Evolvement behavior of carbon minicrystal and pore structure of coal chars at high temperatures

The various slowly and rapidly pyrolyzed chars were prepared with Huainan coal and Guizhou coal at pyrolysis temperatures of 950℃～1400℃,and the evolvement behavior of carbon mincrystal and pore structure of coal chars was investigated during high temperature pyrolysis process.At the same time,the evolvement of pore structure of coal chars was studied.The content of carbon and hydrogen of slowly pyrolyzed chars(SPC) is obviously different from those of rapidly pyrolyzed chars(RPC).As the pyrolysis temperature increases,the carbon minicrystals of coal chars become more and more ordered.Besides,the 'graphitization' degree of SPC is larger than that of RPC.The micropore surface area and pore volume for RPC are obviously larger than those for SPC,indicating that the pores of RPC are much richer than those of RPC.In the initial gasification process of coal chars,the micropore surface area of coal chars decreases,while the micro-and meso-pore surface area of coal chars increases.In the end of coal char gasification process,the total surface area of coal chars decreases rapidly.