Simulation Of Methanation In A Random Packed Catalytic Bed Radial Flow Reactor Based On PFC-CFD

Combined with China's abundant coal,poor oil and low natural gas situation,resource advantages were transformed into economic advantages by the clean and transforming coal resources strategy.It also meets sustainable development policies.In the process of coal-tonatural gas production,the methanation reaction has strong heat release capability and difficulty in heat dissipation inside the methanation reactor.This problem has become a hot research topic at home and abroad.Based on the establishment of the three-dimensional reactor model,the discrete element method(DEM)was used to establish the model of the random accumulation of spherical particles in a radial flow reactor.The flow field distribution and methanation process in a radial flow reactor were numerically simulated by PFC(Particle Flow Code)-CFD(Computational Fluid Dynamics)coupling method.Firstly,the random stacking ring fixed-bed model is established by PFC discrete element software,and the void distribution and flow field distribution was analyzed.Secondly,under the same simulation conditions,the flow field simulation was carried out on random stacked beds with particle sizes of 12 mm,14mm,16 mm,20mm and 28 mm,and the influence of particle size on the flowfield distribution of radial flow reactor was analyzed,and the most evenly distributed configuration of the bed was obtained.Then,on the basis of this model,the diameter of the hole on the inner and outer distribution plates was changed,and the influence of diameter of hole on the field distribution is investigated.Meanwhile,based on the cold simulation,the methanation kinetic equation was added to simulate and analyze methanation process.Concentration distribution of CO and CH4 and temperature distribution in the bed wasextracted.The law of methanation reaction in the bed was obtained.Finally,the effects of catalyst sealing height and length to diameter ratio R on conversion were investigated.The simulation results show that the three-dimensional random stacked bed model was quickly and accurately established bythe discrete element software PFC-3D.The obtained catalyst bed model is closer to the actual accumulation process and more accurately reflects the actual situation.Under the cold simulation,the effects of feild distribution with particle size of 12,14,16,20 and 28 mm and the inner and outer plates apertures of 5mm,10 mm,and 15 mm were studied.The study found that the particle size is 12 mm,the pore size is 5mm,the fluid distribution is the most uniform,and the pressure drop is the largest.Through the thermal numerical simulation,the distribution of concentration of product and the reactants in the axial direction and the radial direction,and the variation of the temperature during the whole process are obtained.The effect of catalyst sealing height on methanation reaction at 20,45 and 70 mm was studied.It was found that the sealing height was optimal at 20 mm.The effect of structure on yield was studied when the aspect ratio R was 2,4,and 6 with the same catalyst volume.It was found that the optimal structure of the reactor is R=2.The relevant conclusions in this paper will provide references for subsequent research.