A population balance model of the particle inventory in a fluidized-bed reactor/regenerator system

A population balance model has been formulated to simulate the time-dependent behavior of the catalyst inventory of a fluidized-bed reactor/regenerator loop. The reactor is operated in the circulating fluidized bed regime while the regenerator operates in the bubbling bed mode. Both reactor and regenerator are equipped with cyclones for solids recovery. The model considers attrition from various sources, i.e., from grid jets, bubble action in the fluidized bed and inside the cyclones. The simulation calculations demonstrate the strong interaction between attrition and efficiency of the solids recovery. A high efficiency of the solids recovery and at the same time a low rate of attrition requires a special design and arrangement of the cyclones. The time-dependent simulations reveal that it takes a considerable time for the system to reach a steady state. The catalyst loss rate from the system stabilizes after roughly 1 week but the Sauter diameter of the catalyst inventory in the loop needs about 3 weeks before a steady state is reached under the conditions investigated.