A Compendium of Thermal Power Plant

1. April 11, 2010 Power Generation in Typical Coal Based Power Plant - Er. Sandip De MBA, B.E. Mechanical

2. Different systems The Process Different Stages – Project, Commissioning, Operations and Maintenance. O&M vs. Non-O&M Coal systems Water systems Furnace systems TG systems Ash systems Power evacuation systems Support systems --Technical and --Non-technical Differences in Gas based and Hydro power projects

3. 3 POWER STATION

4. 1. Coal-how much and how 21. Rotor 2. CHP 22. Stator 3. Coal Conveyor 23. Generator Transformer 4. Boiler Coal Bunker 24. Condenser 5. Bucket Wheel Machine25. Condensate Extraction Pump 6. Coal Feeder 26. Low Pressure Feed Heat 7. Pulverizing Mill 27. Deaerator 8. Primary Air Fan 28. Boiler Feed Pump 9. Boiler light-up 29. High Pressure Feed Heaters 10. Boiler 30. Economizer 11. Forced Draught Fan 31. Steam Drum 12. Air Heater 32. Cooling Tower 13. Electrostatic Precipitator 33. Circulating Water Pumps 14. Induced Draught Fan 34. Circulating Water Make-Up Pumps 15. Main Chimney 35. FGD 16. Super heater 36. Finally.. 17. High Pressure Turbine 18. Boiler Reheater 19. Intermediate Pressure Turbine 20. Low Pressure Turbine

6. Loading place into train

7. Train to the location

8. Unloaded at the location (Wagon Tripler)

9. Transported through conveyors into bunkers

10. From bunkers into mills (Pulverizes)

11. Powdered, put into furnace and burnt

13. To make sure to generate electricity when you want to, you have to make sure the coal is in the right place at the right time

14. Typically 15 days stock is maintained at site

17. Power station coal is not as lumpy as coal used in the home. Typically around half of it is less than 12.5 millimeters across and 95% is less than 50 millimeters

19. Water is sprayed on coal to stop them from getting burnt when in storage yard due to internal heat up or sun heat

20. Coal when powdered is heated and being lifted by hot air that is sent into the “mills”

22. It uses a conveyor to move coal through a fixed gap at a precisely controlled speed

23. Varying the speed controls the amount of coal supplied to the boilers

24. These are precision bits of equipment that have to move exact amounts of coal.

26. Inside the mills, ten giant hollow steel rollers crush the coal into a fine powder

27. Crushing the coal into a fine powder makes it easier to burn it more completely

29. When mixed with a stream of air the powdered coal behaves more like a gas than a solid

31. This is followed by heavy furnace oil (HFO)

32. Once a stable flame is established the coal/air mix is blown through the burner where it lights spontaneously

33. The oil are then shut off. Burner position, coal flow and air flow are controlled to achieve desired output of temperature, pressure and flow and hence the electricity

35. The boiler is lined with steel tubing in which pure boiler feed water is turned to steam by the heat created from the burning of coal

36. Each boiler is as high as 60 mts and weighs about 40,00,000 kg (4000 T)

37. Inside the boiler there is enough steel tubing to stretch the 500 kilometres and they are joined together by about 20,000 joints

39. 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

41. 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

43. These attract the dust or ash from the flue gases

44. At regular intervals the electrodes are rapped with motor-driven hammers and the PFA falls into hoppers below

45. In a year 1,000 MW station may generate 1.5 million ton of ash

46. This is one of the ways to clean up the flue gases or smoke sent up the chimney

48. The gas has already passed through the air heaters and precipitators before it has reached these fans

51. At this point in the process they have now turned the water into a very powerful source of energy

52. This rotates the turbine to which generator is on the other end

56. From here the steam goes straight to the next section of the turbine set

57. The steam has expanded and has less energy when it enters this section, so here the turbine blades are bigger than those in the high pressure turbine

59. To get the most work out of the steam, exhaust pressure is kept very low, just 50 mille-bar above a complete vacuum

62. Together the rotor and stator are known as the generator. The stator weighs 300 tonnes

63. Electricity is generated at over 80 times the voltage in our homes

65. Each 1 MW generates about 8 million units and gives about Rs 2 crores revenue every year

67. Here it is condensed back into water and pumped back to the boiler

70. The pump is driven by a steam turbine or an electric motor

73. Water from the high pressure feed heaters is heated in the economiser from 250°C to 290°C before it continues to the steam drum

75. From here the water flows by natural circulation through downpipes into the boiler

76. Saturated steam collects here ready to go to the superheater

78. This breaks the water up into a very fine spray, increasing the surface area of the water droplets making it easier to cool

79. The cooling tower is designed as a natural draught chimney, drawing cold air from outside through the falling water

80. Cool water is collected in pond at the bottom of the cooling tower

83. It enters the lowest part of the absorber and is further cooled by water used to wash the inlet duct to prevent a build up of solids

84. The main SO2 absorption process, and the washing out of any remaining pulverised fuel ash, occurs as the gas is ‘scrubbed’ by the re-circulating limestone slurry

85. This is taken from the bottom of the absorber and is sprayed downwards from nozzles arranged at five separate levels in the absorber tower

86. As a result of the process chemistry, the recirculating slurry becomes predominantly gypsum and a portion is continuously pumped away for gypsum separation and the removal of water using a hydro-cyclone system

88. The generated power stepped upto 4 lakh volts is transmitted and handed over to distributors at lower voltages