RHEOLOGY OF LOW-VISCOSITY, HIGH-CONCENTRATION BROWN-COAL SUSPENSIONS

The paper describes how the rheology of low concentration brown coal s uspensions can be exploited to produce high concentration, low viscosi ty suspensions which are attractive as a potential coal-water fuel. Br own coal suspensions with solid concentrations approaching those of bi tuminous black coal have been prepared. The high inherent water conten t (almost-equal-to 60 wt%) and macroporosity of the brown coal have be en reduced by thermal and chemical means. The hydrophobicity of the co al surface has been increased sufficiently to reduce the tendency for swelling and water uptake. This, together with densification, has allo wed the solids content to be progressively improved from 30 wt% solids with raw coal to 65 wt% solids with modified coals while maintaining the viscosity of the suspension at a low level. The high solid concent ration was achieved without additives.