Different beneficiation methods or ores of different nature have different concepts for the division of fine mud grades. Flotation fines generally refer to fine fractions of less than 10 microns or less than 5 microns, and froth flotation is suitable for processing finely divided materials. However, the production practice shows that when the material contains more fine mud, the flotation process is seriously deteriorated, and the flotation effect is significantly reduced. The production indicators generally have the problem of “two lows and two highs”, that is, the concentrate has low grade, low recovery rate, high consumption of chemicals, and high water content of concentrate. Therefore, flotation of fine mud has become one of the problems in mineral processing research. The problem of fine mud flotation is related to the physicochemical properties of fine mud. The basic characteristics of fine mud are as follows.

(1) Small mud quality

That is, the fine mud is hard to collide with the air bubbles, and even if it is in contact with the air bubbles, since the mass is small, the momentum is small, and it is difficult to overcome the hydration film between the fine mud and the air bubbles, so that the fine mud is hard to adhere to the air bubbles. However, the fine mud is easy to adhere to the coarse grain surface, or the slime covers the coarse grain surface, which acts as a “suppressing” effect on the coarse flotation, which reduces the floatability of the coarse particles and makes the selection of the flotation process. Sex is bad. However, the mud cover is not all bad, the same composition of the mud cover does not affect its selectivity, carrying the flotation is the use of this principle. It is only the fine mud cover of different minerals that destroys the effective flotation separation.

(2) larger than the surface

That is, the unit mass of the ore has a large total surface area. For example, when a cubic ore with a side length of 1 mm is ground to 10 microns, its surface area is increased by a factor of 100. Since the surface area is large, the amount of adsorbed is large, which destroys the normality of the flotation process and consumes a large amount of flotation reagent.

(3) Larger than surface energy

That is, there is a large amount of unsaturated surface bond force on the surface of the slime. In other words, the surface activity of the slime is very large, so the surface of the slime will selectively adsorb a large amount of flotation agent, and in addition to increasing the consumption of the agent, it will make the slime difficult to sort.

On the other hand, the large surface activity of the slime makes the slime have a strong hydration ability. So it is very good. This brings great difficulties to the selection, concentration and filtration operations.

The fine mud has the distinction of primary fine mud and secondary fine mud. The primary fine mud is fine mud formed by minerals in the deposit due to natural weathering, such as kaolin and clay. Secondary fine mud refers to the fine mud produced during mining, handling, crushing and grinding. Generally, the primary fine mud is harder to float than the secondary fine mud. In order to reduce the damage of fine mud to the flotation process, it is necessary to minimize secondary sludge. In the practice of flotation, in order to overcome the deterioration of the flotation process by fine mud and to eliminate the harmful effects of fine mud, the following measures are often adopted.

(1) Conventional flotation treatment of fine mud

1 When the fine mud is not too much, add a dispersant to reduce its impact.

Generally be added to the water glass, phosphate, sodium hexametaphosphate. The dispersant is a pure electrolyte that acts to increase the electromotive force on the surface of the fine mud. When the fine muds are close to each other, they are mutually repelled due to the same electrical properties, so that the slime acts as a dispersion to prevent non-selective agglomeration of the fine mud.

The method of adding a dispersing agent is relatively simple, and is suitable for a case where the mud is less. However, this method still cannot solve the shortcomings such as poor selectivity and large dosage of chemicals caused by the fine mud, so it is often necessary to strengthen the selection operation in production practice.

2 remove the slime before flotation

There are two ways to remove mud beforehand: flotation de-sludge and mechanical de-sludge. Flotation de-slurry is to use a small amount of foaming agent and collector to float a part of the slime and then carry out coarse flotation. Mechanical desilting is the use of a classifier (such as a hydrocyclone) to remove a portion of the fine mud prior to flotation. The particle size of the general deliming is 10.20 microns. Deslimation grade is mainly determined by the performance of the classification equipment . After de-sludge, the effect of coarse flotation can also be improved. The main problem is difficult to deal with fine mud, fine mud useful if very little mineral content can be discarded, but often useful in fine clay minerals in ore grade and almost, if it abandoned on the Slimes metal lost in vain.

3 mud sand sorting

Process requirements for fine flotation of fine mud

a. It is advisable to use a longer flotation time. According to the data, the flotation time of less than 10 micron size is as long as 40-60 minutes;

b. High concentration of pulp (up to 60%-70% pulp concentration), low concentration flotation (generally less than 20%);

c. Sub-dosing, increase the amount of collector, reduce the amount of foaming agent;

d. Large amount of inflation, small bubbles, weakening the rise of slurry flow.

In actual production, it is difficult to meet the above-mentioned fine mud flotation process requirements, so the index of fine mud flotation is not high. Although the above method of treating fine mud is used for production, it does not solve the special process of fine mud flotation. From the current research trend, there are two ways to increase the flotation speed of fine particles: one is to increase the particle size of fine flotation; the other is to reduce the particle size of flotation bubbles.

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January 28, 2024