Bubble dynamic behaviours at various capillary orifices in a bioreactor with methane oxidizing bacteria suspension

Abstract

AbstractBubble dynamic behaviour has a significant influence on methane bioconversion because a gas mixture including methane and oxygen is usually supplied into a bioreactor with a methane oxidizing bacteria suspension via capillary orifice, forming bubbles. In the work, bubble dynamic behaviours at various capillary orifices were experimentally visualized, as well as the movement of microorganisms was observed during bubble formation evolution. The experimental results showed the chemotaxis effect and the bubble expansion as two key factors affecting the movement of microorganisms in the bioreactor with methane oxidizing bacteria suspension. At the incline angle of 90°, the equivalent departure diameter and departure volume were the smallest, while the departure time was the shortest. With increasing inner diameter, the equivalent departure diameter and departure volume increased, but the waiting time was the longest and the departure time was the shortest at the inner diameter of 0.3 mm. In addition, the successive inrush of bubbles forming at the capillary orifice with 90° incline angle and 0.1 mm inner diameter resulted in the shock of the gas‐liquid interface, affecting the bubble dynamic behaviour. The results in this work contribute to the design of a high‐productivity bioreactor with an optimized aeration system for enhancing mass transfer of methane from the bubble to the bacteria suspension and subsequent methane bioconversion.