Modeling and scale analysis of gaseous fuel reactors in chemical looping combustion systems

Abstract

This work investigates the scale-up of chemical looping combustion (CLC), a next-generation technology for carbon capture and storage, to the industrial scale. The study focused on the bottom bed of the unit, which was considered to be the critical region during scale-up due to the large solids inventory in this zone combined with relatively inefficient gas–solids contact. Two CLC reactors of vastly different sizes (bench and utility scale) were studied to discern their difference related to scale-up via a one-dimensional model. This model considered kinetics that varied with the degree of oxidation and population distribution of the oxygen carriers, the mixing of which accounts for both convective and dispersive transport. The model was validated against bench scale data, and was used to evaluate the performance of a 1000MWth CLC fuel reactor using either syngas or methane as fuels. Sensitivity analyses were also carried out with this model to determine the effects of several parameters on fuel conversion, including solids circulation, oxygen carrier reactivity, bed height, and maximum bubble size. The results show that the mass transfer of gas from bubbles to the emulsion phase represents a significant limiting factor for fuel conversion in the bottom bed of a utility scale fuel reactor.