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Impact of biowaste reducers on continuous solar-driven hematite reduction for carbon–neutral co-production of iron and syngas
(2026-09-15)
Chuayboon, Srirat
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Abanades, Stéphane
Green iron production using bio-reducers and solar energy offers a promising alternative pathway towards carbon–neutral metallurgy. However, the types of raw bio-reducers play an important role in hematite reduction performance. An experimental investigation of continuous hematite reduction with seven agricultural biowastes was conducted in a solar reactor to unravel the impact of bio-reducer types and shapes (pellets and particles) on conversion performance and efficiency at 900–1200 °C. As a result, the most promising biowaste reducers were betel nut, palm oil empty fruit bunch, and beech wood due to their high volatile and carbon content, followed by bagasse, coconut fiber, and particle board. Conversely, rice husk was found to be inappropriate because of low gasification activity due to high ash content. No significant impact of reactant shape between particles and pellets was observed, pointing out that the reactor can accommodate various biomass feedstocks. The syngas yield varied in the range of 23.2–56.9 mmol/g<inf>dry_biomass</inf>, and simultaneous high-purity iron production was confirmed by XRD and SEM/EDS. High process efficiency was demonstrated with maximum carbon conversion of 83.1%, oxygen conversion of 100%, and energy upgrade factor up to 1.00. The solar-to-fuel energy efficiency reached 13.2% at 1200 °C, highlighting the remarkable conversion performance of waste biomass and solar energy to clean syngas fuel and renewable iron.
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Comprehensive analysis of on-sun catalytic reforming of methane with a hydroxyapatite-supported nickel catalyst in a tubular solar reactor
(2026-07-22)
Chuayboon, Srirat
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Kulporm, Ratikorn
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O-Thong, Sompong
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Pham Minh, Doan
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Abanades, Stéphane
Methane reforming offers a suitable pathway for greenhouse gas utilization, but its implementation is hindered by catalyst deactivation due to carbon deposition and thermal sintering. This study shows that hydroxyapatite serves as a stable catalytic support for solar-driven dry, steam, and dual reforming. The influence of oxidizer type and concentration (H<inf>2</inf>O, CO<inf>2</inf>, H<inf>2</inf>O/CO<inf>2</inf> mixture) is experimentally investigated at 800 °C in a tubular solar reactor. A hydroxyapatite-supported nickel catalyst (Ni/HA) achieves methane conversion exceeding 95% with 95% H<inf>2</inf> and 96% CO selectivity. An excess of oxidant (oxidant/CH<inf>4</inf> mole ratio of 1.2-1.5) is recommended to promote CH<inf>4</inf> conversion, improve solar reactor performance, and prevent carbon formation and catalyst deactivation. Through sequential on-sun experimental runs, energy upgrade factor above 1.5 and solar-to-fuel efficiency over 20% are attained, demonstrating high catalytic performance stabilized by the metal dispersion on the support. Dual reforming exhibits the highest syngas yield and performance, with minimized carbon formation and H<inf>2</inf>/CO ratio approaching 2.0. Catalyst characterization (XRD, FTIR, SEM, TEM/EDX) confirms high thermal/chemical stability of Ni/HA under solar heating conditions. These results demonstrate compatibility of Ni/HA catalyst with solar methane reforming, providing a high-efficiency sustainable system for converting greenhouse gases into syngas.
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Complete solar thermal direct reduction of iron ore by hydrogen in a particle-fed reactor under concentrated sunlight
(2026-06-01)
Abanades, Stéphane
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Garcia, Roger
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Chuayboon, Srirat
Solar iron production from H<inf>2</inf>-based direct reduction of iron ore was investigated in a continuously particle-fed reactor for performance analysis. Concentrated solar energy was used as the external source of high-temperature process heat and hydrogen was used as reductant, thereby enabling decarbonation of the iron-making process. The solar reactor featured a rotary kiln composed of a refractory conical cavity, in which the reacting particles were injected and extracted under a flow of H<inf>2</inf> reductant, subjected to real concentrated solar irradiation. The reactor was experimentally tested under both continuous and semi-continuous operation modes to determine and compare the key performance metrics. The on-sun experiments focused on unraveling the effect of the cavity material and operating mode on the process performance including H<inf>2</inf> consumption, particle conversion, and iron product purity. A cavity made of mullite appeared unfavorable for continuous particle flow due to agglomeration and adherence to the walls. Conversely, boron nitride promoted particle flowability while totally eliminating adhesion to the walls. In continuous mode, the conversion was kinetically limited due to a low particle residence time in the cavity. Semi-continuous operation was thus tested with cavity rotation turned off during injection and rotation turned on for particles extraction, which warranted a high-enough reaction duration with particle conversion approaching completion. Maximum conversion up to 99 % was achieved with complete recovery yield of the converted product at the reactor outlet. Characterization of solid products (XRD, SEM/EDX) confirmed the successful production of pure sponge iron. Further scaling-up of the solar reactor concept with longer cavity length will enhance the particle residence time, thereby favoring their conversion in continuous mode.
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Impact of different agricultural biomass residues on the performance of continuous solar-steam gasification
(2025-11-02)
Chuayboon, Srirat
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Abanades, Stéphane
Solar-driven biomass gasification represents a promising avenue for sustainable carbon-neutral fuel production. Nevertheless, the types of raw biomass materials play a vital role in continuous solar gasification performance. In this study, continuous solar-steam gasification with various agricultural crop residues was experimentally carried out in a 1.5 kW<inf>th</inf> solar gasifier to investigate the influence of biomass types on performance and efficiency under different operating temperatures up to 1400 °C. Seven agricultural residues were used as feedstocks, including oil palm wastes (palm mesocarp fiber, palm empty fruit bunch, and palm kernel shell), bagasse, betel nut, coconut fiber, and rice husks. Results demonstrated that the system can effectively perform with all biomass types with high-quantity and high-quality syngas production. The process revealed exceptional performance and efficiency, including the total maximum syngas yield range of 67.9–81.5 mmol/g<inf>dry biomass</inf>, reaching 81.4–95.2 % of the theoretical total syngas yields, maximum energy upgrade factor (1.05–1.35), reaching 94.2–97.3 % of the theoretical values, and maximum carbon conversion (87.2–96.9 %). The feedstock types showed a significant influence on gasification outcomes. Palm oil empty fruit bunch, betel nut, and palm mesocarp fiber were promising candidates for solar gasification with their high volatile content and significant decomposition potential, followed by coconut fiber and bagasse. Nevertheless, palm kernel shell and rice husk were found to be unsuitable biomasses for continuous solar-steam gasification because of the issues of reduced gasification activity and reaction rate limitations, due to a high density for palm kernel shell and a high ash content for rice husk. A temperature of 1300 °C was recommended to carry out continuous solar-steam gasification, leading to the maximum solar-to-fuel energy conversion efficiency in the range 13.7–18.9 %. This study provides insights into the influence of agricultural residue types on the solar-steam gasification process, while assisting in the proper biomass residue selection for efficient continuous solar gasification.
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Green iron and syngas production via continuous solar-driven agricultural waste biomass gasification combined with iron(III) oxide reduction
(2024-10-15)
Chuayboon, Srirat
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Abanades, Stéphane
The production of renewable synthetic fuels and chemicals from solar energy and agricultural waste biomass is considered. Solar thermochemical conversion processes offer a promising pathway to a sustainable fuel economy and green chemical industry. This study investigates the continuous solar-driven gasification of agricultural biomass (betel nut waste) combined with iron oxide (Fe<inf>2</inf>O<inf>3</inf>) reduction to produce carbon-neutral syngas and green metallic iron in a single process. A thermodynamic analysis of the system was initially conducted to predict the distribution of equilibrium products. Then, on-sun continuous processing was experimentally carried out under different operating conditions, including betel/Fe<inf>2</inf>O<inf>3</inf> molar ratios (0.56–1.5) and temperatures (900–1200 °C) to evaluate the process feasibility and reliability. As a result, solar gasification of betel nut waste combined with Fe<inf>2</inf>O<inf>3</inf> reduction performed exceptionally well with continuous reactant particles feeding, demonstrating a feasible pathway for producing green iron and high-quality syngas. The maximum syngas yield reached 63.3 mmol/g<inf>dry_betel</inf>, approaching its theoretical value, and high-purity Fe was simultaneously produced. The process demonstrated high efficiency, with maximum carbon conversion approaching 98 %, energy upgrade factor up to 1.26, and solar-to-fuel energy conversion efficiency up to 14.4 %, highlighting remarkable conversion performance of biomass and solar energy to chemicals.
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Carbon-neutral synfuel production via continuous solar H2O and CO2 gasification of oil palm empty fruit bunch
(2023-10-15)
Chuayboon, Srirat
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Abanades, Stéphane
Solar gasification offers a promising carbon-neutral pathway to thermochemically convert waste biomass and solar energy into synfuel. In this study, a thermodynamic analysis of solar gasification of oil palm empty fruit bunch (EFB) with H<inf>2</inf>O and CO<inf>2</inf> gasifying agents was first performed to predict equilibrium product distribution. Subsequently, on-sun continuous solar gasification of EFB was experimentally carried out in a solar particle-fed gasifier to evaluate the influence of gasifying agent types (H<inf>2</inf>O and CO<inf>2</inf>), gasifying agent/EFB molar ratios (1.8–3.4), temperatures (1050–1350 °C), and to assess overall process feasibility and reliability. As a result, solar EFB gasification performed efficiently with both H<inf>2</inf>O and CO<inf>2</inf> gasifying agents under continuous on-sun operation. Syngas product composition and gasification reaction rate strongly depended on gasifying agent type. Increasing temperature enhanced syngas yield and quality, and changed the CO/H<inf>2</inf> mole ratio, especially in EFB + CO<inf>2</inf> gasification. A gasifying agent/EFB molar ratio of 2.6 (slight excess of gasifying agents) and a temperature of 1300 °C were shown to be optimal for continuous solar EFB gasification. The maximum total syngas yield above 76 mmol/g<inf>dry_EFB</inf>, syngas lower heating value above 22 kJ/g<inf>dry_EFB</inf>, and energy upgrade factor above 1.37 were achieved from both EFB + H<inf>2</inf>O and EFB + CO<inf>2</inf> gasification, which closely approached their theoretical equilibrium values. The maximum carbon conversion exceeding 93% and solar-to-fuel energy conversion efficiency up to 19.3% were achieved, demonstrating efficient EFB-to-synfuel conversion performance. Continuous solar EFB gasification with both H<inf>2</inf>O and CO<inf>2</inf> was thus established to be a reliable process for EFB waste biomass valorization into high-quality and carbon-neutral synfuel.
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Solar metallurgical process for high-purity Zn and syngas production using carbon or biomass feedstock in a flexible thermochemical reactor
(2023-05-05)
Chuayboon, Srirat
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Abanades, Stéphane
Co-production of high-purity Zn and syngas via carbothermal reduction of ZnO was performed in a directly-irradiated concentrated solar reactor, thereby converting and storing intermittent sunlight into high-value chemical fuels and commodities. On-sun experiments were carried out by varying operating parameters including solid carbonaceous feedstocks (either solid carbon or beech wood biomass) in batch and continuous modes at 950–1350 °C, demonstrating solar reactor flexibility and robustness. Decreasing pressure (150–400 hPa) promoted both ZnO reduction rate and net ZnO conversion above 78%, thus enhancing Zn production yield. Nevertheless, CO selectivity decreased because of rising CO<inf>2</inf> due to the residence time decrease. A remarkable increase in gas production rates/yields, CO selectivity, and reaction extent was highlighted when increasing temperature during continuous pellets reactant injection. Furthermore, utilizing wood biomass as a sustainable green reducer was proved to be an attractive choice to produce both metallic Zn and high-quality syngas in a single process consisting of biomass gasification with solid ZnO. Zn content exceeding 90 wt% was demonstrated for both batch and continuous tests, unveiling high reactor performance for the metallurgical process. The energy content of the feedstock was upgraded by the solar power input (maximum energy upgrade factor up to 1.2), and the maximum solar-to-fuel energy conversion efficiency up to ∼ 6% was achieved with continuous reactant injection. The high-purity Zn can be further used to produce fuel via CO<inf>2</inf>-splitting in a complete and fast reaction.
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Continuous solar-driven gasification of oil palm agricultural bio waste for high-quality syngas production
(2022-12-01)
Chuayboon, Srirat
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Abanades, Stéphane
Empty fruit bunch (EFB) from oil palm is a solid agricultural bio-waste obtained from the edible oil process. Continuous solar-driven gasification of EFB offers a bright carbon–neutral avenue to convert both EFB bio-waste and renewable solar energy into sustainable and clean syngas. High-temperature concentrated solar heat is used to provide the reaction enthalpy, and therefore biomass waste feedstock is entirely dedicated to produce hydrogen and carbon monoxide (syngas). Solar energy is stored as a high-quality syngas and can be easily transported as a convertible and dispatchable chemical form. In this study, the performance of continuous steam gasification of EFB, fully powered by concentrated solar heat, was experimentally investigated in a solar gasification reactor. Experiments were carried out with continuous EFB biomass injection to evaluate the influence of temperature (1100–1300 °C) and biomass feeding rate (0.5–1.8 g/min). As a result, syngas yields and reactor performance were substantially enhanced by rising the EFB feeding rate and gasification temperature. An optimal EFB biomass feeding rate enabling maximum gasification performance was found to be 1.4 g/min at 1300 °C and 1.0 g/min at 1200 °C. Carbon conversion approaching 97%, energy upgrade factor of 1.38, and solar-to-fuel energy conversion efficiency up to 20% were demonstrated. Finally, the maximum syngas yield was found to be 81.1 mmol/g<inf>dry biomass</inf> at 1300 °C (with H<inf>2</inf> and CO as the main constituents), closely approaching the maximum theoretical expected value reached at thermodynamic equilibrium (85.2 mmol/g<inf>dry biomass</inf>). Combining concentrated solar energy and biomass waste gasification was shown to be a promising and sustainable pathway toward waste valorization into carbon–neutral solar fuels.
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Thermochemical performance assessment of solar continuous methane-driven ZnO reduction for co-production of pure zinc and hydrogen-rich syngas
(2022-02-01)
Chuayboon, Srirat
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Abanades, Stéphane
Converting renewable solar energy to dispatchable chemical products via solar-driven thermochemical processes is one of the best solutions for long-term solar energy storage and renewable fuel production. This study addresses the performance assessment of continuous methane-driven ZnO reduction, fully powered by renewable solar heat, for co-production of hydrogen-rich syngas and metallic Zn in a solar prototype consuming-bed chemical reactor. On-sun experiments were conducted under continuous ZnO and CH<inf>4</inf> co-feeding to assess the effect of key parameters (inlet CH<inf>4</inf>/ZnO molar ratio: 1–1.5, temperature: 900–1000 °C, and ZnO feeding rate: 0.5–1.5 g/min) in order to maximize syngas and Zn yields, and reactor performance metrics. As a result, a rise in either the CH<inf>4</inf>/ZnO molar ratio or temperature enhanced the reaction extent but favored solid carbon formation, which downgraded syngas products quality, and consumed more solar energy input. Increasing ZnO feeding rate under a constant ZnO/CH<inf>4</inf> molar ratio significantly promoted ZnO + CH<inf>4</inf> reaction performance thanks to both hastened ZnO consumption rate (boosting products yield) and reduced solar energy consumption (improving solar conversion efficiency). However, excessively high ZnO feeding rate caused temporal ZnO accumulation in the reactor. Optimal operating conditions for on-sun continuous methane-driven ZnO reduction were identified (at ZnO feeding rate = 1.2 g/min, CH<inf>4</inf>/ZnO molar ratio = 1.5, and temperature = 950 °C), yielding total syngas yield of 12.3 mmol/g<inf>ZnO</inf>, solid carbon formation down to 0.58 mmol/g<inf>ZnO</inf>, ZnO conversion of 63.0%, methane conversion of 10.6%, energy upgrade factor of 1.08, and solar-to-fuel energy conversion efficiency of 5.3%. High-purity Zn particles with hexagonal morphologies were generated in continuous mode, demonstrating the proposed approach feasibility and reliability for simultaneous methane conversion to syngas and metallic Zn production in a single process.
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Solar Carbo-Thermal and Methano-Thermal Reduction of MgO and ZnO for Metallic Powder and Syngas Production by Green Extractive Metallurgy
(2022-01-01)
Chuayboon, Srirat
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Abanades, Stéphane
The solar carbo-thermal and methano-thermal reduction of both MgO and ZnO were performed in a flexible solar reactor operated at low pressure through both batch and continuous operations. The pyro-metallurgical process is an attractive sustainable pathway to convert and store concentrated solar energy into high-value metal commodities and fuels. Substituting fossil fuel combustion with solar energy when providing high-temperature process heat is a relevant option for green extractive metallurgy. In this study, a thermodynamic equilibrium analysis was first performed to compare the thermochemical reduction of MgO and ZnO with solid carbon or gaseous methane, and to determine the product distribution as a function of the operating conditions. The carbo-thermal and methano-thermal reduction of the MgO and ZnO volatile oxides was then experimentally assessed and compared using a directly irradiated cavity-type solar reactor under different operating conditions, varying the type of carbon-based reducing agent (either solid carbon or methane), temperature (in the range 765–1167<sup>◦</sup>C for ZnO and 991–1550<sup>◦</sup>C for MgO), total pressure (including both reduced 0.10–0.15 bar and atmospheric ~0.90 bar pressures), and processing mode (batch and continuous operations). The carbo-thermal and methano-thermal reduction reactions yielded gaseous metal species (Mg and Zn) which were recovered at the reactor outlet as fine and reactive metal powders. Reducing the total pressure favored the conversion of both MgO and ZnO and increased the yields of Mg and Zn. However, a decrease in the total pressure also promoted CO<inf>2</inf> production because of a shortened gas residence time, especially in the case of ZnO reduction, whereas CO<inf>2</inf> formation was negligible in the case of MgO reduction, whatever the conditions. Continuous reactant co-feeding (corresponding to the mixture of metal oxide and carbon or methane) was also performed during the solar reactor operation, revealing an increase in both gas production yields and reaction extent while increasing the reactant feeding rate. The type of carbon reducer influenced the reaction extent, since a higher conversion of both MgO and ZnO was reached when using carbon with a highly available specific surface area for the reactions. The continuous solar process yielded high-purity magnesium and zinc content in the solar-produced metallic powders, thus confirming the reliability, flexibility, and robustness of the solar reactor and demonstrating a promising solar metallurgical process for the clean conversion of both metal oxides and concentrated solar light to value-added chemicals.

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