Effect of Wettability on Penetration and Flotation Behavior of a Particle in Refining Process

Powder blasting is often performed in refining processes for improving their reaction efficiency. Herein, the effect of wettability on penetration and flotation behavior of a particle was examined via a water model experiment. A polypropylene particle was blasted onto the water surface with Ar gas through a single-hole nozzle, and the behavior of the particle during penetration into water to flotation on the water surface was recorded using a high-speed camera. Wettability between the particle and water was changed by applying a repellent or hydrophilic material on the particle. Based on the penetration of the particle, an air column was generated and a residual bubble remained on the particle after the air column ruptured. Repellent particles floated on the water surface in a short period of time because the maximum penetration depth was short and the diameter of the residual bubble was large. Conversely, hydrophilic particles stayed longer in water than repellent particles because the maximum penetration depth was relatively long and the residual bubble detached from the particle. The mechanism which wettability affects penetration and flotation behavior was analyzed, and it was elucidated that the controlling factor of particle behavior is the adhesion point of the air column on the particle. In the case of repellent particles, the adhesion point changes toward to penetrating direction of the particle and the force caused by the surface tension of water increases. Therefore, the maximum penetration depth decreases and the diameter of the residual bubble increases.