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CHAPTER I

INTRODUCTION

1.1 HISTORY:

Ethylene Glycol (1, 2 – ethanediol), HOCH2CH2OH usually called glycol is the

simplest Diol. Diethylene glycol and Triethylene glycol are Oligomers of Mono ethylene glycol.

Ethylene glycol was first prepared by Wurtz in 1859; treatment of 1,2 dibromoethane with silver acetate yielding ethylene glycol diacetate via saponification with potassium hydroxide and in 1860 from the hydration of ethylene oxide. There to have been no commercial manufacture or application of ethylene glycol prior to World War-I when it was synthesized from ethylene dichloride in Germany and used as substituted for glycerol in the explosives industry and was first used industrially in place of glycerol during World War I as an intermediate for explosives (ethylene glycol dinitrate) but has since developed into a major industrial product.

The use of ethylene glycol as an antifreeze for water in automobile cooling systems was patented in the United States in 1917, but this commercial application did not start until the late 1920s. The first inhibited glycol antifreeze was put on the market in 1930 by National Carbon Co. (Now Union Carbide Corp.) under the brand name “prestone”.

Carbide continued to be essentially the sole supplier until the late 1930s. In 1940 DuPont started up an ethylene glycol plant in Belle, West Virginia based on its new formaldehyde methanol process. In 1937 Carbide started up the first plant based on Lefort’s process for vapor phase oxidation of ethylene oxide.

The worldwide capacity for production of Ethylene Glycol via hydrolysis of ethylene oxide is estimated to be 7×106 ton/annum [1, 2].

1.2 CHEMISTRY:

Compound contains more than one –oly group is called Polyhydric Alcohol (Dihydric alcohol) or polyols (Diols). Diols are commonly known as Glycols, since they have a sweet taste (Greek, glycys= Sweet).

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Dihydric alcohols because compounds contain two –OH groups on one carbon are seldom encountered. This is because they are unstable and undergo spontaneous decomposition to give corresponding carbonyl compound and water.

Figure-1[10]

According to IUPAC system of nomenclature, IUPAC name of glycol is obtained by adding suffix Diol to the name of parent alkanes.

HO OH H H H H

H--C---C--H HO--C---C--OH H--C---C--H

H H H H HO OH

1, 2 Glycol 1, 3 Glycol 1, 4 Glycol

(α- Glycol) (β- Glycol) (γ- Glycol)

Glycols are Diols. Compounds containing two hydroxyl groups attached to separate carbon in an aliphatic chain. Although glycols may contain heteroatom can be represented by the general formula C2nH4nOn-1(OH) 2. [3, 4]

Formula Common name IUPAC name

CH2OHCH2OH Ethylene Glycol Ethane-1, 2-Diol

1.3 USES:

The following is a summary of the major uses of ethylene glycol:

1.3.1 Antifreeze

A major use of ethylene glycol is as antifreeze for internal combustion engines. Solutions containing ethylene glycol have excellent heat transfer properties and higher boiling points than pure water. Accordingly, there is an increasing tendency to use glycol solutions as a year-round coolant. Ethylene glycol solutions are

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also used as industrial heat transfer agents.

 Mixtures of ethylene glycol and propylene glycol are used for defrosting and de-icing aircraft and preventing the formation of frost and ice on wings and fuselages of aircraft while on the ground. Ethylene glycol-based formulations are also used to de-ice airport runways and taxiways as de-icing agent.

 Asphalt-emulsion paints are protected by the addition of ethylene glycol against freezing, which would break the emulsion. Carbon dioxide pressurized fire extinguishers and sprinkler systems often contain ethylene glycol to prevent freezing.

1.3.2 Explosives

 Ordinary dynamite will freeze at low temperatures and cannot then be detonated. Ethylene glycol dinitrate, which is an explosive itself, is mixed with dynamite to depress its freezing point and make it safer to handle in cold weather.  Mixtures of glycerol and ethylene glycol are nitrated in the presence of

sulfuric acid to form solutions of nitroglycerin in ethylene glycol dinitrate, which are added to dynamite in amounts ranging from 25 to 50%.

1.3.3 Polyester Fibers

 The use of ethylene glycol for fibers is becoming the most important consumer of glycol worldwide. These fibers, marketed commercially under various trade names like Dacron, Fortel, Kodel, Terylene etc are made by the polymerization of ethylene glycol with BisHydroxyEthyl Terephthalate (BHET).

 These Polyester fibers are used for recyclable bottles.

1.3.4 Resins

 Polyester resins made from maleic and phthalic anhydrides, ethylene glycol, and vinyl-type monomers have important applications in the low-pressure lamination of glass fibers, asbestos, cloth and paper.

 Polyester-fiberglass laminates are used in the manufacture of furniture, automobile bodies, boat hulls, suitcases and aircraft parts. Alkyd-type resins are produced by the reaction of ethylene glycol with a dibasic acid such as o-phthalic, maleic or fumaric acid. These resins are used to modify synthetic rubbers, in adhesives, and for other applications.

 Alkyds made from ethylene glycol and phthalic anhydride is used with similar resins based on other polyhydric alcohols, such as glycerol or pentaerythritol in the manufacture of surface coatings. Resin esters made with ethylene glycol are used as

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plasticizers in adhesives, lacquers and enamels. 1.3.5 Hydraulic Fluids

 Ethylene glycol is used in hydraulic, brake and shock absorber fluids to help dissolve inhibitors, prevent swelling of rubber, and inhibit foam formation.

 Hydro lubes, which are water-based mixtures of polyalkylene glycols and presses and die casting machines, and in airplane hydraulic systems because of their relatively low viscosity at high pressure. An added advantage of primary importance is that these hydro lubes are inflammable.

1.3.6 Capacitors

Ethylene glycol is used as a solvent and suspending medium for ammonium

perborate, which is the conductor in almost all electrolytic capacitors.

 Ethylene glycol, which is of high purity (iron and chloride free), is used because it has a low vapor pressure, is non-corrosive to aluminum and has excellent electrical properties.

1.3.7 Other uses

 Ethylene glycol is used to stabilize water dispersions of urea-formaldehyde and melamine-formaldehyde from gel formation and viscosity changes. It is used as humectants (moisture retaining agent) for textile fibers, paper, leather and adhesives and helps make the products softer, more pliable and durable.

An important use for ethylene glycol is as the intermediate for the manufacture of Glyoxal, the corresponding dialdehyde. Glyoxal is used to treat polyester fabrics to make them “permanent press.”

 Ethylene glycol derivatives mainly ether and ester are used as absorption fluids, Diethylene Glycol is used as a softener (Cork, adhesives, and paper) dye additive (Printing and stamping), deicing agent for runway & air craft, drying agent for gases (natural gas).

 Triethylene glycol is used for same purpose as Diethylene glycol.

 Poly (ethylene glycol) with varying molecular masses and numerous uses in Pharmaceutical industry (Ointments, Liquids and tabletting) and cosmetic industry (cream lotion, pastes, cosmetic sticks, soaps). They are also used in textile industry (Cleaning and dyeing agents), in Rubber industry (lubricating & Mold parting agents), in ceramics (bonding agents and plasticizers).[3,4]

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CHAPTER II

PROPERTIES

2.1 PHYSICAL PROPERTIES:

 Monoethylene glycol and its lower polyglycols are clear, odorless, colorless, syrupy liquid with a sweet taste.

 It is a hygroscopic liquid completely miscible with many polar solvents, such as water, alcohols, glycol ethers, and acetone.

 Its solubility is low however in non polar solvents, such as benzene, toluene, dichloroethane, and chloroform. It is miscible in ethanol in all proportion but insoluble in ether, completely miscible with many polar solvents, water, alcohols, glycol ethers and acetone. Its solubility is low, however in nonpolar solvents, such as benzene, toluene, dichloromethane and chloroform.

 It is a toxic as methyl alcohol when taken orally.

 Ethylene glycol is difficult to crystallize, when cooled; it forms a highly viscous, super-cooled mass that finally solidifies to produce a glasslike substance.  The widespread use of ethylene glycol as an antifreeze is based on its ability to lower freezing point when mixed with water. [3, 4]

Table 2.1 Physical Properties. [1, 2] Sr. no. Physical Properties 1. Molecular formula C2H6O2 2. Molecular weight 62 3. Specific gravity at 20/20oC 1.1135

4. Boiling point oC at 101.3 KPa 197.60

5. Freezing point oC -13

6. Heat of vaporization at 101.3 KPa; KJ/mol 52.24

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8. Critical Temp. oC 372

9. Critical pressure, KPa 6513.73

10. Critical volume, L/mol 0.1861

11. Refractive index, ŋ 1.4318

12. Cubic expansion coefficient at 20 oC, K-1 0.62 × 10-3

13. Viscosity at 20oC; mPa S 19.83

14. Liquid density (20oC) gm/cm3 1.1135

15. Flash point, oC 111

16. Auto-ignition temp in air oC 410

17. Flammability limits in air; vol%

Upper 53

Lower 3.2

2.2 CHEMICAL PROPERTIES:

Ethylene Glycol contains two primaries –OH groups. Its chemical reactions are therefore, those of primary alcohols twice over. Generally, one –OH group is attacked completely before other reacts.

2.1.1 Dehydration

 With Zinc chloride, it gives Acetaldehyde

HOCH2CH2OH CH3CHO + H2O

(Ethylene Glycol) (Acetaldehydes)

 On heating alone at 500 oC, it gives Ethylene oxide.

 With H2SO4 it gives dioxane which is important industrial solvent. 2.1.2 Oxidation

Ethylene glycol is easily oxidized to form a number of aldehydes and carboxylic acids by oxygen, Nitric acid and other oxidizing agents.

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The typical products derived from alcoholic functions are Glycolaldehyde

(HOCH2CHO), Glycolic acid (HOCH2COOH), Glyoxylic acid (HCO-COOH), Oxalic

Acid (HOOCCOOH), formaldehyde & formic acid.

 With HNO3 oxidation it yields nos. of substance as one or both primary –OH

groups may be oxidized to aldehydes and these carboxylic groups.

HNO3 [O] [O]

HOCH2CH2OH HOCH2CHO HOCH2CH2COOH CHOCOOH

(Ethylene Glycol) (Glycol aldehydes) (Glycolic acid) (Glyoxylic acid)

[O]

HOOC-COOH (Oxylic acid)

[O]

HNO3 [O] [O]

HOCH2CH2OH HOCH2CHO CHOCHO CHOCOOH

(Ethylene Glycol) (Glycol aldehydes) (Glyoxal) (Glyoxylic acid)

2.1.3 Other reactions

The hydroxyl groups on glycols undergo the usual alcohol chemistry giving a wide variety of possible derivatives. Hydroxyls can be converted to aldehydes, alkyl halides, amides, amines, azides, carboxylic acids, ethers, mercaptans, nitrate esters, nitriles, nitrite esters, organic esters, peroxides, phosphate esters, and sulfate esters.  Reaction with sodium at 50 oC to form monoalkoxide and dialkoxide when temperature is raised.

Na at 50 oC Na at 160 oC

HOCH2CH2OH HOCH2CH2ONa NaOCH2CH2ONa

(Ethylene Glycol) (Mono Alkoxide) (Di Alkoxide)

 Reaction with Phosphorus pentahalide (PCl5) it first gives Ethylene

chlorohydrins and then 1, 2 dichloroethane. PBr5 reacts in same way.

PCl5 PCl5

HOCH2CH2OH HOCH2CH2Cl ClCH2CH2Cl

(Ethylene Glycol) (Ethylene chlorohydrins) (1, 2-Dicholorochlorohydrins)  With Phosphorus trihalide (PBr3) to form responding dihalide

PBr3 PBr3

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(Ethylene Glycol) (Ethylene Bromohydrins) (1, 2-Dibromohydrins)  With HCl in two step reaction, form ethylene chlorohydrins at 160oC and second forms 1, 2 dichloroethane at 200oC.

160 oC 200 oC

HOCH2CH2OH HOCH2CH2Cl ClCH2CH2Cl

(Ethylene Glycol) (Ethylene chlorohydrins) (1, 2-Dicholorochlorohydrins)  The largest commercial use of ethylene glycol is its reaction with dicarboxylic acids (1) to form linear polyesters. Poly (Ethylene Terephthalate) (PET) (2) is produced by esterification of teraphthalic acid to form BisHydroxyEthyl Terephthalate (BHET) (3). BHET polymerizes in a transesterification reaction catalyzed by antimony oxide to form PET.

2HOCH2CH2OH

+

HOOC COOH

+

HOCH2CH2OOC COOCH2CH2OH

(1) (2)

+ HOCH2CH2OH

Ethylene glycol esterification of BHET is driven to completion by heating and removal of the water formed. PET is also formed using the same chemistry starting with dimethyl Terephthalate and ethylene glycol to form BHET also using an antimony oxide catalyst.

 Ethylene glycol also produces 1, 4-dioxane by acid-catalyzed dehydration to Diethylene glycol followed by cyclization. Cleavage of Triethylene and higher glycols with strong acids also produces 1, 4-dioxane by catalyzed ether hydrolysis with subsequent cyclization of the Diethylene of the Diethylene glycol fragment. Diethylene glycol condenses with primary amines of form cyclic structures, e.g., methylamine reacts with Diethylene glycol to produce N-methylmorpholine.

Sb2O3 OOC * H COOCH2CH2 *H n (3)

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HOCH2CH2OCH2CH2OH

+

CH3NH2 O N CH3

+

2H2O (6)

 Ketones and aldehydes react with ethylene glycol under acidic conditions to Form 1, 3-dioxolanes cyclic ketals and acetals.

HOCH2CH2OH

+

RCOR+ H + O O R' R H2O

+

(7)

 Ethylene glycol reacts with ethylene oxide to form di, tri, tetra and polyethylene glycols.

 Ethylene glycols is stable compound, but special care is required when ethylene glycol is heated at a higher temperature in presence of NaOH, which is exothermic reaction at temperature above 250 oC of evolution of H2 (-90 to -160

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CHAPTER III

LITERATURE SURVEY

The literature survey has been done with an aim to obtain information concerning Ethylene Glycol and its production from number of sources. Such information sources include chemical abstracts, periodicals and books on chemical technology, handbooks, encyclopedias and internet websites. The literature survey yielded a lot of information on Ethylene Glycol. A brief review of information obtained from the literature survey is presented hereafter.

During the project many Journals, Manuals and Hand book have been sited The manufacturing process have been taken from “Chemical Engineering Journal 107(2005), 199-204.” The selectivity and other process parameters have been taken from “Chemical Engineering Journal 107(2005), 199-204.” The demand growths, Major producer in India & World have been taken from Internet.

3.1 DERIVATIVES OF MONO ETHYLENE GLYCOL:

In addition to Oligomers ethylene glycol dervative classes include monoethers, diethers, esters, acetals, and ketals as well as numerous other organic and organometalic molecules. These derivatives can be of ethylene glycol, Diethylene glycol, or higher glycols and are commonly made with either the parent glycol or with sequential addition of ethylene oxide to a glycol alcohol, or carboxylic acid forming the required number of ethylene glycol submits.

3.1.1 Diethylene Glycol:

Physical properties of Diethylene glycol are listed in Table. Diethylene glycol is similar in many respects to ethylene glycol, but contains an ether group. It was originally synthesized at about the same time by both Lourenco and Wurtz in 1859, and was first marketed, by Union Carbide in 1928. It is a co product (9 - 10%) of ethylene glycol produced by ethylene oxide hydrolysis. It can be made directly by the reaction of ethylene glycol with ethylene oxide, but this route is rarely used because more than an adequate supply is available from the hydrolysis reaction.

Manufacture of unsaturated polyester resins and polyols for polyurethanes consumes 45% of the Diethylene glycol. Approximately 14% is blended into antifreeze. Triethylene glycol from the ethylene oxide hydrolysis does not meet market

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requirements, which leads to 12% of the Diethylene glycol being converted with ethylene oxide to meet this market need. About 10% of Diethylene glycol is converted to morpholine. Another significant use is natural gas dehydration, which uses 6%. The remaining 13% is used in such applications as plasticizers for paper, fiber finishes, and compatiblizers for dye and printing ink components, latex paint, antifreeze, and lubricants in a number of applications.

3.1.2 Triethylene Glycol:

Triethylene glycol is a colorless, water-soluble liquid with chemical properties essentially identical to those of Diethylene glycol. It is a co product of ethylene glycol produced via ethylene oxide hydrolysis. Significant commercial quantities are also produced directly by the reaction of ethylene oxide with the lower glycols.

Triethylene glycol is an efficient hygroscopicity agent with low volatility, and about 45% is used as a liquid drying agent for natural gas. Its use in small packaged plants located at the gas wellhead eliminates the need for line heaters in field gathering systems as a solvent (11 %) Triethylene glycol is used in resin impregnants and other additives, steam-set printing inks, aromatic and paraffinic hydrocarbon separations, cleaning compounds, and cleaning poly (ethylene Terephthalate) production equipment. The freezing point depression property of Triethylene glycol is the basis for its use in heat-transfer fluids.

Approximately 13% Triethylene glycol is used in some form as a vinyl plasticizer. Triethylene glycol esters are important plasticizers for poly (vinyl butyral) resins, Nitrocellulose lacquers, vinyl and poly (vinyl chloride) resins, poly (vinyl acetate) and synthetic rubber compounds and cellulose esters. The fatty acid derivatives of Triethylene glycol are used as emulsifiers, emulsifiers, and lubricants. Polyesters derived from Triethylene glycol are useful as low pressure laminates for glass fibers, asbestos, cloth, or paper. Triethylene glycol is used in the manufacture of alkyd resins used as laminating agents and adhesives.

3.1.3 Tetra ethylene Glycol:

Tetra ethylene glycol has properties similar to Diethylene and Triethylene glycols and may be used preferentially in applications requiring a higher boiling point, higher molecular weight, or lower hygroscopicity.

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Tetra ethylene glycol is miscible with water and many organic solvents. It is a humectants that, although less hygroscopic than the lower members of the glycol series, may find limited application in the dehydration of natural gases. Other possibilities are in moisturizing and plasticizing cork, adhesives, and other substances. Tetra ethylene glycol may be used directly as a plasticizer or modified by esterification with fatty acids to produce plasticizers. Tetra ethylene glycol is used directly to plasticize separation membranes, such as silicone rubber, poly (Vinyl acetate), and cellulose triacetate. Ceramic materials utilize tetra- ethylene glycol as plasticizing agents in resistant refractory plastics and molded ceramics. It is also employed to improve the physical properties of cyanoacrylate and polyacrylonitrile adhesives, and is chemically modified to form Polyisocyanate, polymethacrylate, and to contain silicone compounds used for adhesives.

Tetra ethylene glycol has found application in the separation of aromatic hydrocarbons from nonromantic hydrocarbons (BTX extraction). In general, the critical solution temperature of a binary system, consisting of a given alkyl-substituted aromatic hydrocarbon and tetra ethylene glycol, is lower than the critical solution temperature of the same hydrocarbon with Triethylene glycol and is considerably lower than the critical solution temperature of the same hydrocarbon with Diethylene glycol. Hence, at a given temperature, tetra ethylene glycol tends to exact the higher alkyl benzenes at a greater capacity than a lower polyglycols.

3.2 STORAGE AND TRANSPORTATION:

Pure anhydrous ethylene glycol is not aggressive toward most metals and plastics. Since ethylene glycol also has a low vapor pressure and is non caustic. It can be handled with out any problems: it is transported in railroad tank cars, tank trucks, and tank ships. Tanks are usually made of steel: high grade materials are only required for special quality requirements. Nitrogen blanketing can protect ethylene glycol against oxidation.

At ambient temperature, aluminum is resistant to pure glycol. Corrosion occurs, however, above 100oC and hydrogen is evolved. Water air and acid producing impurities (aldehydes) accelerate this reaction. Great care should be taken when phenolic resins are involved, since they are not resistance to ethylene glycol.

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3.3 SHIPPING DATA FOR ETHYLENE GLYCOL:

 Weight per Gallon at 20°C 9.29 lb  Coefficient of Expansion at 55°C 0.00065  Flash Point, Tag Closed Cup 260°F

Net Contents and Type of Container

 1–Gallon Tin Can 9.0 lb  5–Gallon DOT 17E, Pail 47 lb  55–Gallon DOT 17E, Drum 519 lb

3.4 ENVIRONMENTAL PROTECTION AND ECOLOGY:

Ethylene glycol is readily biodegradable, thus disposal of waste water containing this compound can proceed without major problems. The high LC 50value of over 10000 mg/lit account for its low water toxicity.

3.5 PRODUCT SAFETY:

When considering the use of ethylene glycol in any particular application, review and understand our current Material Safety Data Sheet for the necessary safety and environmental health information. Before handling any products you should obtain the available product safety information from the suppliers of those products and take the necessary steps to comply with all precautions regarding the use of ethylene glycol. No chemical should be used as or in a food, drug, medical device, or cosmetic, or in a product process in which it may come in contact with a food, drug, medical device, or cosmetic until the user has determined the suitability of the use. Because use conditions and applicable laws may differ from one location to another and may change with time, Customer is responsible for determining whether products and the information are appropriate for Customer’s use [5, 6]

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CHAPTER IV

MARKET SURVEY

4.1 ECONOMIC ASPECTS:

Ethylene glycol is one of the major products of the chemical industry. Its economic importance is founded on its two major commercial uses as antifreeze and for fiber production. Since Ethylene glycol is currently produced exclusively from ethylene oxide production plant are always located close to plant that produce ethylene oxide. The proportion of ethylene oxide that is converted to Ethylene glycol depends on local condition, such as market situation and transport facilities. About 60% of total world production is converted to ethylene glycol.

About 50% of the ethylene glycol that is used as antifreeze. Another 40% is used in fiber industry. Consequently the ethylene glycol demand is closely connected to the development of these two sectors In view of the increasing price of crude oil, alternative production method based on synthesis gas is likely to become more important and increasing competitive.

4.2 LEADING PRODUCERS IN WORLD

:

 BASF, Geismer, La. (America).

 DOW, Plaquemine, La .(America)

 OXYPETROCHEMICALS, Bayport, Tex .(America)

 PD Glycol ,Beaumont, Tex. (America)

 SHELL, Geismer,La. (America)

 TEXACO ,Port Neches, Tex.(America)

 UNION CARBIDE, Taft,La.(America)

 BP Chemicals, Belgium, (West Europe).

 IMPERIAL Chemicals Ind. United Kingdom, (West Europe)

 BPC (NAPTHACHIMIE),France , (West Europe)

 STATE COMPLEXES ,USSR, (West Europe)

 PAZINKA, Yugoslavia, (West Europe)

 EASTERN PETROCHEMICAL CO. Saudi Arabia, (Middle East)

 National Organic Chemical, India, (Asia).

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4.3 LEADING PRODUCER IN INDIA:  India Glycol, Uttaranchal (North India).  Reliance Industries Ltd. Hazira (Gujarat).

 Indian Petrochemical Corporation Ltd, Baroda (Gujarat).

 NOCIL, Thane.

 SM Dye chem. Pune.

4.4 MEG PRICE TREND:

Table 4.1 MEG Price Trend

Sr. No. Year Month Price(US$/MT)

1. 2004 November 1095 2. December 988 3. 2005 January 1045 4. February 1095 5. March 1095 6. April 971 7. May 734 8. June 736 9. July 808 10. August 836 11. September 883 12. October 883 13. November 1st week 830 14. 2nd week 822

4.5 DEMAND SUPPLY BALANCE (IN KT):

Table 4.2 Demand supply balance (In KT)

MEG 2002 2003 2004 2005 2006 Capacity 590 615 654 830 830 Production 548 647 691 833 830 Imports 11 64 106 103 90 Exports 8 29 104 133 60 Demand 551 682 750 803 860 Demand Growth % 24% 10% 7% 7%

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4.6 QUALITY SPECIFICATION:

Since ethylene glycol is produce in relatively high purity difference in quality are not accepted. The directly synthesized product meets high quality demands (fiber grade). The ethylene glycol produce in the wash water that is use during ethylene oxide production is normally of a somewhat inferior quality (antifreeze grade). The quality specifications for mono ethylene glycol are compiling in table-2. [5, 6]

Table 4.3 Quality Specification OF Ethylene Glycol

DESCRIPTION FIBER GRADE INDUSTRIAL GRADE

Color, Pt-Co, max 5 10

Suspended matter Substantially free Substantially free

Diethylene glycol, wt.% max 0.08 0.6

Acidity, as acetic acid, wt% max 0.005 0.02 Ash, wt% max 0.005 0.005 Water, wt% max 0.08 0.3 Iron, ppm wt max 0.07 0.05 Chlorides, ppm wt max

Distillation range, ASTM at 760mm Hg:

IBP, C min 196 196

DP, C max 200 199

Odor Practically none

UV transmittance, % min at:

220 nm 70 70

250 nm 90

275 nm 90 95

350 nm 98 99

Specific gravity, 20/20C 1.1151-1.1156 1.1151-1.1156

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CHAPTER V

PROCESS SELECTION AND DESCRIPTION

5.1 MANUFACTURING PROCESSES:

Up to the end of 1981, only two processes for manufacturing ethylene glycol have been commercialized. The first, the hydration of ethylene oxide, is by far the most important, and from 1968 through 1981 has been the basis for all of the ethylene glycol production.

Manufacturing process involves laboratory methods and industrial methods.

5.1.1 Laboratory methods: [3, 4]

 By passing Ethylene in to cold dilute Alkaline permanganate solution i.e. Oxidation of Ethylene to Glycol

 By hydrolysis of Ethylene Bromide by boiling under reflux with aqueous sodium carbonate solution. This reaction mixture is refluxed till an oily globule of ethylene bromide disappears. The resulting solution is evaporated on a water bath and semi solid residue is extracted with ether-alcohol mixture. Glycol is recovered from solution by distillation. The best yield of glycol (83-84%) can be obtained by heating ethylene bromide with potassium acetate in Glacial acetic acid.

 Ethylene glycol can be produced by an electrohydrodimerization of

formaldehyde.

 An early source of glycols was from hydrogenation of sugars obtained from formaldehyde condensation. Selectivity to ethylene glycol was low with a number of other glycols and polyols produced. Biomass continues to be evaluated as a feedstock for glycol production.

5.1.2 Industrial methods: [1, 2, 7, 8]

 The production of ethylene glycol by the hydration of ethylene oxide is simple, and can be summarized as follows: ethylene oxide reacts with water to form glycol, and then further reacts with ethylene glycol and higher homologues in a series of consecutive reactions as shown in the following equations.

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+

O CH2 H2O H2C CH2 O H O H

+

O CH2 H2C CH2 O H O H H2C CH2 O H O CH2 O H CH2 Ethylene Oxide Ethylene Glycol Diethylene Glycol H2C H2C

+

O CH2 H2C H2C CH2 O H O CH2 O H CH2 H2C CH2 O H O CH2 O H CH2 CH2 O CH2 Triethylene Glycol

Ethylene oxide hydrolysis proceeds with either acid or base catalysis or uncatalyzed in neutral medium. Acid-catalyzed hydrolysis activates the ethylene oxide by protonation for the reaction with water. Base-catalyzed hydrolysis results in considerably lower selectivity to ethylene glycol. The yield of higher glycol products is substantially increased since anions of the first reaction products effectively compete with hydroxide ion for ethylene oxide. Neutral hydrolysis (pH 6-10), conducted in the presence of a large excess of water at high temperatures and pressures, increases the selectivity of ethylene glycol to 89-91%. In all these ethylene oxide hydrolysis processes the principal byproduct is Diethylene glycol. The higher glycols, i.e., Triethylene and Triethylene glycols, account for the remainder.

Although catalytic hydration of ethylene oxide to maximize ethylene glycol production has been studied by a number of companies with numerous materials patented as catalysts, there has been no reported industrial manufacture of ethylene glycol via catalytic ethylene oxide hydrolysis. Studied catalyst include sulfonic acids, carboxylic acids and salts, cation-exchange resins, acidic zeolites, halides,

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exchange resins, metals, metal oxide and metal salts. Carbon dioxide as a co catalyst with many of the same materials has also received extensive study.

 Ethylene glycol was commercially produced in the United States from ethylene chlorohydrins which was manufactured from ethylene and hypochlorous acid. Chlorohydrins can be converted directly to ethylene glycol by hydrolysis with a base, generally caustic or caustic/bicarbonate mix. An alternative production method is converting chlorohydrins to ethylene oxide with subsequent hydrolysis.

CH2 CH2

+

HOCl HOCH2CH2Cl (8)

+

NaOH (9)

HOCH2CH2Cl HOCH2CH2OH

+

NaCl

+

Ca(OH)2 (10) HOCH2CH2Cl CH2

+

NaCl O CH2

+

(11) CH2 O CH2 H2O HOCH2CH2OH

 Du Pont commercially produced ethylene glycol from carbon monoxide, methanol, hydrogen, and formaldehyde until 1968 at Belle, West Virginia. The process consisted of the reaction of formaldehyde, water, and carbon monoxide with an acid catalyst to form glycolic acid. The acid is esterified with methanol to produce methyl glycolate. Subsequent reduction with hydrogen over a chromate catalyst yields ethylene glycol and methanol. Methanol and formaldehyde were manufactured on site from syngas.

+

CH2O (12) CO HOOCCH 2OH

+

NaCl

+

H2O H+

+

CH3OH CH3OOCCH2OH

+

(13) HOOCCH2OH H2O

+

H2 (14) CH3OOCCH2OH Cr2O3 HOCH2CH2OH

+

CH3OH

Coal was the original feedstock for syngas at Belle; thus ethylene glycol was commercially manufactured from coal at one time. Ethylene glycol manufacture from syngas continues to be pursued by a number of researchers.

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 Ethylene glycol can be produced from acetoxylation of ethylene. Acetic acid, oxygen, and ethylene react with a catalyst to form the glycol mono and diacetate. Catalysts can be based on palladium, selenium, tellurium, or thallium. The esters are hydrolyzed to ethylene glycol and acetic acid. The net reaction is ethylene plus water plus oxygen to give ethylene glycol. This technology has several issues which have limited its commercial use.

+

O2 (15)

CH3COOH CH2 CH2

+

Te2Br2 CH3COOCH2OOCCH3

+

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CH3COOCH2CH2OH CH3COOCH2CH2OOCCH3 3 H2O 2 HOCH2CH2OH

+

3 CH3COOH

The catalysts and acetic are highly corrosive, requiring expensive construction materials. Trace amounts of ethylene glycol mono-and diacetates are difficult to separate from ethylene glycol limiting the glycol’s value for polyester manufacturing. This technology (Halcon license) was practiced by Oxirane in 1978 and j1979 but was discontinued due to corrosion problems.

 Ethylene glycol can be manufactured by the transesterification of ethylene carbonate. A process based on the reaction of ethylene carbonate with methanol to give dimethyl carbonate and ethylene glycol is described in a Texaco patent; a general description of the chemistry has also been published.

O O

C O

+

2 CH3OH Zr2Cl4 HOCH2CH2OH

+

CO(CH3O)2 (18)

Selectivity to ethylene glycol are excellent with little Diethylene glycol or higher glycols produced. A wide range of catalysts may be employed including ion exchange resins, zirconium and titanium compounds, tin compounds, phosphines, acids and bases. The process produces a large quantity of dimethyl carbonate which would require a commercial outlet.

 Oxalic acid produced from syngas can be esterified and reduced with hydrogen to form ethylene glycol with recovery of the esterification alcohol. Hydrogenation requires a copper catalyst giving 100% conversion with selectivity to ethylene glycol of 95%.

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21

+

2 ROH ROOCCOOR

+

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HOOCCOOH 2 H2O

ROOCCOOR

+

4 H2 Cu HOCH2CH2OH

+

2 ROH (21)

 The Teijin process, which has not been commercialized to date, produces ethylene glycol by the reaction of ethylene with thallium salts in the presence of water and chloride or bromide ions. The major by-product in the reaction is acetaldehyde. A redox metal compound (such as copper) oxidizable with molecular oxygen is added to the reaction medium to permit the regeneration of the thallium salt.

 The DuPont process, based on feeds derived from synthesis gas (CO and formaldehyde), became economically obsolete because of low-priced ethylene. With the high price of oil and natural gas, there has been increasing interest in coal gasification to produce fuel and also synthesis gas for petrochemical manufacture. In 1976, Union Carbide announced that a process for the production of ethylene glycol from synthesis gas was being developed for commercialization in the early 1980.The proposed reaction was based on using a rhodium-based catalyst in tetrahydrofuran solvent at 190-230C and high pressure (3400 atm). The equi molar mixture of CO and H2 would be converted mainly to ethylene glycol and by-product glycerol and

propylene oxide. Methanol, methyl formate, and water would also be produced.[10]

5.2. PROCESS SELECTION:

The process selection is based on different advantages and parameters of the industrial methods.

5.2.1 Comparison of different Processes:

Hydration of ethylene oxide is an industrial approach to glycols in general, and ethylene glycol in particular. Ethylene glycol is one of the major large-scale products of industrial organic synthesis, with the world annual production of about 15.3 million t/yr in 2000. Hydration of ethylene oxide proceeds on a serial-to-parallel route with the formation of homologues of glycol:

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22

Table 5.1 Comparison of different Processes

SR. NO

PROCESSES PARAMETER CATALYST ADVANTAGES/DISA

DVANTAGES 1. Hydrolysis of Ethylene Oxide 1) Non- catalytic Yield : 98% Selectivity: 98% Temp:105oC Pressure : 1.5MPa 2) catalytic: Yield : 95% Selectivity: 90% Temp:200oC Pressure : 1-30 bar 1)Non Catalytic 2) Catalytic: Sulfonic acids, Carboxylic acids and salts, Ion-exchange resins, Acidic zeolites, halides, Metal oxide and Metal salts.

Use large excess water to increase the yield which leads to high energy consumption 1) Use less excess water which leads to low energy consumption 2) High yield & selectivity

3) permit use of low temp & pressure

4) Acid catalyst makes the reaction solution highly corrosive. 2. Ethylene Glycol from Ethylene chlorohydrins Yield :50% Selectivity: 75%

Non Catalytic  very low yield & selectivity  very costly 3. Ethylene glycol from CO,H2,CH3OH & Formaldehyde Yield : 90-95% Temp: 200oC Pressure: 100atm Cromate Catalyst  High pressure process  Discontinued now a day  Low selectivity 4. Ethylene glycol from ethylene carbonate Yield :98% Selectivity: 95% Temp:180oC Pressure:13bar Alkali halide or ammonium salt.

 Give high yield and selectivity

 Utility saving

 Extra purification cost

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23

5. Transesterificati on of ethylene carbonate.

Low yield Zirconium &

titanium compound.  Produced large amount of byproducts 6. Esterification of Oxalic acid and Reduction with H2 Yield : 70% Selectivity: 90% Copper catalyst

 High conversion but catalyst removal is very difficult.

7. Direct one stage

synthesis of

Ethylene glycol from syn gas

Selectivity: 65% Temp: 190-230oC Pressure: 3400atm Rhodium catalyst (Homogeneous catalyst route.)  As crude prices

increase this process will become more economical.

 Use of very high pressure

 Not prove to be indirect route may be viable or not.  Catalyst is very sensitive and expensive. 8. Hydrolysis of glycol diacetate. Yield : 90% Selectivity: 95% Temp: 160oC Pressure: 2.4MPa Pd complexes pdcl2+NaNO3

 Very low conversion

H2O+C2H4O Ko HOCH2CH2OH --- (1)

C2H4O + HOCH2CH2OH Ki HO (CH2CH2O)2 H --- (2)

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24

Now all ethylene and propylene glycols is produced in industry by a non catalyzed reaction. Product distribution in reaction (1) is regulated by the oxide/water ratio in the initial reaction mixture. The distribution factor b = k1/k0 for a non catalyzed

reaction of ethylene oxide with water is in the range of 1.9–2.8. For this reason large excess of water (up to 20 molar equiv.) is applied to increase the monoglycol yield on the industrial scale. This results in a considerable power cost at the final product isolation stage from dilute aqueous solutions. i.e. energy consumption for the distillation of large amount of excess water is high. Also the selectivity of ethylene oxide hydrolysis is low i.e. 10% is converted to Diethylene glycol and tri ethylene glycol.

One of the ways of increasing the monoglycol selectivity and, therefore, of decreasing water excess is the application of catalysts accelerating only the first step of the reaction (1). There are much research has been carried out to improve this process. The search for better catalyst is an objective for increase the selectivity and decrease the excess water. As evident from the kinetic data the distribution factor b = k1/k0 is

reduced -0.1–0.2 at the concentration of some salts of about 0.5 mol/l. This enables to produce monoethyleneglycol with high selectivity at water–ethyleneoxide molar ratio close to 10.

5.2.2 Catalyst:

A cross-linked styrene–divinylbenzene anion exchange resin (SBR) in the HCO3−/

CO3- form, activated by anion exchanging with sodium bicarbonate solution used as

catalysts. (Dow Chemical produced anion-exchange resins: DOWEX SBR). The ethylene oxide hydration process in a catalytic fixed-bed tube reactor was studied .The properties of initial resins are summarized below:

Functional group : - [PhN (CH3)3] +

Total exchange capacity (equiv./l) : 1.4 Particle size (mm) : 0.3-1.2

5.3 PROCESS DESCRIPTION:

This process produced mono ethylene glycol by the catalytic hydrolysis of ethylene oxide in the presence of less excess of water. After the hydrolysis reaction is completed the glycol is separated from the excess water and then refined to produce mono ethylene glycol (MEG). The process is devided in to five different sections.

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25 5.3.1 MEG reaction unit:

Ethylene oxides mixed with recycle water and pumped to glycol reactor where it is reacted with water at 1050C &1.5 MPa in the presence of catalyst. The Reactor is Catalytic Plug flow Fixed bed type. The reaction volume consists of two phase, the liquid phase and ionite (catalyst) phase. The liquid streams through catalyst bed in a plug flow regime. The catalytic and non catalytic ethylene oxide hydration takes place in the ionite phase, and only non catalytic reaction takes place in the liquid phase. The distribution of the components of the reaction mixture between liquid and ionite phases is result of the rapid equilibrium. The glycol reactor operate at approximately 1.5MPa.pressure which is supplied by the reactor feed pump. The reactor effluent goes to the evaporation unit for the evaporation of excess water.

5.3.2 MEG evaporation unit:

The glycol evaporation system consists of multiple effect evaporation system(three effects). The reactor effluent flows by difference in pressure from one evaporator to the next the water content of glycol is reduced to about 15% in the evaporators. The remaining water is removed in drying column, the pressure of the system is such that the reactor effluent is maintained as a liquid and is fed as such in to the vapor portion of the first effect evaporator.

Evaporation in the first effect is accomplished by 12Kg/cm2 (g) pressure steam. The overhead vapor from the first effect is used as heating media in the second effect. The steam condensate from the first effect is goes to the medium pressure condensate header.

The overhead vapor from the second effect is used as heating media in the third effect. The third effect operated under vacuum. The vacuum is maintained by using steam jet ejector. The bottom of the third effect containing 15% water is fed to crude glycol tank via glycol pump, which is then fed to the drying unit. The condensate from first two effects and the vapor from third effect containing water and some amount of glycol are fed to the glycol recovery unit.

5.3.3 MEG drying unit:

The concentrated glycol from the third effect is containing approximately 15% water. Essentially all the water is removed from the aqueous ethylene glycol solution in the drying column. Normally the drying column is fed from the crude glycol tank. The drying column operated under vacuum which is maintained by steam jet ejector. Drying column bottom which are free from water are transferred by column bottom

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26

pump to MEG refining column. Where the MEG is separated from the higher glycol, Water vapors leaving the top of the drying column are fed to MEG recovery unit for glycol recovery. (An inert gas line is provided at the base of the drying column for breaking the vacuum).

5.3.4 MEG refining unit:

Drying column bottoms essentially free of water are fed to the MEG refining column. (PACKED COLUMN). About 15% of the feed to the MEG column enters as vapor due to flashing. MEG product is withdrawn from the top of the column. Some MEG is purged in the overhead to the vacuum jets to reduce the aldehydes in the product. The MEG column bottoms primarily di-ethylene glycols are pumped from the column bottom to the storage tank. The MEG column operates at a pressure of 10mmHg (A). The vacuum is maintained by MEG column ejector system. The MEG column condenser is mounted directly on the top of the MEG column.

5.3.5 MEG recovery unit:

The MEG leaving along with water from the Top of the multiple effect evaporator & drying column are recovered in the MEG Recovery Column (PLATE COLUMN). The column is operated under Atmospheric pressure.MEG leaving from the bottom of the column and the water leaving from the top of the column are Recycle to reactor.

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27

CHAPTER VI

MATERIAL BALANCE

Material balances are the basis of process design. A material balance taken over complete process will determine the quantities of raw materials required and products produced. Balances over Individual process until set the process stream flows and compositions. The general conservation equation for any process can be written as

Material out = material in + accumulation

For a steady state process the accumulation term is zero. If a chemical reaction is taking place a particular chemical species may be formed or consumed. But if there is no chemical reaction, the steady state balance reduces to:

Material out = Material in

A balance equation can be written for each separately identifiable species present, elements, compounds and for total material. [10]

6.1 BASIS:

Basis: 100000TPA

The process is planned and developed as a continuous process. A plant is operated for 24 Hours per day and 333 per year.

No of working days = 333days Capacity =

333 1000000

= 300.3 T/days = 201.47 Kmol/hr.

6.2 MOLECULAR WEIGHT

(

KG / KMOL):

Ethylene Glycol : 62

Water : 18

Carbon Dioxide [CO2] : 44.01

Water [H2O] : 18

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28

6.3 MATERIAL BALANCE OF INDIVIDUAL EQUIPMENT: This is the amount of MEG obtained from the distillation column,

So assuming that 99% of MEG in the feed to the Distillation column (Refining Column) is obtained in the distillate & also 93% of MEG in feed to the Recovery Column is recovered from Recovery Column.

Kmol of MEG in feed to the distillation column

= 204.70 Kmol/hr.

6.3.1 Reactor:

In the reactor following reaction take place

C2H4O + H2O HOCH2CH2OH --- (1)

(Ethylene oxide) (Water) (Mono Ethylene Glycol)

C2H4O + HOCH2CH2OH HOCH2CH2OH --- (2)

(Ethylene oxide) (Mono Ethylene Glycol) (Higher Glycol)

As selectivity = 98%

Moles of undesired product formed = 98

70 . 204

= 2.088 Kmol

Moles of MEG to be produced from reactor = 206.788kmol Moles of ethylene oxide reacted by reaction –I

= 206.788 Kmol.

Moles of ethylene oxide reacted by reaction –I I

Ethylene Oxide = 9190.54 Kg = 208.876 Kmols

Water = 37597.68 Kg = 2088.76 Kmol

Mono Ethylene Glycol = 204.7Kmols = 12691.4 Kg Water = 1881.972 Kmols

= 33875.496Kg Higher glycol = 2.088 Kmol = 221.328Kg

REACTOR Temp. = 100 0C Conversion = 100 % Pressure = 1.5-2MPa

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29

= 2.088 Kmol. Total Moles of ethylene oxide reacted = 206.788 + 2.088

= 208.876 Kmol. As conversion = 100%

[6]

Moles of ethylene oxide charged = 208.876kmol

From the literature we know that the ratio of WATER TO ETHYLENE OXIDE =10 Amount of water fed to reactor = 2088.76 Kmol. (Including excess)

From the reaction moles of water reacted = 206.788 Kmol.

M.B.ON WATER:

Moles of water fed = Moles of water reacted + Moles of water unreacted 2088.76 = 206.788 + Moles of water unreacted

 Moles of water unreacted = 1881.972kmol

M.B.ON MEG:

Moles of MEG in the product = 206.788 – 2.088 = 204.7 Kmol

Table 6.1 Material balance over reactor

Component In, Kg Out, kg

Ethylene oxide 9190.54 -

Water 37597.68 33875.496

Mono Ethylene Glycol - 12691.4

Higher Glycol - 221.328

6.3.2 Triple Effect Evaporator:

Consider the water content of glycol is reduced to 15% i.e. 85% of water is to be removed.

Consider triple effect evaporator as single unit. Amount of water removed = 0.851881.972

= 1599.6762 Kmol. = 28794.1715 Kg Total quantity of water at the top = 1599.6762 Kmol.

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30

= 28794.1716 kg.

Remaining 15% water are still in the bottom along with the MEG and Higher glycol.

 Amount of water in the bottom = 1881.972-1599.6762 = 282.2958 Kmol. = 5081.324 Kg

There is some quantity of glycol carry over along with water from the top of evaporator.

Amount of glycol carry over along with water from 1st effect = 165.58 kg

Amount of glycol carry over along with water from IIst effect = 189.139kg 1st effect evaporator Pressure = 7 kg/cm2 Temp = 159 oC F = 2088.76 Kmol = (46788.224 kg) M.E.G = 204.7Kmol = 12691.4 Kg Water =1881.972 Kmol = 33875.496Kg H.G = 2.088 Kmol = 221.328Kg W1= 8285.66kg MEG = 165.58kg H2O = 8120.08kg 2nd effect evaporator Pressure = 3.5 kg/cm2 Temp = 141 oC W2= 9689.31kg MEG = 189.139kg H2O = 9500.171kg

To MEG Recovery column

Y= 1610.8012kmol

To 3rd effect evaporator To 2nd effect evaporator

From 2nd effect evaporator

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31

Amount of glycol carry over along with water from IIst effect = 335.064 kg

(Finding using VLE calculation)

Total amount of glycol carry over along with water = 689.783 Kgm. =11.125 Kmol Total quantity (water +MEG) leaving from the top of effect = 1599.6762+11.125

Y = 1610.8012 Kmol.

TAKING OVERALL M.B

F = Y + X

2088.76 = 1610.8012 + X X = 477.9588 Kmol.

(Total quantity leaving from the bottom of last effect)

Table 6.2 Material balance over Triple effect evaporator

Component In, Kg Out, Kg

Liquid phase Vapor phase

Water 33875.496 5081.355 28794.141 MEG 12691.4 12001.617 689.783 HG 221.328 221.328 - 3rd effect evaporator Pressure = 0.25 kg/cm2 Temp = 118 oC

To MEG Recovery column

Y= 1610.8012kmol From 3rd effect evaporator To MEG Refining column X = 477.9588 Kmol W3= 11508.96kg MEG = 335.064kg H2O = 11173.89kg

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32 6.3.3 Drying Column:

Consider all the water are removed in the drying column Amount of water removed = 5018.324 Kgm

= 282.295 Kmol.

There is some quantity of glycol carry over along with water from the top of drying column

Amount of glycol carry over along with water from drying column = 456.061kg =7.3558 Kmol. (Finding using VLE calculation)

Total quantity leaving from top of drying column

= (Amount of water +Amount of MEG) = 282.295 +7.3558 = 289.65 Kmol. TAKING OVERALL M.B F = Y + X 477.9588 = 289.65 + X X = 188.306 Kmol.

(Total quantity leaving from the bottom of drying column)  Now ,

Total amount of MEG leaving along with water during evaporation of water

F = 477.9588 kmol = 17304.2585 kg MEG = 12001.606kg H2O = 5081.324 kg. HG = 221.328kg. Y= 289.295 Kmol = 5537.385 kg MEG = 456.061kg H2O = 5081.324 kg . X = 188.306 Kmol = 11766.873 kg MEG = 186.218kmol = 115453545kg HG = 2.088 Kmol = 221.328kg . Drying column Pressure = 0.21 kg/cm2 Temp = 87 oC

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33

= (Amount of MEG leaving from top of TEE + Amount of MEG leaving from top of drying column)

= 689.783+456.061 = 1145.844 Kgm. = 18.4813 Kmol.  Amount of feed to MEG Recovery column

= (Amount of MEG leaving along with water during evaporation + Amount of water removed)

= 18.4813+1881.973 = 1900.451 Kmol. Table 6.3 Material balance over drying column

Component In, Kg Out, Kg

Liquid phase Vapor phase

Water 5081.324 - 5081.324

MEG 12001.606 11545.3545 456.061

HG 221.328 221.328 -

6.3.4 MEG Refining Column (Packed Column):

F = 188.306 Kmol = 11766.873 kg MEG = 186.218kmol =11545.545kg HG =2.088kmol = 221.328kg D= 184.54 Kmol = 11448.8616 kg MEG = 184.355kmol (0.999.high purity) HG = 0.18454kmol W = 3.766 Kmol = 317.664 kg MEG = 1.8523kmol HG = 1.9136kmol

MEG refining column Pressure = 10 mmHg Temp = 93.2 oC

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34

Assuming 99% recovery, of total MEG feed to distillation column, is obtained in the distillate.

 Kmol of MEG in Distillate = 188.306  0.99 x 0.98891

= 184.355 Kmol / hr. = 11431.0818 Kg/hr.  Kmol of Distillate ( D ) = 184.355 / 0.999 = 184.54 Kmol / hr. Avg. M.W. of distillate = (0.999 x 62) + (0.001 x 106) = 62.044 kg / Kmol. Amt. of Distillate (D) = 184.54 x 62.04 = 11448.8618 kg / hr.  Amt. of HG in Distillate = 184.54 x 0.001 = 0.18454 Kmol / hr. = 0.18454 x 106 = 19.561 kg / hr.  Kmol of feed (F) = 188.306 Kmol / hr.

= 11766.873 kg/hr

TAKING OVER ALL M.B.

F = D + W

188.306 = 184.54 + W W = 3.766 Kmol /hr.

M.B. ON MEG

F x (Xf MEG) = D x (Xd MEG) + W x (Xb MEG) 188.306 x 0.9889 = 184.54 x 0.999 + 3.766 x Xb MEG

Xb MEG = 0.4918 (mol.fr.of MEG in Bottoms) XbHG = (1- 0.4918)

= 0.5081 (mol.fr.of HG in Bottoms)  Kmol of MEG in Bottoms = 0.4918 x 3.766

= 1.8521 Kmol / hr Mol. Weight of MEG = 62 kg/Kmol

= 114.831 kg/hr.  Kmol of HG in Bottoms = 0.5081 x 3.766

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35

Mol. Weight of HG =106 kg/Kmol

= 1.9135 x 106 = 202.83 kg/hr.

Table 6.4 Material balance over Refining packed column

Component In, Kg Out, Kg

Liquid phase Vapor phase

MEG 11545.545 114.8426 11430.01

HG 221.328 202.8416 19.56124

6.3.5 MEG recovery column (Plate column):

Assuming 99.9 % of total water in feed to distillation column is obtained in the distillate.

 Kmol of Water in Distillate = 1881.97 x 0.999 = 1880.08 Kmol / hr  Kmol of Distillate ( D ) = 1880.08 / 0.999 = 1881.97 Kmol / hr. Avg. M.W. of distillate = (0.999 x 18) + (0.001 x 62) = 18.044 kg / Kmol. Amt. of Distillate (D) = 1881.97 x 18.044 F = 1900.451kmol = 35021.339 kg MEG = 18.481kmol =1145.844kg H2O =1881.97kmol = 33875.496kg. D= 1881.97kmol = 11766.873 kg MEG =1.88kmol H2O =1880.08kmol W = 18.481kmol =1205.55 kg MEG = 17.122kmol H2O = 1.3584kmol

MEG recovery column

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36

= 33958.266 kg /hr  Amt. of MEG in Distillate = 1881.97 x 0.001

= 1.88 Kmol / hr = 1.88 x 62 = 116.56 kg/ hr.  Amount of feed ( F ) = 1900.451 Kmol/hr

= 35021.339 kg/hr. TAKING OVERALL M.B. F = D+ W 1900.451 = 1881.47 + W W = 18.481kmol / hr M.B. ON WATER F x (Xf H) = D x (Xd H) + W x (Xb H) 1900.451 x 0.99 = 1881.97 x 0.999 + 18.481 x Xb W Xb W = 0.0735 (mol.fr.of Water in Bottoms) Xb MEG = 1- 0.0735

= 0.9264 (mol.fr.of MEG in Bottoms)  Amount of MEG in Bottoms = 18.481 x 0.9264

= 17.122 Kmol / hr = 17.122 x 62

= 1061.56 kg/hr.  Kmol of Water in Bottoms = 18.481 – 17.130 = 1.3584 Kmol / hr = 1.3584 x 18 = 143.99 kg/ hr.

Table 6.5 Material balance over Recovery plate column

Component In, Kg Out, Kg

Liquid phase Vapor phase

Water 33875.496 24.4512 33841.44

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37

Table 6.6 Overall material balances

Equipment Component In, kg Out, Kg

Liquid phase Vapor phase

Reactor Ethylene oxide 9190.54 - -

Water 37597.68 33875.496 - MEG - 12691.4 - HG - 221.328 - Triple effect evaporator Water 33875.496 5081.355 28794.141 MEG 12691.4 12001.617 689.783 HG 221.328 221.328 -

Drying column Water 5081.324 5081.324

MEG 12001.606 11545.3545 456.061 HG 221.328 221.328 - MEG refining column MEG 11545.545 114.8426 11430.01 HG 221.328 202.8416 19.56124 MEG recovery column Water 33875.496 24.4512 33841.44 MEG 1145.844 1061.546 116.56

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CHAPTER VII

ENERGY BALANCE

The first law of thermodynamics demands that energy be neither created nor destroyed. The following is a systematic energy balance performed for each unit of the process. The datum temperature for calculation is taken as 0C.

The different properties like specific heat, heat of reaction, heat of vaporization, etc. are taken to be constant over the temperature range.

7.1 REACTOR: [9,11]

In the reactor following reaction take place

C2H4O + H2O HOCH2CH2OH --- (1)

(Ethylene oxide) (Water) (Mono Ethylene Glycol) C2H4O + HOCH2CH2OH HOCH2CH2OH --- (2)

(Ethylene oxide) (Mono Ethylene Glycol) (Higher Glycol) Table 7.1 Heat capacity and Enthalpy data

COMPONENT ) ( 298 0 kmol kj H f  ( ) k kmol kj Cp IN Ethylene oxide -77704 99.106 Water -285830 75.673 OUT MonoEthyleneGlyocol -454800 75.673 Di-EthyleneGlyocol -285831 189.39 Water -562570 441.602

Assume reference temp. = 250C

7.1.1 Enthalpy of formation of reaction

 For first reaction R f fp f H H H0  0  0  REACTOR Temp. = 100 0C Conversion = 100 % Pressure = 1.5-2MPa Ethylene Oxide = 9190.54 Kg = 208.876 Kmols Water = 37597.68 Kg = 2088.76 Kmol

Mono Ethylene Glycol = 204.7Kmols = 12691.4 Kg Water = 1881.972 Kmols

= 33875.496Kg Higher glycol = 2.088 Kmol = 221.328Kg

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= [-454800] - [-(77704) + (-285830)] = -91266 KJ/ Kmol of EO Reacted = -91266 x 206.788

= -18.872 x 106 KJ / hr  For second reaction

R f fp f H H H0  0  0  = [-562570] – [(-77704) + (-454800)] = -30066 KJ/ Kmol of EO Reacted = -30066 x 2.088 = -62.77x103 KJ / hr

Total enthalpy of formation = (-18.872 x 106 ) + (-62.77x103 ) = -18.9347 x 106 KJ / hr

 Enthalpy of reactants

As reactants are added at 250C, so, its Enthalpy becomes 0.

 Enthalpy of products

mC mC mCp HG

T H WATER p MEG p p      ( ) = [ ( 204.7 x 189.39) + ( 1881.972 x 75.673 ) + (2.088 x 441.60) ] ( 105 – 25 ) = 14.5683 x 106 KJ / hr  Enthalpy of reaction R f p R H H H H     0 0 = (14.5683 x 106) + (-18.9347 x 106) - 0 = - 4.3043 x 106 KJ / hr

So, it indicates that it is an exothermic reaction.

So, to control temp. Inside the reactor, cooling water is passed on shell side to remove the heat.

Assuming cooling water entered at 25 o C and leave at 45 o C Q = m x Cp x ∆T

- 4.3043 x 106 = m x 75.79627 x 20

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7.2 TRIPPLE EFFECT EVAPORATOR: Water to be evaporated = 28794.716Kg/hr Total feed wF = 46788.224 Kg/hr

The balances applying to this problem are:

First effect: wSS + wF (tF – t1) Cp = w11 Second effect: w11 + (wF – w1) ( t1 – t2) Cp = w22 Third effect: w22 + (wF – w1-w2) (t2 – t3) Cp = w33 1st effect evaporator Pressure = 7 kg/cm2 Temp = 159 oC 3rd effect evaporator Pressure = 0.25 kg/cm2 Temp = 118 oC W1= 8285.66kg MEG = 165.58kg H2O = 8120.08kg F = 2088.76 Kmol = (46788.224 kg) M.E.G = 204.7Kmol = 12691.4 Kg Water =1881.972 Kmol = 33875.496Kg H.G = 2.088 Kmol = 221.328Kg To 2nd effect evaporator 2nd effect evaporator Pressure = 3.5 kg/cm2 Temp = 141 oC W2= 9689.31kg MEG = 189.139kg H2O = 9500.171kg

To MEG Recovery column

Y= 1610.8012kmol To 3rd effect evaporator From 2nd effect evaporator From 3rd effect evaporator W3= 11508.96kg MEG = 335.064kg H2O = 11173.89kg To MEG Refining column X = 477.9588 Kmol

To MEG Recovery column

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Material balances: w1 + w2 + w3 = w1-3

tF = 1050C

Consider steam is entered at 12 kg/cm2 so Ts = 190.8250C

(After finding boiling point of solution) Also last effect operates at a vacuum of 0.25 Kg/cm2

So t3 = 106.15oC (steam temp at 0.25 kg/cm2)

Consider for forward feed multiple effect evaporator pressure differences between effects will be nearly equal.

So average pressure difference = 385.056 KPa /effect Table-7.2 Breaking up the total pressure difference:

Pressur e, KPa Steam or vapor temp. C , KJ/Kg (Steam) , KJ/Kg (MEG) Steam chest, 1st effect 1179.69 TS= 190.82 S = 2210.8 Steam chest, 2nd effect 794.63 t1=175.17 1 = 2244.1 1 = 982.935 Steam chest, 3rd effect 409.57 t2=152.585 2 = 2284.0 2 = 1001.15 Vapor to condenser 24.53 t3= 106.155 3 = 2379.1 3 =1022.317 7.2.1 First effect: Cp avg. =  xiCpi = 4.196 KJ/Kg o K  avg = 2016.38 KJ/Kg WSS + wF (tF – t1) Cp = w11 (WS x 1973.62) + (46788.224 x - 70.17 x 4.196) =

w

1 x 2016.38

w

1 = 0.9787WS – 6830.42 --- (1) 7.2.2 Second effect: Cp avg. =  xiCpi = 4.105 KJ/Kg o K  avg = 2088.28 KJ/Kg

(42)

42

w

11 + (

w

F –

w

1) (t1 – t2) Cp = w22

w

1 X 2016.38 + (46788.224 -

w

1) (175.17-152.585) x 4.05 =

w

2 2088.28

Put value of w1 from equation (1) and finally

w

2 = 0.9022WS – 4245.22 --- (2) 7.2.3 Third effect: Cp avg. =  xiCpi = 3.873 KJ/Kg o K  avg = 2207.35 KJ/Kg

w

22 + (

w

F –

w

1-

w

2) ( t2 – t3) Cp

= w

33

w

22088.28 + (46788.224 –

w

1 –

w

2) (152.585 – 106.155)3.873 =

w

3 2207.35

Put value of W2 from equation 2 and finally we get

w

3 = 0.70WS – 697.42 --- (3)

Taking overall Material balances:

w

1 +

w

2+

w

3

= w

1-3

0.9787WS – 6830.42 +0.9022WS – 4245.22 + 0.70WS – 697.42 = 28794.1716 +

689.783 WS = 15.445 x 103 Kg/hr ( steam rate is required.)

From above equations we calculated,

w

1= 8285.66 Kg/hr

w

2 = 9689.31 Kg/hr

w

3 = 11508.96 Kg/hr

Now , Enthalpy out from the bottom of the last effect, Tbottom = 122oC Trefrence = 25oC

T = 97oC.

Enthalpy out from Bottom = (mCpT )MEG + ( mCpT )WATER + ( mCpT )HG

= [(12001.606 x 3.077) + (5081.324 x 4.378) + (221.328 x 4.1032)] x 97 = 5.828 x 106 KJ / hr

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43 7.3 DRYING COLUMN: Toperating = 87 oC Trefrence = 25 oC Hence T = 62o C. Poperating = 0.25 kg /cm2 Enthalpy in = 2.802 x 106 kJ / hr 7.3.1 Enthalpy out from Top

= ( m )water + ( m )MEG +( mCpT )

= [(5081.324 x 2366.1) + (456.061 x 1109 .75)]+ [289.65 x 75.2 x 64] = 12.529 x 106 kJ / hr

7.3.2 Enthalpy out from Bottom

= (mCpT )MEG + ( mCpT )HG

= [(186.218 x 187.90) + (432.72 x 2.088)] x 62 = 2.225 x 106 kJ / hr

Total Enthalpy out = Enthalpy out from (Top + Bottom) = 12.529 x106 + 2.225 x 106

= 14.75 x106 kJ / hr

Q = Total Enthalpy out - Enthalpy of feed Drying column Pressure = 0.21 kg/cm2 Temp = 87 oC Y= 289.295 Kmol = 5537.385 kg MEG = 456.061kg H2O = 5081.324 kg . X = 188.306 Kmol = 11766.873 kg MEG = 186.218kmol = 115453545kg HG = 2.088 Kmol = 221.328kg . F = 477.9588 kmol = 17304.2585 kg MEG = 12001.606kg H2O = 5081.324 kg. HG = 221.328kg.

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44

Enthalpy of feed = 5.828 x 106 kJ / hr Q = 14.75 x106 +5.828 x 106 = 8.926 x 106 kJ / hr Amount of steam required,

Consider the steam enter at 2 kg/cm2 & 118.719oC Steam = 2205.82 kJ / kg

Q = m λsteam

8.926 x 106 = m x 2205.82

m = 4046.6 kg / hr (Rate of steam)

7.4 MEG REFINING COLUMN:

7.4.1 for top:

Ttop = 91.8 oC Trefrence = 25 oC

T = 66.8 o

C Poperating = 10 mmHg

Cpmean of MEG = 189.70 kJ / kmol oK

Cpmean of DEA = 441.6 kJ / kmol oK

MEG refining column Pressure = 10 mmHg Temp = 93.2 oC W = 3.766 Kmol = 317.664 kg MEG = 1.8523kmol HG = 1.9136kmol F = 188.306 Kmol = 11766.873 kg MEG = 186.218kmol =11545.545kg HG =2.088kmol = 221.328kg D= 184.54 Kmol = 11448.8616 kg MEG = 184.355kmol (0.999.high purity) HG = 0.18454kmol

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45

Total Enthalpy out with Distillate = (mCpT ) MEG + (mCpT )DEG

= [(184.355 x 189.70) + (0.18454 x 441.6)] x 66.8 QD = 2.341 x 106 kJ / hr

Reflux Ratio = 0.71 (finding using Mc Cabe & Thiel Method) i.e. L/D = 0.71

L = 0.71D Vapor formed at the top V = L + D = 0.71D + D = 0.71 x 184.355 V = 315.247 kmol / hr Reflux L = 0.71D = 0.71 x 184.355 L = 130.89 kmol / hr  Enthalpy out with vapor:

QV = latent heat + sensible heat associated with that vapor

= m + (mCpT) MEG = 68.578 x 103 kJ / kmol DEG = 72.067 x 103 kJ / kmol AVEG = 68.58 x 103 kJ / kmol QV = [(315.247 x 68.58 x 103) + (315.247 x 188.298 x 66.8)] = 25.58 x 106 kJ / hr  Enthalpy out with Reflux:

QReflux = ( mCpT )Reflux

= [ 130.89 x 188.551 x 66.8 ] = 1.6485 x106 kJ / hr

References

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