ethylene glycol
DESCRIPTION
Ethylene GlycolTRANSCRIPT
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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
Leforts 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 7106 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
(- Glycol) (- Glycol) (- 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
7. Heat of combustion (25oC) MJ/mol 19.07
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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, 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/cm
3 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
HOCH2CH2OH HOCH2CH2Br BrCH2CH2Br
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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.
Sb2O3OOC*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
KJ/Kg).[1,3,4]
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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 20C 9.29 lb
Coefficient of Expansion at 55C 0.00065
Flash Point, Tag Closed Cup 260F
Net Contents and Type of Container
1Gallon Tin Can 9.0 lb
5Gallon DOT 17E, Pail 47 lb
55Gallon 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 Customers 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).
Mitsubishis Petrochemicals, (Japan)
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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, 20/20C 1.1151-1.1156 1.1151-1.1156
Water solubility, 25C Completely miscible
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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 H2OH2C CH2
OH
OH
+
O
CH2 H2C CH2
OH
OH
H2C CH2
OH
O CH2
OH
CH2
Ethylene OxideEthylene Glycol
Diethylene Glycol
H2C
H2C
+
O
CH2H2C H2C CH2
OH
O CH2
OH
CH2
H2C CH2
OH
O CH2
OH
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, anion-
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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 HOOCCH2OH NaCl++ H2OH+
+ CH3OH (13)CH3OOCCH2OH +HOOCCH2OH H2O
+ H2 (14)CH3OOCCH2OH +HOCH2CH2OH CH3OHCr2O3
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.
-
20
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 CH3COOCH2OOCCH3Te2Br2CH2 CH2 +
+ (16)CH3COOCH2CH2OH 2 HOCH2CH2OH3 H2O
CH3COOCH2CH2OOCCH3 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 glycols 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 CH3OHZr2Cl4
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%.
-
21
+ 2 ROH (20)ROOCCOOR +HOOCCOOH 2 H2O
ROOCCOOR + 4 H2Cu
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 190-230C 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:
-
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
-
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)
Where k0,and k1 are the rate constants.
-
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 1.92.8. 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 -0.10.2 at the concentration of some salts of about 0.5 mol/l. This enables to
produce monoethyleneglycol with high selectivity at waterethyleneoxide molar ratio
close to 10.
5.2.2 Catalyst:
A cross-linked styrenedivinylbenzene 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.
-
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
-
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.
-
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
Nitrogen [N2] : 28
-
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
-
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 = 0.851881.972
= 1599.6762 Kmol.
= 28794.1715 Kg
Total quantity of water at the top = 1599.6762 Kmol.
-
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
-
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
-
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
-
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
-
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
= 1.9135 Kmol / hr.
-
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
Plate column
-
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
MEG 1145.844 1061.546 116.56
-
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
-
38
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
kmolkj
H f
)(kkmol
kjC p
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
Rffpf HHH000
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
-
39
= [-454800] - [-(77704) + (-285830)]
= -91266 KJ/ Kmol of EO Reacted
= -91266 x 206.788
= -18.872 x 106 KJ / hr
For second reaction
Rffpf HHH000
= [-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
THGmCpCmCmHWATERpMEGpp
)(
= [ ( 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
RfpR HHHH 00
= (14.5683 x 106) + (-18.9347 x 10
6) - 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
m = 2.8394 x 10
3 Kg / hr (cooling rate) [9,11]
-
40
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
Y= 1610.8012kmol
-
41
Material balances: w1 + w2 + w3 = w1-3
tF = 1050C
Consider steam is entered at 12 kg/cm2 so Ts = 190.825
0C
(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/cm
2)
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
WSS + wF (tF t1) Cp = w11
(WS x 1973.62) + (46788.224 x - 70.17 x 4.196) = w1 x 2016.38
w1 = 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
w11 + (wF w1) (t1 t2) Cp = w22
w1 X 2016.38 + (46788.224 -w1) (175.17-152.585) x 4.05 = w2 2088.28
Put value of w1 from equation (1) and finally
w2 = 0.9022WS 4245.22 ---------------------------- (2)
7.2.3 Third effect:
Cp avg. = xiCpi
= 3.873 KJ/Kg o K
avg = 2207.35 KJ/Kg
w22 + (wF w1-w2) ( t2 t3) Cp = w33
w22088.28 + (46788.224 w1 w2) (152.585 106.155)3.873 = w3 2207.35
Put value of W2 from equation 2 and finally we get
w3 = 0.70WS 697.42 ----------------------------------- (3)
Taking overall Material balances:
w1 + w2 + w3 = w1-3
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,
w1 = 8285.66 Kg/hr
w2 = 9689.31 Kg/hr
w3 = 11508.96 Kg/hr
Now , Enthalpy out from the bottom of the last effect,
Tbottom = 122oC Trefrence = 25
oC
T = 97oC.
Enthalpy out from Bottom = (mCpT )MEG + ( mCpT )WATER + ( mCpT )HG
= [(12001.606 x 3.077) + (5081.324 x 4.378) + (221.328 x 4.1032)] x 97
= 5.828 x 106 KJ / hr
-
43
7.3 DRYING COLUMN:
Toperating = 87 oC Trefrence = 25
oC
Hence T = 62oC.
Poperating = 0.25 kg /cm2
Enthalpy in = 2.802 x 10
6 kJ / hr
7.3.1 Enthalpy out from Top
= ( m )water + ( m )MEG +( mCpT )
= [(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
= (mCpT )MEG + ( mCpT )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 10
6
= 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.
-
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 steam
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 oC
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
-
45
Total Enthalpy out with Distillate = (mCpT ) MEG + (mCpT )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 + (mCpT)
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 = ( mCpT )Reflux
= [ 130.89 x 188.551 x 66.8 ]
= 1.6485 x106 kJ / hr
-
46
Condenser load, QC :
= QV ( QReflux + QD )
= [(25.58 x 106
) (1.6485 x106 + 2.341 x 106 )]
= 21.595 x 106 kJ / hr
Assuming cooling water enters the condenser at 25oC & leave at 45
oC
QC = (mCpT )cooling water
21.595 x 106
= m x 75.7962 x 20
m = 11.63 x 103 kg / hr (Rate of cooling water)
7.4.2 For bottom:
Tbottom = 94.6 oC T = 69.6 oC
Cpmean of MEG = 188.531 kJ / kmol 0K
Cpmean of DEG = 443.2 kJ / kmol 0K
Enthalpy out with Residue, QResidue = ( mCpT )liq
= [(1.8528 x 188.531) MEG + (1.9136 x 443.2) DEG] x 69.6
= 83.34 x 106 kJ / hr
Reboiler Load:
Reboiler heat load is determined from a balance over complete system
QB + QFeed = QD + QW + QC
QFeed = 2.252 x 106 kJ / hr
QB = (21.595 x 106
+ 83.34 x 106 - 2.252 x 10
6 + 2.341 x 10
6 )
= 21.794 x 106
kJ / hr
Amount of steam required,
Consider the steam enter at 2 kg/cm2 & 118.719oC
steam = 2205.82 kJ / kg
QB = m steam
-
47
21.794 x 106
= m x 2205.82
m = 9.88 x 10 3 kg / hr ( Rate of steam )
7.5 MEG RECOVERY COLUMN:
7.5.1 For top:
Ttop = 194oC Trefrence = 25
oC
T = 169 oC
Poperating = 760 mmHg
Cpmean of MEG = 197.24 kJ / kmol oK
Cpmean of H2O = 76.55 kJ / kmol oK
Total Enthalpy out with Distillate = (mCpT )MEG + (mCpT ) WATER
= [(1881.08 x 76.55) + (1.874 x 197.24)] x 169
QD = 24.40 x 106 kJ / hr
Reflux Ratio = 0.51 (finding using Mc Cabe & Thiel Method)
i.e. L/D = 0.51
L = 0.51D
Vapor formed at the top V = L + D
= 0.51D + D
MEG recovery column
Plate column
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
F = 188.306 Kmol = 11766.873 kg
MEG = 186.218kmol
=11545.545kg
HG =2.088kmol
= 221.328kg
-
48
= 0.51 x 1881.97
V = 2841.77kmol / hr
Reflux L = 0.71D
= 0.51 x 1881.97
L = 959.80 kmol / hr
Enthalpy out with vapor:
QV = latent heat + sensible heat associated with that vapor
= m + (mCpT)
MEG = 1023.184 kJ / Kg H2O = 2231.8 kJ / Kg
AVEG = 40.195 x 103 kJ / kmol
QV = [(2841.77 x 40.195 x 103) + (2841.77 x 197.24x 169)]
= 208.95 106
kJ / hr
Enthalpy out with Reflux:
QReflux = (mCpT) Reflux
= [959.80 x 76.67 x 169]
= 12.43 x106 kJ / hr
Condenser load
QC = QV ( QReflux + QD )
= [(208.95 106
) (12.43 x106 + 24.40 x 106 )]
= 172.12 x 106
kJ / hr
Assuming cooling water enter the condenser at 25oC & leaves at 45
oC
QC = (mCpT )cooling water
172.12 x 106
= m x 75.7962 x 20
m = 113.63 x 103 kg / hr (Rate of cooling water)
-
49
7.5.2 For bottom:
Tbottom = 198 oC Trefrence = 25
oC
T = 173 oC
Cpmean of MEG = 197.6285 kJ / kmol 0K
Cpmean of H2O = 76.607 kJ / kmol 0K
Enthalpy out with Residue:
QResidue = ( mCpT )liq
= [(17.122 x 197.6285) MEG + (1.3584 x 76.607 )DEG ] x 173
= 603.39 x 103 kJ / hr
Reboiler Load:
Reboiler heat load is determined from a balance over complete system
QB + QFeed = QD + QW + QC
QFeed = ( mCpT )feed
= [(18.481 x 187.97) MEG + (1881.97x 74.51) WATER] x 80
= 143.71x 103 kJ / hr
Reboiler load
QB = [( 603.39 x 103 + 172.12 x 10
6 + 24.40 x 10
6 ) (143.71x 103) ]
= 196.97 x 106
kJ / hr
Amount of steam required,
Consider the steam enter at 2 kg/cm2 & 118.719oC
steam =2037.51 kJ / kg
QB = m steam
196.97 x 106
= m x 2037.51
m = 97.67 x 10 3 kg / hr ( Rate of steam ) [9,11]
-
50
CHAPTER VIII
REACTIONS KINETICS & THERMODYNAMICS
8.1 REACTOR KINETICS:
Here,
FAO = 208.876 Kmol/hr
= 9190.544 Kg/hr
V0 = 10.649 m3/hr
FAO = CAO V0
208.87 = Cao x 10.649
CAO = 19.6136 Kmol/m3 = 19.6136 mol/lit
Similarly,
CBO = 5.555 Kmol/m3 = 55.555 mol/lit
Now, Rate of reaction is given by
d (C2H4O) = {K0([H2O] + b [Gyi]) + Kct [HCO3]} X
dt {{[H2O] + p [Gyi]}x [Oxide]}
Where,
Gyi = concentration of reactant (mol/lit)
[H2O] = concentration of water (mol/lit)
[Oxide] = concentration of oxide (mol/lit)
b = distribution factor =2.8
p = 1.88
REACTOR
Temp. = 50 0C
Conversion = 100
%
E. O = 9190.54 Kg
= 208.876 Kmols
Water = 37597.68 Kg
= 2088.76 Kmol
Product =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
-
51
d (C2H4O) = rA = {K0(CB + b (CA + CB)) + Kct [HCO3] } X
dt {(CB + p (CA + CB)) x [CA]}
Rate constant Ko is given by,
K0 = exp [9.077 9355]
T
where T = temperature o K
K0 = exp [9.077 9355]
378
K0 = 1.5627 x 10-7
L2 = 0.0005625 L
2
mol2. Sec mol
2. hr
Similarly catalyst Rate constant Kct is given by,
Kct = exp [18.24 10574]
T
Kct = 5.926 x 10-5
L2 = 0.21334 L
2
mol2. Sec mol
2. hr
Now,
CAO XA = CBO XB
a b
19.6136 XA = 55.555 XB
1 1
XB = 0.3530 XA
- rA ={ K0[(CBO(1 0.3530 XA)) + 2.8 (CAO (1 XA) + CBO (1 0.3530 XA))]
+ Kct [0.25]} x {[CBO (1 0.3530 XA) + 1.88 [CAO (1 XA) + CBO (1
0.3530 XA)]}x CAO (1 XA)}
- rA ={ 0.0005625 [55.555 (1 0.3530 XA)) + 2.8 (19.6136 (1 XA) +
55.555 (1 0.3530 XA)] + 0.05533} x {55.555 (1 0.3530 XA) +
1.88 [19.6135 (1 XA) + 55.555 (1 0.3530 XA)]}x
19.6136 (1 XA)}
-
52
Table-8.1 Different value of XA and finding corresponding rate (-rA),
XA = 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.98
-rA = 654.5 532.40 424.57 330.131 248.286 178.2369 119.1836 70.31 30.86 53.60
(1/-
rA)
(lit.hr
/mol)
0.005 0.0018 0.0023 0.00302 0.00402 0.00561 0.0084 0.01 0.03 0.186
From the above data plotting a XA Vs )1
(rA
& finding the area under he curve at
Xa = 0.98
Fig-4 Reactor volume Chart
AREA UNDER THE CURVE = 0.01227
Plug flow equation related to volume is given by [15]
XA
V = d XA
FAO 0 - rA
XA
d XA =Area under the curve
0 - rA
Area under the curve = 0.01227
-
53
FAo
V = 0.01227
V = 2562.90 lit
V = 2.56 m3
Now we have
= Empty volume in bed
Total bed Volume
1 = 1 Empty volume in bed
Total bed Volume
1 = Total Bed Vol Empty volume in bed
Total bed Volume
But Total Bed Empty volume in Bed = Volume of Catalyst.
1 = Volume of Catalyst
Total bed Volume
1 = Volume of Catalyst
2.56 m3
Consider = 0.6
Total Volume of Catalyst = 1.024 m3
8.2 THERMODYNAMICS
As we know the Gibbs free energy is given by following equation
G = -RT lnK
Where K = Kequ = (ka * kb)/ (kc * kd)
From reaction,
ka and kb are rate constants for the products.
Similarly kc and kd are rate constants for the reactants. But assuming reaction is
exothermic and irreversible; the values of kc and kd will not be in consideration to
finding out equilibrium rate constant.
Hence, Kequ is given by
Kequ = ka kb
Enthalpy, Gibbs free energy and specific heat data are below at reaction temperature
100 0C in the form of functional group. [11]
-
54
-O- group: Cp = 19.28 KJ /.Kg K, G = -15.38 KJ / Kg K
H = -1467.62 KJ /.Kg K
-CH2- group: Cp = 20.43 KJ /.Kg K, G = -3.87 KJ / Kg K
H = -1516.94 KJ /Kg K
-OH- group: Cp = -1.83 KJ /.Kg K, G = -36.785 KJ / Kg K
H = 96.75 KJ /.Kg K
H2O: G = -8.728 KJ / Kg K
G total = G product - G reactant
C2H4O + H2O HOCH2CH2OH --------- (1)
(Ethylene oxide) (Water) (Mono Ethylene Glycol)
G = [(-81.31)]-[(-23.12) + (-8.728)]
G = - 49.53 KJ/Kmol K
Ka = exp [-(-49.53) / (8314*373)]
Ka =1.00
ln(K2/K1)= E/R[(1/T1)-(1/T2)] [15]
ln(9.5/8)= E/8.314[(1/368)-(1/373)]
T2 reaction at 100 oC= 373K
T1 reaction at 95 oC=368K
0.26236 = 6.2382* E *10-6
E = 7.52*E*-7 J/mol
-
55
CHAPTER IX
MAJOR EQUIPMENT DESIGN
9.1 DESIGN OF REACTOR AS A SHELL & TUBE HEAT EXCHANGER :
Consider the reactants are flow on tube side and cooling water are on shell side
Catalysts are fill inside the tube.
9.1.1 Process Design: [22]
Consider length of tube = 4m
Diameter of tube = 2.5 cm
Volume of one tube = (d)2 (L) 4
= (2.5 x 10-2)2 (4) 4
= 1.9634 x 10-3
m3
Table-9.1 Properties at arithmetic mean temperature.
Props. Shell Side
(Water) (30oC
)
Tube side
(Ethylene oxide + H2O) (65oC)
Cp 5.1865 (KJ/Kg oK) 4.840 (KJ/Kg
oK)
9 x 10-4
(Kg/m.Sec) 4.187 x 10-4
(Kg/m.Sec)
K 0.62 (w/m.oK) 0.54 (w/m.
oK)
995.40 (Kg/m3) 973.09 (Kg/m
3)
No. of tube = Volume of reactor
Volume of one tube
= 001963.0
56.2
No. of tubes = 1304 Nos.
Area of tube per pass:
Atp = (d) 2
(Ntp)
4
= (2.5 x 10-2)2 (1304) 4
Atp = 0.64 m2
Velocity:
U = Atp
m
-
56
m = 12.996 Kg/Sec
U = 64.009.973
996.12
x
U = 0.02 m/sec
Now, NRe = )1(
x
du
= (2.5 x 10-2
) x (0.02) x (973.09)
(4.187 x 10-4
) x (1 -0.6)
NRe = 2905.09
Now, AO = Nt x x d xL
= (1304) x x (2.5 x 10-2) x (4) AO = 409.66 m
2
Shell diameter:
Ds =
5.02
)(637.0
L
xdoPAox
Ctp
CLR
Consider the Triangular pitch
CTP = 0.9
CL = 0.7
Take PR = Pube pitch ratio
= 1.25
Ds = 0.637 0.7 409.66 x (1.25)2 x (2.5 x 10
-2)
0.5
0.9 4
Ds = 1.123 m
Now, No. of tubes that can be accommodate
Nt = 0.875 CTP __(Ds)2
CL (PR)2 (d)
2
= 0.875 0.9 ____(1.123)2
0.7 (1.25)2 (0.025)
2
= 1452.8 > Total No of tube that is required.
Shell side H.T.C :
k
hoxDe)( =
14.0333.055.0
36.0
w
bxk
Cpxx
DexGsx
For triangular pitch
-
57
De = 4 3 PT2 d2
2 4
d
Pitch ratio = PR = d
PT
1.5= 0025.0
TP
PT = 0.03125 m
De = 4 3 (0.31252 x (2.5 x 10-2)2
2 4
x 0.0025
De = 0.018 m
Gs = As
m
As = TP
DsxCxB
C = PT do = 0.03125 0.025 = 0.00625
B = 0.4 Ds
= 0.4 x 1.125
= 0.45
As = 1.123 x 0.00625 x 0.45 0.03125
As = 0.101 m2
Gs = As
m
= 12.996
0.10
Gs = 128.58 Kg/m2.sec
From the above equation,
-
58
62.0
)018.0(hox = 14.0
333.04355.0
41
62.0
109101865.5
109
58.128018.036.0 x
xxxx
x
xx
ho = 1825.04km
w20
Tube side H.T.C:
Nu = 0.023 (NRe)0.