Liquid-Solid Mass Transfer Behavior of a Stirred-Tank Reactor with a Fixed Bed at Its Bottom

The mass transfer behavior of a new batch stirred tank with a fixed bed of Raschig rings at the bottom was studied using diffusion-controlled dissolution of copper in acidified dichromate. Variables studied, amongst others, were the impeller rotation speed, Raschig ring diameter, fixed-bed height, and impeller geometry. The rate of mass transfer from the fixed bed to the solution increased with increasing impeller rotation speed, decreasing particle size, and decreasing bed height. The axial-flow turbine is more efficient in increasing the rate of mass transfer than the radial-flow turbine. The presented reactor is especially useful for conducting diffusion-controlled liquid-solid catalytic reactions involving reactants that need to be dispersed first, such as sparingly soluble solid particles.