Progress in mineral processing technology of complex refractory iron ore in China

Sustained and stable development of steel industry urgently needs a stable, adequate, high-quality iron ore raw material supply. In the 21st century, with the recovery of the world economy and the acceleration of structural adjustment, especially the rapid development of China's economy, China's steel industry continues to grow at a high rate. China's total steel output has ranked first in the world. 220 million tons, the steel output in 2004 exceeded 270 million tons. With the continuous expansion of China's steel industry, China has surpassed Japan to become the world's largest importer of iron ore. In 2003, it imported 150 million tons of iron ore. In 2004, it imported 208 million tons of iron ore. In 2005, it imported iron ore. Stone reached 275 million tons. The quantity of imported iron ore has accounted for more than half of the total demand for finished iron ore in China. Due to the increase in the supply and demand gap of iron ore, the price of iron ore at home and abroad has skyrocketed, the sea freight rate has risen sharply, and the transportation system is extremely tight. The increase in dependence on iron ore imports has become a major hidden danger to the economic security of China's steel industry. Therefore, there is an urgent need to rely on technological advances to maximize the use of existing domestic iron ore resources, especially complex refractory iron ore that cannot be utilized due to current mineral processing technology limitations, and iron that is currently available but has low quality and utilization. Ore, increase reserves and increase efficiency, fully exploit the production potential of existing iron ore mines, increase the self-sufficiency rate of iron ore, ease the pressure on imported ore, and maintain a stable, sufficient, high-quality supply of iron ore raw materials to ensure the continued stability of the steel industry development of.

I. Development and utilization of iron ore resources and complex refractory iron ore

The main characteristics of China's iron ore are “lean”, “fine” and “hetero”. The average iron grade is 32%, which is 11% lower than the world average. Among them, 97% of iron ore needs beneficiation treatment, and the proportion of complex and difficult to choose red iron ore is large (about 20.8 percent of iron ore reserves). Iron ore deposits are of various types and complex ore types. The proven iron ore resources amounted to 38-41 billion tons.

The main iron ore types are

1 Anshan-type sedimentary metamorphic iron ore is mainly composed of magnetite ore, with a grade of 30-35 percent 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 the provinces and cities of Shanxi, Beijing, western Yunnan and Anhui;

Panzhihua formula â‘¡ is different magmatic ore, magnetite, iron ore mainly titanium, grade 30 percent to 35 percent, mainly in Sichuan Xichang crossing area, an amount of resources 7000000000 T;

3 Daye-style and Yuxing-type contact metasomatic iron ore, mainly magnetite ore, grade 35-60 percent, mainly distributed in the middle and lower reaches of the Qianxing, Laiwu and Yangtze Rivers, with a resource of 5 billion tons. More iron-rich minerals with an iron content greater than 45 percent;

4 Meishan-type porphyry iron ore, mainly magnetite ore, with a resource of 1 billion tons and a grade of 35-60 percent;

⑤ Xuanlong formula and ningxiang deposition type iron to hematite-based, low-grade, high phosphorus-containing, refractory, and mainly in Xuanhua WEST HUBEI area, resources 3-5 billion T;

6 Dahongshan-type and Mengku-type marine volcanic sedimentary metamorphic iron ore, mainly magnetite ore, grade 35-60 percent, mainly distributed in Yunnan and Xinjiang, with a resource of 2 billion t. There are many symbiotic and associated iron ore in iron ore, accounting for 17.9 percent of the resources. Typical deposits include Panzhihua Iron Mine, Bayan Obo Iron Mine, Daye Iron Mine, etc. The total (concomitant) raw components are vanadium and titanium. , rare earth, copper, etc.

At present, the utilization rate of China's siderite or brown iron ore resources is extremely low, most of which are not recycled or not exploited at all; the largest ore selected in China is Anshan-type sedimentary metamorphic iron ore, but some of them are also embedded. The fine grain size and complex mineral composition have not been effectively developed and utilized. For example, the Jiajiabaozi iron ore mine of Benxi Iron and Steel Co., Ltd. is a poor magnetite ore with a reserve of about 150 million tons. Due to the fine grain size and complex structure of the ore, it has not yet been developed and utilized: The Yuanjiacun iron ore mine in the Taiguyu mining area of ​​Shanxi Province, by the end of 1990, has accumulated and retained reserves of 894.5 million tons. The ore types are classified into quartz type and amphibole type, with oxidized ore and primary ore. The size of the ore inlay is fine. The particle size of magnet and hematite is 75-80% less than 0.043 mm, of which quartz-type iron ore is 20-0.010 mm, and amphibole-type iron ore is 100%. 40-0.010mm. The ore grade iron is lower, which is a complex and difficult to choose iron ore. The Dahongshan Iron Mine of Kunming Iron and Steel Co., Ltd. is a magnetite-hematite mixed ore with a reserve of about 460 million tons, of which nearly 200 million tons, hematite, due to the fine grain size of the ore, the composition of the gangue mineral is more complicated. The ore dressing index is low, and it is also a complex and difficult to choose iron ore. Xuanlong-style and Ningxiang-type iron ore accounts 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 harmful The impurity phosphorus is high and has not yet been 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, ores many types, wherein the rare earth reserves in the world first place. Since the ore dressing research on this ore, since the 1960s, a number of research institutes at home and abroad have cooperated with Baotou Steel to carry out a large number of experimental research work. Up to now, weak magnetic-strong magnetic-flotation recovery of iron and rare earth isna The process flow, this process embodies the guiding principle of “iron-based, comprehensive recovery of rare earth minerals”, which has made a major breakthrough in the beneficiation technology of Baiyun Obo Iron Mine of Baotou Steel. The technology is constantly improving. At present, from the technical point of view, the iron concentrate obtained by this process has a low grade. The main reason is that the iron concentrate contains silicate minerals, especially the high content of potassium and sodium, which seriously affects the blast furnace smelting. effect. The recovery rate of rare earth minerals is low, the total recovery rate is less than 20%, and other valuable elements are not recovered.

Second, China's refractory iron ore dressing technology progress

(1) 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 percent by physical beneficiation method, but it is burnt after roasting. Larger and greatly improved iron concentrate grade. 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 the iron concentrate, and the iron concentrate is still a high-quality ironmaking raw material after roasting. We have done a lot of research work on the recycling of iron carbonate minerals in Taiyuan Iron Mine tailings. The occurrence of iron carbonate is mainly based on the iron-magnesium carbonate-like series of minerals. It is recommended to use a screening-strong magnetic separation-flotation combined process, and the final iron concentrate grade is more than 35 percent. After calcination, the iron grade is more than 51%), the SiO2 content is reduced to less than 4%, and the quaternary alkalinity is more than 3, which is both an iron raw material and a property of iron-making flux, and is mixed with an acid iron concentrate. It can greatly improve the metallurgical performance, and the annual budget benefit can reach tens of millions of yuan. Neutral or reductive magnetization roasting-weak magnetic separation is the 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 gradually tends to Warm up. Block iron ore (15-75mm) has long-term successful production practice using shaft furnace roasting. However, for the roasting of powdered iron ore, although a lot of technical research including boiling furnace and rotary kiln roasting has been carried out, There have been no large-scale production practices. In recent years, relevant research institutes in China have re-enhanced research on the roasting technology of powdered iron ore, and proposed the so-called "flicker roasting technology", which uses the rotary kiln roasting technology to rapidly roast the 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 percent.

(2) Limonite ore dressing technology

Since limonite is rich in crystal water, it is difficult to achieve a 60% iron concentrate grade by physical beneficiation method, but the iron concentrate grade is greatly improved after calcination due to large burning loss. In addition, since limonite is easily muddy during the crushing and grinding process, it is difficult to obtain a high metal recovery rate. The limonite beneficiation process 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 due to the properties of limonite ore (very easy to mud), strong magnetic separation equipment (recovery rate of -20μm iron minerals) Poor) and flotation reagents have poorer selection criteria, while reductive magnetization roasting-weak magnetic separation process has higher ore dressing costs, so this type of iron ore is basically not effectively utilized. In order to improve the recovery of fine iron minerals, plant tests was performed using lignite as reducing agent and fuel kiln roasting technique, flocculation - intensity magnetic separation and other industrial test, better results are achieved . We 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%, but the control of flocculation equipment and selective flocculation process conditions has not yet passed. Failed to industrialize. In the past two 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, and still be a high-quality ironmaking raw material. Our experimental results on iron ore in Jiangxi Tiekeng limonite show that the iron grade of reverse flotation concentrate can reach 57%, the SiO2 content can be reduced to about 5 percent, and the iron grade of the product after roasting can be More than 64%, compared with the combined roasting, magnetic separation, and reverse flotation processes, the production cost has dropped drastically, making this type of iron ore economically exploitable and will be put into production in 2005.

(III) Composite iron ore beneficiation technology

Most iron ores in China contain more than two kinds of iron minerals, and the more varieties, the worse their 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. To this end, a large number of related research work has been carried out in recent years, and the more prominent research results are combined processes such as weak magnetic-strong magnetic-flotation and magnetization roasting-reverse flotation. For example, our research on the use of strong magnetic-positive flotation process for fine ore-positive flotation of wine ore (including mirror iron ore, siderite and limonite) shows that it is a single strong magnetic field used in the field. Compared with the selection process, the iron concentrate grade is increased by 2 percentage points (up to 49 percent and more than 58 percent after burning), while the iron metal recovery rate is increased by more than 12 percentage points (more than 74 percent). ). In addition, closely combined with the characteristics of the roasting concentrate of Jiugang, avoiding the multi-stage magnetic separation method and the influence of residual magnetism, the re-grinding-reverse flotation and re-grinding-weakening-reverse flotation process is used to reduce the roasting magnetic separation concentrate. Test for impurity content. Under the conditions of 82-75μm particle size, the impurity content of SiO2+Al2O was reduced from 11% to less than 6 percent, and the concentrate grade was increased from 55 percent to 59 percent. Above (the iron grade after burning is more than 60%), the recovery rate of the miscellaneous work is up to 94%.

(4) 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, resulting in iron concentrate sorting index. The recovery rate of low and co-contributing valuable elements is low. Among them, Baotou Bayan Obo rare earth iron oxide ore is particularly difficult to choose. At present, the iron oxide ore mine of Baotou Steel Concentrator uses the weak magnetic-strong magnetic-reverse flotation process for iron selection. The strong magnetic concentrate is mainly composed of easy-floating fluorite , carbonate and other minerals. Iron silicate minerals. For the mineral-coated blast furnaces such as fluorite and carbonate, it has formed a mature method through decades of research and production practice, namely, water-glass as an inhibitor and GE-28 as a collector. The anti-flotation production process, and the difficult-to-float iron-containing silicate minerals have not been effectively separated, resulting in a lower iron concentrate grade (below 55 percent) and a high potassium content in the concentrate. For the strong magnetic concentrate sample with the fineness of -0.076mm accounting for about 88% and the iron grade of 43.5%, adopting the optimized combination of reverse flotation-positive flotation process, and in the positive Flotation operation adopts new high-efficiency collector. The whole process flotation closed-circuit test index is about 53% of concentrate production rate, 62% of concentrate iron grade, and about 75 percent recovery rate. At the same time, harmful elements such as P The reduction of K2O, Na2O and F is very large, opening up an effective new way to improve the selection of iron ore. In addition, for the Panzhihua vanadium-titanium magnetite ore, the fine screening-re-grinding process and the high-gradient strong magnetic-flotation process were used to select titanium, and the various indexes of the ore were significantly improved.

(5) 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, a large number of ore dressing experiments have been carried out on this type of iron ore. The selection index of the reduction roasting-weak magnetic separation process is relatively good, but because of its technical difficulty, it requires ultrafine grinding, and the current conventional beneficiation equipment It is difficult to efficiently recover -10 μm of fine-grained iron minerals, and thus this type of iron ore resource 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-superfine grinding-selective flocculation (agglomeration)-weak magnetic separation or flotation and other high-efficiency beneficiation processes Or the combination of smelting and smelting has shown its superiority.

(6) 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. Our company has developed a high-efficiency separation process of magnetite and pyrrhotite with high-efficiency activator as the key technology. 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 one is iron concentrate. The sulfur content 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.

Third, the conclusion

Through a large number of mineral processing technology research and research, in recent years, China's complex refractory iron ore beneficiation technology has made gratifying progress, but due to the complex nature of China's iron ore and the low level of comprehensive mineral processing technology, China's complex and difficult to choose The utilization rate of iron ore resources is extremely low, and even some minerals are basically not utilized. Therefore, technical research in the following aspects should be strengthened in the future:

(1) Research and application of efficient multi-grinding and grinding technology and equipment;

(2) Strengthen the research on high-efficiency roasting technology and equipment, focusing on fine-grained (powdered) material roasting technology and equipment;

(3) Strengthening high-efficiency fine-grain grinding grading process and equipment research;

(4) Strengthen the research on high-efficiency fine-grain iron ore beneficiation process and equipment, focusing on deep research on selective flocculation (agglomeration)-reverse flotation combined process, equipment and automatic control, research on combined metallurgy process and bioleaching process, research Strong magnetic separator and flotation equipment for efficient recovery of fine-grained iron minerals;

(5) Develop a flotation agent suitable for the high-efficiency separation of iron minerals and iron-containing silicate minerals, sulfur, phosphorus and other harmful impurities, as well as high-efficiency dispersing agent, flocculation (agglomerating agent), floating of fine-grained iron ore. Choose medicines, etc.

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