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Intro to PPD.docx

Orley G. Fadriquel
Orley G. Fadriquel

Thermal power plants generate over 80% of the world's electricity and work by heating water to create steam that spins turbines connected to generators. There are various types of power plants such as thermal, hydroelectric, nuclear, gas turbine, and diesel. Thermal power plants are the most common and work using the Rankine cycle where steam is created to spin turbines and then condensed to be reused. Key components include the coal and ash circuit to feed coal into the boiler, the steam and feedwater circuit to power the turbines and reuse the steam, and the cooling water circuit to condense the steam.

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INTRODUCTION TO POWER PLANT ENGINEERING Introduction Power plants are used for the generation of electric power. Electric power plays an important role in the growth of industry. A countries development is measured by the power generation industry and its power demand. The standard of living in a country is normally related to the consumption of electricity in that country. The types of power plants which is used to produce the electricity are thermal, hydraulic, nuclear, gas turbine and diesel. In the above said power plants, the thermal power plants generate more than 80 % of the total electricity produced in the world. TYPES OF POWER STATION Conventional Power Stations Thermal Power Station Steam Power Station Geothermal Power Station Nuclear Power Station Hydro-Electric Power Station Gas Turbine Power Station Diesel Power Station Co-Generation/ Combined Heat Power Station MHD Generation or Magneto Hydro Dynamic Power Generation Thermoelectric Power Generators or Seebeck Power Generation Non - Conventional Power Stations Solar power generation. Geo-thermal power generation. Tidal power generation. Wind power generation (energy available from the wind turbines) Renewable sources of energy are continuously produced in nature, and they will not get exhausted eventually in future. Nonrenewable sources of energy will get exhausted eventually in future. THERMAL POWER STATIONS A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical
generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different fuel sources. Some prefer to use the term energy center because such facilities convert forms of heat energy into electricity. Some thermal power plants also deliver heat energy for industrial purposes, for district heating, or for desalination of water as well as delivering electrical power. A large proportion of CO2 is produced by the worlds fossil fired thermal power plants; efforts to reduce these outputs are various and widespread. LAYOUT OF COAL FIRED STEAM POWER PLANT: Figure 1. The Lay - out of a Typical Steam Power Plant The four main circuits one would come across in any thermal power plant layout are: Coal and Ash Circuit Air and Gas Circuit Feed Water and Steam Circuit Cooling Water Circuit Coal and Ash Circuit Coal and Ash circuit in a thermal power plant layout mainly takes care of feeding the boiler with coal from the storage for combustion. The ash that is generated during combustion is collected at the back of the boiler and removed to the ash storage by scrap conveyors. The combustion in the Coal and Ash circuit is controlled by regulating the speed and the quality of coal entering the grate and the damper openings.
Air and Gas Circuit Air from the atmosphere is directed into the furnace through the air preheated by the action of a forced draught fan or induced draught fan. The dust from the air is removed before it enters the combustion chamber of the thermal power plant layout. The exhaust gases from the combustion heat the air, which goes through a heat exchanger and is finally let off into the environment. Feed Water and Steam Circuit The steam produced in the boiler is supplied to the turbines to generate power. The steam that is expelled by the prime mover in the thermal power plant layout is then condensed in a condenser for re-use in the boiler. The condensed water is forced through a pump into the feed water heaters where it is heated using the steam from different points in the turbine. To make up for the lost steam and water while passing through the various components of the thermal power plant layout, feed water is supplied through external sources. Feed water is purified in a purifying plant to reduce the dissolve salts that could scale the boiler tubes. Cooling Water Circuit The quantity of cooling water required to cool the steam in a thermal power plant layout is significantly high and hence it is supplied from a natural water source like a lake or a river. After passing through screens that remove particles that can plug the condenser tubes in a thermal power plant layout, it is passed through the condenser where the steam is condensed. The water is finally discharged back into the water source after cooling. Cooling water circuit can also be a closed system where the cooled water is sent through cooling towers for re-use in the power plant. The cooling water circulation in the condenser of a thermal power plant layout helps in maintaining a low pressure in the condenser all throughout. All these circuits are integrated to form a thermal power plant layout that generates electricity to meet our needs. Advantages Generation of power is continuous. Initial cost low compared to hydel plant. Less space required. This can be located near the load centre so that the transmission losses are reduced. It can respond to rapidly changing loads. Disadvantages Long time required for installation. Transportation and handling of fuels major difficulty. Efficiency of plant is less.
Power generation cost is high compared to hydel power plant. Maintenance cost is high. HYDEL POWER PLANTS Hydroelectric power plants convert the hydraulic potential energy from water into electrical energy. Such plants are suitable were water with suitable head are available. The layout covered in this article is just a simple one and only cover the important parts of hydroelectric plant. LAYOUT OF HYDEL POWER PLANT: Figure 2. A Typical Lay-out of a Hydro Electric Power Plant Dam Dams are structures built over rivers to stop the water flow and form a reservoir. The reservoir stores the water flowing down the river. This water is diverted to turbines in power stations. The dams collect water during the rainy season and stores it, thus allowing for a steady flow through the turbines throughout the year. Dams are also used for controlling floods and irrigation. The dams should be water-tight and should be able to withstand the pressure exerted by the water on it. There are different types of dams such as arch dams, gravity dams and buttress dams. The height of water in the dam is called head race. Spillway A spillway as the name suggests could be called as a way for spilling of water from dams. It is used to provide for the release of flood water from a dam. It is used to prevent over toping of the dams which could result in damage or failure of dams. Spillways could be controlled type or uncontrolled type. The uncontrolled types start releasing water upon water rising above a particular level. But in case of the controlled type, regulation of flow is possible.
Penstock and Tunnels Penstocks are pipes which carry water from the reservoir to the turbines inside power station. They are usually made of steel and are equipped with gate systems. Water under high pressure flows through the penstock. A tunnel serves the same purpose as a penstock. It is used when an obstruction is present between the dam and power station such as a mountain. Surge Tank Surge tanks are tanks connected to the water conductor system. It serves the purpose of reducing water hammering in pipes which can cause damage to pipes. The sudden surges of water in penstock is taken by the surge tank, and when the water requirements increase, it supplies the collected water thereby regulating water flow and pressure inside the penstock. Power Station Power station contains a turbine coupled to a generator. The water brought to the power station rotates the vanes of the turbine producing torque and rotation of turbine shaft. This rotational torque is transferred to the generator and is converted into electricity. The used water is released through the tail race. The difference between head race and tail race is called gross head and by subtracting the frictional losses we get the net head available to the turbine for generation of electricity. Advantages Water the working fluid is natural and available plenty. Life of the plant is very long. Running cost and maintenance are very low. Highly reliable. Running cost is low. Maintenance and operation costs are very less. No fuel transport problem. No ash disposal problem. Disadvantages Initial cost of plant is very high. Power generation depends on quantity of water available which depends on rainfall. Transmission losses are very high. More time is required for erection.

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Intro to PPD.docx

  • 1. INTRODUCTION TO POWER PLANT ENGINEERING Introduction Power plants are used for the generation of electric power. Electric power plays an important role in the growth of industry. A countries development is measured by the power generation industry and its power demand. The standard of living in a country is normally related to the consumption of electricity in that country. The types of power plants which is used to produce the electricity are thermal, hydraulic, nuclear, gas turbine and diesel. In the above said power plants, the thermal power plants generate more than 80 % of the total electricity produced in the world. TYPES OF POWER STATION Conventional Power Stations Thermal Power Station Steam Power Station Geothermal Power Station Nuclear Power Station Hydro-Electric Power Station Gas Turbine Power Station Diesel Power Station Co-Generation/ Combined Heat Power Station MHD Generation or Magneto Hydro Dynamic Power Generation Thermoelectric Power Generators or Seebeck Power Generation Non - Conventional Power Stations Solar power generation. Geo-thermal power generation. Tidal power generation. Wind power generation (energy available from the wind turbines) Renewable sources of energy are continuously produced in nature, and they will not get exhausted eventually in future. Nonrenewable sources of energy will get exhausted eventually in future. THERMAL POWER STATIONS A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical
  • 2. generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different fuel sources. Some prefer to use the term energy center because such facilities convert forms of heat energy into electricity. Some thermal power plants also deliver heat energy for industrial purposes, for district heating, or for desalination of water as well as delivering electrical power. A large proportion of CO2 is produced by the worlds fossil fired thermal power plants; efforts to reduce these outputs are various and widespread. LAYOUT OF COAL FIRED STEAM POWER PLANT: Figure 1. The Lay - out of a Typical Steam Power Plant The four main circuits one would come across in any thermal power plant layout are: Coal and Ash Circuit Air and Gas Circuit Feed Water and Steam Circuit Cooling Water Circuit Coal and Ash Circuit Coal and Ash circuit in a thermal power plant layout mainly takes care of feeding the boiler with coal from the storage for combustion. The ash that is generated during combustion is collected at the back of the boiler and removed to the ash storage by scrap conveyors. The combustion in the Coal and Ash circuit is controlled by regulating the speed and the quality of coal entering the grate and the damper openings.
  • 3. Air and Gas Circuit Air from the atmosphere is directed into the furnace through the air preheated by the action of a forced draught fan or induced draught fan. The dust from the air is removed before it enters the combustion chamber of the thermal power plant layout. The exhaust gases from the combustion heat the air, which goes through a heat exchanger and is finally let off into the environment. Feed Water and Steam Circuit The steam produced in the boiler is supplied to the turbines to generate power. The steam that is expelled by the prime mover in the thermal power plant layout is then condensed in a condenser for re-use in the boiler. The condensed water is forced through a pump into the feed water heaters where it is heated using the steam from different points in the turbine. To make up for the lost steam and water while passing through the various components of the thermal power plant layout, feed water is supplied through external sources. Feed water is purified in a purifying plant to reduce the dissolve salts that could scale the boiler tubes. Cooling Water Circuit The quantity of cooling water required to cool the steam in a thermal power plant layout is significantly high and hence it is supplied from a natural water source like a lake or a river. After passing through screens that remove particles that can plug the condenser tubes in a thermal power plant layout, it is passed through the condenser where the steam is condensed. The water is finally discharged back into the water source after cooling. Cooling water circuit can also be a closed system where the cooled water is sent through cooling towers for re-use in the power plant. The cooling water circulation in the condenser of a thermal power plant layout helps in maintaining a low pressure in the condenser all throughout. All these circuits are integrated to form a thermal power plant layout that generates electricity to meet our needs. Advantages Generation of power is continuous. Initial cost low compared to hydel plant. Less space required. This can be located near the load centre so that the transmission losses are reduced. It can respond to rapidly changing loads. Disadvantages Long time required for installation. Transportation and handling of fuels major difficulty. Efficiency of plant is less.
  • 4. Power generation cost is high compared to hydel power plant. Maintenance cost is high. HYDEL POWER PLANTS Hydroelectric power plants convert the hydraulic potential energy from water into electrical energy. Such plants are suitable were water with suitable head are available. The layout covered in this article is just a simple one and only cover the important parts of hydroelectric plant. LAYOUT OF HYDEL POWER PLANT: Figure 2. A Typical Lay-out of a Hydro Electric Power Plant Dam Dams are structures built over rivers to stop the water flow and form a reservoir. The reservoir stores the water flowing down the river. This water is diverted to turbines in power stations. The dams collect water during the rainy season and stores it, thus allowing for a steady flow through the turbines throughout the year. Dams are also used for controlling floods and irrigation. The dams should be water-tight and should be able to withstand the pressure exerted by the water on it. There are different types of dams such as arch dams, gravity dams and buttress dams. The height of water in the dam is called head race. Spillway A spillway as the name suggests could be called as a way for spilling of water from dams. It is used to provide for the release of flood water from a dam. It is used to prevent over toping of the dams which could result in damage or failure of dams. Spillways could be controlled type or uncontrolled type. The uncontrolled types start releasing water upon water rising above a particular level. But in case of the controlled type, regulation of flow is possible.
  • 5. Penstock and Tunnels Penstocks are pipes which carry water from the reservoir to the turbines inside power station. They are usually made of steel and are equipped with gate systems. Water under high pressure flows through the penstock. A tunnel serves the same purpose as a penstock. It is used when an obstruction is present between the dam and power station such as a mountain. Surge Tank Surge tanks are tanks connected to the water conductor system. It serves the purpose of reducing water hammering in pipes which can cause damage to pipes. The sudden surges of water in penstock is taken by the surge tank, and when the water requirements increase, it supplies the collected water thereby regulating water flow and pressure inside the penstock. Power Station Power station contains a turbine coupled to a generator. The water brought to the power station rotates the vanes of the turbine producing torque and rotation of turbine shaft. This rotational torque is transferred to the generator and is converted into electricity. The used water is released through the tail race. The difference between head race and tail race is called gross head and by subtracting the frictional losses we get the net head available to the turbine for generation of electricity. Advantages Water the working fluid is natural and available plenty. Life of the plant is very long. Running cost and maintenance are very low. Highly reliable. Running cost is low. Maintenance and operation costs are very less. No fuel transport problem. No ash disposal problem. Disadvantages Initial cost of plant is very high. Power generation depends on quantity of water available which depends on rainfall. Transmission losses are very high. More time is required for erection.