The Realization of complete carbon conversion and hydrogen purification in the coal-fueled chemical looping technology using a cost-effective iron-based oxygen carrier

The development of cost-effective and reactive oxygen carriers and the fast and complete conversion of solid fuels are two critical issues in the solid fuel chemical looping technology. Red mud, a solid waste from the alumina industry, was found to be an economic oxygen carrier candidate simultaneously realizing the use of solid wastes and the CO 2 abatement after comparing with other two different iron-based materials (pure Fe 2 O 3 and hematite). This study validated red mud as an excellent oxygen carrier to achieve the almost complete conversion of char in solid fuels (SFs) (99.4%) and meanwhile the hydrogen production with high-purity (97% H 2 purity) and higher H 2 yield (around 500 mL/g), in the optimized pyrolysis procedure of solid fuels with proper gasification agent and rationalized reaction temperatures (1000 °C) and residence time (10mins). Characterizations of red mud using SEM-EDS and XRD revealed that the unique microscopic crystalline structures of both Fe 2 O 3 and Ca 2 Al 2 SiO 7 particles nested on Na 4 Al 2 Si 2 O 9 molten substrate, implying that the existence of Na-containing component of the red mud OC likely accounts for its higher reactivity and stability in multiple redox cycles.