Microfine lean hematite ore dressing technology

I. Current status of industrial application of fine-grained poor hematite

Magnetic separation, often to 74 ~ 0μm of hematite and magnetite 56 ~ 0μm called fine iron ore, and 45 ~ 0μm the hematite and magnetite 30 ~ 0μm called micro-fine iron ore. Iron grade (TFe) is less than 25%. When finely ground to less than 30μm, the iron mineral monomer dissociation degree can reach more than 95%. Hematite is called fine-grained hematite. At present, the classic process for recovering fine-grained lean hematite in industrial production is the weak magnetic separation-strong magnetic separation-reverse flotation process. The Anshan-type lean hematite mine in China adopts this process, and the technical indicators are better. However, the key equipment of stable operation in industrial production has a maximum magnetic induction intensity of about 1.5T, most of which is between 1 and 1.2T. This magnetic field strength magnetic separation equipment does not recover the fine-grained hematite with a particle size of less than 30μm. Up to 40%. At present, the fine-grained hematite mine produced in the industry is a Hunan Jidong iron ore with a grinding grain size of 80% 22μm. The mine is built using the flocculation desliming-reverse flotation process recommended by the Changsha Research Institute of Mining and Metallurgy. / a processing amount beneficiation plant, under conditions TFe32.46% of the ore grade, obtained 35.33% of fine iron mineral, the iron ore grade of 63.02%, 68.59% iron recovery of industrial production index.

Second, the key technology for efficient recovery of fine-grained poor hematite

Low-cost development of fine-grained hematite, the work of mineral processing technology is still carried out around the loss of early loss, the ability to collect early harvest, maximize efficiency, and save costs, in addition to paying attention to multiple crushing and grinding, stage grinding In addition, the following three aspects of work should be taken seriously.

(1) Selective and efficient grinding technology.

The combination of non-fine grinding and over-grinding is the most prominent problem in fine-grain mineral processing technology. Targeted grinding and efficient classification of the already-qualified graded ore in the first time is to reduce over-grinding and improve beneficiation. The most critical part of efficiency. The world famous mineralizer AF Targart has clearly pointed out: "The function and purpose of grinding are different depending on the raw materials they are grinding. The main task in the concentrating plant is to crush the mineral raw materials so that most of the useful minerals can be obtained from the veins. The stone dissociates and in many cases separates the two useful minerals from each other; the next task is to reduce the particle size of the monomer's useful minerals to the extent necessary to reduce their size so that they are in the next beneficiation In the process (such as the flotation process), there are different behaviors." It can be seen that AF Taggart lists dissociated minerals as the main task and primary task of grinding, while reducing particle size is only listed as the second task. Professor Li Qiheng, a famous grinding expert in China, pointed out that “mining and grinding is to prepare for the selection of sufficient but too smashed materials, which is the basic task of crushing and grinding.” Mechanically reducing the size of the ore particles to increase the degree of dissociation will inevitably result in insufficient dissociation and excessive comminution. However, if the mineral can be selectively dissociated along the interface between the minerals, the mineral can be sufficiently dissociated and the fineness of the coarse grinding can be significantly reduced. It can be seen that the iron monomer is fully dissociated but not pulverized, so that the effective particle fraction content which is favorable for sorting is the key technical problem to be solved in the fine-grained iron ore and limonite beneficiation. However, at present, everyone pays much attention to the fineness of grinding, but rarely studies the grinding technology from the effective sorting granularity under the pursuit of full dissociation. Therefore, the formation of sufficient dissociation in mine work is more important than the fineness of grinding is to promote the choice. The premise of the implementation of sexual grinding. Practice has proved that selective grinding can effectively reduce the fineness of grinding and reduce over-grinding under the premise of improving the dissociation degree of useful mineral monomers, so that the mineral composition of the selected materials can be optimized, and the purpose of improving the grade and recovery rate can be achieved.

(2) Ultra-fine grinding technology.

The high cost of ultrafine grinding is a key factor restricting the development and utilization of micro-fine lean hematite. Grinding with ordinary ball mill, with the increase of grinding fineness, the new qualified grain content is significantly reduced, and the unit grinding energy consumption is multiplied. When the grinding fineness requirement is 20μm and 80% or less, the tower mill, the agitating mill and the ISA mill are all good choices. According to the data, in the re-grinding of a pyrite concentrate, when the grinding fineness of 12 μm is 80%, the ball mill (ball medium diameter 9 mm) needs more than 120 kW·h/t of electricity consumption, while the ISA mill (Medium diameter 2mm) only needs 40kW·h/t, and the energy saving effect is remarkable. However, although ultra-fine grinding equipment such as tower mills and ISA mills have been used in many large-scale iron ore applications, the high equipment prices and the fact that ISA mills are difficult to apply in the Chinese market in the near future have restricted their domestic iron ore mines, especially small and medium-sized mines. Applications. For medium and small iron ore mines with fine iron ore inlay size, the vertical mixing mill developed by Changsha Research Institute of Mining and Metallurgy is a better choice for the final fine grinding equipment. Compared with the ball mill, the vertical agitating mill is used for grinding with a fineness of 40 to 20 μm, and the energy consumption is reduced by 70%. Vertical mills have been able to reach a lower grinding particle size of 5 μm. Vertical stirred mill now been used in more than 60 non-ferrous metals and non-grinding, when a fineness of 80% 180μm, 20μm grinding fineness reaches 80%, the effect is significant. For example, the re-grinding and re-election of non-ferrous metal ore concentrates in Shizhuyuan, Hunan Province has used ordinary horizontal ball mills for many years. The grinding grain size has always been -43μm, accounting for 60%, and the iron grade is between 53% and 55%. The fineness of grinding is not up to standard, and the grade of iron concentrate cannot be improved. After many experiments, the perishable metal ore concentrate regrind equipment of Shizhuyuan was made up of a vertical spiral mixing mill developed by Changsha Research Institute of Mining and Metallurgy. Since 2005, it has been applied in the production line of iron ore concentrate recovered from the non-ferrous metal mine tailings of Shizhuyuan. The grinding grain size is -38μm to 95.10%, and the iron concentrate grade is over 65%, which improves the iron concentrate grade and has significant economic benefits.

(3) Strong magnetic separation technology.

The equipment selected is the key equipment for the recovery of hematite. However, when the iron ore is recovered by the strong magnetic separation equipment, the loss of fine-grained hematite of -30 μm is serious, and the problem of recovery of fine-grained iron minerals of less than 30% cannot be solved. Since 2008, Changsha Research Institute of Mining and Metallurgy has adopted a new high-efficiency ZH I type combined wet magnetic separator as the key equipment for recovering fine-grain weak magnetic red (brown) iron ore, and achieved satisfactory results. The machine adopts a coarse screen and a three-distribution disc structure. The pre-installed special coarse device removes the coarse slag in the slurry. The sorting main body adopts multi-layer induction magnetic pole medium with gradient up to 1.0T and medium corresponding to three plates. The parameter forms a weak magnetic separation system with a magnetic induction intensity of 0.1 to 0.3 T on the upper plate to recover a small amount of ferromagnetic Fe ₃ O ₄ , which is a medium magnetic separation system with a magnetic induction intensity of l to 1.5 T, which is used for recovering the coarse-grained grade. Hematite and imaginary hematite, the magnetic induction strength of the lower plate is as high as 1.7-1.8T, which is extremely effective for recovering fine-grained hematite and limonite. Compared with the Shp-like strong magnetic separator and SLon strong magnetic separator commonly used in the industry, the equipment has a magnetic recovery of 0.8T higher than the lower disk, and the iron recovery rate is higher than 10%, and due to different magnetic properties. The iron minerals are sorted in stages, which greatly reduces the magnetic inclusions. Some red limonite ore dressing plants use this equipment to achieve a full magnetic separation process to increase the iron concentrate grade to more than 65%, while the traditional magnetic separator Since there is only one kind of magnetic field strength, the magnetic inclusion is serious, and the magnetic separation iron concentrate grade can only be increased to 43% to 47%. It is necessary to further select by flotation to obtain iron concentrate with more than 65% grade. The zH I type strong magnetic separation device has stronger functions than a single function magnetic separator, and has simple operation, small footprint and low power consumption. Due to the coarseness and magnetic separation of the front end, the coarse and clastic material blockage and magnetic blockage are completely eliminated, the sorting is unimpeded, and the strong magnetic section magnetic separation effect is very obvious, and has a good and wider practicality.

(4) Fine-grain flotation technology and high-efficiency flotation reagents.

Since the Anshan Iron and Steel Company's Donganshan Sintering Plant began to use flotation separation iron ore in 1958, China's iron oxide ore beneficiation technology has made great progress, especially under the support of the national “10th Five-Year” scientific and technological research, Anshan The magnetic and hematite beneficiation technology has reached the world's leading level. Professor Zhang Yusheng from Changsha Institute of Mining and Metallurgy initiated and successfully applied to the weak magnetic separation-strong magnetic separation-anion reverse flotation process of Anshan Iron and Steel Station Concentrator. The classic process of this type of ore, in China's large and medium-sized iron ore concentrator such as Anshan Steel Qidashan Concentrator, Tuanjuntai Concentrator, Gongchangling Concentrator, Taigang Jianshan Iron Mine, Tangshan Siejiaying Iron Mine, An Steel Wuyang Iron Mine is widely used and promoted. The NaOH, causticized starch, lime and fatty acid collectors developed along with this process have also become classic pharmacy systems, and although the institutes and enterprises have made innovations and contends in the types of anionic collectors, 20 For many years, there has been no fundamental technology beyond the principle process established at the beginning of the process development, four kinds of reverse flotation reagents, and flotation temperature above 30 °C. In order to solve the problem of poor flotation efficiency of fine-grained iron ore and tailings entrainment seriously affecting the quality of concentrate, Changsha Institute of Mining and Metallurgy takes the typical fine-grained iron ore of Taiyuan Steel, Yuanjiacun Iron Mine and Hunan Jidong Iron Mine as the research object. The development of new agents aimed at reducing the interference of slime, improving the quality of iron concentrates and reducing the cost of flotation, and the development of new anionic flotation reagents successfully achieved two kinds of flotation reagents (adjusting agents and collectors). At the normal temperature (15 ° C) flotation target, the agent has completed industrial trials and the results are ideal.

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