Chuayboon, Srirat

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Chuayboon, Srirat
Alternative Name
Chuayboon, S.
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Email
srirat.ch@kmitl.ac.th

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    High-Purity and Clean Syngas and Hydrogen Production From Two-Step CH4 Reforming and H2O Splitting Through Isothermal Ceria Redox Cycle Using Concentrated Sunlight
    (2020-07-17)
    Chuayboon, Srirat
    ;
    Abanades, Stéphane
    ;
    Rodat, Sylvain
    The thermochemical conversion of methane (CH<inf>4</inf>) and water (H<inf>2</inf>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<inf>4</inf> and H<inf>2</inf>O splitting over non-stoichiometric ceria (CeO<inf>2</inf>/CeO<inf>2−δ</inf>) redox cycle were experimentally investigated in a volumetric solar reactor prototype. The cycle consists of (i) the endothermic partial oxidation of CH<inf>4</inf> and the simultaneous reduction of ceria and (ii) the subsequent exothermic splitting of H<inf>2</inf>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<inf>2</inf>/CO ratios approaching 2 during the first reduction step, while high-purity H<inf>2</inf> was subsequently generated during the oxidation step. Increasing methane flow rate and CH<inf>4</inf> concentration promoted syngas yields up to 8.51 mmol/g<inf>CeO<inf>2</inf></inf> and δ up to 0.38, at the expense of enhanced methane cracking reaction and reduced CH<inf>4</inf> 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<inf>4</inf> conversion were achieved in the range of 2.9–5.6% and 40.1–68.5%, respectively.
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    Solar chemical looping reforming of methane combined with isothermal H2O/CO2 splitting using ceria oxygen carrier for syngas production
    (2020-02-01)
    Chuayboon, Srirat
    ;
    Abanades, Stéphane
    ;
    Rodat, Sylvain
    The chemical looping reforming of methane through the nonstoichiometric ceria redox cycle (CeO<inf>2</inf>/CeO<inf>2</inf><inf>−</inf><inf>δ</inf>) has been experimentally investigated in a directly irradiated solar reactor to convert both solar energy and methane to syngas in the temperature range 900–1050 °C. Experiments were carried out with different ceria shapes via two-step redox cycling composed of endothermic partial reduction of ceria with methane and complete exothermic re-oxidation of reduced ceria with H<inf>2</inf>O/CO<inf>2</inf> at the same operating temperature, thereby demonstrating the capability to operate the cycle isothermally. A parametric study considering different ceria macrostructure variants (ceria packed powder, ceria packed powder mixed with inert Al<inf>2</inf>O<inf>3</inf> particles, and ceria reticulated porous foam) and operating parameters (methane flow-rate, reduction temperature, or sintering temperature) was conducted in order to unravel their impact on the bed-averaged oxygen non-stoichiometry (δ), syngas yield, methane conversion, and solar reactor performance. The ceria cycling stability was also experimentally investigated to demonstrate repeatable syngas production by alternating the flow between CH<inf>4</inf> and H<inf>2</inf>O (or CO<inf>2</inf>). A decrease in sintering temperature of the ceria foam was beneficial for increasing syngas selectivity, methane conversion, and reactor performance. Increasing both CH<inf>4</inf> concentration and reduction temperature enhanced δ with the maximum value up to 0.41 but concomitantly favored CH<inf>4</inf> cracking reaction. The ceria reticulated porous foam showed better performance in terms of effective heat transfer, due to volumetric absorption of concentrated solar radiation and uniform heating with lower solar power consumption, thereby promoting the solar-to-fuel energy conversion efficiency that reached up to 5.60%. The energy upgrade factor achieved during cycle was up to 1.19. Stable patterns in the δ and syngas yield for consecutive cycles with the ceria foam validated material performance stability.
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    Analysis of process parameters influence on syngas yields and biomass gasification rates in a continuous particle-fed solar-irradiated gasifier
    (2020-12-11)
    Chuayboon, Srirat
    ;
    Abanades, Stéphane
    ;
    Rodat, Sylvain
    Steam gasification of biomass was experimentally investigated with different lignocellulosic biomass feedstocks in a 1.5 kWth continuous particle-fed solar-irradiated gasifier at high temperatures (1100-1300 °C) utilizing highly concentrated sunlight as process heat source, demonstrating the conversion of intermittent solar energy and biomass into synthesis gas without CO2 emissions. Forty-nine on-sun experiments were performed in order to study the effect of process parameters (biomass feeding rate, temperature, biomass composition) on syngas production yield, biomass gasification rate (carbon conversion rate), and reactor performance. As a result, syngas yield, composition (quality), biomass gasification rate, and reactor performance increase significantly with both the biomass feeding rate and temperature because both biomass consumption rates and reaction kinetics are enhanced. However, the performance outputs are reduced when biomass feeding rate exceeds its optimal feeding point. The reactor temperature of 1300°C is recommended to operate reliably the solar biomass gasifier with the considered biomass particle size range (0.3-4 mm) in a continuous feeding mode with complete biomass conversion, as verified by the carbon consumption rate that matches closely the carbon feeding rate. By optimizing biomass feeding rate consistently with operating temperature, the calorific value of the biomass feedstock is solar upgraded by 24% with carbon conversion extent above 90% and solar-to-fuel energy conversion efficiency up to 29%.
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    Stepwise Solar Methane Reforming and Water-Splitting via Lattice Oxygen Transfer in Iron and Cerium Oxides
    (2020-08-01)
    Chuayboon, Srirat
    ;
    Abanades, Stéphane
    ;
    Rodat, Sylvain
    Chemical-looping reforming of methane (CLRM) involves lattice oxygen transfer in metal oxides. This study aims to compare iron (Fe<inf>2</inf>O<inf>3</inf>) and cerium (CeO<inf>2</inf>) oxides as oxygen carrier materials for isothermal solar-driven stepwise CH<inf>4</inf> reforming and H<inf>2</inf>O splitting. Experiments are conducted in a directly irradiated lab-scale solar reactor heated by concentrated sunlight at 950–1150 °C. Using solar energy for process heat reduces the dependence on fossil energy resources and avoids CO<inf>2</inf> emissions, while converting solar energy into chemical fuels. The performance of the oxygen carrier materials is compared and evaluated by determining the amount of oxygen transferred, methane conversion, syngas yield, and thermochemical cycling stability. As a result, iron oxide reduction with methane strongly depends on temperature and displays relatively lower reaction rate than CeO<inf>2</inf>. The reduced iron is not completely reoxidized to Fe<inf>3</inf>O<inf>4</inf> after water-splitting because of low thermal stability resulting in strong sintering and agglomeration, thereby decreasing syngas yield and leading to material deactivation. In contrast, ceria exhibits faster reaction rate and stable syngas yield with H<inf>2</inf>/CO molar ratios approaching two over repeated cycles. Stable patterns in the averaged oxygen nonstoichiometry (δ = 0.35–0.38) demonstrate excellent thermal cycling stability. Thus, using Fe<inf>2</inf>O<inf>3</inf> oxygen carrier is not suitable for solar CLRM, but iron oxide reduction with methane can be promising for solar metallurgy aiming at producing both metallic iron and syngas.