Gasification of Charcoal in Air, Oxygen, and Steam Mixtures over a γ-Al2O3 Fluidized

Charcoal was gasified using air and oxygen as well as with mixtures of oxygen and steam, aiming to produce a gas stream with high hydrogen content. The effects of the equivalence ratio (ER) and steam-to-carbon ratio (S/C) on carbon conversion, producer gas yield, gas heating value, and composition as well as on the apparent energy efficiency (AEE) of the process were studied. The gasification experiments were performed in a laboratory-scale fluidized bed rig working at 1173 K and atmospheric pressure and using gamma-Al2O3 as bed material. Results showed that, on a N-2-free basis, the composition of the producer gas obtained by gasification with air and pure oxygen were comparable when using the same ER Furthermore, carbon fraction converted into gas improved when ER was increased from 0.25 up to 0.35, as well as when the S/C was increased to 0.625. The highest producer gas yield was obtained using ER = 0.35 and S/C = 0.625, while the highest hydrogen concentration in the produced gas was achieved using ER = 0.25 and S/C = 0.625. The highest hydrogen yield (0.412 N m(3)/kg charcoal) and the highest AEE (33.43%) were achieved by using S/C = 0.625 and ER = 0.3 (oxygen). The autothermal gasification of the charcoal was possible in the experimental rig used in this work by selecting ER = 0.3 and S/C = 0.5, allowing the production of a gas with a heating value of 8.3 MJ/Nm(3) while reducing the carbon conversion into gas to 49.4 wt %.