Two-phase Flow Simulation And Process Intensification Of Bubbling Reactor

The bubbling reactor is an important gas-liquid two-phase flow reaction equipment.In this paper,the numerical simulation of the bubbling reactor was carried out in the context of the optimization and reformation of the bubbling reactor of the chlorohydrin chemical section of the propylene oxide production process.A new method of adding internal components to the reactor to reduce bubble aggregation and enhance gas-liquid mass transfer is proposed.This research work can provide a theoretical basis for the optimization of reactor design and the development of new high-efficiency reactors.The main work is as follows:Based on VOF multiphase flow model and standard k-? turbulence model,steady-state numerical simulation of bubbling reactor was carried out.The effects of inlet velocity and opening diameter on the simulation results of the flow characteristics gas-liquid two-phase flow in bubbling reactor were investigated in detail.The simulation results show that the gas hold-up in the reactor increases with the increase of the superficial gas velocity.The diameter of the side wall opening determines the initial size of the bubbles entering the reactor.The larger the diameter of the opening,the larger the initial diameter of the bubbles,and the earlier the coalescence occurs in the reactor.According to the gas hold-up distribution in the reactor,the bubbling reactor is divided into "bubbling section","mixing section" and "coalescing section".The gas hold-up distribution in the mixing section is uniform,which is most conducive to gas-liquid mass transfer and reaction.The study also found that the injection depths of the gas phase at three different inlet velocities are 12 mm,17mm and 22 mm respectively,while at the same inlet velocities,the injection depths of the four bubbling reactors with open diameters are all about 12 mm.It is shown that the depth of gas injection in the reactor is mainly affected by the inlet velocity,which is independent of the diameter of the reactor opening.Aiming at the problem that the bubble coalescence in the reactor leads to the decrease of the contact area between gas and liquid,which is detrimental to the mass transfer and reaction between gas and liquid,a method to intensify the process of bubbling reactor by adding internal components in the reactor is proposed.The effects of bubble breaker on gas holdup and bubble size in the reactor were investigated.The results show that the number of coalescent bubbles in the upper part of the bubble breaker was significantly less than that in the lower part,and the proportion of bubbles decreased from 0.5149 to 0.4792,with a decrease of 7%.This indicates that the bubble breaker can effectively break up the coalesced large bubbles,improve the gas dispersion in the reactor,better control the space position between bubbles,and reduce the coalescence phenomenon between bubbles.In addition,the bubble breaker can effectively restrain the rising speed of bubbles and increase the residence time of bubbles in the reactor,which is conducive to mass transfer and reaction process between gas and liquid phases.The bubble motion behavior in a bubbling reactor at low gas velocity was tested by PIV technology.The experimental results show that the bubble breaker module can effectively break the bubbles in the reactor,greatly improve the uneven distribution of gas phase,and the breaking effect of the bubble breaker on the large bubbles can improve the speed of gas-liquid interface renewal,so that more fresh gases are exposed to liquid water.It is very advantageous to the mass transfer and reaction process between gas and liquid phases,and can realize the purpose of strengthening the process of bubbling reactor.