Ten common problems and solutions in flotation

In mineral flotation, do you often encounter the following 10 kinds of problems?

1. What is the effect of grinding particle size on flotation?

During flotation, coarse ore particles (greater than 0.1mm) and very fine ore particles (less than 0.006mm) do not float well, and the recovery rate is low.

In the flotation of coarse particles, due to the large weight, the ore particle shedding force increases. It is necessary to: (1) use sufficient amount of the most effective collector; (2) Increase the inflation of the pulp, resulting in larger bubbles, and increase the amount of microbubbles precipitated in the water; (3) the mixing strength of the pulp should be appropriate; (4) the pulp concentration should be appropriately increased; (5) The scraper should be rapid and stable when scraping the bubble.

In the flotation of very fine particles (usually less than 5 ~ 10μm slime), (1) because the slime mass is very small, it is easy to adhere to the surface of the coarse particle, so that the flotability of the coarse particle is reduced, so that the selectivity becomes bad; (2) Because the slime is larger than the surface, they will adsorb a large number of flotation agents in the pulp, reducing the concentration of reagents in the pulp, destroying the normal flotation process, and reducing the flotation index; (3) Because the slime is very fine and the surface area is large, the surface activity increases, it is easy to act with various agents, it is not easy to separate, and it has strong hydration, so that the foam is too stable, and the selection will cause trapping, reduce the quality of the concentrate, and reduce the fluidity and concentration efficiency of the foam product.

2. How to prevent and reduce excessive slime in grinding pulp?

Common methods of slime prevention and mitigation are:

(1) Reduce and prevent the formation of slime: multi-stage grinding process can be used, as well as stage beneficiation process. The grinding and grading equipment should be selected correctly to improve the efficiency of the classifier.

(2) Add agents to eliminate the harmful effects of slime: commonly used water glass, soda, caustic soda, etc.; It can reduce the flocculation of slime. In order to reduce the harmful effects of large quantities of adsorbed agents in slime, the method of subsection dosing can be considered.

(3) The ground raw ore is deslimed before flotation and discarded as tailings. If the content of useful ingredients in the slime is high, the removed slime can also be treated by flotation alone, or sent to water metallurgy.

Common desliming methods: ① classifier desliming; ② hydrocyclone desliming; ③ In special cases, a small amount of foaming agent can be added before flotation to remove the easily floating mud by floating beneficiation.

3. Why is the coarse grain difficult to float and what process measures should be taken?

Coarse grinding can save grinding costs and reduce costs. In flotation plants dealing with unevenly distributed ores, there is a tendency to reduce the fineness of coarse grinding under the premise of ensuring the recovery rate. However, because the coarse particle is relatively heavy, it is not easy to suspend in the flotation machine, and the chance of collision with the bubble is reduced. In addition, after the coarse particle is attached to the bubble, it is easy to fall off from the bubble due to the large shedding force. Therefore, the flotation effect of coarse particles is poor under normal process conditions. In order to improve the effect of coarse flotation, the following process measures can be taken:

(1) The use of strong collector, kerosene, diesel and other auxiliary collectors can also be added to strengthen the collection of coarse particles, increase the adhesion ability and fixation strength of ore particles and bubbles, reduce falling off.

(2) Appropriately increase the mass fraction of the pulp and increase the buoyancy of the pulp. Under the premise of ensuring the stability of the foam layer, stir properly to promote the suspension of coarse particles and increase the chance of adhesion with the bubble.

(3) Appropriately increase the air capacity of the flotation machine, resulting in a larger bubble and the formation of a "floating group" composed of large and small bubbles, which has a larger lifting buoyancy and can carry coarse particles to float.

(4) Shallow tank flotation machine is used to shorten the floating distance of mineralized bubbles and reduce the ore particles falling off from the bubbles. Or use special flotation machines suitable for coarse flotation, such as ring jet flotation machine and Skainer flotation machine.

(5) Adopt a rapid and smooth scraping device to scrape out the floating mineralized foam in time to reduce the ore particles falling off again.

4. What are the reasons for the difficulty of fine flotation and the technological measures taken?

Flotation separation of fine grained materials is more difficult, the main reasons are as follows:

(1) The specific surface area of fine particles is large, and the surface energy is significantly increased. Under certain conditions, the surface of different minerals is prone to non-selective mutual condensation. On the other hand, it is also due to the large surface energy of fine particles, although they have a high adsorption force for agents, but the selective adsorption is poor, which makes it difficult to selectively separate fine particles.

(2) The fine particle size is small, and the possibility of colliding with bubbles is small. Fine particles have small mass, and when colliding with bubbles, it is difficult to overcome the resistance of hydration layer between ore particles and bubbles, and it is difficult to attach to bubbles.

The process measures to solve the fine flotation are as follows:

(1) Selective flocculation flotation. The mineral particles or gangue fine mud are selectively flocculated by flocculant and then separated by flotation.

(2) Carrier flotation. The fine particle cover of the target mineral is made to float on the carrier by using ordinary flotation particle size as the carrier. The carrier can be made of similar minerals or different minerals. For example, pyrite can be used as a carrier to float fine gold. Calcite was used as a carrier to remove ultrafine iron and titanium impurities from kaolin.

(3) Agglomeration flotation, also known as emulsion flotation. After the fine mineral is treated by the collector, the oil-like foam with ore is formed under the action of neutral oil. The collector and neutral oil can be mixed into emulsion and then added to the pulp. It is also possible to add neutral oil and collector to the pulp of high quality fraction (solid content up to 70%), stir strongly, control the time, and then scrape out the upper foam. This method has been applied to fine manganese ore, ilmenite and apatite.

5. What is the impact of slime on flotation?

If the flotation pulp contains more slime, it will bring a series of adverse effects on flotation. The main effects are as follows: ① easy to be mixed in foam products, so that the grade of the concentrate is reduced. ② Easy to cover the surface of coarse particles, affecting the flotation of coarse particles. ③ Adsorption of a large number of agents, increase the consumption of agents. ④ make the pulp sticky and the inflation conditions deteriorate.

The technological measures to solve this problem are: ① The use of thinner pulp, reduce the viscosity of pulp, can reduce the inclusion of slime in foam products. ② Add dispersant to disperse the slime and eliminate the harmful effect of the slime cover on the surface of other minerals. ③ Subsection batch dosing, which can reduce the consumption of mineral slime on the agent. ④ the flotation material is deslimed in advance and then flotation. The common desliming method is cyclone stage desliming.

6. What is the main effect of air on flotation?

In addition to oxygen, nitrogen and inert gases, there are carbonates and water vapor in the air.

Air has a certain effect on the buoyancy of minerals:

(1) When the mineral is broken to expose the fresh surface, hydration occurs in contact with water, and it is hydrophilic. However, when the gas is adsorbed to the mineral surface, the hydration can be weakened, resulting in the initial hydrophobicity of the surface.

(2) The use of gas and mineral surface is selective. Among them, oxygen has a great influence on the mineral surface.

(3) The effect of oxygen is favorable to the step hydrophobicity of sulfide ore. However, if the action time is too long, the mineral surface will become hydrophilic. When the gas adsorption conditions are appropriate, it will cause the hydrophobicity of the mineral surface, even in the absence of flotation agents can be flotation (such as dry coal). And only after the initial action of oxygen, galena can react with xanthate and rise.

7. What is the role of pulp mixing?

The mixing of pulp can promote the suspension of ore particles and the uniform dispersion in the tank. Can promote a good dispersion of air, so that it is evenly distributed in the tank; It can promote the air dissolution in the high-pressure area of the tank, and strengthen the precipitation in the low-pressure area to cause a large number of active microbubbles.

Strengthening aeration and agitation is beneficial to flotation, but it should not be excessive, because excessive aeration and agitation will produce the following disadvantages: (1) promotes the merger of bubbles, (2) reduces the quality of the concentrate, (3) increases the energy consumption, (4) increases the wear of various parts of the flotation machine, (5) the pulp volume in the tank is reduced (this is because the volume of the tank is occupied by the bubble increased), (6) excessive stirring may also cause the ore particles attached to the bubble to fall off.

The most suitable aeration and stirring degree in production should be determined by tests according to the type and structural characteristics of the flotation machine.

8. What is the effect of pulp concentration on flotation index?

Pulp concentration can affect the following technical and economic indicators:

(1) The recovery rate is affected. When the pulp concentration is small, the recovery rate is low. When the pulp concentration increases, the recovery rate also increases, but when the recovery rate exceeds the limit, it will decrease. The main reason is that the concentration is too high, which destroys the aeration condition of the flotation machine.

(2) Affect the quality of concentrate. The general rule is that the concentrate quality is higher when flotation in the thinner pulp, and the concentrate quality will be reduced when flotation in the thicker pulp.

(3) Affect drug consumption. When the slurry is thicker, the amount of medicine used for processing each t of ore is less, and when the slurry concentration is thinner, the amount of medicine used for processing each t of ore is increased.

(4) Affect the production capacity of the flotation machine. With the increase of pulp concentration, the production capacity of flotation machine in terms of processing capacity also increases.

(5) Affect water and electricity consumption. The thicker the pulp, the less water and electricity it takes to process each t of ore.

(6) Influence flotation. When the flotation pulp is thicker, the flotation time increases slightly.

In short, when the pulp concentration is higher, it is beneficial to the flotation process. However, if it is too large, the pulp and bubbles cannot flow freely, and the inflation effect will become bad, thereby reducing the quality and recovery rate. Therefore, the flotation department of various ores should determine the appropriate pulp concentration according to the properties of ores and related technical requirements.

9. What is the relationship between pulp concentration and flotation conditions and ore properties?

The determination of the most suitable pulp concentration in flotation is related to the ore properties and flotation conditions, and the general rule is:

(1) The mineral with high flotation density uses a thicker pulp, and the mineral with low flotation density uses a thinner pulp;

(2) Thicker pulp is used for flotation of coarse-grained materials, and thinner pulp is used for flotation of fine-grained and slime materials.

(3) roughage and sweepings use thicker pulp, which can reduce reagent consumption and the number of flotation machines, while the selection uses thinner pulp, which can obtain higher quality Tagger concentrate.

The pulp concentration of coarse ore is 25% ~ 35%, and the flotation of fine ore and high mud ore is 10% ~ 20%.

10. What is the effect of pulp mass fraction on flotation?

Pulp mass fraction is an important process factor of flotation and has a very important effect on flotation. There are generally two ways to express the pulp mass fraction: ① liquid-solid ratio, indicating the ratio of liquid and solid mass (or volume) in the pulp, this method is very convenient in the calculation of the pulp process. (2) percentage of solid content (%), indicating the percentage of solid mass (or volume) in the pulp, this method is widely used in beneficiation experiments and production.

The main effects of pulp mass fraction on flotation are as follows:

(1) Recovery rate. In a certain range, when the pulp mass fraction is low, the recovery rate is low. With the increase of pulp mass fraction, the recovery rate increases correspondingly. But the pulp mass fraction can not be too large, such as too large, the flotation machine is difficult to be normally inflated in the pulp, but the recovery rate is reduced.

(2) Concentrate grade. The general rule is that when flotation in thinner pulp, the grade of concentrate is higher, and when flotation in thicker pulp, the grade of concentrate is lower.

(3) Dosage of medicine. Flotation agents must maintain a certain mass fraction in the pulp to have a good flotation effect. When the pulp is thicker, the mass fraction of the agent is increased accordingly, that is, less of the agent can reach the required mass fraction of the agent, and the dosage of the agent per t of the ore is reduced accordingly. On the contrary, when the pulp is thinner, the dosage of chemicals increases.