Modified Overlapping Grain Size Distributed Model for the Kinetic Study of CO2 Capture by a Synthetic Calcium-Based Sorbent: Structural Changes from the Chemical Reaction and Sintering

In this study, an overlapping grain size distributed model (OGSDM) was proposed to investigate the kinetics of carbonation by CO, of a synthetic zirconia-stabilized Ca-based sorbent composed of 10 wt % ZrO2 and 90 wt % CaO in the subsequent calcium-looping cycle. In the OGSDM, the synthesized calcium-based particle consisted of initial numerous nonuniform spherical grains, which were allowed to overlap. The initial size distribution of grains was obtained through the pore-to-sphere factor method using BET-BJH analysis data. The OGSDM was improved by considering a variable diffusion coefficient of the gaseous reactant through the development of the product layer as a function of overall conversion. Mathematical modeling using the grain size distributed model (GSDM) and the OGSDM was used to calculate the overall conversion over the reaction time. It was found that the assumption of overlapping spherical grains improved the ability of the grain model in the kinetic study of the gas-solid reactions. Profiles of the physical properties of the sorbent, such as porosity, specific surface area, and density, were predicted well using the modified OGSDM during the carbonation reaction.