Experimental study on the fluidization discharging characteristics of Geldart-C kaolin powders in a blow tank with pulsed gas

Abstract

Kaolin powders have been suggested to be able to adsorb heavy metal vapor from coal-fired flue gas. However, due to the influence of inter particle forces, such as liquid bridge force, it is difficult to realize stable pneumatic conveying. In the present work, the fluidization characteristics of kaolin powders were investigated. A series of unstable flow phenomena such as agglomeration, channeling, and slugging occurred during the fluidization process. Also, the fluidization discharging characteristics of kaolin powder in an optimized blow tank were experimentally studied. The results indicated that the introduction of pulsed gas can effectively destroy agglomeration and thus improving the stability of discharging. Visual experiments in pseudo-2D fluidized bed were also confirmed the destructive effect of pulsed gas on agglomeration. With an increase in either fluidization gas velocity Uf or pulsed gas velocity vpulsed, the mass flow rate of kaolin powder G first increased and then decreased. Finally, drying experiments demonstrated that there is free water on the surfaces of the kaolin powders. The analysis of forces indicated that the liquid bridge force Flb between particles is much larger than the particle gravity Fg. The liquid bridge force might be one of key reasons for kaolin powder agglomerating.