NETL researchers have developed novel tri-metallic ferrite oxygen carriers that comprise Cu_xFe_yMn_zO_4-8 – where Cu_xFe_yMn_zO_4-8 is a chemical composition with generally 0.5≤x≤2.0, 0.2≤y≤2.5, and 0.2≤z≤2.5 – for CLC of solid fuels such as coal, pet coke, and biomass. The tri-metallic ferrite oxygen carrier is used by delivering it to a fuel reactor and mixing it with a carbon-based fuel at a reducing temperature, which reduces a portion of the carrier and oxidizes a portion of the fuel. Within the fuel reactor, the tri-metallic ferrite carrier interacts with the fuel and generates a reduced carrier. The reduced carrier subsequently enters an oxidation reactor, where it is infused with oxidizing gas to produce a re-oxidized carrier through an oxidizing reaction. The re-oxidized carrier, which comprises comprise Cu_xFe_yMn_zO_4-8, may then be returned to the fuel reactor for a cyclic operation.

CLC offers a major advantage over conventional coal combustion by directly producing a concentrated stream of CO₂ without expending the significant energy required for CO₂ separation. This NETL technology offers numerous advantages over traditional oxygen carriers for coal CLC. Tri-metallic ferrites perform better when compared to Fe₂O₃, demonstrating high and stable reactivity over multiple reduction/oxidation cycles and high attrition resistance. Ferrite-based oxygen carriers also display a low tendency to agglomerate at high temperatures, as with CuO. These metal ferrites can be produced using readily available materials at a cost comparable to Fe₂O₃ and CuO oxygen carriers.

Advantages

• Improved reduction/oxidation rates, durability and reactivity compared to Fe₂O₃
• Eliminates agglomeration issues associated with CuO
• Stable at high temperatures and over multiple oxidation-reduction cycles
• Can be produced using readily available materials at comparable cost to standard oxygen carriers
• Carriers are environmentally benign