Article Dans Une Revue Frontiers in Energy Research Année : 2020

High-Purity and Clean Syngas and Hydrogen Production From Two-Step CH 4 Reforming and H 2 O Splitting Through Isothermal Ceria Redox Cycle Using Concentrated Sunlight

Résumé

The thermochemical conversion of methane (CH 4) and water (H 2 O) to syngas and hydrogen, via chemical looping using concentrated sunlight as a sustainable source of process heat, attracts considerable attention. It is likewise a means of storing intermittent solar energy into chemical fuels. In this study, solar chemical looping reforming of CH 4 and H 2 O splitting over non-stoichiometric ceria (CeO 2 /CeO 2−δ) redox cycle were experimentally investigated in a volumetric solar reactor prototype. The cycle consists of (i) the endothermic partial oxidation of CH 4 and the simultaneous reduction of ceria and (ii) the subsequent exothermic splitting of H 2 O and the simultaneous oxidation of the reduced ceria under isothermal operation at ∼1,000 • C, enabling the elimination of sensible heat losses as compared to non-isothermal thermochemical cycles. Ceria-based reticulated porous ceramics with different sintering temperatures (1,000 and 1,400 • C) were employed as oxygen carriers and tested with different methane flow rates (0.1-0.4 NL/min) and methane concentrations (50 and 100%). The impacts of operating conditions on the foam-averaged oxygen non-stoichiometry (reduction extent, δ), syngas yield, methane conversion, solar-to-fuel energy conversion efficiency as well as the effects of transient solar conditions were demonstrated and emphasized. As a result, clean syngas was successfully produced with H 2 /CO ratios approaching 2 during the first reduction step, while high-purity H 2 was subsequently generated during the oxidation step. Increasing methane flow rate and CH 4 concentration promoted syngas yields up to 8.51 mmol/g CeO 2 and δ up to 0.38, at the expense of enhanced methane cracking reaction and reduced CH 4 conversion. Solar-to-fuel energy conversion efficiency, namely, the ratio of the calorific value of produced syngas to the total energy input (solar power and calorific value of converted methane), and CH 4 conversion were achieved in the range of 2.9-5.6% and 40.1-68.5%, respectively.

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hal-02925009 , version 1 (28-08-2020)

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Srirat Chuayboon, Stéphane Abanades, Sylvain Rodat. High-Purity and Clean Syngas and Hydrogen Production From Two-Step CH 4 Reforming and H 2 O Splitting Through Isothermal Ceria Redox Cycle Using Concentrated Sunlight. Frontiers in Energy Research, 2020, 8, pp.128. ⟨10.3389/fenrg.2020.00128⟩. ⟨hal-02925009⟩
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