Magnetic separation test analysis (2)

Figure 1 The situation of the ore particles in the AC and DC superimposed magnetic field
1—AC coil; 2—DC coil; 3—Ore grain with large coercive force; 4—Pore with small coercive force [next]

Equipment Construction The instrument is mainly composed of a sorting disc, a feeding hopper and a magnetic pole.
1 Sorting plate The sorting plate is mounted on a body parallel to the magnetic pole surface by a leaf spring or the like, and its amplitude, up and down position, and inclination angle are all adjustable.
2 Feeding hopper The entire hopper part is mounted on the sorting disc and vibrates at the same time as the sorting disc. The amount of feed can be controlled by adjusting the size of the feed opening by adjusting the screw.
3 Magnetic pole part The entire magnetic system is installed inside the body by using two equal height supports. The magnetic system consists of a "U" shaped (or "mountain" shaped) magnet. The upper part of the core is an AC coil winding that is input by a 220V AC through a voltage regulating transformer. Since the voltage can be continuously adjusted, an open, variable alternating magnetic field is created on the AC coil winding. The winding of the lower half of the iron core is a DC winding. The AC current regulated by the voltage regulator is input through the rectified DC current, and an open DC magnetic field is generated on the DC winding. By properly adjusting the excitation current, the required AC-DC superimposed composite magnetic field is obtained.
During the test, the materials are first sieved, dusted and dried. Some materials need to be pre-magnetized in a large DC magnetic field to have a certain residual magnetic induction intensity. Then adjust the distance and angle between the magnetic pole surface and the sorting disc, turn on the AC-DC excitation coil power supply, and adjust the voltage and current appropriately. The size makes the magnetic pole face produce a superimposed composite magnetic field (the general adjustable range is 0~0.09T). Adjust the size of the ore, turn on the power of the sorting disc, adjust the vibration of the sorting disc to the required amplitude, and the material can be sorted to achieve the required purity.
(2) Pre-test laboratories generally use magnetic analyzers (or laboratory-type magnetic separators) for pre-tests. It can be extensively explored with a small number of samples to find out the influence of various factors on magnetic separation. Accelerate the progress of the entire test.
The pre-test is generally carried out on the magnetic analysis of products with different grinding sizes and various sorting conditions, and preliminary determination of the appropriate inclusion size, number of selected sections, approximate selection conditions and possible indicators.
(III) Formal test On the basis of pre-test, more samples can be used for formal tests on a laboratory-type magnetic separator. There are many types of magnetic separators, so it is necessary to select according to the results of pre-test and relevant practical data. For example, strong magnetic minerals can be used with weak magnetic field magnetic separators, weak magnetic minerals require strong magnetic field magnetic separators; coarse particles can be used for dry magnetic separation, and fine particles require wet magnetic separation.
After the magnetic separator is selected, a small part of the sample can be used for exploratory testing. During the test, various influencing factors, such as feed size, feed rate, magnetic field strength and other processes, are adjusted according to the separation conditions. Conditions, trials are performed sequentially until a satisfactory result is obtained. Finally, a large number of samples can be inspected using the most suitable conditions found previously. The results of the inspection test can be used as the final magnetic separation test indicator.
1. Magnetic separation test of strong magnetic ore The main magnetic separator is selected according to the particle size of the mineral, and the coarse-grained centrifugal separator magnetic separator and magnetic pulley are used. The fine particles are magnetic dewatering tanks and wet barrel magnetic separators.
(1) Dry magnetic separation test Generally, a dry magnetic separation test is required under the following conditions:
The dry magnetic separation of one ore is to eliminate the surrounding rock and stone in the ore during mining. It is usually a pre-selection operation in the magnetic separation plant. [next]
The dry magnetic separation test of lump ore is usually carried out in industrial equipment. The magnetic pulley of Ñ„600*630mm is commonly used. Generally carried out: a. Different magnetic field strength test, refer to similar factory and mine production technical conditions; b. Different particle size test, when sorting poor magnetite ore, usually sieved into 75~12 and 12~0mm two levels, if 75~ If the effect is not good at 12mm level, the reason is analyzed. If the classification range is too wide, it should be further classified. c. Moisture test, when the particle size is 75~12mm, the water content in the ore has little effect on the selection index. But when you choose 12~0mm, especially the slime. When the amount is large, the influence of moisture is significant; d. The test of different treatments requires a large number of mineral samples, which is difficult to carry out in the laboratory, and is generally carried out in the field for industrial tests.
2 Dry-drying and dry-selection test In dry and cold areas, and other suitable areas, a dry-selective magnetic separation plant may be considered. For this purpose, a dry magnetic separation test is required. During the test, the selection process, equipment parameters and operating conditions should be selected to determine the possible selection criteria.
At present, the dry weak magnetic separation mainly adopts a cylindrical dry magnetic separator. In production, dry-selection magnetic separation plants usually use dry grinding without a media mill. Since it is very difficult to carry out the medium-free grinding test under laboratory conditions, the particle size composition of the grinding product will not be in line with the actual production situation in the future, and the future production process structure cannot be determined accordingly. The main task of the test is therefore to determine the appropriate grinding size and possible comprehensive indicators.
In the test, the appropriate equipment parameters and operating factors were found, mainly the rotational speed of the magnetic separator drum and the magnetic wheel, and the grinding size. As for other factors, some (such as water) can be learned from experience, no need to test; some (such as the amount of minerals and classification criteria) is difficult to carry out in the laboratory.
(2) Wet magnetic separation test The purpose of the test is to determine a reasonable sorting process, including the number of sorting stages and the equipment used in each sorting section. The number of sorting segments is based on the size of the inlay and the quality of the concentrate. At present, the concentrate grade of most magnetic separation plants is higher than 62% Fe. If there are special requirements, the grade of concentrate should be determined according to requirements.
1 magnetic dehydration tank The laboratory generally uses a small magnetic dehydration tank of Ñ„350mm.
The magnetic dewatering tank is a device with simple structure and good effect. Under the action of magnetic force, the fine-grained magnetite forms a magnetic cluster floc. Under the influence of the rising water flow, the magnetic ore particles will be separated from the fine-grained gangue to achieve enrichment.
The main process factors affecting the magnetic dewatering tank are: rising water flow, magnetic field strength and ore feeding speed. The ascending water pressure test should also be carried out if conditions permit. It is generally possible to conduct tests at the highest possible magnetic field strength to find the optimum ascending water flow rate, feed rate and feed concentration. The maximum amount of rising water should be able to recover finer magnetite particles.
The magnetic dewatering tank is used to treat the magnetically refined final concentrate, which not only acts as a concentrate, but also improves the grade of the antimony concentrate. The magnetic dewatering tank is often used in the stage grinding and stage selection process as the first stage of grinding equipment. For the first stage of the selection, the magnetic dewatering tank or the magnetic separator should be used for comparative tests. If the overflow is significantly smaller than the tailings of the magnetic separator, or when the tailings contain other useful minerals, the dewatering tank is not needed; When there is a lot of slime after grinding, a dewatering tank should be used. In the second stage of grinding after the sorting operation, the grinding size is generally fine. At this time, the dewatering tank is used before the magnetic separation. If the fine fraction yield is more than 20% (for the operation), it is effective. The ground has improved the sorting effect of the next magnetic separator. In some cases, if the grinding size is coarser and the amount of tailings is less, the dewatering tank is not used.
2 Wet drum magnetic separator Generally, the following conditions are tested.
Grinding fineness Grinding fineness is the most important process parameter and will involve the structure of the magnetic separation process. It is mainly based on the grain size characteristics of the mineral.
Magnetic field strength The magnetic field strength is mainly determined by the magnetic properties of the selected ore. The selection of ferromagnetic minerals is generally 0.08~0.2T. The magnetic field strength generally refers to the average magnetic field strength of the magnetic separation machine.
The amount of water added is also a major factor affecting magnetic separation, mainly based on the embedding characteristics of magnetite and the amount of mud in the ore.
Three parallel tests should be performed after finding the best comprehensive process conditions, two of which are close to each other to show that the optimal overall process conditions are stable and reliable. [next]
3 Pre-magnetic and demagnetizer In the continuous test in the laboratory, for the magnetic separation of roasting ore, a pre-magnetic device is often added in front of the magnetic dewatering tank to enhance the magnetic agglomeration of fine-grained minerals and improve the sorting effect. For the stage grinding and phase selection process of roasting ore and natural magnetite, after the first stage of magnetic separation, a demagnetizer should be provided to destroy the magnetic agglomeration of the magnetic minerals to avoid affecting the second stage classification operation. The magnetic field strength of the pre-magnetic device should be greater than 0.04T, and the time for the slurry to pass through the pre-magnetic device should be greater than 0.2s. The maximum magnetic field strength of the demagnetizer is about 0.05T for natural magnetite, 0.085T for roasting magnetite, and 0.065T for mixed magnetite. After about 12 alternating cycles, the demagnetization time should be greater than 0.24s.
A simple inspection method for demagnetization effect can divide the same ore sample into two types, that is, unmagnetized and demagnetized after magnetization, and then carry out sedimentation tests on the two kinds of ore samples, such as demagnetized and unmagnetized ore sedimentation. The same time (to reach the water has been clarified), the demagnetization efficiency is 100%, that is, the demagnetization efficiency:

T
η= —— . 100%
T ₀
Where T ₀ is the settling time of the unmagnetized ore sample, s;
T----settling time of demagnetization ore after magnetization, s;
2. Test weak magnetism magnetic ore currently selected sub-ferrous metal ores applied dry strong magnetic disk separator or magnetic roll separator. These magnetic separators, although they work well, are not suitable for selecting fine ore fines. Since 1965, great progress has been made in the study of wet-type strong magnetic separators suitable for the treatment of fine-grained weak magnetic ores, such as the Jones Wet Magnetic Separator, the High Gradient Wet Magnetic Separator, and the SQC-2770 Wet Strong magnetic separator, Ñ„1500 double vertical ring wet magnetic separator. With the development of low temperature physics and superconducting technology and the increasing energy intensity, superconducting magnetic separators have also developed rapidly. Some research results have been made in the research of magnetohydrostatic separators superior to the heavy liquid method, especially the combination of the high gradient (HG) principle and the magnetic fluid static separation method (MHS), which makes the magnetic fluid static separation method Large-scale industrial applications create an effective approach.
The test content includes: determining the appropriate equipment structural parameters and operating conditions according to the nature of the ore, such as magnetic field strength, medium type, magnetic separator rotation, ore supply, ore concentration, ore size, concentrate area and tailings area. The amount of flushing water, water pressure, etc.
The magnetic separation test technique of weak magnetic ore is introduced below by taking a rotary magnetic separator, an electric disk type strong magnetic separator, a pot-shaped high gradient magnetic separator and a magnetohydrostatic separator.
(1) Spiral type strong magnetic separator The Shp-1 type strong magnetic separator is a strong magnetic separator of the rotary ring type. It is a kind of imitation Jones-type strong magnetic separator designed and manufactured by the Mining and Metallurgical Institute. And industrial testing.
1 Equipment structure As shown in Figure 2, the whole magnetic separator body consists of a steel frame, two "U" shaped yokes are mounted on the frame, and four sets of excitation coils are mounted on the horizontal part of the yoke. The excitation current is 1500A and the magnetic field strength is 1.7T. The outside of the coil has a sealed protective casing (air cylinder) that is cooled by a fan. Between the two "U"-shaped yokes, there are two upper and lower turntables, the diameter of the turntable is 1000mm), the turntable acts as a core, and the yoke forms a rectangular magnetic circuit, a turntable and a sorting box (17, The specification is 80*130mm), each box has two sides on one side and seven pieces on both sides. It is driven by a motor mounted on the top through a belt, a planetary cycloid reducer and a central drive shaft to rotate between the U-shaped magnetic poles. Since the sorting ring (rotation speed is 3~5r/min) is directly fixed to the periphery of the turntable, an air gap is reduced between the magnetic pole and the magnetic pole, thereby reducing the air reluctance and increasing the magnetic field strength. The magnetic pole of the magnetic separator (two pairs of magnetic poles, one pair per disc) is relatively wide, and the height of the toothed plate medium is high, which ensures sufficient sorting time, which is beneficial to improve the sorting index; Under the premise of ensuring sufficient sorting time, the turntable can adopt a large rotating speed. At the same time, there are 4 feeding points and high concentration feeding. These factors make the magnetic separator have a large processing capacity (processing capacity 10~15t/h). In addition, the tooth plate is used as a magnetic magnetic medium, and the concentrate is washed with high-pressure water in the neutral region of the magnetic field. Strictly control the upper limit of the ore size (in the selected ore particle size -1mm) and the strong magnetic mineral content in the production to prevent blockage of the separation gap. [next]

Figure 2 Schematic diagram of Shp-1 type strong magnetic separator
1—yoke; 2—sorting box; 3—coil; 4—turntable; 5—transmission mechanism;
6—feeding mine; 7 one row of mines; 8—middle mine flushing area; 9—concentrate washing area; 10—concentrate;
11—Mining; 12—tailing; 13—feeding

2 Test contents In order to prevent blockage of the sorting gap before the test, it is necessary to exclude ferromagnetic substances, wood chips and sundries in advance. The ferromagnetic material is separated by a weak magnetic field magnetic separator, and the wood chips and debris can be removed by screening or the like. The ore size must be strictly controlled at -1 mm.
The adjustable device parameters of the Shp-1 type strong magnetic separator include excitation current, rotation speed and the like. The operational factors that need to be examined are the ore size, the ore concentration, the amount of ore, and the amount of water flushed by each product.
Feeding particle size The ore size directly affects the sorting effect of the wet magnetic separator. Generally, the recovery of fine mud is not good, so it is possible to consider deliming before magnetic separation, and the lower limit of particle size is usually 20~10μm. In order to determine the magnetic particle size (or grinding size), the lower particle size limit, the necessity of deliming before magnetic separation, etc., it is necessary to perform particle size analysis and chemistry on sampling of ore, concentrate and tailings of the magnetic separator. analysis. The determination of the ore size should be as coarse as possible under the condition that the selection index is met, which not only saves the grinding cost, but also reduces the loss of the fine mud part.
The concentration of the ore is generally between 20 and 50%. Increasing the concentration of the ore can increase the processing capacity of the magnetic separator and the recovery rate of the concentrate, but care must be taken to ensure the quality of the concentrate. [next]
According to the nature of the feed and the type and size of the magnetic separator, the flow rate of the Shp-1 wet magnetic separator is between 1~3L/s, and the quality of the concentrate is guaranteed. Higher recovery rates, while meeting the processing requirements are appropriate.
Excitation current The magnetic field strength of the magnetic separator is flexibly adjusted by changing the magnitude of the excitation current, which is generally between 900 and 1500 A (the range of magnetic field strength varies from 1.25 to 1.5 T).
The speed generally varies between 3 and 5 r/min. The increase in the rotational speed is conducive to improving the recovery rate of concentrate.
Flushing water volume Concentrate flushing water volume should be used to rinse all magnetic products. The flushing water in the mine is generally changed between 0 and 800 mL/s. If the amount of flushing water in the mine is too large, some magnetic products will be washed down; if the amount of flushing water is too small, the magnetic non-magnetic products in the center will not be washed away. The concentrate grade is reduced, so it is necessary to find a suitable medium mine flushing water volume.
3 Test procedure The prepared ore sample is loaded into the mixing tank according to a certain concentration, and the excitation current, the magnetic field area flushing amount and the concentrate area flushing amount of the magnetic separator are adjusted. The magnetic field flushing water is supplied with pressurized water from a constant pressure water tank. After adjusting the parameters of the magnetic separation test, the test can be carried out, and different products can be taken according to the different positions and sequences of the ore-growing tanks, and the concentrate and tailings are divided according to the analytical grades of different products.
(2) Electric disk type strong magnetic separator 1 Equipment structure The electric disk type strong magnetic separator has three kinds of single disk, double disk and three disks. The laboratory usually uses double discs, which are generally suitable for dry strong magnetic separation of coarse and medium particles. The sorting principle and structure of the three disk magnetic separators are basically the same. The magnetic separator generally consists of a "mountain" shaped magnetic pole and a rotatable disc above the magnetic pole to form a closed magnetic system. There is a spring vibration groove between the two poles, and the distance between the vibration groove and the disk can be adjusted to meet the different requirements of the ore size. The working gap between the disc and the vibrating groove is successively decreased, and the magnetic field strength and the magnetic field gradient are sequentially increased to achieve the purpose of selecting different magnetic products. When the machine is working, the mineral is evenly fed from the feeding hopper to the feeding drum (with the weak magnetic field magnetic system). At this time, the ferromagnetic mineral is sucked on the surface of the drum and is carried away from the magnetic field as the drum rotates, and the weak magnetic mineral It is sent to the sorting area below the disc by the vibrating trough, and is sucked on the tooth pole of the disc, and goes to the vibrating trough with the disc, and falls into the magnetic product hopper on both sides of the trough, and the non-magnetic mineral passes through the end of the vibrating trough. Unload in the non-magnetic hopper.
2 Test conditions The adjustment factors of this machine are generally the thickness of the ore layer, the magnetic field strength and working gap, and the amplitude and vibration amplitude of the vibration tank (or the speed of the ore belt).
The thickness of the ore layer is related to the particle size, magnetic strength and magnetic mineral content of the mineral being treated. Under normal circumstances, the thickness of the fine-grained ore layer can reach 10 times of the maximum grain size of the ore, and the thickness of the coarse-grained ore layer can only be within 1.5 times of the maximum grain size of the ore. If the ore layer is too thick, the magnetic particles in the lowermost layer are not only subjected to less magnetic force, but also under the pressure of the layer of non-magnetic ore particles, which cannot be sucked up, thus entering the tailings and reducing the magnetic ore in the concentrate. Recovery rate in the middle. The appropriate thickness of the ore layer should be determined by practice.
The magnetic field strength of the sorting area is adjusted by changing the magnitude of the current. The strength of the magnetic field depends on the magnetic properties of the selected ore and the requirements of the operation. Generally, the roughening and sweeping require a higher magnetic field strength to ensure the recovery rate, so the current should be increased; when selecting, the concentrate grade should be increased, and the magnetic field strength should be Lower, so the current should be reduced. Generally, the magnetic field strength of the black tungsten ore is 0.5-0.8T.
Working gap When the current is constant, the change of the working gap causes the magnetic field strength and the magnetic field gradient to change at the same time. The gap becomes small, and in the case where the pitch is not too large, the magnetic field strength and the magnetic field gradient sharply increase, and thus the magnetic force of the ore particles increases; when the gap becomes large, the magnetic force sharply decreases. Generally, when processing coarse ore particles, the working gap is larger; when processing fine ore particles, the working gap can be smaller. When sweeping, the gap should be adjusted to increase the recovery rate; when selecting, the gap can be adjusted to increase the quality of the concentrate.
When the vibration velocity of the vibrating trough is generally selected, there are many monomer minerals in the material, and their magnetic properties are strong, and the vibration velocity of the vibrating trough can be higher; when sweeping, the material contains more connected organisms, and the magnetic properties of the living body It is weaker. In order to increase the recovery rate, the speed of the vibrating trough should be lower. For the treatment of fine-grained materials, the frequency of the vibrating trough should be slightly higher (favorable for loose ore) and the amplitude should be smaller; while for coarse-grained materials, the frequency should be slightly lower and the amplitude should be larger.
The feeding material size is generally -3mm. The screening requires prior screening and grading. The more screening levels, the higher the selection index, of course, too much is unnecessary, and it is not economical.
The feedstock must be dry, otherwise the ore particles stick to each other and affect the sorting index. If the sample used is for re-election of coarse concentrate, which is wet ore, it must be dried beforehand. Avoid baking at high temperatures when drying. In the process of air drying and preservation, it must be careful and can not be stored for a long time under humid conditions, so as to avoid the change of ore properties and affect the accuracy of the test. At the same time, if there are a variety of metal minerals associated with coarse concentrates, they should be separately recovered by other methods according to the specific conditions before magnetic separation. [next]
3 Process test The purpose of the process test is to determine the number of reasonable selection sections and the fineness of grinding, the number of cleaning, the number of sweeps and the equipment to be used for each operation. Some of the principle issues related to the selection process plan should be initially determined in the pre-test. This is only once again confirmed, and the internal structure of the process is further discussed in detail.
If the ore is coarse-grained or unevenly embedded, it may be a dry magnetic separation or a combined process of dry and wet combination. The dry magnetic separation part needs to be classified.
For the process test of the most common fine-grained poor-poor ore-type ore in China, the following problems need to be studied.
a. It is necessary to adopt several stages of sorting process. Most of the old processes use two-stage sorting, because the ore is mostly strip-like structure, and the useful mineral inlay is fine in size. Some tailings should be discarded under rough grinding conditions. Secondary grinding load, coarse concentrate re-grinding and re-election. At present, the state requires blast furnaces to refine concentrates. In order to obtain high-quality concentrates, it is necessary to increase the number of sorting sections, that is, to adopt three or more stages of sorting, and it is also possible to consider adding a magnetic separation concentrate to reverse flotation. Fine sieving and grinding can also be used to form a regrind system. The product on the screen is sent for regrind, and the product is sent to a multi-stage magnetic separation. Production practice shows that fine screening is one of the effective methods to reduce the silicon content in concentrate and increase production capacity.
b. The number of selections For a single iron ore, it is generally not necessary to select multiple times, so it is not necessary to conduct a comparison test of the selected number of times. For iron ore containing other companion useful ingredients, multiple selections may improve concentrate quality.
c. The application of the dewatering tank is generally set as a sorting device after one-stage and two-stage grinding, excluding some fine-grain tailings and slime; it is set to concentrate and improve the concentrate grade after the magnetic separator, but both must be It can be determined through trials. If the associated heavy minerals (such as ilmenite) are separated, it does not work.
d. Medium-mine processing Regarding the separation process of fine-grained and micro-particle-embedded magnetite and red iron ore and mixed iron ore with associated metals, various methods are generally used (magnetic separation, re-election, flotation, Metallurgical, etc.) combined combing treatment. In the test, a variety of process schemes must be compared (generally, the mud removal operation must be added before the selection. For the magnetic-red or red-magnetic mixed ore, the weak magnetic field magnetic separator must be selected in advance), and the preferred scheme is selected. Design provides the basis.
(3) Tank-shaped high-gradient magnetic separators have different structures due to their different uses, but are mainly used for processing materials with low magnetic content, such as non-magnetic materials ( kaolin , refractory clay and glass sand). Removal of iron, wastewater filtration, etc.
1 Equipment structure As shown in Fig. 3, the tank-shaped high gradient magnetic separator is composed of a magnet, a medium tank, a sorting medium, and the like. The magnet includes a spiral coil and a yoke. Coils are typically square hollow copper tube wound with a low voltage, high current excitation, the cooling water cooled in order to achieve a sufficiently high field strength. The yoke is made of pure iron and functions to form a closed magnetic circuit with the solenoid, eliminating magnetic flux scattering and increasing the magnetic field strength of the solenoid inner cavity. The sorting tank is made of non-magnetic material (stainless steel or copper), and has a slurry inlet and a slurry outlet. The cylinder facilitates the installation of the yoke and the sorting medium. The role of the sorting medium is to generate a magnetic field gradient and attract magnetic mineral particles. The commonly used medium is magnetically permeable stainless steel fluff and steel mesh.

Figure 3 tank high gradient magnetic separator
1—yoke; 2—medium can; 3—coil; 4—feed; 5—power supply; 6—magnetized medium component;
7—magnetic field characteristics between magnetized dielectric elements; 8—magnetized particles [next]

2 Test content The test device is of a periodic type and performs intermittent operation. The magnetic separation process is divided into three stages, namely, cleaning and cleaning of magnetic products and magnetic products. The specific test content is as follows:
Slurry Flow Rate In order to increase the throughput of the high gradient magnetic separator and reduce the impurity content in the concentrate, the slurry flow rate is one of the important factors, and the optimum slurry flow rate is generally determined at the highest field strength.
The amount of ore given to the ore directly affects the slurry flow rate and concentrate quality. As the amount of ore is increased, the magnetic medium adsorbs magnetic products, the interstitial space is reduced, the fluid resistance is increased, and the slurry flow rate is reduced. When the concentration is small, the amount of ore is increased, and the volume of the ore is increased accordingly. Since the slurry itself has a flushing effect, the cleaning effect on the mechanically mixed non-magnetic ore particles is strengthened, which is beneficial to improving the quality of the concentrate.
The ore concentration increases, the collision probability of magnetic ore and magnetic medium increases, and the recovery rate increases, but it has a certain impact on the quality of concentrate. The concentration is too low and the throughput is reduced. Usually between 5~15%.
The strength of the magnetic field increases the field strength, the quality of the concentrate decreases, and the recovery rate begins to increase rapidly. Therefore, the magnetic medium does not reach magnetic saturation, and the magnetic force increases according to the square of the field strength. When the field is strong enough, the magnetic medium has been magnetized to saturation, and the magnetic force increases only by the field strength, so the recovery rate increases slowly. The background field strength is generally between 0.2 and 2T.
Magnetic media filling rate The magnetic media filling rate directly affects the size and distribution of the field strength around it, and also affects the resistance of the fluid. When the filling rate of the medium increases, the surrounding field strength increases, the magnetic field gradient increases remarkably, and the recovery rate begins to increase rapidly. At this time, as the gap between the magnetic media decreases, the fluid resistance increases, which causes more mechanical inclusions and fines. The quality of the mine is reduced. If the filling rate is too low, the field strength around the magnetic medium is lowered, and the magnetic trapping point is reduced, so the recovery rate is significantly reduced. The magnetic medium filling rate is generally between 5 and 10%.
Sorting chamber height The sorting chamber height is different, and the field strength is different under the same excitation current. Due to the higher filling of the magnetic medium layer, the blocking effect on the ore particles is enhanced, and the mechanical inclusions of the non-magnetic ore particles are increased, resulting in a decrease in the quality of the concentrate.
(4) Magnetic fluid static separator Magnetic fluid technology is widely used in various industrial sectors, such as sealing, lubrication, energy conversion, oil-water separation, rapid printing, environmental protection, metal separation, mineral separation and medicine. aspect. Beneficiation technique, not only successfully used to purify the diamond, but also in terms of sorting coal, iron ore, manganese ore, precious metals, precious metals and non-ferrous metals recovered from the slag, also had a significant effect.
1 Equipment structure The structure of the magnetic hydrostatic separation device is relatively simple, mainly composed of magnetic system, feed trough, sorting tank, separation plate, ore discharge (see Figure 4a, b). The magnetic system consists of a core, a coil and a magnetic pole. The magnetic circuit is a rectangular closed magnetic circuit, and the iron core is made of engineering pure iron. The sorting tank is made of plexiglass, and the shape is determined according to the magnetic pole head. The size of the sorting tank is determined by the processing capacity. The length of the sorting belt is generally 40 cm, and the vibrating feeder is provided at the upper end. In order to layer and extract materials of different specific gravity, the separation plate is adjusted up and down by the adjusting rod, and the material is discharged through the lower part of the tank body to obtain light and heavy products respectively.

Figure 4 Magnetic fluid sorter
1—feeding trough; 2—magnetic fluid; 3—iron core; 4—coil; 5—sorting trough;
6—stirring tank; 7—vibrating feeder; 8, 9—discharge device; 10—mineral grain [next]

2 Test content Mainly includes working fluid, magnetic field strength, position of separation plate, inclination angle of sorting tank and feeding speed.
Working Fluid The type and concentration of paramagnetic salt are correctly selected based on the properties of the sorting material and the paramagnetic salt (magnetization coefficient, density and viscosity). More than 30 kinds of iron, manganese, nickel , cobalt salt aqueous solutions such as MnCl ₂ · 4H ₂ O, MnBr ₂ , Mn(NO ₃ ) ₂ , FeSO ₄ , CoSO ₄ , NiSO _{4 ,} etc. may be used in the beneficiation. Since the magnetization coefficient of the paramagnetic salt solution is relatively low, in order to increase the sorting density, the magnetic field strength is greatly increased, thereby complicating the magnetic fluid static sorting machine. Otherwise, it is necessary to reduce the sorting density and affect the application of magnetic fluid static sorting. Therefore, many researchers use magnetic fluids prepared from ferromagnetic materials as working fluids.
The magnetic field strength is generally 1~2T. The magnetic field strength affects the apparent density of the magnetic fluid in the magnetic field space, and the magnetic buoyancy can be adjusted. Under the action of magnetic buoyancy, the ore particles are mainly layered by specific gravity, and products of different specific gravities can be obtained by appropriate methods.
Separation plate position In order to extract different specific gravity materials in layers, the position of the separation plate can be adjusted as needed.
Sorting groove inclination angle The inclination angle is related to the speed at which the suspended ore particles move toward the discharge end. For example, the inclination angle is small, the flow rate is small, the sorting time is long, and the sorting precision is high, but the sorting machine has low efficiency. Conversely, the sorting accuracy will be reduced. The inclination angle is generally between 0 and 10°. When the material particle size is coarse, the inclination angle can be smaller. When the material particle size is fine, the inclination angle can be larger.
The amount of ore to be fed should not be too much, because too much ore will cause the ore particles to squeeze each other and the stratification is not good. If the ore amount is too small and the treatment capacity is reduced, the suitable ore supply amount should be a large and stable feed amount without affecting the stratification effect.
After the pre-strong magnetically selected material enters the sorting zone, the ore particles will be discharged from different discharge ports in order of specific gravity. The sorting process is continuous.
(IV) Measurement of magnetic field strength of magnetic separator The magnetic field strength of magnetic separator has a great influence on the magnetic separation process index. Therefore, it should be checked regularly whether the magnetic field strength of the magnetic separator is satisfactory. At present, a Gauss meter is commonly used to measure the magnetic field strength.
1. Gauss meter measurement principle Gauss meter measurement principle tomb in the Hall effect. It amplifies and converts the measured Hall voltage into a Gaussian number. As shown in FIG. 5, when the semiconductor wafer in the Gauss meter probe is supplied with the current IH and the magnetic field B is applied in the vertical direction of the sheet, a voltage appears in the vertical direction of the plane formed by the direction of the current and the magnetic field. Hall effect, the voltage that appears is called the Hall voltage. The Hall voltage VH is proportional to the current intensity IH and the magnetic field B, namely:

Figure 5 Hall effect diagram

VH = K _H I _H B
Where V _H - Hall voltage, V;
I _H - the operating current of the Gauss meter, A;
B——the magnetic flux density of the measuring point in the magnetic field, T(1T=10 ⁴ Gs);
K _H - related to the shape and size of the Hall element, the size of the element is determined, and KH is a constant.
Since the operating current IH of the Gauss meter is also constant, the Hall voltage V _{H is} only related to the magnetic field B at the point where the probe is located. The Gauss meter amplifies and directly converts V _H into a Gaussian number, and can directly read Gauss or Tesla numbers when measuring.
2. The performance of the Gauss meter is used to measure the constant magnetic field and the alternating magnetic field using the CT3 Gauss meter. The CT5 Gauss meter is only used to measure the constant magnetic field. Both can identify the polarity of the magnetic pole. The effective range is 0~1T, reference range. For 1~2.5T, the magnetic field of 2*10 ^-5 T can be resolved. The main advantage is that the measurement sensitivity and accuracy are high; when measuring, it is not necessary to cut the magnetic field line in the magnetic field, or alternately turn on and off the magnetic field excitation power. Refer to the instrument manual for specific usage and precautions.

Keg Filling And Cleaning Machine

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