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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    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
    ;
    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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    Complete solar thermal direct reduction of iron ore by hydrogen in a particle-fed reactor under concentrated sunlight
    (2026-06-01)
    Abanades, Stéphane
    ;
    Garcia, Roger
    ;
    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.