Simulation on the process of single bubble floating and colliding oil droplet based on improved three-component pseudo-potential Boltzmann method

Abstract

Air floatation is a widely used wastewater treatment technology, often used to remove oily contaminants and suspended matter with a specific gravity close to 1 in wastewater. The key to air float deoiling lies in the process of collision and contact between oil droplets and bubbles. Therefore, it is of great scientific significance and practical value to study the collision process and influencing factors. In this paper, improvement measures such as surface tension adjustment method, multi-relaxation scheme, and thermodynamic inconsistency correction were added to the original multiphase flow pseudo-potential model. On this basis, a multi-component multi-phase lattice Boltzmann program was compiled. The process of bubbles colliding with oil droplets was simulated and compared with experiments to verify the simulation method. Furthermore, the effects of different oil-gas diameter ratios, collision angles, interphase forces between oil and gas phases, and viscosity on the collision results were explored. The simulation results found that under positive collision conditions, when the diameter ratio of oil and gas is greater than 1.22, the bubble lifts the oil droplet at the bottom and the adhesion is relatively stable. As the diameter ratio of oil to gas decreases, the form of adhesion gradually changes, and when the diameter ratio is less than 0.821, it begins to take the form of a package. The collision angle mainly affects the momentum transfer efficiency from the oil droplet to the bubble. The smaller the collision angle, the more obvious the acceleration of the oil droplet. The large angle collision is not conducive to the stable adhesion between the bubble and the oil droplet. The interphase force between the oil and gas mainly affects the contact angle and adhesion stability of the bubbles and oil droplets. The greater the force, the greater the contact angle and the lower the stability. When the viscosity changes from 0.5 to 3 times the kinematic viscosity (2.158 × 10−6 m2/s) of the experimental oil, it has little effect on the simulation results.