Interfacial Effects Of Flotation Conditioning And Process Intensification

Interfacial effects not only appeared on flotation process, and also appeared onthe conditioning process before flotation. With the development of separationtechnology of ultrafine particles, especially for the application of no stirring flotationrepresented by flotation column, the flotation conditioning has been given morecontent and requirements. During flotation conditioning, not only to realize thedispersion of indissolvable reagents and fine particles and the suspension of coarseparticles, but also to complete the adsorption of reagents to particle interfaces,especially for ultrafine and refractory particles. The interfacial effects of flotationconditioning and conditioning intensification is very important for mineral flotation,particularly for ultrafine and refractory particles.According to the outstanding conditioning problems of ultrafine and refractoryparticles, the purpose of present study is to improve the flotation indexes byconditioning intensification. Through studying the interfacial effects of flotationconditioning such as reagent dispersion, adsorption of reagent on particle surfaces,aggregation of particles and so on, combing with the numerical simulation of the flowfield under different structure and operating parameters, the effects of shear rate andturbulence on flotation conditioning were analysised. Based on this, the paper hasdesigned and optimized the flotation conditioning process and equipments. Combingwith the cyclone static micro-bubble flotation column, a short flowsheet of highefficient conditioning and column flotation was developed and the flotationexperiments of different minerals were conducted.The effect of conditioning on flotation and its kinetics was studied. Theinfluences of particle size and surface hydrophobicity of coal on conditioning andflotation were investigated and the result showed that increase the stirring speed caneffectively improve the flotation rate of ultrafine particles, meanwhile higher stirringspeed is required in conditioning with the decrease of particle size and surfacehydrophobicity. For the characteristic of no-slip move with fluid for ultrafines,different conditioning methods of double impeller stirring and variable speed agitationwere researched. The flotation effect was improved by different conditioningmethods.Interfacial effects research of flotation conditioning. The interfacial effects ofbauxite particles were researched by reagent adsorption, microscopic image analysis and sedimentation test. The effect of stirring speed and conditioning time on theadsorption between particles and flotation reagent and agglomeration among particleswere analysised. The result shows that higher stirring speed effectively promoted theregent adsorption rate and capacity on particles surface, enhanced the degree ofagglomeration and its selectivity.Reagents dispersion and solute transfer at solid-liquid interface study under highshear and turbulence conditioning. The conditioning mechanism of ionic and nonioniccollectors was analysised on this paper from reagent dispersion and solute transfer atsolid-liquid interface. The collision frequency among particles and collectors wasimproved significantly by increase shear as it is the dynamic of dispersion for waterinsolubility of nonionic collectors. And the increase of shear rate and fluctuatingvelocity is beneficial to improve the solute transfer efficiency for water solubility ofionic collectors.Particle interfacial effects analysis of turbulence and shear conditioning. Due tosurface hydrophilic, so it is important to achieve the reagent adsorption on particles bythinning of hydration shell for bauxite conditioning. The analysis of interactionsbetween particles shows that the coarse particles have high kinetic energy under lowturbulence, The kinetic energy of particles decrease gradually with the decrease ofparticle size and the energy barrier between particles increase with the decrease ofparticle hydrophobicity. So it is necessary to improve the shear rate and turbulence tointensify conditioning effects for ultrafine and refractory particles.Numerical simulation and analysis of high shear and strong turbulence flow fieldof single shaft stirred tanks. The influences of baffle, stirring speed and impellerdiameter on flow filed characteristics of single phase flow in stirred tanks werestudied systematically and the distribution and variation of fluctuating velocity andshear rate were analysised under different structure and operating parameters. Thetangential velocity greatly reduced but the value and scope of shear rate increasedafter baffles are added. Higher stirring speeds lead to higher fluctuating velocity andshear rate, while shear rate scope has little change. The impeller diameter increaseleading to expand shear rate scope, while shear rate and fluctuating velocity increaseslowly. With the increase of impeller rotate speed or impeller diameter, the powerconsumption increased significantly. So the effect of increasing impeller speed ordiameter on conditioning was limited.New and high efficient stirring methods and process design. Based on the analysis of fluctuating velocity and shear rate of single shaft stirred tanks, a doubleshaft conditioning device was constructed. Comparing with the single shaftconditioning device, the fluctuating velocity and shear rate increased effectively whilethe power consumption decreased slightly. So the shear action of stirring tank is moreprominent. Two conditioning devices with diameters of300mm and600mm andheight of400mm and800mm had been developed on the basis of numericalsimulation and structural optimization.High efficient conditioning and column flotation shortened process development.A series of experiments were conducted by using different conditioning and flotationdevices with the samples of low-grade bauxite of Dengfeng Henan province and slimecoal of Xuehu plant. The results demonstrate the flotation indexes of-0.038mmfractions especially the-0.010mm fraction are improved significantly. The newconditioning devices have superior conditioning effect than the single shaftconditioning devices.