Research On Simulation Method And Application Based On DEM-CFD Sequential Coupling For Fixed Bed Reactor

It is the theoretical basis for interpreting its reaction synthesis process mechanism and mining its process intelligence that Exploring the hydrodynamic characteristics and flow resistance characteristics of complex gap microchannels in the catalyst particle bed of fixed bed reactor.CFD simulation of fixed bed reactor is an efficient technical means to carry out research in this field.However,there is still a lack of efficient and high-precision CFD simulation technology that can simulate the hydrodynamic characteristics in real complex gap microchannels.Aiming at this technical problem,The DEM-CFD sequential coupled simulation method based on sub model and the high precision CFD simulation method of porous media model based on velocity effect correction of viscous resistance coefficient were developed,which lays a technical support for clarifying the hydrodynamic characteristics and flow resistance characteristics of the complex gap channel in the catalyst particle bed for the fixed bed reactor.The DEM-CFD sequential coupling simulation method of fixed bed reactor based on sub model was established,in which firstly,the filling state of catalyst particles was simulated and described by the discrete element simulation software of EDEM,then,the secondary development of Python language programming is used to export the non spherical catalyst particle bed model,so as to accurately reconstruct the threedimensional solid model of the complex gap microchannel of the catalyst particle bed from the particle scale,and solve the technical problem that it is difficult to accurately reconstruct the gap channel model of the non spherical catalyst particle bed.Finally,the CFD software is used to simulate the hydrodynamic characteristics and flow resistance characteristics in the complex gap microchannel,and the experimental results show that the simulation prediction accuracy can meet the technical requirements of engineering calculation accuracy less than ± 5%.A DEM-CFD sequential coupling simulation method based on sub model is proposed to calibrate the viscosity resistance coefficient of porous media model under different apparent flow velocity and catalyst particle morphology.Based on Simulation and experimental means,the synergistic coupling evolution law of viscosity resistance coefficient vs.apparent flow velocity and its correlation regression prediction empirical model were constructed.A new high-precision CFD simulation method with porous media model was proposed in which the influence of velocity on viscous resistance coefficient was corrected by means of regression prediction empirical model.When the apparent flow velocity is in the range of 0 to 4m / s,the relative standard error is controlled within 4.15% to 7.2% between the simulation prediction values of this method and DEM-CFD sequential coupling simulation method.Compared with the traditional CFD simulation method with porous media model,the simulation prediction accuracy is improved by more than 90%.The high-precision CFD simulation method with porous media model corrected by velocity influence of viscous resistance coefficient is successfully applied to the simulation of DN1800 industrial scale ammonia converter reactor.The sudden increasing phenomenon of radial velocity on the top layer of the upper catalytic particle catalyst frame is accurately simulated and predicted,which explains the mechanism that the top layer of the catalyst frame is easy to induce the burning loss of catalyst particles,and the optimized and improved design scheme was put forward to inhibit the burning loss of catalyst particles on the top layer of the catalyst frame.