Shrinking reaction model (SCM) for K2CO3 based carbon capture

https://doi.org/10.1016/j.ccst.2021.100011

“TGA had been employed to study the carbonation kinetics of a single K₂CO₃ particle and supported K₂CO₃ adsorbent particle. Assuming that heat transfer in TGA reactor could be neglected and external diffusion could be eliminated, an unreacted shrinking reaction model (SCM) had been constructed by Zhao et al. to describe the carbonation kinetics of pure K₂CO₃ derived from KHCO₃ (Zhao et al., 2012a). For SCM, the gas-solid carbonation reaction started at the external surface of the K₂CO₃ solid particle, and the reaction proceeded into the unreacted core in center, with compact products layer being formed. As carbonation reaction continued, the products layer grew thicker, and thus increasing the mass transfer resistance for gas diffusion (Fig. 9a). The SCM kinetics model could be described by Eq. (11).”

“in which, CCO20, CH2O0 and CK2CO30 are the concentrations of CO₂, H₂O and K₂CO₃ at the initial moment, R1 is the radius of K₂CO₃ particle, kS and De are the chemical reaction rate constant and the diffusion coefficient, and f(t) is the time-dependent carbonation conversion.”

“Fig. 9. Typical kinetic models for depicting the carbonation kinetic behaviors of potassium-based adsorbents. (a) shrinking core model (SCM); (b) double exponential model (DEM); (c) deactivation model (DM).”