Reactor Network Modeling of a Biomass Dedicated Swirling Combustor and a Fluidized Bed Gasifier

Abstract

Reactor network models of two different and representative biomass conversion applications were developed and tested. The models were integrated in the commercial process simulator ASPEN PLUS. The first modeling case is a biomass-dedicated swirling bed combustor. CFD modeling and experimental temperature profiles in the burner were used to develop a reactor network. A detailed reaction scheme was used for combustion modeling of volatiles. The sensitivity analysis runs led to the localization of key parameters that affect greatly the combustion quality. Modifications of the combustor design resulting in significant drop of the CO concentration in flue gases were proposed. The second modeling case is a biomass bubbling fluidized bed gasifier providing fuel gas for an indirect fired gas turbine plant. The two-phase theory was adopted for the hydrodynamic flow modeling inside the gasifier. Physical, mechanical and chemical processes were described through available models from the literature. A series of plug flow reactors were accordingly built where kinetics of both heterogeneous and homogeneous reactions were implemented. These reactors represent both bubble and dense phase with mass transfer between the two phases. A series of sensitivity studies was run to determine the parameters that affect the quality of the emitted gas fuel. The results are compared to both experimental tests performed at the University plant and data available in the open literature. No CFD calculations were performed for the gasifier modeling. The paper is an overview of the work undertaken in the framework of the Ph.D. thesis of R. El Asri where many details can be found, and which will be submitted in the near future.