Randomly Packed Methanation Fixed-bed Numerical Simulation Of Chemical Reaction With Cylindrical Catalysts And Bed Structure Optimization

In this paper,randomly packed fixed-bed reactor with cylindrical catalysts was chosen as the research object,and a simulation study was conducted on the particle stacking structure,flow field flow,and methanation reaction process inside the bed.The main work and conclusions are as follows:(1)According to the size of the actual catalyst,using the DEM software,a threedimensional model of the cylindrical catalyst that is close to the actual shape is established,which ensures the reliability of the later calculation results.(2)Using the CFD-DEM method,a cold bed simulation was performed on a fixed column of random deposits.The results show that this method can better simulate the deposition process of the cylindrical catalyst bed and the distribution characteristics of the flow field.(3)Under the cold condition,the influencing factors of the catalyst particle stacking structure and the flow field characteristics inside the bed were simulated by the CFD-DEM coupling method.(1)The ratio N of the diameter of the bed to the diameter of the catalyst was changed,and the numerical simulation of the flow field characteristics was performed on the catalyst beds with diameter ratios of 3,5,10,and 20,respectively.The results show that when N=5,the fluid flow inside the bed is smoother and more uniform,and the fluctuation range is smaller,which is favorable for fluid mass transfer and heat transfer.(2)Changing the ratio of the height of the catalyst bed to the diameter of the bed,ie,the ratio of height to diameter H/D,numerical simulation of the flow field characteristics of the catalyst bed with the ratio of height to diameter of 0.5,1,2,3,and 4,respectively.The results show that the higher the height of the bed,the smaller the diameter of the bed and the greater the pressure drop across the bed.(3)Changing the diameter and ratio of the catalyst(d/h),the numerical simulation of the internal flow field of the catalyst bed with d/h of 0.3,0.5,1,2,3,and 4.The result shows particles in the interior of the bed are densest,the voidage is the smallest,and the bed pressure drop is the largest when d/h is 1.(4)Under the thermal condition,the methanation reaction inside the columnar catalytic bed was simulated by the CFD-DEM coupling method.The distribution of characteristic fields such as temperature field,pressure field and component concentration in the bed was obtained.The material import speed and feed were explored.The effect of temperature on the chemical reaction,and the influence of the ratio of the bed height to the bed diameter and the number of bed segments on the chemical reaction are explored.The relevant conclusions obtained provide recommendations for actual production.