快速热解褐煤焦的比表面积及孔隙结构

SPECIFIC AREA AND PORE STRUCTURE OF LIGNITE CHAR UNDER THE CONDITION OF FAST PYROLYSIS

利用热力工况与实际煤粉锅炉相似的管式沉降炉,获得快速热解条件下不同粒度、不同热解时间的煤焦试样,采用美国Micromeritics公司ASAP2020自动吸附仪测定低温氮吸附等温线,不同粒度及不同热解时间的煤焦其吸附等温线都是带回线的Ⅱ型吸附等温线,说明其具有较连续的完整的孔系统,孔径范围小至分子级孔,大至无上限孔(相对而言).各煤焦试样的比表面积及孔径分布具有相似的特点,分布曲线起始部分上翘,在孔直径3～4nm内出现峰值.试验条件下,随着热解时间的增加,煤焦的比表面积和孔容积减小.在各个相同的热解时间条件下,平均粒度29.61μm煤样的煤焦比表面积和孔容积均大于平均粒度72.79μm煤样的煤焦,表明煤粉粒度的减小对其热解后煤焦的孔隙结构有重要影响.

In a drop-tube furnace apparatus with the similar combustion conditions of actual furnace, char samples, different in particle diameters and Pyrolysis time, were prepared and analyzed by Micromeritics ASAP2020 auto-adsorption analyzer to obtain N2 adsorption isotherms. The absorption isotherms of char samples are all type II isotherms with hysteresis loops, which indicates that those samples consist of continuous and complete system of pores. The diameter of pores ranges from molecular scale to upper limit scale (contrast to normal one). There are similar in the specific suface area and the pore size distribution of different samples—the profiles turn up at the initial part, and peaks of curves show up in the range of diameters between 3nm and 4nm. Under the experimental condition, the specific area and volume of pores are reduced with the increase of pyrolysis times. The specific area and the pore volume of char samples with the average size of 29.61μm are larger than that of the ones with average size of 72.79μm, which domenstrates that the reduction of pulverized coal size impacts the coal char pore structure graeatly.