A twin fluidized bed gasification/combustion system based on
the SilvaGas process [16] is used in this study to model syngas
production from biomass fuels. Previously, De Kam et al.
[10] divided biomass fuels into two parts: one part goes to the
gasifier to produce syngas, and the other goes to the
combustor to provide heat for the gasifier (Fig. 3). In this study,
all of the fuel is sent to the gasifier, and the heat needed for the
gasification process is produced in the combustor from char
and a portion of syngas from the gasifier if needed (Fig. 4).
Simulation results have shown similar system thermal performances
for both configurations (Figs. 3 and 4), but the most
important advantage of using the new configuration (Fig. 4) is
that the size of the combustor is reduced, which can decrease
the system cost significantly. In addition, the new configuration
provides greater flexibility for gas cleanup, which is
important especially when the fuel is herbaceous biomass
such as corn stover. Figs. 1 and 2 illustrate the new fluidized
bed gasification/combustion configuration with all biomass
fuel going to the gasifier and a part of syngas sent to the
combustor as needed.