Modeling of Biomass Flow in a Novel Multi-staged Fluidized Bed Concept

Abstract

A mathematical description of the axial mixing of biomass in bubbling fluidized beds was developed and implemented into an already existing mathematical model. Based on the developed model the performance of novel multi-staged fluidized bed concept was investigated. The novel concept works by inserting a chamber into an already existing unit and in that way introducing two reaction zones that can communicate with each other via a slit at the bottom of the walls delimiting the reaction zones. The implementation of the novel concept enables pyrolysis and char conversion to occur in separate environments. Based on simulations it was shown that the results are very sensitive to the pyrolysis kinetics, why more studies of the kinetics would be of interest. Furthermore, it was shown that novel concept could be controlled by varying the pressure difference between the reaction zones. The fluidization velocity could also be used as a means for control, but for too big slit heights, the novel concept becomes insensitive to changes in fluidization velocity.