Influence of steam on gasification of millimetric wood particles in a drop tube reactor: Experiments and modelling

Wood particle conversion in a drop tube reactor was studied between 1000 °C and 1400 °C, both with experiments and simulations using a comprehensive model. Particular attention was paid to the influence of steam on the gasification process, and to the wood particle size. The model included a description of the different phenomena involved in biomass conversion: pyrolysis, gas phase reactions, soot formation and carbonaceous solid gasification. Satisfactory results were obtained in comparison with experiments. The addition of steam in the atmosphere influenced char, tar, soot and gas yields, especially at 1200°C and 1400°C. These changes were linked to char and soot steam gasification, and to gas phase reactions, among which hydrocarbons steam reforming and water-gas shift. At 1400°C, with 25 mol% H$_2$O and after a residence time of 4.4 s, the char seems to be completely gasified, while the soot yield still represents about 5 wt% of the initial dry biomass. Wood particle size in the range 0.35-0.80 mm was experimentally shown to have no influence on products yields for a residence time of a few seconds.