Torrefacción de biomasa en un reactor de tornillo a escala de banco: efecto de la temperatura y del tipo de biomasa

Abstract

The intensive use of fossil fuels contributes significantly to global warming and the growing world energy crisis. Thus, it is necessary to develop alternative energy sources that make the energy matrix more flexible and reduce environmental impacts. An outstanding option is the conversion of residual biomass into energy because it produces a low-emission fuel in terms of CO₂. Therefore, this study aimed to improve the physicochemical properties of two residual biomasses (i.e., pine sawdust and spent coffee ground, SCG) through a torrefaction process. Biomass valorization was carried out in a bench-scale screw reactor (2.8 kg/h). The effect of temperature was evaluated between 200 °C and 300 °C, and the torrefied biomasses were characterized by instrumental techniques: calorific value, infrared spectroscopy analysis, thermogravimetric analysis, and scanning electron microscopy. Both biomasses exhibited an increase in calorific value when the process temperature was raised. This behavior is associated with the thermal degradation of the hemicellulose fraction and the increase in fixed carbon. In addition, the infrared analysis showed a decrease in OH and H-O-H signals associated with polar functional groups. These results show the high potential of the valorization of these two biomasses thanks to the decrease in polar groups, which have a great affinity with water, and the obtaining of calorific values close to those of fossil fuels such as lignite or sub-bituminous coal.