The vast majority of manganese ores in my country are lean ores, and most manganese ores are fine-grained or fine-grained inlaid, containing a considerable amount of high-phosphorus ores, high-iron ores and common (associated) beneficial metals, which undoubtedly brings great benefits to beneficiation and processing great difficulty.
At present, the commonly used manganese ore beneficiation methods mainly include mechanical beneficiation (ore washing, screening, gravity separation, strong magnetic separation and flotation) and special beneficiation (fire enrichment and chemical beneficiation).
Ore washing and screening
Manganese ores generally contain slime, which will not only affect the grade of manganese minerals, but also seriously deteriorate the effect of subsequent beneficiation (flotation, gravity separation and magnetic separation). Therefore, in the case of open-pit mining or more slime, the slime must be removed by ore washing.
Ore washing is the separation of ore and mud by hydraulic flushing or additional mechanical scrubbing, which is mostly used as pretreatment before beneficiation. In manganese ore, manganese carbonate ore is generally sprayed by vibrating screen. The products on the screen are washed ore. The products under the screen are combined with the products on the screen through spiral classification, overflow and waste or further recover manganese minerals. Manganese oxide ore is generally washed once or multiple times by double spiral groove washing machine with strong scrubbing.
Gravity beneficiation is carried out according to the density and particle size of various minerals. Due to the difference in density between manganese ore and silicate gangue, gravity separation can be used to separate manganese minerals from gangue minerals.
It should be noted that different gravity separation equipment has different particle size range for manganese ore separation. The separation particle size range of jig is 0.5 ~ 15mm, that of spiral concentrator is 0.075 ~ 5mm, and that of shaking table is 0.04 ~ 3mm. Therefore, before gravity separation, the ore is generally divided into different particle sizes for separate beneficiation. Jig is used for coarse-grained ore, cone concentrator and spiral concentrator are used for medium-sized ore, and shaking table is used for fine-grained ore.
For manganese ore, the density of manganese oxide ore (such as anhydrite, pyrolusite and brown manganese ore) is about 4G / cm3, which is significantly different from that of silicate gangue. Most of them can be separated by gravity separation. However, the density difference between manganese carbonate ore and gangue is relatively small. Generally, jigging, shaking table and other gravity separation equipment are difficult to work. Only heavy medium beneficiation can play the role of enrichment. In production, manganese carbonate ore mostly adopts the combined process of heavy medium and strong magnetic separation. The surrounding rock is abandoned in the front section to restore the geological grade, and the deep separation is carried out in the rear section.
High intensity magnetic separation
Magnetic separation is a method to separate manganese ore from gangue minerals by using the magnetic difference between minerals in an uneven magnetic field. Manganese minerals have weak magnetism, which can be separated from non-magnetic gangue minerals by strong magnetic separation.
For manganese carbonate ore and manganese oxide ore with simple composition and coarse embedded particle size, better separation indexes can be obtained by using a single high-intensity magnetic separation process. When sorting manganese carbonate ore, the magnetic field intensity of the magnetic separator needs to be more than 480ka / m, while when sorting manganese oxide ore, the magnetic field intensity of the magnetic separator needs to be higher, generally more than 960ka / m.
Different manganese minerals have different floatability, but not all manganese minerals are suitable for flotation. Among manganese minerals, rhodochrosite has better floatability, followed by Pyrolusite and permanganite, and other manganese minerals, especially manganese soil, have poor floatability. Therefore, the flotation method can be used for some fine-grained Rhodochrosite and manganese oxide slime.
Manganese ore flotation process usually includes positive flotation and reverse flotation, but at present, most manganese ore flotation plants adopt anionic reverse flotation process. In addition, due to the complex composition of manganese minerals, close combination with gangue, easy argillization, high treatment difficulty, large reagent consumption and high cost of a single flotation process, the combined process flow of magnetic separation flotation or gravity separation flotation can be adopted. Firstly, part of gangue and slime can be discarded by magnetic separation or gravity separation, and then selected by flotation.
Fire enrichment method
Pyrometallurgical enrichment, also known as manganese rich slag method, is a separation method for treating refractory lean manganese ores with high phosphorus and high iron. Its essence is a high-temperature separation method for selectively separating manganese, phosphorus and iron by controlling their temperature in blast furnace or electric furnace based on different reduction temperatures of manganese, phosphorus and iron.
The pyrometallurgical enrichment process is simple and stable. It can effectively separate iron and phosphorus from the ore to obtain manganese rich, low iron and low phosphorus rich manganese slag. This manganese rich slag generally contains mn35% ~ 45%, Mn / fe12 ~ 38, P / Mn < 0.002. It is a high-quality manganese alloy raw material. At the same time, it is also an artificial rich ore of natural rich manganese ore, which is difficult to meet the above three indexes.
The chemical treatment of complex lean manganese ore starts from ore leaching, and the leaching solution is impurity removed to obtain pure manganese sulfate solution. With manganese sulfate solution, borate, MnO2, electrolytic manganese, manganese alloy, high-purity manganese carbonate, manganese sulfate, manganese carbonate, acid manganese carbonate, manganese nitrate and other manganese salt products can be produced. Among them, pyrolusite can also be directly added with potassium hydroxide to obtain potassium manganate, and then electrolyzed to obtain potassium permanganate. In addition, high-purity manganese salt can be directly produced from product manganese ore.
At present, there are many chemical beneficiation methods for manganese ore, including bisulfate method, black manganese ore method (roasting dilute acid selective phosphorus leaching method) and bacterial manganese leaching method.
In the actual beneficiation process, the beneficiation process of manganese ore often needs to be determined comprehensively according to many factors, such as manganese ore properties, concentrator conditions, investment budget and so on. It is suggested to understand the manganese ore itself before selection, and select a single or combined process flow through the beneficiation test report, so as to strive for ideal technical and economic benefits.
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