04-process description and mebc

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5. PROCESS DESCRIPTION

The detailed process for the batch process manufacture of 3, 5-dichloroaniline

is described below. The entire plant can be split into two main sections:-

( I ) Deamination section.

( II ) Hydrogenation section and subsequent purification.

Section (I)

2, 6-dichloro-4-nitroaniline is major raw material. It is deaminated in first

section to give 3, 5-dichloroaniline. Since, 2, 6-dichloro-4-nitroaniline is solid,

sufficient amount of solvent is used for dissolving it. Here, we used iso-propanol as a

solvent. Around 90% of solvent is recycled back.

Detailed description:

Initially, solid 2, 6-dichloro-4-nitroaniline is charged to R1002. Sufficient

amount of solvent, iso-propanol is added to R1002 from day tank. Solid NaNO2 is

charged to R1001 and to this sufficient amount of water is added which dissolves

NaNO2 and forms NaNO2 solution. Proper heat transfer arrangement is provided for

removing heat of solution. This NaNO2 solution at 250C is charged toR1002. In

addition to this required amount of 98% H2SO4 and process water is added to R1002

from respective day tanks.

Reaction takes place at 500 C, so it is necessary to heat all reactants to 500 C.

After this constant temperature is achieved reaction takes place in around 3 hours.

This reaction is exothermic so constant heat removal is carried out. Here we get one

mole of 3, 5-dichloro-4-nitroaniline per mole of 2,6-dichloro-4-nitroaniline with

100% selectivity and 100% conversion of 2,6-dichloro-4-nitroaniline.

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During this deamination reaction, nitrogen is evolved which is vented

out of the reactor to the atmosphere. Product, 3, 5-dichloro-4-nitroaniline, melts at 65 0

C so it will be in solid state when it comes out of reactor. Thus 3, 5-dichloro-4-

nitroaniline is separated by filtration in the solid form by using agitated nutsche type

of filter. Mother liquor contains mainly H2O and iso-propanol and inorganic salts. Iso-

propanol is recovered by distillation and recycled back. Since, 3, 5-dichloro-4-

nitroaniline is insoluble in water, it will be absent in mother liquor.

Section (II)

Hydrogenation is effected in a CSTR which is Gas-Inducing-Dead-End type of

reactor. Since, hydrogen can form explosive mixture; Dead-End type of reactor is

preferred to ensure safety. Dead-End type of reactor is that in which there is total

consumption of hydrogen in the reactor and no hydrogen gas is vented out.

Detailed description:

3, 5-dichloro-4-nitroaniline which is separated by filtration is heated and

converted into liquid form and fed to R1003 which is hydrogenation reactor. It is

simple CSTR. Sufficient quantity of 50% H2SO4 is prepared in D1004. Required

amount of 50% H2SO4 is charged to R1003 from day tank. Apart from this, R1003 is

charged with Raney-Nickel catalyst and hydrogen gas sparged at five bar pressure in

stoichiometric amount. Hydrogenation of 3, 5-Dichloronitrobenzene is carried out at

700C for around 2.5 hours. Thus all these reactants are to be heated to reaction

temperature and same temperature is maintained in the reactor. Here, all reactants are

preheated and added to R1003. Hydrogenation reaction is exothermic so liberated heat

need to be removed by providing proper cooling arrangement. Here we will get 100%

yield as meta oriented chlorine is not get removed under such mild conditions.

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After reaction gets over, output of R1003 contains 3, 5-dichloroaniline, water

formed in the reaction, suphuric acid charged and catalyst. This mixture is then

filtered at more than 700C to remove catalyst. Mother liquor will contain 3, 5-

dichloroaniline, water formed in the reaction and sulphuric acid charged in the

reactor. Mother liquor from F1002 is fed to phase separator (P1001) to separate

aqueous and organic phases. Aqueous phase will contain most of water and sulphuric

acid which is sent to effluent treatment plant. Solubility of 3, 5-dichloroaniline in

water is very less (0.6 gm/lit) so only small amount of solid will go into water.

Organic phase will mainly contain 3,5-dichloroaniline along with very less amount of

sulphuric acid and water.

Since we require 3, 5-dichloroaniline more than 99% pure we need to remove

this associated sulphuric acid and water. 50% solution of NaOH is added for

neutralizing sulphuric acid and water associated with it will dissolve salt formed and

excess NaOH. After this water wash is required to remove any inorganic part

associated with organic phase. Then aqueous and organic phases are separated by

P1002 to obtain 3, 5-dichloroaniline in organic phase which will be more than 99%

pure. Since there is not any other organic compound with 3, 5-dichloroaniline in

organic phase we need not require distillation unit.

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6.1 MATERIAL BALANCE

Product: 500 TPA of 3, 5-dichloroaniline

Basis: Plant operates for 328 days and hence 1525 Kg of product need to be produced

per day.

Material Balances across the equipments:

Mixer(R1001)

NaNO2 which is nitrosating agent is in the solid form and hence dissolved in

water in this equipment. NaNO2 and water are introduced at 250 C.

IN OUT

Component

Quantity

(kg / day)

Component

Quantity

(kg / day)

NaNO2 1176.4 NaNO2

Solution

2823.3H2O 1646.9

Total 2823.3 Total 2823.3

Reactor (R1002)

2,6-Dichloro-4-nitrobenzene is added to reactor through fresh material and

dissolved in iso-propanol which acts as solvent. NaNO 2 solution prepared in mixer is

also added to this reactor. In addition to that 98 % H 2SO4 and H2O are also added in

sufficient amount.

In Out

Component

Quantity

(kg / day)

Component

Quantity

(kg / day)

2,6-Dichloro-4-

nitrobenzene

1948.1 3,5-Dichloronitrobenzene 1806.9

Iso-propanol 1694 Iso-propanol 1694

Water 2823.3 Water 4507.998% H2SO4 H2SO4-1797.5 Na2SO4 1336.4

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H2O-37.64

NaNO2 Solution

NaNO2-1176.4

H2O-1646.9

HNO2 442.3

H2SO5 1072.8

N2 263.5Total 11123.9 Total 11123.8

Filter (F1001)

The outlet stream from Reactor (1002) enters the filter and gets separated into

solid and liquid phases. Since solubility of 3,5-Dichloronitrobenzene in water is zero,

we take the balance for both the phases with no 3,5-Dichloronitrobenzene in the

mother liquor. We assume that 3,5-Dichloronitrobenzene is sparingly soluble in

organic solvent that is iso-propanol and we consider this quantity as negligible. Thus

all 3,5-Dichloronitrobenzene will be in the form of cake. We will add water, 50% by

weight of cake for washing. Thus amount of water need to be added is 900 kg.

Cake Mother liquor

Component

Quantity

(kg / day)

Component

Quantity

(kg / day)

3,5-

Dichloronitrobenzene

1806.9 Iso-propanol 1694

Water 5407.9

Na2SO4 1336.4

HNO2 442.3

H2SO5 1072.8


Distillation Column (D1001) :

Mother liquor obtained after filtration contains iso-propanol which is need to

be separated. Since, iso-propanol is soluble in water we need to employ distillation to

separate it. Thus after separation of iso-propanol, remaining aqueous phase is sent to

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ETP for further treatment. This iso-propanol which is separated is recycled back to

main storage tank.

IN OUT

ComponentQuantity

(kg / day)

Distillate

(kg / day)

Bottom

(kg / day)

Iso-propanol 1694 1694 0

Water 4507.9 5.13

4502.8

Na2SO4 1336.4 0 1336.4

HNO2 442.3 0 442.3

H2SO5 1072.8 0 1072.8

Total 9053.4 1699.13 7354.3

Reactor (R1003)

Solid product obtained after filtration is turned into liquid by heating

before it is fed to this reactor. In addition to 3,5-Dichloronitrobenzene small amount

50% H2SO4 and required amount of Raney Nickel catalyst is charged into the reactor.

Here, hydrogenation of 3,5-Dichloronitrobenzene is carried out which gives 3,5-

Dichloroaniline and water. For this process hydrogen is sparged from bottom at 5 bar

pressure. Hydrogen is charged in no excess.

IN OUT

Component

Quantity

(kg / day)

Component

Quantity

(kg / day)

3,5-


1806.9 3,5-Dichloroaniline 1524.6

50% H2SO4

H2SO4-1.497

H2O-1.497

H2SO4 1.497

Catalyst 44.737 Water 340.3

H2 56.47 Catalyst 44.737

H2 0


Filter (F1002):

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Output stream from reactor (R1003) is filtered at reaction temperature for

removing catalyst from solution.

Cake Mother liquor

ComponentQuantity

(kg / day)

ComponentQuantity

(kg / day)

Catalyst 44.737 3,5-Dichloroaniline 1524.6

H2SO4 1.497

Water 340.3


Phase separator (PS1001):

Input to this unit is nothing but the mother liquor obtained after filtration. Thus

this outlet stream from filter enters into the separator and gets separated in the

aqueous and organic phases. Since solubility of 3,5-Dichloroaniline in water is 0.6

gm/lit some amount of 3,5-Dichloroaniline will go in aqueous phase. But majority

part of 3, 5-Dichloroaniline will be in organic phase. After separation some amount of

H2SO4 along with some water will go into organic phase.

AQUEOUS ORGANIC

Component

Quantity

(kg / day)

Component

Quantity

(kg / day)

3,5-Dichloroaniline 0.17 3,5-Dichloroaniline 1524.4

H2SO4 1.47 H2SO4 0.03

Water 333.5 Water 6.81

Total 335.14 Total 1531.24

Neutralizer (N1001):

Organic phase obtained from phase separation is charged into this unit for

removing unwanted H2SO4. This is need to be done since we require more than 99%

pure product. Here, we add 50% NaOH solution to neutralize H2SO4 accompanying

organic phase.

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IN OUT

Component

Quantity

(kg / day)

Component

Quantity

(kg / day)3,5-Dichloroaniline 1524.4 3,5-Dichloroaniline 1524.4

H2SO4 0.03 Na2SO4 0.043

Water 6.81 Water 6.85

50% NaOH solution

NaOH-0.025

H2O-0.025


Washing Unit (W1001):

After neutralization unit washing of product with water is done in order to

remove salt formed during neutralization and also excess NaOH. Thus, 2 kg of water

is added to output of neutralizer.

Phase separator (PS1002)

Input to this unit is output of neutralizer and extra 2 kg of washing water

added. Organic phase and aqueous phases are separated after this to get more than

99% pure 3,5-Dichloroaniline.

AQUEOUS ORGANIC

Component

Quantity

(kg / day)

Component

Quantity

(kg / day)

3,5-Dichloroaniline 0.005 3,5-Dichloroaniline 1524.4

Na2SO4 0.043 Water 0.18

Water 8.67


Thus purity of final product is

= (1524.4/1524.58) 100

=99.98%

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Amount of product formed per day

=9.40991621000

=1524.4 Kg/ day

6.2 ENERGY BALANCE

Product: 500 TPA of 3,5-dichloroaniline

Basis: Plant operates for 328 days and hence 1525 Kg of product need to be produced

per day.

Energy balance across the equipments:

In all the calculations the reference temperature is taken as 250 C.

The formula used for calculating the enthalpy of a stream is,

TCmQ P =

The condenser load is calculated by using the formula,

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=.

mQC

Where is latent heat of vaporization of the component which is to be condensed.

The Reboiler load is calculated by taking overall energy balance across the distillation

column as,

FCBDR QQQQQ ++=

Where the subscripts R, D, B, C and F refers to Reboiler, distillate, bottoms,

condenser and feed respectively.

Mixer (R1001)

NaNO2 which is nitrosating agent is in the solid form and hence dissolved in

water in this equipment. NaNO2 and water are introduced at 250 C.

IN OUT

ComponentTemperature

0C

Enthalpy

KJ

ComponentTemperature

0C

Enthalpy

KJ

NaNO2 25 0 NaNO2

solution

25 0H2O 25 0

Total 0 Total 0

Heat of solution =-256800 KJ

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Thus heat need to be removed by cooling water so as to keep outlet stream

temperature constant at 250C = 256800 KJ

Reactor (R1002)

All the reactants are charged at 250C. Reaction takes place at 500 C. Internal

coils are used for reaction mixture to reaction temperature.

IN OUT

Component

Temperature

0C

Enthalpy

KJComponent

Temperature

0C

Enthalpy

KJ

NaNO2

solution

25 0

3,5-


H2O

50

50

66340

471500H2O 25 0

98% H2SO4 25 0 Na2SO4 50 32300

2,6-

Dichloro-4-

nitroaniline

25 0 H2SO5 50 46350

Iso-

propanol

25 0 Iso-propanol 50 64940

HNO2 50 411300

N2 50 6843

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Total 0 Total 1099600

Total heat evolved during reaction=4115300 KJ

Amount of heat need to be provided for heating reaction mixture to 500C = 591280 KJ

Thus amount of heat need to be removed in order to keep reaction mixture

temperature constant = 3608000 KJ

Distillation column (D1001):

Here we want to remove iso-propanol and water from the incoming stream. As iso-

propanol boils at around 790 C which is less temperature compared to temperature at

which water boils. Thus we can get complete separation of iso-propanol and Water

from rest of the mixture. The temperature of the incoming stream is 25 o C. thus the

load on the reboiler is that of heating the mixture upto bubble point and then

supplying the latent heat of vaporization. The load on the condenser is to condense the

upcoming vapors using cooling water.

The reboiler load is found to be 3831400 KJ/day. This heat is supplied by using

saturated steam.

The condenser load is found to be 3633200 KJ/day. This heat is removed by using

cooling water coming in at 25 o C.

Melting operation:

During this operation 3,5- Dichloronitrobenzene is melted. Thus we

need to consider heat of fusion of this compound.

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Thus heat required to melt 3,5- Dichloronitrobenzene

=279690 KJ

Reactor (R1003):

In this stage 3,5- Dichloronitrobenzene in molten form is added to reactor

along with sulphuric acid and catalyst. Reaction is carried out at 70 0 C. Since reaction

is exothermic large amount of heat need to be removed.

IN OUT

Component

Temperatur

e

0C

Enthalpy

KJ

Component

Temperatur

e

0C

Enthalpy

KJ

3,5-

dichloronitrobenzene 70 13267

3,5-

Dichloroaniline 70 119960

50% H2SO4 solution 70 417.53 H2SO4 Solution 70 417.53

H2 70 43993 H2O 70 63788

H2 70 7332

Total 57680 Total 191498

Heat of reaction =5023100 KJ

Thus amount of heat need to be removed = 4889280 KJ/day

= 56590 J/s

Neutraliser:

In this stage unwanted sulphuric acid associated with 3,5- dichloroaniline is

removed. Thus 50% NaOH solution is used for this.

Heat of neutralization

=-57.1 KJ/mole

=-57.1 6.1140.0001

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=-34.911 J

Since, heat evolved in this operation is very small we do not require jacket. Also we

will not try to remove that small quantity of heat.

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04-process description and mebc

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