Bubbles and flotation

气泡和浮选

• 批准号: RGPIN-2014-05847
• 负责人: Finch, James
• 金额: $ 3.21万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=567426
• 关键词: Bubbles; flotation

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.

浮选是回收大多数矿物资源的分离过程。矿石被研磨成粉末并分散在水中以形成浆液，气泡通过浆液分散。疏水性矿物颗粒附着在气泡上并被携带（漂浮）到容器（浮选槽）的表面以作为浮选产品溢流。大多数研究都是关于如何改变颗粒的疏水性。最近的事态发展，其中申请人发挥了重要作用，促使研究泡沫。对气泡的研究可分为产生和运动两个方面。气泡的产生是气体分散装置和溶液组合物的相互作用。由申请人的团队开发的气体分散技术有助于揭示起泡剂表面活性剂在浮选机中气泡生成中的重要作用。起泡剂的加入使气泡尺寸迅速减小，当气泡尺寸达到最小值时达到临界聚结浓度CCC。申请人已经将CCC与起泡剂结构的量度、亲水亲油平衡HLB相关联，作为确定起泡剂性质-结构关系的总体目标的一部分。申请人提出以两种方式扩展研究：探索由H-NMR（质子核磁共振）光谱确定的H-比率作为HLB的替代物;以及应用于起泡剂的另一种性质，即减缓气泡上升的能力。引入了一种新的测量方法，即达到最小速度的浓度CMV，并确定了与HLB和H-比的关系。性质-结构的联系并不能解释起泡剂减小气泡尺寸的机制。起泡剂可通过两种方式起作用：防止聚结和/或促进气泡破裂。一个新的实验装置，以隔离的破碎事件已经设计出来，并将被用来确定泡沫破裂的影响。起泡剂添加时气泡尺寸的减小似乎将“化学”能量分量引入到由气体分散装置赋予的机械能中以实现破裂。这种能量概念将被纳入模型中以预测起泡剂功能，并可能通过最大化起泡剂的贡献来更有效地使用能量。这项工作还将考虑可以替代起泡剂的无机盐的作用。在过去的十年里，人们对气泡运动的理解发生了革命性的变化。对于与浮选相关的1至5 mm直径的气泡，给定尺寸的气泡的上升速度可以显著变化。通常归因于“污染”，气泡形状现在被认为是原因。形状的作用是显而易见的，通过调整生成产生相同体积但不同形状的气泡;球形气泡比扁形气泡上升得慢，并且似乎存在形状-速度关系。申请人通过表明溶质具有相同的形状-速度关系而对该发现做出了贡献，该关系与类型、表面活性剂或无机盐无关。将建立一个测试柱，以跟踪气泡的生成和3D运动，两个摄像头成直角。将确定连接形状和速度的机制。对单个气泡的研究是了解气泡群行为的一个步骤。漂移通量分析（DFA）提供了一个可能的联系。DFA是一系列从颗粒沉降中推导出来的方程，这些方程已经被改编成气泡。该计划是发展泡沫群的关系。该计划下的HQP将通过课程以及在仪器齐全的现代实验室中进行研究技术培训来接触矿物加工的最新技术。这将使他们做好进入该行业的准备，该行业去年为加拿大的GDP贡献了630亿美元。