Numerical Simulation And Optimization Of CMCBR Based On Fluent

With the acceleration of China’s urbanization process and the continuous improvement of people’s awareness of environmental protection,more and more researches have been carried out on the technology of biofilm treatment of sewage.The Circulating Mobile Carrier Biofilm Reactor(CMCBR)is based on the Moving Bed Biofilm Reactor(MBBR)and adds two baffles in the middle of the reactor to force the water flow to circulate,improve the hydraulic flow performance,and avoid The problem of packing build-up and the mass transfer process are enhanced,thereby improving the treatment effect.However,since the aerated gas in the reactor cannot move uniformly to the downflow areas on both sides,it has a great influence on the treatment effect.And there are relatively few researches on this topic at home and abroad.Some of them use experimental methods,but there will be certain errors.There is almost no research on simulation combined with computational fluid dynamics.Therefore,this topic uses theoretical calculations,small tests and computational fluid dynamics simulations.combined methods to conduct research.Through theoretical calculation,it is found that the inlet velocity and the bottom gap height of the guide plate have great influence on the overall hydraulic condition of the reactor.Therefore,we obtained the experimental value with the help of the small test,and obtained the corresponding simulation value with the help of Fluent.By comparing the experimental and simulated values,it is concluded that the simplification of the physical model and the selection of the mathematical model are in line with the actual situation,and the method can be used for subsequent simulation.With the help of fluent software,by changing the speed of the air inlet and the height of the bottom gap of the deflector,the most suitable parameter values are obtained,which solves the problem of uneven aeration,so that the gas can flow uniformly from the upflow area to the downflow area,improving the The efficiency of the reactor to treat sewage.Increasing the inlet velocity from 0.7m/s,we found that the best effect was achieved when the gas velocity was 0.89m/s.Observe the mixture of gas and liquid two phase flow in the reactor liquid content in the vector diagram,figure,turbulent kinetic energy figure,before contrast transform device,we found that when the inlet velocity of 0.89 m/s drop flow region uniform gas distribution,air bubble inside the reactor can cycle to cycle,bubble has a longer contact time with water,turbulence kinetic energy is higher,the overall movement is intense,In a relatively short time,oxygen content can reach saturation,which is conducive to oxygen mass transfer.The inlet speed is set to 0.89m/s,the deflector plate backlash height is increased sequentially from 250 mm,and the optimal floor gap height is 250 mm by comparing the gas content and turbulent flow energy of different heights in the same reactor and the gas content and turbulent flow energy at the same height in different reactors.Compared with the pre-retrofit device,when the floor gap height is 250 mm,the gas content is evenly distributed in the recurrent area,and the turbulence flow energy is better than other situations.By discussing the distribution of the flow field in the reactor at different inlet speeds and deflector floor heights,the length of the deflector plate of the circulating mobile carrier biofilm reactor is modified,and the inlet speed is changed,in order to find the optimal inlet speed and the optimal deflector floor height without increasing the energy consumption,so that the gas can flow uniformly from the upflow zone to the downflow zone on both sides,and the overall gas content and turbulence flow can reach a higher state.The gas and liquid phases in the reactor are fully mixed to improve the processing efficiency of the reactor.