Fast pyrolysis of birch wood in a bubbling fluidized bed reactor with recycled non-condensable gases

Abstract

A fluidized bed reactor pyrolysis process with recycled non-condensable gases was designed for a capacity of 5 kg/h based on previous basic studies of key parts. The main components of the pyrolysis process were introduced, and the performance was appraised. Initial experiments were conducted between 450 °C and 550 °C to characterize the bio-oil at different temperatures, using non-condensable gas as fluidizing medium. Simultaneously, the contents and higher heating value of non-condensable gases were determined. The results showed that the excellent efficiency of cooling and of capturing the organic compounds, contributing to a high yield of bio-oil and clean non-condensable gases. At 500 °C, the highest yield of bio-oil reached 55.6 wt%, and the yields of bio-char and gas were 23.4 wt% and 21 wt%, respectively. Non-condensable gas not only carried the organic compounds, but also participated in fast pyrolysis. However, temperature was the major factor affecting the chemical components of bio-oil. The heavy bio-oil mainly included long chain macromolecules and phenols. Higher temperature favored degradation and gas purification.