STEAM & POWER GENERATION PLANT DURATION 15th June 2012 to 31th July 2012
Submitted to: Training & Placement Section, IFFCO AON AO NLA UNIT, U NIT, U.P. Submitted by:
ASHISH LAL 09113009
Industrial & Production Engg. B.Tech. (Final Year) Dr. B.R. Ambedkar N.I.T. Jalandhar, Punjab 8300/190/VT-52/12-13 Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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It is my great pleasure to express my sincere gratitude to Mr. D. Kalia, DGM(TRG) , IFFCO, Aonla Unit for his deep interest profile inspiration, valuable advice during the entire course of industrial industrial training. I am highly thankful to Mr. Rajeev Trehan , Centre of Trg. & Placement, and Prof. R.K. Garg, Head, Centre of Trg. & Placement, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, Jalandhar , Punjab for taking i nterest and guidance gu idance in my endeavour endeavour to get opportunity opportunity to t o work at IFFCO. I am also thankful to staff of IFFCO, Aonla for their help and assistance during during my m y training period.
ASHISH ASHIS H LAL B.TECH.(FINAL YEAR) INDUSTRIAL & PRODUCTION ENGG. Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, Jalandhar , Punjab
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Company Profile
4
Abstract Abstract
7
Urea
10
Introduction
13
Brief Description Description of S.G.P.G. (Steam & Power Powe r Generation Plant)
15
Various parts of S.G.P.G. S.G.P.G.
Quality of steam
24
Condenser
27
Deaerator
29
Fuel System System
30
Combustion Air System
35
Boiler make up water treatment plant
37
H.R.S.G. H.R.S.G. (Heat Recovery Steam Steam Generation)
38
Gas turbine
40
Industrial Gas turbine turbine
43
Conclusion
45
References
46
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IFFCO has 40,000 member cooperatives. IFFCO has been ranked#37 in top companies in India in 2011 by Fortune India India 500 list. Indian Farmers Fertilizer Co-operative Limited (IFFCO) was registered on November 3, 1967 as a Multi-unit Co-operative Society. On the enactment of the Multistate Cooperative Societies act 1984 & 2002, the Society is deemed to be registered as a Multistate Cooperative Society. The Society is primarily engaged in production and distribution of fertilizers. The byelaws of the Society provide a broad frame work for the activities of IFFCO IFFCO as a Cooperative Society. IFFCO commissioned an ammonia - urea complex at Kalol and the NPK/DAP plant at Kandla both in the state of Gujarat in 1975. Another ammonia - urea complex was set up at Phulpur in the state of Uttar Pradesh in 1981. The ammonia - urea unit at Aonla was commissioned in 1988. In 1993, IFFCO had drawn up a major expansion programme of all the four plants under overall aegis of IFFCO VISION 2000. The expansion projects at Aonla, Kalol, Phulpur and Kandla have been completed on schedule. Thus all the projects conceived as part of Vision 2000 have been realized without time or cost overruns. All the production units of IFFCO have established a reputation for excellence and quality. A new growth path has been chalked out to realize newer dreams and greater heights through Vision 2010. which is presently presently under under implemen implementation. tation. As part part of the new vision, vision, IFFCO has acquired fertilizer unit at Paradeep in Orissa in September 2005. IFFCO has made strategic investments in several joint ventures. Godavari Fertilizers and Chemicals Ltd (GFCL) & Indian Potash Ltd (IPL) in India, Industries Chimiques du Senegal (ICS) in Senegal and Oman India Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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Fertilizer Company (OMIFCO) in Oman are important fertilizer joint ventures. Indo Indo Egyptian Egyptian Fertilize Fertilizerr Co (IEFC) (IEFC) in Egypt is under implementation. As part of strategic diversification, IFFCO has entered into several key sectors. IFFCO-Tokyo General Insurance Ltd (ITGI) is a foray into general insurance sector. Through ITGI, IFFCO has formulated new services of benefit to farmers. 'Sankat Haran Bima Yojana' provides free insurance cover to farmers along with each bag of IFFCO fertilizer purchased. To take the benefits of emerging concepts like agricultural commodity trading, IFFCO has taken equity in National Commodity and Derivative Exchange (NCDEX) and National Collateral Management Services Ltd (NCMSL). IFFCO Chhattisgarh Power Ltd (ICPL) which is under implementation is yet another foray to move into core area of power. IFFCO is also behind several other companies with the sole intention of benefitting farmers. The distribution of IFFCO's fertilizer is undertaken through over 38155 cooperative societies. The entire activities of Distribution, Sales and Promotion are co-ordinate by Marketing Central Office (MKCO) at New Delhi assisted by the Marketing offices in the field. In addition, essential agro-inputs for crop c rop production production are made available to the farmers fa rmers through through a chain of 158 Farmers Service Centre (FSC). IFFCO has promoted several institutions and organizations to work for the welfare of farmers, strengthening cooperative movement, improve Indian agriculture. Indian Farm Forestry Development Cooperative Ltd (IFFDC), Cooperative Rural Development Trust (CORDET), IFFCO Foundation, Kisan Sewa Trust belong to this category. An ambitious project 'ICT Initiatives for Farmers and Cooperatives' is launched to promote e-culture in rural India. IFFCO obsessively nurtures its relations with farmers and undertakes a large number of agricultural extension activities for their benefit every year. At IFFCO IFFCO,, the thirst for ever improvi improving ng the services to farmers farmers and member co-operatives is insatiable, commitment to quality is insurmountable and harnessing of mother earths' bounty to drive hunger away from India in an ecologically sustainable manner is the prime mission. All that IFFCO cherishes in exchange is an everlasting smile on Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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the face of Indian Farmer who form the moving spirit behind this mission. IFFCO, today, is a leading player in India's fertilizer industry and is making substantial contribution to the efforts of Indian Government to increase food f ood grain production production in the country.
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Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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For efficient and uninterrupted running of a fertilizer plant a reliable source of power is very much essential. All the major rotating equipments of Ammonia and Urea plant are driven by electrical motor. To meet the demand of high pressure steam and dependable electrical power, the steam and power generators have been installed. The steam generator of Aonla unit will supply supply high pressure pressure steam to process process plants and and Gas turbine generators will meet the power requirement of the plant. There are two Gas Turbine Generators (GTG), one Steam Generator (SG) and two Heat Recovery Steam Generating units (HRSG). The GTG have been designed to operate on natural gas (NG), high speed diesel (H ( HSD) or Napth Napthaa fuels. The exhaust of GT at about 500 deg C is used in HRSG to generate steam at high pressure. Two HRSG units each having capacity to generate 80 T/hr at 116 atm and 515O C is manufactured by M/s Kawasaki heavy industries , Japan. HRSG is a packed type boiler having bank tubes, a set of super heaters, De-super heaters and and economizer. economizer. The SG unit is a water tube double drum, natural circulation, oil (low sulphur high start, LSHS) or natural gas fired boiler manufactured by M/s Mitsui Engg. Co. Japan. The capacity of the SG unit is 150 tonns/hr of super heated steam at apressure of 116 atm and temp 515 deg C. The SG is designed to use NG or LSHS fuel for regular firing. For initial light up of the SG, HSD will be used. The SG is pressurized furnace with no induced F.D. fan. Two F.D. fans, one turbine driven and other motor driven have been provided to supply combustion air. A direct direct spray type De-super De-super heater heater has has been provided provided between primary primary and secondary s econdary super heater to control cont rol steam ste am temperature. Super heater is of convection type, counter flow, drainable, inverted UAshish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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looped tubes with spiral fins. Super heater section is located in the highest gas temp zone and materials are designed to satisfy the requirement of opearation conditions. Super heater elements are bottom supported by lower header holding plates.
The MD type boiler is provided with a steam drum and a water drum. Both of the drum have a main hole on each end for maintenance and inspection. The steam drum drum is equipped with sets of steam purifiers inside to obtain the required steam purity.
The furnace has an ample volume to secure complete combustion of specified fuel. The furnace walls are of welded longitudinal fin tubes panels to form a completely gas tight enclosure. The furnace floor is covered with a layer of refractory bricks so as to shield the tubes from radiant hea h eatt to secure a good circulation of water.
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IFFCO's Urea is not merely a source of 46% of nutrient nitrogen for crops, but it is an integral part of millions of farmers in India. A bag of IFFCO's urea is a constant source of confidence and is a trusted companion for Indian farmer. farmer. When farmers farmers buy b uy IFFCO's IFFCO's urea, they know tha t hatt what what they get is not just a product product but a complete complete package package of servi s ervice ces, s, ably supported supported by a dedicated team of qualified personnel. More importantly, they are aware that it is their own urea, produced and supplied by a cooperative society owned by themselves.
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About Urea Urea Urea is the most important nitrogenous fertiliser in the country because of its high N content (46%N). Besides its use in the crops, it is used as a cattle catt le feed supplement supplement to replace a par pa rt of protein requirements. requirements. It has also numerous industrial uses notably for production of plastics.
Specification of urea as per Fertiliser 1. Moisture maximum
%
by
Control Order
weight, 1.0
2. Total N % by weight (on dry basis) bas is) minimum minimum
46.0
3. Biuret % by weight, maximum
1.5
4. Particle size Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
90% of the material shall pass through 2.8 mm IS sieve and not less than 80% by weight shall be retained on 1 mm IS sieve. IFFCO AONLA
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If urea is applied to bare soil surface significant quantities of ammonia may be lost by volatilisation because of its rapid hydrolysis to ammonium carbonate. The hydrolysis of urea can be altered by the use of several compound called urease inhibitors. These inhibitors inactivate the enzyme and thereby prevent the rapid hydrolysis of urea when it is added added to soil. The rapid hydrolysis hydrolysis of urea in soils is also responsible for ammonia injury to seedlings if large quantities of this material placed with or too close to the seed. Proper placement of fertiliser urea with respect to seed can eliminate this difficulty.
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Iffco Aonla complex is one of the giant cooperative fetilizer manufacturing industries in India. The Iffco complex at Aonla consists of two Ammonia units of 1350 MT/day capacity and two Urea units of 1100 MT/day each capacity with the required offsite facilities. For efficient and uninterrupted running of a fertilizer plant a reliable source of power is very much essential. All the major rotating equipments of Ammonia and Urea plant are driven by electrical motor. To meet the demand of high pressure steam and dependable electrical power, the steam and power generators have been installed. The steam generator of Aonla unit will supply supply high pressure pressure steam to process process plants plants and and Gas turbine generators will meet the power requirement of the plant. There are two Gas Turbine Generators (GTG), one Steam Generator (SG) and Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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two Heat Recovery Steam Generating units (HRSG). One GTG will be in line while the other is stand by. The stand by unit can come on full load in 13 minutes. The GTG, manufactured by M/S Hitachi limited, Japan has a capacity to generate 25.280 MW at ISO base rating (means atmosphere temperature 15deg C & 60% humidity at sea level) or 18.320 MW power output at the site conditions. The GTG have been designed to operate on natural gas (NG), high speed diesel (HSD) or Naptha fuels. The exhaust of GT at about 500 deg C will be used in HRSG to generate steam at high pressure. There is a provision to by pass the GT exhaust in case it is not required due to shut down of the respective HRSG. In this case exhaust will be vented to t o atmosphere. atmosphere. Two HRSG units each having capacity to generate generate 80 T/hr at 116 atm and 515 O C is manufactured by M/s Kawasaki heavy industries , Japan. HRSG is a packed type boiler having bank tubes, a set of super heaters, De-super heaters and economizer. The temp of exhaust gas from GTG is increased by supplementary firing. The exhaust of GTG is having sufficient quantity of excess air which is utilized for combustion of supplement fuel and so no separate Forced draft (F.D.) fan has been provided. For steam temp control, direct water spray type attemperator has been provided p rovided between primary and secon sec ondary dary super sup er heaters. The SG unit is a water tube double drum, natural circulation, oil (low sulphur high start, LSHS) or natural gas fired boiler manufactured by M/s Mitsui Engg. Co. Japan. The capacity of the SG unit is 150 tonns/hr of super heated steam at apressure of 116 atm and temp 515 deg C. The SG is designed to use NG or LSHS fuel for regular firing. For initial light up of the SG, HSD will be used. The SG is pressurized furnace with no induced F.D. fan. Two F.D. fans, one turbine driven and other motor driven have been provided to supply combustion air. A direct spray type De-super heater has been provided between primary and secondary super heater to control steam temperature.
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GAS TURBINE TUR BINE GENERATOR (GTG) PRINCIPLE PRINCIPLE The gas turbine like any other heat engine is a device of converting part of fuel's chemical energy into useful available mechanical power. It does this in the manner similarily in, many ways to the system used by four stroke cycle reciprocating internal combustion engine. Air is drawn into the compressor, usually through an air filter situated in a "Filter house" to remove any harmful solid particle from the air stream. This air is then compressed to a designed figure by a multi stage axial compressor. The hot compressor air is then fed to the combustion system where it is mixed with injected injected fuel. fu el. Here the fuel burns and add its its energy to the air.
DETAILED DESCRIPTION OF STEAM GENRATION The Mitsui MD (middle to semi large industrial boiler) type steam generator is of outdoor use, self standing natural circulation type. The steam generator is designed to fire HSD, LSHS/FO, and NG with four set of oil and gas combination c ombination burners The steam generator comprises a water cooled furnace, a convection bank, steam and water drum, headers for collecting and distributing water and steam, primary and secondary super heater, framed, casing insulation etc.
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DRUM AND INTERNALS INTERNAL S: The MD type boiler is provided with a steam drum and a water drum. Both of the drum have a main hole on each end for maintenance and inspection. The steam drum is equipped with sets of steam st eam purifiers inside inside to obtain the required steam purity. The steam drum is equipped with internal pipes for feed water, chemical and continous blow-down as well as stream purifier. The internal pipes are arranged so as to ensure good distribution of feed water wat er and chemicals in the drum and to collect relatively highly concentrated boiler water for blow down. The nozzles for feed water and chemicals are of double pipe type so as to reduce thermal stresses due to the temp differences. Finally the steam passes through the scrubbers. This comprises a number of corrugated metal plates. When the steam flows through it, any remaining water particles are efficiently removed. This occurs due to sharp change in the flow direction.
FURNACE: The furnace has an ample volume to secure complete combustion of specified fuel. The furnace walls are of welded longitudinal fin tubes panels to form a completely gas tight enclosure. The furnace floor is covered with a layer of refractory bricks so as to shield the tubes from radiant heat to secure a good circulation of water. The front wall is equipped with burner in two rows. The rear wall forms a partition wall dividing the convection section from the furnace. The rear tubes form a nose baffle to provide a superheater space at the upper part of the furnace. The side walls are provided with lower and upper header which is connected to water and steam drums with connection pipes. Sufficient number of observation holes are provided on the front side walls to check the firing conditon and for maintenance.
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SUPER HEATER: The super heater is provided with two stages of super heaters. In primary and secondary super heater both of then are of convection and pendant type. The primary super heater is located at the lower gas temp part while the secondary is at the higher temp part. The steam flows, contour to gas in the primary super heater and parallel in the secondary heat. The super heater tubes are hung to super heater headers which are mounted on the furnace header. Therefore, thermal, expansion of the tubes are hung to the super heater headers which are mounted on the furnace header. Therefore, thermal expansion of the tubes and headers is free, which avoids excessive stresses. Retractable soot blowers and access doors are provided between the primary and secondary super heater for cleaning and maintenance. maintenance.
DE-SUPER HEATER: A de-super de-super heater is also provided on the connecting connecting pipe between the primary and secondary super heaters to t o control the final steam pre p ressure. ssure. Feed water is sprayed in the steam flow through a spray nozzle which reduces the steam temp. Immediately downstream of the nozzle, a thermal sleeve is furnished so as to provide direct contact of sprayed water to the connecting connecting pipe wall.
ECONOMISER: Economiser is furnished downstream the convection bank to recover waste heat from flue gases. The economiser comprises a number of spiral wound finned tubes, inlet and outlet headers and sufficient frames and casing. It is supported by the Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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steel structure using slide shoes to cater with horizontal thermal expansion. Reciprocating type soot blower with multiple nozzles is furnished to effectively clean the heating surfaces.
BOILER FEED WATER SYSTEM: The requirement of water for the boiler is met from the water treatment plant. In the water treatment plant, DM water temp is raised to 60 deg C by passing it through return condensate cooler before sending to steam generation plant. In deaerator dissolve gases O2 and CO2 are removed up to less than 0.005 ppm by raising the wter temp to 126 deg C and stripping at a pressure of 1.44 kg/cm sq. By steam in deaerator storage tank, Cyclohexamine and Hydrazine are dosed to raise the pH of water to 8.59.5 and further chemical treatment of the boiler water to remove the remaining oxygen to nil. Boiler feed water wat er pump pump takes suction from deaerator. The pump discharge at pressure of 162 kf/cm sq g and temp 126 deg C through economiser it enters the boiler drum. There is boiler feed water preheater located between pump discharge and economizer to raise the BFW temp from 126 deg C to 140 deg C in case the boiler is on LSHS firing. This rise in temp is essential to avoid condensation of oxides of sulphur on coil surface and to prevent corrosion. The outlet of BFW preheater is divided into two branches, the small branch leads to the De-super heaters of the SG and HRSG units to control the steam temp and other leads water to SG and HRSG units through respective economiser. In economiser, feed water utilises the waste heat from the flue gases and temp of water raised to 190 to 310 deg C respectively.
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DEAERATING HEATER: HEATER: Deaerator is very important in the boiler feed water system. Its basic function is to remove O2 and CO2 dissolved in water to a considerable extent and store water for supplying supplying to t o boiler feed pumps. pumps.
DEAERATOR: The deaerator functions on heat and mass transfer process. In deaerator the nozzles and trays have been provided, through which water is sprayed and distribute into fine droplets to increase the surface area of the water. The process removes the dissolved gases upto some extent. Then the stream is mixed with water in mixed box named scrubber. This process also removes the dissolved gases. By the above process, in water, O2 contents get reduced reduced to 0.005 ppm pp m.
STORAGE TANK TA NK:: This is for storing of the feed water which is deaerated. The storage tank is designed to prevent subsequent penetration of oxygen during the feeding water process process after the necessary necessary deaera deaeration. The temp of of th t he water is is also kept constant inside the storage tank by covering the tank with insulating material.
COMBUSTION AIR SYSTEM: The air required for the combustion of air in steam generator is meeting by two centrifugal types forced draft fan (F.D. fan). One fan is driven by electrical motor while other by steam turbine. During the startup of the SG, motor driven fan is taken in service in case steam is not available to driven fan is taken in service in case steam is not available to drive the Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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turbine. The FD fan sucks the air from the atmosphere and discharge to the furnace at a pressure of 90mm-500mm water gauge. The quantity of air is controlled by the vane provided at the suction side of FD fan. Two air heaters have been provided in the discharge duct of FD fans, which are known as steam oil heater and gas air heater. These air heaters raise the temp to 145 deg C.
DESCRIPTION OF HRSG: GENERAL: The boiler consists cons ists of and arranged in the same casing as follows:
Super heater
Evaporator with w ith steam drum
Economiser
All tubes are spiral spiral finned finned and and are arran arranged ged in vertical vertical rows rows with with staggere staggered d tube arrangement to horizontal gas flow. All tubes circuits originate from inlet header and discharge to outlet header, and besides tubes and its header and discharge to outlet header, and besides tubes and its header are arranged so that all tube bank sections are fully drainable. Whole boiler is supported with the bottom casing on the foundation.
STEAM DRUM: Steam drum is of all welded construction, fabricated from carbon steel material and equipped with steam purifier of baffle screen type in steam drum and necessary nozzle and connections. The drum has been mounted on above the boiler and is supported with down corner pipes. Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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EVAPORATOR: Evaporator section is composed of several components which consist of number of tube with spiral fin and each inlet and outlet header. Each component is made up of water circulation circuits separately. Evaporator elements are bottom supported supported by lower header holding holding plates.
WATER WATER CIRCULAT CIRCULATION ION SYSTEM SYSTEM:: The water circulation circuit consists of steam drum, down corner pipes, down corner headers, supply pipes, steam generating tubes (evaporators) and riser pipe. The Th e basic system functions are as follows: Sub cooled water in the steam drum is led to the down corner headers through heated down corner pipes and is disrtributed to each evaporator inlet header from down corner headers. The mixture of water and steam generated by the heat absorption of evaporator flows from evaporator outlet headers to steam drum through the riser pipes.
SUPER HEATER: Super heater is of convection type, counter flow, drainable, inverted Ulooped tubes with spiral fins. Super heater section is located in the highest gas temp zone and materials are designed to satisfy the requirement of opearation conditions. Super heater elements are bottom supported by lower header holding plates.
ECONOMISER: Economiser is of counter flow, drainable, vertical tubes with spiral fines. Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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Economiser selection is composed of several components which consist of number of tubes and inlet header (lower) and outlet header (upper). These components are connected in series with several economiser tubes. Air vent and drain valve is provided provided on the upper and lower header, respectively. Economiser elements are bottom supported by lower header holding plates.
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The quality of steam for high pressure driven turbines is very much essential to keep the equipment in proper running condition and achieve the high high efficiency. efficiency. The quality of steam at Steam Steam Generating Plant Plant shall be maintained as under:
pH
7.0 to 9.0
SiO2
0.02 ppm
Cond.
1.0 Micromhos/cm Micromhos/cm
Total dissolved solids solid s as Na
1.0 ppm
pH of steam is maintained to prevent corrosion of steam pipe line and return condensate line. The Silica concentration in steam to lower value prevents the Silica deposition on the turbine blades. If it is not controlled in long run, this deposition of Silica on the tip of blades reduces efficiency of the blades, increases back pressure, and at worst it makes the rotor unbalanced and results in failure. The analysis of steam for conductivity detects any carry over of salts from steam drum due to some or other reason. reason. These salts, when carried carried over with steam, steam, get deposi deposited ted on the turbine blades blades and reduces reduces the efficiency efficiency of the machine. The total dissolved solids in steam are to be maintained to lower value to prevent any deposition in Super heater tubes and Turbine blades. The deposition of solids in Super heater tubes reduces the heat transfer to steam. This causes the overheating of the tube metal and finally failure of the tube.
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Steam System The steam requirement for steam and power generation plant for their auxiliaries and main consumer plant (Urea) are at different pressures and temperatures. The requirements are as under: 1.
High High pressure steam at 116 Atm and 515°C.
2.
Medium pressure steam at 39 Atm and 478°C.
3.
Medium pressure steam at 39 Atm At m and 400°C.
4.
Low pressure steam at 4.5 Ata and 225°C. 225°C.
High Pressure Pressure Steam (116 (116 Atm and 515°C) 5 15°C) The high pressure steam is generated in Main Steam Generating unit and Heat Recovery Steam Generating Units. The outlet of these units is connected to a header, which is called High Pressure Steam Header. This header supplies steam at 116 Atm and 515°C to Urea Plant and Auxiliaries of Steam and power Generating Units through Pressure Reducing and DeSuperheating Station. The requirement of Medium and Lower Pressure Steam is met through Pressure Reducing and De-Superheating De-Superheating Stations (PRDS). (PRDS). For this purpose two PRDS have been provided in Steam Generating Plant. In PRDS, firstly the pressure is reduced through pressure Control Valve and then boiler water is sprayed at controlled rate through the nozzles to bring down the steam temperature at required value. The requirement of steam for Urea Plant is met from High pressure Header. The High Pressure Header is charged from Steam Generator and Heat Recovery Steam Generator outlet.
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Medium Pressure Steam (478°C) The medium pressure steam at 478°C is required for Boiler Feed Pump and F.D. drive turbines. This is achieved after reducing the high pressure steam to 39 Atm pressure by pressure Reducing Reducing Station St ation No.1.
Medium Pressure Steam (400°C) The medium pressure steam at 400°C required for the following equipment is drawn from Pressure Reducing Station No.1 and further desuperheated to 400°C by De-Superheating station No. 1. 1. Boiler Feed Water Preheater 2. Atomising Atomising Steam Header 3. Soot blowing header for SG and HRSG HRSG soot blowers 4. Ammonia Ammonia Plant Plant Medium Medium steam steam pressure pressure header header 5. Furnace oil bulk storage tank area. 6. Pressure reducing Station No. 2.
Low Pressure Steam (225°C) The exhaust of Boiler Feed Pump drive turbines at 4.5 Atm and 459°C is de-superheated to 225°C by De-Superheating Station No.2 and discharge to L.P. Steam Header. In this header Blow Down tank vent steam and F.D. or drive turbine exhaust steam is discharged. This Low Pressure Header supply steam to the following: 1. 2. 3. 4. 5. 6.
Fuel Gas Superheater HSD Heater FO/LSHS Heater Steam Air Heater Header for DM Plant Deaerator
The shortfall of steam in L.P. header is met through Pressure Reducing Station Stat ion No. No. 2 which which draws steam st eam from from Medium Pressure Steam Header. Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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Diagram of o f a typical water-cooled water-cooled surface condenser.
The surface condenser is a shell and tube heat exchanger in which cooling water is circulated circulated through through the tubes. The exhaust exhaust steam from the t he low pressure turbine enters the shell where it is cooled and converted to condensate (water) by flowing over the tubes as shown in the adjacent diagram. Such condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air and gases from the steam side to maintain vacuum. For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100 oC where the vapor pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum. Thus leaks of non-condensible non-condensible air into into the closed closed loop loop must be prevented. Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning.
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The condenser generally uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through water from a river, river, lake or ocean. ocean.
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Diagram of o f boiler feed water deaerator (with vertical, vertical, domed dom ed aeration section and horizontal water storage section.
A steam generating generating boiler requires requires that t he boiler feed water should should be devoid of air and other dissolved gases, particularly corrosive ones, in order to avoid corrosion of the metal. Generally, power stations use a deaerator to provide for the removal of air and other dissolved gases from the boiler feedwater. A deaerator typically includes a vertical, domed deaeration section mounted on top of a horizontal cylindrical vessel which serves as the deaerated boiler feedwater storage tank. There are many different designs for a deaerator and the designs will vary from one manufacturer to another. The adjacent diagram depicts a typical conventional trayed deaerator. If operated properly, most deaerator manufacturers will guarantee that oxygen in the deaerated water will not exceed 7 ppb by weight (0.005 cm³/L).
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The fuels used in Steam Generator & Heat Recovery Steam Generating units are HSD, Furnace Oil/Low Sulphur Heavy Stock (FO/LSHS) and Natural Gas.
The liquid fuels are stored in two Day Oil Tanks located near Steam Generating Units The Day Oil Tanks have a storage capacity of 80 tons and 175 tons of HSD HSD and FO/LSHS FO/LSHS respectively. The HSD in day tank will be transferred directly from the oil tanker received from Indian Oil Corporation and FO/LSHS will be transferred from Bulk Storage Tanks located in Naphtha Storage Tanks area.
H.S.D. H.S.D. is re required for warming up guns while while startin sta rting g the steam Generator from cold condition when steam is not available for heating FO/LSHS. HSD has the advantage of being less viscous at ambi ambient ent temperatures, requires no heating and has low sulphur contents. The low sulphur reduces the chances of low temperature corrosion in the Air Heater area, which arises due to condensation of sulphur trioxide in the flue gas in in low temperature regions. regions. Having negligible carbon residual, residual, HSD burns completely in a cold furnace and leaves no soot deposits on the colder heat transfer surfaces.
Specification of H.S.D. GCV GCV K.cal/kg K.c al/kg
-
10000
H Hv K.cal/kg
-
9500
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Sulphur Wt%
-
1.0 (Max)
Pour Po ur Point
-
6 °C (max)
The HSD pump draws oil from day tank through strainer and delivers the oil to Steam Generator. The oil pressure at pump discharge is controlled at about 20 kg/cm2 through a pressure control valve automatically. The outlet of the pressure control valve leads to day oil tank. The HSD flow at 20 kg/cm2 is controlled through a flow control valve to achieve the required oil flow for the Furnace and thus pressure reduces to 6-10 kg/cm2
After flow control control valve a Trip Trip Valve has be b een provide provided d which cut off the HSD supply to furnace in unwanted condition. This trip va]ve operates through a Signal received from Burner Management System. The HSD line after Trip Valve gets divided into two branches and supply HSD only two lower tier burners. Trip valves have been provided in each HSD burner line. The HSD burner valve operates through a signal from Burner Management System. The HSD oil in burner gets atomised automatically due to high h igh oil pressure and burns in the furnace.
L.P. Gas Ignitors To ignite the HSD and F.O. burners, the L.P. Gas Igniters have been provided with each burner. The L.P. gas stored in cylinders is led to ignitors located near F.O./HSD burners. The L.P. Gas pressure in the line is controlled through a self pressure control valve. The gas line is divided into four branches, lead to each ignitor. In each gas ignitor line, a Trip valve has been provide provided d which cut off the gas supply when when not require required. d. The signal to operate the Trip valve is received from Burner Management System. Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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FO/LSHS FO/LSHS is required for oil guns to generate steam, Preheating of this oil is necessary to reduce the viscosity for easy transportation and better atomisation.
Specification of F.O. and LSHS F.O.
LSHS
GCV K.Cal/kg
10,000
10,000
LHV K.Cal/kg
9,500
9,500
Sulphur Wt%
4.5
1.0
Pour point °C
37
72
0.95
0.93 0.93
Sp. Gravity at 15°C Viscosity Viscosity
170 Cst Cst
23.87 23.87 Cst Cst
at 50°C
at 95°C
Furnace oil/LSHS from storage tank is led to the oil pump located near day oil tanks at a temperature temperatu re of 50°C to 6.0°C. 6.0°C. This temperature is achieved by using a steam coil heater located in the bottom of the oil tank. The F0/LSHS oil passes through the oil strainer on the suction side of the high pressure gear pump and gets pressurized to about 12 kg/cm2 required for atomization. The pressure control valve, connected to the delivery side of the pump pump controls the oil header pressure automatically automatically and leads to the day tank. FO/LSHS FO/LSHS from the delivery side of of the pump Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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enters the oil heater where it is heated from pumping temperature to about 110°C. The outlet temperature of this oil from the oil heater is automatically maintained at a constant value by automatic temperature regulating valve mounted on the steam supply line to the heater. The temperature regulating valve controls the quantity of steam to heater to maintain the heater outlet oil oil temperature. The flow of FD FD/LSHS /LSHS at 110deg C is controlled through a flow control valve. The oil pressure after flow control valve reduces to 6-8.5 kg/cm2. The flow control valve operates through a signal fed from Automatic Combustion Control System. After this flow control valve there is a Trip valve, which cut off the oil supply to the furnace in unwanted conditions. This valve is operated through a signal from Burner Management System. The main oil header divided into four branches to supply Fuel oil to four branches. In each burner oil line, one Trip Valve has been provided, which cut off the Fuel oil supply to the individual burner, when required. This Trip valve operates through a signal received from Burner Management System. After this Trip Trip valve oil flows to burner, where it gets automise automised d with medium pressure steam and burns in furnace.
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The air is required for combustion of fuel in Steam Generating Unit. To meet this requirement of air in Steam Generator two centrifugal type forced Draft Draft Fans Fans (F.D. fan) have have been provided. One fan is is driven by electrical motor while other by steam turbine. During the startup of the SG, motor driven fan is taken in service in case steam is not available to drive the turbine.
The F.D. fan sucks the air from atmosphere and discharge to the furnace at a pressure of 90 mm- 550 mm water gauge. The quantity of air is controlled by the vane provided at the suction side of the F.D. fan. Two air heaters have been provided in the discharge duct of F.D. fans, which are known as Steam Coil Heater and Gas Air Heater. These Air Heaters raise the air temperature to 145°C. The hot air helps in proper combustion of fuel.
The Forced Draft fans supply cold atmospheric air through Steam Air Heater and Gas Air Heater to the furnace for combustion of fuel. The Gas Air Heater takes takes up waste heat heat from the flue gas of Steam St eam Generator Generator and adds it to the combustion air.
The Counter Current parallel flow of the gas and atmospheric air results in good transfer of heat, thus bringing coldest metal elements in contact with less hot flue gas. gas. If metal temperature temperature is too low, there there is a chance of condensation of corrosive gas on the elements of GAH and consequent corrosion of the heating elements. Generally during cold season and low load operating condition, such troubles are encountered. To prevent or reduce chances of this type of corrosion, the inlet temperature of cold air to Gas Air Heater is controlled by heating it in a steam air heater. The low Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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pressure steam is passed through the heating coils and F.D. fan discharge air is allowed to flow over it. The steam gives up heat, gets condensed and the condensate is drained through a trap. The cold atmospheric air at about 20 to 40°C while passing over the steam coil picks picks up heat and gets heated upto about 50°C. Thus when air of 50°C is allowed at cold end of Gas Air Heater, there is no condensation of corrosive gases and so chance of chemical corrosion is reduced.
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Since there is continuous withdrawal of steam and continuous return of condensate to the boiler, losses due to blow-down and leakages have to be made up for so as to maintain the desired water level in the boiler steam drum. For this, continuous make-up water is added to the boiler water system. The impurities in the raw water input to the plant generally consist of calcium and magnesium salts which impart hardness to the water. Hardness Hardness in the make-up water to the boiler will form deposits deposits on the tube water surfaces which will lead to overheating and failure of the tubes. Thus, the salts have to be removed from the water and that is done by a water demineralising treatment plant (DM). A DM plant generally consists of cation, anion and mixed bed exchangers. The final water from this process consists essentially of hydrogen ions and hydroxide ions which is the ch chemi emical cal composition composition of pure pure water. The DM water, being very pure, becomes becomes highly corrosive corrosive once it absorbs absorbs oxygen oxygen from the atmosphere because of its very high affinity for oxygen absorption. The capacity of the DM plant is dictated by the type and quantity of salts in the raw water input. However, some storage is essential as the DM plant may be down for maintenance. For this purpose, a storage tank is installed from which DM water is continuously withdrawn for boiler make-up. The storage tank for DM water is made from materials not affected by corrosive water, such as PVC. The piping and valves are generally of stainless steel. Sometimes, a steam blanketing arrangement or stainless steel doughnut float is provided on top of the water in the tank to avoid contact with atmospheric air. DM water make-up is generally added at the steam space of the surface condenser (i.e., the vacuum side). This arrangement not only sprays the water but also DM water gets deaerated, with the dissolved gases being removed by the ejector of the condenser itself.
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A heat recovery recovery steam generator or HRSG is an energy energy recovery recovery heat exchanger that recovers heat from a hot gas stream. It produces steam that can be used in a process (cogeneration) or used to drive a steam turbine (combined cycle).
General usage A common common application application for an HRSG HRSG is in a combined-cycle combined-cycle power station, station, where hot hot exhaust exhaust from a gas turbine turbine is fed to an HRSG HRSG to generate generate steam which in turn drives drives a steam turbine. turbine. This This combination combination produces produces electricity more efficiently than either the gas turbine or steam turbine alone. Another application for an HRSG is in diesel engine combined cycle power plants, where hot exhaust from a diesel engine, as primary source of energy, is fed to an HRSG to generate steam which in turn drives a steam turbine. The HRSG is also an important component in cogeneration plants. Cogeneration plants typically have a higher overall efficiency in comparison to a combined cycle plant. This is due to the loss of energy associated with the steam turbine.
HRSGs HRSGs consist of four major components: the economizer, evaporator, superheater and water preheater. The different components are put together to meet the operating requirements of the unit. Modular HRSGs can be categorized by a number of ways such as direction of exhaust gases flow or number of pressure levels. Based on the flow of exhaust gases, HRSGs are categorized into vertical and horizontal types. In horizontal type HRSGs, exhaust gas flows horizontally over vertical tubes whereas in vertical type HRSGs, exhaust gas flow vertically over horizontal tubes. Based on pressure levels, HRSGs can be categorized into single pressure and multi pressure. Single pressure HRSGs have only one steam drum and steam is generated at single pressure level whereas multi pressure HRSGs employ two (double pressure) or three (triple pressure) Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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steam drums. As such triple pressure HRSGs consist of three sections: an LP (low pressure) section, a reheat/IP (intermediate pressure) section, and an HP (high pressure) section. Each section has a steam drum and an evaporator section where water is converted to steam. This steam then passes through superheaters to raise the temperature and pressure past the saturation point.
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A gas turbine, turbine, also called a combustion combustion turbine, turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream tur tu rbine, and a combust combustion ion chamber chamber in-between. in-bet ween.
Energy is added to the gas stream in the combustor, where fuel is mixed with air and ignited. ignited. In the high high pressure environment environment of the combustor, combustor, combustion of the fuel increases the temperature. The products of the combustion are forced into the turbine section. There, the high velocity and volume of the gas flow is directed through a nozzle over the turbine's blades, spinning the turbine which powers the compressor and, for some turbines, drives their mechanical output. The energy given up to the turbine comes from the reduction in the temperature and pressure of the exhaust gas.
Energy can be extracted in the form of shaft power, compressed air or thrust or any combination of these and used to power aircraft, trains, ships, generators, or even tanks.
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Gases passing through an ideal gas turbine undergo three thermodynamic processes. These are isentropic compression, isobaric (constant pressure) combustion and isentropic expansion. Together these make up the Brayton cycle. In a practical gas turbine, gases are first accelerated in either a centrifugal or axial compressor. These gases are then slowed using a diverging nozzle known as a diffuser; these processes increase the pressure and temperature of the flow. In an ideal system this is isentropic. However, in practice energy is lost to heat, due to friction and turbulence. Gases then pass from the diffuser to a combustion chamber, or similar device, where heat is added. In an ideal system this occurs at constant pressure (isobaric heat addition). As there is no change in pressure the specific volume of the gases increases. In practical situations this process is usually accompanied by a slight loss in pressure, due to friction. Finally, this larger volume of gases is expanded and accelerated by nozzle guide vanes before energy is extracted by a turbine. In an ideal system these are gases expanded isentropically and leave the turbine at their original pressure. In practice this process is not isentropic as energy is once again lost to friction and tur t urbulenc bulencee. If the device has been designed to power a shaft as with an industrial generator or a turboprop, the exit pressure will be as close to the entry pressure as possible. In practice it is necessary that some pressure remains at the outlet in order to fully expel the exhaust gases. In the case of a jet engine only enough pressure and energy is extracted from the flow to drive the compressor and other components. components. The remaining remaining high pressure gases are accelerated to provide a jet that can, for example, be used to propel an aircraft. As with all cyclic cyclic heat engines, engines, higher higher combustion combustion temperature temperaturess can allow for greater efficiencies. However, temperatures are limited by ability of the steel, nickel, ceramic, or other materials that make up the engine to Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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withstand high temperatures temperatures and stresses. stresses. To comba c ombatt this many turbines turbines feature complex blade cooling systems. As a general general rule, the smaller smaller the engine engine the higher higher the rotation rotation rate of the shaft(s) must be to maintain tip speed. Blade tip speed determines the maximum pressure ratios that can be obtained by the turbine and the compressor. This in turn limits the maximum power and efficiency that can be obtained by the engine. In order for tip speed to remain constant, if the diameter of a rotor is reduced by half, the rotational speed must double. For example large Jet engines operate around 10,000 rpm, while micro turbines spin as fast as 500,000 rpm. Mechanically, gas turbines can be considerably less complex than internal combustion piston engines. Simple turbines might have one moving part: the shaft/compressor/turbine/alternative-rotor assembly (see image above), not counting the fuel system. However, the required precision manufacturing for components and temperature resistant alloys necessary for high efficiency often make the construction of a simple turbine more complicated than piston engines. More sophisticated turbines (such as those found in modern jet engines) may have multiple shafts (spools), hundreds of turbine blades, movable stator blades, and a vast system of complex piping, combustors and heat exchangers. Thrust bearings and journal bearings are a critical part of design. Traditionally, they have been hydrodynamic oil bearings, or oil-cooled ball bearings. These bearings are being surpassed by foil bearings, which have been b een successfully used in micro turbines and auxiliary auxiliary power p ower units.
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Model series 5000, Simple-cycle, Single-shaft, Heavy duty Gas Turbine with Diesel start
Industrial gas turbines differ from aeroderivative in that the frames, bearings, and blading are of heavier construction. Industrial gas turbines range in size from truck-mounted mobile plants to enormous, complex systems. They can be particularly efficient —up to 60%— when waste heat from the gas turbine is recovered by a heat recovery steam generator to power a conventional steam turbine in a combined cycle configuration. They can also be run in a cogeneration configuration: the exhaust is used for space or water heating, or drives an absorption chiller for cooling or refrigeration. Such engines require a dedicated enclosure, both to protect the engine from the elements and the t he operators operators from f rom the noise. The construction process for gas turbines can take as little as several weeks to a few months, months, compare compared to years years for base load power plants. Their other main advantage is the ability to be turned on and off within minutes, supplying power during peak demand. Since single cycle (gas Ashish Ashish Lal, I.P.E. I.P.E . 09113009 09113009
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turbine only) power plants are less efficient than combined cycle plants, they are usually used as peaking power plants, which operate anywhere from several hours per day to a few dozen hours per year, depending on the electricity demand and the generating capacity of the region. In areas with a shortage shortage of ba b ase load and load load following following power power plant plant capacity capacity or low fuel costs, a gas turbine power plant may regularly operate during most hours of the day. A large single cycle gas turbine typically produces 100 to 400 megawatts of power and has 35–40% 40% thermal t hermal efficiency.
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The study of the Steam & Power Generation Plant at Iffco Aonla was an interactive as well as practical industrial experience. The production of power from the fuel, the heat recovery system, boiler configurations, turbine working, condenser working, and many more processes were made clear with the visual and practical analysis. Apart from the theoretical theoretical knowledge knowledge g ained in the classroom, classroom, the industrial exposure was an opportunity to have real life shop-floor experience. I express my gratitude to Mr. D. Kalia, D.G.M.(Training), IFFCO AONLA for his beneficial guidance and, for sharing his precious practical experience in the field. I am also very thankful to Rajeev Trehan sir, and Dr. R.K.Garg, for their supervision sup ervision and the opportunity provided to us.
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Steam and Power Generation Plant (S.P.G.P.) Manual, IFFCO Aonla, Technical Library.
www.wikipedia.com
www.iffcoaonla.com
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