Impact of fuel-derived chlorine on CuO-based oxygen carriers for chemical looping with oxygen uncoupling

Abstract

During the chemical looping with oxygen uncoupling (CLOU) process for CO2 capture from solid fuels, CuO-based oxygen carriers are expected to efficiently transport oxygen from the air reactor and convert fuel in the fuel reactor by releasing gaseous oxygen. To maintain high fuel conversion and CO2 capture efficiency, it is important to understand the impact of the fuel-derived Cl, which is highly volatile and corrosive, on the CuO/Cu2O in a CLOU environment. In this work, thermodynamic modeling was carried out to predict the characteristics of Cu-Cl interaction and develop a Cu deactivation rate model. Combustion experiments were performed to examine the impact of the Cl-containing flue gas on the CuO-based oxygen carrier. The oxygen transport capacities of the oxygen carriers exposed to the Cl-containing flue gas were measured by TGA. XRD and SEM-EDS were employed to characterize the ashes and oxygen carrier particles, respectively. The modeling results suggest that Cu-Cl interaction leads to the formation of CuCl and Cu3Cl3, causing the loss of effective Cu. The fraction of HCl converted to CuCl/Cu3Cl3 (XHCl) was predicted to be almost linearly correlated with the Cl content, while H2O could hinder the Cu-Cl interaction. The Cu deactivation rate model was successfully developed. For the fuels containing 0.2–0.4 wt% Cl, the Cu loss rate was estimated to be 0.0025–0.01%/cycle with XHCl = 0.12–0.24. The results of combustion experiments and material characterization were consistent with the modeling predictions, clearly demonstrating the Cl-induced deactivation. Given the modeling predictions and experimental findings, potential countermeasures were proposed.