Comparative analysis of a batch and continuous fluidized bed reactors for thermocatalytic decomposition of methane: A CFD-DEM-MGM approach

Abstract

ThermoCatalytic Decomposition of methane (TCD) has shown great potential for synthesis of valuable carbon nanomaterials as well as hydrogen production, however due to the importance of the phenomena operating at different scales, it is a complex process to model and predict. During the TCD process methane is decomposed to hydrogen gas and solid carbon. Carbon is accumulated on the catalyst particle and leads to larger but less active catalyst particles. In this study, a Computational Fluid Dynamics-Discrete Element Method-Multi Grain Model (CFD-DEM-MGM) was employed to investigate two catalytic fluidized bed reactors for TCD with the same dimensions. Case-1 involved a batch of catalyst particles staying in the reactor during the process, while Case-2 featured a continuous reactor with removal of catalyst particles from the bottom and the introduction of fresh particles from the side. Results showed that the continuous reactor had lower catalyst particle growth and reduced deactivation due to limited residence time, yet demonstrated higher carbon production and gas conversion. Case-1, with larger catalyst particles, experienced reduced bubble formation, while in Case-2 the continuous removal/introduction of particles enhanced solids mixing. Internal diffusion limitations affected reactor performance, emphasizing the CFD-DEM-MGM model’s potential for optimizing fluidized bed reactor design and gas-solid contacting in the TCD process.