Dimensionless expansion model for bubbling fluidized beds with and without internal heat exchanger tubes

Abstract

A bed expansion model is presented for bubbling fluidized beds without tubes and for beds with staggered horizontal heat exchanger tubes. There are indications that the model also works for inline tube configurations. The bed expansion ratio is modelled as a function of a dimensionless drag force and, in the case of tubes present in the bed, a dimensionless horizontal and vertical tube pitch function. The data used to derive the model cover a wide range of operating conditions, with varying fluidization velocities, pressures, particle materials (Geldart groups B and D), bed geometries and tube configurations. The dimensionless drag force also takes temperature effects into account, and the model shows good agreement with data from a freely bubbling large-scale atmospheric fluidized bed boiler operating at 850°C.