Flotation Within the Grinding Circuit—Understanding and Application of the Concepts of Unit Cell Operation

Performing flotation within the grinding circuit has been successfully utilized by many concentrators across the globe for decades and has advantages including the reduced need for water, chemicals, and power when compared with the conventional style of flotation. The term “unit cell” is used to encompass all forms of flotation within the grinding circuit and includes both cyclone underflow and mill discharge (cyclone feed) flotation. This paper has been written to provide a review of the current use of unit cell flotation and provide the operator with key information vital to the successful understanding, application and operation of flotation machines within this unique flotation environment. Examples from operating plants are presented and discussed as appropriate. Mill discharge flotation has been highlighted as a key area for future development as it presents a unique opportunity to maximize plant design efficiency, reducing both capital costs and operating costs.

Methods for characterizing operating flash flotation cells are presented and discussed as well as the use of laboratory testing procedures aimed at assisting the identification of ores that are suitable for unit cell recovery.     

Physico-Chemical Modeling of Flotation Systems

Abstract

The methodology of physical-chemical modeling of flotation systems is considered and effectiveness of its application for fundamental investigations in flotation is shown. Using iron sulphides as the example, reliable information has been received on the surface state of iron sulphides, optimal conditions for their activation with copper salts and deactivation with cyanide and sulphide ions, the composition of sorption layer on the mineral surface forming during its interaction with xanthate or dixanthogen, the influence of collector forms sorption on the iron sulphides notability and on the optimal conditions of these minerals flotation.

From a single position the determined physico-chemical models in the form of quantitative equations have been derived for the optimal conditions of flotation and depression of iron sulphides under changing pH value and of the sodium sulphide, cyanide or lime addition. The equations derived were proven in the laboratory and industrial scale and can be used in automatic control systems at the plants as well as for improvement of technological processes of selective flotation of iron sulphides containing ores or coals.     

Coal Flotation in Saline Water: Effects of Electrolytes on Interfaces and Industrial Practice

ABSTRACT

Coal preparation plants are increasingly turning to alternative sources of water to reduce their consumption of fresh water. These alternative sources can vary significantly in ionic content. This review discusses the effect of dissolved inorganic electrolytes on coal flotation. It is argued that increasing process monitoring will enable a better understanding of the effects of salts on the flotation process. A pragmatic approach in monitoring is essential to differentiate significant factors from insignificant ones controlling the performance of coal flotation units in salt water. The effects of inorganic electrolytes on the air–water interface and the solid–liquid interface are reviewed to assist in the interpretation of industrial results.     

Flotation Kinetics

Abstract

The physical variables that influence the rate of flotation are examined. The probabilistic model of flotation is used to establish the effect of the particle si2e and density, bubble size and agitation on the rate of flotation

In quiescent flotation, it appears that the flotation rate is limited by the particle-bubble collision and subsequent attachment of the particle to the bubble. For fine (<20 μm) or low density particles the remedy for low recovery rates would be to either use small bubbles of the order of 100 μm, or to use moderate to high agitation with larger bubbles

In the usual turbulent conditions, the limit is set by the destruction of the bubble-particle aggregates. Broadly speaking, the same parameters favour both attachment and detachment so that the ultimate flotation rate is a compromise between these two competing mechanisms

The bounds which define the best agitation level and bubble size to use are strong functions of the particle size and density. This results in conflicting requirements for the optimum flotation of the fine and the coarse particles. Best conditions for the flotation of each are indicated.     

Collector Chemistry for Bastnaesite Flotation – Recent Developments

ABSTRACT

One of the most important aspects in any flotation separation is the choice of the flotation collector. For this reason, based on both our recent research developments and the results from other researchers, this detailed review focuses on fundamental surface chemistry features of fatty acid, hydroxamate, phosphonate, and phosphate as collectors for the flotation recovery of the rare earth (RE) mineral, bastnaesite, including selectivity considerations with respect to separation from calcite, barite, and quartz.     

Removal of Pyrite in Coal Flotation

In most operating coal-cleaning plants, a significant amount of pyrite is recovered in the froth during flotation of high-sulfur coal. Reducing the pyrite recovery first requires that the primary recovery mechanism should be identified, as different measures are required for reducing entrainment, locked-particle flotation, or true hydrophobic flotation. In this paper, evidence is presented which suggests that hydrophobic flotation is not an important mechanism for recovery of liberated pyrile when the collector is a neutral oil, and that the bulk of the floated pyrite occurs either as a resut of simple entrainment or by mechanical locking with floatable coal particles. Column flotation results are also presented which show that significant sulfur reductions can be achieved by reducing level; of entrainment.     

Oxazolidines as Efficient Reagents for Flotation of Non-Ferrous and Tungsten Metal Ores

Abstract

New representatives of oxazolidines have been prepared by condensation of carbonyl com pounds with aminoalcohols (compounds I-III), or by mutual condensation of formaldehyde with monoethanolamine and acyclic alcohols (compounds IV-IX) according to known methods.

Oxazolidines I, II and IV-VII were tested as frothers in direct selective flotation of lead-zinc ores. Only oxazolidine I in the lead cycle is a worse frother than T-80. In the zinc cycle, the tested oxazolidines were better than oxal T-80 at consumption rates of 10 to 30 g/t.

Compounds III, VIII and IX were tested as additional modifiers in collective flotation of copper-lead-zinc ores and xanthogenate flotation of primary scheelite ores. Compounds III and IX reduce WO₃ losses both in the sulphide product and in the tailings of scheelite flotation. Oxazolidine III is a more efficient modifier than compound IX.

Compound V was tested as a modifier in flotation of scheelite by sodium oleate at pH 9.3–9.6. Oxazolidine V improves the efficiency of sodium oleate in floatation of scheelite, which is due to changes in the proportions of the three forms of oxyhydrylic collector in the liquid phase of the pulp-ionic, molecular, and micellar.     

Concentration of Oil Shale

A review of the literature on oil shale concentration establishes that developments to date, while limited in scope, indicate a moderate degree of kerogen enrichment by limited size reduction and gravity separation; and a high degree of enrichment by fine grinding and flotation. Recoveries of kerogen are improved by the fine grinding. Potential advantages from maximum concentration would be:

a)Production of a solid fuel with low ash and fine particle size suitable for powdered coal combustion technology; or,

b)for the same product, improved pyrolysis characteristics for shale oil production leading to significantly lower retort volumes and costs and the possibility of improved product characteristics.     

CHEMISTRY AND OPTIMAL CONDITIONS FOR COPPER MINERALS FLOTATION: THEORY AND PRACTICE

Reliable information on the surface state of sulphide copper minerals and regularities of sulphidization and flotation of oxidized copper minerals, the composition of sorption layer on the mineral surface forming during its interaction with xanthate or dixanthogen, and the influence of collector forms sorption on the copper minerals floatability and on the optimal conditions for these minerals flotation and depression has been obtained at present. The determined physicochemical models in the form of quantitative equations have been derived for the optimal conditions of flotation and depression of copper minerals under changing pH value and of sodium sulphide, lime, cyanide, zinc–cyanide complexes additions. The equations derived were proven in the laboratory and industrial scale and can be used both in automatic control systems at plants and for improvement of technological processes of selective flotation of copper containing ores.     

The Solution and Interfacial Chemistry of Nonionic Surfactants Used in Coal Flotation

Abstract

The frothers introduced into flotation systems to stabilize the mineralized froth formed by the aeration process are surface active, or adsorb at the air/water interface. However, they are often active at other interfaces in the system and this may be either beneficial or deleterious to the flotation process

This study examines the surface activity of a selection of nonionic surfactants that are commonly used in coal flotation. The surface activity, as a function of concentration in the aqueous phase, was measured at the air/water and at several solid/aqueous solution interfaces. Contact angle studies were used to elicit information about the combined adsorption at the solution/air, solution/solid and solid/air interfaces

The relationship between froth stability and bubble size with surfactant concentration, adsorption at the solution/air interface and film stability was examined in further detail.     

320m~3充气机械搅拌式浮选机内气液两相流的数值模拟

随着经济发展对矿产资源需求的不断增长,大型浮选机以其高效率和低能耗优势已成为国际潮流;作为辅助设计和效能评估的重要工具,CFD技术已成为进行大型浮选机研究、设计的关键技术手段之一。本文利用CFD技术针对320 m3充气机械搅拌式浮选机槽内气液两相流进行仿真计算,在确定合适模型的情况下,将得到的气、液流场、液面气液流速、叶轮功耗等在浮选机工业清水试验中较为重要的参数与工业试验所得的数据进行对比。结果表明,所选用的数学模型可以较准确地描述浮选机槽内气液流场,可以为浮选机的设计、改进提供依据。     

Thermodynamic and Kinetic Flotation Criteria

Abstract

Flotation thermodynamics and notation kinetics are discussed and compared with chemical thermodynamics and chemical kinetics. While chemical thermodynamics can predict whether a reaction will take place under a given set of conditions (temperature and pressure), and can also predict the direction in which the equilibrium will be shifted in response to variation in these parameters, flotation thermodynamics can predict how likely it is for the mineral particle and gas bubble to attach in a moment of their collision. While thermodynamics can predict the probability of particle-to-bubble attachment, it cannot predict the rate of this process, for the energy barrier, G_attach, opposing particle-to-bubble attachment, is not interrelated with the free energy change accompanying the attachment

The thermodynamic (Δ G < 0) and kinetic (τ_i; < τ_c c) flotation criteria are examined by a study of the effect of frothers on flotation. Various hypotheses that explain how the frother can affect flotation rate are discussed with emphasis on unsolved problems.     

Application of Upgrading Curves for Evaluation of Past,Present, and Future Performance of a Separation Plant

The Fuerstenau upgrading plot, relating recovery of an ore component in concentrate (?) versus recovery of the remaining components in the tailing (? _r ), was found suitable for analysis and evaluation of industrial separation data of five copper mineral processing plants. The past, present, and future performance of the flotation plants was analyzed with the Fuerstenau curve. It was found that all the plants tend to produce concentrates with the recovery of the remaining components in the tailing near ? _r  = 95.5%. Additional laboratory flotation tests using industrial final products provided industrial floatability of the ores. The industrial floatability curves had their maximum curvature at about ? _r  = 95.5%. This represents optimum of the industrial separation. Similarity of the industrial performance and the industrial upgradeability of the ores indicates that the flotation plants work near the optimum point as far as the recovery of the remaining components in the tailing is concerned. However, there is fluctuation of the industrial separation results of the other upgrading parameter (always two upgrading parameters are required), that is the recovery of the useful component (Cu) of the ore in the concentrate. For improved evaluation of the considered industrial separation, the reason of the fluctuation has to be determined. Finally, a simplified procedure of relating industrial and laboratory separation results is offered. It can be useful for predicting future industrial separation results.     

Effect of Froth Structure and Mobility on Plant Performance

Abstract

The role of processes operating in the mineralised froth encountered in production scale flotation machines is discussed in relation to both process operation and mathematical modelling techniques used for simulating process response on complex process flowsheets. The structure of froths (and associated drainage patterns) developed on a continuously operated flotation cell over a wide range of operating conditions is reported. The concept of shear induced drainage in the froth is introduced, where mobility in froths on producing cells is seen to reduce froth separation effects. The relation of shear induced drainage to modern cell design is discussed, particularly in terms of maximising froth separation effects to enhance process separation efficiency.     

Contemporary Understanding and Developments in the Flotation Theory of Non-Ferrous Ores

ABSTRACT

Thermodynamic concepts are shown to be inadequate when applied to the complex multi-staged and fast formation process of a flotation complex and the relevance is demonstrated of studying the interaction kinetics of a mineral particle and a gas bubble. A mechanism is proposed explaining the formation of flotation contact, in which both the ionic and physical forms of sorption, active with respect to the gas-liquid interface, play the key role. Sorption is physically represented by either ion-molecular associates or long-chain collectors. While in the flotation of semiconductor sulfides the physically sorbed collector form is formed by an electrochemical mechanism and is represented by xanthate-dixanthogenide associates, where the flotation of dielectric minerals is activated by heavy metal ions, xanthate ion-metal xanthate associates can take on this role. Physically, the collector’s sorption form is present in the collector-free flotation, where polysulfide forms act as the former. It is shown that metal xanthate – dixanthogen – xanthate ion mixtures forming when flotation is activated by copper have especially high collector performance.     

Improved Flotation Separation of Apatite from Calcite with Benzohydroxamic Acid Collector

ABSTRACT

Apatite (Ca₁₀(PO₄)₆F₂) is the most important phosphate mineral, and flotation is the main beneficiation method to separate apatite from its major gangue mineral calcite (CaCO₃). Till date, fatty acids and their salts have been widely used as collectors in the apatite/calcite flotation separation due to their low cost and strong collecting ability, but their selectivity is limited. Therefore, screening or designing a selective collector becomes the key to the efficient separation. In this work, an attempt was made to utilize benzohydroxamic acid (BHA) as the collector for the selective separation of apatite from calcite without any depressant. The single and mixed binary mineral flotation experimental results prove the excellent selectivity of BHA in the apatite/calcite flotation separation. Zeta potential measurement results indicate a greater affinity of BHA on the apatite surface than calcite, which is also confirmed by the higher adsorption energy of BHA on the apatite surface based on the first-principle density functional theory calculations. The X-ray photoelectron spectroscopy analysis shows that the selective chemisorption of BHA on apatite over calcite is due to the stronger reactivity and the higher density of Ca²⁺ ion on the apatite surface than calcite. This work shows that surfactants of hydroxamic acid type can be an ideal collector for phosphate mineral flotation.     

Advances in Technology and Process in the Spent Fuel Reprocessing Operations in France

Abstract

France has resolutely chosen the reprocessing-recycling option for the fuel cycle back end. For that purpose, Cogema, the world's leading company in the field of the nuclear fuel cycle, owns and operates three reprocessing plants located in Marcoule (UP) and La Hague (UP2 and UP3). Reprocessing operations, industrially mastered for many years, remain nevertheless complex and delicate due to the potential risks of the handled products and the high degree of quality required for viability, safety. security and costs. From the point of view of the technologies and processes implemented in the reprocessing plants a very large panoply of mechanical and chemical engineering operations are to be used: UP3, the new plant that entered on stream last August is a good demonstration of the fact that the techniques of chemical metallurgy can be successfully adapted to the reprocessing specific constraints. In that context two specific examples are given of criticality safe and high capacity new equipment specially developed by the CEA to be installed in UP3: (i) the rotary dissolver, and (ii) annular pulsed columns.     

Interactions between a Small Bubble and a Greater Solid Particle during the Flotation Process

ABSTRACT

The interaction between bubbles and solid particles is an important mechanism in many industrial processes and flotation is a significant component of the most utilized applications. While flotation of mineral ores deals with fine particles and larger bubbles, the aim of this review is to focus on the opposite case; the interaction between smaller bubbles and larger particles encountered mostly in plastic flotation. Plastic flotation seems to be one of the appropriate methods for separating plastics, which is necessitated by increasing plastic consumption and the growing need to recycle. The first part of the article focuses on the problem of the collision of a bubble with a particle, both spherical and planar. The collision efficiency is discussed. The second part is devoted to the problem of liquid film rupture and the creation of the three-phase contact line. The third and final part focuses on the problem of the three-phase line expansion and the effect of surfactants on the resulting bubble stability.     

FP-01浮选泡沫图像处理系统

比较了国内外图像处理技术在浮选过程中应用的三个代表性例子 ;介绍了FP - 0 1浮选泡沫图像处理系统 ;指出了图像处理技术在浮选过程控制中的应用前景。     

Comparative Performance Analysis of Frothers — A Review of Available Methodologies

Abstract

Separation efficiency in flotation depends to a considerable extent on the efficiency of the frother used. A successful frother must achieve a delicate balance between froth stability and non-persistency. Ideally the frother is not supposed to influence the state of the surface of coal and a minerals. In practice, however, interaction does occur between the frother, other reagents and solid surfaces.

Various commercially available frothers can differ slightly or significantly in their influence on the flotation results. Therefore, the selection of a suitable frother is a very difficult preposition and can only be made after extensive test work. This paper makes a critical review of the methodologies that have been proposed and are being followed to compare and evaluate frother performance.