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Dissertation - Nihar Phalak.pdf (3.8 MB)

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Calcium Looping Processes for Pre- and Post-Combustion Carbon Dioxide Capture Applications

Phalak, Nihar
http://rave.ohiolink.edu/etdc/view?acc_num=osu1366802833

Abstract Details

2013, Doctor of Philosophy, Ohio State University, Chemical and Biomolecular Engineering.
Calcium looping employs a calcium sorbent – typically in the form of calcium oxide (CaO) – which reacts with CO2 present in the flue or fuel gases to form calcium carbonate (CaCO3). This reaction is reversible and the CaO can be regenerated to release a pure CO2 stream for sequestration. When used in the post-combustion scenario, the process can be used for CO2 removal only; however, in the pre-combustion case, production of H2 from coal-derived syngas, natural gas, etc. can be achieved in addition to carbon capture. The sorbent regeneration step in calcium looping requires high temperatures and leads to a decrease in reactivity toward CO2 due to sintering. While the process has been rapidly scaled up to pilot plant demonstrations, the sintering challenge has persisted and has been the focus of the majority of the recent studies in this area. To overcome this problem, Prof. L.-S. Fan’s research group at The Ohio State University (OSU) has led the development of a unique three-step calcium looping process. The third step is the reactivation of the sorbent using steam hydration. The integration of this sorbent reactivation step reverses the effect of sintering and maintains the reactivity of the sorbent toward CO2 over many cycles. This work advances the development of the calcium looping processes at OSU and builds on the foundation laid by previous researchers. The construction and operation of the sub-pilot scale reactor for hydrogen (H2) production with in-situ CO2 capture is the highlight of this work. Parametric tests quantifying the effect of sorbent loading and steam requirement were performed and it was found that syngas could be converted to a product gas containing 70% H2 at a calcium to carbon mol ratio (Ca:C) of 1.5 and steam to carbon mol ratio (S:C) of 3. Several aspects of the three-step process were also studied. In particular, CaO derived from commercial limestones was subjected to multicyclic carbonation-calcination-hydration and it was found that hydration could successfully maintain the reactivity of CaO over many cycles. Further, a detailed kinetic study of steam hydration of CaO was also undertaken to identify the optimum operating parameters for the calcium looping hydrator. The rate of hydration increased with temperature and steam partial pressure, and decreased with increasing calcination temperature. Finally, the study of non-isothermal carbonation of Ca(OH)2 was also explored and the results showed superior sorbent utilization in the absence of the typical dual-regime reaction The calcium looping process was also investigated for application to energy conversion systems that use natural gas as the feed. From the tests conducted using a bench-scale fixed-bed reactor, high-purity H2 production and CO2 capture were achieved via enhanced reforming of higher hydrocarbons like ethane and propane. Post-combustion CO2 capture from natural gas combined cycle (NGCC) plants was evaluated using Aspen Plus process simulations. The results indicated that calcium looping may not be the best technology for this scenario in terms of efficiency; however, it does present a unique advantage of maintaining the electric output of the plant unlike any other process.
Liang-Shih Fan (Advisor)
David Tomasko (Committee Member)
Jacques Zakin (Committee Member)
273 p.
Chemical Engineering
Carbon capture; calcium looping

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Citations

  • Phalak, N. (2013). Calcium Looping Processes for Pre- and Post-Combustion Carbon Dioxide Capture Applications [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366802833

    APA Style (7th edition)

  • Phalak, Nihar. Calcium Looping Processes for Pre- and Post-Combustion Carbon Dioxide Capture Applications. 2013. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1366802833.

    MLA Style (8th edition)

  • Phalak, Nihar. "Calcium Looping Processes for Pre- and Post-Combustion Carbon Dioxide Capture Applications." Doctoral dissertation, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366802833

    Chicago Manual of Style (17th edition)

osu1366802833
445
© 2013, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.