Experimental Study On Structure Optimization And Aeration Performance Of Cyclone Aerator

The activated sludge method is an economical and efficient method of wastewater treatment.Aeration is the key step of the activated sludge method,and cyclone aerator is widely used because of its long service life,less clogging and uninterrupted operation.To solve the problem of large diameter of aeration bubbles in the cyclone aerator,which leads to low oxygen utilization rate,this paper used CFD numerical simulation method and CFD-PBM coupling model to explore the structural optimization of the cyclone aerator,so that the cyclone aerator can produce more bubbles with smaller diameter and increase its bubble breakage rate.Meanwhile,the optimization results were verified experimentally using clear water aeration and oxygenation experiments.The main work and research results of this paper are:(1)The bubble breakage rate and the inlet and outlet pressure difference of the cyclone aerator were analyzed by changing two factors,the guide plate guide angle and the cutting tooth arrangement angle of the cyclone aerator,through the control variable method.The results show that the bubble breakage rate increases and then decreases with the increase of the guide plate guide angle in the cyclone aerator when the angle of the cutting tooth arrangement is certain.And the inlet and outlet pressure difference increases with the increase of the guide plate guide angle.when the guide plate guide angle is certain,the bubble breaking rate will increase and then decrease with the increase of the cutting tooth arrangement angle.Similarly,the energy consumption increases and then decreases,and the inlet and outlet pressure difference increases and then decreases with the increase of the cutting tooth angle.(2)Numerical simulations were conducted for 25 simulation scenarios and the simulation results were analyzed to derive the primary and secondary influences on the bubble breakage rate and inlet and outlet pressure difference between the guide plate guide angle of the cyclone aerator and the angle of cutting tooth arrangement,as well as the internal structure parameters of the cyclone aerator with optimal aeration performance.Finally,the optimized structure was compared with the original structure for verification.The results show that the guide angle of the guide plate has a greater influence on the bubble breakage rate and the the inlet and outlet pressure difference between of the cyclone aerator,and the optimal structure is the cyclone aerator with 90° guide angle of the guide plate and 30° arrangement angle of the cutting tooth.By comparison,the bubble breakage rate of the optimized structure was found to be increased by 12.5%.(3)Clear water aeration and oxygenation experiments were conducted on the optimized and original structures of the cyclone aerator in the aeration tank.The results show that the total oxygen transfer coefficient of the optimized structure increased by 27.1%compared to the original structure,while the standard oxygen transfer rate increased significantly by 27.7%,and the optimized cyclone aerator bubbles were smaller and denser as shown by processing the test images with imageJ software.In summary,the relationship between the guide plate guide angle and the angle of the cutting tooth arrangement of the cyclone aerator on the bubble breakage rate and the inlet and outlet pressure difference is derived by CFD numerical simulation in this paper,and is verified by clear water aeration experiments,which can provide theoretical and data support for the improvement of the aeration performance of the cyclone aerator.