(391c) Syngas Chemical Looping - 25kWth Sub-Pilot Scale Testing

Pursuit of economically attractive fossil fuel conversion technologies that produce clean energy carriers, in combination with carbon capture, is one of the main focuses of the ongoing energy research in the United States. The Syngas Chemical Looping (SCL) process, developed at The Ohio State University, is a promising solution that provides for 100% carbon capture from various carbonaceous fuels, while co-generating Hydrogen and electricity. A specially tailored Iron based composite medium is moved through three reactors namely; the reducer, the oxidizer and the combustor, to achieve the stated benefits. In the moving bed reducer, high concentration CO₂ stream is generated by fuel combustion using the oxygen provided by the looping medium. The moving bed oxidizer partly replenishes the depleted oxygen in the looping medium with steam, producing high purity H₂. The oxygen carrying capacity of the looping medium is completely restored and the loop is completed, in the combustor, which uses air to combust and entrain the looping medium while producing heat.

Over the past 6 years, the SCL process has been developed from a lab scale unit to a 25kW_th sub-pilot scale unit. Tests prior to the sub-pilot scale construction involved extensive research to find a working oxygen carrier looping medium in a lab scale and validating the operation of the individual reactors using a bench scale unit. The current article will focus on the operational results obtained from the 25kW_th sub-pilot SCL system. This unit has been operated for more than 40 hours and successful results have been obtained. The possibility to continuously generate high purity hydrogen and high concentration CO₂ stream in separate reactors has been confirmed. Post experiment looping medium analysis results will be discussed which include attrition results, reactivity testing and re-pelletization studies. The techno-economic performances of the SCL process as well as the design philosophy of a 250kW_th pilot scale unit are also discussed.