Low-grade iron ore beneficiation process

China's iron ore deposits have been identified about 1760 spots, distributed in more than 600 county 1 billion t of the large-scale mining of this saddle, Panxi, Jidong - Beijing dense pregnant, five Lanxian, Ningwu - 9 in Luohe, Exi, Baotou-Baiyun, Luzhong and Yunnan Huiming, accounting for 67.3% of the total reserves. 51.3% of the total reserves are concentrated in Liaoning, Sichuan and Hebei provinces, accounting for 36.3% of the total reserves.

China's iron ore resources are abundant and not rich. 97.7% of the reserves of about 50 billion tons are lean ore, with an average grade of 33%, which is 11 percentage points lower than the average grade of iron ore in the world, and only rich ore with iron content greater than 50%. 2.3%, most of which must be selected before entering the furnace. The quality of China's iron ore resources is not high, and most of its ore is in the form of fine-grained strips, braids and dispersed dots, and even has a micro-fine structure. Some are multi-metal symbiotic complex deposits, some of the valuable minerals tend to be finely ground to 200 mesh, 90% to monomer separation, sorting and other operations to bring the difficulty. While consuming large amounts of energy during the development process, it also pollutes the environment.

The characteristics of lean iron ore resources determine that its development and utilization are different from other minerals. The amount of mining engineering is large, the output value is low, the profit is small, and the capital utilization rate is low. In recent years, iron ore imports have increased significantly, reaching 210 million tons in 2004, and the amount of imported iron ore has accounted for 50% of China's metal. At the same time, the price of iron ore market has risen. In 2004, the price rose by 18.6%. In April 2005, it rose by 71.5%. The pressure of market competition is getting bigger and bigger.

First, the basic process

(1) Beneficiation of magnetite quartzite

Magnet quartz rock that is taconite, or iron ore Anshan poor, mostly concentrated in the saddle of the five-lan and Jidong area. The ore mainly contains magnetite and quartz. According to the magnetic properties of magnetite quartzite, the magnetic separation of magnetite and quartz is generally used for magnetic separation. The typical type of ore dressing plant has the United States Yili plant and Ming Tucker plant, Canada Adams plant, Kursk ore company of the former Soviet Union, China's Dashihe Nanfen and Dagushan concentrator. The separation process of the magnetite quartzite is crushed to 25-15 mm through three to four stages, or crushed to 350-250 mm through a section, and combined with ball milling (gravel grinding) to carry out three-stage fine grinding to enter multi-stage magnetic separation. The process of magnetite quartzite beneficiation is characterized by a stage grinding and magnetic separation process in order to discharge monomeric gangue at the stage and reduce the amount of grinding in the next stage.

(2) Magnetite ore dressing

Magnetite is a skarn-type ore. The main iron mineral is magnetite. It also contains a small amount of sulfide minerals, accompanied by non-ferrous metals such as cobalt, nickel and vanadium . The gangue is skarn. The ore is spotted, breccia, banded and massive. The magnetization coefficient is similar to that of magnetite quartzite. According to the particle size embedding characteristics, it can be classified into coarse particles, fine particles, fine particles and extremely fine-grained ore. Typical of these types of concentrators are the US Enpell Plant, the Grace Plant, the Canadian Hilton Plant and the Australian Nujiang Plant. China's concentrated distribution in Hubei, Jiangxi, Shandong, Jiangsu and Anhui has Wujiazi iron ore and jade iron ore. According to the physical properties of magnetite ore, the most effective beneficiation method is to recover magnetic minerals by magnetic separation and recover the associated sulfide minerals by flotation. The sorting process is mostly two to four stages of crushing, and one to two sections of dry magnetic separation in the crushing process to select medium or finely divided products. For further deep selection of products, after two to three stages of fine grinding, two to five wet magnetic separations are carried out to obtain a final iron concentrate product using a combined process of magnetic separation-flotation or flotation-magnetic separation to improve iron concentrate At the same time of taste, it can also recover associated minerals into corresponding concentrate products, as well as desulfurization of concentrates. Magnetite ore grinding has a coarser particle size and less muddy particles. Generally, a magnetic separator can be used for deliming. The concentrator that selects the magnet ore is operated according to the full-circulation water supply process, and the circulating water utilization rate is 75% to 85%.

(3) Beneficiation of hematite and red-magnetite ore

1. Hematite and red-magnetite ore account for a high proportion in the ore. Mostly distributed in Anshan, China, the Kursk magnetic anomaly area of ​​the former Soviet Union, Michigan, the United States, Quebec, Canada, Khao Lai and Libya. The ore-based ore is mainly selected from coarse-grained ore with good physical properties, and the utilization of fine-grained hematite ore is still a subject of exploration in the world. China's hematite ore has a disseminated structure of fine-grained and fine-grained inlays, and the proportion of hematite and magnetite in hematite and quartz red-magnetite ore mainly varies greatly, and can be divided according to its proportion. Skarn type (such as the help of ore) and mirror iron type (such as Carol ore).

2. The beneficiation process of red-magnetite ore. Nowadays, magnetic separation-reselection process, magnetic separation-flotation process or re-election--magnetic separation-flotation process are adopted. Some factories first use re-election methods to recover hematite. The magnetite is recovered from the re-selected tailings by magnetic separation; it is also selected by flotation (Norana Lana plant) and electrification (Wash Bush, Canada), or before the final selection. Treat with a fine sieve. Magnetic separation--re-election process firstly recovers magnetite by weak magnetic field magnetic separation, and then recovers hematite from magnetic separation tailings by re-election method; and magnetic separation-flotation process uses flotation as sorting red The main process of iron concentrate is to recover coarse hematite and magnetite by re-election method, and to recover fine-grained magnetite by magnetic separation. For densely crystallized red-magnetite quartzite, the re-election method is widely used for sorting coarse-grained ore, strong magnetic separation or flotation for sorting fine-grained ore. For clay red-magnetite ore, it is mainly used for washing or dry magnetic separation.

3. Beneficiation of hematite ore. Washing, re-election, flotation, magnetic separation and roasting magnetic separation methods, or flotation and electro-election can be used as selection operations, and different types of ore processing processes can be formed according to different ore properties. When coarse or bulk ore is mixed into the lean material, the heavy suspension is used for beneficiation. Some concentrators use jigging ore dressing for granular ore, re-election for medium and fine-grain ore with a spiral concentrator, or magnetic separation with a strong magnetic separator. The fine-grained quartz ferrous rock is treated by flotation or roasting magnetic separation. The Tilden concentrator in the United States finely grinds 80%-0.025mm ore with selective flocculation and cationic reverse flotation. The Anshan Sintering Plant and the Qi Dashan Concentrator have used shaft furnaces. The former Soviet Union Crivo Central Mining and Concentrator has used the rotary kiln to refine and roast fine-grained hematite ore and then magnetically select iron concentrate. .

(4) Beneficiation of vanadium- titanium magnetite ore

The magnetite in the vanadium-titanium magnetite ore is crystallized with titanium minerals and has coarse particles. The gangue is gabbro peridotite and chlorite, and the particles are unevenly distributed and difficult to grind. The ore grindability coefficient is about 1/2 of that of magnetite quartzite. It is an ore that is easy to select, difficult to grind and has low mineral purity, and is accompanied by useful elements such as titanium and vanadium cobalt nickel in industrial grade. Vanadium-titanium magnetite is mainly concentrated in the Panxi area of ​​China and the Ural region of the former Soviet Union. Panzhihua Metallurgical Mining Company directly fine-milled the crushed products, using a process of closed-circuit grinding and two-stage magnetic separation. The concentrator uses a circulating water supply system. In addition to recovering iron concentrates, such ores are simultaneously Titanium minerals and sulfur-nickel mineral products are also recovered. - The dressing of limonite ore The limonite ore is mainly in the form of a scorpion, a powder and a dense block structure, and the size of the granules varies. In addition to the main mineral is limonite, it also contains a small amount of hematite siderite. The gangue is mainly composed of quartz, mudstone, calcite , mud and clay, and also contains impurities such as manganese phosphate .

(5) Dressing of limonite

At present, the combined processes of washing, re-election and magnetic separation are widely used.

(6) Beneficiation of siderite ore

The main metal minerals in the ore are siderite and a small amount of limonite, hematite, magnetite and iron silicate. Non-metallic minerals are quartz and calcite. The use of siderite ore in the world is not widely used, and it is only used in large-scale industrial applications in countries with less iron ore resources in Europe, such as the Czech Republic, Poland, the former Yugoslavia, and Austria. The main beneficiation methods for siderite ore are roasting magnetic separation and re-election. Main equipment - crushing and grinding equipment China's iron ore crushing operation is basically carried out according to five kinds of processes. One section of crushing is mostly used for grinding mill grinding materials. The crushing granularity is 350~0mm or 250~0mm. Open-circuit crushing, three-stage closed-circuit crushing and four-stage crushing are mostly used for ball mill or rod mill grinding materials, and the crushing particle size is 25~0mm, 20~0mm, 15~0mm and 12~0mm. According to the particle size of the crushed product, it is divided into three crushing equipments: coarse crushed, medium crushed and finely crushed. The coarse crusher uses a jaw crusher or a gyratory crusher. The large iron ore dressing plant uses 1500mm×2100mm jaw crusher and 1500mm/300mm or 1200mm/180mm gyratory crusher. The medium crusher uses a standard cone crusher . The fine crusher uses a short-head cone crusher. Grinding mainly uses a section of grinding, two-stage grinding and three-stage grinding process. There are continuous grinding and stage grinding or grinding processes with sorting or fine screening. More than 20 iron ore mines such as Shantoushan, Jinshandian, Shirengou and Handan have more than 70 self-grinding mills, of which more are φ5.5m×1.8m self-grinding machines, and semi-self-grinding technology is self-grinding. A steel ball of 3% to 5% and φ120 to φ150 mm is added to the machine to increase the processing capacity of the self-grinding machine, and the use of gravel grinding has the effect of reducing ball consumption and power consumption for some ores, thereby reducing the cost of dressing.

Second, mineral processing equipment

China iron ore dressing plant has self-grinding mill, rod mill, gravel mill and ball mill, of which self-grinding machine accounts for about 10%, rod mill and gravel mill account for about 3%, and the rest is basically ball mill, iron ore. The most used in the production of the concentrator is the φ2.7m×3.6m and φ3.6m×4.0m ball mills.

(I) Pre-selection equipment China has 29 iron ore dressing plants such as Dashi River, Water Plant and Chengchao Jishan, which are preselected by dry magnetic pulleys. At present, there are φ800×1400mm CT-108 type and φ1250×1270mm permanent magnet magnetic pulley (or bulk magnetic separator). The coarser weighting agent with lower density is used to prepare the heavy suspension with higher density, and the iron ore pre-selection is carried out by the heavy medium vibrating chute. The general classification of the discharged stone and surrounding rock is 75~10mm. The use of trapezoidal, rectangular, circular and large jigs for the pre-selection of weakly granular iron ore with different size lump ore is successful. For the 15~0mm ore, a ZXY-type round jig can be used to pre-discharge the tailings with a yield of about 13% iron containing 14%; for the 3010mm ore, the AM30 large-grip pre-selection can achieve a higher recovery rate. Grade iron concentrate.

(2) Magnetic Separation Equipment Fine-grain magnetite Wet magnetic is selected by single-tube, double-tube and three-cylinder permanent magnet magnetic separators, with φ1200×3000mm (Sweden, Finland, former Soviet Union) and φ1500×3000mm (former Soviet Union) ), φ1500×1500mm (Krupp double cylinder) and CTS, CTB, CTN-1224 (China) and other models, one-stage or two-stage magnetic separators mostly adopt a downstream flow groove; three or four segments are semi-reverse Type; and the multi-purpose countercurrent type of direct magnetic separation of the ball mill. The vertical reduction roaster was used for magnetization roasting of Anshan-type hematite-quartzite, and was subjected to roasting magnetic separation in Qi Dashan, Baotou and Jiugang concentrators to produce iron concentrate. China has more than 130 shaft furnaces with volumes of 50m3, 70m3, 100m3 and 160m3. The rotary roaster performs magnetization roasting of limonite and siderite in the Czech and former Federal German concentrators. Dry induction roller type strong magnetic separator with various structures, Humbold Jones type wet flat ring strong magnetic separator and various types of strong magnetic separator developed on this basis, as well as Swedish Sala high gradient for continuous operation Strong magnetic separators are used in the selection of weak magnetic iron ore.

(III) Flotation equipment Flotation machines of various structural types are used to treat iron-poor ore with fine-grained and fine-grained inlays. Flotation machines manufactured and used at home and abroad are still dominated by mechanical agitation, and have the same development trend, that is, with the increasing amount of difficult and poorly selected materials, the amount of gas is sufficient, the production capacity is large, and the electric energy consumption is small. The selection of indicators is good and easy to operate and maintain. Representative products are Finland OK-16MX-14, WEMCO-144, DR-600H, pneumatic mechanical stirring type BΦP-240, BΦR600 and so on.

(4) Re-election and washing equipment Various types of heavy medium concentrators, jigs, cyclones, spiral chutes, vibrating chutes, spiral concentrators, trough washing machines, washing drums and wet rotary screens Has been widely used. For coarse or bulk ore mixed with depleted materials, heavy suspensions are used for beneficiation. Some ore dressing plants perform jigging ore dressing on granular ore, and re-electing medium and fine-grain ore mainly with a spiral concentrator. Spiral concentrators are widely used in new and old plants in the United States, Canada, Sweden, and other countries. For example, the Carroll plant in Canada uses more than 4,000 units. After a rough selection and two selections, the concentrate is directly obtained, and the rough-selected tailings are magnetically selected. The final iron concentrate grade is 66.5%.

(V) Electrical Separation Equipment The North Crabrador Mine in Canada used a power separator with a productivity of 1.7t/h to sort the weak magnetic lean iron ore and achieved satisfactory results.

(6) Granular Iron Furnace Germany, the Czech Republic, Poland, North Korea, Spain and China have adopted a granular iron furnace with a productivity of 300-800 t/d, which is suitable for processing high-silicon refractory iron ore with fine-grained inlays.

(7) Concentration of dewatering equipment Generally, a concentrator with peripheral transmission or central transmission, and a sloping plate thick box are used. The filter uses a cylinder or a disc vacuum filter, a magnetic filter, and a belt filter press. A cylindrical internal filter vacuum filter can be used to filter magnetic separation and flotation iron concentrate. The magnetic separation iron concentrate is filtered using a cylindrical magnetic filter. The fine flotation iron concentrate was filtered using a disc vacuum filter. The fine-grained slime concentrate is filtered by a filter press. In order to solve the problem of difficult discharge of fine-viscous materials, a belt-type filter has appeared, and the machine area has reached 131.9 m2. In order to improve the efficiency of filtration of the fine-grained material, the filter is being improved around the direction of reducing the resistance of the filter cake and the filter medium, such as adding a flocculant and a filter aid, and selecting a suitable filter medium. Ceramic filters are applications of new porous solid media outside of fabric media.

(VIII) Concentrate and tailings transportation technology The Australian Nujiang Concentrator uses a long-distance iron concentrate conveying pipe with a diameter of φ244mm and a length of about 90km. The pumping station is equipped with a 4×450kW motor-driven plunger pump with a discharge pressure of 105-141MPa. Concentrate 2.5 million t / a, utilization rate of 97%. The tailings hydraulic conveying technology with a concentration of more than 40% is gradually being promoted.

Third, technological progress

(1) Magnetite ore dressing

Fine-grained inlaid magnetite ore dressing technology advances. Mainly in the development and improvement of mineral processing technology, the upgrading and transformation of mineral processing equipment, the continuous improvement of comprehensive mineral processing indicators, etc.: (1) using a new crusher, or transforming the old cone crusher, or changing the road crushing process to closed circuit Process to reduce grinding energy consumption and reduce the size of the ore. In the past two decades, ultra-heavy spring cone crushers and high-energy hydraulic cone crushers and two-axis heavy-duty vibrating screens have emerged abroad, resulting in the so-called “new conventional grinding” process of the new three-stage closed-circuit single-stage ball mill. In order to achieve a particle size of 7 to 8 mm, the product has been “grinded and worn less”, reducing energy consumption. Improve the processing capacity of the mill. High-pressure roller mills are currently widely used in the cement industry and are expected to break from cement clinker into iron ore dressing plants. The development of ultra-fine grinders and out-of-head grinder liners has gone from metal lining to non-metal lining, and then to magnetic lining, with significant economic benefits. (2) Universal use of magnetic pulley pre-selection to form a pre-selection-magnetic separation process In order to improve the capacity of the mill processing and the original ore grade. China's practice has proved that it can discharge 8% large iron gangue containing iron, increase the grade of grinding into 2%, and reduce power consumption by about 2%; (3) change dry self-grinding into wet self-grinding, change closed-circuit wet self-grinding For open or semi-open wet self-grinding. A linear vibrating screen is used instead of a spiral classifier in a grinding grade. A hydrocyclone is used in the second stage classification to improve the grinding classification efficiency. (4) Generally adopting vibrating fine screen or high-frequency fine screen, and grinding and sorting to form a magnetic separation fine screening process, in order to obtain high-quality iron concentrate products containing more than 65% iron under high recovery conditions; (5) Use φ1050mm or φ1250mm large diameter magnetic separator to improve magnetic separation capacity and concentrate grade. For example, when Dagushan adopts BXφ1050mm×2400mm magnetic separation machine, the output is 44.16t/h, the ore particle size is -0.074mm, accounting for 78.62%, the recovery rate is 99.39%, the concentrate grade is 59.54%, which is 0.8 higher than the original magnetic separator concentrate grade. %. (6) extensive use of magnetite ore stage grinding-magnetic separation process to obtain high quality iron concentrate products; (7) Canadian Craigmont plant adopts “granularity-based PSM control”, except for two sets In addition to the PSM-100 being used, PSM-200 is installed in the magnetite recovery circuit for -325 mesh, which accounts for 85% to 95% of the fine grinding particle size, which not only maintains the specified grinding grain size, but also Maximizes the throughput of the mill, which reduces the cost per ton of concentrate.

(2) Hematite ore dressing

The development and utilization of fine-grained hematite ore promotes the development of ore dressing processes such as hematite flotation, re-election, strong magnetic separation and roasting magnetic separation. (1) Hematite full flotation process. The use of fatty acid anion collector , sodium carbonate as a pulp adjuster (pH of pulp of 9.10), flotation of hematite in the ore of quartzite type, solves the problem of large viscosity of the slurry and difficulty in dewatering of the concentrate. The use of two-stage concentration operation reduces metal loss; (2) Strong magnetic-flotation process. The main feature is that the gangue minerals such as monomeric quartz and easily muddy chlorite in the ore are discharged under coarse grinding conditions by strong magnetic separation, which becomes a qualified concentrate, thus creating favorable conditions for further fine grinding and flotation; (3) Roasting-magnetic separation process. Using a shaft furnace for 75 ~ 20mm hematite, blast furnace and coke oven coal mixture gas is heated and reduced to produce artificial magnetite, then magnetic separation of iron concentrate product. The shaft furnace reduced roasting Anshan-type hematite-quartzite with an iron concentrate grade of 65.82% and a recovery rate of 78.41%. (4) Roasting magnetic separation-reverse flotation process. In order to improve the quality of the roasting magnetic iron concentrate, the dodecyl cation collector is used to carry out reverse flotation in neutral pulp. Under the condition of dodecylamine dosage of 120-180 g/t (for magnetic separation concentrate), the index of iron concentrate grade 65.85% and recovery rate 75.85% was obtained; (5) strong magnetic separation process. The treatment of oxidized iron quartzite from the Krivorogog deposit in the former Soviet Union's central mining and conglomerate was transformed into strong magnetic separation by magnetization roasting in 1989. The new process is put into operation, which solves the problem of dust and exhaust gas purification caused by roasting and the high energy consumption of about 100m3 of natural gas per ton of concentrate. The total energy consumption expressed by the equivalent fuel tonnage is reduced from 0.202 for magnetization roasting to strong magnetic separation. 0.054 is a major advancement in the non-calcination of oxidized iron quartzite; (6) stage grinding, heavy magnetic-anion reverse flotation process. Qi Dashan Concentrator uses MZ-21 high-efficiency, low-consumption and non-toxic new agent and Slon-type vertical ring pulsation high-gradient magnetic machine. Under the condition that the metal recovery rate is not reduced and the original production capacity of the plant is maintained, the iron concentrate grade is reached. 67.14%, the cost of mineral processing chemicals decreased by 24.89%, and the traditional roasting magnetic separation process was eliminated. The energy consumption cost was reduced by 48.93%, the processing cost per ton of concentrate was reduced by 3.28%, and the personal safety and environmental pollution caused by roasting using gas were also eliminated.

(3) Magnetic-hematite ore dressing

(1) Re-election - magnetic separation - flotation process. Anshan-type magnetic-hematite ore is partially dissociated from the iron mineral under rough grinding conditions and needs to be recovered early. This process is competitive with high-quality iron concentrate products with high recovery rates. Its main feature is to recover some coarse-grained iron minerals by spiral chute after grading of one grinding cyclone. The fine fraction is recovered by magnetic separation-flotation process, and the intermediate products are combined and subjected to secondary classification grinding, and then returned to the sorting loop. (2) Magnetic separation - re-election process. For fine-grained magnetic-hematite ore, China has developed a process for recovering part of magnet minerals by magnetic separation, recycling weak magnetic minerals with tailings using spiral chutes and centrifugal concentrators. (3) Continuous grinding-magnetic separation (weakening magnetic-strong magnetic)-reverse flotation process. The main feature is the use of continuous grinding, grinding the ore directly to the monomer dissociation, and only controlling the final grinding product size. The weak magnetic magnetic separation can play the dual role of discharging tailings and de-sludge, reducing or eliminating the harmful effects of slime on flotation. Strong magnetic separation deli is the best. The use of reverse flotation (floating quartz and other gangue) adapts to the different proportions of magnetite, hematite and imaginary hematite in the ore, especially the anion reverse flotation has strong adaptability to the slime, such as Angang After the transformation of the military ore dressing plant according to this process, under the condition of 29.60% of the original ore grade, the index of the concentrate grade was over 67.59%, and the tailing grade grade of 10.56% metal recovery rate was 82.24%.

(4) Multi-metal iron ore dressing

Panzhihua Metallurgical Mine Company directly fine-milled the broken products of vanadium-titanium magnetite ore. The process of a closed-circuit grinding and two-stage magnetic separation was used to obtain an iron concentrate with a 51.59% recovery rate of 74.47%. For the Bayan Obo iron ore mine, the weak magnetic-strong magnetic-flotation combined process is used to comprehensively recover iron, antimony and rare earth minerals. It is characterized in that when the grinding particle size reaches 200 mesh and accounts for 95% to 96%, the magnetic iron mineral is recovered by weak magnetic separation, the iron-containing silicate is discarded by strong magnetic separation, and the rare earth mineral and the strontium mineral are in strong magnetic field. The mine is initially enriched, and then the flotation process is used to recover the strontium minerals and rare earth minerals. Good rare earth and antimony concentrate product indexes, as well as iron concentrates with a 65.29% recovery rate of 77.13%.

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