Low-intensity separators are used to treat ferromagnetic materials and some highly paramagnetic minerals.Minerals with ferromagnetic properties have high susceptibility at low applied field strengths and can therefore be concentrated in low intensity (<~0.3T) magnetic separators. For low-intensity drum separators used in the iron ore industry, the standard field, for a separator with ferrite-based magnets, is 0.12 T at a distance of 50 mm from the drum surface. Work has also shown that such separators have maximum field strengths on the drum surface of less than 0.3 T. The principal ferromagnetic mineral concentrated in mineral processing is magnetite (Fe3O4). although hematite (Fe2O3) and siderite Fe2CO3 can be roasted to produce magnetite and hence give good separation in low-intensity machines.
Permanent magnetic drum separators combine the attributes of a high-strength permanent magnetic field and a self-cleaning feature. These separators are effective in treating process streams containing a high percentage of magnetics and can produce a clean magnetic or non-magnetic product. The magnetic drum separator consists of a stationary, shaft-mounted magnetic circuit completely enclosed by a rotating drum. The magnetic circuit is typically comprised of several magnetic poles that span an arc of 120 degrees. When material is introduced to the revolving drum shell (concurrent at the 12 oclock position), the non-magnetic material discharges in a natural trajectory. The magnetic material is attracted to the drum shell by the magnetic circuit and is rotated out of the non-magnetic particle stream. The magnetic material discharges from the drum shell when it is rotated out of the magnetic field.
Permanent magnetic drum separators have undergone significant technological advancements in recent years. The magnetic circuit may consist of one of several designs depending on the application. Circuit design variations include:
The standard magnetic drum configuration consists of series of axial poles configured with an alternating polarity. This type of drum is simple in design and can be effective for low-intensity applications such as the recovery of ferrous metals and magnetite. This configuration typically does not provide a sufficient field strength or gradient for the recovery of paramagnetic minerals at high capacities. A typical axial circuit is shown in Figure 3.
The high-gradient element, as the name implies, is designed to produce a very high field gradient and subsequently a high attractive force. Several identical agitating magnetic poles comprise the element. The poles are placed together minimizing the intervening air gap to produce the high surface gradient. Due to the high gradient, the attractive force is strongest closer to the drum making it most effective when utilized with a relatively low material burden depth on the drum surface and, thus, a lower unit capacity. A high-gradient magnetic circuit is shown in Figure 4.
The interpole-style element utilizes a true bucking magnetic pole or interpole between each main pole. The magnetic field of the bucking element is configured to oppose both of the adjacent main poles resulting in a greater projection of the magnetic field. As a result, the interpole circuit allows for a relatively high material burden depth on the drum surface and thus higher unit capacity or improved separation efficiency. An interpole magnetic circuit configuration is shown in Figure 5.
A second interpole configuration consists of steel pole pieces placed between the magnetic poles. This is commonly termed a salient-pole element. The steel interpoles concentrate the magnetic flux providing a very high magnetic gradient at the drum surface. The magnetic field configuration is similar to the high- gradient type element but with an intensified surface gradient. This configuration offers the strongest field projection of any of the previously described circuits. The salient-pole circuit design is shown in Figure 6.
The magnetic elements described above are axial elements. The magnetic poles run across the width of the drum and are of alternating polarity. Magnetic elements are typically assembled with a minimum of five magnetic poles that span an arc of 110 degrees. (For all practical purposes, an arc of only 80 degrees is required to impart a separation. Non-magnetic particles usually leave the drum surface with a natural trajectory at a point of 60 to 70 degrees from top dead center dependent on the drum speed, particle size, and specific gravity.) The poles have alternating polarity to provide agitation to the magnetic components as they are transferred out of the stream of the non-magnetics. A magnetic particle will tend to rotate 180 degrees as it moves across each pole. This agitation is functional in releasing physically entrapped non-magnetics from the bed of magnetics. Agitating magnetic drums are most effective in collecting fine particles or where the feed contains a high magnetics content.
Dense-medium circuits have been installed in many mineral treatment plants since its original development about thirty years ago. In the intervening period the process has been thoroughly evaluated and many innovations have been introduced. The Heavy Density Cyclone is one of the newer systems which has extended the operating range of this process to 65 mesh size.
Medium recovery is obviously important since any loss is a direct cost against production. In coarse coal dense-medium plants a loss of 1 pound of magnetite per ton is usually acceptable but reduction to pound per ton as has been obtained in some plants.
Efficient cleaning maintains fluidity in the bath and increases sharpness of the coal-waste separation. Most dense-medium systems will tolerate some non-magnetic dilution of the bath but the magnetic separator must be capable of keeping this within workable limits, particularly on difficult coals. In some plants a partial bleed of the operating dense-medium bath is maintained through the magnetic separator to keep it clean.
Operating gravities of dense-medium coal plants are usually low enough so that a straight magnetite bath can be used. The return of a magnetic separator concentrate having 50% or more solids will maintain gravity without need for a thickening device. The use of a drum wiper has permitted the return of a 70% solids concentrate back to the separatory vessel. Operation at a high solids concentrate discharge is recommended since medium cleaning is improved. The colloidal slimes carried over with water are more completely rejected at high solids discharge.
Several types of magnetic separators have been used in magnetic medium recovery.The first magnetic drum separators were electro magnetic types but the development of efficient wet permanent drum separators has resulted in nearly universal acceptance of permanent drums in new plants.
The basic construction of each drum is the same. It consists of a stationary magnet assembly held in a fixed operating position by clamp bearings mounted on the separator support frame. An outer rotating cylinder driven through a sprocket bolted to one of the drum heads carries the magnetic material to the magnetic discharge point.
Normally, extreme cleanliness of the magnetic concentrate is not of prime importance in dense-medium plants but this can be a factor in some coals that separate with difficulty. The concurrent tank, reduced separator loading and in some instances dilution of the feed pulp will improve magnetic cleaning. Recleaning of a primary concentrate would improve cleaning but has not been used in commercial plants.
Magnetic coolant separator is device which cleans coolant liquid of very fine particles; it removes chips from the milling or grinding liquid. It has light and compact structure having strong magnetic power which can remove very fine particles. For precise grinding operations uninterrupted flow of oil is must. The magnetic separator ensures the uninterrupted flow of the liquid.
A magnetic drum with close dense magnetic field is assembled on non-magnetic SS shaft. Magnetic pole shoes are projected out to form fins, for better magnetic field alignment around the drum. The drum is rotated very slowly by a geared motor drive.
Slow rotary motion dumps the dirt collected on closely contoured scrapers. Extended scraper dumps the dirt collected to a bin. Size & number of fins is selected depending on the flow of fluid, viscosity of fluid & quantum of dirt to be handled. Positive rake scraper is selected for volatile fluid like water based emulsion while negative rake scraping is selected for oils. Negative rake scraper keeps the fluid away from bin.
We installed Veeraja's Filtration System (vacuum filter, scraper conveyor, upflow drum) for honing machine. Initially we tried on one machine & with satisfactory results implemented on 3 machines. The results were fantastic. The filtration level was very good, sorted out issues on honing tool jamming issues, size variation due to improper filtration. Appreciate Veeraja teams support for appropriate, cost effective solution, understanding our pain & resolving the same.
We installed Veeraja's Centralized Filtration System (vacuum filter, scraper conveyor, upflow drum) for grinding line and deep hole drilling a few years ago. We were convinced that results would be positive and am glad to announce that our projections were correct. Productivity increased through recycling, lowering electricity bills and improved cycle times on processes. Great investment, great ROI
We installed Veeraja's Centralized Filtration System (vacuum filter, scraper conveyor, upflow drum) for grinding and machining. Our productivity inproved substantially, lowering power supply cost and improved cycle times on processes. Working with Veeraja Industries was a pleasant experience. Very happy. Keep up the good work Veeraja Industries. Profitable investment for our business division.
I have complete confidence in solutions from Veeraja Industries. Veeraja Industries has unmatched application experience in metalworking fluid filtration industry. Also they offer the widest range of technologies to choose from. Low operations cost is another important benefit the user gets. I strongly recommend filtration solutions from Veeraja Industries.
When we were setting up one of our plants, the Management decided to Install Centralised Filtration System for Process media like Coolant, Honing / Lapping Oil. We reviewed lot of providers but ultimately entrusted Veeraja Industries to engineer Centralised Filtration System. We were convinced that results would be positive by Productivity increase through recycling of Coolant, Honing / Lapping Oils, lowering electricity bills and improved cycle times on processes due to Clean Coolant, Honing / Lapping Oils. Great investment, great ROI. Profitable investment for any business division as the functional results are wonderful.
China manufacturing industries are full of strong and consistent exporters. We are here to bring together China factories that supply manufacturing systems and machinery that are used by processing industries including but not limited to: magnetic separator, mining machine, dry magnetic separator. Here we are going to show you some of the process equipments for sale that featured by our reliable suppliers and manufacturers, such as Magnetic Drum Separator. We will do everything we can just to keep every buyer updated with this highly competitive industry & factory and its latest trends. Whether you are for group or individual sourcing, we will provide you with the latest technology and the comprehensive data of Chinese suppliers like Magnetic Drum Separator factory list to enhance your sourcing performance in the business line of manufacturing & processing machinery.
Magnetic separator is for particle size below 3mm magnetite, pyrrhotite, roasted ore, ilmenite and other materials wet magnetic separation, also for coal, non-metallic minerals, building materials and other materials de-ironing. Magnetic separator magnetic system, using high quality rare earth magnets or ferrite material composite, average magnetic flux density of tube surface is 100 ~ 600mT. According to user needs, we can provide a variety of downstream, semi- reflux and reflux products with different magnetic flux density surface. This product has characteristics of simple structure, large capacity, easy to operate and easy to maintain.
Performance Features of Magnetic Separator: 1. For depleted iron ore roughing after coarse/medium crushing, can exclude waste rock to improve ore quality and reduce load for next process. 2. For hematite in a closed reduction roasting operation, select out raw ore that is not fully restored, return it and then burn again. 3. For the ceramic industry, remove mixed iron from porcelain mud to improve the quality of ceramic products. 4. For burning coal, foundry sand, refractory and other industries requires iron removal.
Work Principle of Magnetic Separator: The ore slurry flows into the tank via feed chute, under the effect of the water flow from ore-feeding water pipe, mineral particles in loose state goes into the feeding area of tank. Under the action of the magnetic field, the magnetic mineral particles gather together to form a "magnetic group" or "flux", in the pulp "magnetic group" or "flux" goes to magnetic pole by the magnetic force, and is adsorbed on the cylinder. Because the magnetic poles are alternately arranged along the direction of cylinder rotation, and are fixed while working, when the "magnetic group" or "flux" rotates with cylinder, the magnetic stirring phenomenon generated due to magnetic poles alternating, gangue minerals and other non-magnetic mineral existing in the "magnetic group" or "flux" fall down while rolling, eventually the "magnetic group" or "flux" being sucked in the cylinder surface is the concentrate. The concentrate rotates with cylinder to the magnetic system edge that has the weakest magnetic force, discharged into concentrate tank under the action of flushing water from ore-discharging water pipe. If it is full-magnetic roller, ore discharging is carried out by brush roll. Non-magnetic or weakly magnetic minerals are left with the pulp discharged outside the tank, which are tailings.
For automatic continuous removal of ferrous and even weakly magnetic contaminants. Magnetic drum separators - also called drum magnets - are very suitable for product flows that are heavily contaminated with magnetic particles.Our strongest drum magnets have a higher separation efficiency with small weakly-magnetic contaminants than any other type of magnetic separator.
Easy-to-install drum magnets for the continuous separation of coarse or sharp iron particles. Various magnet strengths (1800-3000-6000-9000 gauss) and types available to separate strong- or weakly- magnetic particles.
When it comes to bodywork, constructions, machines, tanks, wheel rims or bridges, these various products all have one thing in common, and that's a process they undergo during production or maintenance: abrasive grit blasting. Blasting is a surface treatme...
When it comes to bodywork, constructions, machines, tanks, wheel rims or bridges, these various products all have one thing in common, and that's a process they undergo during production or maintenance: abrasive grit blasting. Blasting is a surface treatme...
The materials are uniformly fed to the belt. When materials go through the permanent magnetic drum, the non-magnetic and low-magnetic particles will leave the belt surface because of the centrifugal force and gravitation. Meanwhile, strong-magnetic particles are absorbed to the belt by the magnetic force and then fall into the magnetic trough when the belt leaving the magnetic pulley.
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.
Our Permanent Drum type separator which is most and widely used separating tramp iron from nonmagnetic material processed in large quantity, for the purity of end products, recovery of metal having commercial value and protection of processing plant and machinery. Single Drum Type Magnetic Separator is widely used in all the processing industry for separation of iron contamination from minerals ,chemicals, food, grains, sand, plastic fertilizers, slag,ores and in many more products.
Double Drum Type Magnetic Separators is mostly used for his functionality of highest purity. The material is going to pass through the magnet twice in Double Drum type machine. Mainly it is used for separation of iron contamination from Minerals, Chemicals, Refractory and many other products. In Double Drum Type Magnetic Separators high power permanent magnetic plate is provided at a material outlet. Modern an Isotropic Permanent Magnets are used having highest coercivity and everlasting magnetic strength. Machines are available with vibrating material inlet Hopper and totally enclosed design to avoid dusting and pollution. Online fitting design is also available as per requirement.
Permanent Magnetic Drum consists of a stationary permanent magnetic assembly having a uniform and everlasting magnetic field across the entire width of the drum, which is more effective over approximately half the drum circumferences as shown in above fig.
Drum shell is made up of nonmagnetic stainless steel which revolves around the magnetic field. As the material fed evenly from the chute falls over the drum, powerful magnetic, field attract & holds ferrous particles to the revolving shell. As the revolving shell carries the iron particles through the stationary magnetic field., the nonmagnetic material falls freely from the shell while ferrous particles are firmly held until carried beyond divider and out of the magnetic field.
The biggest strength of the permanent magnetic drum is guaranteed to be greater than a corresponding electromagnetic drum. Permanent magnets used are everlasting magnets and its strength does not diminish during normal use and can be used for a long period of time after the installation.
Ther Permanent Drum Separators are available in standard drum diameters of 300mm, 400mm, 450mm, 500mm, 600mm, 900mm, 1200mm and Drum width range from 300mm to 2000mm. There are also many others sizes which can be made as per your requirement. The larger the diameter and width of the drum the greater is the volume of material which can be handled.
The magnetic separator with ceramic magnet are useful for the application where free and larger iron particles are to be separated. The average magnetic intensity on the magnetic drum surface will be 1500-2000 Gauss.
The magnetic separator with high intensity Rare Earth Nd-Fe-B (Neodymium- Iron- Boron) magnets are useful for removing magnetic contamination with low magnetic properties and fine iron particles are to be separated. The average magnetic intensity on the drum surface will be 3500 5500 Gauss.
Jaykrishna Magnetics Pvt. Ltd. is the leading manufacturer and exporter of Magnetic and Vibratory Equipments in India. We are established since 1978. The unique and premium structural design imparts quality and elegance to our products. Our focus is on continuously improving our process, service and products to exceed the benchmarks set by our competitors and offer better products to you.
We are Manufacturer, Supplier, Exporter of Drum Type Magnetic Separators and our setup is situated in Pune, Maharashtra, India. Magnetic Separators used for Separation, Purification, Filtration, Removing Ferrous Particles, Cleaning, Cleaning Coolant, Oil Filtration, Cleaning Oil, Liquid Cleaning etc. These are generally manufactured as custom made where the separations is required to the highest purity of material, the material to be made free of iron particles is passed over the first magnetic drum and again in continuous process fed to the 2nd magnetic drum and similarly to the third. This process ensures the purity process ensures the purity of the material of the highest order. The drum type magnetic separator is ideally used to separate ferrous particles from non ferrous particles . They are so made by us to provide ultimate protection to crushers, Grinders, Pulverizers and allied equipment and is useful for mining and ore dressing industry. It is so made that one side is magnetized and the other side is not. Applications: It is ideally used in Ceramic, Chemical, Glass, Fertilizer and food industry separates iron particles from granules and powder. The magnetic drums are suitable for capacities up to 2 tons per hour can be given on short deliveries. They have a varying dimension of 300mm. to 600mm. The diameter and length varies up to 1500mm and has a capacity to handle 10 tones.
Eriez Drum Separators are setting industry standards. The newest advances in magnetic circuitry design, plus over a quarter of a century of experience with solid/liquid separation, are combined in Eriez Wet Magnetic Drum Separators.
Innovations in both magnetic circuit design and materials of construction are applied to Eriez wet drum magnetic separators. This results in maximum magnetite recovery while operating with a minimum amount of wear and maintenance. Refinements in the magnetic circuit, tank design, and drive system have resulted in further improvements in metallurgical performance and operation.
Wet drums in heavy media applications provide continuous recovery of magnetite or ferrosilicon. Eriez has set the industry standards in the heavy media industry developing both the design criteria of the magnetic circuit and the benchmark of operation. The 750 gauss Interpole magnetic element, developed by Eriez, is the most acclaimed magnet of engineering standards in the industry. Eriez has also set the benchmark for wet drum performance. The culmination of various inplant tests has demonstrated that the separators will achieve magnetite recoveries in the 99.9+ percent. (This is based on magnetite losses of less than 1 gram/gallon of nonmagnetic effluent).
Two basic tank styles are offered. The drum rotates in the same direction as the slurry flow in the concurrent tank style. The slurry enters the feedbox and is channeled underneath the submerged drum. The slurry then flows into the magnetic field generated by the drum. The magnetite is attracted by the magnetic field, collected on the drum surface, and rotated out of the slurry flow. This tank style results in a very clean magnetic product.
The counterrotation tank style is preferred for heavy media applications. The drum rotates against the slurry flow in the counterrotation tank style. The slurry enters the feedbox and flows directly into the magnetic field generated by the drum. The magnetite is attracted by the magnetic field, collected on the drum surface, and rotated out of the slurry flow. Any magnetite that is not immediately collected will pass through to a magnetic scavenging zone. The short path that the magnetic material must be conveyed between the feed entry point and the magnetics discharge lip, combined with the magnetic scavenging zone, results in high magnetite recoveries.
Wet drum magnetic separators are the most vital part of the upgrading process in magnetite concentration. The upgrading of primary magnetite is always accomplished with wet drum separators. Mill feed is typically upgraded to 65+ percent magnetic iron using a series of wet drum magnetic separators. The number of magnetic separation stages required to upgrade the ore is dependent on the magnetite content and the liberation characteristics of the ore.
The Eriez Wet Drum Magnetic Separators is engineered and fabricated to provide reliable operation in demanding applications. The separator is designed for the continuous treatment of coarse milled ore providing a high level of availability. The tank and drum are fabricated from heavy gauge stainless steel with wear plate in impact areas. Wear areas are protected with hot vulcanized rubber. The drum utilizes heavyduty spherical roller bearings with a B10 life of 100,000+ hours. The drive system utilizes a Mill and Chemical Duty motor coupled to a shaft mounted gear reducer complete with Taconite Seals.
The feed enters the separator at the bottom of the tank and the drum rotates in the same direction as the slurry flow. This tank also has a scavenging zone. The nonmagnetics must migrate through the magnetic field to a full width overflow. This design, with the full width overflow, allows the tank to be selfleveling. There are no tailings spigots that must be adjusted to match the flow of the separator feed. This design is most effective for producing a clean magnetite concentrate. The magnetic element should incorporate several agitating magnetic poles to provide a high degree of cleaning. Since the finisher feed consists of fairly well liberated magnetite, extreme magnetic field strengths are not required for collection.
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.
When material flows onto the drum, a stationary magnetic assembly inside the unit's shell captures tramp metal and holds it securely to the drum's stainless steel surface. With contaminants removed, the good product falls freely to a discharge point. As the drum rotates, cleats sweep the ferrous debris through and out of the magnetic field. The tramp metal is discharged separately, creating continuous self-cleaning separation
The magnetic drum separator consists of a rotating drum and stationary drum magnet designed as per the specific needs of the customer. The Drum separator is supplied with the drive system and SS 304/316 housing along with a feed regulating valve.
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