Sulfur behavior in chemical-looping combustion using a copper ore oxygen carrier

Chemical-looping combustion (CLC) is a promising technology that provides a novel route for CO2 capture with low cost and energy penalty. Interaction between the oxygen carrier and sulfur contaminants in fuel is a significant concern in chemical looping systems, which will degrade the captured CO2 purity and even affect the reactivity of oxygen carrier. Experiments of a sulfur-containing synthesis gas (4000 ppm H2S, 25 vol.% H2, 35 vol.% CO, and 39.6 vol.% CO2) as fuel and copper ore as oxygen carrier were performed by thermogravimetric analysis and Fourier transform infrared spectroscopy (TGA-FTIR). The effects of reducing atmosphere, temperature and redox cycle number were studied. A weight gain was observed in all TGA experiments with 4000 ppm H2S synthesis gas as fuel, due to the sulfidation of the copper ore oxygen carrier. For the reaction of copper ore with H2S-containing synthesis gas, the main metal sulfide products were Cu2S and FeS, while the gaseous sulfur species were mainy SO2, COS, and CS2. H2S was easier to react with copper oxides than iron oxides. Moreover, the sulfidation of copper ore was further investigated in a laboratory scale fluidized bed reactor at 900 °C, using copper ore as oxygen carrier and synthesis gases with/without H2S as fuel. The results showed that the sulfidation of copper ore degraded its oxygen transport capicity and reactivity to some extent.