By

SHUBHAM AGRAWAL

MECHANICAL D

SHARDA UNIVERSITY

STUDY OF SULPHUR RECOVERY SYSTEM AND INCREASE AVAILABILITY OF SULPHUR TRANSFER PUMP

LOCATION : TATA STEEL, JAMSHEDPUR

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.

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.

PRODUCTS OF TISCO Hot and cold rolled coils and sheets

Tubes

Constructions bars

Forging quality steel

Rods

Strips and Barings

Wires

Rolls

5

6

PPE : PERSONAL PROTECTIVEEQUIPMENT

PPEs are necessary at TATASTEEL and no employee andworker are allowed withouttheir PPEs to enter into theindustry

Tata Steel Jamshedpur Works

Over the years, Tata Steel has placed a continuous emphasis onimproving processes, with a view to consistently enhancingefficiencies to achieve better performance benchmarks in allareas of operations. The Financial Year 2012-13 marked a majormilestone in operating history of Tata Steel as the ongoingcapacity expansion at Jamshedpur was completed with most ofthe facilities of 2.9 mtpa brownfield expansion beingcommissioned for production. Full ramp up of the capacity wasachieved in March 2013. The Jamshedpur Works currentlycomprises a 9.7 mtpa crude steel production facility and avariety of finishing mills.

Built at a production capacity of 0.7 million tonne per annum, the cokeoven battery No10 and by-product plant operates with 88 ovens (withstamp charge technology) and is the largest battery at the Jamshedpurworks. It will also produce by-product of coke oven gas (44,000Nm3/hr), coal tar (35,305 tonne per annum) and pure sulphur (1,668tonne per annum).

Stabilisation of the new LD#3 & TSCR plant at Jamshedpur Works,consolidated the Company’s position in the Flat Products market. Withthis new mill, the product mix has expanded to include HR coils up to1680 mm in width and also higher strength materials. The shorter cycletimes of this process has improved the capability of the Company tosupply HR coils at shorter lead times.

BY PRODUCT PLANT IS DESIGNED TO CLEAN COKE OVEN GAS

BY REMOVING TAR AMMONIA NAPTHALENE AND SULPHUR FROM THE GAS

OVEN

HEATING CHAMBER

CLEAN GAS

GAS TO BPP

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.

Cooling water

SULPHUR STORAGE VESSEL

4kg/cm2

steam

SULFUR INTERMEDIATE

VESSEL

BLOW DOWN COOLER

H2S/NH3 vapor from deacidifier

CL

AU

S

RE

AC

TO

R

PR

OC

ES

S G

AS

H

EA

TE

RSULPHUR CONDENSER

Sulphur separator

Purified coke oven gas from external pipe line

Purified coke oven gas to external pipe line

AIR

P

RE

HE

AT

ER

CL

AU

S

KIL

N

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

PFD OF SULFUR RECOVERY UNIT

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

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.

Detailed Process:The composite gas sent from de-acidifier is fed into the burner

of Claus furnace. Under the proportion ratio of air, part ofcomposite gas is burnt and SO2 and H2O are formed.

The optimum proportion of H2S and SO2 is 2:1. The temperatureof process gas in the furnace is kept in the range from about1050℃ to about 1150℃. Under the condition that the temperaturecannot be kept by the combustion of H2S, small amount of gascan be introduced to control the temperature of the furnace. H2Sand SO2 in process gas react in the furnace as follows

Before leaving the furnace, 60% of H2S entering into the furnace

has been converted into mono sulphur. According to the mainbalance state in the furnace, there are COS and CS2 formed inthe furnace.

Air and gas needed for gas combustion are sent by an air blowerand gas booster to burner. The burner is equipped with anautomatic igniter.

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.

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.

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.

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.

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.

H2S/NH3 vapor from deacidifier

Liquid sulfur

vaporClaus kiln

Waste heat boiler

Claus reactor

Process gas h

eater

Sulfur condenser

Sulfur vessel

Sulfur solidification unit

Air from blower

Sulfur storage

950-1150°C

Simple block diagram of sulfur recovery unit

COG

separator

Cooling water

SULPHUR STORAGE VESSEL

4kg/cm2 steam

SULFUR INTERMEDIATE VESSEL

BLOW DOWN COOLER

H2S/NH3 vapor from deacidifier

CLA

US

REA

CTO

R

PR

OC

ESS GA

S HEA

TERSULPHUR CONDENSER Sulphur

separator

Purified coke oven gas from external pipe line

Purified coke oven gas to external pipe line

AIR

PR

EHEA

TER

CLA

US K

ILN

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

PFD OF SULFUR RECOVERY UNIT

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

The basic Claus unit comprises a thermal stage and two or threecatalytic stages. Typical sulphur recoveries efficiencies are in therange 95-98% depending upon the feed gas composition and plantconfiguration.

CLAUS UNIT

The hot gas leaving the first reactor is cooled in the secondsulphur condenser,where LP steam is again produced and thesulphur formed in the reactor is condensed.

The sulphur plant tail gas is routed either to a Tail Gastreatment Unit for furtherprocessing, or to a Thermal Oxidiser toincinerate all of the sulphur compoundsin the tail gas to SO2before dispersing the effluent to the atmosphere.

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 orcanbe provided in their own customized container.

Waste Heat Boiler

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.

Sulphur Condensor #1 and #2

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.

Sulphur Intermediate Vessel

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.

Seperator

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.

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.

Sulphur Storage Vessel

SULPHUR PACKING UNITThe 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.

Sulphur Pellets and Packed Sulphur

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.

Sulphur Transfer Pump

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.

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.

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.

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.

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

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.

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

Modified steam jacketed spool piece

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.