The influence of heavy distillate and middle distillate in the coal liquefaction solvent was investigated with a 5 L batch-autoclave. The following conclusions are obtained. (1) Under the coal liquefaction condition, heavy distillate in the solvent is effective for the coal conversion, but not for the fragment capping, as compared with middle distillate in the solvent. Consequently, the heavy distillate relatively reduces the oil yield. (2) The severe hydrotreatment for both the heavy distillate and the middle distillate enhances coal liquefaction reaction. (3) An increase of the content of donatable hydrogen in the heavy distillate produces high oil yield because of an improvement of the fragment capping, and that in the middle distillate promotes subsequent reaction. Consequently, severe hydrotreatment for the heavy distillate is effective than that for the middle distillate. (4) The heavy distillate is different from the middle distillate on the effect for coal liquefaction and of severe hydrotreatment. It is necessary for the suitable distillate design of the recycle solvent in coal liquefaction system.
Effect of volatile and ash contents on cloud ignition behaviors were examined for pulverized coal dust clouds, that were suspended in a laminar upward flow and heated by a single-pulsed YAG laser. We compared burning times of volatile matter, flame propagation velocities and lean flammability limits for several coals. The coals contains almost same volatile matter, but different ash. The present results showed that the burning time of volatile matter, flame propagation velocity and lean flammability limit were mainly determined by volatile content. The effects of ash content were small. The maximum flame propagation velocity increased with volatile content. The velocity increased the third as much as when volatile content increased from 10% to 20%.