System and method for the dry magnetic concentration of fine iron ore concentrates

Abstract

The present invention relates to a system and a method for the dry magnetic concentration of fine iron ore concentrate. More specifically, the present invention relates to a reprocessing / purification pathway for the enrichment of pellet material by providing a system for improving / increasing the efficiency of the purification step of concentrating pellet material from previous mineral concentration steps, comprising a drying unit, a cooling unit, and a magnetic separation unit, wherein the fed pellet material has an iron content of about 58% to about 64% and achieves high purity levels of more than 67.5%.

Description

Field of the invention

[0001] The present invention relates to a system and method for the dry magnetic concentration of fine iron ore concentrate (pellet material) to obtain high-purity concentrates. More specifically, the present invention represents a reprocessing / purification route for the enrichment of pellet material. Basics of the invention

[0002] In the mining industry, the term pellet material or pellet feedstock refers to the fine fractions of iron ore, where 90% of the particles are smaller than 150 µm. These are typically intended for the pelletizing process, which requires a step of re-grinding these particles to fractions with a size of more than 60% below 45 µm. Alternatively, pellet material can also be processed together with sinter material (with particle size fractions typically between 0.150 mm and 6.35 mm) in the sintering process, although this proportion is typically limited to 40%.

[0003] The stoichiometry of hematite ore exhibits a maximum of 69.94% Fe(T), compared to commercial pellet material with contents between 58 and 64% Fe(T) and impurities such as silicon dioxide (SiO2) and aluminum oxide (Al2O3) of approximately 11.94% and 5.94%, respectively. The presence of these impurities in reduction furnaces significantly increases the consumption of reducing agents and fluxes, causing these furnaces to operate with higher greenhouse gas (GHG) emissions and steelmaking waste. Steelmaking waste is considered Class 1 and / or 2 non-inert material and requires controlled disposal.

[0004] The process used in the mining industry to beneficiate iron ore typically consists of a flotation process in stages known as rougher, scavenger and cleaner, as well as various combinations of these processes to obtain a concentrate with the desired specifications, combined with a preceding or subsequent stage of wet electromagnetic separation (WHIMS) or even just wet electromagnetic separation (WHIMS).

[0005] Current drum and roller type dry magnetic separators made of high intensity rare earth permanent magnets show good efficiency for fractions above 150 µm and some magnetic roller separators are satisfactory for fractions above 75 µm.

[0006] It is worth noting that magnetic separation is a process in which two or more materials with different magnetic susceptibilities are separated from each other, with the primary driving force being the magnetic force (Fm). In addition to the magnetic force, other forces act on the particles, such as the centrifugal force (Fc) and the gravitational force (Fg). In this context, a particle is considered magnetic if Fm > Fc + Fg. For particles smaller than 150 µm, the magnetic force is usually greater than the centrifugal force. Furthermore, as those skilled in the art know, fine particles not only have a lower centrifugal force but are also affected by the magnetic field, so the smaller their diameter, the greater this influence. This also leads to the directing of non-magnetic fine particles into a zone designated for the reception of magnetic particles.In view of this, the magnetic separation of iron ore fines below 150 µm remains a challenge, as conventional separation systems are inefficient for producing concentrates with economically viable iron contents.

[0007] Conventional magnetic separation or slurry devices generally have a splitter that produces a magnetic and a non-magnetic product. State-of-the-art magnetic separators also include two splitters that produce a third mixed product.

[0008] Patent BR102012008340-0, also owned by the applicant, discloses a magnetic separation system and unit for the recovery of iron ore fines. The magnetic separation unit performs sequential separations, producing non-magnetic, mixed, and magnetic fractions. However, this prior art document teaches how to control the feed to the magnetic separation unit by varying the vibration intensity of the vibration motor installed therein, which does not always result in adequate material flow. Furthermore, the feedstock is different from the pellet material and therefore requires additional classification by cyclones prior to magnetic separation. Furthermore, this document is silent on the configuration of splitters in the magnetic separation unit as a means of controlling and optimizing the separation.

[0009] Document US5961055 relates to methods and systems for the dry separation of magnetic material (including iron ore) from mixtures containing non-magnetic material. Within this scope, this document discloses processes involving multi-stage magnetic separation with multiple rounds of magnetic separation with optional classification. Furthermore, this document teaches that dry material can be initially separated by a low-intensity magnetic field, followed by subsequent high-intensity magnetic fields for additional magnetic separation. However, this document mentions magnetic drum separators and therefore has limitations with regard to fine materials.

[0010] The scientific paper, entitled "Comparison between concentration routes: Floatation x mixed circuits," proposes a mixed route for iron ore concentration, in which the rougher and scavenger stages are carried out in magnetic or electromagnetic separators and the cleaner stage is carried out by flotation. The presented results confirm the potential of the mixed circuit to increase mass and metallurgical yield compared to a concentration circuit consisting only of flotation. In this context, a product with an Fe content of 66.76% was achieved. However, this document mentions the use of wet-operated carousel separators (WHIMS) and proposes the application of magnetic or electromagnetic separation before the flotation stage, indicating the possibility of eliminating the desliming stage.

[0011] As explained above, there are efforts in the prior art to implement systems involving magnetic concentration of iron ore fines, combined with or without flotation, aimed at obtaining economically and environmentally viable iron concentrate products. In this context, the present invention proposes a process for obtaining high-purity iron ore concentrates and contributes to the reduction of greenhouse gases (GHG) and the generation of steelmaking waste. Furthermore, it should be noted that the present invention enables the rational use of natural resources and the recycling of the resulting tailings for use in the construction industry, with significant water savings, as it is carried out in a completely dry environment.

[0012] In this scenario, as explained below, the present invention provides an integrated system that allows to obtain high quality concentrates while enabling a significant positive impact on the environment related to the dry concentration route and the reuse of the treatment residues. Summary of the invention

[0013] The present invention provides a system and process for producing high-quality pellet material. More specifically, the present invention provides a dry processing / cleaner process for magnetically concentrating fine iron ore concentrates.

[0014] In this context, the present invention aims to provide a system and method for improving / increasing the efficiency of the cleaner step of concentrating pellet material derived from previous mineral concentration steps, such as flotation and / or wet magnetic or electromagnetic concentration (WHIMS or similar), while achieving high metallurgical and mass yields. More specifically, the present invention starts from pellet material concentrates with Fe(T) contents in the range of about 58% to about 64% (typically, the standard content of 62%) to obtain an iron oxide ore concentrate product with Fe(T) contents above 67.5%.

[0015] The present invention further aims to provide a dry processing / cleaner route that eliminates the use of water as a resource and the need to deposit tailings in tailings dumps. Effectively, the present invention aims to minimize environmental impacts, as the resulting tailings can be used in the construction industry or, depending on the quality achieved, in the steel industry.

[0016] The above objects and further advantages of the present invention will become clearer from the following description. Short description of the drawings Fig. 1 shows a simplified operational flow diagram of the process for concentrating fine iron ore concentrate according to the present invention. Fig.Figure 2 shows the flash dryer with mechanical stirring system used as one of the alternatives in the process of the present invention. Fig. Figure 3 shows a simplified schematic representation of the magnetic roller according to the present invention. Fig. 4 shows a detailed embodiment of the magnetic roller according to the present invention. Fig. Figure 5 shows the cascade arrangement of four magnetic rollers according to the present invention. Fig. Figure 6 shows the arrangement of the splitters for four magnetic rollers according to the present invention. Fig. Figure 7 shows the configuration of magnet thicknesses and air gap thicknesses for four magnetic rollers according to the present invention. Fig.Figure 8 shows the configuration of the magnetic field lines, the gradient (depth of the magnetic field), the magnetic intensity diagram and the points of greatest magnetic intensity compared to the retention area of ​​the magnetic minerals. Fig. Figure 9 shows the design and construction of a block of four magnetic separators according to the present invention. Detailed description of the invention

[0017] To achieve the objects described above, the present invention provides a system and method for dry magnetic concentration of fine iron ore concentrates.

[0018] More specifically, the present invention provides a method and system for dry magnetic concentration of pellet materials, comprising: a drying unit, a cooling unit, and a magnetic separation unit. Fig.Figure 1 shows a simplified flow diagram of the process path for the concentration of fine iron ore concentrate of the present invention.

[0019] The drying unit is designed to promote good dispersion and prevent the formation of pellets and comprises a dryer selected from the group consisting of a rapid dryer with mechanical stirring system, flash dryer, rotary dryer, fluidized bed dryer and the like.

[0020] Fig.Figure 2 shows a flash dryer with a mechanical agitation system 2, which includes agitator shafts 2.2 that bring the particles into contact with the hot gas, thus promoting rapid heat exchange and efficient drying. The hot gas is introduced via inlet 2.1, and a diverter system 2.5 allows the heated gas to contact the wet ore, which is fed in via inlet 2.4 and released as dry ore via the outlet with the double pendulum valve 2.3. The saturated, moist gas, in turn, is discharged via outlet 2.6.

[0021] In a flash dryer, for example, the pellet material is suspended in a column by sucking in hot air from a hot gas generator.

[0022] According to the present invention, the dryer is dimensioned such that the residence time is such that the residual moisture of the pellet material is equal to or less than 0.5% (bu, read on a wet basis).

[0023] The heat source for the dryers comes from the combustion of natural gas, coal, charcoal, coke, fuel oils, diesel, liquid or gaseous steel by-products or petrochemical by-products such as tar, anthracene oil, blast furnace gas, coke oven gas and others.

[0024] In a preferred embodiment, the drying step is carried out at a temperature in the range of about 80°C to about 120°C.

[0025] At the end of the drying process, a process exhaust system promotes forced convection of the gas stream. During this process, as well as at the gas outlets from the dryers, fine particles can be collected in high-performance cyclones. The cyclone gases undergo a dedusting process in which the particles, which are usually smaller than 10 µm, are captured in a process bag filter or electrostatic precipitator.

[0026] Then, cold air is injected to promote cooling of the ore for the next stage of magnetic separation. The cooling is intended to preserve the magnetic intensity of the rare earth magnets for the subsequent magnetic separation stage, which can be demagnetized at temperatures above 80°C. According to the present invention, cooling is carried out in static or dynamic air classifiers, rotary coolers, column coolers, or fluidized bed coolers, with a supply of ambient air at room temperature.

[0027] In a preferred embodiment, the temperature of the pellet material is reduced to less than 65°C in the cooling step.

[0028] Optionally, the present invention comprises an air sorting unit in conjunction with the cooling unit to perform the cutting of the extremes, e.g., particles below 10µm or above 150µm.

[0029] The magnetic separation unit is controlled by means of splitters. In a preferred embodiment, the magnetic rollers of the present invention have at least three splitters that separate the non-magnetic fractions, the mixed fractions, and the magnetic fractions. Fig. Figure 3 shows a schematic and simplified representation of the magnetic roller with its three splitters. The fraction collected to the left of splitter 3 is the magnetic fraction, the fraction collected between splitter 3 and splitter 2 is the mixed fraction, and the fraction collected to the right of splitter 1 is the non-magnetic fraction.

[0030] In addition to "capturing," i.e., the unwanted entrainment of non-magnetic particles along with magnetic particles, there is also unwanted resistance caused by the vacuum created by the high speed of the magnetic roller. In this context, Splitter 2 is not intended to produce a product, but rather to form a barrier against unwanted particle resistance.

[0031] Fig. Figure 4 shows a more detailed configuration of a magnetic roller according to the invention and the arrangement of the three splitters 100, 101, and 102. The combination of the roller speed with the magnetic gradient and the magnetic intensity determines the separation point between the magnetic fraction and the mixed fraction, i.e., the positioning of the splitter 102.

[0032] The preferred arrangement of the aforementioned splitter 102 for four magnetic rollers with a diameter of 150 mm according to the present invention is shown in Fig. 6 shown: - for a first magnetic roller, a positioning 104 between 90 mm and 100 mm; - for a second magnetic roller, a positioning 105 between 80 mm and 90 mm; - for a third magnetic roller, a positioning 106 between 70 mm and 80 mm; and - for a fourth magnetic roller, a positioning 107 between 65 mm and 75 mm.

[0033] The positions 104, 105, 106 and 107 defined here can vary between 5 mm and 7 mm, more or less.

[0034] A larger positioning of the splitter 102, i.e., a greater distance from it to the center of the roller, indicates that the iron ore processed in this stage has a greater magnetic susceptibility, i.e., a higher iron content. Such a configuration can be observed in the first magnetic roller. The opposite is also true: A lower positioning of the splitter 102 indicates that the iron mineral processed in this stage has a lower magnetic susceptibility, i.e., a lower iron content. Such a configuration can be observed in the fourth magnetic roller.

[0035] The magnetic separation unit comprises two to eight stages of mineral concentration. The magnetic separation unit therefore comprises two to eight magnetic rollers. In a preferred embodiment of the present invention, the magnetic separation comprises five concentration stages, divided into two steps.

[0036] In the first step, a low-intensity magnetic separation is performed using a first magnetic roller made of iron-boron permanent magnets with an intensity between 300 and 3500 gauss, preferably between 750 and 1500 gauss. In a preferred embodiment, the first magnetic roller has a diameter of approximately 240 mm to approximately 500 mm.

[0037] In the second step, a sequence of high-intensity magnetic separations is performed using magnetic rollers made of rare-earth magnets (iron-boron-neodymium) with varying intensities between 7500 and 14000 gauss. In a preferred embodiment, four magnetic rollers are arranged in a cascade with an inclination angle between 5° and 55° and have a diameter of approximately 100 mm to approximately 500 mm. In an even more preferred embodiment, the four magnetic rollers are arranged in a cascade with an inclination angle of 21° and have a diameter of approximately 150 mm to approximately 240 mm.

[0038] Each of the four magnetic rollers arranged in a cascade has different intensities, with the first roller having the lowest intensity and the fourth roller having the highest. To this extent, the first roller separates minerals with higher magnetic susceptibility and consequently higher Fe(T) content, while the fourth roller separates minerals with lower magnetic susceptibility and consequently lower Fe(T) content.

[0039] According to the present invention, each of the four magnetic rollers defined above has configurations with different magnet thicknesses for air gap thicknesses. Such configurations are between 3 mm and 20 mm, preferably between 3 mm and 15 mm, for the magnets and between 2 mm and 3 mm for the air gap. In a preferred embodiment, such configurations comprise a ratio of 13:1 to 4:3 of magnet thickness to air gap thickness.

[0040] It should be noted that the higher the ratio of magnet thickness to air gap thickness, the greater the magnetic intensity. Furthermore, the configurations proposed by the present invention, with high magnet thicknesses combined with low air gap thicknesses, not only contribute to reducing the system costs (in terms of the cost associated with the magnets), but also exhibit very high gradients and intensities and create a small area of ​​magnetic attraction (shallow magnetic field depth, with 1 to 2 mm of the surface of the magnetic roller), leading to an increase in separation selectivity.

[0041] Furthermore, the magnetic rollers of the present invention are preferably manufactured by connecting magnets of the same polarity (north) with an air gap in the center, followed by magnets of the same polarity (south) with an air gap in the center, thereby creating magnetic field lines that alternate along the magnetic roller.

[0042] Fig.Figure 7 shows a configuration for the four high-intensity magnetic rollers of the proposed separation unit. The first magnetic roller, with a configuration of magnet thickness 108 to air gap thickness 109 of 13 mm to 3 mm (4.3:1), generates a magnetic intensity of approximately 12,500 Gauss. The second magnetic roller, with a configuration of magnet thickness 110 to air gap thickness 111 of 10 mm to 2 mm (5:1), generates a magnetic intensity of approximately 12,750 Gauss. The third magnetic roller, with a configuration of magnet thickness 112 to air gap thickness 113 of 13 mm to 2.5 mm (5.2:1), generates a magnetic intensity of approximately 13,000 Gauss. The fourth magnet roller with a configuration of magnet thickness 114 to air gap thickness 115 of 13mm to 2mm (6.5:1), generates a magnetic intensity of approximately 13500 Gauss.

[0043] Fig. Figure 8 shows the influence of the magnet and air gap thickness configuration on the formation of magnetic intensity peaks, as explained below.

[0044] For a configuration of 13 mm magnet thickness and 1 mm air gap thickness, a higher magnet strength is achieved with a single tip 116 and a high gradient with a small magnetic attraction area 117 of 0.26 mm 2 observed, which can reach about 14000 Gauss or slightly more.

[0045] For a configuration of 13 mm magnet thickness and 2 mm air gap thickness, a slightly smaller gradient than above is observed, with the formation of two peaks 118 and an area of ​​magnetic attraction 119 of 1.04 mm 2 , which reaches an intensity of about 13500 Gauss.

[0046] In a configuration with a magnet thickness of 13 mm and an air gap thickness of 2.5 mm, a slightly smaller gradient than above is observed, with the formation of two peaks 120 and an area of ​​magnetic attraction 121 of 1.67 mm 2 , which reaches an intensity of about 13000 Gauss.

[0047] For a configuration of 13 mm magnet thickness and 3 mm air gap thickness, a slightly smaller gradient than above is observed, with the formation of two peaks 122 and an area of ​​magnetic attraction 123 of 2.40 mm 2 , which reaches an intensity of about 12500 Gauss.

[0048] For a configuration of 13 mm magnet thickness and 4 mm air gap thickness, a slightly smaller gradient than above is observed, with the formation of two peaks 124 and an area of ​​magnetic attraction 125 of 4.16 mm 2 , which reaches an intensity of about 11500 Gauss.

[0049] For a configuration of 13 mm magnet thickness and 5 mm air gap thickness, a slightly smaller gradient than above is observed, with the formation of two peaks 126 and an area of ​​magnetic attraction 127 of 6.60 mm 2 , which reaches an intensity of about 10500 Gauss.

[0050] To achieve very high separation selectivity and thus obtain a product with a very high Fe(T) content, the present invention proposes a magnetic roller speed of up to 1600 rpm. Preferably, the magnetic roller speed is between 300 and 700 rpm.

[0051] The magnetic roller configurations proposed here, combined with a higher speed than conventional magnetic roller separators, provide additional control of the magnetic separation unit and allow for greater selectivity to obtain a purer magnetic concentrate and reduce “capture”.

[0052] The magnetic separation unit according to the invention can be used to obtain high-purity iron ore concentrates with Fe contents of over 67.5%.

[0053] Fig.Figure 9 shows a block of four industrial-grade magnetic separators with high-intensity rare earth magnets, as designed 119 and as built 120. To enable industrial-scale construction, castings 122, extruded components, stamped parts, CNC turned parts, and low-wear parts were used in the production of injection-molded and rotationally molded plastic (PP) parts 121.

[0054] Against this background, the present invention proposes a novel concentration route for enriching pellet material with a quality equal to or lower than that required for the production of blast furnace pellets (Pellet Feed of Blast Furnace - PFAF) into pellet material with a quality suitable for the production of pellets for the feed of the direct reduction process (Pellet Feed of Direct Reduction - PFDR). Furthermore, it is important to note that the present invention enables the extraction of high-value-added products without generating waste, since the waste and discarded fractions can be destined for the construction industry (or, depending on the quality achieved, for the steel industry). It is therefore clear that the present invention represents an environmentally friendly solution for the enrichment of pellet material.

[0055] The description of the subject matter of the present invention given so far should be considered only as possible embodiment(s), and any particular features introduced therein should be understood only as something provided for ease of understanding. They should therefore not be considered as a limitation of the invention, which is limited to the scope of the claims.

[0056] The examples presented illustrate the range of products produced with the proposed processing / purification system and the process for enriching pellet material concentrate. ExamplesExample 1

[0057] Initial tests were conducted on samples of mixtures of concentrate and tailings with an approximate content of 65% Fe(t) and 62% Fe(t), respectively. Sample characterization is presented in Tables 1 and 2. Table 1: Chemical characterization and particle size characterization of the sample of mixture 01 - PFAF Mixture 01 - PFAF %Fe(t) %SiO2 %Al2O3 % P PPC 64,7 6,22 0,18 0,01 0,24 Particle size Fraction (mm / µm) % cumulative throughput 0.500mm / 500µm 100,00 0.150mm / 150µm 97,10 0.075mm / 75µm 72,82 0.045mm / 45µm 24,93 0.010mm / 10µm 0,61 Table 2: Chemical characterization and particle size characterization of the sample of mixture 02 - PFAF Mixture 02 - PFAF %Fe(t) %SiO2 %Al2O3 % P PPC 61,96 10,19 0,17 0,01 0,27 Particle size Fraction (mm / µm) % cumulative throughput 0.500mm / 500µm 99,06 0.150mm / 150µm 95,84 0.075mm / 75µm 66,73 0.045mm / 45µm 38,00 0.010mm / 10µm 6,13

[0058] Tables 3 and 4 show the results obtained after carrying out the process according to the invention. Table 3: Results for the sample of mixture 01 - PFAF Results of dry concentration - Mixture 01 PFAF concentrate % Mass % Fe % SiO2 % Al2O3 % P %PPC 93,95 68,52 0,87 0,15 0,01 0,17 Processing residues 6,05 5,36 89,23 0,57 0,04 1,31 Table 4: Results for the sample of mixture 02 - PFAF. Results dry concentration - Mixture 02 PFAF concentrate % Mass % Fe % SiO2 % Al2O3 % P % PPC 89,12 68,61 0,9 0,15 0,01 0,18 Processing residues 10,88 7,44 86,29 0,35 0,04 1,06

[0059] As can be seen, the 01 PFAF mixture sample achieved a mass recovery of approximately 93% and a final Fe(T) content of 68.52%. Furthermore, the 02 PFAF mixture sample achieved a mass recovery of approximately 90% and a final Fe(T) content of 68.61%. Thus, products suitable for use as PFDRs were obtained. Example 2

[0060] To demonstrate the efficiency of the proposed system and process, a new sample of a mixture of concentrate and tailings was tested. The sample characterization is presented in Table 5. Table 5: Chemical characterization and particle size characterization of the sample of mixture 03 - PFAF - Annex 02 Mixture 03 - PFAF - Appendix 02 % Fe(t) % SiO2 % Al2O3 % P % PPC 61,73 9,74 0.34 0.02 0.83 Particle size Fraction (mm / µm) % cumulative throughput 0.500mm / 500µm 99,67 0.150mm / 150µm 89,49 0.075mm / 75µm 58,15 0.045mm / 45µm 25,48 0.010mm / 10µm 1,49

[0061] Table 6 shows the result obtained after carrying out the process of the present invention. Table 6: Results for the sample of mixture 03 - PFAF - Plant 02 Dry concentration results - Mixture 03 - PFAF - Plant 02 Products % Mass Fe % SiO2 % Al2O3 %P % PPC concentrate 89,49 68,15 0,7 0,26 0,02 0,75 Processing residues 10,51 7,16 86,71 1,05 0,02 1,55

[0062] As can be seen, a mass recovery of approximately 89.5% was achieved, with a metallurgical recovery of over 98% and a final Fe(T) content of 68.15%. Thus, products suitable for use as PFDR were obtained.

[0063] Since the results of the first tests were satisfactory, new tests were carried out without mixing treatment residues with plant concentrate (concentrates from flotation plants were tested). Example 3

[0064] A series of 5 pellet material concentrate samples from flotation plants were characterized and blended together.

[0065] The mineralogical and chemical properties as well as the particle size of the samples are shown in Tables 7, 8 and 9, respectively. Table 7: Mineralogical characterization of the PFAF samples Mineralogical characterization of the pellet material of a blast furnace sample % HC % HM % Employees % GO % QZ % OT PF01 91,24 0,08 0,45 5,51 2,25 0,46 PF02 38,17 34,37 20,76 4,87 1,47 0,35 PF03 16,22 47,98 16,75 13,55 5,11 0,39 PF04 96,41 0,16 0,09 0,24 2,81 0,29 PF05 22,4 43,19 5,38 24,21 3,24 1,52 HC - Compact Hematite / HM - Martite Hematite / Ma - Magnetite / GO - Goethite / QZ - Quartz / OT - Other Table 8: Chemical characterization of the PFAF samples. Chemical characterization of the pellet material of a blast furnace sample % Fe % SiO2 % Al2O3 % P % Mn % PPC PF01 67,47 2,82 0,38 0,046 0,056 0,7 PF02 67,95 1,87 0,29 0,033 0,078 0,76 PF03 64,74 4,77 0,32 0,086 0,245 1,86 PF04 67,53 2,58 0,21 0,015 0,07 0,32 PF05 63,13 3,8 1,16 0,057 0,386 4,06 Table 9: Characterization of the particle size of the PFAF samples Particle size of the pellet feed of a blast furnace % cumulative throughput Fraction (mm / µm) PF01 PF02 PF03 PF04 PF05 0.500mm / 500µm 99,40 99,38 99,79 99,88 100,00 0.150mm / 150µm 90,22 87,81 91,14 97,87 96,03 0.075mm / 75µm 72,56 59,39 65,00 83,77 76,52 0.045mm / 45µm 48,54 29,86 38,39 45,99 44,70 0.010mm / 10µm 1,24 0,48 4,14 1,45 7,23

[0066] After characterizing the samples, a first mixture of 20% PF01 / PF03 / PF05 and 80% PF02 / PF04 was characterized. The characterization of this mixture is shown in Table 10. Table 10: Chemical characterization and particle size characterization of the mixture Characterization PF01 / PF03 / PF05 20% mixture + PF02 / PF04 80% mixture % Fe % SiO2 % Al2O3 % P % Mn % PPC 67,73 2,02 0,22 0,03 0,1 0,96 Particle size Fraction (mm / µm) % cumulative throughput 0.500mm / 500µm 99,72 0.150mm / 150µm 94,42 0.075mm / 75µm 75,75 0.045mm / 45µm 42,00 0.010mm / 10µm 1,75

[0067] Table 11 shows the result after carrying out the method of the present invention Table 11: Result for the mixture Results PF 01 / PF03 / PF 05 20 % Mixture + PF 02 / 04 80 % Mixture Products % Mass % Fe % SiO2 % Al2O3 % P % Mn % PPC concentrate 90,29 68,85 0,83 0,17 0,02 0,08 0,77 Processing residues 9,71 57,26 13,06 0,69 0,06 0,3 2,70

[0068] As can be seen, a mass recovery of approximately 90.29% and a metallurgical recovery of over 98% were achieved, with a final Fe(T) content of 68.85%. Thus, products suitable for use as PFDRs were obtained. Example 4

[0069] A second blend was formed by modifying the blend of Example 3 with 30% PF01 / PF03 / PF05 and 70% PF02 / PF04, and then the process route of the present invention was followed. Table 12 shows the results obtained. Table 12: Result for the mixture Results PF01 / PF03 / PF05 30% mixture + PF02 / PF04 70% mixture Products % Mass % Fe % SiO2 % Al2O3 % P % Mn % PPC concentrate 83,85 68,76 0,85 0,19 0,03 0,08 0,65 Processing residues 16,15 58,06 12,74 0,71 0,06 0,29 2,54

[0070] After implementing the process according to the invention, a mass recovery of approximately 83.85% and a final Fe(T) content of 68.76% were achieved, considering the test with the 70 / 30 mixture. Thus, products suitable for use as PFDR were obtained.

[0071] All the experiments described in the examples above were carried out in the laboratory and have shown that the waste generated can be recycled in the steel industry.

[0072] To confirm the results obtained in the laboratory, pilot scale tests were carried out Example 5

[0073] A sample of a mixture of concentrate and tailings was tested at pilot scale. The chemical and particle size characterization of this sample is shown in Table 13. Table 13: Chemical and particle size characterization of the PF01 mixture. Characterization pilot test PF01 % Fe % SiO2 % Al2O3 % P % Mn % PPC 67,26 2,96 0,211 0,016 0,065 0,575 Particle size Fraction (mm / µm) % cumulative throughput 0.500mm / 500µm 100,00 0.150mm / 150µm 98,05 0.075mm / 75µm 86,14 0.045mm / 45µm 48,98 0.010mm / 10µm 1,78

[0074] Table 14 shows the result after carrying out the method of the present invention. Table 14: Results for the PF01 mixture Results PF01 - Pilot Plant Products % Mass % Fe % SiO2 % Al2O3 % P % Mn % PPC concentrate 88,88 68,79 0,98 0,19 0,01 0,05 0,49 Processing residues 11,12 55,07 18,78 0,38 0,03 0,14 1,25

[0075] As can be seen, a mass recovery of approximately 89% and a metallurgical recovery of over 98% were achieved, with a final Fe(T) content of 68.79%. Thus, products suitable for use as PFDRs were obtained. Example 6

[0076] A second sample of a mixture of concentrate and tailings was tested at pilot scale. The chemical and particle size characterization of this sample is shown in Table 15. Table 15: Chemical characterization and particle size characterization of the PF02 mixture Characterization pilot test PF02 % Fe % SiO2 % Al2O3 %P % Mn %P PC 66,97 3,16 0,3 0,04 0,08 0,86 particle size Fraction (mm / µm) % cumulative throughput 0.500mm / 500µm 98,97 0.150mm / 150µm 87,70 0.075mm / 75µm 59,27 0.045mm / 45µm 31,75 0.010mm / 10µm 1,24

[0077] Table 16 shows the result after carrying out the method of the present invention. Table 16: Results obtained for the PF02 mixture. Results PF 02 - Pilot Plant product % Mass % Fe % SiO2 % Al2O3 % P %Mn %PPC concentrate 87,59 68,51 1,25 0,25 0,04 0,072 0,66 Processing residues 12,41 56,12 16,63 0,65 0,05 0,17 2,28

[0078] As can be seen, a mass recovery of approximately 87.6% and a final Fe(T) content of 68.51% were achieved. Thus, products suitable for use as PFDR were obtained.

[0079] The results of the pilot scale experiments show that the application of the present invention is possible beyond the laboratory scale. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 5961055

[0009]

Claims

[1] Dry magnetic concentration system for fine iron ore concentrate, characterized by that it includes: - a drying unit; - a cooling unit and - a magnetic separation unit, wherein the fine iron ore concentrates originate from previous mineral concentration steps and have an Fe content of between approximately 58% and approximately 64%. [2] System according to claim 1, characterized by that the drying unit comprises a dryer selected from the group comprising rapid dryers with mechanical stirring system, flash dryers, rotary dryers, fluidized bed dryers and the like. [3] System according to claim 1, characterized by that the drying unit further comprises an exhaust air fan for forced convection of the gas stream from the drying process. [4] System according to claim 1, characterized bythat the drying unit further comprises high-frequency cyclones for dedusting fine particles contained in the gas from the drying process. [5] System according to claim 4, characterized by that the fine particles contain particles that are smaller than 10 µm. [6] System according to claim 4, characterized by that the fine particles are retained in a process bag filter or electrostatic precipitator. [7] System according to claim 1, characterized by that the cooling unit comprises static or dynamic air classifiers, rotary coolers, column flash coolers or a fluidized bed. [8] System according to claim 1, characterized by that it further optionally comprises an air classification unit coupled to the cooling unit. [9] System according to claim 1, characterized by that the magnetic separation unit comprises two to eight magnetic rollers. [10] System according to claim 9, characterized bythat the magnetic rollers of the present invention have at least three splitters. [11] System according to claim 9, characterized by that the magnetic separation unit comprises a first magnetic roller made of iron-boron permanent magnets with a variable intensity between 300 and 3500 gauss and a diameter of about 240 mm to about 500 mm and the remaining magnetic rollers made of rare earth magnets (iron-boron-neodymium) with a variable intensity between 7500 and 14000 gauss and a diameter of about 100 mm to about 500 mm. [12] System according to claim 11, characterized by that the other magnetic rollers are arranged in cascade with inclination angles between 5° and 55°. [13] System according to claim 11, characterized by that the other magnetic rollers have a diameter of approximately 150 mm to approximately 240 mm and are arranged in a cascade with an inclination angle of 21°. [14] System according to claim 12 or 13, characterized bythat each of the other magnetic rollers arranged in cascade has different intensities, with the first of these rollers having the lowest intensity and the last of these rollers having the highest intensity. [15] System according to one of claims 12 to 14, characterized by that the other magnetic rollers arranged in cascade have configurations between 3 mm and 20 mm for the magnets and between 2 mm and 3 mm for the air gaps. [16] System according to claim 15, characterized by that the other magnetic rollers arranged in cascade have configurations that have a ratio of 13:1 to 4:3 between the thickness of the magnet and the thickness of the air gap. [17] Dry magnetic concentration process for fine iron ore concentrates, characterized by that it is carried out with the system according to claim 1, which comprises a drying step, a cooling step and a magnetic separation step. [18] Method according to claim 17, characterized by that the drying step is carried out at a temperature in the range of about 80°C to about 120°C. [19] Method according to claim 17 or 18, characterized by that in the drying step the moisture content of the fine iron ore concentrate is reduced to less than 0.5%. [20] Method according to claim 17, characterized by that the cooling step is carried out with the supply of ambient air at room temperature. [21] Method according to claim 17 or 20, characterized by that the temperature of the fine iron ore concentrate is reduced to less than 65 °C in the cooling step. [22] Method according to claim 17, characterized by that it may include an air classification step after the cooling step. [23] Method according to claim 22, characterized by that in the air classification step, cutting of particles below 10 µm or above 150 µm is carried out. [24] Method according to claim 17, characterized by that the magnetic separation comprises two to eight concentration levels. [25] Method according to claim 24, characterized by that the magnetic separation comprises five concentration levels, which are divided into two steps. [26] Method according to claim 25, characterized by that the first step of magnetic separation is carried out by means of a first magnetic roller made of iron-boron permanent magnets with variable intensity between 300 and 3500 Gauss and a diameter of about 240 mm to about 500 mm. [27] Method according to claim 25, characterized by that the second step of magnetic separation is carried out by means of the remaining four magnetic rollers made of rare earth magnets (iron-boron-neodymium) with variable intensity between 7500 and 14000 Gauss and a diameter of about 100 mm to about 500 mm. [28] Method according to one of claims 17 to 27, wherein the magnetic separation is carried out at a rotational speed of the magnetic rollers of up to 1600 rpm, preferably between 300 rpm and 700 rpm.

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