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

During flotation, both overly coarse particles (greater than 0.1mm) and extremely fine particles (less than 0.006mm) will result in poor flotation results and low recovery rates.

When flotating coarse particles, the particle shedding force increases due to their heavy weight. Overly coarse particles are difficult to attach to bubbles, resulting in metal loss and affecting the improvement of concentrate grade. Therefore, it is necessary to:

(1) Use sufficient amounts of the most effective collector;

(2) Increase the aeration of the slurry to create larger bubbles and increase the amount of microbubbles precipitated in the water;

(3) The stirring intensity of the slurry should be appropriate;

(4) The slurry concentration should be appropriately increased;

(5) The scraper should scrape bubbles quickly and smoothly.

When flotating extremely fine particles (usually referring to ore slimes less than 5-10 μm), (1) too fine particles are easy to attach to bubbles, which reduces the floatability of coarse particles, deteriorates selectivity, poor separation effect, makes flotation separation difficult, and affects the grade of concentrate; (2) Due to the large specific surface area of ore slimes, they will adsorb a large amount of flotation reagents in the slurry, which reduces the concentration of reagents in the slurry, destroys the normal flotation process, and reduces the flotation index; (3) Because the ore slimes are very fine and have a large surface area, the surface activity is increased, which is easy to react with various reagents, difficult to separate, and has strong hydration, making the foam overly stable, causing difficulties in concentration, reducing the quality of the concentrate(xingaonai), and reducing the fluidity and concentration efficiency of the foam product.

2. How to prevent and reduce excessive ore slimes in grinding slurry?

Common methods to prevent and reduce ore slimes are:

(1) Reduce and prevent the formation of ore slimes: multi-stage grinding process and staged beneficiation process can be adopted. Correctly select grinding and classification equipment to improve the efficiency of the classifier; (2) Add reagents to eliminate the harmful effects of sludge: commonly used are water glass, soda, caustic soda, etc.; can reduce the flocculation and covering effect of sludge. In order to reduce the harmful effects of large amounts of sludge adsorbing reagents, the staged dosing method can be considered; (3) Deslim the ground ore before flotation and discard it as tailings. If the content of useful components in the sludge is high, the removed sludge can also be floated separately or sent to water for treatment.

When desliming, the commonly used methods are:

① Desliming with a classifier;

② Desliming with a hydrocyclone;

③ In special cases, a small amount of frother can be added before flotation to remove the easily floatable sludge by flotation.

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

Coarse grinding can save grinding costs and reduce costs. In flotation plants that process unevenly distributed ores, there is a trend to reduce the coarse grinding fineness while ensuring the recovery rate of roughing. However, since coarse particles are relatively heavy, they are not easy to suspend in the flotation machine, and the chance of collision with bubbles is reduced. In addition, after the coarse particles adhere to the bubbles, they are easy to fall off from the bubbles due to the strong shedding force. Therefore, the flotation effect of coarse particles is poor under general process conditions. In order to improve the flotation effect of coarse particles, the following process measures can be taken:

(1) Use a collector with strong collection power, and you can also add auxiliary collectors such as kerosene and diesel to strengthen the collection of coarse particles, increase the adhesion and fixation strength between mineral particles and bubbles, and reduce shedding.

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

(3) Appropriately increase the air volume of the flotation machine to create larger bubbles and form a "float" composed of large and small bubbles. This "float" has a larger buoyancy and can carry coarse particles to float.

(4) Use a shallow tank flotation machine to shorten the distance of mineralized bubbles floating up and reduce the mineral particles falling off the bubbles. Or use a special flotation machine suitable for coarse particle flotation, such as a ring-jet flotation machine and a Skenard flotation machine.

(5) Use a quick and smooth scraping device to scrape out the floating mineralized foam in time to reduce the re-fall of mineral particles.

4. What are the reasons for the difficulty in fine particle flotation and the process measures taken?

The flotation separation of fine particles is relatively difficult. The main reasons are as follows:

(1) Fine particles have a large specific surface area and significantly increase their surface energy. Under certain conditions, the surfaces of different minerals are prone to non-selective coagulation. On the other hand, due to the large surface energy of fine particles, although they have a high adsorption force on reagents, their selective adsorption is poor, which makes it difficult to selectively separate fine particles.

(2) Fine particles are small in size and are less likely to collide with bubbles. Fine particles have a small mass and are difficult to overcome the resistance of the hydration layer between mineral particles and bubbles when colliding with bubbles, making it difficult to attach to bubbles.

The technical measures to solve the problem of fine particle flotation are as follows:

(1) Selective flocculation flotation. Use flocculants to selectively flocculate the target mineral particles or gangue mud, and then separate them by flotation.

(2) Carrier flotation. Use mineral particles of general flotation particle size as carriers to cover the target mineral fine particles on the carriers and float. The carriers can be of the same mineral or different minerals. For example, pyrite can be used as a carrier to float fine gold. Calcite can be used as a carrier to float away fine iron and titanium impurities in kaolin.

(3) Agglomeration flotation, also known as emulsion flotation. After the fine-grained minerals are treated with collectors, they form oily foam with minerals under the action of neutral oil. The collector and neutral oil can be first prepared into an emulsion and then added to the slurry. Alternatively, neutral oil and collector can be added to the slurry with a high mass fraction (solid content up to 70%), stirred vigorously, controlled for a certain time, and then the upper foam can be scraped off. This method has been used for fine-grained manganese ore, ilmenite and apatite, etc.

5. What is the effect of slime on flotation and how to solve it?

If the flotation slurry contains a lot of slime, it will bring a series of adverse effects on flotation. The main effects are as follows:

① It is easy to be mixed in the foam product, which reduces the grade of the concentrate.

② It is easy to cover the surface of coarse particles, affecting the flotation of coarse particles.

③ It absorbs a large amount of reagents and increases the consumption of reagents.

④ It makes the slurry sticky and the aeration conditions worse.

The process measures to solve this problem are:

① Use a thinner slurry to reduce the viscosity of the slurry, which can reduce the inclusion of slime in the foam product.

② Add dispersant to disperse the slime and eliminate the harmful effect of slime covering the surface of other minerals.

③ Add drugs in stages and batches, which can reduce the consumption of slime on reagents.

④ Deslim the flotation material in advance before flotation.

The commonly used desliming method is cyclone graded desliming.

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

In addition to oxygen, nitrogen and inert gases, the air also contains carbonic acid and water vapor.

Air has a certain influence on the floatability of minerals:

⑴ When the mineral is broken and the fresh surface is exposed, it will be hydrated when it meets water, and it will be hydrophilic. But when the gas is adsorbed on the mineral surface, it can weaken the hydration and cause the initial hydrophobicity of the surface.

⑵ The interaction between gas and mineral surface is selective. Among them, oxygen has the greatest impact on the mineral surface.

⑶ The role of oxygen is beneficial to the hydrophobicity of sulfide ore. But if the action time is too long, the mineral surface will become hydrophilic again. When the gas adsorption conditions are appropriate, it will cause the hydrophobicity of the mineral surface, and it can even float without adding flotation agents (such as dry coal powder). Galena can only float up after the initial action of oxygen.

7. What is the role of slurry stirring?

The stirring of slurry can promote the suspension of mineral particles and their uniform dispersion in the tank; it can promote good diffusion of air so that it is evenly distributed in the tank; it can promote the enhanced dissolution of air in the high-pressure area of the tank and the enhanced precipitation in the low-pressure area to form a large number of active microbubbles.

Strengthening aeration and stirring is beneficial to flotation, but it should not be excessive, because excessive aeration and stirring will produce the following disadvantages:

(1) Promote the merger of bubbles;

(2) Reduce the quality of concentrate;

(3) Increase power consumption;

(4) Increase the wear of various parts of the flotation machine;

(5) The volume of slurry in the tank is reduced (this is because the part of the tank volume occupied by bubbles increases);

(6) Excessive stirring may also cause the mineral particles attached to the bubbles to fall off.

The most suitable aeration amount and stirring degree in production should be determined through experiments based on the type and structural characteristics of the flotation machine.

8. What is the effect of slurry concentration on flotation indicators?

Slurry concentration can affect the following technical and economic indicators:

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

(2) Affects the quality of the concentrate. Generally speaking, the concentrate quality is higher when it is floated in a thinner slurry, while the concentrate quality will decrease when it is floated in a thicker slurry.

(3) Affects the consumption of reagents. When the slurry is thicker, the amount of reagent used to treat each ton of ore is less. When the slurry concentration is thinner, the amount of reagent used to treat each ton of ore increases.

(4) Affects the production capacity of the flotation machine. As the slurry concentration increases, the production capacity of the flotation machine calculated by the processing volume also increases.

(5) Affects the consumption of water and electricity. The thicker the slurry, the less water and electricity consumption per ton of ore.

(6) Affects the flotation time. When the flotation slurry is thicker, the flotation time increases slightly.

In short, when the slurry concentration is thicker, it is beneficial to the flotation process. However, if the density is too large, the pulp and bubbles cannot flow freely, and the aeration effect will deteriorate, thereby reducing the quality and recovery rate. Therefore, the flotation of various ores should determine the appropriate pulp concentration according to the properties of the ore and relevant technical requirements.

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

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

(1) Minerals with higher specific gravity use denser pulp, while minerals with lower specific gravity use thinner pulp; (2) Coarse-grained materials are floated with denser pulp, while fine-grained and muddy materials are floated with thinner pulp.

(3) Roughing and scavenging use denser pulp to reduce reagent consumption and the number of flotation machines, while fine concentration uses thinner pulp to obtain qualified concentrates with higher quality.

The pulp concentration is 25% to 35% during rough selection of ore, 10% to 20% for flotation of fine particles and ore with high mud content, 10% to 20% for fine selection, and 20% to 30% for scavenging.

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

The pulp mass fraction is an important process factor in flotation and has a very important influence on flotation. There are generally two ways to express the pulp mass fraction: ① Liquid-solid ratio, which indicates the ratio of liquid to solid mass (or volume) in the pulp. This expression method is very convenient when calculating the pulp flow. ② The percentage of solid content (%), which indicates the percentage of solid mass (or volume) in the pulp. This expression method is widely used in mineral processing experiments and production.

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

(1) Recovery rate. Within a certain range, when the pulp mass fraction is low, the recovery rate is low; when the pulp mass fraction increases, the recovery rate increases accordingly. However, the mass fraction of the ore pulp cannot be too large. If it is too large, it will be difficult for the flotation machine to aerate the ore pulp normally, which will reduce the recovery rate.

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

(3) Amount of reagents used. The flotation reagent must maintain a certain mass fraction in the ore pulp to achieve a good flotation effect. When the ore pulp is thicker, the mass fraction of the reagent increases accordingly, that is, less reagent can be used to achieve the required reagent mass fraction, and the amount of reagent used per ton of ore is reduced accordingly. Conversely, when the ore pulp is thinner, the amount of reagent increases.