Magnetite occupies a large proportion of China’s iron mineral reserves, reaching 48.8%. Finding a reasonable magnetite beneficiation technology and machinery to deal with magnetite is of great significance for the development of our country’s mines and the development of the entire steel industry. In recent years, our country’s beneficiators have made unremitting efforts to make the magnetite beneficiation technology and equipment have been greatly developed, and the iron concentrate grade has been greatly improved. Individual concentrators have reached 70%, and the national average has increased by more than 1%; and the impurity content has dropped significantly, and some concentrators have applied a single magnetic separation method to reduce the silica content to less than 2%. It created favorable conditions for ironmaking and also developed the mine itself. Despite this, there are still some developing problems, which are described as follows:
1. Unreasonable fineness of grinding products: The grain size of magnetite minerals in China is extremely uneven, ranging from a few microns to a few millimeters. The same problem exists in the same ore body in the same mine, which brings great difficulties to the beneficiation operation. In order to separate the monomers of magnetite minerals to meet the technological requirements, the current process will inevitably use the smallest embedded particle size as the standard for grinding, which results in over-grinding of some minerals.
When the mineral is over-grinded, the bond force of the mineral particles is greater than its own inertial force, making the beneficiation process useless. The consequence is the reduction of the concentrate grade and the reduction of the metal recovery rate. This phenomenon exists. There are mainly the following factors.
(1) Single grinding machinery and equipment. China has a single variety of grinding machinery and equipment, and the beneficiation plant can only choose from the few types currently available on the market, nothing more than self-grinding, ball milling, and rod milling. Self-grinding is favored by beneficiaries because of its strong selective grinding effect, but the existence of its hard-to-grind particles has caused great obstacles to popularization and application. This is because the crushing system that handles hard-to-wear particles has strict restrictions on the entry of iron. It is difficult to remove non-ferromagnetic metals, and it is difficult to separate ferromagnetic metals from magnetic minerals. Therefore, it is difficult for the stone crushing system to operate. The production capacity of the mill cannot be increased and cannot meet the requirements of beneficiation production, which limits the popularization and application of the self-grinding machine in magnetite mines. Precise iron removal device and stubborn stone crushing system to relax the limits of ironware are the directions of future research.
In recent years, domestic beneficiaries and equipment manufacturers have conducted research in this area, and some results have been achieved. For example, the column mill has been tested in the field, and some very important data have been obtained, which has laid a certain foundation for future scientific research. The ball mill has the same function except for the specifications, and the range of options is limited. Insufficient attention has been paid to this aspect in the country, and the investment is very small, leaving no choice for the beneficiaries. As a result, the process can only be used to adapt to the equipment, and the beneficiation process cannot be optimal.
In recent years, beneficiators have conducted some research on foreign roller mills, esa mills, and stirring mills. Now they are still in the experimental stage. Due to their high cost, they have also brought certain difficulties to their promotion and application. There is no precedent for the process. The column mill developed in China in recent years provides new grinding equipment for mineral processing workers in a broad sense. This type of grinding equipment has a unique effect on mineral grinding, and is low in cost and low in grinding cost. It is suitable for mineral processing. The author provided new ideas and opened up a new path for grinding. Since it has only entered the market in recent years, and magnetite is still in the experimental stage, its design quality, manufacturing accuracy, wear-resistant materials, continuous operation capability, and maneuverability need to be further improved. Its processing capacity is still very small, which is not conducive to the needs of large-scale production. In the future, further research should be carried out on the adaptation of the large-scale working gap of the equipment. Reduce the number of manual adjustments. Only in this way can it be promoted and applied in magnetite plants.
(2) The feed size of the grinding operation is too wide. The current beneficiation and grinding process is generally two-stage, which has great difficulties in the selection of grinding media. It is difficult to select the grinding medium with a strong target, and the targeted grinding cannot be realized, which causes some minerals to be over-ground, which brings great difficulties to the sorting operation. At the same time, the blind pursuit of short processes is also an important factor in this situation. This is also a misunderstanding. Our research direction should be to increase the number of grinding stages, narrow the ore size, make the choice of grinding media more targeted, and improve the overall grinding efficiency by increasing the grinding efficiency of each stage. The consumption has not increased.
(3) The classification operation needs to be further improved. The classification equipment currently used in magnetite concentrators in China mainly includes spiral classifiers, hydrocyclones, and high-frequency fine screens. Spiral classifiers have been used in most of the concentrators for many years. Due to the increase in the price increase of the iron ore concentrate price market in recent years, people pay more attention to improving the grade of iron ore. The efficiency of the spiral classifier is low and reverse The shortcomings of Fu Ji have also received special attention, so some concentrators have been replaced by other equipment and will eventually be eliminated.
Hydrocyclones are being widely used in ore dressing plants for classification equipment, and there are also some problems: First, because hydrocyclones use gravity field for classification, this requires that the gravity field in the hydrocyclones is stable. . In this way, the minerals can be accurately classified, but our current level of automatic control is difficult to achieve a stable gravity field in the hydrocyclone, so accurate classification cannot be achieved; the second is that the hydrocyclone is caused by misunderstandings in the application. If the ore size is too wide, it will inevitably result in the mixing of small-density large particles and large-density small particles, which cannot be accurately classified. This limits the application and development of hydrocyclones. The future research direction should be placed on self-control to keep the gravitational field in the hydrocyclone stable. Only in this way can the hydrocyclone give full play to its unique functions to achieve the purpose of accurate classification. In recent years, high-frequency fine screens have been widely used in magnetite concentrators, and have played a very important role in improving iron and reducing impurities. The structure of foreign high-frequency fine screens is more reasonable, and the sieving is also relatively high, but the cost is much higher than that in China, and it is less used in mines. In recent years, domestic high-frequency fine screen manufacturers have done a lot of work and achieved good results. Concentrators use more domestic equipment and have received better results in recent years. However, the equipment itself has some problems in its application, and its advantages have not been well utilized. One is the high content of qualified particles on the sieve, and the other is that the screen wears too fast. The above problems are caused by the following reasons. First, the amount of ore fed is too large, which makes the sieve overloaded and cannot meet the working conditions of the sieve. Requirements, resulting in excessively high content of qualified particles on the screen. This is mainly because the high-frequency fine-screen production plant has too high expectations for the production capacity of the high-frequency fine-screen. According to the production capacity calibrated by the production plant or exceed its production capacity, the problem has been changed. It is more serious; second, the design of the mine part is not reasonable, causing the mine part to wear too fast and reducing the service life of the screen; third, the material of the screen is not good. In the future, efforts should be made to improve the accuracy of quality assurance.
2. Problems in the sorting operation: Through the efforts of the workers in the concentrator and the manufacturers, the domestic magnetic separation equipment has developed to a certain extent, but there is still a long way to go to the requirements of the magnetite process. Cylinder-type permanent magnet magnetic separator has a long history as a traditional magnetic separation equipment. Although it is widely used in concentrators, the product is relatively single. People can only make limited choices from a limited variety of minerals. There are different pertinences, and the cylindrical magnetic separator is still ideal for the secretion effect of the minerals to achieve the separation of the monomer, but it is powerless for the continuous sound body.
In recent years, more attention has been paid to the study of magnetism, and the research on the tank is relatively small, and the tank plays a very important role in the selection and should not be ignored. The future development direction of the cylindrical magnetic separator should be more pertinent, and different magnetic systems and tank structures should be designed according to different types of slurry, so as to highlight pertinence and weaken versatility. The production of magnetic concentrators and magnetic separation columns have improved the ability of the beneficiation process, for fine-grained lean conjoined minerals.
Link to this article：Brief Introduction of Magnetite Beneficiation Process and Equipment
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