Screw pyrolysis with integrated sequential hot gas filtration

In this study, the pyrolysis of beech wood chips has been investigated by means of intermediate pyrolysis in a screw reactor with integrated hot gas filtration. Temperatures between 350 °C and 500 °C have been applied to characterize the yields and properties of the pyrolysis products. The yield of the char decreases with increased temperature from 31 wt.% to 18 wt.% whereas, the yield of the oil phase reaches a maximum value of 13,2 wt.% at 450 °C. The viscosity of the oil changed with temperature in the range of 74,6 mPa s to 163,4 mPa s. Acetic acid, furfural and acetaldehyde have been selected to monitor the degradation of the holocellulose derived products, while guaiacol and phenol for that of the lignin-derived ones, showing that it may be possible to treat the pyrolysis of the wood main components adopting a relative small number of liquid organic species. Furthermore, the configuration of the reactor allows the sequential filtration and extraction of the vapors, as well the direct access to the partially pyrolyzed char. The sequential extraction appears as a promising route to concentrate valuable products. Among the results, it has been found that the heating rate in the range of 100 °C/min to 210 °C/min does not play a major role on the characteristics of the produced char.