Fines generally refer to slime that is less than 18 microns or less than 10 microns. Due to the small mass and large specific surface area of ​​the fine-grained ore (mineral mud), a series of special behaviors of the ore during the slurrying and flotation process are caused.
From the action of particles and particles, due to the significant enhancement of the surface energy of the particles, under certain conditions, mutual coagulation between different mineral particles is easy to form non-selective aggregation, and the particles tend to adhere to the surface of the coarse particles to form a slime cover. From the action of the particles and the medium, the particles have a large specific surface area and surface energy. Therefore, the particles have a high adsorption capacity, poor adsorption selectivity, and increased surface solubility, which makes the slurry "inevitable ion" increase. Mechanical entrainment and foam mechanical entrainment 'From the action of particles and bubbles, the contact efficiency of the bubbles is reduced due to the contact efficiency and the adhesion efficiency, and the "armor" phenomenon of the sludge is generated at the same time, which affects the carrying amount of the bubbles.
All of the above-mentioned behaviors are the main reasons leading to slower flotation speed, selective deterioration, lower recovery rate and marked deterioration of flotation index. In order to reduce and prevent the harmful effects of slime and strengthen fine flotation, the following process measures are often used in modern flotation practice:
1 Eliminate and prevent the interference of slime on the flotation process. The main measures are:
1) Desliming This is a way to eradicate the effects of slime. Graded desilting is the most commonly used method. For example, a hydrocyclone is used to separate a certain grade of slurry before flotation, or it is discarded or treated separately with coarse mud. For some easy-to-float slime, it can also be pre-flotted and removed with a small amount of foaming agent before flotation.
2) adding the sludge dispersant sludge sufficiently dispersed can eliminate the deleterious effect "phenomenon between the sludge and the particles covered Hang mutual non-selective coagulation occurs, conventional sludge Li has dispersed. Sodium silicate, sodium hexametaphosphate Sodium and so on.
3) portionwise dosing segment the collector is added portionwise, we can maintain the effective concentration of the agent in the pulp, but also improve the selectivity.
4) flotation to reduce the floating mineral slurry pulp density decreased concentration, one can reduce sludge contaminated foam concentrates, on the other hand may also reduce the slurry viscosity.
2 Select a collector that has chemisorption or chelation of particulate minerals to facilitate the selectivity of the flotation process.
3 Apply physical or chemical methods to increase the apparent particle size of particulate minerals and increase the flotation rate and selectivity of the minerals to be sorted. The new processes developed according to this principle in recent times include:
1) Select flocculation flotation using flocculant to selectively flocculate the target mineral or gangue slime, and then separate by flotation. This method has been used in the flotation of fine-grained hematite (US Tilden processing plant).
2) Carrier flotation The ore particles of the general flotation size are used as a carrier, so that the fine particle cover is placed on the carrier and then floated together with the carrier. The carrier may be a similar carrier (mineral) or a heterogeneous carrier (mineral).
3) Agglomeration flotation, also known as emulsification flotation, fine-grained minerals are treated with a collector and form a mineral-like oily foam under the action of a neutral oil. This method has been used for sorting of manganese ore fines, the titanium ore, apatite. The operating process conditions are divided into two categories: one is that the collector and the neutral oil are first formulated into an emulsion, and the second is in a high concentration slurry (70% solids), which is added with a neutral oil and a collector. Stir vigorously.
4 Reduce the particle size of the bubble to achieve microbubble flotation Under certain conditions, reduce the particle size of the bubble, not only can increase the gas-liquid interface, but also increase the collision probability and adhesion probability of the particles, which is beneficial to the flotation of the particulate mineral. The main processes are:
1) Vacuum flotation is a vacuum flotation method in which a microbubble is precipitated from a solution by a pressure reducing device, and the particle size of the bubble is generally O. 1~O. 5 mm. Studies have shown that it is effective to precipitate fine-grained fine-grained barite , fluorite , quartz, etc. from water. When the other conditions are the same, the conventional flotation method has a grade of 54.4% barite concentrate and a recovery rate of 30.6%, and the vacuum flotation grade can be increased to 53.6 to 63.6%. The corresponding recovery is 52.9-45.7%.
2) Electrolytic flotation The microbubbles are obtained by the method of electrolyzing water. The general bubble size is 0·02-0.06 mm. When used for flotation of fine cassiterite , the flotation of electrolytic hydrogen bubbles is used alone. Significantly improved from conventional flotation, from 35.5% to 79.5%, while the grade increased by 0.8%. In addition, research on other new processes has been carried out in recent years, such as controlling dispersion flotation, branch flotation, etc. for iron ore and black tungsten fine mud flotation, all of which have achieved good results.
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