Discussion on Feasibility of Iron Ore Resources Investigation and Magnetic Separation Technology in China to Improve Iron Ore Grade

Mineral resources are a valuable asset of human society, human development is an essential material basis for national economic development plays an important role in the iron and steel products and iron ore resources, mineral resources are used in a maximum amount of metal. Most of China's iron ore resources are poor ore, with low grade, difficult mineral processing and high production cost, which restricts the development of the steel industry. Magnetic separation technology is one of the most important methods to improve iron ore grade. How to improve China's magnetic separation technology, improve iron ore grade, and make full use of China's poor ore resources is the only way for China to develop mining. This report introduces the characteristics and utilization of iron ore resources in China and the feasibility of magnetic separation technology to enhance the grade of iron ore and the prospect of magnetic separation technology in iron ore applications.

I. Overview of China's iron ore resources

(1) Iron ore finds that resource reserves continue to rise

As of the end of 2009, the national iron ore identified resource reserves were 64.6 billion tons, of which the basic reserves were 21.3 billion tons and the resources were 43.3 billion tons. Most of the identified iron ore reserves in China are poor ore, rich iron ore. The reserves of Ming resources are 1.02 billion tons, accounting for 1.6% of the total proven reserves of iron ore. In 2009, the national iron ore identified a net increase in resource reserves of 609 million tons.

In recent years, China's iron ore exploration has progressed significantly. In the past four years, China has invested 2.3 billion yuan in iron ore exploration and 1.62 million meters of drilling work, which is equivalent to 6.3 times and 4.8 times of the total input and total drilling volume from 1989 to 2003, respectively. China's iron ore exploration has obtained a number of inspiring prospecting achievements and significant progress, and found a number of aeromagnetic anomalies with prospecting significance in key areas such as Dongtianshan, Beishan, Southwest Sanjiang, Daxinganling, Inner Mongolia, and Daye, Hubei; A group of hidden iron ore deposits were discovered in Wutai, Hengshan, Jidong, Liaoning, Anshan, Luxi, Anhui, and other places where iron ore resources were concentrated. Newly discovered Xinjiang in the western part of the iron ore exploration work A number of prospecting targets such as Chagangor and Ruo Dimu; and important exploration results in the deep and peripheral areas of a group of known iron deposits such as Qian'an in Hebei, Daye in Hubei, Gongchangling and Yanzishan in Liaoning, added A batch of resource reserves.

Table 1 China iron ore resource reserves statistics

(2) Iron ore resources are widely distributed and relatively concentrated

A major feature of the distribution of iron ore resources in China is that it is relatively concentrated locally, and the whole is "the girl is scattered." The proven 59.3 billion tons of iron ore resources are distributed in more than 700 counties and cities (flags) in 29 provinces and cities across the country, with a total of 1982 mining areas. The proportion of zoning reserves is 26% in Northeast China, 26% in North China, 18% in Southwest China, 14% in East China, 10% in Central South, and 6% in Northwest China. Among them, Liaoning, Hebei, and Sichuan account for 48% of the country's total reserves, plus Shaanxi, Anhui, and Hubei, and six provinces account for 65%. There are 101 large-scale mining areas with reserves of more than 100 million tons, with total reserves accounting for 68.1%; 470 medium-sized mining areas with reserves of 0.1-100 million tons, total reserves accounting for 27.3%; and 1327 small mining areas with reserves less than 10 million tons, total reserves Accounted for 4.6%. Under the condition that the overall distribution of iron ore resources in China is very scattered, it is partially concentrated in the top ten mining areas. The total reserves of the top ten mining areas account for 64.8% of the total reserves. Among them, the An-Ben mine accounted for 23.5% of the total reserves, the Yan-Mi mining area was 11.8%, the Pan-West mining area accounted for 11.5%, the Wu (Taishan)-Lu (Liangshan) mining area accounted for 6.2%, and the Ning-Yu mining area accounted for 4.12%. Bao-Bai mining area accounts for 2.2%, Luzhong mining area accounts for 1.74%, Yuxing mining area accounts for 1.6%, Edong mining area accounts for 1.34%, and Hainan mining area accounts for 0.8%. This kind of overall scattered and localized distribution characteristics has prompted the development and utilization of iron ore resources in China to adopt a pattern dominated by large and medium-sized mines, supplemented by local small and medium-sized mines, and coexisting private groups.

(3) There are many types of iron ore deposits, and the type of ore is complicated.

The type of iron ore already in the world has been discovered in China. The types of deposits with industrial value are mainly Anshan-type sedimentary metamorphic iron ore, Panzhihua magmatic vanadium- titanium magnetite, Daye-type skarn-type iron deposit, Meishan-type volcanic-type iron ore and Bayan Obo hydrothermal rare earth iron. mine. The main ore types are: magnetite ore, which holds 55.4% of the country's total reserves. The ore is easy to be selected and is the main type of ore currently mined. Vanadium-titanium magnetite ore, with reserves of 14.1% of the country's total reserves, is relatively complex and is one of the most important types of ore currently mined. "Red mine", which is the collective name of hematite, siderite, limonite, mirror iron ore and mixed ore, such iron ore is generally difficult to choose, and some mineral processing problems have been broken, but in general, mineral processing The process is complex and the production cost of concentrate is high. Multi-component co-(concomitant) pig iron ore accounts for a large proportion. The multi-component total (concomitant) raw iron ore reserves account for about one-third of the total reserves. The large and medium-sized iron ore districts involved include Panzhihua, Dumiao, Baiyun Obo, Daye and other mining areas. The main (companion) raw components are vanadium, titanium, rare earth and antimony . According to the iron ore type, magnetite (Fe ₃ O ₄ ) accounts for 35% of the reserves, vanadium titano-magnetite (FeTiO ₃ FeV ₂ O ₅ ) accounts for 17%, and hematite (Fe ₂ O ₃ ) accounts for 21%. %, limonite (nFe ₂ O ₃ nH ₂ O) accounts for 1%, siderite (Fe(CO ₃ ) accounts for 2%, and mixed ore accounts for 24%).

(4) The grade of iron ore is low, and the majority of the poor ore

China's iron ore identified most of its reserves as poor ore. The average grade of identified iron ore reserves in China is about 33%, which is 11% lower than the world iron ore grade. Compared with iron ore in Brazil and Australia. The grades vary greatly. The 2,974 iron ore districts have been identified, with 1,828 magnetites, 1,753 small and medium-sized mines, and only 121 large mines. The iron-rich ore reserves that can directly enter the furnace with an average iron content of about 55% account for only 2.7% of the national reserves, and form a certain mining scale. The iron-rich ore that can be mined separately is even less. The ore must be mineralized to be used in the blast furnace. A total of about 1.48 billion tons of rich iron ore reserves have been discovered nationwide. It can be seen from the tonnage-grade distribution histogram of China's iron ore mines that most of the iron ore grades in China are between 25% and 40%, accounting for 81.2% of the identified iron ore reserves in China; the grade is at 25%. The following identified resource reserves account for 4.6% of the total identified iron ore reserves in China; the identified resource reserves between 40% and 48%, accounting for 11.5% of China's total iron ore reserves; the grade is greater than 48%. The iron ore mine has identified the reserves of resources, accounting for only 1.9% of the identified reserves of iron ore in China.

Table 2 China's iron ore resource tonnage - grade distribution map

(5) It is difficult to use iron ore for a long time, which limits the supply of domestic iron ore. It is difficult to use iron ore reserves of about 19.4 billion tons, of which industrial reserves are about 5.7 billion tons. These iron ore mines are generally difficult to collect, difficult to select, difficult to comprehensively utilize multiple components, and have low grades of iron ore, thin ore bodies, complicated mining conditions and hydrogeological conditions, inconvenient transportation in mining areas, difficult to plan and mine ore mining. Economic indicators are unreasonable, minerals are natural environmental protection zones, and so on. With the improvement of technical standards and the improvement of economic conditions, iron ore will be gradually developed and utilized, and iron ore reserves will be gradually reduced.

Second, the distribution of iron ore in various regions of China

China's iron ore resources are rich in lean ore, and lean ore reserves account for 80% of total reserves; there are more complex ores with multi-element symbiosis. In addition, the ore body is complex; some of the lean iron deposits are made of hematite and the lower part is magnetite.

(1) Iron ore in the Northeast

The northeastern iron ore mine is mainly the Anshan mining area. It is currently the largest mining area in China. The large ore bodies are mainly distributed in Anshan, Liaoning Province (including Dashan, Cherry, East Anshan, Gongchangling, etc.) and Benxi (male). Fen, Shantoushan, Tongyuanbao, etc.), some deposits are distributed near Tonghua, Jilin Province. Anshan Mining Area is the main raw material base of Anshan Iron and Steel and Benxi Steel. The main features of the ore in the Anshan mining area: except for very few rich ore, about 98% of the reserves are lean ore, and the iron content is 20-40%, with an average of about 30%. It must be processed by mineral processing, and the iron content after selection can reach more than 60%. The ore minerals are mainly magnetite and hematite, and some are pseudo-hematite and semi-artificial hematite. The structure is dense and hard, the gangue is evenly distributed and dense, the ore dressing is difficult, and the ore is less reductive. Most of the gangue minerals are composed of quartz stone, and SiO2 is 40-50%. However, the Benxi Tongyuanbao iron ore is an autolytic ore with a basicity (Ca+Mg/SiO2) of 1 or more. And containing 1.29 - 7.5% Mn may be used in place of manganese. The ore contains few S and P impurities. The Benxi Manfen Iron Mine contains very low P and is a good raw material for smelting high quality pig iron. Huadian City of Jilin Province is an important iron ore production base in Jilin Province, with the total number ranking second in the province. The resource reserves are 1221.84 million tons, and more than 99.9% are distributed in the Laoniugou iron deposit. The Laoniugou iron deposit consists of 12 major ore sections and 174 ore bodies. At present, it reserves 122,180,000 tons, iron grade average 30.5--35.11% sulfur <0.10%, a phosphorus-containing <0.05%, processing performed by the experiment proved CRIMM Metallurgical unit, iron grade can be obtained 68.5% and 69.5% of the iron fine powder can also obtain a part of high-purity iron fine powder of 71.5% or more. The remaining iron ore resources are distributed in the Honey Top iron ore mines in Changshan and Badaohezi Towns. The reserves are 0.2 million tons and the iron grades are 40% and 42%.

(2) Iron ore in North China

It is mainly distributed in the areas of Wu'an, Mine Village, etc. in Xuanhua, Qian'an and Anhui, Xingtai, Hebei Province, and Inner Mongolia and Shanxi. It is the raw material base of steel plants such as Shougang, Baotou Steel, Taigang and Handan, Xuanhua and Yangquan. The ore in the Qianyu mining area is Anshan-type lean magnetite, containing acid gangue, with less S and P impurities, and good ore selectivity. The Yuxing mining area is mainly hematite and magnetite. The iron content of the ore is between 40% and 55%. The gangue contains certain alkaline oxides, and some ore contains high sulfur content.

(3) Iron ore in Central South China

The iron ore mines in Central South China are dominated by the Daye Iron Mine in Hubei. Others such as Xiangtan in Hunan, Anyang, Wuyang in Henan Province, Hainan Island in Jiangxi Province and Hainan Island in Guangdong Province have considerable reserves. These mines have become WISCO and Xianggang respectively. And the raw material supply base of the large and medium sized blast furnaces in the region. Daye Mining Area is one of the earliest mining areas in China, mainly including Tieshan, Jinshandian, Chengchao, Lingxiang and other mines. The ore is mainly iron- copper symbiotic ore, the iron mineral is mainly magnetite, followed by hematite, and the other is chalcopyrite and pyrite. The iron content of the ore is 40-50%, and the highest is 54-60%. The gangue minerals are calcite , quartz, etc. The gangue contains about 28% SiO, which has a certain solvent property (CaO/SiO2 is about 0.3), and the ore contains low P (generally 0.027%), and contains S high and fluctuates greatly (0.01). ~1.2%), and contains a color metal such as Cu (0.2 to 1.0%) and Co (0.013% to 0.025%). The ore is less reductive, and the ore is sintered and pelletized into a blast furnace.

(4) Iron ore in East China

The iron ore producing areas in East China are mainly from the Wuhu, Anhui Province, Nanjing, Jiangsu Province, the mountains, Nanshan, Gushan, Taochong, Meishan, Phoenix Mountain and other mines. In addition, Jinling Town in Shandong Province also has a considerable supply of iron ore resources. It is a raw material supply base for Maanshan Iron and Steel Company and other steel companies. The iron ore in the Suining mining area is mainly hematite, followed by magnetite, and some sulfide minerals such as chalcopyrite and pyrite. The grade of iron ore is relatively high, and some of the rich ore (including 50% to 60% of Fe) can be directly smelted into the furnace. Some of the lean ore should be selected by the ore dressing and sintered for a blast furnace. The ore has good reducibility. The gangue minerals are quartz, calcite, apatite and rutile. The ores contain higher S and P impurities (including P is generally 0.5%, up to 1.6%, and Meishan iron ore contains S on average 2% to 3). %), the ore has a certain solvent (such as the average alkalinity of the ore in the concave mountain and Meishan can reach 0.7 to 0.9), and some ores contain non-ferrous metals such as V, Ti and Cu.

(5) Iron ore in other areas

Iron ore in other regions In addition to the above-mentioned iron ore in various regions, China's southwestern regions and northwestern provinces, such as Sichuan, Yunnan, Guizhou, Gansu, Xinjiang, Ningxia, etc., are rich in different types of iron ore resources, namely Panzhihua Iron and Steel Co., Ltd. Raw material base for blast furnace production in large and medium-sized steel plants such as Chongqing Iron and Steel and Kunming Iron and Steel.

Table 3 Regional Statistics Table of Current Status of Domestic Iron Ore Resources Reserves

Third, the use of iron ore resources in China

(1) Current status of China's iron ore resource reserves

The development and utilization of iron ore resources in China is relatively high. There are about 550 mines officially produced and under construction in the country, including 57 open pit mines and 43 pit mines. Among the identified reserves, 511 mines can be planned and utilized, with a reserve of 17.418 billion tons of resources, accounting for 29% of the identified resource reserves, of which the basic reserves are 5.553 billion tons; 93 mines are available for selection, and their exploration level For: 57 detailed surveys, 16 preliminary surveys, 20 census evaluations, accounting for 12.23 billion tons of reserves, including industrial reserves of 7.281 billion tons, an average of 31.96% iron, 10.3 billion tons of magnetite, and 1.92 billion tons of hematite; 69 open-pit mining, with a reserve of 10.17 billion tons; 24 in the pit with a reserve of 2.065 billion tons.

The resources available for selection are mainly distributed in Sichuan, Liaoning, and Hebei, followed by Shanxi, Inner Mongolia, and Anhui. Among them, there are 73 mines with detailed surveys or preliminary surveys, which can be used for planning purposes. China's iron ore production base has been formed for a long time, and has now developed into ten major iron ore production bases: Anshan Yibenxi, Xichangyi Panzhihua, Jidongyi Miyun, Wutai Yiyi County, Baotou Yiyun Obo, and Edong , Ninglang, Jiuquan, Hainan Shilu, Yiyi Xingtai area.

(II) Overview of large and medium-sized iron ore districts in China

1. Anben mining area

At present, China's largest reserves and mining areas, iron ore is distributed in Anshan, Benxi and Liaoyang, Liaoning Province, iron ore deposits are almost all "Anshan" type sedimentary metamorphism. There are 53 large, medium and small iron deposits, of which 19 are large. A total of 10.65 billion tons of iron ore reserves are maintained.

The Anben mining area is the main raw material base for Anshan Iron and Steel and Benxi Steel. The iron ore is mainly composed of metamorphic hematite ore and magnetite ore, of which hematite is mainly composed, followed by magnetite ore, and some refractory ore with high chlorite and carbonate. The ore has iron grade. 28 to 32%, the average particle size of iron minerals is 74 to 37 microns. The inlay is fine in size and the type of ore is complex.

2. Hebei Iron Mine Area

Hebei Province is a large iron ore province with a total resource of 6.03 billion tons, of which the basic reserves are 4.67 billion tons. The iron ore reserves are second only to Liaoning Province, ranking second in the country. The iron ore resources are mainly distributed in the areas of Wu'an and Mine Village in Qian'an, Xuanhua and Xuntai, Hebei Province, and the raw material bases of Shougang, Tangshan Iron and Steel, Xuanhua and Yangquan.

(3) Bayan Obo Mining Area

It is located on the Wulanchabu grassland in central Inner Mongolia, 149km away from Baotou City. The proven iron ore reserves are 1.4 billion tons, forming four industrial deposits of main mine, east mine, west mine and Dongjie Leger. The mineralization range of the whole area is 48km2. Rare earth resources rank first in the world, accounting for 77% of the world's proven reserves, and more than 95% of China's total reserves.

(4) Panxi Vanadium and Titanium Magnetite Mine Area

Located in the southwestern part of Sichuan Province, including more than 20 counties and cities in Panzhihua and Liangshan Prefecture. The Panxi area is a huge cornucopia. The proven iron ore reserves are nearly 10 billion tons, accounting for 20% of the national iron ore reserves. It is the second largest iron ore base in the country after Saddle and Ben. Among them, vanadium-titanium magnetite is about 9.8 billion tons, accounting for 83.2% of the national vanadium-titanium magnetite reserves; 270 million tons of titanium dioxide reserves, accounting for 94.3% of the national reserves; and the reserves of vanadium pentoxide is nearly 20 million tons, accounting for the national reserves. 87% of the reserves of titanium resources rank first in the world, and the reserves of vanadium resources are comparable to those of the United States, which ranks fifth in the world.

Fourth, the main problems restricting the development of China's iron ore mining industry

(1) The characteristics of China's iron ore resources constrain the development of iron ore mining industry

China is a country with a relatively abundant total iron ore resource in the world, but the per capita resources are low, the quality of resources is poor, and the rich and poor are rich. The average grade of iron ore in the country is 33%, which is 11% lower than the average grade of iron ore in the world, 97.2% is poor ore, only 2.5% of the rich ore is more than 55%, and the recoverable reserves of rich ore are only 1.9%. Most of the iron ore is underground, which is difficult to mine. The above characteristics of China's iron ore resources determine the high cost and low profit of domestic iron ore development, which restricts the development of domestic iron ore.

(2) Low comprehensive utilization of resources and serious waste of resource development

Due to insufficient state investment in the mine and lax monitoring, the iron ore resources in China have been subjected to indiscriminate mining for a long time and suffered serious damage. Most non-state-owned mining enterprises basically do not carry out comprehensive recycling. What is more serious is that due to the chaotic mining order, the abundance of poverty, the thinning of mining, the mining of predatory land, the waste of resources, and the shortening of mine life. Some large-scale deposits have been unable to be developed on a large scale due to indiscriminate mining. The comprehensive utilization rate of mine tailings is extremely low, and development and utilization are still in the initial stage.

(3) China's lean iron ore mining technology needs to be further strengthened

Over the years, many achievements have been made in magnetite ore dressing technology and hematite beneficiation technology in China. Various weak magnetic field magnetic separation equipment and reverse flotation process have played a significant role in upgrading iron ore concentrate. . Under current technical conditions. The main industrial value is magnetite, hematite, limonite and siderite. Among them, the weak magnetic iron ore such as limonite, siderite and hematite is a difficult to choose ore. The mining and selection technology of difficult ore is still to be further developed.

V. Feasibility of improving the grade of iron ore by magnetic separation technology

(1) Principle of magnetic separation to enhance iron ore grade

1. The force of magnetic particles in a magnetic field

All magnetic particles are subjected to magnetic force in a magnetic field, and the magnitude of the magnetic force of the magnetic particles in the magnetic field can be expressed by the following formula:

Fm = μ0 ·K ·V ·H ·grad ( H)

In the formula:

00-vacuum permeability; V – volume of magnetic particles;

H-magnetic field strength; grad (H)-magnetic field strength gradient;

K = M / ( V × H), often referred to as the ore volume susceptibility, and M is the strength of the ore.

It can be seen from the above formula that the magnitude of the magnetic force is related to the magnetic field strength and the gradient of the magnetic field, that is, the rate of change of the magnetic field. The magnetic field strength, the larger the gradient of the magnetic field, the larger the magnetic particles received by the magnetic particles.

The direction of the magnetic force is in the direction of the magnetic field gradient, that is, the direction of the magnetic force of the particle points in the direction in which the magnetic field gradient increases. The direction of the magnetic field gradient at a certain point may be parallel to the direction of the magnetic field at the point, or may be perpendicular to the direction of the magnetic field or at an angle, but the magnetic field gradient must be equal to the line of the equal magnetic field (the line connecting the magnetic field strength in the magnetic field) vertical. In an inhomogeneous magnetic field, an elongated magnetic particle must have a long axis direction parallel to the direction of the magnetic field, and its magnetic direction is along the direction of the magnetic field gradient.

2. Basic conditions for magnetic separation

(1) The conditions for ensuring the separation of magnetic particles and non-magnetic particles are:

Fm>∑F machine

Fm in the formula - the magnetic force acting on the magnetic particles

∑F machine - the resultant force of all mechanical forces acting on the particles opposite to the direction of the magnetic force.

(2) If two kinds of solid particles with strong magnetic properties and weak magnetic properties are to be separated, the conditions that must be met are:

F1m>∑F machine>F2m

F1m in the formula - the magnetic force acting on the magnetically strong particles

F2m - the magnetic force acting on the weaker particles

3. Feasibility of magnetic separation technology to improve iron ore grade

The magnetic separation technique is a method of separating in the non-uniform magnetic field by the magnetic force of the particles according to the magnetic difference between the different particles in the material. The iron ore is usually crushed and ground before the magnetic separation of iron ore. Since the magnetic particles containing iron have ferromagnetism and paramagnetism, as long as the strength of the magnetic field and the magnetic field gradient are sufficiently large, the magnetic particles of the iron-containing magnetic particles are sufficiently large. The magnetic separation technology can be used to separate the iron-containing magnetic particles from the iron ore to increase the iron content in the ore, thereby improving the grade of the iron ore.

(2) Possible measures for improving the grade of iron ore by magnetic separation technology

1. Magnetic separation technology is combined with other mineral processing technologies to improve the ore dressing process and improve iron ore grade.

Other beneficiation methods for improving the grade of iron ore mainly include re-election method, flotation method, electric separation method and roasting method. For ferromagnetic iron ore such as magnetite, the lower magnetic field can achieve separation, mainly using magnetic separation, while some weak magnetic iron ore increases magnetic field strength and gradient during magnetic separation, and improves magnetic field characteristics. Other beneficiation techniques work together to improve the grade of iron ore by improving the beneficiation process. The following is a study on the improvement of the beneficiation process of Donganshan and Meishan iron ore to illustrate the feasible measures to improve the ore grade by improving the beneficiation process by cooperating with other mineral processing technologies.

(1) Donganshan Concentrator

The Donganshan Concentrator has been using two-stage continuous grinding, a single alkaline positive flotation process, and the ore dressing index is poor. Especially in recent years, due to the mining of deep ore, the grain size of the inlay is finer, the mineral composition changes are more complicated, and the concentrate grade of the ore dressing plant is declining. The original ore grade is 32.85%, the concentrate grade is 60.16%, the tailings grade is 15.06%, and the recovery rate is 72.23%.

After research, the beneficiation process was reformed and small tests, re-election tests and industrial tests were carried out successively, and on this basis, the beneficiation plant was completely renovated. The process is continuous grinding, medium ore re-grinding, re-election - strong magnetic-anion reverse flotation. The main indicators after the transformation: the original ore grade is about 32%, the concentrate grade is about 64.5%, the tailings grade is about 16.5%, and the recovery rate is about 65%. After the transformation, the grade of concentrate has been greatly improved, from 60% to 64.5%. The main problem is that the grade of tailings is high and the recovery rate is low. It is necessary to strengthen research and take measures to improve the recovery rate.

(2) Meishan Concentrator

Meishan iron ore mineral composition is complex, metal minerals mainly include magnetite, imaginary hematite, siderite, pyrite, etc., and contain harmful impurities such as sulfur and phosphorus. Meishan Iron Mine adopts crushing-grading pre-selection-grinding-desulfurization flotation process. The ore dressing factory faces two major technical problems: First, the problem of phosphorus reduction. Since 1994, the Meishan iron ore mine has entered the high-phosphorus zone, and the phosphorus content of the ore has increased from 0.35% to over 0.40%. The second is the problem of concentrate filtration. The iron concentrate of Meishan Concentrator is one of the most difficult iron concentrates in China. In 1987, it was studied and implemented with graded filtration (ie, the concentrate was graded by a cyclone, and the coarse part was used. Internal filter filter treatment, the fine-grained part is treated by the newly added plate and frame filter press), and the production is barely maintained, but the filtration efficiency is still low, and the filter cake has high moisture content, especially the fine-grained filter press part. The problem that the coarse and fine concentrate filter cake is difficult to mix.

In order to solve these problems, Meishan Iron Mine and related research units have done a lot of multi-program experimental research work. On this basis, the design of the process of adding weak magnetic-strong magnetic dephosphorization to the existing process iron concentrate is adopted. The phosphorus content of the iron concentrate using the weak magnetic-strong deep dephosphorization system decreased from 0.43% to less than 0.25%, and the iron grade increased from 53.5% to 57.5%, meeting the iron ore quality standard required for iron making. In addition to the obvious phosphorus reduction effect, the deep-separation process has a good degumming effect due to weak magnetic-strong magnetic operation, which improves the filtration performance of iron concentrate, thus fundamentally solving another difficult problem of Meishan Iron Mine. Filtration problems ended the history of graded filtration of Meishan iron ore concentrate and eliminated the filter press operation system. A major breakthrough in the beneficiation technology of Meishan Iron Mine was realized.

(3) Improve the level of magnetic separation technology and develop new magnetic separation equipment to enhance iron ore grade

Improve the magnetic field strength and gradient of magnetic separation equipment magnets by developing new magnetic separation equipment, combine the characteristics of separated materials with magnetic field characteristics, improve the magnetic field characteristics of magnetic separation equipment, change the way of magnetic separation beneficiation, or Force field beneficiation technology, in the design of magnetic separation equipment should introduce wind, centrifugal force, gravity, electric field force, water capacity, etc.

The mechanical factors separating the materials to achieve the purpose of efficient sorting. Optimize the process of magnetic separation to improve the rationality of the overall mechanical structure of the magnetic separation equipment to further enhance the iron ore grade. The following describes several newly developed new methods of iron ore magnetic separation.

1. Dry magnetic separation of small particles in suspension

The dry magnetic separation method of the small-grain material in a suspended state is magnetic separation in a suspended state to improve the selectivity of particle sorting. In the suspended state, the magnetic particles are attracted to and deviated from the magnetic system by the magnetic system multiple times, thereby improving the concentrate grade. The dry magnetic separation of suspended magnetite ore with a particle size of 12~0 mm has achieved good results. Compared with the conventional cylindrical magnetic separator , the iron grade of the magnetic product is increased. Doubled.

The principle of dry magnetic separation of small particles in suspension is shown in Figure 1. The application of dry magnetic separation is one of the promising high-efficiency and energy-saving processes for the treatment of mineral raw materials and process materials, especially in the treatment of iron ore and coarse (> 15 mm) smelting slag containing large amounts of coarse inlays. Time. Reducing the particle size of the broken product entering the sorting operation can fully dissociate the continuum, thereby greatly improving the effect of dry magnetic separation. This also ensures a significant reduction in the cost of ore preparation. However, the reduction of the particle size of the dry magnetic separation to the mine will drastically reduce the sorting effect of the cylindrical magnetic separator and the magnetic pulley, especially when the magnetic content of the magnetic ore is increased. This phenomenon occurs when the adhesion of particles, or the magnetic adhesion of small particles to coarse particles and the mechanical entrainment of non-magnetic particles into a magnetic product. A low feed rate magnetic separator can attenuate this negative phenomenon. However, at this time, the magnetic field can only attract the particles once because the length of the effective magnetic separation working area is small. The length of the effective magnetic separation work area is one of the most important factors determining the recovery rate of magnetic components. When the length of the effective magnetic separation working zone is increased, the magnetic force fm of the recovered particles is drastically lowered, and the residence time of the particles in the magnetic field is prolonged. As the residence time of the particles is extended, the recovery probability of the particles increases. Therefore, the effective magnetic separation working area of ​​the magnetic separator is sufficiently long. In order to prevent small non-magnetic particles from mechanically entraining or adhering into the magnetic product, a condition should be created in which the magnetic particles are attracted and removed from the magnetic system multiple times as the particles move toward each other. The detachment of the particles from the magnetic system can effectively separate the mechanically entrained non-magnetic particles, and the relative movement and collision between the detached particles and the attracted particles can purify the small non-magnetic particles. Magnetic separation of materials in suspension allows for the conditions required for such dry magnetic separation. When having a long effective magnetic separation region, the above method allows the particles to be attracted to and detached from the magnetic system multiple times. At this time, one end of the magnetic system is lifted in the direction in which the particles move, that is, the height h of the recovered particle region is gradually increased, so that the particles having the largest specific magnetization coefficient are recovered into the magnetic product. At the same time, the selection of the magnetic products obtained in the previous sorting area was created several times. It can be seen that the best method for dry magnetic separation of sorted small particle materials is dry magnetic separation of the materials in suspension. The material is moved in an electromagnetic field whose magnetic induction intensity changes abruptly along its moving direction, so that the particles can be suspended, and at the same time, not only the ore particles in the material flow are attracted at different speeds, but also some particles are separated from the magnetic product multiple times. . This loosening and shedding of the mechanically entrained ore particles removes the adsorbed fine particles from the small particles, thereby improving the quality of the magnetic product. Separating the vibration of the magnetic product belt can promote the separation of mechanical inclusions and adsorbed non-magnetic particles from the magnetic product. When the specific magnetic force fm acting on the particles is less than fm, the particles will fall off the magnetic system. When the structure and process parameters h, l, and v that determine the fm size are fixed (as shown in Figure 1), fm can be made smaller than fm by reducing the Hgrad H product of the specific magnetic force acting on the particles. In order to achieve a dry magnetic separation material in suspension, the particles should be moved in a magnetic field in which the magnetic field magnetic field strength and the magnetic field gradient change drastically. This ensures that fm < fm in the region where the magnetic field Hgrad H is relatively low, thus causing the particles to fall off the magnetic system. In the next region of fm > fm, the particles are again attracted by the magnetic system.

Table 4 Experimental results of dry weak magnetic field air suspension magnetic separation magnetite

Table 4 shows the extent to which the dry weak magnetic field airflow is suspended at a distance from the beginning of different electromagnetic systems for the magnetite grade. Experiments show that the use of dry weak magnetic field air suspension magnetic separation can greatly improve the grade of iron ore.

2, SLon pulse high gradient new magnetic separator

Pulsating high-gradient magnetic separation is a high-efficiency beneficiation technology for fine-grained weak magnetic minerals. It combines magnetic force with pulsating fluid force or mechanical vibration force for the separation of weak magnetic iron ore such as hematite and ilmenite. The level of high gradient magnetic separation technology has been improved.

1-feed box; 2-pole head; 3-yoke; 4-exciting coil; 5-magnetic medium;

6-pulsation mechanism; 7-linking bucket; 8-valve

Figure 2 Schematic diagram of the periodic pulsation high gradient magnetic separator

2 is a schematic structural view of a periodic pulsating high gradient magnetic separator. The difference between the periodic pulsating high gradient magnetic separator and the ordinary periodic high gradient magnetic separator is that a pulsating mechanism is arranged in the lower part thereof, and the alternating force generated by the eccentric link mechanism pushes the rubber drum membrane to reciprocate. The slurry in the sorting chamber produces a pulsation. Adjusting the lower valve controls the flow rate and level of the slurry; changing the value of the current flowing through the excitation coil adjusts the background field strength of the sorting zone. A steel mesh or round bar made of magnetically conductive stainless steel is used as the magnetic medium. During ore dressing, water is first filled in the sorting chamber to transfer the pulsating energy to the sorting chamber, and then the slurry is fed from the feed box. The magnetic minerals and non-magnetic minerals in the sorting chamber are separated by the combined force field of magnetic force, pulsating fluid force and gravity. The magnetic ore particles are adsorbed on the surface of the magnetic medium, and the non-magnetic ore particles are discharged from the lower part with the slurry. After the ore is finished, drain the water, cut off the excitation current, and then rinse the magnetics out with clean water.

Figure 3 Flow rate of slurry in the beneficiation area

1-magnetic medium; 2-magnetic ore; 3-non-magnetic ore

Figure 4 Principle of pulsation loose

In the pulsating high gradient magnetic separation process, when the pulsating mechanism is working, the pulsating energy is transmitted from the through hole of the lower magnetic pole to the sorting zone, which drives the pulverization of the slurry in the sorting zone. The actual flow rate of the slurry in a pulsation cycle is shown in Fig. 3. The shaded portion below the horizontal axis ωt in the figure indicates that the actual flow velocity of the slurry is opposite to that of the ore supply. At this time, the fluid generates a reverse thrust to the ore that stays above the magnetic medium. The intercepted non-magnetic ore particles shown in Fig. 4 are taken out of the restraint state and enter the tailings. If the slurry flows from top to bottom (Fig. 4), when the direction of the ore is constant, some of the gangue will be trapped by other ore particles or media. Because the fluid direction is downward, these gangues cannot be separated, resulting in fine The grade of the mine drops, and in severe cases it also blocks the magnetic media. The slurry in the sorting zone continuously changes the direction of the flow velocity, which can effectively reduce the mechanical inclusion of non-magnetic ore particles in the medium. The existence of the reverse pulse power can generate a loose force, so that the non-magnetic mineral has more opportunities to enter the tailings, thereby improving The grade of magnetic concentrate to avoid clogging.

Table 5 Test sample iron ore composition

Table 6 Results of magnetic separation experiment of weak magnetic iron ore by newly developed SLon-2500 vertical ring pulsating high gradient magnetic separator

The SLon-type pulsation high gradient new magnetic separator can greatly improve the grade of iron ore. Table 6 shows the results of magnetic separation experiment of weak magnetic iron ore by newly developed SLon-2500 vertical ring pulsating high gradient magnetic separator. Table 6 shows the iron ore composition and average grade of test samples. It can be seen that SLon type pulsation high gradient new magnetic separation The machine has better effect on the magnetic separation of iron ore with weak magnetic particles.

3. Using superconducting magnetic separation technology to improve iron ore grade

The superconducting magnetic separator transplants the superconducting technology magnet to the strong magnetic separator to replace the ordinary magnet, thereby generating a high magnetic field strength. Compared with the constant-conducting magnetic separator, the magnetic separator with superconducting magnet as the magnetic source has the following outstanding advantages: (1) high magnetic field strength, high magnetic field gradient can be achieved; (2) small volume and light weight, superconductivity The current density of the material is two orders of magnitude higher than that of the copper wire, thus greatly reducing the volume and weight of the magnet; (3) low energy consumption, 90% energy saving than the normal-conducting magnet; (4) high magnetic force caused by high magnetic field makes the magnetic separator The processing capacity is greatly improved. The magnetic separation strength of the superconducting magnetic separator can reach 6~10T, while the magnetic strength of other magnetic separators generally does not exceed 2T. The superconducting magnetic separator is very energy-saving, and the small power can obtain a strong magnetic field and good stability. The only energy consumption is the energy required to maintain the superconducting temperature in the system. The following is a brief introduction to two types of superconducting magnetic separators.

(1) British MK4 machine

1--tank neck; 2-vacuum; 3-outer screen; 4-radiation-protected inner screen; 5-two-stage closed-circuit cooler;

6-æ°¦ exchange gas; 7-neck; 8-solid; 9-liquid helium; 10 superconducting coil

Figure 5 Vertical section of the MK4 machine magnet and the configuration of the magnet and sorting pipe

The British MK4 type machine structure is that two solenoid coils of the same size are on the same vertical axis, the two coils are wound in different directions, the adjacent ends are of the same polarity, and the magnetic lines of force at the gap between the two poles are forced to be scattered by scattering. Out, densely to the cylindrical container, the maximum magnetic induction intensity outside the refrigerator is 3.3 to 3.5 T, and the maximum magnetic field gradient is 0.5 R/cm.分选时，矿浆从切线方向给入，磁性颗粒被磁力吸向内壁在矿浆流推动下沿内壁流出，成为磁性产品，非磁性颗粒沿管外壁流出，成为非磁性产品。磁体在恒稳状态下可连续工作。

（2）英国CryofosGLF直线型机

1－密封圈；2－磁体壁；3－60K屏； 1、1'－ 超导线圈；2－漏斗；3－闸门；

4－16K屏；5－4K冷却管；6－支架； 4、4'－ 凸缘；5－物料；6－分离板；

7－磁体壁支撑；8－超导线圈 7－磁体壁；8－磁性物；9－非磁性物

图6 CryofosGLF直线型磁选机 图7 CryofosGLF直线型磁选机分选过程

英国CryofosGLF直线型机的磁体由4个固紧和粘结在一起的“跑道”形线圈组成(见图6),总匝数为9810匝。超导线是铜比为1.4的NbTi线,直径0.4和0.5毫米。额定工作电流为临界电流的60%。超导磁体重量60公斤,磁体尺寸为3000×67×122毫米。分选区磁场为3T。

4、磁分离选矿的发展趋势

（1）更注重磁选技术应该多方位扩展，采用在磁场主导下的多力场选矿技术。

不同物料在磁场中的运动特性是不同的，而国内的诸多研究往往只强调磁场的高强度和高梯度。磁系结构的设计则往往拘泥于高性能永磁材料的选择，而不研究磁性材料其它性能参数对磁场特性的影响，只有将所要分离的物料特性和磁场特性结合起来，方能解决磁选技术的合理性和磁选设备设计的有效性。所以更注重磁选技术应该多方位扩展，采用在磁场主导下的多力场选矿技术通过改变磁分离选矿的方式，优化磁分离的流程在磁选设备设计中引入风力、离心力、重力、电场力、水能力等诸多有利于将物料分离的力学因素，更注重综合力场应用和各种可控力的作用，可提高分选效率、或减弱堵塞，从而达到高效分选的目的。

（2）为适应矿产资源日益减少、贫矿日益增加及工业化应用的形势，磁选设备趋于大型化、个性化发展。

随着我国钢铁工业的飞速发展，对铁精矿的需求越来越大，国内外为应对快速增长的铁矿资源需求，都在加快研制新型高效的大型或超大型磁选设备，大型磁选设备可以提高生产效率和降低选矿成本，获得更高的品位。大型化的趋势也势在必行。

同时，随着复杂难选铁矿资源在高效综合利用选矿工艺研究方面取得的成果，以及我国对低品位矿、表外矿开发利用力度的加大，为适应选矿工艺的要求，磁选设备的针对性越来越强，也就是磁选机的个性化（针对选矿工艺的）越来越明显。也就是针对不同类型的铁矿开发不同的磁选设备。比如，为适应中信泰富澳大利亚SINO铁矿项目的选矿要求，沈阳矿山机械有限公司矿山机械分公司与北京矿冶研究总院机械研究所合作，开发了用于极细粒矿分选的BKB 型磁选机；为适应广东茂名地区褐铁矿预选抛尾的工艺要求，沈矿设计开发了YCGB型磁选机。

（3）铁矿磁选设备向永磁化、超导化发展。

永磁磁系不需激励功耗和冷却系统, 具有性能稳定、结构简单、操作维护方便等优点, 为磁性矿物的选别提供了新型有效的分选设备,是高梯度磁选设备的一个重要发展方向。能产生高磁能积和高矫顽力的铁素体磁铁的出现, 永磁材料得到进一步地推广应用。最近, 由于强力稀土永磁材料的发展, 新一代永磁辊筒式磁选机能产生了较高的磁感应强度。虽然永磁磁选机的磁场磁感应强度不容易调节, 但是, 可以通过合理地选择永磁材料和优化辊的几何外形, 设计出能处理不同粒度组成和不同比磁化系数物料的辊式磁选机.永磁高梯度磁选设备可以在实现选矿厂要求技术指标的同时，节电节水，有很大的研究发展空间。

以超导磁体作磁源的磁选机和常导磁选机相比有以下突出优点：(1)高场强,可达到很高的高磁场梯度；(2)体积小重量轻，超导材料的电流密度比铜导线高二个数量级，因此使磁体体积和重量大大减小；(3)能耗低，比常导磁体节能90%；(4)高磁场带来的高磁力使磁选机处理能力大为提高。将超导技术与磁分离相结合产生了超导磁选机, 这种磁选机具有普通磁选机无法比拟的优越性,它可以在很大的空间内产生很高的磁场强度, 消耗的能量极少, 设备质量很小。导磁铁的主要优点是降低能耗和减少磁选机的重量。超导磁铁还可以应用敞开梯度螺旋管配置而不用介质, 就可以在大体积中产生强磁力。所以，铁矿磁选设备永磁化，超导化是磁分离技术提升铁矿品位的一个重要的发展趋势。

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