Improve reproducibility of determining minimum fluidization velocity via endowing it with a precise definition

Abstract

When the fluidizing agent is given, the minimum fluidization velocity (U_mf) of particles is generally reckoned to be the sole function of their physical properties. However, U_mf determined as per its original definition was found to depend also on how the particles were packed before the experimental measurement, causing the well-known poor reproducibility and difficulty in comparing the U_mf reported by different scholars. The original definition of U_mf neglected the polymorphism of packed particles and did not clearly indicate which of the many states the particles should be packed into before the experimental measurement. To solve this problem, this work proposed a precise definition for U_mf by specifying the initial packing of particles: U_mf characterizes the state transition of particles from “free” packed to fluidized. Such a definition could endow U_mf with a clear physical meaning and a definite value. However, as for mixed particles, no precise and realizable definition for apparent U_mf could be proposed yet. The difficulty lies in specifying a reproducible packed state as the starting point for the experimental measurement, which, first and foremost, should have good mixing. Under such circumstances, a compromise method was proposed to improve the reproducibility of measuring U_mf as per its preliminary definition.

Graphical Abstract

Keywords:

• Minimum fluidization velocity
• measurement
• reproducibility
• definition
• polymorphic

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Nos. 21808232, 21978143, 21878164, and 22108145).