Effect of gangue particle size on flotation (original) (raw)
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International Journal of Mineral Processing, 1999
The tests carried out with solids of different hydrophobicities and densities, floated individually and as a collection of particles in the monobubble Hallimond tube, allowed to characterize flotation in this small-scale laboratory flotation device and determine the maximum size of entrained particles, maximum size of floating particles, particle hydrophobicity, increase of the apparent density of the particle in contact with air bubble due to aggregation with other particles, and flotometric equations interrelating these parameters. Hydrophilic particles do not float in the Hallimond tube but there is some mechanical entrainment governed by the equations: a max .² p ² w /=² w D 0:023 š 0:002 valid for particles with density greater than 2 g=cm 3 and a max .² p ² w /=² w Ð 0:75 D 0:0225 š 0:0025 (cm) applicable for less dense particles, where a max is the maximum size of entrained particles (in cm), ² p is the particle density, and ² w denotes density of the aqueous phase (in g=cm 3). Hydrophobic particles tend to form aggregates and float as a cluster but no interaction was detected for contact angles ( s) below 20º. Thus, for  s < 20º the flotation of a collection of particles can be characterized by the same equations as for flotation of individual particles including the simplified formula of Scheludko D 2 max .² p ² w / D 6¦ g 1 sin 2 . s =2/ in which g is the acceleration due to gravity, ¦ stands for the surface tension of water, and D max is the maximum size of floating particles. Hydrophobic interactions between particles become significant for  s > 20º. When 20º >  s > 55º and the number of particles in the cluster is greater than 1, the flotation of an ensemble of particles is given either by: d 2 max n.² p ² w / D 6¦ g 1 sin 2 . s =2/ or by: d max .² p ² w / D k sin 2 . s =2/ (g=cm 2), where n is defined as .D max =d max / 2 and the term n.² p ² w / represents a new apparent density of the particle in contact with air due to aggregation with other particles which do not touch the bubble, d max is the maximum size of floating and interacting particles, and k is a constant equal to 2.08 g=cm 3. It was established that the clustering does not occur sharply at  s D 20º but it depends on the density of particles and that for less dense particles occurs at higher hydrophobicity. For  s > 55º
The Limits of Fine and Coarse Particle Flotation
The Canadian Journal of Chemical Engineering, 2008
The flotation behaviour of quartz particles was studied over the particle size range from 0.5 µm to 1000 µm and for advancing water contact angles between 0° and 83°. Flotation was performed in a column and in a Rushton turbine cell. Particle contact angle threshold values, below which the particles could not be floated, were identified for the particle size range 0.5–1000 µm, under different hydrodynamic conditions. The flotation response of the particles, either in a column or in a mechanically agitated cell with a similar bubble size, was comparable. Turbulence plays a role, as does bubble‐particle aggregate velocity and bubble size. The stability of the bubble‐particle aggregate controls the maximum floatable particle size of coarse particles. For fine particles, the flotation limit is dictated by the energy required to rupture the intervening liquid film between the particle and bubble. Flotation of very fine and large particles is facilitated with small bubbles and high contac...
Effect of Particle Size and Liberation on Flotation of
2007
This paper presents some investigation results about connection between degree of minerals liberation and flotation, responding to flotation plant “Veliki Krivelj”. There are two main degrees of liberation among the sulphide minerals and gangue, and copper minerals and pyrite. Both of two liberation degrees strongly affect on flotation recovery of copper minerals as well as on copper concentrate grade. This paper deals with figures which give some dependence among the degree of liberation, copper recovery and concentrate grade.
Colloidal-Hydrodynamic Theory of Flotation
Recent advances in the field of colloidal-hydrodynamic flotation theory are reviewed. Factors limiting the flotation of particles of all size classes are analyzed. The role of surface and hydrodynamic forces in the elementary act of flotation is investigated, as is the dependency of efficiency of particle capture by a bubble on the energy of their collision and the rate of its dissipation. Kinetic aspects of the flotation process are examined with consideration of the phenomenon of aggregation of particles and coalescence of bubbles. A brief list is presented on the main problems in flotation theory and certain promising paths of development of flotation technology are suggested.
The limits of fine particle flotation
Minerals Engineering, 2010
Understanding the limits of fine particle flotation is the key to the selective separation of fine mineral particles. Fine particles have low collision efficiencies with gas bubbles and float slowly. There has been a great deal of work aimed at overcoming the inefficient collision of small particles with rising air bubbles. This review deals with the influence of bubble size, particle aggregation, different flow conditions, particle induction time, as well as the action of surface and capillary forces on fine particle-bubble capture. Recommendations for practice are given.
Application of flotometry for characterizing flotation in the presence of particles aggregation
Minerals Engineering, 1988
Different size fractions of coarse magnetite were floated in water in a monobubble Hallimond tube with an increasing dosage of sodium oleate (NaOl), diethyl dixanthate ( (EtX)2) , and hexadecane. All maximum recovery (Rm) vs collector concentration curves plotted for various size fractions were similar in shape having zero recovery at a low and high collector concentration with a maximum recovery in between at a characteristic collector dosage c m, which provides maximum hydrophobicity of the system. Properties of the studied flotation system and literature data indicated that the cessation of magnetite flotation with a high dosage of NaOl is due to hydrophilic layers of oleate ions sorption, while in the other two systems it is due to oil agglomeration of the solids. The values of the maximum particle size which can still be floated (amso), taken from the maximum recovery vs particle mean size at the concentration equal to c m and Rm=50% , seems to be the parameter which well characterizes any solid-collector-water flotation system because this value derives mainly from the hydrophobic properties of the flotation system and particle density in water, 0'. The am50 value and the so-called "flotometry equation" (for our Hallimond tube in the form L m = amsoD') were used for calculation of the parameter L m which in turn was used for a comparison of the floatability of magnetite with different collectors and subsequently with other flotation systems. The values of parameter L m indicated that magnetite floatability increases in the order: collectorless (mechanical carryover), flotation with (EtX)2, flotation in the presence of hexadecane, and oleate flotation. It was established that the floatability of magnetite with NaOl is equal to the floatability of galena with (EtX) 2 and very similar to the collectorless floatability of Teflon. Floatability of the above three systems is most likely the maximum possible floatability of a solid in an aqueous environment.
The entrainment of gangue into a flotation froth
International journal of mineral processing, 2002
The flotation froth structure and motion determine the amount of entrained gangue that is collected to the concentrate. Despite this important role in the overall performance, the behaviour of the froth is still ill understood. To date, predominantly empirical models have been developed to describe entrainment. A fundamentally based model is described and used here in an attempt to improve the understanding of entrainment. Ž. This general froth simulator UMIST FrothSim allows the modelling of a wide range of flotation conditions, as it takes account of a large number of the physical phenomena that occur within flotation froths. The model firstly describes gas motion and bubble coalescence, and the water motion based on gravitational, viscous and capillary effects. The motion of the solids distinguishes between various solids classes based on hydrophobicity, particle size and density and models them by including the effects of Geometric and Plateau border dispersion, particle settling and the motion of the water. The aim of this paper is to show the applicability of this model to explain the observed entrainment and collection of gangue. This is done by comparing model predictions with the experimentally observed relationship between the gangue and water recoveries. The model predicts the identical trends, which are explained in terms of the interaction between the linear effects of water motion and hindered settling and the non-linear effect of particle dispersion.
Maximum size of floating particles in different flotation cells
Minerals Engineering, 2011
Two flotation models, particle at the liquid-gas interface and particle-bubble aggregate, both based on balance of forces, were used for evaluation of experimental data relating the maximum size of floating particles d max and their advancing contact angle. It was noticed, by comparing the experimental and model data, that for a given flotation device and material the maximum size of floating particle d max increases with increasing particle hydrophobicity and at the same time the acceleration a, experienced by the d max particle at the moment of rupture, decreases with particle hydrophobicity. The acceleration values change with cell dynamics and type of flotation device and are usually not available, therefore empirical apparent cell constants A, which characterize flotation dynamics and relate particle acceleration with advancing contact angle have been proposed instead. The values of A were determined by evaluation of experimental data relating d max and advancing (detachment) contact angle for constant: particle density, medium density, surface tension, and flotation cell dynamics. Since A depends on particle density, a tentative formula was proposed to link A with density-independent flotation cell constant A o. The values of A o for selected flotation cells were calculated and presented. Using quartz as an example, it was shown in the paper that a positive advancing contact angle does not guarantee flotation because a prerequisite for flotation is non-zero receding contact angle.