Downdraft gasification of raw and torrefied palm kernel shell

Downdraft gasification is a potential method to produce biomass-based power suited for small-scaled power generation application. In the present study, a downdraft gasifier is used to gasify both raw and torrefied palm kernel shell (PKS). The properties of the palm kernel shells were characterised prior to gasification. Torrefaction of PKS was performed at the maximum temperature of 400 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C. Torrefied PKS shows lower moisture content by 4.8% as compared to raw kernel shell. Gasification of the feedstock showed that torrefied PKS produced higher amount of reactive syngas components, notably 16.4% CO and 9.25% H2 (by volume) than its raw counterpart. The total lower heating value of the syngas produced by torrefied PKS is 7.2 MJ/kg higher than that of raw PKS. Comparison of the temperature profiles within the gasifier for torrefied and raw PKS show distinct differences, with the temperature of the oxidation zone for raw and torrefied PKS being 1115 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C and 1138 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C at the equivalence ratio of 0.41 and 0.30, respectively. Although both feedstock show high potential for synthesis gas production, torrefied PKS produces syngas of higher LHV.