(739b) Sub-Pilot Scale Demonstration of Iron-Based Coal-Direct Chemical Looping Combustion Process

With the fast growing demand of power generation, excessive CO₂ emission from the coal-fired power plants becomes the environmental concern that causes the global warming. In order to regulate the CO₂ emission, many carbon capture technologies have been developed to retrofit to the coal-fired power plants. Among these newly developed technologies, the chemical looping processes exhibit the promising economic and technical feasibility to capture CO₂ from the coal conversion processes. At the Ohio State University, the Coal-Direct Chemical Looping (CDCL) combustion process using iron-based oxygen carriers was developed as coal conversion process with in-situ CO₂ capture. In the previous studies of the CDCL process, the oxygen carrier particles were synthesized and the process scheme with a packed moving bed was proposed. The CDCL system mainly consists of three components; reducer, combustor and riser. In the reducer, reduction of Fe₂O₃ particles yields a mixture of Fe and FeO particles, while converting the coal into CO₂ and steam, which can be readily available for sequestration. The combustor is a fluidized bed that oxidizes the reduced particles back to Fe₂O₃ with air. The oxidation of iron is an exothermic reaction and the heat can be recovered to be used in the coal power plant system. In the riser, there is no chemical reaction, but it pneumatically transports the particles to the reducer.

Objective of this project is to demonstrate the continuous operation of 25kW_th CDCL sub-pilot unit with inputs of various solid fuels. Before the sub-pilot unit is designed and constructed, the cold flow model (CFM) with near 1:1 scale to sub-pilot unit was constructed to have better understanding of the reactor models and develop the solid handling strategy in the actual CDCL sub-pilot unit. From the experience of CFM study, the final design of sub-pilot unit was obtained and the reactor parts are fabricated for the assembly. Moreover, all the peripheral equipments for the sub-pilot unit such as coal feeder, gas injection and sampling system and analysis systems were prepared. The sub-pilot unit was successfully operated with metallurgical coke and sub-bituminous coal. With capability to handle hot solids in the sub-pilot unit, the demonstration works can move forward for more parametric studies, which will be used for the techno-economic studies.