1. 1
VACATIONAL TRAINING
PROJECT
PROJECT TITLE:
TO STUDY
THE PROPERTIES AND PERFORMANCE
EFFECTIVENESS OF CLASS CATALYST
SUBMITTED BY: GUIDED BY:
Narendra Kumar Mr. Rakesh Kumar Verma
VT
B.E, IIIrd YEAR
CHEMICAL ENGINEERING
SIT, TUMKUR
KARNATAKA

2. 2
ACKNOWLEDGMENT
I would like to thank TATA Steel for giving me such a great opportunity
to use its resources and work at industrial platform.
The guidance shown to me by the various people working in this
organization has acted as a stimulant and provided me strength to
complete this project in the present form.
The time, which we spent in TATA STEEL (Jamshedpur) during the
training, was a wonderful experience in itself. We would like to thank all
those who directly or indirectly assisted in successful completion of this
project.
I would like to express my profound gratitude towards:
1. Mr. Rakesh Kumar Verma (Project Guide ,Sr. Manager)
2. Staff members of NBPP
Their support & guidance helped me convert my concepts into
visualization & and also for the guidance throughout the project. Last but
not the least we would like to thank all the staff members of TISCO,
without their corporation this training would not have been possible.

3. 3
Certificate
This is to certify that the project on “TO STUDY
THE PROPERTIES AND PERFORMANCE
EFFECTIVENESS OF CLASS CATALYST” is a
bonafied and original work carried out by Mr. Narendra Kumar
under my supervision and guidance
He has been sincere and an avid learner throughout the 4 weeks
of internship programme .
DATE: 31.6.2016
Rakesh Kumar Verma
Sr.Manager (New- BPP)
Tata Steel Limited
Jamshedpur, Jharkhand

4. 4
Index Page
Introduction 5
Chapter 1 Overview
1.1 Carbonisation 6
1.2 Gas Purification 9
Chapter 2 MajorUnits
2.1 Tar Recovery 12
2.2 Primary Gas Cooler 14
2.3 Electrostatic Tar Precipitator 17
2.4 Exhauster 19
Chapter 3 RemovalOf Ammonia & Hydrogen Sulfide From COG
Through Scrubbing Process
3.1 Principle 20
3.2 Scrubbing of NH3 & H2S from COG through scrubber 26
3.3 Ammonia Stripping And De-Acidifying Unit 33
Chapter 4 Processes After Ammonia & Hydrogen Sulfide Removal
4.1 Claus Process ofSulphur Recovery 34
4.2 Naphthalene Removal ; Naphthalene Distillation Plant 43
4.3 Booster 44
4.4 Waste Water Treatment 46
4.5 Utility Devices 47
Conclusion 48
References 49

5. 5
INTRODUCTION
The coke oven by-product plant is an integral part of the by-product coke
making process. In the process of converting coal into coke using the by-
product coke oven, the volatile matter in the coal is vaporized and driven
off. This volatile matter leaves the coke oven chambers as hot, raw coke
oven gas. After leaving the coke oven chambers, the raw coke oven gas is
cooled which results in a liquid condensate stream and a gas stream. The
functions of the by-product plant are to take these two streams from the
coke ovens, to process them to recover by-product coal chemicals and to
condition the gas so that it can be used as a fuel gas. Historically, the by-
product chemicals were of high value in agriculture and in the chemical
industry, and the profits made from their sale were often of greater
importance than the coke produced. Nowadays however most of these
same products can be more economically manufactured using other
technologies such as those of the oil industry. Therefore, with some
exceptions depending on local economics, the main emphasis of a
modern coke by-product plant is to treat the coke oven gas sufficiently so
that it can be used as a clean, environmentally friendly fuel.
The report focuses on the by-products obtained from the Coke plant in
By-Products Plant. The report gives the overview of the Carbonization
process and the chief emissions from the coking process. Further the
project mentions different kinds of process involved in purifying the
Coke Ovens gas evolved in coke plant, focusing mainly on the NH3
removal from ammonia scrubber.

6. 6
Chapter 1
Overview
1.1 CARBONIZATION
The destructive distillation of bituminous coal, done in the absence of air
in order to obtain coke and other fractions having a greater percentage of
carbon than the original material .The volatile constituents of the coal,
including water, coal-gas and coal-tar, are driven off by baking in an
airless oven at temperatures as high as 1,000 degrees Celsius so that the
fixed carbon and residual ash are fused together.
Most coke in modern times is produced in "by-product" coke ovens, and
the resultant coke is used as the main fuel in iron making blast furnaces.
Today, the hydrocarbons are considered the by-products of modern coke
making facilities (though they are usually captured and used to produce
valuable products).
Coke oven operation is a continuous production process and to ensure the
normal operation, the key is the stability of the charged coal cake. The
bulk density of the coal cake to be required is normally ranged from 1.05
– 1.1 MT/m3 (wet). Hence, for above reason, besides improving the
performance the separated into intervals, i.e. each carbonization coking
process is considered an interval while the process as a whole is
continuous.
Difficult to crush coal
Main unblended Pre crushing Coal mixing room Grinding
Coke Oven Coal Tower Mixing room

7. 7
Battery Details:
Total batteries running 7
Stamp charge 6
Top charge 1
Battery 10&11 details:
Ovens 88
Ovens in each block 44
Volume of oven 36.5m3
Width
524mm
Height 5 m
Length 16m
Dry coalcharge per oven 36.5 ton
Mechanical equipment of Coke –oven
Types of machine 4
SCP(Stamp charging and pushing machine) 3
CGC 3
Loco 3
Cgt 3

8. 8
1.2 Gas Purification
Fig : Layout of Coke By ProductPlant

9. 9
After the charging coal being high-temperature dry distilled in the coke oven
coking chamber, there are about 75 % of coal turned into coke, and the
remaining 25 per cent turned into chemical products and gas. There are
impurities in the coke oven gases (i.e. raw gas) such as aqueous, coal tar,
naphthalene, hydrogen sulphide, cyanide and ammonia, so we need to send
the raw gas to the coke oven gas purification plant to remove the impurities of
the raw gas and get pure gas to the user. The coke oven gas purification plant
is the matching equipment of the coke oven with one battery able to produce
approx. 330 M3 of raw gas per ton of coal. The major products designed are
pure gas, crude tar, sulphur.
The yields of different products are :
Coke 70 to 80 %
Pure coke oven gas 15 to 19 %
Tar 3 to 4 %
Combined water 2 to 4 %
Ammonia 0.25 to 0.30 %
Others 0.90 to 1.10 %
Purified coke ovengas:
a) Pressure (97,000 Nm3/h at battery limit): 3.5kPa (min.)
b) Gas composition (volume %):
CO2 3~4
CnHm
2~2.6
O2 0.6
CO 6~9

10. 10
H2
52~56
CH4
24~26
N2
balance
H2S 0.5
g/Nm3
NH3 0.04
g/Nm3
C10H8 0.12
g/Nm3
Tar 0.02
g/Nm3
c) Temperature: ~28˚C .
d) Content of impurities (the figures are valid for gas flow 88,000Nm3/h)
The calorific value of the gas after purification is 4200 to 4400 kcal/m3,
and specific gravity is 0.48 kg/m3.
From carbonization of coal, coke ovens gas is produced which is a
Volatile Organic Gas comprising CO, H2 (having fuel value), H2S, NH3,
Naphthalene, tar, BTX, Suspended particulate matters as its primary
constituents.
Since it has a high calorific value, it is utilised as a fuel in Blast furnace,
in heating of ovens of Coke Ovens Battery. Before recirculating the gas
into the system, the gas is cleaned from H2S, NH3, Naphthalene, tar, BTX
as these cause corrosion and blockage in the in the passage.
Gas along with tar, coming out of the battery is at a temperature of 8000C
and it has to be cooled down to lower temperature for further treatment
else it will corrode the pipe and equipment, being at a very high
temperature.
Just before the Primary Gas collector, the crude gas along with tar is
mixed with Ammonia liquor which acts as a coolant and reduces the

11. 11
temperature of the gas to 820C. The liquor has affinity for Tar and forms
a solution of Ammonia liquor and Tar. Thus the output contains gas
along with solution of Ammonia liquor and tar. The volumetric flow rate
is almost 1/4th of the volumetric flow rate of the whole effluent. 820C
crude gas from coke oven enters together with tar and ammonia liquor
into the down-comer along gas suction main. Here two phases gets
separated by gravity. Crude gas goes out of the down-comer and
ammonia liquor and tar solution being heavy, enters into the down-
comer.

12. 12
Chapter 2
MAJOR UNITS
2.1 TAR RECOVERY
82℃ crude gas from coke oven enters together with tar and ammonia
liquor into the down-comer along gas suction main. After the separation
of liquid and gas, the crude gas goes out of the down-comer and enters
into a cross tube type primary cooler where gas is cooled in 2 stages. In
the upper stage, 34℃ circulating water is used for cooling and in the
lower stage 14℃ low temperature water is used for cooling crude gas
down to 21℃. The gas discharged from the bottom of cross tube primary
coolers goes into the electric tar precipitator to remove the tar entrained
in gas, and then is boosted to the H2S/NH3 scrubber by gas exhausters.
In order to ensure the cooling effects of coolers, the mixed liquor of tar
and ammonia liquor is used to continuously spray at the upper and lower
stages. Top of the coolers is washed regularly with hot ammonia liquor to
remove tar and naphthalene etc. deposited on tube walls.
The condensate from the upper stage of the primary cooler flows into the
condensate tank for upper stage via the water seal pot, from which it is
sent to the process gas cooler by the upper stage condensate pump.
The condensate discharged from lower stage of the primary coolers flows
into lower stage condensate tank via water seal pot, and then the tar and
ammonia liquor mixture is added into it according to a certain proportion
and delivered by the lower stage condensate pump to the lower stage of
the primary coolers for lower stage spray. The excess condensate flows
by gravity into the condensate tank for upper stage via the bypass pipe.
First, tar and ammonia liquor separated from the decanter enters into the
pre-separator of tar residue where the separation of tar, ammonia liquor
and tar residue are accomplished and a screen is installed at its outlet.

13. 13
Solids bigger than 8 mm will remain in the pre-separator and settle in the
conical bottom and withdrawn by tar press pump. Solids are crushed in
the tar press pump and sent back to the top of pre-separator of tar residue.
The tar and ammonia liquor separated from pre-separator of tar residue
enters into the mechanical ammonia liquor decanter, where ammonia
liquor, tar and tar residue are separated. Conical plate is installed at the
bottom of the mechanical ammonia liquor decanter, by means of the
difference of temperature and gravity, the tar is settled to the bottom
where it is withdrawn by tar intermediate pump to supper class centrifuge
for further dewatering. After dewatering and residue removal, the treated
tar flows by itself to the tar tank where it is delivered to oil depot by tar
pump. Tar residue is sent to the tar residue tank and to the tar residue
adding system of the coal preparation plant. The upper ammonia liquor
of the mechanical ammonia liquor decanter flows into the lower
intermediate tank for flushing liquor and then is sent by the flushing
liquor pump into the gas collecting main to spray and cool coke oven gas.
One part of ammonia liquor at the outlet of flushing liquor pump is
pressurized by a high pressure ammonia liquor pump and sent to the coke
oven for smokeless charging. The coalwater goes out from the upper part
of the tar and ammonia liquor decanter. It flows into No.1 coal water tank
to precipitate and separate light oil and heavy oil first and into No. 2 coal
water tank. Then coal water is delivered to H2S/NH3 scrubber by the coal
water pump.
Tar and ammonia emulsion are taken out from the interface of the
decanter. The tar and ammonia emulsion containing 30~50% tar are sent
to the upper part of the cross tube primary cooler by spraying pump and
used as spraying liquor for gas scrubbing.

14. 14
2.2 PRIMARY GAS COOLER
Lower condensate tank

15. 15
Purpose of cooling:
 To reduce temperature of Coke oven gas as absorption is
favourable at low temperature as well as gas volume is also
reduces according to gas law so pumping cost will be less.
 To condense the most easily condensable (high boiling point)
components like tar, naphthalene and water vapour also.
Technical process:
 After the separation of liquid and gas, the crude gas goes out of the
down-comer and enters into a cross tube type primary gas cooler
where gas is cooled in 2 stages. First cooling water at 340C is used
to cool down the gas in the upper stage from 820C to 400C and
chilled water at 140C is used in the lower stage to further cool it
down to 210C. We don’t directly cool gas with chilled water
because deposition tar and naphthalene will bloke PCDC.
 The cooling process is an indirect contact type heat exchanging
process where cooling water and chilled water is flown inside
pipes and gas is flown continuously from the top .The cooling
process also causes some tar in the air to condense and is taken out
from the bottom.
 In order to ensure cooling effects of primary gas coolers, the mixed
liquor of tar and ammonia liquor is used to continuously spray at
the upper and lower stages. Top of the primary gas coolers is
washed regularly with hot ammonia liquor to remove tar and
naphthalene, etc. deposited on tube walls.

16. 16
 The gas discharged from the bottom of cross tube primary gas
coolers goes into the electric tar precipitators to remove the tar
entrained in gas, and then is boosted to the H2S/NH3 scrubber by
gas exhausters.
 The condensate from the upper stage of the primary gas cooler
flows into the upper condensate tank for upper stage via the upper
seal pot, from which it is sent to the process gas cooler by the
upper condensate pump.
 The condensate discharged from lower stage of the primary gas
coolers flows into the lower condensate tank via the lower seal pot,
and then the tar and ammonia liquor mixture is added into it
according to a certain proportion and delivered by the lower
condensate pump to the lower stage of the primary gas coolers for
lower stage spray. The excess condensate flows by gravity into the
upper condensate tank via the by-pass pipe.

17. 17
2.3 ELECTROSTATIC TAR PRECIPITATOR:
GAS FROM
PDC
SOLID
AND TAR
MIST
DEPOSIT
CERAMIC
INSULATOR IS
FILLED WITH
NITROGEN FOR
PROTECTION
SEAL POT
SLOPE TANK
efficient honeycomb
type electric tar
precipitators
800C
COG TO
EXHAUSTER
Heater

18. 18
This is used mainly to remove tar mist particles. As the raw coke oven gas
is cooled, tar vapor condenses out and forms aerosols (minute mist particl
es) which are carried along with the gas flow. These aerosols would conta
minate and foul downstream processes and would damage gas lines and b
urner nozzles if is not controlled. The tar precipitator is installed
before exhauster.
Gas enters into electric tar precipitator from its bottom, via the gas distrib
ution plate gas is uniformly distributed onto the whole section, then flows
through high voltage electric field of the honeycomb upward to leave elect
ric tar precipitator and enters into the exhauster unit. When gas passes thro
ugh electric tar precipitator, solid and tar mist droplet in gas is deposited o
n surface of honeycomb, the tar flows via the tar outlet at the bottom into
water seal pot, from which it flows into underground slop tank. To enable
electric tar precipitator in normal operation, the hot ammonia liquor sprayi
ng device is provided on the top of electric tar precipitator. Water seal pot
is connected with the pressure equalizing system.
Process feature- High efficient honeycomb type electric tar precipitators
is adopted, tar content in the treated gas can be controlled <50mg/m3, so a
s to be favorable for normal operation of the downstream equipment. The
power supply of electric tar precipitator is a constant power supply that ca
n keep stable electric field. The ceramic insulator is filled with nitrogen fo
r protection so as to reduce repair amount and extend its service life.

19. 19
2.4 EXHAUSTER:
Fig – block diagram of Exhauster
The task of the unit is to boost crude gas from coke oven to the
downstream gas purification system, for this purpose three electrically
driven gas exhausters are installed, two in operations and one as standby.
The gas exhauster is located after electric tar precipitator and before H2S
scrubber. In order to stabilize the pressure of the gas suction main before
primary gas cooler, the gas pressure regulation before primary cooler is
realized by means of regulating speed of exhauster through VVVF.
The condensate deposited in gas pipe at inlet and outlet of gas exhauster
flows via water seal pot into the slop tank from which it is sent to the
decanter VIA COMMON CODENSATE TANK OF PGC AREA.
Water seal pot and slop tank are connected with the pressure equalizing
system.
.
CO GAS FROM
ETP CO GAS TO H₂S/NH₃
SCRUBBER
SLOP TANK
SEAL POT

20. 20
Chapter 3
REMOVAL OF NH3 & H2S FROM
COG THROUGH SCRUBBING
PROCESS
3.1 Principle: Ammonia gas is highly soluble in water. The absorption
of ammonia (or any gas) in a liquid is guided mainly by Henry’s law and
Raoult’s law. Henry’s law says that the partial vapour pressure of the
solute is proportional to its mole fraction in the gas. Raoult’s law states
that the solubility of a solute will depend upon the concentration of solute
in the solution. From these two simplified statements, it can be concluded
that the solubility of ammonia in water will increase if
(a) The temperature of solution is kept low
(b) Partial pressure of ammonia is kept much below equilibrium
(c) Concentration of ammonia in the solution is not allowed to rise
much
Moreover, absorption being a mass transfer phenomena, is heavily
favoured if the area of contact between the gas and liquid is increased.
H2S / NH3 scrubber:
H2S, NH3 and Combi scrubberhelp in the removal of H2S / NH3 from
coke oven gas.
Properties of gas before and after purification:
Content of impurities in crude coke oven gas (excluding tail gas,
charging gas and Respiration gas):
Temperature: 82˚C.
H2S 5~6.5g/Nm3
NH3 10~11 g/Nm3
BTX 30~35 g/Nm3
Tar 35~45 g/Nm3
C10H8(naphthalene) 6~10 g/Nm3

21. 21
HCN 1~1.5 g/Nm3
Purified coke ovengas:
a) Pressure (97,000 Nm3/h at battery limit) 3.5kPa (min.)
b) Gas composition (volume %):
CO2 3~4
CnHm 2~2.6
O2 0.6
CO 6~9
H2
52~56
CH4
24~26
N2
balance
H2S 0.5
g/Nm3
NH3 0.04
g/Nm3
C10H8 0.12
g/Nm3
Tar 0.02
g/Nm
c) Temperature: ~28˚C.
d) Content of impurities (the figures are valid for gas flow 88,000Nm3/h)
Here Combi (Stand by) scrubber can act as both H2S and NH3 scrubber

22. 22
3.2 Scrubbing of NH3 & H2S from COG through scrubber
H2S scrubbing unit:
The coke oven gas from exhauster is first fed into H2S scrubber . Gas
flows upward along H2S scrubber. Gas goes through the cooling stage at
the lower part of H2S scrubber. The heat of superheating in gas is
absorbed by the cooling water. After the heated circulating water is
cooled by the cooler for circulating water . At the upper part of H2S
scrubber , H2S in gas is scrubbed with the lean solution from deacidifier
and enriched ammonia liquor from ammonia scrubber . At the same time
of H2S removal in H2S scrubber, also CO2, HCN and NH3 are absorbed.
Because the absorption process of H2S, CO2, HCN and NH3 is the
exothermic process, therefore both upper stage and lower stage of H2S
scrubber are provided with the coolers and for H2S scrubbing solution
respectively in order to prevent that the heat released heats gas. A part of
cooling water of each cooler is drawn and after it is cooled, it is sent back
to H2S scrubber.
Fig- Block Diagram of H2S Scrubber
H2S
Scrubber
CO gas out
Rich ammonia liquor
Lean liquor
CO gas
in
Enrich liquor

23. 23
NH3 Scrubbing unit:
 In ammonia scrubber, ammonia in gas is washed with softwater
and the stripped water from deacidifier and ammonia stripping
unit. In addition to these, coal water from coal water filtering
system is added to the bottomof ammonia scrubberafter cooling
in coal water cooler to enhance ammonia scrubbing effect. If the
concentration of free ammonia in coalwater is very high, part of
or all coalwater is directly sent to ammonia stripper. Rich
ammonia liquor out of the sump of ammonia scrubberis first
cooled with ammonia liquor cooler and then sent to the top of H2S
scrubber.
 The upper stage of ammonia scrubber is provided with soda
washing stage, where the diluted soda lye, can be added for
further absorbing H2S and HCN in gas. Soda lye out of ammonia
scrubber flows to soda lye tank in deacidifier and ammonia
stripping unit.
 Soft water is used for ammonia scrubbing on top stage of
ammonia scrubber. Ammonia content in purified gas is 0.04
g/Nm3.
 Except soda lye, all scrubbing solutions are finally gathered at the
sump of H2S scrubber, from which they are pumped to enriched
solution tank in deacidifier and ammonia stripping unit.
Fig- Block diagram of ammonia scrubber
NH3
Scrubber
Ammonical liqour
Strip Water
Coal Water
Soda lye
CO gas in
Soft Water
CO gas out
NAOH

24. 24
 In order to keep continuous running and high efficiency of
H2S/NH3 removal, H2S/NH3 scrubber is provided as standby,
that is there are three scrubbers:
o H2S scrubber (Height=46m)
o H2S/NH3 scrubber (Combi-Scrubber) Height=61m
o Ammonia scrubber (47m).
 In normal operation, any two scrubbers out of three present
operate in series. This purification guarantees the desired gas
parameters have been achieved.
 After NH3 scrubber COG goes into Naphthalene scrubber for
naphthalene removal.

25. 25
Fig- Packing material inside scrubbers
Fig: Block diagram of deacidifier and stripper
DE
ACIDIFIER
SOUR
GASES
LEAN
LIQUOR
STEAM
ENRICH
LIQUOR
NH3
STRIPPER
NH3
VAPOUR
STRIPPED
WATER
NAOH
STEAM
WASTE
WATER
BOD
PLANT

26. 26
3.3 DEACIDIFIER AND AMMONIA STRIPPING UNIT:
 In order to remove the H2S & NH3 compounds from the enriched
scrubbing liquor, coming from the H2S & NH3 scrubbers, a
distillation plant, consisting of deacidifier and ammonia strippers
is installed. The vapours leaving the distillation plant mainly
consisting of H2S, NH3 , HCN and CO2.
 The deacidifier and ammonia stripping unit is provided with one
enriched solution tank, one lean solution tank and one stripped
water tank.
 Two de-acidifiers and two ammonia strippers are provided in the
unit with one in operation and one as standby for continuous
running operation. The solution in enriched solution tank is
pumped to lean solution/enriched solution heat exchanger for heat
exchange with lean solution from the sump of de-acidifier and then
sent to the top of de-acidifier where enriched solution is stripped
with ammonia containing vapour out of ammonia stripper, most of
H2S, HCN,CO2 in solution are stripped out.
 The lean solution out of deacidifier is pumped out with the lean
solution pump, part of it is heat exchanged in lean/enriched
solution heat exchanger with enriched solution, then cooled in the
lean solution cooler and sent to H2S scrubber in H2S/NH3
scrubbing unit. The rest is directly sent to ammonia stripper.
 At the upper stages of ammonia stripper, free ammonia in lean
solution from deacidifier is further stripped out, and part of
stripped water is taken after free ammonia stripped out, the
stripped water is first cooled with the cooler and then sent to
ammonia scrubber in H2S/NH3 scrubbing unit for absorbing

27. 27
ammonia in gas. The rest liquor is reached to the lower stage of
ammonia stripper, where soda lye is added for decomposition of
fixed ammonia
 Ammonia-containing vapour out of ammonia stripper enters into
deacidifier for stripping of the enriched solution. The stripped
water out of the sump of ammonia stripper is pumped to the cooler
for stripped water for cooling. After that, it is pumped and a small
part of it is used for diluting soda lye. The rest, namely waste
water is sent to bio-chemical waste water treatment plant.
 The mixed vapour contained with NH3, H2S, HCN and CO2
discharged from the top of deacidifier is first partially condensed
using enrich liquor coming from H2S scrubber to remove water
vapour that is entrained with these sour gases and then sent to the
separator to remove remaining water vapour and then send to
Claus kiln.

28. 28
Steam
NH3SCRUBBER
H2SSCRUBBER
Waste Water
BOD Plant
NAOH
NEPTHALENE
SCRUBBER
DEACIDIFIR
NH3STRIPPER
Lean liquor
Tank
T
Ammonia
Vapour
NH3 and H2S Vapour
TO CLAUS KILN
T=850C
T=960C
T=1150C
T=1000C
To
network
Enrich liquor Tank
Soft Water
Coal water
Water
Strip
water
Strip Water
COG
T=450C
T=240C
T=220C

29. 29
REACTION INVOLVED:
In ammonia scrubber
 Ammonia is highly soluble in water than other gases, so it
forms ammonium hydroxide with water as shown below:-
NH3 + H20 NH4OH + ∆H
(Ammonical liquor)
 This ammonical liquor is used as scrubbing agent in H2S
scrubber.
In H2S scrubber
 NH4OH + H2S (NH4)2S + ∆H
(Enrich liquor)
This enrich liquor is stored in enrich tank, from there it is send
to deacidifier.
In ammonia stripper
 Ammonia present in two forms:-
1. Free ammonia
2. Fixed ammonia
1) Free ammonia can be present in following forms:-
a) Ammonium carbonate
b) Ammonium bicarbonate
c) Ammonium sulfide
d) Ammonium cyanide
2) Fixed ammonia are present in forms :-
a) Ammonium chloride
b) Ammonium thiocyanate
c) Ammonium ferrocyanide
d) Ammonium thiosulfate
e) Ammonium sulfate

30. 30
 Free ammonia can be directly stripped out using steam as :-
(NH4)2S + 2H2O + ∆T H2S + 2NH4OH
(Steam)
NH4OH + ∆T NH3 + H2O
 For fixed ammonia stripping we use caustic soda as :-
Frist convert fixed ammonia into ammonium hydroxide then
ammonia is stripped out from ammonium hydroxide.
NH4SCN + NaOH NH4OH + NaSCN
NH4Cl + NaOH NH4OH + NaCl
(NH4)2 SO4 + NaOH (NH4)2OH + Na2SO4
NH4OH + ∆T NH3 + H2O
(Vapour)
In deacidifier
(NH4)2S + 2H2O + ∆T H2S + 2NH4OH
(Vapour)
Na2S+2 H2O + ∆T H2S + 2NaOH
(Vapour)

31. 31
List of main equipment:
NO Name and Specification QTY
1 Standard equipment
2 Pump for enriched liquor 2
3 Pump for H2S wash water 2
4 Pump for H2S wash water 2
5 Pump for ammonia water 4
6 Pump for softwater 2
7 Coal water pump 2
8 H2S scrubber DN4400 1
9 NH3 scrubber DN5200 1
10 H2S/NH3 scrubber DN4800 1
11 Coal water tank 1
12 Soft water tank 1
13 Seal pot 1
14 Cooler for recycled water 3
15 Cooler for coal water 2
16 Coal water first cooler 2
17 Cooler for H2S wash water 2
18 Cooler for H2S wash water 2
19 Cooler for ammonia water 2
20 Cooler for soft water 2
Redistribution trays are provided between individual stages of packing in
scrubbers to enable full contact between scrubbing solution and gas and
increase scrubbing effect.
Both H2S scrubberand H2S/NH3 scrubberare provided with the
circulating cooling stage to ensure the H2S absorbing efficiency.

32. 32
Composition and Quality Parameter
Stripped waste waterProperties:
Total ammonia content : 150 mg/l
Quantity : 105 m3/hr.
Temperature : 400C
Coalwatercontents (per Lt of coalwater):
H2S : 1 gm/L
NH3 : 3 gm/L
HCN : .15 gm/L
CO2 : 2 gm/L
Enrich liquor contents (per m3
of enrich liquor):
H2S : 3.6 gm/m3
NH3 : 14 gm/m3
HCN : .58 gm/m3
CO2 : 7.26 gm/m3
Lean liquor contents (per m3
of lean liqour):
H2S : 2.5 gm/m3
NH3 : 20 gm/m3
HCN : .58 gm/m3
CO2 : 7.26 gm/m3

33. 33
Waste watercontents (per Lt of waste water):
Ph = 8-10
Phenol : 800 mg/L
Cyanide : 20 mg/L
Ammonia : 150 mg/L
COD : 3500-5500 mg/L
BOD : 950 mg/L
Thiocynide : 300 mg/L
Emulsion liquor properties:
Tar % : 20-40%

34. 34
Chapter 4
Processes After Ammonia & Hydrogen
Sulfide Removal
4.1 CLAUS process for Sulphur recovery:
 Hydrogen sulphide (H2S) is a smelly (with its signature "rotten
egg" smell) , corrosive, highly toxic gas. Besides its other
harmful effects, it also deactivates industrial catalysts. As H2S
is such an obnoxious substance, it is converted to non-toxic
and useful elemental sulphur through the Claus Sulphur
Recovery process.
 The Claus process is a catalytic chemical process. The process
is commonly referred to as a sulphur recovery unit (SRU) and
is very widely used to produce sulfur from the hydrogen
sulphide found in raw natural gas and from the by-product sour
gases containing hydrogen sulphide derived from refining
petroleum crude oil and other industrial facilities.
 There are many hundreds of Claus sulphur recovery units in
operation worldwide. In fact, the vast majority of the
66,000,000 metric tons of sulphur produced worldwide in 2006
was by-product sulphur from petroleum refining and natural
gas processing plants.
 The Claus process is nothing but an improved CYCLASULF
PROCESS mentioned earlier.

35. 35
Fig: Simplified Diagram of Sulphur RecoveryUnit
REACTION INVOLVED:-
For vapour burner (Claus kiln):
H2S + 3/2 O2 SO2 + H2O
2NH3 + 3/2 O2 N2 + 3H20
2HCN + 5/2 O2 N2 + 2CO2 + H20
For cracking reactor:
2NH3 N2 + 3H2
HCN + H2O ½ N2 + 3/2 H2 + CO
For Claus reactor:
2H2S + SO2 3S + 2H2O
1. The composite gas sent from de-acidifier is fed into the burner
of Claus furnace. Under the proportion ratio of air, part of
composite gas is burnt and SO2 and H2O are formed. The
optimum proportion of H2S and SO2 is 2:1. The temperature of
process gas in the furnace is kept in the range from about 1050℃

36. 36
to about 1150℃. Under the condition that the temperature cannot
be kept by the combustion of H2S, small amount of gas can be
introduced to control the temperature of the furnace. H2S and
SO2 in process gas react in the furnace as follows
2. Before leaving the furnace, 60% of H2S entering into the furnace
has been converted into mono sulphur. According to the main
balance state in the furnace, there are COS and CS2 formed in
the furnace. Air and gas needed for gas combustion are sent by
an air blower and gas booster to burner. The burner is equipped
with an automatic igniter.
3. The block valves which are used as cutoff valves are also
installed on gas pipe and ignition pipe and used as safety cutoff
devices.  During normal operation, temperature is controlled by
the control of the amount of gas sent into the furnace.  Air
amount is determined according to the gas flow rate and
compositegas flow rate sent into the furnace.  After process gas
goes through the catalyst layer of the furnace, it enters into
process gas cooler and carries out heat exchange with
demineralized water to generate steam with a pressure of
0.3MPa.  During cooling process, part of liquid sulphur is
condensed and it goes into sulphur intermediate vessel via
sulphur inspection box.
4.  The temperature of the process gas going out of the waste heat
boiler is controlled by a method of regulating its “screw plug” of
central pipe. The steam drum and bottom of the waste heat boiler
are equipped with the blow-down outlets for blow-down.  After
process gas goes out of the waste heat boiler it enters into the
bottom of the first stage of Claus furnace. Reactor is filled with
catalyst. Under the condition of inlet temperature of 250~300℃
 S2 is converted mainly into S6 and S8.  The released heat in
the reaction under normal condition can make the temperature of

37. 37
process gas rise 20~30℃.  After the high temperature process
gas from the outlet of the reaction of Claus furnace goes through
process gas pre-heater, it enters into the first stage of sulphur
condenser.
5. The process gas goes again through indirect cooling to cool and
condense part of sulphur process gas.  The cooled process gas
goes through a sulphur separator to separate sulphur liquid drop
and process gas.  Liquid sulphur goes into sulphur intermediate
vessel via sulphur inspection box.  Then the separated process
gas goes through the pre-heater again, after the heat exchange
with high temperature process gas and its temperature goes up by
about 220℃, it enters into the second stage of Claus reactor to
carry out catalyst reaction.  The low temperature process gas
after reaction goes through the second stage of sulphur condenser
for further separation.
6. After tail gas out of Claus reactor is cooled, it enters into a
negative pressure gas pipeline.  The tail gas pipe has jacket
thermal insulation to prevent the consolidation of liquid sulphur
droplet in tail gas.  With the help of the analyzer, the contents
of H2S and SO2 in tail gas can be kept close, but not less than
4:1.  The water needed by process gas cooler is pre-treated and
preheated.  The liquid sulphur in the intermediate vessel or
storage vessel is delivered to the liquid sulphur filtering system
before a sulphur granulator by liquid sulphur pump.
7. The filtered liquid sulphur is then sent into the sulphur
granulator for liquid sulphur spraying and granulation.  The
cooling water is sprayed by steel strip to condense liquid sulphur
to carry out granulation, then conduct the weighing, bag sewing,
packing and so on.

38. 38
Sulphur Purity – 99.5%
Colour – Bright Yellow
4.1.a Catalyst for sulphur recovery
Why titanium dioxide?
TiO2 is used in the Claus Process to aid in the hydrolysis of carbonyl
sulfide (COS) and carbon disulfide (CS2) into hydrogen sulfide (H2S),
which can then be converted in elemental sulfur; this allows much higher
quantities of sulfur to be recovered and lowers the quantity of COS and
CS2 from going to flare.
Alumina Claus Catalyst: This Alumina Catalyst is a hard working
product that offers a high Surface Area for the conversion of H2S and
O2 to form elemental sulfur and water.
Promoted Alumina Catalyst for Claus Process: The addition of a
promoter to an Activated Alumina Catalyst increases the hydrolysis of
CS2 and COS into H2S, adds resistance to Thermal Aging, lower
operating temperatures in the first Claus Reactor
Blended Titania Alumina Catalyst for Claus Reaction: This Catalyst
is a blend of Activated Alumina Catalyst and Titania Catalyst. Titania
Catalyst is added to the Alumina Catalyst to improve the hydrolyzation
of CS2 and COS to reform HS2, which can be converted into elemental
sulfur. This product has a high resistance to Thermal Aging, lower
operating temperatures in the first Claus Reactor, an increased level of
activity during the hydrolysis of carbonyl sulfide (COS) and carbon
disulfide (CS2), and increased Working Capacity during life span. The
improved rate of hydrolysis of CS2 and COS creates a more efficient
process, which recovers more sulfur than the standard Alumina Catalyst.

39. 39
Super titanium dioxide (TiO2) Titania based Super Claus Catalyst
for Sulfur Recovery: This product contains the highest composition of
titanium dioxide of all Claus Catalyst products. Titania Catalysts are
often used in the first reactor to increase the hydrolyzation of CS2 and
COS to reform HS2, which can be converted into elemental sulfur. Super
claus catalyst is the highest quality product for Sulfur Recovery and
offers the highest levels of efficiency and recovered sulfur. This catalyst
offers a high resistance to Thermal Aging, allows lower operating
temperatures in the first Claus Reactor, high levels of activity during the
hydrolysis of carbonyl sulfide and carbon disulfide, and an increased life
span.
INERTALUMINACERAMIC BALL
Having stable chemical features and a low rate of
water absorption, Inert Alumina ceramic balls can
resist high temperatures and high pressure. Inert
Alumina ceramic balls can also resist the corrosion of
acid, alkali and some other organic solvents, Inert
Alumina ceramic balls are able to stand the thermal
shock (quick change of temperature) during the
manufacturing process. The main role of these Inert
Alumina ceramic balls is to increase the distribution
spots of gas or liquid, and to support and protect the
activating catalyst of low strength in the reactors and column/tower.
Applications:
As refractory bed top plugs and supports in order to protect the catalyst
bed from thermal impurities so that the catalyst bed is kept intact in spite
of wide pressure variation. Inert aluminum Ceramic Ball is widely used

40. 40
in petrochemical industry, chemical industry, fertilizer industry, natural
gas industry and environment protection, etc.
Stoneware Catalyst Bed Supports are used routinely in the following
specific services: Ammonia plants, Hydrotreaters, Bender treaters,
Isomerization units, Chloride absorbers, pretreaters and reactors, Claus
units, Molecular sieve units, Diesel hydrotreaters, Naphtha treaters, Fixed
bed reformers, Reformer pretreaters, Fluidized pollution
control, Hydrocrackers (1st stage), VGO pretreaters, Hydrogen plants.
Specification:
Inert aluminum Ceramic Balls are available in several specifications.
according to the alumina content percent: 17% 25% 65% 95%.
Diameter from 3mm to 25mm or bigger on customer request.
Size Density Free Space Specific Surface area
inches mm lbs/ft3 g/cm3 Percent ft2/ft3 m2/m3
1/8 3 90 1.44 38 350 1150
1/4 6 87 1.4 40 160 520
3/8 10 86 1.38 44 120 390
1/2 13 86 1.38 44 80 260
3/4 19 86 1.37 44 50 160
1 25 84 1.34 46 40 130

41. 41
Chemical Analysis:
SiO2 ---------------------- 65-76%
Al2O3 ----------------------- >25%
SiO2 + Al2O3------------ >90%
TiO2 --------------------- 0.5-0.6%
Fe2O3 ---------------------- <1.0%
Fe leachable ----------- 0.002%
CaO ------------------------ ~0.3%
MgO -------------------- 0.3-0.5%
K2O --------------------- 1.8-2.5%
Na2O ----------------------- ~0.2%
Physical Properties:
Density: ----------------- 2.30-2.45 g/cm3
Bulk Density ----------- 1.35-1.44 g/m3
Water absorption: ------- 0.30-0.60%
Porosity: -------------------- 0.60-1.10%
Crush strength: --------- ~400 N/mm2
H2SO4 solubility: ------------- 0.40%
Mohs Hardness: --------------- 7-8
Thermal expansion: --- 5.5 x 10-6 /°C
Catalyst poisons: ------------- none
A958 sulfur recovery catalyst:
A958 sulfur recovery catalyst is a new-type sulfur recovery catalyst with
a high Claus activity and deoxidization protection features. It can be
separately used as a Claus catalyst and may also work together with
A918 Al2O3 catalyst for the purpose of deoxidization protection catalysis.
In the same device and the same technical conditions, the total sulfur
conversion rate can be increased by about 1.7%. It is particularly suitable
for sulfur recovery unit with considerable fluctuations in acid gas H2S
content and / or flow. A958 catalyst can work with Al2O3 in any
converter of the sulfur recovery unit or be filled in a tiered manner across
the full bed. During tiered filling and application, A958 catalyst can be
deposited on the upper part of the primary converter bed layer,
accounting for at least 1/3 of the total volume, So as to protect the lower
Al2O3 catalysts from sulfating poisoning by the tiny amount of oxygen
existed during the process, or mitigate the poisoning, thus prolonging the
life of the catalyst. The excellent performances of A958 catalysts have
been proven in industrial applications.

42. 42
A988 TiO2 sulfur recovery catalyst:
The A988 Claus catalyst is TiO2 as main active component catalyst, it
has good ability of resistance to sulfate. It’s the flag-ship of sulphur
recovery catalyst series. The performance is in world leading position.
The main advantages of A988 catalyst are:
(1)Owing to high activity of COS and CS2 hydrolysis and Claus
conversion almost reaches the thermodynamics equilibrium level,
therefore it is one of the best catalyst of sulphur recovery
.
(2) It is non-sensitive to the trace O2 in the acid gas and sulfated poison
doesn’t exist.
(3) Because A988 catalyst only needs 3s of contact time and can be used
in the 1200h-1 GHSV, therefore, the reactor volume can be reduced and in
the condition of same contact time, the acid gas loading can be improved
greatly.
(4) A988 catalyst is specially applicable to cope with the lean acid gas
and Claus tail gas. Considering the excellent performance of A988
catalysts, it is recommended to use it in the first reactor to promote the
full hydrolysis of COS and CS2 and in the second and third reactors to
improve Claus conversion rate. A988 catalysts can replace imported
catalysts in an imported device. It can also be more extensively used in
other domestic sulfur recovery devices.

43. 43
4.2 NAPHTHALENE SCRUBBING:
Fig – Naphthalene scrubber
The gas coming from NH3/H2S scrubber which has the temperature of
about 24℃ enters into the naphthalene scrubber which is divided into
two stages. There is no split tray between two stages. The circulating
wash oil sprayed at the top of the first stage of the scrubber contacts with
gas in counter current to absorb the naphthalene in gas. In the second
stage, the mixture of the lean oil sent from the naphthalene distillation
unit and circulating wash oil is used to spray gas in order to absorb the
naphthalene in gas. The gas after naphthalene removal is sent to the user.
The rich oil at the bottom of the scrubber enters into an oil tank. After
residue removal and emulsion breaking, one part of the rich oil is sent to
the top of the first stage of the naphthalene scrubber by a circulating
wash oil pump to spray gas; one part of the rich oil is sent to the top of
the second stage of the naphthalene scrubber and after it is mixed with
the lean oil sent from the naphthalene distillation unit, the mixture is used
to spray gas; one part of the rich oil is sent to the naphthalene distillation

44. 44
unit and after naphthalene removal, it is delivered to the top of the second
stage of the naphthalene scrubber for circulation use. The gate valves are
used at the gas inlet and outlet of the naphthalene scrubber and the
closing and opening are easy.
NAPHTHALENE DISTILLATION:
Fig – Naphthalene distillation plant
The enriched oil delivered from the naphthalene scrubbing unit is
delivered by the circulating wash oil pump and goes in turn through lean
oil/enriched oil heat exchanger and enriched oil pre-heater and is heated
to 180℃ and then enters into naphthalene distillation column, where the
oil vapour from regenerator is used for stripping and distillation. The oil
vapour evolved from the top of the naphthalene distillation column is
cooled via the partial condenser and goes into the oil-water separator.
The separated naphthalene oil flows into reflux tank. Part of naphthalene

45. 45
oil is sent to the top of the distillation column as reflux and the rest of
naphthalene oil flows into naphthalene oil tank. And then naphthalene is
delivered by a naphthalene oil pump to the tar storage tank in the oil
depot unit.
The hot lean oil discharged from the sump of naphthalene distillation
column is pumped with hot lean oil pump to lean-enriched oil heat
exchanger for heat exchange and fed into lean oil tank. After heat
exchange it is pumped with lean oil pump to naphthalene scrubber via
lean oil cooler after it is cooled to 27℃~29℃.
In order to ensure the wash oil quality, 5% hot lean oil is pumped and
sent into a regenerator. The medium pressure superheated steam is used
for stripping and regeneration. The oil vapour at the top of regenerator
enters into the naphthalene distillation column. Regenerated residue is
discharged into an oil residue tank and pumped into the tar storage tank
in the oil depot unit.
The water separated in the oil-water separator flows into the separated
water tank, from which it is pumped to the deacidifier and ammonia
stripping unit.
4.3 BOOSTER:
Boosters are used after naphthalene scrubber for boosting the purified
coke oven gas to the network i.e. mills or blast furnace where the gas is
used as fuel. Boosters also maintain the pressure of COG line.
4.4 WASTE WATER TREATMENT:
Wastewater generated during the process of cleaning coke oven gases is
toxic in nature due to presence of high phenol, ammonia, thiocyanate and
cyanide. This wastewater is commonly treated using biological methods
of treatment, these treatment plants are known as Biochemical Oxidation
and Dephenolisation Plants (BOD Plants) which have two or three stage

46. 46
biological treatment units. However, functioning of these BOD plants is
often affected due to high inlet concentrations, biodegradability and
improper operational control. The overall efficiency of biological
treatment of coke oven wastewater, even after employing well
acclimatized microorganisms, is constrained due to its resistance to
biodegradability and inhibition.
4.5 UTILITY DEVICES
COOLING TOWER (RCPH)
As in primary gas cooler cooled water is used to reduce the temperature
of the gas. The water coming out of the PGC (from upper stage) is sent to
the cooling tower mainly induced draft where it is cooled and recycled
again.
CHILLER PLANT
Chiller plant maintains the temperature of water at 140 C which is used in
primary gas cooler at lower stage of cooling. Warmed outlet water from
lower stage from PGC is sent to hot water tank, near to the Chiller plant.
Primary pump(centrifugal type) sucked out it and sent to the VAM
(vapour absorption machine),where it’s temperature is reduced to inlet
water temperature .This cooled water is stored in chilled water tank, from
there it is sucked out by secondary pump and pumped to lower part of
PGC.This whole process is repeated continuously .
FILTERS
They are used to filter the flushing liquor and the water used in
rcph(recirculating water pump house).The coal water used in scrubber or
the water used in PGC are generally passed through the filter so that it
does not block the nozzles and pipes .
SOFTENING PLANT

47. 47
Softening plant generally remove the hardness of water so that it can be
used in ammonia scrubber and also calcium and magnesium salts ,present
in hard water get deposited on the pipes and cause scaling. So for this
reason hardness of the water is removed.
Make up water is passed through filter to remove TSP (Total Suspended
Solid) after that brine solution is added to filtered water, this whole
solution is sent to softener tank in which resin are used which retained
calcium and magnesium ions .Brine solution acts as regenerator of resin.
Soft water from there is pumped to soft water tank.

48. 48
Conclusion:
Because of its hydrogen sulphide (H2S) content (up to 9 g/Nm3)
unpurified coke oven gas is unsuited for use in many industrial
applications. When the gas has been desulphurised, however, its use
for a variety of applications becomes potentially viable. TATA STEEL
coke plants meanwhile sell sulfur pellets after desulphurisation at a
profit. Desulphurisation for commercial reasons coincides with the
need to protect the environment from the effect of acid rain, because
desulphurised coke oven gas decreases emissions of SO2 at the site of
coke oven gas combustion.Sulfur Recovery Units are installed to meet
mandated air pollution requirements.
sulphur recovery unit (SRU) operating environment, greater emphasis
must be placed on operating reliability than ever before. Most
environmental agencies are very reluctant to grant operating variances
for conditions that would result in emission levels greater than
permitted.  Overall SRU reliability can be increased by increasing the
efficiency of catalyst. And it can be done by improving the property of
catalyst by doping 2 or more metal. The problem with using bare
catalyst for sulphur removal was; the active site on catalyst got
decreased ,also its life duration was very less. So, considering all these
parameter SRU has used catalyst of different composition for better
result.
The catalyst are:
A988 TiO2 sulfur recovery catalyst,
A958 sulfur recovery catalyst
Inert Alumina Ceramic Ball

49. 49
References
 Presentations and Flow diagrams from our Guide
 Wikipedia
 Online Presentations
 Other Internet Encyclopaedias