Design and Operations of a 15 kWₜₕ Subpilot Unit for the Methane-to-Syngas Chemical Looping Process with CO₂ Utilization
2019
Park, Cody | Hsieh, Tien-Lin | Pottimurthy, Yaswanth | Shah, Vedant | Xu, Dikai | Chen, Yu-Yen | Fan, Liang-Shih | Tong, Andrew
The methane-to-syngas (MTS) chemical looping process is an advanced methane reforming technology for the production of high purity syngas. The developed MTS process utilizes metal oxide oxygen carriers in a cocurrent moving bed reactor to partially oxidize the methane such that the resulting syngas stream is undiluted by nitrogen in air or H₂ from overconversion and directly suitable for downstream processing. The oxygen carriers are regenerated with air in a separate fluidized bed reactor producing a spent air stream separate from the product syngas, circumventing the need for cryogenic air separation units. In this work, a 15 kWₜₕ subpilot unit is designed and operated in a continuous manner to experimentally confirm the viability of the MTS process. Reactor design considerations and methodology are discussed in detail. An iron–titanium composite oxygen carrier is used as the oxygen carrier for its ability to achieve high methane conversion while regulating the product syngas to the partial oxidation products, CO and H₂. Syngas is produced with an H₂/CO ratio of ∼2, and a purity of ∼97% is produced with methane conversion exceeding 99%. The coinjection of methane with H₂ and/or H₂O is explored for the purpose of H₂ utilization and flexible H₂/CO ratios, allowing the MTS process to produce syngas for a variety of downstream processes without reactor modification. The results indicate that syngas with H₂/CO ratios ranging from 1.19 to 2.50 with high methane conversion and syngas purity can be produced with coinjection. No evidence of carbon deposition on the oxygen carrier is revealed, and the oxygen carrier retained structural integrity after subjection to reaction and circulation in the subpilot unit.
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