FLASH PYROLYSIS OF COAL FOLLOWING THERMAL PRETREATMENT AT LOW-TEMPERATURE

A new and simple pyrolysis method is presented in which the coal preheated at 150-200-degrees-C for 1 h is pyrolyzed successively without exposure to air. This method was developed based on the experimental fact that the hydrogen bond of coal is broken thermally at 150-200-degrees-C. When eight coals of different rank were pyrolyzed in an inert atmosphere using a Curie-point pyrolyzer, the conversion and the tar yield increased by 3-4% for several lower rank coals as compared with the nontreated coals. These increases were found to be brought about by the suppression of water forming cross-linking reactions, which were effected by the breakage of the hydrogen bond prior to the pyrolysis. A Japanese coal was also pyrolyzed by use of a free-fall pyrolyzer in an inert atmosphere, in which the coal preheated at 200-degrees-C while traveling a screw feeder was continuously fed to the pyrolyzer. The total volatile matter as well as the tar yield increased by 2-5% at the pyrolysis temperatures of 650-850-degrees-C as compared with the pyrolysis yields of the nontreated coal. Thus the proposed method was found to be a simple and effective pyrolysis method.