Towards random pore model for non-catalytic gas-solid reactions

Abstract

The random pore model (RPM) is the most comprehensive model for non-catalytic gas-solid reactions. The application of RPM is critical in some environmental pollutant removal reactions regarding sustainable energy systems. The common examples are flue gas desulfurization (FGD) by various solid sorbents and carbon capture and storage (CCS) systems, including greenhouse gas separation by carbonation reactions. So far, a review paper about the RPM has not been published in the literature. In this review paper, governing conservation equations for the RPM are presented, and RPM applications in various chemical, environmental, and metallurgical reactions are explained. Then, the paper discusses the method of defining the structural parameter, ψ, as the main parameter of the RPM. The RPM various modifications, such as non-linear concentration dependency, bulk flow effects, and predicting changes in pore size distribution (PSD) during the reaction are explained in detail. Kinetic parameters of various reactions, as mentioned above, are also determined comprehensively by applying the RPM on conversion-time experimental results originating from thermogravimetry (TG). In addition, breakthrough curves obtained using the RPM have been observed for some of the studied reactions in a packed bed reactor. Incomplete conversion is considered for the reactions with Z > 1. According to RPM predictions and experimental data, producing large pores by washing them with a weak acid or using a nanostructure pellet can solve this problem. Also, applications of the RPM to other reactions consisting mainly of gasification and combustion are presented. Finally, machine learning applications for multi-scale modeling of gas-solid reactions are discussed.