The Research Of Parameters Optimization And Flow Characteristics On New Impinging Stream Reactor

With environmental problems becoming increasingly rigorous in recent years,the petrochemical industry must face the severe challenge.Developing resource saving and environment friendly new industrial reactors has become the general trend of contemporary industrial development.Gas-liquid impinging stream reactor is a new type of industrial reactor,which has the advantages of high mass transfer efficiency,fast reaction rate and few back-mixing phenomena.The mixing efficiency of the reactor depends on the movement of the fluid,the structural and operational parameters of the reactor.Among them,the movement of the fluid directly affects the mixing effect between fluids,and its specific form can be presented through the distribution and intensity of flow field.Therefore,based on the traditional gas-liquid impinging stream reactor,an emerging gas-liquid two-way mixed impinging stream reactor was constructed in this paper.Not only its structure parameters and operation parameters were optimized,but also the flow characteristics and mixing mechanism of the gas-liquid phase fluid were elaborated,providing theoretical basis for the optimization of the reactor.It is divided into the following two parts:(1)Based on the Euler-Lagrange model,mathematical model of gas-liquid two-phase fluid was constructed.Different physical geometric models were constructed by the method of control variates,and then models were structured grid generation.Furthermore,using air-water as the simulated working fluid,the different structural parameters were calculated and solved one by one through the computational fluid dynamics software.By analyzing the mixing characteristics of gas-liquid flow field,it is found that the length of gas-liquid premixed section(L)has little effect on the distribution characteristics of flow field.Specifically,with the increase of L,the velocity gradient at the stagnation point rises,the stagnation time of the droplet decreases.Moreover,with the increase of the nozzle diameter(d)of the liquid phase acceleration tube,the velocity gradient at the stagnation point rises,the droplets diameter decreases and the droplets is more uniformly distributed;with the increase of the length of the air acceleration tube(L₁),the velocity gradient of the acceleration tube drops faster,the droplet diameter rises and the velocity gradient at the center of the stagnation point is more dispersed.As a result,the optimal structural parameters of the two-way accelerating tube nozzle are L₁=500 mm,d=50 mm,and L=50 mm.(2)Based on the optimized reactor,the fluid mixing characteristics under different operating parameters were explored.The results show that under different operating parameters,the overall distribution of the spatial flow field presents the identical trend:it turbulent violently at the stagnation point and change mildly after moving away from the stagnation point.Specifically,the trend of axial pressure curve always drops,then sharply rises,then sharply drops and finally rises;the trend of radial pressure curve flattens,then rises sharply,then drops sharply and finally flattens;the trend of axial velocity curve always rises,then drops sharply,then sharply rises and finally drops;the trend of radial velocity curve flattens,then sharply rises,then drops sharply and finally flattens.Besides,above curves are all symmetrical about the stationary point.At the same time,under various operating parameters,the droplets diameter and stagnation time were counted,and then the distribution pictures of the Sauter Mean Diameter(SMD)and particle stagnation time were obtained.After collision,the fluid at the same section will be divided into four regions.Furthermore,vortices will appear in each region and the velocity will gradually increase from the inside to the outside.Above all,the optimal operating parameters are an initial gas phase flow rate of 30 m/s,an initial liquid phase flow rate of 15 m/s,and an initial fluid pressure of 2 MPa.