Mejia Thermal Power Station


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Mejia Thermal Power Station is located at Durlovpur, Bankura, 35 km from Durgapur city in West Bengal. The power plant is one of the coal based power plants of DVC

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Mejia Thermal Power Station

  1. 1. MEJIA THERMAL POWER STATION Presentation By:- SAGNIK CHOUDHURY EE, 4th year GURU NANAK INSTITUTE OF TECHNOLOGY Thermal Power Plant Industrial Training
  2. 2. Contents 1.Introduction 2.Overview of Mejia Thermal Power Plant 3.Power plant layout 4.Main and Auxiliary Equipment 5.Stepwise operation
  3. 3. Introduction A Thermal Power Plant converts the heat energy of coal into electrical energy. Coal is burnt in a boiler which converts water into steam. The expansion of steam in turbine produces mechanical power which drives the alternator coupled to the turbine.Thermal Power Plants contribute maximum to the generation of Power for any country . Thermal Power Plants constitute 75.43% of the total installed captive and non-captive power generation in India . In thermal generating stations coal, oil, natural gas etc. are employed as primary sources of energy.
  4. 4. Overview of MTPS  Damodar Valley Corporation was established on 7th July 1948.  The MTPS under the DVC is the second largest thermal plant in West Bengal.  It has the capacity of 2340 MW with 4 units of 210 MW each, 2 units of 250 MW each & 2 units of 500 MW each.  With the introduction of another two units of 500 MW that is in construction it will be the largest in West Bengal.  Mejia Thermal Power Station is located in the outskirts of Raniganj in Bankura District.  The total power plant campus area is surrounded by boundary walls and is basically divided into two major parts, first the Power Plant area itself and the second is the Colony area for the residence and other facilities for MTPSs ͛͛͛employees.
  5. 5. Diagram of a typical coal-fired thermal power station
  6. 6. General Layout of Thermal Power Station
  7. 7. General Layout of Thermal Power Station
  8. 8. Major electrical components of Power Plant:
  9. 9. Main and Auxiliary Equipments 1. Coal handling plant 2. Pulverizing plant 3. Draft fans 4. Boiler 5. Ash handling plant 6. Turbine 7. Condenser 8. Cooling towers and ponds 9. Feed water heater 10. Economiser 11. Superheater and Reheater 12. Air preheater
  10. 10. Coal handling plant •The function of coal handling plant is automatic feeding of coal to the boiler furnace. • A thermal power plant burns enormous amounts of coal. •A 200MW plant may require around 2000 tons of coal daily
  11. 11. Pulverising plant In modern thermal power plant , coal is pulverised i.e. ground to dust like size and carried to the furnace in a stream of hot air. Pulverising is a means of exposing a large surface area to the action of oxygen and consequently helping combustion. Pulverising mills are further classified as: 1. Contact mill 2. Ball mill 3. Impact mill
  12. 12. ASH HANDLING PLANT  The percentage of ash in coal is 5% in good quality coal & about 40% in poor quality coal.  Power plants generally use poor quality of coal , thus amount of ash produced by it is quite large. A modern 1000MW plant produces about 4800 tons of ash daily.  The stations use some conveyor arrangement to carry ash to dump sites.
  13. 13. Boiler  Boiler is an enclosed vessel in which water is heated and circulated until the water is turned in to steam at the required pressure.  Coal is burned inside the combustion chamber of boiler. The products of combustion are nothing but gases. These gases which are at high temperature vaporize the water inside the boiler to steam.  Boilers are classified as: 1. Fire tube boilers 2. Water tube boilers 3. Superheater 4. Reheater
  14. 14. Boiler Operation
  15. 15. • The steam produced in the boiler goes to the steam drum and is then piped through the primary, platen and final super-heaters where it reaches the outlet temperature of 560 C and 160 ksc pressure • At this point in the process they have now turned the water into a very powerful source of energy • This rotates the turbine to which generator is on the other end • From rotating generator electricity is produced
  16. 16. Reheater Some of the heat of superheated steam is used to rotate the turbine where it loses some of its energy. The steam after reheating is used to rotate the second steam turbine where the heat is converted to mechanical energy. This mechanical energy is used to run the alternator, which is coupled to turbine , there by generating electrical energy.
  17. 17. Condenser  Steam after rotating steam turbine comes to condenser. Condenser refers here to the shell and tube heat exchanger (or surface condenser) installed at the outlet of every steam turbine in Thermal power stations of utility companies.  The purpose is to condense the outlet (or exhaust) steam from steam turbine to obtain maximum efficiency and also to get the condensed steam in the form of pure water, otherwise known as condensate, back to steam generator or (boiler) as boiler feed water.  Condensers are classified as: i)Jet condensers or contact condensers, ii)Surface condensers.
  18. 18. Primary Air Fan • Air to blow the coal from the mill to the boiler, called the primary air, is supplied by a large fan driven by a variable speed motor • When mixed with a stream of air the powdered coal behaves more like a gas than a solid • Primary air does two jobs – heating the coal powder and secondly lifting it into the furnace through pipelines
  19. 19. Forced Draught (FD) Fan • Each unit shall have two forced draught fans • The fans draw warm air from the top of the boiler house through large air heaters becoming the primary and secondary air used for the boiler combustion process • The air heater warms the incoming air by transferring heat energy from the outgoing flue gases Air Pre-Heater (APH) • The air heaters use the remaining heat energy in the flue gas to heat up the combustion air for the boiler • Efficiency is increased by using this heat that would otherwise go up the chimney. The air temperature leaving the air heaters is at 300 C • The air heaters use the remaining heat energy and efficiency is increased by using this heat that would otherwise go up the chimney
  20. 20. Induced Draught (ID) Fan • Two induced draught fans draw gases out of the boiler • The gas has already passed through the air heaters and precipitators before it has reached these fans • The heat from the flue gases or smoke is used in the air heaters to heat up the primary and secondary air Chimney • The chimney is 275 meters' high and 50,000 tonnes of reinforced concrete were used to make it • It consists of flues each of which serve typically two or three boilers (two units)
  21. 21. • Each boiler has 4 passes with 7 fields each containing high voltage electrodes • These attract the dust or ash from the flue gases • At regular intervals the electrodes are rapped with motor-driven hammers and the PFA falls into hoppers below • In a year 1,000 MW station may generate 1.5 million ton of ash • This is one of the ways to clean up the flue gases or smoke sent up the chimney • Secondly this ash is used by construction industry for use in building materials (bricks !!, Cement Fillers) Electro-Static Precipitator
  22. 22. Cooling Towers  The condensate (water) formed in the condenser after condensation is initially at high temperature. This hot water is passed to cooling towers.  It is a tower- or building-like device in which atmospheric air (the heat receiver) circulates in direct or indirect contact with warmer water (the heat source) and the water is thereby cooled.  Types Of Cooling Tower- 1. Wet cooling tower 2. Dry cooling tower
  23. 23. Economizer  Flue gases coming out of the boiler carry lot of heat. Function of economizer is to recover some of the heat from the heat carried away in the flue gases up the chimney and utilize for heating the feed water to the boiler.  It is placed in the passage of flue gases in between the exit from the boiler and the entry to the chimney.  The use of economizer results in saving in coal consumption, increase in steaming rate and high boiler efficiency but needs extra investment and increase in maintenance costs and floor area required for the plant.
  24. 24. Steam Turbine  A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft.  The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process.
  25. 25. Alternator  An alternator is an electromechanical device that converts mechanical energy to alternating current electrical energy. Most alternators use a rotating magnetic field. Different geometries - such as a linear alternator for use with sterling engines - are also occasionally used. In principle, any AC generator can be called an alternator, but usually the word refers to small rotating machines driven by automotive and other internal combustion engines.
  26. 26. Transformers  It is a device that transfers electric energy from one alternating-current circuit to one or more other circuits, either increasing (stepping up) or reducing (stepping down) the voltage.  Transformers act through electromagnetic induction; current in the primary coil induces current in the secondary coil. The secondary voltage is calculated by multiplying the primary voltage by the ratio of the number of turns in the secondary coil to that in the primary.
  27. 27. SWITCH YARD
  28. 28. SWITCH YARD  Placed where switching operation of power distribution is performed.  Air insulated switch yard of 220KV-400KV are used. Main Components of Switch Yard:  Circuit breaker  Isolator  Lightening arrester  Bus bar  Current Transformer  Potential Transformer
  29. 29. CIRCUIT BREAKER  These are used for automatic switching during normal or abnormal conditions . Specification: Manufacturer ABB Limited Type of Circuit Breaker SF6 Rated Voltage 245 KV Rated Current Under Site Condition of 40 0C Under Site Condition of 50 0C 4000 A 2000 A Rated Frequency 50 Hz
  30. 30. ISOLATOR  These are used to disconnect transmission line under no-load condition for safety, isolation and maintenance. Specification: Rated current for site conditions 2000 A Rated Voltage 245 KV Rated Frequency 50 Hz Operating time of Isolator Less than 12 sec.
  31. 31. LIGHTENING ARRESTOR  These are used to discharge lightning over voltages and switching over voltages to earth. Specification: Manufacturer Crompton Greaves Ltd, Nasik Model No. ZLA X 25 C Ref. Standard IEC 99 – 4. 1991 Rated Frequency 50 Hz Max. Leakage Current 5 mA
  32. 32. BUS BAR The conductors to which several incoming and outgoing lines are connected. They are made up of Cu & Al, The incoming and outgoing cables are provided for metering purpose.
  33. 33. CURRENT TRANSFORMER These are used to step-down currents for measurement, control & protection. Current transformers are used extensively for measuring current and monitoring the operation of the power grid.
  34. 34. VOLTAGE TRANFORMER VT measure voltage and this parameter used for protection of system. For high voltage CVT (capacitive voltage transformer) is used instead of VT and capacitors play divider role. We can also use these capacitors for PLC system.
  35. 35. Stepwise Operation of Thermal Power Plant 1) First the pulverized coal is burnt into the furnace of boiler. 2) High pressure steam is produced in the boiler. 3) This steam is then passed through the super heater, where it further heated up. 4) This supper heated steam is then entered into a turbine at high speed. 5) In turbine this steam force rotates the turbine blades that means here in the turbine the stored potential energy of the high pressured steam is converted into mechanical energy. 6) After rotating the turbine blades, the steam has lost its high pressure, passes out of turbine blades and enters into a condenser. 7) in the condenser the cold water is circulated with help of pump which condenses the low pressure wet steam. 8) This condensed water is then further supplied to low pressure water heater where the low pressure steam increases the temperature of this feed water; it is then again heated in a high pressure heater where the high pressure of steam is used for heating. 9) The turbine in thermal power station acts as a prime mover of the alternator.
  36. 36. Efficiency of Thermal Power Station or Plant The overall efficiency of a thermal power station or plant varies from 20% to 26% and it depends upon plant capacity.
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