Simulation of thermochemical processes in Aspen Plus as a tool for biorefinery analysis

Abstract

The development of tools for the synthesis, design, and optimization of biorefineries requires deep knowledge of the thermochemical processes involved in these schemes. For this project, three models from scientific literature were implemented to simulate the processes: fast pyrolysis in a fluidized bed, fixed-bed, and fluidized-bed gasification using the Aspen PlusTM software. These models allow the user to obtain performance, consumption, and cost parameters necessary for the design and optimization of biorefineries schemes. The fast pyrolysis model encompasses a detailed description of biomass decomposition and kinetics of the process (149 reactions). In the fixed-bed gasification process, seven reactions that model the process have been integrated into two equilibrium reactors that minimize the Gibbs free energy. The model used for fluidized bed gasification considers both hydrodynamic and kinetic parameters, as well as a kinetic model that considers the change in the combustion reaction rate of biomass with oxygen leading to a change in temperature. Due to the complexity and detail of all these models, it was necessary to use FORTRAN subroutines and iterative Excel macros linked to Aspen PlusTM. Finally, the results of each simulation were validated with data from the model sources, as well as experimental results from the literature.