methanol project

8/18/2019 methanol project

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Production Of Methanol From Natural Gas 1


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Methanol

Methanol is an Alcohol whose chemical formula can be written as CH3OH. It is a clearcolourless liquid with a mild odour, and dissolves readily in most common organic solvents.

Methanol is one of the largest volume chemicals produced, with a world wide annuaproduction of about 13 million tons.

Methanol was first obtained commercially some 150 years agoby the destructive distillation of wood. Today it is producedmainly from the steam reforming of natural gas via a synthesisgas intermediate. Methanol can and is , however also beingproduced from such alternative feed stocks as coal and residualfuel oil.

Methanol has been traditionally used as a chemical intermediate

for the production of formaldehyde, solvents, methylderivatives(chemical groups containing CH3) and increasingly acetic acid. Recently methanohas gained importance as a clean burning fuel and fuel additive in such diverse uses as aboiler fuel for NOx control , as an octane booster for gasoline by direct blending or as a methytertiary butyl ether derivative and for fuel cell application .

1.1 Physical Properties.-

Methanol (CH3OH) is an alcohol fuel. Methanol is the simplest alcohol, containing one carbonatom. It is a colorless, tasteless liquid with a very faint odor and is commonly known as "woodalcohol."As engine fuels, ethanol and methanol have similar chemical and physicacharacteristics. Methanol is methane with one hydrogen molecule replaced by a hydroxy

radical (OH).

Physical Properties

Molecular weight 32.04

Boiling point 64.7°C

Vapor pressure 97 Torr at 20°C

Formula CH3OH

Freezing point -97.68°C

Refractive index 1.3284 at 20°C

Density 0.7913 g/mL (6.603 lb/gal) at 20°C

0.7866 g/mL (6.564 lb/gal) at 25°C

clean burning fuel

x con ro

"woodalcohol


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Dielectric constant 32.70 at 25°C

Dipole moment 2.87 D at 20°C

Solvent group 2

Polarity index (P') 5.1

Eluotropic value on alumina 0.95

Eluotropic value on octadecylsilane 1.0

Viscosity 0.59 cP at 20°C

Surface tension 22.55 dyn/cm at 20°C

Solubility in water Miscible in all proportions

Melting Point -97.7 C

Flash point 11 oC

Auto ignition temperature 455 oC

Explosive limits 7-36 %

Heat of Formation -201.3 MJ/kmol

Gibbs Free Energy -162.62 MJ/kmol

Critical temperature 512.6 K

Critical pressure 81 bar abs

Critical volume 0.118 m³/kmol

Heat of Vaporization 35278 kJ/kmol

Regulatory and Safety Data

Acute effectsPoisonous by ingestion or inhalation, maycause respiratory failure, kidney failure,blindness.

Chronic effects As acute. Skin contact can cause dermatitis.

.


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1.2 Reactions Of Methanol

Methanol is the 1st in a series of aliphatic, monohydric alcohols and undergoes many of thereactions typical of this class of chemical compound , Methanol is also a typical member of thisseries since it contains only one carbon atom . Methanol, for example can not undergo

elimination of the hydroxyl group and hydrogen to form the analogous olefins as do many ofthe higher alcohols.

The reactions of the aliphatic alcohols including methanol generally involve hydroxyl groupeither through breaking of the C-O bond or O-H bond and substitution or displacement of theH or _OH group, . the O-H and C-O bonds in alcohols are relatively strong, albeit polar andkinetically labile. Hemolytic bond dissociation energies are in the order of 90 100 Kcal/ moleBecause of this bond strength in alcohols, some activation of these bonds is often necessaryto achieve acceptable reaction rates.

1.3 CHEMICAL PROPERTIES OF METHANOL: CH3OH

Combustion of Methanol:

Methanol burns with a pale-blue, non-luminous flame to form carbon dioxide and steam.

2CH3OH + 302 ===> 2CO2 + 4H2O

Oxidation of Methanol:

Methanol is oxidized with acidified Potassium Dichromate, K2Cr2O7, or with acidified SodiumDichromate, Na2Cr2O7, or with acidified Potassium Permanganate, KMnO4, to form

formaldehyde.

CH3OH ===> HCHO + H2

Methanol Formaldehyde

2H2 + O2 ===> 2H2O

If the oxidizing agent is in excess, the formaldehyde is further oxidized to formic acid and thento carbon dioxide and water.

HCHO ===> HCOOH ===> CO2 + H2OFormaldehyde Formic

Acid

Catalytic Oxidation of Methanol:

The catalytic oxidation of methanol using platinum wire is of interest as it is used in modelaircraft engines to replace the sparking plug arrangement of the conventional petrol engine.The heat of reaction is sufficient to spark the engine.

breaking of the C O bond or O

pale blue, non-luminous flame

K2Cr2O7,

platinum wireaircraft engines to replace the sparking plug arrangement


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Dehydrogenation of Methanol:

Methanol can also be oxidized to formaldehyde by passing its vapor over copper heated to 300 °C. Two

atoms of hydrogen are eliminated from each molecule to form hydrogen gas and hence this process is

termed dehydrogenation.

Cu

300°CCH3OH ===> HCHO + H2 Methanol Formaldehyde

Dehydration of Methanol:

Methanol does not undergo dehydration reactions. Instead, in reaction with sulphuric acid theester, dimethyl sulphate is formed.

Conc H2SO4 2 CH3OH ===> (CH3)2SO4 + H2OMethanol Dimethyl Water

Sulphate

Esterification of Methanol

Methanol reacts with organic acids to form esters.

H(+)

CH3OH + HCOOH ===> HCOOCH3 + H2OMethanol Formic Methyl Water

Acid Formate

Substitution of Methanol with Sodium

Methanol reacts with sodium at room temperature to liberate hydrogen. This reaction is similarto the reaction of sodium with ethanol.

2 CH3OH + 2 Na ===> 2CH3ONa + H2

Methanol Sodium Sodium Hydrogen

Methoxide

Substitution of Methanol with Phosphorus Pentachloride

Methanol reacts with phosphorus pentachloride at room temperature to form hydrogenchloride, methyl chloride, (i.e. chloroethane) and phosphoryl chloride.

CH3OH + PCl5 ===> HCl + CH3Cl + POCl3 Methanol Phosphorus Hydrogen Methyl Phosphoryl

copper eate to 300 .°

y rogen gas


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Pentachloride Chloride Chloride Chloride

Substitution of Methanol with Hydrogen Chloride

Methanol reacts with hydrogen chloride to form methyl chloride (i.e. chloromethane) and water.

A dehydrating agent (e.g. zinc chloride) is used.

ZnCl2 CH3OH + HCl ===> CH3Cl + H2OMethanol Methyl

Chloride

1.4 USES OF METHANOL:-

The major portion of the methanol produced is used for making formaldehyde and a number ofchemical derivatives. Other applications include its use as solvents extractant and airautomation antifreeze. .

Methanol As A Solvent:-

Methanol is miscible with most organic liquids and is a solvent for variety of substance likedyes, nitro cellulose, polyvinyl, butyl ethyl cellulose, Shellac and modified resin. It is used inthe manufacturing of wood and metal polishes. Water proofing formulation, coated fabrics,aniline, and other inks, and duplicator fluids. Its solution have lower viscosities than similarsolution, made from other alcohols, methanol is uses in combination with 5 to 10 % ofpolyhydroxy alcohol as a solvent for water soluble aniline dyes in the manufacture of non-=grain-raising wood-stain, it is also used as a solvent for aniline dyes for leather and isespecially useful where uniform colour development is essential. Other application of thisproducts include its addition to asphalts paints to decrease their drying time and its use in bothnatural and synthetic rubber solutions to lower the viscosity during processing . Methanol doesnot dissolve cellulose acetate and acetate butyrate, polystyrene, polyethene, methylcrylateresin, polyvinyl chloride, and co-polymers.

Methanol As An Extractant:-

Methanol is employed in a large scale in many industrial chemical processes as an extractantIn the refining of gasoline and heating oil. The unisol process use caustic methanol solutions to

remove undesirable mercaptan impurities. Methanol may also be used to extract the aromaticpotion of petroleum form other hydrocarbons and patent literature describe its use in extractionorganic nitrites. From non polar hydrocarbon in the secondary recovery of crude oil by thmiscible phase method using alcohol methanol is the least expensive and most easyrecovered. A process has been developed to use a solvent of methanol and hexane in theextraction of tars from Texas Lignite deposits.

Methanol is also uses for removing acid impurities from vegetable oils, dewaxing dimmer gum,flash washing water soluble crystals, extracting inorganic salt such as potassium iodide andbarium and strontium halides, purifying hormones and crystallizing steroid.

formaldehyde

miscible

wood and metal polishes

extractant

aroma cpotion of petroleum form other hydrocarbons

acid impurities from vegetable oils, dewaxing dimmer gumflash washing water soluble crystals, extracting inorganic salt such as potassium iodide and

ar um an s ron um a es, pur yng ormones an crys a zng s ero .


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Methanol As A Ceansing Agent:-

Methanol is used in many cleansing operations such as in washing steel surfaces beforecoatings are applied , rinsing the interiors of electronic tubes before they are evacuated ,

cleaning resin sheets before further processing , It is employed as a reducing agent in thevapor phase cleaning of copper, the bright annealing of brass and in soldering fluxes. Its isalso used in special preparation for dry cleaning leather goods, in glass cleaners and influshing fluids for hydraulic brake system.

Methanol As An Anti Freezing Agent

Methanol offers the advantages of low molecular weights, low costs and high efficiency whenused as an automotive or industrial antifreeze. The pressure up cap on the radiator of themodern engine cooling system prevent losses by evaporations. Methanol-antifreeze solutionsare considered less result of internal leakage then the high boiling type. Fuel system antifreeze

and windshield washer fluid based on methanol add to the dependability and convenience ofmotor transport in methyl ester of 2-4 D is a selective weed killer, methyl salicylate is used inmedicines flavorings and perfumes., dimethylpthalate is as insect repellent and a plasticizer forcellulose acetate methyl P=hydroxyl benzoate is a mold inhibitor for aqueous preparationscontaining starch guans and oil. Methylcrylate polymerizes readily to form clear plastics.

Formaldehyde:-

Worldwide, the largest amount of formaldehyde is consumed in the production of urea-formaldehyde resins, the primary end use of which is found in building products such asplywood and particle board .The demand for these resins, and consequently methanol, is

greatly influenced by housing demand. In the United States, the greatest market share forformaldehyde is again in the construction industry. However, a fast-growing market forformaldehyde can be found in the production on acetylenic chemicals, which is driven by thedemand for 1, 4 butanediol and its subsequent downstream product, spandex fibers.

Methyl T-Butyl Ether:-

MTBE is used as an oxygen additive for gasoline. Production of MTBE in the United States haincreased due to the requirements of the 1990 Clean Air Act amendments, and has surpassedformaldehyde as the largest domestic consumer of methanol. Projection for this use ofmethanol are difficult to estimate due to the varying political and environmental considerations

that promote the use of cleaner burning motor fuels.

ACIDS:-

Methanol carbonylation has become the process of choice for production of this staple of theorganic chemical industry, which is used in the manufacture of acetate fibers, acetic anhydrideand terephthalic acid, and for fermentation,

cleansing operationsrinsing the interiors of electronic tubes before they are evacuated


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Methanol As An Alternative Fuel

Utilization of methanol as alternative fuel can be done through two different waysthat is by using directly in an internal combustion engine or by implementing methanol fuel cellpowered vehicles.

Pure methanol (M100) has been used in heavy-duty trucks and transit buses equipped withcompression-ignition diesel engines. Since 1965, M100 has been the official fuel forIndianapolis 500 race cars. (The last time gasoline was used in the Indianapolis 500 was in1964, when the race suffered a pile-up of cars that resulted in a gasoline fire and deaths.)Typically, a blend of 85 percent methanol and 15 percent gasoline (M85) is used in cars andlight trucks. Pure methanol can also be reformed in fuel cells into hydrogen, which is then usedto power electric vehicles. Methanol-powered vehicles have been found largely in the Westprimarily in California. They can also be seen in the fleets of the federal government and theNew York

STORAGE AND SAFETY

Because methanol is corrosive to some metals and damaging to rubber and someplastics, fuel storage tanks and dispensing equipment must be corrosion and damageresistant. California requires that underground storage tanks for methanol be double walled.Because methanol is water soluble, it could be quickly diluted in large bodies of water to levelsthat are safe for organisms. Environmental recovery rates for methanol spills are often fasterthan for petroleum spills. As with gasoline, methanol can be fatal when ingested. Inhalation offumes and direct contact with skin can also be harmful. Because pure methanol flames arenearly invisible in daylight, gasoline is added as a safety precaution to provide color to a flame

Added gasoline also serves to add a smell to this otherwise odorless liquid. Because of its highflash point, methanol is less volatile than gasoline. It burns more slowly and at a lowertemperature. Methanol is transported by barge, truck, or rail. In the event of an

EMISSIONS

The methanol molecule has a simple chemical structure, which leads to cleancombustion; reports from emissions studies, however, vary more widely for methanol than forother fuels probably because of differences among fuel blends used across the country andbecause vehicles may not be optimized for using methanol. Comparisons of M100 withgasoline and diesel have shown these results:

Carbon monoxide: Emissions vary sometimes lower, but are usually equal or slightlyhigher.

Ground-level-ozone-forming potential: 30 to 60 percent less. (In order to take advantage ofthis characteristic, vehicles must be properly adjusted.)

Nonmethane evaporative hydrocarbons: Usually less.

Toxics: M100 contains none of the carcinogenic ingredients such as benzene, 1,3-butadieneand acetaldehyde. M85 (with 15 percent gasoline) has 50 percent fewer toxic air pollutantsthan gasoline.


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Formaldehyde levels: Much higher, although still low. The toxicity of formaldehyde is lowerthan that of other toxics, and formaldehyde emissions can be reduced dramatically with newtechnology, such as improved catalytic converters.

Nitrogen oxides: Usually comparable or less.

Greenhouse gases: Comparable to gasoline.

Particulate matter: Buses using M100 emit significantly less than diesel-fueled buses.

Internal Combustion Engines Using Methanol

Several factors effect the use and selection of any fuel. Among the important ones areengine design, net energy per pound, net energy per gallon and the sulfur content ofalternative fuel properties.

a-Pure methane

b-Octane rating above 100 are correlated with given conc. Of tetra ethyl lead in 150 octane.c-Natural sulfur content very low but measurable.

content. A Btu defined as the amount of heat necessary to raise one pound of water, one-degree Fahrenheit.

At ambient temperature and atmospheric pressure, liquid methanol is basically similar togasoline or diesel fuel. Therefore methanol is easy to be stored and transported compared toCNG & LNG. These characteristics make the price of methanol vehicles and refueling stationlower than the price of CNG or LNG vehicles and refueling station. For a certain type,

methanol vehicle is offered at lower price than gasoline vehicles, for the purchase of certainNo. OF vehicles.

Present design internal combustion engines run on liquid fuels. Methanol required few of anyengine modification to extract the maximum power from this fuel. As compared to gasolinemethanol lowers some tailpipe emissions, namely the sulfur based HC, CO, as well as NO xMethanol contains only half the energy per gallon of gasoline but has a very high octane ratingIncreased compression ratios could yield 5-20 %. More power.

When methanol is used as a gasoline additive antiknock compound and fuel extender, itbecomes economical with very positive results especially from the emissions stand point. It

contains zero sulfur thereby reducing tailpipe acid significantly. Of the six most popularattractive fuels presently available methanol has the second lowest Btu/lb, net energy yield. Asa result, fuel tanks will need to be enlarged for vehicles that run on pure methanol.

1.5 A Historical Overview

In their embalming process, the ancient Egyptians used a mixture of substances, includingmethanol, which they obtained from the pyrolysis of wood. Pure methanol, however, was firstisolated in 1661 by Robert Boyle, who called it spirit of box , because he produced it via thedistillation of boxwood. It later became known as pyroxylic spirit . In 1834, the French chemists Jean


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Baptiste Dumas and Eugene Peligot determined its elemental composition. They also introduced theword methylene to organic chemistry, forming it from the Greek words methu, meaning "wine,"and hyle, meaning "wood". The term methyl was derived in about 1840 by back-formation frommethylene, and was then applied to describe methyl alcohol . This was shortened to methanoin 1892 by the International Conference on Chemical Nomenclature.

In 1923, the German chemist Matthias Pier , working for BASF developed a means to convert synthesisgas (a mixture of carbon monoxide and hydrogen derived from coke and used as the source ofhydrogen in synthetic ammonia production) into methanol. This process used a zinc chromate catalystand required extremely vigorous conditions pressures ranging from 30 100 MPa (3001000 atm), and temperatures of about 400 °C. Modern methanol production has been mademore efficient through the use of catalysts capable of operating at lower pressures.

.The first large scale commercial synthetic methanol process was introduced by BASF in 1923The process was based on the reaction of synthesis gas (a mixture of hydrogen and carbon

oxides) over a zinc chromite catalyst at relative high temp (300 to 400 Co) and high pressure(250-350 atm). The synthesis gas was derived from coal via the water gas reaction.The first synthetic methanol unit in the USA was located at Belle, West Virginia, at theammonia plant of Lazote, Inc, a subsidiary of Dupont and began operation in 1927. The unitwas actually installed to remove the 1 to 2 % carbon monoxide impurity in the ammoniasynthesis gas by utilizing the methanol synthesis reaction as purification step.

Up till the end of World War II, methanol was mainly produced as a co product using synthesisgas from coke via the water gas or blue gas reactions as well as using off-gases formfermentation, coke ovens and steel furnaces. These methanol units were relatively small (lessthan 200 thousand tons per year, most in the 30 to 90 thousand tons per year range).

One of the major technological changes often overlooked in the methanol industry wasconversion from water-gas to natural gas as a source of synthesis gas for feed to the methanolconverters. Natural gas derived synthesis gas was much higher quality , contained much lessimpurities and catalyst poisons , and was readily available in nearly unlimited quantity. 71% ofthe carbon monoxide uses for the synthesis of methanol was obtained form coke or coal ,where as by 1948 about 77% was derived from natural gas.

In 1966 , Imperial Chemical Industries (ICI) in England announced the second major breakthrough in methanol technology , the ICI low pressure process for synthesis of methanol usinga propri9etary copper based catalyst. The high activity copper based catalyst allowed themethanol synthesis reaction to proceed at commercially acceptable levels tat relatively lowtemp. (22-280 oC) thus allowing operation at significantly reduced pressure (50 atm) from thatneeded for the high pressure process (350 atm ).

A number of improvements have been made in these early methanol process, principally in thearea of improved energy efficiency. Subsequent low pressure process have revolutionized theindustry and have allowed for the construction of more energy efficient and cost effective plantNow a days, modern low pressure methanol units have a capacity of about 400-1000 thousandtons per year, operates at 50 to 100 atm.


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RAW MATERIALS

Long-term availability energy consumption and environmental aspects are all considered in

choosing a raw material, however financial consideration are of primary importance.Keeping above described factors in view, a fuel containing sufficient amount of hydrogen andcarbon monoxide is a possible raw material commonly known as synthesis gas for methanoproduction.Major resources from which synthesis gas be produced are1. Natural Gas2. Coal3. Naphtha4. Heavy hydrogen feed stock.Extraction of synthesis gas from these sources is further described here:

2.1 SYNTHESIS GAS FROM COAL:-

The production of gaseous fuel from coal has been practiced for 100 of years but most of theprocess for gasification was gradually replaced in the 1950s and 1960s by processes based onlow cost petroleum hydrocarbons. The oil shortage of the 1970 renewed a worldwide interest incoal as chemical feedstock. However, recent falling prices of oil in the world have moderatedthat short lived interest. During gasification, falling ground coal reacts with oxygen and steamat elevated temp. to form a synthesis gas comprised mainly of carbon monoxide andhydrogen, with lesser amount of carbon-dioxide, methane, nitrogen, argon, hydrogen sulphidetar and phenols. The quantities of the lesser components depend on the amount of impuritiesfound in the coal and in the amount of oxygen fed to the gasifier.

The heart of the coal based partially oxidation process in the gasification step. To achievemaximum efficiency, a gasifier should operate at an elevated pressure, have low oxygen andsteam demand, have high carbon conversions and have low heat losses. It is also desirable toachieve high reliability, to minimize or eliminate by-product formation and to accept a widevariety of coals. Low temperature gasifiers produce considerably more methane, oils, phenolsand tar than high temperature ones. A slagging gasifier operated at temperature above thefusion point so that ash is removed in the molten form; that temperature is typically b/w 2400-2700 oC.

Selecting the best gasifier for a particular operation is usually a matter of compromise, since

the designer must weigh many variables including the type of coal available, capacity, by-product rates, and capital investment efficiency and so on. Most gasifiers fall into one of threegeneral categories atmospheric or low pressure, high pressure and second generation.

2.2 The Koppers-Totzok (K-T):-

Gasifier is an atmospheric process with extensive commercial experience in Europe, Asia and South Africa. It will handle all coals; make virtually no by-products operate with highthermal efficiency and high conversion. However, there is an extra cost associated with this

financial consideration

gas ca onlow cost petroleum hydrocarbons.

a gasifier should operate at an elevated pressure,


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process (Low Pressure Process), because it operates at atmospheric pressure; the productsynthesis gas must be compressed before introduction to methanol synthesis loop. THEWINKLER GASIFIER is another low pressure process widely used in Europe, Japan andIndia. However, as a low-pressure process, it has the same advantages and disadvantages asthe K-T process

A high pressure process, the LURGIDRY ASH GASIFIER is the most widely used commerciaprocess. It has even more disadvantages than K-T process, forms numerous by-products, hasa limited ability to handle caking coals, and produces as large amount of methane (which mustbe purged from the converter loop, if the gas is used for the methanol synthesis).

2.3 The British Gas Council Lurgi (BGC-Lurgi):-

Gasifier is another high pressure process, more efficient than LURGI DRY ASH PROCESS.Due to reduced steam usage and higher capacity, however, it produces great amount of by-

products and has only a limited ability to handle caking coals.

The Texaco and Shell-Koppers:-

Gasifiers are two of the most promising second-generation process. Both offer many ofthe similar advantages as the atmospheric gasifiers, but both are high pressure operations,that accept all coals and make virtually no by- products.

A large number of purification steps are necessarily required to produce methanol synthesisgas from the crude product gas leaving the gasifier since the raw gases contain no largenumber of undesirable by-products.Some or all of the following process steps may be required. Cooling with steam generationwater washing, compression, sulfur removal, shift conversion of carbon monoxide and afterthat hydrogen and carbon dioxide removal.

KopperTotzek

Winkler Lurgi BGC Lurgi Taxaco ShellKopper

Pressure(atm) 1.4 1.4 2.1 20 -27 20 - 27 21 - 83 31Temp.(oC) 1500 930 540-590 480-540 1290 1480

OxygenReqd. High Medium Low Low High High

Steam Reqd. Low Medium High Low None LowCapacity(tons/day)

850 1000 500 1250 2000 1000

Raw Productgas analysis

Vol%

---- ---- ---- ---- ---- ----

Carbonmonoxide

58.1 35.0 24.6 60.6 46.3 67.7

Hydrogen 29.3 40.8 39.8 27.8 35 29.9Carbondioxide

11.0 22.0 24.6 2.6 17 1.1

Methane 0.1 1.2 8.7 7.6 0.2 0.2Hydrocarbon ---- Trace 1.1 0.4 ---- ----Inerts (N2, Ar) 1.5 1.0 1.2 1.0 1.5 1.1

Low Pressure Process),


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2.4 SYNTHESIS GAS FROM NAPHTHA

During the 1950s an oversupply situation in Europe made naphtha an economical feed stockfor steam reforming. A series of alkali promoted catalyst was developed specifically fornaphtha, and by the early 1960s many European procedures where preparing synthesis gasfrom light distillate naphtha. At the present time the price of the naphtha feedstock and mixingit with a hydrogen stream so that the combined stream contain approximately 5% hydrogenstream so that the combined stream contain nickel molybdate catalyst to convert organicsulfur compounds to hydrogen sulfide and also to saturate alkenes. Desulphurization is thenconducted as described above for hydrogenation.

The sulfur free gas is fed to a reformer which contains catalyst specially designed for naphthareforming. A stream to carbon ratio as lo as 2 is used, where pressure range from 1500-4000Kpa (200 to 575 Lb/in

2g). Small amount of carbon dioxide can be added optionally to yield

synthesis gas composition similar to those obtained via hydrocarbon reforming.

2.5 SYNTHESIS GAS FROM NATURAL GAS:-

The majority of methanol synthesis plants now use catalytic reforming of natural gas for theproduction of synthesis gas. The process consists of two steps Desulphurization and thesteam reforming section.

a) Desulphurization:- Natural gas contains both organic and inorganic sulfur compounds that

must be improved to protect the both reforming and down stream methanol synthesiscatalysts. They can position the catalyst even as low as 0.5 PPM. Hydrodesulphurizationacross a cobalt or nickel molybdenum zinc oxide fixed bed sequence is the basis for aneffective purification system.The temperature in the range of 340-370 0C may be necessary.

R-SH + H2 R.H + H2S

ZnO + H2S ZnS + H2O

Zinc oxide is capable to reduce the H2S concentration down to 0.3 PPM.The disadvantagesare that it is non-regenaratable must eventually be replaced. To have the advance warningbefore the ZnO bed is completely converted to ZnS at this point is provided at 755 of beddepth. When the ZnO changes to ZnS at this point, it is the time to renew the bed.Chloridesand mercury may also be found in natural gas, particularly from off shore reservoirs.Activatedalumina or carbon beds can remove these poisons.


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In a similar manner , increasing the partial pressure of the steam would result in a decrease inthe amount of methane in the product. A set of equations , which is used to calculate thecomposition of exit stream, is eq.(4),(5) and eq.(8).

Carbon composition via eq-8 can theoretically be prevented by ensuring that steam is present

in excess of some minimum amount calculated using the equilibrium equations. Any increasein steam also has the effect of increasing methane conversion. Most Commertial reformersoperate safely with steam carbon ratio in the range of 3 to 4.5.

Reforming catalysts contain from 12 to 25 % nickel as nickel oxide supported on calciumaluminate , alumina or calcium titanate .Alkali metal compounds added to prevent carbonformation and increase catalyst durability. The feed stream to the reformer is distributed overhundreds of parallel catalyst filled tubes, the tubes are subjected to a temperature range of 860to 950 oC, wit process gas exit temperature in the range of 750 to 850 oC & pressure rangefrom 4 to 35 atm (450 to 3550 Kpa). Gas hourly space velocities are usually on the order of5000 to 8000 based on wet feed.

The flue gases temperatures are in the range of 980 to 1040

o

C. These hot flue gases aretransferred to a convection section where they are cooled and used to super heat steam forprovide motive power for compressors and large pumps, process steam for reforminf andreboil duty for distillation.

2.6 SELECTION OF RAW MATERIAL

Natural gas is the only most convenient and economical raw material available in Pakistan.This God gifted treasure is found in large reserves at Sui, Mari and some other areas. Naturagas is easily available , cheap raw material , containing low impurities and there are notransportation and storage costs involved. Hence natural gas is the most economically suitable

raw material for synthesis gas.

Coal is another source for the Sun. gas production in Pakistan. Coal available in Pakistan atMAkerwal, Dhodak and Kalabagh but its quality is very poor. However , the largest reservoirsof coal in world now found in Pakistan at Thar. No doubt, these reservoirs contain smalamounts of sulfur about 0.1-0.7% but there are some other factors involved in degrading thecoal selectivity for Syn. Gas production , such as high transportation cost , handling andstorage cost , further more additional equipment (gasifier etc) and process costs. Coal containsmuch impurities and mineral materials (as compared to the natural gas) lead to the formationof the various pollutants during combustion having adverse environmental impacts whenemitted into the atmosphere. The environmental aspects that are associated with the use of

coal are, the formation of pollutants such as fly ash , sulfur oxides, nitrogen oxides and othermineral materials. Also coke formation occur and this is higher compared to the natural gasand this reduces the activity of catalyst and may stick to the walls of steam reformer whichreduce the heat transfer rate.

Naphtha is not economically viable for Syn gas production in Pakistan, its reservoirs are limitedin Pakistan and do not meet sufficiently the other demands (motor fuels). Its costs are toomuch as compared to the natural gas, hence it is not usable , same is the matter involved inselection of heavy hydrocarbons.


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Capacity Selection

As mentioned earlier that currently thee is no methanol producing plant inPakistan and all is being imported from other countries (see in table).Major exporters are Saudi

Arabia and Iran.

Methanol consumption in Pakistan is about 26800 tons / year (90 tons /day), report issued byFederal Bureau of Statistics 2004-2005. Lets take a look to the international market ; methanoproduction is going to increase and foreign methanol producers are extending their capacitiesin order to meet the growing demand (as shown in the tables, where world methanol plantscapacities supply /demand by the year 1998- 2007 are given , which contains the previous present and anticipated capacities and shows comprehensive increasing trend in demand)


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is a matter of greatconsideration for scientists.

As far as Pakistan is concerned , gasoline and diesel prices are high andunstable. CNG and LPG are used as alternative fuels but methanol is easy to be stored andtransported compared to CNG and LPG (it is a liquid fuel. These characteristics make the

prices of methanol vehicles and refueling stations cheaper than the price of CNG and LPGvehicles and refueling stations. These methanol based vehicles will be available by the year2005 in foreign markets and some major motor manufacturing companies may also invest inPakistan,

Raw material foe methanol synthesis (N.G) is cheaper here in Pakistan, which isal friendly. In

Pakistan , methanol is being employed in making urea formaldehyde , acetic acid andmethalated spirit for pharmaceutical and dyes etc. industries. Now a new formaldehyde plantis being installed by Dyno chemicals at Hub Industrial And Trading Estate. Super Chemicals(Karachi) , Wah Nobel Chemicals (Wah Cantt.) and Pakistan Resins (Azad Kashmir) are also

manufacturing urea formaldehyde.

As A result of this brief discussion , we may say that our capacity of 150 tons/day is reasonable , where 90 tons / day is present consumption in Pakistan and remaining 60tons/ day could be exported and If demand of Pakistani market increases , we may reduce orstop its export to fulfill out demand.

3.1 Methanol Imports In Pakistan

Countries 2002-2003 2003-2004 2004-2005

LTR Rs * 10 LTR Rs * 10 LTR Rs * 10

AsianCountries NS

18000 336 26800 610 - -

Bangladesh - - 200000 2700 - -

China - - 132040 5217 - -

Dubai - - 450000 5434 2309723 23752

Germany 210000 2140 9751 534 58612 2478

Indonesia - - 26080 647 - -

Iran - - 101570 1662 4099556 41170Kuwait - - 100000 2892 - -

Laos 13040 200 - - - -

Malaysia 373651 3094 13040 328 114338 1934

Natherland 690180 10042 281600 11671 101100 4481

New Zealand - - 13040 249 - -

Saudi Arabia 254266 213426 31965758 394528 27093185 298683

Singapore - - 440000 11410 13040 273


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South AfricaRep

14768 148 - - 104 40

Spain - - - - 79200 1024

Turke 25600 386 - - - -

Thailand - - - - 200000 2033

U.S.A 424633 2863 - - - -

U.K - - 3000 145 - -

Total (LTR) 27196520 232635 33762679 438026 34068859 375831

Tons 26800 36559 43800


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4.1 Methanol Manufacturing Process

The Methanol Industry in Trinidad began with the construction of a 1,200 MT state-owned

the industry has expanded to include four larger plants with an annual production capability

close to 3 million MT of methanol.

At the MHTL Point Lisas Methanol Complex, methanol is made using the ICI Low PressureMethanol Synthesis Process. The two main raw materials used are natural gas (96% methane)received from the National Gas Company (NGC) to provide the carbon and hydrogencomponents and water from the Water and Sewerage Authority (WASA) to provide the oxygencomponent. These raw materials undergo a series of chemical reactions to produce crudemethanol which is then purified to yield refined methanol, having a purity exceeding 99.9%.

The plants operate continuously 24 hours a day in a production process that can be dividedinto four main stages: Feed Purification, Reforming, Methanol Synthesis and Methanol

Purification as shown in the flow sheet below:

STEP1 FEED PURIFICATION

The two main feed stocks, natural gas and water, both require purification before useNatural Gas contains low levels of sulphur compounds and undergo a desulphurizationprocess to reduce, the sulphur to levels of less than one part per million. Impurities in the waterare reduced to undetectable or parts per billion levels before being converted to steam andadded to the process. If not removed, these impurities can result in reduced heat efficiencyand significant damage to major pieces of equipment.

Feed Purification, Reforming, Methanol Synthesis and Methano

Purification

the sulphur to levels of less than one part per million

eat efficiencyand significant damage to major pieces of equipment.


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STEP 2: REFORMING

Reforming is the process which transforms the methane (CH4) and the steam (H2O) tointermediate reactants of hydrogen (H2), carbon dioxide (CO2), carbon monoxide (CO). Carbon

dioxide is also added to the feed gas stream at this stage to produce a mixture of componentsin the ideal ratio to efficiently produce methanol. This process is carried out in a Reformerfurnace which is heated by burning natural gas as fuel.

STEP 3 : METHANOL SYNTHESIS

After removing excess heto the methanol production stage in the synthesis reactor. Here the reactants are converted tomethanol and separated out as as crude product with a composition of methanol (68%) andwater (31%). Traces of byproducts are also formed. Methanol conversion is at a rate of 5% perpass hence there is a continual recycling of the unreacted gases in the synthesis loop.

This continual recycling of the synthesis gas however results in a build-up of inert gases in thesystem and this is continuously purged and sent to the the reformer where it is burnt as fuel.The crude methanol formed is condensed and sent to the methanol purification step which isthe final step in the process.

STEP 4 : METHANOL PURIFICATION

The 68% methanol solution is purified in two distinct steps in tall distillation columns called thetopping column and refining column to yield a refined product with a purity of 99% methanoclassified as Grade AA refined methanol.The methanol process is tested at various stages andthe finished product is stored in a large secured tankage area off the plant until such time thatit is ready to be delivered to customers. Since

4.2 Methanol Process Description

The Leading Concept Methanol process in use at the Coogee Methanol Plant has variousadvantages compared to the conventional methanol processes. Some of those advantages arethat it is efficient and compact and substantially reduces waste through the internal recycling ofprocess effluents.

Reforming is the process which transforms the methane ( CH4 and the steam ( H2O) tointermediate reactants of hydrogen ( H , carbon dioxide ( CO , carbon monoxide (CO). Carbon

dioxide

furnace


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Natural gas feedstock is delivered to the plant via a pipeline from the main Sui to plant locationcarrying Bass Strait gas. The gas is first compressed and then purified by removing sulphurcompounds. The purified natural gas is saturated with heated and recycled process wastewater. The mixed natural gas and water vapour then goes to the gas heated reformer to bepartially converted to synthesis gas, a mixture of carbon dioxide, carbon monoxide and

hydrogen. This partially converted gas is then completely converted to synthesis gas byreaction with oxygen in the secondary reformer.

The synthesis gas is then converted to crude methanol in the catalytic synthesis converter.The crude methanol is purified to standard quality specifications by removing water andorganic impurities through distillation. The water and organic impurities are recycled.

Process Description

The Coogee Energy plant is designed to produce 164 tones per day of methanol from about 5TJ/day of Bass Strait natural gas.

The plant consists of four main process steps : feed gas preparation, synthesis gas generation,methanol synthesis and distillation supported by utilities and offsite units.

Feedgas Preparation

Natural gas is compressed to about 45 bar and sulphur removed by hyrodesulphurisation inthe purifier. The desulphurising gas is cooled and flows to the saturator where it contacts withhot water over a bed of packing. The saturated gas leaving the vessel contains about 92% ofthe steam required for reforming. Saturator make up is 90% process condensate and thebalance refining column bottoms water. Prior to leaving the saturator the gas stream is

contacted with recycled fusel oil where waste products from methanol synthesis are strippedoff. A blow down stream is required to control dissolved solids. Additional steam generated inthe boiler is made up to the gas stream to achieve 3.0:1 steam to carbon ratio for reforming.

The total feed stream is then heated in the gas heated reformer preheated. Both the preheatedand boiler are fired with a mixture of synthesis loop purge gas and natural gas.

4.3 Synthesis Gas Generation

Reactions

There are three main chemical reactions which occur in this process step :

Steam reforming-

CH4 + H2O = CO + 3H2

Shift reaction - CO + H2O = CO2 + H2


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The net effect of these reactions is the production of a synthesis gas stream which iscomposed of carbon monoxide (CO), carbon dioxide (CO2) and hydrogen (H2).

Description

Preheated gas flows from the preheater to the tube side of the advanced gas heated reformer(AGHR). The feedstock is heated from the feed temperature of 425° C as it passed downthrough the catalyst and the reforming reactions start. The AGHR contains 19 reforming tubeswhich contain the reforming catalyst.

Hot reformed gas exits the bottom of the reforming tubes and flows to the tube side exit of the AGHR at about 700°C. The heat required for the endothermic reforming reaction is derivedfrom cooling the secondary reformer effluent in the shell side of the AGHR. About one quarterof the methane is reformed in the AGHR.

The partly formed gas flows from the AGHR to the combustor/secondary reformer where the

bulk of the reforming takes place. The heat required for the endothermic reforming in both the AGHR and secondary reformer is provided by partially burning the AGHR effluent with pureoxygen in the combustor located integrally at the top of the secondary reformer. Oxygen isinjected into the gas via a specially designed gun. About 0.50 tonne of oxygen per tonne ofmethanol is required.

The oxygen is completely consumed and the resulting hot gas stream passes over thesecondary reforming catalyst. Reforming reactions continue and the gas leaves the secondaryreformer at up to 1000°C with less than 0.5% methane slip. The secondary effluent passes tothe AGHR shell and thence through the heat recovery train to provide heat for the saturatorcircuit and distillation reboilers. The process condensate which condenses out of the reformed

gas is recycled back to the saturator. After heat recovery the reformed gas is finally cooled andthen compressed to about 70 bar g in the synthesis gas compressor to be fed as synthesis gasto the synthesis loop.

Bass Strait natural gas contains about 93.6 mol% of methane, 3.5 mol% of ethane with thebalance being predominantly propane, nitrogen and carbon dioxide. On an offshore facility withless sophisticated gas separation facilities there may be higher levels of higher hydrocarbonssuch as components but the oxygen consumption would increase.

The synthesis gas joins the synthesis loop recycle gas from the circulator to pass through theloop interchanger and be fed to the methanol converter at about 130° C. The converter is a

tubular cooled converter design where the gas is preheated to reaction temperatures inside thetubes as it flows up through the hot catalyst bed. This type of converter maximizes catalystefficiency as it enables a temperature profile to be maintained inside the converter that is closeto the maximum reaction rate curve. The hot reacted gas leaves the converter and providesheat to the saturator water circuit and the loop interchanger before finally being cooled. Crudemethanol is separated from the uncondensed gases in the loop catch pot and the gasesrecirculated back to the converter via the circulator.


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Distillation

Crude methanol from the loop catch pot is filtered to remove traces of wax, let down inpressure and fed to the product purification section. This section consists of a topping column

and a refining column. Unlike most methanol distillation columns these columns are packedwith structured packing. Reboiler duty is provided by reformed gas. The product methanospecification is for a water content of less that 0.10 wt %. The water bottoms from the refiningcolumn has a specification of less than 100 ppm of methanol and is recycled back to thesaturator. Other synthesis byproducts such as higher alcohols are collected as fusel oil andrecycled back the saturator.

4.4 LCM -The Low Cost Methanol Technology

Introduction

The emphasis on reducing the cost of production of methanol is nothing new. Aside from ashort period after the invention and commercial introduction of the Low Pressure MethanoProcess by ICI in the mid-1960s, that pressure has always been present. ICI itself was nostranger to this as many of its older businesses were in commodity products whose profitabilityrelied critically on minimizing the cost of production in order to maintain acceptable marginsHowever, cost of production is not just a case of reducing capital cost, although undoubtedlythis is an important part of the total picture. Often the installed cost of the plant appears to begiven greater weighting than is justified from a simple economic assessment. It isunderstandable, though, that at the time of selection of the technology vendor, everyone'smind tends to be focused on the need to raise the money, and fixed and variable costs ofoperation can recede into the distance.

Methanex and Synetix have been working together for some time to identify the optimum routefor syngas generation for the manufacture of methanol and other GTL products. Many optionswere investigated, but it was determined that the Synetix Syngas Generation (SGG) processoffered the most economic route and the methanol process based on SGG, the LCM Process,was the most attractive option at high capacities.

Historical Perspective

It was against a background of intense competitive pressure on its Fertilizer Business that IC

mandated its Catalyst and Technology Licensing Department (now a part of Synetix) todevelop a compact reforming process to revolutionize the manufacture of ammonia. In many


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ways, the process that was developed, LCA, was revolutionary and ahead of its time, but thefundamental principles behind the project were similar to those operators need to adopt toprosper in today's highly competitive methanol industry.The legacy of ICI's commitment inbuilding the LCA plants at its Severnside Works in the late

1980s is that the Synetix Gas Heated Reformer (GHR) can no longer be thought of as newtechnology. It is well-proven now, with over 30 operating years experience spread over the 4plants that have been built around the technology. These plants are:

Absolutely key to the successful operation of these units has been the adoption of the correcmetallurgy to withstand the conditions within the reformer. There can be no doubt whatsoever,that metal dusting has been overcome as an issue within the range of operating conditions ofthese plants. However, without detracting from the importance of the metallurgy, it is themechanical design of the reformer that turns concept into reality. With the introduction of the

Advanced Gas Heated Reformer (AGHR) into the Coogee Energy MRP in April 1998, Synetixincorporated a number of novel features that significantly simplified the compact reformer interms of design,construction, maintenance and operation.

Key Success Factors

Clearly, many factors are important to an operator/investor in making a project successful. Anumber of these factors is listed below.

Selling price

Financing costs

Gas price

Import tariffs

Delivery costs

Maintenance costsManpower costs

Plant installed cost

Plant efficiency

Plant reliability

Items 1-3 are commercial issues over which the operating company has varying degrees ofinfluence. Items 4 and 5 will be very location specific, with the latter being a key factor asmethanol is transported from more remote locations to the consuming markets. Items 6-10 areinfluenced by location, but it is in these aspects that choice of technology and the standard ofengineering design can have a major impact. The focus of the rest of the paper will be mainly

on these areas.

Compact Reforming

The term "Compact Reforming" implies that the main aim of the new technology is to reducethe size. This was indeed a consideration, and it may be the only benefit offered by certaintypes of compact reforming device. However, when Synetix was developing the syngasprocess for the new ammonia plants for ICI, there was a much broader goal, which includedthe complete elimination of steam generation and the steam system. This required a complete


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METHANOL SYNTHESIS

The heart of any Methanol synthesis process is Methanol converter. The converter containsthe catalyst over which synthesis gas is converted to methanol. The main difference betweencompeting methanol process today lies in the converter and its method of temperature control

and heat recovery.

5.1 TYPES OF CONVERTER:-

The four basic types of converters are

Quench ConverterMultiple Adiabatic ConverterTube-cooled ConverterSteam Raising Converter

1. QUENCH CONVERTER:-

The quench converter was the basis for the initial ICI low pressure methanoprocess. Quench type converters used multiple catalyst beds, typically contain three to sixcatalyst beds. Bed volumes are sized to help control the exothermic methanol synthesisreaction. Additionally, cool feed gas is injected between beds to control or quench catalyst bedinlet temperature. Reaction heat is recovered through added heat recovery exchangers locateddownstream of the converter.

2. MULTIPLE ADIABATIC CONVERTER:-

The adiabatic converter system employs heat exchanger rather than quench gas forintroduce cooling. Because the beds are adiabatic, temperature profile exhibits still the samesaw tooth approach to maximum reaction rate, but catalyst productivity is somewhat improvedbecause all of the gas passes through the entire catalyst volume. Costs for vessels andexchangers are generally higher than for quench converter system.

3. TUBE-COOLED CONVERTER:-

The tube cooled converter functions as interchanger, consisting of a tube filled vessecontaining catalyst on the shell side. The combined synthesis and recycle gas enters the

bottom of the reactor tubes, where it is heated by reaction taking place in the surroundingcatalyst bed. The gas turns at the top of the tubes and passes down through the catalyst bed.The principle advantage of this reactor is in the reduced catalyst volume, since the reductionpath move closely follows the maximum rate line.Converter performance can further be enhanced by extending the catalyst below the tubecooled area to act as a further adiabatic reaction zone.

Quench Converter Multiple Adiabatic Converter

u e coo e onver er Steam Raising Converter

low pressurethree to six

heat exchanger


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4. STEAM RAISING CONVERTER:-

There are varieties of tubular steam raising converters available, which feature radiaor axial flow, with the catalyst on either shell or tube side. The near isotherm reaction of thisrector type is the most thermodynamically efficient of the types used, requiring the least

catalyst volume, lower catalyst peak temperatures also results in reduced by-product formationand longer catalyst life.


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Low pressure drop, both in converter and heat exchanger equipment, to minimizerecycle compression energy.High conversion per pass that reduces required cycle, minimizes synthesis loop capitalcost & maximizes reaction heat recovery.Efficient recovery of exothermic reaction heat of methanol synthesis.

Corrosion resistance to formation of iron carbonyls that can poison the catalyst andpromote formation of undesirable hydrocarbon by-products. A high yielding, commercially proven, long life synthesis catalyst to minimize costlycatalyst replacement.Low capital cost.Good economy of scale, high capacity single train converter.

5.2 METHANOL SYNTHESIS TECHNOLOGY TODAY

Different companies have been involved in practicing their technologies for methanolsynthesis. But the question is which company offers the most dependable and economically

viable process.This is visualized by the percentages obtained by evaluating their practical applications asshown below:

Company Name Production Rate

Imperial Chemical Industry (ICI) 61%

LURGI CORP. 27%

Mitsubishi Gas Chemicals (MGS) 8%

KELLOGG 3%

5.3 ICI LOW PRESSURE METHANOL PROCESS

successfully overcome by the ICI 50atm process.

Methanol was first synthesized commercially at low pressure when ICI commissioned its 300-tons/dayplant at Birmingham in December, 1966. a copper based catalyst, more active andselective was used. The greater activity of this catalyst permits the synthesis of methanol from

gaseous mixture of hydrogen and carbon dioxide at much lower pressure and temperature ofthe order of 50 atm and 250 oC respectively. Several innovatory features were incorporated inthe design. They include a new simple type of quench bed converters, larger in diameter thenconventional converters and easy catalyst charging and discharging procedure. The use ofrotary machine of synthesis gas compression which was significant, because it demonstratedthe concept of single stream unit, well known in large scale ammonia plant, was now apractical proposition for small methanol production units.


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In 1972 ICI commissioned a 1100 tons/day plant based on their latest technology. It operatesat 100 atm and uses a modified version of original low-pressure methanol synthesis catalystFor capacity greater than 500 tons/day, the 100 atm process plants are adopted, whereas forsmaller plants of outputs from 150-500 tons/day, the 50 atm process is used.

5.4 LURGI LOW PRESSURE METHANOL PROCESS

At the end of fifties, Lurgi began development of a low pressure methanol process, usinghighly active copper catalyst at 50 atm pressure. At that time, the space time yield and catalystlife was not satisfactory (Sulfur Poisoning) which resulted in the suspension of furtherdevelopment work.


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In 1964 research work was resumed. At that time the purification of synthesis gas (Using LurgRectisol (50 atm process) was no longer a problem. Several years of development workrequired in selecting from numerousexperience in Fisher Tropsch synthesis reactor, the methanol reactor was based on a designworked out of Fisher Tropsch Synthesis.

This reactor is similar to a verticaland tube heat exchanger andwas a promising solution, to bothreactor design and heat recoveryproblem. The tubes closed attheir lower end by the hinged gridwith boiling water, maintaining asubstantially uniform catalysttemperature over the reactorcross section and over the full

length of the tubes.Early 1970 Lurgi decided to buildits own methanol plant with asmall capacity to serve mainly fordemonstration purposes and alsoto study the problems whichmight come up in the large scaleplants. The first commercial plantwith a capacity of 4000 tones/yrwas built at wesseting (WestGermany) in April, 1971. This plant was built in two days, was designed on the basis of acomputer programme.

5.5 ADVANTAGES OF THE LOW PRESSURE METHANOL PROCESS

Reduced by-product formation resulting in lower feed stock consumption per ton ofmethanol.Reduced compression cost due to lower operating pressure.The ability to use steam directory compressors on small plants.Lower steam pressure through out the plant.The avoidance of CO2 addition in natural gas based plant without incurring largefinancial penalties.

Simplicity in design and low-pressure equipment, suitable for large and small plant.Commissioning period.Proved in wide practical services.

PROCESS SELECTION

In 1966, an Imperial Chemical Industry (ICI) is the first, which announced the lowpressure process for synthesis of methanol using proprietary copper based catalyst.


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pressure processes and proprietary copper-based catalyst; these companies included Lurgi,Mitsubishi etc.Today two processes are mostly used.

1) ICI low pressure (61%)2) Lurgi low pressure process (27%)

ICI process used Cu-Zn-Al catalyst while Lurgi process used CU-Zn-V or Cu-Mn-V catalystBesides the catalyst, these processes differ in their method of temperature control and heatrecovery.

ICI use quench type adiabatic converter with multiple catalytic beds. Bed volumes are sized tohelp control the exothermic methanol synthesis reaction. Additionally, cool feed gas is injectedbetween beds to control or quench catalyst bed inlet temperature. Reaction heat is typicallyrecovered through added heat recovery exchangers located downstream of the converter.

Whereas Lurgi used shell and tube (Isothermal type) converter with boiling water fortemperature controls. Overall results of quench type converter is best than other type ofconverter.

The main drawback of water cooled tubular (Isothermal) converter is that internal tube sheetshave failed in some tubular isothermal methanol converter design. The long down timesassociated with a catastrophic converter failure could financially devastate most procedures. Inaddition converter internal baffles, expansion joints, gas distributors and internal exchangerscan fail and cause internal leaks. These components should be extremely rugged to withstandthe operating abuse imposed by actual commercial operation.Cost is another major factor for the selection of process. ICI process has low cost as compareto the other processes. Therefore the ICI process is also called ICI LCM (Low Cost Methanol)

factor we select the ICI LCM process.


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6.1 DESULPHERIZER CATALYST

Hydrocarbon feeds for steam reforming must have a very low sulfur contents, since nickelreforming catalysts are quite susceptible to poisonings even by levels as low as 0.5PPM. Inmany cases, sulfur can be removed b y adsorption over a bed of activated carbon at 15-50

0C

Frequent regeneration may be necessary; which can be accomplished by heating the bed andfor stripping it with steam or hot gases. The activated carbon bed adsorbs high boiling sulfurcompounds such as mercaptans, much more rapidly than low boiling compounds such as H 2S.As a result, adsorption over a sacrificial guard bed of zinc oxide at temperature in the range of340-370 0C. Hydrodesulphurization may be necessary for organic sulfur compounds that arenot removed by either zinc oxide or carbon bed. This is accomplished by mixing the sulfurcontaining steam with hydrogen, so that the hydrogen contents are approximately 5%, theresulting mixture is passed over a bed of cobalt or nickel molybdate catalyst at temperature of290-370

oC. Under these conditions, sulfur compounds are conditions, sulfur compounds are

converted to hydrogen sulfide, which can be removed in a zinc oxide bed. Now a days, codesare used to represent the catalysts shown here: The KATALCO range of absorbents and

hydrogenation catalysts ensures an optimized system for meeting individual plantrequirements.Sulfur Removal Catalysts Hydrodesulphurization Catalyst.KATALCO32-4 KATALCO 41-6

KATALCO 61-1PURASPEC 2570

These catalysts are used by ICI.

6.2 STEAM REFORMING CATALYST

Reforming catalyst usually contain from 12-25% nickel oxide supported on calcium aluminate

titanate. Calcium aluminate has generally replaced calcium aluminum silicate, has supportmaterial to avoid the problem of silica migration encountered in earlier catalyst formulation.

Alkali metal compounds added to prevent carbon formation and to increase catalyst durabilityinclude potassium aluminum silicate, potassium carbonate and potassium poly aluminatesulfur chlorine and arsenic compounds. Poison the catalyst, sulfur poisoning is reversible, butchlorine and arsenic poisonings are severe and generally irreversible.Synetix has been associated with pre-kvaerner process technology recently launched the new CRGLH series of catalysts. Thesehave been demonstrated to be the most active and robust commercially available product forthis application.

KATALCO 25-4 KATALCO 57-4 KATALCO 23-4

KATALCO 46-Serie KATALCO 23-4Q KATALCO 25-4Q


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6.3 METHANOL SYNTHESIS CATALYST

High Pressure Catalyst

Zinc Chromite catalyst, reduced zinc oxide promoted with Chromia was the catalyst used in the1

st

The zinc Chromite catalyst with improvements over the years was only the catalyst ofconsequence used for the high process methanol process, up until the high pressure process

Although BASF is credited with a 1st commercial methanol process generally attributed to GTART in FRANCE in 1921. He defined his methanol catalyst has being all metal, oxides andsalt active in hydrogenation. Small unit was built near Paris to test catalyst for PARTARTSprocess and began operation in 1923. The unit was designed to operate at 150-200 atmpressure. 300-6000C, with hydrogen to carbon monoxide feed gas ratio of 2:1.The BASF high pressure methanol process was operated at 250-350

0 C, similar to the

conditions purposed by PARTART. Now low pressure, process commonly called ICI lowpressure process is used because of its practical feasibility.

6.4 LOW PRESSURE CATALYST

Early in the developing methanol industry, it was recognized that to significantly improve thehigh pressure methanol process, a much more active catalyst than zinc chromite was needed.

A more active catalyst would permit operation at lower temperatures and pressures, yet stilallow acceptable production rates to be mentioned. Copper based catalysts known from the

known to be much more susceptible to poisoning by sulfur, chlorine, etc. than zinc Chromite,Zinc Chromite, for example, could tolerate sulfur levels of more than PPM in the feed gas,whereas for copper based catalysts, sulfur must be kept below 1 PPM. Generally poor qualityof synthesis gas and the limited purification techniques available at that time resulted in anunacceptably short operating life for the copper based, catalysts and precluded theircommercial use.

A second breakthrough in the methanol technology occurred in 1966 with the introduction o-pressure process for the production of methanol. This was made possible by a major

improvement in synthesis gas quality from the introduction of hydrocarbon steam reformingand improved purification techniques for the hydrocarbon feed stock. The synthesis gas fromsteam reforming contained only trace quantities of impurities and proved ideal for methanol

synthesis with a copper catalyst. The ICI process, using a much more active copper basedcatalyst could operate efficiently at 50 atm pressure and at temp. of 220-280oC.The copper based catalyst developed by ICI was also more selective than the high pressurezinc chromite catalyst and operated at a much lower temp. Consequently, it produced asignificantly lower of impurities than zinc Chromite as shown in following table.


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LEVEL OF IMPURITES PRODUCED BY MS CATALYSTS

Impurity ZnO/Cr 2O3 catalyst Cu/ZnO catalyst

Dimethyl ether 5000-10000ppm 20-150ppm

Carbonyl compds 80-220ppm 10-35ppm

Higher alcohols 3000-5000ppm 100-2000ppm

Methane Variable None

6.5 SOME OTHER SALIENT FEATURES

Copper based catalyst produced no methane.

The possibility of a highly exothermic runaway methanation reaction leading to catalystsintering and possible converter damage was a continual threat in the high pressure processThis improvement is selectivity for the copper based catalyst over zinc Chromite was estimatedto reduce feed stock requirements from 5-10% for the equivalent amount of methanoproduced.Hence ICI methanol catalysts were both active and long lived and generally considered abenchmark in industry and represented a significant achievement in heterogeneous catalysisCatalysts used by ICI in methanol synthesis in accordance with SYNETIX are:-

KATALCO 51-8 PPT for ARC-Reactors.KATALCO 51-8 PPT for Tubular and quench type reactors.

6.6 RECENT CATALYST DEVELOPMENTS

followed with their own alternative low-press. Methanol processes and catalystsCompanies that currently have both a methanol process and catalysts, include ICILurgi, Haldor Topsoe, BASF, Ammonia Casale and Mitsubishi Gas Chemical.

A patent survey of representative copper based methanol catalysts is shows infollowing table.

Company Catalystsystem

Typaical atomicratio

Ammonia casale Cu-Zn-Al-Cr 29:47:6:18

BASF Cu-Zn-AlCu-Zn-Al-Cr-Mn

32:42:3638:38:0.4:12:12

DUPONT Cu-Zn-Al 50:19:31

HALDOR TOPSOPE Cu-Zn- Cr 37:15:48

ICI Cu-Zn-AlCu-Zn-Al

61:30:964:23:13


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LURGI Cu-Zn-VCu-Mn-V

61:30:948:30:22

MITSUBISHI GASCHEMICAL

Cu-Zn-MPCu-Zn- CrCu-Zn-B

55:43:255:43:261:38:1

SHELL Cu-Zn-AgCu-Zn-Re

61:24:1571:24:5

UNITED CATALYSTS Cu-Zn-Al 62:21:17

6.7 CURRENT CATALYST COMPOSITION

All commercial low-pressure methanol catalyst contains copper and zinc oxides together withone or more additional promoters, usually aluminum or chromium oxide. ICI, for example,reports a standard industrial catalyst to contain copper oxide, zinc oxide and Alumina in a ratioof 60:30:10, respectively.


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Calculation of W:-

Water in W = Water in A4 - Water in A= 33.48 tons

CH3COOH in W = CH3COOH in A4 = CH3COOH in M= 0.557 tons

C2H5OH in W = C2H5OH in A4 = 0.561 tons

C3H7OH in W = C3H7OH in A4 = 0.374 tons

C5H11OH in W = C5H11OH in A4

= 0.374 tons

So, W = 35.35 tons

Now,% of H2O = 94.71 %

% of CH3COOH = 1.57 %

% of C2H5OH = 1.58 %

% of C3H7OH = 1.05 %

% of C5H11OH = 1.05 %

Calculation of L:-

HCHO in L = HCHO in A4 - HCHO in A= 0.744 tons

CO2 in L = CO2 in A4 = 0.374 tons

CH3OCH3 in L = CH3OCH3 in A4 = 0.748 tons

Total L = 1.86 tons

% of HCHO = 39.85 %

% of CO2 = 20.04 %

% of CH3OCH3 = 40.09 %


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N2 Balance:-

0.13% A1 = 3% A7

A1 = 2307.69% A7 (2)

Putting Eq (2) in (1),

535.15% A7 = 22% A7 + 201.235

513.15% A7 = 201.23

A7 = 39.21 K.Mol /hrSo,

H2 in A7 = 29.41 K.Mol /hrCO in A7 = 5.09 K.Mol /hrCO2 in A7 = 3.52 K.Mol /hrN2 in A7 = 1.17 K.Mol /hr

So Eq(2) becomes,

A1 = 904.96 K.Mol /hrNow,

H2 in A1 = 693.93 K.Mol /hrCO in A1 = 124.70 K.Mol /hrCO2 in A1 = 85.15 K.Mol /hrN2 in A1 = 1.176 K.Mol /hr

Reactor:-

Now suppose, 50% conversion of CO & CO2 per pass

50% * {( 124.70 + 13% * A6 ) + ( 85.15 + 9% * A6)} = 195.0

50% * {( 209.86 + 22% * A6 )} = 195.0

209.86 + 22% * A6 = 390.03

22% * A6 = 180.17

A6 = 818.98 K.Mol /hr

So,H2 in A6 = 614.23 K.Mol /hrCO in A6 = 106.46 K.Mol /hrCO2 in A6 = 73.70 K.Mol /hrN2 in A6 = 24.56 K.Mol /hr

Balance at point M:-

A= = A1 + A6


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A2 = 1723.95 K.Mol /hr

Balance at point B:- A5 = A6 + A7

A5 = 858.20 K.Mol /hr

Balance Around the Separator:-

A3 = A4 + A5

A3 = 1134.63 K.Mol /hr

Balance Around the Separator1:-

D2

A1 = 904.96 K.Mol /hr

H2 76.68% Mol %H2 57.42% By vol CO 13.78% Mol %CO 10.32% By vol CO2 9.41% Mol %CO2 7.04% By vol N2 0.13% Mol %N2 0.10% By vol W1H2O 25.11% By vol H2O 100%

Overall Balance:-D2 = W1 + A1 D2 = W1 + 904.96 (3)

H2O Balance:-

25.11% * D2 = W1 (4)

Putting (4) in (3),D2 = 25.11% * D2 + 904.96

74.89% * D2 = 904.96D2 = 1208.39 K.Mol /hr

So,H2 in D2 = 693.86 K.Mol /hrCO in D2 = 124.70 K.Mol /hrCO

2 in D

2 = 85.07 K.Mol /hr

N2 in D2 = 1.18 K.Mol /hrH2O in D2 = 303.4 K.Mol /hr

Now putting value of D2 in Eq(4) , we get,

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