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1 ChE 4185 Final Design Project: 1998 AIChE Design Competition Jacob Rendall & Kody Cobb 11/18/2016

1998 AIChE design competition

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Page 1: 1998 AIChE design competition

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ChE 4185 Final Design Project: 1998 AIChE Design Competition

Jacob Rendall & Kody Cobb 11/18/2016

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Table of Contents Executive Summary ...................................................................................................................... 6

Figure 1: Effect of Product Sale Price on ROR .................................................................................... 8

Introduction ................................................................................................................................... 8

Problem Statement ...................................................................................................................... 8

Figure 2: System Flow Schematic ........................................................................................................ 9

Figure 3: System Stream Requirements .............................................................................................. 10

Objectives .................................................................................................................................. 10

Analysis Tools ........................................................................................................................... 10

Discussion..................................................................................................................................... 10

Process Concepts ....................................................................................................................... 10

Figure 4: ANC/TOL X-Y Diagram ..................................................................................................... 11

Figure 5: TOL/XYL X-Y Diagram ..................................................................................................... 11

Process Overview ...................................................................................................................... 12

Figure 6: Initial Flowsheet .................................................................................................................. 12

Acetonitrile Column .................................................................................................................. 12

Figure 7: Effect of Pressure on ACN/TOL Seperation ....................................................................... 13

Figure 8: ACN Column Composition Profile ..................................................................................... 14

Figure 9: Tray vs Packed Column Design .......................................................................................... 15

Toluene Column ........................................................................................................................ 15

Figure 10: Effect of Pressure on TOL/XYL Separation ..................................................................... 16

Figure 11: Toluene Column Composition Profile ............................................................................... 16

Flash Drum ................................................................................................................................ 17

Mixer ......................................................................................................................................... 17

Heat Exchanger and Cooler Network ........................................................................................ 18

Table 1: Integrated Process Streams ................................................................................................... 18

Figure 12: Grand Composite Curve .................................................................................................... 19

Figure 13: Hot and Cold Composite Curves ....................................................................................... 20

Figure 14: Heat Content Diagram ....................................................................................................... 21

Figure 15: Final Heat Exchanger Path ................................................................................................ 22

Pumps ........................................................................................................................................ 22

Piping Design ............................................................................................................................ 23

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Process Description ..................................................................................................................... 23

Figure 16: Final Process Flowsheet .................................................................................................... 23

Equipment Summary.................................................................................................................. 25

Column Design .......................................................................................................................... 25

Figure 17: Structured Packing Selection ............................................................................................. 25

Table 2: Column Design Specifications .............................................................................................. 26

Table 3: Condenser and Reboiler Specifications ................................................................................ 27

Figure 18: Reflux Drum Sizing Chart ................................................................................................. 28

Table 4: Reflux Drum Specifications .................................................................................................. 28

Flash Drum Design.................................................................................................................... 29

Table 5: Flash Drum Specifications .................................................................................................... 29

Mixer Design ............................................................................................................................. 30

Table 6: Mixer Specifications ............................................................................................................. 30

Heat Exchanger and Cooler Network Design ........................................................................... 30

Table 7: Heat Exchanger Specifications ............................................................................................. 31

Table 8: Cooler Specifications ............................................................................................................ 32

Storage Tank Design ................................................................................................................. 32

Table 9: Storage Tank Specifications ................................................................................................. 33

Pump Design ............................................................................................................................. 33

Table 10: Process Pump Specification ................................................................................................ 33

Figure 19: Vacuum Pump Sizing ........................................................................................................ 34

Table 11: Vacuum Pump Specification .............................................................................................. 34

Piping Design ............................................................................................................................ 35

Figure 20: Piping Specifications ......................................................................................................... 35

Utility Summary ........................................................................................................................ 35

Table 12: Utility Costs ........................................................................................................................ 36

Table 13: Annual Utility Usage .......................................................................................................... 36

Table 14: Annual MEK Material Costs .............................................................................................. 37

Table 15: MEK Chiller Justification ................................................................................................... 38

Process Flow Diagram (PFD) ..................................................................................................... 38

Figure 21: Control Loop Hardware ..................................................................................................... 38

Figure 22: Piping and Instrumentation Diagram ................................................................................. 39

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Mass and Energy Balances ......................................................................................................... 40

Table 16: Process Stream Tables ........................................................................................................ 40

Safety, Environmental and Health Issues ................................................................................. 47

Pressure and Vessel Analysis .................................................................................................... 47

Table 17: MAWP ................................................................................................................................ 48

Table 18: MAWT ................................................................................................................................ 49

Fire Protection ........................................................................................................................... 49

Health Considerations ............................................................................................................... 50

Spill Containment ...................................................................................................................... 50

Inherently Safer Checklist ......................................................................................................... 50

HAZOP...................................................................................................................................... 53

Potential Concerns..................................................................................................................... 53

Figure 23: Example Risk Matrix ......................................................................................................... 54

Figure 24: HAZOP Case Summary .................................................................................................... 55

Figure 24a: HAZOP for ACNCOL ..................................................................................................... 56

Figure 24b: HAZOP for TOLCOL ..................................................................................................... 57

Figure 24f: HAZOP for Heat Exchanger Network ............................................................................. 60

Figure 24g: HAZOP for Pipes ............................................................................................................ 61

Figure 24h: HAZOP for Pumps .......................................................................................................... 61

Figure 24j: HAZOP for Makeup ......................................................................................................... 63

FMEA ........................................................................................................................................ 63

Figure 25: FMEA severity ranking ..................................................................................................... 63

Figure 26: FMEA occurrence ranking ................................................................................................ 64

Figure 27: FMEA detection ranking ................................................................................................... 64

Figure 24: FMEA ................................................................................................................................ 68

Process Economics ...................................................................................................................... 68

Table 19: Process Equipment Costs .................................................................................................... 69

Table 21: Additional Cost Allowances ............................................................................................... 70

Table 21: Total Capital Investment ..................................................................................................... 71

Table 22: Xylene Purchase Cost ......................................................................................................... 71

Table 23: Waste Disposal Cost ........................................................................................................... 72

Table 24: Labor Costs ......................................................................................................................... 72

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Table 25: Operating Costs................................................................................................................... 72

Table 26: Annual Revenue .................................................................................................................. 73

Table 27: Annual Depreciation Allowance ......................................................................................... 73

Table 28: Cash-Flow for Solvent Recovery System ........................................................................... 74

Improvement Recommendations ............................................................................................... 74

Acknowledgments ....................................................................................................................... 75

References .................................................................................................................................... 77

Appendix ...................................................................................................................................... 78

Heat Exchanger Network .......................................................................................................... 78

Piping Design ............................................................................................................................ 79

Vacuum Pump Sizing ................................................................................................................ 83

Flash Drum Sizing ..................................................................................................................... 84

Mixer Sizing .............................................................................................................................. 85

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Executive Summary

In this report, we summarize our design for a solvent recovery system. We process waste streams

from our siloxane process into reusable acetonitrile and toluene streams. Our design reduces the

amount of raw materials we need to buy and the amount of waste we produce.

We investigate several different options for separating pure acetonitrile and toluene from a

system containing acetonitrile, toluene, xylene, and siloxane. We create a safe design with three

separation units that complete the required separations. We use two distillation columns and a

flash tank. We break an azeotrope between acetonitrile and toluene in the first column by

operating at a vacuum and by adding xylene as an extractive agent. We cool all product and

waste streams below flash points in order to operate safely.

We optimize each aspect of the design to minimize costs. We analyze operating pressure, feed

location, and reflux ratio on each column. We use pinch analysis to integrate our heat streams in

order to reduce utility cost, and use utilities only where necessary. We reduce our Xylene feed to

the process to an optimum point where the separation occurs without incurring excess material

costs.

We complete an in depth safety analysis in this report to ensure safe operations. We complete a

HAZOP in Figure 24 and a FMEA in Figure 27. We also provide safety recommendations

regarding fire and chemical safety.

We recommend the purchase of two packed distillation columns with reflux drums, reboilers and

condensers, one flash drum, five heat exchangers, four coolers, a mixer, a chiller, and a tank farm

in order to recycle the solvent coming out of the process. We size and summarize the equipment

specifications in the Equipment Summary section. We provide a list of process equipment costs

in Table 19 in the Process Economics section.

We need plant cooling water, electricity, low-pressure steam, and high-pressure steam to

complete this process. We purchase an MEK chiller and recovery system in order to provide

further utilities to the solvent recovery process.

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We provide a detailed process economic evaluation on associated costs, revenue, and cash flow.

We recommend a SOYD depreciation scheme and calculate the economic benefit of

implementing this solvent recovery system. Table 28 shows our cash flow analysis.

We attain our process information using Aspen Plus v9.0. We create a detailed process flowsheet

and use the simulation engine to calculate mass and energy information about our process. We

leverage the software to provide accurate sizing on all of our equipment. We use EconExpert

(http://www.ulrichvasudesign.com/econ.html) to estimate purchase costs for all of our

equipment. We use a price index of 544 based on prices in August 2016.

The solvent recovery system recovers acetonitrile at a rate of 158.2 kg/hr and toluene at a rate of

362.8 kg/hr. These numbers correspond to annual recovery rates of 1265600 kg/ year of

acetonitrile and 2902697 kg/ year of toluene. We show all process stream flows in our mass

balance in Table 16.

We estimate that the implementation of this solvent recovery system will yield a rate of return of

102.9 %. The process requires a $4.6 million total capital investment and $2.2 million annual

product costs but generates $9.7 million in annual revenue. The solvent recovery system will pay

itself back within the first year, and generate almost $90 million dollars of profit through its 20-

year life span. We highly encourage the purchase of this system.

We find that the system is a good investment regardless of material price fluctuation. We see the

effect of material sale price on our rate of return in Figure 1:

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Figure 1: Effect of Product Sale Price on ROR

We see that even when the products approach low sale prices we still achieve greater than 10%

ROR. We recommend that you purchase, install, and operate this system as soon as possible. We

do not include a specific timeline but recommend an aggressive one in order to realize cost

savings as soon as possible.

Introduction

Problem Statement

We complete the task of designing a solvent recovery system. The system contains acetonitrile,

toluene, xylene, and siloxane. Feeds A, B and C enter the solvent recovery system. Feed stream

A has a flow rate of 270 kg/hr consisting of 98.5% toluene and 1.5% siloxane. Feed B has a flow

rate of 60 kg/hr consisting of 96.5% toluene, 2% acetonitrile, and 1.5% siloxane. Feed C has a

flow rate of 200 kg/hr consisting of 19.5% toluene, 78.5% acetonitrile, and 2% siloxane. These

feeds produce two recycle streams and one waste stream. Figure 2 shows the feed streams

entering the solvent recovery system from the process:

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Figure 2: System Flow Schematic

Figure 2 also shows the recycle streams flowing from the solvent recovery process. One recycle

stream has a flow rate of 158.2 kg/hr and an acetonitrile composition of 99.87%. Another

recycle stream has a flow rate of 362.84 kg/hr and a toluene composition of 99.92%. The waste

stream purges the system of siloxane. The waste stream flows at 36.11 kg/hr and consists of

about 75% xylene and 25% siloxane. The waste stream has these compositions to avoid siloxane

precipitation in the system, which occurs at concentrations above 25%. A final make-up feed

adds xylene back into the system. Figure 3 summarizes the flow requirements:

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Figure 3: System Stream Requirements

Objectives

These objectives are the drivers for this project and process optimization.

Maximize solvent recovery and cost savings.

Minimize capital requirements.

Minimize utility usage and variable costs.

Minimize process waste and remediation related costs.

Facilitate a safe operating environment.

We focus on these objectives while completing this project. The basis of all objectives lie in

either economics or safety, so in addition to an extensive design section, we also provide

economic and safety evaluations.

Analysis Tools

We design and analyze this process primarily with Aspen Plus v9.0. This software leverages a

powerful simulation engine to carry out many complex calculations. We model the physical

properties of all the relevant components except for siloxane using Aspen Plus databases. We

receive the physical properties of siloxane from Dr. Liu and manually input them into Aspen

Plus. We use the NRTL-RK thermodynamic equation of state to perform thermodynamic

analysis.

We design the necessary equipment using Aspen Plus, engineering heuristics, several

professional sources, and common sense. We acquire pricing information from EconExpert’s

online database. We use a cost index to extrapolate pricing information from years past.

Discussion

Process Concepts

We face the challenge of overcoming an azeotrope between acetonitrile and toluene in this

system. We investigate how pressure affects this azeotrope in Figure 4:

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Figure 4: ANC/TOL X-Y Diagram

As we lower the pressure in the column, the azeotrope moves further to the right and we can

obtain a higher mole fraction of acetonitrile. We operate at 0.1 bar in our first column, and use

xylene as an extractive agent to fully break the azeotrope and reach the acetonitrile purity

specification.

We separate toluene and xylene in a second column. We investigate the effect of pressure on this

separation in Figure 5:

Figure 5: TOL/XYL X-Y Diagram

We operate the toluene column at atmospheric pressure. We do not gain a large enough benefit

from changing the pressure so we stay at ambient conditions.

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We complete our final separation between xylene and siloxane with a flash tank. We use a flash

tank instead of a column because it is much cheaper and can complete the required separation.

We operate the flash drum in a manner so that the weight percent of siloxane in the liquid bottom

stream does not go over 25%. At concentrations above 25% siloxane precipitates out of the

solution and causes process problems.

Process Overview

We propose using a process with three separation units, an extractive vacuum column, an

ordinary distillation column, and a flash tank. The first column separates acetonitrile from the

system at the required rate. The second column separates Toluene from the system. The flash

tank separates Xylene from a waste stream. We utilize coolers to cool product and waste streams

to safe temperatures (below their flash points). Figure 6 shows our initial basic flowsheet:

Figure 6: Initial Flowsheet

This flowsheet meets all process requirements and is the basis of our final design. We optimize

the initial design by applying engineering heuristics. We manipulate feed locations, reflux ratios,

and heat paths to meet our project objectives.

Acetonitrile Column

The two columns make up the bulk of the design and capital investment. Therefore, we take

careful considerations while we design them. We first consider how to address a boiling point

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azeotrope between acetonitrile and toluene. We separate acetonitrile from the other components

using vacuum extractive distillation, with xylene being the extractive agent. The vacuum requires

more input cost, but provides necessary benefit. Using Aspen Plus binary component analysis,

we find that switching the operating pressure from 1 bar to 0.1 bars moves the azeotrope from

82% pure acetonitrile to 87% acetonitrile. This 5% difference lowers the temperature profile of

the column from 80-110oC to 20-45oC and reduces steam consumption. Figure 7 shows the effect

of pressure on the separation of acetonitrile and toluene:

Figure 7: Effect of Pressure on ACN/TOL Seperation

Further analysis shows that the separation of acetonitrile at 99.87% is impossible without

operating at a vacuum. The addition of xylene eliminates the azeotrope from our range of

operation, and allows us to reach the desired specification.

We decide the feed locations of the fist column based on the composition profile inside the

column, and ease of separation within that profile. We use Aspen Plus to analyze the

composition profile of multiple scenarios. Figure 8 shows the composition profile of the final

design:

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Figure 8: ACN Column Composition Profile

We utilize the height of the column as efficiently as possible by placing the B and C feed

locations toward the bottom (stage 25). We use the top of the column to achieve the final 2%

separation between acetonitrile and toluene. Figure 6 shows the clear effect that xylene has on

the equilibrium between acetonitrile and toluene. We add xylene at stage 10 and there is an

immediate jump in the acetonitrile liquid composition, and a small jump in the vapor

composition.

We adjust the reflux ratio in the column until we achieve the required distillate composition of

acetonitrile in the distillate. The simulation then meets the specified distillate rate by adjusting

the reboiler duty. Our final design uses 28 theoretical stages, a mass reflux ratio of 2.8, and a

distillate rate of 158.2 kg/hr.

We decide to use a packed column instead of a tray column because the flow rates through the

column are relatively low in this system. This causes the diameter of the acetonitrile column to

be small (0.62 meters). We show the difference between a tray and packed column in Figure 9:

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Figure 9: Tray vs Packed Column Design

The packed column has fixed structured packing inside instead of weir trays. The packing

influences the flow profile inside the column and maximizes vapor liquid interactions. Packed

columns are favored in columns with small diameters. Our final acetonitrile column is a 5.98

meter packed column with 5.2 meters of Sulzer MellaPak 750Y structured packing having an

HETP of 0.2 meters, and a partial reboiler. This is the equivalent of 28 theoretical stages.

Toluene Column

The second column separates toluene from xylene and siloxane. We carry this separation out at

atmospheric conditions using ordinary distillation. This column operates at atmospheric pressure

to avoid costly pressure manipulation systems. The temperature gradient within the column is

110oC to 145oC, which we manage using plant utility streams. Figure 10 shows the effects of

pressure on the toluene/xylene separation:

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Figure 10: Effect of Pressure on TOL/XYL Separation

Figure 7 confirms that there is no advantage to operating at non-ambient pressures. We choose

feed locations to best utilize the height of the column. We choose feed locations of 3 and 16 for

the A feed and the feed from the bottom of the first column respectively. These feed locations

give a broad composition profile. Figure 11 shows the composition profile of the toluene

column:

Figure 11: Toluene Column Composition Profile

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We utilize the top of the toluene column to achieve the final few percent of the separation much

like the acetonitrile column. Feed A comes in towards the top of the column and acts as internal

reflux, which minimizes the reflux ratio. We use 23 stages, a reflux ratio of 2.3, and a distillate

rate of 362.8 kg/hr in our final column design.

We decide to use a packed column for the internals of the toluene column because of the column

size (0.45 meter diameter). Our final toluene column is a 4.83 meter packed column with 4.2

meters of Sulzer MellaPak 750Y structured packing having an HETP of 0.2 meters, and a partial

reboiler. This is the equivalent of 23 theoretical stages.

Flash Drum

We utilize a flash block as a low cost option to separate the bottom feed of the second distillation

column into two streams. The liquid waste stream purges the system of siloxane. The stream

leaves the flash tank at siloxane’s solubility limit, 25 wt%. We prevent siloxane precipitation and

potential safety issues by implementing this purge. This stream classifies as Option B waste, and

costs 1.5 $/kg to process.

We recycle the vapor xylene coming off the top of the flash tank. We condense the vapor and

then feed it to a mixer with fresh xylene, and eventually back into the first column. The flash

block meets the 25% siloxane concentration requirement using operating conditions of 140.5oC

and 1 atm. We control the flash tank temperature using a jacket.

Mixer

We use a mixer to mix the condensed recycled xylene with a fresh make up xylene stream. We

choose a makeup flow rate to restore the pure xylene flowrate to 100 kg/hr. We assume that the

xylene make up stream is at ambient conditions. We choose a holding time of 5 minutes to

ensure the makeup stream and recycle stream reach composition and temperature equilibrium.

We use the xylene feed leaving the mixture as the xylene feed to the first distillation column.

This xylene acts as the essential extractive agent.

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Heat Exchanger and Cooler Network

We implement the biggest changes from our initial process flowsheet to our final flowsheet by

integrating our heat streams. We do this through Pinch analysis. We first identify all of our

process streams that need heating or cooling, and designate target temperatures for each stream.

We identify our feed streams as potential cold streams if we preheat them. In order to optimize

our preheat temperature designation we look at our column temperature profiles. We have a

temperature profile of 21oC – 54oC in our fist column so we decide not to preheat feeds B and C.

The second column has a temperature distribution of 110oC to 138oC, but we use the A feed

stream as internal reflux so we only preheat it to 84oC. We include the condensation of the

xylene recycle stream, by including the latent heat of condensation in its heat capacity flow.

Table 1 shows the streams we integrate and their relevant properties:

Table 1: Integrated Process Streams

We use Pinch analysis and a 5oC minimum temperature approach to analyze the heat flow

through the system and to determine the minimum duty required from utilities. We find a Pinch

temperature of 137.9oC indicating that below this temperature, we need only cooling, and above

the pinch temperature we need only heating. Our process operates below the pinch temperature

so we only need cooling. We calculate a minimum cooling duty of 20.81 kW. We create a grand

composite curve in Figure 12 to visualize the heat flow through the system:

Hot Streams Cp, J/kg*K m, kg/hr mCp, W/C Temp Change, K Duty Req, kW Temp In Temp Out

ACNProd 2018.97 158.2 88.72 16 1.42 21.4 5.4

TOLProd 1820.95 362.84 183.53 105.6 19.38 110 4.3

Waste 1447.24 36.11 14.52 115.5 1.68 140.4 27.1

XYLRec --- 72.55 2986.96 2.30 6.87 140.4 138.10

Cold Streams Cp, J/kg*K m, kg/hr mCp, W/C Temp Change, K Duty Req, kW Temp In Temp Out

Feed A 1659 270 132.76 64 8.55 20 84

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Figure 12: Grand Composite Curve

We see that the process does not extend past the pinch temperature and only requires cooling.

We also verify that this minimum cooling requirement is 21.81 kW. We conduct further analysis

and graph the hot and cold composites in Figure 13:

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Figure 13: Hot and Cold Composite Curves

We see again that the process requires no heating, and only 21.81 kW of cooling. We calculate a

minimum number of exchangers of 5 based on 4 hot streams, 1 cold streams, and 1 cooling

utility requirement. We use the minimum 5 exchangers, broken down into 2 heat exchangers and

3 coolers. We designate our exchangers in Figure 14 using a heat content diagram:

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Figure 14: Heat Content Diagram

We designate the heat exchangers based on the heuristic of matching heat blocks on the top of

the hot side with heat blocks on the top of the cold side. We summarize our final heat exchanger

network in Figure 15:

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Figure 15: Final Heat Exchanger Path

We use this heat exchanger path to meet the required temperatures summarized in Table 1. All

coolers cooling process streams below 45oC use MEK as a coolant, otherwise they use cooling

water. This ensures a minimum temperature approach of 10oC for all utility streams.

We save $2,672 annually through heat integration. Through the 20-year life span of the project,

we save $53,440 because of our heat integration. We also reduce the number of exchangers

necessary by one.

Pumps

We use three pumps in our final process to change process pressures. We need a pump on each

of the two outlet streams coming off the first column. The first pump is on the bottoms stream

and brings the pressure up to 1 bar before the bottoms stream enters the second column. The

second pump pressurizes the distillate flow to 1 bar before it arrives at the product storage tank.

We need a vacuum pump on the outlet of the condenser in the first column to control operating

pressure. In addition to the three process pumps, we use 7 pumps to move process material from

one unit operation to the next. We also buy back up pumps for all pump applications to avoid

shutting down operations in the event of a pump failure.

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Piping Design

We use a design heuristic1 to calculate what schedule piping to use, assuming room temperature

operation. We use the largest flow rate that flows in the piping and assume properties similar to

water. We use 316 SS Schedule 5S 3” diameter. We show calculations below:

Largest flowrate = 31.03 𝑚3

ℎ𝑟= 136.6 𝑔𝑝𝑚

Assume water velocity of 5𝑓𝑡

𝑠

V = 0.408𝑄

𝐷2

D = 3.3 in

44 ksi max stress

Schedule = 1000 𝑃

𝑆= 1000 (

14.7

44000) = 0.3 → Schedule 5S

Process Description

We make changes from our initial process flowsheet to increase cost savings, safety, and overall

ease of operating. Figure 16 shows our final process flowsheet:

Figure 16: Final Process Flowsheet

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The major change we made from the initial flowsheet is heat integration. This makes the flow

sheet harder to follow but results in cost savings in relation to utilities. We use E1 and E2 to

exchange heat between feed stream A which needs heating, and product streams that need

cooling. We also use three coolers, C1, C2, and C3 to provide additional cooling to the process

streams. We operate at the minimum cooling duty found in our pinch analysis.

The ACNCOL distillation column separates acetonitrile from other components. PUMP2

pressurizes the distillate stream to 1 bar before it is cooled by MEK in C1 and leaves the process.

PUMP1 pressurizes the bottoms stream from the first column to atmospheric pressure. The

bottoms stream then enters the second column. We use MEK in our ACNCOL condenser and

low pressure steam in our reboiler.

The TOLCOL distillation column separates toluene from xylene and siloxane. The TOL product

stream flows through coolers C2, and C3 until it reaches a temperature below toluene’s

flashpoint. C2 cools the toluene product to 45oC using cooling water. C3 cools the toluene

product to 4.3oC with MEK. The bottoms stream is a mixture of xylene and siloxane. This stream

flows to a flash drum, FLASH for further separation. We use cooling water in our TOLCOL

condenser and high-pressure steam in the reboiler.

The separation of xylene and siloxane does not require a third distillation column. The relative

volatilities between components is great enough so that we complete the separation with a flash

drum. The liquid stream, WASTE1, flows from the flash drum just below 25% siloxane.

WASTE1 flows through E1 and leaves the process at 27oC, which is below the flash point of

xylene.

XYLVAP leaves the flash drum as a vapor and condenses in E2. From this cooler, XYLMID

flows into the mixer, MIX and combines with makeup xylene. XYLREC flows from the mixer to

the first distillation block and completes the internal recycle stream. We reduce the amount of

xylene recycle from 200 kg/hr to 100 kg/hr. This results in equipment, material, and utility cost

savings while maintaining the required separation.

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Equipment Summary

Column Design

We size our column diameters based on the vapor flowrates in the column, and the height based

on the required number of stages to complete the separation. We sized the diameters so that no

section would experience greater than 80% flooding. We use the tower heuristic in table 9-13

from the heuristic handout that suggests structured packing with diameters less than 0.9m.

We pack both columns with stainless steel Sulzer Mellapak 750Y structured packing. This

packing performs well at various temperatures and pressures, which works well with both

columns. We choose MellaPak 750Y because it has a low and constant HETP (0.2 m) at our

ranges of operation. We show this in Figure 17:

Figure 17: Structured Packing Selection

We design the columns using these packings specifications and the operating conditions from the

discussion section. Table 2 shows the final column designs:

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Table 2: Column Design Specifications

We run the columns so that we achieve product concentrations slightly greater than necessary to

avoid for any variation in the feed streams or unforeseen problems. We calculate a total height

for each column by multiplying the height of packing by a factor of 1.15. We use stainless steel

in the construction of each column and in the packing to avoid process side corrosion.

We use a total condenser and partial reboiler in both of our columns. Both condensers are shell

and tube heat exchangers with the process tube side and the coolant shell side. The tubes are

316SS and the shells carbon steel. We use partial kettle reboilers. The reboiler on the first

column uses low-pressure steam (25psig) and the reboiler on the second column uses high-

pressure steam (150psig). We construct the reboilers with SS316. Table 3 shows the condenser

and reboiler specifications:

Specifications

Bottom Temperature [°C]

Top Temperature [°C]

Reflux Ratio

Pressure [bar]

# of Stages

HETP

Diameter [m]

Height [m]

Pack Height [m]

Packing Vendor

Packing Type

Material

Cost

Component Weight Percent Component Weight Percent

Acetonitrile 0.9990 Acentonitrile 0.0005

Toluene 0.0007 Toluene 0.9995

Siloxane trace Siloxane trace

p-Xylene 0.0003 p-Xylene trace

Water 0 Water 0

Acetonitrile 0.0008 Acentonitrile trace

Toluene 0.4804 Toluene 0.0046

Siloxane 0.0249 Siloxane 0.0830

p-Xylene 0.4940 p-Xylene 0.9124

Water 0 Water 0

316SS 316SS

Distillate Stream Compositions (wt%)

Bottoms Stream Compositions (wt%)

Sulzer Sulzer

MellaPak 725 MellaPak 725

$89,744 $60,779

0.62 0.45

5.98 4.83

5.2 4.2

0.2 0.2

21.39 110.01

Distillation Towers with Total Condenser and Reboiler

Column 1 Column 2

53.85 138.29

2.8 2.3

0.1 1

28 23

Page 27: 1998 AIChE design competition

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Table 3: Condenser and Reboiler Specifications

We use EconExpert to do cost estimates, however, for a kettle reboiler there is a 10m3 minimum

volume in the software. We assume this is a minimum reboiler cost and use the cost for 10m3.

We determine the flow rates of coolant to the condenser on the basis that the MEK outlet

temperature cannot exceed -19oC, and that the plant-cooling tower recovers cooling water at

temperatures less than 45oC.

We determine steam flow rates to the condenser so that the steam fully condenses at the outlet of

the exchanger with very little superheating. This ensures the most efficient heat exchange

between steam and the process side (latent heat is better than specific heat). This also minimizes

potential problems with the condensate recovery system.

We size our reflux drums in each column assuming a holding time of 5 minutes. We calculate a

total flowrate into the reflux drums by combining the distillate and reflux streams leaving. We

use these numbers and the procedure in our project handout. We assume a liquid space of 50%.

We use Figure 18 to size our reflux tanks:

Specifications

Area [m2]

Heat Duty [kW]

U [W/m2C]

Type

Cost

StreamACN

ProcessMEK

TOL

Process

Cooling

Water

ACN

Process

Low P

Steam

TOL

Process

High P

Steam

Pressure in [bar] 0.1 1 1 1 0.1 2.74 1 11.35

Pressure out [bar] 0.1 1 1 1 0.1 2.74 1 11.35

Temperature in [°C] 21.39 -29 110.2 35 52.18 130.5 138.3 185.6

Temperature out [°C] 21.39 -19 110.2 45 53.85 130.5 138.3 185.6

Vapor Fraction in 1 0 1 0 0 1 0 1

Vapor Fraction out 0 0 0 0 0.85 0 0.93 0

Flow rate [kg/hr] 601 25236 1197 10446 1313 211 1507 241

$8,490 $6,463 $19,373 $19,373

126.1

1140

KettleShell and Tube Shell and Tube Kettle

850 850 1140

Reboilers

TOL-REB

2.43

131.9135.6 120.5

Condensers

3.53 2.03 1.39

ACN-COND TOL-CON ACN-REB

Page 28: 1998 AIChE design competition

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Figure 18: Reflux Drum Sizing Chart

We get a diameter and length for each tank from this chart. We extrapolate the length of the

length axis in order to intersect our line. Table 4 summarizes our flash tank specifications:

Table 4: Reflux Drum Specifications

We construct our drums with stainless steel. Both drums are relatively small but this makes sense

with the given process flowrates.

Specification Column 1 Column 2

Diameter (m) 0.152 0.457

Length (m) 1.524 1.524

Volume (m^3) 0.028 0.25

flow rate (gal/hr) 202.9 404.7

Reflux Ratio 2.8 2.3

Liquid Space (%) 50% 50%

Material 316SS 316SS

Purchased Cost $6,574 $9,240

Reflux Drums

Page 29: 1998 AIChE design competition

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Flash Drum Design

We size the flash drum using the procedure from “Flash distillation: examples-flash drum,

sizing” by P.C. Wankat. We include all of the calculations in the appendix. We follow the design

heuristics outlined in “Chemical Process Equipmet” by James R. Couper to orientate our vessel.

These heuristics call for a vertical drum in liquid/gas separation applications.

We assumed a liquid hold up time of 5 min in our calculations. We calculate a diameter less than

a foot, so we round up to a minimum diameter of 1 ft. We use the liquid hold up and diameter to

calculate a diameter of 5 ft. We get an H/D of 5, which is consistent with the heuristics. We also

consider a 50% fill percentage and double our volume. Table 5 summarizes the flash drum

design excluding the 50% fill percentage factor:

Table 5: Flash Drum Specifications

Specification

Temperature [C]

Pressure [bar]

Diameter [m]

Height [m]

Volume [m^3]

Heat Duty [kW]

Type

Material

Cost

Component Weight Percent

Acetonitrile trace

Toluene 0.0058

Siloxane 0.0019

p-Xylene 0.9923

Water 0

Acetonitrile trace

Toluene 0.0023

Siloxane 0.2421

p-Xylene 0.7556

Water 0

$24,094

Vapor Stream

Compositions

(wt%)

Liquid Stream

Compositions

(wt%)

1.925

0.224

6.9

Vertical with Demister Pad

316SS

Drum Separator

Flash Drum

140.4

1.01

0.385

Page 30: 1998 AIChE design competition

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The final volume including the 50% liquid fill percentage is 0.224m3. We include a demister pad

in our design to help with the efficiency of the separation and to maximize entrainment removal.

We ensure that the siloxane composition leaving the drum is well below its solubility limit of

25%. We fulfill the flash drum heating requirement (6.9 kW) with an electrical heating jacket.

We calculate the electrical demand of the flash drum using a conservative efficiency of 0.5. The

flash drum requires 1192 MJ/day of electricity.

Mixer Design

We use a motionless mixer because both the xylene recycle stream and make up stream are

predominately xylene (we do not need agitation). We use a hold up time of 5 minutes and a

liquid level of 70%. We assume a length/diameter ratio of 3:1. Table 6 shows the mixer

specifications:

Table 6: Mixer Specifications

We calculate the make-up flow rate of pure xylene so that 100 kg/hr of xylene flows from the

mixer at all times.

Heat Exchanger and Cooler Network Design

We use Aspen Plus to size our integrated heat exchangers and coolers. We get relatively small

areas so we use double pipe heat exchangers for all our exchangers and coolers. We do this in

accordance with the heuristics proved in table 9.11 from the heuristics handout. Table 7 shows

the heat exchanger specifications:

Specification

Hold time [mins]

Volume [m3]

Diameter [m]

Length [m]

Material

Cost

Outgoing Streams

Recycle Make Up Xylene Feed

Pressure [bar] 1 1 1

Temperature [°C] 138.145 25 108.99

Mass Flow Rate [kg/hr] 72.46 28.06 100.5

Incoming Streams

$13,148

316SS

Motionless Mixer

5

0.0153

0.1867

0.56

Page 31: 1998 AIChE design competition

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Table 7: Heat Exchanger Specifications

We use the minimum heat exchanger cost in EconExpert, which specifies a minimum area of

0.65m3. We use overall heat transfer coefficients that correspond with liquid-liquid heat transfer

from the heuristics handout. We save 17.1 kW of heating and cooling utilities by the use of this

heat exchanger network. This heat integration saves $2,673 annually on utilities. We have

process flow on both sides of the heat exchangers so all parts are made of 316SS.

We save money on utilities through implementation of this heat integration network, but we have

to take special considerations with process start up since we cool feed streams with product

streams. We resolve this issue by using utilities to cool both of the product streams.

We use 2 MEK coolers and a water cooler to finish cooling our process streams. We cool the

process below potentially hazardous flash point temperatures with these coolers. Table 8 shows

all cooler specifications:

Specifications

Area [m2]

Heat Duty [kW]

U [W/m2C]

Type

Cost

Stream Waste A FeedXylene

RecycleA Feed

Pressure in [bar] 1 1 1 1

Pressure out [bar] 1 1 1 1

Temperature in [°C] 140.4 20 140.4 33.6

Temperature out [°C] 27 33.6 138.1 84.4

Vapor Fraction in 0 0 1 0

Vapor Fraction out 0 0 0 0

Flow rate [kg/hr] 37 270 73 270

$7,422 $7,422

0.104

1.70 6.87

E1 E2

Heat Exchangers

280 850

Double Pipe Double Pipe

0.166

Page 32: 1998 AIChE design competition

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Table 8: Cooler Specifications

We designate all of the MEK flowrates so that MEK leaves the process at -29oC, and we set the

cooling water flowrate so that it leaves at 45oC.

Storage Tank Design

We follow the storage heuristics outlined in the heuristics handout to size our storage tanks. We

have 12 storage tanks total plus a spill container. We have 6 primary process storage tanks, one

for each feed stream and one for each product or waste stream. Feed streams B and C enter the

first distillation column at the same feed stage location so we use the same storage tank for these

streams. We purchase a backup storage tank for each primary stream as well in case we need to

clean a tank, require additional storage, or some other unknown factor.

We assume that the maximum level in any tank is 80% for 15 days of operation. We assume a

length/diameter ratio of 3/1. We size the spill container so that it is 1.5x the size of the largest

process storage tank. We use a cone roof design because it is the most cost effective. Table 9

summarizes the storage tank specifications:

Specifications

Area [m2]

Heat Duty [kW]

U [W/m2C]

Type

Cost

StreamACN

ProductMEK

TOL

Product

Cooling

Water

TOL

ProductMEK

Pressure in [bar] 1 1 1 1 1 1

Pressure out [bar] 1 1 1 1 1 1

Temperature in [°C] 21.4 -29 110 35 45 -29

Temperature out [°C] 5.4 -19 45 45 4.3 -19

Flow rate [kg/hr] 158 264 363 1082 363 1285

C3

$4,206 $4,206

Double Pipe Double Pipe

850 850

C1 C2

Coolers

$4,206

Double Pipe

850

6.91

0.525

1.42 12.52

0.136 0.501

Page 33: 1998 AIChE design competition

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Table 9: Storage Tank Specifications

Pump Design

We size our pumps based on the power they add to the system. Both process pumps are rotary

pumps. We use rotary pumps because our flow rates are too small for centrifugal pumps.

Centrifugal pumps are inefficient with flow rates below 15 gpm, our flow rates are both 1 gpm.

We show our process pump in Table 10:

Table 10: Process Pump Specification

We size our vacuum pump using the procedure outlined in the project handout. We need to

maintain a rough vacuum at 75 torr. Our operating requirements favor a one-stage liquid ring

pump. We use Figure 19 to size our pump:

L/D

liquid level

holding time (days)

Specifications A Feed B and C Feeds Waste TOL Product ACN Product Make Up Xylene Spill Container

Type cone roof cone roof cone roof cone roof cone roof cone roof cone roof

Diameter (m) 3.91 4.01 2.01 4.28 3.40 1.84 4.90

Height (m) 11.72 12.04 6.04 12.84 10.20 5.52 14.70

Volume (m^3) 140.63 152.40 19.27 184.80 92.63 14.68 277.20

Flow Rate (m^3/day) 7.5 8.128 1.02759 9.856 4.94 0.7827 N/A

Material 316SS 316SS 316SS 316SS 316SS 316SS 316SS

Cost $67,409 $70,349 $25,270 $78,007 $54,206 $22,341 $97,332

Storage Tank Design

3

80%

15

Streams

Specification PUMP-1 PUMP-2

Fluid Power [kW] 0.0062 0.0051

Flow Rate [cum/hr] 0.243 0.202

Head developed [m] 11.16 11.73

Pressure in [bar] 0.1 0.1

Pressure out [bar] 1.01 1

Net Work [kW] 0.021 0.017

Total Efficiency 0.54 0.54

Electrical Demand [kJ/day] 3360 2736

Cost $5,249 $5,023

Pump Sizing

Page 34: 1998 AIChE design competition

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Figure 19: Vacuum Pump Sizing

We use Figure 19 to arrive at a 22 HP requirement. We use this and the following HP/cost

relationship to calculate cost:

𝐼𝑛𝑠𝑡𝑎𝑙𝑙 𝐶𝑜𝑠𝑡 = $28,000 (𝐻𝑃

10)

0.5

(544

297)

We place the vacuum pump coming off the condenser in the first column. We summarize our

vacuum pump specifications in Table 11:

Table 11: Vacuum Pump Specification

Specification One Stage Liquid Ring

Vaccum Pressure [bar] 0.1

Vacuum Pressure [torr] 75

Horse Power 22

Total Efficiency 0.54

Electrical Demand [MJ/day] 2625

Cost $76,070

Vacuum Pump

Page 35: 1998 AIChE design competition

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We calculate an electrical demand in all of our pumps using a driver efficiency of 90% and a

pump efficiency of 60%. We combine these to get an overall efficiency of 54% for our pumps.

We use 2631 MJ/day of electricity with our pumps.

We purchase an additional 6 pumps which are specified in our process flow diagram. We use

these pumps to move material between storage tanks and the process and from one unit operation

to another. We assume a price of $4,000 per pump based on our first two pumps.

We purchase back up pumps in addition to the primary process pumps so we are ready if a pump

breaks. Pumps are relatively cheap and are an integral to operations. Pumps need to be replaced

more frequently than other equipment so we pay more to insure ourselves in the event of a pump

failure.

Piping Design

We choose to use 316SS piping. Our sizing follows Aspen Plus resulting flow rates, design

heuristics, and 316 SS testing data. We provide specifications for the piping in Figure 20:

Figure 20: Piping Specifications

Utility Summary

We use low-pressure steam, high-pressure steam, cooling water, MEK, and electricity as utilities

in our process. We calculate our annual utility cost using given utility costs. We summarize our

utility costs in Table 12:

Diameter [in] 3.3

Mas Stress [ksi] 44

Schedule 5S

Material 316SS

Piping Specifications

Page 36: 1998 AIChE design competition

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Table 12: Utility Costs

We use cooling water and electricity instead of MEK and steam wherever possible because of

cheaper costs. We show our annual utility usage in Table 13:

Table 13: Annual Utility Usage

We notice that the major utility consumption comes from the ACNCOL condenser. This cost is

so high because the first column has a low temperature profile because of its operating pressure.

We need to operate the column with its current specifications to meet the acetonitrile spec so we

cannot reduce this condenser cost.

Utility Cost Amount Units

Cooling Water $0.03 1000 L

MEK $19.70 1000000 kJ

Low P Steam $21.10 1000 kg

High P Steam $24.40 1000 kg

Electricity $0.02 1000 kJ

Cost of Utilities

Equipment Utility Amount Units Cost

Reboiler 1 low P steam 1688 1000 kg/yr $35,617

Reboiler 2 high P steam 1926 1000 kg/yr $46,996

$82,613

Condenser 2 cooling water 84906 1000 L/yr $2,547

C2 cooling water 8795 1000 L/yr $264

$2,811

Condenser 1 MEK 3905 1000 MJ/yr $76,934

C1 MEK 41 1000 MJ/yr $806

C3 MEK 199 1000 MJ/yr $3,920

$81,660

Flash Drum electricity 397440 1000 kJ/yr $7,949

Pump 1 electricity 1120 1000 kJ/yr $22

Pump 2 electricity 912 1000 kJ/yr $18

Vac Pump electricity 874955 1000 kJ/yr $17,499

$25,489

$192,573Total Yearly Utility Cost:

Total Steam Cost:

Total Cooling Water Cost:

Total MEK Cost:

Total Electricity Cost:

Page 37: 1998 AIChE design competition

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The reboilers in each column also drive up the utility cost. The high distillation related costs

show the benefit of operating without a third distillation column. They also verify the cost

savings achieved from lowering the xylene recycle flow rate.

We recycle and reuse our coolant. We do this to comply with coolant recovery laws and to attain

cost savings by reducing coolant disposal. In order to recycle and reuse our coolant we include

an MEK chiller in our process investment. We set aside a $250,000 allowance for the purchase

of a chiller system.

We purchase the MEK material initially, and then purchase more annually to make up for

coolant lost through leaks in the coolant system. We use 28,171 kg/hr of MEK and estimate a

total mass of MEK in our system as 50% of our hourly rate. We use MEK pricing from an online

market overview which reports MEK material costs at 0.551 $/ kg. We estimate MEK leakage at

a rate of 5% annually based on another online report. We use these assumptions to estimate our

initial and annual MEK material costs, which we summarize in Table 14:

Table 14: Annual MEK Material Costs

We find that the MEK material costs are very low relative to the cost of our system. This is

because we allocate a large amount of capital on the MEK chiller, which allows us to recycle and

reuse our MEK. We also comply with EPA regulations because of this coolant recovery system.

We justify the cost of the MEK chiller by looking at costs without one. Without a reuse/recycle

stream, we need to purchase large amounts of MEK annually and pay large disposal fees. We

summarize the cost of operating with and without an MEK chiller in Table 15:

Price [$/kg] 0.551

Total Mass [kg] $14,086

Annual Make-up [kg] $704

Start-up Cost $7,761

Annual Make-up Cost $388

MEK Material Cost

Page 38: 1998 AIChE design competition

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Table 15: MEK Chiller Justification

We find that the continuous purchase and disposal of MEK would cost $500 million dollars

annually, which is obviously infeasible. We decide to purchase the cooler in order to recycle and

reuse our MEK coolant.

Process Flow Diagram (PFD)

We present a piping and instrumentation diagram to show a holistic view of our process with

instrumentation specifics shown. The red dots represent thermocouples and flowmeters around

heat exchangers, coolers, storage tanks, reboilers, reflux drums, flash tanks, mixers, and

condensers. Control loop hardware has mechanical and electrical devices to perform functions

of the actuator, sensor and controller. The sensor converts the temperature to a voltage and sends

information to the controller, which then causes the actuator (valves) to make adjustments12. We

show the instrument in Figure 21:

Figure 21: Control Loop Hardware

Annual Flow [ Gg] $225

Annual Purchase Cost $124,178,870

Annual Disposal Cost $382,935,893

Annual Cost $507,114,763

MEK Recycle Justification

Page 39: 1998 AIChE design competition

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The green dots on the schematic below represent level sensors that monitor the storage vessels to

protect against the possibility of overflow and exposure to hazardous waste. Blue dots represent

pressure gauges. These monitor the pressure around columns, pumps, and storage tanks. Our

piping and instrumentation diagram shows our integrated control scheme in Figure 22:

Figure 22: Piping and Instrumentation Diagram

Page 40: 1998 AIChE design competition

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Mass and Energy Balances

We include the mass and energy data for all the streams in our process flowsheet. All the names

correspond with the names in Figure 16 from the process description. Table 16 includes all final

process and utility streams:

Table 16: Process Stream Tables

A ACN ACNSAFE ACOLD AMID B

MIXED Substream

Temperature C 84.4 21.4 5.4 20.0 33.6 75.0

Pressure bar 1.01325 0.1 0.1 1.01325 1.01325 1.01325

Mass Vapor Fraction 0 0 0 0 0 0

Mass Liquid Fraction 1 1 1 1 1 1

Mole Flows kmol/hr 2.893 3.851 3.851 2.893 2.893 0.659

Mole Fractions

Mass Density kg/cum 806.95 782.66 800.72 868.54 856.03 818.42

Volume Flow cum/hr 0.33 0.20 0.20 0.31 0.32 0.07

Mass Flows kg/hr 270.00 158.20 158.20 270.00 270.00 60.00

ACN kg/hr 0 158.0361282 158.0361282 0 0 1.2

TOL kg/hr 265.95 0.11691243 0.11691243 265.95 265.95 57.9

XYL kg/hr 0 0.04695937 0.04695937 0 0 0

SILOXANE kg/hr 4.05 1.45E-46 1.45E-46 4.05 4.05 0.9

WATER kg/hr 0 0 0 0 0 0

MEK kg/hr 0 0 0 0 0 0

ACN 0 0.998964148 0.998964148 0 0 0.02

TOL 0.985 0.000739017 0.000739017 0.985 0.985 0.965

XYL 0 0.000296835 0.000296835 0 0 0

SILOXANE 0.015 9.16E-49 9.16E-49 0.015 0.015 0.015

WATER 0 0 0 0 0 0

MEK 0 0 0 0 0 0

Mass Enthalpy kcal/kg 54.4468 180.8219 173.1130 27.1536 32.5657 53.6760

Mass Entropy cal/gm-K -0.8102 -0.8967 -0.9229 -0.8937 -0.8758 -0.8182

Enthalpy Flow Gcal/hr 0.0147 0.0286 0.0274 0.0073 0.0088 0.0032

Mass heat capacity, mixture cal/gm-K 0.4563 0.4905 0.4737 0.3911 0.4051 0.4490

Properties

Mass Fractions

Energy Streams

Component Mass Flows

Page 41: 1998 AIChE design competition

41

BOT1 BOT2 C COND1OUT COND2OUT

MIXED Substream

Temperature C 48.4 137.5 75.0 21.4 109.9

Pressure bar 0.1 1 1.01325 0.1 1

Mass Vapor Fraction 0 0 0 0 0

Mass Liquid Fraction 1 1 1 1 1

Mole Flows kmol/hr 13.729 14.137 4.254 14.635 13.002

Mole Fractions

Mass Density kg/cum 841.50 754.53 753.61 782.66 781.53

Volume Flow cum/hr 1.56 2.00 0.27 0.77 1.53

Mass Flows kg/hr 1313.34 1506.77 200.00 601.16 1197.37

ACN kg/hr 6.827882063 8.63E-08 157 600.5372873 0.54077841

TOL kg/hr 903.6515289 13.91220063 39 0.444267234 1196.740366

XYL kg/hr 397.8218195 1483.063995 0 0.178445604 0.090846152

SILOXANE kg/hr 5.042266972 9.797836259 4 5.51E-46 9.55E-06

WATER kg/hr 0 0 0 0 0

MEK kg/hr 0 0 0 0 0

ACN 0.005198855 5.73E-11 0.785 0.998964148 0.000451638

TOL 0.688054215 0.009233104 0.195 0.000739017 0.999472483

XYL 0.302907671 0.984264371 0 0.000296835 7.59E-05

SILOXANE 0.00383926 0.006502525 0.02 9.16E-49 7.97E-09

WATER 0 0 0 0 0

MEK 0 0 0 0 0

Mass Enthalpy kcal/kg 14.8555 -3.1643 172.7838 180.8219 69.6428

Mass Entropy cal/gm-K -0.8822 -0.8693 -0.8046 -0.8967 -0.7743

Enthalpy Flow Gcal/hr 0.0195 -0.0048 0.0346 0.1087 0.0834

Mass heat capacity, mixture cal/gm-K 0.4319 0.5083 0.5165 0.4905 0.4886

Properties

Mass Fractions

Energy Streams

Component Mass Flows

Page 42: 1998 AIChE design competition

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CW1COLD CW1HOT CW2COLD CW2HOT FEED-1

MIXED Substream

Temperature C 35.0 45.0 35.0 45.0 53.8

Pressure bar 1 1 1.01325 1.01325 0.1

Mass Vapor Fraction 0 0 0 0 0

Mass Liquid Fraction 1 1 1 1 1

Mole Flows kmol/hr 579.822 579.822 60.062 60.062 2.009

Mole Fractions

Mass Density kg/cum 984.26 974.48 984.26 974.45 834.47

Volume Flow cum/hr 10.61 10.72 1.10 1.11 0.24

Mass Flows kg/hr 10445.65 10445.65 1082.03 1082.03 202.36

ACN kg/hr 0 0 0 0 0.163872246

TOL kg/hr 0 0 0 0 97.20110822

XYL kg/hr 0 0 0 0 99.95304003

SILOXANE kg/hr 0 0 0 0 5.037010851

WATER kg/hr 10445.64938 10445.64938 1082.033781 1082.033781 0

MEK kg/hr 0 0 0 0 0

ACN 0 0 0 0 0.000809825

TOL 0 0 0 0 0.480349352

XYL 0 0 0 0 0.493948875

SILOXANE 0 0 0 0 0.024891948

WATER 1 1 1 1 0

MEK 0 0 0 0 0

Mass Enthalpy kcal/kg -3779.2804 -3769.3645 -3779.2801 -3769.3319 -3.6134

Mass Entropy cal/gm-K -2.1305 -2.0989 -2.1305 -2.0988 -0.9021

Enthalpy Flow Gcal/hr -39.4770 -39.3735 -4.0893 -4.0785 -0.0007

Mass heat capacity, mixture cal/gm-K 0.9903 0.9993 0.9903 0.9994 0.4237

Properties

Mass Fractions

Energy Streams

Component Mass Flows

Page 43: 1998 AIChE design competition

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FEED-3 MAKEUP MEKCOLD1 MEKCOLD2 MEKCOLD3

MIXED Substream

Temperature C 54.2 25.0 -29.0 -29.0 -29.0

Pressure bar 2.0265 1.01325 1.01325 1 1.01325

Mass Vapor Fraction 0 0 0 0 0

Mass Liquid Fraction 1 1 1 1 1

Mole Flows kmol/hr 2.009 0.264 3.663 350.034 17.825

Mole Fractions

Mass Density kg/cum 834.14 860.55 855.34 855.34 855.34

Volume Flow cum/hr 0.24 0.03 0.31 29.51 1.50

Mass Flows kg/hr 202.36 28.00 264.13 25239.84 1285.28

ACN kg/hr 0.163872246 0 0 0 0

TOL kg/hr 97.20110822 0 0 0 0

XYL kg/hr 99.95304003 28.00486665 0 0 0

SILOXANE kg/hr 5.037010851 0 0 0 0

WATER kg/hr 0 0 0 0 0

MEK kg/hr 0 0 264.125179 25239.84371 1285.28285

ACN 0.000809825 0 0 0 0

TOL 0.480349352 0 0 0 0

XYL 0.493948875 1 0 0 0

SILOXANE 0.024891948 0 0 0 0

WATER 0 0 0 0 0

MEK 0 0 1 1 1

Mass Enthalpy kcal/kg -3.4269 -54.7532 -931.9387 -931.9389 -931.9387

Mass Entropy cal/gm-K -0.9017 -1.0163 -1.4433 -1.4433 -1.4433

Enthalpy Flow Gcal/hr -0.0007 -0.0015 -0.2461 -23.5220 -1.1978

Mass heat capacity, mixture cal/gm-K 0.4240 0.4080 0.4588 0.4588 0.4588

Properties

Mass Fractions

Energy Streams

Component Mass Flows

Page 44: 1998 AIChE design competition

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MEKHOT1 MEKHOT2 MEKHOT3 OH1 OH2

MIXED Substream

Temperature C -19.0 -19.0 -19.0 21.4 110.2

Pressure bar 1.01325 1 1.01325 0.1 1

Mass Vapor Fraction 0 0 0 1 1

Mass Liquid Fraction 1 1 1 0 0

Mole Flows kmol/hr 3.663 350.034 17.825 14.635 13.002

Mole Fractions

Mass Density kg/cum 845.53 845.53 845.53 0.17 2.97

Volume Flow cum/hr 0.31 29.85 1.52 3570.40 402.71

Mass Flows kg/hr 264.13 25239.84 1285.28 601.16 1197.37

ACN kg/hr 0 0 0 600.5372873 0.54077841

TOL kg/hr 0 0 0 0.444267234 1196.740366

XYL kg/hr 0 0 0 0.178445604 0.090846152

SILOXANE kg/hr 0 0 0 5.51E-46 9.55E-06

WATER kg/hr 0 0 0 0 0

MEK kg/hr 264.125179 25239.84371 1285.28285 0 0

ACN 0 0 0 0.998964148 0.000451638

TOL 0 0 0 0.000739017 0.999472483

XYL 0 0 0 0.000296835 7.59E-05

SILOXANE 0 0 0 9.16E-49 7.97E-09

WATER 0 0 0 0 0

MEK 1 1 1 0 0

Mass Enthalpy kcal/kg -927.3213 -927.3203 -927.3188 374.7367 156.1466

Mass Entropy cal/gm-K -1.4248 -1.4248 -1.4248 -0.2383 -0.5486

Enthalpy Flow Gcal/hr -0.2449 -23.4054 -1.1919 0.2253 0.1870

Mass heat capacity, mixture cal/gm-K 0.4654 0.4654 0.4654 0.3029 0.3544

Properties

Mass Fractions

Energy Streams

Component Mass Flows

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REB1COND REB1OUT REB1STM REB2COND REB2OUT

MIXED Substream

Temperature C 130.5 53.9 130.5 185.6 138.3

Pressure bar 2.736939323 0.1 2.736939323 11.35538594 1

Mass Vapor Fraction 0.009994699 0.846399205 1 0.010000278 0.928618183

Mass Liquid Fraction 0.990005301 0.153600795 0 0.989999722 0.071381817

Mole Flows kmol/hr 11.713 13.729 11.713 13.364 14.137

Mole Fractions

Mass Density kg/cum 127.98 0.41 1.49 335.36 3.44

Volume Flow cum/hr 1.65 3174.19 141.36 0.72 437.73

Mass Flows kg/hr 211.01 1313.34 211.01 240.76 1506.77

ACN kg/hr 0 6.827882063 0 0 8.63E-08

TOL kg/hr 0 903.6515289 0 0 13.91220063

XYL kg/hr 0 397.8218195 0 0 1483.063995

SILOXANE kg/hr 0 5.042266972 0 0 9.797836259

WATER kg/hr 211.0098108 0 211.0098108 240.7560472 0

MEK kg/hr 0 0 0 0 0

ACN 0 0.005198855 0 0 5.73E-11

TOL 0 0.688054215 0 0 0.009233104

XYL 0 0.302907671 0 0 0.984264371

SILOXANE 0 0.00383926 0 0 0.006502525

WATER 1 0 1 1 0

MEK 0 0 0 0 0

Mass Enthalpy kcal/kg -3674.4263 97.4281 -3160.4875 -3611.1432 72.1271

Mass Entropy cal/gm-K -1.8387 -0.6276 -0.5654 -1.6971 -0.6861

Enthalpy Flow Gcal/hr -0.7753 0.1280 -0.6669 -0.8694 0.1087

Mass heat capacity, mixture cal/gm-K 1.1007 0.3216 0.4619 1.1999 0.3953

Properties

Mass Fractions

Energy Streams

Component Mass Flows

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REB2STM RECYCLE1 TOL TOLMID2 TOLSAFE

MIXED Substream

Temperature C 185.6 138.3 110.0 45.0 4.3

Pressure bar 11.35538594 1 1 1 1

Mass Vapor Fraction 1 0 0 0 0

Mass Liquid Fraction 0 1 1 1 1

Mole Flows kmol/hr 13.364 0.962 3.940 3.940 3.940

Mole Fractions

Mass Density kg/cum 5.63 753.31 781.41 846.18 883.49

Volume Flow cum/hr 42.75 0.15 0.46 0.43 0.41

Mass Flows kg/hr 240.76 109.52 362.84 362.84 362.84

ACN kg/hr 0 7.39E-10 0.163872245 0.163872245 0.163872245

TOL kg/hr 0 0.5025125 362.6485957 362.6485957 362.6485957

XYL kg/hr 0 99.92551089 0.027529137 0.027529137 0.027529137

SILOXANE kg/hr 0 9.087007958 2.89E-06 2.89E-06 2.89E-06

WATER kg/hr 240.7560472 0 0 0 0

MEK kg/hr 0 0 0 0 0

ACN 0 6.75E-12 0.000451638 0.000451638 0.000451638

TOL 0 0.004588525 0.999472483 0.999472483 0.999472483

XYL 0 0.912436491 7.59E-05 7.59E-05 7.59E-05

SILOXANE 0 0.082974984 7.97E-09 7.97E-09 7.97E-09

WATER 1 0 0 0 0

MEK 0 0 0 0 0

Mass Enthalpy kcal/kg -3139.9311 -13.7738 69.6998 40.0330 23.6683

Mass Entropy cal/gm-K -0.6699 -0.8822 -0.7741 -0.8584 -0.9134

Enthalpy Flow Gcal/hr -0.7560 -0.0015 0.0253 0.0145 0.0086

Mass heat capacity, mixture cal/gm-K 0.4858 0.4694 0.4887 0.4232 0.3810

Properties

Mass Fractions

Energy Streams

Component Mass Flows

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Safety, Environmental and Health Issues

Pressure and Vessel Analysis

We perform a pressure analysis by using a design heuristic MAWP formula. To do so, we add

50 psi to the highest pressure in our system. We specify a piping schedule of 5316 SS pipe that

follows a design heuristic and accounts for the allowable working stress and operating pressure.

We find the maximum allowable working pressure (MAWP) using a design heuristic;

Design pressure (psig) = (1.1 x operating pressure in psia) -14.7

or

50 psi + operating pressure in psig, whichever is greater

WASTE1 WASTE2 XYLMID XYLREC XYLVAP

MIXED Substream

Temperature C 140.4 27.0 138.1 109.1 140.4

Pressure bar 1.01325 1.01325 1.01325 1.01325 1.01325

Mass Vapor Fraction 0 0 0 0 1

Mass Liquid Fraction 1 1 1 1 0

Mole Flows kmol/hr 0.279 0.279 0.683 0.947 0.683

Mole Fractions

Mass Density kg/cum 754.20 864.84 754.00 783.36 3.23

Volume Flow cum/hr 0.05 0.04 0.10 0.13 22.47

Mass Flows kg/hr 36.96 36.96 72.55 100.56 72.55

ACN kg/hr 3.57E-11 3.57E-11 7.04E-10 7.03E-10 7.04E-10

TOL kg/hr 0.084531133 0.084531133 0.417981367 0.418021236 0.417981367

XYL kg/hr 27.93037754 27.93037754 71.99513335 100 71.99513335

SILOXANE kg/hr 8.950007897 8.950007897 0.137000061 0.137010881 0.137000061

WATER kg/hr 0 0 0 0 0

MEK kg/hr 0 0 0 0 0

ACN 9.65E-13 9.65E-13 9.70E-12 6.99E-12 9.70E-12

TOL 0.002286794 0.002286794 0.005761278 0.004157139 0.005761278

XYL 0.755591521 0.755591521 0.992350371 0.994480315 0.992350371

SILOXANE 0.242121685 0.242121685 0.001888351 0.001362546 0.001888351

WATER 0 0 0 0 0

MEK 0 0 0 0 0

Mass Enthalpy kcal/kg -35.1946 -74.7254 -2.5163 -17.0635 78.9158

Mass Entropy cal/gm-K -0.9083 -1.0121 -0.8686 -0.9053 -0.6707

Enthalpy Flow Gcal/hr -0.0013 -0.0028 -0.0002 -0.0017 0.0057

Mass heat capacity, mixture cal/gm-K 0.3886 0.3093 0.5113 0.4843 0.3909

Properties

Mass Fractions

Energy Streams

Component Mass Flows

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Our MAWP is 4.35 bar

Table 17 shows our MAWP analysis:

Table 17: MAWP

We perform a temperature analysis by using a design heuristic MAWT formula. To do so, we

add 50 degrees Fahrenheit to the highest temperature in our system.

We find the maximum allowable working temperature (MAWT) using a design heuristic;

Design Temperature (F) = (50 + operating temperature in Fahrenheit) or 600F minimum.

Our MAWP is 600 Fahrenheit.

Table 18 shows our MAWT analysis:

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Table 18: MAWT

Fire Protection

For passive fire protection, we cool all product and waste streams below their flash point

temperatures and bring them back to atmospheric pressure. Vermiculite cement fireproofs all of

our columns vessels and flash drum as they have the greatest potential for fire. The vermiculite

cement covers all equipment up to 10 meters from ground level. The main objective for the 10m

cement is to prevent failure in the event of a fire in proximity of flammable materials. We place

all storage tanks at a minimum distance of 25 feet away from any other equipment to minimize

their likelihood of fire exposure.

For active fire protection, we put out liquid fires using Monnex powder fire extinguishers

because we can’t put out low flash point liquid materials with water. Our fire detection system

includes flammable gas detectors to detect leaks, infrared detectors to detect flames, and smoke

detectors for smoke detection. We put out non-chemical fires using a sprinkler system. We put

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out chemical fires using fluoroprotein foam. We put out electrical fires using CO2 fire

extinguishers.

We recommend emergency material transfer for our plant. It is necessary to have arrangements

so that in the event of a fire it is possible to transfer flammable material away from the parts of

the plant on fire. A relief header leading to a vent stack allows vapor to vent safely away from

pressure vessels.

We make all fire protection in accordance with NFPA, Dow Minimum Preventive and Protective

Features, and the project handout.

Health Considerations

We provide operators and other employees with safety mandates to ensure our process runs

safely. As part of these mandates, all operators and employees meet certain expectations. All

operators and employees wear personal protective equipment including goggles, non-conductive

work boots, gloves, and hard hats. Work boots protect against heavy objects falling on the foot,

but also prevent electrical conductivity. Gloves protect against burns from hot pipes and heated

streams/equipment. Goggles will serve as eye protection against harmful chemicals within the

plant. We provide safety stations, eyewash stations, and first aid stations for all workers and

operators in the plant.

Spill Containment

We have a spill containment system that is 1.5 times the size of our largest storage container.

This allows us a good margin of safety to redirect streams to a safe place that will not result in

environmental damage. We install grates on the floor that direct any spills to a header, which

leads to the spill containment tank. As a result, the spill container is underground. The volume

of our spill container is 277.2 m3.

Inherently Safer Checklist

To help us think about possible safety issues we utilize the Inherently Safer Checklist. We

explain relevant checklist items via bullet point. We take topics for this checklist from CCPS,

Guidelines for Engineering Design for Process Safety, AIChE, New York, 1996. We note here

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that some of the items are broad concepts of inherent safety. We do not use the checklist as a

“yes/no” manner. We decide what might be possible and then decide what is feasible.

1.) Intensification/Minimization

1.1 – Do the following strategies reduce inventories of hazardous raw materials, intermediates,

and/or finished products?

We use a recycle stream to save as much solvent p-xylene as possible. This reduces the

overall amount of waste from our process.

1.3 – Can other types of unity operations or equipment reduce material inventories?

We use continuous distillation over batch distillation.

1.7 – Can we change process conditions to avoid handling flammable liquids above their flash

points?

We cool products below their flash points to prevent the handling of flammable liquids.

1.8 – Can we change process conditions to reduce production of hazardous wastes or by-

products?

We can’t reduce production of hazardous waste because we have no control over the

composition of the feed streams.

2.) Substitution / Elimination

2.4 – Is it possible to use utilities with lower hazards?

We minimize the use of methyl ethyl keytone because it is hazardous and use it only

when we can’t cool products with cooling water. We use high pressure steam only when

we can’t heat a stream using the lower pressure steam.

3.) Attenuation / Moderation

3.3 – Can we operate at less severe conditions using any other route?

We operate at atmospheric conditions when possible.

4.) Limitation of Effects

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4.1 – Can we design and construct vessels and piping to be strong enough to withstand the

largest overpressure that we can generate within the process?

We design pipes and vessels to handle excess pressure that follows MAWP calculations

4.2 – Can we design equipment to totally contain the materials that might be present inside at

ambient temperature or the maximum?

We design pipes and vessels to handle excess temperatures that follows MAWT

calculations.

4.4-4.5 – Can we locate process units to reduce or eliminate adverse effects from other adjacent

hazardous installations?

We will keep storage vessels away from the process vessels. This eliminates the

possibility of accidental heating

4.6 – For processes handling flammable materials, is it possible to design the facility layout to minimize

the number and size of confined areas and to limit the potential for serious overpressures in the event of a

loss of containment and subsequent ignition?

We operate the process outdoors so we can avoid small spaces by spreading out the

process

We also have a spill container.

4.7 – Can we locate the plant to minimize the need for transportation of hazardous materials?

We minimize the transportation costs because we are recycling toluene and acetonitrile to

a process upstream in our process plant.

5.) Simplification / Error Tolerance

5.2 – Can we design equipment so that it is difficult to create a potentially hazardous situation

due to an operating or maintenance error?

We use Stainless Steel 316 for all process equipment to prevent damage and corrosion.

We size piping to be much stronger than normal because we want a safe process and to

avoid leaks which may be difficult to identify.

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We design our vessels according to heuristics

5.3 – Can we design procedures so that it is difficult to create a potentially hazardous situation

due to an operating or maintenance error?

We will train operators to perform maintenance safely.

HAZOP

We provide a hazard and operability analysis (HAZOP) for our plant to ensure a maximum level

of safety. HAZOP requires steady-state operating, well-built equipment, competent operators,

and clear standard procedures. Operators will adhere to HAZOP protocols during plant

operating to minimize risk. We assume and require continuous maintenance on all plant

equipment.

HAZOP Key Finding

We look at the HAZOP case summary and risk analysis in figure 24 for specific trends. We find

that each unit is susceptible to ruptures or leaks. We assume and require continuous maintenance

on all plant equipment to prevent this problem. We also have back up equipment incase

operators cannot prevent equipment breakdown. Other major concerns include temperatures

becoming too high causing explosions and compositions of products becoming out of

specification. We have instrumentation to monitor temperatures and pressures of the system and

operators monitoring the system around the clock. Operators follow a clear set of standard

procedures to ensure safety and specified product outcomes.

Potential Concerns

We use a Risk Matrix to assign qualitative and quantitative values to each potential concern

within the plant. We show an example of a risk matrix in Figure 19:

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Figure 23: Example Risk Matrix

Columns 1 and 2 contain dangerous chemicals. Operators maintain operating conditions within

design specifications and perform maintenance and preventative disaster techniques.

Maintenance employees follow standard operating procedures when performing maintenance to

minimize their exposure to chemicals. High temperatures can cause a fire or explosion in the

column and results in our largest risk. We show our HAZOP case summary in Figure 24:

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Figure 24: HAZOP Case Summary

We do a complete HAZOP risk analysis in Figure 24:

Parameter Deviation ACNCOL TOLCOL Storage Vessels Mixer Heat Exchangers Pipes Coolers Pumps Streams

High

Low

No

Reverse

High

Low  

High

Low

High

Low

Less

More

other than

Less

More

Electrical No

Leak

Rupture

Unit

Flow

Pressure

Level

Temperature

Composition

Separation

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Figure 24a: HAZOP for ACNCOL

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Figure 24b: HAZOP for TOLCOL

The flash drum can leak or clog. We operate the process within design specifications to prevent

blockage. Operators perform routine maintenance to minimize the risks of a leak. High

temperatures cause a fire or explosion in the flash drum and results in our largest risk.

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Figure 24c: HAZOP for FLASH

The storage vessels can leak, overflow, or explode. Operators perform routine maintenance to

minimize the risks of a leak. We have storage vessels made to have a 15 day holding time, an

80% liquid level to be cautious against liquid surge, and a length to diameter ratio of 3:1.

Routine emptying prevents overflow. Operators operate the process within design specifications

to ensure temperatures stay below flashpoints within the storage vessels. High temperatures can

cause a fire or explosion in the storage vessels and results in our largest risk.

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Figure 24d: HAZOP for Storage Vessels

The mixer can overflow or explode. We expose hazardous material if the mixer overflows.

Operators operate within design specifications to prevent mixer overflow. The liquid has

potential to explode if it is above the flash point. Exchangers must operate correctly to cool

liquids effectively. Too high of a temperature can cause a fire or explosion in the mixer and

results in our largest risk.

Figure 24e: HAZOP for Mixer

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We have hazardous chemicals within all of the exchangers. Operators must perform regular

maintenance to ensure leaks do not occur. If exchangers do not operate correctly, components

raise above their flash points. Engineers can increase cooling flow rates to ensure temperatures

stay flash points. High temperatures can cause a fire or explosion in the heat exchanger network

and results in our largest risk.

Figure 24f: HAZOP for Heat Exchanger Network

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We do pipe design to ensure all pipes operate well within process conditions to prevent leaking.

Operators must perform routine maintenance to ensure there is no leaking. Low flow or lack of

containment leads to overflow of hazardous material, which results in our largest risk.

Figure 24g: HAZOP for Pipes

If pumps fail mechanically, cavitation can occur and permanently damage equipment. Operators

must make sure pumps run effectively through continuous maintenance. Stream pressure and

flash point problems are our largest risk factors according to the risk matrix for our pumps.

Figure 24h: HAZOP for Pumps

Impurities, poor flow rate and volatile temperatures in the feed streams can disrupt design

specifications. A number of possibilities relating to feed streams A, B and C affect the separation

effectiveness within the columns. We find it critical that operators will inspect incoming feed

and monitor separation results in the column. Operators have a requirement to perform routine

maintenance to ensure correct circulation, purity, and temperature.

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Figure 24i: HAZOP for Feed Streams

Impurities, poor flow rate and volatile temperatures in the feed streams can disrupt design

specifications. A number of possibilities relating to the make-up stream affect the separation

effectiveness within the columns. We find it critical that operators inspect incoming feed and

monitor separation results in the column. Operators have a requirement to perform routine

maintenance to ensure correct circulation, purity, and temperature. Calculation error is the most

common error for make-up stream being ineffective. Engineers monitor these calculations

regularly.

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Figure 24j: HAZOP for Makeup

FMEA

We use Failure Mode and Effects Analysis to systematically review our process and determine

all sources of failure defects. An effective FMEA identifies corrective actions to prevent failures

from reaching the customer; and to assure the highest possible yield, quality, and reliability. We

account for failures before implementation to ensure a safe operation. We calculate risk priority

numbers using the tables below:

Figure 25: FMEA severity ranking

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Figure 26: FMEA occurrence ranking

Figure 27: FMEA detection ranking

We calculate initial RPN values by multiplying severity, occurrence, and detection values. We

rank RPN values as the lowest being the most safe and highest having the most dangerous

potentials. We make improvements to threatening RPN values that decrease the original RPN

value (Resulting RPN). Improvement and corrective action must continue until the resulting

RPN is at an acceptable level for all potential failure modes. We calculate Resulting RPN values

until they meet a safe range.

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FMEA Key Findings

We have our largest risk at column one, the A.CN pump and the bottoms pump per the RPN

numbers calculated. Column one can have a material leak due to cracks or broken seals. As a

result, the plant has exposure to hazardous material. Operators, flowmeters, and vapor sensors

are put into place to monitor the issue. When column one has a material leak we shut down the

plant and provide safety showers to the operators. The pumps are flowing out of spec due to

irregular pressures and temperatures. This causes impurities in the final product. The duties are

monitored as well as flowmeters put in place to monitor the process. When the pumps are

flowing out of spec we check the reboiler and condenser.

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Figure 24: FMEA

Process Economics

We calculate the cost of all equipment with EconExpert. EconExpert is an online version of

Chemical Engineering Process Design and Economics. We cost our equipment using a cost

index of 544, which correlates to August 2016. We determine equipment cost by multiplying

purchase cost by pressure and material factors. We use a 10% delivery and freight cost for all

equipment. We use the F.O.B purchase costs reported in the specification tables in our

equipment summary.

We include employee safety and fire protection in addition to basic equipment. We use cement

as a fire retardant to protect each column and flash drum. The cement covers the equipment and

extends an additional 10.7 meters above the equipment. We provide safety such as eye

protection, hearing protection, hand protection, and hazardous shower and eye wash stations for

our employees. We add an additional ten percent to the safety and equipment to account for

miscellaneous items such as piping, supports, sprinklers, fire extinguishers, smoke detectors, and

valves. We summarize all our costs in Table 19:

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Table 19: Process Equipment Costs

Purchase Cost Material Factor Pressure Factor FOB Cost Delivered Cost

Column 1 $16,553 4 1 $81,585 $89,744

Packing 1 $15,373

Column 2 $12,127 4 1 $55,254 $60,779

Packing 2 $6,746

E1 $2,249 3 1 $6,747 $7,422

E2 $2,249 3 1 $6,747 $7,422

C1 $2,249 1.7 1 $3,823 $4,206

C2 $2,249 1.7 1 $3,823 $4,206

C3 $2,249 1.7 1 $3,823 $4,206

Reboiler 1 $10,360 1.7 1 $17,612 $19,373

Reboiler 2 $10,360 1.7 1 $17,612 $19,373

Condenser 1 $4,540 1.7 1 $7,718 $8,490

Condenser 2 $3,456 1.7 1 $5,875 $6,463

Pump 1 $2,386 2 1 $4,772 $5,249

Pump 2 $2,283 2 1 $4,566 $5,023

Vac Pump $76,070 1 1 $76,070 $83,677

Extra Pumps $16,669 2 1 $33,338 $36,672

Flash Drum $5,331 4 1 $21,904 $24,094

Reflux Drum 1 $1,494 4 1 $5,976 $6,574

Reflux Drum 2 $2,100 4 1 $8,400 $9,240

Mixer $4,534 $3 $13,149 $14,463

A Storage $19,260 3.5 1 $67,409 $74,150

B+C Storage $20,100 3.5 1 $70,349 $77,384

Waste Storage $7,220 3.5 1 $25,270 $27,797

TOL Storage $22,288 3.5 1 $78,007 $85,808

ACN Storage $15,487 3.5 1 $54,206 $59,627

Xylene Storage $6,383 3.5 1 $22,341 $24,575

Spill Conatiner $27,809 3.5 1 $97,332 $107,065

Chiller $250,000 $250,000 $275,000

MEK $7,761 $7,761 $8,537

Fire Protection $2,814 $2,814 $3,095

Saftey shower $2,705 $2,705 $2,976

Hearing Protection $91 $91 $100

Eye Protection $180 $180 $198

Gloves $80 $80 $88

Misc $111,057 $111,057 $111,057

$1,274,130

Columns

Miscillaneous

Total Equipment Cost:

Flash Drum

Pumps

Condenser

Reboiler

Heat Exchanger

Fire and Safety Protection

MEK Recovery System

Storage Vessel

Mixer

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We include a miscellaneous allowance of 10% of all other costs. We allocate this for costs

associated with structural support, piping, minor equipment, back up pumps, and any other

expenditure we overlooked in the cost estimation. We use large material factors to account for

the usage of stainless steel in all of our process equipment.

We use the cost of our equipment as a basis to calculate our total capital investment. We use a

modified Lang Factor based on the fluid processing plant model. We take out expenditures that

are not applicable to a plant expansion, and decrease factors that would not require as large of an

investment as a new plant. We assume that the plant already has service, maintenance, office

buildings, and free land. We use an installation factor of 43% and use reasonable numbers for

our other factors. We summarize our additional costs in Table 20:

Table 21: Additional Cost Allowances

We use a total Lang Factor of 3.5, which is reasonable in a plant improvement or modification

setting. We summarize our total capital investment cost break down in Table 21

Additional Costs

Percent of

Equipment

Cost

Equipment Installation 43%

Instrumentation and Controls (Installed) 17%

Piping (Installed) 22%

Electrical (Installed) 12%

Yard Improvements 5%

Engineering and Supervision 31%

Construction Expense 27%

Contractors Fee 21%

Contingency 20%

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Table 21: Total Capital Investment

We estimate a total capital investment of about $4.5 million. Of this investment, 15% is working

capital investment and 85% is fixed capital investment. We invest a majority of our money on

the actual installation and construction of our equipment relative to the purchase cost.

We predict an operating cost based on the variable costs that will incur with our process. We get

our A, B, and C feed streams from an existing process, but we still buy make-up xylene and

MEK. We calculate our xylene cost in Table 22:

Table 22: Xylene Purchase Cost

We pay for the waste disposal of our siloxane purge stream. This stream contains more than 25%

siloxane by weight so we dispose of it as class B waste (1.50 $/kg). We show our waste cost

calculation in Table 23:

Total Equipment Cost (F.O.B) $1,158,300

Delivered Equipment Costs (1.1*TEC) $1,274,130

Equipment Installation $547,876

Instrumentation and Controls (Installed) $216,602

Piping (Installed) $280,309

Electrical (Installed) $152,896

Yard Improvements $63,706

Engineering and Supervision $394,980

Construction Expense $344,015

Contractors Fee $267,567

Contingency $254,826

Fixed Capital Investment (FCI) $3,796,906

Working Capital Investment (15% TCI) $670,042

Total Capital Investment (TCI) $4,466,948

Total Capital Investment

Raw Material Cost [$/kg] $1.70

p-Xylene Flow Rate [kg/hr] 28.07

Annual Operation Hours [hr] 8000

Annual Cost $381,714

Cost of p-Xylene

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Table 23: Waste Disposal Cost

We use these calculations to calculate our total raw material purchase and disposal costs. We

need to calculate our labor costs. To complete this we estimate two operators per shift for 8

shifts. We pay our operators 32 $/hr and include a benefits factor of 1.7. We show our labor cost

calculations in Table 24:

Table 24: Labor Costs

We use these calculations and other estimates to calculate our total annual operating cost. We

allocate 6% of FCI for maintenance costs and 15% of maintenance costs for operating supplies.

We summarize our operating costs in Table 25:

Table 25: Operating Costs

Waste Type B

Cost [$/kg] $1.50

Flow Rate of Waste [kg/hr] 37.028

Annual Operation Hours [hr] 8000

Annual Cost $444,336

Cost of Waste Stream Disposal

Shifts 4

Operators 2

Annual Employee Hours 2000

Houly Wage $32

Total Labor Cost per year $512,000

Benefits Factor 1.70

Total Labor Cost $870,400

Labor Cost

Item Cost

Operating Labor $870,400

Utilities $192,573

Maintenance (6% FCI) $227,814

Operating Supplies (15% Maint.) $34,172

Waste Disposal (Class B) $444,336

Raw Materials (Xylene and MEK) $382,102

Total $2,151,397

Operating Cost

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We use the price of ACN and TOL to calculate the cost savings of our solvent recovery system.

We assume 8000 operating hours per year. We summarize our annual revenue in Table 26:

Table 26: Annual Revenue

We generate annual revenue of over $9 million. We run a cash flow analysis using all of our

costs and revenue to find the rate of return of our solvent recovery system. We use a SOYD

depreciation scheme in order to minimize our annual taxable income. We calculate our annual

depreciation allowance in Table 27:

Table 27: Annual Depreciation Allowance

Annual Revenue Value [$/kg] Recovered [kg/hr] Recovered [kg/yr] Sale [$/yr]

ACN 3.3 158.2 1265600 $4,176,480

TOL 1.9 362.8 2902720 $5,515,168

Total $9,691,648For 8000 operating hours per year:

Year SOYD Factor Depreciation

0

1 0.095 $361,610

2 0.090 $343,530

3 0.086 $325,449

4 0.081 $307,369

5 0.076 $289,288

6 0.071 $271,208

7 0.067 $253,127

8 0.062 $235,047

9 0.057 $216,966

10 0.052 $198,886

11 0.048 $180,805

12 0.043 $162,725

13 0.038 $144,644

14 0.033 $126,564

15 0.029 $108,483

16 0.024 $90,403

17 0.019 $72,322

18 0.014 $54,242

19 0.010 $36,161

20 0.005 $18,081

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We assume no salvage value after a 20-year lifespan. We calculate our cash flow using a 40%

income tax rate. We show our cash flow diagram in Table 28:

Table 28: Cash-Flow for Solvent Recovery System

We convert each annual after tax cash flow to present day value in order to solve for rate of

return. The correct ROR value yields a net present day value equal to the total capital invested.

Using this analysis, we calculate a ROR of 102.9%. This value is much higher than 10%, which

leads us to recommend the adoption of this solvent recovery system.

We recommend purchasing the equipment on July 1, 2017. This is the first day of the third

quarter and allows us to claim bonus depreciation that year. We buy on this date and not later so

that we can install our system as fast as possible and start recovering solvent immediately.

Improvement Recommendations

We designed a very profitable solvent recovery system, but there is always room for

improvement. We recommend exploring further heat integration. We can heat feed A up to 75oC

before lowering the pinch temperature and requiring steam heating. We plan to investigate this

option to reduce our MEK consumption.

Year Total Product Cost Revenue Before Tax Cash-Flow Depreciation Taxable Income Income Tax (40%) After Tax Cash Flow Present Value of ATCF

0 -$4,466,948 -$4,466,948

1 -$2,366,537 $9,691,648 $7,325,111 $361,610 $6,963,501 $2,785,400 $4,539,711 $2,237,459

2 -$2,151,397 $9,691,648 $7,540,251 $343,530 $7,196,721 $2,878,688 $4,661,562 $1,132,362

3 -$2,151,397 $9,691,648 $7,540,251 $325,449 $7,214,802 $2,885,921 $4,654,330 $557,235

4 -$2,151,397 $9,691,648 $7,540,251 $307,369 $7,232,882 $2,893,153 $4,647,098 $274,214

5 -$2,151,397 $9,691,648 $7,540,251 $289,288 $7,250,963 $2,900,385 $4,639,866 $134,940

6 -$2,151,397 $9,691,648 $7,540,251 $271,208 $7,269,043 $2,907,617 $4,632,633 $66,403

7 -$2,151,397 $9,691,648 $7,540,251 $253,127 $7,287,124 $2,914,849 $4,625,401 $32,677

8 -$2,151,397 $9,691,648 $7,540,251 $235,047 $7,305,204 $2,922,082 $4,618,169 $16,080

9 -$2,151,397 $9,691,648 $7,540,251 $216,966 $7,323,285 $2,929,314 $4,610,937 $7,913

10 -$2,151,397 $9,691,648 $7,540,251 $198,886 $7,341,365 $2,936,546 $4,603,705 $3,894

11 -$2,151,397 $9,691,648 $7,540,251 $180,805 $7,359,446 $2,943,778 $4,596,472 $1,916

12 -$2,151,397 $9,691,648 $7,540,251 $162,725 $7,377,526 $2,951,010 $4,589,240 $943

13 -$2,151,397 $9,691,648 $7,540,251 $144,644 $7,395,607 $2,958,243 $4,582,008 $464

14 -$2,151,397 $9,691,648 $7,540,251 $126,564 $7,413,687 $2,965,475 $4,574,776 $228

15 -$2,151,397 $9,691,648 $7,540,251 $108,483 $7,431,768 $2,972,707 $4,567,544 $112

16 -$2,151,397 $9,691,648 $7,540,251 $90,403 $7,449,848 $2,979,939 $4,560,311 $55

17 -$2,151,397 $9,691,648 $7,540,251 $72,322 $7,467,929 $2,987,171 $4,553,079 $27

18 -$2,151,397 $9,691,648 $7,540,251 $54,242 $7,486,009 $2,994,404 $4,545,847 $13

19 -$2,151,397 $9,691,648 $7,540,251 $36,161 $7,504,090 $3,001,636 $4,538,615 $7

20 -$2,151,397 $10,361,690 $12,513,088 $18,081 $12,495,007 $4,998,003 $7,515,085 $5

$4,466,948.44TCI at yr 0:

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We also recommend investigating a better waste treatment plan. We can purchase a dryer or

evaporator to dry out purged siloxane to reduce waste disposal costs. If we dry out siloxane and

dispose of that as class B waste, we can then either recycle the rest of our xylene or condense it

and dispose of it as class A waste for much cheaper.

We design the system to cool streams down to 0.1oC below their flash point temperatures, but to

operate as safely as possible we recommend cooling the streams down further.

Acknowledgments

We acknowledge Dr. Liu for his invaluable lectures, notes, and knowledge. We thank Dr. Liu for

his patience and guidance throughout this project and thank him for the opportunity to design

this system.

Thank You Dr. Liu!!

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References

1. “Analysis, Synthesis, and Design of Chemical Processes,” by Turton, Bailie, Whiting, and Shaeiwitz. Prentice Hall, 1998.

2. “ChE 4185 Process and Product Design I, Fall 2015, 1998 AIChE National Student Design Competition,” Dr. Liu ChE 4185. Virginia Tech Chemical Engineering. 2016.

3. “Notes on Equipment Sizing October 2016,” Dr. Liu ChE 4185. Virginia Tech Chemical Engineering. 2016.

4. Humphrey, J. L. and George E. Keller, Separation Process Technology, McGraw-Hill, New York (1997).

5. “Structured Packings: Energy-efficient, innovative and profitable,” Sulzer Chemtech - Mass Transfer Technology. pg. 6.

6. “ChE 4185 Process and Product Design I Process Economics,” Professor Y. A. Liu Department of Chemical Engineering Virginia Tech. pages 192-193, 304, 325f-325g

7. G.D. Ulrich and P. T. Vasudevan. Chemical Engineering Process Design and Economics, A Practical Guide, 2nd Edition.

8. 1982 AIChE National Student Design Competition Problem. 9. Lees, F.P., Loss Prevention in the Process Industries. Volumes 1 and 2 Pages 528-544.

Buttersworths, Boston (1983). 10. Wankat, Phillip C. Separation Process Engineering: Includes Mass Transfer Analysis. Upper

Saddle River, NJ: Prentice Hall, 2012. Print. 11. Guidelines for Hazard Evaluation Procedures, 3rd. Ed. 2008 AIChE New York. 12. Washington Faculty, Chapter 2 “Control Loop Hardware”

http://faculty.washington.edu/baneyx/436/Orifice.pdf 11/16/2016 13. Sschundler Construction Co. “Schundler Vermiculite Concrete Light Weight and Insulating”

http://www.schundler.com/vermcon.htm 11/16/2016 14. Wayfair, “Speakman Safe-T-Zone Traditional Series Emergency Combination Shower”

https://www.wayfair.com/Speakman-Safe-T-Zone-Traditional-Series-Emergency-Combination-Shower-SE-697-SPK1445.html?source=hotdeals 11/16/2016

15. ULINE, “Uline Reusable Earplugs-Corded” https://www.uline.com/Product/Detail/S-19874/Hearing-Protection/Uline-Reusable-Earplugs-Corded?pricode=WY633&gadtype=pla&id=S-19874&gclid=CMmQlL_0rtACFQZLDQod7RYGcQ&gclsrc=aw.ds 11/16/2016

16. ULINE, “Charguard Gloves – Large” https://www.uline.com/Product/Detail/S-13387L/Heat-Resistant-Gloves/Charguard-Gloves-Large?pricode=WY635&gadtype=pla&id=S-13387L&gclid=CLm64cr1rtACFYtLDQodVAYCWQ&gclsrc=aw.ds 11/16/2016

17. Discount Safety Gear, “Rugged Blue Diablo Safety Glasses” http://www.discountsafetygear.com/rugged-blue-diablo-safety-glasses.html?utm_source=googlepepla&utm_medium=adwords&id=110076584658&gclid=CObTtfj2rtACFZpMDQodcz4BfA 11/16/2016

18. ICIS, “Methyl Ethyl Ether (MEK) Prices and Pricing information” http://www.icis.com/resources/news/2007/11/05/9076042/methyl-ethyl-ketone-mek-prices-and-pricing-information/ 11/16/2016

19. ChemWorld, “Closed Loop Water Leaks” http://www.chemworld.com/Closed-Loop-Water-Leaks-s/1570774.htm 11/16/2016

20. Pinch Analysis Tool, Institution of Chemical Engineers, United Kingdom.

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Appendix

Heat Exchanger Network

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Piping Design

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Vacuum Pump Sizing

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Flash Drum Sizing

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Mixer Sizing

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Reflux Drum Sizing

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