Optimization of depth clarification device for beneficiation circulating water based on solid-liquid two-phase flow simulation

Some beneficiation circulating water contains excess highly dispersed suspended particles, which are difficult to clarify only by simple concentration and sedimentation and cannot meet the requirements of reuse. To solve this problem, a clarification device was developed for removing the solid suspended matter from beneficiation circulating water, which consists of a hydraulic circulation area and a particle sedimentation area and integrating mixing, flocculation, and sedimentation. The flow field inside the gadget has a big influence on how well it works. The structural and operating parameters of the gadget were improved using the computational fluid dynamics approach to increase the device’s performance. A two-dimensional physical model of the deep clarification device for beneficiation circulating water was established. Numerical simulation research on its main structural parameters and operating parameters were conducted by using software Fluent and choosing the Mixture multiphase flow model and RNG k‒ε turbulence model. The effects of feed water nozzle length, throat to nozzle diameter ratio, sludge settling area opening size, and device diameter on the internal flow field were investigated. The average turbulent kinetic energy in the sludge settling zone can be reduced by reducing the length of the nozzle in the hydraulic circulation region, increasing the ratio of the throat to nozzle diameter and the opening size of the sludge settling area, and increasing the diameter of the device. Due to the fact that the turbulent kinetic energy is the kinetic energy of fluid produced by turbulent pulsation, the turbulent degree of the flow field in the sludge settling area is reduced, the effect of turbulent flow in the flow field on particle settling is weakened, and the removal effect of the device on suspended particles is improved. Simultaneously, it is found that at the same suspended solids concentration, reducing the inlet flow rate or increasing the suspended particle size helps to improve the removal rate of suspended solids. When the inlet flow rate is 0.1 m·s^-1 and the coagulated suspended particles form particles with particle size more than 100 μm, the removal effect of slime particles in beneficiation circulating water is remarkable.