CHANGE OF APPARENT VISCOSITY OF COAL SLURRY DURING LIQUEFACTION: AKABIRA COAL/TETRALIN SYSTEM.

Change of apparent viscosity of Akabira coal/tetralin slurry was systematically measured under conditions of hydrogen pressure of 10. 1 MPa and steady reaction temperature of 723K and for a range of heating and cooling rates, stirrer revolution and slurry concentration. This was successfully done by a torque detector fitted to the stirrer of a 50 cm**3 microautoclave. Viscosity of 0. 2 to 12 Pa's was detectable by this torque meter. The results implied that the apparent viscosity increases with the amount of preasphaltene residing on the surface of coal particles while it decreases with deposition of the viscous coal particles onto the reactor and stirrer, surface with dissolution of preasphaltene into the solvent and with conversion of preasphaltene to lower molecular weight species.