Universal methodology of measuring properties for particles based on their settled state in fluidized bed

[Display omitted] •Poor reproducibility of traditional measurements stem from particle packed state.•Desired packed state cannot got with good reproducibility via traditional method.•Particle packed state can obtained with good reproducibility via settling method.•Rules were proposed to unify the choice of settled state from different scholars.•Universal methodology based on particle settled state was successfully established. Physical properties of particles are of great significance either to their storage or handling. However, the traditional measurement of many properties (e.g., loosely-packed density, sphericity, angle of repose, minimum fluidization velocity, and segregation index) suffers from poor reproducibility, making the reported values seldom comparable and hindering development of various particle technologies. These measurements generally involve two independent steps: preparation of desired packed state of particles and specific measurement. From our perspective, the poor reproducibility arises from the first step: The desired packed state cannot be prepared with good reproducibility simply via traditional methods. This work found that many packed states of particles could be acquired with good reproducibility in fluidized beds combining the settling method, i.e., decreasing gas flow gradually from full fluidization to the target velocity. The subsequent measurement based on as-obtained settled state also exhibited excellent reproducibility. Moreover, the obtained settled state was observed to vary significantly with the settling rate. To make the measurement results comparable, benchmarks are required to unify selections of settled state among different scholars. One settled state, which first and foremost complied with common sense and property definition, was revealed to be unique enough to unify the choices. Eventually, the universal methodology of measuring properties for particles based on their settled state could be established.