Large eddy simulation along with a physical fractional-step method was applied to simulate flows near a groin in a straight open channel. The basic idea of this physical fractional-step method is that according to the behavior of each differential operator, the governing equations can be separated into three parts. The first step is a convective problem, which can be solved by the central-upwind deference scheme; the second is a diffusive problem, solved by the central deference scheme; and the third is a source term (pressure equation), solved by the SOR iteration method. The flow phenomenon and characteristics simulated by the proposed method agree well with the experimental data. The research shows that the LES model cooperated with the physical fractional-step method has powerful capacity in the simulation of microstructures of turbulent flows, and can be widely applied to the solution of real engineering problems.
Froth flotation of fine minerals has always been an important research direction in terms of theory and practice. In this paper, the effect and mechanism of Fe3+ on improving surface hydrophobicity and flotation of fine monazite using sodium octyl hydroxamate (SOH) as a collector were investigated through a series of laboratory tests and detection measurements including microflotation, fluorescence spectrum, zeta potential, and X-ray photoelectron spectroscopy (XPS). Flotation tests have shown that fine monazite particles (−26 + 15 μm) cannot be floated well with the SOH collector compared to the coarse fraction (−74 + 38 μm). However, adding a small amount of Fe3+ to the pulp before SOH can significantly improve the flotation of fine monazite. This is because the addition of Fe3+ promotes the adsorption of SOH and greatly improves the hydrophobicity of the monazite surface. This can result in the formation of a more uniform and dense hydrophobic adsorption layer, as shown by the fluorescence spectrum and zeta potential results. From the XPS results, Fe3+ reacts with surface O atoms on the surface of monazite to form a monazite–Osurf–Fe group that acts as a new additional active site for SOH adsorption. A schematic model was also proposed to explain the mechanism of Fe3+ for improving surface hydrophobicity and flotation of fine monazite using octyl hydroxamate as a collector. The innovative point of this study is using a simple reagent scheme to float fine mineral particles rather than traditional complex processes.
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