Studies on the performance of a rotating drum bioreactor for bioleaching processes — Oxygen transfer, solids distribution and power consumption

Abstract

Rotating drum bioreactors have shown the potential for bioleaching processes with high solids concentration. A gas-sparger that can produce small bubbles (∼ 1.0 mm) has been fitted into a rotating drum bioreactor to improve gas–liquid mass transfer performance. Gas–liquid mass transfer, solids distribution and power consumption in the rotating drum bioreactor were evaluated as function of bioreactor operating parameters. k L a of the evaluated rotating drum bioreactor varied in the range between 0.0326 s − 1 and 0.0927 s − 1 with aeration rate varying from 0.286 vvm to 1.43 vvm and rotational speed from 1.67 rpm to 10.0 rpm, which was close to that of typical stirred tank bioreactors. A relative uniform solids distribution was achieved at the rotational speed 3.33 rpm and the aeration rate 0.429 vvm. The specific power consumption of tap water and slurry were 0.0186 W/L (11.0 rpm, without particles) and 0.0407 W/L (11.0 rpm, solids volume fraction 0.097) respectively, and this indicated that the rotating drum bioreactor could provide microbes in a slurry with low particle collision effect. The tested rotating drum bioreactor possessed excellent gas–liquid mass transfer performance and low power consumption, making it suitable for gas–liquid–solid-microbes reaction systems, such as bioleaching processes.