MANUFACTURE OF ACRYLIC ACID BY PARTIAL OXIDATION OF PROPYLENE
Submitted by, P.V.R.Krishna Prasad. M.Prem Kumar.
ACKNOWLEDGEMENT
We hereby place our sincere thanks to Dr.R.KARTHIKEYAN, Head of the Department of Chemical Engineering , Faculty of Engineering and Technology, S.R.M University and the faculty members of Chemical Engineering Department for their full hearted co-operation and encouragement for the completion of this project.
We extend our thanks to our Project guide Mr. K.SELVAM M.Tech for the Motivation, encouragement and guidance provided. We would also like to extend our thanks to each and everyone who have helped us in completing this project successfully.
ABSTRACT This project deals with the manufacture of acrylic acid from propylene by oxidation of propylene. Acrylic acid is a colorless liquid with an irritating acrid odor at room temperature and pressure. 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.
A detailed process flow sheet, Material Balance, Energy Balance, have been prepared. A detailed design of equipments, Cost estimation for plants, plant layout and safety aspects have been discussed.
Contents
1. INTRODUCTION
4
2. PROPERTIES AND USES
6
3. VARIOUS PROCESS
12
4. PROCESS DESCRIPTION
15
5. MATERIAL BALANCE
20
6. ENERGY BALANCE
30
7. EQUIPMENT DESIGN
39
8. COST ESTIMATION AND ECONOMICS
61
9. POLLUTION CONTROL AND SAFETY
68
10. SITE CONSIDERATION AND PLANT LAYOUT
75
11. CONCLUSION
79
12. BIBLIOGRAPHY
82
INTRODUCTION
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 by product, 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 Synonyms: acroleic acid 2-propenoic acid vinylformic acid propene acid ethylenecarboxylic acid Chemical formula: C3H4O2
PROPERTIES AND USES
PHYSICAL PROPERTIES 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 inwater 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. In the absence of inhibitor, peroxides are formed when oxygen is sparged into acrylic acid. .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
temperatureconditions 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. The highly exothermic, spontaneous polymerization of acrylic acid is extremely violent.
USES OF ACRYLIC ACIDS: 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.
Propiolactone Method: This commercial method is based on the polymerization of propiolactone and the destructive distillation of this polymer to form acrylic acid.
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 .
Stoichiometric Carbonyl Reaction: The reaction is very rapid at atmospheric pressureand at mild temperature . The hydrogen shown in the accompanying equation does not appear in gaseous form but is consumed by side reactions
Catalytic Carbonyl reaction: The catalytic reaction requires elevated temperature and superatmospheric pressures. Nickle salts or complexes thereof are used as catalysts.
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. 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. It is generally preferable to saponify the ester to form the corresponding salt. 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.
Vinyl Grignard Method : This interesting synthesis involves the use of the well known carboxylation of a Grignard reagent to form the acid.
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. 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
PROCESS DESCRIPTION : Propylene oxidation process The oxidation process flow sheet shows equipment and typical operating conditions. 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 330-430 C, 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- 360 c 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 220 c to 80 c. 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 counter-
currently 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.
Process Information Background Acrylic acid (AA) is used as a precursor for a wide variety of chemicals in the polymers and textile industries. There are several chemical pathways to produce AA, but the most common one is via the partial oxidation of propylene. The usual mechanism for producing AA utilizes a two step process in which propylene is first oxidized to acrolein and then further oxidized to AA. Each reaction step usually takes place over a separate catalyst and at different operating conditions. The reaction stoichiometry is given below: C3H6+O2
C3H4O+H2O Acrolein
C3 H4 +1/2O2
C3 H4 O2 Acrylic Acid
Several side reactions may occur, most resulting in the oxidation of reactants and products. Some typical side reactions are given below: C 3H 4O+7/2O2 C 3H4 O+3/2 O2
3 CO2 +2H2 O C2 H4 O2+ CO2 Acetic Acid
C3 H6 +9/2O2
3 CO2+3 H2 O
Therefore, the typical process set-up consists of a two-reactor system with each reactor containing a separate catalyst and operating at conditions so as to maximize the production of AA. The first reactor typically operates at a higher temperature than the second unit.
MATERIAL BALANCE
MATERIAL BALANCE Basis : 200 TPD of Acrylic Acid . ( Plant works continuously for 24 hours a day ) CH2=CHCH3 + O2
CH2=CHCHO + H2O acrolein
CH2=CHCHO + ½ O2
CH2=CHCOOH acrylic acid
Compound
Molecular weight
Propylene
42
Acrylic acid(AA)
72
Acetic acid
60
Acrolein
56
Oxygen
16
Carbon dioxide
44
Propylene required to produce 200 TPD of AA 1 kmol of C3H6
Æ 1 kmol of AA
42 kg/hr of C3H6 Æ 72 kg/hr of AA C3H6 required to produce 200 TPD of AA = 200 x (42/72) = 116.67 TPD of C3H6 At a yield of 78% kmol of C3H6 required = 116.67 / 0.78 = 149.57 TPD
= 148.38 kmol/hr Oxygen required : 1 kmol of C3H6 requires : 3/2 kmol of O2 Hence O2 required
= 3/2 x 148.38 kmol/ hr = 222.57 kmol/ hr
REACTOR I Oxidation of Propylene to Acrolein . (From Literature) 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 = 355 C Feed Composition : C3H6 : Air : Steam :: 1 : 7.75 : 3.75 Overall conversion of C3H6 = 100% Conversion to acrolein Conversion to AA
= 70% = 11%
C3H6 fed
= 148.38 kmol/hr
Steam fed
= 556.42 kmol/hr
Air fed
= 148.38 x 7.75 = 1149.94 kmol/hr
O2 entering N2 in
= 241.48 kmol/hr = N2 out
= 908.45 kmol/ hr
O2 used in the reactor
= 148.38 kmol/hr
O2 left unreacted
= 93.1 kmol/hr
Acrolein produced
= 148.38 x 0.7 = 103.866 kmol/hr
AA produced
= 148.0.11 = 16.32 kmol/hr
Steam produced
= 103.866 kmol/hr
Side products produced (CO2 + Acetic acid)=48.38 x 0.19 = 28.192 ( in equal quantities ) kmol/hr Total steam leaving the reactor = 660.286 kmol/hr
REACTOR II Oxidation of Acrolein to Acrylic acid (From literature) 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 – 300 C Acrolein conversion - 100% Yield of AA - 97.5%
Feed: O2
= 93.1 kmol/hr
N2
= 908.45 kmol/hr
Steam
= 660.286 kmol/hr
Acrolein
= 103.866 kmol/hr
Acylic acid
= 16.32 kmol/hr
Acetic acid
= 14.096 kmol/hr
CO2
= 14.096 kmol/hr
AA formed in reactor II
= 101.26 kmol/hr
By products formed
= 2.5966 kmol/hr
O2 reacted
= 51.352 kmol/hr
O2 unreacted
= 41.167 kmol/hr
N2 in
= 908.45 kmol/hr
= N2 out
Total AA formed in 2 reactors
= 101.26 + 16.32 = 117.58 kmol/hr
Total Acetic acid produced
= 15.3942 kmol/hr
Total CO2 produced
= 15.3942kmol/hr
ABSORBER: Feed entering at the bottom of the absorber. Acrylic acid
= 117.58 kmol/hr
Acetic acid
= 15.38 kmol/hr
CO2
= 15.38 kmol/hr
O2
= 41.167kmol/hr
N2
= 908.47 kmol/hr
Steam
= 660.286 kmol/hr
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 : 90% of the steam entering gets condensed. Solvent: Water entering at the top = 488.6 kmol/hr Off gases leaving at the top : CO2
= 15.38 kmol/hr
N2
= 908.4 kmol/hr
O2
= 41.167 kmol/hr
AA
= 1.1758 kmol/hr
Acetic acid
= 0.1539kmol/hr
Product liquid leaving at the bottom of the absorber to recovery section: Acrylic acid = 116.404 kmol/hr Acetic acid = 15.236 kmol/hr Water
= 1082.85 kmol/hr
Mol fraction of AA in the product stream
= 0.0958 = 9.58%
Weight fraction of AA in the product stream = 0.2911 = 29.11%
SOLVENT EXTRACTION COLUMN : Feed from the bottom of the absorber: Acrylic acid = 116.404 kmol/hr Acetic acid = 15.236 kmol/hr water
= 1082.85 kmol/hr
Solvent with high solubility for acrylic acid and acetic acid , and low solubility with water is used to extract AA acid from absorber stream. Assumption: Solvent required for 99 .5% extraction of AA is 500 kmol/hr. Recycled stream from solvent recovery column and waste tower. Acrylic acid
= 0.53 kmol/hr
Acetic acid
= 0.08 kmol/hr
Water
= 129.94 kmol/hr
Total Acrylic acid in = 116.934 kmol/hr Total Acetic acid in = 15.316 kmol/hr Total water in
= 1212.79 kmol/hr
Extract phase contains (to solvent recovery plant): Acrylic acid
= 0.995 x 116.404 = 115.83 kmol/hr.
Acetic acid
= 15.16 kmol/hr
Water
= 21.657 kmol/hr
Solvent
= 488.5 kmol/hr
Raffinate phase contains ( to waste tower): Acrylic acid
= 1.104 kmol/hr
Acetic acid
= 0.156 kmol/hr
Water
= 1191.13 kmol/hr
Solvent
= 11.5 kmol/ hr
SOLVENT RECOVERY COLUMN : Assumption: Complete recovery of solvent occurs. Bottom product contains only acetic acid and acrylic acid. Feed : Extract phase from the liquid-liquid extractor: Acrylic acid
= 115.83 kmol/hr.
Acetic acid
= 15.16 kmol/hr
Water
= 21.657 kmol/hr
Solvent
= 488.5 kmol/hr
Upstream contains (recycled to extraction column) : Solvent
= 488.5 kmol/hr
Acrylic acid
= 0.53 kmol/hr
Acetic acid
= 0.08 kmol/hr
Water
= 21.657 kmol/hr
Column bottoms contain ( to acid tower ) : Acrylic acid
= 115.3 kmol/hr
Acetic acid
= 15.08 kmol/hr
WASTE TOWER Assumption : Bottom product contains water and all acrylic acid , acetic acid entering the column. Feed : Raffinate phase from the liquid-liquid extractor. Acrylic acid
= 1.104 kmol/hr
Acetic acid
= 0.156 kmol/hr
Water
= 1191.13 kmol/hr
Solvent
= 11.5 kmol/ hr
Column bottom stream ( to waste water treatment plant) Water
= 1082 .845 kmol/hr
Acetic acid = 0.156 kmol/hr Acrylic acid = 1.104 kmol/hr Column overhead stream ( recycled to extraction column) Solvent
= 11.5 kmol/hr
Water
= 108.2 kmol/hr
ACID TOWER ( Designed as a major equipment ) Assumption : Top product is 95 wt. % acetic acid Bottom product is 99.5 wt.% acrylic acid.
Feed : Acrylic acid = 115.3 kmol/hr Acetic acid = 15.08 kmol/hr Top product Acetic acid = 14.883 kmol/hr Acrylic acid = 0.14 kmol/hr Acetic acid produced = 21.67 TPD at 95 % purity Bottom product Acrylic acid = 115.16 kmol/hr Acetic acid = 0.197 kmol/hr Acrylic acid produced = 200 TPD at 99.5% purity
ENERGY BALANCE
ENERGY BALANCE Heat capacity: C3H6 : 2.85 + .23 x 10-2 T - 1.2 x 10-4 T2 + 2.3 x 10-8 T3 kJ/kmol K C3H4O : 3.7957 + 4.4 x 10-2 T - 0.1304 x 10-4 T2 - 0.2848 x 10-8 T3 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 T2 + 0.802 x 10-8 T3 cal / mol K
REACTOR 1 Heat in: Feed is preheated to 200 C (molten salt coolant temperature) 473
Heat in with C3H6
= m ΔHf at 25 C+ m ∫ Cp dT 298
473
= 148 .38 ( 20.27 x 10 3 + ∫ Cp dT) 298
= 4999350. 27 kJ / hr Heat in with air
= m Cp ΔT
(Compressed to 5 bar) = 1149.94 x 1.015x 29x (200-25) = 5923484.68 kJ / hr Heat in with steam = 556.42 x ( 2676 x 18 + 2.291 x 18 ) x (200-25) = 30817126.95 kJ / hr Total heat in = 41739961.9 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 103.866 + 254.1 x 103 x 16.32 = 39544444.8 kJ / hr Heat removed by Coolant : The temperature in the reactor reaches an average peak temperature of 355 C due to exothermic reaction. At the end of the catalyst bed, the temperature drops toward that of molten salt coolant (210 C) 483
Heat with acrolein = m ∫ Cp dT 628
483
= 103. 866 ∫ Cp dT 628
= 1493068.88 kJ / hr 483
Heat with Acrylic acid = m ∫ Cp dT 628
483
= 16.32 x ∫ Cp dT 628
= 278848.6 kJ / hr
483
Heat with Acetic acid = m ∫ Cp dT 628
483
= 14.096 x ∫ Cp dT 628
= 205053.1 kJ / hr Heat with air
= m Cp ΔT =1001.55 x 30.35 x ( 628-483) =4408195.62 kJ / hr
Heat with CO2
= m Cp ΔT =14.096 x 47.896 x ( 628-483) =97897.62 kJ / hr
Heat with steam = m Cp ΔT =660.286 x 36.173 x ( 628-483) =3463347.34 kJ / hr Total heat removed by the Coolant = 9946411.17 kJ/hr Heat out:
298
Heat out with Acrolein = m ∫ Cp dT 483
298
=103.866 m ∫ Cp dT = 483
=1509276.32
298
Heat with Acrylic acid = m ∫ Cp dT 483
298
= 16.32 x ∫ Cp dT 483
= 283613.82 kJ/hr 298
Heat with Acetic acid = m ∫ Cp dT 483
298
= 14.096 x ∫ Cp dT 483
= 208578.2 kJ / hr Heat with air = m Cp ΔT =1001.55 x 30.35 x ( 483-298) =5624249.59 kJ / hr Heat with CO2 = m Cp ΔT =14.096 x 42.37 x ( 483-298) =110490.79 kJ / hr Heat with steam = m Cp ΔT =660.286 x 33.913 x ( 483-298) =4142581.4 kJ / hr
Total heat out = 11878790.12 kJ/hr Heat to Waste heat boiler =Heat in + Heat generated - Heat removed by coolant - Heat out =59459205.41kJ/hr Water required in boiler = m = 5945205.41/λ = 22219.43 kg/hr
REACTOR II Heat in from reactor I = 11878790.12 kJ/hr Heat generated: = 254.1 x 10 3 kJ/kmol of Acrylic acid =254.1 x 10 3 x 101.26 =25730166 kJ/hr Heat removed by coolant: The feed to the second reactor enters at temperature of 210 C The temperature in the reactor reaches an average peak temperature of 300 C due to exothermic reaction. At the end of the catalyst bed, the temperature drops toward that of molten salt coolant(210 C) 483
Heat with Acrylic acid = m ∫ Cp dT 573
483
= 117.58 x ∫ Cp dT 573
= 1211152.08 kJ / hr 483
Heat with Acetic acid = m ∫ Cp dT 573
483
= 15.3942 x ∫ Cp dT 573
= 134946.92 kJ / hr Heat with air = m Cp ΔT =949.617 x 30.35 x ( 573-483) =2588415.83 kJ / hr Heat with CO2 = m Cp ΔT =15.3942 x 46.0548 x ( 573-483) =63807.91 kJ / hr Heat with steam = m Cp ΔT =660.286 x 35.42 x ( 573-483) =2104879.2 kJ / hr Total heat removed by the Coolant = 6103201.95 kJ/hr Heat out: 298
Heat with Acrylic acid = m ∫ Cp dT 483
298
= 117.58 x ∫ Cp dT 483
= 2043343.9 kJ / hr 298
Heat with Acetic acid = m ∫ Cp dT 483
298
= 15.3942 x ∫ Cp dT 483
= 54442.55 kJ / hr Heat with air = m Cp ΔT =949.617 x 30.35 x ( 483-298) =5332617.47 kJ / hr Heat with CO2 = m Cp ΔT =15.3942 x 40.528 x ( 483-298) =115421.42 kJ / hr
Heat with steam = m Cp ΔT =660.286 x 36.913 x ( 483-298) =4142581.4 kJ / hr Total heat out = 11861751.85 kJ/hr.
Heat to Waste heat boiler =Heat in + Heat generated - Heat removed by coolant - Heat out =19644022.32 kJ/hr Water required in boiler = m = 19644022.32/λ =7340.8 kg/hr
EQUIPMENT DESIGN
DESIGN OF ACID TOWER Feed to the distillation tower = 115.3 kmol/ hr of acrylic acid + 15.08 kmol / hr of acetic acid. = 130.38 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
= 130.38 kmol/ hr.
Mol fraction of acetic acid in feed = 15.08 / 130.38 = 0.1156 Average molecular weight of feed = 70.37 kg/kmol Distillate: Flow rate of distillate
= 15.029 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
= 115.36 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.
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
Optimum reflux ratio R= 15 Number of ideal stages in enriching section = 7 Number of ideal stages in stripping section = 4+1(reboiler)
AVERAGE CONDITIONS AND PROPERTIES
ENRICHING SECTION I Tray Hydraulics: Tray spacing ts
= 500mm
Hole diameter dh
= 5mm
Hole pitch Lp
= 15mm (Δlar)
Tray thickness tT
= 3mm
Ah / Ap
= 0.10
II Tower Diameter : (L/G)(ρ1/ρg)0.5
= 0.012 (max at the bottom)
(From PERRY : fig 18-10 ; p.no. 18-7) For
ts = 18 in ,
Capacity parameter, Csb (flood) = 0.29 ft/s Gas velocity through net area at flood Unf =Csb (flood) x[σ/20]x[(ρ1-ρg)/ρg)0.5 σ- liq surface tension = 28.985 dyn/ cm ρ1
= 1079.37 kg/m3
ρg
= 0.1636kg/ m3
Unf = 25.36 ft/s = 7.732 m/s For 75% flooding condition , Un = 0.75 x 7.732 = 5.799 m/s Net area AN
= Max. vol. flow rate of vapor / Un = 16582.12 / (3600 x 0.1636 x 5.799) = 4.85 m2
Ratio of weir length to tower dia i.e. LW / DC = 0.75 θc = 2 sin -1(LW / DC) = 97.2 Column C.S.area ,
AC
Down comerC.S.area, AD
=(π/4) Dc2 = 0.785 Dc2 = (π/4) Dc2 (θc/360) – (LW/2) (DC/2) cos(θc/2)
= 0.0879 DC2 AN = AC - A D DC = 2.637 m Take DC = 2.65 m LW = 0.75 x 2.65 = 1.98 m = 2m AC = 5.515 m2 AD = 0.6172 m2 AN = 4.901 m2 Active area AA = AC - 2 AD = 4.28 m2 LW / DC = 0.754 θc = 98.0 Perforated area AP : Area of distribution and calming zone Acz = 2 (LW × 100 × 10-3) = 0.4 m2 Area of waste peripheral zones Awz = 2x[(π/4)Dc2 (a/360) – (π/4)(Dc – 0.12 )2 (a/360) = 0.22 m2 Ap = AC - 2 AD - Acz - Awz = 3.658 m2 Hole area AH = 0.1 x Ap = 0.3658 m2 Number of holes = 0.3658/[(π/4)x0.0052]= 18630
STRIPPING SECTION I Tray Hydraulics: Tray spacing
ts = 500mm
Hole diameter dh = 5mm Hole pitch
Lp = 15mm (Δlar)
Tray thickness tT = 3mm Ah / Ap = 0.10 II Tower Diameter : (L/G)(ρ1/ρg)0.5
=
0.01894 (max at the bottom)
(From PERRY : fig 18-10 ; p.no. 18-7) For
ts = 18 in ,
Capacity parameter, Csb (flood) = 0.29 ft/s Gas velocity through net area at flood Unf =Csb (flood)x[σ/20]x[(ρ1/ρg)/ρg]0.5 σ - liq surface tension = 28.208 dyn/ cm ρ1 = 1078.32 kg/m3 ρg = 0.1767kg/m3 Unf = 24.26 ft/s = 7.396 m/s For 75% flooding condition , Un = 0.75 x 7.396 = 5.547 m/s Net area AN = Max. vol. flow rate of vapor / Un = 17293.88 / (3600 x 0.1767 x 5.547) = 4.901 m2 Ratio of weir length to tower dia i.e. LW / DC = 0.75
θc = 2 sin -1(LW / DC) = 97.2 Column C.S.area ,
Ac = (π/4)Dc2 = 0.785 DC2
Down comerC.S.area, AD = (π/4)Dc2(θ c / 360 ) - (LW /2) (DC / 2 ) cos(θc/ 2) = 0.0879 DC2 AN = AC - AD DC= 2.65 m LW = 0.75 x 2.65 = 1.98 m = 2m AC = 5.515 m2 AD = 0.6172 m2 AN = 4.901 m2 Active area AA = AC - 2 AD = 4.28 m2 LW / DC = 0.754 θc = 98.0 a = 81.99 Perforated area AP Area of distribution and calming zone Acz = 2 (LW × 100 × 10-3) = 0.4 m2 Area of waste peripheral zones Awz = 2x[(π/4)Dc2(a/360)-(π/4)(DC - 0.12 )2 (a / 360) = 0.22 m2 Ap
= AC - 2 AD - Acz - Awz
= 3.658 m2 Hole area AH = 0.1 x Ap = 0.3658 m2 Number of holes = 0.3629/[(π /4)x0.0052] = 18630 COLUMN EFFICIENCY ENRICHING SEC TION Point efficiency : Eog = 1 - exp ( - Nog ) Nog = overall transfer unit Nog = 1 / [ (1/ Ng ) + (λ/N 1) ] Ng = gas phase transfer units Ng = [0.776 + 0.00457hw - 0.238 Ua ρg0.5 + 105 W ] / Nscg0.5 hw = weir height = 10mm Ua = gas velocity through active area = 15564.96 / ( 3600 x 0.1636 x 4.28) = 6.174 m/s W = liquid flow rate m3 / s.m W = q / Df ; Df = (DC + LW )/ 2 = 2.32 m Average liq flow rate = 14751 kg/hr Average liq density = 1079.36 kg / m3 q = 14751 / (3600 x 1079.36 ) = 0.00379 m3/s
W = 0.00379 / 2.32 = 0.001636 m3 /m.s Nscg = gas phase Schmidt number = μg/ ρg Dg = 0.528 Ng =[0.776+0.00457 x10-0.238 x 6.174 x 0.16365 +105 x 0.00163]/0.52805 = 0.55 N1 = k1 a θ1 k1= liq phase transfer coefficient m/s a = effective interfacial area for mass transfer , m2/m3 k1 a = (3.875 x 108 D1 )0.5 ( 0.4 Ua ρg0.5 + 0.17 ) Dl = liq phase diffusion = 3.463 x 10-9 m2/s kl a = 1.354 s-1 θ1 = residence time of liquid in froth ,s = hL AA /( 1000 q) hL = hl` = 12.28 mm θl = 12.28 x 4.28 / (1000x .003463 ) = 13.87 s Nl = 1.354 x 13.87 = 18.77 mtop = 0.333 ; mbottom = 1.01 ; Gm / Lm = 1.653 λt = mt (Gm / Lm ) = 0.55 λb = mb (Gm / Lm) = 1.669 λavg = 1.105 Nog = 1 / [ 1/ Ng + λ/N1 ) = 0.533
Eog = 1- exp (- 0.533) = 0.413 Murphee vapor efficiency : Peclet number Npe = Zl 2 / DE θl Zl
= length of liquid travel ,m = Dc cos(θc / 2 ) = 1.73 m
DE = Eddy diffusion coefficient = 6.675 (10-3) Ua 1.44 + 0.922 (10-4) hl - 0.00562 = 0.0904 m2 / s Npe = 1.732 / 0.0873 x 13.87 = 2.47 λ Eog = 1.105 x 0.413 = 0.456 (From PERRY : fig 18-29a ; p.no. 18-18 ) Emv / Eog = 1.16 Emv = 0.479 Overall Column Efficiency : (L/G)(ρg/ρ1 )0.5 = 0.0116 From PERRY for 80% flooding : Ψ = 0.25 Ea/ Emv = 1 / [ 1 + Emv (Ψ/(1- Ψ))] Ea
= 0.413
Eoc = log [ 1+ Ea (λ – 1)]/log λ1 = 0.425 Eoc = Ntheoritical / N actual
Nact = 7 / 0.425 = 17 Tower height = 500 x 17= 8500mm STRIPPING SECTION Point efficiency : Eog = 1 - exp ( - Nog ) Nog = overall transfer unit Nog = 1 / [ (1/ Ng)+ (λ / N1) ] Ng = gas phase transfer units Ng = [0.776 + 0.00457 hw - 0.238 Ua ρg 0.5 + 105 W ] / Nscg0.5 hw = weir height = 10mm Ua = gas velocity through active area = 16938 / ( 3600 x 0.1735 x 4.28) = 6.336 m/s W = liquid flow rate m3 / s.m W = q / Df ; Df = (DC + LW )/ 2 = 2.32 m Average liq flow rate = 25581 kg/hr Average liq density = 1076.56 kg / m3 q = 25581 / (3600 x 1076.56 ) = 0.0066 m3/s W = 0.0066 / 2.32 = 0.002838 m3 /m.s Nscg = gas phase Schmidt number
= μg /ρg Dg = 0.478 Ng =[0.776+0.0045 x10-0.238 x 6.336 x 0.17355 +105 x 0.002838]/0.4780.5 = 0.711 Nl = kl a θl Kl
= liq phase transfer coefficient m/s
a
= effective interfacial area for mass transfer , m2/m3
kl a = (3.875 x 108 Dl )0.5 ( 0.4 Ua ρg 0.5 + 0.17 ) Dl
= liq phase diffusion = 3.343 x 10-9 m2/s
kl a = 1.395 s-1 θl = residence time of liquid in froth ,s = hL AA /( 1000 q) hL = hl` = 14.99 mm θl = 14.99 x 4.28 / (1000x .0066 ) = 9.72s Nl = 1.395 x 9.72= 13.56 mtop =1.142 ; mbottom = 1.15 ; Gm / Lm = 1.047 λt = mt (Gm / Lm ) = 1.195 λb = mb (Gm / Lm) = 1.204 λavg = 1.119 Nog = 1 / [ 1/ Ng +λ/Nl ) = 0.669 Eog = 1- exp (- 0.669) = 0.488 Murphee vapor efficiency :
Peclet number Npe = Zl 2 / DE θl Zl = length of liquid travel ,m = Dc cos( θc / 2 ) = 1.73 m DE = Eddy diffusion coefficient = 6.675 (10-3) Ua 1.44 + 0.922 (10-4) hl - 0.00562 = 0.091 m2 / s Npe = 1.732 / 0.091 x 9.72 = 3.38 λ Eog = 1.119 x 0.488 = 0.55 (From PERRY : fig 18-29a ; p.no. 18-18 ) Emv / Eog = 1.19 Emv = 0.581 Overall Column Efficiency : (L/G )(ρg/ρ1)0.5 = 0.019 From PERRY for 80% flooding : Ψ =0.17 Ea/ Emv = 1 / [ 1 + Emv (Ψ/(1-Ψ))] Ea = 0.519 Eoc = log [ 1+ Ea ( λ – 1 )]/log λ = 0.533 Eoc = Ntheoritical / N actual Nact = 4 / 0.533 = 8 Tower height = 500 x 8 = 4000mm
PROCESS DESIGN OF INTER STAGE COOLER (Shell and tube heat exchanger) I ) Exchanger Duty: Q = 5535049 kJ/hr = 1537.5 kJ/sec Coolant used is Water at 27 C Cooling water balance: Q
= m Cp ΔT
1537.5 = m x 4.187 x (42 - 27) mw
= 24.498 kg/ sec.
Flow rate of liq mix to be cooled: mmix = 28786.7 kg/ hr = 7.996 kg/sec Liquid mixture Balance: Q = mmix x Cpmix x (Ti - 80 ) 1537.5 = 7.996 x 3.212 x (Ti - 80) Ti = 140 C Hence the liquid mixture must be cooled from a temperature of 140 C to a temperature 40 C
II Log Mean Temperature Difference (ΔTlm) ΔTlm = [(T1 - t2 ) - (T2 - t1 ) ] / ln [(T1 - t2 )/ (T2 - t1 )]. (T1 - t2) = 140 - 42 = 98 (T2 - t1) = 80 - 27 =53 ΔTlm = 73.21 C R = (T1 - T2 ) / ( t2 - t1) = 4 S = ( t2 - t1) / (T1 - t1) = 0.132 {From PERRY Fig 10-14, P.No.: 10-27} FT = 0.97. III Routing of Fluids: Water - Tube side Liquid Mixture - Shell Side IV Heat Transfer Area: {From PERRY Table 10-10 P.No.: 10-44} Assumed Value of Overall heat transfer Coefficient: Ud = 570 W/m2 K.
Dirt factor = 5.283 x 10-4 m2 K/ W. Q = U A( ΔTlm ) FT. A= (1537.5 x 103 ) / (570 x 73.21 x 0.97) = 37.98 m2 V Number of Tubes: Choose D0 (Tube outside dia) = ¾ in Di (Tube inside dia)
= 0.01905 m
= 0.62 in = 0.01575 m
Length = L = 14 ft = 4.2672 m Heat transfer Area : a = πDo = π x 0.01905 = 0.05987 m2 / m length Heat transfer Area for one tube = 0.05987 x 4.2672 = 0.2555 m2 / tube Number of Tubes = 37.98 / 0.2555 = 149 From Tube Count Table (PERRY : table 11-3 ; P.No. 11-13) TEMA P or S ; for 1-2 pass Number of tubes Nt = 198 Shell ID = 438 mm Corrected Heat Transfer Area = 198 x 0.2555= 50.589 m2 Corrected Ud = 427.977 W/m2 K. VI Tube Side (Cooling water) Velocity and Heat transfer Coefficient hi Flow Area
=
at
= π/ 4 x Di2 x(Nt / Np ) = 0.01928 m2
Velocity = vt = ( mt /ρ at) = 24.498 / 993.68 x 0.01905
= 1.278 m / sec = vt Di
Reynolds Number NRe
= 1.278 x 0.01575 x 993.68 / 1.00 x 10-3 = 20001.28 Prandtl Number
NPr
= μCp/k = (1.00x10-3 x 4.187 x 10 3 )/ 0.578 = 7.2439
Nusselt Number Nnu
= 0.023 ( NRe)0.8 (Npr) 1/3 = 143.19
Heat transfer coefficient hi = NNu K / Di = 5254.89 W/m2 K. VII 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. pp = pitch parallel to flow = (√3/2) P† = 21.997 mm pn = pitch normal to flow = (1 / 2 ) P' = 12.7 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 Sm = 0.02398 m2 Shell side velocity = vs = ms / Sm ρ = 7.996 / 0.0479 x 992.99 = 0.3357 m/sec Reynolds Number NRe = vs Do ρ /μ = 0.3357 x 0.01905 x 992.99 / 0.16128 x 10-3 = 39374.1 = μ Cp/k = [0.16128 x 10-3 x 3.205 x 10 3 )/ 0.513
Prandtl Number NPr
= 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 = 197.36 Heat transfer coefficient ho = NNu K / Do = 5314 . 94 W/m2 K. VIII 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/ 5314 . 94] + [(1/ 5254.89) (0.01905/ 0.01575) + [(0.01905 ln (0.01905/ 0.01575)) / (2 x 50 )]
= 4.5459 x 10-4 (1/ Uo) dirt = 4.5459 x 10-4 + 5.283 x 10-4 Uo = 1017.4 W/m2 K Which is greater than the assumed Uo Hence design is acceptable. IX Tube Side Pressure Drop Friction factor (f) = 0.079 x (NRe) -0.25 = 0.079 x (20001 ) -0.25 = 0.0066 Pressure Drop ΔPL = (4 f L vt2 / 2 g Di )ρg = 2 x 0.0066 x 4.2672 x 1.2782 x 993.68 / 0.01575 = 5842.0 N/ m2 Pressure Drop ΔPE = 2.5(ρ vt2 / 2 ) = (2.5 x 993.68 x 1.278 2) / 2 = 2028.7 N/ m2 Total Pressure Drop ΔPT = Np [ΔPE +ΔPL ] = 2 x [5842.0 + 2028.7] = 15741 .48 N/ m2 = 15.74 kPa. which is less than permissible ΔP = 70kpa
X Shell Side Pressure Drop ΔPs = 2ΔPE + (Nb - 1 ) ΔPC + Nb ΔPW ΔP in cross flow section: ΔPC = [ (b fk w2 NC )/ρ Sm2](μw/μb) fk (shell side friction factor ) = 0.15 {PERRY:Fig 10-25a ;P.no.10-31} b= 2 x 10-3 (constant ) w = 7.996 kg / sec Sm = 0.02398 m2 NC = Number of cross flow zones = {DS [ 1- (2 LC / Ds )]} / PP LC = Baffle cut = 0.25 DS = 109.5 mm NC = 438 x [ 1- (2 x 109.5 / 438) ] / 22 = 10 Δ PC = (2 x 10-3 x 0.15 x 7.9962 x 10) / 992.99 x 0.023982 = 0.335 kPa ΔP in end zones Δ PE = ΔPC [ 1 + ( NCW / NC ) ] NCW = Number of effective cross flow region in each window = 0.8 LC / Pp =4 NC = 10
ΔPE = 0.335 x [ 1+ 4/10 ] = 0.469 kPa ΔP in window zones ΔPW = [b w2 ( 2+ 0.6 NCW )] / Sm Sw ρ b = 5 x 10-4 (constant) Sw = Area for flow through window = Swg - Swt Swg = gross window area (From PERRY :Fig 10 -18 ; P.No. 10 - 29) For LC / DS =0.25 ; DS = 17 ¼ in. Swg = 0.029 m2 Swt = window area occupied by tubes =( Nt / 8) (1- Fc ) π Do2 FC = Fraction of total tube in cross flow (From PERRY : Fig 10 - 16 ; P.No. 10 - 28 ) Fc = 0.67 Swt = (198 / 8 ) x (1 – 0.67 ) x π x0.019052 = 0.009311 m2 Sw = 0.029 - 0.009311 = 0.0196 m 2 ΔPw = [5x 10-4 x 7.996 2 x (2 + 0.6 x 4)] / (0.02898 x 0.0196 x 992.99 ) = 0.3013 kPa Total Pressure Drop (ΔPS) Total = 2 (ΔP E ) + (19 - 1 ) ΔP C + (19 ) ΔPW = 12.692 kPa < 70 kPa ( max allowable)
COST ESTIMATION AND ECONOMICS
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. For the year 1999. Utilizing 8000 operating hours / year. Q1 = 50000 tons/year Q2 = 66666.67 tons / year. C1 = $ 24000000. C2 = 24000000 x (66666.67 / 50000)0.6 = $ 28.5 x 106 Cost of the plant in 2002: (Cost of plant in 2002 / Cost of plant in 1999) = (Cost index in 2002 / Cost index in 1999) Cost of plant in 2002 = 28.5 x 106x(402 / 389.9) = $ 29.4 x 106 Fixed Capital Investment (FCI) required = $ 29.4 x 106. = Rs.1411.2 x 106 I Direct cost: (70 - 85 % of FCI ) A. 1. Purchased Equipment (PEC) ( 15 - 40% of FCI)
25% of FCI = Rs 352.8 x 106 2. Installation including insulation and painting ( 25 - 55% of PEC) 30% of PEC = Rs 105.84 x 106 3. Instrumentation and Controls , Installed (6 - 30 % of PEC) 25% of PEC = Rs 88.2 x 106 4. Piping, Installed (10 - 80 % of PEC) 30% of PEC = Rs . 105.84 x 106 5. Electrical ,Installed (10 - 40% of PEC) 25% of PEC = Rs. 88.2 x 106 B. Building, process and auxiliary (10 - 70% of PEC) 40% of PEC = Rs.141.12 x 106 C. Service Facilities and Yard Improvements ( 40 - 100% of PEC) 60% of PEC = Rs.211.68 x 106 D. Land ( 1- 2% of FCI or 4- 8% of PEC) 5% of PEC = Rs. 17.64 x 106 Total Direct Cost = Rs.1111.32 x 106 II Indirect Costs (15 - 30 % of FCI) A. Engineering and Supervision ( 5 - 30 % of Direct Cost) 10% of Direct cost = Rs. 111.132 x 106 B. Construction Expense and Caontractors Fee (6 - 30% of Direct cost )
10% of Direct costs = Rs. 111.132 x 106 C. Contingency (5- 15% of FCI) 5.5% of FCI = Rs. 77.616 x 106 Total Indirect Cost = Rs 299.88 x 106 III Working Capital (10 - 20% of TCI) 15% of TCI = Rs. 249.035 x 106 IV Total Capital Investment (TCI) TCI = FCI + Working Capital TCI = Rs. 1660.23 x 106 ESTIMATION OF TOTAL PRODUCT COST (TPC): I 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. 144.648 x 10 2. Local Taxes (1-4% of FCI ) 4% of FCI = Rs 56.448 x 106 3. Insurance (0.4 - 1% of FCI) 0.7% of FCI = Rs. 9.878 x 106 Total Fixed Charges = Rs. 210.97 x 106 Total Product Cost
TPC
= Fixed Charges / 0.15 = Rs. 1406.467 x 106
B. Direct Production Costs ( about 60 % of TPC) 1. Raw Materials (10 - 50 % of TPC) 10% of TPC = Rs . 140. 64 2. Operating Labor ( 10 - 20 % of TPC ) 15% of TPC = Rs.210.97 3. Direct Supervisory and Clerical Labor ( 10 - 25 % of Operating labor) 15% of Operating Labor = Rs. 31.64 4. Utilities ( 10 - 20% of TPC ) 10 % of TPC = Rs 140. 64 5. Maintenance and Repairs ( 2- 10% of FCI ) 5% of FCI = Rs. 70.56 6. Operating supplies ( 10 - 20% of cost for maintenance and repairs) 15% of cost for maintenance and repairs = Rs. 10.584 7. Laboratory Charges ( 10 - 20% of Operating Labor ) 15% of Operating Charges = Rs 31.645 8. Patents and Royalties ( 0 - 6% of TPC ) 2% of TPC = Rs 28.13 Total Direct Production Cost = Rs 664.808x 106 C. Plant Overhead Cost ( 5 - 10% of TPC)
7% of TPC = Rs 98.453 Total Manufacturing Cost = Rs . 974.231 II General Expenses A. Administrative Costs ( 2- 6% of TPC) 5% of TPC = Rs. 70.323 B. Distribution and Selling Costs ( 2 - 20% of TPC ) 18% of TPC = Rs. 253.164 C. Research and development cost ( 5% of TPC ) 5% of TPC = Rs. 70.32 D. Financing ( 0- 10 % of TCI ) = Rs. 38.432 Total General Expenses = Rs. 432.24 SELLING PRICE: Acrylic acid produced = 200 TPD Selling price of Acrylic acid = $1.92 /kg Acetic acid produced = 21.67 TPD Selling price of Acetic acid = $ 0.794 /kg Total income = selling price x qty of product produced = 128 x 106 + 7.22 x 106 = $ 135.22 x 106 = Rs. 6558.17 x 106 Gross Earning = Total income - Total product cost = 6558.17 x 106 - 1406.467 x 106
= Rs 5151.703 x 106 Tax on gross earning = 40% of gross earning. Net Profit = Gross earning [ 1 - tax rate ] = Rs. 3091.0218 x 106 Rate of return = Net profit / Total capital investment = 3091.0218 x 106 / 1660.23 x 106 = 1.86
POLLUTION CONTROL AND SAFETY
POLLUTION CONTROL AND SAFETY Acrylic acid is a colourless liquid with an irritating acrid odour at room temperature and pressure. Its odour 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 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% 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 lowestobserved- 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 produce Hydroxyl radicals and ozone, resulting in rapid degradation. There is no potential for longrange 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 filtertype 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 (see section 6) 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 like 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. If a wastewater sewer is available, the acid or remainders can also be sparingly washed down after dilution and neutralization prior to being discharged to a water-treatment plant. 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. Spills of the monomer may be diluted and washed into a biological treatment plant. The biodegradability of the material in diluted form is good .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.
Specific Restrictions In the USA acrylic acid as a commercial chemical product is classified as a toxic waste subject to regulation and notification requirements. In the European Economic Community preparations that contain acrylic acid at concentrations greater than 25% should be considered as corrosive and at concentrations of 2-25% as irritant. Member States should ensure that dangerous preparations containing acrylic acid are not placed on the market unless their packages, fastenings and labels comply with requirements laid down . In Canada, the maximum amount of acrylic acid that may be transported on a passenger aircraft, train or road vehicle is one litre. The maximum amount that may be transported on a cargo aircraft is 30 litres.
SITE CONSIDERATION AND PLANT LAYOUT
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 • 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 bytruck.
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 .
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.
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.
General consideration : Open, structural steelwork , building are normally used for process equipment; closed buildings are only used for process operations that require protection from the weather.
CONCLUSION The manufacture of Acrylic Acid from Propylene has been described in detail. The necessary Flow diagram, Material Balance, Energy Balance for the production of 200 TPD of Acrylic Acid has been worked in detail. The design aspects are been concluded that the production of Acrylic Acid from Propylene will be more profitable.
BIBLIOGRAPHY
1. Ullmann,s “Encyclopedia of Industrial Chemistry “ Vol A1 ( page 161 - 172 ) 2. “Encyclopedia of Chemical Technology “, Vol 1 , Kirkothmer (page 330 - 351) 3. “Encyclopedia of Chemical Processing and Design” Vol A1 John. J. Mcketta ( page 285 - 311) 4. “Perry’s Chemical Engineer’s Handbook” , 6 th edition , Robert. H. Perry , Don Green , McGraw Hill Publication 5. “Process Equipment Design “ 3 rd Edition , M.V.Joshi 6. “Mass Transfer Operations” , R.E.Treybal 7. “Plant Design and Economics for Chemical Engineers “Max Peters and Klaus Timmerhaus
Off-
Off-Gas Absorber Water Reactor 2
Compresse d Air
Acid Acetic Acid
Acid Stea
Waste heat
Waste heat
Acrylic Solvent
Propyle
Waste
Waste Tower
MANUFACTURING PROCESS OF ACRYLIC ACID
