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1、本文格式为Word版，下载可任意编辑燃煤锅炉 外文翻译 外文文献 英文文献 中英翻译 Controlling the Furnace Process in Coal-Fired Boilers The unstable trends that exist in the market of fuel supplied to thermal power plants and the situations in which the parameters of their operation need to be changed (or preserved), as well as the tende
2、ncy toward the economical and environmental requirements placed on them becoming more stringent, are factors that make the problem of controlling the combustion and heat transfer processes in furnace devices very urgent. The solution to this problem has two aspects. The first involves development of
3、 a combustion technology and,accordingly, the design of a furnace device when new installations are designed. The second involves modernization of already existing equipment. In both cases,the technical solutions being adopted must be properly substantiated with the use of both experimental and calc
4、ulation studies. The experience Central Boiler-Turbine Institute Research and Production Association (Ts KTI) and Zi O specialists gained from operation of boilers and experimental investigations they carried out on models allowed them to propose several new designs of multicell and maneuverablein o
5、ther words, controllablefurnace devices that had been put in operation at power stations for several years. Along with this, an approximate zero-one-dimensional, zone wise calculation model of the furnace process in boilers had been developed at the Tsk Ti, which allowed Tsk Ti specialists to carry
6、out engineering calculations of the main parameters of this process and calculate studies of furnaces employing different technologies of firing and combustion modes . Naturally, furnace process adjustment methods like changing the air excess factor, stack gas recirculation fraction, and distributio
7、n of fuel and air among the tiers of burners, as well as other operations written in the boiler operational chart, are used during boiler operation.However, the effect they have on the process is limited in nature. On the other hand, control of the furnace process in a boiler implies the possibility
8、 of making substantial changes in the conditions under which the combustion and heat transfer proceed in order to considerably expand the range of 1 loads, minimize heat losses, reduce the extent to which the furnace is contaminated with slag, decrease the emissions of harmful substances, and shift
9、to another fuel. Such a control can be obtained by making use of the following three main factors: (i) the flows of oxidizer and gases being set to move in the flame in a desired aerodynamic manner; (ii) the method used to supply fuel into the furnace and the place at which it is admitted thereto; (
10、iii) the fineness to which the fuel is milled. The latter case implies that a flame-bed method is used along with the flame method for combusting fuel.The bed combustion method can be implemented in three design versions: mechanical grates with a dense bed, fluidized-bed furnaces, and spouted-bed fu
11、rnaces. As will be shown below, the first factor can be made to work by setting up bulky vorticisms transferring large volumes of air and combustion products across and along the furnace device. If fuel is fired in a flame, the optimal method of feeding it to the furnace is to admit it to the zones
12、near the centers of circulating vorticisms, a situation especially typical of highly intense furnace devices. The combustion process in these zones features a low air excess factor ( 1) and a long local time for which the components dwell in them, factors that help make the combustion process more s
13、table and reduce the emission of nitrogen oxides . Also important for the control of a furnace process when solid fuel is fired is the fineness to which it is milled; if we wish to minimize incomplete combustion, the degree to which fuel is milled should be harmonized with the location at which the
14、fuel is admitted into the furnace and the method for supplying it there, for the occurrence of unburned carbon may be due not only to incomplete combustion of large-size fuel fractions, but also due to fine ones failing to ignite (especially when the content of volatiles Daff 20%). Owing to the poss
15、ibility of pictorially demonstrating the motion of flows, furnace aerodynamics is attracting a great deal of attention of researchers and designers who develop and improve furnace devices. At the same time, furnace aerodynamics lies at the heart of mixing (mass transfer), a process the quantitative
16、2 parameters of which can be estimated only indirectly or by special measurements. The quality with which components are mixed in the furnace chamber proper depends on the number, layout, and momenta of the jets flowing out from individual burners or nozzles, as well as on their interaction with the flow of flue gases, with one another, or with the wall. It was suggested that the gas-jet th
