Thermal Power Station

1. Thermal Power Station • Electric power systems • A complex assemblage of equipment and circuits for Generating, Transmitting,  Transforming, and Distributing electrical energy. • Electricity in the large quantities required to supply electric power systems is produced in generating stations, commonly called  • power plants.  • Such generating stations, however, should be considered  as conversion facilities in which the heat energy of fuel  (coal, oil, gas, or uranium) or the hydraulic energy of falling water is converted to electricity. 

2. Thermal Power Station Sources of Energy: Sources of Energy can be categorized into 2 types 1. Renewable Sources of Energy 2. Non- Renewable Sources of Energy

3. Thermal Power Station • Definition of Power Plant: • A power station also referred as generating station, power plant, power house is an industrial facility for the generation of electric power. • Classification of Power Plants: • Power plants are classified by the type of fuel and the type of prime mover installed. • On the basis of primary fuel • In Thermal power stations, mechanical power is produced by a heat engine, which transforms thermal energy, often from combustion of a fuel, into rotational energy.

4. Thermal Power Station • Nuclear power plants use a nuclear reactor's heat to operate a steam turbine generator. • Fossil fuel powered plants may also use a steam turbine generator or in the case of Natural gas fired plants may use a combustion turbine. • Geothermal power plants use steam extracted from hot underground rocks. • Renewable energy plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.

5. Thermal Power Station • On the basis of prime mover installed. • Steam turbine plants use the pressure generated by expanding steam to turn the blades of a turbine. • Gas turbine plants use the heat from gases to directly operate the turbine. Natural-gas fuelled turbine plants can start rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost than base-loaded plants.

6. Thermal Power Station • Hydro turbine plants capture the energy of falling water to generate electricity. A turbine converts the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy. • Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and steam turbine which use the exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and most new base load power plants are combined cycle plants fired by natural gas.

7. Thermal Power Station Coal-fired Power Stations in Andhra Pradesh 1.Dr Narla Tata Rao Thermal Power Station-Vijayawada 2. Rayalaseema Thermal Power Station-Kadapa 3.Sri Damodaram Sanjeevaiah Thermal Power Station-Krishnapatnam 4. Simhadri Super Thermal Power Station-Visakhapatnam District

8. Thermal Power Station • Dr Narla Tata Rao Thermal Power Station-Vijayawada • Dr. Narla Tata Rao Thermal Power Station (Vijayawada Thermal Power Station) is a unique one in the country, unique in its layout and numerous facilities provided for easy operation and maintenance. • Dr. Narla Tata Rao Thermal Power Station (Vijayawada Thermal Power Station) complex consists of four stages.  For Stage-I, II & III each stage consists of 2 x 210 MW Units and for Stage-IV the unit is of 500 MW rating. The total capacity of the station is 1760MW.

9. Thermal Power Station • The large reservoir created by the PRAKASAM Barrage provides an efficient Direct Circulation Cooling Water System and also other requirements of the plant. • Originally the Dr. Narla Tata Rao Thermal Power Station (Vijayawada Thermal Power Station) is linked to Singareni Collieries Company Limited (S.C.C.L.) Khammam District for supply of coal. Dr.NTTPS, Stage-II, III & IV are linked to Talcher Coal Fields in Orissa to meet the increased demand.

10. Thermal Power Station

11. Thermal Power Station • Rayalaseema Thermal Power Station-Kadapa • Rayalaseema Thermal Power Station is located at Kadapa.  The power plant is one of the coal based power plant. It comprises 5 units, each 210 MW. • Rayalaseema Thermal Power Project is a 1050MWcoal plant. Rayalaseema Thermal Power Station is linked to Singareni Collieries Company Limited (S.C.C.L.) Khammam District for supply of coal.

12. Thermal Power Station • 3. Sri Damodaram Sanjeevaiah Thermal Power Station-Krishnapatnam • Sri Damodaram Sanjeevaiah Thermal Power Station is located in Nelatur Village, near Krishnapatnam.  • The power plant is one of the coal-based power plants. The proposed capacity of plant is 1600 MW. • The Power station is designed for blended coal in the ratio of 70% washed domestic coal from Talcher Coalfield to 30% imported coal. • Sea water is proposed for cooling purpose and potable water by desalination.

13. Thermal Power Station • 4. Simhadri Super Thermal Power Station-Visakhapatnam District • Simhadri Super Thermal Power Plant is a coal-fired power plant located in the Visakhapatnam district. • The power plant is one of the coal fired power plants of NTPC, a Government of India enterprise. • The coal for the power plant is sourced from Kalinga Block of Talcher Coal fields in Odisha. • The plant is a national asset, and power generated is shared between multiple states, as the operator is national.

14. Thermal Power Station • Power generated by units 1 and 2, making up for 1,000 MW, is dedicated to power distribution companies owned by the Government of Andhra Pradesh. The remainder 1,000 MW, generated by units 3 and 4, is allocated to the states of Odisha, Tamil Nadu, and Karnataka. • Coal for NTPC Simhadri is sourced from Talcher Coal Fields, Odisha, and transported by East Coast Railway (ECoR), over the Kolkata-Chennai trunk line, with a spur heading towards the plant at Duvvada. It uses fresh water sourced from the Yeluru Canal as working fluid (steam which turns the turbines).

15. Thermal Power Station For cooling, however, the plant uses seawater pumped in from the Bay of Bengal. Seawater, with its salt content, is unfit to be used as working fluid, without desalination.

16. Thermal Power Station • Coal: • Coal is carbonaceous solid black or brownish black sedimentary rock matter vegetation, biological changes originated from the accumulation of partially decomposed vegetation. • Biological changes and subsequent effects of temperature and pressure altered these deposits to coal. • Coal is composed of chiefly carbon and other elements like hydrogen, sulphur, oxygen, nitrogen, moisture and noncombustible inorganic matter containing, silica, iron, calcium, magnesium, mercury etc.

17. Thermal Power Station • Coal has a wide range of composition. • Calorific value of the coal vary widely from one coal reserve to another coal reserve. Coal may be hard or slightly softer depending on the source. • Coal quality plays an important role in its efficient utilization as fuel and for gasification. It should have high calorific value, high carbon content with low ash content, low sulphur, low moisture, low cost. The quality of coal depends upon it rank. The coal rank is arranged in ascending order, Lignite Sub-bituminous coal • bituminous coal anthracite

18. Thermal Power Station • Calorific Value: • The calorific value is the measurement of heat or energy produced, and is measured either as gross calorific value or net calorific value. • Fuels should be compared based on the net calorific value. • The calorific value of coal varies considerably depending on the ash, moisture content and the type of coal.

19. Thermal Power Station Composition of Indian Coal and Other Countries

20. Thermal Power Station Classification of Coal: • PEAT: • Peat is not a coal truly speaking but it is the first stage of coal series. Dry peat contains 62 to 64% Carbon, and around 30% of oxygen. • Dry peat also contains a moisture content of 0.33%, Hydrogen 5.7 to 6.3%, Nitrogen 1.3 to 2.7%, and Sulphur 1%. • The calorific value of the peat (dry) varies between 5000 to 5500kcal/kg. • Applications: • It is mainly used as a fuel for domestic purpose.

21. Thermal Power Station Classification of Coal: • LIGNITE: • The composition of lignites vary according to metamorphosis, which the lignin of the plant has undergone. • Lignites may be black or brown and earthy having woody structure. They readily break or disintegrate when air dried. • The dried material contains 60 to 75% of carbon and 20 to 25% oxygen with moisture content of 15 to 20% . Their calorific value ranges widely from 6000 to 7000kcal/kg. • Applications: • Lignite is used in the production of town gas and as pulverized fuel in steam locomotives.

22. Thermal Power Station Classification of Coal: • BITUMINOUS COAL: • The bituminous coal is formed from lignitous coal. They contain 84 to 91.2% of carbon. • The calorific value is about 8000 to 8500kcal/kg. • Applications: • It has a variety of uses and is a general purpose coal of house hold and industrial purposes. • They are of Two Types: • Sub-Bituminous Coal • Semi-Bituminous Coal

23. Thermal Power Station Classification of Coal: • BITUMINOUS COAL: • Sub-Bituminous Coal: • The carbon content in them is 75 to 83% and 10 to 20% of oxygen, but contains high moisture. • They are black in color and have a calorific value of about 7000kcal/kg. • 2.Semi-Bituminous Coal: • The carbon content in them is 90 to 93% and 2 to 4% of oxygen. Applications: • They are used in steam raising, domestic stoves, etc.,

24. Thermal Power Station Classification of Coal: • ANTHRACITE COAL: • It is the highest rank coal, containing over 93% carbon. • It is one of the most valuable coal and least widely distributed. • It is a valuable fuel for use in stones because of its high density. • It burns almost without smoke. • They have a calorific value of about 8700kcal/kg.

25. Thermal Power Station Classification of Coal: ANTHRACITE COAL: Applications: The chief industrial uses of anthracite are steam raising, domestic stoves and central heating etc.,

26. Thermal Power Station

27. Layout of Thermal Power Station

28. Thermal Power Station

29. Thermal Power Station Main parts of the plant are 1. Coal conveyor 8. Smoke stack 2. Stoker 9. Turbine 3. Pulverizer 10. Condenser 4. Boiler 11. Transformers 5. Coal ash 12. Generator 6. Air Preheater 13. Cooling towers 7. Electrostatic Precipitator 14. High Voltage Power lines

30. Thermal Power Station • Basic Operation: • A thermal power plant basically works on Rankine cycle. • 1. Coal conveyor: This is a belt type of arrangement. With this coal is transported from coal storage place in power plant to the place near by boiler. • 2. Stoker: The coal which is brought near by boiler has to put in boiler furnace for combustion. This stoker is a mechanical device for feeding coal to a furnace.

31. Thermal Power Station • 3. Pulverizer: The coal is put in the boiler after pulverization. For this pulverizer is used. • A pulverizer is a device for grinding coal for combustion in a furnace in a power plant. • Types of pulverizer • a. Ball and Tube Mill • The tube mills are low speed machines that grind the coal with steel balls in a rotating horizontal cylinder.

32. Thermal Power Station Due to its shape only, people call it as Tube Mill and due to use of grinding balls for crushing, it is called Ball Mill. Hence, is the name Ball Tube Mill. b. Vertical Spindle Mill These are medium speed machines that include bowls mills, ring roll mills , ring and ball mills. c. Impact Mill These are High speed impact machines that use beater wheels to crush the coal

33. Thermal Power Station • 4. Boiler: • Boiler is an enclosed vessel in which water is heated and circulated until the water is turned in to steam at the required temperature and 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.

34. Thermal Power Station • Some times this steam is further heated in a superheater as higher the steam pressure and temperature the greater efficiency the engine will have in converting the heat in steam in to mechanical work. • This steam at high pressure and temperature is used directly as a heating medium, or as the working fluid in a prime mover to convert thermal energy to mechanical work, which in turn may be converted to electrical energy.

35. Thermal Power Station • Classification of Boilers: • Boilers are classified as • Fire tube boilers • Water tube boilers

36. Thermal Power Station Fire tube boilers

37. Thermal Power Station • Fire tube boilers: • In fire tube boilers hot gases are passed through the tubes and water surrounds these tubes. • These are simple, compact and rugged in construction. • Depending on whether the tubes are vertical or horizontal these are further classified as vertical and horizontal tube boilers. • In this, since the water volume is more, circulation will be poor.

38. Thermal Power Station • Fire tube boilers: • So they can't meet quickly the changes in steam demand. • High pressures of steam are not possible, maximum pressure that can be attained is about 17.5kg/sq cm. . • Due to large quantity of water in the drain it requires more time for steam raising. • The steam attained is generally wet, economical for low • pressures. • The output of the boiler is also limited.

39. Thermal Power Station Water tube boilers

40. Thermal Power Station • Water tube boilers: • In these boilers water is inside the tubes and hot gases are outside the tubes. • Feed water enters the boiler to one drum (here it is drum below the boiler). • This water circulates through the tubes connected external to drums. Hot gases which surrounds these tubes will convert the water in tubes in to steam.

41. Thermal Power Station • Water tube boilers: • This steam is passed through tubes and collected at the top of the drum since it is of light weight. • The entire steam is collected in one drum and it is taken out from there . • As the movement of water in the water tubes is high, so rate of heat transfer also becomes high resulting in greater efficiency. • They produce high pressure, easily accessible and can respond quickly to changes in steam demand.

42. Thermal Power Station • Water tube boilers: • These are also classified as vertical, horizontal and inclined tube depending on the arrangement of the tubes. • These are of less weight and less liable to explosion. • Large heating surfaces can be obtained by use of large number of tubes. • We can attain pressure as high as 125 kg/sq cm and temperatures from 315 to 575 centigrade.

43. Thermal Power Station 5. Superheater:

44. 5. Superheater: • Most of the modern boilers are having superheater and reheater arrangement. • Superheater is a component of a steam-generating unit in which steam, after it has left the boiler drum, is heated above its saturation temperature. • The superheater may consist of one or more stages of tube banks arranged to effectively transfer heat from the products of combustion. Super heaters raise the temperature of the steam which is coming out from the boiler above its boiling point.

45. 6. Condenser:

46. 6. Condenser: • Steam after rotating steam turbine comes to condenser. • These condensers are heat exchangers which convert steam from its gaseous to its liquid state, also known as phase transition. • The purpose of condenser is to condense the 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.

47. 6. Condenser: Condensers are classified as (i)Jet condensers or contact condensers (ii) Surface condensers. In jet condensers the steam to be condensed mixes with the cooling water and the temperature of the condensate and the cooling water is same when leaving the condenser; and the condensate can't be recovered for use as feed water to the boiler; heat transfer is by direct conduction.

48. Thermal Power Station

49. 6. Condenser: • In surface condensers there is no direct contact between the steam to be condensed and the circulating cooling water. • There is a wall interposed between them through heat must be convectively transferred. • The temperature of the condensate may be higher than the temperature of the cooling water at outlet and the condensate is recovered as feed water to the boiler.

50. 6. Condenser: • Both the cooling water and the condensate are separately with drawn. • Because of this advantage surface condensers are used in thermal power plants. • Final output of condenser is water at low temperature is passed to high pressure feed water heater; it is heated and again passed as feed water to the boiler. • Since we are passing water at high temperature as feed water the temperature inside the boiler does not decrease and boiler efficiency also maintained.