Multiscale CFD modelling of syngas-based chemical looping combustion in a packed bed reactor with dynamic gas switching technology

Abstract

Chemical looping combustion (CLC) is a highly efficient energy conversion technology designed for burning fossil fuel with inherent carbon capture potential. The main advantage of running the CLC process in a packed bed configuration over the conventional circulating fluidized bed setup is the ability to operate at high pressure. In this work, a dynamic multiscale model was developed to simulate packed bed syngas CLC with ilmenite oxygen carrier (OC) particles, subsequently validating simulation results in terms of fuel and OC conversion, and temperature distribution using literature data for both oxidation and reduction steps. The model was used for investigation of multiple cycle operation, intraparticle fuel and OC concentration distributions, as well as effects of particle sizes and flow rates during OC reduction. Results revealed pressure drop reductions by 45% for 50% larger particle sizes and 66% for 50% lower flow rates, as well as better bed utilization for lower particle sizes and flow rates based on fuel breakthrough curves. In addition, a CFD multilayer particle model was developed to strengthen multiscale model results on pressure drops and mass transfer efficiency, and study temperature distribution with respect to particle dimensions during OC oxidation. Results indicated a positive effect on energy efficiency for smaller particles due to higher packing density and particle surface area, reaching intraparticle temperatures of 1110 ℃ and exit gas temperatures of 980 ℃ (i.e., 13% higher than base case size) during OC oxidation.