Pine cone pyrolysis: Optimization of temperature for energy recovery

Abstract

In this work, the pine cones pyrolysis (a mixture of both scales and axis) was investigated under different temperature (500–800°C) at a bench scale fixed bed reactor operating in batch mode. It was found that operating temperature had a slight or more marked influence on the product phase distribution as a consequence of the enhancement of biomass decomposition and also the greater prominence of cracking reactions especially at highest temperatures, yielding a greater gas production. It was found that increasing temperature led to decreasing biochar yields (from 29.4% to 20.4%) and increasing gas yields (from 34.4 to 44.4%), whereas the bio-oil yield passed through a maximum 37.6% at 600°C. The biochars were characterized in terms of proximate and elemental analysis, thermal degradation profiles, high heating value and surface chemistry and morphology. In addition, the composition of gases was determined by gas chromatography. Apart from the changes induced by increasing temperature on the biochar properties such as greater pore volumes at 700°C (used in activated carbon manufacture), it was found that gas production was enhanced, and H2 and CH4 yields were the highest at 800°C. Finally, at 600°C biochar showed the highest heating value of 30.95 MJ kg−1, allowing its use briquette biofuels.