In-situ CO₂ utilization for dual production of hydrogen-rich gas and syngas via sorption-enhanced steam methane reforming chemical looping

A dual-purpose process is designed to produce hydrogen-rich gas (H₂-rich gas) and syngas (H₂/CO) via sorption-enhanced steam methane reforming chemical looping (SE-SMR-CL). The work focuses on improving process operation to be environmentally friendly and producing a value-added product by in-situ utilization of the by-product carbon dioxide (CO₂). Theoretical and experimental studies are used to determine suitable operating windows and investigate parametric effects on H₂ and H₂/CO production. The theoretical results reveal that 93.84 % H₂ purity with low production of CO₂ (1.91 %) can be obtained at 650 °C and 1 bar using a steam to carbon molar ratio (S/C) of 3 in the reforming step. A syngas molar ratio of 1.58 can be produced at 850 °C using a methane to calcium carbonate (CH₄/CaCO₃) molar ratio of 2 in the calcination step. Co-addition of steam enhances a syngas molar ratio up to 2, depending upon amount of the steam feed and operating temperature. The proof-of-concept was experimentally conducted using a multifunctional material Ni/CaO-Ca₅Al₆O₁₄. The results show that 80 vol% H₂ purity is obtained from the reforming step at S/C of 3, T of 650 °C, P of 1 bar, and Weight Hourly Space Velocity (WHSV) of 1800 ml/h g_cat. A syngas ratio of ca. 1 at T of 850 °C and P of 1 bar can be produced during the calcination step. Co-addition of steam reduces carbon formation and increase syngas ratio to ca. 1.2–1.4. This developed technique can improve not only the existing steam reforming technology to be more environmentally friendly but also can enhance its value by co-production of H₂/CO with different qualities, which can be applied for various applications.