The process of crushing iron ore or iron ore products in natural moisture.

Abstract

Summary of the Invention\nProcess for crushing iron ore or iron ore products at natural moisture\nThis invention relates to a process for crushing iron ore or iron ore products (pellet feed, sinter feed, etc.) at natural moisture without the need to add water or include a drying step in the process, which is technically and economically feasible. The crushing process of this invention uses at least one piece of equipment selected from the group consisting of a roller press (HPGR), a vertical roller mill (VRM), a roller crusher (RC), and a high-speed screen of at least 10G.

Description

The process of crushing iron ore or iron ore products at natural humidity. Technical background The invention relates to processes for crushing iron ore or iron ore products with natural moisture. In particular, the invention relates to processes for crushing iron ore containing some water naturally present during mining, or iron ore products (pellet feed, sinter feed, etc.), which leads to significant gains for both the process and the environment. Explanation of prior knowledge Crushing processes refer to the fragmentation of processed materials to reduce the grain size distribution. Mineral crushing plants can be described as a combination of one or more unit operations. They are usually large-scale facilities capable of processing thousands of tons of iron ore per day. Iron ore crushing is commonly done in two basic ways: wet processing and dry processing. This invention provides a new and inventive process for crushing iron ore or iron ore products: processing with natural moisture. The crushing of this invention with natural moisture is suitable for processing raw iron ore or iron ore products (pellet feed, sinter feed, etc.) with a moisture content of up to 12% by weight. The natural moisture content of mineral processing usually occurs in the extraction operation, which involves removing ore from the pit for screening and crushing. From this point on, the process is either wet, with water added, or dry, with a drying step, for the ore to be processed into the next processing step. Fine grinding (where the product has a particle size of less than 1 mm) requires a classification facility to separate the fine fractions (the desired product) from the coarse fractions, which must be re-ground in a circuit. The concentration of iron ore, after the crushing, grinding and classification stages in the iron ore process, is referred to by document BR 102015003408-3. The system claimed by this invention, despite being dry, is focused on the concentration of iron ore by combining magnetic roller separators, aeroclassifiers, cyclones and bag filters. Also, the system in BR 102015003408-3 operates with materials containing 2 to 3% residual moisture. The main problem with performing the crushing, grinding and classification steps with natural moisture is producing a product with a particle size of less than 16 mm, which conventional screens are not able to do effectively and therefore do not guarantee the specific size distribution of the product. In addition, operational issues such as blockage of the sieve screens due to moisture are quite common. For this reason, common crushing processes are either completely wet or completely dry. Dry and wet processing Iron ore naturally contains, on average, 5% to 12% water by weight. This natural moisture content causes the ore to be highly cohesive, making it difficult to mine. Dry processing involves removing water from the iron ore by a drying step, which may be carried out, for example, with dryers, leaving less than 1% residual water by weight in the iron ore. Figure 1 shows the wet iron ore mining (ROM – raw material) process commonly used in the prior art. In wet processing, large amounts of water are added to the iron ore after the crushing and screening step. The step after crushing and screening is called grinding. The purpose of this operation is to increase the fragmentation and adjust the particle size of the iron ore to the desired value. Usually, it is an operation that is carried out in conjunction with the classification step, particle size separation using hydrocyclones or sieves. The wet grinding step is typically performed in ball mills or vertical mills with high electricity and water consumption, but is not limited to that. The wet processing route of iron ore products (pellet feed, sinter feed, etc.) in the prior art can be seen in Figure 2. It should be noted that two grinding steps and an intermediate filtration step are required. In dry iron ore processing (ROM), there is a drying stage before grinding, which consumes a large amount of fuel to heat the drying air. In addition, the drying stage requires large facilities to remove fine suspended particles (dust) that are generated during ore processing and handling. Dry grinding is usually combined with static and / or dynamic classifiers. The grinding facilities commonly used are ball mills which, as mentioned earlier, consume a large amount of electricity. Figure 3 shows the dry iron ore beneficiation process commonly used in the prior art. The dry processing method (route) of iron ore products (pellet feed, sinter feed, etc.), in the prior art, can be seen in Figure 4. Problems encountered with iron ore crushing processes in prior art Conventional processes for crushing iron ore and iron ore products use large amounts of water in their processing or energy and fuel for the drying step. The environmental impact and problems caused by conventional iron ore processing facilities are significant due to the amount of water consumed, the lack of fine iron ore particles, the production of combustion residues and particulate emissions (when drying is required), high energy consumption, etc. Vertical roller mill, roller press, roller crusher and high-speed sieves In some grinding plants commonly used in the cement and coal industries, such as vertical roller mills (VRMs); roller presses (high pressure grinding rollers, HPGRs) and roller crushers (RCs), the materials are fed with their natural moisture content. Vertical roller mills (VRMs) are commonly used to grind materials such as coal, lignite, limestone, clays, clinker. The vertical roller mill (VRM) consists of rotating rollers embedded in it and moved by the rotation of the table. The material enters the center and moves to the edges, where it is crushed by the rollers. These are connected to a hydraulic system that varies the roller pressure as required for materials with a finer particle size. After crushing, the particles are removed by an upward air flow that can be heated, drying the ore while being directed to a dynamic classifier where particles with a particle size below the desired size leave the roller and the coarse particles return to the table to be crushed. Therefore, this installation is part of a completely dry process, the main application of which is in the cement industry. It may also operate by overflow, without the need for air to move the material and without dynamic classification. But, for this purpose, it must work with natural humidity or have a drying step before it. A roller press (HPGR) is usually used as an auxiliary grinding step before or after the ore grinding step. The equipment consists of a pair of rollers rotating in opposite directions, protected by a rigid frame. The material to be ground is fed into the upper part of the equipment between the rollers, compaction of this particle bed is carried out in openings larger than the maximum particle size in the feed. Thus, size reduction is achieved by intergranular crushing. The roller press has a higher energy efficiency compared to conventional crushers and mills (ball mills) because the structural breakage of the material grains is achieved with reduced energy loss in terms of heat and sound. Roller crusher (RC) is usually used as an auxiliary crushing stage in the ore crushing stage. The equipment consists of rollers rotating in opposite directions and the principle of operation is to break the particles between the rollers. The equipment is fed with a thin layer of ore and the rollers touch the particles simultaneously. The rollers operate with a gate smaller than the size of the largest particle, which is set to the desired largest size. For example, if a product with a largest size of 1 mm is required, the machine will set its gate to this value or slightly less. High acceleration screens (greater than 10G, where G is the acceleration of gravity) have a high acceleration screen vibration system, which enhances the effect of releasing the iron ore on the screen, which allows for greater separation / separation of the ore as well as preventing its blockage. In this invention, no water is sprayed on the ore in the screens used. It is important to note that high-speed screens and vertical roller mills (VRMs) are never used in iron ore grinding / sieving circuits. In addition, roller crushers (RCs) are never used for fine crushing (less than 1 mm). Purpose and benefits of the invention The aim of this invention is to provide an efficient crushing process for iron ore or iron ore products (pellet feed, sinter feed, etc.) with natural moisture, with a moisture content of up to 12% by weight, without the need to add water or include a drying step in the process, in a technically and economically feasible manner. The focus of this invention is on the crushing of raw iron ore or iron ore products, such as coal, lignite, limestone, clay and clinker, using and disposing of equipment used in the exploitation of materials with completely different chemical and physical characteristics. Another object is to provide an efficient process for crushing raw iron ore or iron ore products (pellet feed, sinter feed, etc.) with natural moisture, up to 12% by weight in moisture, to produce a product with a particle size of less than 16 mm in the case of raw iron ore crushing and less than 0.074 mm in the case of iron ore product materials (sinter feed or pellet feed for crushing to pelletizing size). The crushing methods of the present invention have important advantages that are beneficial for both industrial processes and the environment: -Without the use of water in the milling processes, it reduces environmental impacts either by not consuming this natural resource, or by reducing the flow that must be disposed of in tailings dams; - Without using the energy and fuels necessary for the drying process; -Exploitation of increased processing of iron ore and iron ore products in: energy consumption, facility size, facility operating cost, operating cost; -More simplicity of operation; -Reduced maintenance and replacement of worn materials used in processing raw iron ore and iron ore products compared to all-wet and all-dry methods; -Reducing auxiliary activities such as replacing grinding media in ball mills (wet and dry); -Without an exhaust system or circuit to collect very fine airborne particles (dust) generated by ore processing and handling, where the natural moisture of the ore prevents these particles from becoming suspended. Brief description of the invention To achieve the above objectives, the present invention provides processing methods for crushing iron ore or iron ore products with natural moisture, without the need to add water or a drying step to the process. The invention includes processing methods that combine grinding and classification equipment for the most efficient crushing process, such equipment including: roller press (HPGR), vertical roller mill (VRM), roller crusher (RC) and sieve with high acceleration of at least 10G. Therefore, the present invention aims at a process for crushing iron ore, which is carried out in natural moisture, from materials coming directly from the mine (ROM) or from previously processed iron ore products (pellet feed, sinter feed, etc.), which process uses at least one of the following equipment: vertical roller mill (VRM), roller press (HPGR), roller crusher (RC) and screen with a high acceleration of at least 10G. For iron ore application, the vertical roller mill (VRM) operates with overflow discharge and the option of drying the ore during grinding is not used. Description of maps The detailed explanation provided below refers to the attached figures, which: -Figure 1 shows a wet iron ore mining (ROM) process, according to prior art; - Figure 2 shows a wet process for the exploitation of iron ore products (pellet feed, sinter feed, etc.) according to prior art; -Figure 3 shows a dry raw iron ore (ROM) exploitation process according to prior art; - Figure 4 shows a dry process for the exploitation of iron ore products (pellet feed, sinter feed, etc.) according to prior art; - Figure 5 shows the process of exploiting raw iron ore or iron ore products with natural moisture according to this invention; -Figure 6 shows nine processing methods of this invention. Detailed explanation of the invention The following detailed description is not intended to limit the scope, use, or embodiment of the invention in any way. Rather, the following description provides an understanding of the exemplary embodiments. Using the teachings herein, those skilled in the art will readily recognize alternatives that may be used without broadening the scope of the invention. As will be clear to any person skilled in the art, the invention is applicable to crushing in the iron ore mining process, without any further steps such as concentration. However, the invention is not limited to such specific examples. Figure 1 shows a prior art wet iron ore mining (ROM) process comprising the steps of crushing 101, screening 102, grinding 103 and concentration 104. The crushing step 101 may be in various stages (e.g. primary crushing to fourth crushing), carried out in external circuit with the screening step 102, which may be carried out, for example, on vibrating screens. The grinding step 103 requires the addition of a significant amount of water. The ore concentration step 104 may be carried out by gravity, magnetic, flotation, etc. Figure 2 shows a prior art wet iron ore product exploitation process (pellet feed, sinter feed, etc.), where the grinding circuit includes a first grinding stage 201, a filtering stage 202 which results in high material moisture content, and a second grinding stage 203. After grinding, the material undergoes a pelletizing stage 204 to obtain the desired final product, in this case iron ore pellets. Figure 3 shows a prior art dry iron ore mining (ROM) process comprising the steps of crushing 301, screening 302, drying 303, grinding 304 and concentration 305. The crushing step 301 may be carried out in various stages (e.g. primary crushing to fourth crushing), which are carried out in circuit with the screening step 302, which may be carried out, for example, on vibrating screens. The drying 303 may be carried out within the milling equipment itself by means of hot air flows from burners and blowers. The concentration 305 may be carried out by gravity, magnetic, electrostatic, etc. methods. Figure 4 shows the process of exploiting prior art dry iron ore products (pellet feed, sinter feed, etc.) where the crushing circuit includes a drying step 401, a first grinding step 402 and a secondary grinding step 403. After crushing, the material undergoes a pelletizing step 404 to obtain the desired final product, which in this case is ore pellets. The following description will refer to nine (9) possible crushing methods of the invention. The methods apply to two possible iron ore sources: 1) a first source of material coming directly from the mine (ROM), and 2) a second source of iron ore products that have been previously processed in the mining facility (pellet feed, sinter feed, etc.) prior to entering the process of the invention. The invention, illustrated in a simplified manner by Figure 5, is a process for exploitation in which the crushing circuit 501 is carried out entirely at natural humidity, either from material coming directly from the mine (ROM) up to 12% moisture by weight, or from previously processed iron ore products (pellet feed, sinter feed, etc.), also up to 12% moisture. After crushing 501, the final product may be crushed iron ore, or the steps of concentration 502, pelletization 503 or sintering 504 may be carried out according to the final product in question. The nine (9) methods of the present invention are shown in detail in Figure 6 and include: -Method 1: 501 crushing circuit, at natural moisture, which is first carried out in a roller press (HPGR) in up to three stages and then reprocessed in a series in a vertical roller mill (VRM) in up to three stages. -Method 2: 501 crushing circuit, natural moisture, first in a vertical roller mill (VRM) up to three stages, and then reprocessed in a roller press (HPGR) up to three stages in series. -Method 3: 501 crushing circuit, at natural humidity, carried out in a roller press (HPGR) and coupled in a circuit with a high acceleration screen (at least 10G), where the coarse product (retained material) is returned to the roller press (HPGR) and the fine product (pass-through material) is the final crushing product; Method 4: The 501 crushing circuit is carried out, at natural humidity, in a vertical roller mill (VRM) and is coupled in a circuit with a high acceleration screen (at least 10G), where the coarse product (retained material) is returned to the vertical roller mill (VRM) and the fine product (pass-through material) is the final crushing product; -Method 5: 501 crushing circuit, at natural humidity, starting in a roller press (HPGR), the processing of the material continues in a vertical roller mill (VRM) and then classified in a high acceleration screen (at least 10G), where the coarse product (retained material) returns to the roller press (HPGR), is closed, and the fine product (pass-through material) is the final crushing product; Method 6: 501 crushing circuit, at natural humidity, starting in a vertical roller press (VRM), the material processing continues in a roller mill (HPGR) and then classified in a high acceleration screen (at least 10G), where the coarse product (retained material) returns to the vertical roller press (VRM), is closed, and the fine product (pass-through material) is the final crushing product; -Method 7: In the 501 crushing circuit, in natural humidity, the material is classified by a high-acceleration screen (at least 10G), and its fine product (pass-through material) is processed by a roller press (HPGR) or vertical mill (VRM) in three stages. The latter product includes the fine product, which is the final product of crushing; and also the coarse material (retained material) is considered a product because it is exchanged in this way (sinter feed); -Method 8: The crushing circuit 501 is carried out, at natural humidity, in a roller crusher (RC) and can be carried out in several stages in the crushing process using equipment with two or more rollers; and -Method 9: The crushing circuit 501, at natural humidity, starts in the roller crusher (RC), and can be carried out in several stages in the crushing series using equipment with double or more rollers, and then classified in a high acceleration screen (at least 10G), where the coarse product (retained material) returns to the roller crusher (RC), is closed circuit and the fine product (pass-through material) comprises the final product. Tests have shown that the present invention produces products with different particle sizes of less than 16 mm, particle sizes of less than 8 mm, particle sizes of up to 99.8% passing a 1 mm mesh, and between 60% and 85% passing a 0.074 mm mesh. Example 1 High-acceleration sieving tests were conducted on a pilot scale using iron ore with about 50% of the material passing at 1 mm, 11% moisture content and a very high loss on ignition (LOI) (about 10%), which is characteristic of a cohesive material that is difficult to sieve at normal moisture content. The recovery at a size of less than 1 mm mesh ranged from 35% to 41%, which was consistent with the amount of fine particles present in the sample, indicating the efficiency of natural moisture sieving even for such a cohesive material. Tables 1a, 1b and 1c show the chemical analyses, particle size distribution of the tested sample and the undersize and oversize separations obtained in the pilot tests as well as the test mass balance. Table 1a: Chemical analysis Chemical Analysis (%) Fe SiO2 P Al2O3 Mn TiO2 CaO MgO LOI 57.0 6.23 0.196 1.610 0.263 0.104 0.023 0.112 9.99 Table 1b: Particle size distribution of high-speed sieving tests Mesh (mm) Test 1 Test 2 Particle Size Distribution (%) Particle Size Distribution (%) Feed Smaller than size Larger than size Feed Smaller than size Larger than size 40,000 100.00 100.00 100.00 100.00 100.00 100.00 31,500 98.04 100.00 96.69 98.38 100.00 97.50 25,000 96.38 100.00 93.89 97.79 100.00 96.59 19,000 92.17 100.00 86.79 95.07 100.00 92.40 16,000 90.09 100.00 83.27 92.63 100.00 88.64 12,500 86.11 100.00 76.57 88.87 100.00 82.84 10,000 82.59 100.00 70.62 85.43 100.00 77.54 8,000 79.09 100.00 64.72 82.21 100.00 72.57 6,300 75.60 100.00 58.83 78.23 100.00 66.44 2,400 57.07 99.27 28.05 57.64 99.50 34.97 1,000 48.37 88.05 21.09 47.01 86.52 25.62 840 47.30 85.75 20.86 45.75 83.34 25.40 710 45.93 82.71 20.64 44.22 79.48 25.12 500 43.42 77.12 20.25 41.58 72.67 24.74 210 37.50 64.55 18.90 35.58 58.24 23.31 150 34.83 59.25 18.04 33.11 53.11 22.28 106 32.20 54.09 17.14 31.06 49.34 21.17 74 31.54 52.92 16.84 29.16 44.80 20.69 45 26.16 43.86 14.00 24.90 38.04 17.78 37 23.77 39.36 13.05 23.32 35.60 16.66 25 18.69 30.06 10.87 19.70 30.13 14.05 15 12.93 19.95 8.10 15.00 23.15 10.59 10 9.40 14.00 6.24 11.72 18.26 8.17. Table 2c: Mass balance of tests with high acceleration sieve Test 1 Mass Flow % Test 2 Mass Flow % Feed 100.00 Feed 100.00 Smaller than size 40.70 Smaller than size 35.10 Larger than size 59.30 Larger than size 64.90 Example 2 Tests were carried out on HPGR and the test results are shown in Table 2. After two runs in the same equipment, it was possible to obtain 56% of the material retained in the 0.074 mm mesh. This highlights the high reduction ratio of fine particles. Table 2: Particle size distribution of HPGR tests Press Feed First Run Second Run Size (mm) % Retained Single % Retained Accumulated % Passed % Retained Single % Retained % Passed % Retained Single % Retained Accumulated % Passed 3.360 0.39 0.39 99.61 0.02 0.02 99.98 0.01 0.01 99.99 1.000 38.53 38.92 61.08 21.16 21.18 78.82 13.72 13.72 86.28 0.710 4.68 43.60 56.40 5.75 26.93 73.07 4.57 18.29 81.71 0.500 5.13 48.73 51.27 5.55 32.47 67.53 4.59 22.88 77.12 0.420 1.89 50.62 49.38 2.65 35.12 64.88 2.40 25.28 74.72 0.300 5.71 56.33 43.67 6.32 41.45 58.55 6.96 32.24 67.76 0.210 4.18 60.51 39.49 5.00 46.45 53.55 5.37 37.61 62.39 0.150 6.02 66.53 33.47 7.42 53.86 46.14 7.48 45.09 54.91 0.074 7.06 73.59 26.41 9.77 63.63 36.37 11.42 56.50 43.50 0.045 4.33 77.93 22.07 6.18 69.81 30.19 7.30 63.81 36.19 bypass 22.07 100.00 0.00 30.19 100.00 0.00 36.19 100.00 0.00 Example 3 The tests were conducted in a vertical roller mill (VRM) and the results are in Table 3. The tests were conducted under high and low pressure conditions, 500 psi and 300 psi, respectively, and under both conditions allowed for material reduction above 1 mm, showing a good reduction ratio of particles in larger fractions. Table 3: Particle size distribution of tests with vertical roller mill Size (mm) High Pressure – 1 Run Low Pressure – 2 Run Product Feed Product Feed 9.525 100.00 100.00 100.00 100.00 6.350 98.72 100.00 100.00 100.00 4.750 96.82 100.00 100.00 100.00 3.350 95.92 100.00 99.90 100.00 2.360 94.80 99.89 99.90 100.00 1.700 94.08 99.78 99.40 99.90 1.180 93.35 99.44 98.70 99.70 0.850 92.79 98.65 94.60 98.80 0.600 92.29 97.75 96.60 97.90 0.425 91.34 96.86 95.80 97.00 0.300 90.89 96.07 95.00 96.10 0.212 89.83 95.12 94.10 95.30 0.150 86.26 93.04 92.10 94.10 0.106 78.99 88.43 89.20 91.90 0.090 71.90 80.97 85.40 89.40 0.075 63.91 76.59 80.70 85.00 0.045 33.41 55.81 56.20 63.90 Example 4 Experimental tests were carried out using a roller crusher (RC) with iron ore with about 43% retained at 1 mm and the results are given in Table 4, which show that material reductions above 1 mm are possible and provide high production of fine particles (less than 0.075 mm). The tests have shown that the roller crusher is efficient in size reduction for various initial particle sizes. Table 4: Particle size distribution of roller brittle tests Size (mm) Feed 1 Run 2 Run 4 Run 5 Run 6 Run 1.00 43.68 13.34 3.88 0.36 0.2 0.12 0.500 56.86 25.92 15.39 6.09 3.99 2.00 0.150 79.93 45.12 33.00 28.70 25.43 21.71 0.106 84.40 50.21 37.41 35.75 32.36 28.81 0.075 88.47 53.73 40.31 41.29 37.78 33.25 0.045 56.79 42.70 46.40 42.32 35.99 There are various variations within the scope of this application. Therefore, it is emphasized that the present invention is not limited to the specific examples / configurations described above.

Claims

Claims 1. A process for crushing iron ore or iron ore products at natural humidity, characterized in that at least two crushing operations are carried out using at least one equipment selected from the group consisting of a roller press (HPGR), a vertical roller mill (VRM), a roller crusher (RC) and a screen with an acceleration of at least 10G, where G is the acceleration of gravity; wherein the at least two crushing operations are carried out at natural humidity and do not include any of the wetting and drying steps.

2. The process according to claim 1, characterized in that a first crushing operation uses a roller press (HPGR) and a second crushing operation uses a vertical roller mill (VRM) in series.

3. The process according to claim 1, characterized in that a first crushing operation uses a vertical roller mill (VRM) and a second crushing operation uses a roller press (HPGR) in series.

4. The process according to claim 1, characterized in that the first crushing operation uses a roller press (HPGR) and a second crushing operation uses screening performed in a sieve with an acceleration of at least 10G in a closed circuit.

5. The process according to claim 1, characterized in that the first crushing operation uses a vertical roller mill (VRM) and a second crushing operation uses screening performed in a sieve with an acceleration of at least 10G in a closed circuit.

6. The process according to claim 1, characterized in that a first crushing operation uses a roller press (HPGR), a second crushing operation uses a vertical roller mill (VRM), and a third crushing operation uses screening performed in a sieve with an acceleration of at least 10G in a closed circuit.

7. The process according to claim 1, characterized in that a first crushing operation uses a vertical roller mill (VRM), a second crushing operation uses a roller press (HPGR), and a third crushing operation uses screening performed in a sieve with an acceleration of at least 10G in a closed circuit.

8. The process according to claim 1, characterized in that a first crushing operation uses screening in a sieve with an acceleration of at least 10G and a second crushing operation uses a roller press (HPGR).

9. The process according to claim 1, characterized in that a first crushing operation uses screening in a sieve with an acceleration of at least 10G and a second crushing operation uses a vertical roller mill (VRM).

10. The process according to claim 1, characterized in that at least two crushing operations use roller crushers (RC) in multiple stages in series.

11. The process according to claim 1, characterized in that a first and second crushing operation uses a roller crusher (RC) in series and a third crushing operation uses screening with an acceleration of at least 10G in a closed circuit.

12. The process according to claims 10 and 11, characterized in that the roller crusher (RC) has 2, 4, 6, 8 or 10 rollers.

13. The process according to any one of claims 1 to 12, characterized in that the iron ore is raw iron ore from a mine and the iron ore products are pellet feed or sinter feed.

14. The process according to any one of claims 1 to 13, characterized in that the iron ore or iron ore products have a moisture content of up to 12% by weight.

15. The process according to any one of claims 1 to 14, characterized in that the process achieves a particle size of less than 16 mm for iron ore.

16. The process according to any one of claims 1 to 14, characterized in that the process achieves a particle size of less than 8 mm for iron ore.

17. The process according to any one of claims 1 to 14, characterized in that the process achieves a particle size of less than 0.074 mm for the iron ore product.

18. The process according to any one of claims 1 to 9, characterized in that the operation on the high-pressure roller press (HPGR) or vertical roller mill (VRM) is carried out in a maximum of three stages.

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