Abstract: Gas-liquid-solid fluidized beds (GLSFB) are widely used in various fields due to their excellent interphase mixing and superior mass and heat transfer. However, the gas-liquid phase interface area of millimeter-scale bubbles is small, resulting in low transfer efficiency. In contrast, the specific surface area of microbubbles has the advantage of a significant increase of several orders of magnitude. Introducing microbubbles into GLSFB can significantly enhance the mass and heat transfer rates and prolong the residence time. Focusing on the hydrodynamic characteristics of the microbubble-liquid-solid three-phase fluidized bed, and based on telecentric imaging technology, the influence law of operating parameters on the multiphase flow behavior is explored. Based on Python programming, combined with telecentric camera and manual correction algorithms, the rapid measurement and calculation of three-phase flow parameters were achieved. The results show that the Sauter diameter of microbubbles and the local gas holdup increase with the increase of the apparent gas velocity, and first increase and then decrease with the increase of the apparent liquid velocity of the main water flow. The solid content rate of the large particle system decreases with the increase of gas velocity, while the change in the small particle system is not obvious.

Key words: gas-liquid-solid fluidized bed, multiphase flow, microbubbles, gas holdup, telecentric optical system