Steady state multiplicity of fluidized bed reactors. The solid-circulation model

A solid circulation model is used to investigate the steady-state multiplicity features of a fluidized bed reactor in which a single, first-order, exothermic reaction occurs. The model predicts that up to five steady-state solutions may exist. Numerical examples seem to indicate that at most two of the states are stable. The temperature profiles computed by the solid-circulation model are similar to those computed by the axial conductivity model. A regular perturbation expansion is used to prove that the axial-conductivity model and the corresponding Danckwerts boundary conditions are a special limiting form of the solid-circulation model attained when the rate of solid exchange between the bubbles and the dense phase is high.