石炭チャーの炭酸ガスによるガス化速度に及ぼす炭種の影響

Abstract

Apparent rates of CO2 gasification of chars obtained from thirteen different kinds of coals were measured at temperatures of 1073-1273 K and under pressures of 0.3-1.6 MPa by means of a high pressure TGA apparatus. Changes of the surface area and the carbon structure of the reaction residue during gasification were also measured at various char conversions from 0 to 0.90.The initial surface area of char obtained by carbonization prior to gasification was shown to depend not only on the coal nature and carbonization temperature but also on the heating rate.For all chars employed the apparent initial reaction rate increased in proportion to P0.25. During gasification the surface area of the reaction residue increased rapidly at the early stage of the reaction and then decreased after showing a maximum which was greater for lower temperatures.The instantaneous rate based on the unit surface area also changed with the conversion. For all coal chars it decreased and leveled off at a conversion less than about 0.3. In a coversion range between 0.3 and 0.8 it was almost steady and decreased again towards completion of the reaction . Though the steady rate decreased with the rank of raw coal, the activation energies were approximately the same for all chars, being 190-210 KJ/mol.The growth of (002) peak in the X-ray diffraction spectrum for some kinds of chars, which was specified as caused by graphite structure formed during reaction, corresponded well to the decrease of instantaneous rate at the final stage of the reaction. The formation of graphite structure in such a low temperature was inhibited by deashing the char before gasification.