Experimental study on the structure and reactivity of char in pressurized O2/H2O atmosphere

Abstract

Pressurized O2/H2O combustion is regarded as a promising high-efficiency CCS technology. In this study, char combustion in a pressurized O2/H2O atmosphere was performed with a pressurized horizontal tube furnace. The effects of pressure (0.1–1.3 MPa) and H2O concentration (0–60%) on char conversion, char physicochemical structure and reactivity were investigated by means of XPS, Raman, temperature-programed desorption and TGA tests. The results show that both pressurization and H2O can promote char conversion and facilitate the formation of carbon‑oxygen bonds on the char surface. Pressure mainly affects the consumption and generation of micropores, while the effect of H2O on the pore structure has no obvious selectivity. Pressurization reduces the relative content of CC, while H2O has the opposite effect. At low pressure (0.1–0.7 MPa) and low H2O concentration (0–40%), pressurization and H2O can promote the formation of C(O) on the surface of char. The reactivity of char first decreased and then increased with increasing pressure and increasing H2O concentration.