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4 Q&A You Need to Know About Froth Flotation Process

xinhai 2021-07-23(09:07:59) 642 0

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Froth flotation refers to the beneficiation process in which solid minerals are floated from the slurry according to the differences in the physical and chemical properties of the mineral surface. Froth flotation has been widely used in the beneficiation industry and is most suitable for the separation of low-grade and fine-grained disseminated ores. Now I will show you more details about the flotation process through 4 Q&A. 

Now let's dive in!

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Flotation Cell 

1. Why is it difficult for coarse particles to float?

Reasons

Rough grinding can save grinding costs. In froth flotation plants that process unevenly embedded ore, under the premise of ensuring the recovery rate of roughing, there is a tendency of coarsening of grinding fineness. However, because the coarse particles are relatively heavy, they are not easy to suspend in the flotation cell and have less chance to collide with the air bubbles. In addition, after the coarse particles are attached to the bubbles, they are easy to fall off from the bubbles due to the strong detachment force. Therefore, the flotation effect of coarse particles is not ideal under general process conditions.

Solutions

(1)Using collectors with strong collecting ability, auxiliary collectors such as kerosene and diesel can also be supplemented to strengthen the collection of coarse particles, increase the adhesion strength of mineral particles and bubbles, and reduce shedding.

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

(3)Appropriately increase the aeration volume of the flotation cell, resulting in larger bubbles and the formation of "floating cluster " formed by the aggregation of large and small bubbles. This "floating cluster" has greater buoyancy and can carry coarse particles to the surface.

(4)Adopt a shallow tank flotation cell to shorten the floating distance of mineralized bubbles and reduce the falling of mineral particles from the bubble. Or use special flotation cells suitable for coarse-grain flotation, such as ring jet flotation cell and Skinner flotation cell.

(5)A rapid and smooth scraping device is used to scrape out the floating mineralized foam in time to reduce the re-shedding of ore particles.

2. Why is it difficult for fine-grained particles to float?

Reasons

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

(2)The small size of the fine particles leads to a small possibility of bubble collision. When the fine particles of small mass collide with the bubbles, it is difficult to overcome the resistance of the hydration layer between the mineral particles and the bubbles, and it is difficult to adhere to the bubbles.

Solutions

(1)Selective flocculation flotation. Flocculants are used to selectively flocculate the target mineral particles or gangue fine mud, and then separated by froth flotation.

(2)Carrier flotation. Use general flotation particles as the carrier, so that the target mineral fine particles are covered and floated on the carrier. The carrier can be of the same kind of minerals or heterogeneous minerals. For example, pyrite can be used as a carrier for the flotation of fine-grained gold. Use calcite as a carrier to float the fine-grained iron and titanium impurities in the kaolin.

(3)Agglomerate flotation, also known as emulsion flotation. Fine grained minerals are treated with a collector and then form an oily froth with minerals under the action of neutral oil. The collector and neutral oil can be formulated into an emulsion before being added to the slurry. It is also possible to add neutral oil and collectors into the high-quality (solid content up to 70%) slurry, stir vigorously within a certain period of time, and then scrape out the upper layer of foam. This method has been used for fine-grained manganese ore, ilmenite, and apatite.

3. What is the impact of mud on froth flotation?

Impacts

(1)Easily entrained in the froth product, so that the concentrate grade decreases.

(2)Easy to cover the surface of the coarse particles, affecting the flotation of coarse particles.

(3)Absorb a large amount of reagent, increasing the consumption of reagent.

(4)Make the pulp sticky and deteriorate the aeration condition.

Solutions

(1)Use thinner slurry to reduce the viscosity of the slurry, which can reduce the entrapment of mineral sludge in the foam product.

(2)Add dispersant to disperse the mineral slurry and eliminate the harmful effect of mineral slurry covering the surface of other minerals.

(3)Section and batch dosing, which can reduce the consumption of chemicals by mineral sludge.

(4)Desliming the flotation materials in advance before flotation  

The common method of desliming is cyclone classification desliming.

4. How does the slurry concentration affect the flotation index?

(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 the recovery rate beyond the limit will decrease. The main reason is that the concentration is too high, which destroys the aeration conditions of the flotation cell.

(2)Affects concentrate quality. The general rule is that the concentrate quality is higher when flotation is done in thinner pulp, while the concentrate quality decreases when flotation is done in thicker pulp.

(3)Affects the consumption of reagent. When the pulp is thicker, the amount of reagent used per ton of ore is less, and when the slurry concentration is thinner, the amount of reagent used per ton of ore is increased.

(4)Affect the production capacity of the flotation cell. As the concentration of the pulp increases, the capacity of the flotation cell according to the processing capacity also increases.

(5)Affect the consumption of water and electricity. The thicker the pulp, the smaller the water and electricity consumption per ton of ore.

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

In conclusion, a thicker pulp concentration is beneficial to the flotation process. However, if it is too large, the pulp and air bubbles cannot flow freely, the inflating effect will become bad, thus reducing the quality and recovery rate. Therefore, flotation of different ores should be based on the nature of the ore and the relevant technical requirements to determine the appropriate pulp concentration.

To Wrap Up

The above introduce coarse flotation, fine-grained flotation, impact of mud and slurry concentration in froth flotation process. When the flotation index fails to meet expectations, the plant staff must analyze the reasons based on the actual situation and find countermeasures to ensure the smooth operation of the entire processing plant.

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