Comparison of Structure and Gasification Reactivity of Rapid Pyrolysis Chars of Coal Water Slurries and Parent Coals

Rapid pyrolysis of coal-water slurries (CWSs) and parent coals were performed in a rapid pyrolysis reactor for three typical Chinese coals (lignite, anthracite, and a petroleum coke as reference). The pyrolysis temperatures ranged from 600 to 1200 degrees C with an interval of 100 8C. Samples were fed into the reactor within 1.5 min, and the pyrolysis time was controlled to 2 min. The effects of temperature on the yields of char were investigated. As CWS gasification processes usually utilize bituminous coal as feedstock, the structure of chars obtained from Shenfu bituminous coals were characterized by using XRD and BET N-2 gas adsorption, and the CO2 gasification reactivity of the chars was examined by using thermogravimetric analysis (TGA). The results show that, as the pyrolysis temperature increases, the char pyrolysis yields differ between CWS and parent coals, in which there is a competition between steam-coal/char reaction and water evaporation in the process. For the Shenfu bituminous coal, the degree of graphitization and the regularity of the microcrystalline structure of CWS chars were slightly higher than those of the parent coal chars, and the specific surface areas of the CWS chars were much higher than those of the parent coal chars. The gasification reactivity of the CWS chars was also higher than that of parent coal chars.