Tracking the Flow Dynamics in Circulating Fluidized Bed through High-Speed Photography

In gas-solid circulating fluidized beds, particle velocity and solids flux are crucial parameters for understanding the gas-solid interaction. In the literature, the time-average information has been investigated intensely, but the analysis of instantaneous information remains lacking. In this work, flow behavior in a narrow rectangular circulating fluidized bed has been recorded using a high-speed camera. Then, with a verified correlation between grayscale and solids holdup, particle velocity is computed by tracking local solids holdup characteristics using a two-dimensional cross-correlation, and solids flux is computed by multiplying the particle velocity with particle density and local solids holdup. The time-average information in this work is found to be consistent with that of previous publications. Instantaneous information of particle velocity and solids flux, including relations with local solids holdup, instantaneous radial distributions, instantaneous solids circulating rates, and impacts of macro-fluctuation is analyzed systematically and discussed in detail for the first time.