Characterization of the effect of pyrolysis in torrefied wood chips

Abstract

The pyrolysis behavior of torrefied wood produced in Portugal was investigated. Torrefaction is the thermochemical upgrading of biomass at approximately 300ºC in an atmosphere free of oxidizing agents to increase fuel density and to improve fuel quality, decreasing moisture and increasing heating value. Torrefied woodchips were pyrolysed at pressurized conditions in an inert atmosphere at 600ºC. All the condensable liquids were sampled for analyses. All pyrolysis hydrocarbon liquids were analysed using simulated distillation (simdis) and gas chromatography mass spectrometry (GCMS). Torrefied wood hydrocarbon liquid showed higher concentrations of aliphatic aldehydes liquid. A decrease in all the other molecular components was observed for the torrefied wood hydrocarbon liquid. The main organic components in the torrefied wood pyrolysis water fractions were acids, alcohols and aliphatic oxygenates. Torrefied wood pyrolysis water exhibited a significantly lower acid concentration when compared to non torrefied wood pyrolysis water. The biomass chars (prepared at 600ºC) were analysed using proximate analyses and carbon dioxide char reactivity. Proximate analyses showed that volatile matter was still present in the torrefied wood, but was almost completely devolatilized after pyrolysis.