Characterization and Modeling Method for Transient Macroscopic Gas-Solid Flow in Circulating Fluidized Bed Riser

Fluidized bed processes are common in the process and energy industries because they have very good and efficient reaction conditions. These conditions are based on very strong mixing and gas-solid hydrodynamics. The hydrodynamics of gas-solid suspension in fluidized beds is very complex and includes several coupled phenomena. Knowing hydrodynamics is key in process design and development. Many types of simulation methods with different accuracy have been used in the design of fluidized beds and in examining the operation of processes. In all previous investigations and simulation attempts, the main challenge has been determining the interaction between the phases, i.e., the magnitude of the drag force under different conditions. This work presents a practical characterization approach to determine the gas-solid drag force. In this method, the interaction is determined experimentally for real solid material, which includes size, shape, and density distributions. In addition, a macroscopic numerical simulation model is presented that can be used to examine time-dependent gas-solid flows. This macroscopic 1D gas-solid flow model is based on the momentum equation of the solid phase, including an experimentally characterized interaction between phases. The developed model is able to predict the steady-state and time-dependent gas-solid flow profiles in the circulating fluidized bed riser. The work presents a description of the interaction term between phases based on experimental results, as well as the validation of the developed flow model in the operating range corresponding to the experimental results. In addition, the flow model simulation results for time-dependent variation in the circulating fluidized bed riser are given, and the results are compared with experimental results.