Role of temperature in the biomass steam pyrolysis in a conical spouted bed reactor

Abstract The steam pyrolysis of pinewood sawdust has been conducted in a bench scale plant provided with a conical spouted bed reactor (CSBR). This process is of uttermost relevance for the in-line valorisation of pyrolysis volatiles, specifically for their catalytic steam reforming for hydrogen production. The influence of temperature on the product yields has been analyzed in the 500–800 °C range. A detailed analysis of the volatile stream (condensable and non-condensable components) has been carried out by chromatographic techniques, and the char samples have been characterized by ultimate and proximate analyses, N2 adsorption-desorption, and Scanning Electron Microscopy. A high bio-oil yield was obtained at 500 °C (75.4 wt%), which is evidence of the suitable features of the conical spouted bed reactor for this process. As temperature was increased, higher gas and lower liquid and char yields were obtained. Steam was fully inert at low pyrolysis temperatures (500-600 °C), and only had a little influence at 700 °C due to the low gas residence time in the conical spouted bed reactor. At 800 °C, the reaction mechanism was controlled by gasification reactions. The composition of the liquid fraction was considerably influenced by pyrolysis temperature, with a less oxygenated stream as temperature was increased. Thus, phenolic compounds accounted for the major fraction at low pyrolysis temperatures, whereas hydrocarbons prevailed at 800 °C. The char obtained in the whole temperature range can be further used as active carbon or energy source.