Co-pyrolysis of wet torrefied bamboo sawdust and soapstock

In the present study, effect of wet torrefaction on biomass properties and co-pyrolysis of wet torrefied biomass and soapstock were investigated. Experimental results indicated that the ash and volatile contents decreased after wet torrefaction. Obvious decrease of hydrogen and oxygen and an increase of carbon were observed at the same time, which resulted in the augment of higher heating value (HHV). Although lower mass yield was observed under a higher temperature, corresponding energy yield was relatively higher. X-ray diffraction (XRD) analysis revealed that wet torrefaction (below 240 °C) can improve the crystallinity degree of bamboo sawdust. Fourier transfer infrared spectrometry (FTIR) analysis showed that wet torrefaction can significantly remove the acetyl groups in hemicellulose. In thermogravimetric (TG) analysis, the thermal properties of wet torrefied samples and soapstock were altered by co-pyrolysis. Pyrolysis-gas chromatography/mass spectroscopy (Py-GC/MS) analysis showed that co-pyrolysis can produce less oxygen-containing compounds and more hydrocarbons after wet torrefaction. Kinetic analysis showed that the addition of soapstock can obtain a lower activation energy compared with biomass pyrolysis individually. The activation energy for co-pyrolysis of pretreated biomass and soapstock was lower than co-pyrolysis of raw biomass and soapstock, suggesting that wet torrefaction has a positive influence on the co-pyrolysis. The results indicated that the combination of wet torrefaction and co-pyrolysis was a feasible technology for obtaining high-grade oil from biomass.