Study On The Hydrophobic Flocculation Process Of Fine Wolframite Based On The Numerical Simulation Of Fluid Field

A large amount of fine wolframite is generated during crushing and grinding due to the brittleness,and it cannot be recovered and loses to the tailings.It is difficult to recover the fine wolframite particles,even though the flotation,which is one of the most effective methods for recovering wolframite.Therefore,how to increase the apparent particle size of wolframite is an urgent problem waiting to be solved on the fine-grained wolframite flotation.In this paper,the hydrophobic flocculation behavior of-10 μm wolframite was studied under four types of stirring devices:single-layer paddle without baffles,single-layer paddle with baffles,double-layer paddles without baffles,and double-layer paddles with baffles.The relationship between the hydrophobic flocculation behavior of fine wolframite and the fluid flow characteristics of stirred tank was established based on the study of the numerical simulation of different flow field conditions on the collisional adhesion and flocculation strengthening of wolframite.The single mineral flotation tests is to select the proper surfactant according to the influence of pH condition and collectors on the flotation behavior of wolframite.By comparing the effects of NaOL,hydroxamic acid and dodecyl surfactant on the floatability of wolframite,it was found that the surfactant NaOL showed a better collection performance for wolframite,and the 89.92%recovery of wolframite was obtained at the optimum condition of 36 mg/L NaOL and pH 8.The hydrophobic flocculation behavior of fine wolframite was discussed by controlling the single factor condition and d50 was used to characterize the agglomeration size.The NaOL concentration was positively correlated with the size of d50,and a higher NaOL concentration led to a larger size of the formed agglomeration.When the dosage increased more than 240 mg/L,the agglomeration size would not increased.As the stirring intensity increased,the agglomeration size d50 of fine wolframite gradually increased,while the increase tend was slowed at the stirring speed up to 1500rpm.The stirring time showed a similar effect on the agglomeration size of wolframite,and the agglomeration size increased slowly when the stirring time was more than 10min.By comparing the strengthening effect on the wolframite agglomerations produced by four different stirring devices,it could be obtained that the strengthening effect of four different stirring devices showed as double-layer paddles with baffles agitation device>single-layer paddles with baffles agitation device>single-layer paddles and baffle-free agitation device≈double-layer paddles and baffle-free agitation device.The three-dimensional stirring model was established based on the selected multi-reference frame(MRF),SIMPLE algorithm,and mixed multi-phase flow turbulence model standard k-ε model by using Workbench.The numerical simulation of the state of mix liquid-solid two-phase and its movement was conducted by Fluent software in a virtual stirred device has a diameter of 80 mm.The numerical simulation results revealed that the velocity distribution was distributed in a layered manner around the agitating paddle and the velocity decreased toward the surrounding layer by layer.The increasing stirring speed expanded velocity gradient distribution area,which was beneficial for the increase of the collision and adhesion probability of the fine particles and the formation of the larger and stable agglomeration.Another conclusion could be obtained as that the turbulent flow symmetrically distributed around the stirring paddle center,and the left and right turbulent energy distributions were layered.As the agitation speed increased,the area and value of the turbulent energy increased,but their changing rates were different at the different of the agitation devices.The consistency between the simulation results of four stirring devices and the results of flocculation tests provided a strong basis for the strengthen formation of the large particle size,stable structure and high selectivity agglomeration by flow field.A relationship model between the hydrophobic agglomeration and the flow characteristics of the stirred device was established.