The industrial magnetic separation machine can be divided into the weak magnetic separator and strong magnetic separator (high-intensity magnetic separator). This article mainly introduces the types of weak magnetic separators, includes dry type, wet type, and auxiliary equipment.
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The iron remover is used to remove the iron lump and iron slag from the raw material, have an electromagnetic type and permanent magnet type. Iron remover installation: fixed suspension and belt suspension. A fixed suspended iron remover is suspended above the conveyor belt to pick up iron from the material flow. The width of the magnet corresponds to the width of the belt conveyor. It needs manually remove the iron from the magnet, so it only used in the small processing plants.
The belt suspension iron remover has two installation methods, as shown in the figure below. One is that the iron remover and the conveyor belt cross at right angles, and the iron is discharged from the side of the conveyor belt; the other is that the iron remover is in the same direction as the conveyor belt, and the iron is discharged from the front end of the material stream. It is used for extracting bulk iron materials, can be used for iron removing or iron recovering from coal, iron slag and steel slag, industrial waste and other materials.
Magnetic pulleys, also known as magnetic rollers, are available in both electromagnetic and permanent magnets. The permanent magnet pulley has a simple structure, no power consumption, reliable work, easy maintenance, and wide application. 1 Equipment structureBarium ferrite constitutes a multi-pole magnetic system with a magnetic wrap angle of 360 degrees, and a rotating cylinder made of a non-magnetic material is placed outside the magnetic system. 2 Magnetic system and magnetic field characteristicsWhen the material size of the treated material is less than 20mm, the alternating polarity is beneficial to improve the beneficiation efficiency. 3 Beneficiation process ore material evenly and constantly feed on the belt, when the ore passes through the magnetic pulley, the non-magnetic or weak magnetic ore particles are separated from the belt surface by centrifugal force and gravity; while the strong magnetic particles attracted to the belt by the action of the magnetic force and is carried by the belt to the lower part of the magnetic pulley. After the belt away the magnetic pulley, the magnetic force of the magnetic ore particles is weakened and falls into the magnetic product tank. The yield and quality of the product are adjusted by the position of the separation baffle mounted under the magnetic pulley.
4 Application Pre-selection for big size (10~120mm) strong magnetic ore, it usually be installed after the coarse crushing operation, separates the surrounding rock. In some concentrating plants, the magnetic pulley is installed between the fine crushing process and the grinding process, picking up part of the tailings, which can reduce the amount of ore and improve the grade. In the operation of the hematite ore roasting, the roasting quality is controlled by a magnetic pulley, so that the ore which is not sufficiently reduced is separated by a magnetic pulley and returned to the roasting furnace for magnetization roasting.
Drum magnetic separator main parts: Permanent magnet fixed magnetic system, feeding part (upper or lower feeding), discharge part, transmission and frame. 1 Structure-The cylinder is made of 2mm FRP and the surface is coated with a layer of wear-resistant rubber. The magnetic system consists of a barium ferrite permanent magnet block with a magnetic envelope angle of 270 degrees. The polarity of the magnetic poles alternates in the circumferential direction and the polarities are uniform along the axial direction. The main reason for the use of FRP for cylinders instead of stainless steel is to prevent the drum from heating due to eddy currents. The drum magnetic separator has two types of a single cylinder and double cylinder. The sorting length of the single-cylinder can be adjusted by the position of the baffle. The double-barrel machine can adjust the magnetic system declination to adapt to the needs of different sorting processes (concentrating or scavenging).
2 Beneficiation process The fine dry ore particles are firstly fed into the upper drum by the electric vibrating feeder, the magnetic ore particles are attracted on the cylinder surface and be discharged. The non-magnetic ore particles are thrown away from the cylinder surface by gravity and centrifugal force, and enter the lower drum for sorting. The non-magnetic ore particles enter the tailings trough, the rich aggregate enters the concentrate tank.
3 Applications Dry tye separation for fine-grained strong magnetic ore; Removing magnetic impurities and purifying magnetic materials from powdery materials, widely used in metallurgy, machinery, chemical, electric power, building materials and so on. Foreign dry-type weak magnetic cylinder magnetic separators include the former Soviet Unions cylindrical magnetic separator and the Sala Mortsell magnetic separator.
Permanent magnetic cylinder magnetic separator main parts: cylinder, magnetic system, sorting tank, feeding port, discharging and overflowing part. The cylinder can transport the adsorbed magnetic particles and prevent the slurry from immersing in the magnetic system. The cylinder and end cap are made of non-magnetic, high resistivity and corrosion-resistant materials. The tank in the magnetic field is made of austenitic stainless steel and is lined with synthetic material to prevent wear. Adding auxiliary magnetic pole to the gap of the main magnetic pole of the permanent magnetic cylinder magnetic separator, which can increase the magnetic field strength and the depth of action, and improve the production capacity and the sorting effect. The wet cylindrical magnetic separator has three tank structures: a forward flow, a reverse flow, and a semi-reverse flow.
The magnetic desilting tank is also called a magnetic dewatering tank. It is a dressing device that combines gravity and magnetic effect, widely used in the magnetic separation process to remove slime and fine-grained gangue, and also as a concentrator before filtration. Advantages of simple structure, no moving parts, convenient maintenance, simple operation, large processing capacity and good beneficiation effect.
In the magnetic desilting tank, the forces that the ore particles receive are gravity, magnetic force and water flow force. Gravity causes the ore particles to settle, and the magnetic force accelerates the sedimentation of the magnetic ore particles and adheres on the surface of the magnetic system. The rising water flow can prevent the sedimentation of the non-magnetic fine-grained gangue and the slime, and cause them to flow into the overflow. Thus, separate from magnetic ore particles from gangue. The ascending water flow can also make the magnetic ore particles loose, flush out and improve the concentrate grade.
In order to improve the beneficiation effect of the magnetic desilting tank, the ore particles are pre-magnetized before being selected, so that the fine-grained ferromagnetic materials are condensed into larger magnetic agglomerates. The sedimentation velocity of the magnetic agglomerates is faster than that of the non-magnetic particles, which is conducive to subsequent magnetic deliming and the like.
The demagnetizer disperses the ferromagnetic agglomerates. The commonly used demagnetizer structure is shown in the figure below. It is a tower-shaped coil that is placed on a non-magnetic material tube and works by alternating current. When the ferromagnetic mass passes through an alternating magnetic field whose magnetic field strength is changed from large to small, the magnetic particle has repeatedly magnetized a plurality of times, so that the magnetic energy product of the magnetic particle is smaller than once, and finally, the residual magnetism is lost.
MAGNETIC SEPARATORS a wide range of MAGNETIX products, designed for metal separation in applications such as: mining, power industry, recycling andfood industry. The magnetic separators are installed on belt conveyors, chutes and pneumatic conveying pipelines.
Magnetic and electromagnetic separators MAGNETIX are products with the best European quality. We can get it because all steps of manufacturing of metal separators from designing, testing and production are in our factory. For building of metal separators we are using the strongest neodymium and ferrite magnets and the best quality parts from our European suppliers. The best quality is signed by ISO certificate TV NORD.
In the offer the Customer can find typical magnetic separators for typical sizes of conveyors, pipelines and chutes. MAGNETIX as a producer realizing also not typical projects where is designing of different sizes and types of magnetic separators for many industrial installations. Special metal separators can be using in explosive zones ATEX like coal mines and power plants, mils, sugar factories etc. with high explosive dustiness.
The science of magnetic separation has experienced extraordinary technological advancements over the past decade. As a consequence, new applications and design concepts in magnetic separation have evolved. This has resulted in a wide variety of highly effective and efficient magnetic separator designs.
In the past, a process engineer faced with a magnetic separation project had few alternatives. Magnetic separation was typically limited and only moderately effective. Magnetic separators that utilized permanent ferrite magnets, such as drum-type separators, generated relatively low magnetic field strengths. These separators worked well collecting ferrous material but were ineffective on fine paramagnetic particles. High intensity magnetic separators that were effective in collecting fine paramagnetic particles utilized electromagnetic circuits. These separators were large, heavy, low capacity machines that typically consumed an inordinate amount of power and required frequent maintenance. New developments in permanent magnetic separation technology now provide an efficient alternative for separation of paramagnetic materials.
Technological advances in the field of magnetic separation are the result of several recent developments. First, and perhaps most important, is the ability to precisely model magnetic circuits using sophisticated multi-dimensional finite element analysis (FEA). Although FEA is not a new tool, developments in computing speed over the last decade have made this tool readily accessible to the design engineer. In this technique, a scaled design of the magnetic circuit is created and the magnetic characteristics of the individual components quantified. The FEA model is then executed to determine the magnetic field intensity and gradient. Using this procedure, changes to the magnetic circuit design can be quickly evaluated to determine the optimum separator configuration. This technique can be applied to the design of both permanent and electromagnetic circuits. As a consequence, any type of magnetic separator can be developed (or redesigned) with a high level of confidence and predictability.
Equally important has been the recent development of rare-earth permanent magnets. Advances in rare-earth magnet materials have revolutionized the field of magnetic separation. The advent of rare-earth permanent magnets in the 1980s provided a magnetic energy product an order of magnitude greater than that of conventional ferrite magnets. Rare-earth magnetic circuits commonly exhibit a magnetic attractive force 20 to 30 times greater than that of conventional ferrite magnets. This development has provided for the design of high-intensity magnetic circuits that operate energy-free and surpass the strength and effectiveness of electromagnets.
Finally, the materials of construction used in the fabrication of magnetic separators have advanced to a point that significantly extends service life while decreasing maintenance. Advanced materials, such as fiber composites, kevlar, ultra high molecular weight polyester, and specialty steel alloys are now commonly used in contact areas of the separator. These materials are lightweight, abrasion resistant, and comparatively inexpensive resulting in significant design advantages as compared to previous construction materials.
The evolution of high strength permanent rare-earth magnets has led to the development of high-intensity separators that operate virtually energy free. The use of rare-earth magnetic separators for beneficiation of industrial minerals has become the industry standard with literally hundreds of separators placed in recent years. The following sections present an overview of the most widely used permanent magnetic separators: rare-earth drum and rare-earth roll-type separators.
Of the roll separators, there are at least fourteen manufacturers. Most of the different makes are based on the original Permroll design concept originated by this author. Various enhancements have been mainly focused on the belt tracking methods. New magnetic roll configurations and optimization of roll designs are relatively recent innovations. Additional optimization efforts are in progress.
At last count, seven manufacturers have commercially available drum separators, most based on magnet circuits derived from the use of conventional ferrite magnet. Two unique designs have been developed with one clearly offering advantages over older configurations.
Rare-earth elements have some unique properties that are used in many common applications, such as TV screens and lighters. In the 1970s, rare-earths began to be used in a new generation of magnetic materials, that have very unique characteristics. Not only were these stronger in the sense of attraction force between a magnet and mild steel (high induction, B), the coercivity (Hc) is extremely high. This property makes the magnetization of the magnet body composed of a rare-earth element alloy very stable, i.e., it cannot easily be demagnetized.
It was a well known fact that permanent magnets positioned on both sides of a flat steel body can magnetize the steel to a high level, if the magnet poles were the same on each side, i.e., the magnets would repel each other. However, in the past, large magnet volumes were required to achieve any substantial magnetization. With the new powerful magnets, the magnet volume could be relatively small to generate high steel magnetization. In 1981 this author determined the optimum ring size for samarium-cobalt magnets. Maximum steel magnetization (near saturation) could be obtained if the rings were stacked to make a roll using a 4:1 ratio of magnet to steel thickness, see Figure 1. Since magnetized particles are attracted to the magnetized steel surface on the roll periphery, this means that 20% of the exposed roll surface would collect such material. This collection area is an order of magnitude greater than what could be achieved with prior art magnets, making the magnetic roll useful for mineral separation.
Although one of the first prototype rare-earth magnetic rolls was calculated to have about 14,000 gauss steel magnetization, it was found in comparative testing with electromagnetic induced roll (IMR) separators operating at about 21,000 gauss, that similar performance was obtained in fine particle processing (smaller than 1 mm). When processing coarser particles an improved performance was established (e.g., less weakly magnetic contaminants remaining in the upgraded product and fewer separation passes to achieve high quality). The improvement results because the magnetic force acting on the particles is high, due to a high flux gradient. An electromagnetic induced magnetic roll separator has an air gap, which must be increased to accommodate the processing of larger particles. The rare-earth magnetic roll (REMR) magnetic separator has no such air gap. Consequently, the magnetic force does not decline in the manner of an IMR set with a large air gap.
As the name implies, suspended magnets are installed over conveyors to lift tramp iron out of the burden. Suspended magnets have been more frequently applied as conveyor speeds have increased. Suspended type magnets are capable of developing very deep magnetic fields and magnet suspension heights as high as 36 are possible.
Suspended magnets are of two basic types (1) circular and (2) rectangular. Because of cost considerations, the rectangular suspended magnet is nearly always used. Magnet selection requires careful analysis of the individual system to insure adequate tramp iron removal. Factors that must be considered include:
The position in which the magnet must be mounted will also influence the size of magnet required. The preferred position is at an angle over the head pulley of the conveyor where the load breaks open and the tramp iron is free to move easily to the magnet face. When the suspended magnet must be mounted back from the head pulley parallel to the conveyor, tramp iron removal is more difficult and a stronger magnet is required.
Magnetic drum separators come in many different styles. Tramp iron drum separators usually use a magnet design referred to as a radial type. In such a unit the magnet poles alternate across the width of the drum and are of the same polarity at any point along the drums circumference. The magnet assembly is held stationary by clamp bearings and the drum shell is driven around this magnet assembly.
Drum-separators lend themselves to installation in chutes or at the discharge point of bucket elevators or screen conveyors.The capacity and type of tramp iron to be removed will determine the size selection of a drum separator. They are available in both permanent and electro magnetic types.
Standard drum diameters are 30 and 36. General guide lines, in diameter selection, are based on (1) feed volume (2) magnetic loadings and (3) particle size. The 30 diameter drum guide lines are roughly maximum of 75 GPM per foot feed volume, 8 TPH per foot magnetic loading and 10 mesh particle size. The 36 guide lines are 125 GPM per foot feed volume, 15 TPH per foot magnetic loading and 3/8 inch particle size.
For many years, wet magnetic drum separator magnet rating has been on the basis of a specified gauss reading at 2 from the drum face. The gauss reading is an average of readings taken at the centerline of each pole and the center of the magnet gap measured 2 inches from the drum surface. This rating tends to ignore edge of pole readings and readings inside of the 2 inch distance, particularly surface readings which are highly important in effective magnetic performance.
We have previously discussed dry drum separators as used for tramp iron removal. A second variety of drum separator is the alternating polarity drum separator. This separator is designed to handle feeds having a high percentage of magnetics and to obtain a clean, high grade, magnetic concentrate product. The magnet assembly is made up of a series of poles that are uniform in polarity around the drum circumference. The magnet arc conventionally covers 210 degrees. The magnet assembly is held in fixed operating position by means of clamp bearings and the cylinder is driven around this assembly.
Two styles of magnet assemblies are made up in alternating polarity design. The old Ball-Norton type design has from 8 to 10 poles in the 210 arc and develops a relatively deep magnetic field. This design can effectively handle material as coarse as 1 inch while at the same time imparting enough agitation in traversing the magnetic arc to effectively reject non-magnetic material and produce a clean magnetic concentrate product. The 30 diameter alternating polarity drum is usually run in the 25 to 35 RPM speed range.
Application of the high intensity cross-belt is limited to material finer than 1/8 inch size with a minimum amount of minus 200 mesh material. The cost of this separator is relatively high per unit of capacity approaching $1000 per inch of feed width as compared to $200 per inch of feed width on the induced roll separator.
This investigation for an improved separator is a continuation of the previously reported pioneering research of the Bureau of Mines on the matrix-type magnetic separator. When operated with direct current. or a constant magnetic field, the matrix-type magnetic separator has several disadvantages, which include incomplete separation of magnetic and nonmagnetic components in one pass and the retention of some of the. magnetic fraction at the discharge quadrant. Since the particle agitation that results from pulsed magnetic fields may overcome these factors, operation with an alternating current would be an improvement. Another possibility is the separation of dry feeds, which may have applications where the use of water must be avoided.
The effects of an alternating field were first described by Mordey and later by others of whom Doan provides a bibliographical resume. The significant feature to note in the description by Mordey is the change from a repulsion in weak fields to an attraction in strong fields, in addition to a difference in response with different minerals. The application by Mordey was with wet feeds using launders and inclined surfaces, although applications by others are with both wet and dry feeds.
Except for occasional later references the interest in alternating current for magnetic separation has almost disappeared. Lack of interest is probably due to the apparent high power consumption required to generate sufficiently intense magnetic fields, a problem that warrants further consideration.
The matrix separator differed somewhat from the slotted pole type described in a previous report in that the flux passed into the matrix from only one side, the inverted U-shaped magnet cores 4 and 7 illustrated in figure 1. Figure 1 shows a front view, side view, and a bottom view of the matrix-type magnetic separator. By this arrangement, an upward thrust could be exerted on the matrix disk during each current peak; the resulting induced vibration would accelerate the passage of the feed as well as the separation of the magnetic particles from the nonmagnetic particles since the applied field during the upward thrust preferentially lifts
The matrix disk 5 rotates successively through field and field-free quadrants. Where a given point on the disk emerges into a field quadrant, feed is added from a vibrating feeder; nonmagnetic particles fall through the matrix, and magnetic particles are retained and finally discharged in the succeeding field-free quadrant.
Two types of disks were used, a sphere matrix illustrated in top and cross-sectional views in figure 2 and a grooved plate type similarly illustrated in figure 3. Both the spheres and grooved plates were mounted on a nonmagnetic support 1 of optimum thickness for vibration movement (figs. 2-3). The sphere matrix disk, similar to that of the earlier model, had a matrix diameter 8 of 8.5 inches and spokes 7 spaced 45 apart; the spheres were retained by brass screens 4 (fig. 2).
The grooved plate disk was an assemblage of grooved steel plates that tapered so that one edge 5 was thinner than the other 6 (fig. 4) to provide a stack in the form of a circle having an outside diameter 9 of 7.9 inches (fig. 3). The plates were retained by two split aluminum rings 8 and 3 clamped in two places 1 and 11. They were stacked so that the vertically oriented grooves of one plate touched the flat side of the second plate. As illustrated in figure 4, two slots 3 and 4 were added to reduce eddy current losses.
Both disks 5 illustrated in figure 1 were rotated by a pulley 1 through a steel shaft 8 held by two aluminum bars 2 and which in turn were fastened to aluminum bars 3 and steel bars 6. The magnetic cores 4 and 7 were machined from 10- by 12-inch E-shaped Orthosil transformer laminations. For wet feeds,
With the information derived from the performance of this separator, a cross-belt-type separator was also constructed as illustrated in figure 5, which shows a front view and a cross-sectional view through the center of the magnet core. The cross-belt separator mentioned here differs somewhat from the conventional cross-belt separator in that the belt 5 moves parallel to the feed direction instead of 90 with the feed direction. The magnetic core, composed of parts 17, 19, 21 and 22 that were machined from 7--by 9 inch E-shaped Orthosil transformer laminations, supplies a magnetic field between one magnetic pole 6, which has grooves running parallel to the feed direction, and the other magnetic pole 14. Owing to the higher intensity field at the projection from the grooves, magnetic particles are lifted from feeder 15 to the belt 5. By movement on flat-faced pulleys 3 supported by bearings 4 the belt 5 carries the particles to the discharge chute 7. Nonmagnetic particles fall from the feeder edge and are discharged on the chute 8. A special 0.035-inch-thick Macarco neoprene-dacron endless belt permits a close approach of the feeder surface to the magnet pole 6. The feeder 15 constructed of plexiglass to prevent vibration dampening by eddy currents, is fastened to a vibration drive at 16 derived from a small vibrating feeder used for granular materials. A constant distance between poles 6 and 14 was maintained by acrylic plastic plates 9 on each side of the poles 6 and 14 with a recessed portion 13 to provide room for the belt 5 and feeder 15. The structural support for the separator, which consisted of parts 1, 2, 11, 18, and 20, was constructed of 2- by 2- by -inch aluminum angle to form a rectangular frame, and part 10 was machined from angular stock to form a support for the magnet core.
Each U-shaped magnet core in figure 1 was supplied with two 266-turn coils and two 133-turn coils of No. 10 AWG (American wire gage) heavy polythermaleze-insulated copper wire. With alternating current excitation, the current and voltage are out of phase so that the kilovolt-ampere value is very high even though the actual kilowatt power is low. This difference may be corrected with either series capacitors to reduce the input voltage or parallel capacitors to reduce the input current. However, the circuit that was selected is illustrated in figure 6 in which the two 266-turn coils are connected in series with the capacitor 2. Power is supplied by the 133-turn drive coil 7 that is connected in series with the 133-turn drive coil 9 on the other U-shaped magnet core. Coils 4 and 6 and the capacitor 2 form a circuit that resonates at 60 hertz when the capacitor 2 has a value of 49 microfarads in accordance with the equation
For the capacitance in the power input circuit, the value is calculated on the basis of the equality of equations 2-3. When the input at point 10 is 10 amperes at 126 volts or 1.26 kilovolt-amperes, the current at point 3 and the voltage at
point 1 are 10 amperes and 550 volts, respectively, or a total of 11.0 kilovoIt-amperes for the two magnet cores, which provides a 5,320-ampere- turn magnetization current. The capacitors, a standard power factor correction type, had a maximum rating of 600 volts at 60 hertz.
Application of alternating current to the cross-belt separator is not successful. In contrast to the matrix-type separator in which the feed is deposited on the magnetized matrix, the feed for the cross belt is some distance below a magnet pole where the field is weaker and the force is a repulsion. Even though the magnetic force with the matrix-type separator may be a repulsion instead of an attraction, it would result in the retention of the magnetic fraction in the matrix. Replacement of the alternating current with an intermittent current eliminates the repulsion effect but still retains the particle vibration characteristics.
For an intermittent current the circuit shown in figure 7 is used. A diode 5 supplies the current to a coil 4, which can be the magnetizing coil for the cross-belt separator, or for one magnet core of the matrix-type separator that is connected in parallel or series with the coil for the other core. A coil 2 is supplied with half-wave-rectified current from a diode 6 but is out of phase with the other coil 4 and is only applicable to a second separator. However, the circuit illustrates the reduction of the kilovolt-ampere load of intermittent magnetizing currents. As an example, measurements were, made with the two magnet cores of figure 1; each core had 532 turns of wire. When the capacitor 9 has a value of 72 microfarads, the current at point 8 is 13 amperes, and the voltages at points 10, 1, and 7 are 75, 440, and 390 volts, respectively. The kilovoIt-ampere input at point 11 is therefore 0.98, and the kilovolt-amperes supplied to the coils is 5.07. This circuit is not a simple resonance circuit, as shown in figure 6, but a circuit in which the correct value of the capacitor 9 depends on the current. At currents lower than 13 amperes, the 72-microfarad value is too large.
However, separations with intermittent current were confined to a simple one-diode circuit. With the matrix-type separator, each magnet core carried 10.5 amperes at 240 volts through 399 wire turns or a total of 21 amperes since the two cores were connected in parallel. For the cross-
belt separator illustrated in figure 5, five 72-turn coils and one 96-turn coil wound with No. 6 AWG heavy polythermaleze-insulated square copper wire were used in series connection. Current-carrying capacity is approximately 40 amperes with an input of approximately 80 volts of half-wave-rectified 60-hertz current. At 40 amperes, the average number of ampere turns would be 18,240. Intermittent current and voltage were measured with the same dynamometer meters used for alternating current; these meters measure an average value.
It is possible to increase the magnetizing current for the matrix-type separator without excessive vibration by increasing the thickness of the plate 1 (figs. 2-3). Another alternative is a combination of intermittent and constant magnetic fields. Although a variety of circuits are possible, the combination of fields was accomplished with the simple adaptation of the stray field losses in a U-shaped magnet core using the circuit of figure 8. The power drawn is full-wave rectification, or half wave for each leg of the magnet core with the flux, from the coils 3 and 4 adding. Owing to magnetic leakage, the flux from the coil nearest to the magnet pole tested predominates. When the magnetic field is measured with a Bell model 300 gaussmeter and observed with a Tektronix type 547 oscilloscope with a type 1A1 amplifier, the results of figure 9 represent a pulsating magnetic field on top of a constant magnetic field plateau.
Although it is known that minerals in water suspension may be separated in the constant-field matrix-type separator at fine sizes, some tests were conducted to investigate if any beneficial effects exist with an intermittent field. One advantage that was found with a minus 325-mesh feed was an increase in the completeness of the discharge of the magnetic fraction with an intermittent field as illustrated in tables 1-2. Both tests had the same average current of 10.5 amperes through the magnetizing coils of each magnet core illustrated in figure 7. The matrix consisted of 1/16-inch-diameter steel spheres.
In the two short-period comparative tests, the wash water for removing the magnetic fraction was the same and was of a quantity that permitted complete discharge with the intermittent field and partial removal with the constant field. After the test was completed, magnetic particles retained with the constant field were determined by a large increase in the intensity of flow of wash water, a flow volume that would not be practical for normal operation. For separation efficiency, the intermittent field had no advantage over the constant field probably because of a lack of vibration response with minus 325-mesh particles at 60 hertz. This will be described later with dry feeds.
Dry magnetic separation at coarse sizes is not a problem because it may be accomplished with a variety of separator types. Difficulty at fine sizes is twofold. First, the feed rate capacity decreases in the separators with moving conveyor surfaces such as the induced roll and cross-belt separators in which the attracted magnetic particles would have to move at nominal feed rates through a thick layer of nonmagnetic particles; second, an agglomeration effect is present that increases with decrease in particle size.
Results of the separation of several mineral combinations in the size range of minus 200 plus 325 mesh are summarized in tables 3-5. Table 3 illustrates the separation of -Fe2O3 from quartz in an ore with one pass through a matrix of 1/8-inch-diameter steel spheres using the alternating current circuit of figure 6.
Application of an intermittent field with a matrix of 75 percent 1/16-inch-diameter steel spheres and 25 percent 1/8-inch-diameter steel spheres is illustrated in table 4 in a one-pass separation of pyrrhotite from quartz using the circuit of figure 7. Unlike table 3, no attempt was made to obtain an intermediate fraction, which would have resulted in raising and lowering the iron compositions of the magnetic and nonmagnetic fractions, respectively, and provided a fraction for repass with increased recovery.
Table 5 gives the results of the application of a partially modulated field using the circuit of figure 8 and the grooved plate matrix of figure 3 in a one-pass separation of ilmenite from quartz. The advantage of the grooved plate over the spheres is that the particles pass through the matrix in a shorter time. The high flow rate obtained using the grooved plate could be increased further, particularly if water is used, by attaching suction chambers under the disk in a manner similar to applications with continuous vacuum filters. Although the grade and recovery of ilmenite are very high, this need not necessarily be attributed to the grooved-plate matrix since the ampere turns are higher than in any of the other tests. Increased ampere turns is a prerequisite for successful application of alternating current separators and intermittent current separators.
When a minus 325-mesh fraction is tested, a separation sometimes occurs, but in most cases the feed passes through without separation. Response at higher frequencies was investigated with a smaller -inch-cross section U-shaped magnet core 1 (fig. 10). Separation was performed with a nonmagnetic nonconducting plane surface 3 moved manually across the magnet pole as illustrated by the direction arrow 4. When separation occurred, the nonmagnetic mineral 5 would move with the plane, and the magnetic mineral would separate from the nonmagnetic mineral by remaining attached to the magnet pole. When no separation occurred, the entire mixture of magnetic and nonmagnetic minerals would either move with the plane or adhere to the magnet pole.
Four magnetising coils of 119 turns each of No. 14 AWG copper wire were used; three were connected in series with a capacitor as in figure 6, and one was connected to a variable-frequency power supply. The current in the resonant circuit is approximately 5 amperes. When the capacitor has a value of 49 microfarads, the resonant frequency is 130 hertz, and no separation occurs. With the capacitor reduced to 10 microfarads to provide a resonant frequency of 300 hertz, a separation occurs. In the case of a minus 325-mesh -Fe2O3-quartz mixture, most of the quartz moves with the plane, and the -Fe2O3 remains attached to the magnet pole. Similar results are obtained with pyrrhotite-quartz. Indications are that the separation may be improved with preliminary treatment of the feed by dry grinding aids.
frequencies, the time per cycle is too short to permit initial magnetization; at very low frequencies, the magnetization is in phase with the field. The frequencies reported here are between these two extremes and probably near, and just above, the low frequency limit. Experimental values on particles in the size range of minus 35 plus 65 mesh were previously published. These data indicate that 0.16 second, the time required to traverse a magnetizing field distance of 0.9 inch at 5.5 inches per second, is adequate time for the magnetization of minerals, but 0.02 second, the time required to traverse approximately 0.1 inch at the same rate, is too short. Time lag has been reported in the literature for magnetic alloys and has been classified, to the exclusion of the eddy current lag, into a lag that is dependent on impurities and a Jordan lag that is independent of temperature.
From evidence derived from the Barkhausen effect, the magnetization does not proceed uniformly and simultaneously throughout a specimen but is initiated in a limited region from which it spreads in a direction parallel to the field direction at a finite velocity. In a changing magnetic field, the number of initiating nuclei is proportional to the cross-sectional area perpendicular to the direction of the field. For a specimen in the form of a cube, the rate of energy W transferred to the cube would therefore be proportional to the aforementioned cross-sectional area so that for a cube of side s,
Application of intermittent current to the cross-belt separator arose from the need for the dry separation of an iron composition material from the copper in a product submitted by personnel of a Bureau of Mines chalcopyrite vacuum decomposition project. Although this product was of a relatively coarse size, the matted mass resulting from the needle shape or fiber form of the copper and the magnetic field coagulation effects of the magnetic particles prevented use of commercial dry separators such as the induced roll separator and constant-field cross-belt separator. The pulsating magnetic field had a separation effect similar to the pulsations in a hydraulic jig; the pulsating magnetic field permits the nonmagnetic fibers to sink back to the vibrating feeder and allows the magnetic particles to rise to the belt. Other applications would include fibrous minerals such as tremolite, actinolite, and chrysolite, and matted and fibrous secondary materials.
Application of alternating and intermittent current to magnetic separation at a relatively high number of ampere turns was made possible by special electronic circuits. Actual power losses are low and include the IR loss, which is the same that occurs in direct-current magnetic separation, and the core loss, which has a magnitude corresponding to the IR loss. Minerals may be dry-separated close to the minus 325-mesh size at 60-hertz frequency and possibly at smaller particle sizes at higher frequency. In the wet separation of minus 325-mesh feeds, intermittent current provides for complete release of the magnetic fraction during the discharge cycle. For matted fibrous and magnetically coagulating feeds, a cross-belt separator with an intermittent magnetizing current provides efficient separations.
Magnetic separations take advantages of natural magnetic properties between minerals in feed. The separation is between economic ore constituents, noneconomic contaminants and gangue. Magnetite and ilmenite can be separated from its nonmagnetic RFM of host rock as valuable product or as contaminants. The technique is widely used in beneficiation of beach sand. All minerals will have one of the three magnetic properties. It is ferromagnetic (magnetite, pyrrhotite etc.), paramagnetic (monazite, ilmenite, rutile, chromite, wolframite, hematite, etc.) or diamagnetic (plagioclase, calcite, zircon and apatite etc.). Commercial magnetic separation units follow continuous separation process on a moving stream of dry or wet particles passing through low or high magnetic field. The various magnetic separators are drum, cross-belt, roll, high-gradient magnetic separation (HGMS), high-intensity magnetic separation (HIMS) and low-intensity magnetic separation (LIMS) types.
Drum separator consists of a nonmagnetic drum fitted with three to six permanent magnets. It is composed of ceramic or rare earth magnetic alloys in the inner periphery (Fig. 12.34). The drum rotates at uniform motion over a moving stream of preferably wet feed. The ferromagnetic and paramagnetic minerals are picked up by the rotating magnets and pinned to the outer surface of the drum. As the drum moves up the concentrate is compressed, dewatered and discharged leaving the gangue in the tailing compartment. The drum rotation can be clockwise or counterclockwise and the collection of concentrate is designed accordingly. Drum separator produces extremely clean magnetic concentrate.
Cross-belt separator consists of a magnet fixed over the moving belt carrying magnetic feed (Fig. 12.35). The magnet lifts the magnetic minerals and puts across the field leaving the gangue to tailing. The system is widely used in mineral beach sand industry for separation of ilmenite and rutile. However, it is replaced by rare earth role magnetic and rare earth drum magnetic separators.
Carrier magnetic separation has been proposed for more effective separation of water and solids from acid mine water to generate very pure water (Feng et al., 2000). As discussed in Chapter 10, dissolved heavy metals like zinc and copper can be recovered from acid mine drainage (AMD) by selective precipitation controlling the pH for the precipitation of specific metals. Following this recovery step, the remaining solution is treated with lime to a pH ~12 to precipitate the residual metal ions. The water thus produced is satisfactory for recycling in mineral processing, but not of the quality for domestic use as it still contains some heavy metal ions. That is because, some of the metal hydroxides are amphoteric and their hydroxides re-dissolve at very high pH. For example, the concentration of lead ion increases from nearly zero at pH 9 to 0,12mg/L at pH 12 as the precipitated lead hydroxide dissolves producing plumbate:
Magnetic filtration has been applied in place of lime treatment by Feng and coworkers (2000). Ultrafine magnetic particles are used as magnetic seeds. At a dosage of 0.5 g/L magnetite, all fine precipitate flocs can be rendered strongly magnetic. The mine water is treated with hydrogen peroxide (to oxidize ferrous iron and manganese), followed by the addition of lime and magnetite to raise the pH to 5, Sodium sulfide and more lime are then added to raise the pH to 8. The heavy metal sulfide precipitates are filtered magnetically using a high gradient magnetic separator with a permanent magnetic assembly. This produces an effluent with heavy metal ion (Cu, Zn, Pb, Cd, Cr, Mn, Ti,) well below the discharge limits. The effluent thus freed from heavy metals is then passed to an ion exchange step, where the calcium ion is removed by a cationic resin and sulfate ions by an anion exchange resin. In the elution step, the cation resin is treated with sulfuric acid and the anion resin is treated with sodium hydroxide and lime. High quality gypsum (calcium sulfate) is produced by both elutions. This is a useful byproduct, which helps to offset the cost of the process for the effective removal of toxic metal ions.
A similar process to separate various metal ions in acid mine water by magnetic seeds has been described by Choung and coworkers (2000). In their laboratory study the metal ions are precipitated as hydroxides and magnetite is added as a magnetic seed. The metal hydroxide precipitates are thought to be locked by the magnetic seed, which is then separated by a hand magnet.
The technique has so far been demonstrated only on a laboratory scale. While it may have considerable potential in removing toxic metals from relatively dilute streams of acid mine water, it has not been applied on a pilot plant scale. Economic factors, in particular, the quantity of magnetite required for large scale treatment is an important factor to be considered.
Lyman and Palmer (1993b) studied the roasting(magnetic separation or selective leaching process). The roasting here aimed at oxidizing neodymium while leaving iron as metallic form at a controlled H2water vapor mixture on the basis of the thermodynamic consideration showing a common stability region of Nd2O3 and Fe. Although selective roasting was successful, the subsequent process such as magnetic separation and acid leaching were not because of the extremely fine grain size of the oxidized scrap. Thus, they discontinued the study in this direction and changed the strategy to total dissolution process as has been described previously.
When large quantities of ferrous scrap are to be separated from other materials magnetic separation is the obvious choice. The two types of magnets are permanent magnets and electromagnets. The latter can be turned on and off to pick-up and drop items. Magnetic separators can be of the belt type or drum type. In the drum a permanent magnet is often located inside a rotating shell. Material passes under the drum on a belt. A belt separator is similar except that the magnet is located between pulleys around which a continuous belt travels. Magnetic separation has some limitations. It cannot separate iron and steel from nickel and magnetic stainless steels. Also, composite parts containing iron will be collected which could contaminate the melt. Hand sorting may be used in conjunction with magnetic separation to avoid these occurrences. (See Chapter 3 for discussion of magnetic separation techniques).
Nickel is mainly extracted from its sulfide ores which are concentrated by magnetic separation and a froth flotation process. After concentration by these processes the concentrated ore is mixed with silica and subjected to a number of roasting and smelting operations. During these operations the iron and sulfide contents are reduced by their conversion first into oxide and then to silicate, which is then removed as slag. The resulting matte of Ni3S2 and Cu2S is allowed to cool for few days, when Ni3S2, Cu2S, and nickel/copper metal form distinct phases which can be separated mechanically. The metal is obtained from the matte electrolytically by casting it directly as an anode with a pure nickel sheet as a cathode and aqueous NiCl2, NiSO4 as an electrolyte. At a temperature of around 50C and at atmospheric pressure, the obtained nickel, which is impure, is then reacted with the residual carbon monoxide to produce the volatile nickel tetra carbonyl which gives back the pure metal and carbon monoxide at 230C.
Adsorption using magnetic adsorbents has emerged as an exigent water remediation technology particularly for wastewater treatment while eliminating filtration shortcomings of nonmagnetic adsorbents. Magnetic separation not only simplifies isolation but also opens the ground for easy washing followed by redispersion. Moreover, mechanisms controlling the adsorption process are also enhanced. Pyrolysis, coprecipitation, and calcination are the methods frequently used for preparation of good-quality and high yield of magnetic biochar (Thines et al., 2017).
Conventional heating and microwave-assisted heating have been used in laboratory scale to generate magnetic biochar adsorbents. Conventional pyrolysis has been successfully integrated in industrial production of magnetic biochars using modified furnace. Cottonwood, pinewood, date pits, pine needles, hydrochar waste, orange peels, and pine bark underwent conventional pyrolysis after being treated with magnetic precursors like FeCl36H2O, Co(NO3)26H2O, natural hematite, Fe(NO3)39H2O, etc., to create magnetic biochars (Yang et al., 2016; Zhu et al., 2014; Zahoor and Ali Khan, 2014; Harikishore Kumar Reddy and Lee, 2014; Wang et al., 2015c; Zhang et al., 2013a,d; Theydan and Ahmed, 2012; Chen et al., 2011a; Liu et al., 2010). All these magnetic biochars used for adsorption of phosphate, arsenate, methylene blue, aflatoxin B1, triclosan, Cd2+, Pb2+, and metallic Hg showed improved performance in magnetic response and adsorptive removal from aqueous phase due to incorporation of the more active sites required for adsorption and enhanced physical properties. This can be attributed to uniform and dispersive reinforcement of -Fe2O3, Fe3O4, and CoFe2O4 forming strong mechanical bonds with biochar matrix. The oxide particles embedded showed particle size within 20nm to 1m with variable shapes such as cubic or octahedral. However, reduction in surface area (Wang et al., 2015c; Zahoor and Ali Khan, 2014; Chen et al., 2011a) and lowered adsorption capacity upon reinforcement of magnetic oxide (Khan et al., 2015) did not appear significant indicating minimum hindrance in adsorptive removal of pollutants by these composites.
Microwave-assisted pyrolysis has also found its way in the production of magnetic biochars from bamboo and empty fruit branch used for the remediation of Cr(VI), Cd2+, methylene blue, and Pb2+ from aqueous phase (Ruthiraan et al., 2015; Mubarak et al., 2014; Zhang et al., 2013d; Wang et al., 2013, 2012, 2011). These magnetic biochars containing hydrous Fe2O3, cobalt oxide, binary CoFe oxide, and metallic Ni crystals adsorbed these contaminants through electrostatic attraction, ion exchange, inner sphere surface complexation, and physisorption. Superparamagnetic cotton fabric biochars were obtained following both conventional pyrolysis and microwave-assisted pyrolysis by ZHu et al. (2014) in order to compare their properties. The authors found that microwave-heated biochar showed no apparent agglomeration and was characterized by more controlled size and dispersion of oxide particles. Modification of magnetic biochar to further improve its functionality has also been reported. For example, chitosan modification of magnetic biochar obtained from invasive species Eichhornia crassipes provided more oxygenated functional groups for greater electrostatic interaction and therefore enhanced Cr(VI) remediation (Zhang et al., 2015a).
Coprecipitation is another process by which magnetic biochar can be fabricated. Yu et al. (2013) employed sugarcane bagasse as the raw material for the production of magnetic-modified sugarcane bagasse through the chemical precipitation of Fe2+ and Fe3+ over the sugarcane bagasse particles in an ammonia solution under ultrasound irradiation at 60C. A large amount of carboxyl groups found on the surface of biochar, which made the surface more negatively charged. Thats why better adsorption was found for the removal of Pb2+ and Cd+ due to the ion-exchange mechanism (Yu et al., 2013). A comparison of two synthesis methods including chemical coprecipitation of iron oxides onto biochar after pyrolysis and chemical coprecipitation of iron oxides onto biomass before pyrolysis for preparing magnetic biochars was studied by Baig et al. (2014). The results suggested that the chemical coprecipitation of iron oxides before pyrolysis led to greater Fe3O4 loading, higher saturation magnetization, improved thermal stability, and superior As(III, V) adsorption efficiency of the biochars (Baig et al., 2014).
Magnetization in biochar can also be introduced via calcination in which biochar is subjected to heat treatment to remove water and drive off CO2, SO2, and other volatile constituents. The simplicity of this process was the main reason behind the wide application of this process in the production of magnetic biochar composites. For instance, calcination of rice hull and ferric acetylacetonate in tube furnace generates magnetic biochar consisting of good dispersion of Fe3O4 particles on the surface. The biochar showed improved lead removal performance through hydroxide precipitation followed by suitable magnetic separation.
Magnetic mineral separation techniques are invariably selective, and not fully representative of the grain size and composition of magnetic minerals present in the sample; however, magnetic separation may be necessary for SEM/TEM, X-ray, Mossbauer, or chemical analyses. The importance of fine SD grains as remanence carriers emphasizes the necessity of making the separation technique as sensitive as possible to the fine grains. As grain shape has become an important criterion for distinguishing detrital and biogenic magnetite, separation procedures to prepare representative extracts for SEM and TEM observation have become more important. A recommended procedure which has been successful for extracting magnetite (including the SD fraction) is as follows: (i) Crush the sample (if necessary) in a jaw crusher with ceramic jaws, (ii) Use a mortar and pestle to produce a powder. (iii) Dissolve carbonate with 1N acetic acid buffered with sodium acetate to a pH of 5, changing the reagent every day until reaction ceases (several weeks), (iv) Rinse the residue with distilled water, (v) Agitate the residue ultrasonically in a 4% solution of sodium hexametaphosphate to disperse the clays. (vi) Extract the magnetic fraction using a high-gradient magnetic separation technique (Schulze and Dixon, 1979), or alternatively, pass the solution (several times, if necessary) slowly past a small rare earth magnet.
Seed receipt and preparation: Following receipt, the seeds are sent for mechanical preparation. This consists of mechanical screening and magnetic separation to remove any impurities which may be present. Following separation are the processes of crushing, flaking, and cooking.
Oil Extraction: The prepared seeds are mixed with hexane in a continuous counter current system to produce a hexane-oil mixture (miscella) and seed cake. The seed cake is separated from the miscella, dried cooled, pressed, and used to produce animal feed. The hexane is recovered from the miscella under vacuum (using direct and indirect steam) and reused in the system. The remaining crude oil is then cooled and sent for refining.
Oil refining packaging: Crude oil and ghee are processed using the following steps:Degumming (for sunflower seeds or soybean) and neutralization gums are removed in a batch process, using phosphoric acid. Neutralization is done by adding caustic soda to remove free fatty acids from crude oil to produce semi-refined oil.Bleaching color is removed from the oil using fuller's earth followed by filtration.Deodorization unpleasant odours are removed from oil by high temperature vacuum distillation.Packaging the reined, bleached, and deodorized (RBD) oil is bottled in automatic filling lines.
Degumming (for sunflower seeds or soybean) and neutralization gums are removed in a batch process, using phosphoric acid. Neutralization is done by adding caustic soda to remove free fatty acids from crude oil to produce semi-refined oil.
Soap and glycerin production: Fats are saponified in a batch process, by mixing with caustic soda and heating with direct and indirect steam. After saponification, soap is separated from the lye solution to be dried, blended with additives, homogenized, cut, and pecked. Glycerin is separated from the lye solution and distilled.
The two main sources of energy are mazot and electricity. Mazot and solar are used in the boilers to generate steam. Average annual consumption 15,000 tons of mazot and 600 tons of solar. Annual electricity consumption is around 10.5 million kWh.
The factory consumes an average of 16,800 m3/day of water of which 1,800 m3/ day is process water, and 1,500 m3/day cooling and vacuum water. This water is taken entirely from group water boreholes within factory premises. Approximately 35 m3 of drinking water is taken from the public network every day.
The factory generates about 16,000 m3/day of industrial wastewater from different factory steams, including process effluents, boiler blow down, cooling water, vacuum water, and steam condensate. The wastewater is discharged to Akhnawy drain near the factory.
Iron-containing residues generated in steel plants contain several toxic elements and require further processing In an integrated process described by Eetu-Pekka and coworkers (2005) the residues go through a magnetic separation step. In the second stage they are agglomerated, before the reduction of iron oxides. The element, which is most problematic is sulfur. Some of it is transferred in to the gas phase during reduction as hydrogen sulfide and carbonyl sulfide (COS). There would still be a large amount of sulfur in the residue after the reduction phase. One way to decrease the amount of sulfur is to separate the residues with high sulfur content before the processing and leave them outside of recycling. Other possible methods suggested are to enhance the transfer of sulfur into the slag phase by controlling the slag composition or by ensuring the carbon saturation of iron. The slag composition can be controlled to enhance the transfer of sulfur by addition of lime to the residue material. Excessive lime should be avoided to prevent precipitation of solid phases like dicalcium silicate. Sulfur content of iron can be lowered by increasing the carbon and silicon content in metal, by adding carbon into the residue material. Optimum quantity depends upon the original composition of the residue material. The process is schematically shown in Figure 8.25
MWI-bottom ash is the solid residue from combustion of municipal waste or in a Municipal Waste Incineration Furnace. Often MWI-bottom ashes have been subjected to a post treatment consisting of magnetic separation of iron and sieving and comminution of particles > 40 mm. Fly ashes from Municipal Waste Incineration are kept separate from the MWI-bottom ash. In the Dutch situation it is forbidden to prepare mixed ashes from fly ash and bottom ashes. In 1996 800,000 tons of MWI-bottom ash were produced in the Netherlands. The last years MWI-bottom ash is utilized for 100%, primarily in granular form as embankment material up to a hight of 10 m or more or as a road base material.
MWI-bottom ashes are supplied to the market with a certificate for its technical and environmental behaviour. The environmental part of this certificate is based on old legislation. MWI-bottom ashes up to now always comply with the demands for environmental certification.
The Building Materials Decree enforces more severe demands than the present regulations. Because of that a large part of the MWI-bottom ashes does not comply with the demands from the Building Materials Decree. To safeguard its outlet to the market the Dutch Ministry of the Environment has developed a Special Category for MWI-bottom ashes. In this category MWI-bottom ashes can be utilized under a set of isolation measures. With the Municipal Waste Incineration sector the appointment has been made to pursue steady quality improvement of its byproducts so that MWI-bottom ashes can be utilized as Category 2 Building Materials in future.
Magnetic separation is an effective mineral processing method to separate the minerals based on the magnetism difference. Magnetic separator machine can effectively select a large number of magnetic minerals, such as magnetite, hematite, limonite, manganese siderite, wolframite, ilmenite, manganese ore, manganese carbonate, metallurgical manganese ore, iron ore, kaolin, manganese oxide ore, rare earth ore.
Wet type? Fine particle and coarse particle? Strong magnetic? . . How many kinds of magnetic separators equipment? Frankly, there are many classification methods of magnetic separator types, join us to solve the puzzle.
According to the state of the material, the magnetic separator is divided into dry type magnetic separator and wet type magnetic separator. Dry magnetic separator refers to the material keep dry, dont need to mix with water in the magnetic separation process. The material for wet magnetic separator must be mixed with water or other media.
The dry magnetic separator generally does not need a tank for accommodating the slurry, and the material is conveyed by a vibrating feeding device, and a dustproof device is often provided. The wet magnetic separator has a tank to accommodate the slurry to maintain the fluidity of the material, and the pump is usually transported by a slurry pump.
Dry magnetic separation function for bulk, coarse particle separation, but also fine mineral separation, while wet magnetic separator can not sort large bulk minerals, most are effective for fine or even fine particles, except for a few models that can select coarse particle. HGMS (high gradient wet magnetic separator) can sort micron-sized materials using a suitable magnetically permeable medium.
Dry magnetic separator requires low water content, dry materials, good liquidity, do not adhesion, agglomeration. The wet magnetic separation operation has certain requirements on the slurry concentration. There is no obvious limit on the concentration of coarse magnetic separation, but the material concentration should not be too low to effectively control the negative fluid force during the mineral processing operation. When magnetically selecting fine particles, the concentration is required to be high to ensure the recovery of magnetic minerals.
Dry weak magnetic separators have features like a simple process, low investment, low water consumer. However, the bottleneck of the dry cylinder magnetic separator is that the dust is difficult to control, so as the environmental protection requirements become stricter, the dry type magnetic separation is gradually replaced by the wet weak magnetic separator. At present, the fine-grained dry magnetic separation machine is only used in the water shortage area and severe cold area.
According to the magnetic field strength, magnetic separator is divided into three types: weak magnetic separator (low intensity magnetic separator), medium magnetic separator and strong magnetic separator (high intensity magnetic separator). The weak magnetic separator is from several hundred to 3000 Gs; the strong magnetic separator generally refers to 3000Gs to 6000 Gs, and the medium magnetic field magnetic separator between the two.
The reason why it is classified according to the strength of the magnetic field is related to the magnetic properties of various common minerals (another post Magnetic Mineral Classification). However, it is necessary to know that there is no absolute standard for different magnetic strength and their matched equipment.
In the actual magnetic separation machine, the magnetic field strength ranges from hundreds of Gauss to 20,000 Gauss, some even exceed 20,000 Gauss, but it is rarely used in general beneficiation production. Excessive magnetic field strength will lead to weak magnetic minerals to agglomerate that is not conducive to beneficiation. So the upper limit of the magnetic field strength of the strong magnetic separator is 20000Gs.
On the working surface of various magnetic separators, the magnetic field strength varies at different points and in different ranges, and the working magnetic field is a non-uniform magnetic field. Generally, the value of the magnetic field strength expressed refers to Max. magnetic strength, some factories may list the average value.
According to the type of magnetic field, the magnetic separator is divided into permanent magnet magnetic separator and electromagnetic magnetic separator. The permanent magnet magnetic separator uses a permanent magnet material such as ferrite or neodymium iron boron to generate a working magnetic field, and the electromagnetic magnetic separator uses a magnet with a yoke, a solenoid, and a magnet to generate a magnetic field.
The magnetic field strength of the permanent magnet magnetic separator is fixed, but the different action areas in the magnetic separation working surface can be designed to have different magnetic field strengths. The electromagnetic magnetic separator can adjust the whole magnetic field, but the magnetic field strength values in the working surface are a balanced, uniform magnetic field.
The magnetic energy of the permanent magnet magnetic separator is low, while the electromagnetic separation requires high energy consumption to generate the excitation current. The energy consumption per unit of the permanent magnetic separator is much lower than that of the electromagnetic magnetic separator.
According to the structure of the main working part of the magnetic separator, it is divided into cylindrical (drum) magnetic separator, roller magnetic separator, disc magnetic separator, ring magnetic separator, in addition, have rotor magnetic separator, belt magnetic separation, conical magnetic separator, but these types of magnetic separators have been used less.
According to the way the magnetic field strength changes: 1) Constant magnetic field magnetic separator. Using a permanent magnet material and a direct current electromagnet, a solenoid, or the like as a magnetic source, the magnitude and direction of the magnetic field strength do not change with time. 2) Alternating magnetic field magnetic separator. An electromagnet that is connected to an alternating current is used as a magnetic source. The magnitude and direction of the magnetic field strength changes over time. 3) Pulsating magnetic field magnetic separator. An electromagnet that simultaneously transmits direct current and alternating current is used as a magnetic source. The magnitude of the magnetic field varies with time, but the direction does not change. And pulse Similar to the dynamic magnetic separator, the use of pulsating water flow causes the slurry to pulsate, affecting the sorting force of the magnetically selected mineral. 4) Rotating magnetic field magnetic separator. A magnet is used as the magnetic source, and the magnetic pole rotates around the axis. The magnitude and direction of the magnetic field strength changes over time.
According to whether the magnetic mineral is reversed in the magnetic field of the magnetic separator, it is divided into a mineral reversal magnetic separator and Nonreversal magnetic separator. The mineral reversal magnetic separator can effectively improve the concentrate grade, and the Non-reversal magnetic separator can select the refractory weak magnetic minerals.
According to the minerals, it also can divide into such as magnetite magnetic separator, hematite magnetic separator, manganese ore magnetic separator, quartz sand magnetic separator, NdFeB magnet, nickel, etc.
In addition to the types listed above, there are many ways to classify magnetic separators. Although each manufacturer has a self-classification method, it lacks standards. In the magnetic separator model selection stage, most prefer using mixed name, such as the hematite wet magnetic separator, actually indicate that the sorting mineral is hematite, and the ore dressing method is wet type, but does not show us whether the magnetic separator is a permanent magnet type or an electromagnetic type, and neither indicate which magnetic separation structure the equipment is.
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Magnetic separators use rare-earth permanent magnets to generate complex flux patterns with huge spatial fluctuations (102 to 105 Tm1) for separating ferrous and nonferrous materials based on their different magnetic susceptibilities.
Batch magnetic separators are usually made from strong rare-earth permanent magnets embedded in disinfectant-proof material. The racks are designed to hold various sizes and numbers of tubes. Some of the separators have a removable magnet plate to facilitate easy washing of magnetic particles (Figure 1). Test tube magnetic separators enable separation of magnetic particles from volumes ranging between about 5L and 50mL. It is also possible to separate cells from the wells of standard microtitration plates. Magnetic complexes from larger volumes of suspensions (up to approximately 5001000mL) can be separated using flat magnetic separators. More sophisticated magnetic separators are available, e.g. those based on the quadrupole and hexapole magnetic configuration.
Figure 1. (See Colour Plate 63). Example of a magnetic separator (Dynal MPC-M) for work with microcentrifuge tubes of the Eppendorf type, with a removable magnet plate to facilitate easy washing of magnetic particles. Courtesy of Dynal, Oslo, Norway.
As magnetic separators progress toward larger capacity, higher efficiency, and lower operating costs, some subeconomic iron ores have been utilized in recent years. For example, magnetite iron ore containing only about 4% Fe (beach sands or ancient beach sands) to 15% Fe (iron ore formations) and oxidized iron ore of only about 10% Fe (previously mine waste) to 20% Fe (oxidized iron ore formations) are reported to be utilized. They are first crushed and the coarse particles pretreated using roll magnetic separators. The magnetic product of roll magnetic separators may reach 2540% Fe and then is fed to mineral processing plants.
where mpap is the inertial force and ap the acceleration of the particle. Fi are all the forces that may be present in a magnetic separator, such as the magnetic force, force of gravity, hydrodynamic drag, centrifugal force, the friction force, surface forces, magnetic dipolar forces, and electrostatic forces among the particles, and others.
Workable models of particle motion in a magnetic separator and material separation must be developed separately for individual types of magnetic separators. The situation is complicated by the fact that many branches of magnetic separation, such as separation by suspended magnets, magnetic pulleys, or wet low-intensity drum magnetic separators still constitute highly empirical technology. Hesitant steps have been taken to develop theoretical models of dry separation in roll and drum magnetic separators. Alternatively, open-gradient magnetic separation, magnetic flocculation of weakly magnetic particles, and wet high-gradient magnetic separation (HGMS) have received considerable theoretical attention. A notable number of papers dealing with the problem of particle capture in HGMS led to an understanding of the interaction between a particle and a matrix element. However, completely general treatment of the magnetostatic and hydrodynamic behavior of an assembly of the material particles in a system of matrix elements, in the presence of a strong magnetic field, is a theoretical problem of considerable complexity which has not been completed, yet. Detailed description of particle behavior in various magnetic separators can be found in monographs by Gerber and Birss (1983) and Svoboda (1987, 2004).
This paper presents preliminary results using the Magnetic Micro-Particle Separator, (MM-PS, patent pending) which was conceived for high throughput isothermal and isobaric separation of nanometer (nm) sized iron catalyst particles from Fischer-Tropsch wax at 260 oC. Using magnetic fields up to 2,000 gauss, F-T wax with 0.30.5 wt% solids was produced from 25 wt% solids F-T slurries at product rates up to 230 kg/min/m2. The upper limit to the filtration rate is unknown at this time. The test flow sheet is given and preliminary results of a scale-up of 50:1 are presented.
Mobile CDW recycling installations have risen in popularity due to the need for traditionally fixed equipment, such as feeders, crushers, magnetic separators and even vibrating screens, used at different locations and at different times. Sometimes it is better, technically and/or economically, to place the CDW recycling plant itself even if in a simplified version at the worksite, instead of transferring the CDW mass to a fixed installation.
Mobile plants will typically be diesel fired, whereas fixed plants are usually connected to the electricity grid and therefore have some inherent advantages, such as higher operation efficiency and lower environmental impacts. Electrical motors, when installed in automobiles, can be as much as three times more efficient than diesel motors (Kendall, 2008). Moreover, electricity may be derived from renewable sources of energy. However, mobile plants reduce material transportation needs, and therefore reduce the noise, dust and gas pollutants typical of diesel motored trucks.
The technology applied in the mobile plant is essentially the same as in fixed plants, though limited to feeders, crushers, vibrating screens and magnetic separators. Its stage of development is similar to that of fixed facilities. Mobile plants are usually mounted on tracks, but there are also some tyre mounted plants commercially available. Their weights vary widely, from 14 up to 215tons, with most of the used equipment between 30 and 50tons (Terex, 2008; Metso, 2009). Capacities can also range from 50 up to 1200ton/h, while remaining fully mobile (Metso, 2012). Usual features include jaw or cone crushers, hydraulic crusher protection mechanisms, flexible variable speed built-in conveyor belts (single or multiple attachable discharge arms), fully automatic discharge adjustment systems, safety and anti-clogging mechanisms, ferrous metals separator (normally as an option), radio control of essential features (e.g. on/off, jaw crusher opening, discharge speed), track mounted extra heavy-duty steel chassis and built-in or optional dust suppression (hose). An example of one of these machines is presented in Fig.9.2, which shows a standard low to medium capacity track mounted model, equipped with a single conveyor belt discharger, magnetic separator and side discharger and a jaw crusher.
Magnetic carriers with immobilized affinity ligand or magnetic particles prepared from a biopolymer exhibiting affinity for the target compound(s) are used to perform the isolation procedure. Magnetic separators are necessary to recover magnetic particles from the system.
Magnetic carriers and adsorbents are commercially available and can also be prepared in the laboratory. Such materials are usually available in the form of magnetic particles prepared from various synthetic polymers, biopolymers or porous glass, or magnetic particles based on inorganic magnetic materials such as surface-modified magnetite can be used. In fact, many of the particles behave like paramagnetic or superparamagnetic ones responding to an external magnetic field, but not interacting themselves in the absence of a magnetic field. This is important due to the fact that magnetic particles can be easily resuspended and remain in suspension for a long time. The diameter of the particles is from ca. 50nm to ca. 10m. Magnetic particles having a diameter larger than ca. 1m can be easily separated using simple magnetic separators, while separation of smaller particles (magnetic colloids with a particle size ranging between tens and hundreds of nanometers) may require the use of high-gradient magnetic separators.
Commercially available magnetic particles can be obtained from a variety of companies. In most cases polystyrene is used as a matrix, but carriers based on cellulose, agarose, silica, porous glass or silanized magnetic particles are also available. Particles with immobilized affinity ligands are available, oligodeoxythymidine, streptavidin, antibodies, protein A and protein G being used most often. Magnetic particles with such immobilized ligands can serve as generic solid phases to which native or modified affinity ligands can be immobilized (e.g. antibodies in the case of immobilized protein A, protein G or secondary antibodies, biotinylated molecules in the case of immobilized streptavidin or adenylated molecules in the case of immobilized oligodeoxythymidine). In exceptional cases, enzyme activity may decrease as a result of usage of magnetic particles with exposed iron oxides. In this case encapsulated microspheres, having an outer layer of pure polymer, are safer. In Table 1 is given a list of companies producing and selling magnetic particles of various types.
In the laboratory, magnetite (or similar magnetic materials such as maghemite or ferrites) particles are usually surface modified by silanization. This process modifies the surface of the inorganic particles so that appropriate function groups become available, which enable easy immobilization of affinity ligands.
Biopolymers such as agarose, chitosan, -carrageenan and alginate can be easily prepared in a magnetic form. In the simplest way, the biopolymer solution is mixed with magnetic particles and after bulk gel formation the magnetic gel formed is broken into fine particles. Alternatively, biopolymer solution containing dispersed magnetite is dropped into a mixed hardening solution or a water-in-oil suspension technique is used to prepare spherical particles. Basically the same procedures can be used to prepare magnetic particles from synthetic polymers such as polyacrylamide or poly(vinylalcohol).
In one of the approaches used, standard affinity chromatography material is post-magnetized by pumping the water-based ferrofluid through the column packed with the sorbent. Magnetic material accumulates within the affinity adsorbent pores thus modifying the chromatography material into magnetic form.
Some affinity ligands (usually general binding ligands) are already immobilized to commercially available carriers (see Table 1). To immobilize other ligands to both commercial and laboratory-made magnetic particles, standard procedures used in affinity chromatography can be employed. Usually functional groups available on the surface of magnetic particles such as COOH, OH or NH2 are used for immobilization; in some cases, magnetic particles are already available in the activated form (e.g. tosyl activated).
Magnetic separators are necessary to separate the magnetic particles from the system. In the simplest approach, a small permanent magnet can be used, but various magnetic separators employing strong rare-earth magnets can be obtained at reasonable prices. Commercial laboratory scale batch magnetic separators are usually made from magnets embedded in disinfectant-proof material. The racks are constructed for separations in Eppendorf microtubes, standard test tubes or centrifugation cuvettes. Some have a removable magnetic plate to facilitate washing of separated magnetic particles (Figure 1). Other types of separators enable separations from the wells of microtitration plates and the flat magnetic separators are useful for separation from larger volumes of suspensions (up to ca. 5001000mL).
Flow-through magnetic separators are usually more expensive and more complicated, and high-gradient magnetic separators (HGMS) are typical examples (Figure 2). Laboratory-scale HGMS are constructed from a column packed with fine magnetic-grade stainless-steel wool or small steel balls placed between the poles of an appropriate magnet. The suspension is pumped through the column, and magnetic particles are retained within the matrix. After removing the column from the magnetic field, the particles are retrieved by flow and usually by gentle vibration of the column.
Figure 2. (See Colour Plate 62). A typical example of laboratory-scale high-gradient magnetic separators. OctoMACS Separator (Miltenyi Biotec, Germany) can be used for simultaneous isolation of mRNA. Courtesy of Miltenyi Biotec, Germany.
MACS, one of the most popular conventional cell isolation methods, has recently been developed in microfluidics to isolate rare cells. Tan and colleagues first introduced micro-magnetic separators for stem cell sorting (Fig.11.24) (Tan et al., 2005). A 3D mixer was integrated in a microfluidic channel to achieve lamination with 180-degree rotations and rapid mixing between cells and magnetic beads. To isolate the target cell from the mixture, magnetic beads conjugated with CD31 antibodies were used to remove CD31+ endothelial cells with an external magnetic field. Up to 90.2% of hMSCs were isolated and recovered. In addition, Souse and colleagues introduced a two-inlet/two-outlet microfluidics device to isolate mouse mESCs using super-paramagnetic particles. To isolate specific embryonic antigen 1 positive (SSEA-1+) mESCs from a heterogeneous population of mESCs, anti-SSEA-1 antibodies were conjugated onto super-paramagnetic beads and mixed with the cell mixture. Once the mixture was injected into the microfluidics channel and the magnetic field was applied, SSEA-1+ mESCs were deviated from the direction of laminar flow according to their magnetic susceptibility and were thus separated from SSEA-1 mESCs.
A great deal of exciting new spectroscopy of nuclei far from stability or with very large Z has been achieved over the last several years when large Ge detector arrays have been coupled to high-transmission magnetic separators. A magnetic separator is a device placed behind the target position which will selectively transport nuclei, produced in a reaction, to its focal plane where they can be detected and identified using a variety of different detectors. Residual nuclei that are not of interest, or scattered beam particles, will not be transmitted through the separator. Very small fractions of the total reaction cross section can be selected using this method. Nuclear structure information is obtained by detecting gamma-rays produced at the target position, in coincidence with recoils detected at the focal plane. One example of the use of this technique is illustrated here.
One of the goals of nuclear physics is to understand the limits of nuclear existence as functions, for example, of angular momentum, isospin, or indeed mass. For example, what are the heaviest nuclei that can exist? For many years now, various models have predicted that an island of superheavy nuclei should exist. However, most models disagree as to the exact proton and neutron numbers categorizing this island and indeed on the extent of the island. Recently, models have predicted that these superheavy nuclei might indeed be deformed. Therefore, it is very relevant to inquire as to what is the structure of the heaviest nuclei accessible to gamma-ray spectroscopy and to ask the simplest type of questions about them, for example, are they spherical or deformed? Unfortunately, the production cross sections for superheavy nuclei are such that, even using very intense beams, only one or two nuclei are produced per week or two. These small numbers are clearly beyond what we can measure with existing gamma-ray facilities. Therefore, we cannot address the spectroscopy of the superheavy elements (yet). However, we can look at the structure of very heavy nuclei lying just below these unattainable regions.
Recently, groups at Argonne National Laboratory in the United States and at the University of Jyvaskyla in Finland carried out tour de force experiments to study the excitation spectrum of 254No(Leino et al., 1999). With Z=102, No is the heaviest nucleus for which gamma-ray spectroscopy has ever been carried out. The gamma-ray spectrum of transitions de-exciting states in 254No is shown inFig. 13. A rotational band structure is clearly visible, indicating that 254No is in fact a deformed nucleus. A very surprising feature of the spectrum is that the rotational band is observed up to very high spins 18 , (an amazing number for such a heavy, fissile nucleus). The existence of a rotational cascade up to spin 18 , well beyond the classical fission barrier limit, indicates that 254No is held together primarily by microscopic shell effects, rather than macroscopic liquid drop binding, as in normal nuclei. Shell effects, for certain favorable proton and neutron numbers and for favorable deformation, can provide an additional 12MeV of binding energy. It is this binding energy, which does not depend strongly on angular momentum, which holds 254No together to such high spin.
FIGURE 13. Spectrum of gamma-rays depopulating excited states in 254No. With Z=102, 254No is the heaviest nucleus for which gamma-ray spectroscopy has ever been accomplished. The gamma-rays are labeled by their transition energies in kilo-electron volts and also by the spin of the state they depopulate. The inserts show the population intensity as a function of spin for the two beam energies, 215 (top) and 219MeV (bottom). More angular momentum is brought into the system at higher beam energies, and this is reflected in the stronger population of higher spin states in the lower spectrum(Leino et al., 1999).
Coalescence separators (Fig. 8.18) are flow-through systems which guarantee a very high degree of separating capacity compared to more simple systems. More sophisticated coalescence separators (coolant cleaners) are equipped with pre filters and magnetic separators to clean the emulsion from floating swarf such as aluminum or other light metal fines as well as from ferromagnetic particles.
The effect of the coalescence principle is based on the flowing together of many droplets to a compact liquid phase (contaminant-oil phase). The coalescence principle is supported by the formation of large surfaces; these are achieved by the arrangement of plate packs or packing elements in a separate tank.
Owing to their large surfaces, a disadvantage must be noted; solids will also adhere to the surfaces. Depending on the contamination of the emulsion, the plate pack or the packing elements must be regularly removed and mechanically cleaned.
Multotec supplies a complete range of magnetic separation equipment for separating ferromagnetic and paramagnetic particles from dry solids or slurries, or for removing tramp metal. Multotec Dry and Wet Drum Separators, WHIMS, Demagnetising Coils and Overbelt Magnets are used in mineral processing plants across the world. We can engineer customised magnetic separation solutions for your process, helping you improve the efficiency of downstream processing and lower your overall costs of production.
Multotec provides a wide range of magnetic separators including: Permanent magnet Low Intensity Magnetic Separators (LIMS) or Medium Intensity Magnetic Separators (MIMS) and electromagnetic High Intensity Magnetic Separators (HIMS). Multotec provides unmatched global metallurgical expertise through a worldwide network of branches, which support your processing operation with turnkey magnetic separation solutions, from plant audits and field service to strategic spares for your magnetic separation equipment.
Whether you need to recover fast moving tramp metal, recover valuable metals in waste streams or enhance the beneficiation of ferrous metals, Multotec has the magnetic separator you require. Dry drum cobber magnetic separators provide an initial upgrade of feed material as well as a gangue material rejection stage. By improving the material fed to downstream plant processes, our magnetic separation solutions reduce the mechanical requirements of grinding, ultimately lowering overall costs. Our heavy media drum separators are ideally suited for dense media separation plants. Our ferromagnetic wet drum separators can be used in iron ore separation plants in both rougher or cleaner beneficiation applications. We also provide demagnetising solutions that reverse the residual effects that magnetic separation has on the magnetic viscosity of ferrous slurries, to return the mineral stream to an acceptable viscosity for downstream processing. These demagnetising coils generate a magnetic field that alters magnetic orientation at 200 Hz.
The trend towards larger and faster travelling conveyors in the African mining industry has highlighted the vital role of overbelt magnets. Solutions need to be optimised to such factors as belt speed and width, the belt troughing angle, the burden depth, the material density and bulk density, the expected tramp metal specifications, ambient operating temperatures and suspension height to provide maximum plant and cost efficiency. Multotec can supply complete overbelt magnet systems, from equipment supply to a turnkey service by means of its strategic partners, including even the gantry work.
Along with the increasing popular of mining project, more and more people invested in producing stone crusher machine for mining process. And with the development of mining machinery industry, there are many kinds of mining machines in the market, do you know how many kinds of magnetic separator there are? We all know that The Magnetic Separator is suitable for wet magnetic separation of materials less than 3mm such as magnetite, calcined ore, etc. and it can remove the iron in the coal, non-metal and construction industries.
And Magnetic roasting can be divided into reduction roasting, neutral roasting and oxidizing roasting according to the principle. Studies have shown that the particle size has significant effect on the magnetic properties. The magnetic susceptibility decreases with the particle size. However, the coercivity value increases with decreases of particle size. Its magnetic system is a ring-shape chain closed magnetic circuit with energizing coils made of copper tube and cooled internally by water. Grooved plates made of magnetic conductive stainless steel are used as magnetic matrix.
With the in-depth development of the research work of the domestic and foreign high-performance permanent magnet materials, the industrialization of the magnetic separator and the constant optimization the upgrading and improvement of the magnetic system and the body structure of traditional permanent magnetic separator speed up the process that the permanent magnetic separation equipment gradually replace the electromagnetic magnetic separator. We also actively used the new high and permanent magnet material (NdFeB) to increase the number of poles.
The additional poles and compound magnetic field urther enhanced the performance of permanent magnetic separator, matured and expended the ranges of applications, especially in the process of magnetite beneficiation. Of course, maybe my summary is not comprehensive. If you have other supplement, you can comment about my article. We learn from each other, and make progress together. Thank you very much for reading my article. I hope you like it. If you have any other question, you can get int our website. china magnetic separator: http://www. mine-crusher. com/separator. htm How many are major types of magnetic separator? By fengyanyanl 990
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Main device comprised feeding unit, weak magnetic roller, drive part, material conveying apparatus, magnetic disc, electromagnetic system, frame and others. The electric control section consists of components of control, voltage regulation, rectification, instrument and so on. It features compact structure, stable performance, easy installation and convenient operation and maintenance, this disc type dry belt magnetic separator has 3 types: 1 pc disc, 2 pcs disc, and 3 pcs disc. The following structure is showing the 2pcs disc dry magnetic separator. The moisture of the feeding material should be under 1%.