Discrete modeling of pore evolution in limestone particle calcination and carbonation

Building on our previous work on discrete modeling of pore evolution in a single limestone particle during calcination, this study extends the model to include both pore expansion due to CO₂ production (forward reaction) and pore shrinkage resulting from CO₂ accumulation in the pore walls (reverse reaction). These competing phenomena are modeled through local thermal energy balances, coupled with the transport of gas species. The local reaction rates for calcination and carbonation are determined by kinetic parameters, active surface area, and gas species partial pressures. The results capture the dynamic evolution of solid grains and pore structures over time, accurately resolving local conversion profiles and pore size distributions. By incorporating both expansion and shrinkage effects, the model provides a realistic representation of structural transformations during thermochemical cycling. Furthermore, the framework enables simulation of the full Ca-looping process by using the calcined product (CaO) as a reactive carrier for CO₂ absorption. The model reveals local pore-scale structural evolution during carbonation, including the formation of occluded or closed pore regions. This mechanistic insight highlights the feedback between pore morphology and reactivity, offering critical guidance for the design of efficient carbon capture and looping systems. These findings are essential for developing accurate single-particle continuum models and contribute significantly to understanding transport in reactive porous media.