A novel approach for simultaneous hydrodynamic characterization of gas–liquid and gas–solid systems

An attempt was made to find an analogy between hydrodynamic structures in fluidized beds and bubble columns in the frequency domain. This approach provides a better picture of hydrodynamic similarities between these two-phase reactors. The experiments were carried out in an air–water bubble column and an air-FCC fluidized bed. Pressure fluctuations were recorded for both systems at various gas velocities, aspect ratios and probe positions and were analyzed in frequency and time-frequency domains. Frequency spectrum of fluidized bed and bubble column revealed differences and similarities which can be related to properties of liquid and solid. Hydrodynamic phenomena were classified into three structures applicable to both bubble column and fluidized bed: macro (0–3.125 Hz), meso (3.125–12.5 Hz) and micro (12.5–25 Hz) structures. It was found that the macro and meso structures exhibit a similar behavior in both systems. The plot of dimensionless standard deviation of pressure fluctuations in bubble column and fluidized bed against dimensionless velocity showed the similar qualitative and quantitative behavior for both systems. The analogous phenomena found for each structure can be used as a criterion for better understanding of both systems.

► Pressure fluctuation was measured in fluidized beds and bubble column.
► Three analogous structures were defined for fluidized bed and bubble column.
► The structures were classified to three classes: macro, meso and micro structure.
► The macro and meso structures show similar trend for bubble column and fluidized.