Fast devolatilization characteristics of 'low cost' biomass fuels, wood and reed

Abstract

Fast devolatilization of woody (mixture of softwoods) and herbaceous (reed) biomasses has been studied in a heated foil reactor coupled to an FTIR spectrophotometer. Biomass fuels were chosen based on their potential for contributing to power generation on an industrial scale through gasification in The Netherlands. Heating rate (600 °C/s) and holding time (10 s) at peak pyrolysis temperature were chosen to correspond to conditions encountered in industrial processes. The effect of peak pyrolysis temperature on pyrolysis products was investigated. Particular emphasis was given to tar collection, and subsequent gravimetric quantification. The results indicated a strong total weight loss increase with temperature, to reach an asymptote char yield of 16.7 wt.% at 800 °C and of 32.4 wt.% at 700 °C for wood and reed, respectively. Reed primary devolatilization reactions ceased at lower temperatures compared to wood. The latter was confirmed by the lower activation energy of reed (32.1 kJ/mol) compared with that of wood (38.4 kJ/mol) during extrapolation of kinetic data from the fast devolatilization experiments. CO2 dominated the gaseous products released at lower temperatures (< 700 °C) while CO became predominant at higher pyrolysis temperatures (> 700 °C) reaching a maximum of 19.1 wt.% and 18 wt.% for wood and reed, respectively, at 1000 °C. Maximum tar yields of 38.8 wt.% (d.b.) of dry wood and 23.3 wt.% (d.b.)of dry reed were able to be recovered at 600 °C. An overall mass balance of approximately 90 wt.% (d.b.) for both biomass fuels was obtained at high (900–1000 °C) pyrolysis peak temperatures.