Influence of operation variables on fast pyrolysis of Miscanthus sinensis var. purpurascens

Fast pyrolysis of Miscanthus was investigated in a bench-scale fluidized bed reactor for production of bio-oil. Process conditions were varied for temperature (350-550 °C), particle size (0.3-1.3 mm), feed rate and gas flow rate. Pyrolysis temperature was the most influential parameter upon the yield and properties of bio-oil. The highest bio-oil yield of 69.2 wt.% was observed at a temperature of 450 °C which corresponded to the end of the thermal composition of hemicellulose and cellulose. In the bio-oil, the water content was 34.5 wt.%, and the main compounds in the organic fraction were phenolics and oxygenates. With increasing temperature, the amount of oxygenates in the bio-oil decreased gradually while that of water and aromatics increased rapidly. The bio-oil yield was not significantly affected by particle sizes or feed rates. The use of product gases as a fluidizing medium aided in increasing bio-oil yield.