Abstract:

Four typical types of biomasses, corn stover, eucalyptus sawdust, bamboo sawdust and hardwood sawdust, were used as raw materials to analyze the effects of temperature and material chemical composition on the properties of pellets by conducting single pellet making experiments. The characteristic thermal transition temperatures of the four raw materials were measured using a differential scanning calorimetry and found the glass transition temperatures(T_g) were in the temperature range of 80-100℃. It was found that the relaxed density(D_RS) and radial maximum stress(M_RS) were lower and the specific energy consumption(E_SC) was higher at 40℃, the relaxed density and radial maximum stress increased and the specific energy consumption decreased in the temperature range of 70-100℃, the relaxed density increased and the radial maximum stress did not present consistent change law and the specific energy consumption increased in the temperature range of 100-160℃. The lowest specific energy consumption located at 100℃ during the characteristic thermal transition temperature range. Besides, the higher the raw material lignin content was, the higher the specific energy consumption and the radial maximum stress were. The micromorphology of the internal cross section of the pellets showed that there were large gaps between the particles at the temperature of lower than the onset of the glass transition temperature and there were few gaps between the particles at the temperature of higher than the endpoint of the glass transition temperature.

Key words: biomass, temperature, pellet, relaxed density, morphology