Effect of Mechanical Fractionation on the Torrefaction of Grass

摘要

Torrefaction is seen as an effective means of ameliorating the properties of biomass as a fuel, which however requires the feedstock being completely dried prior to pyrolysis. To reduce the energy required in thermally drying wet grass, the raw biomass can be subjected to a preceding mechanical fractionation process to extract a biomass "juice." This study examines the effect of mechanical fractionation using a commercial screw press on the torrefaction behavior of grass. The composition of biomass before and after torrefaction is determined using differential thermo-gravimetric analysis of the solid and liquid fractions undergoing pyrolysis. Mineral composition of both the grass juice and pressed grass is determined with inductively coupled plasma spectroscopy. It is found that there is not a significant difference in the torrefaction yields before and after fractionation despite the loss of hemicelluloses and extractives from the biomass, signifying that the pretreatment can partially undertake the function of torrefaction. Furthermore, it is observed that significant quantities of minerals are leached from the solids to the biomass "juice," leading to an improvement in the ash behavior of the pretreated fuel.