Project-Production of Aniline

A Project Report on

PRODUCTION OF ANILINE

SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIRMENTS FOR THE AWARD OF THE DEGRE OF

BACHELOR OF TECHNOLOGY IN CHEMICAL ENGINEERING Submitted By Tejaswi Pothuganti (9626) V. Blessystella (9632) Mallikarjun Reddy G (9647) Mohith Nigam (9671) Under the Guidance of Mrs. Srivani, Associate Professor DEPARTMENT OF CHEMICAL ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY WARANGAL-506004 (A.P)

2012-2013

1

DEPARTMENT OF CHEMICAL ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY WARANGAL-506004

CERTIFICATE

This is to certify that the project entitled “Production of ANILINE” carried out by Ms. Tejaswi Pothuganti (9626), Ms. V. Blessystella (9632), Mr. Mallikarjun Reddy G (9647), Mr. Mohith Nigam (9671) of final year B.Tech Chemical Engineering during the year 20122013 is a bonafide work submitted to the National Institute of Technology, Warangal in partial fulfilment of requirements for the award of degree of Bachelor of Technology.

Project Guide Mrs. Srivani AssociateProfessor Dept. of Chemical Engineering NIT Warangal

Head of the Department Prof. Y Pydi Setty Professor Dept. Of Chemical Engineering NIT-Warangal

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ACKNOWLEDGEMENT We would like to express our deep sense of respect and gratitude toward our supervisor Mrs. K. Srivani, Associate Professor, Department of Electronics and Communication Engineering, National Institute of Technology, Warangal who not only guided the academic project work but also stood as a teacher. Her presence and optimism have provided an invaluable influence on my career and outlook for the future. We consider it as our good fortune to have got an opportunity to work with such a wonderful person. We express my gratitude to Prof. Y.Pydisetty, Head of Department of Chemical Engineering, Mr. Srinu Naik, Project In charge, Department of Chemical Engineering and its faculty members and staff for extending all possible help in carrying out the dissertation work directly or indirectly. They have been great source of inspiration to us and we thank them from bottom of my heart. We would like to acknowledge our institute, National Institute of Technology, Warangal, for providing good facilities to complete our thesis work. We would also like to take this opportunity to acknowledge our friends for their support and encouragement. We are especially indebted to our parents for their love, sacrifice and support.

Tejaswi Pothuganti (09626) V. Blessystella (09632) G. Mallikarjuna Reddy (09647) Mohit Nigam (09671)

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INDEX

Chapter No

Page no Chapter name

1

Introduction

1

2

Market Analysis

2

3

Uses

6

4

Physical & Chemical Properties

8

5

Different Manufacturing Process

14

6

Selection of Process

17

7

Process Description

18

8

Mass balance

22

9

Energy balance

35

10

Design of major Equipment

50

11

Cost estimation

80

12

Plant layout and location

84

13

Pollution control and Safety

89

14

Bibliography

94

4

1. INTRODUCTION: Aniline, phenylamine or aminobenzene is

an organic

compound with

the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors topolyurethane. Like most volatile amines, it possesses the somewhat unpleasant odour of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds. Aniline is colourless, but it slowly oxidizes and resinifies in air, giving a red-brown tint to aged samples.

From a historical perspective, aniline is perhaps one of the more important synthetic organic chemicals ever manufactured. In 1856, Sir William Henry Perkin, a student at the Royal College of Chemistry in London, discovered and isolated a purple dye during the oxidation of impure aniline. The discovery of this dye, known as mauve, created quite a stir and Perkin, seeing the value of his discovery, proceeded to scale up the synthetic process for the production of mauve, which included the synthesis of aniline. This process was to become one of the first commercial processes to generate a synthetic organic chemical. During the last three decades, polyurethane plastics have emerged as a growth industry and aniline once again plays a key role as an industrial intermediate used in the manufacture of MDI, 4,4’-diphenylmethane diisocyanate, a key commercial monomer in the manufacture of polyurethane plastics.

Aniline is produced by the reduction of nitrobenzene, which is produced from the nitration of benzene in a mixture of sulphuric and nitric acid.

5

2. MARKET ANALYSIS: MDI (Methylene Diphenyl Diisocyanate) production accounts for over 75% of world aniline consumption; other large applications include use as a chemical intermediate for rubberprocessing chemicals, dyes and pigments. Since most MDI producers are captive in aniline and its precursor nitrobenzene, typically in integrated units, nearly all MDI expansions result in increased production and consumption of nitrobenzene/aniline. MDI has been the driving force behind world growth in aniline demand since 1982. Future demand for aniline will continue to depend largely on MDI requirements.

MDI is consumed in polyurethane (PU) foam, both rigid and flexible. Most rigid PU foam is used in construction and appliances while flexible PU foam is used primarily in furniture and transportation. As a result, consumption of nitrobenzene/aniline/MDI largely follows the patterns of the leading world economies and depends heavily on construction/remodelling activity (residential and non-residential), automotive production and original equipment manufacturer. MDI growth has been driven by "green" initiatives, sustainability and lowering CO2 emissions. World consumption of aniline grew at an average annual rate of 3% during 2006–2010, the result of a growing global economy during 2001–2008, declines during the economic recession in 2009 and the recovery in 2010, and growth due to increased MDI capacity. Strong Asian demand for all applications of MDI boosted world demand during 2006–2010. World consumption of aniline is forecast to grow at an average annual rate of 3.8% during 2010–2015. Continuing rapid demand growth in some regions, particularly in China, Other 6

Asia

and

Europe,

mainly

the

result

of

continued

expansion

of

integrated

nitrobenzene/aniline/MDI units, will balance out moderate growth in markets such as the Americas. The aniline industry is a concentrated one, with most producers integrated into MDI production. BASF, Huntsman, Bayer and DuPont are the four dominant players, with about 17%, 12%, 12% and 10% of the world's capacity, respectively; only DuPont is not an MDI producer. BASF, Huntsman and Bayer each have plants in several world regions. 2.1. Supply/demand: Global capacity was 4.98m tonnes/year in 2006, with 1.62m tonnes/year in Western Europe, 1.38m tonnes/year in the US, 1.15m tonnes/year in Asia-Pacific (excluding Japan), 474,000 tonnes/year in Japan, 316,500 tonnes/year in Eastern Europe, 70,000 tonnes/year in Latin America and 64,000 tonnes/year in Asia/Middle East. Western Europe is the largest consumer, at about 1.32m tonnes/year, followed by the US at 1.19m tonnes/year and Asia-Pacific at 717,860 tonnes/year. Japan, Asia/Middle East and Latin America consume 319,190 tonnes/year, 98,360 tonnes/year and 73,130 tonnes/year, respectively. Global demand in 2006 was 3.95m tonnes/year. 2.2. Prices: There is a small merchant market and prices typically track benzene. European prices in the fourth quarter were €0.98-1.06/kg. November contracts in the US and Asia-Pacific were $0.62-0.68/lb and $1.29-1.40/kg, respectively. 2.3. Technology Most production is based on the catalytic hydrogenation of nitrobenzene, where benzene is mixed with a solution of nitric acid, hydrogenated and then purified by distillation. Another route, by SABIC/Sud-Chemie partnership Scientific Design, is the vapour phase ammonolysis ofphenol using excess ammonia and a silica-alumina catalyst, but this is now only used by Mitsui. 2.4. Outlook Global demand growth is put at 6%/year to 2010. Annual consumption will rise by 10.5% in Asia-Pacific, 6.5% in Asia/Middle East, 5.6% in Western Europe, 5.1% in the US, and 1.5% in Japan, respectively. Other world regions will grow by 3-4%/year. There is plenty of capacity until 2012. In China, Bayer will build a 247,000 tonne/year unit for 2009 and Yantai Wanhua's hike to 95,000 tonnes/year was due by late 2007. South

7

Korea's Kumho Mitsui will double output to 90,000 tonnes/year in 2009. Japan's Tosoh will expand to 300,000 tonnes/year by 2008. Karun Petrochemical plans a 30,000 tonne/year unit in Iran, for 2009. India's Hindustan Organic Chemicals may restart a 60,000 tonne/year unit by 2008 or later.

2.4. MAJOR GLOBAL ANILINE CAPACITY '000 TONNES/YEAR(Table-1) Company

Location

Capacity

BASF

Antwerp, Belgium

430

Geismar, Louisiana, US

264

Yeocheon, South Korea

60

Yeosu, South Korea

140

Antwerp, Belgium

140

Brunsbuttel, Germany

180

Krefeld, Germany

166

Sao Paulo, Brazil

60

Borsodchem

Ostrava, Czech Republic

150

Dow Chemical

Bohlen, Germany

130

Estarreja, Portugal

125

Baytown, Texas, US

250

Beaumont, Texas, US

150

Bayer

DuPont

Pascagoula, Mississippi, US 240 Huntsman

Geismar, Louisiana, US

460

8

Wilton, UK

450

Lanzhou Chemical Industry

Lanzhou, China

106

Shandong Haihua

Weifang, China

50

Shanghai Lianheng Isocyanate

Caojing, China

177

Shanxi Tianji Coal

Tianji, China

130

Singpu Chemicals

Yancheng, China

90

Sinopec Nanjing Chemical

Nanjing, China

135

Sumitomo Mitsui Chemical

Chiba, Japan

124

Sumitomo-Bayer

Kurosaki, Japan

100

Tosoh

Nanyo, Japan

150

Volzhskiy Orgsintez

Novomoskovsk, Russia

50

* excludes units under 50,000 tonnes/year SOURCE: CHEMPLAN BY TRANTECH CONSULTANTS

9

3. USES OF ANILINE: Aniline, an organic base used to make dyes, drugs, explosives, plastics, and photographic and rubber chemicals. Aniline, a primary aromatic amine, is a weak base and forms salts with mineral acids. In acidic solution, nitrous acid converts aniline into a diazonium salt that is an intermediate in the preparation of a great number of dyes and other organic compounds of commercial interest. When aniline is heated with organic acids, it gives amides, called ‘Anilides’, such as acetanilide from aniline and acetic acid. Monomethylaniline and dimethylaniline can be prepared from aniline and methyl alcohol. Catalytic reduction of aniline yields cyclohexylamine. Various oxidizing agents convert aniline to quinone, azobenzene, nitrosobenzene, p-aminophenol, and the phenazine dye aniline black. The great commercial value of aniline was due to the readiness with which it yields, directly or indirectly, dyestuffs. The discovery of mauve in 1856 by William Henry Perkin was the first of a series of dyestuffs that are now to be numbered by hundreds. Reference should be made to the articles dyeing, fuchsine, safranine, indulines, for more details on this subject. In addition to its use as a precursor to dyestuffs, it is a starting-product for the manufacture of many drugs, such as paracetamol (acetaminophen, Tylenol).It is used to stain neural RNA blue in the Nissl stain. At the present time, the largest market for aniline is preparation of methylene diphenyl diisocyanate (MDI), some 85% of aniline serving this market. Other uses include rubber processing chemicals (9%), herbicides (2%), and dyes and pigments (2%). When polymerized, aniline can be used as a type of nanowire for use as a semiconducting electrode bridge, most recently used for nano-scale devices such as biosensors. These polyanilineg nanowires can be doped with a dopant accordingly in order to achieve certain semiconducting properties. 3.1. Developments in medicine In the late 19th century, aniline emerged as an analgesic drug, its cardiac-suppressive side effects countered with caffeine.[11] In the 20th century's first decade, modifying synthetic dyes to treatsleeping sickness, Paul Ehrlich—who had coined the term chemotherapy for his magic bullet approach to medicine—failed and switched to modifying Béchamp's atoxyl, 10

the first organic arsenicaldrug, and serendipitously attained the syphilis treatment salvarsan, the first successful chemotherapy. Salvarsan's targeted microorganism, not yet recognized as bacteria, was still thought a parasite, however, and medical bacteriologists, believing bacteria not susceptible to the chemotherapeutic approach, overlooked Alexander Fleming's 1929 report on the in vitro effect ofpenicillin.[12] In 1932, Bayer sought medical applications of its dyes. Gerhard Domagk identified as antibacterial a red azo dye, introduced in 1935 as the first antibacterial drug, prontosil, rapidly found atPasteur Institute to be a prodrug degraded in vivo to sulfanilamide—a colorless intermediate for many, highly colorfast azo dyes—already off patent, synthesized in 1908 in Vienna by Paul Gelmofor his doctoral thesis.[12] By the 1940s, over 500 related sulfa drugs were produced.[12] In high demand via World War II (1939–45), these first miracle drugs, chemotherapy of wide effectiveness, propelled the American pharmaceutics industry.[13] In 1939, at Oxford University, seeking an alternative to sulfa drugs, Howard Florey developed Fleming's penicillin into the first systemicantibiotic drug, penicillin G. (Gramicidin, developed by René Dubos at Rockefeller Institute in 1939, was the first antibiotic,

yet

its

toxicity restricted

it

to topical use.)

After WWII, Cornelius

P.

Rhoads introduced the chemotherapeutic approach to cancer treatment.[14]

11

4. PHYSICAL& CHEMICAL PROPERTIES: 4.1. PHYSICAL PROPERTIES[1}:(Table-2) PROPERTY

VALUE

Molecular Formula

C6H7N

Molecular Weight

93.129

Boiling point, 0C 101.3 K Pa

184.4

4.4 K Pa

92

1.2 K Pa

71 0

Freezing Point C

-6.03

Density,liquid,g/mL

1.02173

Density,Vapor,(at bp,air=1)

3.30

Refractive Index

1.5863

Viscosity, mPa.s(=cP) 20 0C

4.35

60

1.62

Enthalpy of dissociation, kJ/mole

21.7

Heat of combustion, kJ/mole

3394

Ionisation potential, eV

7.70 0

Dielectric constant, at 25 C

6.89

Dipole moment at 250C,C.m

5.20*10-30

Specific heat at 250C,J/(g.K)

2.06

Heat of vaporization, J/g

478.5

Flash point,0C Closed cup

70

Open cup

75.5

Ignition Temperature, 0C

615

Lower flammable limit, vol %

1.3

Odour Threshold,ppm

2.4

Physical state and appearance

Liquid. (Oily liquid.)

12

Odour:

Aromatic. Amine like.

Taste:

Burning.

Water/Oil Dist. Coeff.

The product is more soluble in oil; log(oil/water) = 0.9

Critical Temperature

425.6°C (798.1°F)

4.2. CHEMICAL PROPERTIES[1]: Aromatic amines are usually weaker bases than aliphatic amines by the difference in P ka of the conjugate acids of aniline. Pka of Aniline is 4.63 and Pka of cyclo hexyl amine is 10.66. This is due to resonance effect. Aniline is stabilized by sharing its lone-pair electrons with the aromatic ring. Aromatic amines form addition compounds and complexes with many inorganic substances, such as Zinc chloride,copper chloride, Uranium Tetrachloride, or Boron Trifloride.Various metals react with amino group to form metal anilides; Hydrochloric, sulphuric, or Phosphoric acid salts of aniline are important intermediates in the dye industry. 4.2.1 N-alkylation[1]: A number of methods are available for preparation of N-alkyl and N,N-dialkyl derivatives of aromatic amines. Passing a mixture of aniline and methanol over a copper-zinc oxide catalyst at 2500C and 101 kPa reportedly gives N-methylaniline. Heating aniline with methanol under pressure or with excess methanol produces N,N-dimethylaniline. In the presence of sulphuric acid, aniline reacts with methanol to form N-methyl and N,N-dimethyl aniline. This is a two step process as shown. C6H5NH2 + CH3OH C6H5NHCH3 + H2O C6H5NHCH3 + CH3OH C6H5NH(CH3)2 + H2O

13

4.2.2. Ring Alkylation [1]: The aromatic ring undergoes alkylation under certain conditions. For example,2-ethylaniline, 2-6-diethylaniline, or mixture of the two are obtained in high yield when aniline is heated with ethylene in the presence of aluminium-anilide catalyst(formed by heating aluminium and aniline) at 3300 C and 4-5 MPa. 4.2.3. Acylation [1]: Aromatic amines react with acids, acid chlorides, anhydrides, and esters to form amides.In general,acid chlorides give the best yield of the pure product. The reaction with acetic,propionic,butanoic, or benzoic acid can be catalysed with phosphorous oxychloride or trichloride. N-Phenylsuccinimide (succanil) is obtained in essentially quantitative yield by heating equivalent amounts of succinic acid and aniline at 140-1500C. the reaction of a primary aromatic amine with phosgene leads to formation of an arylcarbamoyl chloride, that when heated loses hydrogen chloride to form isocyanate. Commercially important isocyanates are obtained from aromatic primary diamines. Conversion of aniline to acetanilide, by reaction with acetic anhydride, is a convenient method for protecting the amino group. The acetyl group can later be removed by acid or base hydrolysis. 4.2.4. Condensation [1]: Depending on the reaction conditions, a variety of condensation products are obtained from the reaction of aromatic amines with aldehydes, ketones, acetals, and orthoformates. Primary aromatic amines react with aldehydes to form Schiff bases. Schiff bases formed from the reaction of lower aliphatic aldehydes, such as formaldehyde and acetaldehyde, with primary aromatic amines are often unstable and polymerize readily. Aniline reacts with formaldehyde in aqueous acid solutions to yield mixtures of a crystalline trimer of the Schiff base, methylenedianilines, and polymers.

14

4.2.5. Cyclization [1]: Aniline, nitrobenzene, and glycerol react under acid catalysis (Skraup synthesis) to form quinolone. The Skraup synthesis is a chemical reaction used to synthesize quinolines. It is named after the Czech chemist Zdenko Hans Skraup (1850-1910). In the archetypal Skraup, aniline is heated with sulfuric acid, glycerol, and an oxidizing agent,likenitrobenzene to yield quinoline.

In this example, nitrobenzene serves as both the solvent and the oxidizing agent. The reaction, which otherwise has a reputation for being violent ("the Chemical Inquisition"), is typically conducted in the presence of ferrous sulphate.Arsenic acid may be used instead of nitrobenzene and the former is better since the reaction is less violent.

15

4.2.6. Halogenation [1]: The presence of the amino group activates the ortho and para positions of the aromatic ring and, as a result, aniline reacts readily with bromine or chlorine. Under mild conditions, bromination yields 2,4,6- tribromoaniline.

4.2.7. Oxidation [1]: Aniline was selectively converted into the corresponding nitrosobenzene and nitrobenzene by oxidation with 30% aqueous hydrogen peroxide. The reaction was catalyzed by various heteropolyoxometalates, at room temperature, in dichloromethane under two-phase conditions. Findings show that H3PW12O40 is the best catalyst in the oxidation of aniline. Na3PW9Mo3O40 and K4SiW9Mo2O39 also displayed high reactivity in the oxygenation system. Phase transfer agents and temperature increase also contribute to the efficiency of the oxidation 4.2.8.ReactivityProfile[1]: Aniline is a heat sensitive base. Combines with acids to form salts. Dissolves alkali metals or alkaline earth metals with evolution of hydrogen. Incompatible with albumin, solutions of iron, zinc and aluminum, and acids. Couples readily with phenols and aromatic amines. Easily acylated and alkylated. Corrosive to copper and copper alloys. Can react vigorously with oxidizing materials (including perchloric acid, fuming nitric acid, sodium peroxide and ozone). Reacts violently with BCl3. Mixtures with toluene diisocyanate may ignite. Undergoes explosive reactions with benzenediazonium-2-carboxylate, dibenzoyl peroxide, fluorine nitrate, nitrosyl perchlorate, peroxodisulfuric acid and tetranitromethane. Violent reactions may occur with peroxyformic acid, diisopropyl peroxydicarbonate, fluorine, trichloronitromethane (293° F), acetic anhydride, chlorosulfonic acid, hexachloromelamine, (HNO3 + N2O4 + H2SO4), (nitrobenzene + glycerin), oleum, (HCHO + HClO4), perchromates, K2O2, beta-propiolactone, AgClO4, Na2O2, H2SO4, trichloromelamine, acids, FO3Cl, diisopropyl peroxy-dicarbonate, n-haloimides and trichloronitromethane. 16

Ignites on contact with sodium peroxide + water. Forms heat or shock sensitive explosive mixtures with anilinium chloride (detonates at 464° F/7.6 bar), nitromethane, hydrogen peroxide, 1-chloro-2,3-epoxypropane and peroxomonosulfuric acid. It reacts with perchloryl fluoride form explosive products. .

17

5. DIFFERENT WAYS OF PRODUCTION: 5.1. From Nitrobenzene: Nitrobenzene is the classical feedstock for Aniline manufacture. Recently less Chlorobenzene and Phenol are being used in aniline manufacturing processes in several countries. The reduction of nitrobenzene with iron turnings and water in the presence of small amounts of hydrochloric acid is the oldest form of industrial aniline manufacture. It would certainly have been replaced much earlier by more economical reduction methods if it had not been possible to obtain valuable iron oxide pigments from the resulting iron oxide sludge. However, the increasing demand for aniline has far surpassed the market for the pigments, so that not only catalytic hydrogenation processes (both liquid- and gas-phase) but also other feed stocks have been used for aniline production. The modern catalytic gas-phase hydrogenation processes for nitrobenzene can be carried out using a fixed-bed or a fluidized-bed reactor:

Rayer and Allied work with nickel sulfide catalysts at 300-475 °C in a fixed bed. The activation of the hydrogenation catalysts with Cu or Cr, and the use of different supports and catalyst sulfidization methods with sulfate, H2S or CS2 all belong to the expertise of the corresponding firms. The selectivity to aniline is more than 99%. The catalytic activity slowly decreases due to carbon deposition. However, the catalyst can be regenerated with air at 250-350°C and subsequent H2 treatment. Similar processes are operated by Lonza with Cu on pumice, by ICI with Cu, Mn, or Fe catalysts with various modifications involving other metals, and by Sumitomo with a Cu-Cr system. The gas-phase hydrogenation of nitrobenzene with a fluidized-bed catalyst is used in processes from BASF, Cyanamid and Lonza. The BASF catalyst consists of Cu, Cr, Ba, and Zn oxides on a SiO2 support; the Cyanamid catalyst consists of Cu/SiO2. The hydrogenation is conducted at 270-290 °C and 1-5 bar in the presence of a large excess of hydrogen (H2:Nitrobenzene=ca. 9:1). The high heat of reaction is removed by a cooling system which 18

is built into the fluidized bed. The selectivity to aniline is 99.5%; the nitrobenzene conversion is quantitative. The catalyst must be regenerated with air periodically. 5.2. From Chlorobenzene: An alternate manufacturing route for aniline is the ammonolysis of chlorobenzene or of phenol. For example, in the Kanto Electrochemical Co. process, chlorobenzene is ammonolyred to aniline with aqueous NH3 at 180-220 °C and 60-75 bar in the presence of Cucl and NH3Cl (Niewland catalyst).

Aniline can be isolated with 91 % selectivity from the organic phase of the two-phasereaction product. 5.3.From Phenol: Dow stopped operation of a similar process for aniline in 1966. Phenol can also be subjected to gas-phase ammonolysis with the Halcon/Scientific Design process at 200 bar and 425 °C:

Al2O3.SiO2 (possible as zeolites) and oxide mixtures of Mg, B, Al, and Ti are used as catalysts; these can be combined with additional co catalysts such as Ce,V, or W. The catalyst regeneration required previously is not necessary with the newly developed catalyst. With a large excess of NH3, the selectivity to aniline is 87-90% at a phenol conversion of 98%. The byproducts are diphenylamine and carbazole. This process has been operated since 1970 by Mitsui Petrochemical in a plant which has since been expanded to 45 000 tonnes per year. A second plant with a capacity of 90000 tonnes per year was started up by US Steel Corp. (now Aristech) in 1982. 5.4. From Benzene: Du Pont has developed an interesting manufacturing process for aniline. Benzene and NH3 can be reacted over a NiO/Ni catalyst containing promoters including zirconium oxide at

19

350°C & 300 bar to give a 97% selectivity to aniline with benzene conversion of 13%

Since the hydrogen formed in the reaction reduces the NiO part of the catalyst, a catalyst regeneration (partial oxidation) is necessary. Despite inexpensive feedstocks, industrial implementation is still thwarted by the low benzene conversion and the necessary catalyst re-oxidation.

20

6. CHOICE OF PROCESS: The catalytic Hydrogenation of Nitrobenzene to Aniline gives selectivity more than 99%, better than other manufacturing processes. Nitrobenzene is the classical feedstock for Aniline manufacture. The method process is simple, inexpensive catalysts, long life, from product quality, After preheating the hydrogen and nitrobenzene, hydrogenation reaction occurs. Fixed bed gas phase catalytic hydrogenation process has a matured technology, the reaction temperature is lower, equipment has easy operation, low maintenance costs, less investment, without separation of catalyst, good product quality; deficiency is, the reaction pressure is more prone to occurrence of local side effects caused by overheating and catalyst deactivation, the catalyst must be periodically replaced. Currently, most foreign manufacturers of fixed-bed use gas phase aniline hydrogenation process.

21

7. PROCESS DESCRIPTION Rayer and Allied work with nickel sulphide catalysts at 300-475 °C in a fixed bed. The activation of the hydrogenation catalysts with Cu or Cr, and the use of different supports and catalyst sulfidization methods with sulphate, H2S or CS2 all belong to the expertise of the corresponding firms. The selectivity to aniline is more than 99%. The catalytic activity slowly decreases due to carbon deposition. However, the catalyst can be regenerated with air at 250-350°C and subsequent H2 treatment. Similar processes are operated by Lonza with Cu on pumice, by ICI with Cu, Mn, or Fe catalysts with various modifications involving other metals, and by Sumitomo with a Cu-Cr system.

Table 3: Physical properties for aniline and water [2] Aniline

Water

Chemical Formula

C6H7N

H2O

(Mw) (g/mol)

93.128

18.015

Tb(K)

457.15

373.15

Tm(K)

267.13

273.15

Antoine A

7.43481

8.02927

Antoine B(◦C)

1813.917

1713.681

Antoine C(◦C)

213.709

232.633

Vapor pressure A

66.287

73.649

Vapor pressure B(K)

-8207.1

-7258.2

Vapor pressure C

-6.0132

-7.3037

Vapor pressure D

2.84 ·

4.17 ·

10−18

10−6

Vapor pressure E

6

2

Density A(kmol)

1.0405

5.459

Density B(m3)

0.2807

0.30542

Density C(K)

699.0

647.13

Density D

0.29236

0.081

22

23

Antoine equation: Liquid–liquid Properties If liquid–liquid extraction is to be performed, the liquid–liquid equilibrium behaviour must be known. An important liquid–liquid temperature dependent property is the solubility. From Sørensen et al. (14) mol percents representing aniline dissolved in water and water dissolved in aniline are shown in table. Table 4: Solubility of aniline in water and water in aniline[2] Temperature(◦C)

Mol percent aniline

Mol percent water

20.0

0.674

21.3

25.0

0.679

21.8

Weight percent aniline

Weight percent water

20.0

3.39

4.98

25.0

3.41

5.12

The solubility of aniline dissolved in water from table 2.2 show that water is more soluble in aniline than aniline is in water Vapor–Liquid Properties : If distillation separation is to be used to separate the mixture, the vapor–liquid behaviour must be known, and because the aniline–water system does not behave ideally, the activity coefficients are of interest. From Gmehling et al (2) the Margules, van Laar, Wilson, NRTL and UNIQUAC model parameters are listed in table 2.3.

24

Table 5: Model Parameters and γi∞ for different models[2] A12

A21

Margules

1.0041

3.1217

2.73

Van Laar

1.2006

8.3006

3.32 4026.37

Wilson

1608.4375

2513.9461

NRTL

6945.2299 -

22.68

3.11

229.00

3.68

104.01

3.49

554.62

2651.2199 UNIQUAC 1439.0048

-379.5945

In table 5 index 1 represents water and index 2 aniline. All the methods show that

, which is consistent with table 2.2, which shows that

aniline is less soluble in water than water is in aniline. The large γ2∞ found by the Van Laar model is not a typing error, and therefore a strong confirmation of the low solubility of aniline in water. Investigations of a VLE–diagram show that an azeotrope exists for the aniline–water binary system. Horyna et al (16) have found the azeotrope to be at a water weight fraction of x1 = 0.808 (water mol fraction of 0.956) and a temperature of 98.6◦C, at a pressure of 742mmHg. A VLE–diagram estimated using the VLE UNIFAC model at 760mmHg in SMSWIN is shown in figure 2.1 to the right. It is similar to the proportional diagram from Gmehling et al (2), the diagram to the left. Both diagrams show an azeotrope at the weight fraction x1 ≈ 0.96, corresponding to the one determined by Horyna et al, indicating that the VLE UNIFAC model is a good approximating for the vapor–liquid behaviour of a aniline–water binary system.

Figure 1: VLE diagrams for the binary aniline/water system at 1atm. The left diagram is experimentally determined, and the right is estimated using the VLE UNIFAC model[2]. 25

An estimated number of the distillation stages needed to perform the distillations in figure 1 can be found using the Margules equations from Smith et al. (13). The Margules equations represent a commonly used empirical model of solution behaviour and are defined as lnγ1 = x22 [A12 + 2(A21 − A12)x1] lnγ2 = x21 [A21 + 2(A12 − A21)x2]

(3.2)

From the values of A12 and A21 given in table 2.3, the activity coefficients can be determined, and in relation to the vapor pressures, the relative volatility can be determined as done by King (4)

26

27

8. MASS BALANCE: Basis: Production of Aniline (99.5% purity) is 218788.529 tons/year. Assumptions: 

No of plant working days=300 days



100% conversion of Nitrobenzene.



200% excess of Hydrogen is used.



Reactants are pure.

Average molecular weight=0.995*93.1262+0.005*18.0152=92.7506. So, 218788.529 tons per year =30387.29578 kg/hr =327.623 kmol/hr. Based amount of Nitrobenzene required is

=326.632 kmol/hr, =326.632*123.1092, =40211.40421 kg/hr.

The ratio of Hydrogen to Nitrobenzene is= 9:1 Amount of hydrogen required =9*326.632 =2939.688 kmol/hr =5925.82307 kg/hr. Hydrogen from recycle =6*326.632 =1959.792 kmol/hr

=3950.548714 kg/hr.

Fresh feed of Hydrogen= 3*326.632 =979.896 kmol/hr

=1975.274356 kg/hr.

Mass balance for Vaporiser: Stream1A: Pure Nitrobenzene feed in liquid phase=326.632 kmol/hr

=40211.40421 kg/hr

Stream1B: Nitrobenzene from vaporizer in vapor phase=326.632 kmol/hr

=40211.40421 kg/hr

28

Mass balance for the reactor:

Stream1B: Nitrobenzene from vaporizer in vapor phase=326.632 kmol/hr

=40211.40421 kg/hr 29

Stream2: Fresh Hydrogen feed=979.896 kmol/hr = 1975.27436 kg/hr. Stream3: Makeup Hydrogen or recycle=1959.792 kmol/hr = 3950.54871 kg/hr. Stream4: Total amount of Hydrogen

=2939.688 kmol/hr = 5925.82307 kg/hr.

Stream5: Nitrobenzene vapor stream=40211.40421 kg/hr Total Hydrogen feed to the reactor=5925.82307 kg/hr Total feed to Fluidized bed reactor =46137.22728 kg/hr Stream6: Product stream consists of Aniline, water and unreacted Hydrogen, all in vapor phase. Aniline=326.632 kmol/hr = 30417.99696 kg/hr Water=653.264 kmol/hr = 11768.68161 kg/hr Unreacted Hydrogen = 1959.792 kmol/hr = 3950.54871 kg/hr. Table 6: Flow

IN

OUT

Component

Stream 1B(kg/hr) Stream 2(kg/hr) Stream 4(kg/hr)

Stream 6(kg/hr)

Nitrobenzene

40211.40421

---

---

---

Hydrogen

---

1975.27436

3950.54871

3950.54871

Water

---

---

---

11768.68161

Aniline

---

---

---

30417.99696

40211.40421

1975.274356

3950.548714

TOTAL(kg/hr) TOTAL(kg/hr)

46137.22728

46137.22728 46137.22728

30

Mass Balance for the condenser:

Stream6: Reactor Product stream consists of Aniline, water and unreacted Hydrogen, all in vapor phase. Aniline=326.632 kmol/hr

=30417.99696 kg/hr

Water=653.264 kmol/hr

=11768.68161 kg/hr

Unreacted Hydrogen=1959.792 kmol/hr

=3950.54871 kg/hr.

Stream3: Makeup or unreacted Hydrogen or recycle=1959.792 kmol/hr

=3950.54871kg/hr.

Stream7: Consists of condensed Water and Aniline. Aniline=326.632 kmol/hr

=30417.99696 kg/hr

Water=653.264 kmol/hr

=11768.68161 kg/hr

31

Table 7: Flow

IN

OUT

Component

Stream 6(kg/hr)

Stream 3(kg/hr)

Stream 7(kg/hr)

---

---

---

Hydrogen

3950.548714

3950.54871

---

Water

11768.68161

---

11768.68161

Aniline

30417.99696

---

30417.99696

Total (kg/hr)

46137.22728

3950.54871

42186.67857

Nitrobenzene

OUT

Mass balance for the Decanter:

Stream7: Consists of condensed Water and Aniline. Aniline=326.632 kmol/hr =30417.99696 kg/hr Water=653.264 kmol/hr =11768.68161 kg/hr Stream 12: Water=32698.53348 kg/hr

32

Aniline=7042.02739 kg/hr Stream13: Water=5117.73724 kg/hr Aniline=1392.55056kg/hr Stream9: Water=44437.73942 kg/hr Aniline=7102.20424kg/hr Stream 10: Water =5147.21291kg/hr Aniline=31750.37067kg/hr Table 7 Flow

IN

OUT

OUT

Stream

Stream

Stream

Stream

Stream

7(kg/hr)

12(kg/hr)

13(kg/hr)

9(kg/hr)

10(kg/hr)

Nitrobenzene

---

---

---

---

---

Hydrogen

---

---

---

---

---

Component

5147.21291 Water

11768.68161 32698.53348

5117.73724

44437.73942 31750.37067

Aniline

30417.99696

7042.02739

1392.55056

7102.20424

TOTAL(kg/hr)

42186.67857 39740.56087

6510.28780

51539.94366

TOTAL(kg/hr)

88437.52724

36897.58358

88437.52724

Mass balance for the distillation column 1:

33

Stream9: Water=44437.73942 kg/hr Aniline=7102.20424kg/hr Stream 11: Water =11739.20594 kg/hr Aniline=60.17685 kg/hr Stream 12: Water =32698.53348 kg/hr. Aniline=7042.02739 kg/hr

34

Table 8: Flow

IN

Component

Stream 9(kg/hr)

Nitrobenzene

OUT

OUT

Stream 11(kg/hr) Stream 12(kg/hr)

---

---

---

Hydrogen

---

---

---

Water

44437.73942

11739.20594

32698.53348

Aniline

7102.20424

60.17685

7042.02739

Total (kg/hr)

51539.94366

11799.38279

39740.56087

Mass balance for Distillation column2:

Stream 10: Water =5147.21291 kg/hr Aniline=31750.37067 kg/hr Stream13: Distillate stream enriched with water Aniline=1392.55056kg/hr 35

Water=5117.73724 kg/hr Stream14: Bottom stream enriched with Aniline Aniline=30387.29578 kg/hr Water=29.47567 kg/hr Table 9: Flow

IN

Component

Stream 10(kg/hr)

Nitrobenzene

OUT

OUT

Stream 13(kg/hr) Stream 14(kg/hr)

---

---

---

Hydrogen

---

---

---

Water

5147.21291

5117.73724

29.47567

Aniline

31750.37067

1392.55056

30387.29578

Total (kg/hr)

36897.58358

6510.28780

30387.29578

36

37

9. DETAILED ENERGY BALANCE Heat capacity data: Nitrobenzene = 1.4 kj/kg.K Hydrogen[5] = 6.62+ 0.00081T(K) cal/mol.K = 13.727+0.00168T kj/kg.K Aniline[5] =1.415℮5 + 1.712℮2T j/kmol.K Water in liquid phase[6] = (8.712 +1.25*10-3T -0.18*10-6T2)*R Water in gas phase[6] = (3.470 + 1.45*10-3T+0.121/T2)*R Energy balance for the Nitrobenzene vaporizer:

Heat in:

38

Nitrobenzene is at room temperature of 298 K. So enthalpy in =0 Heat out: Nitrobenzene is heated from 298 to 553.15 K Enthalpy associated with Nitrobenzene = m ∫ + m ∆Hv +∫ Enthalpy of vaporization of Nitrobenzene ∆Hv =33 kj/kg. Enthalpy associated with Nitrobenzene +40211.40421*33 +∫

= 40211.40421*∫

kj/hr

=19631609.7 kj/hr Heat supplied by the Vaporizer=enthalpy out-enthalpy in =15690892.1+3940717.6 =19631609.7 kj/hr Table 10: Flow

IN

IN

OUT

Heat supplied Component

Stream1A (kj/hr)

(kj/hr)

Stream1B (kj/hr)

0

19631609.7

19631609.7

Hydrogen

---

---

---

Water

---

---

0

Aniline

---

---

0

Total (kg/hr)

0

19631609.7

19631609.7

Nitrobenzene

39

Energy balance for the reactor:

Heat in: Enthalpy in with Nitrobenzene=19631609.7kj/hr Enthalpy in with Hydrogen=

∫

kj/hr

=5925.82307*∫ =27939805.8 kj/hr Total enthalpy in=19631609.7 +27939805.8 =47571415.5 kj/hr Heat Generated :

Heat generated by reaction = 443 kj/mol=443000 kj/kmol Total heat generated = 443000*326.632 = 144697976 kj/hr 40

Heat removed by Coolant : The temperature in the reactor reaches an average peak temperature of 700 K due to exothermic reaction. ∆Hf0298 of Aniline=31.3 kj/mol=31300 kj/kmol Heat with Aniline

=m∫

+ m ∆Hv

= (42440+10-3 ∫

)*m

=14718691 kj/hr Heat with Water= m ∫

+ m ∆Hv =m∫

+m∫

+ m ∆Hv

=979.896*(40680+∫ +∫

)

=979.896*(40680+5692.6+11543.7) =979.896*57916.3 = 56751950.7 kj/hr Heat with Hydrogen= m ∫ =3950.54871*∫ =26697609.23 kj/hr Total enthalpy out due to products=14718691+56751950.7 +26697609.23 =98168250.93 kj/hr Total heat removed by the Coolant = Total enthalpy in-total enthalpy out+total heat generated by the reaction = 47571415.5 -98168250.93 +144697976 = 94101140.57 kj/kg

41

Table 11: Flow

IN

OUT Heat removed

Component

Stream1B (kj/hr)

Stream4 (kj/hr)

Stream6 (kj/hr)

Stream (kj/hr)

19631609.7

---

---

---

Hydrogen

---

27939805.8

26697609.23

Water

---

---

56751950.7

Aniline

---

---

14718691

19631609.7

27939805.8

98168250.93

Nitrobenzene

TOTAL(kg/hr) TOTAL(kg/hr)

47571415.5

94101140.57

98168250.93

Energy Balance for the condenser:

Enthalpy in: Heat with Aniline =14718691 kj/hr Heat with Water= 56751950.7 kj/hr Heat with Hydrogen= 26697609.23 kj/hr Total enthalpy in due to products = 14718691+56751950.7 +26697609.23 =98168250.93 kj/hr Enthalpy out: As condenser removes the latent heat and sensible heat in gas phase, all streams are cooled to bubble point of Aniline and Water mixture which is 371.69 K. 42

So, Enthalpy with aniline=326.632*10-3*∫ =107008.6 kj/hr Enthalpy with water =979.896

*(∫

)

=5469289.4 kj/hr Enthalpy with Hydrogen= m ∫ =3950.54871*∫ =4159912.7 kj/hr Total enthalpy out=107008.6+5469289.4+4159912.7=9736210.7 kj/hr Heat removed by condenser=387779355.3-98168250.93 =289611104.4 kj/hr.

Table 12: Flow

IN

OUT

OUT

Heat Removed Component

Stream6 (kj/hr)

Stream (kj/hr)

Stream7 (kj/hr)

Nitrobenzene

---

---

---

Hydrogen

14718691

---

4159912.7

Water

56751950.7

---

5469289.4

---

107008.6

289611104.4

9736210.7

Aniline Total (kg/hr)

26697609.23 98168250.93

Energy balance for the pre-cooler: This heat exchanger removes heat such that temperature of the stream is reduced to 303.15 K from 371.69 K. Enthalpy in: Enthalpy with aniline = 107008.6 kj/hr Enthalpy with water

= 5469289.4 kj/hr

Total enthalpy out

= 107008.6+5469289.4 = 5576298 kj/hr 43

Enthalpy out: So, enthalpy with aniline = 326.632*10-3*∫ = 6947.3 kj/hr Enthalpy with water *(∫

= 979.896

)

= 380604.8 kj/hr Total enthalpy out = 6947.3 +380604.8 = 387552.1 kj/hr Heat removed by the heat exchanger = 5576298-387552.1 = 5188745.9 kj/hr

Energy balance for the decanter:

So, stream 7: enthalpy with aniline = 6947.3 kj/hr Enthalpy with water =380604.8 kj/hr Total enthalpy in=6947.3 +380604.8 =387552.1 kj/hr Stream 12: Water=32698.53348 kg/hr =1815.052 kmol/hr Aniline=7042.02739 kg/hr =75.62 kmol/hr Enthalpy with aniline = 75.62 *10-3*∫ =1562.56 kj/hr Enthalpy with water =

*(∫ 44

= 704990.6 kj/hr Total enthalpy =1562.56+704990.6=706553.16 kj/hr Stream13: Water=5117.73724 kg/hr =284.08 kmol/hr Aniline=1392.55056kg/hr =14.95 kmol/hr Enthalpy with aniline =14.95 *10-3*∫ =308.92 kj/hr Enthalpy with water =(284.08)

*(∫

=110340.49 kj/hr Total enthalpy=308.92+110340.49=110649.41 kj/hr Enthalpy out: Stream9: Water = 44437.73942 kg/hr = 2466.68 kmol/hr Aniline =7102.20424kg/hr =76.26 kmol/hr Enthalpy with aniline = 76.26 *10-3*∫ = 1575.79 kj/hr Enthalpy with water =2466.68 *

*(∫

=958091.68 kj/hr Total enthalpy=1575.79+958091.68=959666.79 kj/hr Stream 10: Water =5147.21291kg/hr =285.72 kmol/hr Aniline =31750.37067kg/hr =340.94 kmol/hr Enthalpy with aniline =340.94 *10-3*∫

45

=7044.96 kj/hr Enthalpy with water =285.72 *

*(∫

=110977.49 Total enthalpy = 7044.96+110977.49 =118022.45 kj/hr Table 13:

Flow

Component

IN

IN

IN

OUT

OUT

Stream

Stream

Stream

Stream

Stream

7(kj/hr)

12(kj/hr)

13(kj/hr)

9(kj/hr)

10(kj/hr)

Nitrobenzene

---

---

---

---

---

Hydrogen

---

---

---

---

---

Water

380604.8

704990.6

110340.49

958091.68

110977.49

Aniline

6947.3

1562.56

308.92

1575.79

7044.96

Total (kg/hr)

387552.1

706553.16

110649.41

959666.79

118022.45

Energy balance for distillation column-1:

46

Enthalpy in: Stream9: Water =44437.73942 kg/hr =2466.68 kmol/hr Aniline =7102.20424kg/hr

=76.26 kmol/hr

Enthalpy with aniline =76.26 *10-3*∫ =26474.61 kj/hr Enthalpy with water =2466.68 *

*(∫

=14511181.32 kj/hr Total enthalpy=26474.61 +14511181.32 =14537655.93 kj/hr Enthalpy out: Stream 11: Water =11739.20594 kg/hr =651.628 kmol/hr Aniline =60.17685 kg/hr =0.646 kmol/hr Enthalpy with aniline =0.646 *10-3*∫ =216.6 kj/hr Enthalpy with water = 651.628 *

*(∫

=3714415.04 kj/hr Total enthalpy=216.6+3714415.04=3714631.64 kj/hr Stream 12: Water =32698.53348 kg/hr =1815.052 kmol/hr Aniline =7042.02739 kg/hr =75.618 kmol/hr Enthalpy with aniline =75.618 *10-3*∫ =26589.81 kj/hr Enthalpy with water

47

=1815.052 *

*(∫

=10802091.76 kj/hr Total enthalpy =26589.81+10802091.76 = 10828681.57 kj/hr Total enthalpy out=3714631.64+10828681.57=14543313.21 kj/hr Heat supplied by the distillation column=14543313.21-14537655.93=5657.28 kj/hr Table 14: Flow

IN

OUT

Component

Stream (kj/hr)

Stream (kj/hr)

Stream (kj/hr)

---

---

---

Hydrogen

---

---

---

Water

14511181.32

3714415.04

10802091.76

216.6

26589.81

3714631.64

10828681.57

Nitrobenzene

Aniline Total (kg/hr)

26474.61 14537655.93 14537655.93

OUT

14543313.21

Energy balance for distillation column-2:

48

Enthalpy in: Stream 10: Water = 5147.21291kg/hr =285.72 kmol/hr Aniline=31750.37067kg/hr=340.94 kmol/hr Enthalpy with aniline =340.94 *10-3*∫ =195845.11 kj/hr Enthalpy with water =285.72 *

*(∫

=2627299.22 kj/hr Total enthalpy=195845.11+2627299.22 =2823144.33 kj/hr Enthalpy out: Stream13: Distillate stream enriched with water Aniline = 1392.55056kg/hr=14.953 kmol/hr Water = 5117.73724 kg/hr=284.079 kmol/hr Enthalpy with aniline=14.953 *10-3*∫ =5317.53 kj/hr Enthalpy with water =284.079 *

*(∫

=1707969.4 kj/hr Total enthalpy=5317.53+1707969.4=1713286.93 kj/hr Stream14: Bottom stream enriched with Aniline Aniline=30387.29578 kg/hr=326.302 kmol/hr Water=29.47567 kg/hr=1.636 kmol/hr

49

Enthalpy with aniline= 326.302 *10-3*∫ = 259532.9 kj/hr Enthalpy with water =1.636 *

*(∫

=9836.13 kj/hr Total enthalpy = 259532.9 +9836.13 = 269369.03 kj/hr Total enthalpy out from distillation column=1713286.93+269369.03 =1982655.96 kj/hr Total heat removed by distillation column =1982655.96-2823144.33 =-840488.37 kj/hr Table 15: Flow

IN

OUT

Component

Stream (kj/hr)

Stream (kj/hr)

Stream (kj/hr)

---

---

---

Hydrogen

---

---

---

Water

2627299.22

1707969.4

9836.13

5317.53

259532.9

1713286.93

269369.03

Nitrobenzene

Aniline Total (kg/hr)

195845.11 2823144.33 2823144.33

OUT

1982655.96

50

10. DESIGN OF EQUIPMENTS Symbols used in design of Shell and Tube heat exchanger: A - heat transfer area, m2 or ft2 B - baffle spacing, in cp - specific heat at constant pressure, J/g oC or Btu/lb oF C- clearance, in hi -heat-transfer coefficient for inside of tube ,W/m2 oC or Btu/ft2 oF h hio -heat-transfer coefficient for outside of tube, W/m2 oC or Btu/ft2 oF h ho - shell side heat-transfer coefficient, W/m2 oC or Btu/ft2 oF h G - mass velocity, kg/m2 s or lb/ft2h K -thermal conductivity , W/m oC LMTD -logarithmic mean temperature difference PT – tube pitch, in Q - quantity of heat, J or Btu Re – Reynolds number U - overall heat-transfer coefficient, W/m2 oC or Btu/ft2 oF h

51

10.1 DESIGN OF SHELL AND TUBE HEAT EXCHANGER Cold Fluid Data: Inlet Temperature t1=21 oC =69.8 oF Outlet Temperature t2=210 oC =410 oF Weight flow w=40211.4021 kg/hr Calculation of Heat load: Qh= m Cp ∆T = 40211.4021*1.4*(210-25) =10414753.14 kg/hr Qc= m Cp ∆T m= Qc/(Cp ∆T) = 10414753.14/(∆H) =10414753.14/(2801.5-2643.7) =65999.7 Kg Hot Fluid data: Inlet Temperature T1=250oC Outlet Temperature T2=80oF Weight flow W=65999.7 kg/hr Calculation of ∆TLMTD: ∆TLMTD= ∆T1-∆T2 / ln(∆T1/∆T2) ∆TLMTD= 47.10oF Calculation of R and S values: R= (T2-T1)/(t2-t1) 52

= 0.918 S = (t2-t1)/(T2-t1) = 0.822 Calculation of Correction Factor: FT is found using LMTD correction factor curves From Graph we get, FT=0.845 The values of R and S satisfy with Correction factor value for 4-8 shell and tube heat exchanger. This may be met by four 1-2 exchangers in series or two 2-4 exchangers in series. ∆tln= ∆TLMTD*FT = 47.1*0.845 = 39.79ᴼF Calculation of ud From the literature the UD value of Nitrobenzene ranges from 60-90 W/m2K Assume a value of UD Let the value of UD be 80 Calculation of heat transfer area A= Q/ UD*∆t = 9871279.951/(80*39.79) = 3101.05 ft2 Length of the tube L=16’0’’(3/4 in.OD,16BWG)-Square pitch From the table, Flow area per tube a’t=0.302in2 Outside area per linear ft a’’=0.1963 ft2 Tube inside diameter D=0.62 in (Obtained from tables) 53

No. of tubes per shell, Nt= Heat transfer area/(No. of shell side passes* total surface area) Nt= 3101.05/(2*16*0.1963) = 493.67 = 494 tubes For 4 passes, 3/4in.OD on 1-in. Square pitch (from the table),Nearest count(from 494 tubes): 480 tubes in a 29in.ID shell Calculation of corrected UD: Ud,corr = Q/A* ∆ T LMTD. A= No. of passes * No. of tubes * Length of the tube * Outside area = 2* 480* 16* 0.1963 =3015.16 ft2 UD= Q/(A*∆T) =9871279.951/(3015.16*39.79) =82.27 Tube side Calculation: at = Nt * at/(144n) =480* 0.302/(144*4) = 0.252 ft2 Mass velocity: Gt = w/ at = 65999.7/(0454*0.252) =576880.11 lb/ hr ft2 At Tavg= 180ᴼC 54

Ret = D*Gt / µ Tube inside diameter = D = 0.62in = 0.62/12 =0.0517 Ret = 0.0517*576880.11/(0.0375) =795325.37 J factor for heat transfer curve jH At L/D = 16/0.0517 jH = 750 Cp = 0.47 btu/lb K = 0.0187 btu/ hr.ft2. ᴼF hi = jH *(K/D)*(Cµ/K)1/3 = 750*(0.187/0.0517)*(0.47*0.0375/0.187)1/3 = 265.975 = 266 hio= hi * ID/OD = 265.97 * 0.62/0.75 =220 btu/hr. ft2.ᴼF At Re = 7,95,325.37 F= 0.0001, S= 0.7 Tube side pressure drop (∆Pt) = f Gt2 Ln/(5.22*1010*D *S) ∆Pt= 0.0001*576880.112*16*4/(5.22*1010*0.0517*0.7) =1.125 Psi Gt = 576880.11 v2/2g = 0.037 ∆Pr = 4n/ S*(v2/2g) 55

= 4*4*(0.037)/0.7 =0.84 Total pressure drop (∆PT) = ∆Pt +∆Pr = 1.125+ 0.84 =1.965 Psi Shell side Calculations: B= 12in C = 0.25in PT= C + Tube OD = 0.25+0.75 =1 in Flow area as = ID* C*B/(144PT) = (29*0.25*12)/(144*2) = 0.302 ft2 Mass velocity : Gs= W/as = 40211.4021/(0.454*0.302) = 293282.68 lb/ hr.ft2 T avg= 117.5ᴼC µ = 0.4 Cp = 0.4*2.42 = 0.968 lb/ft. hr Res = De* Gs/µ = 23985.75 JH =80 K = 0.16 W/ m.K = 0.16*6.93 btu/hr. ft2.ᴼF =1.1088 btu/hr. ft2.ᴼF ho = jH* K/ D*(Cµ/K)1/3 = 80*1.1088/0.792*(0.968*0.334/1.1088)1/3 = 742.68 btu/hr. ft2.ᴼF f = 0.0018, S= 0.76 No. of Crosses N+1 = 12L/ B 56

= 12*4*16/12 =64 Shell diameter Ds= 29/12 = 2.41 ft Shell side pressure drop ∆Ps = f Gs2Ds(N+1)/(5.22*1010*0..079*0.76) = 7.619 Psi Clean overall Coefficient Uc: Uc = hio* ho/(hio+ho) = 95.87 btu/hr.ft2.ᴼF Rd = UC- UD/( UC*UD) = 95.87-82.27/(95.87*82.27) =1.72*10-3 hr.ft2.ᴼF/ btu

57

Specification sheet of heat exchanger Item

Heat Exchanger

Type

Two 2-4 shell & tube heat exchangers in series

Operation

Continuous

Inlet temp. processing stream

69.8 °F

Outlet temp. processing temp.

410 °F

LMTD

47.10°F

UC

95.87 Btu /hr. ft2.°F

UD

82.27 Btu /hr. ft2.°F

No.of tubes

480

Pressure drop shell side

7.619 psi

Pressure drop tube side

1.965 psi

Heat transfer area

3015.16 ft2

Length of the tube

16 ft

Tube inner dia

0.0517 ft

Tube outer dia

0.0625 ft

Shell inner dia

1.9375 ft

Pitch

1 inch (square)

Baffle spacing

1 ft

No of baffles

16

58

Symbols used in the Design of the Reactor design: P1 , P2 = pressure of the gas T1 , T2 = temperature of gas V1 , V2 = volume of gas do=tube of outside diameter di =Inside diameter of tube TR =Residence time Vg = volumetric flow rate of gas through reactor V= volume of reactor N= be no. of tubes, A= Heat transfer area Pt=Triangular tube pitch Db = Bundle diameter Di = shell Internal Diameter J = weld joint efficiency factor t =thickness of dome q =Total Heat removed U Heat transfer coefficient: B=baffle spacing

59

10.2 DESIGN OF FIXED BED REACTOR 10.2.1. Estimation of volume of Reacting mixture: 1 kmol : 22.414 m3( at STP) P1V1/T1=P2V2/T2 1*22.414/273= 3* V2/593 V2=17.05 m3 1 kmol of hydrogen at 3 atm and 350 C =17.05 m3 1 kmol of reactant mixture =123.1092*0.1+2.0158*0.9=14.152 gm 46137.22728kg/hr of reactants =3260.12kmol/hr =55585.046m3/hr=15.44 m3/s 10.2.2. Estimation of volume of products mixture: P1V1/T1=P2V2/T2 1*22.414/273 =2*V2/600 V2=24.63 m3 1 kmol of products at 2 atm and 600 K =24.63 m3 1 kmol of product mixture =15.69gm, 46137.22728kg/hr of product mixture =2940.55 kmol/hr = 65909.49 m3/hr=18.31 m3/s Basis: 16.875 m3/s of gas Use 1.5” tubes of outside diameter (BWG 10no) and length =4m Wall thickness for BWG 10 no tube =0.134” Therefore, Inside diameter of tube =1.5-2*0.134=1.232”=31.3 mm Volume of each tube = π/4 * d2*L= π/4 (31.2928*10-3)2*4=3.0764*10-3m3 Assumption:Residence time with in reactor =0.4 sec

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T =volume of reactor/volumetric flow rate of gas through reactor,so volume of reactor is V=Residence time * Volumetric flowrate= 0.4*16.875=6.75 m3. Let ‘N” be no.of tubes, N (3.0764*10-3) = 6.75 N = 2194.12 = 2194 tubes (approx.) Heat transfer area =N (π*do*h) = 2194*π*38.1*10-3* 4= 1050.44 m2 Triangular pitch is used to accommodate 2194 no of tubes. Triangular tube pitch, Pt=1.25do =1.25 *38.1=47.625 mm Bundle diameter:Db =do (Nt/K1)1/n1,Where K1, n1 are obtained from the table below based on the type of tube arrangement.

=38.1(2194/0.319)1/2.142=2358 mm Graph: Shell inside diametervs. bundle diameter By extrapolating the bundle diameter to 2.358 m,we have Shell ID –Bundle dia = 20 + (2010)*(5.41-1.2)/ (1.2-0.2) =31.58 mm Therefore shell ID =Bundle diameter + 31.58 mm= 2358 +31.58=5545.83 mm =2389.58 mm Height of a reactor = 10m Volume of a reactor = (π/4)*D2*H= (π/4) (2.38958)2 *10=44.85 m3 10.2.3. Shell Material of Construction: The preferred construction material for reactor is low alloy steel (IS: 3609) From Code IS 2825, f=12.6 kgf/mm2=1260 kgf/cm2 This is a Class-I vessel. Therefore, J = weld joint efficiency factor = 1 61

Here t = P*Di/(200fJ-P) +CA Where P=3 atm= (3.04*10-2*2389.58)/ (200*1*12.6-3.04 *10-2) + 1=1.029 mm Since t< 12 mm, Use t =12 mm (including corrosion allowance) in order to withstand its own weight. 10.2.4. ellipsoidal dome end: Calculation of Dome end Thickness:t = PDoC/200f J +CA +TA Assume t=10 mm hi =Di/4 =2389.58/4 =597.395 mm ho =hi+ t =597.395 +10 =607.395 mm Ro=0.82Di+ t =0.82 *2389.58 +10 =1969.46 mm ro= 0.15 Di+T =0.15*2389.58 +10=368.437 mm Do=Di+2t =2389.58 +2*12 =2413.58 mm Do2/4Ro= 2413.582/(4*1969.46) = 739.46 mm Sqrt(Do* ro /2)=Sqrt (2413.58*368.437/2)=666.8 mm ho= 668.8 mm ho is least. Therefore hE=ho=668.8 mm hE/Do=668.8/2413.58 =0.277; t/Do=10/2413.5 =4.14*10-3. From graph hE/Do vs C, we have C=1.35t = =PDoC/200f J= (3.04*10-2*2413.58*1.35)/(200*1*12.6)= 0.091 mm So, thickness of dome = 0.067mm Shell side fluid is water. Total Heat removed = 94101140.57 kj/hr 62

Heat removed per tube = (94101140.57*103)/(3600*2194)= 11913.95 W q = UA∆T, Substituting A=1050.44 m2,∆T=370-298 = 72°K, q = 94101140.57 kj/hr We have U = 1244.25 W/m2 °C Internal diameter of vessel = 2413.5 mm We know that Ds/5 < baffle spacing < Ds i.e., 482.7< baffle spacing