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在高温空气点火试验台上,采用不同温度的高温热空气对处于高速湍流流动的烟煤煤粉气流进行快速加热,以模拟煤粉气流在电站锅炉炉膛内受热升温以及初期着火燃烧过程。在煤粉气流发生均相着火前后过程中,对其中不同粒径煤粉的孔隙结构及其比表面积随热风温度的升高而产生的变化进行了试验研究。结果表明,煤粉颗粒孔隙主要受热变形和挥发分析出2方面的影响,产生截然相反的2种变化趋势。由于不同粒径煤粉颗粒传热特性的差异,当粒径较大且热风温度较低时,其孔隙结构的变化以热变形的影响为主,孔隙产生闭合;当粒径较小且热风温度较高时,则挥发分析出的影响占优,孔隙出现增长。随着热风温度的升高,小于3nm的孔隙随挥发分析出的加剧而急剧增加。
In the high temperature air ignition test stand, high temperature hot air with different temperature was used to rapidly heat the stream of bituminous coal in high speed turbulent flow to simulate the heating process of pulverized coal airstream in the boiler hearth and the initial ignition combustion process. During the process of homogeneous flow of pulverized coal airstream, the pore structure and specific surface area of pulverized coal with different particle sizes were experimentally studied with the increase of hot air temperature. The results show that the pores of pulverized coal particles are mainly affected by the deformation and the volatilization of the two aspects, resulting in two diametrically opposite trends. Due to the difference of heat transfer characteristics between pulverized coal particles with different particle sizes, when the particle size is larger and the hot air temperature is lower, the change of pore structure is dominated by thermal deformation and the pores are closed. When the particle size is small and hot air temperature At higher temperatures, the effect of volatilization is dominant and the porosity increases. As the temperature of the hot air increases, the porosity of less than 3 nm sharply increases with the increase of volatilization.