Particle–bubble interaction and attachment in flotation

Flotation is an important unit operation in the minerals industry, among others. Current state-of-the-art flotation modelling combines computational fluid dynamics (CFD) with user-defined algorithms based on the “induction time” concept to describe selective bubble–particle attachment and separation of hydrophobic and hydrophilic particles.We have undertaken experimental studies permitting direct observation of particle–bubble interaction and attachment at the microscale to provide empirical data for comparison with new theoretical predictions.Observations were made on a model system in which 150 μm glass particles were dropped onto a captive 1.3 mm air bubble formed in water within a glass cell. The interactions were recorded on high-speed digital video, permitting direct estimation of relevant parameters such as the approach velocity, and the duration of particle sliding over the bubble surface. A new experimental configuration has allowed the particle path toward, around, and away from the bubble to be totally unimpeded.Particle trajectories show a significant deviation at separations much larger than their own diameter; such deviations are due to the hydrodynamics. Comparisons with theoretical predictions indicate that the bubble surface exhibited mobility intermediate between “full slip” and “no slip”. Theoretical predictions for an immobile bubble surface were practically symmetrical about the bubble's equator, while asymmetry was apparent in the theoretical predictions for a mobile bubble surface. However, the strongest asymmetries were seen in the observed particle trajectories and speeds.Particles dropping more centrally were seen to slide over the surface of the bubble. In several cases the sliding particle ‘jumped in’ toward the bubble, which is interpreted as the precise moment of attachment. This provides for a direct estimate of the threshold duration to achieve attachment, i.e. “induction time”. Among the events observed were rotation of the particle upon jumping in, and particle jump-in below the bubble's equator. Explanations are proposed in terms of particle properties and flow phenomena.     

CFD-based multiscale modelling of bubble-particle collision efficiency in a turbulent flotation cell

In this paper, bubble-particle collision efficiency in a turbulent flow is investigated from a multiscale modelling viewpoint. An integrated CFD-based scheme for the prediction of turbulent bubble-particle collision efficiency is developed. As part of this scheme, the effect of turbulence and the bubble wall effect on bubble-particle collision efficiency are systematically studied using a 3D low turbulent Reynolds number shear-stress-transport turbulence model. Example simulations and comparisons are carried out to illustrate the methodology. The method can also be applied to non-Newtonian slurries.     

PrOx reactor model for fuel cell feedstream processing

We introduce the Pt surface kinetics from our previous work into a monolithic reactor model to describe overall preferential oxidation (PrOx) reactor performance. Model results are presented describing the effects of the amount and location of the O₂ supply, the temperature, and the amount of catalyst. There is some emphasis upon the kinetically-controlled performance because it provides an important upper bound on reactor performance, we are able to derive analytical solutions for this case, and it clarifies several important aspects of full reactor model results.     

Controlling bubble size using a frit and sleeve sparger

This paper describes a frit and sleeve sparger designed to control the size of bubbles produced. The design comprises a porous ring (frit) surrounded by a sleeve through which water is passed to generate shear. A prototype is described and results confirm that bubble size can be controlled independent of gas velocity and is governed by the shear in the annular gap between the frit and sleeve independent of gap size.     

贵州某铅细粒嵌布的高硫铅锌矿浮选工艺研究

针对贵州某铅和硫嵌布粒度细、硫含量较高的铅锌矿开展浮选工艺研究。结果表明,磨矿细度-0.074mm占60%,采用优先浮选流程,铅浮选流程为"一粗三精三扫"、锌浮选流程为"一粗三精三扫"、硫浮选流程为"一粗一精二扫",能获得合格精矿,铅精矿中铅品位43.29%、回收率78.33%,锌精矿中锌含量为44.90%、回收率91.21%,硫精矿硫含量为45.85%、回收率为58.99%。     

四川某氧化铅锌混合矿浮选工艺试验研究

从试样的工艺矿物学研究出发,经过多方案对比和大量试验研究,采用了"阶段磨矿、阶段选别、先铅后锌、先硫后氧"的优先浮选原则流程,取得了良好的分选指标。试验指标为:铅精矿含铅52.45%、铅回收率95.82%,锌精矿含锌35.26%、锌回收率92.52%。     

四川康巴难选铜金银矿综合回收选矿试验研究

四川康巴某铜金银矿含金1.40 g/t、银55.2 g/t、铜0.46%,矿石性质复杂,属难选氧化矿。为综合回收其中的有价金属,开展了选矿试验研究工作。在工艺矿物学研究的基础上,确定采用优先浮选工艺,产品方案为金精矿和铜精矿。试验考察了磨矿细度、药剂制度及流程结构对浮选指标的影响,最终获得金精矿含金79.86 g/t,银3114.07 g/t,铜6.03%;铜精矿含铜35.49%,金12.31 g/t,银553.88g/t。金、银、铜的总回收率分别为81.66%,58.60%和50.58%,分选指标良好,达到综合回收的目的,可为类似矿石高效选别提供借鉴。     

福建马坑选铁尾矿中钼回收试验

福建马坑铁矿区尾矿堆排量已达924万t,铁尾矿中钼含量为0.06%,在经济与技术条件较成熟的当下,对该铁尾矿中的钼进行了钼回收研究。在磨矿细度为-74μm占80%的情况下,采用一次粗选、两次扫选、粗精矿再磨、四次精选、中矿顺序返回的闭路流程处理,可获得钼品位为45.30%、钼回收率为76.41%的钼精矿。     

湖北某地金红石选矿新工艺试验研究

根据湖北某地粗粒嵌布的金红石矿的性质特点,在工艺矿物学和详细条件试验研究的基础上,制定了一种新的选矿工艺流程(磁选-脱泥-浮选),先对矿石磁选抛尾,脱泥后进行浮选,再对浮选精矿进行除杂处理,最终获得高品质的金红石精矿,其品位在90%以上,回收率70%以上,显示出该工艺流程的合理性及先进性,对同类矿石具有一定的参考价值。