97% of China's iron ore needs beneficiation treatment
The main features of China's iron ore is "poor", "fine", "miscellaneous", with an average iron grade of 32%, 11 percentage points lower than the world average grade. 97% of the iron ore needs beneficiation treatment, and the proportion of complex and difficult to choose red iron ore is large (about 20.8% of iron ore reserves). Iron ore deposits are of various types and complex ore types. The proven iron ore resources in China are 38-41 billion tons. The main types of iron ore are: Anshan-type sedimentary metamorphic iron ore, mainly magnetite ore, with a grade of 30% to 35% and a resource of 20 billion tons. Among them, 12 billion tons in the Anben area, 5 billion tons in the eastern part of the country, and about 3 billion tons in Shanxi, Beijing, western Yunnan and Anhui. Panzhihua formula magma profiled iron, magnetite, iron ore mainly titanium, grade 30% to 35%, mainly in the area of Sichuan Xichang to ferry, resources of 70 million tons. Daye-style and Yuxing-type contact metamorphic iron ore, mainly magnetite ore, grade 35% to 60%, mainly distributed in the middle and lower reaches of the Yuxing, Laiwu and Yangtze Rivers, with a resource of 5 billion tons, iron content > 45% of the rich ore is more. The Meishan-type shale-type iron ore is mainly composed of magnetite ore, with a resource of 1 billion tons and a grade of 35% to 60%. Xuanlong ningxiang type and deposition type iron to hematite-based, low-grade, high phosphorus-containing, refractory, and mainly in Xuanhua WEST HUBEI area, the amount of resources 30 to 50 tons. The Dahongshan and Mengku-type marine volcanic sedimentary metamorphic iron deposits are mainly magnetite ore with a grade of 35% to 60%, mainly distributed in Yunnan and Xinjiang, with a resource of 2 billion tons. There are many symbiotic and associated iron ore in iron ore, accounting for 17.9% of the total resources. Typical deposits include Panzhihua Iron Mine, Baiyun Obo Iron Mine, Daye Iron Mine, etc. The common (concomitant) raw components are vanadium , titanium and rare earth. , copper, etc.
At present, the utilization rate of China's siderite or brown iron ore is extremely low, and most of it is not recycled or not exploited at all. The most used ore in China is the Anshan-type sedimentary metamorphic iron ore. However, some of the ore are not yet effectively exploited due to the fine grain size and complex mineral composition. Xuanlong type and Ningxiang type iron ore account for about 12% of China's total iron ore reserves, accounting for 30% of China's red iron ore reserves. Due to the fine grain size of ore, the ore structure is braided and contains high levels of harmful impurities. Currently not yet exploited. Iron header Baiyunebo large complex multi-metal symbiotic iron, iron in addition, there are rare, niobium and other metals, elements 71 have been found, more than 170 kinds of minerals. Baotou Steel currently uses a weak magnetic-strong magnetic-flotation process to recover iron and rare earth. The iron concentrate obtained by this process has a low grade. The main reason is that iron concentrate contains silicate minerals, especially potassium and sodium. The high content seriously affects the smelting effect of the blast furnace; the recovery rate of rare earth minerals is low, the total recovery rate is less than 20%, and other valuable elements are not recovered.
Progress in iron ore technology in China
Siderite ore dressing technology
Because the theoretical iron grade of siderite is low, and it is often symbiotic with calcium, magnesium and manganese , the iron ore grade is difficult to reach more than 45% by physical beneficiation method, but it is burnt due to burning. And greatly improve the grade of iron concentrate. The more economical beneficiation method is re-election and strong magnetic separation, but it is difficult to effectively reduce the impurity content in iron concentrate. The strong magnetic separation-flotation combined process can effectively reduce the impurity content in iron concentrate. Maanshan Mine Research Institute studied the recovery and utilization of iron carbonate minerals in Taiyuan Iron and Steel Mine tailings. The iron carbonate is mainly composed of iron-magnesium carbonate-like series of minerals, and adopts a screening-strong magnetic separation-flotation combined process. The final iron concentrate grade is above 35% (iron grade after roasting) Above 51%), the SiO 2 content falls below 4%, and the quaternary alkalinity reaches 3 or more. It is both an iron raw material and a property of iron-making flux, and the metallurgical performance can be greatly improved by mixing and smelting with an acidic iron concentrate. Neutral or reductive magnetization roasting is a most primitive and reliable siderite ore dressing technology. Although the processing cost is high, with the shortage of iron ore resources and the increase of value, the research and application of this technology is gradually heating up. Block iron ore (15-75mm) is fired in a shaft furnace. For the roasting of powdered iron ore, although technical studies including boiling furnaces and rotary kiln roasting have been carried out, there has not been a large-scale production practice. In recent years, domestic research institutes have re-enhanced research on powdered iron ore burning technology, and proposed the so-called "flicker roasting technology", which uses rotary kiln roasting technology to rapidly roast roasting of powdered iron ore. . The technology was applied to the iron ore rich in iron carbonate minerals such as the strong magnetic concentrate of the Daye Iron Mine of Wuhan Iron and Steel Group, the strong magnetic middle mine of Jiuquan Iron and Steel Co., Ltd., and the Daxigou Iron Mine of Shaanxi Province. The grade of iron concentrate can be improved to 55% to 60%.
Limonite ore dressing technology
Since limonite is rich in crystal water, it is difficult to achieve 60% iron concentrate grade by physical beneficiation method, but the iron concentrate grade is greatly improved after calcination due to large burning loss. Since limonite is easily muddy during the crushing and grinding process, it is difficult to obtain a high metal recovery rate. The beneficiation process of limonite includes reduction magnetization roasting-weak magnetic separation, strong magnetic separation, re-election, flotation and a combined process. In the past, the beneficiation process with industrial production practice has strong magnetic separation, strong magnetic separation-positive flotation, but it is subject to the characteristics of limonite ore (very easy to muddy) and strong magnetic separation equipment (the recovery rate of -20μm iron mineral is poor). ) and the limitation of flotation reagents, the selection index is poor, and the reduction magnetization calcination-weak magnetic separation process has higher ore dressing cost, so this type of iron ore is basically not effectively utilized. In order to improve the recovery of fine-grained iron minerals, semi-industrial tests have been carried out to do, flocculation kiln roasting technology of fuel and reducing agent with brown coal - strong magnetic separation technology industries, such as testing, have achieved good results . For example, Maanshan Mine Research Institute conducted a selective flocculation-strong magnetic separation technology industrial test on Jiangxi Tiekeng limonite ore. The results show that the recovery rate of iron metal can be increased by more than 10 percentage points, but due to flocculation equipment and selective flocculation process conditions. The control has not yet passed and has not been industrialized. In recent years, with the successful development of new high-gradient magnetic separators and new high-efficiency reverse flotation reagents, the strong magnetic separation-reverse flotation-baking combined process has made significant progress in sorting limonite ore, that is, through strong magnetic- Reverse flotation to obtain iron concentrate with low impurity content, and then to produce pellets by ordinary roasting or mixing with magnet concentrate can greatly improve the iron grade of the product. The experimental results of the iron ore of Jiangxi Tiekeng limonite by Maanshan Mine Research Institute show that the iron grade of reverse flotation concentrate can reach 57%, the SiO 2 content can be reduced to 5%, and the iron grade of the product after roasting can be More than 64%, compared with the roasting, magnetic separation, reverse flotation combined process, the production cost has dropped significantly, making this type of iron ore have mining and utilization value.
Composite iron ore beneficiation technology
Most of China's iron ore contains more than two kinds of iron minerals, the more the types, the worse the selectivity. Among these iron ore, symbiotic iron ore, such as hematite, mirror iron ore, goethite, siderite, limonite, etc., are more difficult to select. The conventional beneficiation process can be used to sort the iron ore, but when the ore contains more siderite or limonite, the iron concentrate grade and recovery rate are difficult to increase. At present, the best beneficiation process is a combination of weak magnetic-strong magnetic-flotation and magnetization roasting-reverse flotation. The Maanshan Mine Research Institute used a strong magnetic-positive flotation process for the powder ore (-15 mm) of the wine ore (including mirror iron ore, siderite and limonite), and showed that it was single strong with the field. Compared with the magnetic separation process, the iron concentrate recovery rate is increased by 2 percentage points (more than 49%, more than 58% after burning), while the iron metal recovery rate is increased by more than 12 percentage points (more than 74%). In addition, combined with the characteristics of the roasting concentrate of Jiugang, avoiding the multi-section magnetic separation method and the influence of residual magnetism, the impurities in the roasting magnetic separation concentrate were reduced by the re-grinding-reverse flotation and re-grinding-weakening-reverse flotation process. Content test. Under the conditions of the selected particle size of 82%-75μm, the impurity content of SiO 2 +Al 2 O 3 was reduced from 11% to less than 6%, and the grade of concentrate iron was increased from 55% to over 59%. Good grade of more than 60%), and the recovery rate of miscellaneous operations reached 94%.
Multi-metal symbiotic iron ore beneficiation technology
China's difficult to choose polymetallic symbiotic iron ore mainly includes Baotou Bayan Obo rare earth iron ore and Panzhihua vanadium-titanium magnetite. This type of iron ore is characterized by complex mineral composition and symbiotic relationship, thus resulting in low iron ore concentrate selection index. And the recovery rate of the associated valuable elements is low. Among them, Baotou Bayan Obo rare earth iron oxide ore is particularly difficult to choose. At present, Baotou Steel Concentrator uses the weak magnetic-strong magnetic-reverse flotation process for iron selection. Its strong magnetic concentrate mainly contains minerals such as easy-floating fluorite , carbonate and iron-containing silicic acid. Salt minerals. For easy-floating fluorite, carbonate and other minerals, Baotou Steel Concentrator uses a weak alkaline anti-flotation production process using water glass as an inhibitor and GE-28 as a collector , and it is difficult to float. Silicate minerals have not been effectively separated, resulting in lower iron concentrate grades (below 55%) and high levels of potassium and sodium in concentrates. The research results of the Ma'anshan Mine Research Institute prove that for the strong magnetic concentrate sample taken from the site with a fineness of -0.076mm and about 88% and an iron grade of about 43.5%, an optimized combination of reverse flotation is used. Positive flotation process, and adopting new high-efficiency collector in positive flotation operation, the whole process flotation closed-circuit test index is about 53% concentrate yield, 62% concentrate iron grade, and recovery rate about 75%. At the same time, harmful substances such as P, K 2 O, Na 2 O, and F have a large reduction, which opens up an effective new way to improve the selection index of this type of iron ore. In addition, for the Panzhihua vanadium-titanium magnetite ore, the fine screening-re-grinding process and the high-gradient magnetic-flotation process were used to select titanium, and the various indexes of the ore were significantly improved.
Oolitic hematite ore dressing technology
The braided hematite inlay is very fine and often symbiotic or intertwined with siderite, chlorite and phosphorus-bearing minerals. Therefore, braided hematite is the most difficult iron ore currently recognized at home and abroad. Types of. In the past, China has carried out a large number of ore dressing experiments on this type of iron ore. Among them, the selection index of the reduction roasting-weak magnetic separation process is relatively good, but because of its technical difficulty, it requires ultra-fine grinding, and the current conventional It is difficult to efficiently recover -10 μm fine-grained iron minerals from mineral processing equipment and pharmaceuticals, so this type of iron ore resources is basically not utilized. With the gradual reduction of available iron ore resources in China, the high-efficiency beneficiation technology for the study of braided hematite ore has highlighted its importance and urgency. Relevant preliminary research results prove that ultrafine grinding-selective flocculation (agglomeration)-strong magnetic separation or flotation, reduction roasting-ultrafine grinding-selective flocculation (agglomeration)-weak magnetic separation or flotation Or the combination of smelting and smelting has shown its superiority.
High-sulfur and phosphorus iron ore beneficiation technology
Most of China's iron ore contains harmful impurities such as sulfur and phosphorus. Especially for iron ore rich in pyrrhotite, fine-grained apatite or collophanite, the iron concentrate is extremely difficult to remove. The common processes for desulfurization of iron concentrates are flotation and roasting, while the latter is costly and environmentally polluted. Therefore, the main direction of research is to strengthen flotation. Maanshan Mine Research Institute has developed a high-efficiency separation process of magnetite and pyrrhotite with high-efficiency activator as the key technology through a large number of experimental studies. Through the research and application of sulfur reduction in a variety of pyrrhotite-type high-sulfur magnetites at home and abroad, it is proved that compared with conventional flotation, the iron content of iron concentrate can be reduced by 0.5%, and the important thing is iron. The sulphur content of the concentrate can meet the requirements of subsequent users. A large number of research results prove that the phosphorus removal of iron concentrate can be magnetic separation, reverse flotation, selective flocculation (agglomeration), acid leaching, chlorination roasting - acid leaching, bioleaching and its combined processes, among which magnetic separation - Reverse flotation, selective flocculation (agglomeration)-reverse flotation combined process is more economical, chlorination roasting-acid leaching process has better phosphorus removal effect, but the cost is higher, and bioleaching is the future development direction.
Future development direction
In recent years, China's complex refractory iron ore beneficiation technology has made gratifying progress, but due to the complexity of China's iron ore types and the low level of comprehensive mineral processing technology, the utilization rate of complex refractory iron ore resources in China is still relatively low. Even some minerals are basically not used. Therefore, in the future, China should strengthen the research work in the following aspects: research and application of efficient multi-grinding and grinding technology and equipment; strengthening of high-efficiency roasting technology and equipment research, focusing on fine-grain (powder) material roasting technology and equipment; Strengthening high-efficiency fine-grain grinding grading process and equipment research; strengthening high-efficiency fine-grain iron ore beneficiation process and equipment research, focusing on deep research on selective flocculation (agglomeration)-reverse flotation combined process, equipment and automatic control, research selection Combining metallurgical process and bioleaching process, researching high-efficiency magnetic separation machine and flotation equipment for high-efficiency recovery of fine-grained iron minerals; developing high-efficiency minerals suitable for iron minerals and iron-containing silicate minerals, sulfur, phosphorus and other harmful impurities Separated flotation agent and high-efficiency dispersant of fine-grained iron ore, flocculation (agglomeration) agent, flotation agent, and the like.
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