Kinetic Study On CO Coupling Reaction And CFD Simulation Of The Reactor

Gas phase coupling of CO and methyl nitrite(MN)to prepare dimethyl oxalate(DMO)is the first and most important step in the production of ethylene glycol from syngas.In this paper,Pd/?-Al2O3 catalyst was used to investigate the characteristics of the CO coupling reaction and determine the kinetic data in a tubular fixed bed reactor.The tubular reactor was regarded as a one-dimensional homogeneous model.And the ode45 function of Matlab software(Runge-Kutta algorithm)was used to fit the experimental data to obtain the kinetic equation of the CO coupling reaction.Since the CO coupling reaction is a moderate exothermic reaction,a small-diameter ratio tubular fixed-bed reactor is generally used in the industry.The influence of the relatively severe flow unevenness in the fixed bed with small diameter ratio on the transfer and reaction in the reactor is worthy of further study,which could provide a reference for the design and optimization of industrial reactor.In this paper,the discrete element(DEM)method is applied to simulate the realistic filling by oscillation with PFC software and the random packed bed of equal diameter particles with small diameter ratio(D/d=3-5)is established as the geometric fixed bed model for CFD simulation.After that,the kinetic equation obtained by the experimental fitting was compiled into the model of CFD.Then the flow field distribution of the fixed bed reactor was calculated by Fluent,analyzing how the wall effect and the channel flow affect transfer and reaction.The results show that the wall effect of the reactor with the diameter ratio of 3.14 has the greatest influence,having the largest pressure drop and the minimal conversion rate in the outlet.When the diameter ratio is 4.16,obvious channel flows are generated.The local channel flows reduce the conversion rate in the first half and increase the conversion rate in the second half of the bed.As a result,the activity of the catalyst is fully utilized and the adverse effects of gully flow are reduced.When the diameter ratio grows to 5.20,the flow distribution is relatively uniform,but the heat exchange is insufficient,and the temperature of the bed hot spot reaches 442 K,which is very unfavorable to the reaction.