Abstract
Liquid-solid mass transfer behaviour of a rectangular stirred tank reactor lined with single screens and stacks of closely packed screens was studied in relation to catalytic and electrochemical reactor design by the electrochemical technique. Variables studied were impeller rotation speed, mesh number, and wire diameter of the screen, as well as physical properties of the solution, number of screens per stack, and impeller geometry. The rate of mass transfer increased with increasing impeller rotation speed and decreased with increasing screen mesh number and number of screens per stack. Radial flow turbine impellers produced higher rates of mass transfer than axial flow impellers. The data were correlated by dimensionless mass transfer equations. A comparison between the volumetric mass transfer coefficient at a stirred single-screen electrode and at a stirred flat plate electrode shows that the volumetric mass transfer coefficient at the single screen is higher than that at the flat plate by a factor ranging from 7.3-22.5, depending on the operating conditions. For screen stacks, the ratio between the stack volumetric mass transfer coefficient and the flat plate value ranges from 2-46 depending on the operating conditions.
The importance of the present results in the design and operation of catalytic and electrochemical reactors used to conduct diffusion-controlled reactions was highlighted. The possibility of using screens as turbulence promoters to enhance the rate of heat transfer between the reactor wall and the surrounding cooling jacket was noted.