Mercury beneficiation method

The cinnabar is red, dense, brittle, and naturally floatable. Pre-selection, re-election and flotation or a combination of several methods can be used.
1. Pre-selection of mercury ore is a traditional pre-selection method. Cinnabar is red or dark red, easy to identify with cofferdam and gangue minerals. At the same time, due to the brittleness of the cinnabar, the ore is easily broken from the dense place of the cinnabar in the crushing process, and the cinnabar is often exposed on the broken surface of the ore, which is beneficial to the hand selection. Hand selection is usually carried out on a hand-selected belt with a belt speed of typically 0.1 to 0.4 m/s. The hand selection of large ore is sometimes handled by a special hand selection station before the coarse crushing. There are hand-selected culling culling waste rock and ore two methods, the former for the beneficiation of low grade stone, the latter is selected for the case of a higher grade ore. The ore usually needs to be coarsely crushed and classified before it is selected. The typical hand selection process in China is shown in the figure below. The hand-selected grain size shown in the figure is 20 to 100 mm, and some mines divide the grain size into several grain sizes for hand selection. Hand-selected indicators, each mine has a large difference in different ore grades and different periods. Generally, the rate of hand-selected waste rock is about 40 to 70% (for the amount of minerals selected). It is often necessary to wash the ore on the surface of the ore with flushing water before hand selection. Since the natural sand of the cinnabar is good, the fine granules are easily lost with the washing water, so the corresponding facilities (such as the sedimentation tank) must be used for sedimentation and recovery of the fine granules in the washing water.

Hand selection flow chart
Breaking screening is another pre-selected method for mercury ore. Like all brittle minerals, cinnabar is enriched in fine-grained ore due to selective crushing during the crushing process. Select the appropriate mesh size for grading and discard the on-screen grade for pre-selection purposes. In the Pedernales mercury mine in Mexico, the ore is crushed and sieved, and the +32 mm fraction, which accounts for one-third of the original ore, is discarded, and the -32 mm fraction is sent to the rotary smelting mercury. The Sulphur Bank plant in the United States used a 225 mm sieve to classify the ore, discarding the +225 mm chunk, and screening the 225 mm pellet for screening, scrubbing and re-election. .
2. Re-selecting the density of cinnabar is high, which is conducive to the treatment by re-election. However, in a production practice, a single re-election process is generally not used to treat mercury ore. The reason is that, because the cinnabar is mostly impregnated with coarse and fine grain inhomogeneous inlay or fine grain inlay, the fine-grained cinnabar is difficult to be fully and effectively recovered during the re-election process. Second, due to the crispness of the cinnabar, the natural floatability is good, and the fine-grained cinnabar produced during the grinding process is easy to float and float when re-electing. Therefore, the re-selected tailings are often subjected to flotation treatment by grading and re-grinding. A new plant in Xinhuang Mercury Mine, which used a single re-election process to treat ore with an average grade of 0.186% (Hg) from 1959 to 1963, with an average recovery rate of 56% (Hg) and an average grade of tailings of 0.087% (Hg). The concentrate grade averages 3.4% (Hg). Later in 1964, it was changed to a single flotation process. Therefore, mercury mining plants often use heavy and floating combined processes. Re-election is only used to recover a portion of the coarse-grained cinnabar that has been dissociated from the monomer, or to select a part of the cinnabar product. [next]
The re-election of mercury ore is most commonly used in shakers and jigs. Shakers can be used to produce high quality concentrates for the production of cinnabar products. The jig is mostly used to process the pre-screened sieve size before the ore is milled, or set in the grinding classification circuit to recover the monomer-disintegrated cinnabar in time to avoid over-grinding. At the same time, some of the coarser cinnabar products can be recovered from the jigging concentrate. In recent years, some factories have been experimenting with jigs instead of roughing shakers. In Japan, the Nikko (亻卜厶力) concentrator uses a jig and a natural mercury trap to recover most of the natural mercury in the ore.
3. Flotation flotation is the most common and effective beneficiation method in mercury ore beneficiation. Flotation not only can effectively recover the cinnabar in the ore, but also effectively recover various mercury minerals such as natural mercury and chlorosulfurite. Multi-gold flotation process is also used to belong to mercury ore.
The main target mineral in most mercury ores is cinnabar. Cinnabar has a good natural floatability. Therefore, the flotation process and the pharmaceutical system of a single cinnabar type ore are relatively simple. The commonly used process is one or two stages of grinding. The graded overflow particle size is generally ~85%, -200 mesh, and the flotation granularity of individual plants is coarser. The flotation process often uses one rough selection, one to two selections, and two to three sweeps. Flotation agent, the use of heavy metal salts as cinnabar activator, such as copper sulfate, lead nitrate, lead acetate, mercury chloride. Copper sulphate is the most widely used, and the general dosage is 100~300 g/ton. Some plants do not use activators. The collector of cinnabar is a yellow drug . Ethyl xanthate is commonly used in domestic plants, and the dosage is 80~240 g/ton. Some of the factories have used mixed medicines of xanthate and black medicine, and their selection indicators are almost the same as those of yellow medicine alone. The McDermott plant in the United States treats ore containing cinnabar and chlorsulfuron ore (content ratio of 7:3) and uses isopropyl xanthate as a collector. In Japan, according to the set of wood card selection plant, 70% of the mercury content is natural mercury, 30% is cinnabar ore, and amyl yellow medicine is used as collector. Some experimental data show that in order to improve the concentrate grade of low-grade mercury ore flotation, tannin, tannin, citric acid, carboxymethyl cellulose, starch, water glass, etc. can be selected as gangue inhibitors or ores according to the ore properties. Mud dispersant. However, there are not many applications in production practice. The optimum pulp pH for flotation cinnabar is 6 and 7.5~7.8, but in the range of pH 5~8.5, cinnabar can maintain high flotation recovery rate. Therefore, the general selection plant does not use the pH adjuster, and the natural pH value of the pulp is roughly between 6 and 8.
For a single cinnabar type ore, flotation can obtain a good selection index. When the ore grade is 0.1~0.5% (Hg), the flotation recovery rate can reach 90~96%. When dealing with more complex ores, the recovery is slightly less than 90%. The grades of flotation concentrates vary greatly among the selected plants. The domestic plants are generally between 10~30% (Hg), the highest in foreign countries is 75% (Hg), and the lowest is only 1.5% (Hg). . The level of concentrate grade, in addition to the complexity of the ore grade and mineral composition, often involves the smelting method of concentrate.
For flotation plant equipment, domestically selected plants use small and medium-sized crushing equipment and mechanical agitating flotation machines. A few selected plants use flotation columns as roughing equipment, and their technical and economic indicators are similar to those of mechanically agitated flotation machines. Some large-scale foreign factories have adopted self-grinding machines and larger flotation machines.
4. Heavy-floating combined ore dressing 1 float combined ore dressing process is very common in mercury ore dressing plants. In China, the vast majority of cinnabar products are from the mercury mining plant of this process. In the heavy-floating combined plant of mercury mines, the tailings are generally not abandoned in the re-election stage. Instead, the tailings and overflows after re-election are dewatered, classified and re-ground, all by flotation. check. Otherwise it will affect the total recovery rate of the beneficiation. For a single cinnabar type mercury ore, both test and production practices have shown that the recovery rate of a single flotation is slightly higher than that of the heavy-floating combined process. Moreover, a single flotation plant has less capital investment and lower production costs. Therefore, the selection of plants using the heavy-floating combined process is often due to the nature of the ore (such as the recovery of natural mercury) or the production of cinnabar.
At present, there are mainly two types of production processes in the domestic selection of heavy-floating combined processes. The first type is multi-stage grinding, multi-stage shaker sorting, hydraulic classification before shaker sorting, graded overflow and shaker tailings are sent to flotation through dewatering, grading, regrind and then. Such process is suitable for fine disseminated form of cinnabar ores and ore containing large amounts of denser pyrite and other minerals (e.g. Magnolia mercury processing plant). The advantage is that the cinnabar can be recovered as much as possible in the re-election process, and the recovery of the mercury content in the finished cinnabar can be up to 40-60% (the original ore grade is about 0.3-0.5% (Hg)). ). The disadvantages of this type of process are high water and electricity consumption, high production costs, and large capital investment. Moreover, the re-election of the tailings needs to be dehydrated before entering the re-grinding and flotation operation of the F section, and some fine-grained cinnabars are lost with the overflowing water, which reduces the total recovery rate of the ore dressing. Another type of process is the roughing of the broken ore through a rod mill, the product is not graded (wide grade), and the high concentration shaker is selected. This procedure is applicable to ores with a coarser grain size and a relatively simple composition (for example, Guizhou Mercury Concentrator). The utility model has the advantages that the process is simple, the water and electricity consumption are low, and the dehydration step can be omitted between the heavy and floating operations. Therefore, the production cost is low, the capital investment is small, and the total recovery rate of the beneficiation is high. The downside of this type of process is that the reworked job recovery rate is lower than the previous type of process. Based on the mercury content of the finished cinnabar, the recovery rate of re-election is 30-40% (the original ore grade is about 0.2-0.3% (Hg)).

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