Secondly, the operation of the plant should be such as to provide The fundamental forms of energy with which thermal power stations are. PDF | Today, most of the electricity produced throughout the world is from steam power plants. However, electricity is being produced by some. efficiency among commercial power plants today. established part-load strategies for part-load operation of steam-cycle power plants.
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It is working of thermal power plant. It is also called “Steam Turbine Power Plant.” The theory of thermal power station or working of thermal power station is very. Application of System Analysis for Thermal Power Plant Heat . fired power generators of the Organisation for Economic Co-operation and Development. than ever before. This has become the mainstream type of thermal power plant in Japan. operation of all nuclear power plants owned by The. Tokyo Electric.
On the other hand treated water free from impurities and air is fed to the boiler drum where the combustion heat from the fuel is transferred to water to convert it into high pressure and temperature steam.
Generally, flue gases from the boiler exhaust are at high temperature and if this heat is not utilized will lead to a large amount of losses resulting in reduced boiler efficiencies. So generally this waste heat is recovered by heating either air required for combustion or preheat water before sending it into a boiler.
Flue gases are then allowed to pass through a dust collector or a bag filter to arrest dust particles so as to prevent air pollution before sending it to the atmosphere through a chimney. Fuel storage and handling plant: The most essential part of any power plant is to store the fuel safely in an appropriate amount so that the plant can run smoothly in normal days as well as when the supply of fuel from mines is improper.
So a fuel storage facility is defined in a plant to store an adequate amount of fuel. In a thermal power plant, the first step in process of power generation is that the fuel is brought to breaker house with the help of belt conveyor, here light dust is separated with the help of rotary machine through the action of gravity.
It further goes to the crusher where it is crushed to a size of about 50mm. Water Treatment Plant: In thermal power, plant water is used in large quantity this water is converted into steam and used to rotate the turbine so this water and steam come into direct contact with the boiler, boiler tubes, boiler accessories, and turbine blades.
Normal water is taken from the river, well contains a lot of dirt, suspended particulate matter SPM , dissolved minerals and dissolved gases such as air etc. If the water fed to the boiler is not treated then it will reduce the life and efficiency of equipment by corroding the surfaces and scaling of equipment which may lead to overheating of pressure parts and explosions.
Suspended matter from the water is removed by adding alum into the water tank through gravity separation.
Addition of alum coagulates the suspended particles and due to an increase in the density, it settles at the bottom of the tank through gravity. After gravity separation, water softening is done by ion exchange process. As the hardness comes through the carbonates and bicarbonates of sodium and magnesium, these salts are removed from water anion exchange and cation exchange process.
Water also contains dissolved oxygen and this leads to corrosion and fouling of boiler tubes and surfaces when it comes in their contact. It is there to improve the efficiency of boiler by extracting heat from flue gases to heat water and send it to boiler drum. Advantages of Economiser include 1 Fuel economy: — used to save fuel and increase overall efficiency of boiler plant. The heat transfer area required for evaporation reduced considerably. Air Preheater The heat carried out with the flue gases coming out of economiser are further utilized for preheating the air before supplying to the combustion chamber.
It is a necessary equipment for supply of hot air for drying the coal in pulverized fuel systems to facilitate grinding and satisfactory combustion of fuel in the furnace Reheater Power plant furnaces may have a reheater section containing tubes heated by hot flue gases outside the tubes.
Exhaust steam from the high pressure turbine is rerouted to go inside the reheater tubes to pickup more energy to go drive intermediate or lower pressure turbines. Steam turbines Steam turbines have been used predominantly as prime mover in all thermal power stations.
There is a high pressure turbine at one end, followed by an intermediate pressure turbine, two low pressure turbines, and the generator. Condenser The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be pumped. The functions of a condenser are:- 1 To provide lowest economic heat rejection temperature for steam. We normally use surface condenser although there is one direct contact condenser as well. In direct contact type exhaust steam is mixed with directly with D.
M cooling water. Boiler feed pump Boiler feed pump is a multi stage pump provided for pumping feed water to economiser. BFP is the biggest auxiliary equipment after Boiler and Turbine. Plants designed for lignite brown coal are increasingly used in locations as varied as Germany , Victoria , Australia, and North Dakota.
Lignite is a much younger form of coal than black coal. It has a lower energy density than black coal and requires a much larger furnace for equivalent heat output. The firing systems also differ from black coal and typically draw hot gas from the furnace-exit level and mix it with the incoming coal in fan-type mills that inject the pulverized coal and hot gas mixture into the boiler.
Plants that use gas turbines to heat the water for conversion into steam use boilers known as heat recovery steam generators HRSG.
The exhaust heat from the gas turbines is used to make superheated steam that is then used in a conventional water-steam generation cycle, as described in the gas turbine combined-cycle plants section. Boiler furnace and steam drum[ edit ] The water enters the boiler through a section in the convection pass called the economizer.
From the economizer it passes to the steam drum and from there it goes through downcomers to inlet headers at the bottom of the water walls.
From these headers the water rises through the water walls of the furnace where some of it is turned into steam and the mixture of water and steam then re-enters the steam drum. In the steam drum, the water is returned to the downcomers and the steam is passed through a series of steam separators and dryers that remove water droplets from the steam. The dry steam then flows into the superheater coils.
The boiler furnace auxiliary equipment includes coal feed nozzles and igniter guns, soot blowers , water lancing, and observation ports in the furnace walls for observation of the furnace interior. Furnace explosions due to any accumulation of combustible gases after a trip-out are avoided by flushing out such gases from the combustion zone before igniting the coal. The steam drum as well as the superheater coils and headers have air vents and drains needed for initial start up.
Superheater[ edit ] Fossil fuel power stations often have a superheater section in the steam generating furnace. Here the steam picks up more energy from hot flue gases outside the tubing, and its temperature is now superheated above the saturation temperature.
The superheated steam is then piped through the main steam lines to the valves before the high-pressure turbine. Nuclear-powered steam plants do not have such sections but produce steam at essentially saturated conditions. Experimental nuclear plants were equipped with fossil-fired superheaters in an attempt to improve overall plant operating cost. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and efficiency of the cycle increases.
Diagram of a typical water-cooled surface condenser. Such condensers use steam ejectors or rotary motor -driven exhausts for continuous removal of air and gases from the steam side to maintain vacuum. For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam.
Thus leaks of non-condensible air into the closed loop must be prevented.
The large decrease in volume that occurs when water vapor condenses to liquid creates the low vacuum that helps pull steam through and increase the efficiency of the turbines. The limiting factor is the temperature of the cooling water and that, in turn, is limited by the prevailing average climatic conditions at the power station's location it may be possible to lower the temperature beyond the turbine limits during winter, causing excessive condensation in the turbine.
Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning. The condenser generally uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through cooling OTC water from a river, lake or ocean. In the United States, about two-thirds of power plants use OTC systems, which often have significant adverse environmental impacts.
The impacts include thermal pollution and killing large numbers of fish and other aquatic species at cooling water intakes. The circulation flow rate of the cooling water in a MW unit is about Nevertheless, they may become internally fouled during operation by bacteria or algae in the cooling water or by mineral scaling, all of which inhibit heat transfer and reduce thermodynamic efficiency. Many plants include an automatic cleaning system that circulates sponge rubber balls through the tubes to scrub them clean without the need to take the system off-line.
If the water returns to a local water body rather than a circulating cooling tower , it is often tempered with cool 'raw' water to prevent thermal shock when discharged into that body of water.
Another form of condensing system is the air-cooled condenser. The process is similar to that of a radiator and fan. Exhaust heat from the low-pressure section of a steam turbine runs through the condensing tubes, the tubes are usually finned and ambient air is pushed through the fins with the help of a large fan.
The steam condenses to water to be reused in the water-steam cycle. Air-cooled condensers typically operate at a higher temperature than water-cooled versions.
While saving water, the efficiency of the cycle is reduced resulting in more carbon dioxide per megawatt-hour of electricity. Reheater[ edit ] Power station furnaces may have a reheater section containing tubes heated by hot flue gases outside the tubes. Exhaust steam from the high-pressure turbine is passed through these heated tubes to collect more energy before driving the intermediate and then low-pressure turbines.
Air path[ edit ] External fans are provided to give sufficient air for combustion. The Primary air fan takes air from the atmosphere and, first warms the air in the air preheater for better economy.
Primary air then passes through the coal pulverizers, and carries the coal dust to the burners for injection into the furnace.
The Secondary air fan takes air from the atmosphere and, first warms the air in the air preheater for better economy. The induced draft fan assists the FD fan by drawing out combustible gases from the furnace, maintaining a slightly negative pressure in the furnace to avoid leakage of combustion products from the boiler casing.
Steam turbine generator[ edit ] Main article: Turbo generator Rotor of a modern steam turbine, used in a power station The turbine generator consists of a series of steam turbines interconnected to each other and a generator on a common shaft. There is usually a high-pressure turbine at one end, followed by an intermediate-pressure turbine, and finally one, two, or three low-pressure turbines, and the generator.
As steam moves through the system and loses pressure and thermal energy, it expands in volume, requiring increasing diameter and longer blades at each succeeding stage to extract the remaining energy. It is so heavy that it must be kept turning slowly even when shut down at 3 rpm so that the shaft will not bow even slightly and become unbalanced.
This is so important that it is one of only six functions of blackout emergency power batteries on site. The other five being emergency lighting , communication , station alarms, generator hydrogen seal system, and turbogenerator lube oil. The hot reheat steam is conducted to the intermediate pressure turbine, where it falls in both temperature and pressure and exits directly to the long-bladed low-pressure turbines and finally exits to the condenser.
There is generally no permanent magnet , thus preventing black starts. The rotor spins in a sealed chamber cooled with hydrogen gas, selected because it has the highest known heat transfer coefficient of any gas and for its low viscosity , which reduces windage losses. This system requires special handling during startup, with air in the chamber first displaced by carbon dioxide before filling with hydrogen.
This ensures that a highly explosive hydrogen— oxygen environment is not created. The desired frequency affects the design of large turbines, since they are highly optimized for one particular speed.In this process the coal feeded to the coal feeder from the coal bunker. This article explains how electricity is generated in thermal power plants.
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Efficiency of a Thermal Power Station A huge amount of heat is lost in various stages of the plant. Skip to main content. You use it for heating, cooling, cooking, refrigeration, light, sound, computation, entertainment The dry steam then flows into the superheater coils. Along with boiler we also have experience in providing energy solutions to our customers thereby saving you a lot on the operating cost.
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