Production and separation of rice husk pyrolysis bio-oils from a fractional distillation column connected fluidized bed reactor

Abstract

Rice husks are pyrolyzed in a fluidized bed pyrolyzer and the produced vaporized bio-oils are immediately separated by fractional distillation. The effects of the pyrolysis temperature, rice husk feeding rate and superficial gas velocity on the distributions of chars, bio-oils and syngases in the product are studied. When the pyrolysis temperature is 500°C, the rice husk feeding rate is 20g/min and the superficial gas velocity is 0.340m/s, the mass fraction of bio-oil in the product shows the highest value of 30.4%. The decomposable volatiles in the chars are the lowest for the chars obtained at the lower rice husk feeding rate of 10g/min and higher superficial gas velocity of 0.425m/s. GC–MS analyses indicate that the major chemicals in the bio-oils are acetic acid, furfural, phenol and phenol derivatives. The fractional distillation separates the bio-oil into a light fraction (C4–C7) and a heavy fraction (C7–C10). Relatively high content of acetic acid in the light fraction of the bio-oil is responsible to the lower pH value of the light fraction of the bio-oil. Phenolic compounds are rich in the heavy fraction. Vaporized bio-oils directly from the fluidized bed pyrolyzer are successfully graded by fractional distillation.