| The cyclone-static micro-bubble flotation column(FCSMC)has shown unique advantages in fine-grain mineral separation due to its multiple mineralisation steps.The column flotation unit of the flotation column is dominated by countercurrent mineralization,and the static separation environment is required to obtain higher separation efficiency.However,as the column flotation unit and the cyclone separation unit are connected vertically,the strong swirling flow field generated in the reversed cyclone unit will move upwards,thereby destroying the static separation environment required for the column flotation unit.In order to solve this problem,this paper referenced the sieve-plate packing method,introduced it into the column flotation unit,and the computational fluid dynamics(CFD)technology was used to optimize the sieve-plate packing.Firstly,particle image velocity(PIV)technology was used to obtain the single-phase flow field information in a laboratory cyclone-static micro-bubble flotation column,and then compared the single-phase flow numerical simulation results calculated by different turbulence models(Standard k-?,RNG k-?,Realizable k-?,RSM),the results show that the calculation values of RSM turbulence model relatively close to the experimental values.On the basis of this,combined with the Eulerian multiphase flow model,the calculation results of different drag models(Universal,Tomiyama,Schiller-naumann,Morsi and Alexander)were compared and it was found that the calculation results of the Universal drag model are closer to the experimental data in the literature.Therefore,the RSM turbulence model and the Universal drag model are determined as the calculation model for the subsequent study in this paper.Using the above calculation model,the internal flow field of the flotation column without sieve-plate and with sieve-plate packing was simulated.The results show that the tangential velocity is greatly suppressed by the sieve-plate,which makes the gas holdup distribution in the column flotation unit more uniform,the sieve-plate packing is conducive to the realization of the static separation environment.Based on this,the effects of the circulation volume and aeration rate on the flow field in single-layer sieve-plate packing flotation column were studied:(1)When the circulation volume was1.5m~3/h and the aeration rate was 0.5L/min,1L/min,1.5L/min,and 2L/min,respectively,the tangential velocity changes little with the increase of aeration,and the axial velocity in the center region increases from 0.073m/s to 0.089m/s,while the axial velocity in the near wall region decreases.The gas holdup in the column flotation unit increases significantly.(2)When the aeration rate was 1L/min and circulation volume was 1m~3/h,1.25m~3/h,1.5m~3/h,and 1.75m~3/h,respectively,with the circulation volume increases,the axial velocity in the center region increases from 0.069m/s to 0.083m/s,the axial velocity in the near wall region decreases,and the gas holdup in the column flotation unit increases first and then decreases.The single-phase flow and two-phase flow numerical simulations for five kinds of hole diameter(6mm,8mm,9mm,10mm,12mm)uniform sieve-plate were carried out,the results show that when the hole diameter is 9mm,the tangential velocity is minimum and the gas holdup distribution is more uniform,but the gas holdup rate is lower than others.In order to further improve the efficiency of sieve-plate,based on the 9mm hole diameter sieve-plate,two kinds of non-uniform sieve-plate were designed and studied,the results show that the non-uniform sieve-plate that the hole diameter in the edge area small than center area showed a better packing performance.The research in this paper has a guiding significance for realization of the static separation environment of flotation column and optimal design of the sieve plate structure. |
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