Efeito da torrefação de resíduos de Eucalyptus grandis

Abstract

Torrefaction is a thermal process that occurs in the endothermic phase of pyrolysis at temperatures between 200ºC and 300ºC. The growing study of the process is related to the conversion of lignocellulosic raw materials into a “carbonized” product with the capacity to be inserted as fuel for power plants, gasifiers, combustion units, etc. The aim of this study was to verify the changes produced in the biomass from Eucalyptus grandis when submitted to the torrefaction process. Three torrefaction temperatures (200 ºC, 250 ºC and 300 ºC) with three residence times (20 min, 30 min and 40 min) were applied, and the biomass was analyzed for its Gravimetric Yield, Energy Yield and PCS. The variation in energy density, improvement in grinding and rest and slip angles of the torrefaction materials was determined, always in comparison with the fresh sample. It was observed that the temperature of the torrefaction process is the most impactful factor in modifying the physicochemical structures of the biomass, with the temperature of 300 ºC being the one that provided the most significant improvements to the material. The highest PCS obtained was for torrefaction performed at 300 ºC, showing an increase of 12.23% when compared to fresh biomass. The increase in temperature generates a material of smaller granulometry and more friable, facilitating the grinding operations, with the torrefaction carried out at 300 ºC, producing a material with a diameter 25% smaller when compared to the fresh sample. After grinding, this biomass trated at 300 ºC had a diameter 39.33% smaller when compared to the same torrefaction sample and 54.24% smaller when compared to the unground fresh sample. In relation to energy density, the increase in the apparent specific mass provided a gain of 24.85% and 28.25% for the apparent specific mass and bed. The angle of repose decreased as a result of the increase in temperature, with the slip angle showing the opposite behavior. Torrefaction proved to be a pre-treatment capable of adding energy value to the material, in addition to improving its physical characteristics, making it a more suitable fuel for insertion in energy generation systems.