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

Abstract

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 CO2 abatement after comparing with other two different iron-based materials (pure Fe2O3 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% H2 purity) and higher H2 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 Fe2O3 and Ca2Al2SiO7 particles nested on Na4Al2Si2O9 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.