Numerical simulation of the attachment process of particles and bubbles in a turbulent environment

The study of the attachment process between particles and bubbles in a turbulent environment is essential for understanding the microscopic process of flotation. The interaction force model between particles and bubbles is developed based on the API (Application Programming Interface) secondary development module of EDEM. The model establishes a three-dimensional discrete element method (DEM) to simulate the interaction process between particles and bubbles. Isotropic turbulence is generated by constructing regular grids in the Fluent software. The turbulent environment is then incorporated into the EDEM software using the computational fluid dynamics discrete element (CFD-DEM). The simulation consists of regular particles with sizes ranging from 0.10 to 0.30 mm and densities of 1500, 2000 and 2500 kg/m³. Additionally, the irregular particles with sphericity values ranging from 0.746 to 0.854 are included. Bubble sizes are set at 1.00, 1.20, 1.60, and 2.00 mm. To study the attachment process between particles and bubbles, the distance between the grid and the bubble in the turbulent environment are set as 1.00, 1.50, 2.00, and 3.00 mm. The results demonstrate the existence of a critical detachment flow rate (the minimum turbulent flow velocity where particles and bubbles cannot achieve a stable attachment state) for both regular and irregular particles adhering to bubbles in a turbulent environment. It is found that the particles with larger density and diameter exhibit a smaller critical detachment flow velocity when adhering to bubbles, indicating that particles with larger diameter and density have difficulty in achieving stable attachment with bubbles. As the bubble diameter increases, the critical detachment flow velocity required for stable particle-bubble attachment decreases, making it more difficult for particles to achieve stable attachment. At the same flow velocity, a smaller distance between the bubbles and the grid results in a higher turbulent flow intensity, leading to a smaller critical detachment flow velocity for stable particle-bubble attachment, suggesting that an increase in turbulent intensity is detrimental to the stable attachment of particles and bubbles. Furthermore, the particles with lower sphericity also exhibit a smaller critical detachment flow velocity for stable attachment to bubbles, indicating that the particles with lower sphericity have difficulty in achieving stable attachment with bubbles.