Influence Of Micro-vortex On The Flocculation Settlement Of Minerals

The development of the economy expands the demand for mineral resource,but also makes the increase of the discharge of tailings.Flotation tailings have the characteristics of fine grain size and slow natural sedimentation.Therefore,sedimentation technology of tailings is focused.In addition,with the depletion of mine resources,the grain size of useful minerals is refined,resulting in more fine ore particles.This increases the difficulty of concentration and dewatering of slurry.Therefore,improving the efficiency of concentration operations is very important to the increase the production efficiency.In this paper,in order to achieve better solid-liquid separation,the effect of micro-vortex on the flocculation settlement of minerals was studied.This paper mainly carried out the following research:(1)Conventional flocculation settlement exploration test on tailingsTaking the common flotation tailings as the research object,the research on the flocculation of tailings was carried out.Single factor tests and comparative test were performed to examine the effects of slurry concentration,pH value of slurry,type and amount of flocculants on the flocculation sedimentation efficiency of tailings.The optimal flocculation conditions of the minerals were obtained,which provides reference for the subsequent study on the effect of micro-vortex on the flocculation sedimentation of minerals.(2)Computational fluid dynamics simulationThe numerical simulations of the formation and properties of Karman vortex street and Taylor Vortex street were performed by computational fluid dynamics(CFD)method.The effects of diameters of cylinders,Reynolds number and annular space on the morphology,size distribution,direction,and average turbulent kinetic energy of Karman vortex street and Taylor Vortex street were investigated.Through simulation,it is found that Karman vortex street is not generated when no cylinder is present.The larger the cylinder diameter is,the larger the Karman vortex street size is.Within a certain range of Reynolds numbers,a symmetric vortex street is formed,i.e.constant vortex.The size of the vortex has a certain relationship with the diameter of the cylinder,and beyond this range,there will be vortexes that are periodically alternate downward flows,i.e.non-constant vortex.The magnitude of the annular space has a greater influence on the Taylor vortex.Taylor vortices do not appear in the smaller and larger annular space.The Taylor vortices are formed at size of annular space ranging from 7.5 mm to 15 mm.With the gradual increase of the annular space,the size of the vortex also gradually increases,but at the same inner cylinder speed,the smaller the annular space is,the more Taylor vortex pairs appear.As the inner cylinder speed increases,the average turbulent kinetic energy in the reactor gradually increases,while at the same Renault number,the lower the annular space is,the greater the average turbulent kinetic energy is in the reactor.(3)Flocculation settlement test in Karman Vortex and Taylor Vortex devicesThe tailings flocculation settlement test was carried out in the reactors of Carmen Vortex and Taylor Vortex.The influence of the micro-vortex generated by these two devices on the flocculation settlement was investigated under the conditions of the type and amount of flocculants,slurry concentration,and pH value of slurry.In addition to the flocculation settling test,micro-vortex images online video was performed using high-speed camera technology.The micro-processing and image analysis of the flocculated flocks were carried out,and the effects of different micro-vortexes on flocculation settlement were comprehensively analyzed by detecting the fractal dimension of the flocks and the turbidity of the supernatant.The study found that for the Karman vortex street,the fractal dimension of the floe first increases and then decreases with the increase of the slurry flow rate.The fractal dimension of flocs is the largest when the Reynolds number is 160.It shows that the slow or fast flow rate is not conducive to the formation of flocs;In addition,the effect of non-constant vortex flocculation is better than that of constant vortex.The symmetry and even alternating vortices formed by non-constant vortex are more conducive to the combination of flocculants and mineral particles,and the fractal dimension is larger.For Taylor Vortex,the flocculation effect increases gradually as the speed of the inner cylinder increases.The flocculation effect is decreased when the rotating speed is too high or too low;the effect of flocculation and settling is best when the annular space is 10 mm,the shape of the floc formed is larger,and the settling speed is also faster.Based on the combination of flocculation test and numerical simulation,this paper found out the influence of micro-vortex on the flocculation settlement of tailings particles,and provided theoretical and practical basis for efficient flocculation and dewatering process of flotation tailings.