Acetic anhydride

Manufacture of acetic anhydride

1. Introduction :-

Acetic anhydride also known as ethanoic anhydride or

methyl carboxylic anhydride is a colourless liquid, very similar to acetic acid in its

pungent, acrid odour, viscosity, density & refractive index. It does not occur

naturally & was 1st synthesized by C.F.Gerhardt in 1852 by the reaction of benzoil

chloride & molten potassium acetate. Today it is one of the most important organic

intermediates & is widely used in both research & industry.

About 40% of the acetic anhydride produced throughout

the world is used for the production of Vinyl acetate monomer(VAM) which is

used for the production of downstream products such as adhesives, textiles, and

paints.

Apart from this acetic anhydride has many other utilities

such as in the manufacture of “Aspirin” an important medicine, in the production

of acetanilide which is used as a starting material in the manufacture of some

sulpha drugs, it is also useful in manufacture of perfumes, herbicides, acetyl

peroxide bleach & plasticizers.

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Production of acetic anhydride (in kt) :-

Country 1961 1971 1974 1979 1980 1981 1982 1989 1990 1996 2001

United

States

571 686 741 - - 567 481 778 830 1000 1160

Germany 32 47 74 91 85 77 76 108 112 - -

Japan 33 96 115 114 150 145 144 205 1160 - -

Major producers in India :-

Sr. No. Manufacturer Capacity(TPA)

1VAM Organics Ltd,

33000

2Andhra sugars Ltd, Andhra.

3058

3Ashok Brothers, Mumbai

6600

4IOL chemicals & pharmaceuticals Ltd, Punjab

12000

5Vasantdada Shetkari SSK

3000

6Trichy distillers & chemicals Ltd, Trichy

2,100

7R L G Group of industries, Gujrat

10000

8Naran Lala Private Ltd, Gujrat

-

9FISCHER Chemic Ltd, Chennai

-

10Mysore Acetate & chemicals Ltd., Mysore

6000

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Markets :-

Vinyl Acetate Monomer (VAM) :-

It is the largest consumer of acetic anhydride and constitutes nearly 40% of the

demand. VAM is usually used in the downstream products such as adhesives,

textiles, and paints.

Drugs/ Pharma :-

Drugs and pharmaceuticals constitute 18% of the total production. It is used in the

manufacturing of Aspirin. About 0.8 tons of anhydride is required to produce 1 ton

of Aspirin. This constitutes 3% of the total production. Manufacturing 0.9 ton of

Paracetamol requires 1 ton of acetic anhydride and it constitutes 9% of the total

demand. Vitamins constitute nearly 1% of the total demand and intermediates like

MCA account for 5% of total demand.

Cellulose acetate :-

These account for nearly 9 % of the total demand for anhydride. Cellulose acetate.

is used in the downstream products such as cigarette filters. About 1 ton of

anhydride is required to produce 1 ton of the cellulose acetate.

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Dyes and pigments :-

This constitutes about 18% of the total production.

Capacity structure :-

VAM organics is the largest producer with an installed capacity of 33,000 ton per

annum. Ashok organic, Mysore acetate and IOL have smaller capacities. The total

installed capacity is around 62,000 ton per annum whereas the demand hovers

around 42000 ton per annum. Most of the consumption is captive.

Demand and pricing :-

Demand has seen a steady rise, but the capacity utilization has been around

65-70%. The main reason for the slow growth has been the plant change-overs

where anhydride capacity can be used for acetic acid production.

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The prices are dependent on the prices of the raw

material namely acetic acid. The import duty for acetic anhydride was reduced

from 65% in 1994-95 to 40% in 1996-97. Unlike acetic acid domestic prices were

pegged slightly lower than the landed costs. All the major manufacturers of acetic

anhydride also manufacture acetic acid. Hence the sizeable difference between

international and domestic prices of acetic acid allows the producers to peg the

prices of acetic anhydride just below the landed cost.

Outlook

The demand is expected around 55000 tonnes this year. However, with the

reducing of import duty the flexibility of the local manufacturers will be eroded.

The declining international prices of acetic acid have resulted in the reduction of

the prices of the anhydride. This has resulted in the reduction of the

competitiveness among domestic producers.

Import :-

Market estimated at Rs. 90 crs. Import not high - around 3%

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Price :-

Historical (1994 - 1999): 45 Rs./kg , Current: 50 Rs/kg.

1.1 Historical background :-

The oldest process for making acetic anhydride is

based on the conversion of sodium acetate with the excess of an inorganic chloride

such as thionyl chloride, sulfuryl chloride or phosphoryl chloride. In this process

half of the sodium acetate is converted to acetyl chloride, which then reacts with

the remaining sodium acetate to form acetic anhydride as follows:-

CH3COONa + X-Cl → CH3COCl + X-ONa

CH3COONa + CH3COCL → (CH3CO)2O + NaCl

Where, X= SOCl, SO2Cl, POCL2

A further development, the conversion of acetic acid

with phosgene in the presence of aluminium chloride, has the advantage that it

allows continous operation.

2CH3COOH + COCl2 → (CH3CO)2O + 2HCl + CO2

Two other methods also were used in the past:

The cleavage of ethylidene diacetate to form

acetaldehyde and acetic anhydride in the presence of acid catalyst such as zinc

chloride & the second method is by the reaction of vinyl acetate with acetic acid on

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palladium to form acetaldehude and acetic anhydride. None of these processes is

having any industrial importance.

Today, acetic anhydride is made mostly by either the

ketene process or the oxidation of acetaldehyde. Production by another process, the

carbonylation of methyl acetate (Halcon process ) was begun in 1983. In western

Europe, 77% of the acetic anhydride is made by the ketene processand rest 23% by

the oxidation of acetaldehyde. In United States 25% of the acetic anhydride is

made by the Halcon Process & the rest 75% by the ketene process.

1.2. Physical Properties of Raw Material:-

Acetic Acid :-

Auto-ignition temperature (°C) 565

Boiling point at 760mm Hg (°C) 118.1

Colour colourless

Critical pressure, (atm) 57.2

Critical temperature, (°C) 321.6

Molecular Weight 60.0530

Heat of Combustion (Kcal/mole) -208.7

Heat of Formation (Kcal/mole) -116.2

Heat of Fusion (cal/g) 44.7

Heat of Vapourisation (cal/g) 96.8

Heat of Solution at 18°C (Kcal/mole) 0.375

Refractive index 1.3718

Specific Heat at 0°C (cal/g) 0.468

Surface Tension at 20°C in air, (dyne/cm) 27.6

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Taste acrid

Viscosity (cp)

At 20°C 1.18

At 40°C 0.82

Specific Gravity 1.049

1.3. Physical Properties Of The Product :-

Acetic Anhydride :-

Property Vapour Liquid

Molecular Weight 102.090 102.090

Melting Point (°C) - -73

Normal Boiling Point (°C) - 139

Specific Gravity 3.52 1.084

Coefficient of expansion (20°C) - 0.00112

Critical Temperature (°C) - 326 -

Critical Pressure (atm) - 43 -

Critical Volume (cc/g-mol) - 290 -

Surface Tension (dyne/cm, 20°C) air - 33

Viscosity (cp, 20°C) 0.008 0.91

Specific Heat (cal/g °C) 0.23 0.434

Heat of Fusion (cal/g) - 24.6

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Heat of Vapourisation (at NBP, cal/g) - 93

ΔHf° (cal/g) at 25°C -1347.8 -1460.9

ΔGf°(cal/g) at 25°C -1116.0 -1144.8

Heat of Hydrolysis (cal/g) at 25°C - 136.9

1.4. Chemical Properties Of Acetic Anhydride :-

On chlorination it produces chloro-acetyl chloride. In addition small quantities

of dichloro-acetyl chloride, acetyl chloride, chloro-acetic acid & HCl are

formed.

(CH3CO)2O + Cl2 → Cl-CH2COCl + CH3COOH

Acetic anhydride chloro-acetyl Acetic acid

chloride

On reaction with hydrogen chloride under pressure it gives acetyl chloride.

(CH3CO)2O + HCl → CH3OCl + CH3COOH

Acetic anhydride acetyl chloride Acetic acid

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It undergoes hydrolysis slowly with water but rapidly hydrolysed with alkali to

form acetic acid.

(CH3CO)2O + H2O → 2CH3COOH

Acetic anhydride Acetic acid

On reaction with acetaldehyde it forms ethylidene di-acetate.

(CH3CO)2O + CH3CHO → CH3CH(OCOCH3)2

Acetic anhydride Acetaldehyde Ethylidene di-acetate

1.5. Storage & Transportation :-

For storage & transportation of pure acetic

anhydride tanks made of aluminium, stainless ste.6el ( 18% Cr, 8% Ni & 2% Mo )

or poly-ethylene are generally used. Although glass or enamel containers also may

be employed. Iron is highly resistant to acetic anhydride, provided moisture is

excluded. Hence it is possible to use iron in the production & workup in certain

instances for example in pumps & tanks.

1.6. Health & Safety Aspects :-

Acetic anhydride penetrates the skin

quickly and painfully forming burns and blisters that are slow to heal. Anhydride is

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especially dangerous to the delicate tissues of the eyes, ears, nose & mouth. The

threshold value for eyes is 0.36 mg/m3. When handling acetic anhydride, rubber

gloves that are free of pinholes are recommended for the hands, as well as plastic

goggles for the eyes, and Face-marks to cover the face and ears.

Acetic acid is dangerous in combination with various

oxidizing substances and strong acids. Chromium trioxide and anhydride react

violently to burn, thermal decomposition of nitric acid in acetic acid is accelerated

by the presence of anhydride.

1.7. Applications :-

The biggest use of acetic anhydride is in the manufacture of cellulose

acetates( about 86% of world production ). Acetates produced include cellulose

acetate, cellulose di-acetate, cellulose tri-acetate, cellulose acetate propionate &

cellulose butyrate. The remaining 14% is consumed in various miscellaneous

uses which are as given below.

It is used in the production of polymethyl-acylamide or hard foam, acetic

anhydride is used for binding ammonia that is liberated on conversion of two

amide groups to an imide group.

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It is used in dyeing industry, where acetic anhydride is used chiefly in mixtures

with nitric acid as a nitrating agent. Here the solvent and dehydrating properties

of acetic anhydride are used.

It is used in the manufacture of various organic intermediates such as chloro-

acetyl chloride, di-acetyl peroxide, higher carboxylic anhydrides, acetates and

boron tri-fluoride complex.

It is used in the manufacture of certain pharmaceutical products such as acetyl

salicylic acid(aspirin), p-acetyl amino phenol, acetanilide, acetophenacetin,

theophyllin, sulfamides, a number of hormones & vitamins.

It is used in the detergent industry for the production of cold-bleaching

activators such as tetra-acetyl-ethylene diamine.

It is used in the manufacture of explosives, particularly hexogen production.

It is used in the manufacture of acetylated plastic auxiliaries such as glycerol

tri-acetate acetyl tri-butyl citrate & acetyl ricinolate.

It is used in the food industry, mainly in the acetylation of animal & plant fats

in order to obtain the desired solubilities, in the production of acetostearin, in

the edible packing materials & to clarify plant oils.

It is used in the manufacture of flavours & fragrances.

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It is used n metallography, etching & polishing of metals and in semiconductor

manufacture.

Small % of acetic anhydride in acetic acid or cold water solutions are used as

powerful fungicides & herbicides.

2. Different Routes Of Manufacture :-

(a) Acetaldehyde oxidation :-

Acetaldehyde oxidation for the production of acetic

anhydride co-produces acetic acid. The reaction conditions are about 60ºC at 1atm

pressure and 70ºC at 6atm. Oxygen or air is employed for the oxidation purpose in

the presence of cobalt acetate catalyst promoted by copper acetate. The reactions

taking place are :-

CH3CHO + O2 → CH3COOOH

Acetaldehyde peracetic acid

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CH3COOOH + CH3CHO → (CH3CO)2O + H2O

Peracetic acid Acetic acid Acetic anhydride

(CH3CO)2O + H2O → 2CH3COOH


The last reaction is to be minimized if acetic

anhydride yield is to be maximum. Overall selectivity of acetaldehyde plus the

acetic acid is maintained at 95-98% while the weight ratio of overall yields can be

from 0.5-9 (anhydride to acid ). The higher ratios require a vapor product from the

reactor to rid the product mixture of the catalyst quickly. An azeotropic solvent,

such as ethyl acetate also enhances water vaporization from the reaction zone. Heat

of reaction is adequate to vaporize the product and unconverted acetaldehyde, but a

high recycle of low oxygen content off-gas is required for stripping because of the

low vapor pressure of the reaction products.

(b)Methyl Acetate Carbonylation :-

Acetic anhydride can be made by the carbonylation

of methyl acetate. Methanol acetylation is an essential 1 st step in anhydride

manufacture by carbonylation, the reactions taking place are :-

CH3COOH + CH3OH → CH3COOCH3 + H2O , ∆H= -4.89

KJ/mol

Acetic acid Methanol Methyl acetate

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CH3COOCH3 + CO → (CH3CO)2O , ∆H= -94.8 KJ/mol

Methyl acetate Acetic anhydride

The catalyst stream for the methyl acetate carbonylation

process involves rhodium chloride tri-hydrate, methyl iodide, chromium metal

powder and alumina support or nickel carbonyl complex with tri-phenyl

phosphine, methyl iodide and chromium hexa-carbonyl. In another, the alumina

catalyst support is treated with an organosilicon compound having either a terminal

organophosphine or similar ligands and rhodium or a similar noble metal. Such a

catalyst enabled methyl acetate carbonylation at 200ºC under 20 MPa pressure.

Conversion is 42.8% with the 97.5% selectivity. In anhydride purification, iodide

purification is of considerable significance, potassium acetate is employed for this

purpose. Because of the presence of iodide in the reaction system, titanium is the

most suitable material of construction.

(c) Ketene processes :-

(i) Acetone Cracking :-

Acetic anhydride can be manufactured by

acetone cracking. In this process acetone is 1st cracked to ketene and in the next

step ketene reacts with acetic acid to form acetic anhydride. The 1 st step of the

reaction is carried out in a pyrolysis heater at about 700ºC and 1.5 atm pressure.

The reaction goes to achieve 20-25% of acetone and 70-75% selectivity to ketene.

The reaction taking place are :-

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CH3-CO-CH3 → CH2=CO + CH4

Acetone Ketene Methane

CH2=CO + CH3COOH → (CH3CO)2O + H20

Ketene Acetic acid Acetic anhydride

Quenching of the high-temperature reaction by

evaporating an injected mixture of acetic acid and acetic anhydride preceeds

cooling and ketene absorption by acetic acid. At the available pressure, chilling is

unnecessary, however both excess acetone and ketene must be absorbed from a

relatively large volume of gas. Water formed inside the reaction leads to some

hydrolysis of acetic anhydride. Water wash of the vent gas recovers acetic acid

vapor and recycle acetone.

(ii) Acetic Acid Dehydration :-

Acetic anhydride can be

manufactured by the thermal decomposition of acetic acid. The 1st step of the

reaction is the dehydration of acetic acid at pressures of about 15-20 KPa and

temperature of about 700ºC to form ketene, the 2nd step involves the reaction of

ketene with acetic acid to form acetic anhydride at a temperature of about 50ºC.

The reactions taking place are :-

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CH3COOH → CH2=CO + H20 , ∆H=147 KJ/mol

Acetic acid Ketene

CH2=CO + CH3COOH → (CH3CO)2 , ∆H= -63 KJ/mol

Ketene Acetic acid Acetic anhydride

Tri-ethyl phosphate is commonly used as a

dehydration catalyst for the water formed in the 1st step. It is neutralized in the exit

gases with ammonia. Aqueous 30% ammonia is employed as a solvent in the

second step because water facilitates the reaction, and the small amount of water

introduced is not significanr overall. Nickel-free alloys for example, ferrochrome

alloy, chrome-aluminium steel, are needed for the acetic acid pyrolysis tubes,

because nickel promotes the formation of soot and coke, and reacts with carbon

monoxide yielding a highly toxic metal carbonyl. Conventional operating

conditions furnish 85-88% conversion, selectivity to ketene is 90-95%.

3. Process Selection :-

(a) Acetone process :-

It can be used only when acetone is relatively

expensive, but the major disadvantages are that methane is formed during the

process which is very harmful and extra measures are to be taken to remove it.

Coke formation at the severe conditions is more of a problem than with acetic

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acid dehydration process, also low conversion demands more heater duty for

the ketene produced.

(b) Acetaldehyde oxidation :-

Acetic anhydride formed during the process may

undergo hydrolysis to form acetic acid according to the reaction :-

(CH3CO)2 + H2O → 2CH3COOH


This reaction is to be minimized in order to achieve

the maximum yield of acetic anhydride. Also acetaldehyde is to be manufactured

1st because it is not available directly, this makes the process uneconomical & the

cost of the production increases.

(c) Methyl Acetate Carbonylation :-

Catalyst recovery is the major operating problem

because rhodium is very costly metal & every trace must be recovered, otherwise it

may lead to a major economic loss. Hence additional process would be required for

the recovery of the catalyst which makes the process a bit expensive. Also the

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process is still in a developing phase and only 15% of the acetic anhydride

produced in the world is being manufactured using this process.

(d) Acetic Acid Dehydration :-

Ketene reacts readily with acetic acid to produce

acetic anhydride hence the process is economically and practically more viable this

is the why about 85% of the acetic anhydride produced in the world is being

manufactured by this process. Also the raw material required is only acetic acid

which is readily available which makes the process more economical.

Thus from above considerations it is clear that the

acetic acid process is the one which is generally employed because it is

economically and practically more viable. Thus acetic acid process is being

selected taking in to account its advantages than the other processes of

manufacture.

4. Process Description :-

(i) Principle :-

Production of acetic anhydride from

acetic acid comprises of two steps :-

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(a) Pyrolysis of acetic acid to form ketene.

(b) Reaction of ketene obtained with acetic acid

The first conversion which is highly endothermic is

carried out in vapor phase at high temperature at about 700ºC, and at reduced

pressure about 10-20 KPa, very short residence time in the neighborhood of 1

sec, and the presence of catalyst, serve to limit the formation of by products.The

catalyst system employed for dehydration are usually organic phosphates (tri-

ethyl, tri-cresyl, di-methyl ammonium, pyridium phosphates, etc.) which are

added directly and continuously in to the gas feed stream, at the rate of 0.2-

0.5% weight.

The addition of water in small concentrations(10%

weight) to the acetic acid offers similar advantage to those procured in steam

cracking. In particular it slows down the formation of coke. The addition of

small amounts of ammonia (< 1000 ppm) exerts an indirect inhibiting effect on

the polymerization of ketene. If these precautions are taken then once-through

conversion is about 85-90% and the molar yield 90-95%.

The second conversion, which is exothermic, can

be can be carried out in the absence of catalyst, by absorption in acetic acid,

between 45-55ºC, at reduced pressure 7-25 KPa. Higher temperatures and

pressures facilitate the dimerisation of ketene to di-ketene, whose boiling point is

127.4ºC which is fairly close to that of anhydride. Less than 2% weight is generally

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formed, so that the yield of operation, with respect to both acid and ketene is about

95-98 molar percent.

(ii) Industrial Manufacture :-

The industrial manufacture of acetic anhydride

using acetic acid consists of four main sections :-

(a) Acetic acid pyrolysis

(b) Ketene absorption

(c) Acetic acid purification.

(d) Recovery of unconverted acetic acid.

The first step which is the pyrolysis of acetic acid

involves the thermal decomposition of acetic acid preheated to about 110ºC and

containing continuous additions of triethyl phosphate catalyst, which contains

nickel and facilitate the complete cracking of the reactants and products, as well

as the formation of coke, it is preferable to use high-chromium steels as the tube

material, or alloys of chromium (23%), aluminium (1.5%), and silicon (1.5%).

If not, coking can be slowed down by the addition of carbon-di-sulfide to the

feed.

The reactor effluents, available at about 700ºC, first

receive an inline injection of ammonia to neutralize the catalyst. They are then

cooled rapidly to 0ºC in a series of heat exchangers. The liquid obtained by

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condensation and containing about 35% weight acetic acid is sent to the

recovery section.

Ketene absorption takes place on the off gases, with

a countercurrent of acetic acid, collecting about 95% of the available ketene.

The unit operates at around 45-55ºC and the pressure of about 5-15 KPa

absolute. The liquid leaving the absorption stage contains more than 90% acetic

anhydride. It is sent to the purification system.

Purification takes place by distillation in a series of

two distillation columns, the first column separates acetic acid from the top

which is sent to the recovery section and acetic anhydride of about 99% purity

from the bottom, the heavier components are collected at the bottom of the final

fractionation.

The recovered acetic acid ( unconverted acetic acid)

is reconcentrated in a distillation column which removes water from the top and

acetic acid of 95% purity at the bottom.

5. Thermodynamics :-

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Thermodynamic properties of raw materials & product are as given below :-

(i) Acetic Acid :-

Property A B C D

Specific Heat(Cp), J/mol K

-18.944 1.0971 2.8921 ×10-3 2.9275 ×10-

6

∆Hf (KJ/mol) -44.988 -0.00983 2.46×10-6 -

∆G (KJ/mol) -47.916 0 5.04×10-6 -

(ii) Ketene :-

Property A B C D

∆Hf (KJ/mol) -44.988 -0.00983 2.46×10-6 -

∆G (KJ/mol) -47.916 0 5.04×10-6 -

(iii) Water :-

Property A B C D


92.053 -3.9953×10-2 -2.1103×10-4 5.3469×10-7

∆Hf (KJ/mol) -238.41 -0.01226 2.77×10-6 -

Also, ∆G at 298K for Water = 238.59 Kj/hr

(iv) Acetic Anhydride :-

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Property A B C D


71.831 8.8879 ×10-1 -2.6534 ×10-3 3.3501 ×10-

6

∆Hf (KJ/mol) -44.988 -0.00983 2.46×10-6 -

∆G (KJ/mol) -47.916 0 5.04×10-6 -

Reaction 1 :-

CH3COOH → CH2=CO + H2O Acetic acid Ketene

a) Heat of Reaction :-

Ketene :- ∆H0 = A + BT + CT2 (KJ/mol)

∆H0 = -44.988 – 0.00983×T + 2.46×10-6×T2

Therefore. at 298K

∆H0298 = -44.988 – 0.00983×298 + 2.46×10-6×2982

= -74.063 KJ/mol

And, at 700 ºC that is at 973K ∆H0

973 = -44.988 – 0.00983×973 + 2.46×10-6×9732

= -51.23 KJ/mol

Acetic acid :-

∆H0 = A + BT + CT2 (KJ/mol)

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∆H0 = -422.584 – 4.8354×10-4×T + 2.46×10-6×T2

Therefore. at 298K

∆H0298 = -422.584 – 4.8354×10-4×298 + 2.3337×10-5×2982

= -434.84 KJ/mol

And at 973K

∆H0973 = -422.584 – 4.8354×10-4×973 + 2.3337×10-5×9732

= -408.3 KJ/mol

Water :-∆H0 = A + BT + CT2 (KJ/mol)

∆H0 = -238.41 – 0.01226×T + 2.77×10-6×T2

Therefore. at 298K

∆H0298 = -238.41 – 0.01226×298 + 2.77×10-6×2982

= - 241.8 KJ/mol

And at 973K

∆H0973 = -238.41 – 0.01226×973 + 2.77×10-6×9732

= -246.4 KJ/mol

Therefore, At 298K∆H0

reaction = ∑ H products – ∑ H reactants

= ( ∆H0ketene + ∆H0

water ) – (∆H0acetic acid )

= (-74.063-241.8) – (-434.84)

= 118.977 KJ/mol

And at 973K

∆H0reaction = ∑ H products – ∑ H reactants

= ( ∆H0ketene + ∆H0

water ) – (∆H0acetic acid )

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= (-51.23-246.4) – (-408.3)

= 110.09 KJ/mol

(b) Feasibility of Reaction :-

Ketene :-

∆G0 = A + BT + CT2 (KJ/mol)

∆G0 = -47.916 + 0×T + 5.04×10-6×T2

Therefore, At 298K

∆G0298 = -47.916 + 0×298 + 5.04×10-6×2982

= -47.47 KJ/mol

Acetic acid :-


∆G0 = -435.963 + 1.9346×10-1×T + 1.6362×10-5×T2

Therefore, At 298K

∆G0298 = -435.963 + 1.9346×10-1×298 + 1.6362×10-5×2982

= -365.69 KJ/mol

Water :-

For water ∆G0298 = -238.59

Thus,

∆G0reaction = ∑ ∆G products – ∑ ∆G reactants

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= ( ∆G0ketene + ∆G0

water ) – (∆G0acetic acid )

Therefore, at 298K

∆G0298 = (-47.47-238.59) – (-365.69)

= 79.63 KJ/mol

Since, ∆G is positive, the reaction is not feasible at 298K.

Now, ∆G0298 = -RT ln K

ln K1 = (-79.63×1000)/(8.314 × 298)

= -32.14

Therefore, K298 = 1.1×10-14

Now,

Therefore, ln(K2/K1) = (-∆H0

298 /R) × [(1/T2)-(1/T1)]

ln(K2/K1) = (-118.977×1000/ 8.314) × [(1/973)-(1/298)]

= 33.314

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Therefore, (K2/K1) = 2.938 × 1014

K2 = 3.232

∆G0973 = - RT (ln K2)

= -8.314 × 973 × ln 3.232 = -26.15 KJ/mol

Since, ∆G0973 is negative, the reaction is feasible at 973K

Reaction 2 :-

CH3COOH + CH2=CO → (CH3CO)2

Acetic acid Ketene Acetic Anhydride

(a) Heat of Reaction :-

Ketene :-


∆H0 = -44.988 – 0.00983×T + 2.46×10-6×T2

Therefore, at 50 ºC that is at 323K ∆H0

323 = -44.988 – 0.00983×323 + 2.46×10-6×3232

= -47.9 KJ/mol

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Acetic acid :-


∆H0 = -422.584 – 4.8354×10-4×T + 2.46×10-6×T2

Therefore, at 323K

∆H0323 = -422.584 – 4.8354×10-4×323 + 2.3337×10-5×3232

= -420.23 KJ/mol

Acetic Anhydride :-


∆H0 = -554.715 – 8.4124×10-2×T + 4.3618×10-5×T2

Therefore, at 323K∆H0

323 = -554.715 – 8.4124×10-2×323 + 4.3618×10-5×3232

= -577.615 KJ/mol

And at 323K

∆H0reaction = ∑ H products – ∑ H reactants

= (∆H0acetic anhydride ) – ( ∆H0

ketene + ∆H0acetic acid )

= (-577.615) – (-47.9 – 420.23)

= -109.485 KJ/mol

(b) Feasibility of Reaction :-

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Ketene :-


∆G0 = -47.916 + 0×T + 5.04×10-6×T2

Therefore, At 323K

∆G0323 = -47.916 + 0×323 + 5.04×10-6×3232

= -47.39 KJ/mol

Acetic acid :-


∆G0 = -435.963 + 1.9346×10-1×T + 1.6362×10-5×T2

Therefore, At 323K

∆G0323 = -435.963 + 1.9346×10-1×323 + 1.6362×10-5×3232

= -371.75 KJ/mol

Acetic Anhydride :-


∆G0 = -578.076 + 3.3162 ×10-1×T + 2.5188 ×10-5×T2

Therefore, at 323K∆G0

323 = -578.076 + 3.3162 ×10-1×323 + 2.5188 ×10-5×3232

= -468.334 KJ/mol

L.I.T. Nagpur


Thus,

∆G0reaction = ∑ ∆G products – ∑ ∆G reactants

= ∆G0acetic anhydride – ( ∆G0

ketene + ∆G0acetic acid )

Hence, at 323K

∆G0323 = -468.334 – (–47.39–371.75)

= –49.194 KJ/mol

Since, ∆G0323 is negative, the reaction is feasible at 323K

Now, ∆G0323 = -RT ln K

ln K = (-∆G0323) / (RT)

= (49.194 × 1000)/ (8.314 × 323)

= 18.32

Therefore, K = 9.032 × 107

L.I.T. Nagpur


6. Material Balance :-

Plant capacity = 50 tonnes/day

= (50 × 1000)/ 24 = 2083.33 Kg/ hr

Therefore, Acetic Anhydride to be produced = 2083.33 Kg/hr Considering 5% overall loss

Hence, acetic Anhydride to be produced actually = 1.05 × 2083.33 = 2187.5 Kg/hr

Molecular weight of Acetic Anhydride = 102

Therefore, Acetic Anhydride to be produced = 2187.5/102

= 21.446 Kmol/hr

The main reaction is :-



% Yield based on ketene required is = acetic anhydride formed/ ketene required 0.9 = 21.446/ketene required

L.I.T. Nagpur


Therefore, ketene required = 21.446/0.9 = 23.83 Kmol/hr

% yield base on acetic acid required = acetic anhydride formed / acetic acid required Therefore, acetic acid required = 21.446/0.85

= 25.23 Kmol/h

The first reaction taking place is :-

CH3COOH → CH2=CO + H2O Acetic acid Ketene

Ketene to be produced = 23.83 Kmol/hr

Hence, water produced = 23.83 Kmol/hr

% yield based on acetic acid required = 0.9 = ketene formed / acetic acid required

Therefore, Acetic acid required = 23.83/ 0.9 = 26.478 Kmol/hr

% conversion based on acetic acid = 0.88 = acetic acid required / acetic acid fed

Therefore, acetic acid to be fed = 26.478/0.88 = 30.1637 Kmol/hr

33% excess of acetic acid is taken :-

0.33 = (fed-reacted)/fed

Therefore, total acetic acid to be fed = (25.23 + 26.478) / 0.77

= 77.18 Kmol/hr

L.I.T. Nagpur


(i) Pyrolysis Heater :-

Acetic acid input = 30.1637 Kmol/hr

Acetic acid reacted = 26.478 Kmol/hr

Hence, acetic acid remaining = 30.1637-26.478 = 3.6857 Kmol/hr

1.5% of the unreacted acetic acid gets converted in to flue gases

Therefore, flue gases produced = 0.015 × 3.6857

= 0.0553 Kmol/hr

Acetic acid remaining = 3.6857 – 0.0553 = 3.6304

Component Input (Kmol/hr) Output (Kmol/hr)

Acetic acid 30.1637 3.6304

Water - 23.83

Ketene - 23.83

Flue gases - 0.0553

L.I.T. Nagpur


Considering overall 0.1% loss of ketene, 0.5% loss of acetic acid & 0.2% loss of

water in condenser, cooler & chiller.

(ii) Separator :-

3% water goes from the top :-

Therefore, water in the upstream = 23.83 × 0.03 = 0.715 Kmol/ hr

And, water in the downstream = 23.83 – 0.715 = 23.782 Kmol/hr

1% ketene goes in the downstream :-

Hence, ketene in the downstream = 0.01 × 23.86 = 0.2383 Kmol/hr

And, ketene in upstream = 23.806 – 0.2383 = 23.59 Kmol/hr

The bottom product contains 35% by weight acetic acid

Hence, acetic acid in the bottom product = 0.35 × 3.612 = 1.2565 Kmol/hr

And, acetic acid in the top product = 0.65 × 3.612 = 2.3478 Kmol/hr

Component Input (Kmol/hr)

Output (Kmol/hr)( Upstream )

Output (Kmol/hr)( downstream )

L.I.T. Nagpur


Acetic acid 3.612 2.3478 0.2383

Water 23.782 0.715 1.2565

Ketene 23.806 23.59 23.115

Flue gases 0.055 0.055 -

(iii) Ketene Absorber :-

Total acetic acid fed = 2.3478 + 47.09 = 49.44 (Kmol/hr) Acetic acid required = 25.23(Kmol/hr)

Hence, acetic acid remaining = 49.44 – 25.23 = 24.21(Kmol/hr)

95% acetic anhydride is produced

Hence, acetic anhydride formed = 0.95 × 23.59 = 22.41 Kmol/hr

12% acetic anhydride goes from the top

Hence, acetic anhydride in the top product = 0.12 × 22.41 = 2.6892 Kmol/hr

And, acetic anhydride in the bottom product = 0.88 × 22.41 = 19.7208

Total acetic acid fed = 2.3478 + 47.09 = 49.44 (Kmol/hr) Acetic acid required = 25.23(Kmol/hr)

Hence, acetic acid remaining = 49.44 – 25.23 = 24.21(Kmol/hr)

80% acetic acid goes from the top

Hence, acetic acid in top product = 24.21 × 0.8 = 19.368 Kmol/hr

L.I.T. Nagpur


And, in the bottom product = 0.2 × 24.21 = 4.842 Kmol/hr

0.4 % water goes from the bottom

Hence, water in the bottom product = 0.004 × 0.715 = 0.00286 Kmol/hr


Output (Kmol/hr)( Upstream )


Acetic acid 49.44 19.368 4.842

Water 0.715 12.816 0.00286

Ketene 23.59 1.18 -

Flue gases 0.055 0.055 -

Acetic anhydride - 2.6892 19.368

(iv) Tail gas scrubber :-

2% Water goes from the top :-

Hence, Water in the top product = 0.02 × 0.712 = 0.01424 Kmol/hr

1% acetic anhydride goes from the top

Hence, acetic anhydride in the top product = 0.01 × 2.6892 = 0.0268 Kmol/hr

0.5% acetic acid goes from the top

L.I.T. Nagpur


Hence, acetic acid in the top product = 0.05 × 19.368 = 0.097 Kmol/hr

Component Input(Kmol/hr) Output (Kmol/hr)( Upstream )


Acetic acid 19.368 0.097 19.271

Water 0.712 0.01424 0.698

Ketene 1.18 1.18 -

Flue gases 0.055 0.055 -

Acetic anhydride

2.6892 0.0268 2.6623

(v) Jet Condensor :-

Considering 0.2% loss of Acetic acid, 0.1% loss of acetic anhydride and 0.5% loss of

water in jet condenser :-


Output (Kmol/hr) (Upstream)

Output (Kmol/hr) (Downstream)

L.I.T. Nagpur


Acetic acid 0.097 - 0.0968

Water 0.01424 - 0.01417

Ketene 1.18 1.18 -

Flue gases 0.055 0.055 -

Acetic anhydride

0.0268 - 0.02677

(vi) Acetic acid column :-

Input Feed (F):

1) Acetic acid (CH3COOH) = 20.632 Kmol/hr

2) Water (H2O) = 23.827 Kmol/hr

Total feed to the distillation column = 20.632 + 23.827

= 44.459 Kmol/hr

Mole fraction of components in the feed :-

Xf1 (CH3COOH) = 20.632/44.459 = 0.464

Xf2 (H2O) = 23.827/44.459 = 0.536

Top Product (D) :-

L.I.T. Nagpur


Mole fraction of components in the top product :-

Xd1 (CH3CO0H) = 0.1 Xd2 (H2O) = 0.9

Bottom Product (W):

Mole fraction of components in the bottom product :-

Xw1 (CH3COOH) = 0.95

Xw2 (H2O) = 0.05

Taking overall material balance :-

F= D + W

Putting the values in above equation :-

44.459 = D + W --------------------------------------------- (1)

Now, taking component balance :- F Xf= D Xd +W Xw

For Water :-

44.459 ×0.536 = D × 0.9 + W × 0.05

23.827 = 0.9 D + 0.05 W -------------------------------- (2)

Solving equations 1 & 2, we get :-

Top product (D) = 24 Kmol/hr

L.I.T. Nagpur


Bottom product (W) = 20.45 Kmol/hr

Hence, acetic acid in the top product = 0.1 × 24 = 2.4 Kmol/hr

And, Water in the top product = 0.9 × 24 = 21.6 Kmol/hr

Acetic acid in the bottoms product = 0.95 × 20.45 = 19.4275 Kmol/hr

Water in the bottoms product = 0.95 × 20.45 = 1.0225 Kmol/hr

Reflux Ratio = 2.25 ( calculated below )

Hence, Ln = 2.25 × D = 2.25 × 24 = 54 Kmol/hr

(vii) Acetic anhydride column :-

Input Feed (F):

1) Acetic acid = 4.842 Kmol/hr

2) Acetic anhydride = 19.7208 Kmol/hr


= 24.563 Kmol/hr


Xf1 (CH3COOH) = 4.842/24.563 = 0.197

Xf2 (Acetic anhydride) = 19.7203/24.563 = 0.803

L.I.T. Nagpur


Top Product (D) :-


Xd1 (CH3CO0H) = 0.9 Xd2 (Acetic anhydride) = 0.1

Bottom Product (W):



Xw2 (Acetic anhydride) = 0.99


F= D + W


24.563 = D + W --------------------------------------------- (1)


For Acetic acid :-

24.563 ×0.197 = D × 0.9 + W × 0.01

4.842 = 0.9 D + 0.01 W -------------------------------- (2)


L.I.T. Nagpur


Top product (D) = 5.164 Kmol/hr


Hence, acetic acid in the top product = 0.9 × 5.164 = 4.6476 Kmol/hr = 278.856

Kg/hr

And, Acetic anhydride in the top product =0.1 × 5.164 = 0.5164 Kmol/hr =

52.6728 Kg/hr

Acetic acid in the bottoms product = 0.01 × 19.398 = 0.194 Kmol/hr = 11.64 Kg/hr

Acetic anhydride in the bottoms product = 0.99 × 19.398 = 19.2 Kmol/hr = 1958.4

Kg/hr

7. Energy Balance :-

Component Specific heat (J/mol K) Latent Heat of Vaporization ( cal/g)

Acetic Acid -18.944–1.0971×T + 2.8921×10-6×T2 96.8

Acetic Anhydride

78.831 – 8.8879×10-1T+ 2.6534×10-6T2 93

(i) Pyrolysis Reactor :-

Reaction Temperature = 700ºC

Temperature of acetic acid entering = 110 ºC

Taking enthalpy balance around the pyrolysis Reactor :-

L.I.T. Nagpur


Heat to be supplied by the fuel gas = Heat required to raise the temperature of acetic acid

+

Heat required for the decomposition of acetic acid to form ketene.

That is, ∆Hf (theoretical) = Q1 + Q2

Q1 =

=

= 12.9 × 106 KJ/hr

Q2 = Heat of reaction × amount of acetic acid cracked

= 110.09 × 103 × 30.1637

= 3.32 × 106

Therefore, ∆Hf (theoretical) = Q1 + Q2

= (12.9 + 3.32) × 106

= 16.22 × 106 KJ/hr But, efficiency of the furnace = 0.65

Therefore, heat to be supplied actually = ∆Hf (theoretical) /0.65

= 16.22 × 106/0.65

= 24.954 × 106 KJ/hr

L.I.T. Nagpur


(ii) Waste Heat Boiler :-

Heat removed =

=

= - 685.341 × 103 KJ/hrHeat lost = Heat gained by the cooling medium (water)

Inlet temperature of water = 25ºC

Outlet temperature of water = 210ºC

Cooling water flowrate = ?

Heat gained = mwater × Cpwater × ∆T

mwater = 685.341 × 103/[4.184 × (483-298)]

= 885.4 Kg/hr

(iii) Cooler :-

Heat removed =

=

= - 726.226 × 103 KJ/hrHeat lost = Heat gained by the cooling medium (water)

L.I.T. Nagpur


Inlet temperature of water = 25ºC

Outlet temperature of water = 195ºC

Cooling water flowrate = ?

Heat gained = mwater × Cpwater × ∆T

mwater = 726.226 × 103/[4.184 × (468-298)]

= 1021.012 Kg/hr

(iv) Chiller :-

Heat removed =

=

= -283.495 × 103 KJ/hrHeat lost = Heat gained by the cooling medium (ammonia)

Inlet temperature of ammonia = -33ºC

Outlet temperature of ammonia = 50ºC

ammonia flowrate = ?

Heat gained = mammonia × Cpammonia × ∆T

mammonia = 283.495 × 103/[2.114 × (323-298)]

= 1615.7 Kg/hr

L.I.T. Nagpur


(iv) Ktene Absorber :-

The reaction taking place in the ketene absorber is :-



Above reaction is exothermic and the amount of heat released = -109.485 KJ/mol

This is the amount of heat released when one mole of acetic anhydride is formed.

Hence, for the formation of 22.41 Kmol acetic anhydride, the amount of heat

released wil be :-

∆H = -109.485 × 1000 × 22.41

= -2453.56 × 103 KJ/hr

The negative sign shows that the heat is released,

that is the reaction is exothermic.

(v) Acetic Acid Column :-

L.I.T. Nagpur


Temperature of feed = 382K

Temperature of distillate = 373K

Temperature of the bottoms product = 392K

Reference Temperature = 273K

Heat in feed (F×HF) = Heat in acetic acid + Heat in water

=

+

=

+

= 765.31 × 103 + 239.075 × 103

= 1004.385 × 103 KJ/hr

Heat in Distillate (D×Hd) = Heat in acetic acid + Heat in water

=

+

L.I.T. Nagpur


=

+

(D×Hd) = 80.50 × 103 + 198.834 × 103

= 279.334 × 103 KJ/hr

Heat in bottoms (WHW) = Heat in acetic acid + Heat in water

=

+

=

+

= 799.542 × 103 + 11.32 × 103

= 810.862 × 103 KJ/hr

Average Latent heat ( Lavg ) = Lacetic acid × Xacetic acid + Lwater × Xwater

= 18 × 2200 × 0.9 + 60 × 96.8 × 4.184 × 0.1

= 38.07 × 103 KJ/Kmol

Condenser duty ( Qc ) = Vn × Lavg

L.I.T. Nagpur


= 78 × 38.07 × 103

= 2969.46 × 103 KJ/hr

Taking overall Heat balance on distillation column :-

Heat in Feed (FHF) + Reboiler duty (Qr) = Heat in distillate (DHd)+Heat in bottoms(WHW) + Condenser duty (Qc)

Hence, (Qr) = (DHd) + (WHW) + (Qc) - (FHF)

= ( 279.334 + 810.682 + 2969.46 – 1004.385 ) × 103

= 3055.091 × 103 KJ/hr

Therefore, quantity of steam required = (Qr) / Lsteam

= 3055.091 / 2200

= 1388.67 Kg/hr

(v) Acetic anhydride column :-

Temperature of feed = 403K

Temperature of distillate = 392K

Temperature of the bottoms product = 413K

Reference Temperature = 273K

L.I.T. Nagpur


Heat in feed (F×HF) = Heat in acetic acid + Heat in acetic anhydride

=

+

=

+

= 221.491 × 103 + 202.099 × 103

= 423.59 × 103 KJ/hr

Heat in Distillate (D×Hd) = Heat in acetic acid + Heat in anhydride

=

+

=

+

L.I.T. Nagpur


(D×Hd) = 191.272 × 103 + 4.844 × 103

= 196.117 × 103 KJ/hr

Heat in bottoms (WHW) = Heat in acetic acid + Heat in anhydride

=

+

=

+

= 9.704 × 103 + 211.942 × 103

= 221.647 × 103 KJ/hr

Average Latent heat ( Lavg ) = Lacetic acid × Xacetic acid + Lanhydride × Xanhydride

= 60 × 96.8 × 4.184 × 0.9 + 102 × 93 × 4.184 × 0.1

= 25.84 × 103 KJ/Kmol

Condenser duty ( Qc ) = Vn × Lavg

= 24.227 × 25.84 × 103

= 626.025 × 103 KJ/hr

Taking overall Heat balance on distillation column :-

L.I.T. Nagpur


Heat in Feed (FHF) + Reboiler duty (Qr) = Heat in distillate (DHd)+Heat in bottoms(WHW) + Condenser duty (Qc)

Hence, (Qr) = (DHd) + (WHW) + (Qc) - (FHF)

= ( 196.117 + 221.647 + 626.025 – 423.59 ) × 103

= 620.199 × 103 KJ/hr

Therefore, quantity of steam required = (Qr) / Lsteam

= 621.199 / 2200

= 281.91 Kg/hr

8. Equipment Design :-

L.I.T. Nagpur


(i) Acetic Anhydride column :-

Input Feed (F):


2) Acetic anhydride = 19.7208 Kmol/hr


= 24.563 Kmol/hr


Xf1 (CH3COOH) = 4.842/24.563 = 0.197

Xf2 (Acetic anhydride) = 19.7203/24.563 = 0.803

Top Product (D) :-


Xd1 (CH3CO0H) = 0.9 Xd2 (Acetic anhydride) = 0.1

Bottom Product (W):



Xw2 (Acetic anhydride) = 0.99


L.I.T. Nagpur


F= D + W


24.563 = D + W --------------------------------------------- (1)


For Acetic acid :-

24.563 ×0.197 = D × 0.9 + W × 0.01

4.842 = 0.9 D + 0.01 W -------------------------------- (2)


Top product (D) = 5.164 Kmol/hr


Hence, acetic acid in the top product = 0.9 × 5.164 = 4.6476 Kmol/hr = 278.856

Kg/hr

And, Acetic anhydride in the top product =0.1 × 5.164 = 0.5164 Kmol/hr =

52.6728 Kg/hr


Acetic anhydride in the bottoms product = 0.99 × 19.398 = 19.2 Kmol/hr = 1958.4

Kg/hr

L.I.T. Nagpur


Boiling point of acetic acid = 118 ºC

Boiling point of acetic acid = 139 ºC Hence, acetic acid is more volatile component ( MVC)

Acetic acid- acetic anhydride (x-y data) :-x 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0y 0.225 0.41 0.56 0.66 0.735 0.795 0.85 0.9 0.94 1.0

ya = α xa/ 1+( α-1)xa

substitute, y = 0.225 & x= 0.1

we get, α = 2.613

from graph :-

(xd/R+1)min = 0.26

(0.9/R+1)min = 0.26

Therefore, Rmin = 2.461

But, Ropt = 1.5 Rmin

Therefore, Ropt. = 1.5 × 2.461 = 3.6915

R = Ln/ D

Hence, Ln = 3.6915 × 5.164 = 19.063 Kmol/hr

Or, D = 52.6728 + 278.856 = 331.53 Kg/hr

Therefore, Ln = 1223.842 Kg/hr

Vn = Ln + D = 19.063 + 5.164 = 24.227 Kmol/hr

0r, Vn = 1223.842 + 331.53 = 1555.372 Kg/hr

Lm = Ln + F = 19.063 + 24.563 = 43.626 Kmol/hr

L.I.T. Nagpur


Or, Lm = 1223.842 + (19.7208 × 102 + 4.842 × 60 ) = 3525.88 Kg/hr

Vm = Lm – W = 3525.88 – (11.64 + 1958.4 ) = 1555.84 Kg/hr

Or, Vm = 43.626- 19.398 = 24.228 Kmol/hr

Therefore, equation of upper operating line :-

Therefore, yn = 0.7868 xn+1 + 0.192

Hence, y-intercept = 0.192 & slope = 0.7868

Equation of lower operating line (LOL) :-

Therefore, number of theoretical plates = 14 -1=13 (from graph)

One plate is deducted for reboiler

L.I.T. Nagpur


Efficiency of the column = 62%

Therefore actual no. of plates required = 13/0.62 = 23 plates

Feed plate = 6/0.62 = 10th plate.

For atmospheric columns generally, tray spacing = 0.457m

Therefore, height of the distillation column = (N+1) × 0.457

= 24 × 0.457 = 10.968m=11m

Take 100 mm of water as the pressure drop per plate in the column.

Therefore, column pressure drop = 100 × 10−3 × 1000 × 9.81× 23

= 20601 Pa = 20.601 KPa.

Therefore, Top pressure = 101.325 KPa.

Bottom pressure = 101.325 + 20.601= 127.926 KPa.

At the bottom of the distiilation column vapor density can be calculated as follows;

The density of liquid at the bottom of the column can be calculated by multiplying

the density of each component with the mole fraction.

L.I.T. Nagpur


At the top of the distiilation column vapor density can be calculated as follows;

The density of liquid at the bottom of the column can be calculated by multiplying

the density of each component with the mole fraction.

Calculation of Parachor value (P) :-

L.I.T. Nagpur


Ptop = 134.16 × 0.9 + 228.2 × 0.1 = 143.56

Pbottom = 134.16 × 0.01 + 228.2 × 0.99 = 227.26

Surface tension :-

Similarly :-

Liquid-vapor flowrate factor FLV is given by :-

L.I.T. Nagpur


tray spacing = 0.457 m.

From graph in RC-6 page-568 we get;

Bottom k1 = 0.086, Top k1 = 0.096

For liquid surface tension (0.02 N/m) take K1 as it is otherwise:-

Maximum velocity at top and bottom can be calculated as follows;

Bottom:

L.I.T. Nagpur


Top:

Now we will design the column for 70% flooding, therefore the velocities will be

given by;

Bottom: uf = 1.8 × 0.7 = 1.26 m/s.

Top: uf = 2.145 × 1.5015 m/s.

Maximum volumetric flow rate of vapor can be calculated as follows:

Bottom Q =

Top Q =

Now area at the bottom and at the top of the tower can be calculated as follows:

L.I.T. Nagpur


Net area(An) bottom

Net area(An) top

Now let us take 15% of the area as the downcomer area,

Ad = 0.15AT

But, AT = An + Ad

Therefore, An/0.15 = AT

Therefore, Bottom area =

Top area

Now, area =

L.I.T. Nagpur


Column diameter can be calculated as follows;

Take 0.4644 m as inside diameter of the column.

Liquid Flow Pattern :-

Now, maximum volumetric flowrate at the bottom

Provisional Plate Design :-

Column diameter Dc = 0.4644 m.

Area of column,

Now area of downcomer is 15% of the area of the column.

Also Net area is given by,

Active area,

Take hole area as 10% of active area.

Therefore Ah = 0.1×0.11858 = 0.011858 m2.

For 15% downcomer area, from graph of (Ad/Ac) ×100 Vs

For, (Ad/Ac) = 0.15,

L.I.T. Nagpur


Therefore Length of the weir, Iw = 0.82 × O.4644 = 0.38 m.

Take weir height as 50 mm.

Plate thickness = 5mm

Hole diameter = 5mm

Check Weeping :-

Maximum liquid rate,

LW

At 70% turndown the liquid rate is,

= 0.7 × 0.9794 = 0.6856 kg/sec.

The height of the liquid crest over the weir can be estimated using the Francis weir

formula. For a segmental downcomer this can be written as:

Where, lw = weir length, m,

how = weir crest, mm liquid,

Lw = liquid flow-rate, kg/s.

At the maximum flow rate of liquid the liquid crest over the weir can be calculated

using the maximum liquid flow rate calculated above, while for the conditions at

minimum flowrate are assumed to be the 70% turndown conditions.

Maximum how = 13.31 mm.

L.I.T. Nagpur


Minimum how = 10.53 mm.

At minimum rate, hw + how = 50 + 10.53 = 60.53 mm.

From graph of K2 Vs (hw + how), K2 = 30.3

Where, K2 is a constant dependent on the depth of the clear liquid on the plate.

The minimum design vapour velocity is given by

,

Where, uh = minimum vapour velocity through the holes(based on the

hole area), m/s,

dh = hole diameter, mm,

K2 = a constant, dependent on the depth of clear liquid on the plate

Actual minimum vapour velocity is given by,

Actual uh = Minimum vapour rate/Ah

This is well above the weeping velocity(minimum vapor velocity), therefore the

design is acceptable.

Plate Pressure Drop :-

L.I.T. Nagpur


Maximum vapour velocity through the holes is given by,

For (plate thickness)/(hole dia) = 1, from graph of (Ah/Aa)×100 Vs Co

For, (Ah/Aa)= 0.1;

Co = 0.84

The pressure drop through the dry plate can be estimated using expressions derived

for flow through orifices.

……..(bottom)

Residual Head :-

L.I.T. Nagpur


= 11.53 mm.

Total Head :-

This is less than the assumed per plate pressure drop of 100 mm, thus the design is

acceptable.

Downcomer Liquid Backup :-

The height above the bottom edge of the apron is calculated as follows:

hap

Thus the clearance area under the apron is given by,

Aap = haplw = 0.04×0.38 = 0.0152 m2.

This is less than the area of the downcomer Ad.

Thus use Aap in the equation given below :-

Head loss in the downcomer can be estimated by the following equation:

Where, Am = Ad or Aap whichever is smaller.

L.I.T. Nagpur


Lwd = liquid flowrate in the downcomer.

In terms of clear liquid, the downcomer backup is given by;

= 50 + 10.53 + 95.5+ 0.586 = 156.616 mm.

= 0.156 m.

Now tray spacing + weir height = 0.38 + 0.05 = 0.43 m.

Therefore he tray spacing is within acceptable limits.

Downcomer Residence Time :-

The residence time of the liquid over the downcomer is given by;

This is greater than 3 seconds therefore it is acceptable.

L.I.T. Nagpur


Entrainment :-

The entrainment can be estimated by the following realationships which give

entrainment as a function of percentage flooding.

% flooding =

Therefore from graph of FLV Vs % flooding.

(fractional entrainment), , this is less than 0.1, therefore it is acceptable.

Trial Layout :-

0.38m 0.4644m

L.I.T. Nagpur


Number Of Holes :-

Area of one hole,

Number of holes,

holes.

MECHANICAL DESIGN

Design of shell :-

Taking material of construction as Stainless Steel

Maximum allowable stress f = 1420 kg/cm2

Operating pressure = 101.325 KN/m2 = 101325/(9.81 x 10000)

= 1.033 Kg/cm2

Design pressure is 10% excess of operating pressure = 1.033 x 1.1

= 1.1363 kg/cm2

Thickness of shell (ts) = (P x Di)/(2fJ –P) = (1.1363 x 46.44)/(2 x 1420 x 0.85 – 1.1363)

= 0.218 mm

Taking allowance = 3 mm

Shell thickness = 3.218

Use thickness of 3.5 mm

Therefore, Outer diameter of the column (Do) = Di + 2t

= 0.4714m

Design of heads :-

L.I.T. Nagpur


Elliptical heads are used

th = (P DiV)/(2fJ)

Where,

Di = internal diameter of the column P = design pressure = 1.1363 kg/cm2

th = thickness of head

J = welded joint efficiency = 0.85

V = stress intensity factor

And, V = (2 + k2)/6 k = ratio of major axis to minor axis = 2:1 =2

Therefore, V = 1

th = (1.1363 x 46.44 x 1) / (2x1420 x0.85)

=0.0218 cm

= 0.218 mm

Taking allowance = 3 mm

Thickness of head = 3.218 mm

Therefore, use thickness of 3.5mm

Design of gasket and bolt size :-

Gaskets are used for making leak proof joint between two surfaces

Gasket: Asbestos with suitable binder (3mm thick)

Gasket factor m = 2.0

L.I.T. Nagpur


Minimum design sitting stress for asbestos with suitable binder (3 mm

thick) is Ya = 112 kg / cm2

Go/Gi = [(Ya – Pi x m)/(Ya – Pi (m + 1))]0.5

= [(112 – 1.1363 x 2)/(112 – 1.1363(2+1)] 0.5

= 1.010

Gi = 46.44 + 2 x 0.0816

= 46.6 cm

Go = 1.010 x 46.6

= 47.07 cm

Mean gasket diameter G = (Go + Gi)/2

= 46.835 cm

Basic gasket sitting width

bo = ( Go - Gi )/4

= 0.1175 cm

= 1.2 mm

Taking it as 1 mm.

Effective gasket sitting width as bo is less than 6.3 mm

b = bo

b = 1.2 mm

Force acting on bolt under atmospheric condition

Wm1 = 3.14 x b x G x Ya

= 3.14 x 0.12 x 46.835 x 112

L.I.T. Nagpur


= 1977.514 kg

Force acting on the bolt under operating condition

Wm2 = 3.14 x 2b x G x m x Pi + 3.14 x G2 x Pi / 4

= 3.14 x 2 x0.12 x 46,835 x2 x1.1363 + 3.14 x 46.8352 x 1.1363 / 4

= 2037.85 kg

Maximum bolting area :-

Bolting material is rolled carbon steel.

Am1 = Wm1 / fa

Am2 = Wm2 / fb

Where,

fa = allowable stress for bolt material under atmospheric Conditions = 545 kg / cm2

fb = allowable stress for bolt material under operating condition = 545 kg / cm2

Am1 = 1977.514/545

= 3.628 cm2

Am2 = 2037.85/545

= 3.74 cm2

Therefore, minimum bolting area is taken as 3.74 cm2

No. of bolts = mean diameter of gasket/2.5

= 46.835/2.5

= 18.734

Since the total no. of bolts must be a multiple of 4

L.I.T. Nagpur


No. of bolts = 20

If Am is the area of one bolt then,

Am x 20 = 3.74

Am = 0.187 cm2

Therefore, 3.142 x db2 /4 = 0.187

db = 0.487 cm

Diameter of bolt = 0.487 cm

Pitch circle diameter = outside diameter of gasket + 2xdiameter of bolt + 1.2

= Go + 2 x db + 1.2

= 47.07 + 2 x 0.487 + 1.2

= 49.244 cm

Bolt spacing = (3.14 x pitch circle diameter)/no. of bolts

= 3.14 x 49.244 / 20

= 7.73 cm

Flange design :-

Outside diameter of the flange = Pitch circle diameter + 2 x diameter of bolt

= 49.244 + 2 x o.487

= 50.218 cm

Thickness of the flange tf = G x (Pi/kf)0.5

L.I.T. Nagpur


Where, k = 1/[0.3 + (1.5 x Wm x Hg) /(HxG)]

G = diameter of the gasket load reaction or mean diameter of gasket

Wm = maximum bolt load = 53678.106 kg

Hg = radial distance from gasket load reaction to the bolt circle

= (pitch circle diameter – G)/2

= (49.244 – 46.835)/2

= 1.2045 cm

H = hydrostatic end force

= (3.14 x G2 x Pi)/4

= (3.14 x 46.8352x 1.1363)/4

= 1956.6 Kg

k = 1/[0.3 +(1.5 x 53678.106 x 1.2045)/(1956.6x 46.835)]

= 0.736

tf = 46.835 x (1.1363/0.736x1420)0.5

= 1.544 cm

Design of skirt support :-

The stresses due to vessel dead weights, wind load and seismic load

are taken into account while the column is designed to withstand

L.I.T. Nagpur


maximum values of tensile or compressive stresses.

The stresses are:

1. Due to dead weight

fd = W/(3.14 x Dsk x tsk)

Dsk = outside diameter of skirt support

tsk = thickness of skirt support

W = total weight of the vessel including attachments

Weight of shell can be calculated as :-

lnW = 0.694 + 0.882 lnB

B = {[(L/D) + 1.82] P D3}/(25600 + 1.2P) + 20L

Where W = weight of column without internals (kg)

D = diameter of column (inches)

D = 0.4644 m = 18.283 inches

P = design pressure (Psig)

= 1.1363 kg / cm2 = (14.7 x 1.1363)/1.1 = 15.185 Psig

L = column height of cylindrical shell and heads (inches)

L = 10.968 m = 431.81 inches

Therefore, B = 7638.05 kg

L.I.T. Nagpur


W = 5323.42 kg

Weight of the contents = volume of contents x Avg density

= [(3.14 x 0.46442 x 10.968) x (0.803 x 1084 + 0.197 x 1049)]/4

= 1790.295 kg

Assume, Weight of accessories = 200 kg

∑W = 1790.295 + 200 + 5323.42

= 7313.715 kg

Dsk = Gi = 46.6 cm

fd = ∑W/(3.14 x Dsk x tsk)

= 7313.715/(3.14 x 46.6 x tsk

= 49.98 / tsk kg/cm2

2. Due to wind load

PLW = K1 x K2 X P x H x Do

Where K1 = coeff depending on shape factor = 0.7

K2 = 1

L.I.T. Nagpur


P = wind pressure = 152 kg/m2 (assuming)

Do = 0.4714 m

H = 10.968 + 2 = 12.968 m

PLW = K1 x K2 x P x H x Do

= 0.7 x 1 x 152 x 0.4714 x 12.968

= 581.67 kg

The bending moment due to wind at the base of skirt is

Mw = PLW x H/2

= 581.67x 12.968/2

= 3372.813 kg-m

fw = Mw / Z

= 3372.813/[(3.14 D2sk tsk)/4]

= 19785.67/tsk kg / m2

= 0.528138/tsk kg /cm2

2. Due to seismic load

fs = 4 Mw / (3.14 D2o tsk)

but, Mw = (2 x C x H x W)/3

therefore, fs = (2 x 4 x C x H x W)/(3 x 3.14 D2o tsk)

Where, C = seismic coefficient = 0.8

H = 10.968 + 2 = 12.968 m

W = 7313.715 kg; Do = 0.4714 m

L.I.T. Nagpur


fs = (2 x4 x 0.8 x 12.968 x 7313.715)/(3 x 3.14 x 0.4714 3 x tsk)

= 25.932/tsk kg/cm2

Maximum tensile stress at the bottom of the skirt

= fd - (fw or fs)

= (49.98-25.932)/tsk

= 20.048/tsk kg/ cm2

Permissible tensile stress = 1420 kg/ cm2

tsk = 20.048 / 1420

= 0.0169 cm

= 0.169 mm

fc (max) = (49.98/tsk) + (25.932/tsk)

= 75.912/tsk kg/ cm2

fc (permissible ) = yield point stress / 3

= 2000 / 3

= 666 kg/ cm2

L.I.T. Nagpur


tsk = 75.912/ 666

= 0.114 cm

= 1.14 mm

Therefore, thickness of 2 mm is used.

2. Acetic acid column :-

Input Feed (F):


2) water = 23.827 Kmol/hr


= 44.459 Kmol/hr


L.I.T. Nagpur


Xf1 (CH3COOH) = 20.632/44.459 = 0.464

Xf2 (water) = 23.827/44.459 = 0.803

Top Product (D) :-


Xd1 (water) = 0.9 Xd2 (CH3CO0H) = 0.1

Bottom Product (W):



Xw2 (water) = 0.05


F= D + W


44.459 = D + W --------------------------------------------- (1)


For Acetic acid :-

44.459 × 0.464 = D × 0.1 + W × 0.95

L.I.T. Nagpur


20.632 = 0.1 D + 0.95 W -------------------------------- (2)


Top product (D) = 24 Kmol/hr


Hence, acetic acid in the top product = 0.1 × 24 = 2.4 Kmol/hr = 144 Kg/hr

And, water in the top product =0.9 × 24 = 21.6 Kmol/hr = 388.8 Kg/hr


water in the bottoms product = 0.05 × 20.45 = 1.0225 Kmol/hr = 18.405 Kg/hr

Boiling point of acetic acid = 118 ºC

Boiling point of water = 100 ºC Hence, water is more volatile component ( MVC)

Water-Acetic acid (x-y data) :-x 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0y 0.173 0.32 0.447 0.557 0.654 0.74 0.815 0.883 0.944 1.0

ya = α xa/ 1+( α-1)xa

substitute, y = 0.173 & x= 0.1

we get, α = 1.89

from graph :-

(xd/R+1)min = 0.36

(0.9/R+1)min = 0.36

L.I.T. Nagpur


Therefore, Rmin = 1.5

But, Ropt = 1.5 Rmin

Therefore, Ropt. = 1.5 × 1.5 = 2.25

R = Ln/ D

Hence, Ln = 2.25 × 24 = 54 Kmol/hr

Vn = Ln + D = 54 + 24 = 78 Kmol/hr

Lm = Ln + F = 54 + 44.459 = 98.459 Kmol/hr

Vm = 98.459 – 20.45 = 78.009 Kmol/hr

Therefore, equation of upper operating line :-

Therefore, yn = 0.692 xn+1 + 0.277

Hence, y-intercept = 0.277 & slope = 0.692

Equation of lower operating line (LOL) :-

L.I.T. Nagpur


Therefore, number of theoretical plates = 14 -1=13 (from graph)

One plate is deducted for reboiler

Efficiency of the column = 65%

Therefore actual no. of plates required = 13/0.65 = 20 plates

Feed plate = 6/0.65 = 10th plate.

9. Material of Construction :-

Acetic acid, ketene & acetic anhydride require a

suitable material to be used to avoid any corrosion and spoiling of the product.

Aluminium though can be used throughout the

process except in the hot zones of pyrolysis where stainless steel is used. Stainless

steel 316 and copper are best suitable material that can be used in the process

equipment. Stainless steel for process equipment has an additional advantage over

copper of causing less discolourization and moreover for pure acetic anhydride

condenser silver coils are used. In general stainless steel of composition 33%

chromium, 1.5% aluminium, 1.5% silicon is used.

L.I.T. Nagpur


For storage & transportation of pure acetic

anhydride tanks made of aluminium, stainless steel ( 18% Cr, 8% Ni & 2% Mo ) or

poly-ethylene are generally used. Although glass or enamel containers also may be

employed. Iron is highly resistant to acetic anhydride, provided moisture is

excluded. Hence it is possible to use iron in the production & workup in certain

instances for example in pumps & tanks.

Nickel is avoided in the alloys for a high

temperature applications, since it is reported to accelerate the coking on heater tube

walls unless pacified periodically by special pretreatment or injection of sulfur

compounds.

Cost Estimation & Economics :-

Determining Purchased Equipment cost(PEC) :-

Acetic Anhydride column :-

Internal diameter of the column = Di = 0.4644 m

External diameter of the column = Do = 0.4644 m

Volume of the distillation column = volume of the cylindrical shell

+

volume of elliptical heads

L.I.T. Nagpur


Therefore, V =

= 0.118 m

2

Density of stainless steel = 8000 kg/m3

Hence, weight of the material used for the column = 8000 × 0.118

= 944 kg

Considering the weight of the accessories to be = 150 kg

Hence, total weight of the material used for the column = 1094 kg

Cost of stainless steel = 192 Rs/kg

Cost index of 2004 = 432

Cost index of 2006 = 606.5

L.I.T. Nagpur


Therefore, the cost of the material for the column = (606.5 × 192 × 1094)/432

= 294893.778/- Rs

Cost of fabrication = 50% of the cost of material

Hence, the total cost of the column = 1.5 × 294893.778

= 442340.67 /- Rs.

Considering the cost of accessories i.e. condenser and reboiler to be = 2lakh

Hence, total cost of the column along with the accessories = 642340.67 /- Rs.

Sr. No. Equipment Quantity Cost

1 Acetic acid column 1 622000

2 Waste heat boiler 1 320000

3 Cooler 1 370000

4 Chiller 1 420000

5 Separator 1 325000

6 Ketene absorber 1 678000

7 Tale gas scrubber 1 288000

8 Vacuum jet 1 301000

9 Storage tanks 2 1022000

10 Pyrolysis heater 1 1522000

L.I.T. Nagpur


Total PEC = 642340.67 + 622000 + 320000 + 370000 + 420000 + 325000 +

678000 + 288000 + 301000 + 1022000 + 1522000

Therefore, PEC = 6510340.67 Rs.

For a fluid processing plant the following quantities must be added to the PEC to

get the physical plant cost or the PPC.

Installation charges = 50% of PEC.

= 3255170.335

Piping = 70% of PEC = 4557238.469

Instrumentation = 20% of PEC = 1302068.134

Electrical 10% of PEC = 651034.067

Site development = 5% of PEC = 325517.0335

Buildings and land cost = 1 Crore.

Therefore total Physical plant costs (PPC) = 26601368.71 .

Design and engg. = 30% of PPC = 7980410.613

Contractor’s fees = 5% of PPC = 1330068.436

Contingency = 10% of PPC = 2660136.871

Total indirect costs = 56250000.

Fixed capital investment(FCI) = Total direct costs + Total indirect costs

= 26601368.71 + 11970615.92

= 38571984.63

Working capital(WC) = 40% of FCI

= 15428793.85

L.I.T. Nagpur


Total Capital investment(TCI) = FCI + WC = 50400000

Production Costs :-

FIXED CHARGES

Depreciation is 10% on machinery and equipment and 3% on buildings.

Depreciation = 0.1 × FCI + 0.03 × Buildings.

= 0.1 × 38571984.63 + 0.03 × 10000000

= 4157198.463

Local taxes = 4% of FCI = 1542879.385

Insurance = 1% of FCI = 385719.8463

Therefore total fixed charges = Depreciation + Local taxes + Insurance

= 6085797.694

DIRECT PRODUCTION COSTS

Total product charges (TPC):

Fixed charges = 10% of TPC.

Therefore TPC = 60857976.94

Cost of raw material = 25 × 60 × 51 × 24 × 300

= 550800000

L.I.T. Nagpur


Operating labour = 15% of TPC = 9128696.541

Supervisory control and clerical labour = 25% of operating labour

= 2282174.135

Utilities = 20% of TPC = 12171595.39

Maintenance = 10% of FCI = 3857198.463

Operating supplies = 1% of FCI = 385719.8463

Patents and royalties = 5% of TPC = 3042898.847

Plant overheads cost = 15% of TCI = 8100116.772

Manufacture Cost = 650626376.9

GENERAL EXPENSES

Administrative expenses = 6% of TPC = 3651478.616

Distribution and selling costs = 15% of TPC = 9128696.991

Research & development cost = 5% of TPC = 3042898.8

Financing = 10 % of TCI = 5400077.848

General Expenses = 21223152.26

Therefore, Total production cost(TPC) = Manufacture Cost

+

General Expenses

= 650626376.9 + 21223152.26

= 671849529.2

L.I.T. Nagpur


Selling price = Rs 56 per kg.

Total income = 50 × 19.2 × 102 × 24 × 300 = 705024000

Total profit = Total income − TPC = 3.32 Crore

Tax on income = 40% of total profit = 1.328 Crore.

Net profit = 1.992 Crore.

Dividend = 10% of Net profit = 0.1992 Crore.

Tax on dividend = 10% = 0.01992 Crore.

Therefore total dividend = 0.21912 Crore.

Profit = 1.77288 Crore.

Rate Of Return =

Pay Back Period = 1/0.3517 = 2.85 YEARS = 35 MONTHS

L.I.T. Nagpur


Process Control & Instrumentation :-

Digital feedback control of pyrolysis heater :-

The direct digital feedback control of pyroysis

heater is shown in the figure. The temperature inside the pyrolysis heater is

measured by the thermocouple and the signal is sampled using a sampler switch.

The discrete time signal in the analog form is converted in to digital signal by

analog to digital converter. The electronic error detector generates the error which

is the difference between the measured value and the set point. The generated error

is minimized by the digital feedback controller monitored by computer. The output

command signal from the digital feedback controller is converted into analog from

by digital to analog converter. The hold element is used to convert the discrete time

analog signal into the continuous analog signal. Electro-pneumatic transducer is

used to convert the electric signal in to pneumatic signal. The output from the

electro-pneumatic transducer acts on the diaphragm actuator of the pneumatic

control valve which in turn regulates the flowrate of the fuel gas in order to

L.I.T. Nagpur


maintain the temperature inside the pyrolysis heater at a desired value. The signals

are transmitted through the transmission lines. The flowrate of fuel gas is the

manipulated variable.

Digital Feedforward control of distillation column :-

The direct digital feedforward control of distillation

column is shown in the figure. The two principal disturbances inlet flowrate and

inlet composition are measured and the signals are samples using the sampler

switch. The discrete time signal is converted in to digital form by analog to digital

converter.The electronic comparator generates the errors which are nothing but the

difference between the set points or the desired values and the corresponding

measured values. The generated errors are minimized by the digital feedforward

controller monitored by computer. The output command signals from the computer

are in the digital form and converted in to analog signals using digital to analog

converters. The discrete time signals are converted in to the continuous analog

signal using hold elements. The electro-pneumatic transducers are used to convert

the electric signal in to pneumatic signal.

L.I.T. Nagpur


The pneumatic signal from the electro-pneumatic

transducer in the transmission line used for the inlet feed composition

measurement acts on the diaphragm actuator of the pneumatic control valve which

in turn regulates the steam pressure in the reboiler. The pneumatic signal from the

electro-pneumatic transducer in the transmission line used for inlet feed flowrate

measurement acts on the diaphragm actuator of the pneumatic control valve which

in turn regulates the reflux ratio. The signals are carried through the transmission

lines. The steam pressure in the reboiler and the reflux ratio are the manipulated

variables.

SCADA Configuration :-

The SCADA system configuration consist of

following control units.

1) Supervisory control station

2) PLC & RTU

3) Computer network segment.

The process information such as temperature,

flowrate, composition etc. are communicated between the process plant and PLC’s

of control system.

Sr. No. Control Equipment Sensor

1 Pyrolysis heater Thermocouple

2 Cooler Thermocouple

L.I.T. Nagpur


3 Separator Composition measurement

4 Ketene absorber Thermocouple & Composition measurement

5 Acetic acid column Flowmeter & Composition measurement

6 Acetic anhydride column Flowmeter & Composition measurement

Plant Location & Layout :-

The location of the plant can have a crucial effect on

the profitability of a project, and the scope for future expansion. Many factors must

be considered when selecting a suitable site, the principal factors to consider are:

1. Location, with respect to the marketing area.

2. Raw material supply.

3. Transport facilities.

4. Availability of labour.

5. Availability of utilities: water, fuel, power.

6. Availability of suitable land.

7. Environmental impact, and effluent disposal.

8. Local community considerations.

9. Climate.

L.I.T. Nagpur


10. Political and strategic considerations.

Marketing Area :-

Acetic anhydride is widely used in the production

of dyes as an intermediate. Hence, it is necessary to locate the plant near to dye

factories. From this prospective Mumbai is the ideal place for acetic anhydride

plant since many dye factories are located close to Mumbai.

Raw Materials :-

The raw material for the plant is acetic acid. As Most

of the acetic acid is produced from petroleum, hence it can be obtained very easily

from the refineries. Hence it is advised that the site of the plant should be nearer to

the refineries, so that the transportation cost is reduced. From this prospective

Mumbai or any place nearer to Mumbai is the most suitable region for the plant.

Transport :-

The transport of materials and products to and from the

plant will be an overriding consideration in site selection. If practicable, a site

should be selected that is close to at least two major forms of transport: road, rail,

waterway (canal or river), or a sea port. Road transport is being increasingly used,

L.I.T. Nagpur


and is suitable for local distribution from a central warehouse. Rail transport will

be cheaper for the long-distance transport of bulk chemicals. Air transport is

convenient and efficient for the movement of personnel and essential equipment

and supplies, and the proximity of the site to a major airport should be considered.

All these facilities of transport are very easily available in a place like Mumbai,

hence from the prospective transportation facilities Mumbai is the ideal place for

the project.

Availability Of Labour :-

Labour will be needed for construction of the plant

and its operation. Skilled construction workers will usually be brought in from

outside the site area, but there should be an adequate pool of unskilled labour

available locally; and labour suitable for training to operate the plant. Skilled

tradesmen will be needed for plant maintenance. Local trade union customs and

restrictive practices will have to be considered when assessing the availability and

suitability of the local labour for recruitment and training.

Utilities (services)

Chemical processes invariably require large

quantities of water for cooling and general process use, and the plant must be

L.I.T. Nagpur


located near a source of water of suitable quality. Process water may be drawn

from a river, from wells, or purchased from a local authority. At some sites, the

cooling water required can be taken from a river or lake, or from the sea; at other

locations cooling towers will be needed.

Electrical power will be needed at all sites. A

competitively priced fuel must be available on site for steam and power generation.

Environmental impact, and Effluent disposal :-

All industrial processes produce waste products, and

full consideration must be given to the difficulties and cost of their disposal. The

disposal of toxic and harmful effluents will be covered by local regulations, and

the appropriate authorities must be consulted during the initial site survey to

determine the standards that must be met. An environmental impact assessment

should be made for each new project, or major modification or addition to an

existing process.

Local Community Considerations :-

The proposed plant must fit in with and be

acceptable to the local community. Full consideration must be given to the safe

L.I.T. Nagpur


location of the plant so that it does not impose a significant additional risk to the

community. On a new site, the local community must be able to provide adequate

facilities for the plant personnel: schools, banks, housing, and recreational and

cultural facilities

Land (site considerations)

Sufficient suitable land must be available for the

proposed plant and for future expansion. The land should ideally be flat, well

drained and have suitable load-bearing characteristics. A full site evaluation should

be made to determine the need for piling or other special foundations.

Climate :-

Adverse climatic conditions at a site will increase

costs. Abnormally low temperatures will require the provision of additional

insulation and special heating for equipment and pipe runs. Stronger structures will

be needed at locations subject to high winds (cyclone/hurricane areas) or

earthquakes.

Political and strategic Considerations :-

Capital grants, tax concessions, and other inducements

are often given by governments to direct new investment to preferred locations;

L.I.T. Nagpur


such as areas of high unemployment. The availability of such grants can be the

overriding consideration in site selection.

GENERAL PLANT LAYOUT FOR A CHEMICAL INDUSTRY:

L.I.T. Nagpur

Maintain-ance

Building

Fire Station

Medical Centre

Quality Control

Laboratory

Sec-urity

Garden

Main Plant

Storage

Building

gg

Future

Expa-

nsionScrap YardResearch

and Develo-pment Centre

Sec-urity


L.I.T. Nagpur

Cooling towersControl

Room

Wash and Changing Room

Canteen

Training

Centre

Administration

Building

Power

Station

Parking

Space

Tank Yard

ETP

Utilities

Genera-

tion


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Documents

Acetic anhydride