Development of a new microbubble system and its performance

Microbubbles are defined as bubbles with diameters less than 50 μm. Microbubbles have many advantages, such as huge interfacial area, low rising velocity in liquid phase, high inner pressure and fast dissolution. In this study, an accelerator was developed, and a system consisted of a conventional water pump and the accelerator was used as a microbubble aerator, with the expectation that it could be low in cost and easy to scale up. The produced microbubbles had a mean count diameter of less than 40 μm. In the experiments of 20 L volume, when the liquid flow rate was 20 L·min^-1 and the gas flow rate was 2.67 L·min^-1, the mass transfer coefficient of oxygen was more than 1.7 min^-1 and the oxygen utilization efficiency was higher than 42%. Higher temperature was good for the mass transfer from the gas phase to the liquid phase. In the pilot-scale study of 90 L volume, a mass transfer coefficient of more than 0.18 min^-1 and an oxygen utilization efficiency of more than 27% were achieved at a liquid flow rate of more than 14 L·min^-1 and the gas flow rate of lower than 2 L·min^-1. Compared with the Nikuni system, this system allows higher gas flux, generates smaller microbubbles, consumes less energy and performs better in mass transfer and oxygen-supply capacity.