(58e) In-Situ Gasification Chemical Looping Combustion vs. Chemical Looping with Oxygen Uncoupling: Exergy Comparison for Power Generation with CO2 Capture

Authors: 
Zhang, Y., The Ohio State University
Tong, A., The Ohio State University
The chemical looping combustion (CLC) technology is one of the most promising CO2 capture technologies for fossil fuel power generation applications, which allows effective separation of CO2 from fuel combustion by avoiding contact between fuel and air. When applied to coal-based power plant, CLC can cost-effectively generate clean electricity with high net plant energy efficiency compared to amine-based post combustion CO2 capture process. CLC refers to the use of a metal oxide or metal sulfate as an oxygen carrier to supply oxygen from air to the fuel through a reduction and oxidation reaction pathways of the oxygen carrier, respectively. Similar to oxy-combustion carbon capture, a CO2 product stream is produced, undiluted with the N2 inherently present in air. In contrast, the oxygen carrier redox reaction pathway replaces the need for an energy intensive air separation unit. This work focuses on two CLC process configurations of coal combustion: in-situ gasification chemical looping combustion (iG-CLC) and chemical looping with oxygen uncoupling (CLOU). CLOU process utilizes a copper-based oxygen carrier (OC) in a dual circulating fluidized bed reactor system consisting of 2 reactors: the reducer reactor, where the Cu-based OC releases O2 for coal combustion, and the combustor reactor for OC regeneration by air. Both reactors and both flue gas streams can generate high quality heat for power production. In the iG-CLC process, an iron-based OC is circulated between a counter-current moving bed reducer reactor for full combustion of coal and a fluidized bed combustor reactor for OC regeneration by air. High quality heat can be extracted from reducer flue gas, combustor flue gas and combustor for power generation. The present work analyzes the iG-CLC and CLOU coal-based power plants to investigate the power generation potential of CLC technology as well as compare the pros and cons of both configurations. Specifically, this study developed the overall models of iG-CLC and CLOU coal-based power plants with ASPEN PLUS process simulation software. Previous bench-scale and sub-pilot experimental results performed at Ohio State were incorporated to iG-CLC model. CLOU model was constructed with reference to literature and report. Energy and material balance information generated by the models was utilized to perform detail exergy analysis on iG-CLC and CLOU configurations. The results showed exergy intensive point for process optimization. Parametric studies were also conducted on system pressure, reactor temperature, etc., to investigate important parameters of both CLC configurations.

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