Thermal Power Generation Full Seminar Report - Download as Word Doc .doc /.docx), PDF File .pdf), Text File .txt) or read online. a report on thermal. PDF | THIS paper briefly states the remedial measures to minimize the loss of performance on account of variations in uncontrollable input. A Seminar Report on " THERMAL POWER PLANT " For the partial fulfillment of the Layout of surface condenser (scroll to page 11 of 34 pdf pages)
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Thermal Power Generation Paper Presentation & Seminar Preview of the attached files: A thermal power station is a power plant in which the. Trends and Future Outlook for Thermal Power Plants. Fuji Electric's Medium- capacity Steam Turbines “FET Series”. Present Developmental Status of Fuji . 4 INTRODUCTION Kota Super Thermal Power Plant is Rajasthan's first major Coal fired Power plant. It is located on the left bank of the Chambal River at.
Pulverized coal is air-blown into the furnace through burners located at the four corners, or along one wall, or two opposite walls, and it is ignited to rapidly burn, forming a large fireball at the center. The thermal radiation of the fireball heats the water that circulates through the boiler tubes near the boiler perimeter. The water circulation rate in the boiler is three to four times the throughput.
As the water in the boiler circulates it absorbs heat and changes into steam. It is separated from the water inside a drum at the top of the furnace. The saturated steam is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace.
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 gas turbine combined-cycle plants section below.
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 down comers 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 super heater coils and headers have air vents and drains needed for initial start up. The steam passes through drying equipment inside the steam drum on to the superheater, a set of tubes in the 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.
Nuclear-powered steam plants do not have such sections but produce steam at essentially saturated conditions. Experimental nuclear plants were equipped with fossil-fired super heaters 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.
The surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is cooled and converted to condensate water by flowing over the tubes as shown in the adjacent diagram.
Such condensers use steam ejectors or rotary motor-driven exhausters 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 plant'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 water from a river, lake or ocean.
A Marley mechanical induced draft cooling tower The heat absorbed by the circulating cooling water in the condenser tubes must also be removed to maintain the ability of the water to cool as it circulates. The circulation flow rate of the cooling water in a MW unit is about The condenser tubes are made of brass or stainless steel to resist corrosion from either side.
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 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 of electricity. 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.
The Primary air fan takes air from the atmosphere and, first warming it in the air preheater for better combustion, injects it via the air nozzles on the furnace wall. 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 backfiring through any closing. There is a high pressure turbine at one end, followed by an intermediate pressure turbine, two 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. The entire rotating mass may be over metric tons and feet 30 m long. 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 five functions of blackout emergency power batteries on site. Other functions are emergency lighting, communication, station alarms and turbogenerator lube oil. Superheated steam from the boiler is delivered through 14—inch — mm diameter piping to the high pressure turbine where it falls in pressure to psi 4.
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. The generator, 30 feet 9 m long and 12 feet 3.
In operation it generates up to 21, amperes at 24, volts AC MWe as it spins at either 3, or 3, rpm, synchronized to the power grid. 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 the 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.
The electricity flows to a distribution yard where transformers increase the voltage for transmission to its destination. The steam turbine-driven generators have auxiliary systems enabling them to work satisfactorily and safely. The steam turbine generator being rotating equipment generally has a heavy, large diameter shaft. The shaft therefore requires not only supports but also has to be kept in position while running.
To minimize the frictional resistance to the rotation, the shaft has a number of bearings. The bearing shells, in which the shaft rotates, are lined with a low friction material like Babbitt metal. Oil lubrication is provided to further reduce the friction between shaft and bearing surface and to limit the heat generated. The gas exiting the boiler is laden with fly ash, which are tiny spherical ash particles. The flue gas contains nitrogen along with combustion products carbon dioxide, sulfur dioxide, and nitrogen oxides.
The fly ash is removed by fabric bag filters or electrostatic precipitators. Once removed, the fly ash byproduct can sometimes be used in the manufacturing of concrete.
This cleaning up of flue gases, however, only occurs in plants that are fitted with the appropriate technology. Still, the majority of coal-fired power plants in the world do not have these facilities.
Legislation in Europe has been efficient to reduce flue gas pollution. Japan has been using flue gas cleaning technology for over 30 years and the US has been doing the same for over 25 years.
China is now beginning to grapple with the pollution caused by coal-fired power plants. Other devices use catalysts to remove Nitrous Oxide compounds from the flue gas stream.
A typical flue gas stack may be — metres — ft tall to disperse the remaining flue gas components in the atmosphere. The tallest flue gas stack in the world is In the United States and a number of other countries, atmospheric dispersion modeling studies are required to determine the flue gas stack height needed to comply with the local air pollution regulations.
In the case of existing flue gas stacks that exceed the GEP stack height, any air pollution dispersion modeling studies for such stacks must use the GEP stack height rather than the actual stack height. The fly ash is periodically removed from the collection hoppers below the precipitators or bag filters.
Generally, the fly ash is pneumatically transported to storage silos for subsequent transport by trucks or railroad cars. This hopper is always filled with water to quench the ash and clinkers falling down from the furnace. Some arrangement is included to crush the clinkers and for conveying the crushed clinkers and bottom ash to a storage site.
Ash extractor is used to discharge ash from Municipal solid waste—fired boilers. For this, continuous make-up water is added to the boiler water system. Impurities in the raw water input to the plant generally consist of calcium and magnesium salts which impart hardness to the water. Hardness in the make-up water to the boiler will form deposits on the tube water surfaces which will lead to overheating and failure of the tubes. Thus, the salts have to be removed from the water, and that is done by a water demineralising treatment plant DM.
Any ions in the final water from this process consist essentially of hydrogen ions and hydroxide ions, which recombine to form pure water. Very pure DM water becomes highly corrosive once it absorbs oxygen from the atmosphere because of its very high affinity for oxygen. The capacity of the DM plant is dictated by the type and quantity of salts in the raw water input.
However, some storage is essential as the DM plant may be down for maintenance. For this purpose, a storage tank is installed from which DM water is continuously withdrawn for boiler make-up. The piping and valves are generally of stainless steel. Sometimes, a steam blanketing arrangement or stainless steel doughnut float is provided on top of the water in the tank to avoid contact with air.
DM water make-up is generally added at the steam space of the surface condenser i. This arrangement not only sprays the water but also DM water gets deaerated, with the dissolved gases being removed by a de-aerator through an ejector attached to the condenser. The coal is next pulverized into a very fine powder. The pulverizers may be ball mills, rotating drum grinders, or other types of grinders. Some power stations burn fuel oil rather than coal. The oil must kept warm above its pour point in the fuel oil storage tanks to prevent the oil from congealing and becoming unpumpable.
Boilers in some power stations use processed natural gas as their main fuel. Other power stations may use processed natural gas as auxiliary fuel in the event that their main fuel supply coal or oil is interrupted. In such cases, separate gas burners are provided on the boiler furnaces.
Once the unit is "tripped" i. This is because the heat inside the turbine casing tends to concentrate in the top half of the casing, making the top half portion of the shaft hotter than the bottom half. The shaft therefore could warp or bend by millionths of inches. This small shaft deflection, only detectable by eccentricity meters, would be enough to cause damaging vibrations to the entire steam turbine generator unit when it is restarted.
The shaft is therefore automatically turned at low speed about one percent rated speed by the barring gear until it has cooled sufficiently to permit a complete stop.
It supplies the hydraulic oil system required for steam turbine's main inlet steam stop valve, the governing control valves, the bearing and seal oil systems, the relevant hydraulic relays and other mechanisms.
The so called control rods are important tools to control reactor. These are made of neutron absorbing materials and can be moved between the fuel assemblies. For example, if one wishes to decrease the power of the reactor it is sufficient to push a control rod a little inner.
The control rods are particularly useful for the short term control and stopping the reactor chain reaction. For long term regulation usually Boric acid dissolved in the moderator is used. H2O and D2O Moderation is a process of the reduction of the initial high kinetic energy of the free neutron. Since energy is conserved, this reduction of the neutron kinetic energy takes place by transfer of energy to a material known as a moderator. It is also known as neutron slowing down, since along with the reduction of energy comes a reduction in speed.
Heavy Water as a Moderator Heavy water is used both as a moderator and coolant. The moderator system comprises of Heavy water and Helium system. Moderator D2O system circulating pump take suction from bottom of callandria and discharge back to the callandria through moderator heat exchanger for maintaining moderator temperature.
It is a high pressure and high temperature circuit. The heat generated in the fuel bundles, as a result of uranium fission, is removed by the heavy water serving as a primary coolant. High pressure high temperature heavy water areas have been separated from the high pressure high temperature light water for recovery of high isotopic purity of heavy water. Shutdown System Fig. Control Rods in Reactor Building They have two diverse and independent shut down system, one of them is fast and other is slow.
Primary Shutdown System The system is meant to shut down the reactor whenever any operating parameter crosses a set limit. The system operates automatically and can also be operated manually.
The system has 14 rods of Cadmium sandwiched in stainless steel as neutron absorbing element. Any trip signal actuates the mechanical drum assembly and the criticality is reduced to sub criticality in a span of 2. Secondary Shutdown System The Secondary Shutdown system comes into action when the primary shutdown system fails to operate. It is provided as a backup protective system. Future Prospects19 9. 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, oil, or natural gas are often referred to collectively as fossil-fuel power plants. Some biomass-fueled thermal power plants have appeared also. Non-nuclear thermal power plants, particularly fossilfueled plants, which do not use cogeneration, are sometimes referred to as conventional power plants.
In thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy, often from combustion of a fuel, into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations.
Not all thermal energy can be transformed into mechanical power, according to the second law of thermodynamics. Therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or district heating, the power plant is referred to as a cogeneration power plant or CHP combined heat-and-power plant. In countries where district heating is common, there are dedicated heat plants called heat-only boiler stations.
An important class of power stations in the Middle East uses by-product heat for the desalination of water.
Other large companies or institutions may have their own usually smaller power plants to supply heating or electricity to their facilities, especially if heat or steam is created anyway for other purposes. Shipboard steam-driven power plants have been used in various large ships in the past, but these days are used most often in large naval ships.
Such shipboard power plants are general lower power capacity than full-size electric company plants, but otherwise have many similarities except that typically the main steam turbines mechanically turn the propulsion propellers, either through reduction gears or directly by the same shaft.
The steam power plants in such ships also provide steam to separate smaller turbines driving electric generators to supply electricity in the ship. Shipboard steam power plants can be either conventional or nuclear; the shipboard nuclear plants are mostly in the navy. There have been perhaps about a dozen turbo-electric ships in which a steam-driven turbine drives an electric generator which powers an electric motor for propulsion.
Thermal power station is a power plant in which the prime mover is steam driven. 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 electrical energy. 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 New York and London, in , also used reciprocating steam engines. As generator sizes increased, eventually turbines took over they encres the hose power.