TRAVANCORE TITANIUM PRODUCTS Ltd Kochuveli Thiruvananthapuram Pin: 695021
Report on Inplant Training Submitted by Mahendran S Rohan Baby Mathews Rohan Stephen Luke Sarun Jolak George
Mar Baselios College Of Engineering And Technology Thiruvananthapuram
Acknowledgement This is a report on inplant training at Travancore Titanium Products Ltd during 28th june 2010 to 2nd July 2010 by the 7th semester BTech Mechanical Engineeerig students of Mar Baselios College of Engineering and Technology, Trivandrum. We Take this opportunity to express our hearty thanks to the members of the organization who helped us a lot during this period. We also sincerely thank our college and management for arranging the inplant training.
CERTIFICATE This is to certify that the following studentd of Mar Baselios College of Engineering and Technology, Thiruvananthapuram has undergone an inplant training in Travancore Titanium Products Limited, Thiruvananthapuram during the period of 28th June 2010 to 2nd July 2010. 1. Mahendran S 2. Rohan Baby Mathews
3. Rohan Stephen Luke 4. Sarun Jolak George
INTRODUCTION Travancore Titanium products is one of the main major titanium dioxide producing industry in India from the abundant minerals like ilmenite occurring in beach sands Manavalakurichi of Tamil Nadu and Chavara in Kollam district. TTP is one of the profitably running public sector units managed by the government of Kerala. At present this plant has a capacity of 45 tonnes per day. TTP Ltd was set up in 1951 in collaboration with the British Titanium Products Ltd(now Tioxide), with technology from national Lead(NL), USA. Before 1951, the beach sand containing rare earth minerals was being exported to Europe. The unit was promoted by the princely administration of Travancore, in technical collaboration with the British Titanium Products Ltd. Sree Chithra Thirunal Balaramavarma Maharaja
of Travancore and his Diwan, Sir C P Ramaswamy Iyer gave the inspiration for starting the venture. Two main plants in TTP are 1. Titanium Dioxide Plant 2. Sulphuric Acid Plant
TITANIUM DIOXIDE PLANT
Production Of Titanium Dioxide Titanium
Dioxide is mainly produced from the raw material illmenite, which is a complex compound of oxides of titanium and iron. The composition of illmenite is as follows.
Kollam Grade Titanium Dioxide Ferrous Oxide(FeO) Ferric Oxide(Fe2O3) Oxides of other elements
59-60% 09-10% 24-25% 05-08%
MK Grade 53-54% 25_26% 15-16% 04-07%
Process The two mai processes for the separation TiO2 from Ilmenite are 1. Sulphate process 2. Chloride process TTP Ltd is using the sulphate process.
Raw Materials The major raw materials used are 1. ilmenite 2. Sulphuric Acid 3. Scrap Iron 4. Glyceryl Mono Stearate 5. Aluminium Dust 6. Pottasium Sulphate(K2SO4) 7. Mono Ammonium Phosphate
Process Description The production of TiO2 from ilmenite requires a number of operations and some unit processes. The various sections in the route for its production are 1. 2. 3. 4. 5.
Grinding Digestion Clarification Concentration Precipitation
6. 7. 8. 9. 10. 11. 12. 13. 14.
Post precipitation filtration Pre precipitation filtration Leaching Post Leaching filtration Treatment De watering filtration Calcination Pulverization Packing
Here TiO2(Anatase) is the main product.
Grinding Ilmelite is brought to this section from godown using the belt conveyor. The purpose of grinding is to reduce the size and hence to increase the surface area of the ore to achieve maximum reaction efficiency.Here the equipment used for grinding is a ball mill.
The main sections of a milling are 1. 2. 3. 4. 5. 6. 7. 8. 9.
Ball mill Rotary classifier Mill fan Double cone classifier Cyclone separator Viscobeth Ductings Dampers Vent Pipe
Working The material is fed into the ball mill from silo using constant weight feeder. By the action of the fan the ground product along with the air is sucked into rotary classifier, where the coarser particles are sent back to the mill for regrinding. Then the air product mixture is sucked into the double cone classifier, where the oversize is separated and sent back to the mill. The air leaving the double cone classifier with the required size particles reaches the cyclone separator where a whirling action prevails. The product is separated and sent into a bunker
through an air locked rotary valve connected at the bottom of the cyclone separator By the action of the mill fan, air is discharged into the ball mill, at the same time air leaving the cyclone separator is sucked by the fan. Air from atmosphere enters at certain regons of the ductings, so suction increases over discharge which may imbalance the whole system. Inorder to prevent this condition, extra air is removed through a vent pipe to the atmosphere.
Digestion Digestion is the second section in the manufacture of TiO2 pigment. It consists of five stages. 1. 2. 3. 4. 5.
Reaction Baking Dissolution Reduction Final Adjustment
Digestion is a Reinforced Cement Concrete (RCC) cylindrical vessel conical at the bottom. It is first lined with lead and then a double layer of acid resisting bricks. The necessity of having a RCC vessel is to withstand the pressure and vibrations that develop during the reaction. The consistent unit to the digester are trident and service line, sturm box with the strainer bottom ‘T’, service ‘T’, stand pipe and fume cupboard with exist stack. The three arms of the trident are connected with compressor air line, water line and stream line, and the common service line from the trident enters at the bottom of the digester through the service ‘T’, and bottom ‘T’. The other lines entering through the top digester cover are the ground ilmenite, weak liquor and cutting water inlet lines.
Clarification
The crude liquor is sent to a settler which is the equipment used for settling operation. Reduced liquor contains unreacted ilmenite, residue due to scrap iron and finely divided colloidal particles which are to be removed Settling Operation The settler is actually a thickener. This is as large fairly shallow tank with slow moving radial rakes driven from a central shaft. Its bottom is conical. Dilute feed slurry flows from an inclined trough or launder into the centre of the thickener. The feed dlurry being more denser than water tends to flow downward until it reaches a zone of equal density. Then it moves radially outward at a constantly decreasing velocity and the flow gradually divides between the downward moving suspension and the upward moving flow that is nearly free of solids. Liquor moves radially at a constantly decreasing velocity allowing the solids to settle at the bottom of the tank. Clear liquor is obtained as the overflow. The rake arms gently agitate the sludge and move it to the centre of the tank, where it flows through a large opening to the inlet of a sludge pump. Here the feed is fed into the settler through a feed well, so that it will not spread at the top but reaches the centre. The temperature inside the settler is minium 600C. An organic flocculent is used which causes agglomeration and hence faster settling of particles. Clear overflow is obtained from the top through pipes connected around the settler. The rakes rotating at a speed of 1/13 rpm, gently agigate the sludge and move it to the centre of the tank. The overflow from the settler contains TiOSO4 andFeSO4 in acid medium which is collected into the SLS tanks from where it is pumped to the concentration feed tanks. Weak Liquor Preparation The sludge from the settler is withdrawn through the bottom valve and sent to the sludge dilution tanks. After specified quantity is withdrawn it is diluted to the required specific gravity and pumped to sludge settlers. Weak liquor overflow from the sludge settlers is collected in weal liquor storage tanks.
Concentration
The overflow from the settler has a concentration of 140 gpl. The purpose of the concentration is to increase the concentration of the liquor by evaporating the water content and hence to increase the content of solids in the liquor per litre. There are 3 concentration units. The main parts of concentration unit are 1. 2. 3. 4. 5. 6.
Concentration feed tank Overhead tank preheater Concentrator Vapour separator Discharge lute
Working The liquor from the concentration feed tank is fed to the overhead tank from where it is fed to the preheater. Preheater is a shell and tube type Heat Exchanger. There are 22 tubes inside the preheater. The tubes and shell are made of electrolytic copper. The liquor from the preheater is fed to the bottom of the bottom of the concentrator. The concentrator has 32 tubes inside it which works independently. The tube side is made of electrolytic copper and the shell side is made of mild steel which has insulations to prevent heat loss. The shell side is fed with fed with steam. The liquor when passes through the tube side gets the water content reduced by evaporation. The concentrated liquor and vapour are sent to the vapour separator. The liquor at the bottom of the vapour separator is collected into the discharge lute. The vapour is sent to the preheater. Since the preheater is used, the amount of steam that is to be used in the concentrator is reduced and concentration is carried in less time with less expense and the once used steam can be recycled.
Precipitation Titanium Dioxide is separated from the concentrated liquor by precipitation. Precipation is effected through thermal hydrolysis. Maximum precipitation takes place at a temperature of 110 0C. The tank is made up of mild steel which has a brick lining inside made up of
acid and heat resistant bricks which prevents heat loss and also protects mild steel. There is a rubber lining outside. The concentrated liquor at a temperature of 900C is fed into the tank. Nuclei is charged and kept for three hours. Steam is injected and cutting water is added. This brings about precipitation by thermal hydrolysis. Temperature raises to about 1100C and the tank is sealed with steam and is maintained for 3 hours. Then it is left there for about 2 1/2 hours of cooling. TiOSO4 + 2H2O -- TiO(OH)2 + H2SO4 Hydrated titanium dioxide is precipitated. Ferrous sulphate remains as such. It will not coprecipitate. It is during the precipitation stage that the black liquor is changed to white one.
Filtration Here rotary drum filter is used. It is a continuous vacuum filter. Here is liquor is sucked through a moving septum to deposit a cake of solids. The cake is moved of the filtering zone washed, sucked dry and dislodged from the septum, which then reenters the slurry to pickup another load of solids. Some part of the septum is in the filtering zone always, part is in the washing zone and part is being relieved of solids, so that the discharge of both solids and liquids from the filter is uninterrupted. Working of Rotary Drum Filter A horizontal drum with a slotted face turns at 1/3 rpm in an agitated slurry trough. A filter medium such as canvas covers face of the drum which is partly submerged in liquid. Under the slotted cylindrical face of the drum which is a second smaller drum with a solid surface. Between the two drums are radial partitions dividing the annular space into separate compartments each connected by an internal pipe to one hole in the rotating plate of the rotary valve. Vacuum and air are already applied to each compartment as the drum rotates. A strip of filter cloth covers the exposed face of each compartment to form a succession of panels. There are three zones for a rotary drum filter 1. Catch up zone 2. Wash up zone 3. Drying and releasing zone
The drum is kept in such a way that 1/3rd of the drum is immersed in the slurry trough. The slurry is sucked up by the catch up zone. A vacuum is used to create the suction. Solids remain on the surface of the filter cloth, and the liquid along with the dissolved impurities is sucked into the tubes. At the top of the drum water is constantly sprayed which washes the pulp when it comes in the washing zone. The water and the dissolved ferrous sulphate is sucked into the tubes. As the drum rotates, when it comes down vacuum is released at some region and so slurry is released. There are 16 tubes inside which are connected to a single tube lead which leads to a catch pot. The fumes from the catch pot are sent to a water scrubber. The cleaned gas is sent to a common line, which is connected to a vacuum pump. The catch pot and the scrubber are water sealed. For maximum removal of ferrous sulphate and other impurities the filtration is carried in four stages. 1. Post Precipitation Filtration 2. Pre Leaching Filtration 3. Post Leaching Filtration 4. Dewatering Filtration
Post Precipitation Filtration The precipitated liquor from the batch storage is sent to the filtration unit. There are four numbers of post precipitation filters. Size Length - 16 inch Diameter – 08 inch The pulp is diluted and is sent to the repulping tank. The repulped mass is sent to the preleaching filters.
Pre Leaching Filteration Four numbers of filters are available. The feed is from post precipation filters and dorr tanks. The purpose of filtration is to wash off ferrous sulphate and increase the TiO2 content in pulp. The filtrate goes to the dorr tank.
Specification: Specific Gravity- 1.231.25
Leaching The purpose of leaching is to reduce the non washable ferric sulphate to washable ferrous sulphate. As the pulp passes through different filtration operations, some ferrous sulphate may get converted to ferric sulphate due to aerial oxidation. Here Al dust is added along with particular amount of sulphuric acid. This produces nascent hydrogen which is a good reducing agent.
Post Leaching Filtration The leached pulp is washed and filtered for the specific gravity 1.291.30 and an iron content of 0.001gpl. Four numbers are available.
Treatment In treatment section specific amount of potassium sulphate solution and mono ammonium phosphate are added and K2SO4 is also added to improve the tone, texture, PH and quality. Mono Ammonium Phosphate is added to impart antirutile properties. No. of treatment tank in one stream is two.
Dewatering Filter The pulp is again filtered to remove the water present. In the dewatering filter the vacuum is adjusted in such a way that to get a solid of 37% in the pulp
Calcination It is the process of slow heating of the pulp, which takes hours, to reach the other end of the calciner. Calciner is a long inclined rotary kiln, cylindrical rotating at a speed of 1/17 rpm. Its inclination is towards the furnace end. Two numbers of calciners are available here. They have a capacity of 30 tonnes per day. The purpose of calciners are 1. To decompose hydrated titanium into TiO2 2. To remove residual acid. 3. To develop crystal unit.
The cake is dried in a calciner by burning it in the combustion chamber with kerosene as a fuel. Kerosene is sprayed into the combustion chamber using a blower. There are two calciners used. The dried up TiO2 is blown off into the combustion chamber in the form of crystals by the aid of induced draught fans and thus providing draught in the chamber. The TiO2 crystals is then passed through a cooler and passed onto the milling section. The temperature at the firing end 1200oC, is measured by R-type thermocouple. The temperature at the feed end 450oC is measured by S-type thermocouple. The temperature at the firing end is controlled at 1200oC by manually controlling the flow of kerosene to the blower. The gas produced is evacuated through the main dust which further splits into two with an ID fab provided in each of the two sub dusts.These gases are taken through a cooling tower and an electrostatic precipitator.
Pulverisation TiO2 obtained after cooling is in the form of granules. This is transferred using belt conveyors to bucket elevator which inturn lifts the product and dumps into a silo having a capacity of 40 tonnes. The particle size is reduced in a Bradely Pulverizer Mill. Bradely Pulverizer is a pendulum type mill which powders TiO2 to a very fine size of about 625 mesh. The pendulum rotate vertically with close tolerances to the casing of the mill. To send the feed in required quantity and to prevent overloading and to increase milling efficiency an auto feeder is provided. The main accessories of milling are 1. Fan 2. Cyclone Separator 3. Viscobeth The product coming out of the cyclone separator is sent into the packing bumker.
Packing A weighing machine is kept below the bunker. TiO2 is filled into plastic sacks kept over the weighing machine. 25 Kg is fed in each sack and sacks are tied. This is then sent into the market.
SULPHURIC ACID PLANT
Production of Sulphuric Acid Introduction Sulphuric Acid is a main raw material for the production of Titanium Dioxide pigment in Titanium Travancore Products Limited. During the expansion in 1965 a sulphuric acid plant with 50 tonns per day capacity was also started. In 1996 a new sulphric acid plant was commissioned with Double contact double Absorption process with a capacity of 350 tonns per day.
A>Water Treatment Plant Water treatment plant is a division of the sulphuric acid plant where the water(steam) necessary for the production of the acid is generated. For steam production PHD water is used.
Equipments The main equipments used are 1. M.G. Filter (multi grade filter) 2. SAC unit (Strong Acid Cation unit ) 3. DE gas sump 4. SBA unit 5. Mixed bed 6. D.M. Storage Tank Multi Grade filter This is used to remove clay or wood. It has a sand or gravel unit on the top and mesh arrangement on the bottom. The water at 2.5Kg/cm2 is given to the top of the filter. As it passes through large layers of the filter the large impurities are removed and rate of flow is 15m3/hr. SAC unit This contains a Zeocarbon resin which produces hydrogen. Chlorides of Magnesium, calcium etc is removed in this unit. Oxides of carbon and sulphur is converted to carbonic acid and sulphuric acid etc. water
leaving from this section has a ph of 2.5-4 and regeneration resins is done using sulphuric acid. De-Gaser sump Water from SAC unit is sent here to remove the carbonic acid. Water is sprayed to sump from top and air is supplied using a fan. The acid is converted to co2 and h2o and co2 is sent to atmosphere. SBA unit (Strong Base Anion Unit) Water from the De-Gaser is sent here. In this section the acidity of water is removed. For that resins having OH ions are used. Conductivity is 6.8-7.5. Regeneration of resins is done by NaOH. Mixed Bed Water from the SBA unit has low acidity and high alkalinity is not best for steam production and so the water is demineralised using a mixed bed. It has two resins with the same principle of SBA and SAC units. Demineralised Water Storage Tank Water is demineralised and stored in a storage tank. The water for steam production is obtained by using water treatment plant at a temperature of 33-350c. The water is given to a boiler but the temperature has to be increased and so using a deaerator the temperature of water is increased to 901000c .
B>Procedure for the production of sulphuric acid Sulphuric acid is produced by double contact absorption process. Sulphur is the main raw material . sulphur is melted, filtered and then oxidized to so2. So2 is further oxidized to so3 by passing through a catalytic convertor having vanadium pentoxide v2o3 as catalyst. The converted so3 is absorbed in concentrated sulphuric acid. Then the absorbed sulphuric acid is converted to sulphuric acid. Description of the main steps The flow diagram of the DCDA process contains the following equipments
1. 2. 3. 4. 5.
Melting pit Burner Convertor Absorber Scrubber The raw material used for the large scale manufacture of sulphuric acid is sulphur . sulphur is a by-product of petroleum industry.
1.Melting Pit The sulphur obtained may contain impurities like Selenium, Tellurium, ash, mud etc. so sulphur is to be purified to about100%. The purification is done by melting. When sulphur is melted the impurities present in it remain in the molten sulphur itself. Sulphur has a melting point of 1300c. Sulphur is stored in a sulphur go down. With the help of an Electrically operated crane it is transferred to a silo. Ratted quantity is fed to the melting pit by using a belt conveyor. For melting the sulphur steam coils are used. The high pressure steam melts the sulphur at a temperature of 140-1500c and 6.27kg/cm2. The velocity of the molten sulphur is maintained ina specified value so that the easy flow of sulphur is achieved. The specific gravity Of molten sulphur is 1.8. The impurities in the sulphuric acid raises the temperature of sulphur from 130-1500c. In order to neutralize the acid impurities, which are produced by the contact of molten sulphur with atmospheric oxygen, sulphurous acid, hydrated lime is added at the rate of 250gm/tons of sulphuric acid produced. The undissolved impurities are separated by settling in the melting pit itself. The overflow from the melting pit is collected in a dirty pit. From the dirty pit sulphur is pumped to leaf filter . The leaf filter is in horizontal inclined position. The filterate from the leaf filter are collected in a clean pit. The temperature of molten sulphur is maintained at a value of 1300c and at a pressure of 2.5kg/cm2. If the temperature is below 1300c the pumping of molten sulphur becomes difficult and above that temperature causes firing of molten sulphur. 2.Burner S+O2->SO2 The molten sulphur reacted with compressed air gives sulphur di oxide gas. A furnace is used for burning molten sulphur and compressed air. The furnace is a horizontal, cylindrical vessel with two sulphur guns. The length of the furnace is 7m and diameter is 4m. The furnace is made up of carbon steel,acid proof bricks and fire resistant bricks. Molten Sulphur is pumped from a storage tank through heated lines and sprayed in to the furnace using burners. Dry air from air drying
tower is introduced into the furnace. The temperature of furnace is kept at about 950-10200c, otherwise leakage of sulphur takes place . The conversion is exactly 10.5% by mole so2
Waste Heat Boiler-1 Before the gases are fed to the first stage of the converter, they are adjusted to the minimum temperature at which catalyst rapidly increases the speed of reaction,usually 425 to 4400c. For that purpose a waste heat boiler has shell side and tube side. So2 gas at a temperature of 10000c is passed through the tube side and water is passed through shell side. Thus by the principle of heat transfer the temperature of so2 gas is reduced to about 4350c and water gets converted to steam. But there is a chance for reduction the temperature below this value. So the outlet of the waste heat boiler is given to a mixing chamber where mixing of so2 from boiler and furnace takes place. As a result the temperature of so2 can be kept at 4350c. 3.Convertor The chemical conversion of sulphur dioxide to sulphur trioxide is designed to maximize the conversion by taking into consideration that 1. Equilibrium is an inverse function of temperature and a direct function of the oxygen to the sulphur dioxide ratio 2. Rate of reaction is a direct function of temperature. 3. Gas composition and amount of catalyst affect the rate of conversion and the kinetics of the reaction. 4. Removal of sulphur dioxide formed allows more sulphur dioxide to be converted. The commercialization of these basic condition makes possible high overall conversion by using a multipass convertor. A four pass convertor is used for conversion in the sulphuric acid plant. It has 4 beds of ring and start type materials coated with vanadium pentoxide catalyst for better conversion. The conversion takes place in two stages. Stage-1 Sulphur dioxide gas from the mixing chambers is given to the 1st layer of the 4 pass convertor. The conversion reaction is 2SO2+O2>2SO3. This reaction is highly exothermic. Thus the temperature increases to 6000c. if this conversion stream is directly given to the 2nd layer of the convertor then the catalytic bed may be spoiled. In order to avoid that condition the outlet from the first layer is given to a super heater.
Super Heater The gaseous stream from the first stage of the convertor is given to the tube side of the superheater and stream is passed through the shell side. Then the temperature is reduced to 425oC. The outlet of the superheater is givan to the second bed of the convertor where 28% of conversion of SO2 to SO3 takes place. The conversion raises the temperature of gas to 520oC. For cooling this gas before it is given to the third layer a hot heat exchanger is used.
Hot Heat Exchanger The outlet from the 2nd layer of the catalytic convertor is given to the tube side of the hot heat exchanger. Hot gas is passed through the shall side. Thus the temperature of SO3 gas reduces to 430oC. The gas stream from the hot heat exchanger is given to the third layer of the convertor. In the third layer 6% conversion of SO2 to SO3 takes place and the temperature raises to 450oC. This completes the first stage of conversion of SO2 to SO3. For absorption of converted SO3 its temperature should be reduced. Thus a haet exchanger and an economizer is used.
Cold Heat Exchanger The outlet from the third layer of the catalytic convertor is given to the tube side of the cold heat exchanger and cold gas is passed through the shell side. Then the temperature of the SO3 gas decreases to 330oC from 450oC.
Economiser-1 For the further reduction of the temperature to 1800C an economizer is used. In the economizer gas is flowing through the tube side and water is flowing through the shell side. Thus the temperature is reduced to 180oC.
4.a.Interpass absorption tower The so3 gas from economizer-1 is absorbed in an interpass absorption tower. It is cylindrical in shape and the gas is absorbed in 98.5% sulphuric acid. The acid is sprayed from the top of the IPAT and gas is given through bottom. The temp of IPAT is 700c.
In order to reduce the temperature of sulphuric acid before it is sprayed to IPAT and FAT a plate cooler is used. Water is passed through the plates and acid is passed in between the plates. Thus the transfer of heat takes place and as a result of this temperature of acid is reduced and water become steam. Stage-2 The unabsorbed SO3 gas from the interpass absorption tower is given to the 4th bed of the catalytic convertor which is at a temperature of 4300c and 5.75% conversion of so2 to so3 takes place in the second stage and temperature is increased due to exothermic reaction. Economiser-2 It is similar to that of economizer-1 and having so3 gas in the tube side and water in the shell side. Reduction of temperature takes place and the outlet from economizer-2 has a temp of 180 0c. The outlet gas is absorbed in final absorption tower.
4.b.Final absorption tower Second stage absorption of so3 gas is done in the final absorption tower. It is similar to IPAT sulphuric acid at 98.5% concentration and reduced temperature is sprayed from the top of the FAT and so3 gas from the economizer-2 is given to the bottom of FAT absorption of so3 results. The outlet of both the IPAT and FAT has the formula H2S2O7(oleum) SO3+H2SO4->H2S2O7 The oleum is collected in acid pumping tank.
Acid pumping tank The acid pumping tank having capacity of 150m 3 and it is cylindrical in shape. Inorder to maintain the concentration at 98.5% dilution water is constantly given to the acid pumping tank. There are six acid collecting tank in acid plant. When the volume of sulpuric acid in the acid pumping tank becomes greater than 150m 3 it is transferred to the acid collecting tank steam is a by product of acid collecting tank steam byproduct of acid plant. Air circuit Air for sulphur burner is supplied by electric blower is used. During the starting of the acid plant and power filure condition electric blower is used. All the other time steam turbine blower is used.
Air from the athmosphere is sucked through a filter for removing dust and compresed by turbine driven air blower and it is given to air drying tower to remove entire atmospheric oxygen. During is done with the help of sulphuric acid. The dry air given to the burner for burning of molten sulphur.
5.Pollution control(scrubber unit) Gases from the final absorption tower contains SO2. SO3 atmospheric pollutant. Gasses from the final absorption tower are taken to a packed scrubber. During normal operation the gasses passes through dry scrubber. During start up or disturbed conditions caustic solution from the solution tank is fed to the foot of the scrubber by gravity. SO 2 from the gases is absorbed in the surculatting stream of caustic solution. Scrubbed gases are vented to atmosphere through a 26 meter tall chimney. The specified limit is 300ppm SO2 ,100mg/Nm3 of SO3, as prescribed by the pollution control standards. Precommissioning of plant Before the plant is made ready for commissioning, it is necessary that individual sections of the plant are checked and necessary test carried out on the equipment to ensure their smooth functioning during commissioning and normal running of the plant. Preheating The main step in precommissioning activities for first start is drying of bricks in sulphur furnace, startup furnace and convertor. Drying of brickwork shall be carried out by wood firing is sulphur furnace startup furnace and convertor. Sulphur circuit 1. For first startup clean all sulphur pits. Flush all the steam coils by steam to remove any dirt and scale etc. 2. Fill sulphur melter with sulphur through the belt conveyor. Once substantial amount of sulphur is added to melter, start steam in melter coils and check for proper operation of traps. Allow the sulphur to melt and gradually go on adding solid sulphur till level of liquid sulphur is above the agitator level. 3. Now start the sulphur agitator, check the amperage of agitator motor, also check for any vibration on sound and start feeding sulphur gradually and continuously at maximum possible rate without any lump formation in sulphur pool. 4. Add lime accordingly to neutralize acidity. After sometime sulphur will overflow to dirty sulphur pit.
5. At this time start steam flow through coils in dirty sulphur pit. When liquid sulphur level comes to agitator level and check for smooth operation. 6. Open steam in dirty sulphur jacketed pipe and heat the same. Once sufficient amount of liquid sulphur is filled in dirty pit, start sulphur pump to recirculate sulphur. Once smoother operation of dirty sulphur pump is established transfer the sulphur to precoat pit and fill the same. 7. Add filter aid and start the agitator in precoat pit. Now system is ready for precoat operation of sulphur filter. Start steam in all jacketed pipes and in jackets of sulphur filter. 8. For filling the sulphur filter, first start steam in jacket and ensure that all are well heated. Ensure that lid flanges are tightened properly. Open the vent/overflow valve and start precoat sulphur oump. Keep sulphur valve position in suitable open/close position. Once sulphur starts overflowing close vent valve and allow the sulphur to recirculate in precoat pit. 9. Once the precoat cycle is over filter cycle can be started. Adjust the valves so that low from duty sulphur pump goes to filter and then to clean sulphur. If found in limits continue the filteration cycle. In case of ash being excessively check for possibility of improper precoat or damaged filter leaves. 10. Once the filteration cycle is over as indicated by reduced sulphur flow in filter outlet, prepare to open and clean the sulphur filter. 11. Keep clean sulphur tank sufficiently full well before scheduled date of sulphur firing. Take a trial of clean sulphur pump amd circulate sulphur in all relevant pipelines. Normal Operation Sulphur Section 1. Check the ash content in sulphur once in a shift. Higher ash content may be due to improper precoat or damage to the screen. Take the corrective action accordingly. 2. Choking of filter as indicated by reducing in sulphur flow indicates filteration cycle. At such time arrange for cleaning sulphur filter. 3. Analysis ash content and acidity of dirty sulohur feed to filter. This will ensure corrosion free operation and help in anticipating filteration cycle. 4. Incase filter aid contains chlorides wash the same thoroughly before feeding to filler to avoid corrosion Gas circuit
1. Analyse so2 at convertor inlet regularly. Plant is designed to operate at 10.5% so2 convertor inlet. 2. Convertor 2nd bed inlet temperature can be controlled by operation of super heater bypass valves. 3. Inlet temperature of 3rd pass is controlled by hot heat exchanged tube side bypass valve. Acid Circuit 1. Amperage of circulation pump should be noted regularly. 2. Acid samples should be analysed once a day check operation of analyser. 3. Level indicator readings should be checked frequently by manuel level measurement. 4. Observe flow of acid in tower distributor once a day through sight glasses. Boiler circuit 1. Check boiler feed water sample and boiler blow down sample once a day. Any abnormality observed it should be corrected immediately in water treatment, chemical closing or blow down frequency. 2. Ensure that steam flow is deaerator is maintained and BFW is at a temperature of 100-1050c. 3. Safety valves should be checked regularly to ensure safety of high pressure equipment. 4. Level gauges should be drained and checked once a shift. 5. In no case boiler water level should be allowed to go below normal level 6. While operating boiler feed water pump, corresponding recirculation line valve should be kept open.
General Guidelines for Good Operation 1. Always have a spare sulphur gun for service 2. When plant is shutdown, leave steam flowing through the sulohur burner jacket. This will serve as a coolant to protect the gun from the radiant heat until the furnace refractory has cooled. 3. Repair any shell or duct leaks at the earliest opportunity and repair all insulation. 4. Avoid use if cold feed water to an operating boiler except in an emergency. 5. Never allow the boiler exit gas temperature to drop below 2750c. 6. Although convertor-operating conditions will vary with time and service, never allow the catalyst temperature to exceed 6200c.
7. Elevate catalyst temperature slightly before a hot shutdown to facilitate startup. 8. Frequently check all thermocouples specially convertor thermo couples against a standard. 9. Never attempt to operate plant without acid circulation on all three towers. If a pump fails and cannot be restarted immediately shut the plant down. 10. Keep the spare acid pump in excellent condition and reay for quick start. 11. Verify the reading of conductivity meters once a day. 12. Try to keep acid plant circulating pumps running all the time, whether the plant is operating or not, if it is necessary to stop circulation for maintenance reasons, check the distribution section and clean if needed. 13. Establish and rigourously follow a procedure for collecting and recording data on plant operations. These would include temperature and pressure profiles of systems.
Shutdowns In any shutdown, the first thing to turn off is the sulohur feed. For hot shutdowns, the blower should be turned off immediately after the sulphur is turned off. For shutdowns, those are expected to last more than 5-10 min, the acid cooling water should be turned off. Do not stop the circulation of acid over the towers unless it is necessary to do so. When possible increase catalyst temperature a few degrees before shutdown. These will simplify the subsequent start up. Make sure that dilution water is cut off. Shutting down for a prolonged period Before shutting down for a prolonged period allow the strength of the process acid run up to 0.1-0.2% above normal operating strength. This will serve as a buffer against the small decreases in strength normally observed during a prolonged shutdown. Then stop dilution water. Turnoff the sulphur feed, and reduce the dry airflow to about 50% of design. Cool all catalyst leads with air to about 50 0c at a rate not greater in the boiler approaches atmospheric temperature, the vent valve on the steam drum must be opened to prevent formation of vacuum inside boiler. If the boiler is to be entered during shutdown, cool raw water may be used as feed water after all steam generation has stopped, and the circulation. A boiler should not be drained until it is cooled throughout.
Temperature and conversions in each stage of the 4pass convertor
Location Gas entering 1st pass Gas leaving 1st pass Rise in temperature
Temperature 0 c 430 600 170
Gas entering 2nd pass Gas leaving 2nd pass Rise in temperature
430 520 90
Gas entering 3rd pass Gas leaving 3rd pass Rise in temperature
430 450 20
Gas entering 4th pass Gas leaving 4th pass Rise in temperature
430 445 15
TOTAL
Equivalent conversion 60%
28% 6%
5.75% 99.75%
Conclusion Travancore Titanium Products Ltd is one of the profit gaining public sector units. The major asset of this company is skilled staff. Moreover the efficient management of the resources have helped them to overcome the slump in the sales over the last few years. Through this inplant training it was able to fulfill the objective of our study. Detailed study on the processes was made possible by giving emphasis on the practical side of the theory. All together it was a good experience to see the company and various processes carried out in the plants and the various functions of the company.
