煤粉在高温空气中着火前后孔隙结构的变化

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3 nm的孔隙随挥发分析出的加剧而急剧增加。

Change in Pore Structure of Pulverized Coal Before and After Ignition in High Temperature Air

The ignition and early stage homogeneous combustion of bituminous pulverized coal stream in power station boilers is investigated in a high-temperature air (HTA) ignition test facility. The pulverized coal stream is heated rapidly by HTA with various temperatures and the flow is turbulent. The pore size distribution and specific area of the pulverized coal are measured as functions of pulverized coal particle size and HTA temperature, before and after the homogeneous flame appears. The experiments indicate that, the deformation and the volatilization have major influence on the pore structures of particles, and the change tendencies are opposite. Because of different thermal characteristic of the different particle size of pulverized coal，when the particle size is big and the HTA temperature is low, the influence of the deformation is dominating on the change of pore structure，make pore close; When the particle size is small and the HTA temperature is high, the influence of the volatilization become dominating and makes the number of pores increase. If the HTA temperature is increased, pulverized coal volatilization will be enhanced, and the volume of sub-3 nm pore will be also increased remarkably.