Numerical simulation of CO2 and dye separation for supercritical fluid in separator

Influence Mechanism of Gas–Containing Characteristics of Annulus Submerged Jets on Sealing Degree of Mixing Zone

The introduction of air into a submerged annular jet will result in dispersion of the jet, which will affect the degree of enclosure of the gas–water mixing zone in the annular jet nozzle, and then have a significant impact on air suction and the formation of the foam system in the floatation process. A numerical simulation method is used to analyze the characteristics of the distribution of the axial flow velocity of annular jets, gas–phase volume, and turbulence intensity in the gas–water mixing zone in the nozzle with different air–liquid ratios, and thereby reveal the mechanism whereby gas–containing in annular jets affects the degree of enclosure of the gas–water mixing zone. The results show that as the air–liquid ratio increases, the degree of air–liquid mixing will increase and the radial flow velocity will decrease gradually, resulting in the effective enclosure of the gas–water mixing zone. Meanwhile, the dissipation of jet energy, the range of turbulent flow and the vorticity intensity will increase, but the turbulence intensity will decrease. When the gas–water mixing zone is fully enclosed, as gas–containing continues to increase, the degree of dispersion of the annular jet will further increase. Consequently, the area of the gas–water mixing zone with bounced–back water will become larger, resulting in a higher axial flow velocity, larger local turbulence intensity and larger vorticity intensity. This will lead to the dissipation of jet energy, which is not favorable for air suction.

Effect of Closure Characteristics of Annular Jet Mixed Zone on Inspiratory Performance and Bubble System

In the flotation process, gas-liquid properties and the bubble system greatly influence bubble mineralization. In order to clarify how the mechanism applies to the closure characteristics of an annular jet mixed flow zone on the inspiratory performance and the bubble system, different degrees of closure on the velocity field and gas-liquid ratio in the mixed flow zone were investigated using numerical simulation. The variations in the characteristics of bubble size distribution, rising velocity, and gas content under different closure levels were measured with a high-speed dynamic camera technology. The results confirmed that when the closure degrees of the mixed flow zone improved, the inlet jet could gradually overcome the static pressure outside the nozzle effectively. It formed a gas-liquid mixing zone with high turbulence first, and a large pressure difference at the gas-liquid junction second. This helped to increase the inspiratory capacity. At the same time, the gas-liquid ratio rose gradually under conditions of constant flow. When the nozzle outlet was completely closed, the gas-liquid ratio gradually stabilized. For the bubble distribution system, an enhancement in the closure degrees can effectively reduce the bubble size, and subsequently, the bubble size distribution became more uniform. Due to the improved gas-liquid shear mixing, the aspect ratio of the bubbles can be effectively changed, consequently reducing the bubble rising speed and increasing the gas content and bubble surface area flux of the liquid.