Influence of Reaction Temperature, Pretreatment, and a Char Removal System on the Production of Bio-oil from Rice Straw by Fast Pyrolysis, Using a Fluidized Bed

Rice straw is one of the main renewable energy sources in Korea, and bio-oil from rice straw
is produced using a bench-scale plant that is equipped mainly with a fluidized bed and a char
removal system. We investigated how the reaction temperature affected the production of bio-oil
and the efficiency of a char removal system. To elucidate how the temperature was dependent
on the production of bio-oil, experiments were conducted between 400 °C and 600 °C at a feed
rate of ∼1 kg/h. The mass balance was established in each experiment, and the produced gas
and oil were analyzed with the aid of gas chromatography and a gas chromatography−mass
spectroscopy (GC−MS) system. The effect of pretreating rice straw was also investigated by
comparing the yield of bio-oil and the content of alkali metals in the bio-oil from the experiments
on unwashed rice straw with the corresponding values of washed rice straw. The char removal
system is composed of a cyclone and a hot filter. After every experiment, we examined the particle
distribution of each char and the content of solids in the bio-oil, to demonstrate the efficiency of
the char removal system. In the experiments, we observed that the char removal system and the
pretreatment effectively reduced the content of alkali metals in the bio-oil, and that the optimum
reaction temperature range for the production of bio-oil is 410−510 °C.