Numerical investigation of fine sand removal in vortex-enhanced spiral pipeline separators via coupled CFD-DEM simulation

In this study, a coupled numerical simulation approach integrating Computational Fluid Dynamics (CFD) for continuous fluids and the Discrete Element Method (DEM) for particulate phases was employed to investigate the hydrodynamics of sand-laden wastewater within a spiral separator. The effects of varying inlet velocities on the distribution and separation efficiency of sand particles across different size ranges were examined. To validate the numerical model, experimental tests were conducted using the spiral separator to treat municipal wastewater containing fine sand particles (<200 μm), with the simulation results benchmarked against the experimental data. The findings demonstrated that the spiral separator exhibited pronounced flow-guiding and swirling effects, resulting in efficient particle separation. The optimal flow velocity for effective sand particle separation was determined to be 0.25 m/s. Notably, particles sized 150–200 μm demonstrated superior separation at lower flow velocities, while increasing the inlet velocity significantly enhanced the separation efficiency for particles in the 50–100 μm size range. The proposed spiral separator design achieved low hydraulic losses and high separation efficiency, establishing a novel framework for low-resistance, high-performance sand removal in municipal wastewater treatment.