Coarse Particle Flotation Research Articles

The effect of amine type, pH, and size range in the flotation of quartz

Cationic reverse flotation of quartz is the most important technique for the concentration of itabirite iron ores for the production of pellet feed. Mineral processors dealing with this industrial system face two major challenges: (i) coarse quartz particles do not respond well to the action of the amine collectors; (ii) fine iron oxide particles do not respond well to the depressant action of the gelatinised corn starch. The first challenge is addressed in this paper. Bench scale experiments were performed in a conventional mechanical machine aiming at investigating the flotation performance of quartz particles of different size ranges in the presence of four dosages of ether monoamine and ether diamine, at three pH levels. It was observed that ether diamine was more effective in the flotation of medium and coarse quartz, while ether monoamine performs better in the case of fine quartz, and also that the flotation of coarse particles is enhanced by the presence of fine particles in the system.

Picobubble Enhanced Fine Coal Flotation

Froth flotation is widely used in the coal industry to clean −28 mesh fine coal. A successful recovery of particles by flotation depends on efficient particle‐bubble collision and attachment with minimal subsequent particle detachment from bubble. Flotation is effective in a narrow size range beyond which the flotation efficiency drops drastically. It is now known that the low flotation recovery of particles in the finest size fractions is mainly due to a low probability of bubble‐particle collision while the main reason for poor coarse particle flotation recovery is the high probability of detachment. A fundamental analysis has shown that use of picobubbles can significantly improve the flotation recovery of particles in a wide range of size by increasing the probability of collision and attachment and reducing the probability of detachment. A specially designed column with a picobubble generator has been developed for enhanced recovery of fine coal particles. Picobubbles were produced based on the hydrodynamic cavitation principle. They are characterized by a size distribution that is mostly below 1 µm and adhere preferentially to the hydrophobic surfaces. The presence of picobubbles increases the probability of collision and attachment and decreases the probability of detachment, thus enhancing flotation recovery. Experimental results with the Coalberg seam coal in West Virginia, U.S.A. have shown that the use of picobubbles in a 2″ column flotation increased fine coal recovery by 10–30%, depending on the feed rate, collector dosage, and other flotation conditions. Picobubbles also acted as a secondary collector and reduced the collector dosage by one third to one half.

Role of Bubble Size in Flotation of Coarse and Fine Particles—A Review

Froth flotation is the dominating mineral beneficiation technique and has achieved great commercial success. This process has also found many applications in other industries where physical separation of materials is needed. However, its high process efficiency is often limited to a narrow particle size range of approximately 10–100 µm. Considerable efforts have been made to extend this size range to the lower limit of a few microns, even submicrons, and the upper limit of 1–2 mm, in response to increased needs for higher process efficiency and expanded applications of flotation. The particle–bubble collision, attachment, and detachment are the most critical steps in the flotation process. These individual elementary processes (microprocesses) and their effects on flotation efficiency are discussed and the most recent findings are reviewed. The low flotation recovery of fine particles is mainly due to the low probability of bubble–particle collision, while the main reason for poor flotation recovery of coarse particles is the high probability of detachment of particles from the bubble surface. Fundamental analysis indicated that use of smaller bubbles is the most effective approach to increase the probability of collision and reduce the probability of detachment.

Overloading of gas bubbles in column flotation of coarse particles and effect upon recovery

This communication presents experimental results obtained in the column flotation of relatively coarse silica sand ( d 80=l90 μm) conditioned with dodecylamine. It is shown that air bubbles might become completely covered with particles giving rise to bubble–particle aggregate densities close to that of water. Under these circumstances, mineralised bubbles do not have enough buoyancy to rise along the column and tend to accumulate close to the bottom, giving rise to a gas holdup profile that decreases from bottom (50–60%, v/v) to top of the column (around 20%, v/v), and to a decrease in solids recovery (as low as 30% for the more severe conditions: J t=1.5 cm/s and 35% solids slurry). It is postulated that the drop in recovery observed is due to both bubble coalescence caused by overloading (loss of bubble surface area) and to entrainment of mineralised bubbles in the tails stream. The occurrence and magnitude of the phenomenon was photographically documented.

The dynamic behaviour of coarse particles in flotation froths. Part III: Ore particles

A froth separating device was tested in which heavy, hydrophobic particles break froth films and sink to the bottom, while light, hydrophilic particles are supported by the froth to form a top tailings product. Two potential industrial applications for the reverse froth flotation process were evaluated. As a coarse particle flotation technique for sulphide bearing ores, it was found that xanthate pre-conditioning of the ore results in concentrating the sulphur bearing particles to the concentrate. By increasing the xanthate addition, the relative mass recovery as well as sulphur recovery increases. This increase in mass and sulphur recovery is not linear. These results were promising in terms of finding a coarse particle flotation technique for the pre-concentration of sulphide bearing minerals. Preliminary tests indicated that the reverse froth flotation process is not suitable for the replacement of grease belts for fine (−3 mm) diamond recovery. The major concern is the high potential losses of valuable material to the tailings. These losses are mainly due to the fact that the major separation process in the reverse froth flotation cell is based on particle mass beyond a certain critical value. The surface properties of the particle account only for a secondary separation process. Nevertheless, this technique still offers the potential to be applied to coarse coal flotation and recycling waste separation within certain operating limits.

On the turbulence-controlled microprocesses in flotation machines

In flotation machines, the operation takes place in a highly turbulent flow. Therefore, the modelling as well as the optimization of a flotation process necessitate the application of essential results of the statistical turbulence theory, where an extensive simplification of the complicated laws is typical for the application in processing. Three effects of turbulence are important in flotation: the turbulent transport phenomena (suspension of particles), the turbulent dispersion of air and the turbulent particle–bubble collisions. While the transport phenomena are mainly caused by the macroturbulence, the microturbulence controls the two last-named microprocesses. In the paper a brief introduction of the theoretical background is given as far as it is necessary for modelling. The effect of turbulence damping by fine particles is also discussed. Models of the microprocesses air dispersion and particle–bubble collisions are presented, and it is clearly demonstrated that the particle–bubble attachment almost exclusively occurs in the zone of high energy dissipation rates, i.e., in the impeller stream. Further on, it is shown that the entrainment of fine particles into the froth lamellae is a result of the suspension state and, therefore, can be influenced by the design of the turbulence generating system (impeller–stator system). Finally, it is demonstrated that there is no feasibility to achieve optimum hydrodynamics for all particle sizes simultaneously. For coarse particle flotation, the power input should be minimized (generation of coarser bubbles; stronger buoyancy and lower turbulent stresses acting on the particle–bubble agglomerates!). In contrast to this, fine particle flotation requires high turbulent collision rates, i.e., a higher power input.

Comparison by g.c.-m.s. of liquefaction extracts from coal maceral concentrates

Dodecylamine (DDA) is a commonly used collector in the froth flotation of quartz particles. The present work for the first time studies the effect of DDA nanobubbles (NBs) on the flotation of coarse particles (−425 + 300 μm, −300 + 212 μm and − 212 + 106 μm). For this purpose, 50 mg/l DDA was employed as a primary material for producing bulk NBs via hydrodynamic cavitation technique to be used in the flotation kinetics tests. For comparative purposes, pine oil (PO), Methyl Isobutyl Carbinol (MIBC) and polypropylene glycol (A65) with a concentration of 22.4 mg/l were utilized for generating NBs and also as a frother. According to the results, generated NBs categorized based on the stability and mean bubble size as DDA > PO > MIBC>A65. The flotation rate constants (k) and ultimate recoveries (Rmax) obtained in the presence of the DDA-NBs were substantially improved compared to the corresponding values given for the frother types NBs. That was mainly related to the chemical functionality of the agent together with its extended stability. The experimental results showed a Rmax of 97.5% using the DDA-NBs in the condition of without any frother; however, the highest recovery using common air bubbles (CBs) was obtained 90.8% by the PO. Additionally, the influential order of the three frothers and the DDA on flotation rate constant was shown as DDA > PO > MIBC>A65 for each fraction size. Finally, the results indicated that the k and Rmax of coarse particles were improved by 22% and 21% in the presence of the DDA-NBs.

Modelling of negative bias column for coarse particles flotation

A model for coarse particle flotation in columns operating with negative bias is presented. The model assumes plug flow of particles and bubbles, low turbulence, and a collection mechanism based on bubble-particle interception. Experimental results obtained with quartz and calcite are in close agreement with the predicted values for particle sizes in the range 100 to 700 microns. For a given column length recovery depends mainly on bubble size, air hold up and particle size.

Flotation of coarse particles in a counter-current column cell

The effect of particle size on the flotation of coarse particles is analyzed. It is concluded that turbulence and the presence of the froth layer are detrimental to the recovery of coarse particles during conventional flotation. A counter-current column cell is proposed to avoid these two factors. In this column, a net upwards flow of water is prevalent, such that no froth is allowed to form on the top. Also, the levitation of heavy bubble-particle aggregates is helped by the ascending water current. Preliminary work at laboratory level with kilogram-size samples indicated that under similar conditions recoveries in the column were much higher than in conventional cells. Flotation results obtained with coarsely sized phosphate and quartz samples are presented. One interesting feature of this type of column is very fast flotation kinetics. Thus, a short column (only 55-cm collection zone) yielded full recovery of floatable values.

The interaction of flotation chemistry and size reduction in the recovery of a porphyry copper ore

In the industrial-scale processing of low grade porphyry copper ores, the cost of size reduction represents the major capital and operating expense item. The goal of grinding is to achieve a small enough particle size range of the feed ore so that valuable minerals are sufficiently liberated from undesired gangue enabling the process of flotation to be efficiently used. The purpose of this paper is to demonstrate that the proper choice and use of flotation reagents, especially of the frother, can help significantly in reducing the amount of grinding required per ton of feed ore and yet maintain reasonable mineral recovery from flotation. This is achieved by using specific types of frother chemistry which enhance the recovery of coarser and partially liberated mineral particles over normal practice. A related benefit to enhanced coarse particle flotation is the minimization of mineral recovery losses associated with fine (slime) particles.

The air flow number in flotation machine scale-up

The flotation cell is quantified as a mixing device for one, two, and three phase systems using combinations of water, air, and solids. To do this, power consumption was measured as a function of impeller speed, rate of aeration, and solids concentration. Initial suspension of solids and dispersion of suspended solids throughout the water or water/air system were also studied as influenced by impeller speed, particle size and solids concentration. The power number and air flow number were used to correlate the data. Flotation studies with a zinc ore using three sizes of cells of the same design, showed that aeration had to be controlled in the smaller cells to duplicate the results in the cell of commercial size. For optimum results the flow number range in the smallest cell was less than the critical value for suspension of coarse particles. Operating flow numbers for the three cell sizes under optimum conditions were close; commercial cells of the same size operating elsewhere appear to have two to three times higher flow numbers. The general relationships among air flow, impeller speed, particle suspension and flotation are discussed with particular reference to scale-up problems and coarse particle flotation. Both impeller speed and aeration should be considered as variables requiring systematic study and independent adjustment.