Configuration Optimization and Mass Transfer in a Dual-Impeller Bioreactor

Abstract

The bioreactor configuration including a dual-impeller combination, spacing between the impellers, and the diameter of the ring sparger is optimized based on solid suspension (N-jsg) and gas dispersion (N-f and k(L)a) in this work. Then, the solid suspension and gas dispersion performance in this optimized bioreactor are systematically studied. It is found that a smaller sparger (D-s/T = 0.32) achieves better performance in gas dispersion. A pitched-blade disc turbine down-pumping (PDTD) as a bottom impeller achieves the lowest N-jsg value, and has lower N-f value compared with PBTD (pitched blade turbine down-pumping) and TBHA (three-bladed helical agitator). Techmix 335 hydrofoil impeller down-pumping (TXD) as an upper impeller provides higher k(L)a values. TXD+PDTD are more suitable for the requirements of a bioreactor. k(L)a decreases slightly with increasing solid loading, which is beneficial to good gas dispersion in such bioleaching reactors with higher solid loadings (>20 wt%).