Numerical Simulations of gas-liquid-solid flows in froth flotation

Three-phase gas-liquid-solid flows are used in a variety of industrial processes, including froth flotation, where air bubbles are used to separate hydrophobic and hydrophilic particles in a slurry. As bubbles rise, hydrophobic particles are captured and brought to the top while the hydrophilic ones remain in the water. We present results from numerical simulations of bubbles rising through a suspension of solid particles, using the Generalized Navier Boundary Condition (GNBC) to model the contact line, where particles stick to bubbles. Particles colliding with the bubbles are attached, using a simple attachment model. The particles slide toward the back of the bubbles, where they accumulate and reduce the rise velocity of the bubbles due to their weight. The passage of the bubbles reduces the volume fraction of the freely suspended particles, as the captured particles are carried upward with the bubbles. A simple averaged model is introduced to model the rise of the bubbles and their scavenging of hydrophobic particles, and it is shown that relatively simple closure models capture the evolution reasonably well. We also show preliminary results for suspensions containing both hydrophobic and hydrophilic particles and the formation of particle-laden foam at the free surface.