and End values to 0 and 30 oC. The Increment will be 2.

Figure 7-16 the changed start, end and increment values.

We now need to change the calculation type.

Click on the Calculation Type object in the tree view.

After changing the start, end and increment boxes. Click the Calculation Type object


Figure 7-17 the calculation type

The default calculation type is isothermal. We need to perform a precipitation point calculation.

Click the Type of Calculation button.

Figure 7-18 Selecting precipitation point.

The dialog will change.

Figure 7-19 New items for selection.

Click this button


We need to select an inflow to adjust and also select a solid to precipitate.

Select CaSO4•2H2O from the left window, and then select CaSO4 from the right.

Figure 7-20 Selecting variables.

Click OK and we are ready to start the calculation.

What is a precipitation point calculation? Before we start the calculation, we should discuss what is involved in a precipitation point calculation.

To do this we first need to discuss the chemistry model. When we added the inflow species for water and calcium sulfate, we created a model with many species;

Inflow Species We entered two “Inflow” species. These species are the same as what we entered on the inflow grid. H2OIN CaSO4IN The “IN” indicates to the program (internally) that these are inflow entered in the grid. We also find additional inflow species in our database that have common elements as our species. These are: CaSO4.2H2OIN SO3IN Ca(OH)2IN H2SO4IN Ca(HSO4)2IN These species are normally masked from the user but can be displayed if required.


Aqueous Species Many aqueous species are retrieved from our database. These species are: H2O SO3

o

CaSO4o

H2SO4o

H+

OH-

Ca2+

CaOH+

HSO4-

SO42-

H2OVAP SO3VAP H2SO4VAP CaSO4.2H2O(s) CaSO4(s) Ca(OH)2(s) There are 16 species on this list. These, in terms of mathematical equations, are unknowns. We need to generate 16 mathematical equations.

Equilibrium Equations We automatically create in the software the mass action relationships. H2O=H+ + OH- SO3o +H2O=H2SO4

o

CaSO4o

=Ca2+ + SO42-

H2SO4o=H+ + HSO4

-

CaOH+=Ca2+ + OH-

HSO4-=H+ + SO42-

H2OVAP=H2O SO3VAP=SO3

o

H2SO4VAP=H2SO4o

CaSO4.2H2O=Ca2+ + SO42- +2H2O

CaSO4(s)=Ca2++SO42-

Ca(OH)2(s)=Ca2++2OH-

These are then converted into the traditional equilibrium relationships.

OH

OHHOH a

OHHK2

2][][ −

−+

+=γγ

OHaqaqSO

SOHSO aSO

SOHK233

42423 ][

][γ

γ=

][][][

44

2424

22

4aqaqCaSO

SOCaCaSO CaSO

SOCaKγ

γγ −−

++=


][][][

4242

4442 o

aqSOH

HSOHSOH SOH

HSOHKγ

γγ −−

++=

][][][ 2

2+

+

−−

++

+ =CaOH

OHCaK

CaOH

OHCaCaOH γ

γγ

][][][

44

2424

4 −−

−−

++

− =HSO

SOHKHSO

SOHHSO γ

γγ

TotalSO

oaqSO

vapSO PYSO

K3

333

][φ

γ=

TotalSOH

oaqSOH

vapSOH PYSOH

K42

424242

][φ

γ=

TotalOH

OHOvapH PY

aK2

22 φ

=

22

2424

22)(22.4 ][][ OHSOCasOHCaSO aSOCaK −

−+

+= γγ

][][ 2424

22)(4

−−

++= SOCaK SOCasCaSO γγ

2222)(2)( ][][ −

−+

+= OHCaK OHCasOHCa γγ

This gives us 12 equations but we have 16 unknowns. This required 4 more equations.

Electroneutrality We now write an equation were we sum up the cations and anions.

[H+] + 2[Ca2+] + [CaOH+] = [OH-] + [HSO4-] + 2[SO4

2-]

This gives us one more equation for a total of 13, we still need thee more equations:


Hydrogen Balance We will sum up all the hydrogen in the equations. What comes in must go out. In reality, we have a choice of writing either a hydrogen balance or an oxygen balance. Either is acceptable but you should not write both.

2H2OIN + 4CaSO4.2H2OIN + 2Ca(OH)2IN + 2H2SO4IN

+ 2Ca(HSO4)2IN = 2H2O + 2H2SO4

o + H+ + OH- + CaOH+ + HSO4- + 2H2OVAP + 2H2SO4VAP + 4CaSO4.2H2O(s) + 2Ca(OH)2(s) This gives us one more equation for a total of 14. We need a total of 16, 2 more equations are required.

Calcium Balance We only have two other atoms left (besides oxygen). These are calcium and sulfur. First we will balance the total calcium. CaSO4IN + CaSO4.2H2OIN + Ca(OH)2IN + Ca(HSO4)2IN = CaSO4

o + Ca2+ + CaOH+ + CaSO4.2H2O(s) +CaSO4(s) + Ca(OH)2(s) This is one more equation for a total of 15. The sulfur equation is the final equation.

Sulfur Balance CaSO4IN + CaSO4.2H2OIN + SO3IN + H2SO4IN + Ca(HSO4)2IN =

SO3o + CaSO4

o + H2SO4o + HSO4- + SO4

2- + SO3VAP + H2SO4VAP + CaSO4.2H2O(s) + CaSO4(s)

This gives a total of 16 equations which match the total number of unknowns. The solution to these equations can now be computed.

Back to the precipitation point… To discuss the precipitation point calculation, we had to discuss the chemical model first. In a normal “Isothermal” calculation, the user provides the temperature, pressure and inflow amounts of the species. These equations above are then evaluated.

The precipitation point calculation is a bit different. In this, we hold the amount of a particular solid, in our case CaSO4•2H2O, at a specified amount. We then “Back Solve” our equations for an inflow amount that satisfies our specified amount.

Scaling Tendency To perform this back solving, we need to define a new concept, Scaling Tendency. Essentially, this is the ratio of ions in solution to the thermodynamic solubility product for a particular solid.


In our case, we are concerned about CaSO4•2H2O. The Scaling tendency for this solid is defined as:

)(22.4

22

2424

22

22.4][][

sOHCaSO

OHSOCaOHCaSO K

aSOCaST−

−+

+=γγ

When this value is less than 1.0, we can say that the solid is under-saturated. This means that there are insufficient ions in solution to form the solid. If the value is greater than 1.0, then the solid is super-saturated and there more than enough ions to form the solid.

In a standard “Isothermal” calculation, the program will adjust the ions such that any excess ions are combined into the solid and removed from solution. The scaling tendency becomes exactly equal to 1.0 at saturation.

In the precipitation point calculation, we force the scaling tendency for the indicated solid (CaSO4•2H2O) to be exactly equal to 1.0. To do this, we must adjust some variable.

The easiest variable to adjust is an inflow variable that contains some or all of our solid. There are two mass balance equations of interest here:

CaSO4IN + CaSO4.2H2OIN + Ca(OH)2IN + Ca(HSO4)2IN = CaSO4

o + Ca2+ + CaOH+ + CaSO4.2H2O(s) +CaSO4(s) + Ca(OH)2(s) CaSO4IN + CaSO4.2H2OIN + SO3IN + H2SO4IN + Ca(HSO4)2IN = SO3

o + CaSO4o + H2SO4

o + HSO4- + SO42- + SO3VAP + H2SO4VAP + CaSO4.2H2O(s) +

CaSO4(s) These equations are very similar. In the program, we selected the inflow species CaSO4 which has been bold-faced above. The other inflow values remain constant. We now allow the program to vary the inflow amount to match the scaling tendency of 1.0. As this occurs, the relative amounts of the other species are also calculated. In a precipitation point calculation it is important to make sure you select the proper precipitating solid (it must be able to form under the conditions you specify) and the proper adjusting species.

Back to the application… The application window should now look like this:


Figure 7-21 Read to go!


We would now like to see the solubility of CaSO4•2H2O as a function of temperature. When the program stops spinning the “Electron”…



Figure 7-22 Default plot

This is the default plot for this simulation. We would like to see a different plot showing the amount of calcium sulfate (CaSO4) that had to be adjusted to form the first tiny amount of solid. This to be displayed versus temperature.


Figure 7-23 the customize dialog

Double-click this item


We do not wish to see the Dominant Aqueous Species.

Double-Click the Dominant Aqueous Species in the right hand window to remove the entry.

Figure 7-24 Expanding the Inflows Tree

Click the “+” next to the Inflows item in the tree to expand the list.

Double-Click CaSO4 from the list.

Figure 7-25 CaSO4 Selected

Click OK

Click the “+” to expand the tree


Figure 7-26 The solubility of CaSO4 in water v. Temperature.

We now have a plot of the solubility of calcium sulfate in water as a function of temperature. We forced the program to consider the solid phase of gypsum (CaSO4•2H2O).

Adding sodium chloride What would happen if we added a new compound such as sodium chloride. It is been long suspected that adding sodium chloride increased the solubility of calcium sulfate in water but why?

To simulate this we are going to look at a single temperature (25 oC) and vary the concentration of sodium chloride. As we did with the temperature survey, we will allow the program to calculate the precipitation point for gypsum as we vary the amount of sodium chloride.

Figure 7-27 Clicking on the stream object

Click on the Stream1 object.


Figure 7-28 Selecting a new survey

Click on the Add Survey button.

The program updates the tree and grids for the new calculation.

Figure 7-29 Updated grid

The default calculation is for temperature. We will need to change the survey type.

Click the Survey By button.

Figure 7-30 Click the button that currently says "Temperature"


Figure 7-31 Select Composition

Select Composition.

As before, we need to change the specifications of this calculation. First we need to add a new component to the inflow grid.

Add NaCl to the inflow grid.

Figure 7-32 Adding NaCl

We also need to change the units.

Select Tools from the menu line.


Select Units Manager from the menu.

Figure 7-34 Select Units Manager

Add NaCl to the grid


Figure 7-35 The Units Manager Dialog

Click the Custom radio button.

Figure 7-36 Use the drop down arrow to find Mass Fraction.


The units are now in mass fraction. We now need to change the specifications for the calculation. We need to define the component we are going to vary (NaCl) and to specify the precipitation point calculation.


Figure 7-37 Select the specs... button

Click the Custom Radio Button


Figure 7-38 Changing specs...

Since we are adding sodium chloride…

Click on the NaCl object.

We now need to change the range of the survey.

Click on the Survey Range tab.

Figure 7-39 Composition survey range

We want the survey to start at 0 weight percent NaCl and finish at 15 weight percent.

Change the Start value to 0, the End value to 15 and the Increment to 1.0

Click on NaCl


Figure 7-40 The filled out start, end and increments.

We now need to specify a precipitation point calculation as we did before.

Figure 7-41Click on Calculation type

Click on Calculation Type in the tree-view.

This will bring up a dialog that is similar to the previous dialogs.

Figure 7-42 Default calculation type.

Click on the Type of Calculation button (it currently displays Isothermal).

Figure 7-43 Select Precipitation Point.

Select Precipitation Point.


Figure 7-44 Selecting inflows and solids.

This dialog is similar to the previous dialog of this type. The addition of sodium chloride had added additional options. We will continue with the same options as before.

Select CaSO4.2H2O from the left-hand window (Solid Precipitate) and CaSO4 from the right-hand window (Adjusted Inflow).

Figure 7-45 Selected options.

Click OK to continue.

Click the Calculate button to start.

When the calculation finishes, Click the Plot tab.



As before, we are going to change the plot to view the amount of CaSO4 added. This time the amount of NaCl has been varied.


We do not wish to see the Dominant Aqueous Species.

Double-Click the Dominant Aqueous Species in the right hand window to remove the entry.

Click the “+” next to the Inflows item in the tree to expand the list (You may have to scroll up or down to find Inflows).

Double-Click CaSO4 from the list.

Click OK


Figure 7-47 Solubility of CaSO4 v. NaCl

As you can see from the figure, the solubility of calcium sulfate (with CaSO4•2H2O as the precipitating solid) increases. Compare the solubility maximum of approximately 0.66 weight percent CaSO4 (at approximately 11 percent NaCl) to the value at 25 oC in the solubility v. Temperature plot in Figure 26 (approximately 0.21 weight percent).

Adding sodium chloride increases the solubility about approximately three times. The question remains, why does adding sodium chloride increase the solubility?

Let’s plot the various forms of aqueous sulfates versus NaCl.

Click on the Customize Button.

Remove CaSO4 from the Y-Axis window.

Scroll up or down in the Variables window to find the Aqueous item. Expand the tree if necessary.

Select the following variables.

CaSO4

H2SO4

HSO4-1

NaSO4-1

SO4-2

Click OK.


Figure 7-48 Sulfate Species

The aqueous sulfate species are displayed. The faint blue line is the concentration of NaSO4

-1 ion. It seems to follow the solubility curve for CaSO4.

We can see that a great deal of sulfate ion is complexed as NaSO4-1

.What does this imply?

We have two equilibrium equations that are affected:

CaSO4•2H2O = Ca2+ + SO42- + 2H2O

NaSO4-1 = Na+ + SO4

2-

As NaSO4-1

forms, sulfate ions are effectively removed from solution. That is to say the second equilibrium is shifted to the left. Since equilibrium must be maintained, the CaSO4•2H2O solid must increase its dissolution to replace the sulfate ion. This has the effect of increasing the solubility of the CaSO4•2H2O solid.

Save your work Now would be a good time to save your work.


Conclusion The solubility of one salt in a complex aqueous mixture can be significantly affected by the presence of other salts. Accurate modeling of these types of systems requires a robust activity coefficient model that includes the interactions of all species. When done properly, reliable simulation of complex processes provide a powerful tool for process optimization and reducing operating costs.

Figures 7-47 and 7-48 illustrate the significant effect that one salt has on the solubility of other salts in a complex aqueous mixture. Accurate modeling of these types of systems requires a robust activity coefficient model that includes the interactions of all species. The OLI software predictions are based on parameters that are regressed from reliable experimental data. In most cases, binary data is sufficient to accurately represent a systems (e.g., NaCl and H2O, or CaCl2 and H2O). In some cases, the regressions are performed on ternary systems (e.g., NaCl, CaCl2, and H2O). The OLI Databank contains the thermodynamic data and regressed parameters needed to reliably model aqueous systems over the range of –50 to 300 °C, 0 to 1500 bar, and ionic strength 0 to 30 molal.


Advanced Problems 1. Given a gypsum concentration of 5 weight percent and a sodium

chloride concentration of 10 weight percent at 1 atmosphere, what temperature would be required to evaporate 95 % of the solution?

2. What is the normal boiling point of the solution?

Raising your AQ IQ Chapter 8 H2S-CO2 Injection • 125

Chapter 8 H2S-CO2 Injection

Out of Sight – Out of Mind? • The behavior in subsurface environments (pH, mineral dissolution, scale

formation, and corrosion) can be reliably simulated based on surface samples.

• Water laboratory analyses need to be “adjusted” to account for normal laboratory error and down hole or process environments.

Production of natural gas frequently occurs from gas and oil fields that are particularly sour. This means that a large percentage of the gas that is produced contains hydrogen sulfide. There are some issues with hydrogen sulfide:

• H2S is a noxious compound and should be removed from natural gas.

• H2S causes corrosion and scaling problems in process equipment

• What to do with the removed H2S?

• No commercial market for H2S

• Cheap Disposal

A typical disposal method for hydrogen sulfide is to re-inject the gas back into a depleted reservoir. There could be some problems in re-injecting the gas. The produced water may have been altered such that re-injecting the brine back into the formation causes plugging of the reservoir. Other problems may involve increased corrosion behavior. We will investigate the potential for increased plugging.

In this application, we will take a water sample, measured at surface conditions, and reconcile it for changes in pH and electroneutrality. We will then simulate the sample at reservoir conditions. We will then add the gas containing hydrogen sulfide to the reservoir at various ratios to see if new solids (plugging) will occur.

Let’s get started ... We will be using a different OLI/Analyzer™ program. This program is the Lab Analyzer program. We begin by starting the OLI/LabAnalyzer Program. This may be accomplished by clicking the LabAnalyzer icon or by using the Start button and finding the LabAnalyzer under Programs/OLI Systems.

126 • Chapter 8 H2S-CO2 Injection Raising your AQ IQ

We will first start the LabAnalyzer™.

Locate the LabAnalyzer icon on your desktop or find it via the start button.

Figure 8-1 The OLI LabAnalyzer Icon for version 1.3



After a few moments, the main OLI/LabAnalyzer welcome screen will display.



This window is similar to the StreamAnalyzer window. We will not discuss the features here.




and has the name:

H2S-CO2 Injection.laa1

The following window should be displayed:



Figure 8-4 The loaded file

We have pre-loaded a water analysis and a stream for you. Many of the icons on the window are the same as in the StreamAnalyzer. However, there are two new icons.

Figure 8-5 Add a Water Analysis

This icon allows us to add a water analysis to the program. We will look at the analysis already loaded.

Figure 8-6 Adding a Composite analysis

This icon allows us to “Blend” analysis to make a single analysis. An analysis needs to exist before we can use this icon.


The produced water was measured at the surface. The conditions and concentrations are:

Temperature 25 oC

Pressure 1 Atmosphere

pH 6.4

density 1.158 g/mL

TDS2 223,000 ppm

Ca2+ 17,589 ppm HCO3- 340 ppm

Na+ 46,631ppm Cl- 110,442 ppm

K+ 2,700 ppm SO42- 1,470 ppm

Sr2+ 393 ppm

Mg2+ 2,045 ppm

Fe2+ 11.5 ppm

C12H26 283 ppm

Click on the WaterAnalysis1 icon in the explorer view:

Figure 8-7Clicking on WaterAnalysis1

This will display the current input state for the water analysis. We have purposely left out two cations in the analysis. Magnesium ion and ferrous ion. We will have to add these ions before continuing.

2 Total dissolved solids

Click on this icon


Figure 8-8 Incomplete input grid

Add the following concentrations to the Cations section of the grid

Mg+2 2045 ppm(mass)

Fe+2 11.5 ppm(mass)

Figure 8-9 Add ions

Figure 8-10 The ions have been added

Add the missing ions


Once the ions have been added, we now need to reconcile the sample for pH and electroneutrality.

Click the Add Reconciliation button.

Figure 8-11 Add a reconciliation

This will add a reconciliation to our sample.

Figure 8-12 The reconciliation window

You can see that the tree-view on the left has added a new object. This was automatically created when we clicked the Add Reconciliation button. The program will automatically reconcile our same for electroneutrality. This enforces our rule that the sum of positive charges must equal the sum of negative charges. We can also calculate the solution pH and determine if it matches our measured pH.

Before we go any further, we need to examine the different methods of reconciling the electroneutrality of the solution.


Reconciling Electroneutrality

Figure 8-13 The reconciliation box.

Click the Specs…button.

Clicking the Specs… button allows us to change how the sample is reconciled. There are many options.

Figure 8-14 Default reconciliation

This is the default electroneutrality balance. This method is known as Dominant Ion. In this case, the difference in cation and anion charges are determined. It is found that there is more positive charge than negative. The imbalance, on an equivalent basis, is 0.001431 equivalents/Kg.

To balance this, we need to add a negative species in the amount of –0.001431 eq/Kg. The Dominant Ion method takes the counter ion with the largest concentration and then adds the amount. In this case, 50.751 ppm of chloride ion is to be added.

Why Electroneutrality? Almost all water samples that are measured have small experimental errors associated with each ion. This is the nature of the experiment. For example, the concentration of the sodium ion may only be accurate to ± 5 % while the bicarbonate ion may only be accurate to ± 10 %. These uncertainties will usually result in the cation concentration not equaling the anion concentration. The OLI software requires that this equality be enforced. As an aside, any sample that balances perfectly is to be treated with suspicion. It just does not a happen in nature.


The determination of the amount of counter ion is as follows:

KgmgCl

gClmgCl

moleClgCl

eqmoleCl

Kgeq −

−

−

−

−−

=

751.501000453.351001431.0

We can now toggle trough the other reconciliation methods:

Figure 8-15 The type of balance button.

Click the Type of balance button.

Figure 8-16 Types of balance

Select each option to see how the reconciliation changes.

Prorate An equal percentage of all deficient species is added. In this case we are keeping the relative amounts of the anions constant (since we have too much positive charge). All the anions are then added.

Figure 8-17 Adding all anions

Prorate Cations Equal percentages of the cations are either added or subtracted to reconcile the sample.

Figure 8-18 Removing cations.

In this case, since there is too much positive charge, we are removing the cations.


Prorate Anions Equal percentages of the anions are either added or subtracted to reconcile the sample.

Figure 8-19 Adding anions

In this example, the Prorate Anions option is the same and Prorate.

Na+, Cl- Sodium is added when there is an excess of negative charge, chloride is added when there is an excess of positive charge.

Figure 8-20 Adding chloride

In this case, since there is too much positive charge, chloride is added. For this example, this is the same as the Dominant Ion method.

Make Up Ion The specified ion is either added or subtracted to balance the charge.


Figure 8-21 Selecting make-up ion for sodium

With the make-up ion option, either a cation or anion can be used to adjust the Electroneutrality. Since in this example, there is an excess of positive charge, selecting a cation will result in ions being removed. In this example, the sodium ion has been selected and 32.9 ppm has to be removed.

User Specification The user specifies the cation or anion required to balance the sample.


Figure 8-22 Selecting user choice

Since there is an excess of positive charge, only the anions are available for selection with this option. 68.8 ppm of SO4

2- is needed to balance the sample.

Make sure the Type of Balance button is set to Dominant Ion and the click the OK button.


The summary box updates with the electroneutrality

Figure 8-23 Updated electroneutrality

Back to the reconciliation We are now ready to reconcile our sample. The electroneutrality has already been done so now we need to adjust the pH. It is generally a good idea to see how close are prediction is to the measured pH.


After the calculation finishes, the summary box will update with new values.

Figure 8-24 Updated values


The pH of the sample is calculated to be 5.9 which is somewhat lower than the measured pH of 6.4. We will now add the pH reconciliation.

Figure 8-25 Selecting pH reconciliation

Check the Auto NaOH/HCl radio button in the Reconciliation box.

This will automatically use NaOH to raise the calculated pH or HCl to lower the calculated pH.

The input grid is now updated with a new section.

Figure 8-26 Calc Parameters now appears

We need to tell the program about the pH.

Figure 8-27 pH's entered

Click the Calculate button

Add a recorded pH of 6.4 and a target pH of 6.4


The summary window updates with the amount of acid or base added.

Figure 8-28 Updated information

Approximately 172.7 ppm mg/L of NaOH was added to raise the pH from 5.9 to the measured pH of 6.4

Converting an Analysis into a stream We are now ready to take our analysis and convert it into a stream. All streams in the OLI/Analyzers have inputs that are molecular. This means we can not support ions in a stream input grid. Only the LabAnalyzer supports ions as input.

Fortunately we have an automatic method of converting the ions in our reconciliation into a molecular stream.

Figure 8-29 Locating Add as Stream

Locate the Add as Stream button at the bottom of the reconciliation input grid.

Click this button.


Figure 8-30 The converted Analysis

The reconciled water analysis has been converted into a molecular stream. In our example, this has been created as Stream3. You can rename this stream to a more desirable name.

Figure 8-31 The new stream

Right-click the new stream “Stream3” and select Rename

Figure 8-32 the right-click menu


Figure 8-33 Highlighting the stream

The stream name will be highlighted which indicates that we can rename this tream.

Rename the stream to Produced Water.

Figure 8-34 The renamed stream

Simulations at reservoir conditions We now will simulate injecting just this produced water into the formation. The formation is at 160 oF and 2500 PSIA.

Select the Add Single Point button.

The input grid will be displayed. We have seen this type of grid many times before. The stream parameters are still the same as for the water analysis.

Figure 8-35 The stream parameters

We need to change the temperature and pressure.

Figure 8-36 Selecting units

Click in the Unit field for temperature and select oF.

Click in the Unit field for Pressure and select PSIA.


Figure 8-37 Correct units!

Enter a temperature of 160 oF and a pressure of 2500 PSIA

Figure 8-38 New temperature and pressures

Click the calculate button.

As with the Water Analysis, we can save the results of a calculation as a stream.

Figure 8-39 Locating Add as Stream

Locate the Add as Stream button at the bottom of the input grid.

Click this button.

Figure 8-40 Removing phases

As we save this calculation as a new stream, we will be given the option to remove phases. This could simulate a filtering operation. The filtered material could also be saved as a new stream.

We will not do any of these options at this time.



A new object has appeared in the Tree-View. It usually has the name of the parent object that created it (in this case a SinglePoint case) and a number to update the object so it does not overwrite another object.

This can be confusing. As before, rename the new object as Aquifer

Figure 8-41 The renamed object

Adding the waste gas We are now ready to inject the waste sour gas into the brine in the aquifer. To do this, we will you a mix calculation.

Figure 8-42 Select Streams

Select Streams from the menu items.

Figure 8-43 Select Add Mixed Stream

Select Add Mixed Stream


Figure 8-44 The mix stream input

From this window we can select several streams to mix. We wish to mix the Aquifer stream with the H2S/CO2 Gas stream.

Select the H2S/CO2 Gas steam and then click the >> button.

Select the Aquifer stream and then click the >> button.


Figure 8-45 The selected Stream

As you can see, the grid has updated with a considerable amount of information.

What we now need to determine is the ratios of the gas to the aquifer in which solids may form. The Mixed Streams calculation has this type of calculation.

Click the Type of Survey button.

Select Ratio

Figure 8-46 Ratio selected

We need tell the program which stream to adjust in the ratio. We also need to specify the ranges for the calculation.


Remember that we are simulating at reservoir conditions. Change the temperature and pressure to 160 oF and 2500 PSIA


Figure 8-47 The default range dialog

We want the H2S/CO2 Gas stream to vary over a wide range of flows.

Change the range from Linear to Log.

Change the Start value to 1.0E-06

Change the End value to 1.0

Change the Number of Steps to 10.

Figure 8-48 The completed ranges

We now need to tell the program what stream to vary.

Figure 8-49 Select General


Select the General object in the Category view.

Figure 8-50 Select the correct stream

Select the H2S/CO2 Gas stream.

Click OK.


Reviewing the results When the calculation has completed…

Click the Plot tab.


Figure 8-51 Default plotThis default plot is not very usable

Right-click on the plot and select Toggle X-axis Log.

Figure 8-52 X axis in log


We still need to see the solids.

Click the customize button.

Remove Dominant Aqueous by selecting it in the Y axis window and then clicking the << button.

Locate Dominant Solids under the Solids object in the Variables list. Select it and click the >> button.

Click OK.

Figure 8-53 Dominant solids

A faint line is present for FeS. This may be hard to see.


Select Variable Settings.


Figure 8-54 Variable Settings.

Select FeS – Sol

Select a more a color with more contrast.

Change the line style or line width if you desire.

Figure 8-55 FeS now shows up more clearly.


What does this all mean? The ratio at the left-hand side of the diagram represent conditions where the gas has not been injected into the reservoir. You can see that CaCO3, SrSO4 and CaSO4•2H2O are initially present in the reservoir.

Adding the gas, which is represented by higher ratio values, shows that we have a dissolution of CaCO3 which indicates that we may actually have an increase in porosity in the formation.

There is a slight increase in the amount of CaSO4•2H2O which may be due the increased presence of calcium ions as the CaCO3 solid dissolves. There appears to be little effect on SrSO4

A new solid appears as we add the gas. FeS begins to form in larger amounts. This material may plug the formation or remain suspended in the aquifer. This material may re-enter the production well and cause corrosion problems.

Save your file. Now would be a good time to save your work.

Conclusion The behavior in subsurface and other oilfield environments (pH, mineral dissolution, scale formation, and corrosion) can be reliably simulated based on surface samples. Water laboratory analyses need to be “adjusted” to account for normal laboratory error and down hole or process environments. The Analyzers perform like a desktop laboratory, readily performing simulations that may be difficult or impossible to perform in the field or laboratory.

The OLI calculations assume thermodynamic equilibrium. For some systems, kinetics may be important. For example, some solids, although thermodynamically predicted to form, are formed so slowly that the solid does not exist in the real world. The mineral dolomite is an example of a solid that may form slowly in the H2S injection Case. OLI software allows you to easily omit such solids form the calculation. OLI’s ESP aqueous flowsheet simulator can be used for cases where a process is to be modeled including the effects of kinetics,


Advanced Problems 1. Given a solution of 1 weight percent MgCl2 and 1 weight percent CaCl2

and 200 ppm CO2 determine the solubility of calcium carbonate.

2. Repeat the calculation with the GEOCHEM database.

3. Was the solubility in both cases the same? If not, why?

Raising your AQ IQ Chapter 9 Organic Acid Removal • 153

Chapter 9 Organic Acid Removal

When Henry’s Law Constants don’t really help you • The partitioning behavior of many chemicals is very dependent on pH.

• Simple methods such as the use of Henry’s law coefficients or other “distribution factor” approximation approaches do not work for real aqueous solutions. Effective separations for these systems can only be achieved when taking into account the complete speciation of the system.

Produced waters from oil and gas production frequently contain organic acids. These acids, which are undesirable in oils must be washed. Of course, these acids are also undesirable in the produced water that is to be discharged.

In this application we will take an oil/water mixture that has organic acids. The pH of the water indicates that the acids are in the water phase. This is a problem. We will adjust the solution pH to force the organic acids out of the water phase into the hydrocarbon phase.

Finally we need to remove the organic acids from the hydrocarbon phase. We will take the hydrocarbon and wash it with a high pH solution to remove the acids.



154 • Chapter 9 Organic Acid Removal Raising your AQ IQ







and has the name:


Organic Acid Removal.sta1

In this example we have preloaded several streams and calculations.

Figure 9-3 The Organic Acid removal example

Our example uses a stream named “Produced Oil”. This stream has the following composition:

Temperature 25 OC

Pressure 1.0 Atmospheres

H2O 55.508 mole

C12H26 (Dodecane) 5000 mole

HCOOH (Formic Acid) 0.1 mole

CH3COOH (Acetic Acid) 0.1 mole

CH3CH2COOH (Propanoic Acid) 0.1 mole

NaCl 0.5 mole 1 The file extension may not be displayed depending on your folder option settings.


CaCO3 0.1 mole

Mg(OH)2 0.02 mole

HCl 0 mole

NaOH 0 mole

The large quantity of organic (dodecane) simulates an “Oil” phase. This means we need to ensure that we are allowing the 2nd Liquid Phase to form.

Click on the Produced Oil object in the tree-view.

Figure 9-4 The loaded tree-view

This will display the input grid. We have already filled this out for you.

Figure 9-5 Input conditions

Click on “Produced Oil”


Figure 9-6 Chemistry menu item

Click on Chemistry


This will display the Chemistry model options.

Figure 9-7 Chemistry Menu

Select Model Options…

This will display the chemistry model options.

Figure 9-8 Chemistry Model Options

There are several tabs on this dialog. We can add databases and redox if necessary. We will not do that at this time.

Click on the Phases tab.


Figure 9-9 The phases tab


Solution pH Let’s find the solution pH. We have already added a single point calculation for you.

Figure 9-10 the tree-view

Select the SinglePoint1 calculation below the Produced Oil.

Click the Calculate button after selection.

After the calculation finishes, review the Summary box.

Make sure the Second Liquid check box is selected.

Why Select Phases? We can select and unselect entire phases in the chemistry model. Why would you want to do that? If you know you did not have an Second Liquid phase, you can exclude it from the calculations. This speeds up the calculations. By default, this option is unchecked. Also, you can remove specific solid phases. You may know that a particular solid can not form in the time frame of the simulation. Excluding the solid speeds the calculation.

Select SinglePoint1


Figure 9-11 Summary box

The pH is approximately 6.4. This is fairly “Neutral” pH.

How much of the organic acids are present in the aqueous phase at this pH?


Scroll down to the Molecular Output (Apparent Species) section.

Figure 9-12 Molecular Output

The Molecular Output section represents the species on a total molecular basis. You will notice that there are no ions present in this section of the report. This section has taken the true species and converted them to neutral species. The conversion is some what arbitrary but for each phase it is a quick view of the species.

In the aqueous phase, you can see that the organic acids and their ions are mostly tied up as complexes. Remember, there is approximately 0.1 moles of each acid. You can see that roughly ½ of the acids are still in the aqueous phase at this pH.


Washing the acids out of the aqueous phase. There are some rules for a species to enter the second liquid phase. These are:

1. The species must be neutral

2. The species must have a possible vapor species in the model

This means that if we can shift the form of the organic acid away from it’s ions towards the neutral form, it can dissolve into the second liquid.

Figure 9-13 Selecting the survey

Click Survey2

Figure 9-14 the survey

This survey has been set up for you . It is a pH survey from a pH=0 to a pH=14 range with 0.5 pH increments. The survey first determines the natural pH of the solution and then adds the acid titrant (in this case hydrochloric acid) and performs

Select Survey2


the first pH set point. This continues up to the natural pH. Above the natural pH the base titrant is added to the end of the range.

Click Calculate.

There should be 29 calculated point.


We have predefined the plot for you.

Figure 9-15 Plotting material balance groups v. pH

In this figure we are plotting the material balance groups (MBG) for the various acid forms as a function of pH.

For example, the variable MBG Aqueous ACETATEION is actually the sum of all acetate containing species in the aqueous phase. For example:

MBG Aqueous ACETATEION = C2H3O2-1 + C4H8O4 + Ca[C2H3O2]+1 + Ca[C2H3O2]2 +

Mg[C2H3O2]+1 + Mg[C2H3O2]2 +Na[C2H3O2]

This is true for the other material balance groups as well.

We can see that at high pH’s, greater than the natural pH of 6.4, that the dominant form of the acids are the aqueous ions. At lower pH’s, the dominant form are the acids dissolved into the organic liquid.


Figure 9-16 The same plot again.

It appears that if we lower the pH to 2.0, most of the organic acids will have been washed out of the aqueous liquid and are soluble in the organic liquid.

We can save a point from the survey as a single point. We have already done this for you.

We have taken the 5th point and saved it as a stream. This can be seen in the tree-view. We have also separated out the aqueous portion and the organic portion of the streams.

Figure 9-17 Saved streams

The aqueous brine can now be treated and disposed of an in appropriate manner.

Removing the organic acids from the 2nd liquid phase We can now wash the organic stream with a high pH solution to remove the acids from the hydrocarbon. A 1 molal sodium hydroxide solution has been created for you in this file. We will mix this stream with the organic stream containing the acids.

How much base do we need to remove the acids?

In this region, the dominant form of the acids are the aqueous ions. Most of the acid is in the water phase.

In this region, the dominant form of the acids are the acids dissolved in to the organic liquid.

Both of these streams were saved from the 5th data point. the first stream is the aqueous stream with any solids or vapors. The second stream is the 2nd liquid stream with only organic liquid.


Figure 9-18 Using the mixed stream

Click on the MixedStream5 object.

Figure 9-19 The input for the mix calculation.

We have a mix calculation that has selected the saved organic liquid point from the previous survey. This is indicated by the stream Point 5 of 29, pH = 2.0 2nd Liquid,3. The base stream has also been selected and is represented by the stream 1 m NaOH.

This case will add increasing amounts of the sodium hydroxide stream to the organic stream. We can then plot the various acids in each of the phases.



Figure 9-20 Washing with NaOH

It would appear from this plot, that most of the organic acids have been removed from the organic phases and are in the aqueous phase at a ratio of 0.3. This is a 0.3:1 ratio of the NaOH stream to the organic stream. There is approximately 1140 L of the organic stream and a total of 1.0 L of the sodium hydroxide stream. The ratio value of 0.3 indicates that only 0.3 L (300 mL) of the base solution was required to remove the acids from the organic liquid.

Save, save, and save again. Now it would be a good time to save your work.

Conclusion The partitioning behavior of many chemicals is very dependent on pH. Simple methods such as the use of Henry’s law coefficients or other “distribution factor” approximation approaches do not work for real aqueous solutions. Effective separations for these systems can only be achieved when taking into account the complete speciation of the system.

OLI software is useful for designing and evaluating separations systems involving aqueous electrolytes along with a second liquid phase such as oil or organic solvents. As such, OLI electrolytes technology is a useful complement to conventional simulation products that often do not accurately handle electrolytes. The Analyzer ratio “Mix” feature allows many simple processes to be simulated on your desktop. You can test an almost endless set of innovative options to deal with challenging process problems.


Advanced Problems Given a stream with the following conditions:

Temperature 75 oC

Pressure 200 Atmosphere

H2O 55.508 mole

CO2 1 mole

1. What would the temperature be if the pressure was reduced to 1 atmosphere?

Raising your AQ IQ Appendix A OLI Company Profile • 167

Appendix A OLI Company Profile

OLI Software Simulation Tools ... Providing Real World Answers

Do you have these problems? pH control Corrosion in process operations Scaling and fouling of towers, heat exchangers Oil and gas wells production slowdown Effluent discharge limits Regulatory and liability issues Water and offgas treatment

The wrong answer is worse than no answer at all OLI offers unsurpassed rigor in simulation for reactive phase equilibrium for aqueous electrolytes

OLI Clients have an edge on their competition

Corrosion Solutions Understanding the effect of the corrosion environment on rates of general and localized corrosion

Oil Field Solutions Understanding the behavior of scaling and brine

chemistry in production

Process Chemistry Solutions Understanding the behavior of complex aqueous

systems

• Predict the behavior of complex mixtures of chemicals in water

• Anticipate and diagnose problems and develop solutions for costly problems

• Optimize plant and lab operations and oilfield production

• Simulate and predict complex chemical and electrochemical phenomena in aqueous and mixed solvent environments

Meet OLI

OLI is a cutting edge chemical process technology and computer software company whose products and services save the worldwide Chemical Process Industry (CPI) and related industries millions of dollars every year. OLI's unique, powerful, and valuable software provides process, corrosion, and environmental chemistry solutions in the plant, in the lab, in the oilfield, and in the environment. Our software makes it easy for users to: Anticipate, diagnose, avoid and fix costly problems in chemical and petroleum operations while minimizing the time, cost, inaccuracy and risk of the lab, pilot or plant / field tests.

168 • Appendix A OLI Company Profile Raising your AQ IQ

Accurately predict the behavior of any mixture of chemicals in water and mixed solvents and simulate aqueous or mixed solvent processes and corrosion

Develop unique solutions and great cost savings for problems involving corrosion, oil and gas well plugging, and wastewater contamination and chemical processing plant operation and optimization

The result for you is:

o Saved engineering, lab and pilot plant time

o Lower cost engineered solutions

o Improved process operations

o Increased production

o Avoided problems

o Reduced risk

OLI software and technology is the standard for simulation of aqueous electrolyte systems. OLI has established an extensive CPI client base and reputation for excellence based upon our products and our technical support. We have served the CPI and related industry for 30 years, specializing in complex aqueous electrolyte systems. OLI products are now used by hundreds of process engineers, industrial chemists, chemical process technologists, researchers, corrosion specialists, and process design engineers within chemical manufacturing and engineering service companies, and public and private research organizations in over 35 countries on 6 continents worldwide, including nearly all of the world’s 30 largest chemical and petroleum companies. In about 1990, OLI “cracked the code” when it comes to rigorous prediction of the chemical reaction and phase behavior of complex mixtures of chemicals in water under modest to extreme conditions of temperature, pressure, and ionic strength. The combination of thermophysical properties models, solvers, and databank that enable this unique capability is known as the OLI Engine. Since 1990, OLI has built on this technology base a family of simulation technology and software products, with applications covering Chemical Processes, Rates of Corrosion, Oilfield Scale Prediction, Water Treatment, and Environmental Simulation. The OLI Engine is also available through all of the major process flowsheet simulators currently in use worldwide, including Aspen Plus, HYSYS, PROII, gPROMS, and IDEAS.

What Makes OLI Different? OLI has four passions that drive everything we do:

o The right chemistry o Advanced technology o Easy to learn and use interfaces o Expert service

OLI is proud to be a different kind of simulation company, dedicated to technology development and committed to customer service, tech support, and training. We believe that no matter what your process problem is, you start by getting the chemistry right. This relentless pursuit of accurate chemical simulation has allowed OLI to address problems that no one else can even attempt let alone succeed in solving. A case in point is the new Mixed Solvent Electrolyte (MSE) chemistry model that enables chemical process simulations that heretofore were not possible to accomplish. And we never stop looking for new applications and simulation technology to leverage this powerful chemistry capability.

Chemical Process Technology

OLI software can help you address a single stream, a single unit operation, a complete process flowsheet, or an environmental process. On the stream level, OLI’s StreamAnalyzer provides a virtual chemistry lab on your PC. With StreamAnalyzer you can predict reaction products, phase splits, and complete speciation of all phases for a complex mixture of chemicals in water. You can predict bubble and dew point, pH and pH adjustments, precipitation point, acid/base/chelant titrations curves, and temperature, pressure, and composition dependence of thermo-physical properties. With the LabAnalyzer, you can define a process stream on an ionic basis, evaluate the quality of and reconcile

Providing the CPI

Value Through Technology

for the Plant

the Laboratory

the Oilfield

the Environment

Innovative Chemical Process

SolutionsAdvanced Technology

Simulations Powerful User-Friendly

Software Expert

Service

Raising your AQ IQ Appendix A OLI Company Profile • 169

laboratory analyses, and then use these results in StreamAnalyzer or a process simulator such as ESP. At the process level, OLI’s ESP (steady state) and DynaChem (dynamic) are the only rigorous aqueous process simulators. ESP includes unit operations such as mixing, precipitator, pH adjustment, reactive separations towers (including mass transfer), bioreactor, solvent extraction, ion exchange, and membrane separations. The crystallization model under development will include prediction of crystal size distribution and include particle kinetics such as growth, nucleation, agglomeration, and attrition. OLI’s electrolyte technology is also available through all of the major process flowsheet simulators currently in use worldwide, including Aspen Plus, HYSYS, PROII, gPROMS, and IDEAS.

Corrosion Technology

OLI has developed the world’s first predictive rates of general corrosion and localized models. OLI’s corrosion technology allows corrosion engineers and specialists to understand the effect of the corrosion environment on the likelihood and extent of corrosion. Using this unique capability, users can:

o Anticipate the occurrence and extent of corrosion

o Locate corrosion “hot spots” for monitoring o Interpret the results of plant coupon and

monitoring data o Reduce corrosion laboratory time and expense o Conduct virtual experiments without risking the

lab and plant o Rapidly identify corrosion causes and

corrective actions o Simulate and predict the effects of process and

material changes o Optimize process conditions to minimize

corrosion damage The mechanistically-based model is made possible by refinements to the OLI Engine to include rigorous redox chemistry and predictive models for transport properties such as electrical conductivity, viscosity, and diffusivity. The corrosion rate prediction model is based first on an accurate thermodynamic view of corrosion, precisely defining the conditions of activation and passivation at the surface. Then by taking into account all of the partial electrochemical and transport processes in the bulk aqueous phase and in the boundary layer at the metal/fluid interface, as well as the presence or absence of passive films, the model calculates the ion transport and hence the corrosion rate at the surface. CorrosionAnalyzer allows the prediction of rates of general and localized corrosion as a function of pressure, temperature, composition, and flow

conditions. The software tool also provides real solution stability (Pourbaix) diagrams and theoretical polarization curves to aid the engineer and corrosion specialist in understanding the mechanism, causes, and possible fixes for the corrosion situation being studied. CorrosionAnalyzer is available now for a broad array of common chemical systems and for carbon and stainless steels, and nickel-based alloys. Under a research award from the US Department of Energy, OLI is expanding the applicable metallurgy and chemistry to include essentially all of the alloys and environments of industrial interest.

Oilfield Technology

OLI’s dedicated oilfield product is ScaleChem, the world’s premier mineral scale prediction tool. Designed by and for production chemists and engineers, ScaleChem uses OLI’s rigorous aqueous chemistry model to predict the formation of scale in the reservoir, well, and surface facilities. ScaleChem provides both the most accurate as well as the most versatile tool for scaling scenario analysis. Recent enhancements include adding in the oil phase and providing a facilities Wizard to determine downhole conditions based on surface samples.

OLI Engine - Aqueous Electrolytes and MORE

OLI Engine, the world’s first and only rigorous predictive aqueous model is based on the combined work of Helgeson, Pitzer, Zemaitis, Bromley, Meisner, and OLI scientists, and a comprehensive databank that has taken over 25 years to develop. The OLI Engine has now been expanded to include Mixed Solvent Electrolyte systems. This proprietary model, the first and only one of its kind, will allow a whole new dimension of chemical process simulation for industry. The new model, by combining the best aqueous and non-aqueous (i.e., UNIQUAC) models, provides for the comprehensive thermo-physical properties engine for systems that exist beyond the limits of the aqueous models. Most notably, these include very high ionic strength solutions, and solutions containing 2 electrolyte solvents (e.g., water and ethanol).

170 • Appendix A OLI Company Profile Raising your AQ IQ

Raising your AQ IQ Appendix B References • 171

Appendix B References

1. Anderko, A. and M.M. Lencka. 1997. Computation of electrical conductivity of multicomponent

aqueous systems in wide concentration and temperature ranges. Ind. Eng. Chem. Res., v36 p1932.

2. Anderko, A. and M.M. Lencka Modeling self-diffusion in multicomponent aqueous solutions in wide concentrations. Ind. Eng. Chem. Res., in press.

3. Anderko, A., S.J. Sanders, and R.D.Young. 1997. Real solution stability diagrams: A thermodynamic tool for corrosion modeling. Corrosion v53, p.43.

4. Bromley, L.A. 1973. Thermodynamic properties of strong electrolytes in aqueous solutions. AIChE J., v19 p313.

5. Lencka, M.M., A.Anderko, S.J. Sanders, and R.D. Young. Modeling viscosity of multicomponent electrolyte solutions. Int. J. Thermophysics, In press.

6. Meissner, H.P. and C.L. Kusik. 1973. Aqueous solutions of two or more strong electrolytes-vapor pressures and solubilities. IEC Proc. Des. Dev., v12, p205.

7. Meissner, H.P. and N.A. Peppas. 1973. Activity coefficients - aqueous solutions of polybasic acids and their salts. AIChE J., v19, p806.

8. Rafal, M, J.W. Berthold, N.C. Scrivner, and S.L. Grise. 1994. “Models for Electrolyte solutions”. in Models for thermodynamic and phase equilibria calculations, S.I. Sandler, ed. Marcel Dekker, Inc. New York.

9. Shock, E.L. and H.C. Helgeson. 1988. Calculation of the thermodynamic and transport properties of aqueous species at high pressure and temperatures: Correlation algorithms for ionic species and equation of state predictions to 5 kb and 1000 deg. C. Geo. et Cosmo. Acta, v52, p2009.

172 • Appendix B References Raising your AQ IQ

10. Shock, E.L. and H.C. Helgeson. 1990. Calculation of the thermodynamic and transport properties of aqueous species at high pressure and temperatures: Standard partial molal properties of organic species. Geo. et Cosmo. Acta, v54, p915.

11. Shock, E.L. H.C. Helgeson, and D.A. Sverjensky. 1989. Calculation of the thermodynamic and transport properties of aqueous species at high pressure and temperatures: Standard partial molal properties of inorganic neutral species. Geo. et Cosmo. Acta, v53, p2157.

12. Sverjensky, D.A. 1987. “Calculation of the thermodynamic properties of aqueous species and the solubilities of minerals in supercritical electrolyte solutions.” In: Reviews in Mineralogy v117, I.S.E. Carmichael and H.P. Eugster, Eds. Mineralogical Society of America, Washington, DC.

13. Sverjensky, D.A. and P.A. Molling. 1992. A linear free energy relationship for crystalline solids and aqueous ions. Nature, v356(19), p231.

14. Tanger, J.C. IV. 1986. Calculation of the standard partial molal thermodynamic properties of aqueous ions and electrolytes at high pressure and temperature. Ph.D. Dissertation, Univ. California at Berkeley.

15. Zemaitis, J.F, Jr., D.M. Clark, M. Rafal, and N.C. Scrivner. 1986. Handbook of aqueous electrolyte thermodynamics. AIChE. Washington, DC. 851 pages

Raising your AQ IQ Appendix C Product Description Sheets • 173

Appendix C Product Description Sheets

Overview This appendix contains product description sheet for the following products:

• ESP (Environmental Simulation Program™)

• CorrosionAnalyzer™

• StreamAnalyzer™ and LabAnalyzer™

• ScaleChem™

• Aspen™ OLI

174 • Appendix C Product Description Sheets Raising your AQ IQ


Environmental Simulation Program (ESP)

The Environmental Simulation Program (ESP) is a steady-state aqueous process simulator with a proven record in enhancing the productivity of engineers and scientists. With applications industry-wide, the software is not only applied to the environmental applications but to any aqueous chemical processes.

FEATURES

• Chemistry Model Where the chemistry for the system is defined

• Process Build Units are selected and streams are defined. Unit connections are made by naming the output stream of one operation as input to the next.

• Process Analysis Process is run

• Reports Stream and unit reports and export to MS Excel The conventional and environmental unit operations, and controllers, that are available include: Mix Precipitator Manipulate Electrodialysis Split Reactor Controller Saturator Separate Exchanger Feedfoward Dehydrator Neutralizer Extractor Crystallizer Membrane (UF,RO) Absorber Component Split Clarifier Bioreactor Stripper Incinerator Sensitivity Compressor

APPLICATIONS

• Design, debottlenecking, retrofitting, troubleshooting, and optimizing either existing or new processes • Waste water treatment • Upstream waste minimization • Regulatory limits • Simulation of Chlor-alkali plants, Claus plants • Separations with mass transfer and kinetics, including absorbers, strippers, and extractors, scrubbers • Gas treatment, Sour gas sweetening, amines • Reaction kinetics • Rigorous biotreatment, including heterotrophic and autotrophic biological degradation, multiple

substrates • Biotreatment processes, including sequential batch reactors and clarifiers with multiple recycle

FC

Emergency Chlorine Scrubber

Caustic25 oC

1 Atm

1000g/hr total

10 wt% NaOH

Waste Gas25oC

1 Atm

Cl2 5.8 mol/hr

CO2 52 mol/hr

N2 58 mol/hr

Overhead

Bottoms

3 Stages

25 oC

1 Atm


CAPABILITIES • Flowsheet simulation with

speciation

thousands of organics. Data service provides customized coverage of client chemistry in the form of private databanks.

• Comprehensive data bank Facility to allow the user to determine easily the sensitivity of output results to changes in the unit parameters and physical constants.

• Sensitivity Analysis Process flowsheet with multiple recycles and control loops are allowed. Feedfoward and feedback Controllers and Manipulate blocks help to achieve process specifications.

• Controllers Process flowsheet with multiple recycles and control loops are allowed. Feedfoward and feedback Controllers and Manipulate blocks help to achieve process specifications.

• Mixed Solvent Applications On an individual application for OLI consortium members, ESP is available for process using OLI’s mixed solvent electrolyte framework.

RELATED PRODUCTS With an ESP lease, these software packages are also included:

• DynaChem: The dynamic response of a process can be studied using the dynamic simulation program, DynaChem, to examine control strategy, potential upsets, scheduled waste, controller tuning, and startup/shutdown studies. Discrete dynamic simulation of processes with control can be accomplished. Studies of pH and compositional control, batch treatments interactions, multistage startup and shutdown, controller tuning, multicascade and adaptive control are all possible.

• Stream Analyzer/Lab Analyzer: The OLI Stream Analyzer and Lab Analyzer provide flexible stream

definition and easy single-case (e.g. bubble points) and parametric-case (e.g., pH sweep) calculations. These tools allow the user to investigate and understand the stream chemistry, as well as develop treatment ideas before embarking on process flowsheet simulation. The Analyzers also allow direct transfer of stream information to other simulation tools for parallel studies.


Corrosion Analyzer

OLI's Corrosion AnalyzerTM addresses the cause of corrosion by understanding the corrosion environment. This is in contrast to most corrosion treatments that address the symptoms by measuring corrosion rates, determining life expectancy and periodically replacing corroded material and equipment. Now with the Corrosion AnalyzerTM, you can investigate and determine the causes of corrosion before they happen, allowing preventive actions to be evaluated and implemented. This includes choosing correct operating conditions and corrosion resistant materials. OLI Clients save material, equipment, and time, in corrosion related costs.

FEATURES • Pourbaix Diagrams Graphical depiction of EH vs. pH for any mixture of chemicals in water is

available to evaluate stable and meta-stable corrosion and redox products. Real-solution chemistry is used, accounting for all activities, and assessing the effect of passivating species without any simplifying assumptions.

• Stablity Diagrams Flexible selection of independent variables and graphical depiction of local

and global equilibria in various projections are available. Depictions include EH vs. composition and composition vs. pH for any chemical mixture, including trace components, to assess stable and metastable species in real solutions.

• Yield Diagrams A graphical tool is provided for designing the synthesis of compounds (e.g.,

ceramics) with desired yield for virtually any chemical mixture, including trace components.

• Rates of Corrosion Titrations, plotting, and mix/separate phases for further calculations.

• Polarization Curves Calculations and display of polarization curves to support the rates

calculations. The polarization curves show the rate at which the reactions at the metal surface are proceeding. The sum of all the reactions results in the net current, or polarization curve.

• Potential for Pitting The corrosion potential is calculated and plotted against the repassivation

potential. In regions where the corrosion potential is larger than the pitting repassivation potential, localized corrosion will occur.

APPLICATIONS • Screening to focus lab and plan test • Materials selection • “Hot spots” for sensor locations • Useful remaining life • Process changes and corrections actions testing • Outage planning • Lab and plant screening sensitivity studies


• pH, composition, and temperature effects • Failure diagnosis and avoidance

CAPABILITIES • Automatic inclusion of Corrosion and

Redox chemistry

Elemental and alloy metal oxidation and the reduction reactions for 79 inorganic elements and thousands of species are available in the OLI Databank. The Corrosion Analyzer automatically generates the redox reactions and the resulting species and solves for equilibrium conditions using its predictive thermodynamic model.

• Kinetic Parameters of Corrosion Calibrated on literature and field data

• Electrical Conductivity and Oxidation-Reduction Potential (ORP)

Rigorous prediction of electrical conductivity and ORP for multicomponent systems is computed for aqueous solutions

• Real-Solution Calculations Non-ideal behavior modeled with activity coefficients for complex, high Based on the combined work of Bromley, Zemaitis, Meissner, Pitzer and OLI technologists.

RELATED PRODUCTS With a Corrosion Analyzer lease, these software packages are also included.

• Stream Analyzer Stream Analyzer provides a virtual desktop chemistry laboratory on your PC. Real systems are complex and concentrated. Stream Analyzer predicts the significant, non-intuitive departure from ideal solution behavior. Capabilities include complete phase equilibrium and speciation, along with accurate thermophysical properties (e.g. pH). Single point calculations, survey, and mix and separate operations are included.

• Lab Analyzer Lab Analyzer is companion software to the OLI Analyzers that enable you to evaluate the quality of laboratory data and then use the laboratory data (ionic composition) directly in your simulations. Used in conjunction with all of the other OLI software, the Lab Analyzer provides the “translator” from real laboratory analyses to molecular input.


Stream Analyzer and Lab Analyzer

Stream AnalyzerTM is simulation software which provides a virtual desktop chemistry laboratory on your PC. Real systems are complex and concentrated the Stream AnalyzerTM can predict the significant, non-intuitive departure from ideal solution behavior. The software produces complete phase equilibrium and speciation, along with accurate thermophysical properties (e.g., pH). The software calculates single point, multiple point, mix and separate operations, and accepts further calculations on the mixed stream. Lab AnalyzerTM is companion software to the OLI Analyzers that enables you to evaluate the quality of laboratory data, and then use the laboratory data (ionic composition) directly in your simulations. Used in conjunction with all of the other OLI software, the Lab AnalyzerTM provides the “translator” from real laboratory analyses and all other simulation.

FEATURES

• Flexible Stream Definition OLI’s public databank, ready to support searches for a component via formula and common synonyms, organics structure to help locate organics, Names Dictionary to custom tailor the names of components you display.

• Single Point Calculations Isothermal, adiabatic, bubble and dew points, set pH, precipitation point, composition targets, vapor fraction or amount equilibrium calculations

• Survey Calculations Temperature, pressure, composition, and pH surveys on any stream. Both a primary (one variable adjustment) and a covariant (two variable adjustment) are supported. Graphical reporting of the results.

• Mix and separate Titrations, plotting, and mix/separate phases for further calculations

• Import/Export Analyze a stream’s electrolyte behavior while still modeling a process in your flowsheet simulator of choice.


APPLICATIONS

• Four-phase flash • pH adjustment • Solids deposition • Waste water treatment • Upstream waste minimization • Meeting regulatory limits

• Laboratory water analysis, including reconciliations • Process chemistry sensitivity studies • Titration curves • Reagent screening and selection • Partitioning into second-liquid phase • Trace metal removal

CAPABILITIES

• Complete speciation

The OLI model predicts and considers all of the true species in solution in the range of –50 to 3000 C to 1500 bar, and 0 to 30 molal ionic strength.

• Robust standard state framework

Based on the Helgeson Equation-of-state, parameter regression and proprietary estimation techniques

• Activity coefficients for complex, high ionic strength systems

Based on the combined work of Bromley, Zeimaitis, Meisnner, Pitzer, and OLI technologists

• Comprehensive databanks

The Complete OLI Databank with 79 inorganic associated compounds andcomplexes, and thousands of organics. Data service provides customized coverage of client chemistry in the form of private databanks.

• Thermo physical properties

OLI has developed unique chemical/physical based models to compute thermodynamic and transport properties for complex aqueous mixtures.


ScaleChem

ScaleChem is simulation software for the assessment of scaling problems in oil and gas production. ScaleChem is synonymous with accurate olifield scaling prediction. OLI System’s expertise is in aqueous chemistry. ScaleChem calculates the phase separation and scaling tendencies of brines at the extreme, high T, P conditions characteristic of today’s well conditions.

The standard solids chemistry covered by ScaleChem includes analysis for these solids. Scaling tendencies for these solids are reported for every calculation request. anhydrite CaSO4 iron sulfide FeS barite BaSO4 halite NaCl calcite CaCO3 celestite SrSO4 gypsum CaSO4.2H2O dolomite CaMg(CO3)

2 siderite FeCO3

EXPANDED SOLIDS With ScaleChem is expanded chemistry, the solids analysis has been expanded to include all solids which are covered by the extensive OLI databanks. This allows solids analysis from the new cations and anions which have been added. Over 275 solids are available in the ScaleChem databank. Scaling tendencies for every solid with a scaling index > 1.0E-05 will be reported for a calculation request which uses expanded solids.

FEATURES • Well Profiles ScaleChem can be used to calculate scaling tendencies at user specified

temperatures and pressures. Detailed phase reports and solids formation is given at each point.

• Mixing Compatible Waters

Check the compatibility of different waters at user specified ratios, in order to find safe ratios (no solids formation) for injection and disposal operations.

• Saturation at Reservoir Conditions

Saturate a water with respect to one or more solids to simulate reservoir conditions.

• Facilities Calculations Simulate the filtering, mixing and separating of waters in post-processing operations.

• Downhole Wizard Determine downhole conditions by analyzing the surface sample


CAPABILITIES

• Complete speciation The OLI model predicts and considers all of the true species in solution in the range of -50 to 300o C, 0 to 1500 bar, and 0 to 30 molal ionic strength.

• Robust standard state framework

Based on the Helgeson Equation-of-state, parameter regression and proprietary estimation techniques

• Activity coefficients for complex, high ionic strength systems.

Based on the combined work of Bromley, Zeimaitis, Meisnner, Pitzer and OLI technologists

• Comprehensive databanks The Complete OLI databank with 79 inorganic associated compounds and complexes, and thousands of organics. Data service provides customized coverage of client chemistry in the form of private databanks.

• Thermo physical properties OLI has developed unique chemical /physical based models to compute thermodynamic and transport properties for complex aqueous mixtures.

SCALECHEM V3.1 Robust, stable, with these new features

• Hydrocarbon phase A for all calculations, defined in one of three ways as: Characteristic C1 - C20, Pseudocomponents, or Petroleum fractions. For petroleum fractions, ASTM D86, D1160, D2887 or TBP curves supported

• High-calcium brine predictions

Updated literature searches and updated data regressions

• Gas hydrate effects on brine chemistry

Methanol, ethanol and propylene glycol as components - These components used in gas hydrate treatment can have an effect on brine chemistry


HYSYS™ Electrolytes OLI (HEO)

HYSYS Electrolytes OLI (HEO) is a joint product by Aspen Tech OLI Systems. This product allows the OLI thermodynamic framework to be specified as property package within HYSYS. The complete OLI databank and the accuracy of OLI’s predictive electrolyte handling software produce accurate aqueous simulations when and where you need them, within your current flowsheet simulator.

FEATURES

• Electrolytes OLI Property Package

Built on OLI’s thermodynamic framework and available in HYSYS along with all other fluid packages.

• Electrolytes Component Database

Access to the complete OLI component databases in addition to Hyprotech’s traditional databases

• Electrolyte Properties Calculation and display of thermodynamic and transport properties specific to electrolyte systems such as pH, osmotic pressure, ionic strength and electrical conductivity.

• Unit Operations In addition to HYSYSTM range of unit operations, HEO has three additional electrolyte operations: Precipitator, Crystallizer, & Neutralizer.

• Electrolyte Column OLI's column solution method for solving electrolyte towers.

APPLICATIONS • pH control • Trace metal removal • Brine handling • Produced water management • Regulatory and environmental limits • Amines • Sour gas • Gas sweetening • Waste water treatment

• Chlor-alkali brines • Acid stream neutralization • Solids deposition • Organic acid removal in brines • Scrubbers • Caustic wash tower • Foul feed stripper • Multi-effect evaporator


CAPABILITIES HYSYS Electrolytes OLI is built on OLI’s time-proven approach to electrolyte systems.


• Robust standard state framework Based on the Helgeson Equation-of-state, parameter regression and proprietary estimation techniques




• Thermo physical properties

OLI has developed unique chemical /physical based models to compute thermodynamic and transport properties for complex aqueous mixtures.


Aspen OLI Aspen OLI is a joint product by Aspen Tech and OLI

Systems. This product allows the OLI thermodynamic framework to be specified as property package within Aspen Plus as well as other elements of the Aspen Engineering suite (AES). The complete OLI databank and the accuracy of OLI’s predictive electrolyte handling software produce accurate aqueous simulations when and where you need them, within your current flowsheet simulator.

FEATURES • Electrolytes OLI

Property Package Built on OLI’s thermodynamic framework and available in Aspen Plus and as an option to Properties Plus.

• Electrolytes Component Database

Access to the complete OLI component databases in addition to Properties Plus traditional databases.

• Electrolyte Properties

Calculation and display of thermodynamic and transport properties specific to electrolyte systems such as pH, osmotic pressure, ionic strength and electrical conductivity.

• Unit Operations In addition to any applicable Aspen Plus unit operations, Aspen OLI can be applied to two OLI user-added unit operations (4 Phase Flash and Tower).

• Chemistry Wizard To assist in component selection and chemistry model generation.

APPLICATIONS • pH control • Trace metal removal • Brine handling • Produced water

management • Amines • Sour gas • Regulatory and

environmental limits

• Crystallization • Gas sweetening • Chlor-alkali brines • Acid stream

neutralization • Solids deposition • Waste water

treatment

• Organic acid removal in brines

• Scrubbers • Caustic wash tower • Foul feed stripper • Multi-effect

evaporator


BENEFITS • Common Interface Use OLI’s electrolyte package without learning a new interface to another

software package

• OLI Electrolytes within Aspen flowsheets

Use electrolyte handling when working with water-based streams, with “out-of-the-box” water chemistry simulation with OLI’s complete databank

CAPABILITIES Aspen OLI is built on OLI’s time-proven approach to electrolyte systems.


• Robust standard state framework Based on the Helgeson Equation-of-state, parameter regression and proprietary estimation techniques




• Thermo physical properties OLI has developed unique chemical /physical based models to compute thermodynamic and transport properties for complex aqueous mixtures.

CONTACT US Aspen OLI is sold as a joint product between Aspentech and OLI Systems. To find out more, contact your Aspentech Agent, your OLI Agent, or OLI directly. Contact OLI PHONE

973.539.4996 x28 FAX 973.539.5922

ADDRESS OLI Systems, Inc. 108 American Road Morris Plains, NJ 07950

EMAIL [email protected] [email protected] [email protected] www.olisystems.com