NEWTONIAN VISCOSITY OF HIGH SOLIDS KRAFT BLACK LIQUORS - EFFECTS OF TEMPERATURE AND SOLIDS CONCENTRATIONS

The Newtonian (zero shear rate) viscosities of four different softwood kraft black liquors from a four variable-two level factorially design ed experiment for pulping slash pine were determined for solids concen trations up to 84 % and temperatures up to 140-degrees-C (413.2 K). Me thods of measurement and estimation of zero shear rate viscosities fro m viscosity-shear rate data have been described and compared. The comb ination of the absolute reaction rates and free-volume concepts were u sed to express the relationship between the Newtonian viscosity and te mperature. Attempts were made to obtain a generalized correlation for Newtonian viscosity as a function of temperature and solids concentrat ions. The results of this model and results of our previous empirical correlation have been compared and discussed.