At the operation of 1t/d Process Supporting Unit (PSU) on the coal liquefaction test using Wyoming coal, the blockade was occured in the coal slurry line. The rheological properties of coal-slurries prepared with the coals used on test of PSU were researched and the fluid state in the pipes were studied. There were differences in the rheological property between not only the kinds but also the lots of coal. It was found that increasing with coal concentration in slurry, it became to show the Pseud-plastic behavior in the lower region of shear rate, and then it had a tendency of occurence of blockade under this condition in the pipe.
