CHAPTER 2 CRU-1

7/25/2019 CHAPTER 2 CRU-1

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CHAPTER 2


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2.0 THEORETICAL PROCESS DESCRIPTION

Any reaction is governed by 2 factors Thermodynamics & Kinetics.

For any chemical reaction the thermodynamicsdictates the possibility of its

occurrence and the amount of products and unconverted reactants. In fact,

some reactions are 100% completed i.e. all the reactants are converted into

products. Others are in equilibrium i.e. part of the reactants only are

converted. The amount of products and reactants at equilibrium depends

upon the operating conditions and is dictated by the thermodynamics. Note

that thermodynamics do not mention the time required to reach the

equilibrium or the full completion of a reaction.

Kineticsdictates the rate of a chemical reaction. Kinetics is dependent upon

operating conditions but can also be widely modified through the use of

properly selected catalysts. One reaction (or a family of reactions) is

generally enhanced by a specific catalyst.

In other words, thermodynamics dictates the ultimate equilibrium

composition assuming the time is infinite. Kinetics enables to forecast the

composition after a finite time. Since time is always limited, when several

reactions proceed simultaneously, kinetics is generally predominant.

A heterogeneous catalyst generally consists of a support (alumina, silica,

magnesia) on which (a) finely divided metal(s) is (are) dispersed. The metal is

always responsible for the catalytic action. Very often, the support has also a

catalytic action linked to its chemical nature. A catalyst is not consumed but

can be deactivated either by impurities in the feed or by some of the

products of the chemical reactions involved, resulting in coke deposit on the

catalyst.


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2.1.0 FUNDAMENTAL REACTIONS

The chemical reactions involved in reforming processes are of two

types:

Desirable reactions, i.e. reactions which lead to an increased octane

number and to high purity hydrogen production. These are the

reactions to promote.

Adverse reactions, i.e. reactions which lead to a decreased octane

number, a decrease in hydrogen purity or a loss in products yield.

These are the reactions to minimize.The heat of the reactions mentioned hereafter as well as their relative rate

are necessary to understand the process. They are listed for the ease of

reference in Table , below. A catalyst is being used to promote the desirable

reactions at the expense of the adverse ones through its action on reaction

kinetics.

REACTIONS

HEAT OF

REACTION

1) KCAL/MOLE

RELATIVE

RATE

2) APPROX.

Naphthenes dehydrogenation - 50 30

Paraffin dehydrocyclization - 60 1 (base)

Isomerization: Paraffins + 2 3

Naphthenes + 4

HydroCracking + 10 0.5


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A) Desirable reactions with hydrogen production

a) Naphthenes dehydrogenation

Naphthenic compounds, cyclohexane, methylcyclohexane, dimethylcyclohexane up to C10 naphthenes are dehydrogenated respectively into

benzene, toluene, xylenes, C9and C10aromatics with the production of 3

moles of hydrogen per mole of naphthene.

The cyclohexane reaction, for instance, proceeds as follows:

Cyclohexane Benzene

CH

CH

CH

CHHC

HC

CH2

CH2

CH2

H C2

H C2

+ 3H 2

CH2

Note: Cyclohexane and benzene are generally schematically represented as

follows:

Cyclohexane Benzene

Thermodynamically the reaction is highly endothermic and is favored by

high temperature and low pressure. In addition the higher the number of

carbon atoms, the higher the aromatics production at equilibrium.

From a kinetic view point, the rate of reaction increases with temperature

and is not affected by the hydrogen partial pressure . The rate of reaction is

high compared to other reactions (table 1). It also increases with the number

of carbon atoms.

At the selected operating conditions the reaction is very fast and almost

total. It is promoted by the metallic function of the catalyst. Since it yields a


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high octane product, promoting this reaction is most desirable: refer to

octane number below:

RON MON

Cyclohexane = 83 77.2

Methylcyclohexane = 74.8 71.1

1.3

dimethylcyclohexane

= 71.7 71.0

Benzene = 114.8 > 100

Toluene = 120 103.5 m-Xylene = 117.5 115.0

RON : Research Octane Number

MON : Motor Octane Number

Note :Throughout this document, "octane" is generally used for "octane

number"

b) Paraffins dehydrocyclization

This is a multiple step process which applies either to the normal paraffins

(linear) or iso-paraffins (branched). It involves a dehydrogenation with a

release of one hydrogen mole followed by a molecular rearrangement to

form a naphthene and the subsequent dehydrogenation of the naphthene.

The molecular rearrangement to build a naphthene is the most difficult

reaction to promote but the subsequent aromatization of the naphthene

yields a noticeable octane increase.

The reaction can be summarized as follows:

C H7 16

+ H

2

C H7 14

CH2

CH2

CH2

CH2

CH2

CH3

CH3

CH

CH3

CH3

CH2

CH2

CH2CH


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Methylcyclohexane

CH2

CH2

CH CH2 CH3CH3

CH

CH2

CH2

CH2

CH2

CH

CH3

H C2

Toluene

H C2

2 CH2

CH2

CH2

CH CH3 CH3

CH CH

CH CH

HC

C

+ 3H2

The paraffin dehydrocyclization step becomes easier as the molecular weight

of the paraffin increases, however the tendency of paraffins to hydrocrack

increases concurrently .

Kinetically, the rate of dehydrocyclization increases with low pressure and

high temperature , but altogether, at the selected operating conditions, this

rate is much lower than that of naphthene dehydrogenation (30/1). The

reaction is promoted by both catalytic metallic and acidic functions.

c) Effect of parameters on naphthene dehydrogenation

The tables below summarize the effect of the main parameters governing the

dehydrogenation and dehydrocyclization reactions.

Thermodynamics dictates the equilibrium which could be theoretically

reached (i.e. if the time was infinite). Kinetics dictates the rate of reaction,

i.e. the possibilities to reach a state close to equilibrium in a finite time.


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Increase of Effect on dehydrogenation due

to thermodynamics to kinetics

Pressure decreases unaffected

Temperature increases increases

H2/HC ratio (1) slightly decreases slightly decreases

Ratio of pure hydrogen (mole) to hydrocarbon feed (mole).

d) Effect of parameters on paraffin dehydrocyclization

Increase of Effect on dehydrocyclization due

to thermodynamics to kinetics

Pressure decreases decreases

Temperature increases increases

H2/HC ratio slightly decreases slightly decreases

B) Desirable reactions without hydrogen production

a) Linear paraffins isomerization

Reaction is as follows:

C H7 16 C H

7 16

These reactions are fast, slightly exothermic and do not affect the number ofcarbon atoms. The thermodynamic equilibrium of isoparaffins to paraffins

depends mainly on the temperature. The pressure has no effect.

Iso-N paraffin equilibria

Carbon atom C4 C5 C6 C7 C8

%Isoparaffin 500C 44 58 72 80 88


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The paraffins isomerization results in a slight increase of the octane number.

From a kinetic view point , high temperature favors isomerization but

hydrogen partial pressure has no effect. These reactions are promoted by the

acidic function of the catalyst support.

b) Napththenes isomerization

The isomerization of an alkylcyclopentane into an alkylcyclohexane involves

a ring rearrangement and is desirable because of the subsequent

dehydrogenation of the alkylcyclohexane into an aromatic. Owing to the

difficulty of the ring rearrangement, the risk of ring opening resulting in a

paraffin is high.

The reaction is slightly exothermic. The reaction can be summarized as

follows:

Theoretically, at the selected operating temperature (about 500C) the

thermodynamics limits the alkylcyclohexane formation. But the subsequent

dehydrogenation of the alkylcyclohexane into an aromatic shifts the reaction

towards the desired direction. This type of reaction is also easier for higher

carbon number.The octane number increase is significant when considering the end product

(aromatics) as shown:

CH3

AlkylcyclohexaneMeth lc clohexan

Alkylcyclopentane

Eth lc clo entane

C2H5


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RON MON

Ethylcyclopentane = 67.2 61.2

Methylcyclohexane = 74.8 71.1

Toluene = 120 103.5

C) Adverse reactions

a) Cracking

Cracking reactions include hydrocracking and hydrogenolysis reactions.

Hydrocracking affects either paraffins normal or iso) or naphthenes. It

involves both the acid and metallic function of the catalyst. It is, to some

extent, a parallel reaction to paraffin dehydrocyclization.

It can be represented schematically by a first step of dehydrogenation which

involves the metallic function of the catalyst, followed by a cleavage of the

resulting olefin and the hydrogenation of the subsequent short chain olefin.

The second reaction is promoted by the acidic function of the catalyst.

+ H2

C H7

(m)

16C H

7

14

+ H2

(a)

+

C H4 8

C H3 8

C H7 14


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+ H2

C HC H4

(m)

8 4 10

(m) Catalyst metallic function

(a) Catalyst acidic function

The first reaction involves the same reactants as the dehydrocyclization and

is likewise catalysed by the metallic function.

Hydrocracking also affects the naphthenes, the overall reaction can be

summarized as follows:

+ H2

C H16

or

+ H2

C H6

CH - C H3

or

or

145 9

CH - C H3 6 11 7

At the selected operating conditions, hydrocracking reaction could be almost

complete. Fortunately it is somewhat limited by its kinetics. Compared toits desirable concurrent reaction (dehydrocyclization), hydrocracking

becomes significant as the temperature increases. It is also favored by high

pressure.

The main effects of hydrocracking are:


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a decrease of paraffins in the reformate which results in an increase

of the aromatics percentage (i.e. an increase in octane) and a loss of

reformate.

a decrease in hydrogen production.

an increase of LPG production.

b) Hydrogenolysis

This undesirable reaction has some similarity with hydrocracking since it

involves hydrogen consumption and cleavage of bonds. But it is promoted

by the metallic function of the catalyst and leads to lighter hydrocarbon C1+

C2- even less valuable than LPG ,C3+ C4.It can be represented schematically as follows:

+ H2

C H7

CH4

+ H2

C H2

C H

or

+

+

16

C H7 16

6

C H6 14

5 12

Like hydrocracking it is exothermic and favored by high pressure and high

temperature.

c) Hydrodealkylation

Hydrodealkylation is the breakage (or cleavage) of the branched radical (-

CH3or -C2H5) of an aromatic ring.

Xylene (two radical groups) can be dealkylated into toluene (one radical

group) which in turn can be dealkylated to benzene.

The standard representation is:


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+ H2

Xylene Toluene

+ CH4

+ H2

Toluene Benzene

+ CH4

Hydrodealkylation consumes hydrogen and produces methane. It is favoredby high temperature and high pressure and promoted by the metallic

function of the catalyst.

d) Alkylation :Alkylation is a condensation reaction which adds an olefin

molecule on an aromatic ring. It results in an aromatic with an increased

molecular weight. The reaction proceeds as follows:

Benzene Propylene Isopropylbenzene

HC

CH3

+ CH = CH - CH32

3

This reaction, promoted by the catalyst metallic function, is not hydrogen

consuming. But it leads to heavier molecules which may increase the end

point of the product. In addition the high molecular weight hydrocarbons

also have a high tendency to form coke. This reaction must be avoided.

e) Transalkylation Alkyl disproportionation)

Two toluene rings (one branched CH3 radical) can disproportionate to

produce one benzene ring (no branched radical) and one xylene ring (two

branched radicals), as shown:


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+

XyleneBenzene

+

Toluene Toluene

This reaction, promoted by the catalyst metallic function, occurs mainly in

very severe conditions of temperature and pressure.

f) Coking

Coke formation on the catalyst results from a very complex group of

chemical reactions, the detailed mechanism of which is not fully known yet.

Coke formation is linked to heavy unsaturated products such as polynuclear

aromatics (or polycyclics which can be dehydrogenated) resulting either

from the feed or from the polymerization of aromatics involved in some of

the reforming reactions (dehydrocyclization, disproportionation). Traces of

heavy olefins or diolefins may also result from the reforming reactions

(dehydrocyclization, alkylation, for instance) and promote coke formation.

A high end boiling point of the feed means greater amount of polyaromatics

and then a higher coking tendency. Since condensation is promoted by high

temperature, poor distribution in a reactor favors local high temperatures

and coke build up . Coke deposit on the catalyst reduces the active surface

area and greatly reduces catalyst activity.

2.1.1 KINETIC ANALYSIS OT THE CHEMICAL REACTION

The effect of the main operating conditions on the rate of the reactions

involved in the reforming process using the selected catalyst is summarized

below.

A)

Effect of hydrogen partial pressure

At 10 barg hydrogen partial pressure, the dehydrogenation of naphthene is

about 10 times, faster than isomerization, 30 times faster than

dehydrocyclization and 50-60 times faster than cracking (hydrocracking and

hydrogenolysis).


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At relatively high pressure (above 20 barg) the rate of coking is low

compared to the other reactions but it increases noticeably at lower pressure.

To sum up, there is an incentive to operate at low pressure: cracking rate

will be reduced and dehydrocyclization rate increased as well as the coking

rate.

On another hand thermodynamics also favors low pressure for

dehydrogenation and dehydrocyclization. The only drawback of low

pressure is the high coking rate.

B)

Effect of temperature

Dehydrogenation has a moderate energy of activation (~ 20 Kcal. mole -1) asdoes isomerization (~ 25 Kcal. mole -1) and consequently temperature only

slightly increases the rate of these reactions.

Cracking and coking have higher energy of activation (45 and 35 Kcal. mole -

1respectively). The rate of these undesirable reactions is more significantly

increased by temperature.Very high temperature( > 543 C) may even lead to

thermal reactions which will decrease reformate yield and catalyst stability.

To sum up, a higher temperature clearly favors the undesirable reactions

more than the desirable one. However a controlled temperature rise is

required during the catalyst life to maintain catalyst activity and therefore

product octane.

C)

Effect of carbon number

The kinetic study of the chemical reactions becomes even more complicated

owing to the presence of molecules with different numbers of carbon atoms.

As is the case for thermodynamic equilibria, it appears that the rates of thereactions are affected by the length of the chain of the reactant. The

cracking reaction rate, (the sum of hydrocracking and hydrogenolysis),

increases regularly with the number of carbon atoms, whereas

dehydrocyclization rate exhibits a sudden increase between hexane and

heptane as well as between heptane and octane, while the variation between

the higher homologues remains relatively slight.


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To sum up, the dehydrocyclization of C

6

paraffins to benzene is more

difficult than that of C

7

paraffin to toluene, which itself is more difficult

than that of C

8

paraffin to xylenes. Accordingly the most suitable fraction to

feed a reforming process is the C

6

- C

10

fraction.

CONCLUSIONS:

From the above analysis it can be concluded:

a) Dehydrogenation reactions are very fast, about one order of

magnitude faster than the other reactions.

b) Low pressure favors all desirable reactions and reduces cracking. To

compensate the detrimental effect of low pressure on coking, lowpressure reformer requires continuous catalyst regeneration. For

semi regenerative reformer the recommended lowest operating

pressure to have acceptable cycle length is about 12 kg/cm2g.

(c) An increase in temperature favors the kinetics of dehydrogenation,

isomerization, dehydrocyclization, but accelerates the degradation

reactions (cracking, coking) even more. Consequently an increase in

temperature leads to an increased octane associated with a decrease

in reformate yield.

(d)

The reaction rates of such important reactions as paraffins

dehydrocyclization increase noticeably with the number of carbon

atoms. Cyclization is faster for C8 paraffin than for C7, and for C7

than for C6. Consequently the C7- C10fraction is the most suitable

feed.

D)Catalyst distribution in reactors

Thermodynamics and kinetics have shown that there is an optimum

operating temperature range, approximately 450C-520C in order to

simultaneously favor the rate of the desirable reactions and limit the

undesirable ones to an acceptable level. For each specific case, the most


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appropriate operating temperature is selected taking into account the feed

quality (P0NA, distillation range) and product requirement (octane).

Owing to the great endothermicity of the most important and desirablereactions (naphthenes dehydrogenation and paraffins dehydrocyclization)

this optimum temperature cannot be sustained through out the whole

catalyst volume. In addition, dehydrogenation is also, by far, the fastest

reaction, which means that the temperature drops very sharply over the first

part of the catalyst. In order to restore the catalyst activity, when

temperature has dropped to a certain level which depends upon the reactions

involved, the reactor feed is reheated. To achieve this, the catalyst is

distributed in several reactors ( 3 or 4) and intermediate heaters areprovided.

In 22R02 only 10% of the catalyst has been loaded because naphthenes

dehydrogenation results in temperature too low to sustain the reaction any

longer.The reactor effluent is reheated to allow naphthene dehydrogenation

to continue and dehydrocyclisation reaction to start. Over the next 20% of

catalyst, distributed in the 2nd reactor, temperature drops again to a level

where reheating is required to enable the paraffin dehydrocyclization to

proceed.So the catalyst distribution is as follows :R02(1streactor) = 10%

R03(2ndreactor) = 20%

R201(3rdreactor) = 70%

Each specific case, obviously, requires a specific catalyst distribution.

In a somewhat simplified but practical way, for operational guidance, the

main reactions take place in the various reactors can be represented in thefollowing order:

1streactor:

Dehydrogenation

Isomerization

2ndreactor:


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Dehydrogenation

Isomerization

Cracking

Dehydrocyclization

3rdreactor:

Cracking

Dehydrocyclization


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2.2.0

GENERAL PROCESS DESCRIPTION

2.2.1 FEED AND GAS PREHEATING SECTION

Pretreated naphtha from unit-21 is fed to the unit by the pump 22 P01C/D,

and regulated by 22 FC02. Feed naphtha mixed with the recycle gas from 22

K01 A / B is pre-heated in the welded plates exchanger 22-E-101 (Packinox

exchanger). 22 E01 A/B is kept as standby for feed preheating. The mixture is

also preheated in 22-E-02 against the third reactor effluent and then is

further heated to the required first reactor inlet temperature in pre-heater

22-F-01.Completely vaporized feed from the above exchangers enter the

furnace tubes of 22 F01 and is heated up to the reaction temperature beforeentering the reactor 22 R02.

For the start-up, Naphtha is directly pumped by 22P01 C / D to 22CO1

bypassing the Reaction section for which a 3" line is provided. In case of

emergency shut down, a push button switch 22.PB.06 can be used to stop the

feed. A low- low flow alarm 22 FALL 02 is coupled with the flow transmitter

22FT 02 will actuate 22 P 01 C/D Trip .

2.2.2 FURNACE AND REACTION SECTIONS

Completely vaporized naphtha and gases heated to the reactor temperature

in 22 F01 enter at the top of the first down flow Reactor 22 R02.

Operating conditions are :

Operating pressure = 27.3 kg/cm g

Operating temperature = 488 C

The reactor is filled with UOP Platforming R-98 catalyst, it is a

bimetallic platinum(0.25wt.%) rhenium (0.25wt.%) catalyst supported on

very high purity alumina . When the feed comes in contact with catalyst,

reforming reactions take place. Due to endothermicity of reactions, the

temperature of reactants decreases. The effluent from the first reactor is


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therefore, reheated in furnace 22 F201 to make up the loss of heat in the first

Reactor. Reheated effluent is then passed through the 2nd Reactor 22 R03.

Operating conditions:

Operating pressure = 26.3 kg/cm g

Operating temperature = 507 C SOR

512 C EOR

Containing R-98 platinum rhenium catalyst where further reforming

reactions take place. Effluent from the second Reactor is again reheated infurnace 22 F02 and passed through Reactor 22 R 201 containing R-98

catalyst to complete the reforming reactions for obtaining the product with

desired octane number. Reactors 22 R02 and 22 R03 are spherical and 22 R

201 is vertical cylindrical type.

The Reactors are equipped with thermocouples to follow the temperature

profile during normal running and regeneration. Number of thermocouples

in each Reactor is as follows

22R02 : 6 22 TI 20/21/22/23/24/25

22R03 : 8 22 TI 28/29/30/31/32/33/34/35

22 R201 being radial reactor with no skin Thermocouple

Differential pressure gauges 22 PDI 03, 04 and 04201 are provided to indicate

the pressure drop across the Reactors. Required Reactor inlet temperatures

are controlled by 22TC 01, 22 TIC 5101 and 22TC02. These controllers inturn act on the fuel gas quantity to the furnace burners.

During catalyst regeneration, instrument air is introduced at the compressors

22 K01 A, B by means of 22 FC 05 and at the same time an adequate quantity

of nitrogen is recycled by means of the centrifugal compressors 22 K01 A

and B as a carrier medium. During special operations like Start-Up or


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PNE

A.R.MUKHOPADHYAY

SPNM

S.K.SARKAR

CPNM

Page 20of 23

Regeneration Nitrogen of 99.8% purity is introduced in the system at the

compressors 22 K01 A / B and during normal operation, blinds are used in

the air line. 22 F 01 and 22 F02 are having 2 passes and 22 F 201 is having 4

passes only two furnace 22 F01 & 22F201 consist of convection section.

Sulphiding is done by injection of DMDS (Di-methyl Disulphide) by means

pump 22 P 203 A during start-up. The other pump 22 P 203 B for the same

service will be stored in the warehouse .The chlorine agent (Carbon Tetra

Chloride, pure or diluted with reformate) are stored in two separate

containers and their injection is controlled by pump 22 P03. The Flowrate

of CCL4solution can be read from 22FI 02201.

2.2.3 REACTOR EFFLUENT COOLING SYSTEM

The effluent from reactor 22 R 201 is cooled and partially condensed in a

series of exchangers as follows

- In the tube side of 22 E02 to preheat feed,

- In the tube side of 22 E03 to re-boil stripper bottoms,

-

In the Packinox exchanger 22 E 101 to preheat feed, &

- In shell side of water cooler 22 E04.

The effluent thereafter is sent to the separator drum 22 B01.

2.2.4 SEPARATOR DRUM AND RECYCLED GAS SECTION

The reactor effluent is split into gaseous and liquid phases in separator

drum.

- The liquid phase is sent to the stabilizer column,

- A part of gaseous phase is recycled as recycle gas within

CRU

- Another part is sent as make up gas to Naphtha

Pretreatment section (under 22FC01)


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Page 21of 23

- Remaining to Kero-HDS section and New PSA under

pressure control 22 PC01 cascaded with 22 FIC 01203 and

22FIC 01202 selected with 22 HS 01202 .

The liquid level in separator is controlled by regulator 22 LC 02. The vessel is

provided with a low level alarm (22 LAL 02) and a high level alarm (22 LAH

02). The drum is also equipped with a high level alarm and compressor cut

off (22 LAHCO 01) to prevent any liquid flow to the compressors. A push

button (22 PB 05) is also used to stop the compressors. A wire mesh sieve

(demister pad) is placed at the top section of the separator to prevent liquid

entrainment in the gaseous phase.

The pressure in the section is maintained by controller 22 PC 01 which

allows the excess gas to other units as well as fuel gas system. The separator

drum is connected to an ejector to create vacuum in the unit during start up

and shut down purging operations. The Hydrogen Rich gas from the

separator drum is recycled by means of the centrifugal compressors 22 K01

A/B. Part of the compressed gas is mixed with the pretreated naphtha as

described earlier.

A low flow alarm (22 FAL 03) along with the low flow alarm cut off (22

FALCO 03) is connected to the discharge line of the compressors 22 K01 and

the furnaces 22 F01, 22 F201 and 22 F02. This facilitates to stop the latter in

case of compressor failure alongwith the tripping of feed pump. The

compressors 22 K01 A/B are stopped automatically in case of very high level

in the separator drum 22 B01. The complicated lube and seal oil system of

22K01A/B shown in the diagram H/CRU/03.

2.2.5 STABILIZER SECTION

The liquid from the separator drum is fed to the stabilizer. The liquid is

reheated in the shell side of the exchangers 22 E06 A/B with the stabilizer

bottoms product on the tube side and enters the stabilizer. The stabilizer

column comprises of

- 18 valve trays below the feed point &


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PNE

A.R.MUKHOPADHYAY

SPNM

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CPNM

Page 22of 23

- 10 valve trays above the feed point

A part of the stabilizer bottom product is reboiled in thermosyphon type

exchanger 22 E03. The temperature of reboiled effluent is controlled by a

controller, 22 TC 04, which acts in split Range on 22TV03201A and

22TV03201B. 22TV03201A takes care of the flow through tube side of 22C01

Reboiler 22E03 and 22TV03201B the Bypass. Normal mass flow rate across

22TV03201A = 5813 kg/hr ( Vapour phase)22TV03201B = 42284 kg/hr (

Vapour phase)22TV03201A will operate from 0-100% opening on getting

signal from 22TRC04 and 22TV03201B will be set to operate between 40% -60% opening to control the reboiler outlet temperature.

This is done to take care of the following situation :

When 22TV03201A put in line at 0-50% operating range of TC04 it will

open from 0-100% with 22TV03201B at 40% opening.

At 50-100% operating range of TC04 22TV03201B starts opening from 40%-

60%

Opening of 22TV03201B at 40% from the start is selected based on

difference of material flow between the two valves. This will take care of

remaining material flow in the circuit when TC04 will be operating at 0-50%

range .

The stabilizer bottom level is controlled by the controller 22 LC 04 by

regulating the stabilized reformate flow.

The stabilizer overhead vapors are cooled and partially condensed by

condenser 22 E 105 and are collected in the overhead horizontal reflux drum

22-B-02 with Boot . Draining facility is controlled by 22 LIC 07 and routed

to CBD via 22 LV07 . Stabilizer Column overhead pressure is controlled by

split range controller 22PIC05 by regulating flow of overhead vapors to 22


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B02 through 22PV 05B and flow of OFF gases to LPG recovery of ISOM unit

/ Fuel gas header through flow recorder 22FI07.

Corrosion inhibitor is added by pump 22PO2 and introduced at the top ofthe stabilizer.

The stabilizer bottom part is passed through exchangers 22 E06 A/B and

cooler 22 E07 before it is sent to storage and feed to reformate splitter in unit

85. A 2" dia draw-off from top reflux built-in accumulator (above plate 28) of

22 C01 has been provided for tapping of LPG from Reformer gas. This stream

enters a water separating pot prior to entry into Crude Distillation unit

stabilizer 11C04. A rotameter has been provided for measurement of LPGrich stream from reformer to Column 1 1 C04.

2.2.6 NITROGEN BULLET 61 B 111)

99.9% pure Nitrogen supplied by NGU is stored in a Bullet at 5

kg/cm.Nitrogen from Bullet is consumed in Gr-20 Units for blanketing the

HP-system with inert atmosphere, flushing of isolated compressors and Heat

Exchangers for maintenance job, stripping out undesirable gases from lube

oil, circulated in H2-Compressors & during shut down/start up and duringregeneration of BM-catalyst of U-22Nitrogen is also supplied from storage

Bullet to SRU, LOB, and TPS (P & U Section) as per their requirement.In

Gr.20 Units (U21/22/23) Nitrogen line connections are provided at all the top

of Reactors, Compressors Suction & Discharge lines, Additive dosingVessels

of ATF-product and to Degasser in Seal Oil return line of H2-Compressors to

22-B-03.

Documents

CHAPTER 2 CRU-1