Identification of HCl corrosion mechanism on Cu-based oxygen carriers in chemical looping combustion

Abstract

In chemical looping combustion (CLC) of coal, HCl has been demonstrated as the primary gaseous products of the chlorine in coal. Therefore, a comprehensive characterization of Cu-based oxygen carriers (OC) by HCl corrosion was meticulously conducted, including the activity retention, composition distribution and apparent morphology. The experiment consisted of three parts: (I) evaluating of the OC performance for 100 redox cycles with 7.8 vol% CH4; (II) investigating HCl-corrosion of OC by adding 50 ppmv HCl with 7.1 vol% CH4 for the subsequent 50 cycles; (III) regenerating of OC without HCl addition during the last 50 cycles. The reactivity of OC was attenuating via the HCl addition during the 101st–150th cycles (part II) due to the competition adsorption between HCl and CH4, especially for the partly reduced OC. While, in part III, the reactivity performance of OC was partially recovered because of the abundant cracks on the surface of OC particles which ensured the sufficient gas–solid contact. It should be noted that the single particle hardness index and service life were irreversibly decreased for the HCl-treated OC. Moreover, OC particles were fragmented and the inside Al2O3 balls were exposed on the surface of the HCl-treated OC in SEM image. This work will contribute to understanding the mechanism of Cl-corrosive OC and designing the Cl-resistant OC.