Structure Optimization of an Improved Inner-Circulating Biological Fluidized Bed by Numerical Simulation

Abstract

Recently, the structure of inner-circulating biological fluidized beds has been improved for the sake of making them more efficient. In the present paper, the separation zone composed of staggered triangle cones is added, which could prevent the loss of carriers. The presence of more carriers could provide more surfaces for biofilms and is helpful to the mixing of solid, liquid, and gas. The wastewater treatment efficiency could be improved. The main focus of this paper is to optimize the structure parameters of the separation zone by simulating the improved inner-circulating biological fluidized bed. The mixture model and the standard k-ε model are employed to simulate the gas–liquid–solid three-phase turbulent flow. Experiments are performed in a lab-scale CFB. The agreements between simulation and experiments verify the reliability of the methods employed in this paper. By simulation, the distributions of velocity and volume fraction in the CFB are obtained. The influences of the structure parameters of the separation zone on separation efficiency are investigated and the optimized separation zone is presented. Based on the optimization, wastewater experiments are conducted to check the function of the improved CFB with the optimized separation zone in wastewater treatment. All these results give good evidences for further design and optimization of the improved CFB, as well as the improvement of wastewater treatment efficiency.