Process Intensification in Stirred Tanks

A summary of methods for process intensification in stirred reactors is presented, based mainly on the experience from R&D in the minerals processing industry. The process intensification concept is broadened to include innovations which lead to dramatically increased throughput for large-scale processing reactors, in contrast to the traditional definition of reactor size reduction, which has so far been ignored by the minerals industry. Methods enabling operating at high solids concentrations in processing tanks are reviewed to increase the throughput. It is proposed that the agitation power constraint at a high solids loading can be overcome by removal of baffles, for slowly reacting slurry systems typical in minerals processing. It is also suggested that the difficulty of pumping of high-concentration slurry feed can be overcome by operating with stratification, such that the solids residence time is made longer than the bulk flow residence time. Production loss through tank downtime is common in the mineral process industry, thus, a need to reduce the tank downtime should not be underestimated in the context of process intensification. Methods including the swirl flow technology developed by CSIRO and Queensland Alumina Ltd in Australia to suppress the scaling growth, and agitator design principles to reduce erosion are introduced. Enhanced mass transfer toward process intensification is also discussed.