Nitrobenze producion

July 22, 2017 | Author: Sarah Rasheed | Category: Chemical Reactions, Chemical Reactor, Nitric Acid, Redox, Benzene
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AL- Nahrain University College of Engineering Chemical Engineering Department  

NITROBENZENE PRODUCTION

   

A Final Year Project Submitted to the Department of Chemical Engineering in the Engineering of Nahrain University in

     

Partial Fulfillment of the Requirements for the Degree Bachelors in Scienece of Chemical Engineering

by SARAH RASHEED Ghayeb

Jumada II

1430

June

2009

Abstract

Nitrobenzene or caswell No. 600 chemical material use in the manufacture of various plastic monomers and polymers, rubber chemicals, drugs, pesticides, soaps, and as a solvent in petroleum refining and manufacture of cellulose ethers and cellulose acetate…ect The production capacity of nitrobenzene 70000 ton/year, this capacity was take as rough estimation for the requirements of our country. Nitrobenzene is manufacture commercially by the direct nitration of benzene using a mixture of nitric acid and sulfuric acid, many processes for this manufacture but the more safety, economic and lower capital cost is the continuous isothermal nitration process. In this project material balance, energy balance, design of the nitrator, settler, heat exchanger and distillation column, process control, plant location & Toxicity and Effect of Nitrobenzene.

I  

List of Contents Content

Page

Abstract

I

List of Content

II

List of Figures

VI

List of Tables

VII

Nomenclature

VIII

Chapter One: Introduction 1.1

History

1

1.2

Specification of Nitrobenzene

2

1.3

Identity

4

1.4

Physical Properties

4

1.5

Chemical Properties

5

1.6

Uses

11

1.7

Nitrobenzene Derivative

12

Chapter Two: Production Methods of Nitrobenzene 2.1

General

14

2.2

Batch Process

16

2.3

Tubular Reactor Process

17

2.4

Continuous Process

18

2.4.1

Adiabatic continuous process

19

2.4.2

Isothermal continuous process

21

II  

2.5

Non-Industrial Sources

21

2.6

Process Selection

23

2.7

Description of the Selected Process

23

Chapter Three: Material Balance 3.1

General Information

27

3.2

Material Balance on Nitrator

28

3.3

Separator Material Balance

30

3.4

Washing Process Material Balance

30

3.4.1

1st Washing Process Material Balance

32

3.4.2

2nd Washing Process Material Balance

32

3.5

Reconcentrator Material Balance

35

3.6

Distillation Material Balance

38

Chapter four: Energy Balance 4.1

Energy Balance on Nitrator

42

4.2

Separator Energy Balance

46

4.3

Energy Balance on Evaporator

48

4.4

Washing Process Energy Balance

52

4.4.1

1st Washing process Energy Balance

52

4.4.2

2nd Washing process Energy Balance

54

4.5

57

Distillation Energy Balance

III  

Chapter Five: Equipment Design 5.1

Nitrator Design

64

5.2

Settler Design

77

5.3

Heat Exchanger Design

82

5.4

Distillation Design

90

Chapter Six: Control System 6.1

Introduction

104

6.2

Control of Nitrator

105

6.3

Settler Control

107

6.4

Vaporizer Control

108

6-5

Heat Exchanger Control

109

6.6

Distillation column control

110

Chapter Seven: Plant Layout 7.1

Site Considerations

113

7.2

Site Layout

116

7.3

Plant Layout

118

7.4

Utilities

119

7.5

Environmental Consideration

120

7.6

Waste Management

120

7.8

Nitrobenzene Plant Location

122

IV  

Chapter Eight: Toxicity and Effects of Nitrobenzene 8.1

General

123

8.2

Effects on humans

124

8-3  Effects on organisms in the environment

125

8.4

Hazard and risk evaluation

126

8.5

Industrial safety

128 129

References Appendixes Appendix A: Physical Properties

A-1

Appendix B: Equilibrium Data

B-1

V  

List of Figures Figure No.

Title

1-1

Reduction products of nitrobenzene

6

1-2

Key intermediates derived from nitrobenzene

13

2-1

production of Nitrobenzene- continuous process

19

2-2

Flow sheet for the production of nitrobenzene adiabatically

20

2-3

22

2-4

Atmospheric reactions generating and removing nitrobenzene Typical continuous Nitrobenzene Process

4-1

Process Flow Diagram

63

5-1

Vapor-Liquid Equilibrium diagram (Isothermal) at 70oC

91

6-1

Nitrator Control

106

6-2

Settler control

107

6-3

Settler control

107

6-4

vaporizer control

108

6-5

Heat Exchanger control

109

6-6

Temperature pattern control

111

6-7

Composition control

111

6-8

Composition control

112

7-1

A typical site plant

118

VI  

page

26

List of Tables Table NO.

Title

1-1

Specification for technical-Grade Nitrobenzene

3

1-2

Specifications for Distilled-grade Nitrobenzene (mirbane oil)

3

1-3

Some Physical Properties of Nitrobenzene

5

1-4

Reduction products of nitrobenzene

7

1-5

Type and estimated consumption of nitrobenzene in Western Europe in 1994 nitrobenzene production capacities in European countries in 1985

11

3-1

Material Balance on Nitrator

29

3-2

Material balance on separator

31

3-3

Material Balance on 1st Washing Unit

33

3-4

Material Balance on 2nd Washing Unit

35

3-5

Material Balance on Reconcentrator

38

3-6

Material Balance on Distillation

39

3-7

Overall Material Balance

40

3-8

all Streams of Material Balances

41

4-1

all Streams of Energy Balances

62

2-1

VII  

Page

15

Nomenclature Symbol

Definition

Aa

Active Area

m2

Aap

Area under Apron

m2

Ac

Distillation Column Area

m2

Ad

Downcomer Area

m2

Ah

Hole Area

m2

Ai

Area or the Interface

m2

Am

Clearance Area under Downcomer

m2

An

Net Area

m2

Ao

Heat Transfer Area

m2

Ap

Total Area available for perforation

m2

As

Cross flow Area

m2

a

Blade Width

m

b

Baffle Width

m

C

Corrosion Allowance

Co

Orifice Coefficient

cp

Specific heat

D

Diameter

m

DA

Agitator Diameter

m

Db

Bundle Diameter

m

Deff

Effective Column Diameter

m

mm KJ/Kg.mol.K

VIII  

Unit

de

Equivalent Diameter

m

dh

Diameter of Hole

di

Inside Tube Diameter

m

dm

Diameter of Manholes

mm

do

Outside Tube Diameter

m

dp

Droplet Diameter

FC

Flow Controller

-

FLV

Liquid Vapor Factor

-

Ft

Correction factor for ∆TLm

-

FW

Wind Load

mm

µm

N/m

f

Material Tensile Strength

N/mm2

Gt

Mass Velocity of the Fluid Tube Side

Kg/m2.s

Gs

Mass Velocity of the Fluid Shell Side

Kg/m2.s

HA

Height of agitator

m

HL

Height of the nitrator content

m

hap

Height of bottom edge of the apron above the plate

mm

hb

Downcomer back-up

mm

hbc

Clear liquid back-up

mm

hd

Pressure drop through the tray plate

mm Liquid

hdc

Head loss in downcomer

mm Liquid

hi

Inside (tube) Heat Transfer coefficient

W/m2.oC

hid

Inside tube foaling coefficient

W/m2.oC

ho

outside (shell) Heat Transfer coefficient

W/m2.oC

IX  

Outside tube foaling coefficient

how

Weir Crest (height of the liquid over weir)

hr

Residence Head

s

hT

Total Height of Distillation Column

m

ht

Total plate drop head

mm

hv

Heat transfer to vessel

W/m2.oC

hw

Weir Height

J

Joined Efficiency

-

jf

Friction Factor

-

Kf

Thermal Conductivity

LC

Level Control

Lc

Continuous phase Volumetric flowrate

m3/s

Lm

Liquid mass flowrate

Kg/s

Ln

Liquid mass flowrate

Kg/s

LW

Weir Length

lB

Baffle spacing

mm

lp

Hole Pitch

mm

Ms

Bending moment at any plane

N.m

m

Mass flowrate

Kg/s

N

Agitator Speed

rps

Np

Power Number

-

Np

Number of passes

-

Nt

Number of Tubes

-

P

Pressure Design

N/mm2

.

mm Liquid

mm

W/m.oC -

m

X  

W/m2.oC

hod

PA

Shaft Power

W

Pch

Sugden’s Parachor

Pt

Pitch

mm

Pw

Wind Pressure (Load per unit area)

N/m2

-

r

Blade Length

m

S

Distance measured from the free end

m

T

Temperature of the fluid in shell side

o

TC

Temperature Controller

-

TM

Measuring Element

o

t

Temperature of the fluid in tube side

tr

Residence time

Uo

Overall Heat Transfer coefficient

uc

Velocity of Continuous phase

m/s

ud

Settling velocity through hole

m/s

uf

Flooding Velocity

m/s

uh

Vapor Velocity through Hole

m/s

Actual minimum Velocity of the Vapor

m/s

ut

Linear Velocity of the Fluid flow in Tube

m/s

uv

Corrected Flooding Vapor Velocity

m/s

V

Volume of Nitrator

m3

Vm

Vapor mass flowrate

Kg/s

Vn

Vapor mass flowrate

Kg/s

umin

C

s

XI  

C

W/m2.oC

Greek Notation µ

Viscosity

Pa.s

µc

Viscosity of the Continuous phase

Pa.s

µd

Viscosity of the dispersed phase

Pa.s

µw

Viscosity at the wall Temperature

Pa.s

τ

Residence Time

min

νo

Initial Volumetric flowrate

m3/hr

σ

Surface Tension

mJ/m2

ρ

Density

Kg/ m3

ρc

Density of the Continuous phase

Kg/ m3

ρd

Density of the dispersed phase

Kg/ m3

λ

Latent Heat

KJ/Kg.mol

∆TLm

Mean Logarithm Temperature

o

C

∆Tm

Mean Temperature Difference

o

C

∆Pt

Pressure Drop in Tube Side

pa

∆Ps

Pressure Drop in Shell Side

pa

XII  

Dimensionless Groups Nu = h d /K

Nusselt Number

Pr = cp µ / K

Prandtle Number

Re = ρ u d / µ

Reynolds Number

XIII  

      Chapter One Introduction                

Chapter One Introduction 1.1 History The earliest aromatic nitro compounds were obtained by MITSCHERLISH in 1834 by treating hydrocarbons derived from coal tar with fuming acid [1, 2, &3]. By 1835 LAURENT was working on the nitration of naphthalene, the most readily available pure aromatic hydrocarbon at that time. DALE reported on mixed nitro compounds derived from crude benzene at the 1838 annual meeting of the British Association for the Advancement of Science. Not until 1845, however, did HOFMANN and MUSPRATT report their systematic work on the nitration of benzene to give mono- and dinitrobenzenes by using a mixture of nitric and sulfuric acids [1]. The first small-scale production of nitrobenzene was carefully distilled to give a yellow liquid with a smell of bitter almonds for sale to soap and perfume manufacturers as “essence of mirbane.”[1] The number of naturally occurring nitro aromatic compounds is small; the first to be recognized was chloramphenicol, an important compound extracted from cultures of a soil mold Steptomyces venezuelas and identified in 1949 [1]. This discovery stimulated investigations into the role of nitro group in pharmacological activity, following the earlier (1943) discvery of the antibacterial activity of nitrofuran derivatives. Many synthetic pharmaceuticals and agrochemicals contain nitro aromatic groups, although the function of the nitro group is often obscure [1]. The choice of nitro compounds covered here is influenced strongly by their commercial application of compounds in the 1981 European core 1  

Inventory. Most nitro compounds, or their derivatives, are intermediates for colorants, agrochemicals, pharmaceuticals, or other fine chemicals with a few major volume outlets for synthetic materials and explosives [1].

1.2 Specifications of Nitrobenzene Nitrobenzene [98-95-3](oil of mirbane),C6H5NO2, is colourless to pale yellow oily liquid with on odour resembling that of bitter almonds or "shoe polish." Depending on the purity, its color varies from pale yellow to yellowish brown [2 & 3]. Product

specifications

have

been

developed

for

technical-grade

nitrobenzene and for distilled-grade nitrobenzene, also called mirbane oil. An example of a typical set of specification used by a major manufacturer of nitrobenzene is given in Tables 1-1 and 1-2. Equivalent specifications are usually negotiated between manufactures and major customers. Specification on technical-grade nitrobenzene often is drawn up as an internal quality standard since most nitrobenzene is converted captively to aniline. The type of aniline process used and certain design details of the plant can result in small changes in the specifications deemed necessary for technical-grade nitrobenzene. The presence of small amounts of water is little consequence in the operation of aniline plants; water is formed in process in the catalytic hydrogenation of nitrobenzene and is a required reactant in the Bechamp process. However, sulfur is known to be catalyst poison in the catalytic hydrogenation of nitrobenzene, and dinitrobenzene and dinitrophenol are thought to form tarlike deposits on the catalysts. The level of sulfur in technical-grade nitrobenzene is controlled through specifications on its level in the feedstock benzene. Nitrophenols are 2  

easily removed to a level of below 10 ppm through an alkaline wash. The fraction of dinitrobenzene found in commercial nitrobenzene plants is usually well below 100 ppm, and at this low level dinitrobenzene can be tolerated as a minor impurity of the nitrobenzene fed to an aniline plant [4]. Mirbane oil is produced by purification of technical-grade nitrobenzene through distillation. Trace contamination by aniline plant to the nitrobenzene plant. Again, specifications for distilled-grade nitrobenzene are usually negotiated between the manufacturer and major customers. Through distillation it is possible to further reduce the fraction of low and high boiling impurities in technical-grade nitrobenzene [4].

Table 1-1 Specification for technical-Grade Nitrobenzene [4] Pale yellow oil with a characteristic order. It may be slightly hazy owing to the presence of small globules of free water 0.5% (maximum) 1.206-1.209 0.1% (maximum)

Appearance Water content Specific gravity (15.5/15.5oC) Dinitrobenzene content Low-boiling impurities (benzene + aliphatic hydrocarbons) Sulfur- containing impurities (CS2 + nitrothiophene +elementary sulfur)

0.25% (maximum) 2.5 ppm (maximum, as sulfur)

Table 1-2 Specifications for Distilled-grade Nitrobenzene (mirbane oil) [4] Appearance

Clear yellow oil free from visible water and boiling at approximately 211oC at 760 mmHg pressure

Distillation range (5-95Ml)

0.5oC (maximum)

Crystallization point

5.5oC (minimum)

Specific gravity (15.5/15.5oC)

1.208 – 1.211

Aniline content

0.0075% (maximum)

3  

 

1.3 Identity [5]

Common name:

nitrobenzene

Chemical formula:

C6H5NO2

Chemical structure:

Relative molecular mass:

123.11

CAS name:

nitrobenzene

IUPAC name:

nitrobenzene

CAS registry number:

98-95-3

NIOSH RTECS

DA6475000

Synonyms:

nitrobenzol, mononitrobenzol, MNB, C.I. solvent black 6, essence of mirbane, essence of myrbane, mirbane oil, oil of mirbane, oil of myrbane, nigrosine spirit soluble B

1.4 Physical properties Nitrobenzene is a colorless to pale yellow oily liquid with an odor resembling that of bitter almonds or "shoe polish." It has a melting point of 5.7 °C and a boiling point of 211°C. Its vapor pressure is 20 Pa at 20°C, and its solubility in water is 1900 mg/liter at 20°C. It represents a fire hazard, with a flash point (closed cup method) of 88°C and an explosive limit (lower) of 1.8% by volume in air [3].

4  

Table 1-3 Some Physical Properties of Nitrobenzene [1,2,3&5] Mp.oC Bp.oC Viscosity pa.sec Thermal conductivity W/moC Surface tension (20oC) mN/m Specific heat J/goC At 25 oC At 30 oC Latent heat of fusion J/g Latent heat of vaporization J/g Heat of combustion (at constant volume)MJ/mol Flash point (closed cup) oC

5.58 210.9 1.900599219*10-3 0.14473 43.35 1.473 1.418 94.1 331 3.074 88

Auto ignition temperature oC Explosive limit in air (93 oC)vol% Vapor pressure pa At 20 oC At 25 oC At 30 oC Solubility in water mg/liter At 20 oC At 25 oC Solubility in organic solvent Density (25oC)Kg/m3

482 1.8 20 38 47 1900 2090 Freely soluble in ethanol, acetone, ether 1198.484586

1.5 Chemical properties Nitrobenzene reactions involve substitutions on the aromatic ring and reactions involving the nitro group. Under electrophilic conditions, the substitution occurs at a slower rate than for benzene, and the nitro group promotes meta substitution. Nitrobenzene can undergo halogenations, sulfonation, and nitration, but it does not undergo Friedel-Crafts reactions. Under nucleophilic conditions, the nitro group promotes ortho and para substitution [2]. 5  

The reduction of the nitro group to yield aniline is the most commercially important reaction of the nitrobenzene. Usually the reaction is carried out by the catalytic hydrogenation of nitrobenzene, either in the gas phase or in solution, or by using iron borings and dilute hydrochloric acid (the Bechamp process). Depending on the conditions, the reduction of nitrobenzene can lead to variety of products. The series of reduction products is shown in figure 1-1 Nitrosobenzen, Nphenylhydroxylamine, and aniline are primary reduction products. Azoxybenzene is formed by the condensation of nitrosobenzene and N-phenylhdroxylamine in alkaline solutions,

and

azoxybenzene

can

be

reduced

to

form

azobenzene

and

hydrazobenzene. The reduction products of nitrobenzene under various conditions are given in Table 1-4 [2].

Figure 1-1 Reduction products of nitrobenzene [1, 2&14]

6  

Table 1-4 Reduction products of nitrobenzene [2] Reagent

Product

Fe, Zn or Sn + HCL

aniline

H2 + metal catalyst + heat (gas phase or aniline solution) SnCL2 + acetic acid

aniline

Zn + NaOH

hydrazobenzene, azobenzene

Zn + H2O

N-phenylhydroxylamine

Na3AsO3

azoxybenzene

LiALH4

azoxybenzene

Na2S2O3 + Na3PO4

Sodium phenylsulfamate, C6H5NHSO3Na

The process used most commonly for the manufacture of aniline is the catalytic hydrogenation of nitrobenzene which has largely replaced the older Bechamp process. In this latter process nitrobenzene reacts with iron and water in the presence of small amounts of hydrochloric acid to form aniline, iron oxide, and hydrogen. The chemistry of the two nitrobenzene-based aniline processes is described through the following stoichiometric equations [4]: C6H5NO2 + 3H2

CU/SiO2

C6H5NO2 +3 Fe + 4 H2O

C6H5NH2 + 2H2O

HCL/Fecl

C6H5NH2 +Fe(OH)2 + FeO + Fe (OH)3 + 0.5H2

1.1 1.2

Nitration, which is introduction of nitro group or the NO2 group into the molecule, is achieved by bringing mixed acid and the compound to be nitrated into intimate contact under vigorous agitation. Care must be taken to remove the heat of nitrating. The acid left on completion of the nitration reaction is called spent acid. In benzene nitration of the reaction is heterogeneous; benzene and nitrobenzene have 7  

very low solubility in the mixed and spent acids. The overall stoichiometry for the reaction of benzene and nitric acid to form nitrobenzene and water is NO2

+ HNO3

+ H2O

∆Ho = -34.825 Kcal/g.mol

1.3

H2SO4

Sulfuric acid is a catalyst in the nitration reaction and does not enter directly into the stoichiometry of Equation 1.3. The role of sulfuric acid is two fold: it acts as a dehydrating agent by absorbing the water formed in the nitration reaction and it is responsible for the dissociation of nitric acid and through which the reactive species, the nitronium ion, is formed. The positively charged nitronium ion, NO2, reacts with the aromatic compound by electrophilic attack to form a positively charged complex. This complex breaks down fast through reaction of the proton with an anion such as HSO4. The reaction mechanism is described through the following stoichiometric equations[4]: 

8  

Equations 1.4 to 1.7 add up to Equation 1.3. The rate-controlling reaction is that of Equation 1.5. The rate of nitration reaction is a function of many variables, but most importantly it is a function of sulfuric acid strength, which is capable of changing the rate by several orders of magnitude. The steep increase of the nitration rate with the sulfuric acid strength is generally though to be due to the parallel increase in the concentration of the nitronium ion in the mixed acid. It is the nitronium ion which is the reactive species in the rate-controlling Equation 1.5 [4]. The nitronium ion is also present in strong nitric acid, and benzene can be nitrated using nitric acid alone. The incentive for this process is that it would eliminate the sometimes costly disposal or reconcentration of the spent sulfuric acid. No commercial plant appears to be operating using a nitric acid only process. Of concern would be the fact that mixtures of nitric acid and benzene or nitrobenzene can be detonated [4]. The main by-products formed in commercial nitrobenzene plants are dinitrobenzene (C6H4 (NO2)2), dinitrophenol (C6H3OH (NO2)2), and picric acid (C6H2OH (NO2)2). The fraction of dinitrobenzene obtained is usually well below 100 ppm, but can reach a few hundred ppm if the nitration is accidentally operated with excess nitric acid. The introduction of nitro groups into the benzene ring lowers the electron density, thereby impeding electrophilic attack. Substantial rates of conversion to dinitrobenzene are possible only at high spent acid strengths. Furthermore, commercial nitrobenzene plants usually operate with excess benzene which will consume most of the nitric acid well before significant quantities of dinitrobenzene can be formed [4]. A possible but not proven mechanism is the one where the nitronium ion becomes attached to the benzene ring through one of its oxygen atoms instead of the nitrogen 9  

atom, the product being phenol and the nitrosyl ion, NO+. The phenol then reacts with nitric acid, possibly through a complex between the nitrosyl ion and the phenol, to form nitrophenol and nitrous acid, HNO2. The one-to-one molar ratio between nitrophenol and nitrous acid is confirmed through experiment. Nitrophenol is further nitrated to dinitrophenol and picric acid. The rates for this di- and trinitration are relatively fast; there is usually only a trace of mononitrophenol found in the crude nitrobenzene. The stoichiometry of the reactions is shown in the following equations [2]:

Other by-products are formed from trace impurities in the benzene feedstock or in the recycle sulfuric acid. There is also the possibility that very small amounts of 10  

benzene and nitrobenzene undergo other reactions. Most of these by-products are removed in the washing stage of the process together with the nitrophenols. The yield loss caused by these side reactions is negligible. Of more concern is the fast that some of these trace impurities from surface-active compounds which can oceasionally lead to the formation of stable emulsions in the washing section [4].

1.6 Uses Nitrobenzene is used primarily in the production of aniline, but it is also used as a solvent and as an ingredient in metal polishes and soaps. In the USA, around 98% of nitrobenzene produced is converted into aniline; the major use of aniline is in the manufacture of polyurethanes. Nitrobenzene is also used as a solvent in petroleum refining, as a solvent in the manufacture of cellulose ethers and cellulose acetate (around 1.5%), in Friedel-Crafts reactions to hold the catalyst in solution (it dissolves anhydrous aluminium chloride as a result of the formation of a complex) and in the manufacture of dinitrobenzenes and dichloroanilines (around 0.5%). It is also used in the synthesis of other organic compounds, including acetaminophen [3]. According to the BUA (1994), nitrobenzene is used in Western Europe for the purposes shown in Table 5-1 [5].

Table 5-1 Type and estimated consumption of nitrobenzene in Western Europe in 1994 Main application areas or chemical manufacture Aniline m-Nitrobenzenesulfonic acid m-Chloronitrobenzene Hydrazobenzene

Nitrobenzene consumption (tones/year) in Western Europe 380 000 5 000 4 300 1 000 11

 

Dinitrobenzene Others (solvents, dyes) Total

4 000 4 000 398 300

Dunlap (1981) reported that most of the production of aniline and other substituted nitrobenzenes from nitrobenzene go into the manufacture of various plastic monomers and polymers (50%) and rubber chemicals (27%), with a smaller proportion into the synthesis of hydroquinones (5%), dyes and intermediates (6%), drugs (3%), pesticides and other specialty items (9%) [5]. Past minor uses of nitrobenzene included use as a flavouring agent, as a solvent in marking inks and in metal, furniture, floor and shoe polishes, as a perfume, including in perfumed soaps, as a dye intermediate, as a deodorant and disinfectant, in leather dressing, for refining lubricating oils and as a flavouring agent. It is not known whether it may still be used in some countries as a solvent in some consumer products (e.g., shoe polish) [5]. The 22,680 metric ton of nitrobenzene left was used to produce a variety of other products, such as para-aminophenole [123-30-8] (PAP) and nigrosine dyes. The U.S. producers of PAP are Mallinckrodt, Inc., Rho^ne-Poulene, and Hoechst Celanese, with combined production capacities > 35,000 metric tons (as of may 1995). Mallinckrodt is the largest producer, with over 50% of capacity. PAP primarily is used as an intermediate for acetaminophen [103-90-2] [2].

1.7 Nitrobenzene Derivatives • • • •

2,5-dichloronitobenzene 2,5-dimethoxynitrobenzene Dinitrobenzene O-nitrobenzene 12

 

• • • • • •

M-nitrobenzenesulfonic acid, sodium salt O-nitrochlorobenzene P-nitrochlorobenzene M-nitrochlorobenzene [15]. 1,3,5-Trinitrobenzene 1, 3-Dinitrobenzene [1].

Figure 1-2 Key intermediates derived from nitrobenzene

13  

      Chapter Two Production Methods of Nitrobenzene

Chapter Two Production Methods of Nitrobenzene

2.1General World production of nitrobenzene in 1994 was estimated at 2 133 800 tones; about one-third was produced in the USA [5]. In the USA, there has been a gradual increase in nitrobenzene production, with the following production/demand amounts, in thousands of tones, reported: 73 (1960), 249 (1970), 277 (1980), 435 (1986), 533 (1990) and 740 (1994). Based on increased production capacity and increased production of aniline (the major end-product of nitrobenzene), it is likely that nitrobenzene production volume will continue to increase [5]. Production of nitrobenzene in Japan was thought to be around 70 000 tones in 1980 and 135 000 tones in 1990. Patil & Shinde (1989) reported that production of nitrobenzene in India was around 22 000 tones per year [5]. Nitrobenzene is produced at two sites in the United Kingdom with a total capacity of 167 000 tones per year. It has been estimated that a maximum of 115 400 tones of aniline was produced in the United Kingdom in 1990. If it is assumed that 98% of the nitrobenzene in the United Kingdom is used to make aniline, then the total amount of nitrobenzene used in the United Kingdom would be around 155 600 tones per year [5].

14

Capacities for nitrobenzene production are available for several Western European countries and are shown in Table 3-1 Production for Western Europe was reported as 670 000 tones in 1990 [5]. Table 2-1 nitrobenzene production capacities in European countries in 1985 Country Belgium Germany Italy Portugal Switzerland United Kingdom USA Japan

Capacity (tones) 200 000 240 000 18 000 70 000 5 000 145 000 434 000 97 000

Nitrobenzene is manufactured commercially by the direct nitration of benzene using a mixture of nitric acid and sulfuric acid [2, 4, 7, &8]. This commonly is referred to as mixed acid or nitrating acid. Because two phases are formed in the reaction mixture and the reactants are distributed between them, the rate of nitration is controlled by mass transfer between the phases as well as by chemical kinetics. The reaction vessels are acid-resistant, glass-lined steel vessels equipped with efficient agitators. By vigorous agitation, the interfacial area of the heterogeneous reaction mixture is maintained as high as possible, thereby enhancing the mass transfer of reactants. The reactors contain internal cooling coils which control the temperature of the highly exothermic reaction [2&3]. Nitrobenzene can be produced by either a batch or continuous process [2&3]. 15

2.2Batch process With a typical batch process, the reactor is charged with benzene, then the nitrating acid (56-60 wt % H2SO4, 27-32 wt% HNO3, and 8-17 wt % H2O) is added slowly below the surface of benzene. The temperature can be raised to about 90oC toward the end of reaction to promote completion of reaction. The reaction mixture is fed into a separator where the spent acid settles to the bottom and is drawn off to be refortified. The crude nitrobenzene is drawn from the top of the separator and washed in several steps with a dilute base, such as sodium carbonate, sodium hydroxide, magnesium hydroxide, etc, and then water. Depending upon the desired purity of the nitrobenzene, the product can be distilled. Usually a slight excess of benzene is used to ensure that little or no nitric acid remains in the spent acid. The batch reaction time generally is 2-4 hours, and typical yields are 95-98 wt % based on benzene charged [2]. Based on yield of 1000 kg of nitrobenzene, material requirements for the process are as follows [3] Material Quantity, kg Benzene 650 Sulfuric acid 720 Nitric acid 520 Water 110 Sodium carbonate 10 The separation of the nitrobenzene is accomplished in large conicalbottomed lead tanks, each capable of holding one or more charges. The nitrator charges are permitted to settle here for 4-12 hr, when the spent acid is drawn off from the bottom of the lead tanks and delivered to the spent-acid tanks for additional settling or for treatment with benzene next to be nitrated, in order to

16

extract the residual nitrobenzene. The nitrobenzene is then delivered to the neutralizing house [9]. The neutralizing tub may be either a large lead conical-shaped tub containing an air-spider, which is used for agitating the charge of nitrobenzene during the washing process, or a standard cast-iron kettle similar to the nitrator with sleeve-and –propeller agitation. The neutralizing vessel is prepared with a "heel" of warm water, which is delivered from an adjacent vat, and the nitrobenzene is blown into it. The charge is thoroughly agitated and warmed with live stream for 30 min, or until neutral to congo, and then allowed to settle for a similar period. The supernatant acid water is then run off through side outlets into a labyrinth where practically all the enmeshed nitrobenzene will settle out. The charge is now given a neutralizing wash at 40-50oC with a warm sodium carbonate solution, until alkaline to phenolphthalein [9].

2.3 Tubular Reactor process Most homogeneous gas-phase flow reactor is tubular [19]. The nitrator also can be designed as a tubular reactor, e.g., a tube-and-shell heat exchanger with appropriate cooling, involving turbulent flow. Generally, with a tubular reactor, the reaction mixture is pumped through the reactor in a recycle loop and aportion of the mixture is withdrawn and fed into the separator. A slight excess of benzene usually is fed into the nitrator to ensure that the nitric acid in the nitrating acid is consumed to the maximum possible extent and to minimize the formation of dinitrobenzene. The temperature of nitrator is maintained at 50100oC by varying the amount of cooling. The reaction mixture flows from the nitrator into a separator or centrifuge where it is separated into two phases [2].

17

The tubular reactor [i.e., plug-flow reactor (PFR)] is relatively easy to maintain (no moving parts), and it usually produces the highest conversion per reactor volume of any of the flow reactors. The disadvantage of the reactor and hot spots can occur when the reaction is exothermic. The tubular reactor is commonly found either in the form of one long tube or as one of a number of shorter reactors arranged in a tube bank [10].

2.4 Continuous process A typical continuous process for the production of the nitrobenzene is given in Figure 2. Benzene and the nitrating acid (56-65 wt % H2SO4, 20-26 wt % HNO3, and 15-18 wt % water) are fed into the nitrator, which can be a stirred cylindrical reactor with internal cooling coils and external heat exchangers or a cascade of such reactors [2]. The basic sequence of operations for a continuous process is the same as that for a batch process; however for a given rate of production, however, for a given rate of production, the size of the naitrators is much smaller in the continuous process. A 0.114-m3 (30-gal) continuous nitrator has roughly the same production capacity as a 5.68-m3 (1500-gal) batch reactor [3]. The nitration in continuous process can take place with elimination of heat of reaction, e.g. adiabatically, or isothermally [11].

18

Figure 2-1 production of Nitrobenzene- continuous process [1]

2.4.1 Adiabatic Continuous Process The processes where the heat of nitration is used to directly boil off water, benzene and nitrobenzene from the nitrator [4]. An adiabatic nitration process was developed for the production of nitrobenzene. This method eliminated the need to remove the heat of reaction by excessive cooling. The excess heat can be used in the sulfuric acid reconcentration step. An additional advantage of this method is the reduction in reaction times to 0.5-7.5 minutes. The nitration step is carried out at higher than usual temperatures 120-160oC. because excess benzene is used, the higher temperature allows water to be removed as a water-benzene azeotrope. The water is separated and the benzenephase, containing approximately 8 %nitrobenzene, is recycled back into the reactor. The dry sulfuric acid is then reused continuously [2]. The adiabatic process integrates nitration with sulfuric acid concentration, thus using the heat of nitration to reconcentrate the spent sulfuric acid. This is 19

achieved by circulating a large volume of sulfuric acid through the nitrators, absorbing the heat of nitration without undue temperature rise. the spent acid is then flash concentrated under vacuum [4]. One observes that the nitrobenzene stream from the separator is used to heat the benzene feed. However, care must be taken so that the temperature never exceeds 190oC, where secondary reactions could result in an explosion. One of the safety precaution is the installation of relief valves that will rupture before the temperature approaches 190oC, thereby allowing a boil-off of water and benzene, which would drop the reactor temperature [10].

Figure 2-2 Flow sheet for the production of nitrobenzene adiabatically

20

2.4.2 Isothermal Continuous Process The isothermal process is different from the adiabatic process only in the nitration section. In the isothermal process, typically a minimum of 2 nitrators in series is used with up to 4 nitrators in large plants. Spent acid and crude nitrobenzene are usually separated through gravity settlers, but in some designs centrifugal separation is used. The spent acid is stripped free of dissolved nitrobenzene and nitric acid either by steam srripping or through benzene extraction-prenitration. It is then either reconcentrated and recycled or discharged, often for use in phosphate rock digestion. Spent acid stripping is sometimes omitted in small plants; yield losses and emissions of nitrobenzene and nitrogen oxide must then be tolerated [4].

2.5 Non-Industrial Sources Nitrobenzene has been shown to be emitted from a multiple-hearth sewage sludge incineration unit in the USA. The unit consisted of 12 hearths and operated at a rate of 13–15 tones per hour, with a maximum temperature of 770 °C at the sixth hearth. Nitrobenzene was monitored at the scrubber inlet and outlet. The concentrations measured were 60 µg/m3 at the scrubber inlet (corresponding to an emission of 3.2 g/h) and 16 µg/m3 at the scrubber outlet (corresponding to an emission of 0.9 g/h). The scrubber reduced the nitrobenzene concentration by 71% [5]. The levels of nitrobenzene in air have been measured at five hazardous waste landfills and one sanitary landfill in New Jersey, USA. Samples were collected over a 24-h period at five locations within each landfill. Mean levels 21

measured in the five hazardous waste landfills were 0.05, 0.65, 2.7, 1.0 and 6.6 µg/m3. The maximum level recorded was 51.8 µg/m3. At the sanitary landfill, nitrobenzene was below the detection limit (0.25 µg/m3) at all locations [5]. Nitrobenzene has been shown to be formed from the atmospheric reactions of benzene in the presence of nitrogen oxides. The reaction is thought to be initiated by hydroxyl radicals. Nitrobenzene, once formed, reacts quite slowly in the atmosphere; this could therefore provide a major source of atmospheric nitrobenzene, although it has not been possible to quantify this source. Atkinson et al. (1987) reported that aniline is slowly oxidized to nitrobenzene by ozone. These reactions are summarized in Figure 2-3 [5].

Figure 2-3 Atmospheric reactions generating and removing nitrobenzene 22

2.6 Process Selection A continuous nitration process generally offers lower capital costs and more efficient labor usage than a batch process; thus, most, if not all, of the nitrobenzene producers use continuous processes [2&3]. In contrast to the batch process, a continuous process typically utilizes a lower nitric acid concentration and, because of the rapid and efficient mixing in the smaller reactors, higher reaction rates are observed [3]. The continuous nitration can take place with elimination of heat of reaction, e.g. isothermally, or adiabatically [11]. In adiabatic process, the heat of reaction is not dissipated by cooling during the process, but instead is subsequently used for evaporating the water of reaction, so that a sulfuric acid suitable for recirculation obtained. One factor common to all the processes which have been proposed for this purpose is that they require new installations of special corrosion-resistant materials to accommodate the high process temperatures (up to 145oC.) and they also require considerably more stringent safety measures. This offsets the potential advantages of these processes [12]. The isothermal processes such that considerable economic and ecological advantages are obtained over the state-of-the-art [12].

2.7 Description of the Selected Process The production of nitrobenzene by subjecting benzene to isothermal nitration with a mixture of nitric acid and sulfuric acid [9], concentrated sulfuric acid has 23

two functions: it reacts with nitric acid to form the nitronium ion, and it absorbs the water formed during the reaction, which shifts the equilibrium to the formation of nitrobenzene [4, 8, 13, &14]

A charge of benzene into a nitrator (a slight excess of benzene is added to avoid nitric acid in the spent acid [1, 2, &3]), then slowly feeding in a mixed nitrating acid (60 wt. % H2SO4, 25 wt. % HNO3, 15 wt. % H2O [2&14]), and thereafter digesting the reaction mixture in the same vessel. Since the addition of the mixed acids requires several hours in order to avoid uncontrollable rises in temperature, and the digestion period requires several more hours, the apparatus used, particularly the nitrator, has to be large in order to provide a high production rate, and constant operator surveillance must be maintained. In addition, an explosion hazard is present at the start of any run due to the large unreacted charge in the nitrator [15]. The temperature in the nitrator is held at 50oC [2, 3, 16&17], governed by the rate of feed of benzene. Reaction is rapid in well-stirred and continuous nitration vessels. The reaction must be cooled to keep it under control. Good heat transfer can be assured by the use of jackets, coils, and good agitation in the

24

nitration vessel [16]. Nitration vessels are usually made of stainless steel, although cast iron stands up well against mixed acids [16&18]. It then enters a separator tank from which a portion of spent acid is removed from bottom, and the crude nitrobenzene is drawn off the top of the separator [18]. The removed of spent acid (sulfuric acid & water) is enter to evaporator in order to concentrating the sulfuric acid with fresh sulfuric acid (98 wt. % [4]) and then with fresh nitric acid (64 wt. % [4]) to the nitrator [12]. The crude nitrobenzene (nitrobenzene, benzene, sulfuric acid &water) is drawn from the top of the separator and is wash with the sodium carbonate in order to remove sulfuric acid from crude nitrobenzene, fellowing by final washing with calcium sulfate (anhydrite) to remove the water from react the calcium sulfate with water to formed calcium sulfate (Gypsum) [2,12,&14]. The product is topped in still to remove benzene and give pure product (96-99 wt. %) [1,2 & 3].

25

Benzene

Nitrating acid Nitric acid 64wt. %

nitrator

Fresh sulfuric acid 98 wt. %

Na2CO3

CaSO4

Crude nitrobenzene

Acid separation

1st washing

2nd washing

Distillation

NaSO4 H2CO3

Gypsum

Nitrobenzene

H2O Spent acid

Sulfuric acid reconcentration (Evaporator)

Fig. 2-4 Typical continuous nitrobenzene process

26  

Benzene

    Chapter Three Material Balance  

Chapter Three Material Balance Note: Data necessary in appendix A.

3.1 General Information Main Reaction C6H6 + HNO3 H SO 2 4

C6H5NO2 +H2O … (3.1)

Capacity = 70000 ton/year [5] Year = 300 working day = 233.333333 ton/day

= 9722.222222 Kg/day

= 78.9718188 Kg.mol/hr

No nitric acid remains in the spent acid [2&14] Conversion = 100 % [2&14,1&4] From stoichiometry: Benzene required = 78.97183188 Kmol/hr Water formed = 78.97183188 Kg.mol/hr Required nitric acid = 78.97183188 Kg.mol/hr

27

3.2 Material Balance on Nitrator 4

3

5 Nitrator

Usually a slight excess of benzene (3.24 wt %) is used to ensure that little or no nitric acid remains in the spent acid [2, 4, 16&21]. Wt. of benzene = 78097183188 * 78.11 = 6168.489788 Kg/hr Wt. of benzene excess = 6168.489788 * 0.0324 = 199.8590691 Kg/hr Total wt. of benzene input = 6168.489788 + 199.8590691 Total wt. of benzene input = 6368.348857 Kg/hr Total nitric acid input = 78.97183188 * 63.02= 4976.804845 Kg/hr Nitrating acid composition H2SO4 60 wt %, HNO3 25 wt %, & H2O 15 wt % [2&21]. Total weight of nitrating acid =

= 19907.21938 Kg/hr

Wt. of sulfuric acid input = Wt. of sulfuric acid input = 11944.33163 Kg/h Wt. of water input =

= 2986.082907 Kg/hr

Wt. of water formed = 78.97183188 * 18.02 = 1423.07241 Kg/hr 28

Water output in Stream 5 = 2986.082907 + 1423.07241 Water output in Stream 5 = 4409.155317 Kg/hr

Table 3-1 Material Balance on Nitrator 3

4

Component

[Kg/hr]

[Kg/hr]

5 [Kg/hr]

C6H6

-

6368.348857

199.8590691

HNO3

4976.804845

-

-

H2SO4

11944.33163

-

11944.33163

H2O

2986.082907

-

4409.155317

C6H5NO2

-

-

9722.222222

19907.21938

6368.348857 26275.56824

Total 26275.56824

29

3.3 Separator Material Balance

7 5 Aid Separation

6

1 wt % of total acid solution (sulfuric acid + water) will goes with crude nitrobenzene [16]. Stream 5 Acid solution input to separator = 4409.155317 + 11944.33163 = 16353.48695 kg/hr Stream 7 (Crude Nitrobenzene) = excess BZ.+ N.B. + 1 wt. % of acid solution Excess BZ. = 199.8590691 Kg/hr N.B. = 9722.222222 kg/hr Wt. of acid solution in stream 7 = 0.01 * 16353.48695 = 163.5348695 Kg/hr * 100 = 73.03843924 %

Wt. % sulfuric acid in acid solution =

Wt. % water in acid solution = 26.96156076 % this above acid wt% is the same for stream 6 & stream 7. Wt. of sulfuric acid in stream 7= 163.5348695 * 0.73038439

30

Wt. of sulfuric acid in stream 7 =119.4433163 Kg/h Wt. water in stream 7 = 163.5348695 * 0.2696156076 = 44.09515532 Kg/hr Stream 6 (spent acid) = water + sulfuric acid 99 Wt % of total acid solution will goes in stream 6(spent acid).Wt. of spent acid = 16353.48695 * 0.99 = 16189.95208 Kg/hr = stream 6 Wt. of sulfuric acid in spent acid = 16189.95208 * 0.7303843924 Wt. of sulfuric acid in spent acid = 11824.88831 Kg/hr Wt. of water in spent acid = 16189.9520 * 0.2696156076 Wt. of water in spent acid = 4365.063767 Kg/hr

Table 3-2 Material balance on separator Component

5

6

7

[Kg/hr]

[Kg/hr]

C6H6

199.8590691

-

199.8590691

HNO3

-

-

-

H2SO4

11944.33163

11824.88831

119.4433163

H2O

4409.155317

4365.063767

44.0915532

C6H5NO2

9722.222222

-

9722.222222

16189.95208

Total 26275.56824

[Kg/hr]

10085.61616

26275.56824

31

3.4 Washing Process Material Balance 3.4.1 1st Washing process Material Balance Na2CO3 8 7

10 1st Washing

9

Na2CO3 + H2SO4

Na2SO4 + H2CO3

From stoichiometry Mole of Na2CO3 input in stream 8 = mole of sulfuric acid in stream 7 Mole of sulfuric acid in stream 7 =

Mole of sulfuric acid in stream 7

= 1.217815215 Kg.mol/hr

Wt. of Na2SO4 input = 1.217815215 * 106.00 Wt. of Na2SO4 input = 129.0884128 Kg.mol/hr = stream 8 Mole of Na2SO4 = 1.217815215 Kg.mol/hr Wt. of Na2SO4 = 1.217815215 * 142.05 Wt. of Na2SO4 = 172.9906513 Kg/hr

32

Mole of H2CO3 = 1.217815215 Kg.mol/hr Wt. of H2CO3 = 1.217815215 * 62.03 Wt. of H2CO3 = 75.4510778 Kg/hr Wt. of water input in stream 7 = wt. of water output in stream 9 Wt. of water input in stream 7 = 44.0915532 Kg/hr

Table 3-3Material Balance on 1st Washing Unit Component

9

8

10

7 [Kg/hr]

[Kg/hr]

[Kg/hr]

[Kg/hr]

C6H6

199.8590691

-

-

199.8590691

HNO3

-

-

-

-

H2SO4

119.4433163

-

-

-

H2O

44.0915532

-

-

44.0915532

C6H5NO2

9722.222222

-

-

9722.222222

Na2CO3

-

129.0884128

-

-

Na2SO4

-

-

172.9906513

-

H2CO3

-

-

75.4510778

-

10085.61616

129.0884128

248.5317291

9966.172836

Total

10214.70457

10214.70457

33

3.4.2 2nd Washing process Material Balance

CaSO4 11 10

13 2nd Washing

12 CaSO4.2H2O (Gypsum)

CaSO4 + 2H2O

CaSO4.2H2O

Wt. of water input in stream 10 = 44.0915532 Kg/hr = 2.446812053 Kg

Mole of water input in 10 =

From stoichiometry Mole of CaSO4 = 1.223406027 Kg.mol/hr Wt. of CaSO4 = 1.223406027 * 136.14 = 166.5544965 Kg/hr = stream 11 Mole of CaSO4.2H2O = 1.223406027 Kg.mol/hr Wt. of CaSO4.2H2O = 1.223406027 * 172.18 Wt. of CaSO4.2H2O = 210.6460497 Kg/hr = stream 12

34

Table 3-4 Material Balance on 2nd Washing Unit 11

10

12

13

Component

[Kg/hr]

[Kg/hr]

[Kg/hr]

[Kg/hr]

C6H6

199.8590691

-

-

199.8590691

HNO3

-

-

-

-

H2SO4

-

-

-

-

H2O

44.0915532

-

-

-

C6H5NO2

9722.222222

-

-

9722.222222

CaSO4

-

166.5544965

-

-

CaSO4.2H2O

-

-

210.6460497

-

9966.172836 166.5544965 210.6460497

Total

10132.72733

9922.0812

10132.72734

3.5 Reconcentrator Material Balance

3

1 2 mixing point nd

18 1st mixing point

H2O 6 16

2 Sulfuric acid reconcentration 1 35

The concentrated of nitric acid added in stream 1 is 64wt. %, and the concentrated of sulfuric acid added in stream 2 is 98 wt. % [4]. Material balance on nitric acid Stream of fresh nitric acid = stream 1 0.64 stream 1 = 0.25 stream 3 Stream 1 =

= 7776.25757 Kg/hr

Wt. of nitric acid input in stream 1 = 0.64 * 7776.25757 = 4976.804845 Kg/hr Wt. of water in stream1 = 0.36 * 7776.25757 = 2799.452725 Kg/hr Material balance on sulfuric acid Stream of fresh sulfuric acid = stream 2 Amount of sulfuric acid input in stream 2 equal to amount that consumed in 1st washing process = 119.4433163 Kg/hr Stream 2 =

= 121.880935 Kg/hr

Wt. of water in input in stream 2 = 121.880935 * 0.02 = 2.4376187 Kg/hr Material balance on water that must be removed Total wt. of water input = 2799.452725 + 2.4376187 = 2801.890344 Kg/hr Wt of water in stream 17 (after reconcentrator) = wt. of water in nitrating acid – total wt. of water input 36

= 2986.082907 - 2801.890344 = 184.1925633 Kg/hr Wt. of water must be removed in stream17 = wt. of water in spent acid (stream 6) – water after reconcentrator in stream17 = 4365.063767 - 184.1925633 = 4180.871204 Kg/hr = stream 16 Material balance on reconcentrator Stream 6 = stream 16 + stream 17 Stream 17 = 16189.95208 - 4180.871204= 12009.08088 Kg/hr Wt. of water in stream 17 = 184.1925633 Kg/hr Wt of sulfuric acid in stream 17 = 12009.08088 - 184.1925633 Wt of sulfuric acid in stream 17 = 11824.88831 Kg/hr Material balance on 1st mixing point Stream 17 + stream 2 = stream 18 Stream 18 = 12009.08088 + 121.880935= 12130.96182 Kg/hr Wt. of water in stream 18 = 184.1925633 + 2.4376187 Wt. of water in stream 18 =186.630182 Kg/hr Wt. of sulfuric acid in stream 18 = 12130.96182 + 186.630182 Wt. of sulfuric acid in stream 18 = 11944.33163 Kg/hr

37

Table 3-5 Material Balance on Reconcentrator 6 component [Kg/hr]

16

17

18

2

1

[Kg/hr]

[Kg/hr]

[Kg/hr]

[Kg/hr]

[Kg/hr]

HNO3

-

-

H2SO4

11824.88831

-

-

-

-

11824.88831 11944.33163 119.4433163

3 [Kg/hr]

4976.804845 4976.804845 -

11944.33159

H2O

4365.063767 4180.871204

186.6301817

2.4376187

2799.452725 2986.082907

Total

16189.95208 4180.871204 12009.08088 12130.96181

121.880935

7776.25757

184.192563

3.6 Distillation Material Balance

14

13 Distillation

Stream 13 = 97722.081291 Kg/hr

15

Benzene in stream 13 = 199.8590691 Kg/hr Nitrobenzene in stream 13 = 9722.222222 Kg/hr Purity between 96 – 99 wt. % [2 & 14] 38

19907.21934

Select purity = 99 wt. % = 9820.426487 Kg/hr

Stream 15 (bottom) =

Benzene in stream 15 = 9820.426487 - 9722.222222 Benzene in stream 15 = 98.20426486 Kg/hr Benzene in stream 14 (top) = 199.8590691 – 98.20426486 = 101.6548042 Kg /hr Table 3-6 Material Balance on Distillation

Component

C6H6 C6H5NO2

Total

13

14

15

[Kg/hr]

[Kg/hr]

[Kg/hr]

101.6548042

98.20426486

-

9722.222222

101.6548042

9820.426987

199.8590691 9722.222222

9922.081291 9922.081291

39

3.7 Overall Material Balance

Table 3-7 Overall Material Balance In ( Kg/hr) Stream

Comp.

No.

1

[Kg/hr]

2

[Kg/hr]

4

[Kg/hr]

Out (Kg/hr) 8

[Kg/hr]

11

[Kg/hr]

9

[Kg/hr]

12

[Kg/hr]

16

14

15

[Kg/hr]

[Kg/hr]

[Kg/hr]

6368.348857 101.6548042 98.20426486 C6H6 4976.804845 HNO3 119.4433163 4180.871204 H2SO4 2799.452725 2.376187 H 2O C6H5NO2 9722.222222 129.0884128 Na2CO3 75.4510778 H2CO3 172.9906513 Na2SO4 166.5544965 CaSO4 210.6460497 CaSO4.2H2O 7776.25757

Total

121.880935

6368.348857

129.0884128

166.5544965

14562.13027

210.6460497

4180.871204

14562.13027

40  

248.5317291

101.6548042

9820.426987

Table 3-8 all Streams of Material Balances

  Stream  NO. COMP.

2

1

[Kg/hr]

3

[Kg/hr]

4

[Kg/hr]

5

[Kg/hr]

6

[Kg/hr]

7

[Kg/hr]

8

[Kg/hr]

[Kg/hr]

[Kg/hr]

[Kg/hr]

[Kg/hr]

14

13

12

11

[Kg/hr]

15

17

16

[Kg/hr]

[Kg/hr]

[Kg/hr]

[Kg/hr]

18

[Kg/hr]

[Kg/hr]

C6H6

-



-

6368.348857

199.8590691

‐ 

199.8590691

-

-

199.8590691

-

-

199.8590691

101.6548042

98.20426486

-

-

-

HNO3

4976.804845

 

4976.804845

-

-

‐ 

-

-

-

-





-

-

-

-

-

-

H2SO4

-

‐ 

11944.33163

-

11944.33163

11824.88831 

119.4433163

-

-

-



-

-

-

-

11824.88831

11944.33163

H2O

2799.452725

119.4433163 

2986.082907

-

4409.155317

4365.063767 

44.0915532

-

-

44.0915532





-

-

-

4180.871204

184.192563

186.6301817

C6H5NO2

-

2.4376187 

-

-

9722.222222

‐ 

9722.222222

-

-

9722.222222





9722.222222

-

9722.222222

-

-

-

Na2CO3

-

‐ 

129.0884128

-

-





-

-

-

-

-

-

-

-

 

H2CO3

-

‐ 

-

-

-

-

-

75.4510778

-





-

-

-

-

-

-

Na2SO4

-

‐ 

-

-

‐ 

-

-

172.9906513

-

-

-

-

-

-

-

-

-

CaSO4

-

‐ 

-

-

‐ 

-

166.5544965

-

-

-

-

-

-

-

CaSO4.2H2O

-

-

-

-

-

-

-

-

-

-

210.6460497

-

-

-

-

-

-

Total

7776.25757

121.880935

16189.95208

10085.61616

129.0884128

248.5317291

9966.172836

166.5544965

210.6460497

9722.0812

101.6548042

9820.426987

4180.871204

12009.08088

12130.96181

 

19907.21938

6368.348857

-

-

-

26275.56824

41   

10

9

-

      Chapter Four Energy Balance

Chapter Four Energy Balance H.W

4

3

C.w

70oC

30oC

H.W

60oC

C.W

30oC  

5  

Note: Data necessary in appendix A.

4.1 Energy Balance on Nitrator C6H6 + HNO3

H2SO4

C6H5NO2 + H2O

∆Hr = -146948.0527 KJ/Kg.mol Qr =

* -146948.0527 = -11604756.91 KJ/hr

Q3 =

* ∆Hi * ni

∆Hi =

cpi dT

Qr = ∆HHNO3 = 131.250 (325.15 – 298.15) –

(323.152 – 298.152) +

*10-3 (325.153 – 298.153) = 2745.87058 KJ/Kg.mol 42   

*2745.87058 = 216846.4298 KJ/hr

QHNO3 =

*10-3(323.152-298.152) +

∆HH2O = 32.243 (323.15 – 298.15) + (323.153-298.153) –

*10-5

*10-9(323.154-298.154)

∆HH2O = 843.7765567 KJ/Kg.mol

* 843.7765567 = 139,821.6844 KJ/hr

QH2O =

* (502-252) = 3623.65625 KJ/Kg.mol

∆HH2SO4 = 139.1(50-25) +

* 3623.65625 = 441294.3716 KJ/hr

QH2SO4 =

Q3 = 216846.4298 + 139,821.6844 + 441294.3716 = 797962.4858 KJ/hr Q4 = ∆H4 * nBZ. ∆H4 = -33.917 (303.15-298.15) + (303.153-298.153) + Q4 =

*10-1(303.152-298.152) –

* ∆Hi * ni

∆Hi =

cpi dT

∆HBZ. = -33.917 (323.15-298.15) + *10-4(323.153-298.153) +

*10-1(323.152-298.152) – *10-8(323.154-298.154) 43 

 

-4

*10-8(303.154-298.154) = 416.7382512 KJ/Kg.mol 

* 416.7382512 = 33976.886 KJ/hr

Q5 =

*10

∆HBZ. = 2160.861183 KJ/Kg.mol QBZ. =

* 2160.861183 = 5528.96818 KJ/hr * (502-252) = 3623.65625 KJ/Kg.mol

∆HH2SO4 = 139.1(50-25) + QH2SO4 =

* 3623.65625 = 441294.3716 KJ/hr *10-3(323.152-298.152) +

∆HH2O = 32.243 (323.15 – 298.15) + (323.153-298.153) –

*10-5

*10-9(323.154-298.154)

∆HH2O = 843.7765567 KJ/Kg.mol QH2O =

* 843.7765567 = 206456.2648 KJ/hr (323.152-298.152) +

∆HN.B. = 295.3 (323.15-298.15) –

(323.153-298.153) = 4580.779561 KJ/Kg.mol QN.B. =

* 4580.779561 =361752.5534 KJ/hr

Q5 = 5528.96818 + 441294.3716 + 206456.2648 + 361752.5534 Q5 = 1015032.158 KJ/hr

The over all heat balance around nitrator Heat input + Heat generation = Heat out + Heat accumulation 0.0 S.S Q3+ Q4- Qr = Q5 + Qcooling Qcooling = 797962.4858 + 33976.886 + 11604765.9 – 1015032.158 44   

*10-3

Qcooling = 11,421,664.11 KJ/hr Qcooling = QJacketed + QCoil QJacketed = 0.75 Qcooling & QCoil = 0.25 Qcooling [explanatory note in chapter five] QJacketed = 0.75*11,421,664.11 = +8,566,248.085 KJ/hr QCoil = 0.25*11,421,664.11 = 2,855,416.028 KJ/hr Water inter jacket at T=30oC and leaves at T=65oC. QJacketed = ∆HH2O * n H2O *10-3 (338.152-303.152) +

∆HJacketed =32.243 (338.15 -303.15) + (338.153-303.153) –

*10-5

*10-9 (338.154-303.154)

∆HJacketed = 188.206832 KJ/Kg.mol n H2O =

= 7,209.391374 Kg.mol/hr

m. jacket = 129,913.2326 Kg/hr flow rate of water in jacket Water inter coil at T=30oC and leaves at T=70oC. ∆Hcoil = 32.243 (34315 -303.15) + (343.153-303.153) –

*10-3 (343.152-303.152) +

*10-9 (343.154-303.154)

∆Hcoil = 1353.828196 KJ/Kg.mol ncoil =

= 2,109.142088 Kg.mol/hr



mcoil = 38,006.74043 Kg/hr flow rate of water in coil

45   

*10-5

4.2 Separator Energy Balance

7

6

Separator  5

Assume perfect insulated system, so there is no energy loose through system. Q5 = 1015032.158 KJ/hr Q6 =

* ∆Hi * ni

∆Hi =

cpi dT * (502-252) = 3623.65625 KJ/Kg.mol

∆HH2SO4 = 139.1(50-25) + QH2SO4 =

* 3623.65625 = 436881.4277 KJ/hr *10-3(323.152-298.152) +

∆HH2O = 32.243 (323.15 – 298.15) + (323.153-298.153) –

*10-9(323.154-298.154)

∆HH2O = 843.7765567 KJ/Kg.mol

46   

*10-5

* 843.7765567 = 204391.7023 KJ/hr

QH2O =

Q6 = 436881.4277 + 204391.7023 = 641273.13 KJ/hr Q7 =

* ∆Hi * ni

∆Hi =

cpi dT

∆HBZ. = -33.917 (323.15-298.15) + (323.153-298.153) +

*10-1(323.152-298.152) –

*10-4

*10-8(323.154-298.154)

∆HBZ. = 2160.861183 KJ/Kg.mol QBZ. =

* 2160.861183 = 5528.96818 KJ/hr * (502-252) = 3623.65625 KJ/Kg.mol

∆HH2SO4 = 139.1(50-25) + QH2SO4 =

* 3623.65625 = 4412.943716 KJ/hr *10-3(323.152-298.152) +

∆HH2O = 32.243 (323.15 – 298.15) + (323.153-298.153) –

*10-5

*10-9(323.154-298.154)

∆HH2O = 843.7765567 KJ/Kg.mol QH2O =

* 843.7765567 = 2064.562649 KJ/hr

∆HN.B. = 295.3 (323.15-298.15) –

(323.152-298.152) +

(323.153-298.153) = 4580.779561 KJ/Kg.molQN.B. = 4580.779561 =361752.5534 KJ/hr 47   

*10-3 *

Q7 = 5528.96818 + 4412.943716 +2064.562649 + 361752.5534 Q7 = 373759.0279 KJ/hr

4.3 Energy Balance on Evaporator

16 3

1 HNO3 64wt. %

6

18

H2SO4 98 wt.%

250oC

2

17 Out

Steam 250oC 3973000 pa

17 In

Q6 = 641273.13 KJ/hr ∆H16 = 32.243 (373.15 – 298.15) + (373.153-298.153) –

*10-3(323.152-298.152) +

*10-9(373.154-298.154) + 40683

∆H16 = 2545.822066 + 40683 = 43228.82207 KJ/Kg.mol Q16 =

* 43228.82207 = 10029641.36 KJ/hr

Q17 =

* ∆Hi * ni

∆Hi =

cpi dT

48   

*10-5

∆HH2SO4 = 139.1(100-25) + QH2SO4 =

* (1002-252) = 11163.28125 KJ/Kg.mol

* 11163.28125 = 1345886.562 KJ/hr *10-3(323.152-298.152) +

∆HH2O = 32.243 (373.15 – 298.15) + (373.153-298.153) –

*10-9(373.154-298.154) + 40683

∆HH2O = 43228.82207 KJ/Kg.mol QH2O =

* 43228.82207 = 441866.1228 KJ/hr

Q17 = 1345886.562 + 441866.1228 = 1,787,752.684 KJ/hr Q6 + QSteam = Q16 + Q17 QSteam = Q16 + Q17 - Q6 QSteam = 10029641.36 + 1,787,752.684 + 641273.13 = 11,176,120.91 KJ/hr



mSteam =

= 6,512.131986 Kg/hr

nsteam = 361.383573 Kg.mol/hr

Heat Exchanger Energy Balance

17

Cooling water 30oC

17  

100oC

65.5 oC 50oC

49   

*10-5

Q17(In H.Ex.) = 1,787,752.684 KJ/hr * (65.52-252) = 5,919.256238 KJ/Kg.mol

∆HH2SO4 = 139.1(65.5-25) + QH2SO4 =

* 5,919.256238 = 713,674.4704 KJ/hr *10-3(338.652-298.152) +

∆HH2O = 32.243 (338.65 – 298.15) + 5

(338.653-298.153) –

*10-9(338.654-298.154)

∆HH2O = 1,369.293843 KJ/Kg.mol QH2O =

* 1,369.293843 = 13,996.32311 KJ/hr

Q17(Out..Ex.) = 713,674.4704 + 13,996.32311 = 727,643.7935 KJ/hr Q17(In H.Ex.) = Q17(Out..Ex.) + Qcooling Qcooling = Q17(In H.Ex.) - Q17(Out..Ex.) Qcooling = 1,787,752.684 - 727,643.7935 = 1,060,108.891 KJ/hr *10-3(323.152-303.152) +

∆HCooling = 32.243 (323.15 – 303.15) + *10-5(323.153-303.153) –

*10-9(323.154-303.154)

∆HCooling = 675.3912584 KJ/Kg.mol nCooling =

= 1,569.621871 KJ/hr



mCooling = 28,284.58611 Kg/hr Energy Balance on 1st. mixing point Because high concentration of H2SO4 added (98wt.%) the heat of mixing is Zero p.433, figure (12.17) [26]. 50   

*10-

Q2 =

* ∆Hi * ni

∆Hi =

cpi dT * (302-252) = 716.93625 KJ/Kg.mol

∆HH2SO4 = 139.1(30-25) +

* 716.93625

QH2SO4 =

= 873.0958735 KJ/hr *10-3(303.152-298.152) +

∆HH2O = 32.243 (303.15 – 298.15) + 5

(303.153-298.153) –

*10-

*10-9(303.154-298.154)

∆HH2O = 168.3852983 KJ/Kg.mol QH2O =

* 168.3852983

= 22.77797736 KJ/hr

Q2 = 873.0958735 + 22.77797736 = 895.8738509 KJ/hr Q18= Q17(Out..Ex.) + Q2 Q18 = 727,643.7935 + 895.8738509 = 728,539.6673 KJ/hr

*139.1(T-25) +

Q18 =[

32.243 (T – 298.15) +

* (T2-252)] +[

*10-3(T2-298.152) +

*10-9(T4-298.154) ] Find T18 by trial & error T18 = 65.15oC Note Heat of mixing of HNO3 not takes under consideration. ∆Hdil.(mix.) = 11,864.53747 KJ/Kg.mol (5.104) [21]. 51   

*

*10-5 (T3-298.153) –

4.4 Washing Process Energy Balance 4.4.1 1st Washing process Energy Balance Na2CO3 + H2SO4

Na2SO4 + H2CO3

∆Hro = -699.65 – 1413.891 + 1131.546 ∆Hro = -170.485 KJ/g.mol ∆Hro = -170,485 KJ/Kg.mol ∆Hr = ∆Hro + ∆HProduct - ∆HReactant ∆HNa2CO3 = 111.08 ∆T ∆HNa2CO3 = 111.08 * (30 – 25) = 555.4 KJ/Kg.mol ∆HH2SO4 = 139.1(50-25) +

* (502-252) = 3,623.65625 KJ/Kg.mol

∆HH2CO3 = 126.1128611 ∆T ∆HNa2SO4 = 128.229 ∆T ∆HProduct - ∆HReactant = 126.1128611 ∆T + 128.229 ∆T - 3,623.65625 - 555.4 ∆HProduct - ∆HReactant = 254.3418611 ∆T – 4,179.05625 ∆Hr = -170,485 + 254.3418611 ∆T – 4,179.05625 ∆Hr = -174,664.0563 + 254.3418611 ∆T Qr =

[-174,664.0563 + 254.3418611 ∆T]

Qr = 1.217815215 [-174,664.0563 + 254.3418611 ∆T] Qr = -212,708.5452 + 309.7413883 ∆T Q7 = 373759.0279 KJ/hr 52   

∆H8 = 111.08 * (30 – 25) = 555.4 KJ/Kg.mol Q8 =

* 555.4 = 676.374704 KJ/hr

Q9 =

* ∆Hi * ni

∆Hi =

cpi dT

∆HNa2SO4 = 128.229 ∆T ∆HH2CO3 = 126.1128611 ∆T Q9 = [

* 128.229 ∆T] + [

* 126.1128611 ∆T]

Q9 = 156.1592272 ∆T + 153.5821611∆T Q9 = 309.7413883 ∆T Q10 = ∆HMixture * ni ∆HMixture =

cpMixture dT

cp10 = cpMixture = 277.604511 - 0.823102128 ∆T + 1.594487804*10-3∆T2 + 2.067652194*10-9∆T3 ∆T2 +

∆H10 = ∆HMixture = 277.604511 ∆T ∆T3 +

*10-3

*10-9∆T4

∆HMixture = ∆H10 = 277.604511 ∆T - 0.411551064 ∆T2 + 5.314959347*10-4 ∆T3 + 5.169130485 *10-10 ∆T4 Q10 = 83.97733129 [277.604511 ∆T - 0.411551064 ∆T2 +5.314959347*10-4 ∆T3 + 5.169130485 *10-10 ∆T4 53   

Q10 = 23,312.48936 ∆T – 34.56096004 ∆T2 + 0.04463361 ∆T3 + 4.340897832 * 10-8 ∆T4 Heat input + Heat generation = Heat out + Heat accumulation 0.0 S.S Q7 + Q8 - Qr = Q9 + Q10 373759.0279 + 676.374704 – (-212,708.5452 + 309.7413883 ∆T) = 309.7413883 ∆T + 23,312.48936 ∆T – 34.56096004 ∆T2 + 0.04463361 ∆T3 + 4.340897832 * 10-8 ∆T4 587,143.9477 = 23,931.97214 ∆T - 34.56096004 ∆T2 + 0.04463361 ∆T3 + 4.340897832 * 10-8 ∆T4 This equation above is solved by trial and error until the right hand equals the left hand. T = 62.88295021 oC Q7 = 373759.0279 KJ/hr Q8 = 676.3475704 KJ/hr Q9 = 11,733.91759 KJ/hr Q10 = 563,676.1122 KJ/hr Qr = - 200,974.6276 KJ/hr

4.4.2 2nd Washing process Energy Balance

CaSO4 + 2H2O

CaSO4.2H2O

∆Hro = -2,024.021 + (2* 286.025) + 1,435.097 ∆Hro = -16.874 KJ/g.mol ∆Hro = -16,874 KJ/Kg.mol 54   

∆Hr = ∆Hro + ∆HProduct - ∆HReactant∆HH2O = 32.243 (336.0329502 – 298.15) + *10-3 (336.0395022-298.152) +

*10-5(336.03295023-298.153) -

*10-9 (336.03295024-298.154) ∆HH2O = 1,280.433889 KJ/Kg.mol ∆HCaSO4 = 99.73 (30 – 25) ∆HCaSO4 = 498.65 KJ/Kg.mol ∆HCaSO4.2H2O = 186.149 ∆T ∆HProduct - ∆HReactant = 186.149 ∆T - 498.65 – (2* 1,280.433889) ∆HProduct - ∆HReactant = 186.149 ∆T - 3,059.517779 ∆Hr = -16,874 + 186.149 ∆T - 3,059.517779 ∆Hr = -19,933.51778 + 186.149 ∆T Qr =

[-19,933.51778 + 186.149 ∆T]

Qr = -24,386.78579 + 227.7358085∆T Q10 = 563,676.1122 KJ/hr ∆H11 = 99.73 (30 – 25) ∆H11 = 498.65 KJ/Kg.mol Q11 =

* 498.65 = 610.0514153 KJ/hr

∆H12 = ∆HGypsum = 186.149∆T Q12 =

* 186.149 ∆T

Q12 = 227.7358085 ∆T 55   

Q13 = ∆HMixture * ni ∆HMixture =

cpMixture dT

Cp13=cpMixture = 284.968122 – 0.847861952 ∆T+ 1.642023363 *10-3∆T2 + 2.237621333 *10-9∆T3 ∆T2 +

∆HMixture =284.968122 ∆T -

*10-3 ∆T3 +

*10-9 ∆T4 ∆HMixture = ∆H13 =284.968122 ∆T - 0.423930976 ∆T2 + 5.47341121*10-4 ∆T3 + 5.594053333 *10-10 ∆T4 Q13 = 81.53051923 [284.968122 ∆T - 0.423930976 ∆T2 + 5.47341121*10-4 ∆T3 + 5.594053333 *10-10 ∆T4] Q13 = 23,233.59895 - 34.56331259∆T2 + 0.044625005 ∆T3 + 4.560860728 *10-8 ∆T4 Heat input + Heat generation = Heat out + Heat accumulation 0.0 S.S Q10 + Q11- Qr = Q12 + Q13 563,676.1122 + 610.0514153 – (-24,386.78579 + 227.7358085∆T) = 227.7358085 ∆T + 23,233.59895 - 34.56331259∆T2 + 0.044625005 ∆T3 + 4.560860728 *10-8 ∆T4 588,672.9494 = 23,789.07057 ∆T- 34.56331259∆T2 + 0.044625005 ∆T3 + 4.560860728 *10-8 ∆T4 This equation above is solved by trial and error until the right hand equals the left hand. T= 63.33466274 oC Qr -15,656.61038 KJ/hr Q12 = 10,646.90855 KJ/hr 56   

Q13 = 567,379.1321 KJ/hr

4.5 Distillation Energy Balance

14 R 13 IN

63.335oC

80.1oC

D

13 Out

192.1oC 15 200.87oC

From calculation of bubble point at feed finds T13 (OUT H.EX.) = 192.1oC, & find T= 200.87oC at bottom section.

Heat Exchanger Energy Balance

13 In

63.334 oC

Steam 250oC

Steam 210oC

Q13(IN H.EX.) = 567,379.1321 KJ/hr

57   

13 Out

192.1oC

Q13 (OUT H.EX.) = ∆Hi =

* ∆Hi * ni

cpi dT

∆HBZ. = ∆HLiquid + λ + ∆HVapoure ∆HLquid =

cpi dT *10-1(353.252-298.152) –

∆HLiquid = -33.917 (353.25-298.15) + *10-4(353.253-298.153) +

*10-8(353.254-298.154)

∆HLiquid = 5,012.048424 KJ/Kg.mol λ = 30,781 KJ/Kg.mol ∆HVapour =

cpi dT

∆HVapoure = 8.314 [ -0.206 (465.25 – 353.25) + 353.252) –

* 10-3 * (465.252 –

* 10-6 (465.253 – 353.253)

∆HVapoure = 12,607.37459 KJ/Kg.mol ∆HBZ = 5,012.048424 + 30,781+ 12,607.37459 = 48.42302 KJ/Kg.mol QBZ. =

* 48.42302 = 123,841.5502 KJ/hr

∆HN.B. = 295.3 (465.25-298.15) –

(465.252-298.152) +

(465.253-298.153) = 34,706.15308 KJ/Kg.mol QN.B. =

* 34,706.15308 = 2,740,808.486 KJ/hr

Q13 (OUT H.EX.) = 123,841.5502 + 2,740,808.486 = 2,864,650.036 KJ/hr 58   

*10-3

Q13(IN H.EX.) + QHeating = Q13 (OUT H.EX.) QHeating = Q13 (OUT H.EX.) - Q13(IN H.EX.) QHeating = 2,864,650.036 - 567,379.1321= 2,279,270.904 KJ/hr



QHeating = m * ( hg2 – hg1)



m=

= 765,756.968 Kg/hr

Distillation Energy Balance Q13 (OUT H.EX.) + QReboiler = Q14 + Q15 + QCondencer Material Balance on Condenser R = Reflux ratio = Rm =

[

–α

]

α = poBZ./ PoN.B α=

= 19.54121672

Rm =

[

–19.54121672 *

Rm = 1.1718560223 Ractual = 1.2 Rm Ractual = 2.062272268 V=L+D L = Ractual * D 59   

L = 2.062272268 * 101.6548042 L = 209.6398836 Kg/hr L = 2.68390582 Kg.mol/hr V = 209.6398836 + 101.6548042 V = 311.2946878 Kg/hr V = 3.985337189 Kg.mol/hr QCondencer = V λBZ. QCondencer = 3.985337189 * 30,781 QCondencer = 122,672.664 KJ/hr Q14 = ∆HBZ. * ni ∆HBZ. = -33.917 (353.25-298.15) + *10-4(353.253-298.153) +

*10-1(353.252-298.152) – *10-8(353.254-298.154)

∆HBZ. = 5,012.048424 KJ/Kg.mol Q14 = QBZ. =

* 5,012.048424 = 6,522.83704 KJ/hr

Q15 =

* ∆Hi * ni

∆Hi =

cpi dT

∆HBZ. = ∆HLiquid + λ + ∆HVapoure ∆HLquid =

cpi dT *10-1(353.252-298.152) –

∆HLiquid = -33.917 (353.25-298.15) +

60   

*10-4(353.253-298.153) +

*10-8(353.254-298.154)

∆HLiquid = 5,012.048424 KJ/Kg.mol λ = 30,781 KJ/Kg.mol ∆HVapour =

cpi dT

∆HVapoure = 8.314 [ -0.206 (474.02 – 353.25) + 353.252) –

* 10-3 * (474.022 –

* 10-6 (474.02– 353.253)

∆HVapoure = 13,716.10935 KJ/Kg.mol ∆HBZ = 5,012.048424 + 30,781+ 13,716.10935 = 49,509.15778 KJ/Kg.mol QBZ. =

* 49,509.15778 = 62,245.68482 KJ/hr

∆HN.B. = 295.3 (474.02-298.15) –

(474.022-298.152) +

*10-3

(474.023-298.153) = 36,925.461 KJ/Kg.mol QN.B. =

* 36,925.461 = 2,916,071.298 KJ/hr

Q15 = 62,245.68482 + 2,916,071.298 = 2,978,316.983 KJ/hr

Q13 (OUT H.EX.) + QReboiler = Q14 + Q15 + QCondencer QReboiler = Q14 + Q15 + QCondencer - Q13 (OUT H.EX.) QReboiler = 6,522.83704 + 2,978,316.983 +122,672.664 - 2,864,650.036 QReboiler = 242,862.4479 KJ/hr

61   

Table 4-1 all Streams of Energy Balances

Stream NO.

2

1

3

4

5

6

7

8

10

9

12

11

13 IN

17 out

14

15

17 IN

16

17 OUT

18

COMP.

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr] [KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[Kg/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

[KJ/hr]

C6H6

-

-

-

33976.886

5528.96818

-

-

-

-

8567.670381

-

-

8676.50917

123841.5502

6522.83704

62245.68484

-

-

-

-

HNO3

43435.94798

-

216846.4298

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

H2SO4

-

873.0958735

441294.3716

-

441294.3716

436881.4277

4412.943716

-

-

-

-

-

-

-

-

-

-

713647.4704

714329.4225

H2O

26159.21003

22.77797736

139821.6844

-

206456.2648

204391.7023

2064.562649

-

-

3132.981073

-

-

-

-

-

-

10029641.36

441866.1228

13996.32311

14055.2733

C6H5NO2

-

-

-

-

361752.5534

-

361752.5534

-

-

551975.5477

-

-

558702.6315

2740808.486

-

2916071.298

-

-

-

-

Na2CO3

-

-

-

-

-

-

-

676.3745704

-

-

-

-

-

-

-

-

-

-

-

-

H2CO3

-

-

-

-

-

-

-

-

5915.772227

-

-

-

-

-

-

-

-

-

-

-

Na2SO4

-

-

-

-

-

-

-

-

5818.145361

-

-

-

-

-

-

-

-

-

-

-

CaSO4

-

-

-

-

-

-

-

-

-

-

610.0514153

-

-

-

-

-

-

-

-

-

CaSO4.2H2O

-

-

-

-

-

-

-

-

-

-

-

10646.90855

-

-

-

-

-

-

-

-

Total

69595.15801

895.8738509

797962.4858

33976.886

1015032.158

641273.13

373759.0279

676.3745704

11733.91759

563676.1992

610.0514153

10646.90855

567379.1321

2864650.036

6522.83704

2978316.983

10029641.36

1787752.684

727643.7935

728384.6957

Pressure atm

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

Temperature o C

30

30

50

30

50

50

50

30

62.88295021

62.88295021

30

63.33466274

63.33466274

192.1

80.1

200.87

100

100

65.5

65.15

62   

14

Feed Benzene

8 4 7 3

7

Washing Tank nd 1

13

13 10 Heater

9 1

18

5

                  

15

Settler

Product N.B

  10

Nitrator

6

Distillation Column

11

2 Washing Tank st 2

13

12 17

17 Vaporizer Cooling

 

Production of Nitrobenzene

 

63  

  Figure 4-1 Process Flow Diagram

      Chapter Five Equipment Design

Chapter Five Equipment Design Note: Data necessary in appendix A.

5.1 Nitrator Design A simple stirred tank reactor is used, sized to give sufficient residence time, and provided with sufficient agitation to promote dispersion of the organic phase [4]. Good heat transfer can be assumed by use external jacket & internal coil. Nitration vessel made of stainless steel (18Cr/8 Ni) (316) [4&16]. Calculation of Nitrator volume Residence time = τ = 10 min [29] τ = 0.166666666 hr τ

=

νo = stream 3 + stream 4 νo = [

+

+

νo = 20.37924292 m3/hr V = τ * νo V = 0.166666666 * 20.37924292 64

+

]

V = 3.396540473 m3 = 897.1088536 gal This volume is very satisfied and very close to reference [16]. Added 10% to the volume of nitrator for safety and increase the efficiency of mixing. V = 3.396540473 * 1.1 V = 3.73619452 m3 D= D = 2.181070978 m Agitator Design According to figure (9-16) [30] illustrated the relationship between vessel volume and viscosity, so selected turbine impeller (disk mounted flat blade turbine). DA = D/3 DA = 2.181070978/3 = 0.727023659 m HA = D/3 HA = 2.181070978/3 = 0.727023659 m r = D/4 r = 2.181070978/4 = 0.545267744 m a = 2.181070978/5 = 0.436214195 m HL = D = 2.181070978 m 65

Also use four symmetric baffles b = width of baffle = D/10 b = 2.181070978/10 = 0.2181070978 m

0.218

2.181 0.7

0.73

2.181

Calculation the shaft power required to drive the an agitator The shaft power required to operate the stirrer can be calculated by the following equation [31]: PA = NP* ρ * N3 *D5A NP = Power Number, determined from figure (9.7)[31]. Re =

66

Assume the agitator rotation per minute (N) = 100 rpm =1.67 rps. Re = Re = 8.074454885 * 104 [is very suitable] NP = 5 PA = 5 * 1173.870615 * (1.67)3 * (0.727023659)5 PA = 5,519.239048 watt = 5.519239048 Kwatt

Design the Jacket around Nitrator The jacket is used to cool the nitrator content and keep temperature at 50oC. Select dimple jacket, assume the spacing between jacket and vessel wall is 100mm and the jacket is fitted with a spiral baffle, the pitch between the spirals is 200mm. The jacket is fitted to the nitrator section and extend to a height of 80% from the height of the nitrator. HJacket = 0.80 * 2.181070978 = 1.744856782 m The baffle forms continuous spiral chanel section 100mm * 200mm. Number of spirals = height of jacket / pitch Number of spirals =

= 8.72428391

9

Cross- sectional area of channel = 100 * 200 * 10-6 = 0.02m2 67

de =

= 133.333mm

length of channel = 9 *

* 2.181070978 = 61.66832905 m

From Energy Balance: . mJacket = 129,913.2326 Kg/hr Physical properties of water at mean temperature

= 47.5oC as fellows

[32]: Cp= 4.174 KJ/Kg.oC, ρ = 989.25 Kg/m3, µ = 5.755 * 10-4, pr = 3.74 & K = 0.64225. u=

*

u = 1.823958001m/s Nu = 0.023 Re0.8 Pro.33 [

]0.14

Water is not viscose so neglect viscosity correction term. Nu = 0.023 Re0.8 Pro.33 Re =

Re =

= 62,867.15905

68

Re = 4.180355498 * 105 Nu = 0.023 * (418,035.5498)0.8 * (3.74)0.33 Nu = 1,116.21033 Nu =

= 5,376.659075 W/m2.oC

hj =

∆p = 8 jf (

)(

)

jf = 2* 10-3 from figure (12.24) [23]. ∆p = 8 * (2 * 10-3)

]*

]

∆p = 12,177.17195 pa = 1.767PSI < 10 PSI (acceptable) Design the Coil inside the Nitrator Diameter of pipe of coil = D/30 Diameter of pipe of coil =

= 0.072702365 m

Not found pipe diameter 72.7mm in standerd, so take outside diameter standard steel pipe as 76.1mm, wall thickness as 3.65mm [34] Inside diameter = di = do + 2Lw

69

di = 76.1- 3.65 = 68.8mm Physical proprieties of vessel content at 50oC as fellows [22, 23, 28&33]: Kav. = 0.326087319, ρav. = 1,425.7889 Kg/m3, µav. = 2.228013388 *10-3 pa.s & cpav. = 1.947772473 KJ/Kg.k The heat transfer coefficient of vessel can be calculated from equation below: =C

[

]a [

]b [

]c

C,a,b,c are constants according to type of agitator and surface type (coil or jacket) C = 1.1, a = 0.62, b = 0.33, c = 0.14 [23] Neglect the viscosity correction term. = 1.1

] 0.62

[ ]

[ hv = 4,269.214368 W /m2.oC Tube side hi = 4200 (1.35 + 0.02 t) ut0.8 / di0.2 t=

= 50oC

70

A=

d i2

A=

* (68.8)2

A = 3717.635083 mm2 u=

*

*

u = 2.869804254 m / s hi = 4200 (1.35 + 0.02 (50)) (2.869804254)0.8 / (68.8)0.2 hi = 9,841.95296 W / m2. oC =

+

+

+

*

Kw = 16.3 for stainless steel [32]. =

+

+

+

= 7.705482183 * 10-4

Uo = 1,297.777318 W/m2.oC Q = Uo Ao ∆T From Energy Balance: Qcoil = 2,855,416.028 KJ /hr = 793,171.1189 J/s 71

*

= 15.27941481 m2

Ao =

Length of tube =

Length of tube =

= 63. 910491481m

Assume Number of turns = 19 turns = 1.090535489m

Diameter of turn=

1m

Mechanical Design [23&30] Calculation of the cylindrical part Thickness of cylindrical part of Nitrator can be calculated directly from equation bellow: t=

+C

J = 0.85, f = 175N/mm2, C = 1mm P= 1.1*1 =1.1atm = 0.1114575N/mm2 t=

t = 1.817438078mm

+1

2mm 72

Calculations of the Reactor cover thickness Thickness of the cover can be calculated from: t=

J = 1[The cover consist of one piece] t=

t = 0.694606292mm Calculations of the Height of cover The height of cover (distance from the head of reactor to the tangent line) can be calculated by knowing the major &minor axis. Rs = a2/b , Rs = Di = 2.181070978 m 2a = major axis = Do Do = Di + 2(thickness) Do = 2.181070978 + 2(1.817438078*10-3) Do = 2.184706233 m 2b = minor axis = 2h h = height of head from tangent line a = 2.184706233/2 = 1.092353117m b = a2/Rs 73

b = 1.0923531172/2.184706233 = 0.546176558 m h = 0.546176558 m height of cover Calculation of the volume of Nitrator V = 0.05Di3 + 1.65 t D2 V = 0.05* 2.1810709783 + 1.65 * 0.694606292*10-3 * 2.1810709782 V = 0.524227513 m3 Over all volume of Nitrator = volume of cylindrical part + volume of covers VTotal = 3.73619452 + 2(0.524227513) VTotal = 4.784649546 m3 Overall length of reactor = length of cylindrical part + 2*length of cover LTotal = 2.181070978 + 2* 0.546176558 LTotal = 3.273424094 m Calculation of the weight of Nitrator Wv = 240 Cv Dm (Hv + 0.8 Dm) t Cv = 1.08, factor to account weight of nozzles Dm = Di + t Dm = 2.181070978 + 1.817438078*10-3 = 2.182888416 m Hv = Di = 2.181070978 m Wv = 240 * 1.08 * 2.182888416 (2.181070978 + 0.8 * 2.182888416) 74

Wv = 2222.130942 Kg Design the supporting of Nitrator The reactor supporting legs depend mainly on the weight of Nitrator and material inside. Wv = 2222.130942 Kg Weight of material inside = 26,275.56824 Kg Total weight of Nitrator = 2222.130942 + 26,275.56824 = 28,497.69918 Kg Density of stainless steel (18% Cr, 8% Ni) = 7,817 Kg/m3 [32]. Each support bear weight of =

Each support bear weight of =

= 7,124.424796 Kg

= 0.911401405 m3

The volume of one leg support =

For supporting leg L/D = 8 V=

D 2L

V=

D2 (8D) =2

D=

D3

= 0.525424043m 75

L = 8* 0.525424043 = 4.203392345m Wind load The effect of the wind on tall vessels (over 50m) although the calculation about this small effect is made. Wind load = Fw = Pw * Deff Pw = 1280 N/m2 Deff = Do = 2.184706233 m Fw = 1280 * 2.184706233 = 2,796.423978 N/m Bending moment at any plane = Ms = Fw / 2 *S2 S = Di = 2.181070978m Ms =

* (2.181070978)2 = 6,645.304084N.m

The Nitrator does not consider tall vessel so the effect of wind is not high.

76

5.2 Settler Design [23] Design of Settler (Decanter) to separate a crude nitrobenzene from a spent acid (heavy phase). Crude nitrobenzene flow rate (stream 7) = 10,085.61616 Kg/hr Spent acid flow rate (stream 6) = 16,189.95208 Kg/hr ρd(Croude Nitrobenzene) = 1,173.870615 Kg/m3 [22,28&33]. ρC(Spent Acid) = 1,582.722727 Kg/m3 [22,28&33]. µd(Croude Nitrobenzene) = 1.280716063 * 10-3 pa.s µc (Spent Acid) = 2.81813726 * 10-3 pa.s Take dd = 150µm (droplet diameter) ud =

ud = ud = -1.779029395 * 10-3 m/s (rising) As the flow rate is small, use a vertical cylindrical vessel.

LC =

*

= 2.84143826 * 10-3 m3/s

77

ud > uc ( the decanter vessel is sized on the basis that the velocity of the continuous phase must be less than settling velocity of the droplets of the dispersed phace) [23]. Ai = Lc/uc Ai =

= 1.597184548 m2

Ai =

r=

= 0.71302148 m

Diameter of vertical cylinder = 1.426048961 m Take the height as twice the diameter, a reasonable value for a cylinder. Height = 2.852085922 m Take the dispersion as 10 percent of the height =0.285208592 m Check the residence time of the droplets in the dispersion band =

= 160.3169644 s = 2.671949407 min

This is satisfactory , atime of 2-5 min is normally recommended. Check the size of the spent acid (continuous, heavy phase) droplets that could be entrained with the crude Nitrobenzene (light phase).Velocity of the *

Velocity crude Nitrobenze phase = 78

*

Velocity crude Nitrobenze phase = 1.494254608 * 10-3 m/s (stock’s law)

dd =

dd =

dd = 9.267388216 * 10-5 m = 92.67388216 µm ( which is very satifactory; below 150µm). Piping Arrangement To minimize entrainment by the jet of the liquid entering the vessel, the inlet velocity for a decanter should keep below 1m/s. Flow-rate =

*

Flow-rate = 5.22803863 * 10-3 m3/s Area of pipe =

Pipe diameter =

= 5.22803863 * 10-3 m2

= 0.081587655 m = 81.587655 mm say

88.9 diameter of the standerd steel pipe [34]. Take the position of the interface as half-way up the vessel and the light liquid off-take as at 90 percent of the vessel height. 79

Z1 = 0.9 * 2.852085922 = 2.56687733 m Z3 = 0.5 * 2.852085922 = 1.42604296 m Z2 =

Z2 =

+ 1.426042961

Z2 = 2.272174706 m Proposed Design

Liquid- light

D = 1.4 m Heavy liquid

take off

take off

Crude N.B

Z1 = 2.6 m

Z3 = 1.4 m

Z2 =2 m

Spent Acid

80

Mechanical Design The material of construction used is stainless steel [4], select stainless steel (18 Cr / 8 Ni) (304) which is corrosion resistance. Calculation of the Thickness of Decanter Thickness of the decanter can be calculated directly from equation bellow: t=

+C

J = 0.85, f = 145N/mm2, C = 1mm, D = 1.426 * 103mm P= 1.1*1 =1.1atm = 0.1114575N/mm2 t=

t = 1.645072183 mm

+1

2mm less than 7mm so that take the thickness 6mm [23]

Calculation the thicness of domed ends: Select the ellipsodial heads t=

t=

t = 0.644838821mm

0.645mm

81

5.3 Heat Exchanger Design [23]

Spent Acid T2=65.5oC Cooling water

hot water

o

t2=30oC

t1 =30 C

Spent Acid T1=100oC

The heat exchanger which is used as cooller to cool the spent acid from vaporizer from 100oC to 65.5 by using cold water. water is corrosive more than Spent acid, so assign to tube side. Operating Condition Temperature of a hot spent acid inputT1 = 100oC Temperature of a cold spent acid outputT1 = 65.5oC Temperature of a cold water input t1 = 30oC Temperature of a hot water input t2 = 50oC

T1=100oC ∆T1

{ T2=65.5oC

o

T2=50 C

}∆T t1=30oC

82

2

The hot spent acid & cold water passed counter currently ( more efficient than co-current). From energy balance: QCooling = 1,060,108.891 KJ/hr = 294.4746919 KWatt

.

mH2O = 28,284.58611 Kg/hr = 7.856829475 Kg / s Mean Temperature Difference (∆Tm) ∆Tlm =

∆Tlm =

(T

1

− t 2 ) − ( T2 − t1 ( T1 − t 2 ) ln ( T2 − t1 )

)

(100 − 50) − (65.5 − 30) (100 − 30) ln (65.5 − 30)

= 42.33696435 o C

∆Tm = Ft ∆Tlm Use one shell and two tube passes.

T2 = 65.5 °C

R = ( T1 – T2 ) / ( t2 – t1 )

t1 = 30 °C

S = ( t2 – t1 ) / ( T1 – t1)

t2 = 50 °C

R = (100 – 65.5) / ( 50 –30)= 1.725

T1 =100 °C

S = ( 50 – 30 ) / (100 – 30 ) = 0.285714285 From figure (12.19) [23] at R = 1.725 & S = 0.285714285 → Ft = 0.95

∆Tm = 0.95 * 42.33696435 = 40.22011613oC From table (12-1) [23] choose U = 800 W/m2.oC. 83

Provisional area Q = U A ∆Tm A=

= 9.151971708 m2

Pipe Dimension Choose 20mm o.d, 16mm i.d, 4.88m long tube table (12.3) [23] Allowing for tube sheet thicness, take L = 4.83m, material of construction Cupro-Nickel. Area of one tube = π do L Area of one tube = π* 20*10-3 * 4.83 * 10-3= 0.30347785 m2 Number of tubes = Nt = A / At Number of tubes = 9.151971708 / 0.30347785 = 30.15696763

30 tube

Use 1.25 Triangular pitch, this type of pitch is more efficient than rectangular pitch. Db = bundle diameter = do (Nt / k1 ) 1/n1

Pt Flow

From table (12-4) [23], k1 = 0.24, n1= 2.207 Db = 20 * (30 / 0.249)1/2.207 Db = 175.3490987 mm

Triangular Pitch

Use a split-ring floating head type, assume clearance = 30mm Shell diameter; Ds = 175.3490987+ 30 = 205.3490987 mm

84

Tube – Side Coefficient Mean temperature = (30 + 50) /2 =40°C Physical properties of water at mean temperature [32]: Cp = 4.174kJ/kg.°C, ρ = 992.04 kg/m3, µ = 6.556 * 10-4 pa.s, Kf =0.6328 W/m °C , Pr = 4.334. tube cross-sectional area = π di2 /4 = π (16)2 /4 = 201.0619296 m2 tube per pass = 30 / 2 = 15 total flow area = At = 15 * 201.0619296 * 10-6 = 3.015928947 * 10-3 m2

.

Mass velocity (G) = mH2O/At Mass velocity (G) = 7.856829475/ 3.015928947*10-3 Mass velocity (G) = 2,605.110934kg/m2.s Water linear velocity = 2,605.110934 / 992.04 = 2.626014005 m/s Re = ρ ut d /µ Re = 992.04 * 2.626014005 * 16 * 10-3 / 6.556 * 10-4 = 6.357805817 * 104 hi = 4200 (1.35 + 0.02 t) ut0.8 / di0.2 hi = 4200 ( 1.35 + 0.02 (40)) (2.626014005)0.8 / (16)0.2 hi = 11,227.97364 W/m2.oC or hi d i = J h Re Pr 0.33 ( µ / µ w kf

)0.14

Negiect (µ/µw) 0.14 From Figure (12.23)[23], jh = 3.1×10-3 85

hi = (0.6328/16 * 10-3) ( 3.1 * 10-3) (6.357805817 * 104) (4.334) 0.33 hi = 12,647.03674W/m2 °C take the lower value hi = 11,227.97364 W/m2.oC calculation of tube teperature hi (tw – t) = U (T – t) 11,227.97364 (tw – 40) = 800 (82.75 – 40) tw = 43.03245965oC

43 oC

µw = 6.199243243 * 10-4 pa.s at 43 oC

[

]0.14 =

[

]0.14 = 1.007864243

1[no correction factor

needed] Shell – Side Coefficient Choose baffle spacing = lB = 0.2Ds [23] lB = 0.2 * 205.3490987 = 41.06981914mm tube pitch = 1.25 do = 1.25 (20) = 25mm As =

= 1.686730069*10-3m2

As =

.

mspent acid = 12,009.08088 Kg/hr = 3.3358558 Kg/s Gs =

= 1977.705776 Kgde = 86

( pt2 – 0.917 do )

de =

(252 – 0.917 * 202 ) = 14.201 mm

all physical properties at 82.75oC of spent acid [24, 28&32]: Cp = 1.590330869 kJ/kg.°C ρ = 1,748.959499 kg/m3 µ = 5.376377382 * 10-3 pa.s Kf =0.401408274 W/m °C Pr = 2.130055474 Re =

=

= 5.223851997 * 103

Choose 25 percent baffle cut, from figure ( 12.29) [23], jh = 2.4 * 10-2 hs =

jh Re pr1/3 [

]0.14

Negiect (µ/µw) 0.14 hs =

* 2.4 * 10-2 * ( 5223.851997) * ( 2.130055474)1/3

hs = 4,559.6671 W /m2.oC Calculation of the Shell Temperature hS (T–Tw) = U (T – t) 4,559.6671 (tw – 40) = 800 (82.75 – 40) tw = 75.24945243oC

75.25 oC

87

µw = 6.077856682* 10-3 pa.s at 75.25 oC

[

]0.14 =

]0.14 = 0.982977327

[

1[no correction factor

needed] Checking for over all Heat Transfer Coefficient The value of over heat transfer coefficient must be checked and the new value of U must be greater than assumed value (800 W/ m2.oC).

1 = Uo

d ln(d o / d i ) d 1 d 1 1 1 + + o + o + o 2 kw ho hod d i hid d i hi

Kw = 50 W / m .oC (for curpo-Nikel) [32]. Take the foaling coefficient as 6000 W/ m2.oC [23]. =

+

+

+

*

+

*

= 7.28006325 * 10-4 Uo = 1,373.614614 W/ m2.oC (Above the assumed value of 800 W/ m2.oC) Calculation of Pressure Drop Tube Side Pressure drop in the tube side can be calculated from equation below, the pressure drop calculated must be smaller than 10 psi. ∆Pt = Np [ 8jf

+ 2.5]

jf = 3 * 10-3 from figure (12.24) [23]. 88

∆Pt = 2[ 8 * 3 * 10-3 *

+ 2.5]

∆Pt = 66,666.10822 pa = 9.671766996 psi < 10 psi ( acceptable). Shell Side ∆Ps = 8jf us = GS /ρ = 1977.705776 / 1748.959499 = 1.130789922 m/s from figure (12.30) [23], at Re = 5.223851997 * 103 → jf = 5.7 * 10-3 ∆Ps = 8* 5.7 * 10-3 * ∆Ps = 75,096.10397 pa = 10.89477156 psi considered suitable not mor large than 10 psi . Input and Output Manholes Diameter of manholes is given in equation below: dm = 282 m.0.52 ρ-0.37 Manhol for Input Hot Spent Acid dm = 282 * ( 3.3358558)0.52 * ( 1,748.959499)-0.37 dm = 33.30338513 mm Manhol for Input Cold Water dm = 282 * ( 7.856829475)0.52 * (992.04)-0.37 dm = 64.13010051 mm

89

5.4 Distillation Design [23,30&35] Feed

Top

Comp.

Wt.%

Mol.%

C6H6

2.014285745

3.31381848

Bottom

Wt.% Mol.% Wt.%

C6H5NO2

97.98571425 96.86168152

TemperatureoC

192.1

Mol.%

100

100

1

1.567082484

-

-

99

98.43291752

80.1

200.87

Vapor-liquid equilibrium data for Benzene-Nitrobenzene [36]: (see appendex B) X 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1

Y 0 0.451 0.759 0.923 0.957 0.969 0.975 0.981 0.985 0.988 0.989 0.99 0.992 0.994 0.995 0.996 0.996 0.997 0.999 0.999 1

90

1

Benzene Vapor Mole Fraction 

0.8

0.6

0.4

0.2

0 0

0.2

0.4

0.6

0.8

1

Benzene Liquid Mole Fraction

Figure 5-1 Vapor-Liquid Equilibrium diagram (Isothermal) at 70oC R = 2.062272268 Intercept =

=

= 0.326554895

0.33

From equilibrium curve by Mc cabe-Tiele method find the number of stages equal 3. Number of theoretical plate = 3 + 1 = 4 91

assume column efficiency of 60 percent. Take reboiler as equivalent to one stage. =5

No. of real stages = Estimate base pressure

Assume 100mm water, pressure drop per plate. column pressure drop = 100 * 10-3 * 1000 * 9.81 * 5 = 4905 pa top pressure, 1 atm = 101.325 * 103 pa bottom pressure drop = 101.325 * 103 + 4905 = 106,230 pa = 106.230 Kpa Column Diameter At Top of the Column Top temperature = 80.1 oC = 353.25 K Top pressure = 101.325 * 103 pa FLV =

Ln Vn

ρV ρL

From material Balance: Ln = 209.6398836 Kg/hr = 0.058233301Kg/s Vn = 311.2946878 Kg/hr = 0.086470746 Kg/s

ρV = ρV =

P Mwt. RT = 2.694828052 Kg/m3

ρL = 815.0831896 Kg/m3 at 80.1 oC [28]. 92

FLV =

= 0.038722801

Take plate spacing 0.45 [ The plate spacing is reduced to avoid the problem of supporting a tall, slender column] [30]. From figure (11.29) [23] at FLV = 0.038722801 and plate spacing = 0.45, K1 = 7.5 * 10-2 Correction for surface tension 4

σ=

* 10-12

pch for Benzene = ( 4.8 * 6) + ( 17.1 * 6) = 131.4 4

* 10-12

σ=

σ = 3.488266696 mJ/m2 = 3.488266696 * 10-3 J/m2 (K1)correct = [σ / 20 * 10-3 ]0.2 * K1 (K1)correct = [3.488266696 * 10-3]0.2 * 7.5 * 10-2 (K1)correct = 0.013081 uf = (K1)correct

93

uf = 0.013081

= 0.227120984 m/s

for design a value of 80-85 percent of the flooding velocity should be used. uv = 0.85 * uf uv = 0.85 * 0.227120984 = 0.193052836 m/s maximum volumetric flow-rate =

= 0.032087667 m3/s

maximum volumetric flow-rate =

= 0.16621184 m2

An =

At first trial take downcomer area as 12 percent of total. Ac =

= 0.188877091 m2

=

Dc =

= 0.490393497 m

At Bottom of the Column Top temperature = 200.87 oC = 474.02 K Top pressure = 106.230 Kpa FLV =

Lm Vm

ρV ρL

From material Balance: 94

0.5 m

Lm = Vm + stream 15 Vm = Vn = 0.086470746 Kg/s Stream 15 = 9,820.426487 Kg/ hr = 2.727896246 Kg/s Lm = 0.086470746 + 2.727896246 = 2.814366992 Kg/s ρL(mix.) = 1002.856487 Kg/m3 at 200.87 oC [28] ρV(mix.) = Mwt. av. = 122.4048129 Kg/Kg.mol = 3.229930538 Kg/m3

ρV(mix.) =

FLV =

= 1.847096398

From figure (11.29) [23] at FLV =1.847096398 and plate spacing = 0.45, K1 = 1.8 * 10-2 Correction for surface tension σ=

4

* 10-12

pch for Benzene = ( 4.8 * 6) + ( 17.1 * 6) = 131.4 ρV BZ. =

= 0.032994305 Kg/m3

ρL BZ. = 656.0793695 Kg/m3

95

4

* 10-12

σBZ. =

σ BZ. = 1.483518856mJ/m2 = 1.483518856 * 10-3 J/m2 pch for Nitrobenzene = (4.8*6) + ( 17.1*5) + (12.1*1) + (20*2) = 166.8 = 3.266436233Kg/m3

ρV BZ. = ρL N.B = 1,008.377286 Kg/m3

4

σN.B =

* 10-12

σN.B = 3.49273426 mJ/m2 = 3.439273426*10-3 J/m2 σmix. = (1.483518856 * 10-3 * 0.01567082484) + (3.439273426*10-3 * 0.9843291752) = 3.408625139 * 10-3 J/m2 (K1)correct = [σ / 20 * 10-3 ]0.2 * K1 (K1)correct = [3.408625139*10-3]0.2 * 7.5 * 10-2 (K1)correct = 0.012635206 uf = (K1)correct

uf = 0.013081

= 0.219920976m/s

for design a value of 80-85 percent of the flooding velocity should be used. uv = 0.85 * uf 96

uv = 0.85 *0.219920976 = 0.186932829 m/s maximum volumetric flow-rate =

= 0.026207778 m3/s

maximum volumetric flow-rate =

An =

= 0.140198909 m2

At first trial take downcomer area as 12 percent of total. Ac =

= 0.159316942 m2

=

Dc =

= 0.450387201 m

So we will take column diameter Dc = 0.490393497 m

0.5 m

Provisional Plate Design Column diameter Dc = 0.5 m Column area Ac = 0.19634954 m2 Downcomer area Ad = 0.12 Ac = 0.12*0.19634954 = 0.03561944 m2 Net area An =Ac - Ad = 0.19634954 - 0.03561944 = 0.172787595 m2 Active area Aa = Ac- 2Ad = 0.19634954 – 2* 0.03561944 = 0.14922565 m2 Holes area Ah = take 10 percent Aa as first trial Ah = 0.1 * Aa Ah = 0.1 * 0.14922565 Ah = 0.014922565 m2 97

Weir length from figure (11.31) [23], at Ad/ Ac = 12 → lw = 0.76 Dc lw = 0.76 * 0.5 =0.38 m Take: weir height hw = 50mm Hole diameter dh = 5 mm Plate thickness = 5 mm Check weeping how = 750

[

]2/3

maximum liquid rate = 2.814366992 Kg/s

]2/3 = 28.44243839 mm Liquid

maximum how = 750 [

minimum liquid rate, at 70 percent turn down. minimum liquid rate = 2.81436699 * 0.7 = 1.970056894 Kg/s

]2/3 = 22.42326516 mm Liquid

minimum how = 750 [

At minimum rate hw + how = 50 + 22.42326516 = 72.42326518 mm From fig (11.30) [23], K2 = 30.6 uh min. =

uh min. =

= 6.810578219 m/s

actual minimum vapour velocity = minimum vapour rate / Ah 98

actual minimum vapour velocity = 0.7 * 0.02607778 / 0.014922562 actual minimum vapour velocity = 1.22937613m/s < 6.810578219 m/s So minimum operating rate below weep point, so reduced the hole area. Second Trial Take: dh = 4.167 mm Ah = 0.02 Aa = 0.02 * 0.14922565 =2.984513 * 10-3m2 uh min. =

= 5.21179869 m/s

actual minimum vapour velocity = 0.7 * 0.02607778 / 2.984513 * 10-3 actual minimum vapour velocity = 6.116390178m/s > 5.21179869 m/s So minimum operating rate will be well above weep point. Plate Pressure Drop Dry plate drop Maximum vapor velocity through holes uh =

uh =

hd = 51 [

= 8.737700255 m/s

]2 [

]

from figure (11.39) [23], at Ah / AP

Ah / Aa =0.03,

plate thicness / hole diameter = 5 / 4.167 = 1.2 99

Co = 0.81 ]2 [

hd = 51 [

hr =

=

] = 19.30499388 mm Liquid

= 12.46439562 mm Liquid

Total Plate Pressure Drop ht = hd + ( hw + how ) + hr ht = 19.30499388 + (50 + 28.4424389) + 12.46439562 ht = 110.2118279 mm liquid 100mm was assumed to calculate the base pressure. The calculation could be repeated with a revised estimate but the small change in physical properties will have little effect on the plate design. 110.219279 mm per plate is considered acceptable. Downcomer Liquid back-up Downcomer pressure loss Take hap = hw - 10 = 50 – 10 = 40 mm Aap = hap lw = Am Aap = 40 * 10-3 * 0.38 = 0.0152 m2 hdc = 166 [

hdc = 166 * [

]2 ]2 = 5.65854496 mm 100

hb = ( hw + how ) + ht + hdc hb = (50 + 28.4424389) + 110.2118279 + 5.65854496 hb = 194.3128113 mm = 0.1943128112 m hb < ½ (tray spacing + wier hight) 0.1943128112 m < ½ (0.45 + 0.05) 0.2632 m < 0.25 m So tray spacing acceptable. Check Residence Time tr =

tr = tr = 1.631438149s < 3 sec ( not satifactory) Check Entrainment uv =

= 0.15167627 m/s

percentage flooding =

percentage flooding =

* 100 = 68.96853282%

from figure ( 11-29) [23], ψ =0.03 well bellow 0.1, satifactory plate Layout use sieve plate. Allow 50mm unperforated strip round plate edge; 101

50mm wide callming zones. 50 mm

Perforated Area From figure (11.32) [23], At lw / Dc = 0.76 lw= 0.38

θo = 99o

θ

D = 0.5 m

α

α = 180 o – 99o =81o mean length of unperforated edge strip = (0.5 –0.01)( π / 180 * 81) = 0.636172512 m Area of unperforated edge strips = 0.636172512 * 50 * 10-3 Area of unperforated edge strips = 0.031808625 m2

Area of calming zones = 2 (0.05) * ( 0.38 – 2 * 0.05) = 0.028 m2 Ap = active area – unperforated edge strip area – calming area Ap = 0.14922565 – (0.031808625 + 0.028 ) = 0.089416724 m2 At (Ah/ Ap) = 2.984513*10-3/ 0.089416724 = 0.03337757 From fig. (11.33) [23] lp/dh = 4 lp = 4 * 4.167 = 16.668 mm (pitch). Number of holes Area of one hole = (π/4) dh2 = (π/4) (0.004167) 2 = 1.363756653*10-5 m2 102

50 mm

Number of holes = hole area / area of one hole Number of holes = 2.984513*10-3/ 1.363756653*10-5 Number of holes

= 219 holes

Total Height of Distillation Column hT = (Tray Spacing * No. plate) + thicness of plate hT = (0.45 * 5) + 0.005 = 2.255m

103

    Chapter Six Control System  

Chapter Six Control System

6.1 Introduction Instruments are provided to monitor the key process variables during plant operation. They may be incorporated in automatic control loops, or used for the manual monitoring of the process operation. They may also be part of an automatic computer data lagging system. Instruments monitoring critical process variables will be fitted with automatic alarms to alert the operators to critical and hazardous situations. The primary objectives of the designer when specifying instrumentation and control schemes are: 1. Safe plant operation: a) To keep the process variables within known safe operation limits. b) To detect dangerous situations as they develop and to provide alarms and automatic shut-down systems. c) To provide interlocks and alarms to prevent dangerous operating procedures. 2. Production rate: To achieve the design product out put. 3. Product quality: To maintain the product composition within specified quality standards. 4. Cost: 104   

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

6.2 Control of Nitrator Nitration reactions must be considered potentially hazardous. This is because of heat of nitration is substantial but also because further heat release is possible through nitric acid oxidation if the reaction gets out of hand. An incident is reported where a batch nitrobenzene plant caught fire after the belt drive of an agitator slipped, and unreacted benzene and nitric acid were allowed to accumulate without adequate cooling. Great care has to be taken to properly design the control system for a nitration plant and to properly size the pressure relief system, which serves as last resort [4]. In the isothermal process, nitric acid and benzene are fed in a fixed molar ratio of C6H6 / HNO3, usually about 1.05. The sulfuric acid rate is matched in proportion to give a spent acid strength of about 70% H2SO4. Temperature in the nitrator is controlled by throttling the cooling water flow rate to the nitratar. High temperature switches will shut off the feeds and open the cooling water valve wide. A low speed or power switch on the nitrator agitator will also shut off all feeds. The level in the nitrator is set by gravity overflow [4]. Control of the adiabatic process also requires control of the benzene and nitric acid feed in affixed molar ratio. No direct temperature is required since sulfuric acid is the heat sink of the process. The temperature is controlled by controlling the sulfuric acid circulation rate. Safty interlocks must be provided to shut the process safely in the case of failure of sulfuric acid circulation. Control of the acid concentrator, in particular of the sulfuric acid 105   

strength produced, must be integrated with the nitration section [4], figure 6-1 illustrated the control of isothermal nitrator [23].

FC

Feed FC

TC TC

FC

LC FC

Figure 6-1 Nitrator Control

106   

6.3 Settler Control Decanter are normally designed for continuous operation, the position of the interface can be controlled, with or without the use of the instruments, by use of the siphon take-off for the heavy liquid [23].

Liquid- light take off

Heavy liquid take off

Crude N.B Feed

Spent Acid

Figure 6-2 Settler control

Liquid- light Feed LC

Heavy liquid

Figure 6-3 Settler control 107   

6.4 Vaporizer Control Level control is often used for vaporizers; the controller controlling the steam supply to the heating surface, with the liquid feed to the vaporizer on flow control, as shown in figure 6-4. An increased the feed results in an automatic increase in steam to the vaporizer to vaporize the increased flow and maintain the level constant [23].

TC

LC

Feed

Steam

Trap

Figure 6-4 vaporizer control

108   

6-5 Heat Exchanger Control Exchangers do not always require special temperature control. Since their purpose in a process is to provide the maximum recovery of heat, there is reason to restrict their performance by the use of controls [22]. When a fluid is cooled in an exchanger, it usually passes through a cooler and its temperature is controlled by a flow adjustment of the water. It is not possible to control both the flow quantities and the outlet temperatures of both streams passing through an exchanger at the exchanger itself, since one adjustable quality must always be present. Thus, if the outlet temperatures of both streams are to be controlled and the flow or temperature of one stream may vary, the flow or outlet temperature of the other stream must also vary [22]. Most of the problems of exchanger instrumentation are encountered when the two streams are of unequal size, the one being very much larger than other [22]. If the heat exchanger is between two process streams whose flows are fixed, by-pass control will have to be used, figure 6-5 shows the control of heat exchanger [23].

TC

Figure 6-5 Heat Exchanger control 109   

6.6 Distillation column control The primary objective of distillation column control is to maintain the specified composition of the top and bottom products, and any side streams; correcting for the effects of Disturbances in: 1. Feed flow-rate, composition and temperature. 2. Steam supply pressure.

3. Cooling water pressure and header temperature. 4. Ambient conditions, which cause changes in internal reflux The compositions are controlled by regulating reflux flow and boil-up. The column overall material balance must also be controlled; distillation columns have little surge capacity (hold-up) and the flow of distillate and bottom product (and side-streams) must match the feed flows. Column pressure is normally controlled at a constant value [23]. The use of variable pressure control to conserve energy, Feed temperature is not normally controlled, unless a feed preheater is used. Temperature is often used as an indication of composition. The temperature sensor should be located at the position in the column where the rate of change of temperature with change in composition of the key component is a maximum [23]. Near the top and bottom of the column the change is usually small. Top temperatures are usually controlled by varying the reflux ratio and bottom temperatures by varying the boil-up rate. If reliable on-line analyzers are available they can be incorporated in the control loop, but more complex control equipment will be needed [23]. 110   

Figure 6-6 Temperature pattern control

With this arrangement interaction can occur between the top and bottom temperature controllers, figure 6-5 [23].

Figure 6-7 Composition control. Reflux ratio controlled by a ratio controller, or splitter box, and the bottom product as a fixed ratio of the feed flow, figure 6-6 [23].

111   

Figure 6-8 Composition control Top product take-off and boil-up controlled by feed; figure 6-7 [23].

112   

      Chapter Seven Plant Layout

Chapter Seven Plant Layout

7.1 Site Considerations [23] The location of the plant can have a crucial effect on the profitability of a project, and the scope for future expansion. Many factors must be considered when selecting a suitable site, and only a brief review of the principal factors will be given in this chapter. The principle factors to consider are: 1) Marketing area For materials that are produced in bulk quantities; such as cement, mineral acids, and fertilisers, where the cost of the product per tonne is relatively low and the cost of transport a significant fraction of the sales price, the plant should be located close to the primary market. This consideration will be less important for low volume production, high-priced products; such as pharmaceuticals. In an international market, there may be an advantage to be gained by locating the plant within an area with preferential tariff agreements; such as the European Community (EC). 2) Raw materials The availability and price of suitable raw materials will often determine the site location. Plants producing bulk chemicals are best located close to the source of the major raw material; where this is also close to the marketing area.

113  

3) Transport The transport of materials and products to and from the plant will be an overriding consideration in site selection. If practicable, a site should be selected that is close to at least two major forms of transport: road, rail, waterway (canal or river), or a sea port. Road transport is being increasingly used, and is suitable for local distribution from a central warehouse. Rail transport will be cheaper for the long-distance transport of bulk chemicals. Air transport is convenient and efficient for the movement of personnel and essential equipment and supplies, and the proximity of the site to a major airport should be considered. 4) 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. Skilled tradesmen will be needed for plant maintenance. Local trade union customs and restrictive practices will have to be considered when assessing the availability and suitability of the local labor for recruitment and training. 5) Utilities (services) Chemical processes invariably require large quantities of water for cooling and general process use, and the plant must be located near a source of water of suitable quality. Process water may be drawn from a river, from wells, or purchased from a local authority.

At some sites, the cooling water required

can be taken from a river or lake, or from the sea; at other locations cooling towers will be needed. Electrical power will be needed at all sites. Electrochemical processes that require large quantities of power; for example, 114  

aluminium smelters, need to be located close to a cheap source of power. A competitively priced fuel must be available on site for steam and power generation. 6) Environmental impact, and effluent disposal All industrial processes produce waste products, and full consideration must be given to the difficulties and cost of their disposal. The disposal of toxic and harmful effluents will be covered by local regulations, and the appropriate authorities must be consulted during the initial site survey to determine the standards that must be met. An environmental impact assessment should be made for each new project, or major medication or addition to an existing process. 7) Local community considerations The proposed plant must fit in with and be acceptable to the local community. Full consideration must be given to the safe location of the plant so that it does not impose a significant additional risk to the community. On a new site, the local community must be able to provide adequate facilities for the plant personnel: schools, banks, housing, and recreational and cultural facilities. 8) Land (site considerations) Sufficient suitable land must be available for the proposed plant and for future expansion. The land should ideally be flat, well drained and have suitable load-bearing characteristics. A full site evaluation should be made to determine the need for piling or other special foundations.

115  

9) Climate Adverse climatic conditions at a site will increase costs. Abnormally low temperatures will require the provision of additional insulation and special heating for equipment and pipe runs. Stronger structures will be needed at locations subject to high winds (cyclone/hurricane areas) or earthquakes. 10) Political and strategic considerations Capital grants, tax concessions, and other inducements are often given by governments to direct new investment to preferred locations; such as areas of high unemployment. The availability of such grants can be the overriding consideration in site selection.

7.2 Site Layout [23] The process units and ancillary buildings should be laid out to give the most economical flow of materials and personnel around the site. Hazardous processes must be located at a safe distance from other buildings. Consideration must also be given to the future expansion of the site. The ancillary buildings and services required on a site, in addition to the main processing units (buildings), will include: 1. Storages for raw materials and products: tank farms and warehouses. 2. Maintenance workshops. 3. Stores, for maintenance and operating supplies. 4. Laboratories for process control. 5. Fire stations and other emergency services. 116  

6. Utilities: steam boilers, compressed air, power generation, refrigeration, transformer stations. 7. Effluent disposal plant. 8. Offices for general administration. 9. Canteens and other amenity buildings, such as medical centres. 10. Car parks. When roughing out the preliminary site layout, the process units will normally be sited first and arranged to give a smooth flow of materials through the various processing steps, from raw material to final product storage. Process units are normally spaced at least 30 m apart; greater spacing may be needed for hazardous processes. The location of the principal ancillary buildings should then be decided. They should be arranged so as to minimize the time spent by personnel in travelling between buildings. Administration offices and laboratories, in which a relatively large number of people will be working, should be located well away from potentially hazardous processes. Control rooms will normally be located adjacent to the processing units, but with potentially hazardous processes may have to be sited at a safer distance. The sitting of the main process units will determine the layout of the plant roads, pipe alleys and drains. Access roads will be needed to each building for construction, and for operation and maintenance. Utility buildings should be sited to give the most economical run of pipes to and from the process units. 117  

Cooling towers should be sited so that under the prevailing winds the plume of condensate spray drifts away from the plant area and adjacent properties. The main storage areas should be placed between the loading and unloading facilities and the process units they serve. Storage tanks containing hazardous materials should be sited at least 70m (200ft) from the site boundary. A typical plot plant is shown in figure 7-1.

Figure 7-1 A typical site plan

7.3 Plant Layout The economic construction and efficient operation of a process unit will depend on how well the plant and equipment specified on the process flow-sheet is laid out. The principal factors to be considered are: 1. Economic considerations: construction and operating costs. 118  

2. The process requirements. 3. Convenience of operation. 4. Convenience of maintenance. 5. Safety. 6. Future expansion. 7. Modular construction.

7.4 Utilities [23] The word “Utilities” is now generally used for the ancillary services needed in the Operation of any production process. These services will normally be supplied from Central site facility; and will include: 1. Electricity. 2. Steam, for process heating. 3. Cooling water. 4. Water for general use. 5. Demineralised water. 6. Compressed air. 7. Inert-gas supplies. 8. Refrigeration. 9. Effluent disposal facilities.

119  

7.5 Environmental Consideration [23] All individuals and companies have a duty of care to their neighbors, and to the environment in general. In the United Kingdom this is embodied in the Common Law. In addition to this moral duty, stringent controls over the environment are being introduced in the United Kingdom, the European Union, the United States, and in other industrialized countries and developing countries. Vigilance is required in both the design and operation of process plant to ensure that legal standards are met and that no harm is done to the environment. Consideration must be given to: 1. All emissions to land, air, water. 2. Waste management. 3. Smells. 4. Noise. 5. The visual impact. 6. Any other nuisances. 7. The environmental friendliness of the products.

7.6 Waste Management [23] Waste arises mainly as byproducts or unused reactants from the process, or as off- specification product produced through mis-operation. There will also be fugitive emissions from leaking seals and flanges, and inadvertent spills and discharges through mis-operation. In emergency situations, material may be 120  

discharged to the atmosphere through vents normally protected by bursting discs and relief values. The designer must consider all possible sources of pollution and, where practicable, select processes that will eliminate or reduce (minimize) waste generation. Unused reactants can be recycled and off-specification product reprocessed. Integrated processes can be selected: the waste from one process becoming the raw material for another. For example, the otherwise waste hydrogen chloride produced in a chlorination process can be used for chlorination using a different reaction; as in the balanced, chlorinationoxyhydrochlorination process for vinyl chloride production. It may be possible to sell waste to another company, for use as raw material in their manufacturing processes. For example, the use of off-specification and recycled plastics in the production of lower grade products, such as the ubiquitous black plastics bucket. Processes and equipment should be designed to reduce the chances of misoperation; by drains, and pumps should be sited so that any leaks flow into the plant effluent collection system, not directly to sewers. Hold-up systems, tanks and ponds, should be provided to retain spills for treatment. Flanged joints should be kept to the minimum needed for the assembly and maintenance of equipment. When waste is produced, processes must be incorporated in the design for its treatment and safe disposal. The following techniques can be considered: 1. Dilution and dispersion.

121  

2. Discharge to foul water sewer (with the agreement of the appropriate authority). 3. Physical treatments: scrubbing, settling, absorption and adsorption. 4. Chemical treatment: precipitation (for example, of heavy metals), neutralization. 5. Biological treatment: activated sludge and other processes. 6. Incineration on land, or at sea.

7.8 Nitrobenzene Plant Location Based on these previous factors which are required in nitrobenzene manufacturing plant, I select AL- Basrah as plant location in a place at which the wind pass through the plant must not hit the cities and inter to the goverarate because nitrobenzene plant causing ambient air pollutant which may effected on people negatively this location will provide to the plant utilities which need since it near the river and Shatt AL-Arab which also contain a large harbor which we can use it for export purposes. The foundation of the refinery in Basrah “AL Rumela Refinery” which provide low cost of transport requirement, also labors and local community which satisfied the labor requirement.

122  

    Chapter Eight Toxicity and Effects of Nitrobenzene  

Chapter Eight Toxicity and Effects of Nitrobenzene

8.1 General Nitrobenzene is very toxic substance; the maximum allowable concentration for nitrobenzene is 1 ppm or 5 mg/m3. It was exposed for eight hours to 1 ppm nitrobenzene in the working atmosphere, about 25 mg of nitrobenzene would be absorbed, of which about one-third would be by skin absorption and the remainder by inhalation. The primary effect of nitrobenzene is the conversion of hemoglobin to methemoglobin; thus the conversion eliminates hemoglobin from the oxygen-transport cycle. Exposure to nitrobenzene may irritate the skin and eyes. Nitrobenzene affects the central nervous system and produces fatigue, headache, vertigo, vomiting, general weakness and in some cases unconsciousness and coma. There generally is a latent period of 1-4 hours before signs or symptoms appear. Nitrobenzene is a powerful methemoglobin former, and cyanosis appears when the methemoglobin level reaches 15%. Chronic exposure can lead to spleen and liver damage, jaundice, and anemia. Alcohol ingestion tends to increase the toxic effects of nitrobenzene; thus alcohol in any form should not be ingested by the victim of nitrobenzene poisoning for several days after the nitrobenzene poisoning or exposure. Impervious protective clothing should be worn in areas where risk of splash exists. Ordinary work clothes that have been splashed should be removed immediately, and the skin washed thoroughly with soap and worm water. In areas of high vapor concentration (>1 ppm), full face mask with organic-vapor

123   

consters or air-supplied respirators should be used. Clean work clothing should be worn daily, and showering after each shift should be mandatory [2&3]. With respect to the hazards of fire and explosion, nitrobenzene is classified as modrate hazard when exposed to heat or flame. Nitrobenzene is classified by the ICC as a class-B poisonous liquid [2&3].

8.2 Effects on Humans Nitrobenzene is toxic to humans by inhalational, dermal and oral exposure. The main systemic effect associated with human exposure to nitrobenzene is methaemoglobinaemia [5]. Numerous accidental poisonings and deaths in humans from ingestion of nitrobenzene have been reported. In cases of oral ingestion or in which the patients were apparently near death due to severe methaemoglobinaemia, termination of exposure and prompt medical intervention resulted in gradual improvement and recovery. Although human exposure to sufficiently high quantities of nitrobenzene can be lethal via any route of exposure, it is considered unlikely that levels of exposure high enough to cause death would occur except in cases of industrial accidents or suicides [5]. The spleen is likely to be a target organ during human exposure to nitrobenzene; in a woman occupationally exposed to nitrobenzene in paint (mainly by inhalation), the spleen was tender and enlarged [5]. Neurotoxic symptoms reported in humans after inhalation exposure to nitrobenzene have included headache, confusion, vertigo and nausea. Effects in

124   

orally exposed persons have also included those symptoms, as well as apnoea and coma [5].

8-3 Effects on Organisms in the Environment 

 

Nitrobenzene

appears

to

and

an

8-day

lowest-observed-effect

concentration of 1.9 mg/litre for the blue-green be toxic to bacteria and may adversely affect sewage treatment facilities if present in high concentrations in influent. The lowest toxic concentration reported for microorganisms is for the bacterium Nitrosomonas, with an EC50 of 0.92 mg/litre based upon the inhibition of ammonia consumption. Other reported values are a 72-h no-observed-effect concentration of 1.9 mg/litre for the protozoan Entosiphon sulcatum alga Microcystis aeruginosa [5]. For freshwater invertebrates, acute toxicity (24- to 48-h LC50 values) ranged from 24 mg/litre for the water flea (Daphnia magna) to 140 mg/litre for the snail (Lymnaea stagnalis). For marine invertebrates, the lowest acute toxicity value reported was a 96-h LC50 of 6.7 mg/litre for the mysid shrimp (Mysidopsis bahia). The lowest chronic test value reported was a 20-day NOEC of 1.9 mg/litre for Daphnia magna, with an EC50, based on reproduction, of 10 mg/litre [5]. Freshwater fish showed similar low sensitivity to nitrobenzene. The 96-h LC50 values ranged from 24 mg/litre for the medaka (Oryzias latipes) to142 mg/litre for the guppy (Poecilia reticulata). There was no effect on mortality or behaviour of medaka at 7.6 mg/litre over an 18-day exposure [5].

125   

8.4 Hazard and Risk Evaluation Methaemoglobinaemia and subsequent haematological and splenic changes have been observed in exposed humans, but the data do not allow quantification

of

the

exposure–response

relationship.

In

rodents,

methaemoglobinaemia, haematological effects, testicular effects and, in the inhalation studies, effects on the respiratory system were found at the lowest doses tested. Methaemoglobinaemia, bilateral epididymal hypospermia and bilateral testicular atrophy were observed at the lowest exposure level studied, 5 mg/m3 (1 ppm), in rats. In mice, there was a dose-related increase in the incidence of bronchiolization of alveolar walls and alveolar/bronchial hyperplasia at the lowest dose tested of 26 mg/m3 (5 ppm). Carcinogenic response was observed after exposure to nitrobenzene in rats and mice: mammary adenocarcinomas were observed in female B6C3F1 mice, and liver carcinomas and thyroid follicular cell adenocarcinomas were seen in male Fischer-344 rats. Benign tumours were observed in five organs. Studies on genotoxicity have usually given negative results [5]. Although several metabolic products of nitrobenzene are candidates for cancer causality, the mechanism of carcinogenic action is not known. Because of the likely commonality of redox mechanisms in test animals and humans, it is hypothesized that nitrobenzene may cause cancer in humans by any route of exposure [5]. Exposure of the general population to nitrobenzene from air or drinkingwater is likely to be very low. Although no no-observed-adverse-effect level could be derived from any of the toxicological studies, there is a seemingly low

126   

risk for non-neoplastic effects. If exposure values are low enough to avoid nonneoplastic effects, it is expected that carcinogenic effects will not occur [5]. Acute poisonings by nitrobenzene in consumer products have occurred frequently in the past. Significant human exposure is possible, due to the moderate vapour pressure of nitrobenzene and extensive skin absorption. Furthermore, the relatively pleasant almond smell of nitrobenzene may not discourage people from consuming food or water contaminated with it. Infants are especially susceptible to the effects of nitrobenzene [5]. There is limited information on exposure in the workplace. In one workplace study, exposure concentrations were of the same order of magnitude as the lowest-observed-adverse-effect levels in a long-term inhalation study. Therefore, there is significant concern for the health of workers exposed to nitrobenzene [5]. Nitrobenzene shows little tendency to bioaccumulate and appears to undergo both aerobic and anaerobic biotransformation. For terrestrial systems, the levels of concern reported in laboratory tests are unlikely to occur in the natural environment, except possibly in areas close to nitrobenzene production and use and areas contaminated by spillage [5]. Using the available acute toxicity data and a statistical distribution method, together with an acute: chronic toxicity ratio derived from data on crustaceans, the concentration limit for nitrobenzene to protect 95% of freshwater species with 50% confidence may be estimated to be 200 µg/litre. Nitrobenzene is thus unlikely to pose an environmental hazard to aquatic species at levels typically reported in surface waters, around 0.1–1 µg/litre. Even at 127   

highest reported concentrations (67 µg/litre), nitrobenzene is unlikely to be of concern to freshwater species [5]. There is not enough information to derive a guideline value for marine organisms [5].

8.5 Industrial Safety • Storage precaution: store in a refrigerator or in a cool, dry place [37]. • Skin contact: Flood all areas of body that have contacted the substance with water. Don’t wait to remove contaminated clothing; do it under the water stream. Use soap to help assure removal. Isolate contaminated clothing when removed to prevent contact by others [37]. • Inhalation:

leave contaminated area immediately; breathe fresh air.

Proper respiratory protection must be supplied to any rescuers. If coughing, difficult breathing or any other symptoms develop, seek medical attention at once, even if symptoms develop many hours after exposure [37]. • Eye contact: remove any contact lenses at once. Flush eyes well with copious quantities of water or normal saline for at least 20-30 minutes. • Ingestion: if convulsions are not present, give a glass or two of water or milk to dilute the substance. Assure that the person’s

airway is

unobstructed and contact a hosnital or poison center immediately for advice on wiether or not to induce vomiting [37].

128   

References 1- Ullmann’s Encyclopedia of Industrial Chemistry, 2005 Wiley-VCH Verlag GmbH & Co. KGaA. 2- Krik and Othmer, “Encyclopedia of Chemical Technology”, Vol.17, 4th Ed., p (133-152). 3- Krik and Other, “Encyclopedia of Chemical Technology”, Vol.15, 3rd Ed., p (917-932). 4- John J.Mcketta, “Encyclopedia of Chemical Processing & Design”, Vol. 31, p. (165-188). 5- http:// Whqlibdoc.Who.int / ech / who.EH.C.230. 6- www. Technology bank.dupont.com. 7- “ Hydrocarbon Processing”, Vol.58,1979, NO.11 8- “Hydrocarbon Processing”, 1978. 9- P.H.Grogins, “Unit Process Organic Synthesis”, fifth edition. 10- H.Scott Fogler, “Elements of Chemical Reaction Engineering”. 11- U.S.pat. 7,326,816 B2 (Feb. 5, 2008). 12- U.S.pat. 4,772,757 (Sep.20, 1988). 13- Sami Matter & Lewis Hatch, “From Hydrocarbon to Petrochemicals”. 14- Sami Matter & Lewis F. Hatch, (2000), “Chemistry of petrochemicals Processes”, 2nd. 15- U.S.pat. 2,773,911 (Dec.11, 1956). 16- James G. Speight, “Chemical & Process Design Handbook”. 17- Austin, G.T., (1984), “Shreve’s Chemical Process Industries”, 5th Ed., p. (772). 18- SEP Handbook, “Petrochemical & Downstream Projects”. 19- Robert H. Perry (1997), “Perry’s Chemical Engineer’s Handbook”, 7th Ed. 129  

20- John A. Dean, (1999), “Lange’s Handbook of Chemistry”, Fifteenth Edition, McGraw-Hill, INC. 21- David R. Lide, (2000-2001), “CRC Handbook of Chemistry & Physics”, editor-in-chief. 22- Donald Q. Kern, (2005), “Process Heat Transfer”, Twelfth reprint 2005. Tata McGraw-Hill Edition. 23- Coulson & Richardson’s, (2005), “Chemical Engineering Design”, Vol.6, Fourth Edition. 24- David M. Himmelblau, (1989), “Basic Principles & Calculation in Chemical Enginnring”, Fifth Edition. 25- Jack Winnick, (1997), “Chemical Engineering Thermodynamics”, John Wily & Sons, Inc. 26- J M Smith & H C Van Ness, (2003), “Introduction to Chemical Engineering Thermodynamics”, Sixth Edition, Tata McGraw-Hill Publishing Company Limited. 27- Reid & Prausintz, (1987), “The Properties of Gases & Liquids”, Fourth Edition. 28- Chemicad 6.0.1 Program. 29- Stanley M. Walas, (1990), “Chemical Process Equipment Selection & Design”, Butterworth-Heinemann Series in Chemical Engineering. 30- H. R. Backhurts & J. H. Harker, (1973) “Process Design”, Heinemamm Education Books. 31- Brodkey & Hershey, (1988), “Transport Phenomena”, McGraw-Hill Book Company. 32- Holman, (1981), “Heat Transfer”, 5th edition, McGraw Hill. 33- Coulson & Richardson’s, (1999), “Chemical Engineering”, Vol.1, Sixth Edition. 130  

34- Alan S. Foust, (1980), “Principles of Unit Operation”, Second Edition. 35- Coulson & Richardson’s, (2002), “Chemical Engineering”, Vol.2, Fifth Edition. 36- Shuzo Ohe, (1989), “Vapor-Liquid Equilibrium Data”. 37- Lawrence H. Keith & Douglas B. Walters, “Compendium of Safety Data Sheets for Research & Industrial Chemicals”, Part III.

131  

      Appendixes

Appendix A Physical Properties 1- General Properties [19,20,21,22,23,24,25,26,27&28] Comp.

∆Hof

Mwt. [Kg /Kg.mol]

B.P [oC]

C6H6 (L) HNO3 (L) H2SO4 (L) H2O (L) C6H5NO2 (L) Na2CO3 (c)

78.11 63.02 98.08 18.02 123.11 106

80.1 100 210.9 -

49.1 -173.230 -811.32 -285.840 12.500 -1131.546

30781 40683 -

H2CO3 (aq) Na2SO4 (c) CaSO4 (c) CaSO4.2H2O(c)

62.03 142.05 136.14 172.18

-

-699.65 -1413.891 -1432.7 -2024.021

-

(298.15K)

[KJ /g.mol]

λ [KJ / Kg.mol]

(Soda Ash)

(Gypsum)

2- Specific Heat Capacity A- Specific Heat Capacity of Liquid [KJ / Kg.mol.K] [23&28] Cp = A + BT + CT2 + DT3 Comp. C6H6 (L) HNO3 (L) H2O (L) C6H5NO2 (L)

A -33.917 131.250 32.243 295.3

B 4.743 * 10-1 -0.1219 1.923 * 10-3 -0.8907

A-1  

C -3.017 * 10-4 0.1704 *10-3 1.055 * 10-5 1.705 * 10-3

D 7.130 * 10-9 -3.596 *10-9 -

Specific Heat Capacity of Sulfuric acid [KJ / Kg.mol.oC] [24] Cp = A + BT Comp. H2SO4 (L)

A 139.1

B 0.1559

B- Specific Heat Capacity of Crystals [19,20,21,24&25] Cp [KJ / Kg.mol.oC] 111.08 128.229 99.73 186.149

Comp. Na2CO3 (c) (Soda Ash) Na2SO4 (c) CaSO4 (c) CaSO4.2H2O(c) (Gypsum)

C- Specific Heat Capacity of Carbonic acid (predicted) [24] Cp = K (Mwt.) a For Acids: K = 0.91, a = -0.152 Cp =0.91* (63.03)-0.152 Cp = 0.485921283 cal /g.oC = 126.1128611 KJ /Kg.mol.oC

D- Specific Heat Capacity of Vapor [KJ / Kg.mol.K] [26] Cpig / R = A + BT + CT2 + DT-2 Comp.

A

B

C

C6H6 (V)

-0.206

39.064*10-3

-13.301*10-6

H2O (V)

3.470

1.450*10-3

0.121*10+5

A-2  

4- Density of Liquids , [Kg.mol / m3][28]

ρ= Comp.

A

B

C

D

C6H6 (L) HNO3 (L) H2SO4 (L) H2O (L) C6H5NO2 (L)

1.0259 1.5943 0.8322 5.4590 0.69123

0.26666 0.2311 0.19356 3.0542*10-1 0.24124

562.05 520 925 6.4713*102 719

0.28394 0.1917 0.2857 8.1*10-2 0.28135

Range Temperature K 279-562 232-373 284-364 273-333 279-719

5- Viscosity of Liquids, [pa.s][28]

µ = exp. [A + B/T + C LnT + DTE] [28] Comp.

A

B

C

D

E

C6H6 (L) HNO3 (L) 96wt.% H2SO4 (L) 98wt.% H2O (L) C6H5NO2 (L)

7.5117 -28.886

294.68 1940

-2.794 2.678

-

-

Range Temperature K 279-545 240-356

-179.84

10694

24.611

-

-

284- 367

-51.964 -34.557

3.6706*103 2611.3

5.7331 3.4283

-5.349*10-29 -

10 -

273-643 273-481

µ H2SO4 (60wt.%) = 3.65*10-3 pa.s at 50 oC figure (14) [22] µ HNO3 (60wt.%) = 1.47*10-3 pa.s at 50 oC figure (14) [22].

A-3  

6- Thermal Conductivity of Liquids, [W / m.oC] K = A + BT + CT2 + DT3 Comp.

A

B

C

D

C6H6 (L) HNO3 (L) 96wt.% H2SO4 (L) 98wt.% H2O (L) C6H5NO2 (L)

0.23444 0.12107

-0.00030572 0.0005383

-

-

Range Temperature K 279-413 233-433

0.014247

0.0010763

-

-

283-371

-0.4267 0.1869

0.00569 -0.0001305

-8.0065*10-6 -

1.815*10-9 -

273-633 283-371

6-Vapor Pressure of liquids using Antoine’s Equation, [mmHg] Ln po = A -

[23]

T = Temperature in K Comp. C6H6 (L)

A

15.9008

Log po = A -

B

2788.51

C

-52.36

Range Temperature o C 7-104

[25]

T = Temperature in oC Comp.

A

B

C

C6H6 (L) C6H5NO2 (L)

7.1156 6.90565

1746.6 1211.033

201.8 220.79

A-4  

Range Temperature o C 134-211 8-103

Appendix B Equilibrium Data

XY data for Benzene / Nitrobenzene NRTL

Bij 659.89

T Deg C 210.635 151.914 126.933 112.693 103.357 96.798 92.010 88.401 85.524 82.944 80.129

Bji -263.35

P atm 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000

Alpha 0.311

X1 0.00000 0.10000 0.20000 0.30000 0.40000 0.50000 0.60000 0.70000 0.80000 0.90000 1.00000

Aij 0.00

Aji 0.00

Mole Fractions Y1 Gamma1 0.00000 1.416 0.82031 1.376 0.93286 1.340 0.96616 1.303 0.98015 1.261 0.98727 1.214 0.99139 1.162 0.99406 1.108 0.99603 1.057 0.99781 1.017 1.00000 1.000

B-1  

Cij 0.00

Cji 0.00

Gamma2 1.000 1.001 1.005 1.013 1.031 1.063 1.123 1.228 1.418 1.778 2.529

Dij 0.00

Phi1 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000

Dji 0.00

Phi2 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000

B-2  

‫ﺷﻜﺮ و اﻟﺘﻘﺪﻳﺮ‬ ‫اﻟﺤﻤﺪ ﷲ ﻋﻠﻰ ﻣﺎ اﻧﻌﻢ‪ ،‬و ﺻﻼﺗﻪ و ﺳﻼﻣﻪ ﻋﻠﻰ رﺳﻮﻟﻪ اﻻﻣﻴﻦ اﻟﻤﺒﻌﻮث رﺣﻤﺔ ﻟﻠﻌﺎﻟﻤﻴﻦ و‬ ‫ﺑﻌﺪ‪:‬‬ ‫ﻣﻦ ﺑﻐﺪاد اﻟﺤﺒﻴﺒﺔ ﻋﺎﺻﻤﺔ اﻟﺤﻀﺎرة اﻻﺳﻼﻣﻴﺔ اﻗﺪم ﺷﻜﺮي و ﺗﻘﺪﻳﺮي اﻟﻰ اﻧﺎس‬ ‫ﻋﻈﻤﺎء ﺑﻌﻄﺎءهﻢ اﻟﻰ آﻨﻮز ﺑﻐﺪاد اﺳﺎﺗﺬة اﻟﺠﺎﻣﻌﺎت اﺧﺺ ﺑﺎﻟﺬآﺮ اﺳﺎﺗﺬة ﺟﺎﻣﻌﺔ اﻟﻨﻬﺮﻳﻦ‬ ‫ﻗﺴﻢ اﻟﻬﻨﺪﺳﺔ اﻟﻜﻴﻤﻴﺎوﻳﺔ ‪ ،‬ﺷﻜﺮ و ﺗﻘﺪﻳﺮ ﺧﺎص اﻟﻰ رﺋﻴﺲ اﻟﻘﺴﻢ اﻟﻤﺤﺘﺮم اﻟﺪآﺘﻮر ﻗﺎﺳﻢ‬ ‫ﺟﺎﺑﺮ اﻟﺴﻠﻴﻤﺎن و ﺟﻤﻴﻊ اﻟﻜﺎدر اﻟﺘﺪرﻳﺴﻲ ﻣﻦ اﺳﺎﺗﺬة و ﻣﻌﺪﻳﻦ اﻟﺬﻳﻦ آﺎن هﻤﻬﻢ اﻟﻮﺣﻴﺪ‬ ‫اﻳﺼﺎل اﻟﻤﻌﻠﻮﻣﺔ اﻟﻤﻔﻴﺪة ﻟﻨﺎ دون اي ﺗﻤﻴﺰ او ﺗﻔﺮﻳﻖ‪.‬‬ ‫اﻗﺪم ﺷﻜﺮي و ﺗﻘﺪﻳﺮي اﻟﻰ اﺳﺘﺎذي د‪ .‬ﺳﺮﻣﺪ اﻟﺬي ﻳﺮﺟﻊ ﻟﻪ اﻟﻔﻀﻞ ﻓﻲ اﻧﺠﺎز هﺬا اﻟﻌﻤﻞ‬ ‫و ﻣﺤﺎوﻟﺔ ﺗﻄﺒﻴﻖ ﺟﻤﻴﻊ اﻟﻤﻮاد اﻟﺪراﺳﻴﺔ ﻓﻴﻪ ‪ ،‬و آﺬﻟﻠﻚ اﻟﺪﻋﻢ اﻟﻤﻌﻨﻮي اﻟﻤﺴﺘﻤﺮ اﻟﺬي‬ ‫ﺳﺎﻋﺪﻧﻲ ﺑﺸﻜﻞ آﺒﻴﺮ ﻓﻲ ﺗﻘﻮﻳﺔ ارادﺗﻲ ﻋﻠﻰ اﺗﻤﺎم هﺬا اﻟﻌﻤﻞ‪.‬‬

‫ﺷﻜﺮ و ﺗﻘﺪﻳﺮ اﻟﻰ ﻣﻮﻇﻔﻲ اﻟﻤﻜﺘﺒﺔ اﻟﻤﺮآﺰﻳﺔ ﺟﺎﻣﻌﺔ اﻟﻨﻬﺮﻳﻦ ﻋﻠﻰ ﺗﻌﺎﻣﻠﻬﻢ اﻻآﺜﺮ ﻣﻦ‬ ‫اﻟﺮاﺋﻊ ﻣﻊ اﻟﻄﻠﺒﺔ دون اي آﻠﻞ او ﻣﻠﻞ‪.‬‬

‫ﺟﺎﻣﻌﺔ اﻟﻨﻬﺮﻳﻦ‬ ‫آﻠﻴﺔ اﻟﻬﻨﺪﺳﺔ‬ ‫ﻗﺴﻢ اﻟﻬﻨﺪﺳﺔ اﻟﻜﻴﻤﻴﺎوﻳﺔ‬

‫‪ ‬‬

‫اﻧﺘﺎج اﻟﻨﺎﻳﺘﺮوﺑﻨﺰﻳﻦ‬

‫ﻣﺸﺮوع ﺗﺨﺮج‬ ‫ﻣﻘﺪم اﻟﻰ ﻗﺴﻢ اﻟﻬﻨﺪﺳﺔ اﻟﻜﻴﻤﻴﺎوﻳﺔ ﻓﻲ آﻠﻴﺔ اﻟﻬﻨﺪﺳﺔ ﺟﺎﻣﻌﺔ اﻟﻨﻬﺮﻳﻦ‬ ‫وهﻲ ﺟﺰء ﻣﻦ ﻣﺘﻄﻠﺒﺎت ﻧﻴﻞ ﺷﻬﺎدة اﻟﺒﻜﻠﻮرﻳﻮس ﻓﻲ اﻟﻬﻨﺪﺳﺔ اﻟﻜﻴﻤﻴﺎوﻳﺔ‬

‫ﻣﻦ ﻗﺒﻞ‬ ‫ﺳﺎرة رﺷﻴﺪ ﻏﺎﻳﺐ‬

‫ﺟﻤﺎدى اﻷﺧﺮ‬ ‫ﺣﺰﻳﺮان‬

‫‪1430‬‬ ‫‪2009‬‬

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