Manufacture of Terepthalic Acid

PROJECT REPORT on

MANUFACTURE OF TEREPTHALIC ACID Submitted in partial fulfillment for the award of the degree of BACHELOR OF TECHNOLOGY in

CHEMICAL ENGINEERING by MRIDUL SABOO D. DINESH KUMAR

(10704009) (10704004)

under the guidance of Ms. S. VISHALI, M.E., (Lecturer, Department of Chemical Engineering)

FACULTY OF ENGINEERING AND TECHNOLOGY

SRM UNIVERSITY (under section 3 of UGC Act,1956) SRM Nagar, Kattankulathur – 603 203 Kancheepuram Dist. May 2008 1

ACKNOWLEDGEMENT

We take this opportunity to thank the Associate Director Dr. C..Muthamizhchelvan for providing us with an excellent infrastructure and conducive atmosphere for developing our project.

We would also like to thank the Head of Department of Chemical engineering Dr.R.Karthikeyan, for encouraging us to do our project.

We sincerely thank our project guide Ms. S. Vishali for her valuable guidance, support and encouragement in all aspects of this project and for its completion

We would also like to thank our faculty members and technicians of our Chemical Department who helped in the successful completion of our project.

2

CONTENTS

Page no

1. INTRODUCTION ……………………………………………………………........5 1.1 INTRODUCTION 1.2 HISTORY 2. PROPERTIES………………………………………………………………………7 2.1 PHYSICAL AND CHEMICAL PROPERTIES 3. APPLICATION…………………………………………………………………….8 3.1 APPLICATION OF TEREPTHALIC ACID 4. VARIOUS METHODS OF PRODUCTION………………………………………9 4.1 METHODS OF SELECTION 5. REASONS FOR SELECTION…………………………………………………….10 5.1 REASONS FOR PARTICULAR PROCESS 5.2 ADVANTAGES OF USING THIS PROCESS 5.3 DISADVANTAGES OF OTHER PROCESSES 6. PROCESS DESCRIPTION………………………………………………………..12 7. MASS BALANCE…………………………………………………………………16 7.1 MASS BALANCE FOR MIXED TANK 7.2 MASS BALANCE FOR REACTOR 7.3 MASS BALANCE FOR FIRST CRYSTALLIZER 7.4 MASS BALANCE FOR SECOND CRYSTALLIZER 7.5 MASS BALANCE FOR THIRD CRYSTALLIZER 7.6 MASS BALANCE FOR FILTER 7.7 MASS BALANCE FOR DRIER

3

8. ENERGY BALANCE…………………………………………………………….24 8.1 ENERGY BALANCE FOR MIXED TANK 8.2 ENERGY BALANCE FOR REACTOR 8.3 ENERGY BALANCE FOR FIRST CRYSTALLIZER 8.4 ENERGY BALANCE FOR SECOND CRYSTALLIZER 8.5 ENERGY BALANCE FOR THIRD CRYSTALLIZER 8.6 ENERGY BALANCE FOR FILTER 8.7 ENERGY BALANCE FOR DRIER 9. PROCESS DESIGN……………………………………………………………….42 9.1 DESIGN OF REACTOR 9.2 DESIGN OF DRIER 9.3 DESIGN OF MIXED TANK 10. COST ESTIMATION……………………………………………………………..47 11. PLANT LAYOUT………………………………………………………………….54 12. INSTRUMENTATION AND CONTROL………………………………………...58 12.1

INSTRUMENTS

12.2

OBJECTIVES

12.3

TYPICAL CONTROL SYSTEMS

13. SAFETY AND HAZARD ANALYSIS……………………………………………62 14. CONCLUSION…………………………………………………………………….65 15. BIBLIOGRAPHY………………………………………………………………….67

4

INTRODUCTION

5

1.1 INTRODUCTION Terephthalic acid is one isomer of the three phthalic acids. It finds important use as a commodity chemical .Principally as a starting compound for the manufacture of polyester (specifically PET), used in clothing and to make plastic bottles. It is also known as 1,4benzenedicarboxylic acid, and it has the chemical formula C6H4(COOH)2.. The acids are produced by oxidation of the methyl group on the corresponding p- xylene[106-42-3]. Terephthalic acid are used to make saturated polyesters with aliphatic diols as the comonomer. Terephthalic acid is commercially available as polymer grade (greater than 99.9 weight % pure, exclusive of some residual water) and technical grade (typically greater than 97-98% pure). Impurities include p-toluic acid, 4-formylbenzoic acid, residual water, trace metals and ash (trace metal oxides).( It has recently become an important component in the development of hybrid framework materials.

1.2 HISTORY Phthalic acid (the ortho isomer of terephthalic acid) was obtained by French chemist Auguste Laurent in 1836 by oxidizing naphthalene tetrachloride. Believing the resulting substance to be a naphthalene derivative, he named it naphthalenic acid. Swiss chemist Jean Charles Galissard de Marignac determined its formula and showed Laurent’s supposition to be incorrect, upon which Laurent gave it its present name, with teres meaning well-turned, refined, elegant in latin [3] (symmetry increased over ortho and meta isomers).

6

PROPERTIES

7

2.1 PHYSICAL AND CHEMICAL PROPERTIES

Molecular Weight

: 166.14

Physical State

: Solid

Melting Point

: Sublimes at 402 deg C (755.6 deg F) at atmospheric

pressure, without melting.(14,15,22) Reported to melt at 427 deg C (800.6 deg F) in a sealed tube. Boiling Point

: Sublimes

Relative Density (Specific Gravity) : 1.522 at 25 deg C (water = 1) Solubility in Water

: Practically insoluble (1.7 mg/100 g) at 25 deg C.

Solubility in Other Liquids

: Soluble in dimethyl sulfoxide, dimethylformamide and

alkalies, such as potassium and sodium hydroxide; slightly soluble in cold ethanol, methanol, formic acid and sulfuric acid; very slightly soluble in chloroform, diethyl ether and glacial acetic acid Coefficient of Oil/Water Distribution (Partition Coefficient)

: Log P(oct) = 1.25; 1.96; 2.0 (measured)

pH Value

: .16 (saturated solution (0.002% in water))

Vapour Density

: Less than 0.0013 kPa (0.01 mm Hg) at 20 deg C (13);

0.067 kPa (0.5 mm Hg) at 120 deg C Saturation Vapour Concentration : Very low at normal temperatures Evaporation Rate: Probably very low at normal temperatures. Other Physical Properties

: ACIDITY: Weak acid; pKa1 = 3.54 (Ka1 = 2.9 X 10(-

4)); pKa2 = 4.46 (Ka2 = 3.5 X 10(-5)) at 25 deg C.(14,15) NOTE: Very small amounts of terephthalic acid in water are reported to substantially lower the pH of the solution and form a fairly strong acid.(13) TRIPLE POINT: 427 deg C (800.6 deg F)

8

3.1 APPLICATIONS : •

Nearly all purified terephthalic acid (PTA) is consumed in polyester production including polyester fibre, polyethylene terephthalate (PET) bottle resin and polyester film.

•

For most grades of polyester used in textiles and food and beverage containers, it is more economical to use PTA than the alternative dimethyl terephthalate (DMT) intermediate.

•

The remaining PTA is used in making cyclohexanedimethanol, terephthaloyl chloride, copolyester-ether elastomers, plasticisers and liquid crystal polymers.

•

PTA applications include coatings and composite materials, based on unsaturated polyester resins, and hot-melt adhesives.

•

Terephthalic acid is also widely used to make dyes, medicine, and synthetic perfumes, pesticides, and other chemical compounds.

9

4.1 VARIOUS METHODS OF PRODUCTION The various methods of production of Terephthalic Acid are as follows: 1. Oxidation of p-xylene by oxygen from air. 2. Re arrangement of phthalic acid to terephthalic acid via the corresponding potassium salts. 3. Oxidizing para-dederivatives of benzene 4. Oxidizing caraway oil, a mixture of cymene and cuminol with chromic acid

10

5.1 REASONS FOR PARTICULAR PROCESS : Catalytic, liquid phase-air oxidation of p-xylene: This method is most widely used all over the world to produce technical grade Terephthalic acid. This method was developed by Mid –Century Corp. The process generally uses acetic acid as the solvent and a catalyst to oxidize p-Xylene in liquid phase by air oxidation. The process is also called as the Amoco process. This uses a catalyst usually a heavy metal eg. Cobalt. The process may use typically multivalent metals like manganese as catalyst for oxidation and bromine serves as the renewable source of free radicals.

5.2 ADVANTAGES OF USING THIS PROCESS: 1. The reaction is very simple with a single step. 2. The raw materials used in this process are easily available since it is a byproduct of a petroleum industry. 3. The Terephthalic acid produced in this process has a yield of almost 100% with the presence of 4-formylbenzoic acid in trace amount. 4. The oxidation process is highly efficient when compared to the other methods it brings about a conversion of about 95 wt%. 5. The product purity is very high 99%. 6. The process has very few pollution problems. 7. The solvent and the catalyst can be recovered and reused. The recovery of solvent is possible till 90%.

5.3 DISADVANTAGES OF OTHER PROCESSES: 1. Henkel process is now obsolete as the Terephthalic acid produced by that method cannot be used in the manufacture of polymers. 2. Oxidizing benzene and caraway oil are not economically viable on Industrial Scale.

11

PROCESS DESCRIPTION

12

6.1 PROCESS DESCRIPTION: The process can be divided into different units: •

Reactor Unit

•

Crystallization Unit

•

Separation and Drying Unit

Reactor Unit:

The reactor unit comprises of a mixing tank and a reactor. The raw materials p-Xylene, air, acetic acid (solvent) and the catalyst (cobalt) are fed continuously into the feed mixing tank. The residence time is 5-10 min.The mixed stream pumps the reactor , and the air is flown into the reactor through four inlets. The reactor is maintained at a temperature of 150ºC and a pressure of 1500 kPa – 3000kPa. The air is added in greater stoichiometric ratio to minimize the formation of byproducts. The heat of reaction is removed by condensing and refluxing acetic acid The residence time of this reaction varies from 30 minutes to 3 hours. More than 95% of p-Xylene is converted to product.. The outlet from the reactor is a slurry, since it is soluble to a limited extent in the solvent.used.

13

Crystallization Unit:

The oxidation reaction is conducted in two stages, first stage being the agitated oxidation reactor, while the second stage is the agitated first crystallizer. Exothermic heat of reaction is removed by condensing the boiling reaction solvent. A portion of this condensate is withdrawn to control the water concentration in the reactor. Reactor effluent is depressurized and cooled to filtering conditions in a series of three crystallizing vessels ( first crystallizer, second crystallizer and third crystallizer ) for the secondary reaction and crystallization step. Air is fed to the first crystallizer for additional reaction, which used to do polishing oxidation of unreacted paraxylene from the reactor.

Separation And Drying Unit:

The separation and drying unit consists of a rotary filter and a rotary drier. In the filter most of the water content is removed from the product (Terephthalic acid). There are two streams leaving the filter. One stream is sent to the recovery unit. And the other is sent to the rotary drier. The solid stream is sent to the drier. Preheated air is sent to the through the drier to remove the moisture present in the final product. The product from the drier is 99% pure Terephthalic acid.

14

MANUFACTURE OF TERETHALIC ACID

1. Paraxylene 2. Water 3. Acetic acid 4. Air 5. Mixed Tank 6. CSTR Reactor 7. First Crystallizer 8. Second Crystallizer 9. Third Crystallizer 10. Rotary Filter 11. Rotary Drier 12. Crude TPA

15

MASS BALANCE

16

MASS BALANCE

BASIS: 15 Kmole of Paraxylene/ Hour ~ 14.8 Kmole of Terepthalic Acid/ Hour

7.1 MASS BALANCE OF MIXED TANK Solvent from Scrubber 1038kg of Acetic acid 90kg of water Raw Material 1590 kg of Paraxylene feed

Reaction Mixture 7038 kg of Acetic Acid 428.4 kg of water

Solvent 6000 kg of Acetic acid 338.4 kg of water Feed

Mixed tank

Inlet = 9056.4 Kg= Outlet

17

1590 kg of Paraxylene

7.2MASS BALANCE OF REACTOR Air 1780.8kg of oxygen 5861.8kg of nitrogen

Liquid Stream 1590 kg of Paraxylene 6000 kg of acetic acid 338.4 kg of water 535 kg of Water 2290.8 kg of TPA

Liquid Stream 127.2 kg of Paraxylene Reactor

Solvent from Scrubber 1038 kg of acetic acid 90kg of water Reflux Stream 17610 kg of acetic acid 3150 kg of water

Vapour stream 19220 kg of acetic acid 3043.4 kg of water 705.6 kg of oxygen 5861.8 kg of nitrogen 240 kg of Carbon dioxide

Inlet = 37459 Kg=Outlet

18

5428 kg of Acetic Acid

Error!

7.3 MASS BALANCE OF FIRST CRYSTALLIZER Air 65.6kg of Oxygen 215.9kg of Nitrogen

Liquid Stream 5428kg of acetic acid 2290.8kg of TPA 227.16kg of water 535 kg of water 127.2 kg of paraxylene

Liquid Stream 4293kg of acetic acid First Crystalizer

Vapour Stream 1135kg of Acetic acid 311.84kg of water 215.9kg of Nitrogen 1.6kg of Oxygen 21.2 kg of paraxylene

Inlet = 8662.5 Kg = Outlet

19

2456.8 of TPA

7.4 MASS BALANCE OF SECOND CRYSTALLIZER Dilution Solvent 780kg of Acetic acid 43.9kg of water

Liquid Stream 4293kg of acetic acid

Liquid Stream 4416kg of Acetic acid Second Crystallizer

227.16kg of water 2456.8 kg of TPA

203.4kg of water 2456.8kg of TPA

Vapour Stream 660kg of Acetic acid 64.78kg of water

Inlet = 7801 Kg = Outlet

20

7.5 MASS BALANCE OF THIRD CRYSTALLIZER Solvent

1476kg of Acetic acid 208.8kg of water

Liquid Stream 4416kg of Acetic acid 203.4kg of water 2456.8kg of TPA

Liquid Stream 4410kg of Acetic acid 203.4kg of water Third Crystallizer

Air .336kg of Oxygen 1.106kg of Nitrogen Vapour Stream 1482kg of Acetic acid 208.8kg of water .336kg of Oxygen 1.106kg of Nitrogen

Inlet = 8762.4 Kg = Outlet

21

2456.8kg of TPA

7.6 MASS BALANCE OF ROTARY FILTER

Solvent 552kg of Acetic acid 28.8kg of water

Liquid Stream 4410 kg of Acetic acid 203.4 kg of water 2456.8kg of PTA

Filter Cake 496.2kg of acetic acid Rotary Filter

Filterate 4465.8kg of acetic acid 208.44kg of water


22

23.76kg of water 2456.8kg of PTA

7.7 MASS BALANCE OF DRIER Air 6.72 kg O2 196 kg N2 27 kg H2O

2456.8 of TPA

2456.8kg of Crude TPA

Filter cake

Dried Scrubber Bottoms Drier

496.2 kg of acetic acid 23.76 kg of water

2320.2kg of acetic acid 158.58kg of water

Solvent 1824kg of acetic acid 111.6 kg of water

Air 6.72kg O2 196kg N2 3.78 kg Water


23

ENERGY BALANCE

24

ENERGY BALANCE

Specific heat constant Paraxylene

= 44.8 cal/Mol K

Acetic Acid (l)

= 31.2 cal/Mol K

Acetic Acid (g)

= 24 cal/Mol K

Terepthalic Acid

= 47.6 cal/Mol K

Water (l)

= 18 cal/Mol K

CO2 (g)

= 10.34+0.00274T–19550 cal/Mol K

H2 O(g)

= 8.22+0.00015T+0.00000134T2 cal/Mol K

N2 (g)

= 6.5+0.00100T cal/Mol K

O2 (g)

= 8.27+0.0002587T – 187700/T2 cal/Mol K

Latent Heat of Vaporization Paraxylene

= 81 cal/g

Acetic Acid

= 96.48 cal/g

Water

= 544.8 cal/g

Latent Heat of Formation Terepthalic Acid

= -731.9 KJ/Mol

H2O

= 285.8 KJ/Mol

Paraxylene

= -24.4 KJ/Mol 25

8.1 MIXED TANK Reference Temperature = 283K Reactants: Paraxylene Q = 15 x 103

= 20160 Kcal

Solvent (a) Acetic Acid Q = 100 x 103

= 224640 Kcal

(b) Water Q = 18.8 x 103

24364.8 Kcal

Solvent from Scrubber (a) Acetic Acid Q = 17.3 x 103

= 16192.8

(b) Water Q = 5 x 103

= 2700 Kcal

∆QReactant = 288057.6 Kcal

26

Products: Paraxylene Q = 15 x 103

= 41664 Kcal

Solvent (a) Acetic Acid Q = 100 x 10

= 193440 Kcal

(b) Water Q = 18.8 x 103

= 20980.8 Kcal

Solvent from Scrubber (a) Acetic Acid Q = 17.3 x 103

= 33465.12 Kcal

(b) Water Q = 5 x 103

= 5580 Kcal

∆Q product = 295129.92 Kcal HEAT CHANGE ∆Qreq = ∆QPdts – ∆Qreact + ∆HoR = 295129.92- 288057.6 + 0 = 7072.32 Kcal Heat to be supplied by the system = 7072.32 Kcal

27

8.2 REACTOR Reference Temperature = 335K Reactant: Paraxylene Q = 15 x 103

= 6720 Kcal

Solvent (a)

Acetic Acid Q = 100 x 103

(b)

= 31200 Kcal

Water

Q = 18.8 x 103

= 3384 Kcal

Solvent from Scrubber (a)

Acetic Acid Q= 17.3 x 103

(b)

= 5397.6 Kcal

Water Q = 5 x 103

= 900 Kcal

Air (a)

Oxygen

Q = 55.65 x 103

+ 0.0002587T‐18770/T2 dT

= 55.65 x 103 x 1044.34 = 58117.52 Kcal

(b) Nitrogen Q = 209.35 x 103 = 209.35 x 103 x 709.31 = 14849.40 Kcal

28

Reflux (a) Acetic Acid Q = 293.5 x 103

= 1007292 Kcal

(b) Water Q = 175 x 103

= 346500 Kcal

∆Q Reactants = 1474360.52 Kcal

Product: Liquid stream (a) Acetic acid Q = 90.5 x 103

= 426363.6 Kcal

(b) Terepthalic acid Q = 13.8 x 103

= 99188.88 Kcal

(c) Water Q = 29.7 x 103

= 80724.6 Kcal

(d) Paraxylene Q = 1.2 x 103

= 8117.6 Kcal

Vapour stream (a) Acetic Acid Q = 320.3 x 103

= 1160767.2 Kcal

29

Ql = mλ = 96.48 x 320.3 x 103 x 60 = 1854152.64 Kcal (b) Water Q = 169 x 103

+ 0.00015T + 0.00000134T2 dT

= 169 x 103 x 1285 = 217165 Kcal Ql = mλ = 169 x 103 x 18 x 544.8 = 1657281.6 Kcal (c) Oxygen Q = 22.05 x 103

+ 0.0002587T‐18770/T2 dT

= 22.05 x 103 x 1454.04 = 32061.58 Kcal (d) Nitrogen Q = 209.35 x 103 =209.35 x 103 x 1043.49 = 218454.6 Kcal (e) Carbon dioxide Q = 6 x 103

0.00274T – 19550/T2 dT

= 6 x 103 x 1860.66 = 11163.96Kcal ∆Q Reactant = 5248276.26 Kcal Reaction: C8H10 +2O2

C6H4(COOH)2+2H2O

∆HoR= [∆HL (C6H4(COOH)2+ 2∆HF(H2O)]–[∆HF 2O2 + ∆HF C8H10] = –731.08+2(-285.8)+24.4 = –1278.28 KJ/ mol = -305.8 Kcal / mol HEAT CHANGE ∆Qreq = ∆QPdts – ∆Qreact + ∆HoR = 5248276.26 – 1174362+(13.8 × 103 × -305.8) = – 146,125.74Kcal Heat given to the system = 146125.74 Kcal

30

8.3 FIRST CRYSTALLIZER Reference Temperature = 363K Reactants: (a) Acetic Acid Q =90.5 x 103

= 347302.8 Kcal

(b) Terepthalic Acid Q =13.8 x 103

= 80796.24 Kcal

(c)Water Q =29.7 x 103

= 65755.8 Kcal

Air (a) Oxygen Q = 2.05x 103 = 2.05 x 103 x 910.54

+ 0.0002587T‐18770/T2 dT = 1866.61 Kcal

(b)Nitrogen Q = 7.7 x 103 = 7.7 x 103 x 517.54 = 3985.06 Kcal ∆Q Reactants = 499106.51 Kcal Products: 1.

Liquid Stream (a)

Acetic acid Q = 71.55 x 103

(b)

= 247791.96 Kcal

Water Q = 12.62 x 103

= 25214.76 Kcal

31

(c)

Terepthalic Acid Q = 14.8 x 103

= 78197.28 Kcal

2. Vapour Stream (a)

Acetic Acid Q = 18.9 x 103

= 50439.6 Kcal

Ql = mλ = 96.48 x 18.9 x 103 x 60 = 109408.32 Kcal (b)

Water Q = 17.32 x 103

+ 0.00015T + 0.00000134T2 dT

= 17.32 x 103 x 1274.39 = 22072.43 Kcal Q = mλ = 17.32 x 18 x 103 x 544.8 = 169846.84 Kcal (c)

Nitrogen

Q = 7.7 x 103 = 7.7 x 103 x 767.95 = 5913.22 Kcal (d)

Oxygen Q = 0.05 x 103

+ 0.0002587T‐18770/T2 dT

= 0.05 x 103 x 1146.82 = 57.34 Kcal (e)

Paraxylene Q = 0.2 x 103

= 994.56 Kcal

Ql = mλ = 0.2 x 106 x 103 x 81 = 1717.2 Kcal ∆QPdts = 711653.51 Kcal ∆HoR = -305.8 Kcal/mol HEAT CHANGE ∆Qreq = ∆QPdts – ∆Qreact + ∆Ho ∆Q Required = –499106.51 +711653.51+(–305.8 × 14.8 × 103) = –4313293 Kcal Heat given to the system = 4313293 Kcal

32

8.4 SECOND CRYSTALLIZER Reference temperature = 363k Reactant: (a)


(b)

= 247791.96

Water Q = 12.62 x 103

(c)

= 25214.76 Kcal

Terepthalic acid Q = 14.8 x 103

= 78197.28 Kcal

Dilution Solvent (a) Acetic acid Q = 13 x 103

= 45021.6 Kcal

(b) Water Q = 2.4 x 103

= 4795.2 Kcal

∆Q Reactants = 401020.8 Kcal Product: Liquid Stream (a) Acetic acid Q = 73.6 x 103

= 167631.36 Kcal

(b) Water Q = 11.3 x 103

=14848.2 Kcal

33

(c) Terepthalic acid Q = 14.8 x 103

= 51427.04 Kcal

Vapour Stream: (a) Acetic acid Q = 11 x 103

= 19272 Kcal

Ql = mλ = 11 x 103 x 60 x 96.48 =63676.8 Kcal (b)

Water Q = 3.6 x 103

+ 0.00015T + 0.00000134T2 dT

= 3.6 x 103 x 850.25 = 3060.9 Kcal Ql = mλ = 3.6 x 18 x 103 x 544.80 = 35303.04 Kcal ∆QPdts = 355219.34 Kcal

HEAT CHANGE ∆Qreq = ∆QPdts – ∆Qreact + ∆HoR ∆Qreq = 355219.34 - 401020.8 = -45801.46 Kcal Heat given to the system = 45801.46 Kcal

34

8.5 THIRD CRYSTALLIZER: Reference Temperature = 273K Reactant: Liquid Stream (a)


(b)

Water Q = 11.3 x 103

(c)

= 374300.16 Kcal

= 33154.2 Kcal


= 114830.24 Kcal

Air (a)

Oxygen Q = 0.0105 x 103

+ 0.0002587T‐18770/T2 dT

= 0.0105 x 103 x 970.146 = 10.20 Kcal (b)

Nitrogen Q = 0.0395 x 103 = 0.0395 x 103 x 169.64 = 6.70 Kcal

Solvent (a)


= 38376 Kcal

35

(b)

Water Q = 11.6 x 103

= 10440 Kcal

∆Qreact = 57111.75 Kcal Product: Liquid stream (a) Acetic acid Q = 73.5 x 103

(b)

Water Q = 11.3 x 103

(c)

= 213267.6 Kcal

= 18916.2 Kcal


= 65516.64 Kcal

Vapour Stream (a) Acetic Acid Q = 24.7 x 103

= 55130.4 Kcal

Ql = mλ = 24.7 x 60 x 103 x 96.48 = 142983.36 (b) Water Q = 11.6 x 103

+ 0.00015T + 0.00000134T2 dT

= 11.6 x 103 x 781.73 = 9068.07 Kcal Ql = mλ = 11.6 x 103 x 544.8 = 113754.24 Kcal (c) Oxygen

36

Q = 0.0105 x 103

+ 0.0002587T‐18770/T2 dT

= 0.0105 x 103 x 1018.61 = 10.70

(d) Nitrogen Q = 0.0395 x 103 = 0.0395 x 103 x 634.21 = 25.05 Kcal ∆QPdts = 618672.26 Kcal

HEAT CHANGE ∆Qreq = ∆QPdts – ∆Qreact + ∆HoR ∆QReq = 618672.26 – 57111.75 = 561560.51 Kcal Heat to be supplied by the system = 561560.51 Kcal

37

8.6 ROTARY FILTER Reference temperature = 353k Reactants: Liquid Stream (a) Acetic acid Q = 73.5 x 103 (b)

Water Q = 11.3 x 103

(c)

= 9158.24 Kcal

Acetic Acid Q = 9.2 x 103

(b)

= 2644.2 Kcal


Solvent (a)

= 29811.6 Kcal

= 5740.8 Kcal

Water Q = 1.6 x 103

= 576 Kcal

∆Qreact = 47930.84 Kcal Product: Filter cake (a) Acetic acid Q = 8.27 x 103 (b)

= 2580.24 Kcal

Water Q =13.2 x 103

= 237.6 Kcal

38

(c)


Filterate (a)


(b)

= 7044.8 Kcal

= 23222.16 Kcal

Water Q = 11.58 x 103

= 2084.4 Kcal

∆QPdts = 35169.2 Kcal HEAT CHANGE ∆Qreq = ∆QPdts – ∆Qreact + ∆HoR ∆QReq = 35169.2 – 47930.84 = –12761.64 Kcal Heat given to the system = 12761.64 Kcal

39

8.7 DRIER Reference temperature = 303K Reactant: Filter cake (a) Acetic acid Q = 8.27 x 103 (b)

Water Q = 1.32 x 103

(c)

= 1425.6 Kcal


Air (a)

= 15481.44 Kcal

= 42268.8 Kcal

Oxygen Q = 0.21 x 103

+ 0.0002587T‐18770/T2 dT

= 0.21 x 103 x 814.20 = 170.98 Kcal (b)

Nitrogen Q = 7 x 103 = 7 x 103 x 409.98 = 2869.86 Kcal

(c)

Water Q = 1.5 x 103

= 1620 Kcal

Solvent (a) Acetic acid Q = 30.4 x 103

= 9484.6 Kcal

40

(b)

Water Q = 6.2 x 103

= 1116 Kcal

∆QReact = 74437.28 Kcal Product: Crude TA Q = 14.8 x 103

= 73970.4 Kcal

Drier Scrubber Bottoms (a) Acetic acid Q = 38.67 x 103 (b)

= 126486.36 Kcal

Water Q = 8.81 x 103

= 16650.9 Kcal

Dried Air (a) Oxygen Q = 0.21 x 103

+ 0.0002587T‐18770/T2 dT

= 0.21 x 103 x 1456.5 = 305.87 Kcal (b)

Nitrogen Q = 7 x 103

(c)

= 7 x 103 x 95.34 = 667.38 Kcal Water Q = 0.21 x 103

= 52.92 Kcal

∆Q Pdts = 218133.83 Kcal ∆Q Required = ∆QPdts – ∆QReact + ∆H0R = 218133.83 – 74437.28 + 0 = 143696.55 Kcal

Heat to be supplied by the system = 143696.55 Kcal

41

PROCESS DESIGN

42

PROCESS DESIGN 9.1 DESIGN OF REACTOR • We have a CSTR Reactor • Calculation of volume, length and diameter of the reactor • Density values of the reactant are: (a) Paraxylene = 860 kg/m3 = 1049 kg/m3 (b) Acetic acid (c) Water = 1000 kg/m3 (d) Oxygen = 1.429 kg/m3 (e) Nitrogen = 1.251 kg/m3 Volume occupied by each reactant is found out by:Volumetric feed rate in m3/min = Specific volume × mass of the reactants entering •

•

•

•

•

Paraxylene Vo = mo/ρ = 0.0308 m3/min Acetic acid Vo = 0.1118 m3/min Water Vo = 0.00714m3/min Oxygen Vo = 1.038 m3/min Nitrogen Vo = 3.905 m3/min

Total volumetric feed rate Taking safety factor as 10% Vo Space time (CSTR) Space time Volume = 30 × 56.023 = 168.69 m3

= (1590)/(860x60)

= (7038) / (1049×60)

= (428.4) / (1000×60)

= (55.65 × 32)/(60×20×1.429)

= (209.35 × 28)/( 60×20×1.251) = 5.093 = 5.6023 = V / Vo = 30 min = Space time × Vo

43

π × D2 × L 4 Assumption L /P = 1.5 V=

π × D 2 × 1 .5 D 4 1 6 8 0 .7 × 4 D3= π × 1 .5

V =

D = 1.126m L = 1.689m

Agitator Design Agitator design involves the calculation of diameter and height of the impeller from the bottom, length and width of the blade. 1. 2. 3. 4.

Diameter of the impeller Height of the impeller from the bottom Length of the blade = LB Width of the blade = WB

44

= DA = D/3 =D/3 =DA/4 =DA/5

= 0.375m = 0.375m = 0.0937m = 0.075m

9.2 DESIGN OF MIXING TANK Basic: Designing mixing tank • To find the diameter , the length and the design pressure • To find the tank volume Density of inlet streams • Paraxylene = 860 Kg/m3 • Acetic acid = 1049 Kg/m3 • Water = 1000 Kg/m3 Volume occupied by the each reactant 1. Paraxylene V0 = m0 / ρ = (15 × 106)/ (860 × 60) = 0.0308m3/min 2. Acetic acid V0 = 0.111 m3/min 3. Water V0 = 7.14 × 10-6 m3/min V0

= (117.3 × 60)/(1049 × 60)

= (23.8 × 18) / (1000 × 60) = 0.179m3

Space time = 5min V/Vo =5 V = 5 × 0.149 = 0.745m3 Assume 10% allowance V = 0.815m3 Assume L / D ratio is 0.5 Calculation: Volume = π/4 × D2 × 0.5D 0.81952 = = π/4 × 0.5D3 D3 = 2.806 D = 1.277m λ = 0.6385m = 9057.828/0.8195 Pavg = mass/Volume 3 = 11052.9kg/m Pressure(p) =p1 × g × L = 11052.87 × 9.8 × 0.6385 = 0.692atm Hence the design pressure = 0.692 × 1.1 = 0.7612atm

45

8.3 DESSIGN OF DRIER Air flow rate Leaving air humidity Y1 Area = ms /mv ms mv ms ms = 206.77kg/hr mv Area = ms / mv = 206.77/ 500 Area D2 D

= 202.72Kg dry air/hr = 0.020 = mass flow rate of wet air (kg / hr) = maximum air velocity (kg/ m2hr) = Gs + ( Gs × Y1) = 202.72 + (202.72 × 0.02) = 500kg/m2hr = 0.414 = (π/4) × D2 = (4/π)(0.414) = 0.726m

Heat duty: Qt Cs =1243.55 J/kg0C

= Gs × Cs (tg1 – tg2 ) = heat capacity of the dry solid

Qt

= 14117018 KJ/hr

G

= 500kg /m2hr

Tb

= 400 C (By psychometric chart)

ΔT =

(90-40)-(44-40) = 18.210C ⎡ 90-40 ⎤ ln ⎢ ⎣ 44-40 ⎥⎦ qT 0.125π DG 0.67 ΔT

Length of the dryer

=

D = 0.726m q T0F

= 2.36feet = 13380.44 Btu/hr = 59.32 0 F

L =

qT L = 10.86ft= 3.31m 0.125π×2.38 (102.42) 0.67×59.32

46

COST ESTIMATION

47

COST ESTIMATION Number of working days per year

= 350

Cost of 1kg of Terepthalic Acid

=Rs 70

Production of Terepthalic Acid

= 58963.2 Kg/Day

Gross sales for 1 yr or total income

=58963.2 x 350 x 70 = Rs 144,45,98,400

TURN OVER RATIO: It can be defined as the ratio of total income to fixed capital investment. Turn over ratio

=

Total Income Fixed capital Investment

For chemical industries the turn over ratio is one. Thus, Fixed capital investment = Gross Annual Sales = Rs 144,45,98,400 But,

Fixed capital investment = Direct cost + Indirect cost

DIRECT COST: It is taken as 70% of the fixed capital investment= 0.7 x 1444598400 = Rs 1011218880 The costs involved in the direct cost are, i.

Equipment cost

ii.

Installation & Painting cost

iii.

Instrumentation Cost

iv.

Electrical cost

v.

Piping Cost

vi.

Building, process and auxiliary cost

vii.

Service facilities & yard improvement cost

viii.

Land cost

48

Equipment cost It is taken as 24% of fixed capital investment

= 0.24 x 1444598400 = Rs 346703616

Painting and installation cost It is taken as 40% of the equipment cost

= 0.4 x 346703616 = Rs 138681446.4

Instrumentation cost It can be taken as 10% of equipment cost

= 0.1 x 346703616 = Rs 34670361.6

Piping cost It is 25% of the equipment cost

= 0.25 x 346703616 = Rs 86675904

Electrical cost I

t can be taken as 25% of equipment cost

= 0.25 x 346703616 = Rs 86675904

Building, process and auxiliary cost It is 39.1677% of equipment cost

= 0.391677 x 346703616 = Rs 135795832.2

Service facilities & yard improvement cost It can be taken as 10% of equipment cost

= 0.1 x 346703616 = Rs 34670361.6

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Land cost It is usually taken as 1% of fixed capital cost = 0.01 x 1444598400 = Rs 14445984

INDIRECT COST: Indirect cost = Fixed Capital Investment – Direct Cost = 1444598400 – 1011218880= Rs 433379520 It consists of the following items i.

Engineering and supervision cost

ii.

Contingency

iii.

Working capital

Engineering and supervision cost It can be taken as 10% of equipment cost = 0.1 x 346703616

= Rs 34670361.6

Contingency It can be taken as 3.7% of fixed capital = 0.037 x 1444598400

= Rs 53450140.8

Working capital It is 20% of total capital investment Total capital investment = fixed capital + working capital = 1444598400 + (0.2 x 1444598400) = Rs 1733518080 Working capital = 0.2 x 1733518080 = Rs 346703616

Estimation of total product cost Annual income = Rs 1444598400 Gross earning is 10% of annual income = 0.1 x 1444598400 Product cost = Total annual income – Gross earnings = 1444598400 – 144459840 = Rs 1300138560

50

= Rs 144459840

Direct production cost It can be taken as 60% of the total product cost = 0.6 x 1300138560 = Rs 780083136

Raw materials cost It is 2% of the total product cost = 0.02 x 1300138560 = Rs 26002771.2

Operating labor cost It can be taken as 15% of total product cost = 0.15 x 1300138560 = Rs 195020784

Direct supervisory & clinical labor cost It is 20% of operating labor cost = 0.2 x 195020784 = Rs 39004156.8

Utilities It can be taken as 15% of total product cost = 0.15 x 1300138560 = Rs 195020784

Maintenance & repair cost It is 3.6% of fixed capital investment cost = 0.036 x 1444598400 = Rs 52005542.4

Laboratory charges It is taken as 6.67% of operating labor cost = 0.0667 x 195020784 = Rs 13007886.29

Royalties It is taken as 1.45% of the fixed capital cost = 0.0145 x 1444598400 = Rs 20946676.8

51

Fixed charges It can be taken as 20% of product cost = 0.2 x 1300138560 = Rs 260027712

Plant overheads This includes cost for general upkeep and overhead packaging, medical services, safety and protection, recreation, sewage, laboratories, and storage facilities. It is 5% of the total product cost = 0.05 x 1300138560 = Rs 65006928

Depreciation Depreciation for machinery is 10% of fixed capital cost

= 0.1 x 1444598400 = Rs 144459840

Depreciation of building is 3% of the land cost

= 0.03 x 14445984 = Rs 433379.52 = 144459840 – 433379.52

Total depreciation value

= Rs 144026460.5

Insurance It is 1% of the fixed capital cost = 0.01 x 1444598400

= Rs 14445984

Rent value It is 3.033% of the total product cost = 0.03033 x 1300138560 = Rs 39433202.52

General expenses Administrative cost includes cost for officer, legal fees, office supplier and communication. It is 5% of the total; product cost = 0.05 x 1300138560

52

= Rs 65006928

Distribution and selling cost I

t accounts for 7% of the total product cost = 0.07 x 1300138560 = Rs 91009699.2

Research and development cost It is 1% of the total product cost = 0.01x 1300138560

= Rs 13001385.6

Financing It is 2% of the total product cost = 0.02 x 1300138560

= Rs 26002771.2

Net profit It is obtained after deduction of taxes from the Gross Earnings. Net profit is 40% of the Gross Earnings = 0.4 x 1444598400 = Rs 577839360

Determination of Pay-Back period (without interest charges) =

Depreciable fixed capital investment

(Average profit + average depreciation)/yr =

1444598400

(577839360 +144459840) =

2 yrs.

53

PLANT LAYOUT

54

PLANT LAYOUT PLANT LOCATION : The major factors that are involved in the selection plant size and plant location are 1. Availability of raw materials 2. Markets 3. Transportation facilities 4. Water supply 5. Energy Availability 6. Climate 7. Labour

Availability of raw materials: The source of raw materials is one of the important factor in the selection of plant site.

Market: The locations of markets or intermediates distribution centers affect the cost of the product distributed.

Transport Facilities: Transportation depends on the type of raw materials and products. Water, railroads and highways are the three types of transportation. Plant should have at least two of these.

55

Water supply: We use water for cooling. So plant should be located where adequate water supply should be available.

Energy Availabilty: Power and fuel are to be considered as major factors in the choice of plant site.

56

.

57

INSTRUMENTATION AND CONTROL

58

INSTRUMENTATION AND CONTROL The process flow sheet shows the arrangement of the major equipments and thus, the control of such major equipments is necessary.

13.1 INSTRUMENTS Instruments are provided to monitor the key process variable during plant operation. They may be incorporated in automatic control loops, or used for the manual monitoring of the process operation. It is desirable that the process variable to be monitored be measured directly: Often, however, this is impractical and some dependent variable, that is easier to measure, is monitored in its place.

13.2 OBJECTIVES SAFE PLANT OPERATION 1) To keep the process variables within known safe limits. 2) To detect dangerous situations as they develop and to provide alarms and automatic shut down systems. 3) To provide inter locks and alarms to prevent dangerous operating procedures.

PRODUCTION RATE To achieve the design product output.

PRODUCT QUALITY To maintain the product composition within the specified quality standards.

COST To operate the lowest production cost, commensurate with the other objectives.

59

13.3 TYPICAL CONTROL SYSTEMS LEVEL CONTROL In any equipment where an interface exists between two phases (liquid-vapor), some means of maintaining the interface at the required level must be provided. The control valve should be placed on the discharge line from the pump. In this process, a level control valve is used in the reactor, neutralization tanks and Decolorization tanks.

PRESSURE CONTROL Pressure control will be necessary for most systemshandling vapor or gas. The method of control will depend on the nature of the process.

FLOW CONTROL Flow control is usually associated with inventory control in a storage tank or other equipment. There must be a reservoir to take up the changes in flow rate. To provide flow control on a compressor or pump running at a fixed speed and supplying a next constant volume output, a by-pass would be used. Flow control valves are used in the reactors, neutralization tanks and Decolorization tanks to control the flow of input and output streams.

CASCADE CONTROL With this arrangement, output of one controller is used to adjust the set point of another. Cascade control can give smoother control in situations where direct control of the variable would lead to unstable operation. In reactor and neutralization tank 1 temperature control is cascaded with flow controls.

60

REACTOR CONTROL The schemes used for reactor control depend on the process and the type of the reactor. If a reliable on-line analyzer is available, and the reactor dynamics are suitable, the product composition can be monitored continuously and the reactor conditions and feed flows controlled automatically to maintain the desired product composition and yield. More often, the operator is the final link in the control loop, adjusting the controller set points to maintain the product within specification, based on periodic laboratory analyses.Reactor temperature will normally be controlled by regulating the flow of the heating or cooling medium. Pressure is held constant. Material balance control will be necessary to maintain the correct flow of reactants, products and unreacted materials.

61

SAFETY AND HAZARD ANALYSIS

62

SAFETY AND HAZARD ANALYSIS: The term “engineered safety ” covers the provision in the design of control systems, alarm traps, trips , pressure- relief devices, automatic shutdown systems, duplication of key equipment services, fire-fighting equipment, sprinkler systems and blast walls to contain any fire or explosion. Any organization has a legal and moral obligation to safeguard the health and welfare of its employees and the general public. The term “loss prevention” is an insurance term, the loss being the financial loss caused by an accident. These losses will not only be the cost of replacing damaged plant and third party claims, but also the loss of earnings from lost production and lost sales opportunities. All manufacturing processes are to some extent hazardous, but in chemical processes there are additional, special, hazards associated with the chemicals used and the process conditions. The designer must be aware of these hazards, and ensure, through the application of a sound engineering practice that the risks are reduced to acceptable levels. Safety is the loss prevention in process design can be considered under the following broad headings: 1.Identification and assessment of potential hazards. 2.Control of the hazards: Eg. Explosion & Corrosion Fine dust dispersed in air in sufficient concentrations, and in the presence of an ignition is a potential dust explosion hazard. 3. Control of the process 4. Limitation of the losses: The damage and injury caused if an incident occurs can be prevented by providing pressure relief, safe plant layout, fire fighting equipments etc. Process can be divided into those that of intrinsically safe, and those for which the safety has to be engineered in. An intrinsically safe process in one in which safe operation

63

is inherent in the nature of the process i.e a process which causes no danger or negligible danger under all foreseeable circumstances. The safe operation of such processes depends on the design and provision of engineered safety devices, and on good operating practices, to prevent dangerous situations developing, and to minimize the consequences of any accident that arises from the failure of these safeguards. The process designer will be concerned more with the preventive aspects of the use of hazardous substances. 1.Substitution : Substitution of the processing route with the less hazardous material 2.Containment: Sound design of equipment and piping to avoid leaking. 3.Ventilation : Use open structures or provide adequate ventilation systems 4.Disposal: Provision of effective vent stacks to dispose material 5. Emergent Equipment : Escape routes, rescue equipments, safety devices It is the duty of the designer to select a process that is inherently safe whenever it is practical, and economical, to do so. However, most chemical manufacturing processes are, to a greater or lesser extent, inherently safe, and dangerous situations can develop if the process deviates from the design values. Workers attitude to safety is very important and it depends on whole array of factors, ranging from social and religious background to his own circumstances and character. It can be said that usually workers themselves are not the driving force in accident prevention activities. Even in technically advanced countries where workers are relatively well off, tremendous efforts are required to make them safety minded. This seems to show that workers are seldom spontaneously interested in safety even though their lives are at stake. This situation can be improved by organizing safety committee which takes care of job safety.

64

CONCLUTION

65

CONCLUSION Terepthalic Acid is an important chemical of considerable value. As a component of a lot of polymers, it has grown to be a large volume synthetic organic chemical. Our project analyses the material abd energy balances involved in the process and also deal with the design and cost estimation aspects.

66

BIBLIOGRAPHY

67

BIBLIOGRAPHY (1) M. Gopala Rao and Marshall Sittig, “Dryden’s Outlines of Chemical Technology”, 2nd Ed., East-West press, Page No: 431-433. (2) Kirk-Othmer, “Encyclopaedia of Chemical Technology”, 5th Ed, Volume-1, John Wiley & Sons Inc., Page No: 286-290. (3) S.D Shukla and Pandey “A text book of chemical Technology”Vol-1, Inorganic (4) I.Mukhlyonov & I.Furmer, “The most important industrial chemical process” part-2 MIR publishers. (5) R. H. Perry and Don W. Green, “Perry’s Chemical Engineers’ Hand Book”, 6th and 7th Ed. Mc-Graw Hill International edition, (6) H.Sawistowski &W.smith, “Mass Transfer Process calculations”, Interscience publishers, Page No:54-99 (7) R. K. Sinnott, “Coulson and Richardson’s Chemical Engineering Series, volume-6, Chemical Equipment Design” 3rd Ed., Butter Worth-Heinemann, Page No: 828-855, 891-895 (8) Joshi M. V., “Process Equipment Design”, 2nd Ed., Mc-Millan India Ltd, (9) Max S. Peters and Klaus Timmerhaus, “Process Plant Design and Economics For Chemical Engineers”, 3rd Ed., Mc-Graw Hill Book Company, Page No: 207-208, 484-485. (10) Indian standard “Specification for Shell and Tube Heat Exchangers”, IS 4503-1967, Page No: 5-66

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Manufacture of Terepthalic Acid

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