Torrefaction of biomass pellets using the thermogravimetric analyser

Greater heating values, greater energy density and improved physical properties such as shape stability, homogeneity and hydrophobic behaviour are advantages of torrefied biomass. All this leads to an overall reduction in transport costs, storage capacity and to lower requirements for factory equipment. The properties of the different types of biomass used before and after torrefaction and the effect of torrefaction at the different process conditions were studied. For the laboratory tests of torrefaction, wood and grass waste biomass were used. For these selected materials, a number of measurements were performed to verify the most suitable torrefaction conditions (heating temperature and retention time). Experiments were carried out on a small scale on TGA 701 (LECO). Waste biomass was heated to a final temperature of 200, 225, 250, 275 and 300 °C with a retention time at these temperatures of 10, 20 and 45 min. The heating rate was set up to 15 °C min⁻¹. The determination of the appropriate temperature depended on the optimum ratio between mass loss and higher heating values (in case of grassy material from 200 to 225 °C and for woody material at 250 °C). From the results we can state that it is possible to do fast and exact test in TGA before the torrefaction process on the pilot unit to shorten the whole process.