Investigation on characterization of powder flowability using different testing methods

The powder flowability of pulverized coal and glass bead powders were characterized by using different testing methods, including fluidization test, packing properties test, AOR test and shear test, which correspond to different stress levels of the powders, from the highly dispersed state in fluidized beds to the highly consolidated state in shear testers. The data obtained from these testing methods were compared and evaluated to establish internal relationships between them. The results show that the results of these testing methods are highly dependent on particle size, as powder particle size increases, the values of HR, CI, AOR, c decrease, while the value of FF increases gradually, which indicates a decrease of powder cohesiveness, and the powder flowability becomes better. Meanwhile, there exists a good linear relationship between tan AOR and 1/ρpdp. The empirical correlation equations describing the quantitative relationship between tan AOR and 1/ρpdp were proposed for pulverized coal and glass bead powders, respectively. The results of testing methods which measure flow behavior at relatively similar degrees of stress state can be transferred between each other; otherwise, the results cannot be correlated well. It was found that there exists a non-linear relationship between AOR and HR within our experimental range.