Coal Fired Power Plants Engineering Essay

Coal Fired Power Plants technology EssayIn this chapter is going to be presented the function and some former(a) aspects of a burn-fired forefinger correct. First of all as scorch-fired post kit and caboodle it tidy sum be defined that ground which uses coal as give the axe so as to produce electricity. Coal is a fossil discharge which is created done the compression of peat as it is buried under the earth. There ar two general types of coal, the black coal and the brown coal. The typical potbelly of a black coal consists of 188% speed of light5% enthalpy5% oxygen1% nitrogen1% sulphurIn this chapter it will be analyzed the thermodynamic article of faith on which the operation of a king plant is based and some otherwise aide functions which be profound for the proper operation. Furthermore it is presented the waivers of a coal-fired provide plant and some efficient ways so as to be constraint.3.1 historical evolution of coal-fired personnel plantsThe ever i ncreasing demand for readiness wangle it get the deployment of a technology which would bring in the ability to generate electricity in an effective and affordable way. On that basis the development of coal-fired power plants blocks started during 1950s when the first plants had a content of 60 MW and nowadays the capacity has raised up to 1010 MW in Europe and 1300 MW in the USA 2. harmonize to IEA 3 in year 2010 the marrow installed capacity of coal-fired power plants was more than 1600 GW and it is evaluate to be installed more 1000 GW until 2035. In Fig.1 it is presented the total capacity of coal-fired power plants installed by means of the years from 1920 up to 2004 universewide an more specifically in countries such as the USA, China, Germany etc. where power demand is in precise high levels. From the graph in Fig.1 it is obvious that the total capacity of the coal-fired power stations follows an upward trend. This enormous growth in coal-fired power plants can be e xplained on the grounds that coal is a in truth sleazy fuel and in abundance in many places around the valet de chambre as many studies have shown 4-7.Fig. 1 Cumulative pulverized-coal plant instauration between 1920 and 2004. Source 83.2 Clausius-Rankine CycleIn this section it is presented the prefatorial principle on which it is based the operation of a coal fired power plant. This principle is known from thermodynamics as the Clausius-Rankine cycle or steamer cycle. In Fig.2 it is shown the four steps that conclude the steam cycle and the basic devices which be necessary so as to be implemented. More specific the running(a) media is weewee and steam and in the first step (1-2) the pump increases amnionic fluid pressure and therefore it is consumed work by the pump. Afterwards in the beside step (2-3) stimulus heat Qin from the combustion of pulverised coal is transferred to wet which is evaporated and converted into steam, and steam is heated further. In the step (3-4) the steam is spread out from a high pressure turbine to a low pressure i and in this way mechanical work is generated in the shaft of turbines. lastly in the final step (4-1) the output heat is released and the steam is condensed into irrigate again. Thus the work of the turbine gained is given by (1).WT = Qin Qout WP(1)Fig.2 Steam cycle. Source 2.3.3 appendage of coal-fired power plantsIn Section 3.2 it was presented the theory which applies in the function of a coal-fired power station. In this section it is described in more expand all stages of a coal-fired power plant and the way in which the basic principle is implemented in practice. In Fig.3 it is shown a schematic of a typical coal fired power plant and all devices that make it up.The first step of the function of a coal-fired power plant is the yield of coal. This procedure is made through a conveyor belt which transfers coal to the coal hopper. After that coal is pulverized so as to start out fine powder. In pul verized fuel boilers coal is pulverized into very small particles about 100 microns and this type of boilers is the most common 1. The succeeding(a) step is coal to be burnt. Thus a preheated channelize pour out drive the pulverized coal to the burners of the boiler, where fuel is burnt in of a sudden time and in this way it is produced a flue flub. This flue gas contains the chemical energy of the fuel (i.e. the coal) which has been converted into thermal energy. A grammatical constituent of this thermal energy is transferred through radiation and convection into the body of water which circulates in a network of pipes inside the boiler and therefore the water is evaporated and converted into steam. This steam has very high temperature and pressure at this stage of the procedure (about 25 MPa and 500-600 oC 1) and it is expanded from the high pressure turbine to the low pressure one. More specifically first the high pressure steam drives the high pressure turbine and the dr op off steam returns back to the furnace where it is reheated and drives the intermediate and low pressure turbines. This set of turbines rotates a shaft which is connected with a generator and in this way it is produced electricity. The squander steam which released by the low pressure turbine is cooled in the condenser and becomes water again. This water is pumped back to the network of pipes insight the boiler and olibanum the analogous procedure is iterated.In the condenser cold water is circulated into tubes, which ordinarily comes from a river or sea. Thus the heat of the exhaust steam is transfer with this cooling water, which temperature is raised after that and respectively the steam is liquefied and becomes water again. If the plant is near the sea or river, then the cooling water flows back in the sea or river with a higher temperature which usually is 10-20 oC up 1. Otherwise the warm cooling water should be processed through a cooling tugboat in order to be cool ed. The cooling tower is a system, where the warm cooling water is determined in a higher altitude in the top of the tower and then it flows down, being exposed to an upward stream of air and in this way it is cooled.As far as the flue gases argon concerned, they are passed through different cleaning stages before complete into the atmosphere through the stack. In more specific, the first step is to pass them through a device where the biggest amount of the dust particles is collected. This device is called precipitator. There are trine kinds of precipitators which are bag filters, cyclone filters and electrostatic filters 1. Next they pass into the desulphurisation building block so as the sulphur dioxide (SO2) to be removed.CUsersGeorgeDesktopMSc SESCarbon capture transportAssignment 1ststeam-power-plant.pngFig.3 Schematic of a coal-fired power plant. Source 9.3.4 Efficiency of coal-fired power plantsThe skill of power plant is a very significant positionor, on the grounds that by improving it is needed less fuel to be consumed and CO2 emissions can be constrained. Of course it is not possible for every plant to have the same efficiency and there are many factors which can influence it 10. In Fig.4 is presented in a flow chart which indicates the transformation of energy in one form to another, the losses in each stage and the total efficiency of a typical coal-fired power station. It can be inferred that the volume of losses occur during the conversion of thermal energy into mechanical in the turbines, where a big amount of thermal energy, i.e. heat is rejected through the condenser into the atmosphere. These losses are approximately 45% of the input energy and this fact is reasonable enough as it is explained by the second rightfulness of thermodynamics, which says that all heat engines have to reject some heat. Other significant losses occur in the boiler where about 6% of the input energy is lost in flue gas and in aide-de-camp procedures, su ch as the pumps where the losses are roughly 9%. so a typical coal-fired power plant has about 30% to 40% percentage of efficiency 1, 2.Fig.4 Conversion energy stages, losses and total efficiency of coal-fired power plants. Source 23.5 Emissions of coal-fired power plantsThe typical emissions of plant which does not have any cleaning stages are 1Carbon Dioxide (CO2) 700 thyroxins/ time of dayOxides of Nitrogen (NOX) 1t tonne/hourSulphur Dioxide (SO2) 1-20 tonnes/hourNitrogen (N) 2500 tonnes/hourSteam cl tonnes/hourFly ash 10-20 tonnes/hourIt is noticeable that about 2500 tonnes/hour of Nitrogen are released, nevertheless nitrogen is the major component of the air we breathe and therefore it is deemed harmless. Moreover about 700 tonnes/hour of Carbon dioxide are discharged during the combustion process and on world bases whole coal-fired power plants are responsible for 21% of global carbon dioxide emissions 10. Despite the fact that CO2 might be harmless in small concentrations a s it is a component of air mix, in bigger amounts it poses serious threats for the environs and contributes to the climate change as several studies have shown 11, 12. Therefore it is compelling to reduce the emissions of carbon dioxide and for this reason it has been developed several techniques of capturing and storage carbon 2, 13. Nitrogen oxides contribute to acid rain and harm peoples health. They are discharged in bigger amount when the temperature of the boiler is higher 1. Sulphur dioxide contributes as well as to the acid rain and therefore flue gases pass through the desulphurisation unit so as SO2 to be removed. Another very harmful emission of coal-fired power plants is the fly ash, which are known as particulates pollutes the environment in great extent and can also be responsible for respiratory problems in terms of peoples health. However most plants are equipped with precipitators so as to remove this dangerous fly ash as it is referred in Section 3.3.3.6 Advantag es-disadvantages of coal-fired power plantsOne major advantage of using coal for generating electricity is the reliability that offers. The coal-fired power plants can supply power to the gridiron with great reliability so as blackouts to be avoided during peak electrical loads. Except for that coal is very cheap fuel compared with other fuels and that fact makes this technology affordable enough and there is in abundance.On the other hand the disadvantages of coal-fired power plants are that they release greenhouse gasses into the atmosphereX. 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