1. Thermal Power Plant

2. Layout of a Pulverized Fuel Power Plant

3. 11. High pressure steam turbine 20. Forced draught (draft) fan
Typical diagram of a coal-fired thermal power station
1. Cooling tower
10. Steam Control valve
19. Superheater
2. Cooling water pump
11. High pressure steam turbine
20. Forced draught (draft) fan
3. transmission line (3-phase)
12. Deaerator
21. Reheater
4. Step-up transformer (3-phase)
13. Feedwater heater
22. Combustion air intake
5. Electrical generator (3-phase)
14. Coal conveyor
23. Economiser
6. Low pressure steam turbine
15. Coal hopper
24. Air preheater
7. Condensate pump
16. Coal pulverizer
25. Precipitator
8. Surface condenser
17. Boiler steam drum
26. Induced draught (draft) fan
9. Intermediate pressure steam turbine
18. Bottom ash hopper
27. Flue gas stack

4. Working Principle Rankine Cycle (Modified Rankine Cycle)

5. Chemical Energy is converted to Heat Energy by combustion
Of fuel in Boiler.
Generator is coupled to Turbine, where mechanical energy is converted to electrical energy.
Heat energy converts water to high pressure, high temperature steam. (in Boiler)
Steam is admitted to Turbine through pipes.
In Turbine, steam expands as it is passed through number of nozzles. Heat energy is thus converted to kinetic energy.
Pump delivers condensed water from Condenser back to Boiler.
Steam exhausted from turbine condenses in Condenser, rejecting unavailable heat energy.
Steam is then passed over blades, arranged on shaft of Turbine. Shaft rotates & Kinetic energy is thus converted to mechanical work

6. Main Plants/Machines CHP : To Handle Fuel Coal WTP : To Treat Water
Boiler : Generate High Press, High Temp Steam
Turbine: As a prime mover to Generator
Generator: To Generate Electricity
Transformer : For required Voltage
Switch yard : On ward Transmission of Power

7. Introduction What is a Boiler?
The equipment used for producing and transferring steam is called Steam generators/Boilers.
Thermal energy released by combustion of fuel issued to make steam at the desired temperature and pressure.
Hot water or steam used to transfer heat to a process

8. The steam produced is used for:
1)For generating power in steam engines or steam turbines.
2)Heating the residential and industrial buildings.
3)Performing certain processes in the sugar mills, chemical and textile industries.

9. Boiler System
This system consists of
Furnace System
Super Heater System
Re heater System
LTSH System
Economizer System
Air Heater System
PA System
SA System
I D System
Mill System

10. Pressure parts of Boiler
Waterwall
Economiser
Superheater
Reheater
Boiler drum

11. Selection of boiler: The working pressure & quality of steam.
Steam generation.
Floor area available.
Accessibility for repair & inspection.
Comparative initial cost.
Erection facilities.
The fuel & water available.
Operating & maintenance cost.

12. Classification of Boilers
Boilers can be classified as follows:
According to geometric orientation of boiler
According to relative position of water and hot gases
According to location of furnace
According to method of water circulation
According to working pressure
According to mobility of boiler
According to number of tubes in the boiler

13. According to geometric orientation of boiler
If the axis of boiler is horizontal then it is called horizontal boiler.
Example:- Lancashire boiler, Locomotive boiler etc.
b) If the axis of boiler is vertical then it is called vertical boiler.
Example:- Cochran boiler .
c) If the axis of boiler is inclined then it is called inclined boiler
Example:- Babcock and Wilcox boiler.

14. According to relative position of water and hot gases
Fire tube boilers:- If the hot gases of combustion from the furnace pass through the tubes and water is surrounding the tubes is called fire tube boilers.
Example:- Cochran, Lancashire, Locomotive etc.
Water tube boiler:- If the water passes through the tubes and hot gases surrounding the tubes is called water tube boiler.
Example:- Babcock and Wilcox boiler, Stirling etc.

15. According to location of furnace
Externally fired boilers:- In this boiler the furnace is placed outside the boiler shell. Generally water tube boilers are externally fired.
Example:- Babcock and Wilcox boiler, Stirling boiler etc.
b) Internally fired boilers:- In this boiler the furnace is placed inside the boiler shell. Generally fire tube boilers are internally fired.
Example:- Lancashire, Cochran boiler etc.

16. According to method of water circulation
Natural circulation boilers:- In this boiler, water flow take place naturally, by density difference of water. The flow of water and steam are set up due to density difference resulting from difference in temperature.
Example:- Lancashire, Babcock and Wilcox boiler etc.
Forced circulation boilers:- In this boiler, water flow takes place by a pump.
Example:- Benson boiler, Lamont boiler, Velox boiler etc.

17. According to working pressure
High pressure boiler:- Boilers producing steam 80 bar and above are called High pressure boilers. Example:- Babcock and Wilcox Boiler, Lamont Boilers, Velox Boilers, Benson Boilers etc. Low pressure boiler:- Boilers producing steam Lower than 80 bar are called Low pressure boilers. Example:- Cochran Boilers, Cornish Boiler, Lancashire Boiler, Locomotive Boiler etc.

18. According to mobility of boiler
Stationary boiler:- This boiler cannot be moved easily from one place to another place. This are used in power generation or process heating in industries.
Example:- Lancashire, Babcock and Wilcox boiler.
Mobile boiler:- It is portable boiler and can be easily moved. This is used in marine and locomotive.
Example:- Locomotive boiler.

19. According to numbers of tubes in the boiler
Single tube boiler:- This boiler having only one fire or water tube for circulation of hot gases or water.
Example:- Cornish boiler.
Multi-tube boiler:- This boiler having two or more fire or water tubes for the circulation of hot gases or water.
Example:- Locomotive, Cochran, Lancashire, Babcock and Wilcox boiler.

20. Boiler mainly classified as: a. fire tube b. water tube

21. A. FIRE TUBE BOILERS

22. B. WATER TUBE BOILERS

23. Comparison between Fire-tube & water-tube boilers
S no.
Particulars
Fire tube boilers
Water tube boilers 1.
Mode of firing
Internally fired
Externally fired 2.
Rate of steam production
lower
Higher 3.
construction
Difficult
Simple 4.
transportation 5.
Treatment of water
Not so necessary
More necessary 6.
Operating pressure
Limited to 16 bar
Under high pressure as 100 bar 7.
Floor area
More floor area
Less floor area 8.
Shell diameter
Large for same power
Small for same power 9.
explosion
Less
More
10.
Risk of bursting
lesser
More risk

24. TYPES OF FIRE TUBE BOILERS
There are mainly five types of fire tube boilers :
1) Simple vertical boiler
2) Cochran boiler
3) Cornish boiler
4) Lancashire boiler
5) Locomotive boilers

25. 1) SIMPLE VERTICAL BOILER
It consist of a cylindrical shell, the greater portion of which is full of water & remaining is the steam space.
At the bottom of the fire box is grate on which fuel is burnt and the ash from it falls in the ash pit.
A simple vertical boiler is self-contained & can be easily transported.
The steam ratings normally does not exceeds 2500 kg per hour and pressure is limited to 10 bar.

27. One or more cross tubes are either flanged or riveted to the water space and are located in the fire box to increase the heating surface area and to improve the water circulation.
The boiler consists of a pressure gauge, water level indicator, safety valve , steam stop valve and a man hole as mountings to provide safety and ease of working.
The water circulation in the boiler depends on the density difference in the water, created by temperature difference in the water.

28. 2) COCHRAN BOILER
It is one of the best types of vertical multi-tubular boiler and has a number of horizontal fire tubes.
It is the modification of a simple vertical boiler with increase in heating surface area.
Cochran boiler consist of a cylindrical shell with a dome shaped top where the space is provided for steam.
Its steam generation rate is approximately 3600 kg/h with working pressure limited to 11 bar.

29. The outstanding features of this boiler are :
It is very compact and requires minimum floor area
Any type of fuel can be used with this boiler
Well suited for small capacity requirements
It gives about 70% thermal efficiency with coal firing .
This boiler mountings includes man hole, mud hole, pressure gauge, blow off cock, feed check valve, feed pump, fusible plug and chimney are provided for proper functioning of the boiler.

32. 3) CORNISH BOILER It is very similar to Lancashire boiler
It is horizontal, fire tube, internally fired, natural circulation, stationary boiler.
It is differs from a Lancashire boiler in two respects.
It is small in size
It has only one flue tube.
It consists of a cylindrical shell with flat ends through which passes a smaller flue tube containing the furnace.
The products of combustion pass from the fire grate forward over the brickwork bridge to the end of the furnace tube.

34. The various mountings are provided on this boiler are pressure gauge, water level indicator, steam stop valve, fusible plug, blow off cock, high steam and low water safety valve, feed check valve and man hole.
The steam generation capacity is 6500 kg/h at a pressure of 10.5 bar.

35. 4) LANCASHIRE BOILER
It is stationary fire tube, internally fired, horizontal, natural circulation boiler.
This boiler is set in brickwork forming external flue so that the external part of the shell forms part of the heating surface.
This boiler is reliable, has simplicity of design, ease of operation & less operating & maintenance costs.
It is commonly used in sugar-mills & textile industries where along with the power system & steam for the process work is also needed.
This is a widely used boiler because of its good steaming quality and its ability to burn coal of inferior quality.

38. The boiler is provided with usual mountings like pressure gauge, water level indicator, steam stop valve, safety valve, low water and high steam safety valve, man hole on top of the shell.
The blow off cock and feed check valve is also provided in front of boiler.
The fusible plug is provided in the main flues just over the grates to prevent overheating of the boiler tubes by extinguishing the fire, when water level falls below a particular level.

39. Advantages
The feed pipe projecting into the boiler is perforated to ensure uniform water distribution.
Its heating surface area per unit volume at the boiler is considerably large.
Its maintenance is easy.
It is suitable where a large reserve of hot water is needed. This boiler due to the large reserve capacity can easily meet load fluctuations.
Super-heater and economizer can be easily incorporated into the system, therefore; overall efficiency of the boiler can be considerably increased (80-85%).

40. 5) LOCOMOTIVE BOILERS

41. Locomotive boiler is a horizontal fire tube type mobile boiler.
The main requirement of this boiler is that it should produce steam at a very high rate. Therefore, this boiler requires a large amount of heating surface and large grate area to burn coal at a rapid rate.
In order to provide the large heating surface area, a large number of fire tubes are setup and heat transfer rate is increased by creating strong draught by means of steam jet.
It generates the steam at a pressure of about 25 bar with a steam rate of kg/h per square meter of the heating surface.

42. ADVANTAGES : a. Large rate of steam generation per square meter of heating surface. To some extent this is due to the vibration caused by the motion. b. It is very compact. c. The pressure of the steam is limited to about 25 bar.

43. WATER TUBE BOILERS ARE CLASSIFIED AS :
1) Horizontal Straight tube boiler There are two types of Horizontal straight tube boiler: a. Longitudinal drum b. Cross drum there are three types of cross drum boiler : 1. two drum 2. four drum 3. three drum 2) Bent tube boiler There are one type of bent tube boiler : a. Low head three drum

44. BABCOCK WILCOX BOILER

45. Advantages of Babcock and Wilcox Boiler
The steam generation capacity of the boiler is very high, about 2000 to 40,000 kg/hr.
Replacement of defective tubes is easy.
The draught losses as compared to other boilers is minimum.
It is used in power station for generation large quantity of steam.
Boiler is required less space area compared to fire tube boilers, and offers greater operational safety.

46. This boiler is used in stationary and marine engine
This boiler is used in stationary and marine engine. This is exclusively used when pressure above 10 bar and steam generating capacity more than 7000 kg/hr. is required.

47. High-Pressure Boiler
The pressure of the steam generated in this boiler is above 80 bar.
Salient features of high pressure boiler
Forced circulation of water
Large no. of small diameter tube.
High steam pressure and temperature.
Improved mode of heat transfer and heating.
Pressurised combustion.
Compactness.
High efficiency and intensive heating.
Once through construction.

48. Loffler Boiler
This is also a modern high pressure water tube boiler using the forced circulation principle and named after Prof. Loeffler.
It uses superheated steam for vapourisation of feed water in the evaporator.
Hot flue gases from the furnace are mainly used for superheating of steam.

50. The major difficulty experienced in La-Mont boiler is deposition of salt and sediment on the inner surfaces of water tubes. The deposition reduces the heat transfer, ultimately, the generating capacity.
This difficulty was solved in Loeffler boiler by preventing the flow of water into the boiler tubes.
Feed water is evaporated in the drum using part of the superheated steam coming out from the water-heater. Thus only the dry saturated steam passes through the tubes.
Poor feed water can, therefore, be used without any difficulty in the boiler, which is great advantage of this boiler

51. The Various parts of given boiler are as follows:
Economiser
Evaporated Drum
Mixing Nozzles
Steam circulating pump
Radiant superheater
Convection superheater
Steam outlet
Capacity: Capacity of the Loeffler boiler is about 100 tonnes/hr of superheated steam generated at a pressure of 140 bar and at a temperature of 500 degree Celsius.

52. LaMont boiler
A LaMont boiler is a type of forced circulation water-tube boiler in which the boiler water is circulated through an external pump through long closely spaced tubes of small diameter.
The mechanical pump is employed to in order to have an adequate and positive circulation in steam and hot water boilers.

54. Principle
The circulation of water and the water steam mixture takes with the help of an external pump which supplies water at a higher pressure than in a natural circulation boiler.
Working
A centrifugal pump which forms the heart of this boiler is responsible to circulate water within the boiler system.
It receives water from the drum and delivers this water to a distribution header as shown in the diagram.
The number of headers may differ in numbers and depends on the size and boiler design of each boiler.

55. The boiler heating surfaces includes a number of tubes arranged in a parallel form and the inlet ends are welded to the distributors or the headers.
A circulation pressure is to be provided during the installation of the pump as per the boiler design and it should be sufficient enough to over come the resistance offered by the tubes.
An even circulation takes place with the helps of the inlet nozzles provided at the inlet of tubes which creates the differential pressure adequate to cover the variations occurring at fluctuating loads or uneven firing conditions.
The riser tubes outlet is welded to the collector headers and also directly to the drum containing steam and water.

56. Banson Boiler
The ppt of Benson is as follows: PPT.

57. Some Industrial boiler
Pulverized fuel boiler
Most coal-fired power station (near about 90%) runs on pulverized fuel boiler and large water tube boiler are pulverized fuel boiler.
The coal is grounded (pulverised) to a fine powder, so that less than 2% is 300 micrometre (µm) and 70-75% is below 75 microns, for bituminous coal.
The pulverised coal is blown with a part of combustion air in to the boiler plant through a series of burner nozzles.
Secondary and tertiary air may also be added.

58. Combustion takes place at a temperatures of 1300-1700ºC depending largely on coal grade.
This system has many advantages such as
ability to fire varying quality of coal
quick response to changes in load
use of high pre-heat air temperatures etc.
One of the most popular systems for firing pulverised coal is the tangential firing using four burners are placed corner to corner to create a fireball at the centre of the furnace.

59. Fluidised bed combustion boiler
In this boiler, the slightly compressed air is passed upward through a finely divided bed of solid particles such as sand supported on a fine mesh.
The fuel in powder form is fed downward.
The air velocity supports the fuel in the air and creats bubble formation, vigorous turbulence and rapid mixing and combustion of fuel, and the bed is said to be fluidized.
If the sand in fluidized state is heated to the ignition temperature of the coal and the coal is injected continously into the bed, the coal will burn rapidly and the bed attains the uniform temperature due to effective mixing.

60. Proper air distribution is very important for maintaining uniform fluidisation across the bed.
Some of the important benefits of fluidized bed combustion boiler over conventional firing system are as follows:
Fuel flexibility
Reduced emission of noxious pollutants such as SOx and NOx
Compact boiler design
Higher combustion efficiency

61. BOILER MOUNTINGS AND ACCESSORIES?

62. Boiler Mountings:
The necessary devices installed or mounted for the safety of boiler and its control are called boiler mountings.

63. Boiler Accessories:
The devices which are installed in the boiler for their efficient operation and smooth working are called Boiler Accessories.

64. Boiler Mountings for safety:
Two water level indicators- 2 no.
Safety valves- 2 no.
Combined high steam and low water safety valve – 2 no.
Fusible plug- 1 no.

65. Boiler Mountings for control:
Pressure gauge- 1 no.
Junction or stop valve- 1 no.
Feed check valve- 1 no.
Blow-off cock- 1 no.
Man hole- 1 no. and mud hole- 1 no.

66. Boiler Accessories for efficient operation:
Water heating devices.
Water feeding devices (Feed pump)
Super heater
Economizer
Air preheater
Steam injector
Steam separator
Steam trap
Boiler drought equipments

67. BOILER MOUNTINGS

68. WATER LEVEL INDICATOR

69. Water level indicator is located in front of the boiler in such position that the level of water can easily seen by the attendant.
Two water level indicators are used on all boiler.
It consist of
Metal tube and glass tube with markings
Gunmetal hollow pipes
Steam cock, water cock and drain cock bolted with flanges
Balls inside the gunmetal pipe

70. 2. PRESSURE GAUGE (Bourdon’s)

71. It reads pressure of the steam in the boiler and is connected to the steam space by the siphon tube.
The most commonly used gauge is the Bourdon pressure gauge
Bourdon pressure gauge consist of :
An elliptical spring tube is also called Bourdon tube, made up of special quality Bronze, whose one end connected to siphon tube and other end is connected by levers and gears to pointer.
Plug (P) is provided for cleaning the siphon tube.
Siphon tube is filled with cold water to prevent the hot steam entering into the bourdon tube and spring tube remains comparatively cool.

72. Working
When fluid pressure acts on the Bourdon tube, it tries to make its cross section changes from elliptical to circular.
In this process, lever end of the tube moves out as indicated by an arrow.
The tube movement is magnified by the mechanism and given to the pointer to move over a circular scale indicating the pressure.
The siphon tube connects the steam space of the boiler to the bourdon gauge
The steam pressure is transferred by water to the Bourdon pressure gauge.

73. 3. SAFETY VALVES Safety valve are located on the top of the boiler.
They guard the boiler against the excessive high pressure of the steam inside the drum.
If the pressure of the steam in the boiler drum exceeds the working pressure then the safety valve allows to blow-off a certain quantity of steam to the atmosphere, and thus the pressure of the steam falls in the drum.
The escape of steam makes an audible noise as alarm to warm the boiler attendant.

74. Lever Safety Valve
Dead Weight Safety Valve

75. High Steam and Low Water Safety Valve
Spring Loaded Safety Valve

76. There are four types of safety valves.
Dead-weight safety valve
Lever-loaded safety valve
Spring-loaded safety valve
High steam and low water safety valve
When the steam pressure is greater than the working pressure it lifts the valve with its weights. So the steam escape from the boiler and the steam pressure thereby decrerases.

77. Merits:
Simplicity of design.
Gives quite a satisfactory performance during operation.
Demerits
Unsuitable for use on any boiler where extensive vibration and movement are experienced (e.g., locomotive and marine work).
It is not suitable foe high pressure boiler because large amount of weights are required to balance the steam pressure.
Uses
It is mainly used for low pressures, low capacity, stationary boilers of the cornish and Lancashire types.

78. b) Lever-loaded safety valve
When the steam pressure becomes greater than the normal working pressure, the valve is lifted with lever and the weight.
Consequently, the steam escape through the passages between the valve and seat and the steam pressure decreases.
Disadvantages
It admits of being tempered with and the effect of a small addition to the weight is magnified considerably in its action on the valve.

79. c) Spring-loaded safety valve
Spring loaded valve is used on locomotive marine and on high pressure boiler.
It consists of
Two steam passages in form of U with two valve
Central helical spring
Extended lever
The operating pressure of the valve is adjusted by varying the tension in the spring.
The extended spring is provided to check the function of valve from time to time.
When upward force of steam exceeds the downward spring tension, the valve open and some steam escapes to the atmosphere.
Thus lowers the steam pressure in the boiler and the valve are again closed under the spring force.

80. d) High steam and low water safety valve
It is used in Cornish and Lancashire boiler.
One of the valve is lever loaded and is operated when steam pressure in the boiler exceeds the working pressure.
The second valve operates and blows off steam with louder noise, when water level in the boiler falls below the normal level.

81. 4. STEAM STOP VALVE

82. The steam stop valve located on the highest part of the steam space.
The valve used to regulate the steam supply from the steam pipe to the prime mover (steam engine or steam turbine) is called Stop Valve.
The steam stop valve can be operated manually or automatically.

83. 5. FEED CHECK VALVE

84. It is used to supply the high-pressure feed water to the boiler.
Feed check valve works as NRV (Non- return valve).
Prevents the back flow of water from the boiler when the feed water pump is either not working or in case of its failure
It consist of two valves: feed valve and check valve.
The feed valve is operated by a hand wheel for its opening and closing.

85. 6. BLOW-OFF COCK

86. The function of the blow-off cock is to discharge mud and other sediments deposited in the bottom-most part of the water space in the boiler, while the boiler is in operation.
It can also be used to drain off the boiler water.
Hence it is mounted at the lowest part of the boiler.
When it is open water under the pressure rushes out, thus carrying sediments and mud.

87. 7. FUSIBLE PLUG Plugs P and S are made up of Gun Metal.
Plug S is made up of Copper.
Plug S is screwed to the plug P.
Plug P is locked into plug S by a metal like tin or lead.

88. It is a very important safety device which protects the fire-tube boiler shell against overheating.
It consists of
Gunmetal plug fixed in gunmetal body with fusible molten metal.
During the normal boiler operation, the fusible plug is covered by water and its temperature does not rise to its melting state.
But when the water level falls too low in the boiler, it uncovers the fusible plug.
The furnace gases heat up the plug, the fusible metal of the plug melts and the inner plug falls down.
The water and steam then rush through the hole and extinguish the fire before any major damage occurs to the boiler due to overheating

89. 8. MANHOLE
This is provided at suitable position on the boiler shell so that the man can enter into boiler shell for inspection, maintenance and repairs. This hole is usually made in elliptical shape of the size convenient for a man to enter through this hole. The opening is closed by steam tight cover.

90. 9. STEAM TRAP
Steam trap is used to collect and automatically drain away the water resulted from partial condensation of steam without steam to escape with this condensate through a valve. The valve after draining the condensate is closed. Is presses the leakage of steam from the trap.

91. 10. ANTIPRIMING PIPE
It is attached below the stop valve to avoid the water particles being carried away along with steam. It has closed pipe with closed ends of 1m and 2m length. The top side of the pipe has perforations. When the steam passes through it, due to inertia effect, the moisture of steam falls into the pipe and the steam with reduced moisture passes into the stop valve.

92. BOILER ACESSORIES
The devices used to improve the performance and operation of the boilers are called boiler accessories. Main accessories used are:

93. Air prehaeter Function:
The function of the air pre-heater is to increase the temperature of air before it enters the furnance. It is generally placed after the economiser.

94. Economiser
Function:
An economiser is a device in which the waste heat of the flue gases is utilised for heating the feed water.
Economiser are of two types :
Independent type, and
Integral type

95. Injector
Function: The function of an injector is to feed water into the boiler. It is also used where the space is not available for the installation of a feed pump

96. Feed pump
Function:
Its is a pump which is used to deliver feed water to the boiler.
The appliances in common use for delivering the feed-water into the steam boilers are:
Reciprocating pump
Rotary pump

97. THANK YoU..