| Coal is the main primary energy of electric industry in current and future longer period of time in China. China is rich in coal resources, but as the growth of coal consumption and the constraint of coal production level and transport, as well as the change of the international coal market, the price of the coal rose sharply in recent years in China. The cost of the fuel accounted for the general expense of coal-fired power plant more than 70 percent. Thus, the reduce of coal consumption and the improving of the economy of coal had become a focus for coal-fired power plant. Usually, pulverized coal-fired boiler can not use the normal designed coal, and even coal is far from the design coal. Consequently it will impact the stability of the combustion in the boiler, and reduce the thermal efficiency of boiler. Thus, it is very important to study the combustion characteristics of different coal. In this paper, thermal analysis method is used to analyze the combustion characteristics of several single coal and mixed coal.The change of oxygen concentration and temperature which is pulverized-coal come through from the burner nozzle to end the furnace, is very complicated, and the oxygen concentration and temperature are very important factors on pulverized-coal combustion. Therefore, in this paper, the combustion characteristics of pulverized coal in different oxygen concentration and temperature were studied. The time of pulverized-coal when ejected from the burner nozzle until ignited is very short, and pulverized-coal will achieve to a high temperature speedily after bursting into flame. In the process of coal combustion, burning rate and burnout time of pulverized-coal is mainly deiced by the char because the char occupies most of the weight and heat of pulverized-coal's combustion. Based on the above consideration, the constant temperature thermal analysis method was used in this paper, warming up through the procedures, so that the char will burn in a set constant temperature. In this paper, Pingshuo 5000 and anthracite were tested in different oxygen concentration by constant temperature TGA. According to result of test, the burnout time and average burning rate of coal coke was computed. By analyzing the law of oxygen concentration's influence on average burning rate, the difference combustion characteristics of pulverized-coal was studied. At the same time, in order to close to the condition of the practical combustion, the combustion characteristic of single particle coal was deduced. On the base of research on oxygen concentration's influence on coal combustion, the constant temperature thermal test was been done. Anthracite, Wenjialiang coal and Pingshuo 5000 bituminous were tested in different oxygen concentration and temperature condition, and the temperature's influence on characteristics of pulverized-coal was mainly studied. According to analyze the change of average burning rate with the different temperature, the optimally combustion temperature region of the char was researched. Through comparing the average burning rate between the char and the coal, the influence of carbon fixation on combustion was also studied.Finally, the combustion characteristic of mixed coal which was composed by anthracite and Pingshuo 5000 (1:1) was researched. By the thermal test on mixed coal in different oxygen concentration and temperature condition, analyzing the influence of oxygen concentration and temperature on mixed pulverized-coal's combustion. The difference characteristic of combustion between mixed coal and single coal was also been studied. The research on above will be give a reference suggestion on the research of combustion of mixed coal. |
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