Simulation of biomass gasification in bubbling fluidized bed reactor using aspen plus®

The direct (with air) gasification process of biomass in bubbling fluidized bed reactor was simulated using Aspen Plus (R). The reactor was divided in three parts: the pyrolysis zone, combustion zone and reduction zone. The pyrolysis process simulation was supported by an external MS-Excel (R) subroutine to define the yield and composition of the main components, namely, char, gas and tar. Whereas the combustion and reduction processes were simulated using a kinetic model. These models were calibrated and thereafter validated with a set of distinct results from gasification of four different types of biomass using a pilot-scale bubbling fluidized bed reactor, with different equivalence ratio (from 0.17 to 0.35) and temperature (from 709 degrees C to 859 degrees C). The results obtained from the simulation, namely the concentration of CO, CO2, H-2, CH4, C2H4 in the producer gas, were in good agreement with the experimental ones for a set of biomass types and operating conditions. Amongst the gases analysed, H-2 gas was predicted with the lowest accuracy, always being overestimated; despite that, the highest absolute error obtained for H-2 was only 4.4%. Finally, the tar concentration predicted was between 20 and 42 g/Nm(3) and it decreased with the increase of equivalence ratio, temperature and biomass particle size.

Automated summary

The direct gasification process of biomass in a bubbling fluidized bed reactor was simulated and validated using different models for pyrolysis, combustion, and reduction. The simulation results showed good agreement with experimental results, particularly for gases such as CO, CO2, H-2, CH4, and C2H4. However, the accuracy of H-2 gas prediction was found to be the lowest among the gases analyzed.