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Article

Upscaling Severe Torrefaction of Agricultural Residues to Produce Sustainable Reducing Agents for Non-Ferrous Metallurgy

Université Grenoble-Alpes, CEA, LITEN, DTCH, Laboratoire Réacteurs et Procédés (LRP), F-38000 Grenoble, France
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Academic Editor: Petros E. Tsakiridis
Metals 2021, 11(12), 1905; https://doi.org/10.3390/met11121905
Received: 28 October 2021 / Revised: 19 November 2021 / Accepted: 23 November 2021 / Published: 26 November 2021
(This article belongs to the Special Issue Sustainable Metallurgical Processes for Metallic Waste Valorization)
Torrefaction of almond shells and olive stones, which are typically considered agricultural waste in the southern regions of the European Union, was investigated in this work for application as reducing agents in the metallurgical industry. Four different temperatures were tested: 250, 280, 300 and 350 °C. The evolution of the solid yields with the temperature was determined with TGA measurements. This showed that the duration of torrefaction should not exceed 45 min. The kinetic profiles were successfully fitted using the pseudo-first-order rate equation (PFORE). Then, torrefaction for 45 min was systematically carried out at every temperature and for each resource in a laboratory-scale batch device. The raw and torrefied biomasses were characterized using proximate, ultimate and calorific analyses. The carbon/oxygen ratio and the heating values were increased as a result of the torrefaction severity (from 20 MJ/kg for both raw biomasses to 30 MJ/kg at 350 °C). The highest mass losses were obtained at the highest temperature (67.35 and 65.04 %w for almond shells and olive stones, respectively, at 350 °C). The fixed carbon value also increased, being higher than 67 %w for torrefaction at 350 °C. The large-scale torrefaction at 350 °C (45 min) of these biomasses was carried out in a continuous pilot plant. The solids were characterized as well, and their properties were close to those of the biomasses torrefied in the laboratory-scale batch reactor under the same conditions. This thermal treatment provided biochars with all the required properties to be used as reducing materials in metallurgy. View Full-Text
Keywords: agricultural biomass; almond shells; olive stones; pilot-scale torrefaction; reducing agents agricultural biomass; almond shells; olive stones; pilot-scale torrefaction; reducing agents
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MDPI and ACS Style

Demey, H.; Rodriguez-Alonso, E.; Lacombe, E.; Grateau, M.; Jaricot, N.; Chatroux, A.; Thiery, S.; Marchand, M.; Melkior, T. Upscaling Severe Torrefaction of Agricultural Residues to Produce Sustainable Reducing Agents for Non-Ferrous Metallurgy. Metals 2021, 11, 1905. https://doi.org/10.3390/met11121905

AMA Style

Demey H, Rodriguez-Alonso E, Lacombe E, Grateau M, Jaricot N, Chatroux A, Thiery S, Marchand M, Melkior T. Upscaling Severe Torrefaction of Agricultural Residues to Produce Sustainable Reducing Agents for Non-Ferrous Metallurgy. Metals. 2021; 11(12):1905. https://doi.org/10.3390/met11121905

Chicago/Turabian Style

Demey, Hary, Elvira Rodriguez-Alonso, Elie Lacombe, Maguelone Grateau, Nicolas Jaricot, André Chatroux, Sebastien Thiery, Muriel Marchand, and Thierry Melkior. 2021. "Upscaling Severe Torrefaction of Agricultural Residues to Produce Sustainable Reducing Agents for Non-Ferrous Metallurgy" Metals 11, no. 12: 1905. https://doi.org/10.3390/met11121905

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