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BioResources
Ramos-Carmona, S., Delgado-Balcázar, S., and Perez, J. F. (2017). "Physicochemical characterization of torrefied wood biomass under air as oxidizing atmosphere," BioRes. 12(3), 5428-5448.

Abstract

The effects of torrefaction under an oxidizing atmosphere on the physicochemical properties of patula pine wood chips were studied. Raw and torrefied pine were characterized to evaluate the effect of temperature and residence time on biofuel properties, such as bulk density, equivalent Hardgrove grindability index (HGIeq), ultimate and proximate analyses, heating value, and fuel value index (FVI). In contrast, the torrefaction process was characterized by mass and energy yields, and by the energy-mass co-benefit index (EMCI). Torrefaction was performed in a rotary kiln at temperatures between 180 °C and 240 °C during residence times between 30 min and 120 min. The torrefaction process under an oxidizing atmosphere tended to increase the fixed carbon/volatile matter ratio (from 0.19 to 2.5), while the H/C and O/C atomic ratios decreased 73% and 55%, respectively. The best properties of wood reached in the experimental plan were obtained at 210 °C during 75 min. For this torrefaction condition, energy yield, FVI, and EMCI were 85.91%, 1.91 MJ/cm3, and 4.41%, respectively. Additionally, the lower heating value for torrefied pine (18.65 MJ/kg) was higher than for the raw material (17.76 MJ/kg), and the HGIeq was 17% greater, which resulted in a better grindability behavior.


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