sgm magnetics - engineering and manufacturing of magnetic and separation equipment

sgm magnetics - engineering and manufacturing of magnetic and separation equipment

SGM Magnetics started in 1954 in Manerbio (Brescia), north of Italy, a region rich and famous for its competitive steel mills and metals industry. Our name and logo reflect our first two historical core businesses which have been lifting magnets to the steel industry and magnetic separation to the metal recycling industry.

Through the years, SGM has developed a position of pioneer and leader on industrial lifting magnets and has extended its magnetic separation expertise to other in-house separation technologies that are inductive based sensor separators, X-ray separators, color sorters, gravimetric separation and processes.

The SGM business model is based on providing technological expertise and to being close to its customers through a network of SGM Magnetics corporations located in Italy, Germany, UK, USA, China and India as well as a few long standing agents with extensive experience in the SGM products and technologies. SGM disposes of three SGM demo/test centers which are located in Italy, USA and China.

SGM starts off with standard circular electromagnets for lifting scrap and plates followed by new magnetic lifting solutions as more sophisticated mill applications were developed (slabs, billets, coils, multi-plates, rails, bundles of construction bars, structural, pipes ,...).

In order to meet new safety, performance and weight requirements of the oil industry for pipe lifting applications on offshore drilling platforms, SGM introduced a new generation of Rare Earth Electro-Permanent Lifting Magnets. This new technology was quickly transferred to various lifting magnet steel industry applications.

Introduction of the octagonal SGM Mega Scrap Lifting Magnet featuring a proprietary double magnetic circuit allowing for handling more ferrous scrap and in a more compact way than the traditional two large round magnet solution. These scrap magnets rapidly become the reference solution for the quick and gentle loading/unloading operations of railcars and are also specifically suited for belt loading with Consteel technology.

Introduction of the proprietary VHG Magnetic Circuit consisting of the use of both rare earth magnets (Neodymium ) and ferrite magnets thus combining the deep but not that strong attraction force of the Ferrite permanent magnets with the very strong but shallower attraction force of the rare earth magnets.

Introduction of the proprietary SGM Dynamic Ferrous Separators (DSRP) representing a technological evolution to the traditional magnetic pulleys resulting in the possible segregation of sellable ferrous nuggets from magnetic trash.

Introduction of the proprietary SGM Polishing Drum Magnets (PDM) for separating the electrical rotors (so-called meat ball) from a ferrous scrap stream hence reducing the copper content in ferrous scrap.

Introduction of the proprietary SGM Lifting Magnets for eye horizontal steel coils (CDMD). The CDMD measures the possible flexing and dynamic stress of those coils when handled and allows for innovative and greater safety in their handling with lifting magnets.

Introduction of the proprietary SGM lifting magnets with no side magnetic dispersion. These lifting magnets are especially suited for steel service centers where magnets can enter racks of steel bundles with no disturbing side attraction with steel columns or other bundles/packs next to the one being handled.

Introduction of the proprietary SGM Eddy Current Separator TVIS spinning at 6.000 rpm provided with a titanium protection sleeve to contain the centrifuge forces of the permanent magnet blocks. Still today SGM is not only the pioneer of the high frequency ECS but, most probably, the quantity of high Frequency ECS (from 3.000 up to 6.000 rpm) supplied by SGM represents a multiple of the ones supplied by all the other brands put together.

Introduction of the proprietary SGM Scrap Cleaning Line for Heavy Melt Scrap. The solution is designed to drastically reduce the about 5% non-ferrous trash present in the HMS for optimization of efficiency of the electric arc furnace.

Introduction of the proprietary SGM MIMS (Medium Intensity Magnet Separator) for the iron ore mining industry. The proprietary magnetic circuit of the SGM MIMS constitutes a true technological breakthrough to the state of the art of magnetic separators for iron ore.

Introduction of the SGM proprietary Smart Ballistic Separator (SBS) for processing Incinerated Municipal Waste (IBA). The separator allows the processing of wet IBA and the concentration of the solid pieces including the metals in a fraction larger than 2 mm and dryer than the infeed IBA. The SGM SBS represents a performing evolution of the state of the art for ballistic separators.

Introduction of the SGM proprietary Convection Electro Lifting Magnet (CELM) for hot materials. The design of the CELM drastically extends their possible duty cycles (and life time) on hot steel loads like slabs and billets. The SGM CELM constitutes revolutionary technological breakthrough innovation related to electro lifting magnets.

Introduction of the SGM proprietary Convection Electro Permanent Lifting Magnet (EPCLM) for hot materials. The design of the EPCLM drastically extends their possible duty cycles (and life time) on hot steel loads like slabs and billets.

Introduction of the SGM Dry Media Plant for shredder residue zorba as an alternative to the more capital and labor intensive wet media plants for the separation of light metals (Aluminum and Magnesium) from heavier metals (copper, brass, zinc, led,...).

Introduction of the SGM latest generation of X-ray separator (XRS) for the process of shredder residue fluff to reduce the chlorine and bromine content to less than 1% in over 70% of the fluff residue.

pneumatic in-line magnets | bunting

pneumatic in-line magnets | bunting

Buntings in-line magnets offer effective, high strength magnetic separation that is easy to install and integrate with your existing systems. Buntings design has no maintenance required aside from cleaning the ferrous metal contamination it captures. The design of Buntings in-line magnetic separation equipment features full-flow architecture that leaves the product stream unobstructed. In-line magnets are suitable for a diverse range of industries, including food, grain and milling, powder and bulk, plastics, and recycling.

Bunting offers gravity, pneumatic, and center-flow in-line magnetic separation equipment. As material flows across the surface of a powerful rare earth magnet, the magnetic force captures and traps ferrous metal contamination, holding it against the face of the magnet to prevent it from re-entering the product stream. In gravity and pneumatic in-line magnets, tapered transitions guide material directly over the face of a hinged plate magnet, which swings away from the housing to enable quick external cleaning. In center-flow in-line magnets, the magnet achieves optimal contact with the product flow by suspending a conical magnet in the center-line of the housing. All of our designs can come with 10,000 gauss to comply with food standard.

To deliver powerful magnetic separation, our in-line magnetic separation equipment comes standard with rare earth magnets, although we do offer other options based on your needs. For optimum safety, metal-detectable gaskets and grommets are standard in the housing of in-line magnets. All of our pneumatic units come with a lock out tag out feature, allowing operators to lock the unit in order to prevent injury or tampering from personnel. All of our pneumatic units come with a sensor backplate, so operators can install a sensor to tell them when the magnet is open or when the magnet was last cleaned. This helps operators know if it is safe to run their product, or if maintenance is keeping up with cleaning. Our in-line magnets excel at removing ferrous fines as well as larger pieces of tramp metal contamination from your material, and extensive customization options are available. Additionally, Buntings units are designed to prevent the product from degradation and do not cause it to splinter.

Pneumatic in-line magnets are built for use in dilute phase pneumatic conveying systems. They can be installed easily with optional factory-supplied compression couplings, and work best in horizontal runs with the plate magnet down to take advantage of material stratification. Pneumatic in-line magnets feature full-flow architecture to allow an unobstructed product stream.

Center-flow in-line magnetic separators are engineered to remove ferrous fine particles and larger pieces of tramp iron from dry particulates as they travel through dilute-phase pneumatic conveying lines. To achieve optimum contact with the product flow, a conical magnet is suspended in the center-line of the housing. This tapered, exposed-pole cartridge has a stainless steel nose cone to direct the flow of materials around the magnet. The magnets tapered poles allow ferrous fine particles to collect out of the direct air stream. Additionally, the trailing end of the magnet is an active pole which will collect any tramp metal that gets swept down the cartridge. The magnets shell is designed to give long magnetic exposure to dry powders in order to ensure your product achieves maximum magnetic separation.

These magnets allow you to utilize our powerful plate magnets in round, sloping spouting where material is under gravity flow. For effective tramp capture, spouting should be angled no more than 60 from horizontal. These units are perfect for applications that are tight on space.

industrial metal detection equipment | bunting

industrial metal detection equipment | bunting

The most common of foreign material within processing is metal. Bunting Metal Detection equipment senses and removes the presence of ferrous, non-ferrous and stainless metals in the process flow in-line, in free-fall applications, and in conjunction with conveyors. These units also find metal encapsulated in the individual particle.

Bunting Metal Detectors utilize triple coil design for the search head. This is comprised of windings around an aperture opening, whether round, or rectangular. There is a transmitter in the center, and two receivers (one at entrance of the search head, and one at the exit). Within the aperture opening, an electromagnetic field is created. When a piece of metal passes through the coil opening, a signal is generated and calculated at each and activates further operations or devices.

All search heads are filled with a catalyzed epoxy. There are no empty voids inside the housing, thereby eliminating the possibility of water intrusion to the coil, making them easy to clean. This exclusive epoxy also reduces the effect of vibration to the search head. Coils and electronics can be rated from IP54, to IP66 and IP69K.

Additionally the search head is manufactured with a special shielding against outside interferences. This allows Bunting Metal Detectors to perform better in difficult environments, and require shorter metal free zones than our competition.

Depending on the level of electronics you select, Bunting Metal Detectors have recording and reporting functions within the software. Optional features allow your organization to network detectors for remote monitoring, reporting or control.

In our pipeline series, we have two styles, the pipeLINE system is used for liquids or pastes in pressure conveying lines. The meatLINE system is also used for liquids or pastes but it uses simple integration with a vacuum filter.

In our pipeline series, we have two styles, the pipeLINE system is used for liquids or pastes in pressure conveying lines. The meatLINE system is also used for liquids or pastes but it uses simple integration with a vacuum filter.

Using the most advanced controls, our metal detectors and metal separators deliver superior results with ease of use. They are equipped with 1 of 3 different versions of controls and displays that are specific to the system type and application needs: Simple 03 controls to full color 07 controls that allow ease of use, accessibility of information and traceability of products.

Using the most advanced controls, our metal detectors and metal separators deliver superior results with ease of use. They are equipped with 1 of 3 different versions of controls and displays that are specific to the system type and application needs: Simple 03 controls to full color 07 controls that allow ease of use, accessibility of information and traceability of products.

These Flat Coil Detectors prevent costly repairs and production downtime. Units are self-monitoring for added reliability. The ProfiLine features advanced circuitry which reduces false signals and product waste.

These Flat Coil Detectors prevent costly repairs and production downtime. Units are self-monitoring for added reliability. The ProfiLine features advanced circuitry which reduces false signals and product waste.

These Flat Coil Detectors prevent costly repairs and production downtime. Units are self-monitoring for added reliability. The ProfiLine features advanced circuitry which reduces false signals and product waste.

These Flat Coil Detectors prevent costly repairs and production downtime. Units are self-monitoring for added reliability. The ProfiLine features advanced circuitry which reduces false signals and product waste.

eriez permanent magnetic equipment

eriez permanent magnetic equipment

Eriez Permanent Plate Magnets provide dependable and economical solutions to problems associated with tramp iron contamination in processing lines. Plate Magnets installed in chutes, spouts, ducts, pipes, or suspended over conveyors remove tramp iron to help prevent costly shutdowns associated with machinery damage, prevent spark caused fires and explosions, prevent product contamination and improve product purity.

Powerful, permanent magnetic protection against fine and tramp iron contamination. The Xtreme RE separators available from Eriez remove weakly magnetic or very fine iron contaminants. They have more strength at a greater distance than conventional permanent magnets, higher gradients and increased holding force.

Eriez line of powerful, permanent magnetic Ferrous Traps provide magnetic protection for liquid lines and processing equipment. They preserve product purity by removing small particles of magnetic scale, rust and fine iron contamination.

Eriez' Magnetic Hump and Round Pipe Separators provide a simple and effective way to remove tramp iron contamination from gravity or pneumatically conveyed dry, free flowing products such as feed, grain, wood ships, food stuffs, sand or plastic.

Replace your standard pulley with our powerful permanent magnetic pulley to transform your belt conveyor into a powerful self cleaning magnetic separator. The axial interpole magnetic circuit provides a uniform magnetic field to remove tramp iron from material on almost any belt conveyor.

Replace your standard pulley with our powerful permanent magnetic pulley to transform your belt conveyor into a powerful self cleaning magnetic separator. The axial interpole magnetic circuit provides a uniform magnetic field to remove tramp iron from material on almost any belt conveyor.

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.

Eriez magnetic drums have been used for many years in scrap metal yards to separate iron and steel from other materials. Using our sophisticated design software and unique magnetic circuits, Eriez provides scrap drums with deeper magnetic fields to reclaim ferrous materials in shredded car bodies, scrap metals, municipal solid waste, wood waste, slag, incinerator bottom ash, foundry sand and minerals processing applications.

Eriez magnetic drums have been used for many years in scrap metal yards to separate iron and steel from other materials. Using our sophisticated design software and unique magnetic circuits, Eriez provides scrap drums with deeper magnetic fields to reclaim ferrous materials in shredded car bodies, scrap metals, municipal solid waste, wood waste, slag, incinerator bottom ash, foundry sand and minerals processing applications.

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.

Dry Low Intensity Magnetic Separators (DLIMS) for automatic continuous concentration of magnetic ores, removal of magnetite from fly ash, purification of ground slag, foundry sand, cement and minerals.

These DHIMS provide maximum efficiency in the separation of weak magnetic particles for product purification applications. Eriez applied sophisticated finite element analysis in magnetic circuit design to produce an energy-free separator capable of generating the exceptionally high field-strengths needed to remove unwanted fine iron contaminants.

Eriez Coolant Cleaners are designed for use with surface grinders, gear grinders, honing and lapping machines, broaches, milling and drilling machines face grinders, oil reclaiming machines - wherever clean coolant is needed. These cleaners keep machine tools running longer and more accurately with lower costs per unit produced.

Eriez Permanent Magnetic Flocculators aid in the separation of minute magnetic particles from liquids and slurries. Used widely in the iron and coal mining industries to speed settling of fine magnetic particles in ore slurries and heavy media slurries, they are finding new use in steel and other industries for agglomerating fine magnetic contaminants in quench water, cooling oils, etc.

fountain essays - just another wordpress site

fountain essays - just another wordpress site

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dry high intensity magnetic separators lsv - sollau s.r.o. - magnetic separation

dry high intensity magnetic separators lsv - sollau s.r.o. - magnetic separation

Mobile laboratory-sized version Separation of weakly magnetic particles Automatic cleaning without the interruption of the material flow Integrated vibrating feeder with a hopper Magnetic flux up to 11 000 G Made-to-measure separators Excellent for materials heavily contaminated with ferrous particles

The laboratory highly magnetic separator LSV equipped with an extra strong magnetic roll, is a scaled-down (but fully operational) version of the permanent multi-stage magnetic separator VMSV. It is used for a continuous and automatic separation also of very small (even c.30 m) and lightly magnetic particles (e.g. magnetic stainless steel or also some kinds of paramagnetic minerals) in laboratory conditions.

This extraordinarily powerful as well as compact and modular magnetic separator consists of a vibratory feeder and a pair of rollers. The drive roller is magnetic (with a rotational speed control according to the character of cleaned material and working needs) and the driven one is non-magnetic. This roller pair is mutually connected to each other with a very thin, but extremely sturdy conveyor belt from kevlar or glass-teflon (available also in a non-sticky version). The magnetic field of the magnetic roller reaches the height of maximally c. 10 mm, and therefore the height of the material transported on the conveyor belt should not exceed 5 mm (and we recommend the max. height of 2 mm in order to achieve the highest efficiency).

After loosening the material by means of a vibrating feeder, the material falls down on the conveyor belt. Ferrous particles are caught up through the magnetic field of the roller and brought behind its axis into the container for ferromagnetic contaminants. The purified material (i.e. non-magnetic particles) will fall off by the instrumentality of gravitation into the container for the pure product - situated under the driving roller. Thanks to a special flow divider of the magnetic and non-magnetic material (angularly and axially adjustable) it is also possible to separate even the third fraction from the pure material. The third kind of the material can be found between the pure material and the ferromagnetic contaminants (thus it involves the lightly magnetic material, i. e., partly contaminated with iron particles). The separative process can be repeated as often as needed, because both the pure material and partly contaminated material and also the separated ferromagnetic particles are stored in independent containers under the conveyor belt (let us bear in mind, that the LSV, as an extremely strong magnetic separator, is able to catch also pieces of plastic, rubber, stones or wood slightly contaminated with e. g. iron oxides. That is why, its role is irreplaceable when doing laboratory testing and evaluating the processed materials.).

The vibratory feeder with an integrated filling hopper is the inseparable part of this special magnetic separator. The dimensions of the filling hopper accurately correspond with the conveyor belt width and the needed material dosing can be preset by means of a vibration regulator. The LSV magnetic roller is equipped with an appliance for a simple set up of the optimum conveyor belt tensioning and the drive roller motor is provided with a variable speed unit, which enables regulating the conveyor belt speed when required.

The rare earth roll separator is determined for the most demanding customers, requiring the separation even of the finest ferromagnetic particles. In case of using extremely thin conveyor belts (e. g. from kevlar or glass-teflon), the maximum particles size coming into contact with this separator, should not exceed 5 mm. Bigger particles could namely damage the conveyor belts very fast (when processing bigger fractions of metal contaminants and/or the material itself, thicker conveyor belts can be used, however, their application will lead to the diminution of magnetic efficiency of this special separator).

Thanks to the material quality used, when producing the magnetic roller (combination of extra strong NdFeB magnets with special steel washers and the very thin but highly sturdy kevlar or glass-teflon conveyor belt) this top separator is able to achieve a surface magnetic induction up to 21,000 gauss. This is a value, which has been reached so far only by electromagnetic separators. On the other hand, let us bear in mind that the reached value of the magnetic induction of the magnetic roller is not so important as the density of the magnetic poles, because the LSV is often used for catching small ferromagnetic particles. Should the distances between the magnetic poles be too large (in order to achieve the maximum magnetic induction), the very strong magnetic field generated in this way will not be exploitable for catching tiny impurities because these would slip through due to big distances between the magnetic poles. Therefore, in combination with the very dense poling the optimum value of the magnetic induction on the roller surface ranges about 11,000 gauss (to achieve the maximum capture also of very small ferromagnetic particles).

Automatic belt tensioner Wide range of conveyor belts Mobile version (on wheels) Up to three types of materials can be separated: non-magnetic, weakly magnetic, magnetic Application: e. g. in the area of material testing

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.

The laboratory variant of the roll magnetic separator finds its use in the food-processing industry (especially for material testing or final cleaning of meat and bone meal or salt from salt mines), in pharmaceutics, at e-scrap recycling (e.g. for removing undesirable slightly magnetic stainless particles), in the foundry industry (for purification of various sorts of foundry sand), in the glass and ceramic industry (for separation of undesirable magnetic particles from silica and various sorts of glass sand, china clay, limestone, clay).

dry high intensity magnetic separators (dhims)| eriez lab equipment

dry high intensity magnetic separators (dhims)| eriez lab equipment

Eriez Rare Earth Roll Separators provide an alternative in handling a wide variety of materials which do not respond well to traditional methods of processing on low intensity dry drum separators or high intensity induced magnetic roll separators.

The extremely powerful high gradient magnetic circuits in the RE Roll are at least ten times the attractive force of conventional ceramic magnets. These separators are capable of recovering particles with a wide range of magnetic susceptibility, and will handle feeds from onehalf inch (13 mm) down to very fine material. Optional lower intensity magnetic materials are also available as a lower cost alternative for specific applications.

PRINCIPLE OF OPERATIONThe continued improvement of high energy rare earth permanent magnetic materials has contributed to an unprecedented acceptance by several industries of rare earth permanent magnetic separators. The evolution of these high strength permanent magnets has led to the development of high intensity separators that operate energy-free. The Rare Earth Roll separator was designed to provide peak separation efficiency and is typically used when a high level of product purity is required. The roll's permanent magnetic discs alternating with thin steel pole pieces along a shaft. The steel poles are saturated with magnetic flux and produce a magnetic field in excess of 21,000 gauss.

The Rare Earth Roll is used as a head pulley, and a thin belt connects the roll to a Dynaloc, self cleaning tail pulley. The standard belting is Teflon coated, graphite filled KEVLAR with thickness of 5 and 10 mils. Accepted belting is also available for food and pharmaceutical applications. The belt conveys the feed material to the magnetic field or separation zone. When the feed enters the magnetic field, the magnetic and/or paramagnetic particles are attracted to the roll while the nonmagnetic material follows the natural discharge trajectory. A splitter arrangement is used to segregate the two streams. Other components of the Rare Earth Roll separator include a vibratory feeder with a mounted hopper, stainless steel product discharges, TEFC gearmotor and controls. The rare earth roll separators are avail- able in single, double and triple stage versions with either nonmagnetic or magnetic rerun.

APPLICATIONSThe Rare Earth Roll separator has been accepted by a number of industries as the most effective magnetic separation method for the purification of nonmagnetic materials. These industries and their specific applications are listed below.

Industrial MineralsEffectively reduces the level of iron from beach sands, feldspar, silica sand, calcium carbon- ate, magnesite, kyanite, bauxite, andalusite, etc. by removing iron bearing minerals such as hematite. Magnetically concentrates weakly magnetic minerals, such as garnet, ilmenite, musovite, mica, etc.

AbrasivesExtremely high levels of product purity are obtained by removing the very fine iron of abrasion and iron smeared on the abrasives. Specific abrasive material treated includes aluminum oxide, silicon carbide, glass beads, tumbling media.

PlasticsIron and/or stainless steel encapsulated in pel- lets are effectively removed from the product stream. Free stainless steel and very fine iron is also removed with very high levels of efficiency.

RecyclingThe RE roll is capable of sorting the nickel and cobalt bearing metal turnings from titanium or zirconium metals. Other applications include removal of shredded aluminum from PET, separation of chrome from crushed automobile grills, and sorting of paramagnetic, synthetic diamonds from natural diamonds.

5-inch Single Rare Earth Magnetic Roll Single non-magnetic tail pulley, belt, adjustable splitter and frame. 1/3 HP RPM motor 230 volt, 3 phase, 60 Hz with variable speed control. 1-1/4 cu. ft. mild steel hopper and mild steel frame mounted on separator frame. Eriez Model 26C Vibratory Feeder, 115V/60Hz with 4" x 20" stainless steel tray. Unicon Feeder Control included.

Single Rare Earth Magnetic Roll. 5 inch magnet width. Single non-magnetic tail pulley, belt, adjustable splitter and frame. 1/3 HP RPM motor 230 volt, 3 phase, 60 Hz with variable speed control. 1-1/4 cu. ft. mild steel hopper and mild steel frame mounted on separator frame. Eriez Model 26C Vibratory Feeder, 115V/60Hz with 4" x 20" stainless steel tray. Unicon Feeder Control included.

high intensity dry roll magnetic separator

high intensity dry roll magnetic separator

The rare-earth roll, generating magnetic field intensities, is very effective for concentrating or removing weakly magnetic minerals from a dry process stream. The rare-earth roll magnetic separator is designed to provide peak separation efficiency and is typically used when a high purity product is required. The roll is constructed of thin neodymium-boron-iron permanent magnetic discs sandwiched with thin steel pole pieces. Roll diameters typically range from 3 to 4 inches, although machines as large as 12-inches in diameter have been built and tested. The steel poles are saturated with magnetic flux and generate a magnetic field in excess of 21,000 gauss. The magnetic roll is configured as a head pulley in the separator. A thin belt, usually 3 to 20 mils in thickness, runs around this magnetic head pulley and conveys feed material to the magnetic field. When feed enters the magnetic field, the non-magnetic particles are discharged from the roll in their natural trajectory. The paramagnetic, or feebly magnetic, particles are attracted to the roll and are deflected out of the non-magnetic particle stream.

A splitter arrangement is used to segregate the two streams. This separator has a roll width up to 60 inches. The schematic diagram shown in Figure 7 illustrates the magnetic circuit arrangement for a typical rare-earth roll magnetic separator.

The rare-earth roll magnetic separator can effectively treat a wide variety of industrial minerals resulting in high purity products. In fact, it is the separator of choice for upgrading the raw materials for glass production such as silica, quartzite, feldspar, and fluorspar.

The roll separator is capable of processing 100 kg/hr/cm of roll width of 20 by 200 mesh material resulting in capacities up to 10 TPH on a 1.5-meter wide separator. Typically iron levels are reduced to 0.02 to 0.05 percent. This separator is also used in many specialty and value-added type applications, such as high-purity quartz, as well as many ceramic feedstocks such as alumina, kyanite, mullite, and zircon.

It is typically the case that a double-stage separation is required with the magnetic cleaning of industrial minerals. The non-magnetic product from the first stage separation is repassed to a second stage to further remove any residual iron-bearing components. Generally, between 60 and 75 percent of the magnetics removed in a two-stage separation are removed in the first separation stage. Table I provides a listing of various industrial applications currently using rare-earth roll separators.

With any type of rotating separator, the magnetic attractive force is opposed by centrifugal force. The primary variables affecting separation efficiency are the magnetic field strength, feed rate, linear speed of the separator surface, and particle mass. An effective separation requires an equilibrium among these variables. In assessing the feed rate, a balance must be struck between an economic feed rate, product specifications, and recovery. As the feed rate increases, the burden depth on the separator surface increases resulting in a loss of efficiency. The increase in burden depth can be offset by increasing the drum speed, resulting in an improved collection of magnetic particles. A practical limit exists, however, due to the centrifugal force acting on the particles. The centrifugal force exerted by the drum or roll surface is the critical factor affecting separation. Beyond the critical speed, the centrifugal force overcomes the magnetic attractive force and the separation efficiency deteriorates.

Particle size also affects separation efficiency. Coarse particles provide a high burden depth on the separator surface and respond with a relatively high magnetic attractive force. Coarse particles typically provide high unit capacities with high separation efficiencies. Fine particles demonstrate a lower magnetic attractive force. As a consequence, lower burden depths must be maintained resulting in lower process capacities.

Locked particles consisting of a magnetic portion and a non-magnetic portion are usually collected with a magnetic separator. In some applications the collection of these particles can be problematic. A locked particle reporting to a magnetic concentrate will in many cases account for any trace contamination, such as the case of silica in hematite or ilmenite concentrates.

intensity magnetic separator - an overview | sciencedirect topics

intensity magnetic separator - an overview | sciencedirect topics

The Jones wet high-intensity magnetic separator (WHIMS) was developed in 1956. The structure of the Jones separator is shown in Figure 9.6 and consists mainly of an iron-core electromagnet, a vertical shaft with two (or more) separating rings, a driving system, and feeding and product collection devices. Grooved plates made of magnetic conductive iron or stainless steel serve as a magnetic matrix to enhance the field gradient of the electromagnet. The plates are vertically arranged in plate boxes that are placed around the periphery of the rotors. When the Jones magnetic separator is operating, its vertical shaft drives the separating rings with the matrix plates rotating on a horizontal plane.

When a direct electric current passes through the energizing coils, a high magnetic field with a high gradient is established in the separating zone located in the electromagnetic system, with the focused magnetic field at the teeth top of the grooved plates reaching 0.82T, which is adjustable. The slurry is gravity fed onto the matrix at the leading edge of the magnetic field where the magnetic particles are captured on the teeth top of the grooved plates, while the nonmagnetic fraction passes through and is collected in a trough below the magnet. When the plate boxes reach the demagnetized zone half-way between the two magnetic poles, where the magnetic field changes its polarity, the magnetic field is essentially zero and the adhering magnetic particles are washed out with high-pressure water sprays.

In the past, cross-belt and rotating disc high-intensity magnetic separators were used for concentration of relatively coarse weakly magnetic particles such as wolframite and ilmenite, etc., under dry conditions. In the operation of these two magnetic separators, material is distributed onto the moving conveyor belt in a very thin layer, through a vibrating feeder. Such magnetic separators are not effective even inapplicable for the treatment of fine materials.

With the increasing reduction in liberation size of valuable components in magnetic ores, the conventional cross-belt and rotating disc high-intensity magnetic separators are almost replaced by gravity and flotation, particularly by high-gradient magnetic separators, as a result of its effectiveness to fine materials and high solids throughput. In the recent years, however, a wet permanent disc high-intensity magnetic separator as shown in left Figure7 seems applicable in recovering fine magnetic particles from tailings. In this disc separator, slurry is fed across a round tank, in which vertically rotating discs with permanent magnet blocks pick up fine magnetic particles, and they are brought up and scraped down by rotating scrapers, near the top of discs. Nonmagnetic particles are discharged at the bottom of tank.

And, a dry high-intensity roll magnetic separator as shown in right Figure7 is replacing the conventional roll magnetic separators and is used for concentration of relatively coarse magnetic particles. The design of such a roll magnetic separator is similar to that of the conventional roll magnetic separator, but it achieves a higher magnetic induction and its installation requires a much smaller occupation for space.

Ferromagnetic solids of high magnetic permeability can be separated in a Low Intensity Magnetic Separator (LIMS) using permanent magnets of less than 2 T (see Figure 1.56). A typical unit operates continuously and comprises a rotating non-magnetic drum inside which four to six stationary magnets are placed. The wet or dry feed contacts the outer periphery of the drum and the magnetically susceptible particles are picked up and discharged leaving the weakly or non-magnetic material to pass by largely unaffected. Alternative designs include the disc separator and the cross-belt separator where dry solids are conveyed towards a cross-belt which moves across a series of permanent magnets.

The efficiency of magnetic separation is generally improved by maximising both the intensity and the gradient of an applied non-uniform field. By doing so paramagnetic material of low magnetic permeability can be separated in a High Intensity Magnetic Separator (HIMS). Electromagnets, with intensities in excess of 2 T, are used in continuous equipment such as the Jones rotating disc separator to affect separations of dry feeds down to 75 m and wet feeds to finer sizes. Very weakly paramagnetic material cannot usually be separated satisfactorily with a HIMS, and a High Gradient Magnetic Separator (HGMS) must be used (Figure 1.56). In these units a matrix of fine stainless steel wool is placed between the poles of either electromagnetic or superconducting magnets, the latter generating magnetic intensities up to 15 T. Very high magnetic gradients are produced adjacent to the wool fibres and this allows for the separation of very fine particulates. Although the capital cost of HGMS can be relatively high compared with more conventional equipment, commercial units are readily available.

Iron ore processors may also employ magnetic separation for beneficiation of classifier output streams. Wet high-intensity magnetic separators (WHIMS) may be used to extract high-grade fine particles from gangue, due to the greater attraction of the former to the applied magnetic field.

In addition to beneficiating the intermediate middlings streams from the classifier, WHIMS may be used as scavenger units for classifier overflow. This enables particles of sufficient grade to be recovered that would otherwise be sacrificed to tails.

Testwork has been performed on iron ore samples from various locations to validate the use of magnetic separation following classification (Horn and Wellsted, 2011). A key example was material sourced from the Orissa state in northeastern India, with a summary of results shown in Table 10.2. The allmineral allflux and gaustec units were used to provided classification and magnetic separation, respectively.

The starting grade of the sample was a low 42% Fe. It also contained significant ultrafines with 58% passing 20m. This is reflected in the low yield of allflux coarse concentrate; however, a notable 16% (abs) increase in iron grade was eventually achieved. The gaustec results for the middlings and overflow streams demonstrate the ability to recover additional high-grade material. With the three concentrate streams combined, an impressive yield of almost 64% was achieved with minimal decline in iron grade.

Various classification schemes exist by which magnetic separators can be subdivided into categories. Review of these schemes can be found in monographs by Svoboda (1987, 2004). The most illustrative classification is according to the magnitude of the magnetic field and its gradient.

Low-intensity magnetic separators (LIMS). They are used primarily for manipulation of ferromagnetic materials or paramagnetic of high magnetic susceptibility and/or of large particle size. These separators can operate either in dry or wet modes. Suspended magnets, magnetic pulleys, and magnetic drums are examples of these separators. Operation of a dry drum separator is shown in Fig. 3.

High-intensity magnetic separators. They are used for treatment of weakly magnetic materials, coarse or fine, in wet or dry modes. Induced magnetic rolls (IMR), permanent magnet rolls and drums, magnetic filters, open-gradient (OGMS) and wet high-intensity magnetic separators (WHIMS) are examples of this class of separators.

Weakly paramagnetic minerals can only be effectively recovered using high-intensity (B-fields of 2T or greater) magnetic separators (Svoboda, 1994). Until the 1960s, high-intensity separation was confined solely to dry ore, having been used commercially since about 1908. This is no longer the case, as many new technologies have been developed to treat slurried feeds.

Induced roll magnetic (IRM) separators (Figure 13.19) are widely used to treat beach sands, wolframite and tin ores, glass sands, and phosphate rock. They have also been used to treat weakly magnetic iron ores, principally in Europe. The roll, onto which the ore is fed, is composed of phosphated steel laminates compressed together on a nonmagnetic stainless steel shaft. By using two sizes of laminations, differing slightly in outer diameter, the roll is given a serrated profile, which promotes the high field intensity and gradient required. Field strengths of up to 2.2T are attainable in the gap between feed pole and roll. Nonmagnetic particles are thrown off the roll into the tailings compartment, whereas magnetics are held, carried out of the influence of the field and deposited into the magnetics compartment. The gap between the feed pole and rotor is adjustable and is usually decreased from pole to pole (to create a higher effective magnetic field strength) to take off successively more weakly magnetic products.

The primary variables affecting separation using an IRM separator are the magnetic susceptibility of the mineral particles, the applied magnetic field intensity, the size of the particles, and the speed of the roll (Singh et al., 2013). The setting of the splitter plates cutting into the trajectory of the discharged material is also of importance.

In most cases, IRM separators have been replaced by the more recently developed (circa 1980) rare earth drum and roll separators, which are capable of field intensities of up to 0.7 and 2.1T, respectively (Norrgran and Marin, 1994). The advantages of rare earth roll separators over IRM separators include: lower operating costs due to decreased energy requirements, less weight leading to lower construction and installation costs, higher throughput, fewer required stages, and increased flexibility in roll configuration which allows for improved separation at various size ranges (Dobbins and Sherrell, 2010).

Dry high-intensity separation is largely restricted to ores containing little, if any, material finer than about 75m. The effectiveness of separation on such fine material is severely reduced by the effects of air currents, particleparticle adhesion, and particlerotor adhesion.

Without doubt, the greatest advance in the field of magnetic separation was the development of continuous WHIMSs (Lawver and Hopstock, 1974). These devices have reduced the minimum particle size for efficient magnetic separation compared to dry high-intensity methods. In some flowsheets, expensive drying operations, necessary prior to a dry separation, can be eliminated by using an entirely wet concentration system.

Perhaps the most well-known WHIMS machine is the Jones separator, the design principle of which is utilized in many other types of wet separators found today. The machine has a strong main frame (Figure 13.20(a)) made of structural steel. The magnet yokes are welded to this frame, with the electromagnetic coils enclosed in air-cooled cases. The separation takes place in the plate boxes, which are on the periphery of the one or two rotors attached to the central roller shaft and carried into and out of the magnetic field in a carousel (Figure 13.20(b)). The feed, which is thoroughly mixed slurry, flows through the plate boxes via fitted pipes and launders into the plate boxes (Figure 13.21), which are grooved to concentrate the magnetic field at the tip of the ridges. Feeding is continuous due to the rotation of the plate boxes on the rotors and the feed points are at the leading edges of the magnetic fields (Figure 13.20(b)). Each rotor has two feed points diametrically opposed to one another.

The weakly magnetic particles are held by the plates, whereas the remaining nonmagnetic particle slurry passes through the plate boxes and is collected in a launder. Before leaving the field any entrained nonmagnetics are washed out by low-pressure water and are collected as a middlings product.

When the plate boxes reach a point midway between the two magnetic poles, where the magnetic field is essentially zero, the magnetic particles are washed out using high-pressure scour water sprays operating at up to 5bar. Field intensities of over 2T can be produced in these machines, although the applied magnetic field strength should be carefully selected depending on the application (see Section 13.4.2). The production of a 1.5T field requires electric power consumption in the coils of 16kW per pole.

There are currently two types of WHIMS machines, one that uses electromagnetic coils to generate the required field strength, the other that employs rare earth permanent magnets. They are used in different applications; the weaker magnetic field strength produced by rare earth permanent magnets may be insufficient to concentrate some weakly paramagnetic minerals. The variables to consider before installing a traditional horizontal carousel WHIMS include: the feed characteristics (slurry density, feed rate, particle size, magnetic susceptibility of the target magnetic mineral), the product requirements (volume of solids to be removed, required grade of products), and the cost of power (Eriez, 2008). From these considerations the design and operation of the separator can be tailored by changing the following: the magnetic field intensity and/or configuration, the speed of the carousel, the setting of the middling splitter, the pressure/volume of wash water, and the type of matrix material (Eriez, 2008). The selection of matrix type has a direct impact on the magnetic field gradient present in the separation chamber. As explained in Section 13.4.2, increasing magnetic field can in some applications actually cause decreased performance of the magnetic separation step and it is for this reason that improvements in the separation of paramagnetic materials focus largely on achieving a high magnetic field gradient. The Eriez model SSS-I WHIMS employs the basic principles of WHIMS with improvements in the matrix material (to generate a high field gradient) as well as the slurry feeding and washing steps (to improve separation efficiency) (Eriez and Gzrinm, 2014). While this separator is referred to as a WHIMS, it is in fact more similar to the SLon VPHGMS mentioned in Sections 13.4.1 and 13.5.3. Further discussion on high-gradient magnetic separation (HGMS) may be found in Section 13.5.3.

Wet high-intensity magnetic separation has its greatest use in the concentration of low-grade iron ores containing hematite, where they are an alternative to flotation or gravity methods. The decision to select magnetic separation for the concentration of hematite from iron ore must balance the relative ease with which hematite may be concentrated in such a separator against the high capital cost of such separators. It has been shown by White (1978) that the capital cost of flotation equipment for concentrating weakly magnetic ore is about 20% that of a Jones separator installation, although flotation operating costs are about three times higher (and may be even higher if water treatment is required). Total cost depends on terms for capital depreciation; over 10 years or longer the high-intensity magnetic separator may be more attractive than flotation.

In addition to recovery of hematite (and other iron oxides such as goethite), wet high-intensity separators are now in operation for a wide range of duties, including removal of magnetic impurities from cassiterite concentrates, removal of fine magnetic material from asbestos, removal of iron oxides and ferrosilicate minerals from industrial minerals such as quartz and clay, concentration of ilmenite, wolframite, and chromite, removal of magnetic impurities from scheelite concentrates, purification of talc, the recovery of non-sulfide molybdenum-bearing minerals from flotation tailings, and the removal of Fe-oxides and FeTi-oxides from zircon and rutile in heavy mineral beach sands (Corrans and Svoboda, 1985; Eriez, 2008). In the PGM-bearing Merensky Reef (South Africa), WHIMS has been used to remove much of the strongly paramagnetic orthopyroxene gangue from the PGM-containing chromite (Corrans and Svoboda, 1985). WHIMS has also been successfully used for the recovery of gold and uranium from cyanidation residues in South Africa (Corrans, 1984). Magnetic separation can be used to recover some of the free gold, and much of the silicate-locked gold, due to the presence of iron impurities and coatings. In the case of uranium leaching, small amounts of iron (from milling) may act as reducing agents and negatively affect the oxidation of U4+ to U6+; treatment via WHIMS can reduce the consumption of oxidizing agents by removing a large portion of this iron prior to leaching (Corrans and Svoboda, 1985).

At the CliffsWabush iron ore mine in Labrador, Canada (Figure 13.22), the cyclone overflow from the tailings of a rougher spiral bank is sent to a magnetic scavenger circuit utilizing both low-intensity drum separation and WHIMS. This circuit employs the low-intensity (0.07T) drum separators to remove fine magnetite particles lost during the spiral gravity concentration step, followed by a WHIMS step using 100th1 Jones separators which are operated at field strengths of 1T to concentrate fine hematite. Cleaning of only the gravity tailings by magnetic separation is preferred, as relatively small amounts of magnetic concentrate have to be handled, the bulk of the material being essentially unaffected by the magnetic field. The concentrate produced from this magnetic scavenging step is eventually recombined with the spiral concentrate before feeding to the pelletizing plant (Damjanovi and Goode, 2000).

The paramagnetic properties of some sulfide minerals, such as chalcopyrite and marmatite (high Fe form of sphalerite), have been exploited by applying wet high-intensity magnetic separation to augment differential flotation processes (Tawil and Morales, 1985). Testwork showed that a Chilean copper concentrate could be upgraded from 23.8% to 30.2% Cu, at 87% recovery.

By creating an environment comprising a magnetic force (Fm), a gravitational force (Fg), and a drag force (Fd), magnetic particles can be separated from nonmagnetic particles by MS. Magnetic separators exploit the differences in magnetic properties between particles. All materials are affected in some way when placed in a magnetic field.

where V: particle volume (determined by process); X: magnetic susceptibility; H: magnetic field (created by the magnet system design) in mT; GradH: magnetic field gradient (created by the magnet system design) in mT (mT: milli Tesla, 1kGauss=100mT=0.1T). Materials are classified into two broad groups according to whether they are attracted to or repelled by a magnet. Non/diamagnetics are repelled from and ferro/paramagnetics are attracted to magnets. Ferromagnetic substances are strongly magnetic and have a large and positive magnetism. Paramagnetic substances are weakly magnetic and have a small and positive magnetism. In diamagnetic materials, the magnetic field is opposite to the applied field. Magnetisms are small and negative. Nonmagnetic material has zero magnetism. Ferromagnetism is the basic mechanism by which certain materials (such as Fe) form permanent magnets, or are attracted to magnets. Ferromagnetic materials can be separated by low-intensity magnetic separators (LIMSs) at less than 2T magnetic intensity. Paramagnetic materials can be separated by dry or wet high-intensity magnetic separators (HIMSs) at 1020T magnetic intensities. Diamagnetic materials create an induced magnetic field in the direction opposite to an externally applied magnetic field, and are repelled by the applied magnetic field. Nonmagnetic substances have little reaction to magnetic fields and show net zero magnetic moment due to random alignment of the magnetic field of individual atoms. Induced roll separators, with field intensities up to 2.2T, and Permroll separators can be used for coarse and dry materials (>75m). Fine materials reduce the separation efficiency due to particlerotor and particleparticle agglomeration. For wet HIMS, Gill and Jones separators are used at a maximum field of 1.4 and 1.5T, at 150m size [80]. Dry LIMSs are used for coarse and strongly magnetic substances. The magnetic field gradient in the separation zone (approximately 50mm from the drum surface) ranges between 0.1 and 0.3T. Below 0.5cm, dry separation tends to be replaced by wet LIMS. Concurrent and countercurrent drum separators have a nonmagnetic drum containing three to six stationary magnets of alternating polarity. Separation depends on the pick up principles. Magnetic particles are lifted by magnets and pinned to the drum and then conveyed out of the field. Field intensities up to 0.7T at the pole surfaces can be used. Coarse particles up to 0.56mm can be tolerated. The drum diameter is 1200mm and the length 6003600mm. Concurrent operation is normally used as a primary separation (cobber) for large capacities and coarse feeds. Countercurrent operation is used as a rougher and finisher for multistage concentration.

Moderately magnetic dry substances on a conveyor/belt can be collected by overhead, cross-belt, or disc separators using magnetic field intensities between 0.8 and 1.5T. Very weakly paramagnetic substances can only be removed if field intensities are greater than 2.0T. At 5200mm size fractions, overhead permanent magnets are used to remove ferromagnetics. Magnetic separators, such as dry low-intensity drum types, are widely used for the recovery of ferromagnetic materials from nonferrous metals (Al and Cu) and other nonmagnetic materials (plastic and glass) at 5mm in size. The magnetic field may be generated by permanent magnets or electromagnets. There have been many advances in the design and operation of HIMS due mainly to the introduction of rare-earth alloy permanent magnets with the capability of providing high field strengths and gradients. There are, however, some problems associated with this method. One of the major issues is agglomeration of the particles, which results in the attraction of some nonferrous fractions attached to the ferrous fractions [81]. This leads to low efficiency of this method. Through the process of MS, it is possible to obtain two fractions: the magnetic fraction, which includes Fe, steel, Ni, etc., and the nonmagnetic fraction, which includes Cu [82]. For WEEE, MS systems utilize ferrite, rear-earth or electromagnets, with high-intensity electromagnet systems being used extensively. Veit et al. [81] employed a magnetic field of 0.60.65T to separate the ferromagnetic elements, such as Fe and Ni. The chemical concentration of the magnetic fraction was 43% Fe and 15.2% Ni on average. However, there was a considerable amount of Cu impurity in the magnetic fraction as well. Yoo et al. [83] used a two-stage MS for milled PCBs. The milled PCBs of particle size >5.0mm and the heavy fraction were separated from the <5.0mm PCB particles by gravity separation. In the first stage, a low magnetic field of 0.07T was applied, which led to the separation of 83% of Ni and Fe in the magnetic fraction and 92% of Cu in the nonmagnetic fraction. The second MS stage was conducted at 0.3T, which resulted in a reduction in the grade of the NiFe concentrate and an increase in the Cu concentrate grade.

Magnetic separations depend on a particle's magnetic susceptibility in a magnetic field. Based on magnetic susceptibility, materials can be one of two types: paramagnetic (those attracted by a magnetic field) and diamagnetic (those repelled by a magnetic field). It is usual to consider strongly magnetic materials as being in a separate category called ferromagnetic.

Magnetic separators are divided into low-intensity and high-intensity separators, the former being used for ferromagnetic minerals (and some paramagnetic minerals of high magnetic susceptibility) and the latter used for paramagnetic minerals of (lower) magnetic susceptibility. (In effect, a third category of separator exists: that used for removing tramp iron from process streams.) High- and low-intensity separation can be carried out wet or dry: tramp separators operate only on dry streams.

The most common separator, the wet low-intensity, consists of a revolving drum partly submerged in a suspension. An arc of magnets within the drum pulls the magnetically susceptible material against the drum, lifting it out of the slurry and over a discharge weir. Permanent ceramic magnets are now typical in these units.

Dry high-intensity separators use powerful electromagnets that induce a magnetic field in a comparatively small diametered roll, against which the magnetically susceptible particles are held until they pass a suitable discharge point.

where r=radial distance; V=particle volume; p, m=magnetic susceptibility of particle and medium, respectively. This shows that the force depends on both the strength and the gradient of the magnetic field. The latter component is especially significant in WHIMS, where high curvature ferromagnetic surfaces (e.g., wire, balls) are used to produce very high gradients.

An indication of the lower limits of particle size that can be treated in a magnetic separator can be obtained by balancing the magnetic force against the likely opposing forces (usually fluid drag and gravitation), but with the addition of centrifugal forces in drum separators. Mechanical considerations usually determine the upper particle size limit.

In principle, separability and performance curves can be used to predict separator performance. However, difficulties arise in determining properties independent of experimental conditions, so the approach has not been widely used.

Two simple models of wet low-intensity drum separators have been described. One uses a probability concept while the other empirically correlates losses of magnetic material near the drum take-up and discharge with feed rate and drum speed.

Nanomaterials have also been prepared by ball milling the parent materials. High-energy ball milling not only prepares nanoparticles quickly but it also uses little chemicals as compared to the sol-gel methods. However, it has low energy efficiency because it dissipate a lot of energy in form of heat.

Planetary ball mill was used to synthesize iron nanoparticles. The synthesized nanoparticles were subjected to the characterization studies by X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques using a SIEMENS-D5000 diffractometer and Hitachi S-4800. For the synthesis of iron nanoparticles, commercial iron powder having particles size of 10m was used. The iron powder was subjected to planetary ball milling for various period of time. The optimum time period for the synthesis of nanoparticles was observed to be 10h because after that time period, chances of contamination inclined and the particles size became almost constant so the powder was ball milled for 10h to synthesize nanoparticles [11]. Fig. 12 shows the SEM image of the iron nanoparticles.

The next step involved the crushing of the pyrite particle by high-energy ball milling at a rate of 320rpm for various periods of time, that is, 2, 4, and 6h which ultimately resulted in the formation of pyrite nanoparticles.

The process of ball milling was employed under controlled parameters about 298K temperature and 760 torr pressure. Stainless steel made ball and bowl were utilized for the process. In the process, ball:pyrite ratio of 10:1 was selected and at varying time periods of 2h, the samples were removed. The method was named as interrupted milling. The synthesized nanoparticles were washed with ethyl alcohol thrice to eradicate contamination. The nanoparticles were dried in an oven for 4h at 50C [12,13]. Fig. 13 shows the SEM image of the nanoparticles.

Jaw and cone crushing was performed on the martite ore until they became within the size range of 0.52cm. The sample was further crushed by ball and rod milling until the particles size was reduced to 3050lm. Ultimately, the particles were subjected to interrupt high-energy planetary ball milling for different time durations, that is, 2, 4, and 6h to get the nanoparticles of martite. The ball:martite ratio of 10:1 was selected and a rotation speed of 320rpm was chosen [14]. Fig. 14 shows the SEM images of martite nanoparticles.

Caron onions preparation was carried out by employing graphite carbon having high purity. A reported method was used to synthesize AlCuFe quasicrystal. The synthesis of alloy was carried out under ambient environment. The percentage composition of alloy material was set to be Al64Cu24Fe12. The alloy was solidified under ambient conditions. Annealing of the synthesized alloy was performed under argon environment at 700C for 96h. The synthesized composite material is brittle and inclines to be fractured when subjected to ball milling process. In this typical procedure, the reaction of moisture with aluminum in the composite results in the formation of aluminum oxide film over the surface but simultaneously, the release of atomic hydrogen incites cleavage fracture of the composite material and occasionally it was observed that the whole material got converted into fine powder after a few days. Graphite and the composite materials were mixed in 1:1 ratio and then high-energy ball milling was performed on the mixture under ambient environment. Ball milling was performed for various time periods of 1.5, 3, 6, and 10h. The ball milling media was composed of hard steel vials and balls having a ratio of powder:ball to be 1:7. The mixture was grinded using a grinding medium size of 12.7mm. The synthesized nanocomposites were characterized using various techniques including XRD, Raman spectroscopy, TEM, and the size of the nanoparticles was observed to be within 412nm [15]. Fig. 15 shows the TEM image of the nanoparticles.

A modified ball milling device having assistance of ultrasonication was employed in the synthesis of zinc oxide nanoparticles. The synthesis of nanoparticles involved analytical grade zinc acetate dihydrated salt as the zinc precursor material. Ball milling medium of stainless steel with diameter of balls of 2mm was employed. The ratio of milling balls to the zinc precursor was set to be 1:100. The frequency and power of the microwave were 2450MHz and 0.8kW, respectively. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, XRD, TEM, fluorescence measurements, and electroconductivity detections. The average size of the nanoparticles was observed to be 15nm [16]. Fig. 16 shows the TEM image of the nanoparticles.

The synthesis of Na3MnCO3PO4 nanoparticles involved dry ball milling of the precursors. The precursors of the nanoparticles were Mn(NO3)2.4H2O (A), Na2HPO4.2H2O (B), and Na2CO3.H2O (C). The concentrations optima were evaluated by doing extensive preliminary experiments and the amount of 8mmol of A and B and 12mmol of C. Planetary ball milling of the mixture was performed by keeping a ball: mixture ratio of 30:1. The mixture was ball milled for different time periods, that is, 15, 30, 60, and 180min at a rate of 300rpm. The synthesized billed nanoparticles were then added into deionized distilled water under continuous stirring so that the nanoparticles can be separated from impurities. The nanoparticles were separated and characterized by various techniques [17]. SEM image of the nanoparticles are provided in Fig. 17.

wet high intensity magnetic separator, dry drum magnetic separator, magnetic separator suppliers - longi magnet co., ltd

wet high intensity magnetic separator, dry drum magnetic separator, magnetic separator suppliers - longi magnet co., ltd

Thailand has plenty of river sand resource which is high quality of silica sand, upto 99.6% SiO2. In the northest, the river sand had been proved that the high iron contaimination Fe2O3 upto 0.165% can be lowered down to 0.065% by high gradient magnetic separation technology.

Recycling aluminum refers to the scrap aluminum as the main raw material to obtain aluminum alloy after pretreatment, smelting, refining, and ingot casting. Aluminum has features of strong corrosion resistance, low loss during use, and will not lose its basic characteristics after repeated recycling for many times, and has extremely high recycling value.

Wet magnetic separation is widely used in the purification of quartz sand, which has the characteristics of significant iron removal effect, large handling capacity and no dust pollution. In the primary stage of quartz sand purification, wet magnetic separation is generally considered to be an excellent way of iron removal purification, but in the stage of high-purity quartz cleaning, the conventional wet magnetic separation purification effect is not obvious, the reasons can be summarized as three points.

LONGi magentic separator bring hot sales, recently,RCBD flame-proof electromagnetic separator in addition with excellent iron removel performance, excellent heat dissipation efficiency and perfect service guarantee ability successfully won the bid for the domestic leading coal enterprises, a total of 39 sets, lay a good foundation for the market follow-up development.

eriez - dry high intensity magnetic separation

eriez - dry high intensity magnetic separation

With the ever increasing demand for high-purity feedstocks used in manufacturing, Eriez offers its Dry High IntensityRare Earth Roll Magnetic Separators. These provide maximum efficiency in the separation of weak magnetic particles for product purification applications. Eriez applied sophisticated finite element analysis in magnetic circuit design to produce an energy-free separator capable of generating the exceptionally high field-strengths needed to remove unwanted fine iron contaminants.

Magnetic cleaning has been applied to the most basic industry foundations such as industrial minerals, metals recycling, glass batch and cullet, abrasives and refractories, chemicals, pharmaceuticals, and plastics.

magnetic separators

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.

the history of the development of the magnetic separators - minerallurgy

the history of the development of the magnetic separators - minerallurgy

The application of magnetic separation techniques have been largely developed and applied for specific purposes for example, in mineral beneficiation and recovery as a means of eradicating pollution and in recycling applications (Dahe, 2004).

Since it is difficult and costly to treat ultra-fines and slimes by conventional methods such as gravity and flotation processes, it was necessary to continue to investigate the feasibility of new magnetic separation techniques (Arol and Aydogan, 2004). This is especially so for complex mineral compositions as the iron impurities are often locked within non-metallic ores and minerals, such as kaolin, feldspar and quartz which reduce the commercial values of these ores.

Magnetic separation is also favoured due to its simple design and operation, renewability and its low cost (Newns and Pascoe, 2002; Jiao et ai., 2007; Chen et ai., 2012). It is thus to review its development history.

Numerous magnetic separation techniques have been developed over the years to meet the requirements of the mineral processing industry, with the available equipment having its own benefits and limitations.

The selection of a separator is based on the susceptibility difference of particles within a material, the magnitude of the magnetic field generated within the separator, the desired product quality, material throughput and design configuration of the equipment for beneficiating different ores.

The fact that materials experience different forces in the presence of magnetic field gradients, is responsible for the physical separation of the components and mixtures under an applied external field (Svoboda and Fujita, 2003; Joseph et al., 2010). For example, iron being a paramagnetic material will be separated from its associated diamagnetic gangues phases (Chakravorty, 1989; Dahe, 1998; Zheng and Dahe, 2003; Dahe, 2004; Dobbins et al., 2009; Angadi et al., 2012).

Magnetic separators are grouped into either low intensity or high intensity, and can be either dry or wet operational types (Svoboda, 1987; Dobbins et al., 2007 and Joseph et al., 2010, Chakravorty, 1989).

In general, the view within industry is to reduce operational costs thus the wet process is more favourable in the early stages of the flow-sheet as a means for reducing both the drying and storage costs (Svoboda 1987; Chakravorty, 1989; Dahe, 1998; Zheng and Dahe, 2003; Svoboda 2003; Dahe, 2004; Dobbins et ai., 2007; Dobbins and Sherrell, 2009, Angadi et al., 2012).

The dry magnetic separators are used for beneficiating coarse and highly susceptible mineral particles. They are also used for removing tramp iron and magnetic impurities, concentrating highly susceptible magnetic values and in a cleaning stage for a variety of minerals (Svoboda, 1987; Svoboda and Fujita, 2003; Dobbins et al., 2009; Chen et ai., 2012; Angadi et al., 2012).

The different types of dry separators include the high intensity roller and drum type magnetic separators. The roIler type separators are of magnitude between 5% and 10% higher in magnetic field, they offer better separation efficiencies at low costs per ton compared to their drum type counterpart (Arvidson and Henderson, 1996). The commercial drum separators can treat up to 8 mm size fraction at feed rates of over 150 tlhr (Chakravorty, 1989).

The main operational limitation experienced by the dry magnetic separators is that the feeds are commonly wet ground and have to be completely dry prior to processing which means additional operational cost. In this case, separation efficiency at fine sizes to reduced and requires high magnetic field intensity and monolayer feeding for effective separation.

The magnets as the source of the magnetic field are best operated at ambient temperatures due to their sensitivity to high temperatures (Arvidson and Henderson, 1996). At elevated temperatures of 120C to 150 C, which is normally experienced the dry approach, the magnets tend to lose their magnetism and a cooling system may be required in order to prevent overheating and to maintain an efficient separation. This is also an added operational cost (Arvidson and Henderson, 1996; Dobbins et al., 2009).

The generation of dust during dry processing is also a major setback meaning that some efforts for dust pollution control will be required. Finally there is the need for sufficiently high magnetic field to achieve separation (Dobbins et al., 2009).

Cross-belt magnetic separators are used in the beneficiation of moderate magnetically susceptible ores, and they consist of two or more poles of electromagnets as the source of the magnetic field. A continuous cross-belt allows for the magnetic particles to be attached and collected in a separate container. While the conveyor pulls towards its end pulley, the non-magnetic particles are discharged and also collected in a separate container.

For efficient separation, the feed needs to be sized into narrow size ranges and the height of the poles should be adjusted to 2.5 times the coarsest size particles ranging between 75 !lm and 4 mm. The main benefit of this unit is that a single pass of the feed through the separator is sufficient to recover almost all the magnetic particles compared to other dry separators which require several passes (Chakravorty, 1989).

Permanent Roll Magnet (Permroll) uses a Samarium-Cobalt (Sm-Co) and Neodymium-Iron-Boron (Nb-Fe-B) permanent magnet as the source for generating a magnetic field of up to 1.6 Telsa (T), which facilitates separation of economic values from gangue minerals.

The benefit of this equipment is their capability to treat large particle sizes of material up to 25 mm. Energy consumption the by Permroll is low at 10% of the electrical energy required by Induced Roll Magnets (Svoboda 1987; Svoboda and Fujita, 2003).

The limitation of these separators is their low throughputs capacity, the high cost of replacing worn magnets and belts, along with the speed of the belt determining the separation efficiency of the system. The use of a belt affects separation by reducing the magnetic field, magnetic intensity and electrostatic interactions generated by the fine particles attached to the belt (Svoboda, 1987).

Rare Earth Roller (RER) separators are low capacity units when compared to Rare Earth Drum (RED) separators. However they are high in capacity when compared to Induced Roll Magnetic (IRM) separators. They are mostly used in the beneficiation of mineral sands, in multi process stages, for example in the final cleaning and scavenging stages to improve the quality of the product and increase recovery (Dobbins et al., 2007).

They use thin and open designed belts with the aim of minimising the interference with the magnetic force. The open design has limitations in that, fine particles are easily blown off and build up on the belt, thus reducing the belt life and increasing the maintenance cost. In another instant, as the material travels along the belt, there is a possibility of the particles rubbing against each other, causing the particles to be magnetised and attached to the belt.

Separation efficiency can be compromised and can only increase by ensuring that the feed is in a monolayer to prevent compaction which can lead to non-magnetic particles being trapped within the feed bed and fine particle reporting to the bottom of the feed bed (Dobbins and Sherrel, 2009).

Its limitation is that it is generally of low capacity due to the narrow allowable gap size situated between the feed pole and the roll, and also limited to a particle size range of 100 11m to 2 mm (Chakravorty, 1989). Treating particles sizes >2 mm on the IRM will require a much bigger gap size thus reducing magnetic field strength.

The feed material is fed at the top of the equipment in a controlled thin layer by means of a vibrating feeder. The gap between the feed pole and the roll together with the splitter are adjustable and are of great importance for an efficient separation.

In order to achieve good and effective results, the material to be treated must be dry, free-flowing and within the size range of 100 11m to 2 mm. The gap size should be adjusted to approximately 2.5 times the average particle size as with the cross-belt separators (Chakravorty, 1989). With the many operational limitations of the IRM, it is increasingly replaced by rare earth rollers (RER).

A cross-belt magnetic separator was used by AI-Wakeel and EI-Rahman, 2006 in beneficiating iron ore from Egypt. The ore treated was at +53 /Jm size fraction and a reported head grade of 34.30% Fe. An upgrade to 49.85% Fe and a low Fe recovery were obtained. The author reported that a finer grind is required to liberate the locked iron ore mineral in order to meet the commercial grade product specification.

The application of a Permroll separator was used by Alp, 2008 in beneficiating colemanite tailings at +75 /Jm size fraction and a head grade of 31.52% B203 An upgrade to 43.74% B203, and recovery of95.06% with a mass reduction of 31.47% was obtained using only magnetic separation. This was compared to a previous investigation conducted on the same tailings by Ozdag and Bozkurt (1987) where a better B203 recovery of 97.7% was achieved but at a lower grade using a multi stage process consisting of attrition scrubbing/washing.

Dobbins et al. (2007) used an Outotec RED magnetic separator to recover mineral sands and to validate previous results obtained of 70% ilmenite from aeolian tailings. The results showed that a good quality product at 66% ilmenite was produced at the acceptable commercial specification.

In order to improve both grade and recovery of the low magnetic susceptible material, Bhatti et al. (2009) conducted investigations on a low grade chromium ore from Balochistan in Pakistan with a head grade of 28% Cr203. The investigations were carried out under different test parameters including the magnetic field intensity, particle size and feed rate. The results showed that a magnetic field intensity of 4000 Gauss was the optimum and any increase above this point resulted in a reduced product grade. It was noted that, as the particle size was reduced and the feeding rate increased the efficiency of separation was reduced. However, a product grade of 40% Cr203 and 90% Cr203 recovery was obtained.

The industrial use of dry high intensity magnetic separators such as the cross belt, Permroll, RER, RED and fluidised bed are sharply declining due to the difficulties experienced in their operations (Svoboda, 1987; Svoboda and Fujita, 2003; Dobbins et al., 2007 Dobbins et aI., 2009; Chakravorty, 1989). Fine materials are difficult to beneficiate as the result of mechanical entrapment of non-magnetic particles, thus causing inefficient separation, high maintenance and replacement costs (Svoboda, 1987; Chen et al., 2012).

Researchers have noted that better liberation of coal through grinding will improve the efficiency of separation. The difference in the coal magnetic properties has led to various research programmes being conducted in order to increase the magnetic susceptibility mainly for those rich in pyrite prior to magnetic separation.

Microwave energy has been used in treating coal to facilitate the change of FeS2 into a more magnetically susceptible FeS (Zavitsanos et al., 1978; Zavitsanos et al., 1982; Butcher and Rowson 1995; Cicek et ai., 1996). The authors used flash pyrolysis prior to the magnetic separation. The results showed that pyrite was converted into iron sulphides based on the temperature of the pyrolysis test. In addition, the result showed that after beneficiation of the -100 !lm particle size, a reduction of 35% sulphur content was obtained by flash pyrolysis and magnetic separation.

A study on sulphur and ash removal from low-rank lignite coal by low temperature carbonization and dry magnetic separation was investigated by Celik and Yildirim (2000). The result was successful but there was a serious concern regarding air pollution by sulphur during the low-temperature carbonization. There appears to be an improvement in the magnetic susceptibility potential of coal for High Gradient Magnetic Separator (HGMS) beneficiation technique, at least for pyrite removal, but it was found that much work still has to be done to improve this process and to evaluate the technical and economic feasibility of the whole process for coal cleaning.

Wet magnetic separators were introduced as a result of the many limitations faced by dry magnetic separators. The inability of the dry separators to beneficiate high magnetic susceptible minerals such as magnetite more efficiently, at high throughput rates for a very fine size particle, and to separate minerals under high magnetic field intensity, was responsible for the design of the currently available wet high intensity magnetic separators. These separators have shown capabilities of treating various ore types and fine fractions less than 1 mm, for either strong or weakly magnetic minerals.

The benefits of wet separators are that they are robust with high capacity, ease of operation and in addition, they also use an electromagnet as a source for generating the magnetic field or matrixes such as groove plates or filaments for generating disturbance within the magnetic field commonly referred to as high intensity (Corrans et al., 1979; Svoboda, 1987; Chakravorty, 1989; Hearn and Dobbins, 2007).

All WHIMS units operate under the same principles but, they differ in the magnitude of the magnetic field, the type of matrix and in some instances the arrangement of the rotating rotor (Chakravorty, 1989).

The application of a matrix as the point for collecting magnetic particles in WHIMS made a huge impact and improved the magnetic separation process of materials that were previously considered too fine or to have too low magnetic susceptibility. These traditional types of separators came about as a result of Joness idea for a magnetised matrix in the form of steel wool and Frantzs idea of a high magnetic field with the aim of increasing the localised magnetic force (Svoboda and Fujita, 2003).

The simple design is composed of a horizontal rotor with the matrix packed in a chamber and placed between the poles of electromagnets to generate the localised magnetic field gradient. The feed in slurry form is fed onto the matrix, the magnetic particles are collected and attach onto the matrix and the non-magnetic particles pass through the matrix and into a separate container. When the current is switched off, the magnetic particles are released from the matrix and flushed with water to ensure that all particles are collected into a separate container. Based on this idea, many advanced designs came into being (Chakravorty, 1989).

Although traditional WHIMS is relatively easy to operate, for effective separation it is important to use a suitable matrix for the feed under investigation, and an appropriate feed rate, particle size, magnetic field intensity, and location of the feed and wash water.

The matrixes in high intensity separators generate a strong localised magnetic field as high as 104 %, with the selection of the matrix based on the characteristics of the slurry being treated. There are many types of matrixes available; steel wool, groove plates or steel balls or rods to capture the weakly magnetic particles (Svoboda, 1981; Zeng and Dahe, 2003). They serve as the collecting points for magnetically susceptible material and also as a region where the highest magnetic field is experienced, while the gaps facilitate a passage for the removal of the non-magnetic particles (Hearn and Dobbins, 2007). It is also observed that effective separations are achieved at particle sizes> 1 00 ~m (Corrans et ai., 1979 Dobbins and Hearn, 2007).

The many limitations of the traditional WHIMS have resulted in low separation efficiency of very fine size fractions as a result of entrainment, clogging of the matrix and low throughputs, compared to the latest technology of high intensity magnetic separators (Dobbins and Hearn, 2007; Das et ai., 2010). Poor selectivity during separation and the clogging of the matrix has resulted in diminished industrial use.

These limitations drove the development of a vertical magnetic separator (VMS) which was designed in the Czech Republic and later became the foundation for developing the SLon VPHGMS (Zeng and Dahe, 2003; Hearn and Dobbins, 2007).

The improvements on the VMS included a vertical rotor instead of the horizontal one, reverse water flush to keep the matrix clean and a bottom feeder with a mechanism for controlling the velocity of the slurry. This design configuration made it possible to treat finer particles which were considered untreatable or too fine for processing under gravity techniques (Dobbins, 2007).

China made further improvements on the VMS to achieve better separation efficiencies by introducing the SLon VPHGMS. It has a similar design to the VMS but it has an additional feature, a pulsating mechanism that agitates the slurry and keeps particles in suspension to assist in improving the product quality and recovery (Dahe et af., 1998; Zeng and Dahe, 2003; Dahe, 2004).

Another set of separators are the superconducting magnetic separators. These are considered to be of highly advanced technologies which are able to generate high magnetic field strengths of up to 2T. With the initiatives put forward by both Jones and Frantz, many high intensity magnetic separators have been designed and commercialised (Svoboda, 1987, 2003).

Extensive work has been conducted using different wet high intensity magnetic separators. The early successful application of the WHIMS separator was on kaolin purification, iron-ore and beach sand beneficiation (Svoboda and Fujita, 2003). Investigations were conducted for the removal of gangue phases from a low grade iron ore using WHIMS by many researchers. For example, Angadi et af. (2012); Arol, (2004); Jamieson et af. (2006); Dobbins et af. (2007); Das et af. (2010) and Padmanabhan and Sreenivas, (2011) concentrated different ores from their gangue minerals and attained grades suitable for commercial applications. Iron ore with suitable grades for blast furnace application was also recovered from a low grade ore by AI-Wakeel and EI-Rahman, (2006).

The inferior separation efficiency experienced by the high intensity magnetic separator when processing fines was investigated by Chen et af. (2011). These investigations were in contrast to those reported on the influence of key variables such as magnetic field intensity, matrix type and shape and slurry velocity on the performance of the high intensity magnetic separator (Li and Watson, 1995; Newns and Pascoe, 2002). The results showed a higher recovery for finer magnetic particles due to the smaller magnetic leakage factor, higher magnetic induction and no direct contact of feed flow on the magnetic deposits on the vertical magnetic matrix elements of the newly designed separator.

With continuing research on improving the separation efficiencies of the existing high intensity separators, a new separator called the superconducting magnetic separator was used by Li et al. (2011) to beneficiate extremely fine red mud particles at <100 /-lm. The results showed that the ability to separate fine weakly magnetic minerals, and the capability to generate a very high magnitude of magnetic field makes this separator a potentially superior separator to other units.

Investigations into the optimisation of a high intensity magnetic separator to beneficiate scandium (Sc) by removing the Fe contaminant were conducted by Likun and Yun, (2010). The head grade for the material treated was reported to be 48.90 glt Sc, 11.45% Fe. Mineralogical analysis showed that scandium was the major mineral and biotite, tremolite, ilmenite, and tantalite were the dominant gangue mineral phases present.

Ilmenite was separated from the other gangue minerals by using its high specific gravity, and it was removed by a gravity technique. A -37 /-lm sized fraction feed was used and the results showed that a magnetic product containing 62.34% Fe and Sc grade of8.l4 glt with a loss of 0.97% Sc was achievable, and a non-magnetic Sc product with an upgrade to 51.40% Sc was also attained.

Pilot scale investigations were carried out on the same size fraction using the same material and flow-sheet, along with the same low magnetic separator followed by high intensity magnetic separators. The results showed that 315 glt Sc at 78% recovery was achievable and that other rare earth elements which have low magnetic susceptibility could also be concentrated through high intensity magnetic separation.

Fine and super fine bauxite was treated by magnetic separation with the potential to evaluate the occurrence of iron bearing minerals and to verify the possibilities of minimising the iron content of the bauxite by Kahn et al. (2003). The results showed that for bauxite fine and superfine products, Fe203 grades of 8% Fe203 and 6% Fe203, with 53 to 55% of total Ah03 were obtained from fine and superfine bauxite feed, with 19.50% Fe203 and 18.40% Fe203 grades, respectively. The author concluded that without further comminution, potential aluminum recoveries of about 90% by gravity concentration or magnetic separation could be attained.

The separation of gangue from a low grade iron ore using traditional WHIMS (Gaustec G-340) with a capacity of 200 tlhr was conducted by Angadi et af. (2012) to enhance the quality of the low grade ore. A low grade iron ore from Kolkata, India was used with a head grade of 49.27% Fe. The mineralogical report showed that the iron mineral was mainly present in the hematite and goethite phases with quartz and kaolinite as the major gangue mineral phases within the ore. The results showed that an upgrade of up to 62% Fe in the concentrate stream was achievable using WHIMS.

An iron and titanium material containing vanadium as gangue was treated in a SLon VPHGMS (Dobbins et af., 2007). The objective was to remove 17% to 20% gangue in order to improve the product quality of the fine magnetite and titanium. The results reported an upgrade to 47.50% Ti02 and doubling the recovery at the same time. By discarding the majority of the mass by magnetic separation, the SLon VPHGMS technology also showed that it could be used as a waste rejecting stage prior to the flotation process.

Zheng et af. (2003) used the SLon VPHGMS separator in a test in a Qidashan mineral processing plant in China. The aim of the investigation was to meet metallurgical specifications of 66% Fe and reduce the high energy used in the plant. Previous tests with the WHIMS 2000 in the same plant showed that it was only capable of beneficiating up to a grade of 63% Fe, 3% short of meeting the required specifications. The material was then treated by a SLon-1500 and the results showed magnetic products with much higher Fe grades and recoveries, with low Fe losses to the tailings streams. The improved quality product was a result of the pulsating mechanism provided by the SLon VPHGMS, preventing the matrix from clogging. By keeping the matrix clean the particles have more attaching space which increases the recovery.

Mohanty et af. (20I0) conducted a set of experiments on slimes from mines around the Barbil area, eastern India. One set of the experiments comprised of desliming prior to magnetic separation and another test was a direct magnetic separation using traditional WHIMS. The feed used was -150 ~m at a head grade of 58.64% Fe, and was analysed through polished sections at size range of -150+ 1 00 ~m. The result showed that the major phases are hematite with a substantial quantity of goethite. The slimes were then subjected to magnetic separation using Jones WHIMS at various intensities.

The investigation showed that by increasing the magnetic field intensity of the WHIMS, low magnetic susceptible iron minerals were attracted thus reducing the product grade. However, the authors concluded that beneficiation by WHIMS was capable of beneficiating Fe to >61% Fe grade with a high mass yield of -80%. Another investigation was conducted by Srivastava and Kawatra (2009) on a low grade hematite ore from Minnesota in a USA stockpile. Mineralogical investigations on the ore showed that hematite (Fe203), silica (Si02), and manganite (MnO.OH) were present as major phases. The magnetic separation results reported a beneficiation of the feed from 27.30% Fe to 45.24% Fe with a 42.06% Fe recovery for the -25 ~m size fraction. However major Fe losses to the tailings stream were reported, indicating that WHIMS was not entirely efficient in beneficiating this particular ore at this fine size.

dry high intensity magnetic separator magnetense

dry high intensity magnetic separator magnetense

100 mm diameter and 300 mm rollers with working heights ranging between 1,000 to 1,500 mm. can be installed in our machines in order to meet the specific customers needs. MAGNETENSE can produce rollers larger than 300 mm.diameter.

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