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Applications of Chemical Looping Technologies to Coal Gasification for Chemical Productions

Hsieh, Tien-Lin
http://orcid.org/0000-0002-4050-8410
http://rave.ohiolink.edu/etdc/view?acc_num=osu1520269709048255

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Chemical Engineering.
Two chemical looping processes are scaled-up and developed for the efficient conversion of coal into hydrogen or syngas. Chemical looping combustion (CLC) is an advanced technology for converting fossil fuel while achieving in-situ capture. A CLC process utilizes metal oxide materials, known as oxygen carriers, to inherently separate the combustion products and spent air into different outlet streams. The high purity CO2 generated in the combustion product stream is sequestration/utilization ready, which makes chemical looping one of the most attractive carbon emission control technology. In this paper, the authors present the design, simulation, and experimental operation results of the 250 kWth high-pressure syngas chemical looping (SCL) pilot plant. The pilot plant's unique counter-current moving bed design allows near-full conversion of coal-derived syngas with simultaneous production of high purity, carbon-free H2¬ Critical aspects of the design efforts, including heat and material balances, reactor sizing approach and solid flow control and measurement devices are presented. An ASPEN Plus® model is built to predict the gas and solid conversions of the SCL process the gas and solid conversions of the SCL process under different experimental conditions. The highest syngas conversion achieved was 97.95% with 16.03% oxygen carrier conversion, which was close to the thermodynamic limits for both the gas and solid phases in the reducer. Differences between the experimental results and predicted conversion values were more significant under conditions with lower oxygen carrier to fuel ratio. Greater than 99% purity H2 was produced from the moving bed oxidizer, and the scalability and feasibility of SCL process were successfully demonstrated. A novel design of a coal gasifier using the chemical looping concept is introduced in the present study for high purity, H2-rich syngas generation using coal and methane as co-feeds. In this work, an iron-titanium composite metal oxide (ITCMO), capable of cracking the heavy hydrocarbons produced in coal pyrolysis as well as regulating the product syngas purity, is used as the oxygen carrier. The co-current moving bed avoids back-mixing of solid and gas reactants, allowing both phases to interact, reaching thermodynamic equilibrium conditions at the reactor gas outlet. This paper focuses on demonstrating the co-current moving bed reducer with the ITCMO oxygen carrier. A sensitivity analysis is performed to determine the optimal operating conditions for converting PRB coal using ASPEN Plus modeling. The tar-cracking capability is ascertained by the GC-MS analysis. The bench-scale moving bed reducer substantiated its capability of achieving near-full conversion of the carbon species. The co-feeding of methane can yield a high purity syngas with H2/CO ratio of 2 or higher, which is suitable for downstream chemical synthesis. The gas and solid compositions obtained at reducer outlets match the predictions from the ASPEN Plus model. The results indicate that the extent of char gasification at the top moving bed is a critical factor for achieving a high coal conversion. The results further indicate that the sulfur in the coal is mostly converted into the gas phase emitted with the syngas product in the reducer, while the remainder is retained in the ash.
Liang-Shih Fan (Advisor)
Andre Palmer (Committee Member)
Lisa Hall (Committee Member)
165 p.
Chemical Engineering
chemical looping; coal gasification; syngas conversion; syngas production; carbon capture; hydrogen production

Recommended Citations

Citations

  • Hsieh, T.-L. (2018). Applications of Chemical Looping Technologies to Coal Gasification for Chemical Productions [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1520269709048255

    APA Style (7th edition)

  • Hsieh, Tien-Lin. Applications of Chemical Looping Technologies to Coal Gasification for Chemical Productions. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1520269709048255.

    MLA Style (8th edition)

  • Hsieh, Tien-Lin. "Applications of Chemical Looping Technologies to Coal Gasification for Chemical Productions." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1520269709048255

    Chicago Manual of Style (17th edition)

osu1520269709048255
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This open access ETD is published by The Ohio State University and OhioLINK.