Acrylic Acid - Mohit

INTRODUCTION Acrylic acid and its derivatives are primarily used in the preparation of solution and emulsion polymers. The objective of this project is to design an acrylic acid plant that will produce glacial acrylic acid, which is at 99.0% purity. Because acetic acid, a byproduct, is also a marketable commodity, purification of acetic acid to 95% purity is also desirable. Acrylic acid is produced via the catalytic partial oxidation of propylene. The desired products must be separated from the rest of the reactor product stream. This stream consists of acrylic acid, acetic acid, water, oxygen, nitrogen, and carbon dioxide. Goal is to produce 200 TPD of 99.0% acrylic acid utilizing 8000 hours a year. The one month of shut-down time is most likely for catalyst regeneration and equipment maintenance.

PRODUCT IDENTITY Common name: Acrylic acid CAS name: 2-Propenoic acid CAS registry number: 79-10-7 EEC No: 607-061-00-8 DOT UN: 22-18-29 RTECS Number: AS 4375000 Synonyms: acroleic acid 2-propenoic acid vinylformic acid propene acid ethylenecarboxylic acid propenoic acid ethene carboxylic acid Chemical formula: C3H4O2

GENERAL PROPERTIES: State: Water Solubility: Melting Point: Boiling Point: Specific Gravity: Auto- ignition: Molar Mass:

Clear Liquid, colourless Soluble 12ºc 141-142ºc 1.047-1.051 435ºc 72.06 gm/mol

PROPERTIES OF ACRYLIC ACID Acrylic acid is a colorless liquid with an irritating acrid odor at room temperature and pressure. Its odor threshold is low (0.20-3.14 mg/m3). It is miscible in water and most organic solvents. Acrylic acid is commercially available in two grades: technical grade (94%) for esterification, and glacial grade (98-99.5% by weight and a maximum of 0.3% water by weight) for production of water-soluble resins. Acrylic acid polymerizes easily when exposed to heat, light or metals, and so a polymerization inhibitor is added to commercial acrylic acid to prevent the strong exothermic polymerization. The inhibitors that are usually used in acrylic acid preparations are the:     

Monomethyl ether of hydroquinone (methoxyphenol) at 200 ± 20 ppm Phenothiazine at 0.1% Hydroquinone at 0.1% Methylene blue at 0.5 to 1.0% N,N'-diphenyl- p-phenylenediamine at 0.05% can also be used.

Acrylic acid reacts readily with free radicals and electrophilic or nucleophilic agents. It may polymerize in the presence of acids (sulfuric acid, chlorosulfonic acid), alkalis (ammonium hydroxide), amines (ethylenediamine, ethyleneimine, 2-aminoethanol), iron salts, elevated temperature, light, peroxides, and other compounds that form peroxides or free radicals. The presence of oxygen is required for the stabilizer to function effectively. Acrylic acid must never be handled under an inert atmosphere. Freezing of acrylic acid occurs at 13°C. Rethawing under inappropriate temperature conditions is another frequent reason for acrylic acid polymerization. Acrylic acid is a strong corrosive agent to many metals, such as unalloyed steel, copper and brass.

CHEMICAL PROPERTIES: Acrylic acid undergo reactions characteristics of both unsaturated acids and aliphatic carbolic acids or esters. The high reactivity of these compounds stems from the two unsaturated centers situated in the conjugated position. The β carbon atom, polarized by carbonyl group, behaves as an electrophile; this fovours the addition of large variety of nucleophiles and active hydrogen compounds to the vinyl group. Moreover, the carbon-carbon double bond undergoes radical-initiated addition reactions, Diels-Alder reactions with dienes, and polymerization reactions. The carboxyl function is subject to the displacement reactions typical of aliphatic acids and esters, such as esterification and transesterification. Joint reactions of the vinyl and carboxyl functions, especially with bifunctional reagents, often constitute convenient route to polycyclic and heterocyclic substances. Acrylic acids polymerise very easily. The polymerization is catalysed by heat, light, and peroxides and inhibited by stabilizers, such as monomethyle ether of hydroquinone or hydroquinone itself. These phenolic inhibiters are effective only in the presence of oxygen. Thehighly exothermic, spontaneous polymerization of acrylic acid is extremely violent.

USES OF ACRYLIC ACIDS Acrylic acid undergoes the typical reactions of a carboxylic acid and forms acrylic esters - basic alkyl esters are methyl, butyl, ethyl acrylate, and 2-ethylhexyl acrylate. Acrylic acid and its esters undergo the reactions of the double bond which readily combine with themselves or other monomers (e.g amides, methacrylates, acrylonitrile, vinyl, styrene and butadiene) to form homopolymers or co-polymers which are used in the production of coatings, adhesives, elastomers, super absorbent polymers, flocculants, as well as fibres and plastics. Acrylate polymers show a wide range of properties dependent on the type of the monomers and reaction conditions. Alkyl acrylates are clear, volatile liquid; slightly soluble in water and complete soluble in alcohols, ethers and almost organic solvents; Acrylate esters containing a double bond and functional carboxyl group are used chiefly as a monomer or co-monomer in making acrylic and modacrylic fibers. It is used in formulating paints and dispersions for paints, inks, and adhesives. It is used in making cleaning products, antioxidant agents, amphoteric surfactants. It is used in making aqueous resins and dispersions for textiles and papers. Methyl acrylate also used in making vitamin B1 The worldwide production of acrylic acid in 1994 was estimated to be approximately 2 million tonnes. Acrylic acid is used primarily as a starting material in the production of acrylic esters; as a monomer for polyacrylic acid and salts, as a comonomer with acrylamide for polymers used as flocculants, with ethylene for ion exchange resin polymers, with methyl ester for polymers. Acrylic acid is used in the field of application of:                 

plastics paper manufacture and coating exterior house paints for wood and masonry coatings for compressed board and related building materials flocculation of mineral ore fines and waste water , and treatment of sewage printing inks interior wall paints floor polishes floor and wall coverings industrial primers textile sizing, treatment and finishing leather impregnation and finishing masonry sealers lubricating and fuel oil additives lacquers for automotive, appliance and furniture finishes pharmaceutical binders hot metal coatings.

VARIOUS COMMERCIAL PROCESSES Ethylene Cyanohydrin Method: This process involves the acidic hydrolysis and dehydration of ethylene cyanohydrin (from ethylene oxide and hydrogen cyanide) and the removal of the product from the reaction mixture by distillation. Like all other preparation of polymerizable monomers, care must be exercised to remove the product from the reaction mixture and either inhibit or appropriately cool it before uncontrolled polymerization can ensue . H2SO4

HOCH2CH2CN + H2O

HOCH2CH2COOH

CH2=CHCOOH +H2O

-NH3

Propiolactone Method: This commercial method is based on the polymerization of βpropiolactone and the destructive distillation of this polymer to form acrylic acid. CH2CH2CO

-CH2CH2COOCH2CH2COOCH2CH2COO-

CH2=CHCOOH

O

Carbonyl Reaction: Basic raw materials in the preparation of acrylic acid by the carbonyl reaction are acetylene carbon monoxide (supplied as such or in the form of nickel carbonyl ) , and water . Three distinct methods are known. Stoichiometric Carbonyl Reaction: The reaction is very rapid at atmospheric pressure and at mild temperature . The hydrogen shown in the accompanying equation does not appear in gaseous form but is consumed by side reactions Ni(CO)4 + 4 HC≡CH + 4H2O + 2H+

4 CH2 =CHCOOH + Ni++ + 2H

Catalytic Carbonyl reaction: The catalytic reaction requires elevated temperature and superatmospheric pressures. Nickle salts or complexes thereof are used as catalysts. CO + HC≡CH + H2O

CH2=CHCOOH

Semicatalytic Carbonyl Reaction: The catalytic reaction ( catalytic as regards nickel carbonyl) of acetylene, carbon monoxide and water is superimposed upon the stoichiometric reaction of nickel carbonyl , acetylene , water and acid. In this way the very mild conditions characteristic of the stoichiometric reaction can be used , with a large proportion of the total CO being supplied as carbon monoxide gas, the remainder being supplied in the form of nickel carbonyl.

Acrylonitrile Method: Care must be exercised in this acid hydrolysis since both the starting Acrylonitrile and the product acrylic acid are polymerizable. The Acrylonitrile should remain in the reaction zone and , hence, must be well inhibited . A major advantage of this method is the

increase in molecular weight on hydrolysis from 53 to 72, which provides a definite yield improvement. 2 CH2= CH CN + H2SO4 + 4 H20 CH2=CHCOOH + (NH4)2SO4 Propylene Method: This recently developed process involves the oxidation of propylene to hydroxypropionic acid : oxides of nitrogen or nitric acid act as catalyst for the reaction. Subsequent dehydration yields acrylic acid. The stepwise representation can be shown as follows: CH3CH=CH2 + 3/2 O2

CH 3CHOHCOOH

CH2=CHCOOH + H2O

An alternative route is the catalytic oxidation to acrolein , CH2CHCHO , and then to acrylic acid with oxygen and certain metallic catalyst such as Mo, Co, or Ce.

Acrylic Ester Method: This method is hamperaed by the ready polymerisability of the starting material , and the low boiling points of the most available esters and the formed alchohols as compared with that of the product , acrylic acid. H2SO4

CH2=CHCOOCH3 + H2O

CH2=CHCOOH + CH3OH

It is generally preferable to saponify the ester to form the corresponding salt. CH2=CHCOOCH3 + NaOH

CH2=CHCOONa + CH3OH

The salt can then be converted to the acid by :  Neutralizing the calcium salt with sulphuric acid, removing precipitated calcium sulfate by a difficult filtration procedure, and obtaining the formed acrylic acid in aqueous concentrate.  Treating an aqueous solution of sodium salt with ion- exchange resin to remove sodium ions, removing the resin by filtration, and obtaining an aqueous concentrate of acrylic acid.

Maleic Acid Method: This patented method involves the decarboxylation of maleic acid to form the desired acrylic acid. HOOCCH=CHCOOH

CH2=CHCOOH + CO2

Potassium Vinyl Method: The low temperature conversion of vinly chloride with potassium metal and a subsequent treatment of the cold vinyl potassium with dry ice is reported to give potassium acrylate in 70% conversion . Customery methods produce acrylic acid. K

CO2

CH2=CHK

CH2=CHCl

CH2=CHCOOK

Vinyl Grignard Method: This interesting synthesis involves the use of the well known carboxylation of a Grignard reagent to form the acid. HX

CH2=CHMgX + CO2

CH2=CHCOOMgX

CH2=CHCOOH + MgX2

CHOICE OF PROCESS Various methods for the manufacture of acrylic acid are mentioned above. For a route to be commercially attractive the raw material costs and utilization must be low, plant investment and operating cost not excessive, and waste disposal charges minimal. Acrylic acid commercially is, and here also is being produced from propylene which is a by-product of ethylene and gasoline production. CH2=CHCH3 + 3/2 O2

CH2=CHCOOH + H2O

A lead time of several years for development and plant construction is important in a period where and availability of hydrocarbon raw materials are changing rapidly and significantly. Natural gas costs are expected to increase steadily while the supply is decreasing. Acetylene should be in short supply with rising costs in the next decade unless new technology based on coal is developed . Hence, acrylic acid manufacture by acetylene routes will be increasingly uneconomical. Ethylene cost, dependent on crude oil are expected to increase ,but not sharply. Propylene may be considered a byproduct from the large volume manufacture of ethylene from heavy petroleum feed stocks. New ethylene facilities , based on naphtha and other heavy feed stocks will ensure a large supply of coproducts including propylene. Propylene requirements for acrylic acid will be small,compared to other chemical uses ( polypropylene , Acrylonitrile, propylene oxide , isopropanol and cumene for acetone and phenol). Hence , although the cost of propylene is expected to rise, this should be at a slower rate than the increases for any of the other raw materials . The favourable supply and cost projection for propylene suggest that all new acrylic acid plants will employ propylene oxidation technology for atleast the next two decades. The most economical process for the manufacture of acrylic acid is based on the two stage vapour phase oxidation of propylene to acrylic acid. Process based on acetylene - the high pressure Reppe process (BASF), the modified Reppe process (Rohm Haas) - or on Acrylonitrile are still being used for the production of acrylic acid. A ketone and an ethylene cyanohydrin process were once commercially important, but are no longer used. The propylene oxidation process is attractive because of the availability of highly active and selective catalysts and the relatively low cost of propylene.

PROCESS DESCRIPTION The reactors are of the fixed-bed shell-and-tube type (about 3-5m long and 2.5cm in diameter) with a molten salt coolant on the shell side. The tubes are packed with catalyst, a small amount of inert material at the top serving as a preheater section for the feed gases. Vaporized propylene is mixed with steam and air and fed to the firststage reactor. The preheated gases react exothermically over the first-stage catalyst with the peak temperature in the range of 330 - 4300c, depending on conditions and catalyst selectivity. At the end of the catalyst bed, the temperature of the mixture drops toward that of the molten salt coolant. The acrolein rich gaseous mixture containing some acrylic acid is then passed to the second stage reactor, which is similar to the first stage reactor but packed with catalyst designed for selective conversion of acrolein to acrylic acid. Here the temperature peaks in the range of 280 – 3600c depending on condition. The temperature of the effluent from the second stage reactor again approximates that of the salt coolant. The heat of reaction is recovered as steam in external waste heat boiler. The process is operated at the lowest temperature consistent with high conversion. Conversion increases with temperature: the selectivity generally decreases only with large increase in temperature. Catalysts are designed to give high performance over a range of operating condition permitting gradual increase of salt temperature over the operating life of the catalysts to maintain productivity and selectivity near the initial levels, thus compensating for gradual loss of catalyst activity. The first unit the product stream enters is the absorption tower, which quickly lowers the temperature of the entering stream from about 220oc to less than 800c. The purpose is to put the acrylic acid into a cool, liquid state that will not readily dimerize. Also, this separates out the gaseous material in the product stream such as nitrogen, carbon dioxide, oxygen, and propylene. These components exit out the top along with some fugitive acrylic and acetic acid that is still in the vapor phase. The gases entering the gas absorber are absorbed using deionized water. The water absorbs the acrylic and acetic acids and allows the other gases to continue on to an incinerator to be burned.The aqueous effluent from the bottom of the absorber is 20 - 30 % acrylic acid which is sent to the recovery .The overall yield of acrylic acid in the oxidation reaction steps is in the range of 73 - 83 % depending on the catalysts and condition employed. The acrylic acid is extracted from the absorber effluent with a solvent. The acid extractor is a liquid-liquid extraction column. The acid containing water enters through the bottom feed stream. The top feed stream contains an organic solvent . The two liquid phases flow countercurrently through a liquid-liquid extractor. The acids enter solution with the solvent and exit out the top stream with a fraction of the water, and the water exits out the bottom stream with a very small amount of solvent.

The top stream continues on to the solvent tower, which is a packed distillation column. Because of acrylic acid's ability to dimerize easily at high temperatures, all of the distillation processes are performed in part with vacuum distillation. The solvent and remaining water leave in the distillate stream at 0.12 bar and 13oC. Refrigerated water is used to condense the distillate. Some is refluxed back into the column, but the distillate is then heated up to 40oC and used as a recycle and is re-fed into the acid extractor. Meanwhile, the acids leave the solvent tower in the bottoms and are fed into the acid tower. The acid tower is a distillation column that again operates in vacuum conditions. The acetic acid leaves the top at 0.07 bar, while the acrylic acid leaves in the bottoms. Both the acrylic and acetic acids are warmed and compressed to normal pressure levels. Both now meet the given requirements. Namely, that acrylic acid must be 99% pure and that acetic acid must be 95% pure. Only one detail remains. The bottom stream from the acid extractor is nearly completely water save for a small amount of solvent. This stream is fed to another distillation column. Here, the solvent is separated out the top stream and then joins the solvent recycle stream re-entering the acid extractor tower. The bottom stream is sent to wastewater treatment The oxidation process flow sheet shows equipment and typical operating conditions.

DETAILED MATERIAL BALANCE Basis: 100 TPD of Acrylic Acid . CH2=CHCH3 + O2

CH2 = CHCHO + H2O (acrolein)

CH2=CHCHO + ½ O2

CH2=CHCOOH (acrylic acid) Molecular weights: Propylene = 42; Acrylic acid(AA) = 72; Acetic acid = 60; Acrolein = 56; Oxygen = 16; Carbon dioxide = 44

ACID TOWER ( Designed as a major equipment ) Assumption : Top product is 95 wt. % acetic acid Bottom product is 99.5 wt.% acrylic acid. Apply Overall Balance= Y*64.81=0.05*6.944 +0.995*57.87 Y=0.8938 Input Feed : Acrylic acid = 0.8938*64.81=57.92 kmol/hr Acetic acid = 64.81-57.92=6.88 kmol/hr

SOLVENT RECOVERY COLUMN : Assumption: 1. Complete recovery of solvent and water occurs. 2. Bottom product contains only acetic acid and acrylic acid. 3. 98% of solvent entering in extraction column present in extract phase(Feed to Solvent tower). 4. 0.5% of acetic acid and acrylic acid present in feed stream is present in recycle Stream. OUTPUT= Acrylic acid=57.92 kmol/hr Acetic acid=6.88 kmol/hr. By applying balance we get:

Feed : Extract phase from the liquid-liquid extractor: Acrylic acid = 58.21 kmol/hr. Acetic acid = 6.9145kmol/hr Water = 10.83 kmol/hr Solvent = 245 kmol/hr Upstream contains (recycled to extraction column) : Solvent = 245kmol/hr Acrylic acid = 0.29 kmol/hr Acetic acid = 0.0345 kmol/hr Water = 10.83 kmol/hr

SOLVENT EXTRACTION COLUMN : Solvent with high solubility for acrylic acid and acetic acid , and low solubility with water is used to extract AA acid from absorber stream. X=Acetic acid Y=Acrylic acid Assumptions: 1. Solvent required for 99 .5% extraction of AA is 250 kmol/hr. 2. All acrylic and acetic acid in recycle stream went to raffinate phase. 3. 0.5 of acrylic and acetic acid feed is in raffinate phase. 4. 98% of solvent entering is in extract phase. Recycled stream from solvent recovery column and waste tower. Acrylic acid = 0.29 kmol/hr Acetic acid = 0.3450 kmol/hr Water = 10.83 kmol/hr Extract phase contains (to solvent recovery plant): Acrylic acid = 58.21 kmol/hr. Acetic acid = 6.9145 kmol/hr Water = 10.83 kmol/hr Solvent = 245 kmol/hr Raffinate phase contains ( to waste tower)X Acrylic acid = 0.005*Y +0.29 kmol/hr Acetic acid = 0.005*X +0.0345kmol/hr Water = 595.6 kmol/hr Solvent = 5 kmol/ hr By applying balance we get: Feed from the bottom the absorber: Acrylic acid = 58.79 kmol/hr Acetic acid = 6.984 kmol/hr water = 541.42 kmol/hr

ABSORBER:

From literature: Acrylic acid and acetic acid is absorbed using water as solvent. Gases CO2 , O2 , N2 and small amount of steam leave the absorber at the top. Assumptions: Solvent:

1% of acrylic and acetic acid feed went to off gases. Water entering at the top = 244.3 kmol/hr

Off gases leaving at the top: CO2 = 6.399 kmol/hr N2 = 458.75 kmol/hr O2 = 20.784 kmol/hr AA = 0.5632 kmol/hr Acetic acid = 0.07695 kmol/hr Steam=33.0135 kmol/hr Product liquid leaving at the bottom of the absorber to recovery section: Acrylic acid = 58.79 kmol/hr Acetic acid = 6.984 kmol/hr water = 541.42 kmol/hr By material balance we get:Feed entering at the bottom of the absorber: Acrylic acid =59.38 kmol/hr Acetic acid = 7.055 kmol/hr CO2 = 6.399 kmol/hr O2 =20.784 kmol/hr N2 = 458.75 kmol/hr Steam =330.135 kmol/hr

REACTOR II: Oxidation of Acrolein to Acrylic acid CH2=CHCHO + ½ O2

CH2=CHCOOH (acrylic acid) Catalyst composition= Mo12 V1.9 Al 1.0 Cu2.2 ( support - Al sponge) Contact time = 1 - 3 sec Average temperature = 300oc Acrolein conversion = 100% Yield of AA = 97.5% ASSUMPTIONS=1. 97.5% conversion of acrolein to acrylic acid. 2. 2.5% converted to acetic acid and CO2. Output:Total AA formed in 2 reactors = 59.38 kmol/hr Total Acetic acid produced = 7.055 kmol/hr

Total CO2 produced = 7.055 kmol/hr N2 in = N2 out = 458.75 kmol/hr By applying balance we get:= Feed: O2 = 47.01 kmol/hr N2 = 458.75 kmol/hr Steam = 333.135 kmol/hr Acrolein = 52.4515 kmol/hr Acrylic acid = 8.2424 kmol/hr Acetic acid = 6.399kmol/hr CO2 = 6.399 kmol/hr O2 reacted = 26.225 kmol/hr O2 unreacted = 20.784 kmol/hr

REACTOR I: Oxidation of Propylene to Acrolein .

CH2=CHCH3 + O2

CH2 =CHCHO + H2O (acrolein) Catalyst composition= Ni. Fe. Zn. Bi. or Zn + Co (Fe promotion ) Contact time = 3.6 sec Average temperature = 355oc ASSUMPTIONS=1. Feed Composition= C3H6 : Air : Steam :: 1 : 7.75 : 3.75 2. Overall conversion of C3H6 = 100% 3. Conversion to acrolein = 70% 4. Conversion to AA = 11% OUTPUT GIVEN= Acrolein produced = 52.4515 kmol/hr AA produced = 8.2424 kmol/hr Steam produced = 51.93 kmol/hr Side products produced (CO2 + Acetic acid)=12.80 kmol/hr Total steam leaving the reactor = 333.135 kmol/hr By applying balance we get= C3H6 fed = 74.188 kmol/hr Steam fed = 280.987 kmol/hr Air fed = 580.7075 kmol/hr O2 entering = 121.74 kmol/hr N2 in = N2 out = 458.75 kmol/ hr

O2 used in the reactor = 74.188 kmol/hr O2 left unreacted = 47.01 kmol/hr

DETAILED ENERGY BALANCE Data: Heat capacity: C3H6 : 2.85 + .23 x 10-2 T - 1.2 x 10-4 T 2 + 2.3 x 10-8 T 3 ( kJ/kmol K ) C3H4O : 3.7957 + 4.4 x 10-2 T - 0.1304 x 10-4 T 2 - 0.2848 x 10-8 T 3 (cal / mol K) C3H4O2: 1.6828 + 6.9212 x 10-2 T - 0.4475 x 10-4 T2 + 1.10186 x 10-8 T3 ( cal / mol K) C2H4O2: 2.0142 + 5.6065 x 10-2 T - 0.3401 x 10-4 T 2 + 0.802 x 10-8 T 3(cal / mol K) REACTOR I

Heat in: Feed is preheated to 200oc (Molten Salt Coolant Temperature) 473

Heat in with C3H6 = m ∆Hf at 25oc + m ∫298 Cp dT 473

= 74.188 ( 20.27 x 10 3 + ∫298 Cp dT) = 2499675.27 kJ / hr Heat in with air(Compressed to 5 bar) = m Cp∆T = 574.957 x 1.015x 29x (200-25) = 2961742.34 kJ / hr Heat in with steam = mλ+mCp∆T = 278.205 x ( 2676 x 18 + 2.291 x 18 ) x (200-25) = 15408286.55 kJ / hr Total heat in = 20869704.03 kJ / hr Heat Generated : Heat generated by reaction 1 = 340.8 kJ / mol Heat generated by reaction 2 = 254.1 kJ / mol Heat generated by other side reactions are neglected. Total heat generated = 340.8 x 103 x 51.93 + 254.1 x 103 x 8.16 = 19771200 kJ / hr Heat removed by Coolant : The temperature in the reactor reaches an average peak temperature of 355oc due to the exothermic reaction. At the end of the catalyst bed, the temperature drops toward that of molten salt coolant (2100c) 483

483

Heat with acrolein = m ∫628 Cp dT= 51.93 x ∫628 Cp dT = 746491.31 kJ / hr 483

483

Heat with Acrylic acid = m∫628 Cp dT = 8.16x ∫628 Cp dT = 139424.3 kJ / hr 483

483

Heat with Acetic acid = m∫628 Cp dT = 7.045 x∫628 Cp dT = 102482.9 kJ / hr Heat with air = m Cp ∆T = 500.762 x 30.35 x ( 628-483) = 2203728.37 kJ / hr Heat with CO2 = m Cp ∆T =7.045 x 47.896 x ( 628-483) = 48926.96 kJ / hr

Heat with steam = m Cp ∆T = 330.135 x 36.173 x ( 628-483) = 1731586.13 kJ / hr Total heat removed by the Coolant = 49726399.74 kJ/hr Heat out: 298

298

Heat out with Acrolein = m∫483 Cp dT = 51.93 ∫628 Cp dT = 754594.56 kJ/hr 298

298

Heat with Acrylic acid = m∫483 Cp dT = 8.16 x∫483 Cp dT = 141806.91 kJ/hr 298

298

Heat with Acetic acid = m∫483 Cp dT = 7.045 x∫483 Cp dT = 104244.7 kJ / hr Heat with air = m Cp ∆T = 500.762 x 30.35 x ( 483-298) = 2811653.44 kJ / hr Heat with CO2 = m Cp ∆T = 7.045 x 42.37 x ( 483-298) = 55221.88 kJ / hr Heat with steam = m Cp ∆T = 330.135 x 33.913 x ( 483-298) = 2071235.62 kJ / hr Total heat out = 5938757.11 kJ/hr Heat to Waste heat boiler =Heat in + Heat generated - Heat removed by coolant - Heat out =29729506.95 kJ/hr Water required in boiler = m = 59459205.41/λ = 11109.68 kg/hr REACTOR II

Heat in from reactor I = 5938757.11 kJ/hr Heat generated = 254.1 x 10 3 kJ/kmol of Acrylic acid = 254.1 x 10 3 x 50.63 = 12865083 kJ/hr Heat removed by coolant: The feed to the second reactor enters at temperature of 210oc The temperature in the reactor reaches an average peak temperature of 300oc due to the exothermic reaction. At the end of the catalyst bed, the temperature drops toward that of molten salt coolant (210oc) 483

483

Heat with Acrylic acid = m∫573 Cp dT = 58.79 x∫573 Cp dT = 605576.04 kJ / hr 483

483

Heat with Acetic acid = m∫573 Cp dT = 7.695 x∫573 Cp dT = 67473.46 kJ / hr Heat with air = m Cp ∆T = 474.488 x 30.35 x ( 573-483) = 1294207.915 kJ / hr Heat with CO2 = m Cp ∆T = 7.695 x 46.0548 x ( 573-483) = 31903.955 kJ / hr Heat with steam = m Cp ∆T = 330.135 x 35.42 x ( 573-483) = 1052439.6 kJ / hr Total heat removed by the Coolant = 3051600.975 kJ/hr Heat out: 298

298

Heat with Acrylic acid = m∫483 Cp dT = 58.79 x∫483 Cp dT = 1021671.95 kJ / hr 298

298

Heat with Acetic acid = m∫483 Cp dT = 7.695 x∫483 Cp dT = 27221.275 kJ / hr Heat with air = m Cp ∆T = 474.488 x 30.35 x ( 483-298) = 2664131.498 kJ / hr Heat with CO2 = m Cp ∆T = 7.695 x 40.528 x ( 483-298) = 57710.71 kJ / hr Heat with steam = m Cp ∆T = 330.135 x 36.913 x ( 483-298) = 2254460.552 kJ / hr Total heat out = 5930875.925 kJ/hr. Heat to Waste heat boiler =Heat in + Heat generated - Heat removed by coolant - Heat out =9821363.21 kJ/hr Water required in boiler = 9821363.21/λ = 3670.16 kg/hr ABSORBER: Heat in: Heat in from the second reactor =5930875.925 kJ/hr Absorbing solvent water enters at 30oc Heat in with water = m Cp ∆T = 244.3 x 4.186 x 18 x (30-25) =92037.55.1 kJ/hr Total heat in = 6022912.925 kJ/hr

Heat out along with the offgas: The off gas leave the column at 70oc 298

298

Heat with Acrylic acid = m∫343 Cp dT = 0.5632 x∫343 Cp dT = 2080.07 kJ / hr 298

298

Heat with Acetic acid = m∫343 Cp dT = 0.07695 x∫343 Cp dT = 242.52 kJ/hr Heat with air = m Cp ∆T = 474.488 x 30.35 x ( 343-298) = 648031.986 kJ / hr Heat with CO2 = m Cp ∆T = 7.695 x 40.52 x ( 343-298) = 14031.06 kJ / hr Heat with water = m Cp ∆T = 33.0143 x 33.913 x ( 343-298) = 5034.7 kJ / hr Total heat out with the off gas= 714732.63 kJ/hr. Heat out along with the bottom product: The bottom products leave the column at 80oc 298

298

Heat with Acrylic acid = m∫353 Cp dT = 58.22 x∫353 Cp dT = 265746.83 kJ / hr 298

298

Heat with Acetic acid = m∫353 Cp dT = 7.695 x∫353 Cp dT = 30510.825 kJ / hr Heat with water = m Cp ∆T = 541.42 x 4.186 x 18x ( 343-298) = 2243740.995 kJ / hr Total heat out with the bottom product = 2539998.65 kJ/hr. Heat to inter stage cooler (Minor equipment) =Heat in - Heat out with off gas - Heat out at the bottom = 2768181.645 kJ/hr

PROCESS DESIGN (Vacuum distillation Tower)

Feed to the distillation tower = 57.655 kmol/ hr of acrylic acid + 7.54 kmol / hr of acetic acid. = 65.195 kmol/ hr. Top product from the distillation tower is 95 wt% acetic acid. Bottom product from the distillation tower is 99.5 wt% acrylic acid . Feed: Flow rate of feed = 65.195 kmol/ hr. Mol fraction of acetic acid in feed = 7.54 / 65.195 = 0.1156 Average molecular weight of feed = 70.37 kg/kmol Distillate: Flow rate of distillate = 0.1156/0.958 x 65.195 = 7.867 kmol/hr Mol fraction of acetic acid =( 95/60 )/ [ (95/60 )+ (5/72)] = 0.958 Average molecular weight of distillate = 60.5 kg/kmol . Residue: Flow rate of residue = 65.195-7.867 = 57.328 kmol/hr. Mol fraction of acetic acid = (0.5/ 60 ) / [( 99.5/72 )+ (0.5/ 60)] = 0.006 Average molecular weight = 71.92 kg/kmol.

VLE data : Liquid Mole frac of acetic acid (x) Vapor Mole frac of acetic acid (y)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.0

0.21

0.37

0.51

0.63

0.715

0.795

0.86

0.92

0.96

1.0

Feed is a liquid at its boiling point q=1; i.e. q line is vertical line passing through x=y=xF . From x-y plot , xD / (Rm + 1) = 0.13  Rm = 6.369 Therefore, Optimum reflux ratio R= 15 Number of ideal stages in enriching section = 6 Number of ideal stages in stripping section = 4+1(reboiler) Number of stages = 11 Slope of bottom operating line = 1.313 Slope of top product = 0.959 Flow Rates: Molecular weight of feed = 70.37 kg/kmol Flow rate of feed = 65.195 kmol/hr = F Flow rate of distillate = 7.867 kmol/hr = D Flow rate of residue = 57.328 kmol/hr = F-D Physical Properties: Estimate base pressure, assume column efficiency of 60% Take reboiler as equivalent to 1 stage, No. of real stages = (11-1)/0.6 = 17 Assume 100mm water pressure drop per plate. Column pressure drop = 100 x 10-3 x 1000 x 9.81 x 17 = 16677 Pa Top pressure, 1 atm(14.7 lb/in2) = 101.4 x 103 Pa Estimate bottom pressure = 101.4 x 103 + 16677 = 118077 Pa = 1.18077 bar

Column Diameter: Flv = (L/G)x(ρL/ρG)1/2

At bottom, L= 11294.9kg/hr G= 8961.94kg/hr ρL= 1078.32 kg/m3 ρG= 0.1767 kg/m3 (Ref: digitallibrary.srmuniv.ac.in/4001.pdf) Therefore, Flv(bottom) = 0.814 At top, L= 6819.25kg/hr G= 7273.9kg/hr ρL= 1083.94 kg/m3 ρG= 0.1569 kg/m3 (Ref: digitallibrary.srmuniv.ac.in/4001.pdf) Therefore, Flv(top) = 0.0113 From Richardson vol. 6 Fig 11.27, taking tray spacing 0.5m, Base k1= 8x10-2 Top k1= 9.1x10-2 Correction for surface tension, Base k2= (57/20)0.2x 8x10-2 = 0.0986 Top k2= (23/20)0.2x 9.1x10-2 = 0.0935 Base uf = 0.0986 x((1078.32-0.1767)/0.1767)1/2 = 7.7 m/s (R&C vol.6 eq 11.81) Top uf = 0.0935 x((1083.94-0.1569)/0.1569)1/2 = 7.77 m/s (R&C vol.6 eq 11.81) Design for 85% flooding at maximum flow rate Base Uv = 7.7x0.85=6.545 m/s Top Uv = 7.77x0.85=6.6045 m/s Maximum flow rate Slope of bottom operating line = 1.313 Lm`/Vm` = 1.313 Vm`= Lm`-57.328 = 1.313 Vm` - 57.328  Vm`= 183.156 kmol/hr  Lm`= 240.48 kmol/hr Therefore, for base, maximum flow rate= (183.156x71.92)/(0.1767x3600)= 20.71 m3/hr for top, maximum flow rate= (240.464x60.5)/(0.1569x3600) = 25.76 m3/hr Net area required, Bottom= 20.71/6.545 = 3.165 m2 Top= 25.76/6.6045 = 3.9 m2 At first trial take downcomer area as 12% of total. Column cross-sectional area, base= 3.165/0.88= 3.597m2 Top= 3.9/0.88= 4.43m2 Column diameter, base= (3.597x4/3.14)1/2 = 2.14m Top= (4.43x4/3.14)1/2 = 2.38m

Use same diameter above and below feed, reducing the perforated area for plates above the feed. Liquid flow pattern Maximum volumetric liquid rate= (240.48x71.92)/(3600x1078.32)=0.0045 m3/hr Provisional plate design Column diameter Dc = 2.38m Area Ac = 4.43m2 Downcomer area Ad = 0.12x4.43 = 0.5316m2 (at 12%) Net area An = Ac- Ad = 4.43-0.5316 m2 = 3.8984m2 Active area Aa = Ac- 2Ad = 3.3668m2 Hole area Ah(take 10% Aa at first trial) = 0.33668m2 From R&C vol.6 fig 11.31, Lw/Dc = 0.77  Weir length = Lw = 2.336m

PROCESS DESIGN (INTER STAGE COOLER) (Shell and tube heat exchanger)

Exchanger Duty: Q = 2768181.645 kJ/hr = 768.93 kJ/sec Coolant used is Water at 27oc Cooling water balance: Q = m Cp ∆T  768.93 = m x 4.187 x (32 - 27)  Mw = 36.72 kg/ sec. Flow rate of liq mix to be cooled, mmix = 3.998 kg/sec Liquid mixture Balance, Q = mmix x Cpmix x (Ti - 80 )  768.93 = 3.998 x 3.212 x (Ti - 80)  Ti = 140oc Hence the liquid mixture must be cooled from a temperature of 140oc to 40oc Properties (at mean temperature), Water: ρ= 993.68 kg/m3 Cp= 4.187 kJ/kgoK μ= 1 cp k= 0.578 W/mok Liq. Mix: ρ= 992.99 kg/m3 Cp= 3.212 kJ/kgoK μ= 0.1612 cp k= 0.513 W/mok Log Mean Temperature Difference (∆Tlm):

∆Tlm = [(T1 - t2 ) - (T2 - t1 ) ] / ln [(T1 - t2 )/ (T2 - t1 )]. (T1 - t2) = 140 - 32 = 108 (T2 - t1) = 80 - 27 =53 ∆Tlm = 77.2oc R = (T1 - T2 ) / ( t2 - t1) = 12 S = ( t2 - t1) / (T1 - t1) = 0.044 {From PERRY Fig 10-14, P.No.: 10-27} FT = 0.985 Routing of Fluids: Water - Tube side Liquid Mixture - Shell Side

Heat Transfer Area: {From PERRY Table 10-10 P.No.: 10-44} Assumed Value of Overall heat transfer Coefficient, Ud = 550 W/m2 K. Dirt factor = 5.1 x 10-4 m2 K/ W. Q = U A( ∆Tlm ) FT.  A= (768.93 x 103 ) / (570 x 73.21 x 0.97) = 18.38 m2 Number of Tubes: Choosing D0 (Tube outside dia) = ¾ in = 0.01905 m Di (Tube inside dia) = 0.62 in = 0.01575 m Length = L = 14 ft = 2.13 m Heat transfer Area: a = 3.14xDo = 3.14 x 0.01905 = 0.05987 m2 / m length Heat transfer Area for one tube = 0.05987 x 2.13 = 0.1277 m2 / tube Number of Tubes = 18.38 / 0.1277 = 144 From Tube Count Table (PERRY : table 11-3 ; P.No. 11-13) TEMA P or S ; for 1-2 pass, Number of tubes Nt = 228 Shell ID = 438 mm Corrected Heat Transfer Area = 228 x 0.1277= 29.11 m2 Corrected Ud = 427.977 W/m2 K. Tube Side (Cooling water) Velocity and Heat transfer Coefficient (hi) Flow Area = at = 3.14 / 4 x Di2 x(Nt / Np ) = 0.0222 m2 Velocity = vt = ( mt /ρ at) = 36.72 / 993.68 x 0.0222 = 2.12 m / sec Reynolds Number NRe = vt Di ρ/μ = 2.12 x 0.01575 x 993.68 / 1.00 x 10-3 =33178.9 Prandtl Number NPr = μ Cp/k = 1x10-3 x 4.187 x 103 )/ 0.578 = 7.2439 Nusselt Number NNu = 0.023 ( NRe)0.8 (NPr)1/3 = 184.1 Heat transfer coefficient hi = NNu K / Di = 6756.17 W/m2 K. Shell Side ( Liquid Mixture ) Velocity and Heat Transfer Coefficient ho: Assumption: Shell Dia is equal to tube bundle dia. Pitch: Equilateral Triangular Pitch is used. P' = standard pitch = 1 in = 25.4 mm. Sm = Cross flow area at center of shell = [(P' - Do ) Ls ] Ds / P' Ls = baffle spacing . = Ds / 2 = 0.219 m

Nb = number of baffles Nb + 1 = L / Ls = 20  Nb = 19 2  Sm = 0.02398 m Shell side velocity = vs = ms / Sm ρ = 3.998 / 0.02398 x 992.99 = 0.1678 m/sec Reynolds Number NRe = vs Do ρ/μ = 0.1678 x 0.01905 x 992.99 / 0.16128 x 10-3 = 19681.18 Prandtl Number NPr = μCp/k = 0.16128x10-3 x 3.205 x 103)/ 0.513 = 1.0076 Nusselt Number NNu = jH (NRe) (NPr)1/3 (From PERRY : Fig 10- 19 ; P.No 10-29 ) jH = 5 x 10-3 NNu = 98.65 Heat transfer coefficient ho = NNu K / Do = 2656.67 W/m2 K. Overall Heat Transfer Coefficient Uo: (1/ Uo) clean = 1/ ho + 1/ hi (Do / Di ) + Do ln (Do / Di ) / 2 Kw Kw = 50 W/m2 K. (1/ Uo)clean = [1/2656.67]+[(1/6756.17)(0.01905/ 0.01575)] +[(0.01905 ln (0.01905/ 0.01575))/(2x100)] = 5.9165 x 10-4 (1/ Uo) dirt = 5.9165 x 10-4 + 5.1 x 10-4 Uo = 907 W/m2 K This is greater than the assumed Uo, Hence design is acceptable.

COST ESTIMATION AND ECONOMICS C2 = C1 ( Q2 / Q1)n C1 = Fixed capital cost of a plant of Capacity Q1 C2 = Fixed capital cost of a plant of Capacity Q2 n= 0.6(Pg.186, Table 19, P. Timmerhaus) For the year 1999(as reference) Utilizing 8000 operating hours/year (Ref: digitallibrary.srmuniv.ac.in) Q1 = 50000 tons/year Q2 = 33333.335 tons / year. C1 = $ 24000000. C2 = 24000000 x (33333.335 / 50000)0.6 = $ 18.8 x 106 Cost of the plant in 2016: (Cost of plant in 2016 / Cost of plant in 1999) = (Cost index in 2016 / Cost index in 1999) Cost of plant in 2016 = 18.8 x 106 x(852 / 389.9) = $ 41.08 x 106 Fixed Capital Investment (FCI) required = $ 41.08 x 106 = Rs 2246.66 x 106 Direct cost: (70 - 85 % of FCI ) A. 1. Purchased Equipment (PEC) ( 15 - 40% of FCI) 25% of FCI = Rs 561.66 x 106 2. Installation including insulation and painting ( 25 - 55% of PEC) 30% of PEC = Rs 168.49 x 106 3. Instrumentation and Controls, Installed (6 - 30 % of PEC) 25% of PEC = Rs 140.41 x 106 4. Piping, Installed (10 - 80 % of PEC) 30% of PEC = Rs. 168.49 x 106 5. Electrical ,Installed (10 - 40% of PEC) 25% of PEC = Rs. 140.41 x 106 B. Building, process and auxiliary (10 - 70% of PEC) 40% of PEC = Rs.224.66 x 106 C. Service Facilities and Yard Improvements (40 - 100% of PEC) 60% of PEC = Rs.336.696 x 106 D. Land ( 1- 2% of FCI or 4- 8% of PEC) 5% of PEC = Rs. 28.083 x 106 Total Direct Cost = Rs 1468.39 x 106 Indirect Costs: (15 - 30 % of FCI) A. Engineering and Supervision (5 - 30 % of Direct Cost) 10% of Direct cost = Rs. 146.889 x 106 B. Construction Expense and Contractors Fee (6 - 30% of Direct cost) 10% of Direct costs = Rs. 146.889 x 106 C. Contingency (5- 15% of FCI)

5.5% of FCI = Rs. 30.89 x 106 Total Indirect Cost = Rs 324.66 x 106 Working Capital: (10 - 20% of TCI) 15% of TCI = Rs. 336.99 x 106 Total Capital Investment (TCI): TCI = FCI + Working Capital  TCI = Rs. 2583.65 x 106 ESTIMATION OF TOTAL PRODUCT COST (TPC): Manufacturing Cost: A. Fixed Charges (10 - 20% of TPC) 1. Depreciation (10% of FCI + 2 - 3% of building value for building ) 10% of FCI + 2.5% of Building value = Rs. 230.28 x 106 2. Local Taxes (1-4% of FCI ) 4% of FCI = Rs 89.86 x 106 3. Insurance (0.4 - 1% of FCI) 0.7% of FCI = Rs. 15.72 x 106 Total Fixed Charges = Rs. 335.86 x 106 Total Product Cost TPC = Fixed Charges / 0.15 = Rs. 2239.06 x 106 B. Direct Production Costs (about 60 % of TPC) 1. Raw Materials (10 - 50 % of TPC) 10% of TPC = Rs. 223.906 x 106 2. Operating Labor (10 - 20 % of TPC) 15% of TPC = Rs.335.859 x 109 3. Direct Supervisory and Clerical Labor (10 - 25 % of Operating labor) 15% of Operating Labor = Rs. 50.37 x 106 4. Utilities (10 - 20% of TPC) 10 % of TPC = Rs 223.906 x 106 5. Maintenance and Repairs (2- 10% of FCI) 5% of FCI = Rs. 112.33 x 106 6. Operating supplies (10 - 20% of cost for maintenance and repairs) 15% of cost for maintenance and repairs = Rs. 16.34 x 106 7. Laboratory Charges (10 - 20% of Operating Labor) 15% of Operating Charges = Rs 50.37 x 106 8. Patents and Royalties (0 - 6% of TPC ) 2% of TPC = Rs 44.78 x 106 Total Direct Production Cost = Rs 1053.36 x 106 C. Plant Overhead Cost (5 - 10% of TPC) 7% of TPC = Rs 156.73 x 106 Total Manufacturing Cost = Rs. 1547.95 x 106

General Expenses: A. Administrative Costs (2- 6% of TPC) 5% of TPC = Rs. 111.953 x 106 B. Distribution and Selling Costs (2 - 20% of TPC) 18% of TPC = Rs. 403.03 x 106 C. Research and development cost (5% of TPC) 5% of TPC = Rs. 111.953 x 106 D. Financing (0- 10 % of TCI) = Rs. 77.509 x 106 Total General Expenses = Rs. 704.44 x 106 SELLING PRICE: Acrylic acid produced = 100 TPD Selling price of Acrylic acid = $2.9 /kg (Ref: Chemical Marketing Reporter) Acetic acid produced = 10.33 TPD Selling price of Acetic acid = $ 0.8 /kg (Ref: Chemical Marketing Reporter) Total income = selling price x qty of product produced = Rs. 5455.81 x 106 Gross Earning = Total income - Total product cost = 5455.81 x 106 – 2239.06 x 106 = Rs 3216.75 x 106 Tax on gross earning = 40% of gross earning. Net Profit = Gross earning [1 - tax rate] = Rs. 1930.05 x 106 Rate of return = Net profit / Total capital investment = 1930.05 x 106 / 2583.65 x 106 = 0.74 Payback Period = 2246.66/(1930.05+230.28) = 1.03 years

SITE CONSIDERATION AND PLANT LAYOUT The location of the plant can have a crucial effect on the profitability of a project, and the scope for future expansion. Factors considered while selecting a plant site are:                 

Transportation Sources and costs of raw materials Prospective market for products Corporation long range planning Water source - quality and quantity Special incentive Climatic conditions Pollution requirements(Waste disposal) Utilities - cost, quantity and reliability; fuel - costs, reliability and availability Amount of site preparation necessary(site conditions) Construction costs Operating labor Taxes Living conditions Corrosion Expansion possibilities Other factors.

Three factors are usually considered the most important. These are the location of the markets and raw materials and the type of transportation to be used. Transportation: 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. The least expensive method of shipping is usually by water; the most expensive is by truck. Raw materials: The availability and price of suitable raw materials will often determine the site location. Propylene is the major raw material for the manufacture of Acrylic acid, hence the plant can be located near any plant producing propylene. It will reduce transportation and storage costs. Location of markets: Consumer products often are delivered in small shipment to a large number of customers. In an international market, there may be an advantage to be gained by locating the plant within an area with preferential tariff agreements. Since acrylic acid acts as a raw material for the production of consumer goods like paints, plastics, pharmaceutical binders etc., it is always advantages for the plant to be situated in a industrial area. Long Range Corporate Planning: The object of long range planning is to optimize a whole network of operations instead of each one individually. This means that each plant site is not considered only for itself and that its chosen location might not be the one that would be selected if only the economics of the one plant had been considered. Placing the plants throughout the country allows each plant to be located optimally.

Water: Water is needed by every processing plant for a number of different purposes. Potable water is needed for drinking and food preparation. The plant site must have an adequate amount of each type of water at all times of the year. Not only the amount and quality but the temperature of the water is important. The size of the heat exchanger is inversely proportional to the temperature difference between the cooling water and the material being cooled. Climatic Conditions: 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 or earthquake. Pollution and Ecological Factors: 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 must be met. Site Conditions: An ideal chemical plant site is above the flood plain, flat, has good drainage , a high soil- bearing capability , and consists of sufficient land for the proposed plant and for future expansion. Availability of labor: Labor 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 labor available locally; and labor suitable for training to operate the plant. Political and Strategic considerations: Capital grants, tax concession and other inducements are often given by governments to direct new investment to preferred locations; such as areas of high unemployment. Local Community Considerations: The proposed plant must fit in with and be acceptable to the local 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. Corrosion: Once the general area for the plant has been determined, the effect of neighboring industries should be considered when picking the specific site. Their presence may indicate an increased corrosion rate.

PLANT LAYOUT The economic construction and efficient operation of a process depend on how well the plant and equipment specified on the process flow sheet is laid out. The principal factors to be considered are:  Economic consideration: construction and operating costs.  The process requirement.  Convenience of operation.  Convenience of maintenance  Safety.  Future expansion  Modular construction Costs: The cost of construction can be minimized by adopting a layout that gives the shortest run of connecting pipe between equipment, and the least amount of structural steel works. Operation: Equipment that needs to have frequent operator attention should be located convenient to the control room. Valves, sample points and instruments should be located at convenient positions and heights. Sufficient working space and headroom must be provided to allow easy access to equipments. Safety: Blast walls may be neede to isolate potentially hazardous equipment, and confine the effects of an explosion. At least two escape routes for operators must be provided from each level in process buildings. Plant expansion: Equipments should be located so that it can be conveniently tied in with future expansion of the process. Modular construction: In recent years there has been a move to assemble sections of plant at the plant manufacturer’s site. These modules will include the equipment, structural steel , piping and instrumentation. The modules are then transported to the plant site, by road or sea. The advantages of modular construction are:  Improved quality control.  Reduced construction cost.  Less need for skilled labor on site. Some of the disadvantages are,  Higher design costs & more structural steel work.  More flanged constructions & possible problems with assembly, on site. General consideration: Open, structural steelwork, buildings are normally used for process equipment; closed buildings are only used for process operations that require protection from the weather.

A TYPICAL PLANT LAYOUT:-

INSTRUMENT AND PROCESS CONTROL Instrumentation is the most important factor in ensuring safety and smooth working of the plant. A separate control room is provided in modern plants where on panels indicators and recorders are present. Instruments are used in the industry to measure process variables such as temperature, pressure, density, level specific heat, conductivity, humidity, flow rate, chemical composition etc. The primary objectives of the designer when specifying instrumentation and control schemes are: 1. Safe plant operation: (a) To keep the process variables within known safe operating limits. (b) To detect dangerous situations as they develop and to provide alarms and automatic shut-down systems. (c) To provide interlocks and alarms to prevent dangerous operating procedures. 2. Production rate:To achieve the design product output. 3. Product quality: To maintain the product composition within the specified quality standards. 4. Cost: To operate at the lowest production cost, commensurate with the other objectives. These are not separate objectives and must be considered together.

TEMPERATURE CONTROL / MEASUREMENTS: Various instruments are used for eg. 1. Thermocouple 2. Resistance Thermometers 3. Thermistors 4. Mercury in Glass Thermometers. Controllers are used to maintain temperature within specified limits. Every temperature control problems is essential one. The temperature lay involved in the measurement of this variable is an important factor. Thermal element is usually placed in a well to protect it and allow servicing of element without interrupting the process. The location of the temperature element often has as much to do with the efficiency element often as other parts of the control loops. Temperature bulb should always be located at point where the coefficient of heat transfer will be as large as possible e.g. if vapors and liquid are at same temperature, then bulb should be kept in liquid because of high heat transfer coefficients.

PRESSURE CONTROL / MEASUREMENTS: It is quite necessary for most system handling vapours of gas. It can be measured by using pressure gauges. Self operated pressure regulation is often used in pressure control. It is installed directly in the line the control sensing apparatus is paced about 10 diameter from the unit. This location eliminates erroneous pressure caused by turbulence. Sudden change in velocity, shock and vibrations difficulties often occur when self operated regulation are used with liquids.

LEVEL CONTROL / MEASUREMENT:

The measurement of level can be defined as the determination of location of interface with respect to a fixed plane. The main objective of a level control system is to maintain the level of the liquid in a tank at the Act point value. The different is pressure transmitter senses the pressure difference / a function of liquid level in the tank) and gives out an electrical signal, which after signal conditioning is given to the P.I.D. controller. The controller compares the measured variables with the set point and depending upon the error, gives an output to the control valve. The control value, in turn controls the flow. Due to the control of flow, the level is controlled to its set point.

FLOW CONTROL / MEASUREMENTS: It is defined as volume per unit time at specific temperature and pressure conditions. It is generally measured by positive displacement of rate meters.

CONDENSER CONTROL: Temperature control is unlikely to be effective for condensers, unless the liquid stream is sub-cooled. Pressure control is often used, or control can be based on the outlet coolant temperature.

DISTILLATION COLUMN CONTROL: The primary objective of distillation column control is to maintain the specified composition of the top and bottom products, and any side streams; correcting for the effects of disturbances in: 1. Feed flow-rate, composition and temperature. 2. Steam supply pressure. 3. Cooling water pressure and header temperature. 4. Ambient conditions, which cause changes in internal reflux. The compositions are controlled by regulating reflux flow and boil-up. The column overall material balance must also be controlled; distillation columns have little surge capacity (hold-up) and the flow of distillate and bottom product (and side-streams) must match the feed flows. The feed flow-rate is often set by the level controller on a preceding column. It can be independently controlled if the column is fed from a storage or surge tank. Feed temperature is not normally controlled, unless a feed pre heater is used. Temperature is often used as an indication of composition. The temperature sensor should be located at the position in the column where the rate of change of temperature with change in composition of the key component is a maximum. Near the top and bottom of the column the change is usually small. With multi component systems, temperature is not a unique function of composition. Top temperatures are usually controlled by varying the reflux ratio, and bottom temperatures by varying the boil-up rate. If reliable on-line analyzers are available they can be incorporated in the control loop, but more complex control equipment will be needed.

PID LEGENDS

Instrument locally mounted Instrument at control center Instrument transmitting

Process connecting lines Orifice for flow meas. Electric lines

Control valve pneumatic

Pneumetic lines

Controller self contained

Capillary lines

FIRST LETTER D- Density F-Flow H-Hand activated L-Level M-Moisture P-pressure T-Temperature

SECOND LETTER A-Alarm C-Control E-Element G-Glass I-Indicating R-Recorder S-Safety weir

THIRD LETTER A-Alarm C-Control V-Valve

PID OF DISTILLATION COLUMN

Temperature Control

Composition Control (R controlled and bottom product as fixed ratio of feed flow)

Composition Control (Top product controlled by feed)

PID OF REACTOR

INSTRUCTIONS FOR OPERATION Before starting, always make sure that the followings:  No visible damage is evident in the system.  All electrical switches are turned off.  All water valves are closed.  All valves are tightly closed. Start up procedure.  Check the level in the tank.  Switch on the main supply.  Turn on the main pump.  Open valve for pump.  Start mechanical pump.  Open the steam valve.  Check the flow, temperature& pressure during the operation. System shut down.  Reduce the flow of the feed & steam.  Reduce all flow rates & wait for pasture to drop.  Turn off the pump.  When the flow slow down close the valve tightly to avoid cavitations.  Disconnect the packing line.

POLLUTION CONTROL AND SAFETY Acrylic acid is a colorless liquid with an irritating acrid odor at room temperature and pressure. Its odor threshold is low (0.20-3.14 mg/m3). It is miscible in water and most organic solvents. Acrylic acid polymerizes easily when exposed to heat, light or metals, and so a polymerization inhibitor is added to commercial acrylic acid to prevent the strong exothermic polymerization. The inhibitors that are usually used in acrylic acid preparations are:     

monomethyl ether of hydroquinone (methoxyphenol) at 200 ± 20 ppm phenothiazine at 0.1% hydroquinone at 0.1%. Methylene blue at 0.5 to 1.0% N,N'-diphenyl- p-phenylenediamine at 0.05%

The presence of oxygen is required for the stabilizer to function effectively. A head space containing sufficient air should always be maintained above the monomer to ensure inhibitor effectiveness. Dissolved oxygen takes part in the inhibition reaction and therefore is gradually consumed. The level of dissolved oxygen should periodically be replenished. This can be accomplished by thoroughly aerating the liquid phase, i.e. recirculation of the inventory in tanks or agitating drums (rotating). Acrylic acid must never be handled under an inert atmosphere. Freezing of acrylic acid occurs at 13°C. Rethawing under inappropriate temperature conditions is another frequent reason for acrylic acid polymerization. During the crystallization process the inhibitor and oxygen concentrate in the mother liquor. Therefore no mother liquor should be withdrawn from a partially frozen container. This may result in a severe deficiency of the inhibitor system in the crystalline matrix. If direct heat is applied, polymerization will start immediately, often with great violence. Under no circumstances must steam be used to thaw frozen acrylic acid, nor must thawing be carried out at temperatures above 35°C. Acrylic acid is a strong corrosive agent to many metals, such as unalloyed steel, copper and brass. Frequently the hydrolysis of such metalic materials generates a deep discoloration in acrylic acid. Polyvalent metal salts formed during hydrolytic reactions could also induce polymerization. Therefore, under no circumstances should acrylic acid be stored or transported with equipment which contains the above-mentioned metals. Acrylic acid does not affect stainless steel. Analytical Methods Acrylic acid residues in air and other media can be quantified by means of gas chromatographic, high performance liquid chromatographiC was found to be 14 mg/m3 (14 ppm) in air and down to 1 mg/kg or 1 mg/litre (1 ppm) in other media. Human Exposure No data on general population exposure are available. However, consumers may be exposed to unreacted acrylic acid in household goods such as polishes, paints and coatings, adhesives, rug backing, plastics, textiles and paper finishes. A potential source of internal exposure to acrylic acid may result from metabolism of absorbed acrylic acid esters. Acrylic acid also occurs in wastewater effluent from its production. It is estimated that thousands of workers could be exposed to acrylic acid, but exact figures are not available.

Kinetics and Metabolism Inhalation and contact with skin are important routes of occupational exposure. Regardless of the route of exposure, acrylic acid is rapidly absorbed and metabolized. It is extensively metabolized, mainly to 3-hydroxypropionic acid, CO2 and mercapturic acid, which are eliminated in the expired air and urine. Owing to its rapid metabolism and elimination, the half-life of acrylic acid is short (minutes) and therefore it has no potential for bioaccumulation. Effects on Animals Most data indicate that acrylic acid is of low to moderate acute toxicity by the oral route, and of moderate acute toxicity by the inhalation and dermal routes. Acrylic acid is corrosive or irritant to skin and eyes. It is unclear what concentration is non-irritant. It is also a strong irritant to the respiratory tract. A chronic drinking-water study on rats showed no effect at the highest dose tested (78 mg/kg body weight per day). For inhalation studies a lowest-observed- adverse effect level (LOAEL) of 15 mg/m3 (5 ppm) was observed in mice exposed to acrylic acid for 90 days. Available data do not provide evidence for an indication of carcinogenicity of acrylic acid, but the data are inadequate to conclude that no carcinogenic hazard exist. Effects on Humans There have been no reports of poisoning incidents in the general population. No occupational epidemiological studies have been reported. Because acrylic acid toxicity occurs at the site of contact, separate guidance values are recommended for oral and inhalation exposure. Guidance values of 9.9 mg/litre for drinking-water and 54 μg/m3 for ambient air for the general population are proposed. Effects of the Environment No quantitative data on environmental levels of acrylic acid in ambient air, drinking-water or soil have been reported. Acrylic acid is miscible with water and, therefore, would not be expected to adsorb significantly to soil or sediment. Under soil conditions, chemicals with low Henry's Law constants are essentially non-volatile. However, the vapour pressure of acrylic acid would suggest that it may volatilize from surfaces and dry soil. Acrylic acid may be formed by Hydrolysis of acrylamide monomer from industrial waste in soil, especially under aerobic conditions. The toxicity of acrylic acid to bacteria and soil microorganisms is low. Acrylic acid emitted into the atmosphere will react with photochemically produced hydroxyl radicals and ozone, resulting in rapid degradation. There is no potential for long-range atmospheric transport of acrylic acid because it has an atmospheric lifetime of less than one month. When released into water, acrylic acid readily biodegrades. The fate of acrylic acid in water depends on chemical and microbial degradation. When added to water acrylic acid is rapidly oxidized, and so it can potentially deplete oxygen if discharged in large quantities into a body of water. Acrylic acid has been shown to be degraded under both aerobic and anaerobic conditions. On the basis of the low octanol-water partition coefficient of acrylic acid, bioconcentration in aquatic organisms is unlikely. There have been no reports of biomagnification of acrylic acid in food chains. Symptoms of poisoning The principal hazard of acrylic acid is its corrosive effect on tissues. Both vapour and liquid can be irritating or corrosive to the mucous membranes, skin and eyes. The severity of these effects is dependent on the duration of contact, which, if prolonged, may result in blisters and burns. Blister formation can appear as late as 24 h after exposure. Severe corneal burns could occur to the eyes. Permanent tissue damage may result if prompt and appropriate emergency response is

not provided. Inhalation of concentrated vapours and mist could produce moderate to severe irritation of the respiratory tract. High concentrations could result in pulmonary oedema while lower concentrations could produce nasal and throat irritation. Lacrymation may also result from inhalation exposure. Although ingestion is not an expected route of human exposure, swallowing of acrylic acid may cause severe irritation or burning of the mouth, throat, oesophagus or stomach. No serious health effects have been reported to result from single exposure or repeated exposure at low concentrations of acrylic acid. Safety in Use Acrylic acid should only be handled in well-aerated and well-ventilated places. If exposure to concentrated vapour can not be excluded (as in the case of an accident), selfcontained breathing apparatus or air supply masks must be worn. Care must be taken when using filter-type masks to ensure that the filter capacity is not exceeded for the intended time of use and expected concentration. In areas where a release of acrylic acid is possible, eye protection devices, face shields, neoprene gloves and rubber boots should be worn. A chemical suit with a selfcontained breathing apparatus is strongly recommended if larger spills or emissions have to be cleared. Appropriate protective clothing should be worn for work involving breaking or entering into a closed acrylic acid system. Owing to its vapour pressure, the concentration of acrylic acid in closed rooms can reach high values. If clothing or shoes have accidentally been contaminated with acrylic acid, they must be removed immediately. Contaminated leather shoes or other leather goods must be discarded. For timely and appropriate emergency response, it is advisable to provide complete sets of safety protection equipment near places where accidents with acrylic acid are possible. Explosion and Fire Hazards Acrylic acid has a flash point of 54-68°C and does not form explosible vapour mixtures at ordinary ambient temperatures. However, ignition may occur if excessive amounts of mist or aerosols have formed in air. Ignition sources can include spark discharges from static electricity, and this can occur when acrylic acid is flowing through or being discharged from a line. During transfer from one container into another, the containers should be electrically interconnected and properly grounded. Splashing into a tank should be avoided by using a dip tube. Since acrylic acid and water are miscible in any proportion, water can be used to extinguish fires. Small fires can be fought with carbon dioxide or dry chemical extinguishers, whereas for larger fires foam (alcohol or universal type) can be used. If a fire occurs in or close to a tank farm containing acrylic acid, tanks and pipes should be cooled by spraying with water in order to prevent the acid from polymerizing. Storage Acrylic acid should be stored in a detached, cool, well-ventilated, non-combustible place and its containers should be protected against physical damage. Acrylic acid can be stored only in vessels lined with glass, stainless steel, aluminum or polyethylene. In order to inhibit polymerization during transport and storage, 200 ppm MeHQ (the monomethyl ether of hydroquinone) is commonly added to acrylic acid by the manufacturer. The presence of oxygen is required for the inhibitor to be effective. A major concern during the storage of acrylic acid is the avoidance of elevated temperatures as well as freezing, since both can lead to a failure of the inhibitor system. Ideally acrylic acid should be stored within a temperature range of 15 to 25°C. Acrylic acid and its solutions should be kept out of reach of children and unauthorized persons as well as away from food, drink and animal feed. If any container in the store is leaking, appropriate precautions should be taken and personal protective equipment used.

Transport Acrylic acid is shipped in containers in compliance with regulations according to ADR/RID/GGVS/GGVE, Class 8 Packing Group B specifications. Acrylic acid is commonly shipped in steel drums with polyethylene inserts or in self-supporting highdensity polyethylene drums impermeable to ultraviolet light. White polyethylene container are translucent to ultraviolet light and therefore may promote polymerization. Stainless steel ISO containers are recommended for the transport of quantities of acrylic acid up to 1 tonne. Spillage Before dealing with any spillage, appropriate personal protective equipment should be used. Small spills of up to 5 litres can be absorbed in commercially available clean-up kits (using sand or clay). If a wastewater sewer is close by, the spill can also be washed down with water provided that it is not a storm-sewer or ditch that is routed to surface water. Large spills should be contained, if possible, within a dike area. A temporary dike can be arranged by stacking sand bags or similar devices. Avoid run-off into storm sewers routed to public surface water. If possible, the material should be recovered in appropriate containers for reuse or disposal. During all handling operations of large spills a chemical suit with a self-contained or air-supplied breathing device must be worn. In the event of accidental spillage of acrylic acid to surface water or to a municipal sewer system, the pollution control agencies must be notified promptly. However, acrylic acid may be toxic to the system if the bacteria have not been conditioned properly to this material. Accordingly, the initial feed rate should be low with a stepwise increase if a significant amount is to be fed into the biological treatment plant. The maximum concentration should not exceed 1000 mg per litre. It should be kept in mind, however, that large quantities may affect the optimal acidity of the milieu and may therefore need to be neutralized by the simultaneous addition of sodium hydroxide. Disposal Acrylic acid is a highly corrosive material. Accordingly it should always be handled with appropriate safety equipment. Solid materials containing acrylic acid, such as absorbents or polymeric material, can be disposed of by incineration. Disposal in landfills must be thoroughly checked with the authorities and should be practiced only as a last resort. For the disposal of waste materials originating from laboratory samples, great care must be taken to keep the monomer separated from incompatible material, such as peroxides, which may initiate polymerization.

REFERENCES

Books:          

Sinnot, R.K, “Coulson and Richardson’s Chemical Engineering”, vol-6, Fourth edition, 2005 Trrybal, Robert E., “Mass transfer Operations”, Third edition, 1981 Perry, Robert H, Green, Don W., “Chemical Engineers’ Handbook”, 1999, 7th edition. Chattopadhyay, P “Unit Opeartions of Chemical Engineering”, vol-1, 2003 McCabe, Warren L, Smith, Julian C, Harriott Peter “Unit Operations Of Chemical Engineering”, Sixth edition, 2001 Eckman, Donald P., “Industrial Instrumentation”, 1991 Hesse, Herman C., Rushton, J.Henry, “Process Equipment Design”, Peters, Max S.,Timmerhaus,Klaus D. “Process Design and Economics for Chemical Engineers”, Fourth edition , 1958 Loh, H.P, Lyons, Jennifer, “Process Equipment Cost Estimation”, Jan 2002 Raju, K.S. “Fluid Mechanics, Heat Transfer and Mass Transfer: Chemical Engineering Practice.”

Internet References:     

www.google.co.in www.wikipedia.org/wiki/acrylic acid digitallibrary.srmuniv.ac.in/4001.pdf sbioinformatics.com www.chemicalland21.com