permanent magnetic separation

magnetic separator and permanent magnet

The magnetic separator uses the magnetic difference between minerals for sorting, plays the role of improving the grade of ore, purifying solid-liquid materials, and recycling waste. It is the most widely used and highly versatile machine in the industry. One.

Magnetic separators are widely used in mining, wood, kiln, chemical, food and other industries. For mining, the magnetic separator is suitable for wet or dry magnetic separation of manganese ore, magnetite, magnetite, roasted ore, ilmenite, hematite and other materials with a particle size below 50mm. , Non-metallic mines, building materials and other iron removal operations and waste disposal operations

The magnetic separator (take wet permanent magnetic cylinder magnetic separator as an example) is mainly composed of 6 parts: cylinder, magnetic roller, brush roller, magnetic system, tank and transmission part. The cylinder is welded into a cylinder by 2-3mm stainless steel plate, and the end cover is cast aluminum or workpiece, which is connected to the cylinder with stainless steel screws. The motor drives the cylinder, magnet roller and brush roller to rotate through a speed reducer or a step-less speed regulating motor.

After the ore slurry flows into the tank through the ore feed box, the ore particles enter the ore feeding area of the tank in a loose state under the action of the water flow of the ore spray pipe. Under the action of the magnetic field, the magnetic ore particles are magnetically aggregated to form a magnetism group or magnetism chain. The magnetism group or magnetism chain is subjected to a magnetic force in the slurry and moves toward the magnetic pole and is adsorbed on the cylinder . Since the polarities of the magnetic poles are alternately arranged along the direction of rotation of the cylinder and are fixed during operation, the magnet or flux rotates with the cylinder, and the magnetic stirring phenomenon occurs due to the alternating magnetic poles and is mixed. The non-magnetic minerals such as gangue in the magnetism or magnetism chain fall off during the tumbling, and the magnetism or magnetism chain that is eventually attracted to the surface of the cylinder is the concentrate. The concentrate is transferred to the weakest part of the magnetic system edge with the cylinder, and it is discharged into the concentrate tank under the action of the flushing water sprayed from the unloading water pipe, and the non-magnetic or weakly magnetic minerals are left in the slurry and discharged out of the tank with the slurry , That is tailings.

Dry magnetic separator: Separation in the air, mainly used to separate large and coarse particles of strong magnetic ore and fine particles of weak magnetic ore. At present, it is also trying to sort fine ferromagnetic ore;

In addition, it can be classified according to the way the magnetic ore particles are selected, the movement direction of the feed material, the method of discharging the selected products from the selected section, and the structural characteristics of the discharged magnetic products.

The closed circuit through which magnetic flux is concentrated is called a magnetic circuit. The magnetic system of the magnetic separator needs to generate a certain intensity of magnetic field, and most of the magnetic flux in the magnetic field can be concentrated through the separation space. The height, width, radius and number of poles of the magnetic system, the magnetic potential difference between adjacent poles, the pole distance, the width of the pole face width and the pole gap width, the shape of the pole and pole face, and the pole face to the center of the arrangement The distance and so on have no small effect on the magnetic field characteristics.

The magnetic separator shown in the following figure is an example. The magnetic circuit part adopts a five-pole magnetic system. Each magnetic pole is formed by bonding a ferrite and a neodymium-iron-boron permanent magnet block. It is fixed to the magnetic guide plate with a screw through the center hole of the magnetic block On the upper side, the magnetic guide plate is fixed on the shaft of the cylinder through the bracket, the magnetic system is fixed, and the cylinder can rotate. The polarities of the magnetic poles are alternately arranged along the circumference, and the polarities are the same along the axial direction. Outside the magnetic system is a roller made of stainless steel non-magnetically conductive material. The non-magnetically conductive material is used to avoid that magnetic lines of force cannot enter the selected zone through the cylinder and form a magnetic short circuit with the cylinder. The part of the tank close to the magnetic system should also be made of non-magnetic materials, and the rest should be ordinary steel plates or hard plastic plates.

For the permanent magnet separator, the permanent magnet is the most important component, and the quality of the permanent magnet determines its performance characteristics. The permanent magnets of magnetic separators are generally made to a certain size (for example, length width height = 85 65 21 mm), so they are traditionally called permanent magnet blocks or magnetic blocks for short. The permanent magnet materials that can be used in the magnetic system of the magnetic separator include permanent magnet ferrite, aluminum nickel cobalt, iron chromium cobalt and manganese aluminum iron, samarium cobalt permanent magnet materials, and neodymium iron boron permanent magnet materials. At present, the mainstream permanent magnetic materials used in domestic magnetic separation equipment are mainly permanent ferrite (strontium ferrite, barium ferrite), followed by neodymium iron boron permanent magnetic materials.

In the design of the magnetic system, it is necessary to choose which permanent magnetic material to use according to the specific conditions of various aspects. The influencing factors can be summarized into the following aspects:

Magnetic field strength: A constant magnetic field must be generated in the designated workspace. The strength of this magnetic field determines which permanent magnetic material is required. The magnetic properties of NdFeB permanent magnets are much higher than ferrites.

magnetic separators

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 separation | dynequip inc | st paul mn

Permanent and electromagnetic magnetic separators from Eriez are available in a variety of designs. Whether your product is gravity fed through pipes and chutes, loosely transported on conveyors, and/or pumped through pipelines, Eriez has the magnetic separation solution.

Permanent Magnetic Separators: require no electric power. With proper care, they can last a lifetime with very little loss of field strength. Eriez manufactures permanent magnetic separators using ceramic or rare earth material for increased strength and extended magnet life. Common types of permanent magnets include: tube magnets, plate magnets, grate magnets, trap magnets, magnetic humps, and magnetic pulleys.

Electric or Electro Magnets: provide tramp metal collection from conveyed materials. The suspended electromagnet is a widely used magnetic separator. The electromagnet is typically mounted or suspended over a conveyor belt to remove large pieces of tramp metal that represent a hazard to downstream crushers, mills, pulverizers, and grinders. For larger industrial separation jobs, count on Eriez electromagnetic separators. These units use wire coils and direct currents to provide a magnetic field that separates ferrous material from nonferrous product.The powerful and reliable separators are mainly used in coal, limestone, sand, and other aggregates applications.

Most items in stock for quick shipoffer a solution to every process application.Most items are in stock and available for quick shipment!Whether you need a low-cost plate magnet for equipment protection or a high power, easy to clean grate magnet to ensure product purity, ProGrade gives you the best for less.

permanent overband magnetic plates dnd-ac - sollau s.r.o. - magnetic separation

Automatic cleaning without the interruption of the material flow Suspension height up to 450 mm Separation of magnetic particles from 0,5 mm Max. conveyor belt speed: 3 m/s 10-year warranty Ferrite as well as light neodymium variants Some models constantly in stock Made-to-measure overband separators Material testing

It is designed to capture in a quick and easy way valuable ferromagnetic particles from a product stream and at the same time the overband magnetic plate with automatic cleaning protects your machinery (shredders, mills, grinders, screw conveyors etc.) that subsequently treat the material. The tramp ferrous metal extracted from the conveyor is removed by a heavy duty rubber belt into a skip or a collection bin at the side of the conveyor.

In order to achieve the highest possible degree of separation, it is recommended that especially in case of a higher layer of material on the conveyor belt the overband magnet DND is combined with the magnetic pulley MV (that is able to attract ferromagnetic particles from lower material layers).

Most commonly the overband magnetic separator DND-AC is suspended above and across the belt, however it is also possible to place it at the head of the conveyor (parallel to the belt). The kind of applied magnets depends on the position of the separator: if the magnetic separator is parallel to the conveyor belt.

It is possible to use weaker magnets (as at the end of the conveyor belt the material is quite loose). On the contrary, if the magnetic separator is suspended across the belt, we recommend that stronger magnets are applied (as the material layer on the belt might be higher and compacter)

The standard version of the overband magnetic separator DND-AC M is fitted with strong permanent ferrite magnets. However, if you need stronger magnetic force (e. g. for mobile lines, grinders, mills), we recommend that the overband magnetic separator is equipped with extremely powerful neodymium NdFeB magnets from rare earth ores. A careful interference shielding ensures that the magnetic field is concentrated only on the material on the conveyor belt.

In total there are eight types of DND-AC self-cleaning overband magnets (five ferrite and three neodymium ones, see below), so that even standard products can satisfy the needs and requirements of the broadest possible spectrum of clients. At the same time, our customers can be sure that the parameters of the product are in accordance with their needs and that they will not pay extra money for an above standard equipment that would be unnecessary for their specific application.

The main benefits of ferrite overband magnets include the following: high temperature resistence, long-term magnetic stability, affordable price, deep and very strong magnetic field (in case of stronger models).

Combines a standard performance with an interesting price. These separators are intended for medium-duty applications with the maximum installation height of 200 mm, and they are capable of trapping larger ferromagnetic particles (above 1 mm). A very good rate of return (price/performance ratio) is a significant benefit of this kind of plate.

ProductMaximum width of conveyor belt (mm)Maximum recommended installation height (mm)Datasheet crosswiselongwise DND-AC M1 F PANTHER 500 650 170 display PDF DND-AC M2 F PANTHER 800 650 200 display PDF DND-AC M3 F PANTHER 1000 650 200 display PDF DND-AC M4 F PANTHER 1200 650 200 display PDF DND-AC M5 F PANTHER 1400 650 200 display PDF DND-AC M6 F PANTHER 1600 650 200 display PDF DND-AC M7 F PANTHER 1800 650 200 display PDF

ProductMaximum width of conveyor belt (mm)Maximum recommended installation height (mm)Datasheet crosswiselongwise DND-AC Ms2 F JAGUAR 800 850 270 display PDF DND-AC Ms3 F JAGUAR 1000 850 300 display PDF DND-AC Ms4 F JAGUAR 1200 850 320 display PDF DND-AC Ms5 F JAGUAR 1400 850 320 display PDF DND-AC Ms6 F JAGUAR 1600 850 320 display PDF DND-AC Ms7 F JAGUAR 1800 850 320 display PDF DND-AC Ms8 F JAGUAR 2000 850 320 display PDF

ProductMaximum width of conveyor belt (mm)Maximum recommended installation height (mm)Datasheet crosswiselongwise DND-AC Mp2 F LION 800 1050 290 display PDF DND-AC Mp3 F LION 1000 1050 320 display PDF DND-AC Mp4 F LION 1200 1050 340 display PDF DND-AC Mp5 F LION 1400 1050 340 display PDF DND-AC Mp6 F LION 1600 1050 340 display PDF DND-AC Mp7 F LION 1800 1050 340 display PDF DND-AC Mp8 F LION 2000 1050 340 display PDF

ProductMaximum width of conveyor belt (mm)Maximum recommended installation height (mm)Datasheet crosswiselongwise DND-AC Mm2 F TIGER 800 1200 320 display PDF DND-AC Mm3 F TIGER 1000 1200 350 display PDF DND-AC Mm4 F TIGER 1200 1200 400 display PDF DND-AC Mm5 F TIGER 1400 1200 400 display PDF DND-AC Mm6 F TIGER 1600 1200 400 display PDF DND-AC Mm7 F TIGER 1800 1200 400 display PDF DND-AC Mm8 F TIGER 2000 1200 400 display PDF

Is the strongest of all SOLLAU magnetic overband separators. Magnetic induction of these devices is at the limit of the capabilities of the strongest permanent magnets and can only be surpassed by electromagnetic separators. This series is intended for the most challenging separation from extreme depths and high and heavy material layers. The maximum suspension height of these devices is 450 mm (an interesting fact: the strongest ferrite DND-AC Mx F series is approximately five times heavier than the lightest DND-AC M F series!).

Model*Maximum width of conveyor belt (mm)Maximum recommended installation height (mm)Datasheet crosswiselongwise DND-AC Mx3 F BEAST 1000 1450 450 display PDF DND-AC Mx4 F BEAST 1200 1450 450 display PDF DND-AC Mx5 F BEAST 1400 1450 450 display PDF DND-AC Mx6 F BEAST 1600 1450 450 display PDF DND-AC Mx7 F BEAST 1800 1450 450 display PDF DND-AC Mx8 F BEAST 2000 1450 450 display PDF

Budget version (attractive price/performance ratio) Magnetically as strong as the branded overband DND-AC Ms F JAGUAR Suspension height up to 320 mm Separation of magnetic particles from 1 mm Max. conveyor belt speed: 1,5 m/s

Overband magnetic separator DND-AC EKO is a low-cost variant of an overband magnet. From the magnetic point of view there is no difference between the standard version DND-AC and the economic version DND-AC EKO.

Both generate the same magnetic induction (what is quite exceptional, as the economic models of our competitors are generally magnetically weaker in comparison with their standard models). On the other hand, the clients acquiring our DND-AC EKO version have to accept the fact that this model is equipped with the engine CANTONI and with the gearbox VARVEL, there are unprotected bearings and only the bottom part of the separator is protected by metal sheets.

DND-AC EKO is designed to handle product stream with a high content of ferromagnetic particles (exceeding the capacities of the manually cleaned magnetic plates). This separator can capture in a quick and easy way valuable ferromagnetic particles from a product stream and at the same time the overband magnetic plate with automatic cleaning protects your machinery (shredders, mills, grinders, screw conveyors etc.) that subsequently treat the material. The tramp ferrous metal extracted from the conveyor is removed by a heavy duty rubber belt into a skip or a collection bin at the side of the conveyor.

ModelRecommended for a belt with a maximum width (mm)Maximum recommended installation height (mm)Datasheet crosswiselongwise DND-AC Ms2 F EKO 800 850 270 display PDF DND-AC Ms3 F EKO 1000 850 300 display PDF DND-AC Ms4 F EKO 1200 850 320 display PDF DND-AC Ms5 F EKO 1400 850 320 display PDF DND-AC Ms6 F EKO 1600 850 320 display PDF DND-AC Ms7 F EKO 1800 850 320 display PDF DND-AC Ms8 F EKO 2000 850 320 display PDF

Some products from this model family are available for immediate purchase. We are constantly extending the offer of our magnetic separators in stock so that we can deliver them to you immediately. Please, contact our dealer to inform for their current availability.

An extremely strong (but relatively short) magnetic field and a low weight are the most significant benefits of neodymium overband separators. That is why the application of the neodymium separators is preferred at the places where it would not be possible to use heavy ferrite magnets or where a very high separation efficiency at shallower depths is required (e. g., in cases of mobile crushing and recycling lines).

ProductMaximum width of conveyor belt (mm)At crosswise installation above the conveyorMaximum recommended installation height (mm)Datasheet DND-AC N1 JACKAL 500 200 display PDF DND-AC N2 JACKAL 700 200 display PDF DND-AC N3 JACKAL 1000 200 display PDF DND-AC N4 JACKAL 1200 200 display PDF DND-AC N5 JACKAL 1400 200 display PDF DND-AC N6 JACKAL 1600 200 display PDF DND-AC N7 JACKAL 1800 200 display PDF

Separator constantly in stock (immediately available) Twin pole neodymium variant with a ferrite releasing pole Suspension height up to 170 mm Separation of magnetic particles from 0,5 mm Max. conveyor belt speed: 1,5 m/s

Some products from this model family are available for immediate purchase. We are constantly extending the offer of our magnetic separators in stock so that we can deliver them to you immediately. Please, contact our dealer to inform for their current availability.

Is a stronger neodymium variant (with a maximum installation height of 220 mm), intended for medium-duty applications. Its benefits include: a high magnetic induction (at a short distance), a separation of smaller Fe particles and a low weight.

ProductMaximum width of conveyor belt (mm)At crosswise installation above the conveyorMaximum recommended installation height (mm)Datasheet DND-AC Ns1 HYENA 500 220 display PDF DND-AC Ns2 HYENA 700 220 display PDF DND-AC Ns3 HYENA 1000 220 display PDF DND-AC Ns4 HYENA 1200 220 display PDF DND-AC Ns5 HYENA 1400 220 display PDF DND-AC Ns6 HYENA 1600 220 display PDF DND-AC Ns7 HYENA 1800 220 display PDF

Some products from this model family are available for immediate purchase. We are constantly extending the offer of our magnetic separators in stock so that we can deliver them to you immediately. Please, contact our dealer to inform for their current availability.

This is the strongest neodymium model, particularly intended for mobile applications where an extremely high magnetic induction at shallower material depths is needed. Maximum installation height: 250 mm.

ProductMaximum width of conveyor belt (mm)At crosswise installation above the conveyorMaximum recommended installation height (mm)Datasheet DND-AC Nm1 WOLF 500 250 display PDF DND-AC Nm2 WOLF 700 250 display PDF DND-AC Nm3 WOLF 1000 250 display PDF DND-AC Nm4 WOLF 1200 250 display PDF DND-AC Nm5 WOLF 1400 250 display PDF DND-AC Nm6 WOLF 1600 250 display PDF DND-AC Nm7 WOLF 1800 250 display PDF

Some products from this model family are available for immediate purchase. We are constantly extending the offer of our magnetic separators in stock so that we can deliver them to you immediately. Please, contact our dealer to inform for their current availability.

eriez - permanent magnetic drum separators

Eriez Drum Separators remove both large and small pieces of iron contaminants from material processing lines. Powerful permanent magnets enable more efficient separation performance for a broader range of applications than ever before. The complete line includes standard models in diameters from 12 to 36 inches (305 to 915 mm), and widths from 12 to 60 inches (305 to 1525 mm). These units provide efficient separation on volumes up to 25,600 cubic feet (725 cubic meters) per hour. They provide years of troublefree automatic removal of tramp iron from heavy flows of bulk materials, including large and highly abrasive materials.

As material reaches the drum, the magnetic field attracts and holds ferrous particles to the drum shell. As the drum revolves, it carries the material through the stationary magnetic field. The nonmagnetic material falls freely from the shell, while the magnetic particles are held firmly until they are carried out of the magnetic field.

Type CC Model Drum Separators have a unique criss cross magnetic circuit. A powerful permanent magnetic field uniformly covers the entire drum width to ensure maximum tramp iron removal. The smooth stainless steel shell with single wiper strip assures positive tramp iron discharge and a minimum of product carryover on powdery or cohesive materials.

Rare Earth Drum Separators should be used for applications where a high degree of product purity is required. Rare Earth Drums are effective in removing very fine ferrous particles, locked particles, and even strongly paramagnetic particles. Magnetic lines of flux are concentrated in each internal pole, creating an extremely highgradient magnetic field.

Type A AgitatorType Drum Separators automatically removes difficulttoseparate magnetic contamination from nonmagnetic materials. This Drum (available with or without HFP housing) has a specially designed magnetic element that causes agitation of materials passed over it. The agitation moves the material in and out of a set of magnetic fields, and thereby physically shakes nonmagnetic materials from ferrous materials, even when entangled.

magnetic separation

Permanent tube magnets are used where manual cleaning is possible. A guide strip is fitted to the inside of the housing which ensure that the material to be cleaned is well dispersed when it comes in contact with the magnetic core.

The material flow passes the magnet system. To remove the ferrous contamination, the material flow is stopped and the flap valve turned. By rotating the magnets, the magnetic field is removed from the ferrous particles collected so they fall through the side opening to the outside.

This type of ferrous separation system from BLS Magnet is equipped with a powerful permanent magnet that produce a magnetic field which causes the ferrous particles on the belt to move so that any non-ferrous particles which had been hold by the iron particles can drop back into the material flow.

Drum magnets, also called separation drums, contain two sectors - one magnetic and the other not. There is a drum which rotates around the outside of these and over which the material flows or is dropped.