Oxygen Uncoupling Enhanced Iron Oxides for Solid Fuel Gasification – Oxygen Carrier Development, Reactive Testing, and Process Analyses

Oxygen Uncoupling Enhanced Iron Oxides for Solid Fuel Gasification – Oxygen Carrier Development, Reactive Testing, and Process Analyses

Feng He, Nathan Galinsky, Yan Huang, Fanxing Li*

Department of Chemical and Bimolecular Engineering

North Carolina State University

Raleigh, NC 27695

* Email: fli5@ncsu.edu

Carbon dioxide emitted from fossil energy conversion is estimated to account for ~ 20% of the greenhouse effect. In order to mitigate the anthropogenic CO₂ emissions, effective carbon capture, utilization and storage (CCUS) approaches need to be developed and adopted for fossil fuel conversions. Chemical looping processes, which include chemical looping combustion (CLC) and chemical looping gasification (CLG), utilize novel, indirect strategy for fossil fuel conversion and CO₂ capture. The CLC process is developed to produce heat/electricity. CLG, on the other hand, converts fuels into separate streams of sequestrable CO₂, hydrogen, and heat/electricity.

Although Fe-based metal oxide is considered as the only suitable oxygen carrier for the CLG process, the reaction between solid fuels such as coal and iron oxide tends to be slow. In order to improve the reaction rate of the aforementioned reaction, we propose to incorporate a secondary oxygen carrier such as CuO to the iron oxide based oxygen carrier for chemical looping gasification of solid fuels.

To validate the feasibility of this approach, oxygen carriers with varying combinations of copper and iron oxides are synthesized. Reactions between the oxygen carriers and coal/coal char are performed in both a Thermal-Gravimetric Analyzer (TGA) and a bench-top fluidized bed reactor. Equilibrium based ASPEN Plus® process simulation is also carried out to predict the reactor and process performances.  The simulation results indicate that copper oxide addition simplifies the process heat integration scheme, and hence a high energy conversion efficiency for the proposed bimetallic CLG concept can be expected. The potential environmental impacts of the chemical loping process are also evaluated in the present study.