EFFECT OF COAL RANK ON RHEOLOGICAL BEHAVIOR OF COAL SOLVENT SLURRIES DURING HEATING

The change in apparent viscosity of coal slurries with temperature fro m 323 to 663 K was examined using six kinds of coals ranging from 66 t o 84% C and hydrogenated anthracene oil (HAO). The measurement was per formed using a closed type of concentric double cylinder viscometer eq uipped with a sampling line for examining the change in properties of the solid and liquid phases in the slurry. In relation to the viscosit y change, the change in swelling ratio of the coals in the HAO with te mperature up to 623 K was also measured with an apparatus that detecte d the height of the coal layer in an autoclave utilizing X-rays. The s lurries of middlerank coals, Taiheiyo, Wandoan, and Illinois No. 6, pr esented two viscosity peaks around 450 and 570 K in the curves of appa rent viscosity versus temperature, although there was no clear viscosi ty peak in the slurries of the lower rank coals, Estevan and Wabamun. The maximum of the second viscosity peak increased with coal rank up t o 84% C, although the first viscosity peak was hardly observed in the slurry of the higher rank coal, Lingan. The theological behavior of th e coal slurries up to 570 K corresponded well to the swelling behavior of the coals: slight swelling, swelling in two steps, and drastic swe lling in one step for the lower, middle, and higher rank coals, respec tively, On reaching 570 K, the coals began to dissolve with the start of the liquefaction reaction and then disintegrated above 620 K, leadi ng to a decrease in the slurry viscosity. Thus, the theological behavi or of the coal-solvent slurry during heating was found to vary with bo th the solvent-absorption characteristics and the initial liquefaction characteristics of the coal.