7 Factors Affecting Froth Flotation

Release time:20 December 2018

What’s Froth Flotation?

The full name of the flotation is called froth flotation. It is the process of selecting minerals from the pulp by means of the buoyancy of the bubbles, depending on the difference in the surface properties of the various minerals. Where to buy flotation machines?

Working principle

The specific process of flotation is to add various flotation reagents to a certain concentration of slurry, and a large number of diffuse bubbles are generated by stirring and aeration in the flotation machine. At this time, the suspended ore collides with the bubbles, and some of The floatable ore particles adhere to the bubbles, and float up to the surface of the ore to form a foam product, which is the concentrate; the non-floating mineral remains in the slurry and becomes the tailings. Thereby, achieve the purpose of mineral sorting.

Froth Flotation machine plays an indispensable role in the mineral beneficiation process, flotation is susceptible to a number of factors during the process, including grinding fineness, slurry concentration, pulp pH, pharmaceutical system, aeration and agitation, flotation time, water quality and other process factors. The factors that affect the flotation process are detailed below.

You may interest in Froth Flotation Method Overview.

Gold and Silver Ore Flotation Processing Technology2
Gold and Silver Ore Flotation Processing Technology
Gold and Silver Ore Flotation Processing Technology1

1 Grinding Particle Size

Both large ore particles (larger than 0.1mm) and small ore particles (less than 0.006mm) affect flotation efficiency and mineral recovery.
In the case of flotation coarse particles, due to the heavyweight, it is not easy to suspend in the flotation machine, and the chance of collision with the bubbles is reduced. Further, after the coarse particles adhere to the air bubbles, they are easily detached from the air bubbles due to the large dropout force. Therefore, the coarse particles have a poor flotation effect under the general process conditions.

During the fine particles flotation separation process, the fine particles are small in volume and the possibility of collision with the bubbles is small. The fine grain quality is small, and when it collides with the bubble, it is difficult to overcome the resistance of the hydration layer between the ore particle and the bubble, and it is difficult to adhere to the bubble.

The content of the coarse-grained monomer must be less than the upper limit of the particle size of the mineral flotation. At present, the upper limit of flotation particle size is generally 0.25-0.3 mm for sulfide minerals; 0.5-1 mm for natural sulfur; and the upper limit of particle size for coal is 1-2 mm.3.Avoid muddy as much as possible. When the flotation particle size is less than 0.01 mm, the flotation index will decay significantly.

The most appropriate grinding fineness must be determined by testing and reference to production practice data. For some ores, the stage grinding and stage selection process are often used to avoid over-grinding of the ore, so that the dissociated ore particles are selected in time.

2 Excessive Ore Slurry

If the froth machine contains much ore slurry, it will bring a series of adverse effects on flotation cells mineral processing. The main influences are as follows
1 Easy to be mixed in the foam product, so that the concentrate grade is reduced.
2 Easy to cover the coarse grain surface, affecting the flotation of coarse particles.
3 Adsorption of a large number of agents, increase drug consumption.
4 The pulp is sticky and the aeration conditions are deteriorated.

3 Flotation Reagent

The type and quantity of the agent added during the flotation process, the dosing place and the dosing method are collectively referred to as the drug system, also known as the prescription. It has a major impact on flotation indicators.

In the ore dressing, it is necessary to pass the ore selectivity test in order to determine the type and quantity of the agent, and in practice, the number, location and mode of dosing should be constantly revised and improved.

4 Aeration And Mixing

In addition to oxygen, nitrogen and inert gases, there are carbon dioxide and water vapor in the air.
The gas has a selective effect on the surface of the mineral, oxygen is the most important factor affecting the surface of minerals. Oxygen is beneficial to the hydrophobicity of sulphide ores/ sulfine flotation, however, if the action time is too long, the mineral surface will return to hydrophilicity. When the gas adsorption conditions are appropriate, the mineral surface will be drained, the flotation mineral processing can be done even without a flotation agent. The Galena mine can only float up with the action of xanthate through the initial action of oxygen.

Stirring the slurry can promote the suspension of the ore particles and evenly disperse in the tank, thus promote the good dispersion of the air and make it evenly distributed in the tank, further can promote the enhanced dissolution of air in the high-pressure area of the tank, and strengthen the precipitation in the low-pressure area.
Enhanced aeration and agitation are advantageous for flotation separation, but not excessively, as excessive aeration and agitation can have the following disadvantages:
(1) Promoted the merger of bubbles
(2) Reduced concentrate quality
(3) Increased power consumption
(4) Increased wear of various parts of the flotation machine
(5) The volume of the slurry in the tank is reduced (this is because the volume of the tank is increased by the portion occupied by the bubble)
(6) Excessive agitation may also cause the ore particles attached to the bubbles to fall off.
The optimum amount of aeration and agitation in production should be determined by experimentation depending on the type and structural characteristics of the flotation machine.

Inflation and agitation are carried out simultaneous in the flotation machine. Strengthening them is beneficial to increase the flotation index, but if it is determined too much, it will cause shortcomings such as bubble merger, degraded quality, increased electric energy consumption, and mechanical wear. Therefore, aeration and agitation must be appropriate.

5 Slurry Concentration

The slurry concentration can affect the following technical and economic indicators:
(1) Recovery rate. When the slurry concentration is small, the recovery rate is low. As the concentration of the slurry increases, the recovery rate also increases, but the recovery rate exceeds the limit. The main reason is that the concentration is too high, which destroys the aeration condition of the flotation machine.
(2) Quality of concentrates. The general rule is that the quality of the concentrate is higher in the flotation of the leaner slurry, and the quality of the concentrate is reduced in the flotation of the richer slurry.
(3) Consumption of pharmaceuticals. When the slurry is thicker, the amount of treatment per ton of ore is less, and when the concentration of the slurry is thinner, the amount of treatment per ton of ore is increased.
(4) The production capacity of the flotation equipment. As the concentration of the slurry increases, the production capacity of the froth flotation machine calculated according to the treatment amount also increases.
(5) Water and electricity consumption. The thicker the pulp, the smaller the water and electricity consumption per ton of ore processed.
In short, when the concentration of the slurry is thick, it is beneficial to the flotation process. However, if the slurry and bubbles do not flow freely, the aeration will deteriorate, thereby reducing the quality and recovery. In this case, the various ore sections of the flotation should determine the appropriate concentration of the slurry according to the nature of the ore and relevant technical requirements.

6 Interaction of pulp density, flotation conditions and ore properties

The most suitable ore pulp concentration during the flotation process is related to the ore property and the flotation processing conditions. The general rules as flow:
(1) Pulp Density. The mineral with large flotation density uses a thicker slurry, while the mineral with a small flotation density uses a thinner slurry. Flotation of coarse-grained materials with thicker slurry, flotation of fine-grained and muddy materials with thinner ore.
(2) Pulp PH Value. The pH of the pulp refers to the concentration of OH– and H+ in the slurry, which is generally expressed by the PH value. Various minerals have a “floating” and “non-floating” pH when using different flotation agents for flotation, The pH of the critical pH. By controlling the critical pH, it is possible to control the effective sorting of various minerals. Therefore, controlling the pH value of the slurry is one of the important measures to control the flotation process.
(3) Flotation Time. The flotation time directly affects the quality of the indicator. The time is too long, the grade of the concentrate is reduced; the time is too short and the grade of the tailings is increased. Therefore, the flotation time required for various Minerals must be determined by experimentation.
(4) Water Quality. Floating water should not contain a large number of suspended particulates, nor can it contains soluble substances and various microorganisms that may interact with minerals or flotation reagents. This problem should be specially noticed when using backwater, pit water, and lake water.
(5) Pulp Temperature. Flotation is generally carried out at room temperature, but sometimes it is necessary to warm the slurry in order to obtain a good sorting effect. The specific heating or not needs to be determined according to the actual situation. If it is heated, it is best to adapt to local conditions and use waste heat and exhaust gas as much as possible.

7 Pulp Quality

The main effects of pulp quality score on froth flotation process in metallurgy are as follows:
(1) Recovery rate. Within a certain range, when the pulp mass fraction is low, the recovery rate is low; the pulp mass fraction is increased, and the recovery rate is correspondingly increased. However, the mass fraction of the slurry should not be too large. If it is too large, the flotation machine is difficult to inflate normally in the slurry, which in turn reduces the recovery rate.

(2) Concentrate grade. The general rule is that the concentrate grade is higher when ore flotation is carried out in a leaner slurry, while the concentrate grade is reduced when it is floated in a thicker slurry.

(3) The dosage of the agent. The flotation agent should maintain a certain mass fraction in the pulp to have a good flotation effect. When the pulp is thicker, the mass fraction of the medicament is correspondingly increased, that is, the required medicament mass fraction can be achieved with fewer chemicals, and the amount of medicament per tan ore is correspondingly reduced. Conversely, when the pulp is thinner, the amount of the agent increases.

That’s all 7 main variables affecting froth flotation. Contact us to know more info about industrial gold mining equipment, get free froth flotation PDF, flotation process flow chart, and related industry cases of gold froth flotation, zinc froth flotation, copper flotation, ore flotation.

Since the content of useful components in the ore that needs flotation treatment is getting lower and lower, the particle size of the impregnation is getting finer and finer, and the composition is more and more complicated and difficult to separate. Therefore, how to design an efficient mineral flotation flow is of the utmost importance.

Flotation Machines for Sale

JXSC, a mineral processing equipment provider and processing flow designer, provides froth flotation equipment and other mining equipment globally. Contact us for details.

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