Bio-oil production from the torrefied biomass

Abstract

Biomass is an important source of renewable energy which is derived from the living mechanism such as photosynthesis of plant due to the lower contents of sulfur and nitrogen in the biomass. Pyrolysis is a technology that can directly produce a liquid fuel from biomass which can be readily stored or transported. However, many researches have reported the negative properties of the bio-oils compare with the conventional fuel oil. The undesirable properties of the bio-oils included low heating value, low pH value, incompatibility with conventional fuels, high viscosity, and chemical instability. These undesirable properties of the bio-oils are mainly brought about by the high oxygen content in the biomass. On the other hand, it is known that the oxygen content in the biomass could be reduced by the torrefaction at the temperatures below 300°C. So, in this study we try to upgrade the biomass first by torrefaction at the temperatures below 300°C. It was found that the oxygen content of Leucaena leucocephala decreased from 46.2 wt% to 36.7 wt% when torrefy at 303°C whereas the torrefied lecaena yields decreased with the increase in torrefaction temperature. Then, the torrefied leucaena will be pyrolysed at 550°C to produce bio-oils. The bio-ols were fractionated into light oil and heavy oil fractions which were analyzed by GC-MS to examine the effect of fraction on the bio-oils properties. It was found that the acetic acid and furans were decreased in light oil fraction with the increase in torrefaction temperature. The pH value of bio-oils was slightly increased that was consistent with decreasing of acetic acid in light oil fraction. These results indicated that torrefaction process could improve bio-oils properties prior pyrolysis process.