Supercritical extraction of biomass as an effective pretreatment step for the char yield control in pyrolysis

• Published in: Renewable energy 2021-06, Vol.170, p.107-117
• Main Authors: Trubetskaya, Anna, Budarin, Vitaliy, Arshadi, Mehrdad, Magalhães, Duarte, Kazanç, Feyza, Hunt, Andrew John
• Format: Article
• Language: English
• Subjects: Char yield; Fluidisation; Förnyelsebar bioenergi; Heating rate; Renewable Bioenergy Research; Scots pine; Supercritical extraction
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2021.01.116

This work demonstrates that the coupling of supercritical carbon dioxide extraction with pyrolysis is an effective method for the removal of extractives from forestry residues and generation of solid char with different properties from the remaining solid wood fractions. Extraction of the needles and stumps shows greater yields of resin acids, terpenes, steroids and other derivatives than that of pinewood bark, cones and branches. The char yields of both non-treated and scCO2 extracted wood fractions varied from approximately 17.5 to 38.5 wt. % on dry basis at fast heating rates. The catalytic effect of extractives is significant on the yields and morphology of solid chars in fast pyrolysis and less pronounced at slow heating rates. These results are promising as they show that both the composition and location of extractives inclusions in the interior of wood particle can affect the morphology of char samples. Moreover, the impact of alkali metals on the wood devolatilization appears to be less compared to the lignocellulosic composition in slow pyrolysis. These results demonstrate that supercritical carbon dioxide extraction can be integrated in biorefinery as a pretreatment step to control the properties of pyrolysis products by varying the heating rate. •Solid char yield from pyrolysis of non-treated and extracted wood is different.•The catalytic effect of extractives depends on the heating rate.•Strong plasticization of the char surface was caused by fast heating rate.•Extractives did not have a strong impact on devolatilization at slow heating rates.