In the floating beneficiation process, the selection of scavenger tailings or foam products are commonly referred to in the mine. Generally, the mineral grade is lower than the concentrate and higher than the original ore, and its floatability is lower than that of the concentrate and higher than the tailings. For the treatment of medium mines, we must first analyze the situation of the continuous organisms in the middle ore. It is necessary to study the floatability of the mines and the requirements for the quality of the concentrates before we can determine the treatment methods of the mines. For the proper treatment of medium ore, there are four common methods for improving the mineral processing index. The more common methods are as follows.
(1) Returning the medium mine to the appropriate location in front of the floating beneficiation. If the useful minerals of the medium ore mine have been substantially dissociated, that is, return it to the appropriate location in the front of the floating beneficiation, there are two methods.
1 Sequential return As shown in Figure 6-27, the sequential return, that is, the intermediate mine obtained by the subsequent action, returns to the previous operation. When the useful minerals floatability of poor returns in order to reduce re-selected metal loss, ensure recovery, the number of re-election in the mine should be reduced, in sequential mining process is appropriate to return as well.
2 Centralized return As shown in Figure 6-28, all the mines will be merged together to return to the front of the flotation beneficiary for proper operation. When the medium ore mine has good buoyancy and the quality of the concentrate is high, the centralized return of the medium mine is appropriate. As the medium mine has been selected several times, the quality of the concentrate can be improved.
(2) When the middle ore returns to the grinding and grading cycle, it is better to return to the grinding and grading cycle, as shown in Figure 6-29.
If the mine contains some ore particles separated from the partially monomer, it can be returned to the classification operation. In order to increase the mechanical scrub on the surface of the mine, it can also be returned to the mill.
(3) Separate treatment of medium ore is complicated for the nature of medium ore, such as complex inlay, the difference between floatability and ore minerality, and when there is more mud, if the mine returns to the original flotation beneficiation cycle, it is bound to Deteriorating the entire floating beneficiation process. In this case, the medium ore should be treated separately, as shown in Figure 6-30.
(4) Other methods of treatment If the above methods are used to treat the middle ore, no good results can be obtained. Chemical treatment can be considered, but the experimental work should be carried out on the medium mine. According to the test results, the scheme should be comprehensive. Comparing technical and economic indicators, it is necessary to obtain a value that is technically reasonable and economically cost-effective. In addition, it is also considered that it will not be processed and it is possible to sell low-grade concentrates.
In short, in the process of flotation and beneficiation, it is necessary to carefully study the treatment method of the medium ore, and choose a reasonable plan, which is of great significance for improving the mineral processing index. As a general rule, the mine should be returned to work of similar grade. If the concentration of the medium ore is too low or the drug content is too large, so as to affect the normality of the near-back operation, it is necessary to return after dehydration and drug removal treatment.
Different beneficiation methods or ores of different nature have different concepts for the division of fine mud grades. Floating beneficiation fines generally refer to fine-grained grades of less than 10 microns or less than 5 microns, and froth flotation beneficiation is suitable for processing fine-grained materials. However, the production practice shows that when the material contains more fine mud, the flotation process is seriously deteriorated, and the floating beneficiation effect is significantly reduced. The production indicators generally have the problem of “two lows and two highsâ€, that is, the concentrate has low grade, low recovery rate, high consumption of chemicals, and high water content of concentrate. Therefore, the flotation of fine mud has become one of the problems in mineral processing research. The problem of fine mud floating beneficiation is related to the physical and chemical properties of fine mud. The basic characteristics of fine mud have the following aspects:
(1) The fine mud is small in mass, that is, the fine mud is difficult to collide with the bubbles. Even if it is in contact with the bubbles, the momentum is small because the mass is small, and it is difficult to overcome the hydrated film between the fine mud and the bubbles, so that the fine mud is hard to adhere to the 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-grained floating beneficiation, which reduces the floatability of the coarse particles and makes the selection of the floating beneficiation 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 floating beneficiation is the use of this principle. Only the fine mud cover of different minerals destroys the effective separation of floating beneficiation.
(2) The ore particles larger than the surface, that is, the unit mass, have 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. Due to the large surface area, the amount of adsorbed drug is large, which destroys the normality of the floating beneficiation process and consumes a large amount of floating dressing agent.
(3) It is larger than the 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 floating mineral processing agent. In addition to increasing the consumption of the chemical, the slime is difficult to sort. On the other hand, the large surface activity of the slime makes the slime have a strong hydration ability, so when the slime adheres to the surface of the bubble, the water film on the surface of the bubble does not easily flow away, and the stability of the bubble 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 floating beneficiation process, it is necessary to minimize the secondary fine mud.
In the practice of floating beneficiation, in order to overcome the deterioration of the fine dressing process and to eliminate the harmful effects of fine mud, the following measures are often adopted.
(1) Conventional floating beneficiation treatment of fine mud
â‘ When less long fine mud, a dispersing agent may generally be added to mitigate the effects of 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 fundamentally solve the shortcomings caused by fine mud and the large amount of chemicals, so it is often necessary to strengthen the selection work in production practice.
2 There are two ways to remove the mud before demineralization before floating ore dressing: floating beneficiation and de-sludge. Floating beneficiation is to use a small amount of foaming agent and collector to float a part of the slime, then carry out coarse flotation and beneficiation. Mechanical desilting is the use of a classifier (such as a hydrocyclone) to remove a portion of the fine mud before floating beneficiation. Generally, the particle size of deliming is 10-20 microns. Deslimation grade is mainly determined by the performance of the classification equipment . After de-sludge, it can also improve the effect of coarse-grained flotation. The main problem is that the fine mud is difficult to handle. If the content of useful minerals in the fine mud is very small, it can be discarded. However, the grade of useful minerals in the fine mud is similar to that of the original ore. If it is discarded, the metal in the fine mud is lost.
3 Process requirements for silt separation and fine mud separation and beneficiation: a. It is advisable to use a longer floating beneficiation time. According to the data, the floating beneficiation time of less than 10 micron is as long as 40 to 60 minutes; b. Pulp (up to 60% to 70% pulp concentration), low concentration floating beneficiation (generally less than 20%); c. Sub-dosing, increase the amount of collector, reduce the amount of foaming agent; d. , small bubbles, weakening the rising slurry flow.
In actual production, it is difficult to meet the above-mentioned process requirements for fine mud flotation, 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 floating beneficiation. From the current research trends, there are two ways to improve the fine-grained flotation rate: one is to increase the fine-grained flotation particle size; the other is to reduce the particle size of the floating beneficiation bubble.
(2) Special process for treating fine mud
1 Method for increasing the particle size of fine mud flotation
a. Selective flocculation floating beneficiation. For example, high molecular compounds such as starch and 3# coagulant (polyacrylamide) may have some polar groups attached to the fine mud by electrostatic attraction, hydrogen bonding or other forces in their molecules. Because the molecules are very long and large, they can be connected between two fine mud particles, called "bridge" or "bridge", thereby bonding a lot of dispersed and isolated fine muds together to form flocs. If the added flocculant not only causes flocculation of the fine mud, but also their polar group and the action of the slime are selective, the fine mud of the same mineral can be bonded together. While other fine muds remain dispersed, this effect is selective flocculation. Selective flocculation floating in the mineral beneficiation of iron ore has achieved good results. For example, China uses sodium humate as a selective flocculant to treat a certain subway ore. Since sodium humate only flocculates fine-grained hematite, it does not substantially flocculate with quartz and other gangue. Therefore, after this selective flocculation, and then deliming or anti-floating beneficiation to remove the gangue, the concentrate grade and recovery rate are significantly improved.
Flocs have two major classes of hydrophilic and hydrophobic. The above-mentioned selective flocculant for treating hematite fine mud is a hydrophilic high polymer (polymer compound), and the obtained floc is hydrophilic and difficult to float, so that it is delimed or de-floating and demineralized to remove veins. stone. The floc can be floated as long as the polymeric flocculant does not interfere with the hydrophobic action of the subsequent addition of the collector. In the process of flotation and beneficiation, the collector adsorbs on the surface of the fine particles to form a hydrophobic membrane. Due to the attraction between the hydrophobic groups, a "bridge" between the fine particles is formed, and the fine particles are flocculated. In addition, after a large amount of non-polar oil collector adheres to the surface of the slime, the floc is generated by the hydrophobic agent due to the molecular attraction between the molecules, and the floc produced by the hydrophobic agent is hydrophobic.
It can be seen that the hydrophilic and hydrophobic nature of the floc depends on the nature of the agent that causes the coagulation or flocculation.
b. Carrier floatation beneficiation. Carrier floating ore dressing is also called carrying floating ore dressing. By using the principle of agglomeration, even if the mineral particles adhere to the surface of the coarser and easy-to-float mineral, a dense cover is formed, and the coarse-grained floating mineral is used as a carrier to float together with the bubble adhesion.
The method of carrier flotation and beneficiation to treat fine mud is in the experimental research stage.
2 Reducing air bubbles and improving fine flotation and beneficiation effect Fine-grained floating beneficiation requires micro-bubbles. There are basically two types of micro-bubble floating ore dressing fine particles: vacuum floating beneficiation and electrolytic flotation beneficiation.
a. Vacuum floating beneficiation. It uses a vacuum method to supersaturate a gas dissolved in water to precipitate a gas from the liquid phase to form fine bubbles. In addition to the precipitation of microbubbles, vacuum floating beneficiation has a strong selectivity for adhesion of bubbles to fine mud.
b. Electrolytic floating beneficiation. It utilizes an applied electric field to electrolyze water in the floating beneficiation slurry, and to precipitate oxygen and hydrogen microbubbles as a carrier or auxiliary vehicle for fine mineral ore flotation.
In addition to the generation of microbubbles, electrolytic flotation is itself a kind of regulator. It has an atomic state when it is precipitated from the surface of the electrode. Although the time is short, it has a certain influence on the surface of the mineral and the floating ore dressing agent, which can improve the selectivity.
At present, electrolytic floating beneficiation is also in the experimental research stage.
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