21-11-2012, 02:33 PM
SURATGARH THERMAL POWER STATION
SURATGARH THERMAL POWER STATION.docx (Size: 1.06 MB / Downloads: 51)
INTRODUCTION
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 part of human CO2 emissions comes from fossil fueled thermal power plants; efforts to reduce these outputs are various and widespread.
Natural gas is frequently combusted in gas turbines as well as boilers. The waste heat from a gas turbine can be used to raise steam, in a combined cycle plant that improves overall efficiency. Power plants burning coal, fuel oil, or natural gas are often called fossil-fuel power plants. Some biomass-fueled thermal power plants have appeared also. Non-nuclear thermal power plants, particularly fossil-fueled plants, which do not use co-generation, are sometimes referred to as conventional power plants.
Steam-driven power plants have been used in various large ships, but are now usually used in large naval ships. Shipboard power plants usually directly couple the turbine to the ship's propellers through gearboxes. Power plants in such ships also provide steam to smaller turbines driving electric generators to supply electricity. Shipboard steam power plants can be either fossil fuel or nuclear.
HISTORY
Reciprocating steam engines have been used for mechanical power sources since the 18th Century, with notable improvements being made by James Watt. The very first commercial central electrical generating stations in the Pearl Street Station, New York and the Holborn Viaduct power station, London, in 1882, also used reciprocating steam engines. The development of the steam turbine allowed larger and more efficient central generating stations to be built. By 1892 it was considered as an alternative to reciprocating engines Turbines offered higher speeds, more compact machinery, and stable speed regulation allowing for parallel synchronous operation of generators on a common bus. Turbines entirely replaced reciprocating engines in large central stations after about 1905. The largest reciprocating engine-generator sets ever built were completed in 1901 for the Manhattan Elevated Railway. Each of seventeen units weighed about 500 tons and was rated 6000 kilowatts; a contemporary turbine-set of similar rating would have weighed about 20% as much.
ELECTRICITY COST
The direct cost of electric energy produced by a thermal power station is the result of cost of fuel, capital cost for the plant, operator labour, maintenance, and such factors as ash handling and disposal. Indirect, social or environmental costs such as the economic value of environmental impacts, or environmental and health effects of the complete fuel cycle and plant decommissioning, are not usually assigned to generation costs for thermal stations in utility practice, but may form part of an environmental impact assessment.
PRINCIPAL & WORKING
PRINCIPAL & WORKING DIAGRAM OF THERMAL POWER PLANT
WORKING
In a coal based power plant coal is transported from coal mines to the power plant by railway in wagons or in a merry-go-round system. Coal is unloaded from the wagons to a moving underground conveyor belt. This coal from the mines is of no uniform size. So it is taken to the Crusher house and crushed to a size of 20mm. From the crusher house the coal is either stored in dead storage( generally 40 days coal supply) which serves as coal supply in case of coal supply bottleneck or to the live storage(8 hours coal supply) in the raw coal bunker in the boiler house. Raw coal from the raw coal bunker is supplied to the Coal Mills by a Raw Coal Feeder. The Coal Mills or pulverizer pulverizes the coal to 200 mesh size. The powdered coal from the coal mills is carried to the boiler in coal pipes by high pressure hot air. The pulverized coal air mixture is burnt in the boiler in the combustion zone.
Generally in modern boilers tangential firing system is used i.e. the coal nozzles/ guns form tangent to a circle. The temperature in fire ball is of the order of 1300 deg.C. The boiler is a water tube boiler hanging from the top. Water is converted to steam in the boiler and steam is separated from water in the boiler Drum. The saturated steam from the boiler drum is taken to the Low Temperature Superheater, Platen Superheater and Final Superheater respectively for superheating. The superheated steam from the final superheater is taken to the High Pressure Steam Turbine (HPT). In the HPT the steam pressure is utilized to rotate the turbine and the resultant is rotational energy. From the HPT the out coming steam is taken to the Reheater in the boiler to increase its temperature as the steam becomes wet at the HPT outlet. After reheating this steam is taken to the Intermediate Pressure Turbine (IPT) and then to the Low Pressure Turbine (LPT). The outlet of the LPT is sent to the condenser for condensing back to water by a cooling water system. This condensed water is collected in the Hotwell and is again sent to the boiler in a closed cycle. The rotational energy imparted to the turbine by high pressure steam is converted to electrical energy in the Generator.
COAL HANDLING PLANT
If you’ve ever read a book to a small child on the subject of food or digestion, you’ve probably come across the analogy that our stomachs are like a furnace and our digestive system much like an engine. We explain to the youngster that what we eat is important, because our body needs the right fuel in order to operate properly. If little Susie or Danny insisted on eating only candy day after day, their bodies would become weak and sick.
In much the same way a coal power plant is like a living organism, eating fuel in order to function. But instead of meats and vegetables, it eats coal, and the coal handling department of a power plant acts as a dinner table. It’s where the food is placed and prepared before it enters the diner’s mouth.
The coal our power plants consume comes from one of two places, underground mines or strip mines. It all depends on the particular geology of the area from which the coal is harvested. According to the US Energy Information Administration, underground mines are more common in the eastern United States, while strip mines are more common in the western states. The coal from underground mines is excavated by means of shafts and tunnels which are dug deep beneath the earth’s surface in order to provide access to the buried coal deposits. In strip mines the deposits are just below the surface, so the topsoil is merely stripped away with heavy earthmoving machinery, like bulldozers, to reveal the coal. In both types of mining activity excavating machines and conveyors are required to remove the coal from the mine so it can be loaded for shipment to its ultimate destination.
Once harvested, coal is shipped to power plants primarily by train, river barge, or ship. Its journey can cover thousands of miles. It culminates in delivery to a power plant, where it is unloaded by means of a huge piece of machinery called a rotary dumper. This machine is capable of grabbing onto 100 ton railcars and turning them upside down. The coal spills into a large collection hopper positioned next to the railroad track.
If the coal has found its way to a plant located near a waterway, that means of transport was most likely have been made by flat barge or ship. In this case a large crane with a clamshell bucket is used for unloading. The crane drops its bucket into a pile of coal located within the ship’s hold, takes out a large bite, then hoists and dumps its contents into a large collection hopper next to the crane.