Experimental Study Of Oxygen-Accessibility Specific Surface Area And Effective Reaction Specific Surface Area During Pulverized Coal Combustion

A lot of physical and chemical processes are carried out in coal particle surface and pore during the ignition and combustion of pulverized coal. The specific surface area, pore volume and pore structure of pulverized coal become the important parameter affecting the pulverized coal combustion. Different kinds of coal have different specific surface characteristics, which can result in the diversity of combustibility. So, studying different kinds of coal and their specific surface characteristics in combustion has very important theory significance and practical application value.In this paper, five kinds of coal were selected for studying the variations of Oxygen-Accessibility Specific Surface Area(OASSA) during pulverized coal combustion under atmospheric pressure and pressurization, with TG experiments and N2/BET specific surface area tests. Five kinds of coal char were obtained in Drop Tube Furnace(DTF). Though TG experiments and SCT(Simple Collision Theory) model, the variations of Effective Reaction Specific Surface Area(ERSSA) and Critical Activation Energy(CAE) with burnout degree during coal char combustion were reached.The results showed that: when the average pore diameter of coal was greater than a certain value, the Cumulative Specific Surface Area(CSSA) correlated well with burnout degree, whether the pulverized coal combustion was under atmospheric pressure or pressurization. The CSSA increased first and then decreased in combustion under atmospheric pressure TG, but their OSSA increased gradually in the reaction. The CSSA and OASSA both increased in combustion under PTG. The CSSA and OASSA under atmospheric pressure TG was greater than that under PTG.The ERSSA increased first and then decreased with temperature and burnout degree during coal char combustion. Its change curve with the temperature was similar with DTG curve. The ERSSA and the combustion rate almost reached peak at the same temperature. When the burnout degree was 90%, the ERSSA reached maximum. The CAE increased with burnout degree during coal char combustion, and it reached greatest value in combustion telephase. Compared with the DTG curve, the reactive activity of coal char, which was in different atmosphere, coincided with the combustion rate comparatively. And it showed that the CAE, which was calculated by SCT model, can response the reactive activity during coal char combustion in truth.