CPFD simulation of a fast fluidized bed steam coal gasifier feeding section

摘要

Coal gasification in fluidized beds is a process that can be strongly influenced by gas-solid suspension flow patterns. Fast fluidized beds can be designed to maximize coal gasification yields providing an optimum syngas composition with minimum operational upsets. In order to accomplish this, a comprehensive model for steam coal gasification is valuable. With this end, a 2D CPFD (computational particle fluid dynamics) dynamic model is considered in the present study. The proposed model uses a Lagrangian-Eulerian approach and describes the flow patterns in the gasifier feeding section, as well as the local particle velocities, particle solid fractions and gas composition. As a reference and for comparison, an ideal PFR (plug flow reactor) model is also considered. It is found that compositions from the 2D CPFD model provide close gas compositions with respect to the PFR. It is observed that the 2D CPFD model is valuable for predicting particle flows in the feeding near region keeping it unaffected by fast fluidized bed upsets such as suspension chocking. It is also found that the 2D CPFD model is particularly useful for describing fast fluidized beds operation involving significant amounts of rich ash recycled feeds.