Kinetic study and modeling on the regeneration of Li4SiO4-based sorbents for high-temperature CO2 capture

Abstract

Li4SiO4 is acknowledged as a promising sorbent candidate in high-temperature CO2 adsorption. However, reaction kinetics for the regeneration process of Li4SiO4, especially its dependence on CO2 pressure is lack of understanding. This work designed and carried out a series of isothermal tests on the regeneration of pure Li4SiO4 and K-Li4SiO4 under CO2 partial pressure of 0–0.5 atm and temperature of 625–725 °C. For the first time, the expression of (Peq − PCO2)n is introduced into the regeneration rate equation so as to reveal its dependence on CO2 pressure. The reaction order (n) is found to grade according to the value of (Peq − PCO2), and the apparent activation energy is calculated as 284.42 kJ•mol−1 and 146.31 kJ•mol−1 for the regeneration of Li4SiO4 and K-Li4SiO4, respectively. Furthermore, this work proposes that power law model with m = 4/3 is the most probable mechanism function for the regeneration of Li4SiO4-based sorbents.