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By V. Ogarlaci

Over 90% of the Romania's lignite reserve is located in the region of Oltenia, which is why this area is given special attention in the country's coal resources. Because the lignite deposit of Oltenia is comprised of 1-8 exploitable coal layers, their capitalizing calls for urgent arrangements to ensure rational exploitation under conditions of total safety, minimum losses and efficiency. The technology used the coal pits of North-Western Oltenia is the technology of excavation, transport and dumping in a continuous flow by using the complexes of excavation, transport and high-capacity dumping. The theme of this paper is of particular importance because the rhythmic operation in complete safety, is necessary both for sizing and keeping within the bounds of acceptable values, throughout the process of excavation of the geometric elements of the coal faces, marked by: the height of benches, slope angle and width of berms. Geometric dimensions of the benches of the open pits, the height of benches, slope angle and width of berms shall be calculated and shall be based on: the massif structure that forms the benches; physical-mechanical characteristics of rocks from the bench; working conditions, characterized mainly by mining and extraction methods applied; functional parameters of the mechanical equipment used to perform various operations on the coal face etc. For this study it was necessary a broad field for task tracking, measurement, research and design elements of the coal face, for land survey and a desk activity by: processing of topographic data, laboratory analyses on physical and mechanical properties of rocks and numerous specialized studies. In the final part, we bring some contributions to elucidating the issues of special importance for the lignite coal pits of Oltenia, coming up with data, graphics, formulas, solutions and concrete dimensioning of coal faces in terms of using technology in a continuous flow.

Aug 1, 2013

By S. Lun Sin

In this study, the effect of silicon on the microstructure, mechanical properties and hot tearing susceptibility of permanent mould cast AZ91E magnesium alloy was investigated. Varying amounts of silicon (0.5, 1.0 and 1.5 wt.%) were added to AZ91E in the form of an Al-53 wt.% Si master alloy. The phase formation, grain size and solidification behavior of each alloy were characterized and related to their tensile properties and hot tearing susceptibility. The results showed that the addition of silicon resulted in the formation of Mg2Si particles. The presence of these particles led to an increase of the hardness, but was detrimental to the tensile strength and elongation of AZ91E. However, silicon significantly reduced the hot tearing susceptibility of AZ91E. This was attributed to the reduction of the grain size and the decreased freezing range of AZ91E, which contributed to improve the interdendritic feeding during the last stage of solidification.

Jan 1, 2011

By C. I. Walker

Field tests at a number of large mineral processing operations have been undertaken to better understand the wear life impact of different aspects of pump design, materials of construction and maintenance procedures. Data are presented for wear rates, and typical result variability is explored. To improve the availability of pumping equipment in a milling circuit it is not only important to improve the wear life, but also reduce the variability in the wear life of components so that the incidence of premature failure is lessened. Localised gouging wear due to flow separation and turbulent eddy formation is often the point at which part-holing occurs. A number of improvements to the design of pump impeller and throatbush (suction side liners) to reduce the localised gouging wear are outlined. Also, results are presented on the use of composite materials (mix of metal, rubber and ceramic) for throatbush materials to protect specific areas against wear.

Jan 1, 2012

By A. Montini, M. H. Moys

"A conductivity probe mounted in the shell of the mill has been used to measure the behaviour of the load in the mill as a function of operating variables. It was found that certain properties of the conductivity signal correlate strongly with the per cent solids of the slurry passing through the mill; in particular the angular location ?D of the shoulder of the load is an increasing function of the per cent solids. A method for measuring the viscosity of the pulp discharging from the mill has also been developed. The use of the measurements in mill control is illustrated by simulating various control strategies for open circuit milling. It is shown that the use of ?D allows very tight but imprecise control of the slurry rheology in the mill, while the use of viscosity is subject to severe limitations in speed of response. A cascade control system involving both measurements provides adequate control of slurry rheology within the mill. Applications to closed circuit milling are discussed.IntroductionMultivariable control of milling circuits continues to receive a lot of attention in the literature. Hulbert and co-workers and Niemi, et al. have described the use of Inverse Nyquist Array (INA) techniques while Herbst has recently described the use of Optimal Control. It is significant that in neither of these three projects was any variable associated with the grinding mill itself (e.g. power or properties of the mill discharge) used in the control strategy. Pauw, et al.do, however, use mill power in their multivariable peak-seeking controller for pebble-mill control. Little work has been published on the use of measurements of the properties of the slurry being discharged from grinding mills, in spite of the fact that milling efficiency is known to be strongly affected by slurry rheology».Moys has recently developed a technique for measuring the dynamic behaviour of the load in the grinding mill. This method involves the monitoring of the response of a conductivity probe mounted in the shell of the mill which gives a measurement of the orientation of the load inside the mill. It was found that the load behaviour was strongly influenced by slurry rheology. In this project a technique was also developed for the measurement of the viscosity of the slurry in the mill discharge. It was, thus, decided that it would be worth investigating the use of these measurements in mill control schemes since direct control of the slurry rheology in the mill must inevitably increase the efficiency and productivity of the grinding circuit as a whole.This will be done by using the dynamic responses measured by Moys and Montini to simulate the behaviour of an open circuit ball mill. While the control of open circuit mills is of little interest, this simulation provides a simple but powerful demonstration of the advantage provided by these measurements, advantages which should apply to closed circuit operation of any mill type (including autogenous milling). Investigations into multivariable control of a closed circuit ball mill are currently nearing completion and will be published soon."

Jan 1, 1987

By DALE MacGREGOR, VERA TUREK

The Blue Mountain nepheline syenite deposit has been the subject of several detailed studies. It has been variously referred to as an intrusive stock, a metasomatic deposit, an intrusive sill and a metamorphic-metasomatic body. The body is divided into six mineralogical zones, the first five being based on the characterizing accessory mineral; muscovite, muscovitemagnetite, biotite-muscovite, biotite, hornblende and pink syenite. Mining currently takes place only in the biotite zone. Foliation is particularly prominent in the central (hornblende) zone and near the margins of the nepheline syenite. Majic bodies within the nepheline syenite may represent basic rocks that have been less altered by metasomatism, metamorphosed basic dykes or sloped blocks of metasediments. The most prominent structural features are the northeast-trending folds that have been modified by later north west-trending folds.

Jan 1, 1984

Real Time Monitoring of Cemented Paste Backfill Introduction Methods ?how to instrument a Long Hole stope Key Results from 2 case studies: barricade pressures and displacement, in-stope pressures Importance of Real Time Monitoring How binder, rise rate, cement content affect fence pressures

May 1, 2010

By James F. Archibald

Testing has been accomplished to substantiate recent laboratory trials which have demonstrated that thin liner membranes, applied to rock core samples, can significantly enhance the structural performance of such rock materials. A range of Canadian polymer liner materials (MineguardTM, RockguardTM and RockWebTM) have been tested side-by-side to evaluate strength and other physical property improvements generated for two highly homogeneous, though differently sourced, granodioritic rock materials. Tests were conducted on physically similar core materials, utilizing 104 to 113 samples of each respective rock type. For both rock sample populations, cores were coated using linings at thicknesses varying between 1 and 7.3 mm, typical of the application range currently used underground by mines contemplating use of such membrane agents. Results of rock failure tests, following application of passive lining covers upon the very large sample populations of each rock type, have indicated that noticeable strength improvement and enhancement of post-yield failure characteristics can be developed by the entire range of spray-on liner materials evaluated. It is shown that all of the tested liner agent materials currently available can and do act to positively reinforce rock support capabilities of modeled core pillars. Where liner materials can be effectively placed underground, it is anticipated that they may provide similar benefit and be successfully used in partial replacement for either screen or shotcrete to provide advantageous area support for rock.

May 1, 2001

By N. Morrison, E. J. Rogans, A. J. Macintosh, N. Schoeman

"The design of carbon-in-pulp (CIP), and carbon-in-leach (CIL) adsorption circuits has essentially remained unchanged since the early days of the carbon process for gold recovery. For CIP circuit the pulp residence time is traditionally fixed at one hour per contactor with a carbon concentration of between 15 and 20 grams per litre, and the counter current carbon transfer rates are in the region of 15% pulp recycle. For CIL, the pulp residence time is usually three hours per contact or, with lower carbon concentrations ( 5 to 10 grams per litre).The drawbacks of using the counter current CIP/CIL adsorption circuits are discussed using modeling developed for CIP/CIL plant design. Counter current CIP/CIL, circuits are then compared with the carousel method of adsorption circuit design.The use of equipment suitable for the carousel approach is discussed which is, the AAC cylindrical and pumping (MPS) screens, the AAC pump-cell plant and launder designs.Finally, two plants at the Vaal Reefs Gold Mining and Exploration Company that use carousel adsorption circuits, namely the Vaal Reefs No. 1 Gold Plant, a CIL plant with stepped contactors, and the Vaal Reefs No. 2 Gold Plant, a CIP using a very short residence time (AAC pump-cell) are discussed."

Jan 1, 1998

By Jaroslaw W. Drelich

Despite the success of DLVO and extended-DLVO models that have been developed for homogeneous and smooth surfaces, a vast majority of practical surfaces encountered in mineral ore beneficiation are typically rough at various scales; they are also typically heterogeneous. The interactions of gas bubbles with particles having rough and heterogeneous surfaces are much more complex than the commonly used DLVO or extended-DLVO models predict. The effects of surface roughness on flotation and colloidal interactions have been reported many times in the past, although a clear understanding of their origins has been lacking. To explain differences in colloidal interactions for spherical hydrophobic particles, a theoretical analysis of the interaction potential was carried out for a model rough particle interacting with a bubble surface in an electrolyte solution in this study. The attractive hydrophobic interaction potential was added to repulsive retarded van der Waals and repulsive electrical double layer interaction potentials. The rough microscopic particles were modeled as spheres decorated with nano-sized asperities. Parameters that reflect common flotation separation systems were selected for testing this theoretical model and computation of the energy barrier applicable to particle – flat bubble surface interactions. It was found that hydrophobic asperities with the height of only several nanometers can reduce the repulsive interaction energy by an order of magnitude. Theoretical analysis also reveals that surface coverage of microscopic particles by nano-sized asperities is important as well. The findings of this research suggest that manipulating and engineering the particle surface topography could lead to better control over flotation separation.

Jan 1, 2016

By H. R. Manouchehri

"It is well understood that, apart from particle hydrophobicity, the flotation process is strongly influenced by the cell hydrodynamics. Once the chemical conditions were optimized and fixed, the flotation rate is essentially determined by impeller speed and the air flow rate.The collection efficiency in flotation is a product of collision, attachment and stability/detachment efficiencies. The collision efficiency for a given particle diameter is increased by decreasing the bubble size and bubble velocity as well as increasing the power input to the cell. The attachment efficiency, however, is defined by bubble size and its velocity. The detachment/stability depends on the relative magnitudes of the attachment force between the bubble and particles and the detachment force acting on the bubble-particle aggregates. For the particles having specific contact angle, the stability decreases as the energy input increases. Therefore, there must be an optimum energy dissipation to maximize recover of defined size fraction.A comprehensive laboratory study was devoted to determine the effect of power input in recovery of finely grind Cu-Ni bearing ore. Several flotation tests were conducted to define the hydrodynamic parameters for a laboratory scale Runge cell under different impeller speeds. An increase in flotation recovery of finely ground ore was observed when the impeller speed was increased from 450 to 1,200 rpm. The experimental results have shown increasing in water recovery and improving in flotation kinetics of fines by increasing the power input to the flotation cell. Implementation of the Wark flotation model to the experimental data revealed a good correlation between the experimental data and the model. For the particles having enough hydrophobicity the flotation rate increases by increasing the impeller speed due to a higher value for collision efficiency within the cell."

Jan 1, 2016

By P. MacPhail, G. S. Dobby, I. M. Flint

"The objective of the laboratory work described in this paper has been to develop a method f or producing small gas bubbles at moderate to high gas rates in a flotation column. Small bubbles are particularly important for attaining reasonable flotation rates of fine particles. An ultrasonic aerosol generator has been employed to add frother solution directly to the gas stream. Using porous glass and filter cloth spargers, aerosol frother addition has produced bubbles at 1/2 to 2/3 the diameter of those produced by conventional frother addition to the liquid, at a lower frother consumption.IntroductionGas bubbles are generated in a flotation column most commonly by forcing gas through a porous medium called a sparger. Typical sparger material includes rubber (pierced with small holes) , fabric (such as filter cloth), fritted glass, or porous metal (steel or bronze) . Solid sparger material is suitable for laboratory use; however, for industrial applications a flexible sparger such as rubber or fabric is necessary to prevent the eventual plugging of orfices with solid particles and/ or precipitates. An exception to this is the use of a gas liquid contactor external to the column in combination with pressure release of gas in water, a method that has been demonstrated to produce very small gas bubbles. The typical objective of bubble generation for flotation column purposes is to produce bubbles with diameter of about 0.1 cm (and less) at a gas superficial velocity of 1 cm/s to 3 cm/s. In general, the smaller the bubble, the better. In man y cases, though, there is little , or nothing, gained by generating bubbles less than about 0.05 ern in diameter.Several factors affect bubble size when generated by a sparger: gas rate, orifice diameter, sparger surface area, surfactant type, surfactant dosage, and static head. At very low gas rates bubble diameter is independent of flow rate and is proportional to orifice diameter. At the moderate gas rates encountered in flotation columns bubble diameter, db' is related to gas flow by: db oc vg n, where vg is superficial gas velocity (rate of gas flow per unit column area). For porous steel and filter cloth, n has a value of about 0.25 for vg between 0.2 cm/s and 2 cm/s(2). The magnitude of the effect of orifice diameter at these gas rates is unclear. The effects of frother type and concentration on bubble size issuing from a single orifice have been measur ed by Miagkovaru , shown here in Figure I(IS). The reduction in bubble diameter upon surfactant addition is due to the lowering of interfacial tension created by adsorption of surfactant at the gas liquid interface."

Jan 1, 1988

By W. A. Kracht

The McGill Bubble Size Analyzer, with the original image-capturing device (digital video camera), has a proven record for measuring bubble size distributions that are relatively narrow, such as in mechanical cells with frother. However, some problems arise when dealing with bubble size distributions characterized by a bi-modal shape and wide range of sizes such as found in some flotation columns. To measure wide bubble size distributions it is necessary to increase both the resolution to image the small bubbles and the viewing area to include the large bubbles. This can be done using a digital still camera: digital still cameras can have higher resolution than the digital video cameras currently used and with the proper lens the viewing area may be increased without resolution loss. The digital still camera approach was used to measure bubble size distributions in flotation columns at different operations in Chile. A comparison with typical bubble size distributions generated with mechanical cells is presented.

Jan 1, 2007

By Rodrigo A. Marinho

Erratic high grade values are as common in Nature as they are a source of problems for resource estimators. In some highly erratic metal deposits, less than 2% of the drilling samples can represent more than 10% of the total metal in the blocks and they are associated with a high risk level. There is a risk of local overestimation but also of global overestimation, with the high grades being projected over too large a volume. Capping or restriction of these outliers control is being widely used in the industry and commonly applied in resource estimation for the last three decades. The primary purpose of this paper is to present and describe the most applied methodologies for restricting the extrapolation of high grade samples and discuss the results based on a theoretical simulated model. Additionally, this paper demonstrates the economical impact associated with the high-grade and the project risk profile associated with each method.

Oct 1, 2009

By J. E. Danoczi

Shore Gold Inc. (Shore) is presently designing a diamond processing plant for the Star and the Orion South kimberlite deposits in the Fort à la Corne area kimberlite field in central Saskatchewan. The first step in the plant is diamond liberation and occurs in the comminution section. Diamond liberation is the process of breaking up the kimberlite rock, as ?gently? as possible since essential to the diamond liberation process is the minimization of diamond damage, particularly for the larger, high value diamonds. The Southern African diamond mines traditionally use Jaw and Gyratory crushers as their primary comminution method. However, these diamond mines generally process the harder, competent kimberlite that is located in the diatreme zone as well as the root zone of the volcanic pipe. Softer kimberlite is typically located in and around the crater area of a volcanic pipe and it is this source of kimberlite that makes up the majority of kimberlite for both the Star and Orion South deposits. These softer kimberlites can be readily broken up using abrasion and attrition imparted by AG mills, this being the preferred method of comminution for minimizing diamond damage.

Nov 1, 2011

By Corby G. Anderson

"Laboratory testing using industrial electrowinning solutions was performed to determine the best Faradic cell efficiency for copper cathode recovery. The variables tested were solution flow rate, recycle ratio, reagent addition combinations of guar and thiourea, and addition amount of acid mist suppressant CAL FAX DBA-70. The ideal flow rate was determined to be 37.85 litre/min. Additionally, the ideal recycle ratio was determined to be 10:1. The reagent addition scheme from testing which showed the highest efficiency was with 680 g/tonne guar of cathode copper won and with 135 g/tonne thiourea of cathode copper won. These values for reagent addition only reflect the best efficiency and should not be assumed to be the best reagent concentration for copper purity. The amount of foaming agent that showed the best efficiency was the test with 2 ppm of foaming agent. Again this amount of reagent is based on efficiency and should not be taken as the amount of reagent that does the best acid mist suppression. Additional proprietary surface characterization work indicates these additives may have enhanced the cathodic reduction surface morphology of some noble minor impurities. Subsequently, these operating parameters were introduced into the plant operation and proved successful after their implementation.BACKGROUNDCopper electrowinning has become a dominant technology for the production of marketable high grade copper cathode products. The literature is robust with applications, optimizations, additives and developments in this field (e.g., Classens & Harris, 1990; Pfalzgraff, 1999; Tozawa, Su, & Umetsu, 2003; San Martin, Otero, & Cruz, 2005; Houlachi, Edwards, & Robinson, 2007; Romero, Avila, Fester, & Yacher, 2007; Marsden, 2008; Beukes & Badenhorst, 2009; Vainio & Weatherseed 2009; Bender, 2010; Joy, Staley, Moats, Perkins, Uhrie, & Robinson, 2010; Khouraibchia & Moats, 2010; Moats, 2010; Rutledge & Anderson, 2015).Tests of forty hours duration and at room temperature were performed for this project using samples of actual industrial electrowinning solutions. These industrial solutions were comprised of 60 g/L Cu plus 65 g/L Ni, 3 g/L Fe, and 30 g/L free sulfuric acid. Other confidential minor impurities were also present including some solubilized precious metals. The testing apparatus utilizing stainless steel anodes and cathodes is illustrated in Figures 1 and 2."

Jan 1, 2016

By L. C. Bird, A. I. A. Salama, M. W. Mikhail

"A program of sampling in Canadian washeries was carried out by the Coal Research Laboratory (CRL) over a period of two years to evaluate the performance of various density separators in these operations(1). Operating data on quality and recovery of products, separation efficiencies and cutpoints for each separator type are compared with data predicted using computer models developed from previously existing data.The Heavy Medium Cyclone (HMC), Heavy Medium Bath (HMB) and jig models give predictions of recoveries and qualities of products for sizes coarser than 10mm with absolute value of error mean less than 7 per cent, whereas predictions of the Water Only Cyclone (WOC) model for -10mmfine coal are with absolute value of error mean less than 8 per cent. Although less accurate for -10 mm fine coal, the HMC and jig models produce predictions of recoveries with absolute value of error mean less than 2 per cent and quality of products predictions with absolute value of error mean less than 28per cent which are generally acceptable because more liberation in the fine fractions appears to compensate for any difference in the accuracy of separation, resulting in good prediction of the clean product. However, ash content of the actual fine refuse was lower than predicted. The difference is attributed to the highly friable nature of Canadian coals which tends to cause an excessive loss of coal fines to the fine refuse.A comparison study based on quality and recovery of products is made between the Dutch State Mines (DSM) models and the recently modified models, both produced comparable predictions."

Jan 1, 1985

By Z. Zhang, X. -G. Chen, F. Breton, A. Arici

"The microstructure of Al-10Si-0.3Mg-0.5Mn alloy with 0.27% Zr and 0.19% V addition was quantitatively analysed and compared to the base material. The addition of Zr and V in the AlSi10Mg alloy exhibit a beneficial effect on the Si modification, resulting in the reduction of the size of eutectic Si particles on both as-cast and T6 conditions. The quantitative image analysis results show that the Zr and V addition and T6 treatment can reduce the size of the intermetallic phases. In addition, the presence of Zr and V is favour to the partial dissolution of the intermetallic phases during the T6 treatment. Different heat treatment procedures were tested to optimize treatment parameters. The mechanical properties of the alloys were evaluated using hardness measurements and tensile tests. The results show that the addition of Zr and V can remarkably improve the mechanical properties on as-cast and T6-treated conditions. The correlation between the microstructure and mechanical properties of the alloys is discussed.INTRODUCTION Al-Si-Mg foundry alloys have been widely used in automotive and aerospace industries due to their high strength-to-weight ratio, heat-treatable capability and excellent castability. The alloying elements such as Cu, Mn, Fe are traditionally added into Al-Si-Mg alloys to improve their mechanical properties (Mohamed, Samuel, Samuel & Doty, 2009). In recent years, the attention has been paid to the effect of the transition elements such as Zr, V, Ti, etc, as minor alloying additives, on the properties of aluminum alloys (Elhadari, Patel, Chen, & Kasprzak, 2011; Kasprzak, Amirkhiz & Niewczas, 2014; Shaha, Czerwinski, Kasprzak, Friedman & Chen, 2015; Shaha, Czerwinski, Kasprzak & Chen, 2014; Mahmudi, Sepehrband, Ghasemi & 2006; Meng, Cui, Zhao & Zuo, 2013). Kasprzak et al., (2014) and Shaha et al., (2015) reported that additions of Zr, V, and Ti in Al-Si-Cu-Mg cast alloys can improve the alloy mechanical properties at high temperature by forming stable intermetallics and precipitates on as-cast and heat treatment conditions. On the other hand, the mechanical properties of near-eutectic and eutectic Al–Si cast alloys depend not only on the chemical composition but also, even more importantly, on microstructural features such as the morphology and size of eutectic silicon and intermetallic particles, which are present on both as-cast and heat treatment conditions (Mohamed et al., 2009). However, there is rather limited information on the effect of Zr and V on the microstructure features and mechanical properties of near-eutectic Al-Si-Mg cast alloys."

Jan 1, 2018

By Avinash Kandalam, Markus Reuter, Jörg Kleeberg, Michael Stelter

The Top Submerged Lance (TSL) technology has obtained significant importance in the pyrometallurgy industry for nearly four decades. One of the advantages of TSL furnace is its high reaction rate, which is caused by splashing and turbulence of the melt. In contradiction, this phenomenon stands as a barrier for conducting experimental investigations to validate the simulation models. The highly turbulent and splashing environment in the TSL furnace is caused due to the immersion of the lance into the slag layer and thus the effect of the flame structure is directly related to the splashing, turbulence, reaction kinetics and life-span of the lance. Moreover, the material properties such as viscosity, density and the surface tension will also influence the flame structure. As a first step to understand the flame structure, attempts are made to generate a stable flame of the lance in an open environment. INTRODUCTION Top Submerged Lance (TSL) technology was invented during the 1970s at Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia by Floyd and Denholm. This technology was later commercialised and currently, there are about 100 TSL plants around the world commissioned by various licence holders such as AUSMELT (Outotec) and ISASMELT (Xstrata- Glencore Technology). Copper is the most produced non-ferrous metal followed by lead and zinc, see Hunt (2005). Today, a wide range of primary, secondary, and complex recycling materials are used as a feed material in the TSL, Alvear et al. (2010), Kaye et al. (2008). The working principle of TSL technology lies on inserting and submerging a lance from the top of a vertical cylindrical chamber into the slag layer. The lance is considered as the heart of the furnace, where the air and fuel are transported through two concentric tubes and are mixed in a combustion chamber, which is approximately 7 cm from the tip of the lance (considering the pilot-scale TSL furnace at the Institute for Nonferrous Metallurgy and Purest Materials - INEMET). The TSL furnace is very flexible with the type of fuel, feed material and the air input. The fuel can be natural gas/heating oil/fine coal particles and the air could be enriched with oxygen (Figure 1). The general mechanism of the TSL furnace lies on feeding the material from the top of the furnace and the material is pulled into the molten bath due to the high turbulent atmosphere, which results in high reaction rates. The thermocouples installed in the furnace (i.e. in the ceramic linings) allow the operator to know the temperature of the melt. For example, in the case of copper production the tapped material (i.e. matte/metal) can be transported to a settler for further processing or directly used.

Jan 1, 2019

By G. E. Agar, J. J. Barrett

"Traditionally, batch bench-scale flotation tests have been used for evaluating flotation reagents by comparing the results of tests done with various additions of the reagent in question. Usually, comparisons are made of the concentrate grade and recovery or some figure of merit involving an empirical combination of both. In some cases, statistical methods have been used to make the comparison and even to identify optimal combinations of reagents.None of the preceding technology utilizes the fact that flotation separations can be described by relatively simple kinetic equations that will serve not only to quantitatively describe the influence of a reagent, but will also aid in designing an optimal separation procedure. Examples of the use of a first-order rate equation for evaluating the impact of a reagent addition and for optimizing the reagent addition are given.IntroductionThe classical method of evaluating flotation reagents is to conduct batch bench-scale tests while varying one factor at a time. Some of the shortcomings of this technique have been pointed out and statistical design and evaluation of experiments has been advocated. Although the statistical approach is superior to the one-at-a-time method, it still is dependent on the results of a batch test conducted for a specific duration.That flotation is primarily a rate process than can be described by a first-order rate equation has been recognized for a long time, but the application of this knowledge to the evaluation of reagents has received little attention. In this work, it is demonstrated how the parameters of the first-order rate equation can be utilized to evaluate the influence of reagents on flotation."

Jan 1, 1983

By J. Bouchard, R. del Villar, A. Vazirizadeh

"Industrial flotation is a continuous and often multistage process, where particles of a given mineral species (usually the targeted one), present in different sizes, encounter a large amount of gas bubbles (normally air) to produce mineral–bubble aggregates, which are removed from the flotation device (cell or column) as a valuable product (concentrate). The bubble content inside the cell is characterized by the prevailing hydrodynamic conditions (known as gas dispersion variables), which in turn are known to influence the flotation performance. Although most researchers and practitioners agree that the relationship between the hydrodynamic variables and flotation performance exists, the lack of an adequate method foronline measuring the average bubble diameter has prevented such studies.The aim of this study is to apply appropriate hydrodynamic variables for flotation kinetic modeling (as a key feature of flotation performance) for a given introduced particle size distribution (PSD). In this regard, experiments were conducted in a laboratory flotation column (5.6 cm internal diameter for a total height of 650 cm), and mixtures of quartz (hydrophilic gangue) and talc (naturally hydrophobic mineral), classified in four different size fractions. The correlation between the flotation rate constant and given hydrodynamic variables were analyzed. Results suggest that the relative importance of hydrodynamic variables for flotation rate modeling depends on the PSD. Finally the suggested hydrodynamic variables for each of the various particle size-classes considered were used to produce single variable models for the flotation rate constant. INTRODUCTIONIndependently of the prevailing flotation conditions, the mechanisms for bubble-particle aggregation and the residence time of the phases inside the device must also be considered. In this regard, one of the most used approaches to represent the overall flotation process is as a pseudo-chemical reaction between a particle and a bubble, whose rate (at a given time) is proportional to the amount of remaining floatable species. The proportionating constant is called the kinetic constant or the flotation rate constant."

Jan 1, 2016