PARTICLE REMOVAL FROM LIQUID-PHASE USING FINE GAS-BUBBLES

Cold model study was undertaken to investigate the particle removal fr om the liquid phase using fine gas bubbles. Fine gas bubbles were crea ted by flowing water through a tube in which a constriction was implan ted, and injecting air underneath the constriction. The strong turbule nt conditions underneath the constriction warranted formation and disp ersion of fine bubbles in the tube. It was found that the probability of attachment of particles to bubbles in the tube was unity. When the aggregates of particle/bubble were discharged into the bottom tank whe re an abrupt change occurred in their relative movements, large partic les were detached from the bubbles due to high inertial force and pene trated into the liquid in the tank, while small particles were kept at tached to the bubbles and quickly floated up to the free surface of th e tank. Under the present experimental conditions, polystyrene particl es smaller than 500 x 10(-6) m in diameter were mostly kept attached t o the bubbles and floated up to the free surface of the bottom tank, w hile the ones larger than 500 x 10(-6) m were detached from the bubble s and remained in the tank, circulating with water. This was in good a greement with the results predicted by the mathematical model reported previously. The wettability of a particle with-the liquid was found t o be an important factor in determining the removal efficiency of part icles by attachment to bubbles. It was demonstrated that the process e mployed in the present study can be an effective technique for removin g non-metallic inclusions from molten metals such as steel.