Experimental assessment of woody biomass gasification in a hybridized solar powered reactor featuring direct and indirect heating modes

Abstract

Solar thermochemical gasification is an opportunity for the production of sustainable fuels from carbonaceous resources including biomass. Substituting conventional gasification processes by solar-driven technologies may enable cleaner production of H2-rich syngas while saving feedstock resources and alleviating CO2 emissions. This work addresses hybrid solar-autothermal gasification of mm-sized beech wood particles in a lab-scale 1.5 kWth spouted-bed reactor. Hybridization under reduced solar power input was performed by injecting oxygen and additional biomass inside the gasifier for complementary heat supply. Increasing O2:C molar ratios (in the range 0.14–0.58) allowed to heat the reactor cavity and walls progressively, while gradually impairing the reactor performance with an increase of the syngas CO2 content and a decrease of the reactor cold gas efficiency (CGE). Gasification with mixed H2O and O2 was then assessed at thermodynamic equilibrium and global trends were validated experimentally, showing that control of H2:CO ratio was compatible with in-situ combustion. The impact of reaction temperature (1200–1300 °C) and heating mode (direct or indirect) was experimentally studied during both allothermal and hybrid gasification. Higher H2 and CO yields were achieved at high temperatures (1300 °C) under direct reactor heating. Hybridization was able to counterbalance a 40% drop of the nominal solar power input, and the measured CGE reached 0.82, versus values higher than 1 during allothermal gasification.