Flotation Machine Research Articles

Ways of usage of multizone flotation machines. Part 1. Activation of particle adhesion to air bubble to improve the flotation speed and selectivity

Ways of usage of multizone flotation machines. Part 1. Activation of particle adhesion to air bubble to improve the flotation speed and selectivity

Concentration of main elements in mineral matter of Polish coking coal and its cleaning products

The chemical composition of coal mineral matter, and particularly the content of major elements (Al, Si, Fe, Ca, K, Na, Mg), plays an important role in the processing and use of bituminous coals. Mineral matter is the ballast, reducing the calorific value of the fuel. The aim of the study was to analyze the concentrations of main elements of coking coal mineral matter and products of its cleaning in heavy media, jiggers and flotation machines. Analysis of elements was performed through the technique of the atomic absorption spectrometry AAS. The results of main elements concentrations of coal mineral matter and its cleaning products are discussed in relation to each operation of mechanical treatment. As a result of the cleaning process in heavy media, the content of mineral substances decreased seven times, mainly due to the removal of components such as silicon, aluminum and iron from coal. Similar results were obtained in the case of cleaning in jiggers, leading to a significant reduction of the contents of silicates and aluminosilicates. In both cases, there was an increase in the content of sodium. Despite the significant reduction of the contents of alkali metals’ compounds, their content in concentrates as converted to oxides is quite high (0,43–0,81% of dry coal). The lowest alkalis content is the displayed by a coal concentrate from the flotation process dewatered in a centrifuge.

The importance of middlings in the beneficiation technology of Polish copper ore and new possibilities of their processing

In the paper, the middlings (tailings of I cleaner flotation) were characterized, and new possibilities of their processing were presented. The advantages of introducing a separate circuit for middlings processing were emphasized. This circuit should be adapted to the properties of the processed middlings and characterized by relative simplicity. An important element of the separate processing of middlings is grinding. The paper presents the advantages of the grinding process in the magnetic mill (MM), which has not been used until now in the enrichment of mineral raw materials. The importance of introducing for the difficult to treat middlings a separate flotation in a flotation machine characterized by a high dynamics of the process was emphasized.

The importance of middlings in the beneficiation technology of Polish copper ore and new possibilities of their processing

In the paper, the middlings (tailings of I cleaner flotation) were characterized, and new possibilities of their processing were presented. The advantages of introducing a separate circuit for middlings processing were emphasized. This circuit should be adapted to the properties of the processed middlings and characterized by relative simplicity. An important element of the separate processing of middlings is grinding. The paper presents the advantages of the grinding process in the magnetic mill (MM), which has not been used until now in the enrichment of mineral raw materials. The importance of introducing for the difficult to treat middlings a separate flotation in a flotation machine characterized by a high dynamics of the process was emphasized.

Bubble movement in a rotating eddy: The implications for particle-bubble detachment

Bubbles are an essential part of the froth flotation process for the separation of mineral particles. However, little information is available on the behaviour of bubbles in the turbulent flows in a flotation machine. It has been noted in flotation kinetics studies that the behaviour of bubbles in turbulent eddies is a significant factor in bubble-particle collision, attachment and detachments. In this paper, the performance of single bubbles and groups of bubbles inside a rotating eddy have been studied experimentally. Bubbles were released into a turbulent rotating field in a wall cavity, where a confined eddy was developed by controlling the water flow into the water channel over the open mouth of the wall cavity. To study the behaviour of particles attached to bubbles in the turbulent eddies, particle-bubble aggregates were generated in an external fluidized bed and introduced into the rotating eddy with no frothers added. The process of particle detachment due to centrifugal movement was captured by a high-speed camera. The traditional theory of particle-bubble detachment, which assumes a centrifugal motion of the attached particle on the surface of the bubble, was experimentally verified. However, other modes were also observed. For example, bubbles carrying particles can be brought together in a turbulent vortex, resulting in bubble coalescence and consequent detachment of particles. Inertial detachment modes are also seen, due to rapid changes in the trajectory of the bubble, or because of oscillations of the bubble’s surface.

State and trends of development of flotation machines for solid mineral concentration in Russia

State and trends of development of flotation machines for solid mineral concentration in Russia

Performance criteria for the use of flotation machines

Performance criteria for the use of flotation machines

Gas holdup estimation in flotation machines using image techniques and superficial gas velocity

This paper presents an indirect method for determining the local gas holdup in the collection zone of flotation machines. The method includes a linear model to describe the gas holdup as a function of the superficial gas velocity and the percent area, defined as the 2D area fraction occupied by bubbles in binary images. Such images were recorded using a bubble viewer. More than 250 images of bubbles were processed to obtain suitable percent area estimations. The ability of the model to describe local gas holdup was tested at laboratory and industrial scale. The latter included self-aerated and forced-air mechanical cells from 8.5m3 to 300m3 and industrial columns from 42m3 to 160m3. The model was able to estimate the gas holdup ranging from 2.5% to 15% in laboratory and from 6.0% to 21.0% in industrial machines. As a result, a database of industrial gas holdup is presented, which includes 8 copper concentrators. The proposed methodology is a promising tool for gas dispersion characterization using a unique measurement system.

An experimental investigation of hard-to-float fine coal

ABSTRACTTo improve the separation efficiency of hard-to-float fine coal, the properties of coal sample were analyzed, the roughing conditions were explored, and the three different flotation flows were compared. The optimal roughing reagent doses were collector 200 g/t, frother 90 g/t. The separation effect improved after adopting classified flotation, especially the combined process of the flotation machine and the flotation column, recovery increased by 4.15%, and ash decreased by 0.22%. Meanwhile, this process is easily applied in industrial production.

Experiments on the detachment of particles from bubbles in a turbulent vortex

In this paper we present a new method for studying the detachment of particles from bubbles in a rotating turbulent eddy. The eddy is formed in a wall cavity in a two-dimensional water tunnel with transparent walls. When water flows through the tunnel, a vortical flow field develops in the cavity. The properties of the eddy can be modulated by changing the free-stream velocity of the water in the tunnel. Bubbles are pre-loaded with one or more particles in a fluidized bed flotation device located beneath the vortex cavity. Loaded bubbles are released one at a time into the cavity, and the motion of the bubble-particle aggregate is studied using a high-speed video camera. The diameters of the particles and the bubbles, and the number of particles initially attached to the bubble, can be varied.The trajectories taken by the bubbles are quite complicated. In some cases, the bubble moves to the centre of the eddy, and particles rotate around its axis. If the rotational speed is sufficient, particles may detach due to centrifugal force. However, other modes were observed, including inertial detachment due to rapid changes in direction of the surface of the bubble, because of changes in trajectory of the bubble as a whole, or because of pulsations and oscillations of the bubble surface. Clusters of bubbles held together by particles were seen to form and reform.In the traditional explanation for the detachment of particles in flotation cells, it is assumed that particles detach from bubbles rotating in an eddy due to centrifugal force (Schulze, 1977) [1]. Although the conditions assumed in Schulze's theory may exist, it is only one of a range of phenomena that can lead to the detachment of particles from bubbles in a turbulent vortex. The interactions between bubbles and particles is stochastic in nature, and it is impossible to model precisely the series of events that take place when a particle and a bubble make contact with each other and move through the liquid. There can be no simple model for the recovery of hydrophobic particles in flotation machines.

Gas holdup estimation using Maxwell equation in flotation systems: Revisited

Estimation of gas holdup from electrical conductivity measurements has been used in lab and industrial installations. The approach is based on the application of Maxwell’s model, which relates the concentration of a dispersed phase in a continuous medium to measurements of the electrical conductivity of the dispersed phase, continuous medium and the resulting mixture (dispersion). When applied to inferring the collection zone gas holdup in a three phase system and to facilitate real-time on-line measurement, the slurry is assumed to behave as the continuous medium and gas bubbles as a non-conducting dispersed phase. This article derives an equation for estimating gas holdup in a three phase system, eliminating the assumption that the slurry behaves as a continuous medium but rather as a dispersion of non-conducting solid particles in water. In this formulation only water behaves as the continuous medium in the sense of Maxwell, and gas holdup in a three phase system is then calculated from the application of the Maxwell model twice: (1) to determine solid content in a two-phase system, and (2) to determine solid plus gas holdup in a three phase system. To validate the new equation and quantify the errors incurred by assuming slurry is the continuous phase a laboratory flotation cell was instrumented to continuously measure the conductivity of two and three phase dispersions with known solids contents. As the amount of gas in a lab flotation machine is difficult to measure directly or by another indirect technique such as using pressure signals, 2.5mm dielectric plastic spheres having a density of ca. 1.3g/cm3 were used instead of air bubbles for validation. Experimental results demonstrated that the continuous medium assumption underestimates gas holdup and that the resulting bias error increases linearly with the solid content and decreases with the magnitude of gas holdup.

Effective Beneficiation of a Fine Coking Coal Using a Novel Flotation Scheme

ABSTRACTEffective flotation of fine coal remains challenging due to flotation inefficiency, of coarse, intergrowth particles, and contamination due to fine particles. In this article, a novel flotation scheme, named split-conditioning and bulk-flotation (SCBF), has been proposed to improve flotation efficiency of coarse and fine particles. The conditioning time and impellor speed of the flotation machine for coarse and fine particles were optimized using the nine well-planned orthogonal experiments. The results demonstrated that, by using the SCBF approach, an increase of 12.43% recovery for +0.074 mm particles and a decrease of 2.42% ash content in the -0.074 mm fractions were obtained compared to the conventional flotation. Based on the orthogonal experiments analysis, the optimal mixing conditions for +0.074 mm particles were an impellor speed of 2100 rpm and a conditioning time of 240 s, whereas, for the -0.074 mm size particles, an impellor speed of 2100 rpm and a conditioning time of 60 s were found to be the most important factors in SCBF. It was found that, for +0.074 mm particles, a higher impellor speed and a longer conditioning time improved the recovery of coarse particles, and a shorter conditioning time for the -0.074 mm particles reduced the contamination in clean coal.

Break-up in formation of small bubbles: Break-up in a confined volume

Small bubbles play the critical role in flotation of providing the large interfacial area for collecting and transporting selected (hydrophobic) mineral particles. The generation of these bubbles is a physical process chemically assisted by addition of surfactants (frothers). The prime action of frothers is commonly considered to be coalescence inhibition. In contrast, the possible role of frothers in the initial air break-up has attracted little attention. In this paper, we investigate the effect of frothers on break-up. An experimental setup was designed to isolate break-up from coalescence. Single bubbles were produced through mechanically-induced deformation of a trapped air volume, the design aiming to mimic the break-up of the air cavity behind an impeller blade in a mechanical flotation machine. The results show that the bubble size produced at break-up is strongly affected by the presence of frother, but weakly by the input mechanical energy and the volume of trapped air. The proposed mechanism is that frothers induce surface tension gradients which increase the instabilities along the air/water interface. For a finite air volume, increasing the number of instabilities means that more and smaller bubbles will break away. Frothers of different types and concentrations were tested.

Effect of Stabilizing the Final Density of Thickened Pulp on the Quality of Concentrate

A study is made of the effect of the final density of the pulp in the pulp-thickening operation on the quality of the final flotation product at the Talnakh Concentrator Plant. The effect of the reagents that are used on the flotation process is thoroughly analyzed. The main relations which express the dependence of the quality indices of the finished concentrate on the thickening operation are examined and results obtained under actual production conditions are reported. The effect of the density of the incoming pulp in a flotation machine on the quality of the concentrate is evaluated.

Determination of Static Characteristics of Flow Flotation Machines Based on Experiments of the Kinetics of the Batch Coal Flotation

Abstract In the theory and a simulation technique of a coal flotation process a density function of a distribution of particles flotability is widely used. The characteristics of this type in the design of the flotation circuits as well as to optimize of the settings of the industrial flotation machines may be used. The density function of the distribution of the fraction f (k) based on the kinetics experiments to measure the recovery of material as a function of time in the laboratory flotation machines (in the batch coal flotation process) is determined. The problems of the determining of the flotability spectrum are relatively well resolved. An important problem is the determination of the concentrate quality. The concentrate quality directly depends on the ash content in the concentrate. In the paper a mathematical model of the separation of the mass of ash at the process of the kinetics of the batch flotation has been proposed. The research at different values of the air flow rate was carried out. The results of the analyses in tables and graphs are shown. The static characteristics of the single-cell of the flow flotation machine based on the characteristics of the distribution density of the fraction f (k) and the distribution of the ash content ak(k) were determined. Knowledge of these relationships will allow for a better assessment of the phenomena occurring in the enrichment process. This may be one of the basic information used in the supervisory control system of the flotation process.

Comparison of flash and column flotation performance in an industrial sulphide rougher application

A survey has been conducted on a refractory gold (pyrite) concentrator which utilises flash flotation on the cyclone underflow stream and a flotation column on the cyclone overflow stream. Both cells are considered to be performing a first rougher operation on their respective streams. A comparison of the size and nature of the target mineral for flotation (pyrite) in the concentrates from both these unit operations has shown that they both recover predominantly liberated pyrite in the fine and intermediate size classes (−150μm). The flash flotation machine on this particular circuit recovers fast floating well liberated particles, with a minimal froth depth and short residence time; while the rougher column has a very deep froth and long residence time. To date no comparison of a flash flotation cell and a column cell has been published in the literature and the results presented here are the first of their kind to the best of the authors’ knowledge.Analysis of the liberated pyrite recovery data has culminated in the development of a mathematical relationship which takes the form: kfi2∝kci∗mRi. This relates the first order rate constants for liberated pyrite in the flash flotation machine (kf) and the rougher flotation column (kc) for each size class (i) in the floatable size range (+38/−150μm), using the mass recovery (mR) of each size class within the flash flotation machine. To account for the considerable differences in both feed properties and operating strategy of the two flotation machines, the rate constant data was normalised using the mass recovery of the total solids to concentrate by the flash flotation machine, allowing a relationship to be developed.The ability to relate these two very different unit operations via particle specific properties provides impetus for further investigation into the methods used to analyse flotation data. The similarities of both the properties of the recovered pyrite particles and the rate constants of both machines for the size range +38/−106μm are also of interest for the possibility of mill discharge (cyclone feed) flotation. The rougher column receives the fine split of the cyclone feed, while the flash flotation machine receives the coarse split, if a single machine could be used to recover all these particles in a single stage it would result in considerable cost savings to the industry via decreased plant footprint and operating costs, most notably via reduced water and reagent consumption.

Effect of foamability index of short chain alkyl amines on flotation of quartz

Amines can be used for flotation of various minerals, especially quartz. The flotation efficiency of quartz depends on the amine type and dose. It was proved that the shorter alkyl amine, higher amine concentration has to be used to recover quartz at the same level. In flotation amines play a role of both collectors and frothers. The ability of a amine to collect particles can be expressed in the form of contact angle, while the foaming properties by different parameters including dynamic foamability index (DFI) and critical coalescence concentration (CCC). Determination of DFI and CCC requires advanced techniques and methods. Therefore, in this paper a rapid and facile method for determination of foaming properties of amines and also other surfactants was used. It was based on measuring the initial foam and froth heights in a conventional flotation machine at different concentrations of surfactants. The foam height-concentration curve was described by utilizing an empirical equation which was based on one-adjustable parameter called the foamability index (FI ). In this work the foamability index was determined for butylamine (ButNH2 ), hexylamine (HexNH2 ) and octylamine (OctNH2 ) as examples of short chain alkyl amines. The determined foamability indices were 92, 12 and 4 mg/dm3 for ButNH2 , HexNH2 and OctNH2 , respectively. It was shown that when the flotation results of quartz were presented in the form of recovery versus normalized amine concentration in relation to the foamability index (c/FI ), all the experimental data points converged to one curve. It indicates that amines act similarly but at different concentrations expressed as FI . The foamability index seems to be a useful parameter for characterizing any flotation frother.

Study of the Sonication Influence on Improving the Efficiency of Sylvinite Ore Flotation

The article presents the study aimed at improvement of the efficiency of flotation by sonication of the process flows. We performed experiments on the influence of ultrasonic radiation in laboratory conditions using the ultrasonic device IL 100-6 and fluidized bed flotation machine 237 FL. We exposed to sonication the rough sylvinite flotation product, the rough sylvinite flotation feed, and the rough sludge flotation feed. We stated the possibility of using ultrasound in the process of sylvinite ore flotation at the cleaner stage, rough sylvinite and sludge flotation. Cleaner flotation of tailings of the rough sylvinite flotation with preliminary sonication increases the recovery of valuable components by reducing the loss of potassium chloride in sludge. It is shown that to improve the efficiency of the sylvinite ore dressing during the rough sylvinite flotation, the duration of the ultrasound exposure should not exceed 2 minutes, and the insoluble residue content in the sylvinite flotation feed should be as low as possible. We found out that sonication of moderate intensity (5.82 W/ cm2) at the stage of sludge flotation reduces the loss of potassium chloride in the sludge froth and increase the weight fraction of the insoluble residue in the froth product. During the research of the ultrasonic treatment of the sludge flotation feed, we noted that sonication should be performed prior to the supply of flotation reagents. Otherwise, the effectiveness of the ultrasonic treatment significantly decreases.

An Approach to Processing of Lithium-Ion Batteries for the Zero-Waste Recovery of Materials

A low-temperature, low-energy method for recovering all the valuable, economically viable, components from the spent lithium-ion batteries has been developed which has allowed the determination of pathways for complete recycling of the battery. Lithium present in the electrolyte has been selectively leached from lithium-ion batteries. Leaching conditions were optimized including time, temperature, solid/liquid ratio, and stirring velocity. All the samples were analyzed using ICP-MS for chemical composition. Leaching is conducted in a flotation machine that was able to separate plastics by flotation, creating bubbles without the use of any external chemical excess reagents. The pregnant solution was concentrated with lithium to a higher amount in order for it to be precipitated, and it was shown that the solution could be concentrated by recirculation of the leach solution. The next set of experiments were composed of battery shredding, steel separation by magnets, leaching with distilled water, and sizing using wet sieving to account for all the components of the battery. Every fraction is sent to rare-earth rolls separation and eddy current separation for full recovery.

Indirect estimation of bubble size using visual techniques and superficial gas rate

In this paper, an indirect method for determining the Sauter mean diameter of a bubble population is presented. The technique relies on the estimation of the percent area occupied by bubbles in a 2D image as well as on the superficial gas rate. The percent area was defined as the quotient between the black pixels (bubble representation) divided by the total pixels in a binary image. A linear model to describe the Sauter diameter as a function of the percent area and the superficial gas rate was proposed. The regressions showed a fairly good predictive capacity in laboratory and industrial flotation machines under bubbly regime, which makes the proposed methodology a promising tool for monitoring and controlling gas dispersion in real time.