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Coal-Direct Chemical Looping Combustion Process for In-Situ Carbon Dioxide Capture – Operational Experience of Integrated 25-kWth Sub-Pilot Scale Unit

Kim, Hyung Rae
http://rave.ohiolink.edu/etdc/view?acc_num=osu1352996758

Abstract Details

2012, Doctor of Philosophy, Ohio State University, Chemical and Biomolecular Engineering.
At Ohio State University (OSU), the Coal-Direct Chemical Looping (CDCL) process using iron-based oxygen carriers has been developed as a coal conversion process for electric power generation with in-situ CO2 capture. The CDCL system cycles iron-based oxygen carriers between three reactors, i.e. reducer, combustor and riser, in order to convert the coal for electric power generation. The reducer reactor features a unique design of a gas-solid counter-current moving bed configuration to achieve the reduction of Fe2O3 particles to a mixture of Fe and FeO, while fully converting the coal into CO2 and steam. The CO2 stream from the reducer is sequestration-ready after the steam condensation. The combustor reactor is a fluidized bed that oxidizes the reduced particles back to Fe2O3 with air. The oxidation reaction of iron with air is a highly exothermic reaction and the heat can be recovered for electricity generation. Lastly, the oxidized iron particles in the combustor are pneumatically transported back to the reducer through the riser. The 25-kWth CDCL sub-pilot unit was successfully operated with metallurgical coke, lignite and sub-bituminous coal. The 25-kWth CDCL sub-pilot plant at OSU is the first integrated chemical looping demonstration unit for the direct conversion of solid fuels with a circulating moving bed system. Throughout a number of test runs of the sub-pilot unit, the total operation time has exceeded 430 hours to date. The longest continuous operation time was 200 hours with voluntary shut-down. Among these test runs, the results for two runs are reported in this Dissertation. Specifically, the tests with metallurgical coke and sub-bituminous coal resulted in 81% and 97% carbon conversions in the reducer with once-through, respectively. The units can be further optimized to yield a full carbon conversion in the reducer. Both tests yielded CO2 purity greater than 99% indicating the complete oxidation of volatile gases in the moving bed reducer. The gas analyses from the combustor outlet demonstrated a proper regeneration of oxygen carriers. Low CO2 concentration in the combustor confirmed no unconverted carbon transfer to the combustor and hence eliminated the need of an additional carbon separation device such as a carbon stripper. It was also confirmed the non-mechanical L-valve is practical in the application of CDCL process. Additionally, the emissions of sulfur and NOx were analyzed. The demonstration results from the sub-pilot system substantiate the process concept of the CDCL, which is capable of processing coal continuously with reactor in-situ CO2 capture and the cyclic usage of oxygen carriers.
Liang-Shih Fan (Advisor)
Umit Ozkan (Committee Member)
Aravind Asthagiri (Committee Member)
Jeff Kuret (Committee Member)
Chemical Engineering
Coal-Direct Chemical Looping; Chemical Looping; Coal; Carbon Capture; Moving Bed; Demonstration; Oxygen Carrier

Recommended Citations

Citations

  • Kim, H. R. (2012). Coal-Direct Chemical Looping Combustion Process for In-Situ Carbon Dioxide Capture – Operational Experience of Integrated 25-kWth Sub-Pilot Scale Unit [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1352996758

    APA Style (7th edition)

  • Kim, Hyung. Coal-Direct Chemical Looping Combustion Process for In-Situ Carbon Dioxide Capture – Operational Experience of Integrated 25-kWth Sub-Pilot Scale Unit. 2012. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1352996758.

    MLA Style (8th edition)

  • Kim, Hyung. "Coal-Direct Chemical Looping Combustion Process for In-Situ Carbon Dioxide Capture – Operational Experience of Integrated 25-kWth Sub-Pilot Scale Unit." Doctoral dissertation, Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1352996758

    Chicago Manual of Style (17th edition)

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© 2012, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.