The axial and radial phase holdup distribution of bubble-induced three-phase inverse fluidized bed

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Simultaneous and visual measurements of local gas and solid phase holdups with high-precision in a gas-liquid-solid circulating fluidized bed is of great importance for the design and scale-up of such a reactor. However, such measuring techniques are still limited due to the difficulty of discrete phase identification of gas bubble and solid particle phases in the complex three-phase flow. Immersed telecentric camera method developed based on the digital image processing is such a measuring technique, but its measuring precision is to be improved due to the existing three problems in the depth-of-field particle extraction, reconstruction of dim bubbles, and counting of overlapping particle clusters. This work has solved these problems by developing corresponding algorithms and the relative errors of measured solid holdup and gas holdup are as low as 0.3% and 1.0%, respectively.

Section: Experimental Results Of Particle Extraction Effectmentioning

confidence: 82%

Section: Experimental Results Of Particle Extraction Effectmentioning

confidence: 99%

Section: Experimental Results Of Particle Extraction Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Method to concurrently measure local gas and solid holdups visually with higher precision in circulating fluidized bed

Zhang

et al. 2021

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The bubble size and rise velocity of bubble‐induced three‐phase inverse fluidized bed (BIFB)

Ma,

Sun,

Shao

et al. 2023

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The bubble size and rise velocity were investigated in detail using a new telecentric photographic probe in a pilot‐scale bubble‐induced three‐phase inverse fluidized bed (BIFB). By the influence of the bubble flow behavior, the particle bed goes through four different flow regimes with increasing gas velocity in BIFB. An obvious normal bubble size distribution caused by bubble coalescence and breakup was observed. A parameter of “size span” was proposed to describe the distribution width of bubble size. The average bubble size increases with the axial distance from the column bottom and with the gas velocity until reaching a relatively stable size. The radial distributions of the average bubble size are almost uniform but experience a decreasing trend near the column wall. The bubble rise velocity increases with the bubble size and the gas velocity. An empirical equation was established to predict successfully the bubble rise velocity in BIFB.

Experimental study of bubble breakup in water and solid suspension by using the image‐based method

Wang,

Duan,

et al. 2024

This work investigates the bubble breakup process with and without particles in turbulent conditions using the image‐based method. A binocular high‐speed camera was employed to capture breakup events. A deep learning‐based image identification software (Large Deformation Dispersed Phase Analysis in Multiphase Flows) and a highly deformed bubble volume/surface area quantification method (Dense Adaptive Segmentation Method) are proposed. An energy barrier is found during the bubble breakup process, with the maximum increase in surface area (ΔSmax) being two to three times the final increase after breakup (ΔSfinal). This indicates that the critical energy required for bubble breakup is underestimated in most breakup models. The presence of suspended particles raises this energy barrier, thus reducing the breakup probability. The daughter bubble size distribution follows an M‐type distribution in water, while the addition of particles leads to a tendency towards equal‐size breakup. This work provides a reliable technology and the experimental data for further clarifying the bubble breakup mechanism.