Non-stoichiometric equilibrium model applied to autothermal and allothermal biomass gasification in a circulating fluidized bed gasifier

  • Maria E. K. Fuziki
  • Jhon J. R. Behainne


Biomass gasification is thermochemical route to obtain cleaner gaseous fuels from renewable resources. A non-stoichiometric equilibrium model was applied in order to assess the effect of the gasification temperature and the operating mode (autothermal or allothermal) in biomass gasification process. Simulations results indicated the production of a gas with greater HHV from the allothermal mode, due to the higher concentration of fuels compounds found in the energetic gas. Allothermal sawdust gasification at 1000K with equivalence ratio (ER) of 0.22 produced a fuel gas with HHV of 6.14 MJ/m$_{n}^{3}$, whereas the autothermal gasification with the same ER produced a gas with HHV of 6.08 MJ/m$_{n}^{3}$. However, the need of external heat supply made the efficiency of allothermal process lower in comparison with that of the autothermal process. The maximum cold gas efficiency (62%) was obtained with equivalence ratio of 0.25 in autothermal gasification of sawdust.