Behavior of coal slag during gasification

Coal slag and refractory samples from an entrained slagging gasification process development unit were examined by microscope. Rapid wear of 90% Al/sub 2/O/sub 3/ - 10% Cr/sub 2/O/sub 3/ refractories was caused mainly by dissolution of the refractory matrix and removal of large Al/sub 2/O/sub 3/ grains. Unfired refractories were especially susceptible to this wear mechanism. Alumina grains dissolved in the slag, which resulted in the precipitation of dendritic hercynite during cooling. Reduction of FeO in the slag resulted in the precipitation of mullite crystals. Both mechanisms are believed to increase the apparent viscosity of the slag which can adversely affect slag tapping.