(570f) Effects of Support On the Reaction Mechanism of Iron Based Chemical Looping Gasification Particles – Platinum Marker and Computational Studies

The Syngas Chemical Looping (SCL) gasification process flexibly converts carbonaceous fuels such as coal and/or biomass derived syngas into carbon free energy carriers such as hydrogen and/or electricity while capturing 100% carbon in the fuel. The process, successfully demonstrated at 2.5 kW_th and 25 kW_th scales at the Ohio State University (OSU), is currently being scaled up to a 250 kW_th pilot scale. The SCL process utilizes iron oxide based looping particles to indirectly convert the fuel into separate streams of CO₂ and products via cyclic redox reactions. Techno-economic analyses published by both OSU and the U.S. Department of Energy (USDOE) indicate that the looping particle performance, i.e. particle reactivity, recyclability, and attrition resistance, is of vital importance to both the process efficiency and economics. Experiments carried out in both Thermogravimetric Analyzer (TGA) and differential bed reactor indicate that the transfer of iron cation and/or oxygen anion to/from the grain surface may be the rate limiting step of the redox reactions. It is also observed that the addition of inert metal oxide support may contribute to enhanced ionic diffusivity. Both inert marker technique and computational chemistry methods are utilized to investigate the effects of inert support on the redox reaction mechanism of the looping particles and its potential implications to the looping particle performance. It is determined, using Pt-Marker, that during the oxidation stage, the significant outward diffusion of iron forms a dense layer of iron oxide outside of the grain, reducing the overall reactivity of the particles. When support is added to iron, in contrast, inward diffusion of oxygen ion is notably enhanced, thereby increasing both the reactivity and recyclability of the looping particle. In addition to the marker studies, plane-wave periodic Density Function Theory (DFT) method implemented in the Vienna ab initio simulation program (VASP) was employed to explore the effect of support addition on the interactions between the looping particles and reactant molecules or ions.