Experimental study and kinetics on CO2 mineral sequestration by the direct aqueous carbonation of pepper stalk ash

Abstract

While carbon capture, utilization, and storage (CCUS) is recognized as a highly promising technology for large-scale CO2 reduction from power and chemical industries, there have not been many investigative efforts on CCUS using biomass feedstock such as pepper stalk ash (PSA). Therefore, in this study, the direct carbonation of incinerated PSA via an aqueous route was studied under low-medium pressure conditions in an autoclave reactor. To optimize the reaction conditions in order to achieve the maximum carbonation efficiency, the complex effects of various operating parameters, such as the reaction temperature, liquid–solid (L/S) ratio, reaction time, pressure, and reaction gas, on the CO2 sequestration characteristics were systematically investigated. Under the theoretical framework of the shrinking core model (SCM) and assuming that the diffusion coefficient is a function of time, a new kinetic equation was proposed to provide a more precise fit to the experimental data of the heterogeneous direct carbonation. In addition to solid carbonates, PSA carbonation yielded dry residues from liquid products, which included 58.03 wt% potassium oxide and hence can potentially be used as feedstock for potassium fertilizers.