Model HMDA Wet Drum Separators improve the efficiency and reduce the costs of media recovery in heavy media operations. Obsoleting the old "gauss at two inches" standard for selecting wet drum separators, Eriez engineers base their design and application on two fundamental factors: flux density and flux gradient within the separation area.
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 cri- teria of the magnetic circuit and the benchmark of operation. The 750 gauss Interpole mag- netic element, developed by Eriez, is the most acclaimed magnet of engineering standards in the industry. Eriez has also set the benchmark for wet drum performance. The culmination of various inplant tests has demonstrated that the separators will achieve magnetite recoveries in the 99.9+ percent. (This is based on magnetite losses of less than 1 gram/gallon of nonmag- netic effluent).
The Eriez Wet Drum Magnetic Separators uti- lized the 750 gauss Interpole magnetic element as standard equipment. The Interpole style ele- ment utilizes a true ceramic bucking magnetic pole or interpole between each main pole. The magnetic field of the bucking elements are charged to oppose both of the adjacent main poles resulting in increased magnetic field at depth. The Interpole element allows relatively high magnetic loading resulting in higher unit capacity and improved separation efficiency.
Two basic tank styles are offered. The drum rotates in the same direction as the slurry flow in the concurrent tank style. The slurry enters the feedbox and is channeled underneath the submerged drum. The slurry then flows into the magnetic field generated by the drum. The magnetite is attracted by the magnetic field, collected on the drum surface, and rotated out of the slurry flow. This tank style results in a very clean magnetic product.
The counterrotation wet drum tank style is preferred for heavy media applications. The drum rotates against the slurry flow in the counterrotation tank style. The slurry enters the feedbox and flows directly into the magnet- ic field generated by the drum. The magnetite is attracted by the magnetic field, collected on the drum surface, and rotated out of the slurry flow. Any magnetite that is not immediately collected will pass through to a magnetic scav- enging zone. The short path that the magnetic material must be conveyed between the feed entry point and the magnetics discharge lip, combined with the magnetic scavenging zone, results in high magnetite recoveries.
48X16 Pilot Plant Wet drum (HMDA or CDA applications. Interchangeable tank MMPB- 470 PC-506 48 inch diameter by 16 inches drum width, 12 inches magnet width. HMDA construction, cast aluminum heads, 304 SS shell. 304 SS wear wrap 1-1/2 HP motor with chain and sprocket drive. (Available for 460/60 or 380/50) 1000 Gauss Interpole magnetic element (see available optional elements below) Universal carbon steel support frame; accepts other tank styles without modifications 304 SS Counter-Current tank style (See available interchangeable tanks below). NOTE: THESE TANKS ARE COMPLETE AND ARE FULLY INTERCHANGEABLE WITH COUNTER-CURRENT TANK
12" diameter X 6" magnet width Lab model L-8 electro wet drum magnetic seperator (WLIMS) (B-810) (PC-518) Universal stainless steel tank for concurrent and counter-rotation operation with one plexiglass side for observation. 1/3 HP TENV drive motor. Eriez Model LWD control box incorporating a variable DC power supply with ammeter, voltmeter and drum motor starter reversing switch for operation from voltage specified below. (A) Remote Mounted Control for operation from 115/60 - use drawing 2N-201311056 AND 1N-201313045 and C-1N-661137. (B) Remote Mounted Control for operation from 220/50 or 230/60- use 1N-201306424 and 2N-201311056 Approximate Wattage: 470 NOTE: DOES NOT INCLUDE FRAME EXTENSION WITH CASTERS
Metso Lims separators are designed around the revolving magnetic drum with an internally stationary magnetic array. Theyare available in several types for vast number of duties and could be seen as split into two categories, dry separation and wet separation.
The wet versions are designed for material of a few micrometer size to less than around 6 - 8 millimeters suspended in water. For both separator types a number of magnetic systems are available for highest possible efficiency of each application.
Wet low intensity magnetic separators, LIMS Metso has been involved in magnetic separation for more than one hundred years. Metso has produced more than five thousand magnetic drums used in both dry and wet processing. Metso wet magnetic separators are continuously undergoing improvements to meet the everincreasing demands of our customers. Metso has been and is still the leader in the development of high capacity, high performance wet low intensity magnetic separators (LIMS) for several decades. 2 Wet low intensity magnetic separators Designs and sizes Metsos wet magnetic separators are...
e.g. glass sand and feldspar production. It is also commonly installed for removal of ferromagnetic matter ahead of WHIMS (Wet high intensity magnetic separators) or HGMS (High gradient magnetic separators) units. In dense media circuits LIMS is standard equipment; ask for our special brochure for dense media recovery. After market services Our greatest asset is the experience of our people which assures competent technical field services and parts supply for systems and equipment designed, manufactured and supplied by Metso. Our safety certified field service engineers have specialized...
Tank design CC and CR CC Concurrent The concurrent style of magnetic separator features: The counter-rotation style of magnetic separator features: Feed box with serrated weir overflow for even distribution of the feed slurry Feed box with feed tubes; Feed entry section to improve on feed pulp distribution thus ensuring full width feed to drum; Short pick-up zone, which reduces the risk of coarse material settling on tank bottom. Exchangeable outlet spigots in tank bottom to allow coarse material to discharge trouble free; Suited for processing of coarse ore up to 6 - 8 mm (3...
Tank design CTC and DWHG CTC Countercurrent DWHG Counter-rotation The countercurrent style of magnetic separator features: The DWHG style of magnetic separator features: Feed box with serrated weir overflow for even distribution of the feed; Basically counter-rotation tank design Extremely long pick-up zone; Feed entry section to improve on feed pulp distribution with full width feed to drum; Entry chamber designed to allow for entrapped air to escape and to improve concentrate drainage; Medium long pick-up zone; Longer magnet assembly arc to compensate for disturbances...
CR feed tubes are protected by polyurethane saddles against abrasion. Features and benefits Magnetic system The heart of the magnetic separator is the magnet assembly. Metso provides basically two different assemblies: high capacity and high gradient, (HG). The high capacity assembly is the standard magnetic system. The main differences between the two magnet assemblies are pole pitch, pole sizes, and number of poles. The magnet assemblies are similar in design with both having a number of main poles and a number of intermediate cross poles for flux control and enhancement of the magnetic...
Magnet positioning Direct gear motor drive Features and benefits Adjustment of magnet and drum position Feed boxes Drum drive system The magnetic drum and magnetic assembly can easily be adjusted to obtain the best process performance. The adjustment possibilities include The feed system for primary distribution of the pulp to the feed boxes that are supplied with the separators is normally not part of the equipment supply; however, Metso can optionally supply or advise on solutions for these systems. The drum on any Metso magnetic separator has a drive shaft, which can be adapted to any...
Adjustable concentrate overflow weir CR tank with pulp level bars Concentrate discharge and collection Effluent (tailings) discharge and collection An overflow weir is provided for the magnetic concentrate discharge. This weir, manufactured of HDPE or, optionally, in polyurethane, is adjustable to obtain optimum discharge conditions. The launders for collection of the concentrate that is discharged over the weir are made of a rubber-lined combination of mild and stainless steel and are bolted to the separator tank frame. Depending on the installation situation, standard launders or,...
Application guide lines Absolute guidelines for model selection and dimensions are not available due to the widely varying nature of iron ores; hence, the data shown in the table below are only indicative and, when in doubt of the properties of a specific ore, the lower feed rate should be used. Testing in a laboratory, followed by on site testing is always advisable especially when planning for larger installa- tions. Sizing of full-size machines using only laboratory data is normally not sufficient to determine the number of magnetic separators that are required. The capacities in the...
Metso Minerals Industries, Inc. 2715 Pleasent Valley Road, York, PA 17402, USA, Phone: +1 717 843 8671 etso Minerals (South Africa) (Pty) Ltd. M Metso Minerals (Australia) Ltd. Metso Minerals (India) Pvt Ltd 1th floor, DLF Building No. 10, Tower A, DLF Cyber City, Phase - III, Gurgaon - 122 002, India, Phone: +91 124 235 1541, Fax: +91 124 235 1601 Metso Minerals (Chile) S.A. Metso Brasil Indstria e Comrcio Ltda. Av. Independncia, 2500 den, 18087-101 Sorocaba-SP - Brazil, Phone: +55 15 2102 1300 www.metso.com E-mail: [email protected] Metso Corporation, Fabianinkatu 9...
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 . 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 . 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 . For WEEE, MS systems utilize ferrite, rear-earth or electromagnets, with high-intensity electromagnet systems being used extensively. Veit et al.  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.  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 . 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 . 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 . 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 . 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 . SEM image of the nanoparticles are provided in Fig. 17.
Magnetic separation, as a powerful technique for the manipulation of magnetic particles, has attracted worldwide attentions and achieved tremendous applications in the past several decades, due to its effectiveness, simple operation, low cost, and environmental sustainability. In the field of mineral processing, magnetic separation is mainly used for concentration of magnetic components and for removal of magnetic impurities, under dry or wet conditions. Basic theoretical principle of magnetic separations and three types of magnetic separators, i.e., low-intensity, high-intensity, and high-gradient magnetic separators, and their technological innovations and operational practices are reviewed. In particular, pulsating high-gradient magnetic separation, a landmark progress in the treatment of fine weakly magnetic minerals such as iron oxide ores and ilmenite, and its continual developments and operational variables are expatiated. Practical cases in the processing of typically magnetic ores, i.e., magnetite, hematite, limonite, ilmenite and nonmetallic ores where magnetic techniques are well embodied, are introduced. At the end of this chapter, the merits and limitations of current magnetic techniques and the future trends in the research and development of potential magnetic techniques are discussed.
Silicon Carbide is a man made mineral of extreme hardness and sharpness. It is the ideal abrasive for grinding / sanding materials of low tensile strength such as Cast Iron, Brass, Aluminum, Bronze etc. Its thermal properties make it an excellent medium for use in the manufacture of refractory products and crucibles.
Silicon Carbide is produced by a process involving the electrochemical reaction of silica in the form of quartz with Carbon in the form of raw petroleum coke. The stoichiometric mixture is reacted in an electrical resistance furnace at a temperature greater than 2200?C to yield high quality crystals. The large crystals are then segregated, crushed, cleaned of magnetic impurities in high intensity magnetic separators and classified into narrow size fractions to suit the end use. Dedicated lines produce products for different applications.