2. STUDY OF SULPHUR RECOVERY SYSTEM AND INCREASE AVAILABILITY
OF SULPHUR TRANSFER PUMP
LOCATION : TATA STEEL, JAMSHEDPUR
3. INTRODUCTION :- Company profile
Established in 1907, Tata Steel is Asia's first and India's largest
private sector steel company. Tata Steel is among the lowest cost
producers of steel in the world and one of the few select steel
companies in the world that is EVA+ (Economic Value Added).
Tata Steel is the world’s 6th largest steel company with an existing
annual crude steel production capacity of 30 Million Tonnes.
Tata Steel has a balanced global presence in over 50 developed
European and fast growing Asian markets, with manufacturing
units in 26 countries.
Tata Steel`s Jamshedpur (India) Works has a crude steel
production capacity of 8.8 MTPA which is slated to increase to 10
MTPA by 2020.
4. Determined to be a major global steel player, Tata Steel has recently
included in its fold NatSteel, Asia (2 MTPA) and Millennium Steel
(1.7 MTPA) and also acquired Corus creating a manufacturing
network in eight markets in South East Asia, Europe and Pacific
countries.
While the Company is focused in the pursuit of its operational
goals, it is also committed to being a good corporate citizen. Tata
Steel extends support to the economically underprivileged not by
charity but by strengthening and empowering them with expertise
and knowledge. It community outreach programmes covers the Tata
Steel managed city of Jamshedpur and over 600 villages in and
around.
5. PRODUCTS OF TISCO
Hot and cold rolled coils and sheets
Tubes
Constructions bars
Forging quality steel
Rods
Strips and Barings
Wires
Rolls
5
7. PPE : PERSONAL PROTECTIVE
EQUIPMENT
PPEs are necessary at TATA
STEEL and no employee and
worker are allowed without
their PPEs to enter into the
industry
8. Tata Steel Jamshedpur Works
Over the years, Tata Steel has placed a continuous emphasis on
improving processes, with a view to consistently enhancing
efficiencies to achieve better performance benchmarks in all
areas of operations. The Financial Year 2012-13 marked a major
milestone in operating history of Tata Steel as the ongoing
capacity expansion at Jamshedpur was completed with most of
the facilities of 2.9 mtpa brownfield expansion being
commissioned for production. Full ramp up of the capacity was
achieved in March 2013. The Jamshedpur Works currently
comprises a 9.7 mtpa crude steel production facility and a
variety of finishing mills.
9. Built at a production capacity of 0.7 million tonne per annum, the coke
oven battery No10 and by-product plant operates with 88 ovens (with
stamp charge technology) and is the largest battery at the Jamshedpur
works. It will also produce by-product of coke oven gas (44,000
Nm3/hr), coal tar (35,305 tonne per annum) and pure sulphur (1,668
tonne per annum).
Stabilisation of the new LD#3 & TSCR plant at Jamshedpur Works,
consolidated the Company’s position in the Flat Products market. With
this new mill, the product mix has expanded to include HR coils up to
1680 mm in width and also higher strength materials. The shorter cycle
times of this process has improved the capability of the Company to
supply HR coils at shorter lead times.
10. BY PRODUCT PLANT IS DESIGNED TO CLEAN
COKE OVEN GAS
BY REMOVING TAR AMMONIA NAPTHALENE AND
SULPHUR FROM THE GAS
13. SULPHUR RECOVERY UNIT
This report thus focuses on various process involved in
removal of sulphur from COG and focuses on
transmission of this recovered sulphur through
sulphur transfer pumps. Thus this report gives the
complete detail process of recovery of sulphur and
increase availability of sulphur transfer pumps.
14. Coolin
g
water
PFD OF SULFUR RECOVERY UNIT
SULPHUR STORAGE
VESSEL
4kg/cm2
steam
SULFUR
INTERMEDIATE
VESSEL
BLOW DOWN
COOLER
H2S/NH3 vapor
from
deacidifier
CLAUS
REACTO
R
PROCESS GAS
HEATER
SULPHUR
CONDENS
ER
Sulphur
separator
Purified coke
oven gas to
external pipe
line
Purified coke
oven gas from
external pipe
line
AIR
PREHEATER
CLAUS
KILN
WASTE HEAT
BOILER
Steam
condensate
4kg/cm2 steam
to deacidifier &
NH3 stripper
Soft water
from
external
pipeline
Air from
blower
condensat
e
Sulphur
packing
machine
DEGASSIFI
ER
Tail gas
to PGC
3734Kg/H, 100°C,
1.35 BAR(A)
10552
Kg/H
,
250°C,
1.134
BAR
10495 Kg/H, 135°C,
1.024 BAR
412.4
Kg/H,
135°C,
1.8 BAR
4819 Kg/H,
130°C, 1.35 BAR
300 m3/H,
26°C,
1.045BAR
270°C
950-1150°C
>=90°
C
6030
Kg/H,
143°C,
4BAR
4000
Kg/H,
793 Kg/H,
120°C, 2BAR
8000m3/H,
20°C,
1.5BAR
40000 Kg/H, 34°C, 5BAR
15. Tata Steel contribute to the importance of overall SRU operating
reliability. Most environmental districts require complete
emission monitoring reports, some districts even require on-line
measurements be continuously sent to their offices, and
violations require immediate action. It is imperative for the
profitability of the refinery or gas plant that the SRU operate at
very near 100% on-stream time.
Overall SRU reliability can be increased through proper design
methods and practices. Many of the features that can be
incorporated into a design are difficult and/or significantly more
expensive to implement into an existing plant. Therefore, it is
extremely important for the plant owner to insure the SRU is
designed for optimum reliability at the earliest stage of design.
16. Detailed Process:
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℃ 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
17. 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.
18. 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
composite gas 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.
19. 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 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.
20. 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.
21. 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.
22. The filtered liquid sulphur is then sent into the sulphur
granulator for liquid sulphur spaying 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.
23. Simple block diagram of sulfur recovery unit
H2S/NH3 vapor from
deacidifier
Liquid sulfur
Claus
reactor
vapor
Claus kiln
Waste heat boiler
Process gas
heater
Sulfur
condenser
Sulfur
vessel
Sulfur
solidification
unit
Air from blower
Sulfur storage
950-1150°C
COG
separator
24. Cooling
water
PFD OF SULFUR RECOVERY UNIT
SULPHUR STORAGE VESSEL
4kg/cm2 steam
SULFUR
INTERMEDIATE VESSEL
BLOW DOWN COOLER
H2S/NH3 vapor
from deacidifier
CLAUS
REACTOR
PROCESS GAS HEATER
SULPHUR
CONDENSER Sulphur
separator
Purified coke
oven gas to
external pipe
line
Purified coke
oven gas from
external pipe
line
AIR PREHEATER
CLAUS KILN
WASTE HEAT
BOILER
Steam
condensate
4kg/cm2 steam to
deacidifier & NH3
stripper
Soft water
from external
pipeline
Air from blower
condensate
Sulphur
packing
machine
DEGASSIFIER
Tail gas
to PGC
3734Kg/H, 100°C,
1.35 BAR(A)
10552
Kg/H,
250°C,
1.134
BAR
10495 Kg/H, 135°C,
1.024 BAR
412.4
Kg/H,
135°C,
1.8 BAR
4819 Kg/H,
130°C, 1.35 BAR
300 m3/H,
26°C,
1.045BAR
270°C
950-1150°C
>=90°C
6030
Kg/H,
143°C,
4BAR
4000 Kg/H,
793 Kg/H,
120°C, 2BAR
8000m3/H,
20°C,
1.5BAR
40000 Kg/H, 34°C, 5BAR
25. CLAUS UNIT
The basic Claus unit comprises a thermal stage and two or three
catalytic stages. Typical sulphur recoveries efficiencies are in the
range 95-98% depending upon the feed gas composition and plant
configuration.
26.
27. The hot gas leaving the first reactor is cooled in the second
sulphur condenser,where LP steam is again produced and the
sulphur formed in the reactor is condensed.
The sulphur plant tail gas is routed either to a Tail Gas
treatment Unit for furtherprocessing, or to a Thermal Oxidiser to
incinerate all of the sulphur compoundsin the tail gas to SO2
before dispersing the effluent to the atmosphere.
28. WASTE HEAT BOILER
Approximately 25% of the usable energy of the fuel gas is
released in the exhaust of the gas engine.
This heat exits the engine at ~450oC as ‘high grade heat’,
contrasting to ‘low-grade heat’ available from the generator
cooling circuits.
This high temperature and flow makes it well suited for
utilization in a waste heat boiler. The superheated steam
produced in the boiler is typically available at 1-25 bar pressure
for utilization with nearby steam users.
Steam boilers are utilized in a range of different gas applications
with this being a popular solution for hospitals, sewage
treatment works and industrial process plants.
Exhaust heat boilers are connected to the exhaust of the gas
engine and can either be housed in an adjacent building orcan
be provided in their own customized container.
30. SULPHUR CONDENSER
The Claus SRU process consists of three repeating steps (heating,
reaction, and cooling/condensing).
Sulphur condensers serve the primary function of cooling and
condensing sulphur formed in the upstream reaction step.
Sulphur condensers are normally horizontal, kettle type shell
and tube boilers. However, sulphur condensers are unique heat
exchangers.
In addition to condensing product sulphur from the process
gases, the liquid sul-fur must also be separated from the process
gases before they flow to the next processing step.
This is normally done in an oversized outlet channel. Sulphur
condensers are also unique because the process gas flow rate
through the condenser must be maintained within a specific
operating range/velocity or there will be adverse effects on the
process.
32. SULPHUR INTERMEDIATE VESSEL
Liquid sulphur after being extracted from waste heat boiler is
transferred to intermediate sulphur vessel and the remaining
sulphur after being processed through clausreacter and
processing unit and condenser is also then stored in this
intermediate vessel.
Liquid sulphur thus from this intermediate vessel is transferred
to the main sulphur storage vessel through sulphur transfer
pumps.
Thus this liquid is transferred with extreme care to the main
storage vessel from where it is further distributed.
34. SEPARATER
Sulphur Separater are used to separate process gas and liquid sulphur
drop and thus transfers the liquid sulphur drop tosulphur intermediate
vessel and the process gas goes to Claus reactor again.
Process gas from the outlet of the reaction of Claus furnace goes
through process gas pre-heater where it enters into the first stage of
sulphur condenser.
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.
36. STORAGEVESSEL
Storage vessels for liquid sulphur are utilized in many refineries and sour
gas processing facilities for temporary storage of liquid sulphur produced
in the sulphur recovery plant. They are usually constructed from carbon
steel and insulated and heated to maintain the liquid at a temperature
125°C. Depending on the facility, the vessel may receive liquid sulphur
which has been treated to remove H2S dissolved in the sulphur or it may
be filled with undegassed product
A typical sulphur storage vessel does not store sulphur for long periods.
Normally a vessel is used to store liquid sulphur only as a holding point
before shipping, forming or blocking. Thus, the vessel is rarely full or
empty. It is normally receiving sulphur and may be pumped down from
several times a day to once every two or three days.Generally all vessels are
susceptible to unusual conditions that can cause them to remain in most
any condition for extended periods, and they must be heated to withstand
these conditions.
37. Different heating methods are employed to maintain the sulphur
in liquid state.These methods range from internal submerged
coils to external heating panels. Saturated steam is most
alwaysthe heating medium utilized. Historically, heating
methods have not considered the temperature
of internal vessel surfaces. The relationship between these
surface temperatures and vesselperformance will be explored
along with the effectiveness of various heating methods to
maintain these internal temperatures.
39. SULPHUR PACKING UNIT
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.
The filtered liquid sulphur is then sent into the sulphur
granulator for liquid sulphur spaying and granulation.
The cooling water is sprayed by steel strip to condense
liquid sulphur to carry out granulation and formation of
sulphur pellets, then conduct the weighing, bag sewing,
packing and so on.
41. LIQUID SULPHUR TRANSFER PUMP
Liquid sulphur pump were developed as Single-stage, single-suction,
vertical centrifugal pump,with enclosed impeller,
mainly used for liquid sulphur transfer. The pump with a
warming pipe for the sulphur easy crystallizes at normal
temperature .The shaftwas supported with plain bearings in the
pump casing and bearing spiders. The pump is equipped with
flexible coupling.
43. Application Considerations
Most customers are using sulphur in its molten state so it is more
economical to receive sulphur in the molten form and pump it
directly into a storage vessel or pit
Sulphur solidifies at about 238degF, and become very viscous
above 320degF. The successful handling of molten sulphur in the
molten state depends upon restricting the temperature to 260-
300degF
For economical reasons, most pipelines and pumps handling
sulphur are heated with steam at pressures between 35 and 85
psig. Either steam jacketing or steam tracing is used.
Sulphur is a very poor conductor of heat, and is very difficult to
reheat in piping once the temperature has dropped below 240
deg F. So temperature above that must be maintained.
44. The most common material of construction for pipe, valves and
pumps in sulphur service is steel or ductile iron.
Pumps moving molten sulphur must be steam jacketed. Also, as
a result of the high specific gravity (1.78), larger motors are
required.
Large quantities of molten sulphur are stored in vessels, which
are usually made of steel. For small quantities, pits are used
which are generally rectangular. A steam jacketed sump pump
should pump the molten sulphur out of the vessels or pits.
45. INCREASE AVAILIBILITY OF SULPHUR TRANSFER
PUMP
Sulphur transfer pump plays a vital role in sulphur
recovery unit and thus has to be taken extreme care of.
If any unit or part of sulphur pump is damaged then the
whole sulphur recovery unit has to be shut down as this
could overflow the intermediate vessel and can lead to fatal
accident .
Thus running of sulphur pump is must compulsory for the
running of sulphur recovery unit.
Thus any fault or damage in the pump has to be dealt
immediately and we have to increase its availability for the
smooth operation of SRU.
46. Operational Checks:
Prior to putting a pump in service steam should be on the jacket
for several hours which will allow all the pump parts to attain the
normal operating temperature.
The sulphur inside and outside the pump should be liquid at the
normal operating temperature.
Prior to starting the pump, the pump shaft should be rotated by
hand to ensure that it is free to turn.
Sulphur may freeze the pump shaft causing the motor to
overload on startup.
The pump must be fully supplied with sulphur otherwise
extensive damage may occur to the pump.
During operation, a small amount of liquid sulphur is pumped
upward through and around the internal bearings lubricating
them.
47. Bypass passages are provided to return this sulphur back to
the vessel or pit.
Steam should always be supplied to any installed stand-by
pumps to ensure they are ready to operate as required.
The pump shafts should be rotated by hand on a regular
basis to ensure it is free to turn and not frozen by sulphur.
Pump shafts may freeze if the vessel or pit is operated at
low levels.
Raising the sulphur level will sometimes be sufficient to
melt the sulphur and free up the pump shaft
48. MECHANICAL CHECK POINTS
Modified steam jacketed spool piece is provided to stop
frequent jamming of liquid sulphur.
Keep all pipeline hot thus steam trap is provided in drain
linethus sustaining temperature.
The pump must undergoes Preventive Maintenance
The pump must have spare parts for easy replacement of the
faulted parts
Continuous availability of steam for steam jacketing of all liquid
sulphur lines should be there.
Proper maintenance of temperature in the pipeline so that so
that it can avoid liquid sulphur to solidify in the pipeline that
create blockage.
49. Make all the pipeline free-draining.
Utilize crosses at all direction changes in all liquid sulphur lines
and Slope all liquid sulphur lines to promote draining
By employing a distributed external heating system such as
Contro Trace to maintain the temperature of all tank
internal surfaces above 120°C prevents Corrosion which
results from the combination of solid sulfur and liquid
water metalsurfaces.
In case of any blockage or cracks in the pipeline, provision of
extra line should be there such that down time of pumping
should be less as the flow will be switched to new pipeline
51. Conclusion
In today’s 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 through proper design
methods and practices. Many of the features that can be
incorporated into a design are difficult and/or significantly more
expensive to implement into an existing plant. Therefore, it is
extremely important for the plant owner to insure the SRU is
designed for optimum reliability at the earliest stage of design.
