CRITICAL IMPELLER SPEED FOR SOLID SUSPENSION IN GAS INDUCING TYPE MECHANICALLY AGITATED CONTACTORS

Critical impeller speed for solid suspension (Ncs), has been measured in gas inducing mechanically agitated contactors (GIMAC) fitted with t wo impellers. Five different impeller designs were employed. It was fo und that the multiple impeller system having both pitched blade downfl ow turbines was the most energy efficient for the suspension of solid particles. The interimpeller clearance (C-3), and the impeller bottom clearance (C-l) were found to be important parameters, Further, for th is optimum combination, the design of the: lower impeller was optimize d in terms of impeller diameter (D), blade width (W), blade angle (A), and the number of blades (n(b)). An empirical model has been proposed based on the mechanism of fluidization.