Study of rice husk continuous torrefaction as a pretreatment for fast pyrolysis

Rice husk (RH) is one of the most available biomasses in southern Brazil. One possible solution is to carry out the fast pyrolysis of RH. To improve the quality of liquid products biomass can be torrefied before being pyrolyzed. The influence of torrefaction on the physical and chemical properties of pyrolysis products was explored. Both torrefaction and pyrolysis reactions were performed in a fluidized bed reactor in a continuous mode. Sample with torrefaction and pyrolysis at 500 degrees C presented the highest biochar yield (44.2 wt.%). The torrefaction step produced a lower yield of bio-oil. In contrast, the highest bio-oil yield (43.6 wt.%) was achieved in the sample without torrefaction at 500 degrees C. The increase in temperature to 750 degrees C provided a specific area of 16.7 m(2)/kg for biochar. The highest value of HHV for bio-oil, 28 MJ/kg, was obtained via direct pyrolysis at 750 degrees C, which also led to the lowest water content of 5.9 wt%. According to the NMR analysis, the torrefaction liquid (TL) presented a high quantity of water and alcohols in its composition (92.5 %).