Micro-scale simulation and intensification of complex Sabatier reaction system in cylindrical catalyst bed

Abstract

The methanation process based on the Sabatier reaction is becoming a key instrument in solving CO2 emissions and surplus electricity. A Sabatier fixed-bed reactor model with randomly stacked cylindrical particles was established by discrete element method (DEM), and the variation of the substances distribution, reaction characteristics and carbon deposition in the micro-scale catalyst was simulated by computational fluid dynamics (CFD). The effects of catalyst hole number and operating conditions on CO2 conversion and CH4 yield were also discussed. The result shows that as the reaction proceeds, the concentration distribution of the substances in the catalyst changes from a ring to a uniform, and the distribution of the reaction rate values in the catalyst changes from a V-shape to a U-shape. In the steady state, the catalyst is only effectively used in about 10% of the outer layer. The carbon deposition in the outer layer of the catalyst and the inlet of the reactor is more serious. And the average porosity value in the catalyst decreased by 0.012 as the reaction progressed to 1000 s. In the steady state, CH4 yield from high to low catalyst bed arrangement is 4 holes, 7 holes, 1 hole and solid. The CH4 yield can be increased by increasing the heat transfer coefficient and decreasing the inlet flow rate, and the reaction can reach a steady state faster by increasing the inlet temperature and pressure.