2D gas and solids flow prediction in circulating fluidized beds based on suction probe and pressure profile measurements

Abstract

A fluid-mechanical model for the recirculation zone of circulating fluidized bed (CFB) risers is presented which considers the local flow structure of the CFB to be composed of an upward flowing lean suspension and downward flowing strands or clusters of particles. The model parameters are obtained by fitting the model to at least one measured horizontal profile of the upward and one downward solids fluxes and making use of a measured pressure profile along the riser height. The model allows the two-dimensional gas and solids flows inside the whole recirculation zone to be predicted. The model has been developed on the basis of measurements in a pilot-scale CFB unit (riser height 15.6 m, 0.4 m diameter). The application of the model to large-scale CFB combustors of Chalmers University, Göteborg/Sweden and Stadtwerke Flensburg/Germany illustrates its practical applicability.