Numerical simulation of a chemical looping combustion system using 2D computational fluid dynamics

Abstract This work develops a 2D numerical simulation of a chemical looping combustion (CLC) system, which utilizes syngas (CO + H 2 ) as fuel and natural ilmenite as the oxygen carrier, with a particle diameter of 150 µm. The CLC process consists of two interconnected fluidized bed reactors: the “air reactor (AR),” where oxygen carrier oxidation reactions occur in the presence of air, and the “fuel reactor (FR),” where fuel combustion takes place using oxygen from the carrier, in the absence of air. The theoretical result is the complete combustion of the fuel, which occurs in two independent reactors that only communicate through interconnecting pipes transporting the oxygen carrier material; however, in practice, some studies show incomplete combustion of the fuel. The interest in understanding and modeling this process is based on its feasibility as an alternative to prevent the emission of CO 2 mixed with N 2 into the atmosphere, as occurs in conventional combustion. In this process, both gases are emitted in separate reactors; that is, CO 2 is released mixed only with water vapor, which can be easily condensed. This approach helps avoid the high costs associated with separating CO 2 from N 2 . Computational Fluid Dynamics (CFD) simulated the CLC system in a 2D domain. Using the Eulerian multiphase model, the behavior of oxygen carrier particles and the corresponding heterogeneous reactions were simulated in both the FR and the AR. The aim was to analyze the functioning and performance of the reactor, as well as the oxidation (combustion) of CO and H 2 . These results were validated with previously published data. The details of the particle motion reveal that the particles remain in a regime of bubble fluidization as the chemical reactions take place. The results also indicate that exploring new configurations, operating conditions, or boundary conditions in future studies to promote fuel oxidation and achieve complete combustion may be possible.