Practical application of magnetic separation (2)
Fourth, non-ferrous and rare metals ore magnetic separator is widely used non-ferrous and rare metal ore (veins tungsten ore, tin ore vein, sand beach placer tin and other minerals) crude concentrate re-election selection.
In these ores typically contain a variety of magnetic minerals, such as magnetic iron ore, hematite, pyrrhotite, titanium ore, wolframite, tantalite, columbite and monazite. The specific gravity of the metal minerals is generally greater than that of the gangue minerals, and they are usually first enriched by re-election to obtain a mixed coarse concentrate. The coarse concentrate is dried and sieved into several grades, and depending on its mineral composition, particle size composition and other properties, single magnetic separation or magnetic separation and other mineral processing methods (flotation, flotation, electrification and re-election) may be used. The joint process is selected to achieve the purpose of improving concentrate quality and comprehensive utilization of mineral resources.
(1) Selection of crude tungsten concentrate
Whether it is the re-election of coarse ore concentrate of vein tungsten or vein tin or the re-election of coarse concentrate of sand ore, in addition to black tungsten ore and cassiterite, it also contains other minerals. For vein fine ore concentrates, it also contains magnetite, hematite and various sulfide minerals, while sand concentrates contain a variety of rare metal minerals such as zircon , rutile, monazite and brown peony. Yanxi Select Factory has a wide range of raw material properties. According to the content of tin and sulfur, it is divided into high tin tungsten concentrate and high sulfur tungsten concentrate. According to the grade of tungsten, it is divided into high grade tungsten concentrate and low. Grade tungsten concentrate. For high-grade crude tungsten concentrate and high-tin coarse tungsten concentrate, the process of first magnetic re-floating and re-floating is adopted, while for low-grade crude tungsten concentrate and high-sulfur crude tungsten concentrate, the process of first re-floating magnetic separation is adopted. . The selection process of a black tungsten ore re-election of coarse concentrate is shown in Figure 10.
Figure 10 Selected process of tungsten ore re-election of coarse concentrate
Firstly, the mixed coarse concentrate is crushed to less than 3 mm by a closed-circuit process, and then divided into three stages by a vibrating sieve: -3 + 0.83 mm, -0.83 + 0.2 mm, -0.2 mm, respectively, and fed into a dry disc type strong magnetic separator. Sorting. Production practice proves that the classification is better than the non-grading.
The crude tungsten concentrate generally contains some magnetite. Therefore, the magnetite should be separated by a weak magnetic field magnetic separator before the material is fed into the strong magnetic separator to ensure the normal operation of the strong magnetic separator. Strong magnetic separation equipment currently uses a double disc dry type strong magnetic separator. In the rough selection operation, the magnetic field strength of the first disk is slightly lower, and the high-quality black tungsten concentrate is selected. The magnetic field strength of the second disk is slightly higher, and a part of the continuous body is selected in addition to the monomeric black tungsten ore. Known as secondary concentrate. The tailings are cleaned in the same way to obtain qualified black tungsten concentrate and secondary concentrate. The coarse concentrates and the selected secondary concentrates are combined and selected twice to obtain qualified black tungsten concentrates and miscellaneous sands (tailings). The main minerals of the sand are white tungsten , cassiterite and other sulfides, which are sent to the next step to comprehensively recover the useful components. As can be seen from the process, most of the qualified black tungsten concentrates are selected by strong magnetic separation. The strong magnetic separation indicators obtained according to this process are shown in Table 14.
Ore type | Raw ore grade, % | Concentrate grade, % | Tailings grade | Recovery rate,% | ||||
WO 3 | Sn | WO 3 | Sn | S | WO 3 | Sn | ||
Gao Xi Yi election 1 Gao Xi Yi Xuan 2 Low tin easy to choose High sulfur is difficult to choose High sulfur and high tin are difficult to choose Low sulfur and low tin are difficult to choose | 59.19 55.89 55.67 46.87 24.9 58.27 | ±4.0 ±7.0 ±1.4 ±0.1 24.56 0.15 | 71.09 71.39 71.05 68.83 65.35 71.27 | 0.079 0.094 0.035 0.054 1.095 0.022 | 0.42 0.23 0.51 1.1 1.27 0.39 | 7.51 11.93 22.27 13.70 2.25 19.88 | 23.18 31.63 5.69 1.58 51.85 1.18 | 92.45 89.03 88.25 75.40 63.37 85.13 |
(2) Separation of strontium-monazed mineral coarse concentrates The refinement of coarse ore concentrates containing strontium minerals has complex mineral composition, including zircon, brown strontium and other strontium minerals. A variety of minerals such as magnetite, ilmenite, monazite, quartz , mica , garnet, tourmaline and limonite. The magnetite content is high, and it is recovered by the weak magnetic field magnetic separator. The magnetic properties of the strontium minerals are different from those of monazite and ilmenite. The magnetic separation cannot fully achieve the purpose of separating and separating these minerals. In combination with other methods, monazite and zircon can be floated with sodium oleate, water glass, carbon and sodium. In addition, minerals are conductive minerals, and monazite is not a conductive mineral. Separation by electricity is also effective. Therefore, for this coarse concentrate, a magnetic separation-grain floating, magnetic separation-electrical selection process can be used. The magnetic separation-grain flotation selection process of a re-selected mixed concentrate containing niobium minerals in a plant is shown in Figure 11.
Figure 11 Selected process of a plant containing strontium-monazed coarse concentrate
The mineral composition of the re-election of coarse concentrates is: magnetite accounts for about 50%, ilmenite accounts for about 30%, monazite accounts for about 2%, zircon accounts for about 5%, and brown ore accounts for about 2%. %, quartz accounts for about 9%, and cassiterite, mica, garnet, tourmaline and limonite account for about 2%.
The operation first uses a weak magnetic field magnetic separator to separate the magnetite to ensure that the ore that enters the strong magnetic separation operation does not contain magnetite. The purpose of rough magnetic field selection and strong magnetic field sweeping is to recover as much as possible the weak magnetic minerals such as strontium minerals, monazite and ilmenite into magnetic products. The magnetic product is obtained by concentrating-selecting the ilmenite concentrate with medium magnetic separation.
The middle ore selected by the medium magnetic separation tailings and the strong magnetic field are mainly brown sorghum or monazite. The particles are floated with sodium carbonate, water glass and sodium oleate. The floating material is monazite concentrate and sediment. tantalum niobium concentrate. The main minerals of the tailings sweeped by the strong magnetic field are zircon and quartz. The same agent is used for the flotation. The float is a zircon concentrate and the sink is quartz. The sorting indicators are as follows:
钽铌ä¸çŸ¿â€”(Nb•Ta) 2 O5 content is 5.94%, and the recovery rate is 4.92%;
The monazite concentrate—(R 2 O 3 ) content is 60.94%, and the recovery rate is 65.43%;
Zircon concentrate - ZrO 2 content is 59.83%, the recovery rate is 88.49%;
Ilmenite concentrate - TiO 2 content is 43.24%, the recovery rate is 89.99%;
The magnetite concentrate has a Fe content of 67.18% and a recovery of 95.45%.
A plant selected from the group of tantalum and niobium ore selected based weathering crust deposit tantalum and niobium iron, niobium tantalite useful minerals, zircon, zircon-rich hafnium, rubidium mica; gangue minerals as quartz, feldspar, mica, kaolin And clay, etc.
The strong magnetic separation process adopted by the plant is shown in Figure 12. The selected material of the strong magnetic separation is the fine mud in the re-election process, and the indicator is shown in Figure 12. The sorting index indicates that the recovery rate of antimony ore is 90.72%, and the zirconium-rich zircon and sericite are also enriched in the coarse concentrate, achieving the purpose of comprehensive recovery. [next]
Figure 12 Wet strong magnetic separation process of a mine mud
The main recovered minerals in the reclaimed coarse concentrate of seashore sand mines are ilmenite, monazite, rutile and zircon. Ilmenite is the most magnetic, followed by monazite, rutile and zircon are non-magnetic minerals, while rutile is much more conductive than zircon. Therefore, when dealing with such ore, a magnetic separation #electrical combined process can generally be employed.
A ore deposit in China is dominated by coastal sandstones and alluvial sands. The main metal minerals are zircon, rutile, anatase, magnetite and limonite, while gangue minerals are mainly quartz, feldspar and mica. The magnetic separation used in the mine! The electrification selection process is shown in Figure 13.
Figure 13 Flow chart of a factory sand mine ore dressing
In the re-election of coarse concentrates, there are many weak magnetic minerals, such as ilmenite, hematite, garnet , amphibole, epidote, vermiculite and ilmenite, which are used in strong magnetic field separators. separate from. In the magnetic separation tailings, the rutile and anatase, which mainly contain non-conductive minerals, and the conductive minerals, can be separated by electro-election and obtain qualified concentrate. Due to the high degree of pollution of rutile and anatase, and the inclusion of more zircon inclusions and other minerals, it is difficult to select qualified products, so it is thrown away as tailings.
The magnetic separation equipment used is mainly dry single-disc and double-disc strong magnetic separator, and the recovery rate is 96~98%. The electrification operation was selected twice, and the recovery rate was over 94%. The final concentrate zircon grade (including ZrO 2 ) is more than 60%.
The average production index of the ore dressing in the mine from 1976 to 1980 is shown in Table 15.
Raw ore grade, % | Concentrate grade, % | Recovery rate,% |
0.258 | 60.72 | 67.18 |
V. Total average index of mineral processing Recycling and regeneration of ferromagnetic heavy medium
The recovery and regeneration of the ferromagnetic heavy medium (such as ferrosilicon or magnetite) used in the resuspension separation cycle system includes the separation of the resuspension from the selected product, the magnetization before the resuspension is concentrated, and the magnetic separation of the concentrated product. Dehydration of magnetic products (heavy media), demagnetization of magnetic products and preparation of resuspension at the required concentration.
Separation of the resuspension from the selected product is carried out on a sieve. Most (90 to 95%) of the resuspension is relatively easy to vent from a small screen, and the vented resuspension maintains its own density directly from the pump to the resuspension separation unit. The remaining resuspension on the sieve remains between the nuggets and on the surface of the nugget, and is washed with a higher pressure of water from most of the sieve front.
The resuspension is magnetized in order to allow the heavy medium to form magnetic agglomeration and precipitation upon concentration, which reduces the area of ​​the concentrator required.
The concentrated product enters the magnetic separator to separate the heavy medium from the non-magnetic ore and slime. In order to reduce the loss of heavy medium during magnetic separation, usually the magnetic separation operation includes two sections, that is, a rough selection operation and a section of the cleaning operation.
It is desirable to obtain a regenerated suspension having a maximum density so as not to reduce the density of the working resuspension. For thick reconstituted resuspension, a sunken spiral classifier can be used.
Demagnetization of heavy media is the last work in the resuspension cycle. This work is necessary because the heavy medium is magnetized after magnetic separation, and the magnetized heavy medium is unstable.
The process of recovery and regeneration of the ferromagnetic heavy medium is shown in FIG.
Figure 14 Recycling process of strong magnetic heavy medium
In recent years, a high field strength magnetic separator has been developed, and there is no need to worry about the loss of heavy medium. The washed heavy suspension can directly enter the magnetic separator, which simplifies the recycling process of the heavy medium in the magnetic separation. There can be no magnetization and concentration before.
6. Magnetization of water The research and application of magnetization technology for water has a long history in foreign countries, and has been applied in many fields in the fields of industry, agriculture, medicine and biology with good results.
The theoretical basis of magnetization is based on the changes in the physical and chemical properties of water, the dynamics of water fluids, and the characteristics of magnetic fields. However, on the whole, the basic research on magnetization theory is still not perfect enough to continue to explore.
The magnetically treated objects of water include process water, pulp and flotation reagent solutions.
In order to adapt to various fields of application, foreign (such as the Soviet Union) have produced corresponding magnetization equipment, and some equipment has been serialized.
There are many methods of magnetic processing, but the general principle is to allow the fluid to be treated to stay in a magnetic field of a certain parameter for a certain period of time. These parameters are the magnetic field strength, the magnetic field gradient, the number of magnetic fields (generally let the fluid pass through several magnetic fields) and the processing time (or the speed at which the fluid passes). When magnetic processing, they are controlled. If an alternating magnetic field is used, it is also necessary to control the frequency of the magnetic field.
There are three ways in which a fluid can pass through a magnetic field:
(1) the magnetic field lines of the vertical magnetic field in the direction of movement of the fluid;
(2) The direction of motion of the fluid is consistent with the direction of the magnetic field line of the magnetic field;
(3) The fluid makes a rotational motion in the magnetic field. This rotational motion is achieved by a cylindrical cyclone placed in a magnetic field.
The magnetic field is generated by energized coils or permanent magnets. Fluids are typically flow through a magnetic field through a working pipe made of a non-magnetic material such as plastic, cement or diabase .
The following is an introduction to the research and application examples of permanent magnetic processing. [next]
(1) Prevention of hard water scaling Studies have shown that water passes through a magnetic field and has an effect on the crystallization process of substances precipitated from the solution. This phenomenon has long been applied to the industry to prevent hard water scaling in boilers and their pipelines. At this point, the structure of the precipitated material has changed, and a soft, easy-washing mud is formed on the pipe instead of a strong scale film.
The study pointed out that when water is magnetically processed, the following conditions must be implemented:
(1) During magnetic processing, the direction of motion of water should be perpendicular to the magnetic lines of alternating alternating magnetic fields;
(2) The larger the number of such magnetic fields, the lower the magnetic field strength. There are 7 to 10 fields in the water preparation (treatment) device used in front of the boiler, and their maximum magnetic field strength is measured in a few hundred kiloamperes per meter (several thousand Oe). If a single-polar device is used, the best effect can be observed when the magnetic field strength is 530~570kA/m (6700~7200Oe), and the magnetic field strength is 190~220kA/m when there are four devices with alternating polarity. A similar effect can be obtained (2400~2800Oe). A similar effect can be obtained when the magnetic field strength is 120~160kA/m (1500~2000Oe) when there are six devices with alternating polarity.
(3) There is a suitable value for the speed of water passing through the magnetic field. Increasing the number and total length of the magnetic field increases the speed value. In a general magnetization device, the speed varies from 0.1 to 2 m/s;
(4) Suitable water treatment systems and the ionic composition of water are related to the structural characteristics of the device;
(5) With the increase of the magnetic field strength, the change of water properties has complex features, with many maximum and minimum values;
(6) After the water is magnetically treated, the abnormality of the water property remains for a long time.
(II) Improving the beneficiation index The magnetic treatment of water not only affects the crystallization process of the precipitated material, but also significantly changes the wettability of various minerals by water. Magnetic coils of alternating polarity were applied in the study (connected in parallel with each other, with 12 poles). The currents in the coil are typically 0.2, 0.4, 0.6, 0.8 and 1.0 A, and the corresponding radial magnetic field components are 3, 6, 12, 18, 24 and 30 kA/m (37, 75, 150, 225, 300 and 375 Oe). All experimental conditions (such as temperature, flow velocity of the liquid, inclination of the magnetizing device, and experimental regimen) remain strictly constant, and the variable factor is only the current in the coil, ie the magnetic field strength (from 0 to 30 kA/m or 375 Oe). The experiment was carried out in distilled water and industrial water.
The relationship between the floatability of various pure hematite, limonite and magnetite in distilled water and hard water and the magnetic field strength of magnetized pulp and the magnetization time of the slurry in a magnetic field of suitable magnetic field strength have been studied.
The results show that the floatability of these minerals increases in both distilled water and hard water as the magnetic field strength increases from 0 to 120 kA/m (1500 Oe) and then decreases. It has also been shown that the magnetization time of the slurry in a constant magnetic field with a magnetic field strength of 167 kA/m (2100 Oe) affects the floatability of these minerals.
Flotation is carried out in distilled water and hard water. The magnetic field strength is 120kA/m and the magnetization time is 2rain. Before the flotation dosing, the magnetization slurry is stirred for 0 to 10 minutes. Experiments have shown that increasing the stirring time of magnetized pulp, the floatability of hematite, limonite and magnetite is increasing in both distilled and hard water.
The magnetite is magnetized in a magnetic field with a magnetic field strength of 167 kA/m for 3 min, and then stayed in the slurry for 24 h. The results of the flotation experiment show that the magnetite is stabilized by magnetization and is stable. It does not disappear after 24 hours. .
Three different iron ore samples were floated under laboratory conditions in foreign countries to test the relationship between the floatability of iron ore and the magnetization treatment in a magnetic field with a magnetic field strength of 120 kA/m. The test results are shown in Table 16.
ore | product | Slurry is not magnetized | Slurry magnetization | ||||
Yield,% | grade,% | Recovery rate,% | Yield,% | grade,% | Recovery rate,% | ||
Magnet hornblende | Raw ore Concentrate Tailings | 100.0 68.0 32.0 | 38.2 49.2 20.3 | 100.0 84.0 16.0 | 100.0 68.0 32.0 | 38.2 53.4 6.0 | 100.0 95.0 5.0 |
Hematite-brown iron hornblende containing iron mica | Raw ore Concentrate Tailings | 100.0 58.0 42.0 | 33.8 42.3 22.1 | 100.0 72.4 27.6 | 100.0 63.5 36.5 | 33.8 45.3 14.1 | 100.0 85.0 15.0 |
Silicate-magnetite ore | Raw ore Concentrate Tailings | 100.0 65.0 35.0 | 33.2 42.0 17.0 | 100.0 82.0 18.0 | 100.0 70.0 30.0 | 33.2 44.2 7.6 | 100.0 98.0 2.0 |
Magnetic treatment of water for flotation manganese carbonate ore is also affected. Table 17 shows the effect of industrial water and slurry on the flotation results of manganese carbonate ore after magnetic treatment.
Processing conditions | Magnetic field strength kA/m | Flotation time Min | Concentrate, % | ||
Yield | grade | Recovery rate | |||
Unmagnetized | 0 | 3 6 | 30.0 29.1 | 15.9 19.2 | 31.1 69.1 |
Water magnetization | 48 | 3 6 | 44.6 30.0 | 19.3 17.8 | 56.6 91.6 |
135 | 3 6 | 47.7 28.3 | 19.2 17.4 | 60.8 93.5 | |
The slurry is magnetized | 48 | 3 6 | 50.0 24.5 | 20.2 15.3 | 67.8 92.6 |
215 | 3 6 | 53.4 22.8 | 20.3 15.6 | 70.6 93.6 | |
It can be seen from the table that the magnetized water is used for flotation of manganese carbonate ore, and the recovery rate is improved under the same flotation time conditions, and the recovery of the slurry before the contact of the collector is improved. To be significant.
It has also been studied abroad that water and slurry can improve the flotation index of copper- molybdenum ore after magnetization treatment. Through experiments, the effect of flotation is related to the composition of water, the strength of the magnetic field, and the flow velocity of the liquid.
Under laboratory and industrial conditions, experiments have confirmed that the magnetic treatment of water and slurry can increase the flotation rate by 20~30%, which significantly improves the recovery of copper and molybdenum concentrate. The industrial test results are shown in Table 18 under good conditions in the factory.
index | Unmagnetized | Magnetization |
Processing ore, t Recovery rate,% Cu Mo Increase recovery rate, % Cu Mo | 21890 77.21 78.84 - - | 23900 79.99 85.79 +2.78 +6.95 |
index | Unmagnetized | Magnetization |
Yield,% Clean coal Tailing coal Ash, % Clean coal Tailing coal raw coal Recovery rate of combustible materials in clean coal, % | 86.7 13.3 8.24 61.54 15.34 93.9 | 89.2 10.8 8.50 70.89 15.25 96.3 |
The magnetization treatment of aqueous xanthogenate has been applied in many large-scale concentrators abroad. For example, such a method is used in lead-zinc concentrator USSR (1968), 0.44% higher lead recovery catch, another concentrator, 0.5 percent copper recovery.
(3) Strengthening concentration and filtration
In order to separate finely dispersed solid suspended matter from water, concentration and filtration methods are widely used in the industry. Since the magnetization process can improve the agglomeration process of the solid suspension and reduce the formation of scale, the magnetization treatment can significantly enhance the concentration and filtration.
The suspended matter is subjected to magnetization treatment, and the sedimentation speed is accelerated due to coagulation, and at the same time, the water permeability of the filter cake in the filter is also increased during filtration, and the filtration speed is also increased.
In order to strengthen the concentration process and apply magnetization treatment, it is generally not contradictory to apply different coagulants or flocculants simultaneously for the same purpose. The practice of many plants has confirmed that the concentration effect of the suspension after it has been magnetized is very obvious. The industrial test results of a foreign coal preparation plant are shown in Table 20.
index | Unmagnetized | Magnetization (without polyamine) | |
No polyamine | Polyacrylamide | ||
Solid content, g/l Feed mine Concentrator overflow Concentrate bottom flow Clarification efficiency | 103 48 169 53.4 | 108 50 112 54.0 | 118 5 187 95.5 |
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