magnetic separation - an overview | sciencedirect topics

magnetic separation - an overview | sciencedirect topics

Magnetic separation takes advantage of the fact that magnetite is strongly magnetic (ferromagnetic), hematite is weakly magnetic (paramagnetic), and most gangue minerals are not magnetic (diamagnetic).

The current research and development initiatives and needs in magnetic separation, shown in Fig. 7, reveal several important trends. Magnetic separation techniques that have been, to a greater extent, conceived empirically and applied in practice, such as superconducting separation, small-particle eddy-current separation, and biomedical separation, are being studied from a more fundamental point of view and further progress can be expected in the near future.

In addition, methods such as OGMS, ferrohydrostatic separation, magnetic tagging, and magnetic flocculation of weakly magnetic materials, that have received a great deal of attention on academic level, are likely to enter the development and technology transfer stages.

The application of high-Tc superconductivity to magnetic separation, and novel magnetism-based techniques, are also being explored, either theoretically or empirically. It can be expected that these methods, such as magnetic flotation, magnetic gravity separation, magnetic comminution, and classification will take advantage of having a much wider control over these processes as a result of the presence of this additional external force.

Magnetic separation takes advantage of the fact that magnetite is strongly magnetic (ferromagnetic), hematite is weakly magnetic (paramagnetic), and most gangue minerals are not magnetic (diamagnetic). A simple magnetic separation circuit can be seen in Figure 1.2.5 [9]. A slurry passes by a magnetized drum; the magnetic material sticks to the drum, while the nonmagnetic slurry keeps flowing. A second pass by a more strongly magnetized drum could be used to separate the paramagnetic particles from the gangue.

Magnetic separation can significantly shorten the purification process by quick retrieval of affinity beads at each step (e.g., binding, wash, and elution), and reduce sample dilution usually associated with traditional column-based elution. The method can be used on viscous materials that will otherwise clog traditional columns and can therefore simplify the purification process by eliminating sample pretreatment, such as centrifugation or filtration to remove insoluble materials and particulates. The capability of miniaturization and parallel screening of multiple conditions, such as growth conditions for optimal protein expression and buffer conditions for purification, makes magnetic separation amenable to high-throughput analysis which can significantly shorten the purification process (Saiyed et al., 2003).

Paramagnetic particles are available as unmodified, modified with common affinity ligands (e.g., streptavidin, GSH, Protein A, etc.), and conjugated particles with specific recognition groups such as monoclonal and polyclonal antibodies (Koneracka et al., 2006). In addition to target protein purification, they can also be used to immobilize a target protein which then acts as a bait to pull down its interaction partner(s) from a complex biological mixture. See Chapter 16.

Magnetic separation of cells is a simple, rapid, specific and relatively inexpensive procedure, which enables the target cells to be isolated directly from crude samples containing a large amount of nontarget cells or cell fragments. Many ready-to-use products are available and the basic equipment for standard work is relatively inexpensive. The separation process can be relatively easily scaled up and thus large amount of cells can be isolated. New processes for detachment of larger magnetic particles from isolated cells enable use of free cells for in vivo applications. Modern instrumentation is available on the market, enabling all the process to run automatically. Such devices represent a flexible platform for future applications in cell separation.

IMS play a dominant role at present but other specific affinity ligands such as lectins, carbohydrates or antigens will probably be used more often in the near future. There are also many possibilities to combine the process of cell magnetic separation with other techniques, such as PCR, enabling the elimination of compounds possibly inhibiting DNA polymerase. New applications can be expected, especially in microbiology (isolation and detection of microbial pathogens) and parasitology (isolation and detection of protozoan parasites). No doubt many new processes and applications in other fields of biosciences and biotechnologies will be developed in the near future.

Magnetic separation methods are widely used for isolation of a variety of cell types. Magnetic particles with immobilized antibodies to various antigens have been employed for the rapid isolation of populations T-(CD4 +, CD3 +, CD8+) and B- (CD19+) of lymphocytes, NK cells, and monocytes. Similarly, immobilization of glycoconjugates on magnetic beads allows the isolation of cell populations expressing a particular carbohydrate-recognizing molecule [19, 20]. Glycosylated magnetic beads can be prepared by loading biotinylated probes onto streptavidin-coated magnetic beads. The glycoparticles are then incubated with a cell suspension and the subpopulation of interest is fished out by means of a magnetic device [20].

When these materials are used in the biological field, special restrictions should be considered and all possible reactions with the biological materials should be predicted. Magnetic properties should be maintained for a specific time during the test. Some applications can be classified as follows:

Magnetic separation is used for clinical application, such as in the separation of proteins, toxemic materials, DNA, and bacteria and viruses. This is also used for real time detecting of viruses. The most important stage in this field is the labeling of molecules with magnetic materials by a reliable connection. Magnetic beads from iron oxide are typically used for biological separation. The main properties of iron oxide are super paramagnetic properties (Meza, 1997).

Effective drug delivery can greatly improve the process of treatment and reduce side effects. In this method, while the amount of drug decreases, the concentration of the drug in the target area increases. Protecting the drug before its gets to the target area is one of the most important factors, because after releasing the drug in the blood stream, white cells detect the drug and swallow them in a short time. An ideal nanoparticle for drug delivery should have the potential to combine with a relatively high-weight drug and disperse uniformly in the blood stream (Shultz et al., 2007).

Also, while chemotherapy is one of most effective methods for cancerous tissues, many of the other healthy cells are destroyed in the process. So the conventional thermotherapy has many side effects. In hyperthermia treatment, after delivering the drug to the target area, an AC magnetic field is used to generate controllable energy and increase temperature. Heat transfer in this process is a balance between blood flow, heat generation, and tissue porosity and conductivity (Sellmyer and Skomski, 2006).

Magnetic Resonance Imaging (MRI) is considered a great help in the diagnoses of many diseases. The advantages of this imaging are high contrast in soft tissue, proper resolution, and sufficient penetration depth for noninvasive diagnosis. In fact, in MRI imaging magnetization of protons is measured when exposed to the magnetic field with radio frequency (Corot, 2006).

Magnetic separation: based on the generation of magnetic forces on the particles to be separated, which are higher than opposing forces such as gravity or centrifugal forces. This principle is used to separate ferromagnetic particles from crushed scrap mixtures.

Eddy current separation: is a particular form of magnetic separation. An alternating magnetic field induces electrical eddy currents on a metal particle. This results in a magnetic field whose direction is opposite to the primary magnetic field. The exchange interactions between the magnetic fields result in a repulsive force on the metallic particle; the net effect is a forward thrust as well as a torque. This force and hence the efficiency of separation is a function of the magnetic flux, or indirectly of the electrical conductivity and density and the size and shape of the metallic particles.

Air separation/zigzag windsifter: Air-based sorting technique, which separates the light materials from the heavier. The most prominent application is in shredder plants producing the shredder light fraction, or in fridge recycling, removing among others the polyurethane (PUR) foam from the shredded scrap.

Screening: Separation of the scrap into different particle size classes is performed to improve the efficiency of the subsequent sorting processes and/or to apply different processing routes for different size fractions (based on material breakage and hence distribution over various size fractions).

Fluidized bed separation: A fluidized bed of dry sand is used to separate materials based on density. This technology is in principle a dry sink-float separation, which is still hampered by several difficulties (tubular or hollow particles filling up with sand and tend to sink; formation of unsteady current due to the use of high velocity air, etc.). The fluidized bed could also be heated for simultaneous de-coating and combustion of organic material.

Image processing (including colour sorting): Colour sorting technologies, which sense the colour of each particle and use computer control to mechanically divert particles of identical colour out of the product stream (red copper, yellow brass, etc.). A complicating issue is that shredding results in mixtures of particles that show a distribution in composition, size, shape, texture, types of inserts, coatings, etc. The variance of these properties complicates identification that is solely based on this principle.

X-ray sorting: Dual energy X-ray transmission imaging (well known for luggage safety inspections at airports) identifies particles based on the average atomic number, particle shape, internal structure (e.g. characteristic variations of thickness) and presence of characteristic insert material. It is rather sensitive to particle thickness and surface contaminations.

LIBS (laser induced breakdown spectroscopy) sorting: A series of focused ablation laser pulses are delivered to the same spot on each particle. A pulse of an ablation laser vaporizes only the first nanometres of the surface, i.e. the first pulses are necessary to clean the surface of oxide layers (different composition than the mother metal), the last pulse vaporizes a tiny amount of metal generating a highly luminescent plasma plume. The light from the plasma is collected and analysed to quantitatively determine the chemical composition. This determines to which bin the particle is directed (e.g. by air pulse).

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.

The automatic separation system, developed by Magnetic Separation System of Nashville, Tennessee, uses X-ray, IR, and visible spectra sensors for separating the post-consumer recyclate bottles or flakes into individual plastics and into different color groups. X-ray sensors, used for separating PVC, are very accurate and can operate at as high as 99% or better efficiency. IR and visible sensors are used to separate the colored bottles into individual polymers and color groups.

The separation system (Figure 4) essentially consists of a metering inclined conveyer, air knife, special disk screen, singulating infeed conveyor, and sensor module. A motor control system provides operator interface screens which control the sorting functions, including the number of bottles sorted into each fraction, ejection timing, and sort positions. Individual systems currently in use in Germany, Switzerland, and the United States are described in a paper by Kenny and Vaughan.16 The systems are customized, based on the composition of the post-consumer recyclate and the end application of the separated streams. Some systems use X-ray and IR sensors in two locations to achieve better separation. In addition to sorting equipment, some systems also use equipment for breaking the bales and splitting the bottles into more than one stream for smooth operation. Grinders are used when the bottles have to be ground into flakes for further processing. Whereas PVC separation is accomplished at 99%. HDPE and PET separation is between 80 and 90%, depending on the level of contamination.

Automated separation provides two advantages: improved quality and lower labor cost for sorting. The automatic separation system at Eaglebrook Plastics uses the Magnetic Separation System (MSS), which detects and separates the bottles into different categories based on the type of the resin and color, and eliminates impurities such as broken pieces of plastics, rocks, aluminum cans, and other contaminants.17 Metering the feed is critical to obtain maximum throughput at Eaglebrook. This is accomplished by a special debaling device and an incline metering system. Factors contributing to proper operation include clear height, width, spacing, belt speed, and incline angle. Proper presentation of the bottle to the sensor is critical. The bottles are split into four streams and two to three bottles are presented to the sensor per second, one at a time.

The primary identification sensor uses a multibeam, near-IR array to identify the bottles into three classes: Class 1, PVC, PET; Class 2, natural HDPE, PP; Class 3, mixed color HDPE and opaque containers. This sensor is also capable of separating colored PET from clear PET and PP from milk jug HDPE. The X-ray sensor identifies PVC, and a machine vision sensor system provides up to seven color classifications of the plastic bottles. After identification, the containers are ejected from the conveyors into appropriate collection stations using high-speed pulsed air nozzles. The motor control center (MCC) of the separation system controls motor protection, sequential slant up for the system, fault indication, and operation control. In addiiton, a touch screen input panel allows the operator to select any available sort to be directed to any ejection station. Visible light color sensors have been added which sort pigmented HDPE into different colors. The system also includes a decision cross-checking device between the primary sensor and the color sensor. This compares the decisions of the two sensors by comparing them with a logic file. The latter then provides correct identification in case there are discrepancies between the two decisions. The system has successfully operated for the last three to four years at a capacity of 5000 bottles h1.

The debaling system designed for Eaglebrook requires that the bales be presented to the debaling equipment in the same orientation as the original compression. This design feature requires less horsepower, reduces bottle clusters, and requires minimum energy. The debaling and declumping system incorporates a surge bin and metering conveyor to feed the screening system. The improved capacity and higher separation accuracy, due to increased metering efficiency, reduces bottle clusters and provides a more uniform feeding system. The separation efficiency depends on several factors. Timing and catcher bounceback accounts for 12% accuracy loss; contamination, container distortion, and loose labels contribute to about 34%, and nonsingulation of the bottles 510% of accuracy loss.

Asoma Instrument of Austin, TX, is a leading manufacturer of automated bottle sorting equipment. The company uses an X-ray fluorescence spectrophotometer sensor. The identification is completed in 10ms and the separation takes about 20s per bottle. The sorted PET streams have less than 50ppm PVC. National Recovery Technology of Nashville, TN, uses a proprietary electromagnetic screening process which can handle the bottles either in crushed or whole form and does not require any special positioning or orientation of the bottle to achieve high efficiency. Chamberlain/MCR, Hunt Valley, MD, and Automation Industrial Control of Baltimore, MD, offer a paysort bottle sorting system, which uses a sophisticated video camera and color monitor incorporating a strobe to detect and distinguish colors of post-consumer bottles following a near-IR detection system which also determines the primary resin found in each bottle.

A substantial amount of research is focused on microseparation techniques and on techniques which can reject bottles with trace amounts of harmful contaminant. Near-IR spectrometry is being used to separate bottles for household chemicals and ones with hazardous waste residues.

Sorting of automotive plastics is more difficult than sorting of plastics from packaging recyclates. Whereas only five to six polymers are used for packaging, post-consumer automotive plastics contain large numbers of engineering and commodity plastics, modified in various ways, including alloying and blending, filling, reinforcing, and foaming. Hence, sorting of automotive plastic recyclate poses several challenges. Recently, a systematic study, PRAVDA, was undertaken by a German car manufacturer and the plastic suppliers in Europe to investigate the potential of various analytical techniques in separating post-consumer automotive plastics.18

The techniques examined in this study include near-IR spectroscopy (NIR), middle-IR spectroscopy (MIR), Fourier transform Raman spectroscopy (FTR), pyrolysis mass spectrometry (PY-MS), pyrolysis IR spectroscopy (PYIR), and laser-induced emission spectral analysis (LIESA). X-ray methods were excluded because they have insufficient sensivitity to polymers, other than ones containing chlorine. Since commercial spectrophotometers were not available for most techniques except NIR, either laboratory models (MIR, FTR) or experimental stage instruments (PY-MS, PY-IR, and LIESA) were used in this study. A large number of parts (approximately 7000) were analyzed. The techniques were compared in respect to their success in identification, fault rate, time for identification, degree of penetration, and sensitivity to surface quality. The fault rate is the number of wrong identifications, given as percent. If the sum of the identification and fault rate is less than 100, the difference gives the rate of incomplete correct identification. The biggest stumbling block was the identification of black samples which could not be analyzed by NIR and FTR. MIR is the only technique which not only identified the black samples, but gave the highest identification rate. Some difficulties were experienced, however, in MIR analysis in the case of blends of two similar polymers such as PP/EPDM or nylon 6/nylon 66. The pyrolytic methods showed poorer identification rates and higher fault rates. The LIESA method is very fast and a remote technology, particularly for fast identification of heteroatoms. It is therefore suitable for identifying fillers, minerals, reinforcing fibers, pigments, flame retardants, and stabilizers specific to the individual plastic. The difficulty with MIR is that it is sensitive to surface micro-roughness and, hence, the samples need to be very smooth. Also, paint or surface coats on the part have to be removed for correct identification of the resin used for making the parts. Further, at this stage, no fiber optic or separated probe is available with MIR technology and, hence, the part has to be brought close to the spectrophotometer instead of the probe reaching the part. Another method of measuring efficiency is the level of contamination. Contamination of parts sorted by the MIR method was less than 1%, whereas contamination of parts sorted manually, using a Car Parts Dismantling Manual, is greater than 1015%. When the level of contamination is high, further separation by swim-sink or hydrocyclone techniques are necessary.

The cost of a MIR spectrophotometer is approximately DM 100000. The cost calculated for small dismantlers (dismantling less than 25 cars per day) is approximately DM 0.34 per kg and that for large dismantlers is somewhat less than DM 0.19. Manual sorting, on the other hand, would cost DM0.71 and DM0.23 per kg for small and large dismantlers, respectively. Spectrophotometric identification of plastics in automotive plastics waste therefore makes substantial economic sense.

china magnetic separator producer | fote machinery

china magnetic separator producer | fote machinery

Applied material: magnetite, pyrrhotite, calcined ore, ilmenite, etc. Advantages of FTM magnetic separator: larger capacity, higher efficiency, and lower operating costs. in addition, It requires no electric power.

Magnetic separator is mainly used for separating various minerals such as ferrous metals, non-ferrous metals, precious metals, non-metals. When the magnetic separator is working, minerals with stronger magnetism will be absorbed to the strong magnetic field while non-magnetic minerals would be discharged from the discharge port along another trajectory.

Magnetic drum separator can be divided into two types: one is dry magnetic separator, the other is wet magnetic separator. The dry magnetic separator is designed for material with 2 to 200 millimeters which is in dry or nearly dry state like crushed iron ore. The wet drum magnetic separator is suitable for the ores with a few micrometer size to less than around 6 - 8 millimeters suspended in water.

Dry magnetic separators are mainly for separating dry magnetic minerals. One of its models is a permanent magnetic drum separator that installing a rare earth roll (RE Roll). Rare earth roll is one of the worlds highest-intensity and can separate strong and weak magnetic material from non-magnetic material in a dry state.

The permanent magnet system is made of high-quality ferrite or composite including ferrite material and rare earth magnetic steel. The average magnetic induction intensity of the drum surface is at the range of 100~600mt.

The permanent magnetic drum wet separator is suitable for the ores like magnetic pyrite, roasted ore, ilmenite, and other materials with a particle size of less than 3mm. It is also used to process coal ores, non-metallic ores, and building materials.

Just like a dry magnetic separator, the wet magnetic separator is also made of powerful rare earth magnets. It is used in the fine grain range from 1 m up to 3000 m (0.001 mm 3 mm) to separate magnetic particles from process liquids, sludges or emulsions. The processing objective here can be both the recovery of valuable iron particles and the avoidance of disruptive iron particles, e.g. upstream of membrane or ultra-filtration.

Countercurrent-slurry feed direction is opposite to the drum rotating direction. the magnetic concentrate is discharged on one side of the feed opening while the tailings are discharged on the other side.

Semi-countercurrent: the slurry feed direction is half the same and half opposite of the drum rotating direction, and the difference with the cocurrent type is that the ore slurry turns a circle in the tank.

The slurry is washed completely by the water, which can prevent inclusions. The movement direction of the slurry is consistent with the direction of the magnetic force, which is conducive to further recycling. semi-countercurrent method also benefits for getting high-grade magnetic concentrate from strong magnetic ore with 0.5-10mm by coarse separation and scavenging, keeping stable slurry surface and operation.

The solution for separating titanium ore concentrate not only ensures the quality but increases the recovery rate by 10-25 percentage points. The annual output of titanium concentrate of our customers has increased from 50 thousand tons to 500 thousand tons.

Facts have proved that magnetic drum separator manufactured by Fote supplier can improve the classification efficiency, especially increase the concentration of underflow, and reduce the phenomenon of overflow and roughness. It has significantly raised the recovery rate and product quality and greatly improved the comprehensive utilization rate of resources.

As a leading mining machinery manufacturer and exporter in China, we are always here to provide you with high quality products and better services. Welcome to contact us through one of the following ways or visit our company and factories.

Based on the high quality and complete after-sales service, our products have been exported to more than 120 countries and regions. Fote Machinery has been the choice of more than 200,000 customers.

separator functional principle: how does a separator work?

separator functional principle: how does a separator work?

The separator, or disc centrifuge, is a vertically arranged centrifuge. It is used for separating and clarifying liquids. In a disk stack separator, solid-liquid mixtures or liquid-liquid mixtures are separated by centrifugal force. Compared to a decanter centrifuge, the separator differs significantly in its technical design and application.

A disk stack separator is based on the basic principle of sedimentation. In a solid/liquid mixture, the heavy solids collect on the bottom of the container. They sink due to gravity. (1) In a continuous solid/liquid separation system, not all the solid particles have sufficient time to settle on the bottom. They leave the system together with the liquid phase. The separation is not complete. To prevent this, several flat inserts are used in the form of vanes or plates. (2) The actual separation takes place in the space between the disks in the disk stack. The more vanes or disks there are, the larger the clarifying surface. In order to prevent clogging of the plates, the bottoms are not mounted horizontally, but rather tilted. The solid particles slide to the bottom. (3)

Separation by gravity (1 G) is slow and for many industrial applications it is not efficient. Disk stack separators accelerate the separation process significantly. They use centrifugal force to separate the mixture of solid phase and liquid phase materials. The geometric surface (clarifying surface) and centrifugal acceleration are used to calculate the "equivalent clarifying surface," which is the measure of the efficiency of a separator.

The high G forces allow the separator to achieve high separation performance. Compared to a decanter, the separator operates at higher speeds and separates significantly finer solids (particles down to about 5 m) from a liquid.

The mixture to be separated is fed through a stationary infeed pipe (1) into the distributor of the rotating bowl (2) (the container that holds the liquid). There it accelerates to the circumferential speed of the separator bowl. It is important that no unnecessary shear forces occur during distribution of the mixture. Such forces could break up the fine particles or produce emulsions. Slots or holes are provided on the outer edge of the distributor foot through which the product to be separated enters the disk pack. The separation takes place within the disk pack of the separator (3). The solids push outwards and collect in the so-called solids space (4). The separated liquid phases flow through the disk pack into the upper part of the bowl, and then through an impeller (gripper) or a fixed weir (5). The configuration used depends on the application.

The collected solids run off through a separate outlet (solids discharge). Disk pack separators that have a self-cleaning bowl (continuous separators) and manual separators are available. In a separator with a self-cleaning bowl, the bowl has an opening mechanism through which the separated solids are discharged at regular intervals (6). In this case, the bowl consists of the bowl bottom part, where the hydraulic emptying mechanism is located, and the bowl cover.

Using the hydraulic ejection mechanism, the separator opens at the outermost part of the centrifuge housing where the solids collect. After the solid phase has run off, the separator closes again. This happens in a few tenths of a second.

Separators are perfect for separation tasks in which a high degree of selectivity is required or in which the separation of the finest particles is important. They are also used for separating solid/liquid mixtures having only a small difference in density. Disk stack separators have many applications that can be found in the most diverse branches of industry, for example:

wet magnetic drum separator

wet magnetic drum separator

Low-intensity separators are used to treat ferromagnetic materials and some highly paramagnetic minerals.Minerals with ferromagnetic properties have high susceptibility at low applied field strengths and can therefore be concentrated in low intensity (<~0.3T) magnetic separators. For low-intensity drum separators used in the iron ore industry, the standard field, for a separator with ferrite-based magnets, is 0.12 T at a distance of 50 mm from the drum surface. Work has also shown that such separators have maximum field strengths on the drum surface of less than 0.3 T. The principal ferromagnetic mineral concentrated in mineral processing is magnetite (Fe3O4). although hematite (Fe2O3) and siderite Fe2CO3 can be roasted to produce magnetite and hence give good separation in low-intensity machines.

Permanent magnetic drum separators combine the attributes of a high-strength permanent magnetic field and a self-cleaning feature. These separators are effective in treating process streams containing a high percentage of magnetics and can produce a clean magnetic or non-magnetic product. The magnetic drum separator consists of a stationary, shaft-mounted magnetic circuit completely enclosed by a rotating drum. The magnetic circuit is typically comprised of several magnetic poles that span an arc of 120 degrees. When material is introduced to the revolving drum shell (concurrent at the 12 oclock position), the non-magnetic material discharges in a natural trajectory. The magnetic material is attracted to the drum shell by the magnetic circuit and is rotated out of the non-magnetic particle stream. The magnetic material discharges from the drum shell when it is rotated out of the magnetic field.

Permanent magnetic drum separators have undergone significant technological advancements in recent years. The magnetic circuit may consist of one of several designs depending on the application. Circuit design variations include:

The standard magnetic drum configuration consists of series of axial poles configured with an alternating polarity. This type of drum is simple in design and can be effective for low-intensity applications such as the recovery of ferrous metals and magnetite. This configuration typically does not provide a sufficient field strength or gradient for the recovery of paramagnetic minerals at high capacities. A typical axial circuit is shown in Figure 3.

The high-gradient element, as the name implies, is designed to produce a very high field gradient and subsequently a high attractive force. Several identical agitating magnetic poles comprise the element. The poles are placed together minimizing the intervening air gap to produce the high surface gradient. Due to the high gradient, the attractive force is strongest closer to the drum making it most effective when utilized with a relatively low material burden depth on the drum surface and, thus, a lower unit capacity. A high-gradient magnetic circuit is shown in Figure 4.

The interpole-style element utilizes a true bucking magnetic pole or interpole between each main pole. The magnetic field of the bucking element is configured to oppose both of the adjacent main poles resulting in a greater projection of the magnetic field. As a result, the interpole circuit allows for a relatively high material burden depth on the drum surface and thus higher unit capacity or improved separation efficiency. An interpole magnetic circuit configuration is shown in Figure 5.

A second interpole configuration consists of steel pole pieces placed between the magnetic poles. This is commonly termed a salient-pole element. The steel interpoles concentrate the magnetic flux providing a very high magnetic gradient at the drum surface. The magnetic field configuration is similar to the high- gradient type element but with an intensified surface gradient. This configuration offers the strongest field projection of any of the previously described circuits. The salient-pole circuit design is shown in Figure 6.

The magnetic elements described above are axial elements. The magnetic poles run across the width of the drum and are of alternating polarity. Magnetic elements are typically assembled with a minimum of five magnetic poles that span an arc of 110 degrees. (For all practical purposes, an arc of only 80 degrees is required to impart a separation. Non-magnetic particles usually leave the drum surface with a natural trajectory at a point of 60 to 70 degrees from top dead center dependent on the drum speed, particle size, and specific gravity.) The poles have alternating polarity to provide agitation to the magnetic components as they are transferred out of the stream of the non-magnetics. A magnetic particle will tend to rotate 180 degrees as it moves across each pole. This agitation is functional in releasing physically entrapped non-magnetics from the bed of magnetics. Agitating magnetic drums are most effective in collecting fine particles or where the feed contains a high magnetics content.

Dense-medium circuits have been installed in many mineral treatment plants since its original development about thirty years ago. In the intervening period the process has been thoroughly evaluated and many innovations have been introduced. The Heavy Density Cyclone is one of the newer systems which has extended the operating range of this process to 65 mesh size.

Medium recovery is obviously important since any loss is a direct cost against production. In coarse coal dense-medium plants a loss of 1 pound of magnetite per ton is usually acceptable but reduction to pound per ton as has been obtained in some plants.

Efficient cleaning maintains fluidity in the bath and increases sharpness of the coal-waste separation. Most dense-medium systems will tolerate some non-magnetic dilution of the bath but the magnetic separator must be capable of keeping this within workable limits, particularly on difficult coals. In some plants a partial bleed of the operating dense-medium bath is maintained through the magnetic separator to keep it clean.

Operating gravities of dense-medium coal plants are usually low enough so that a straight magnetite bath can be used. The return of a magnetic separator concentrate having 50% or more solids will maintain gravity without need for a thickening device. The use of a drum wiper has permitted the return of a 70% solids concentrate back to the separatory vessel. Operation at a high solids concentrate discharge is recommended since medium cleaning is improved. The colloidal slimes carried over with water are more completely rejected at high solids discharge.

Several types of magnetic separators have been used in magnetic medium recovery.The first magnetic drum separators were electro magnetic types but the development of efficient wet permanent drum separators has resulted in nearly universal acceptance of permanent drums in new plants.

The basic construction of each drum is the same. It consists of a stationary magnet assembly held in a fixed operating position by clamp bearings mounted on the separator support frame. An outer rotating cylinder driven through a sprocket bolted to one of the drum heads carries the magnetic material to the magnetic discharge point.

Normally, extreme cleanliness of the magnetic concentrate is not of prime importance in dense-medium plants but this can be a factor in some coals that separate with difficulty. The concurrent tank, reduced separator loading and in some instances dilution of the feed pulp will improve magnetic cleaning. Recleaning of a primary concentrate would improve cleaning but has not been used in commercial plants.

structure and working principle of wet permanent magnet drum-type ptms magnetic separator - news - foshan powtech technology company limited

structure and working principle of wet permanent magnet drum-type ptms magnetic separator - news - foshan powtech technology company limited

Wet permanent magnet drum-type PTMS magnetic separator is mainly composed of six parts: cylinder, roller, brush roller, magnetic system, tank and transmission. The cylinder is welded into a cylinder by a 2-3mm stainless steel plate coil. The end cover is cast aluminum or workpiece and connected to the cylinder with stainless steel screws. The motor drives the cylinder, the magnetic roller and the brush roller to rotate through the reducer or direct stepless speed regulating motor. The magnetic system is an open magnetic system, mounted in a cylinder and exposed to the full magnetic. The magnetic block is mounted on the bottom plate of the magnetic yoke with stainless steel bolts. The shaft of the magnetic yoke extends out of the cylinder, and the shaft end is fixed with a crank arm. Pull the arm to adjust the deflection Angle of the magnetic system, and fix it with the pull rod after proper adjustment. The working area of the tank is made of stainless steel plates, and the frame and other parts of the tank are welded with ordinary steel.

After the slurry flows into the tank through the feed tank, under the action of the water flow of the feed water pipe, the ore particles enter into the feed area of the tank in a loose state. Under the action of the magnetic field, the magnetic particles form a "magnetic mass" or "magnetic chain". The "magnetic mass" or "magnetic chain" in the slurry is affected by the magnetic force, moving towards the magnetic pole, and is adsorbed on the cylinder. Due to the polarity of the magnetic poles along the cylinder rotation direction are arranged alternately, and fixed at work, "magnetic group" or "magnetic chain" in the cylinder rotates, with alternating polarity magnetic stirring, was mixed in the "magnetic group" or "magnetic chain" of the gangue and other non-magnetic minerals in turn off, has finally been sucked on the surface of the cylinder, the "magnetic group" or "magnetic lotus" is to concentrate. The concentrate is transferred to the edge of the magnetic system with the cylinder, where the magnetic force is the weakest, and is discharged into the concentrate tank under the action of the flushing water gushing out of the discharge pipe. If it is a full magnetic roller, the discharge is carried out with a brush roller. Non-magnetic or weakly magnetic minerals are left in the slurry to be drained out of the tank, which is tailings.

preparation and application of monosized magnetic particles in selective cell separation | springerlink

preparation and application of monosized magnetic particles in selective cell separation | springerlink

Some of the basic principles of formation of monosized macroporous particles by the method of activated swelling and the preparation of superparamagnetic particles based upon these particles are discussed. A short review of the applications of monodisperse, magnetic polymer particles in cell separation, with emphasis on recent work, is given. Some new work concerning non-specific adhesion of antibodies and cells on different beads, and the prevention of this unwanted phenomenon by help of casein are described. A method for the removal of excess magnetic beads by gradient centrifugation is presented. Positive cell separation, with easy liberation of free cells after magnetic isolation of rosetted cells, is obtained by use of particles with covalently coupled aminophenyl boronic acid at the surface.

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