A METHOD FOR DETERMINING THE BOUNDARY BETWEEN STAGNANT AND FLOW REGIONS OF HIGH-CONCENTRATION SLURRY IN A STIRRED VESSEL USING AN ELECTRIC-CONDUCTIVITY METHOD

This paper presents a method using an electrode probe system to determine the boundary between stagnant and flow regions of a slurry which has the characteristics of a Bingham fluid, in a stirred vessel. The probe consists of a fine tube playing the roles of an anode and a tracer injector, and eight fine needles serving as cathodes. The distance between an anode and each cathode is kept constant at 8 mm. The tracer including electrolyte was injected from the fine tube at constant feed rate into the fluid. The output potentials from each cathode were measured with a signal-processing circuit. As a demonstration, a slurry with high solid concentration of 50 wt.% fine CaCO3 powder in tap water was used as the Bingham fluid. It was found that the boundary of the fluid flow in the Rushton turbine and 6-blade paddle impellers mixer can be measured by the proposed method. The experimental results were confirmed by another visualization method using an Indian ink. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.