Bubbles and flotation

浮选是回收大多数矿产资源的分离过程。矿石被磨成粉末，分散在水中形成泥浆，气泡通过泥浆分散。疏水矿物颗粒附着在气泡上，并被携带(漂浮)到容器(浮选室)的表面，作为浮选产品溢出。大多数研究都集中在如何改善颗粒的疏水性上。申请人在其中发挥了重要作用的最新发展推动了对泡沫的研究。*对泡沫的研究可分为生成和运动。气泡的产生是气体分散装置和溶液组合物的相互作用。申请者团队开发的气体分散技术有助于揭示起泡表面活性剂在浮选机中产生气泡的关键作用。当气泡尺寸达到最小值时，起泡剂的加入迅速将气泡尺寸减小到临界聚结浓度Ccc。申请人已经将CCC与起泡剂结构的测量相关联，作为确定起泡剂性质-结构关系的一般目标的一部分。申请人建议以两种方式扩展研究范围：探索从H-核磁共振(质子核磁共振)谱确定的H-比率作为HLB的替代品；以及将起泡剂的另一特性--减缓气泡上升的能力应用于此。引入了一种新的测量方法，即达到最小速度CMV的浓度，并确定了它与HLB值和H比的关系。*性能-结构联系不能解释起泡剂减小气泡尺寸的机理。起泡剂有两种作用方式：防止聚合和/或促进气泡破裂。设计了一种新的分离破裂事件的实验装置，并将用于确定起泡剂对破裂的影响。添加起泡剂后气泡尺寸的减小似乎在气体分散装置提供的机械能中引入了一种“化学”能量成分，以实现破碎。这一能量概念将被纳入预测起泡剂功能的模型中，并可能通过最大化起泡剂的贡献来更有效地利用能源。这项工作还将考虑可以替代起泡剂的无机盐的作用。*过去十年见证了一场理解泡沫运动的革命。对于与浮选有关的直径1-5 mm的气泡，给定大小的气泡的上升速度可能会有很大的变化。泡泡的形状通常被归因于“污染”，现在则被认为是原因。形状的作用是显而易见的，通过调整生成的气泡产生相同体积但不同形状的气泡；球形气泡的上升速度比扁平气泡慢，似乎存在形状-速度关系。申请人通过证明溶质提供了与类型、表面活性剂或无机盐无关的相同的形状-速度关系，从而对这一发现做出了贡献。将建造一个测试柱，以跟踪气泡的生成和在3D中的运动，并使用两个直角相机。将确定连接形状和速度的机构。*对单个泡沫的研究是朝着了解泡沫群的行为迈出的一步。漂移通量分析(DFA)提供了一个可能的联系。DFA是一系列方程，源于颗粒的沉降，这些颗粒已经适应了气泡。我们的计划是为泡沫群发展关系。*该计划下的HQP将通过课程以及在设备齐全的现代实验室进行的研究技术培训，接触到矿物加工的最新技术。这份遗嘱为他们进入去年为加拿大GDP贡献630亿美元的行业做好了准备。

Flotation is the separation process in recovery of most mineral resources. Ores are ground to powder and dispersed in water to form slurry through which bubbles are dispersed. Hydrophobic mineral particles attach to bubbles and are carried (floated) to the surface of the vessel (flotation cell) to overflow as the float product. Most research has been on how to modify particle hydrophobicity. Recent developments, in which the applicant has played a major role, have prompted research into the bubble.*Research into the bubble can be divided into generation and motion. Bubble generation is an interplay of the gas dispersion device and the solution composition. The gas dispersion technology developed by the applicant's team helped reveal the essential role of the frother surfactant in bubble generation in flotation machines. The addition of frother rapidly decreases bubble size to a critical coalescence concentration CCC when bubble size reaches a minimum. The applicant has correlated the CCC with a measure of frother structure, the hydrophilic-lipophilic balance HLB, as part of a general objective to determine the frother property-structure relationship. The applicant proposes to extend the study in two ways: to explore the H-ratio determined from H-NMR (proton nuclear magnetic resonance) spectra as a substitute for HLB; and to apply to another property of frothers, the ability to slow bubble rise. A novel measure, the concentration to reach minimum velocity CMV is introduced and the relationship to HLB and H-ratio will be determined.*The property-structure link does not explain the mechanism by which frothers reduce bubble size. There are two ways frothers may act: coalescence prevention and/or promotion of bubble breakup. A novel experimental setup to isolate the breakup event has been devised and will be used to determine the impact of frothers on breakup. The reduction in bubble size upon frother addition appears to introduce a `chemical' energy component to the mechanical energy imparted by the gas dispersion device to effect breakup. This energy notion will be incorporated into models to predict frother function and may lead to more efficient use of energy by maximizing the contribution of frother. The work will also consider the action of inorganic salts which can substitute for frothers. *The last ten years has seen a revolution in understanding bubble motion. For bubbles 1 to 5 mm diameter relevant to flotation, rise velocity of a given size of bubble can vary significantly. Commonly ascribed to `contamination', bubble shape is now argued as the cause. The role of shape is evident by adjusting generation to yield bubbles of same volume but different shape; spherical bubbles rise slower than oblate bubbles and there appears to be a shape-velocity relationship. The applicant has contributed to this finding by showing that solutes give the same shape-velocity relationship independent of type, surfactant or inorganic salt. A test column will be built to follow bubble generation and motion in 3D with two cameras at right angles. The mechanism linking shape and velocity will be determined. *Research into single bubbles is a step towards understanding the behaviour of bubble swarms. Drift flux analysis (DFA) provides a possible link. DFA is series of equations derived from sedimentation of particles that has been adapted to bubbles. The plan is to develop the relationships for bubble swarms. *The HQPs under this program will be exposed to the latest technology in mineral processing through courses as well as training in research techniques in well instrumented modern labs. The will ready them to enter the industry that last year contributed $63b to Canada's GDP.