Demonstration of CO2 capture with CaO and Ca(OH)2 in a countercurrent moving bed carbonator pilot

Abstract

Decoupling the carbonation and calcination stages of Calcium Looping (CaL) facilitates the capture of CO2 from small point sources, or even the atmosphere, by transporting CO2 as CaCO3 to centralized calcination plants to obtain pure CO2 and regenerate the Ca-sorbent. In this work, we provide the experimental proof of a novel countercurrent moving bed carbonator particularly suited for such applications. We conducted experiments in a 3-meter-long moving bed reactor with an internal diameter of 0.15 m, using Ca-sorbent particles of varying sizes (in the mm and cm scale). Simulated flue gases with varied concentrations of CO2 (up to 8.5 %v), superficial gas velocities (0.5–2 m/s) and inlet gas temperatures (250–630 °C) have been tested. The temperature profiles we observed along the axial direction confirm the formation of a carbonation zone at optimum temperatures (i.e., 550–700 °C), together with a CO2 polishing region towards the gas exit that leads to CO2 capture rates over 99 % in some cases. Using Ca(OH)2 as a CO2 sorbent, we achieved a molar conversion to CaCO3 of approximately 0.7.