VISCOSITY AND THERMAL-CONDUCTIVITY OF BLACK LIQUOR

Simple techniques were developed to measure the viscosity and thermal conductivity of high-solids black liquor. The method using a Brookfield viscometer for measuring viscosity was modified by applying a thin film of silicone oil on the surface of black liquor to prevent evaporation and skin formation. These two phenomena take place at high temperatures and high solids contents, affecting the viscosity measurements when the conventional method is used The results of the modified method compared well with the vibrating blade and coaxial cylinders viscometers for a hardwood liquor at 67.7% solids level. A line source method was used to measure the thermal conductivity of black liquor up to 83% solids. We found that the data published earlier by Harvin and Brown (1) could be extrapolated to high-solids contents.