CFD simulation of syngas chemical looping combustion with randomly packed ilmenite oxygen carrier particles.

Chemical looping combustion (CLC) offers innovative carbon capture via oxygen carrier (OC) circulation between separate reactors. Circulating fluidized beds facilitate OC transport between fuel and air reactors for reduction and oxidation. By avoiding direct contact between fuel and air, minimal energy is required for CO₂ separation. Disadvantages resulting from the conventional circulating fluidized bed system are the additional energy necessary for OC transportation and the challenge to operate at elevated pressure. A novel approach to CLC is proposed by considering a packed bed system with stationary OC particles undergoing periodic reduction and oxidation stages by shifting feed gas streams. The major design benefit lies in the prospect of process operation at high pressure. Finding optimal operating conditions is a mandatory step prior to implementing the process at industrial level. In this work, COMSOL Multiphysics was used for computational fluid dynamics (CFD) modelling in order to simulate the syngas-based CLC process with ilmenite OC in a packed bed reactor configuration. Mass, momentum and heat transfer mechanisms were accounted for to describe the combustion, purge and regeneration stages within a bed of randomly packed spherical OC particles at both macro- and micro-scale dimensions. The scope of the particle-resolved CFD multiscale model with realistic bed morphology was the in-depth analysis of the intraparticle phenomena occurring during the redox reactions, with emphasis on heat transport. Model results agree with published literature and provide additional understanding regarding the process in order to contribute towards the design of a flexible and energy efficient power plant concept. [ABSTRACT FROM AUTHOR]