EA040958B1 - METHOD AND SYSTEM FOR COMPLETELY DRY BENEFITING OF ORE USING A MAGNETIC SEPARATION UNIT - Google Patents

Description

Technical field

The present invention relates to a method and system for completely dry processing of iron ore, including fine and ultrafine particles, less than 150 microns, in a completely dry mode. Iron ores, including fine and ultrafine particles, are found in waste dumps and ore tailings of existing plants.

Modern cold beneficiation plants operated by large mining companies are initially expected to process ores that have a high iron content, such as Fe content above 54%, so all material with a lower percentage is considered tailings, which increasingly limits the process. enrichment due to the lack of ore with an iron content above 54%.

However, from the point of view of the present invention, it is possible to use these tailings as a starting material in the application of the method and system for completely dry enrichment of ore containing iron oxides using a magnetic separation unit.

In this regard, the aim of the present invention is to simplify the process of extracting iron ore, which is still contained in said tailings, which provides a high metallurgical yield and weight yield. Thus, it is possible to obtain a product having excellent marketable properties, more precisely, an ore concentrate having an Fe content of more than 63%, and the adjustment to increase the final Fe content of the concentrate, which can reach 67% (total), can be easily achieved. This result represents a significant step forward in terms of environmental protection, given the long-standing danger of artificial tailings ponds in the mining industry in Brazil and around the world.

The innovative features of the dry process of the present invention advantageously meet the requirements of the mining industry in terms of economy, environmental protection and development strategy at the same time, as they allow to improve the recovery from tailings that pose a high risk of adverse environmental impact, and allow them to be converted into a marketable commodity in a technically and economically feasible manner, as well as allowing the use of low iron ores that are currently tailings in existing plants.

This dry method uses no water and the final residual material creates a mound of waste, eliminating the need for a waste dump altogether. In addition, when using the dry method according to the present invention, the resulting waste becomes a semi-finished product for enterprises producing road and building blocks, as well as for the cement industry.

Said road and building blocks are made from sand and cement. In a number of states in Brazil, sand as a source material is obtained as a result of the destruction of hills from modified granite. At the same time, when performing this process, the modified granite is removed by mechanical destruction or using a water jet and crushed, followed by screening and hydrocyclone, during which the sand fraction of sand is separated from the clay fraction. In order to settle this clay and extract water, it is necessary to build a dump for waste. Another way to obtain this raw material is to extract the sand fraction from quarries using drainage and separate the sand fraction from the clay fraction by hydrocyclone, during which the clay is returned to the quarry. At the end of this process, due to the removal of a large part of the substances that make up the soil, large lakes arise, usually without the possibility of economic use of such liabilities. Such an example is the vicinity of the city of Seropedica, Rio de Janeiro, Brazil, with large liabilities, consisting in the presence of large lakes, rich in mineral sediments, which arise from the excavation of sand, without the possibility of any life forms or the possibility of economic use.

State of the art

At the beginning of mining on an industrial scale, little was known about tailings disposal methods. The low interest in this area was also due to the fact that the amount of waste produced was rather small, and in the implementation of activities in this industry, no one was yet concerned about environmental problems.

Therefore, tailings were usually arbitrarily dumped into rivers. However, due to the growth of the mining sector, growing public concern about environmental protection, and accidents associated with tailings dumps, back in the seventies in various parts of the world, including Brazil, mining companies were faced with the need to operate industrial installations to minimize the adverse impact on the environment and reduce the risk of accidents through the use of more careful and optimized approaches.

Generally speaking, there are three methods used to dispose of tailings from mining, namely:

wet method using dump ponds; dry method using mounds of tailings; or technology using paste-like mass (paste fill).

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The difference between dry disposal and wet disposal is that the wet dump method stores liquid along with the discharged solid material. In order to ensure a continuous flow of material, magnetic separation is usually applied at high magnetic induction, usually in wet mode, this is a process that is known in the world as

Wet magnetic separation at high magnetic induction (WHIMS).

An alternative to conventional practice is the disposal of the material in the form of a pasty mass, the advantages of which are, for example, greater recovery and circulation of water, greater limit angles of repose and less adverse environmental impact. However, this process has a high cost of implementation and implementation.

For example, the Brazilian patent application BR PI0803327-7 describes a method for increasing the concentration using magnets, characterized by low water consumption and the creation of a small amount of sludge. By using wet magnetic separation and draining of magnetic waste, the discharge of magnetic waste into settling ponds can be significantly reduced. However, this process cannot provide recovery from such tailings. Therefore, there is no effective reduction of the risk to the environment associated with its implementation.

Another document, BR PI0103652-1, describes a method for recovering from tailings containing iron oxides. These tailings can be obtained directly from the recovery of fines in the reduction processes used in the steel industry, as well as from changes in the return of fines from companies that supply iron ore to the steel industry. The material is loaded into a feed hopper and fed through chutes and belt conveyors into a rotary kiln. The dried material is discharged for storage without any sorting/concentration being done for it, or is then sent directly to the reduction ovens by means of a belt conveyor system.

BR 102012008340-0, also registered in the name of the same applicant, describes a system and method designed to separate both fine particles and ultrafine particles equally, but which allow the treatment of ores considered as tailings. However, the separation unit described in this document is not functionally suitable for processing minerals with high magnetic susceptibility (eg magnetite - FeOFe ₂ O ₃ ). In addition to this, the control of the supply of separation units in the hoppers of this system is carried out by changing the intensity of the vibrations of the vibration motor installed there, which does not always ensure adequate flowability of the material when it enters the separator. Finally, the system and method described in this document does not allow immediate disposal of the separated non-magnetic fraction.

As regards the step of drying the tailings for subsequent separation, the state of the art generally uses a rotary drum dryer. Using this technique, the presence of small particles in the dryer leads to the formation of a significant amount (30-50%) of pellets in it (which, of course, defeats the purpose of recovering fine particles), this causes low efficiency of the equipment when working with large particles and further increases inefficiency. when working with fine particles, since the particles are not released, which makes it impossible to separate minerals containing iron oxides and impurities.

For large particles, it is recommended to use fluidized bed dryers that create fluidized beds, but it is not possible to create a fluidized bed for small particles.

Currently, in the ceramic industry, in the preparation of masses for the production of ceramic floor tiles, Spray Dry technology (dry spraying) is widely used. However, for Spray Dry drying, it is necessary to create a slurry with a solids content of 50% in order to facilitate the atomization of particles ejected against the flow of hot air. In order to achieve a flow rate of 500 t/h, it is necessary to install a magnetic separation unit that has a satisfactory efficiency when working with materials that are usually impossible to process using magnetic separators with rollers made of permanent rare earth magnets with high magnetic induction (for example, iron -boron-neodymium), and ferrite magnets having a low magnetic induction (for example, iron-boron).

Such tasks are solved in an absolutely effective way with the reduction of potential environmental hazards during the deployment of the system, the promotion of rational use of natural resources, the recovery of tailings that may pose a risk to the environment in the event of accidents at dump ponds or embankments, and respect for the surrounding area. .

In today's increasingly demanding environment, the present invention provides a clear solution to the problem of obtaining economic results in an environmentally friendly manner, and its main features are:

higher yield of iron by weight and metallurgical yield;

recovery of fine iron ore particles < 100 mesh (150 microns) without loss due to entrapment during wet magnetic separation;

clean combustion without residual substances;

no emissions into the atmosphere;

- 2 040958 more efficient separation of iron with the creation of cleaner tailings with a lower iron content;

optimization of logistics using localized processing;

protection of water sources and aquifers;

eliminating the risk of accidents at tailings dumps;

reducing the physical space allocated for deployment;

low energy consumption;

modularity and flexibility of the system;

increase in the service life of workings due to the possibility of working with ores with a significantly lower content of iron oxides.

As already mentioned, the specificity of the solution proposed by the present invention is the use of a completely dry method in the processing of minerals, which requires the introduction of a block for drying and disaggregation before feeding finer fractions to the magnetic separator.

The method on which the present invention is based can be generally characterized as follows: the amount of moisture in the ore is reduced using a mechanical agitation dryer (using natural gas to prevent the creation of pollutants or burning biomass), and the ore is sorted into different fractions at different cyclonic stages and then separated by means of magnets in each of the ranges created during the sorting, with the important difference being that the process is carried out in a completely dry mode.

Brief description of the drawings

In FIG. 1 schematically shows enrichment for fines from a tailings dump and/or from tailings.

In FIG. 2 is a process flow diagram for tailings dump fines.

In FIG. 3 shows a process flow diagram for the processing of tailings using existing plants operating using the wet method.

In FIG. 4 shows a mechanical agitation quick dryer/mechanical agitation system used in the method and system of the present invention.

In FIG. 5 shows the arrangement of a group of cyclones.

In FIG. 6 is a diagram of a magnetic separation unit according to the present invention.

In FIG. 7 is a cross-sectional view of a magnetic separation unit according to the present invention.

In FIG. 8-12 are graphs illustrating the particle size distribution for various samples obtained in the example described in the text, according to the exemplary embodiment of the present invention.

Detailed description of the invention

Before starting a discussion of the present invention, it is worth noting that the values indicated here are given as an example, so they should not be taken as limiting the scope of protection of this invention. A person skilled in the art, when considering the presented concept, will understand how to set the values appropriate for a particular case in order to accomplish the objectives of the present invention.

In FIG. 1, reference numbers 1-8 indicate steps and components generally used in the prior art, and are therefore not included in the innovations offered by the present invention.

In this regard, in the case of artificial tailings ponds, the removal of fine and ultrafine particles from iron ore begins with excavation using a dredge 2 and pumping to a dry place to drain excess water and create a material loading embankment. On a dry site, a series of embankments are created in order to separate the water from the tailings as much as possible. Once a moisture content of approximately 6-8% has been reached, the tailings are collected using a 3 excavator and moved to a 4 dump truck for transportation to a hopper, or hopper, 5.

In the case of tailings, the process begins with excavation with the help of an excavator 3, which directly loads a dump truck 4 for transportation to the bunker, or funnel, 5.

The outlet of the hopper, or funnel, 5 is equipped with a conveyor belt, which provides feed to the sieve 7, designed to perform pre-separation.

The sieve 7 may be, for example, a vibrating sieve for removing contaminant material. As a result, the material is fed into the intermediate mound 8.

The volume of the intermediate mound 8 can be determined according to the capacity of the plant.

In addition, a water curtain can be provided around the funnel to prevent dust from escaping from the funnel. In this regard, the conveyor belt can be completely enclosed, thus preventing possible loss of material and the consequent emission of dust into the atmosphere.

Below the intermediate mound 8, a channel may be provided containing a vibrating feeder (not shown) which transfers the ore to a conveyor belt.

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From the conveyor belt at the intermediate embankment 8, the material is then directed to the first of three separate operations that form the present invention relating to a method and system for the dry recovery of fine and ultrafine particles of iron oxides.

The first separate operation is a dry operation for the disaggregation of fine particles. The process of drying fine and ultrafine particles is usually considered a technically difficult operation, since the presence of other impurity minerals, such as clay minerals and iron hydroxide, when performing a drying process using a rotating drum, leads to the creation of pellets, which are a combination of different minerals, which does not allow magnetic separation process.

Thus, in order to eliminate this problem in drying/disaggregation of fine particles and obtain 100% separated particles in order to achieve the maximum efficiency of the magnetic separation process, it is proposed to use a dryer 9 with mechanical agitation, which is shown in FIG. 4.

The dryer 9 includes a heating chamber 10 which generates hot air (temperature approximately 850°C) introduced into the main body, inside which two shafts 9.1 are provided with a plurality of vanes 9.2 moving the particulates in both vertical and horizontal directions. These gases pass through the labyrinth system 9.5 causing heated air to come into contact with the material. The vertical movement of the particles, in addition to bringing the particles into contact with hot air to increase the efficiency of the drying process, also facilitates the removal of fine particles by a negative pressure fine particle collection system provided by an exhaust fan.

In the dryer 9, another effective step of disaggregation of fine particles of ore containing iron oxides and non-magnetic fractions is performed by moving the particles in the vertical direction, as a result of which the dry material moves along the main body to the discharge point 9.3.

The design of the dryer can be chosen to provide a capacity of up to 600 t/h. For greater productivity, it is enough to add drying modules. Based on the characteristics of the material to be dried, the dryer, for example, can be configured to dry, disaggregate and, at the same time, remove fine particles, in the mass of which the material fed to the downstream dryer and having a size of 100 mesh (approximately 150 microns) can be up to about 98%.

The following are the main characteristics of the dryer used in the tests.

It is equipped with two shafts driven by an appropriately designed electric motor. The shafts are equipped with a plurality of paddles having different positions, namely, inclined towards the discharge point, which forces the material to move forward, straight blades to push the material upward, and blades inclined towards the feed point, which will reduce the speed or control the speed of the material inside the dryer.

Discharge fraction>100 mesh dry product.

Valves for both supply and discharge of >100 mesh, these valves will prevent cold air from entering the system as well as hot gas from escaping, allowing operation at hot gas temperatures i.e. ensuring the optimization of the heat balance.

There are two safety valves for each dryer in case an explosion occurs.

Hot air generator with channels connecting this generator to the dryer, which are covered with refractory materials.

Cold air valves to balance temperatures measured using thermocouple and pyrometers, these temperatures can be displayed on the control panel and can be controlled from this panel.

A group of cyclones and connecting channels for the exit of gases and products, as well as worms with rotary valves; a supporting structure is provided for the cyclones;

A channel connecting the cyclones with bag filters 22, as well as augers for the exit of products, an exhaust fan and a chimney.

Electrical cabinet for the system, made with the possibility of installing devices for automation, measurement and control.

During the drying process, the dryer 9 must operate under vacuum to remove the water vapor generated during this process. Therefore, the dryer must be connected to an exhaust system. During the removal of water vapor, the exhaust system also captures fine particles with a size of less than 150 microns. For this reason, the exhaust system includes various cyclonic stages and a final collection system located in the vicinity of baghouses 22 to prevent any release of particulate matter to the atmosphere. To create heat, as already mentioned, natural gas and / or biomass is used, which, together with adequate control of the air flow, when setting the correct air / fuel ratio, provide clean and complete combustion with the output of gases that have passed bag filters 22.

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The removal of gases, water vapor and small particles is carried out by means of an exhaust fan having a high capacity, which is installed at the end of the chain. Associated with the exhaust system chain is a component enabling the dryer to be integrated into the so-called single operation of the process according to the present invention. In other words, it is a series of cyclones installed in series, the design of which properly takes into account the losses of the corresponding load in order to ensure separation into different granulometric ranges.

Thus, the second distinct step of this innovative process is to provide a series of cyclones in series, each cyclone design being chosen to define a particle size range, where the particle size ranges are determined according to the output particle size distribution of the iron oxide containing ore with its associated associated minerals. In this case, the number of cyclones can be set from one to six, in accordance with the processed granulometric range. Cyclones are typically pieces of equipment used to collect fine particles larger than 10 microns, which is exactly what is required to reduce the loading of fine particles into bag filters 22. according to the required granulometry. Therefore, cyclones can collect, in fact, 100% of particles larger than 10 microns.

According to the embodiment shown in FIG. 5, the design of the listed cyclones, installed in series and in accordance with the expected granulometric cutoff, is as follows: three cyclones are installed that collect particles in the following granulometric ranges: in the first cyclone 11, the granulometric range of collected particles is from less than 150 microns to more than 45 microns, in the second in cyclone 14, the particle size range of collected particles is from less than 45 microns to more than 22 microns, and in the third cyclone 17, the particle size range of collected particles is from less than 22 microns to more than 10 microns.

And finally, as for ultrafine particles with a size of less than 10 microns, they are sucked in and discharged into the bag filter group 22.

The products collected in each of the successive cyclones 11, 14, 17 are then sent to the respective cooling columns 12, 15, 18, the function of which is to reduce the temperature in the range from 70 to 100°C to a temperature of approximately 40°C. This cooling is necessary to maintain the magnetic induction of rare earth magnets (iron-borneodymium).

The material collected in the first cyclone 11, which corresponds to fractions with sizes less than 150 microns and more than 45 microns, is sent to the first cooling column 12 and then fed to the first magnetic separation unit 13. The material collected in the second cyclone 14, which corresponds to fractions with sizes less than 45 microns and more than 22 microns, is sent to the second cooling column 15 and then fed to the second magnetic separation unit 16. The material collected in the third cyclone 17, which corresponds to fractions with sizes less than 22 microns and more than 10 microns, is sent to the third cooling column 18 and then fed to the third magnetic separation unit 19.

In fact, magnetic separation is the next separate step of the present invention.

At the stage of magnetic separation, the products of each of the cyclones 11, 14, 17, which are sequentially fed to the cooling columns 12, 15, 18 and classified according to different granulometric ranges, are sent to the corresponding groups 13, 16, 19 of magnetic separators installed in the form of a cascade and having two to four magnetic rollers, or more, as required. However, this configuration depends mainly on the separability characteristics of the available minerals containing iron oxides.

For each of the particle size ranges separated in different cyclones installed in series, when fed into the respective separators with high magnetic induction rollers made of rare earth magnets (iron-boron-neodymium), proper speed control is provided, as well as the positioning of separators, which will be discussed later.

In FIG. 6 shows a diagram of a magnetic separation with three rollers installed in the form of a cascade. In the first magnetic separation unit 13, the material from the first cyclone 11 and the first cooling column 12 is fed to the first magnetic roller, which can have low and/or high magnetic induction and creates the first non-magnetic fraction, which must be immediately disposed of, the first magnetic fraction, which represents is a final product with an Fe (tot.) content above 64%, and a first mixed fraction, which is fed to a second magnetic roller having a high magnetic induction. In the same sequence, the second magnetic roller creates a second non-magnetic fraction, which is also utilized, a second magnetic fraction with an Fe (total) content above 64%, and a second mixed fraction, which is fed to the third magnetic roller. The third magnetic roller, in turn, creates a third non-magnetic fraction, which is disposed of in the same way, a third magnetic fraction with an Fe (total) content above 64%, and a third mixed fraction, which is disposed of together with the third non-magnetic fraction.

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And so on: products from the second cyclone will be fed into the cooling column, and then in the second magnetic separation unit 16 in the same sequence as in the case of the first magnetic separation unit, the supply of products to the first magnetic roller, which may have a low and / or high magnetic induction and creates a first non-magnetic fraction, which must be immediately disposed of, a first magnetic fraction, which is the final product with an Fe (tot.) content above 64%, and a first mixed fraction, which is fed to a second magnetic roller having a high magnetic induction. In the same sequence, the second magnetic roller creates a second non-magnetic fraction, which will also be disposed of, a second magnetic fraction with an Fe (total) content above 64%, and a second mixed fraction, which will be fed to the third magnetic roller. The third magnetic roller, in turn, creates a third non-magnetic fraction, which is disposed of in the same way, a third magnetic fraction with an Fe (total) content above 64%, and a third mixed fraction, which is disposed of together with the non-magnetic fraction. The same will happen in the third block 19 of the magnetic separation.

In addition, in FIG. 6 shows a diagram of a magnetic separation with three rollers installed in a cascade, where the first roller can have a low or high magnetic induction. Depending on the characteristics of the material to be separated, the use of a low magnetic induction roller may be preferable given that the permanent magnets are composed of iron-boron, have a magnetic induction in the range of 500-3000 gauss (0.05-0.3 T) and designed to separate minerals with high magnetic susceptibility (eg magnetite FeOFe ₂ O ₃ ). On the other hand, in the case of rollers with high magnetic induction, the permanent magnets are composed of iron-boron-neodymium, have a magnetic induction in the range of 7500-13000 Gauss (0.75-1.3 T) and are designed to separate minerals having a low magnetic susceptibility (for example, hematite and iron limonite hydroxides).

In FIG. 7, which shows a cross-section of the magnetic separation unit, shows in detail all the elements of the magnetic separation unit in the form of a cascade, which in the case shown as an example, has three rollers located one above the other. As can be easily seen, each of the cyclones, with a properly selected granulometry, provides a supply to the corresponding group 13, 16, 19 of the magnetic separators. According to FIG. 7, the group contains a receiving hopper 30, while the supply to one group can be changed by controlling the vibration intensity of the motor with a gearbox (not shown, will be discussed later). At the same time, in the preferred case, in the hopper 30, the angles of inclination are chosen such as to improve the flowability of the material when it enters the magnetic separator assembly.

The material is then unloaded onto a polyester belt 34 coated with polyurethane (PU, PolyUrethane), the belt is tensioned by a first low-induction magnetic roller 32 of ferritic magnets (iron-boron) and a support roller 33.

The magnetic separation is controlled by changing the speed of the magnetic roller and by positioning the separators. An acrylic plate is installed to ensure the distribution of the powder and the direction towards the magnetic roller. Separator 36 separates the non-magnetic fraction from the mixed fraction, and separator 37 separates the mixed fraction from the magnetic fraction. The first non-magnetic fraction is collected by chute 38, the first mixed fraction is collected by chute 39, and the first magnetic fraction is collected by chute 40. The first mixed fraction chute feeds into hopper 41 for a second high-induction roller 42 of rare earth magnets ( iron-boron-neodymium). The second roller 42 with high magnetic induction of rare earth (iron-boron-neodymium) magnets, as a result of magnetic separation, creates a second non-magnetic fraction, which will be discharged through the chute 43, a second magnetic fraction, which is discharged into the chute 45, and a second mixed fraction, which is discharged into the chute 44, this fraction is fed through the chute 44 and through the hopper 46 to the third magnetic roller 47 with high magnetic induction of rare earth magnets (iron-boron-neodymium). The third magnetic roller 47 with high magnetic induction of rare earth magnets (iron-boron-neodymium) as a result of magnetic separation creates a third non-magnetic fraction, which will be discharged through the chute 48, a third magnetic fraction, which will be discharged into the chute 50, and a third mixed fraction, which is unloaded along the chute 49 together with other, non-magnetic fractions. The element 51 in the three blocks of magnetic separation contains support rollers for the belt 34 made of polyester coated with polyurethane.

The low and high magnetic induction rollers are tilted and the angle of inclination can be in the range of 5 to 55°, ideally in the range of 15 to 25°, the angle of inclination being set as a function of the resulting iron oxide granulometry. This slope, on the basis of tests already carried out, increases the efficiency of separating the magnetic fraction from the non-magnetic fraction.

Other features of this equipment are shown below.

The high magnetic induction roller consisting of permanent magnets producing a magnetic field with a large gradient is preferably made using heavy duty neodymium magnets that are temperature resistant up to 60°C and a high permeability steel disc.

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The magnetic roller can be driven by a 2.0 HP AC motor. (1.471 kW) (having a variable speed and a frequency inverter (not shown).

A belt tensioning and alignment system 50 is provided to prevent problems due to small spacing between small diameter rollers for thin belt.

Thus, it is possible to change the tape in a few minutes, without the need for special tools. The guide systems used on each of the magnetic rollers allow the respective belts to be tensioned and aligned, thus increasing their service life.

The separating belt 34 is of the type of polyester fiber belt coated with a layer of polyurethane, with a thickness ranging from 0.6 to 1.00 mm.

The positioning systems 30, 41, 46 of the hopper type operate with gravity discharge, the angle of inclination being properly chosen to ensure uniform discharge through the hopper, for this reason even the use of a vibratory system can be dispensed with.

Alternatively, if a vibratory driven hopper feeding system is used, the latter may have the following characteristics: 2.0 hp power. (1.471 kW), 220 VAC three-phase power supply and frequency inverter for feed rate control. The system includes a storage hopper, this type of feeder makes a controlled and uniform supply possible.

Support structure made from carbon steel profiles with matching finish to achieve a compact and easy assembly. It is also possible to provide a fully dustproof control panel (not shown) including meters, speed controllers, frequency inverters, supply voltage: 220 W AC, 60 Hz, three-phase.

This is how the magnetic separators, shown schematically in Fig. 1 under reference numbers 13, 16, 19.

Example 1

Tailings sample analysis.

In order to test the effectiveness of the method and system for completely dry concentration of ore containing iron oxides using a magnetic separation unit, the composition of a sample taken from an artificial reservoir with tailings was studied and the sample was processed in a pilot unit with simulation of the same technological route that is used in plant used in carrying out the method of the present invention.

The ore sample from the tailings mound had an extremely simple mineralogy and consisted essentially of iron-bearing minerals and a non-magnetic fraction. Minerals from the sample taken, containing iron, consisted of hematite, as well as oxides and hydroxides of iron, as shown below. The non-magnetic fraction consists essentially of silica and a small amount of clay in the form of kaolinite. The percentage composition of these minerals is indicated in the table below. 1.

Table 1. Mineralogy of the tailings sample

Minerals Chemical formula % by weight Hematite Ge ₂ O ₃ 46 Silica _SiO2 52 Iron oxides and hydroxides Ge(OH) ₂ 2

When analyzing the composition of the tailings sample, it was found to have an Fe (total) content of 33.62%, the results of the analysis can be seen in the table below. 2.

Table 2. Chemical analysis for main constituents

Chemical analysis Main components Ge (gen.)=33.62%

Was conducted granulometric analysis of the tailings sample, the sample had the following granulometry, which is shown in the following table. 3.

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Table 3. Particle size distribution in tailings sample

Mesh (ASTM) Hole size, µm log(hole size) Weight, g Delayed, % Delayed in total, % Passed in total, % Total elapsed, calculated, % Log(Total elapsed) > 100# 149 2.17 0.12 0.12 0.12 99.88 99.58 0.829 > 200# 74 1.87 11.26 10.98 11.09 88.91 79.01 0.342 > 325# 44 1.64 18.69 18.22 29.31 70.69 45.93 0.089 > 400# 37 1.57 9.36 9.12 38.44 61.56 36.29 -0.019 > 500# 25 1.40 17.20 16.77 55.21 44.79 20.01 -0.226 > 600# 22 1.34 10.24 9.98 65.19 34.81 16.27 -0.369 10 1.00 16.79 16.37 81.56 18.44 4.23 -0.691 5 0.70 9.61 9.37 90.92 9.08 1.24 -1.022 1 0.00 6, 74 6.57 97.49 2.51 0.07 100.01 97.49 0.10001 Slope = 1.24 d ₈₀ (mm) = 54 Linear factor = -1.95 d ₅₀ (mm) = 28 Correction factor = 1.00 d ₂₀ (mm) = 11

The sample from the second cyclone had the following distribution: 80% (d80) by weight less than 55 microns, with a median diameter (d50) of 29 microns, and 20% (d20) by weight less than 12 microns. These values can be seen in the graph shown in Fig. 8.

A tailings sample was air-classified in a pilot plant, with the system consisting of three cyclones in series, bag filters and a centrifugal exhaust fan. During operation, samples were taken from each of the three cyclones and from bag filters, and the granulometric analysis of these samples was carried out, which gave the following results.

The granulometric distribution for the first cyclone is shown in table. 4.

ric distribution for the first cyclone

Table 4

Mesh (ASTM) Hole size, microns log(hole size) Weight, g Delayed, % Delayed in total, % Passed in total, % Total elapsed, calculated, % log(total elapsed) > 100# 149 2.17 0.23 0.22 0.22 99.78 99.58 0.785 > 200# 74 1.87 21.82 21.27 21.50 78.50 79.01 0.187 > 325# 44 1.64 34.35 33.49 54.98 45.02 45.93 -0.223 > 400# 37 1.57 9.91 9.66 64.64 35.36 36.29 -0.360 > 500# 25 1.40 16, 07 15.67 80.31 19.69 20.01 -0.659 > 600# 22 1.34 3.47 3.38 83.69 16, 31 16.27 -0.749 10 1.00 13.35 13.01 96.71 3.29 4.23 -1.475 5 0.70 1.77 1.73 98.43 1.57 1.24 -1,801 1 0.00 1.61 1.57 100.00 0.00 0.07 102.58 100.00 0.10258 Slope = 1.79 d ₈₀ (mm) = 75 Linear factor = -3.16 d ₅₀ (mm) = 47 Correction factor = 1.00 d ₂₀ (mm) = 25

The sample from the first cyclone had the following distribution: 80% (d80) by weight less than 75 microns, with a median diameter (d50) of 47 microns, and 20% (d20) by weight less than 25 microns. These values can be seen in the graph shown in Fig. 9.

The granulometric distribution for the second cyclone is presented in the table below. 5.

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Table 5. Particle size distribution for the second cyclone

Mesh (ASTM) Hole size, microns log(hole size) Weight, g Delayed, % Delayed in total, % Passed in total, % Total elapsed, calculated, % log(Total elapsed) >100# 149 2.17 0.00 0.00 0.00 100.00 100.00 1.207 > 200# 74 1.87 0.03 0.03 0.03 99.97 99.54 0.916 > 325# 44 1.64 4.63 4.07 4.09 95.91 87.05 0.505 > 400# 37 1.57 20.05 17.61 21.71 78.29 77.27 0.184 > 500# 25 1.40 35.48 31.17 52.88 47.12 51.08 -0.196 > 600# 22 1.34 29.16 25.62 78.49 21.51 43.10 -0.616 10 1.00 11.72 10.30 88.79 11.21 12.21 -0.925 5 0.70 7.11 6.25 95, 04 4.96 3.53 -1.293 1 0.00 5.65 4.96 100.00 0.00 0.18 113.83 100.00 0.11383 Slope = 1.86 d80 (mm) = 39 Linear factor = -2.74 d50 (mm) = 25 Correction factor = 0.98 d20 (mm) = 13

The sample from the second cyclone had the following distribution: 80% (d80) by weight less than 39 microns, with a median diameter (d50) of 25 microns, and 20% (d20) by weight less than 13 microns. These values can be seen in the graph shown in Fig. 10.

The granulometric distribution for the third cyclone is presented in the table below. 6.

Table 6. Particle size distribution for the third cyclone

Mesh (ASTM) Hole size, microns log(hole size) Weight, g Delayed, % Delayed in total, % Passed in total, % Total elapsed, calculated, % log(total elapsed) >100# 149 2.17 0.00 0.00 0.00 100.00 100.00 1.207 > 200# 74 1.87 0.45 0.43 0.43 99.57 99.95 0.736 > 325# 44 1.64 0.83 0.80 1.24 98.76 96, 53 0.643 > 400# 37 1.57 1.81 1.75 2.98 97.02 92.30 0.546 > 500# 25 1.40 11.50 11.10 14.08 85.92 75.13 0.292 > 600# 22 1.34 16, 42 15.84 29.92 70.08 68.02 0.082 10 1.00 36, 64 35.36 65.28 34.72 28.35 -0.370 5 0.70 29.53 28.50 93.78 6.22 10.70 -1.192 1 0.00 6.45 6.22 100.00 0.00 0.92 103.63 100.00 0.10363 Slope = 1.56 d80 (mm) = 27 Linear factor = -2.04 d50 (mm) = 16 Correction factor = 0.98 d20 (mm) = 8

The sample from the third cyclone had the following distribution: 80% (d80) by weight less than 27 microns, with a median diameter (d50) of 26 microns, and 20% (d20) by weight less than 8 microns. These values can be seen in the graph shown in Fig. eleven.

The granulometric distribution for fine particles collected by bag filters is presented in the table below. 7.

- 9 040958

Table 7. Particle size distribution for bag filters

Mesh (ASTM) Hole size, microns log (hole size) Weight, g Delayed, % Delayed in total, % In total, it has passed Total elapsed, calculated, % log(total elapsed) >100# 149 2.17 0.00 0.00 0.00 100.00 100.00 1.207 > 200# 74 1.87 0.55 0.62 0.62 99.38 99.90 0.707 > 325# 44 1.64 1.32 1.48 2.10 97.90 98.86 0.587 > 400# 37 1.57 0.41 0.46 2.56 97.44 97.92 0.564 > 500# 25 1.40 1.68 1.88 4.44 95.56 93.83 0.493 > 600# 22 1.34 1.13 1.27 5.70 94.30 91.81 0.457 10 1.00 19.30 21.63 27.33 72.67 72.51 0.113 5 0.70 26.89 30.14 57.47 42.53 51.41 1 0.00 37.95 42.53 100.00 0.00 17.06 89.23 100.00 0.08923 Slope = 0.84 d80 (mm) = 13 Linear factor = -0.73 d50 (mm) = 5 Correction factor = 0.97 d20 (mm) = 1

The baghouse sample had the following distribution: 80% (d80) by weight less than 13 microns, with a median diameter (d50) of 5 microns, and 20% (d20) by weight less than 1 micron. These values can be seen in the graph shown in Fig. 12.

Chemical analysis of the products obtained in three consecutive cyclones, as well as the product from the bag filters gave the following results, shown in the following table. 8.

_______________ Table 8. Chemical analysis _______________

Product % by weight % Fe Fe content % of total Fe content 1st cyclone 52.3 34.67 18, 13 53, 93 2nd cyclone 22.6 33.23 7.51 22.34 3rd cyclone 16, 2 31, 64 5, 13 15, 25 Bag filters 8.9 32.05 2.85 8.48 Total 100 33, 62 100.00

As can be seen, the first cyclone captured 52.3% of the particles by weight with an Fe (tot.) content of 34.67%, which is 53.93% of the total iron content. The second cyclone retained 22.6% of particles by weight with an Fe content (tot.) of 33.23%, which corresponds to 22.35% of the total iron content. The third cyclone retained 16.2% of the particles by mass with an Fe (total) content of 31.64%, representing 15.25% of the total iron content. The bag filters retained 8.9% of particles by weight with an Fe (total) content of 32.05%, representing 8.53% of the total iron content.

All products collected in each of the cyclones 11, 14, 17 were classified into different particle size ranges in accordance with the above particle size distributions. Each of the fractions was processed in a magnetic separation unit, which in this case corresponds to the magnetic separation units 13, 16, 19 of the pilot plant, containing two magnetic rollers one above the other. All magnetic rollers are high magnetic induction rollers made of rare earth magnets (iron-boron-neodymium).

Each of the products obtained in the cyclones 11, 14, 17, respectively for each of the magnetic separation units 13, 16, 19, as shown in FIG. 7 was introduced into the first hopper 30 for the first magnetic roller 32 having a high magnetic induction to obtain a first non-magnetic fraction, which was ejected from the magnetic separation unit through the chute 37. This separation ensures that the first magnetic fraction is removed through the chute 38 and will additionally create a mixed fraction that will be fed to the second magnetic roller, the material will be collected and sent to the second hopper 39 through the accumulation chute 43. The hopper 39 for the second magnetic roller provides feed to the second magnetic roller 40 with high magnetic induction of rare earth magnets, in in turn, creating a second non-magnetic fraction, which will be collected and removed from the magnetic separation unit along the storage chute 41, and a second magnetic fraction, which will be collected using the chute 42, as well as a second mixed fraction, which is collected using the chute 44, this fraction combines with the second non-magnetic fraction.

All non-magnetic products from the first roller and the second roller having a high magnetic induction, i.e. coming from the chutes 37, 41, as well as the mixed fraction coming from the chute 44, are collected on a conveyor belt, which is non-magnetic.

All magnetic products from the first roller and the second roller having a high magnetic induction, i.e. received from the troughs 38, 42, are collected on a conveyor belt, which is non-magnetic.

For each of the magnetic separation units, after being processed on the first magnetic roller, all the first magnetic products, the first non-magnetic products, and the first mixed products from the first roller were collected and their weight ratio was calculated and chemical analysis was carried out.

For each of the magnetic separation units, the mixed fraction from the first magnetic roller was fed to the second high magnetic induction roller, the generated products were collected as the second magnetic products, the second non-magnetic products and the second mixed products, and the mass ratio was also calculated for them and chemical analysis.

The results of calculating the ratio by mass and chemical analysis for the first magnetic rollers with high magnetic induction are shown in table. 9.

Table 9. Extraction results for the first magnetic rollers with high magnetic induction

1st magnetic roller of three magnetic separation units Product % by weight % Fe Fe content % of total Fe content Fraction - 150 and +10 microns, 1st magnetic 28.28 65.41 18.50 55, 02 Fraction -150 and +10 microns, 1st mixed 32.90 35, 10 11.55 34.35 Fraction - 150 and +10 microns, 1st non-magnetic 29, 92 2.42 0.72 2.15 91.10 91.52

In three cyclones installed in series 11, 14, 17, which correspond to a magnetic fraction of -150 and +10 microns, an extraction of 28.28% by weight was provided, with an Fe content (tot.) of 65.41% and a metallurgical yield of 55.02% . A non-magnetic fraction of -150 and +10 microns, 29.92% by weight, with an Fe(total) content of 2.42% was obtained, corresponding to a metallurgical loss of 2.15%. In addition, a first mixed fraction of -150 and +10 microns, 32.90% by mass, with an Fe (tot.) content of 35.10% was obtained, in which, in addition, there was 34.35% of the total iron content, which was to be separated on the second magnetic roller with high magnetic induction.

The results of calculating the ratio by weight and chemical analysis when re-processing mixed fractions on the second magnetic rollers are shown in table. 10.

Table 10. Extraction results for the second magnetic rollers with high magnetic induction

2nd magnetic roller Product % by weight % Fe Fe content % of total Fe content Fraction - 150 and +10 microns, 2nd magnetic 14.90 64.20 9.57 28.46 Fraction - 150 and +10 microns, 2nd non-magnetic 18.00 11.79 1.98 5, 90 32.90 34.36

For the magnetic fraction of -150 and +10 microns from the three rollers of the magnetic separation units, a recovery of 14.90% by weight is observed with an Fe (tot.) content of 64.20% and a metallurgical yield of 28.46%. In addition, there is a combination of non-magnetic and mixed fractions -150 and +10 microns, 18.00% by weight with an Fe (tot.) content of 11.03%, which corresponds to a metallurgical loss of 5.90%.

The ratio for the final metallurgical balance (this includes magnetic fractions from the first rollers and magnetic fractions from the second rollers) is shown in the table below. eleven.

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Claims (10)

Table 11. Extraction (1st magnetic and 2nd magnetic) When the magnetic products from the first magnetic rollers are combined with those from the second magnetic rollers, the recovery is 43.18% by weight, with an Fe (tot) content of 64.99%, corresponding to a metallurgical yield of 83.48% iron content. The ratio for the final metallurgical balance (this includes non-magnetic fractions from the first rollers, as well as non-magnetic and mixed fractions from the second rollers) is shown in the table below. 12. Table 12. Disposal (1st non-magnetic, 2nd non-magnetic and 2nd mixed) Disposal (1st non-magnetic, 2nd non-magnetic and 2nd mixed) Product % by weight % Her Contents Her % of the total content of Her Fraction - 150 and +10 microns, 1st non-magnetic 29, 92 2.42 0.72 2.15 Fraction - 150 and +10 microns, 2nd non-magnetic 18.00 11.03 1.98 5, 90 Total 47.92 5.65 2.71 8.06 Thus, 47.92% by mass is discarded, with an Fe (tot.) content of 5.65%, corresponding to 8.92% of unrecovered iron. In bag filters, the particle size fraction of less than 10 microns, which cannot be removed using magnets in the method of the present invention, is 8.9% by weight, with an Fe (tot.) content of 32.05%, and contains 8.48% of unrecovered iron as shown in the table below. 13. Table 13 Collection from bag filters Collection, bag filters Product % by weight % Fe Contents Her % of the total content of Her Fraction -10 microns, bag filter 8.90 32.05 2.85 8.48 Modifications within the spirit and principles of this invention, which will become apparent to a person skilled in the art upon reading this specification, will also be considered to be within the scope of this invention, which is defined in the appended Claims. CLAIM 1. A system for dry processing of ore containing iron oxides, which includes fine and ultrafine particles and is located in tailings dumps and ore tailings with a low content of these oxides, and this system contains: drying agent; a group of air classifiers performing cyclonic separation of particles according to granulometric ranges, and the group of air classifiers is functionally connected to - 12 040958 with the release of the drying means and contains from at least one to five cyclones (11, 14, 17) installed in series, which classify fine and ultrafine particles of iron ore according to predetermined granulometric ranges in accordance with the degree of complexity of the magnetic separation of the material; and a group of magnetic separators for particles in particle size ranges obtained from air classifiers, each of the magnetic separators (13, 16, 19) included in the group of magnetic separators contains from two to four magnetic rollers (32, 42, 47) installed in the form of a cascade and made of rare-earth magnets having low and/or high magnetic induction, the magnetic rollers being installed with an inclination, moreover: the drying means comprises a dryer (9) performing drying by introducing hot air, with mechanical agitation means and shafts equipped with blades (9.2) for disaggregating and moving the material in horizontal and vertical directions; each of the cyclones (11, 14, 17) is connected to a cooling unit (12, 15, 18) in the form of a column to reduce the temperature of the ore containing iron oxides, with iron ore particles coming from each of the cyclones to the corresponding group of magnetic separators through the corresponding unit (12, 15, 18) cooling in the form of a column; and each of the magnetic rollers is provided with a means for utilizing a non-magnetic fraction, a means for collecting a magnetic fraction, and a means for transferring the mixed fraction to the next magnetic roller, while at the last magnetic roller, the means for utilizing the non-magnetic fraction is also designed to collect the mixed fraction. 2. System according to claim 1, characterized in that the drying means is connected to a heating chamber (10) intended to be heated at a temperature of approximately 850°C. 3. The system according to claim 1 or 2, characterized in that the outlet of the drying means is a means of removing gases resulting from drying, water vapor present inside the dryer, and fine and ultrafine particles of ore containing iron oxide. 4. System according to any one of claims 1 to 3, characterized in that the cooling unit is a water cooling tower which reduces the temperature of the material to approximately 40°C. 5. The system according to any one of claims 1 to 4, characterized in that the rare earth magnets having a low magnetic induction, which are used in magnetic rollers, are made of iron-boron, and the magnets having a high magnetic induction are made of iron-boron- neodymium. 6. System according to any one of claims 1 to 5, characterized in that the first magnetic roller (32) is made of rare earth magnets having a low magnetic induction and the other rollers are made of rare earth magnets having a high magnetic induction. 7. System according to any one of claims 1 to 6, characterized in that the angle of inclination is in the range from 15 to 25°. 8. System according to any one of claims 1 to 7, characterized in that a group of bag filters (22) is provided, connected to the last cyclone in the group of air classifiers, for sucking in and retaining ultrafine particles that are smaller than the particle size distribution for said cyclone. 9. The method of dry enrichment of ore containing iron oxides, which includes fine and ultrafine particles and is located in dumps for tailings and ore tailings with a low content of these oxides, carried out in the system for dry enrichment of ore according to claim 1 and comprising the following steps: perform drying; performing air classification of iron ore, including fine and ultrafine particles, according to predetermined granulometric ranges in accordance with the degree of complexity of the magnetic separation of the material; and perform magnetic separation using magnetic rollers of rare earth magnets having low and/or high magnetic induction, which are installed in the form of a cascade, and the magnetic rollers are installed with an inclination, and: the drying step is performed by introducing hot air and with mechanical agitation, disaggregation and movement of the material in horizontal and vertical directions; after the air classification step, a step of cooling the iron oxide-containing ore in the cooling tower is performed; and the magnetic separation step further includes, for each magnetic roller, utilizing the non-magnetic fraction, collecting the magnetic fraction, and transferring the mixed fraction to the next roller, and utilizing the mixed fraction together with the non-magnetic fraction for the last magnetic roller, the iron ore particles are supplied from each of the cyclones to the corresponding group of magnetic separators through the corresponding cooling unit (12, 15, 18) in the form of a column. 10. The method for dry processing of iron oxide containing ore, which includes fine and ultrafine particles, according to claim 9, characterized in that the drying step is performed by heating to a temperature of approximately 850°C. -