Eriez Flotation is the world leader in column flotation technology with over 900 installations. Columns are used for floating well-liberated ores. Typically they produce higher grade and have lower power costs than conventional cells. Applications include Roughers Scavengers Cleaners
Eriez Flotation is the world leader in column flotation technology with over 900 installations. Columns are used for floating well-liberated ores. Typically they produce higher grade and have lower power costs than conventional cells. Applications include
The HydroFloat fluidized bed flotation cell radically increases flotation recoveries of coarse and semi-liberated ores. Applications include: Split-feed flow-sheets Flash flotation Coarse particle recovery
The StackCell uses a 2-stage system for particle collection and froth recovery. Collection is optimized in a high shear single-pass mixing canister and froth recovery is optimized in a quiescent flotation chamber. Wash water can be used.
The StackCell uses a 2-stage system for particle collection and froth recovery. Collection is optimized in a high shear single-pass mixing canister and froth recovery is optimized in a quiescent flotation chamber. Wash water can be used.
The CrossFlow is a high capacity teeter-bed separator, separating slurry streams based on particle size, shape and density. Applications include: Split-feed flow-sheets with the HydroFloat Density separation Size separation
The rotary slurry-powered distributor (RSP) is used to accurately and evenly split a slurry stream into two or more parts, without creating differences based on flow, percent solids, particle size or density. Applications include Splitting streams for feeding parallel lines for any mineral processing application
The rotary slurry-powered distributor (RSP) is used to accurately and evenly split a slurry stream into two or more parts, without creating differences based on flow, percent solids, particle size or density. Applications include
Eriez Flotation provides advanced engineering, metallurgical testing and innovative flotation technology for the mining and minerals processing industries. Strengths in process engineering, equipment design and fabrication positionEriez Flotation as a leader in minerals flotation systems around the world.
Applications forEriez Flotation equipment and systems include metallic and non-metallic minerals, bitumen recovery, fine coal recovery, organic recovery (solvent extraction and electrowinning) and gold/silver cyanidation. The company's product line encompasses flotation cells, gas spargers, slurry distributors and flotation test equipment.Eriez Flotation has designed, supplied and commissioned more than 1,000 flotation systems worldwide for cleaning, roughing and scavenging applications in metallic and non-metallic processing operations. And it is a leading producer of modular column flotation systems for recovering bitumen from oil sands.
Eriez Flotation has also made significant advances in fine coal recovery with flotation systems to recover classified and unclassified coal fines. The group's flotation columns are used extensively in many major coal preparation plants in North America and internationally.
Eriez Flotation provides advanced engineering, metallurgical testing and innovative flotation technology for the mining and minerals processing industries. Strengths in process engineering, equipment design and fabrication positionEriez Flotation as a leader in minerals flotation systems around the world. Read More
Froth flotation is a process that selectively separates materials based upon whether they are water repelling (hydrophobic) or have an affinity for water (hydrophilic). Importantly, the word flotation is also used in the literature to describe the process in density separation in which lighter microplastics float to the surface of a salt solution. However, this process is based upon density alone and should not be confused with the process of froth flotation. Thus, the process of froth flotation is not solely dependent upon the density of the material; it is also dependent upon its hydrophobic nature. For example, froth flotation is a technique commonly used in the mining industry. In this technique, particles of interest are physically separated from a liquid phase as a result of differences in the ability of air bubbles to selectively adhere to the surface of the particles, based upon their hydrophobicity. The hydrophobic particles with the air bubbles attached are carried to the surface, thereby forming a froth which can be removed, while hydrophilic materials stay in the liquid phase272 (Fig. 9.8).
Since plastics are generally hydrophobic materials, froth flotation has successfully been used for the separation of plastic materials.5,1375137 For example, two plastic materials which are buoyant in a specific liquid phase can be separated from one another by the addition of a wetting agent which selectively adsorbs to one of the plastics and not the other. Thus, the wetting agent acts as a flotation depressant by selectively adsorbing to the surface of a specific plastic, thereby rendering it hydrophilic. However, adsorption to the other plastic is far less pronounced. Consequently, the hydrophobic plastic will continue to float while hydrophilic plastic will sink to the bottom as a result of depressed flotation. The floating plastic can then be recovered from the surface of the mixture. However, there are many factors to take into account in the process of froth flotation, such as the surface free energy of the microplastics and the surface tension of the liquid in the flotation bath, as well as the critical surface tension, which defines the surface tension at which the liquid completely wets the solid microplastics. Ultimately, the selective separation of inherently hydrophobic microplastics requires that the microplastics are only partially wetted by the liquid in the flotation bath, thereby allowing the bubble to adhere to the surface of the solid phase and bring the microplastics to the surface of the liquid phase to be collected, while the sediment particles are completely wetted and sink. Nevertheless, the technique has rarely been used for the separation of microplastics from sediments.198,436198436 Perhaps the reason for this is that while recovery rates of up to 93% have been reported,436 the technique was found to be negatively influenced by the presence of wetting agents or additives in the plastics.
Froth flotation is a long established technique in mineral processing. Extensive discussion of flotation can be found in the book by Leja (1982); see also recent work by Fecko et al. (2005) and Melo and Laskowski (2006). Basically, particles are either hydrophilic or hydrophobic (Gutierrez-Rodriguez et al., 1984). Surface properties of particles are modified with a surfactant (collector). Bubbles, produced by mechanical (froth flotation) or passive (column flotation) aeration and stabilized by a frother (a surfactant), are used to bring hydrophobic particles to the surface. Macerals, with some variation as will be discussed, and pyrite are hydrophobic and will adhere to the bubbles while clays and other silicates are hydrophilic and will sink. Whether pyrite is truly hydrophobic or entrained by the bubbles or interlocked with floatable particles is a matter of research, but one necessary to develop mechanisms that suppress pyrite from being recovered with clean coal product (Kawatra and Eisele, 1997).
Since froth flotation (and oil agglomeration) relies on the surface properties of coal in separating particles, coal petrology plays an important role in the process. Arnold and Aplan (1989) reported a number of studies which examined maceral partitioning or lithotype partitioning, generally without consideration of the maceral association. In order of decreasing floatability, they noted that liptinite > vitrinite > fusinite and vitrain > clarain > durain > fusain. For an eastern Kentucky coal, Hirt and Aplan (1991) noted the relationship, in order of decreasing floatability: pseudovitrinite (high Rmax) > pseudovitrinite (low Rmax) > vitrinite (high Rmax) > vitrinite (low Rmax) = micrinite = exinite (liptinite) = semifusinite > resinite > fusinite. Note, this differs from the ICCP (1998) maceral definitions, but pseudovitrinite does have a usage precedent in the coal petrology literature (Benedict et al., 1968b). Arnold and Aplan (1989) also examined microlithotype relationships, finding vitrite to be concentrated in the faster floating fractions and inertite in slower floating fractions. In order of decreasing floatability, microlithotypes follow the general order vitrite > inertite > vitrinertite > clarite > duroclarite. A rank relationship exists, with hydrophobicity increasing sharply through the high volatile bituminous rank range (Aplan, 1993). Honaker et al. (1996) investigated differences in maceral partitioning in column flotation related to pH. Since different researchers have used a variety of coals with varying petrographic composition and varying rank, exact comparisons between studies are difficult (Arnold and Aplan, 1989). Overall, the behavior of particles is best understood by understanding the composition of the entire particle (Sarkar et al., 1984; Ofori et al., 2006), although it is really only the outer surface that is important in processing.
Flotation, generally conducted on <0.5 mm particles, is processing particles from the lithotype to microlithotype scale. The maceral and microlithotype composition of the particle can be used as a proxy for the surface interface with the surfactants. Ofori et al. (2006) and O'Brien et al. (2003, 2006) have developed a semiautomated image analysis system to diagnose coal grains by their grain size, composition, and density and relate this directly to flotation performance. Imaging is used to classify grains as liberated (single component) or composite and to derive the density of each grain from maceral and mineral type and abundance (O'Brien et al., 2006). This method provides a tool for tracking behavior in the flotation circuit and for optimizing processes in advance.
Weathering has an influence on hydrophobicity. In a study of Spanish bituminous coals, Garcia et al. (1991) demonstrated that the formation of humic acid complexes and the oxidation of Fe led to poor flotation recovery at the same pH as unweathered coal. Adjustment of the pH towards the basic range did yield some improvement in recovery.
Froth flotation is influenced by several operating factors. The most important of these is pH. Interaction with collector and formation of hydrophobic film at a mineral occurs within certain pH range. In the case of sulfide minerals, at pH above a certain value, called critical pH, the collector uptake does not occur and the mineral ceases to float. This critical pH varies for different minerals and is taken advantage of for selective separation of minerals from slurry containing more than one mineral.
Another influence of pH is in influencing the state of ionization of the collector. Amines are cationic in acidic pH range. In alkaline pH, the long chain amines occur in neutral molecular state and not suitable as cationic reagente. In between the two ranges, within a narrow pH range they occur as ionomolecular complexes comprising ionic and neutral molecule species and they are highly surface active in this form. This also applies to weak acid collectors like sodium oleate, which is anionic in the alkaline pH range, but occurs in neutral molecular state at pH below 4. For further discussion see Rao and Leja (2004).
In froth flotation, the mineral surface plays an important role in the process of reagent adsorption, which determines the geometry and strength of adsorption, and the difference in properties of mineral surfaces is the premise of mineral separation by flotation. We employed the quantum method to model the galena (100) and the pyrite (100) surfaces and investigate the electronic structure and property of the surfaces. The results show that the dissociation of a galena surface results in the breakage of PbS bonds, and the Pb and S atoms are changed from six-coordinated as in the bulk to five-coordinated in the surface. The pyrite Fe and S atoms are five-coordinated and three-coordinated respectively at the surface instead of six in the bulk. The decrease in the coordination number of surface atoms may lead to the variation of their reactivity.
Surface relaxation of galena (100) and pyrite (100) surfaces had been discussed in our previous study , and the results showed that the top three layers of both galena and pyrite surfaces underwent the surface relaxation; however, pyrite underwent greater relaxation than galena.
The Mulliken electron of each layer of PbS (100) and FeS2 (100) surfaces are shown in Fig.6.8. The electron distributions for galena and pyrite are quite different. The outermost layer of both PbS and FeS2 surfaces is electronegative, but PbS carries more negative charge than FeS2 surface.
The DOS of the galena Pb and S atoms and the pyrite Fe and S atoms are shown in Figs.6.9 and 6.10, where the numeral beside the symbol of element represents the layer number. For example, S1 represents S atom in the first layer. Compared with the deep layers (Pb5 and Pb7), the DOS of the surface Pb3 6p state is slightly stronger. It is clearly noted that the DOS of S1 and S3 atoms are quite different from those of S5 and S7 atoms, indicating that electronic properties of surface atoms are different from the deep layer atoms. Moreover, the PbS surface S1 and S3 states dominate around the Fermi level, while the S5 and S7 states have few contributions to the Fermi energy, suggesting that surface Satoms show greater reactivity than the bulk S atoms.
For the pyrite surface, by comparison with the bulk Fe12 layer, the DOS peak of the outermost Fe3 states is obviously enhanced around2.0eV, and Fe 3d state in the conduction band increases from one peak to two peaks. Compared to the deep layer Satoms (S5, S7, and S9), the surface S 3p states (S1 and S4) around2.5 to0eV increase obviously, especially at2.0eV. By comparison to PbS, the Fe atom shows a larger sharp DOS peak at the Fermi level, indicating that the FeS2 Fe atom is more reactive than the PbS Pb atom.
The depressing action of cyanide on pyrite during froth flotation is well known (Sutherland and Wark, 1955) and is widely exploited on many flotation plants to selectively separate copper minerals from pyrite. Depression of pyrite by cyanide during froth flotation appears to take place in solutions containing free cyanide, ferro/ferri cyanide (Sutherland and Wark, 1955), thiocyanate (Plaksin etal., 1949; Adams, 2013), and cuprous cyanide mainly in the form of Cu(CN)32 (Guo etal., 2014). Thedepressing action in the presence of free cyanide seems to be caused by a decrease in the pyrite surface electrochemical activity, leading to lower collector adsorption (Prestige etal., 1993; De Wet etal., 1997). The depressing effect is reversible and is achieved by diluting the pulp with cyanide-free solution. As an illustration of this washing and repulping effect, a cyanide residue from a gold mine with cyanide-free water was sufficient to negate the depressing effect of the cyanide on the pyrite (Hodgkinson etal., 1994). The most widely used method of reversing the depressing effect of cyanide in the past has been to condition the flotation pulp at a pH value in the range 3.54 with sulfuric acid, or bubbling sulfur dioxide into the slurry, and then add copper sulfate to complex the cyanide and subsequently float the pyrite (Clay and Rabone, 1951; Malloy and Tapper, 1978). Amine collectors are also effective at floating cyanide-depressed pyrite in alkaline solutions, although the flotation rate is slow (Ramsay, 1978; Broekman etal., 1987).
The most widely accepted method for upgrading ultrafine coal is froth flotation. Froth flotation is a physicochemical process that separates particles based on differences in surface wettability. Flotation takes place by passing finely dispersed air bubbles through an aqueous suspension of particles (Fig. 17). A chemical reagent, called a frother, is normally added to promote the formation of small bubbles. Typical addition rates are in the order of 0.05 to 0.25 kg of reagent per tonne (0.1 to 0.5 lb per ton) of coal feed. Coal particles, which are naturally hydrophobic (dislike water), become selectively attached to air bubbles and are carried to the surface of the pulp. These particles are collected from a coal-laden froth bed that forms atop the cell due to the frother addition. Most of the impurities that associate with coal are naturally hydrophilic (like water) and remain suspended until they are discharged as dilute slurry waste. Another chemical additive, called a collector, may be added to improve the adhesion between air bubbles and coal particles. Collectors are commonly hydrocarbon liquids such as diesel fuel or fuel oil. In the United States, flotation is typically performed on only the finest fractions of coal (<0.1 mm), although coarse particle flotation (<0.6 mm) is practiced in Australia where coal floatability is high and the contaminants in the process feed low. The removal of clay slimes (<0.03 mm) is carried out ahead of some flotation circuits to minimize the carryover of this high ash material into the froth product. The ultrafine clay slimes are typically removed using large numbers of small diameter (15 mm or 6 inch) classifying cyclones (Fig. 18).
Most of the industrial installations of flotation make use of mechanical (conventional) flotation machines. These machines consist of a series of agitated tanks (four to six cells) through which fine coal slurry is passed. The agitators are used to ensure that larger particles are kept in suspension and to disperse air that enters down through the rotating shaft assembly. The air is either injected into the cell using a blower or drawn into the cell by the negative pressure created by the rotating impeller. Most commercial units are very similar, although some variations exist in terms of cell geometry and impeller design. Industrial flotation machines are now available with individual cell volumes of 28.3 m3 (1000 ft3) or more. Coal flotation is typically performed in a single stage with no attempt to reprocess the reject or concentrate streams. In some cases, particularly where high clay concentrations are present, advanced flotation processes such as column cells have been used with great success. Conventional flotation cells allow a small amount of clay slimes to be recovered with the water that reports to the froth product. A column cell (Fig. 19) virtually eliminates this problem by washing the clay slimes from the froth using a countercurrent flow of wash water. This feature allows columns to produce higher quality concentrate coals at the same coal recovery.
Foam fractionation, also called protein skimming, air stripping and froth flotation, removes surface active (surfactants) dissolved organics and suspended solids, which may be produced in the culture system. If aeration is vigorous, the process can also drive ammonia and volatile components directly to the atmosphere. Additional benefits include the removal of fine particulates and excellent aeration. The process can be very efficient but in some applications has been disappointing. It can be very sensitive to small design details and choices in values of operating variables. The process is believed to be most effective in marine applications, especially in lightly loaded systems. Most seawater applications have been aquarium reuse systems. If it is to be combined with ozonation, some users have strongly recommended, for system control reasons, to separate the two processes by not using ozone in the foam fractionator's gas supply but applying it separately. The equipment, unlike biofilters, does not require much space and maintenance is usually minimal. It is sometimes used in combination with biofilters instead of as a substitute.
Foam fractionation involves agitating aerated seawater to produce a foam rich in dissolved organics and suspended solids. The resulting foam must be collected and discharged to the drain. The performance of this process depends on the organic load and composition, surface tension, temperature, viscosity, pH, salinity, bubble size, air-water ratio, and contact time. Not all these parameters are independent. The ideal bubble size is about a diameter of 0.8 mm (0.03 in.) (Spotte, 1979). High air-water ratios and long bubble contact times increase removal efficiency (Wheaton et al., 1979).
There are a number of configurations for foam fractionators. Some look like airlift pumps and others have a counter-flow arrangement between air and water to increase the contact time (Spotte, 1979; Wheaton et al., 1979). The process water may enter and leave submerged from the bottom or the process water may enter above the surface and counter-flows through the rising foam. In fact, any vigorous diffuser type aerator with an airlift pipe can be used in this manner, if the resulting foam is removed. Probably the most common configuration is the injection of air with a venturi and discharge of the resulting high velocity air-water mixture tangentially near the bottom of a column. This imposes a vigorous circulation, which delays the rise of the small bubbles, increasing contact time. Dimensional design information on the column and venturi (Hagen, 1970) and equations for guidance in optimization are available (Lawson and Wheaton, 1980; Weeks and Timmons, 1992; Timmons et al., 1995). A good review of its use in aquaculture is presented in Timmons (1994). There are indications that small dimensional changes and differences in operating parameters can have large impacts on performance. There is also evidence that prolonged use can lead to depletion of trace materials, especially some metals.
Lead is mostly extracted from galena PbS which is concentrated by a froth flotation process. This concentrated ore is then roasted in a limited supply of air to give lead oxide, which is then mixed with coke and a flux such as limestone and reduced in a blast furnace:
In both cases the obtained lead contains a number of unwanted metal impurities such as copper, silver, gold, zinc, tin, arsenic, and antimony, some of which are clearly valuable in themselves. Lead bullion is melted at a temperature just above its freezing point, then copper rises to the surface as an insoluble solid and therefore copper is the first element to be removed as an impurity. Tin, arsenic, and antimony are removed by oxidation in a reverberatory furnace. The lead may still contain silver, gold, and bismuth. Silver and gold are removed on the basis of their preferential solubility in zinc. The mixed metals are cooled slowly when the Zn solidifies as a crust which is skimmed off; the excess of dissolved zinc is then removed either by a preferential reaction with chlorine or by vacuum distillation or oxidation in a reverberatory furnace. Finally, lead is purified by the process of electrolysis where massive cast leads act as anodes in an electrolyte of acid PbSiF, or a sulfamate; during electrolysis almost 99.99% pure lead is deposited on cathode, which is further purified by zone refining.
Frother -terpineol, MIBC, and DowFroth200 (DF200) together contribute to more than 90% of frother usage in froth flotation industry in the world. Fig.5.19 displays the structure of these three frothers.
DFTB+ module, which is based on the tight-binding method, is used to obtain the initial structures of the interactions between frother molecules and water molecules. For this module, the geometry optimization is built with an algorithm of conjugate gradient. Mio (CHONSP) and divide-conquer are selected as the Slater-Koster library and eigensolver, respectively. The convergence criteria for structure optimization are set to (a)energy tolerance of 0.05kcal/mol, (b)max. force tolerance of 0.5kcal/mol/, and (c)max. iterations of 9999. The smearing is set at 0.005 Ha and all the qualities are under the medium level.
Based on the DFTB+ calculation results, the adsorption of the frother molecule at gasliquid interface is simulated. The interactions between the polar head group of the frother with different numbers of water molecules are performed by Dmol3 module. This module is widely used for its accuracy for not only the molecule structure but also the molecule properties. In this module, no special treatment of core electrons are considered, and all electrons are included. More specifically, spin-unrestricted is performed and the symmetry is also used. The SCF convergence is fixed to 106 Ha, and the convergence criteria for structure optimization are set to (a)energy tolerance of 1.0105 Ha, (b)max. force tolerance of 0.002 Ha/, and (c)max. displacement tolerance of 0.005. The smearing is set at 0.005 Ha, and all kinds of qualities are under the fine level.
For the reason that the exchange-correlation functional and the basis set are the core parameters in DMol3 module, the dOH and HOH of H2O molecule are calculated under different functionals (all with the DNP+ basis set), and the result is shown in Table5.7.
It is clearly shown in Table5.7 that the calculated dOH, HOH, and hydrogen bond energy of the optimized H2O under the functionals of GGA-BP and GGA-VWN-BP are quite close to the experimental values, which are tested at 298K. So in this study, GGA-BP is selected as the exchange-correlation functional.
To find out how the layer of frother molecules absorbs at the gasliquid interface, the molecular dynamics method is used. In the study, the Forcite module is selected, and its temperature, the pressure, and the forcefield are all adjustable. The smart module is chosen as the algorithm, and the convergence criteria are set to (a)energy tolerance of 2.0 105 kcal/mol, (b)max. force tolerance of 0.001kcal/mol/, (c)max. displacement tolerance of 0.005, and (d)max. iterations of 5000. The forcefield of cvff_nocross_nomorse is suitable. In addition, atom-based electrostatic and atom-based van der Waals are selected in simulation method. All the qualities are under the ultrafine level.
where E here is the binding energy; Efrother-nH2O is the total energy of the frother with the water molecules; Efrother is the total energy of the frother molecule; and EH2O is the energy of one water molecule that is calculated under the same condition.
The schematic representation of a foam fractionation column shows a launder foam collection unit that is typical of the foam collection method used in froth flotation. The foam reaches the top of the column and discharges over a weir into a launder vessel around the periphery of the column with a bottom slanted to a discharge tube. Depending on the stability and rheology of the foam at the top of the column, the gas disengages from the foam by drainage and collapses thereby enabling a liquid product to be discharged from the launder, or the foam itself flows out of the discharge line. The major advantage is that launder collection enables relatively large amounts of foam to be collected. The foam handling capacity can be still further enhanced by designing a so-called donut launder that enables discharge around the periphery of the column, as well as into a well in the center. A further idea gained from the design of flotation column is that of a froth crowder which is a solid block that is positioned at the column top to help direct foam over the weir and into the launder.
It should be noted that the launder method of foam handling means that there is a free surface of foam at the column top, and therefore surface coalescence of bubbles is enabled. As mentioned above, coalescence, whether in the bulk or on the foam surface, diminishes the liquid flux but engenders internal reflux. The rate of surface coalescence is currently unpredictable, but it has been shown to be dependent upon environmental humidity,14 and indeed, when the free surface of the foam is open to atmosphere, the environmental humidity is a critical determiner of the performance of a foam fractionation unit: When humidity is low, bubble coalescence is high, meaning that the liquid overflow rate is reduced by the effects of internal reflux are enhanced, meaning that the production rate of the foamate is lower but the enrichment is typically improved.
In general, the collection of foam into a launder is useful for very wet foams (approximately greater than 3% liquid fraction) because these exhibit relatively low viscosity and can therefore flow easily into the launder and discharge. However, relatively dry foams exhibit a high viscosity and therefore tend not to flow easily. Instead, the foam forms a crown on top of the column that can become quite voluminous and bypass the launder vessel. In our laboratory, we can sometimes ameliorate this problem by recycling liquid foamate and using it to spray the foam in the crown to enhance flowability; the spray is targeted to the side on the crown so as not to form a source of external reflux that travels down the column. If antifoams are being used downstream of the launder it is absolutely critical that this spray does not enter the column itself or the process will be killed. The location of spraying should be sufficiently far from the column riser itself so that antifoam cannot travel into the tube by diffusion.
However, a better method for the collection of relatively dry, and therefore viscous, foams is to dispense with the launder and instead pass the foam directly from the top of the column into an inverted U-bend (that can be either solid or a flexible hose) so that the foam is discharged downward into a collection vessel. Such an arrangement is used in the foam fractionation of Nisin described in Section 126.96.36.199.1. The inclined section of the rising in fact sees the Boycott effect of enhanced segregation occur in it, and therefore enhances liquid drainage from the foam (see Section 188.8.131.52).
Thus, the general heuristic is to use a launder collection method if the foam at the top of the column has a liquid fraction of above about 3% and large volumes are to be handled (stripping of surface active material from wastewater falls into this category), whereas for drier foams with lower production volumes (as are typical in bioprocessing) the use of an inverted U-bend circumvents the low flowability of the foam.
The geological conditions create new challenges in your copper mine. Declining ore grades mean less metal production for each ton processed. And as you have to dig deeper and into harder rock you face longer haulage distances and increased wear of your equipment which translates into higher operational costs.
To remain productive, you need endurable and reliable equipment that increases your productivity. As a full flowsheet provider, we have proven ourselves as a supplier of premium equipment in every step of the process from comminution to filtration. Your solution will be based on our more than 130 years of experience with processing equipment combined with more than 40 years in the copper industry.
This experience gives you bigger and more efficient equipment capable of increasing production at reduced costs. Examples are larger grinding equipment, large capacity high density thickeners, and new flotation cells that help brownfield mines gain a higher throughput in order to maintain production. Our energy efficient equipment also helps you keep operational costs at a minimum and reduce your environmental impact.
How you manage water has a direct impact on your license to operate in the copper mining industry. Governments across the world are enforcing new water regulations, and tensions with local communities about the right to use the water can be time consuming and costly.
Together with Goldcorp, we have developed EcoTailsthat blends filtered tailings with waste rock creating a high-density geotechnically stable product called GeoWaste. This makes dry-stacking possible even for large scale operations, and even in areas with high seismic activities. Furthermore, EcoTails enables recirculation of 90-95 per cent of your process water.
Not only does this save you operational costs on your copper mine, it also reduces closure costs and makes it easier to obtain your social license to operate, as it reduces the risk of water contamination. EcoTailsTM can bring an end to tailings dam and thus eliminate the risk of tailings dam failures as well as lessen your projects environmental impact.
Rapid Oxidative Leach (ROL) is another of our innovative about to rock your world. This mechano-chemical process can leach 97-99% copper directly on site, from concentrates as low as 5% copper in less than six hours. This makes it feasible for you to produce cathode copper from concentrate directly at the site rather than to sell the concentrate to a smelter. The ROL process can even leach copper from arsenic-ladden concentrates.
FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.
The Froth Flotation Process is about taking advantage of the natural hydrophobicity of liberated (well ground) minerals/metals and making/playing on making them hydrophobic (water-repel) individually to carefully separate them from one another and the slurry they are in. For this purpose we use chemicals/reagents:
The froth flotation process was patented by E. L.Sulman, H. F. K. Pickard, and John Ballot in 1906, 19 years after the first cyanide process patents of MacArthur and the Forests. It was the result of the intelligent recognition of a remarkable phenomenon which occurred while they were experimenting with the Cattermole process. This was the beginning. When it became clear that froth flotation could save the extremely fine free mineral in the slime, with a higher recovery than even gravity concentration could make under the most favorable conditions, such as slime-free pulp, froth flotation forged ahead to revolutionize the nonferrous mining industry. The principles of froth flotation are a complex combination of the laws of surface chemistry, colloidal chemistry, crystallography, and physics, which even after 50 years are not clearly understood. Its results are obtained by specific chemical reagents and the control of chemical conditions. It not only concentrates given minerals but also separates minerals which previously were inseparable by gravity concentration.
This new process, flotation, whose basic principles were not understood in the early days, was given to metallurgists and mill men to operate. Their previous experience gave them little guidance for overcoming the serious difficulties which they encountered. Few of them knew organic chemistry. Those in charge of flotation rarely had flotation laboratories. Flotation research was done by cut and try and empirical methods. The mining industry had no well equipped research laboratories manned by scientific teams.
Froth flotation, as pointed out previously, was a part of the evolution of milling during the first quarter of the 20th centurya period during which the progress of milling was greater than in all of its previous history. It marks the passing of the stamp battery, after 400 years service to the mining industry, and the beginning of grinding with rod mills, ball mills, and tube mills without which neither the cyanide process nor the froth flotation process would have reached full realization. More than all of these, it was the time when custom and tradition were replaced by technical knowledge and technical control.
This volume, then, is dedicated to those men who, with limited means, made froth flotation what it is today. It is designed to record the impact of this great ore treatment development on the mining industry both present and future.
The single most important methodused for the recovery and upgrading ofsulfide ores, thats howG. J. Jameson described the froth flotation process in 1992. And its true: this process, used in several processing industries, is able to selectively separatehydrophobic fromhydrophilic materials,by taking advantage of the different categories of hydrophobicity that areincreased by using surfactants and wetting agents during the processalso applied to wastewater treatment or paper recycling.
The mining field wouldnt be the same without this innovation, considered one of the greatest technologies applied to the industry in the twentieth century. Its consequent development boosted the recovery of valuableminerals like copper, for instance. Our world, full of copper wires usedfor electrical conduction and electrical motors, wouldnt be the same without this innovative process.
During the froth flotation process, occurs the separation of several types ofsulfides,carbonatesandoxides,prior to further refinement.Phosphatesandcoalcan also be purified by flotation technology.
Flotation can be performed by different types of machines, in rectangular or cylindrical mechanically agitated cells or tanks, columns, aJameson Flotation Cellor deinking flotation machines. The mechanical cells are based in a large mixer and diffuser mechanism that can be found at the bottom of the mixing tank and introduces air, providing a mixing action.The flotation columnsuse airspargersto generate air at the bottom of a tall column, while introducing slurry above and generating a mixing action, as well.
Mechanical cells usually have a higher throughput rate, but end up producing lower quality material, while flotation columns work the other way around, with a lower throughput rate but higher quality material.The Jameson cell just combines the slurry with air in a downcomer: then, a high shear creates the turbulent conditions required for bubble particle contacting.
Advantages of froth flotation: first of all, almostallmineralscan be separatedbythis process. Then, the surface propertiescan be controlledandaltered by the flotationreagent. Finally, this technique is highly appropriate for the separation ofsulfideminerals.
To help towards an understanding of the reasons for the employment of specific types of reagents and of the methods of using them, an outline of the principal theoretical factors which govern their application may be of service. For a full discussion of the theory of flotation the various papers and text-books which deal with this aspect should be consulted.
The physical phenomena involved in the flotation of minerals, those, for example, of liquid and solid surface-tensions, interfacial tension, adsorption, flocculation, and deflocculation, are the manifestations or effects of the surface-energies possessed by all liquids and solids in varying degree. These, in turn, arise from the attractions which exist between the interior molecules of every substance and are responsible for their distinctive propertiesform, fluidity, cohesion, hardness, and so on. It follows, therefore, that every substance must exhibit some degree of surface-energy.
All the solids normally present in an ore i.e., metallic, non-metallic, and rock-forming mineralshave their particular contact-angle and hysteresis values and therefore tend to be wetted in varying degrees in accordance with such values. These differences, however, are not usually sufficient to allow of the effective separation of the mineral and gangue constituents from each other. It is the function of the flotation reagents employed to accentuate or magnify these differences to a degree which renders separation by flotation practicable. Some reagents (modifiers) are added with the object of decreasing the contact-angle and so increasing the degree of wetting of the unwanted particles, which are usually more prone to become wetted than the wanted minerals. Others (promoters) are added to increase the tendency toward non-wetting shown by the valuable minerals by coating them with a film of yet higher contact-angle value. Such films are said to be adsorbed in respect of the water.
In this connection reference to Fig. 28 will indicate that a reagent which decreases the surface-tension of water tends thereby to increase wetting of the solid, since, if the value of S1 and therefore of its horizontal component, is lessened, the water-edge, as at P, will tend to extend over the solid surface, making therewith a smaller contact-angle.
The reagents added to promote the separation of the wanted minerals by increasing the water/solid contact-angle consist of substances whose molecules or minute suspensions have a markedly lower attraction for water molecules than the latter exert between themselves. Finely divided oil emulsions in water, dissolved xanthates, and other promoters are typical of such reagents. Substances of such nature, when dissolved in or disseminated through water, are pre-eminently adsorbed, or thrust towards the water boundaries, where the intra-molecular attractions are less uniformly balanced. Normally, this would occur at the free or air/water surface. In a pulp, however, from which air surfaces are absent, but in which mineral particles are suspended, the same thing takes place at the water/solid boundaries, adsorption being most pronounced at those faces where the interfacial tension is greatest viz., those with the highest contact-angle value and lowest adhesion for water. The minute particles of oil or xanthate molecules are thus virtuallythrust into adherence with the more floatable solids, whose surfaces they therefore film, increasing the contact-angles to their own high values and so rendering the solid more floatable. Experimental work indicates that the film so formed is of the order of one molecule in thickness.
Adsorption can be both positive and negative. Substances whose molecules have less attraction for water than the water molecules have for each other are concentrated at the water boundaries as explained in the foregoing paragraph ; this is termed positive adsorption, but substances whose molecules have a greater attraction for water molecules than the latter have for each other will tend to be dragged away from the surface layers, at which their concentration thus becomes less than in the interior of the liquid ; this is negative adsorption. Substances that are negatively adsorbed are those which tend to form chemical compounds or definite hydrates with water, such as sulphuric acid. In froth flotation we are concerned more with positive than with negative adsorption.
In some cases a chemical reaction between the solid and the reagent occurs at the interface ; for instance, in the activation of sphalerite by copper sulphate a film of copper sulphide is deposited on the mineral following adsorption of the copper salt at its surface. In many cases there is no evidence of any chemical change, but, whether chemical action takes place or not, there is no doubt that the filming of the mineral is due primarily to the adsorption property of the liquid itself, by virtue of which the promoting reagent dissolved or suspended in it is concentrated at the interface.
The chemical action of flotation reagents has been and still is the subject of a great deal of research work, which is bringing the various theories into common agreement, but there are still too many doubtful points and unexplained phenomena to make a simple explanation possible in these pages.
The foregoing paragraphs can be summarized by stating that the reagents employed in froth flotation can be classified into three general groups, comprising frothers, promoters, and modifiers, respectively, the purposes of each class being as follows :
The operation of flotation is not always confined to the separation of the valuable constituents of an ore in a single concentrate from a gangue composed of rock-forming minerals. It often happens that two classes of floatable minerals are present, of which only one is required. The process of floating one class in preference to another is termed selective or preferential flotation , the former being perhaps the better term to use. When both classes of minerals are required in separate concentrates, the process by which first one and then the other is floated is often called differential flotation , but in modern practice the operation is described as two-stage selective flotation .
Selective flotation has, therefore, given rise to two other classes of reagents, each of which may be regarded as falling within one of the classes already mentioned. They are known as depressing and activating reagents.
The use of these reagents has been extended in recent years to three- stage selective flotation. For example, ores containing the sulphide minerals of lead, zinc, and iron, can be treated to yield three successive concentrates, wherein each class of minerals is recovered separately more or less uncontaminated by the others.
Although the flotation of the commoner ores, notably those containing copper and lead-zinc minerals, has become standardized to some extent, there is nevertheless considerable variation in the amount and nature of the reagents required for their treatment. For this reason the running costs of the flotation section of a plant are somewhat difficult to predict accurately without some test data as a basis, more especially as the cost of reagents is usually the largest item. Tables 32 and 33 can therefore only be regarded as approximations. Table 32 gives the cost of the straightforward treatment in air-lift machines of a simple ore such as one containing easily floated sulphide copper minerals, and Table 33 that of the two-stage selective flotation of a lead-zinc or similar complex ore.
From Table 32 it will be seen that the reagent charge is likely to be the largest item even in the flotation of an ore that is comparatively easy to treat, except in the case of a very small plant, when the labour charge may exceed it. At one time the power consumption in the flotation section was as expensive an item as that of the reagents, but the development of the modern types of air-lift and pneumatic machines has made great economies possible in expenditure under this heading. As a ruleCallow-Maclntosh machines require less power than those of the air-lift type to give the same results, while subaeration machines can seldom compete with either in the flotation of simple ores, although improvements in their design in recent years have resulted in considerable reductions in the power needed to drive them. It should be noted that the power costs given in the table include pumping the pulp a short distance to the flotation machines, as would be necessary in an installation built on a flat site, and the elevation of the rougher and scavenger concentrates as in circuits such as Nos. 9 and 10.
The power costs decrease with increasing tonnage because of the greater economy of larger units and the lower price of power when produced on a large scale. The cost in respect of reagents and supplies also decreases as the size of the plant increases, due to better control and organization and to lower first cost and freight rates of supplies when purchased in bulk. The great disadvantage of a small installation lies in the high labour cost. This, however, shows a rapid reduction with increase of tonnage up to 1,000 tons per day, the reason being that with modern methods a flotation section handling this tonnage requires few more operators than one designed for only 200 tons per day. For installations of greater capacity the decrease is comparatively slight, since the plant then generally consists of parallel 1,000-ton units, each one requiring the same operating force ; the reduction in the cost of labour through increase of tonnage is then due chiefly to the lower cost of supervision and better facilities for maintenance and repairs. Provided that the installation is of such a size as to assure reasonable economy of labour, research work and attention to the technical details of flotation are generally the most effective methods of reducing costs, since improved metallurgy is likely to result in a lower reagent consumption if not in decreased power requirements.
The costs given in Table 33 may be considered as applying to a plant built on a flat site for the two-stage selective flotation of a complex ore in subaeration machines with a tank for conditioning the pulp ahead of each stage and one cleaning operation for each rougher concentrate. It is evident that the reagent charge is by far the largest item of cost. This probably accounts for the more or less general use of machines of the mechanically agitated type for complex ores in spite of their higher power consumption and upkeep costs, since the high-speed conditioning action of the impellers and provision for the accurate regulation of each cell offer the possibility of keeping the reagent consumption at a minimum. As in the case of single-stage flotation, the charge for labour falls rapidly as the capacity of the plant increases to 1,000 tons per day ; beyond this point the rate of decrease of this and all other items of cost with increase of tonnage is less rapid. The remarks in the previous paragraph concerning the importance of research work and attention to technical details apply with added force, because of the possibility through improved metallurgy of reducing the much higher reagent and power costs which a complex ore of the class in question has to bear.
Review of researches in control of flotation plants with mechanical flotation cells.Hierarchy of flotation control levels is often described through 3 or 4 levels.MPC is the result of advanced control method in a multi-variable environment.Expert knowledge based methods still to find their place in existing schemes.
Successful control of flotation plants in modern conditions represents a challenging and complex task that has yet to be accomplished. There have been multiple attempts, however, to find an appropriate control technique that would completely cover the dynamic, complex and poorly-defined flotation system. This paper presents a literature review of current theoretical and applied researches in the field of control of flotation plants with mechanical flotation cells. Significant aspects of the stratification of control levels are described in the paper, with emphasis on advanced techniques that include predictive and intelligent control methods.
Traditional PID controllers are found not suitable for the comprehensive control of dynamic flotation systems, except, in part, for the lower hierarchy levels. In the area of advanced control, model predictive methods can improve flotation process performances, but as a rule, in a short period of time. Intelligent methods are playing a significant role in flotation process control, increasing its flexibility, although none of the available variations completely satisfy all the process control aspects.Get in Touch with Mechanic