Influence of Bed Movement and Amount of Supplied Air on Updraft Gasification of Hardwood Pellet

This work presents the results of hardwood pellet gasification with different amounts of air as a gasification medium. The effects of bed movement and the equivalence ratio (ER) on the temperature profile, gas composition, carbon conversion efficiency and the energy balance were taken into account. Slow movement of the bed promotes high combustion and reduction zones, while fast bed movement leads to high pyrolysis zones and higher caloric values of syngas. When the amount of air increased from 12 to 23 Nm3/h, the gas yield increased from 1.4 to 1.6 Nm3/kgbiomass for slow bed movement, and from 1.0 to 1.3 Nm3/kgbiomass for fast bed movement. These results show that in both Cases similar specific energy values were obtained. However, in Case 1 lower fuel consumption was reached. Chemical energy in the syngas represents 80 % of the output energy for slow bed movement (265 MJ/h) and 75 % for fast bed movement (295 MJ/h). A significant effect of bed movement in the reactor suggests that the gasifier could be considered as a flow reactor, and additionally the fast movement of the bed with 20 Nm3/h of supplied air yielded the highest-quality gasification process. Moreover, fast bed movement in the reactor leads to a high amount of generated char with high energy potential.