High Intensity Magnetic Separation Research Articles

Prediction of Separation Performance of Dry High Intensity Magnetic Separator for Processing of Para-Magnetic Minerals

High intensity dry magnetic separators are gaining popularity for the separation of para-magnetic minerals due to the cost economic factor. Induced roll magnetic separator is found to be an effective dry separator for the separation of fine particles. Separation efficiency of this separator depends on mineral characteristics and the design features of equipment along with the optimization of process variables. Present investigation focuses on the prediction and validation of separation performance of minerals while treating in induced roll magnetic separator. Prediction of the separation is expressed in terms of separation angle at which a particle leaves the rotor surface by using a modified particle flow model derived by Cakir. The validation of the model is carried by capturing the particle trajectory using an image analyzer. It is found that Cakir’s mathematical model produces reliable results and a new model is proposed to increase the reliability of separation angle prediction by including the particle shape factor.

Magnetic separation studies on ferruginous chromite fine to enhance Cr:Fe ratio

The Cr:Fe ratio (chromium-to-iron mass ratio) of chromite affects the production of chrome-based ferroalloys. Although the literature contains numerous reports related to the magnetic separation of different minerals, limited work concerning the application of magnetic separation to fine chromite from the Sukinda region of India to enhance its Cr:Fe ratio has been reported. In the present investigation, magnetic separation and mineralogical characterization studies of chromite fines were conducted to enhance the Cr:Fe ratio. Characterization studies included particle size and chemical analyses, X-ray diffraction analysis, automated mineral analysis, sink-and-float studies, and magnetic susceptibility measurements, whereas magnetic separation was investigated using a rare earth drum magnetic separator, a rare earth roll magnetic separator, an induced roll magnetic separator, and a wet high-intensity magnetic separator. The fine chromite was observed to be upgraded to a Cr:Fe ratio of 2.2 with a yield of 55.7% through the use of an induced roll magnetic separator and a feed material with a Cr:Fe ratio of 1.6.

Processing of Lean Iron Ores by Dry High Intensity Magnetic Separation

Dry high intensity magnetic separation (DHIMS) is investigated to process a lean hematite ore. It was found that the feed particle size and the drum rotation speed have significant influences on the separation performance, and a magnetic concentrate assaying 36.22% Fe with 75.97% recovery is achievable from the ore assaying 29.14% Fe at a coarse particle size below 10 mm. While the DHIMS is applied to process a lean limonite ore, a similar separation phenomenon is observed to that of the hematite ore. It was concluded that DHIMS may significantly improve the economic viability for exploration of lean iron ores.

Evolution of Nil Waste Process for Utilization of some Mine Wastes

The demand for quality concentrates, depletion of high grade reserves, increase in operating costs and environmental constraints poses challenging problems to all mineral industries. Closure of mines due to environmental problems force the industries to look for processing of mine wastes and old plant tails. It is in this context an effort is made to process some of mine wastes by nil waste technology yielding usable products for diverse industries thereby solving vexed problem of waste management and meeting the demand for raw materials. The clayey ferruginous bauxite reject sample from waste dumps of Kolli hills, Namakkaltaluk, Salem district, Tamil Nadu was subjected to characterization, process diagnostic amenability tests followed by process evolution studies comprising of of soaking, scrubbing, wet screening over 150 micron double deck screen oversize produced metallurgical grade assaying 46.50% Al2O3,1.49% reactive SiO2 and 21.70% Fe2O3 with 76.8% Al2O3 distribution at weight % yield of 67.0 and a dewatered screen under size cement / pottery grade concentrates assaying 28.63% Al2O3,32.28% Fe2O3 13.57% SiO2 and 20.41% LOI at wt% yield of 33.0. A wollastonite mine reject sample from Sirohi, Rajasthan was subjected to beneficiation process comprising of [1] Rougher calcite flotation at -150mesh,D8080 microns, 33%S, pH 7 using 2kg/t H2SO4 and 1kg/t of sodium oleate [2] two cleanings of rougher calcite float and recirculation of dewatered cleaner tails to rougher feed [3] Wet high intensity magnetic separation of Rougher tails at 19200 gauss. The above flotation –WHIMS process yielded a ceramic grade concentrate assaying 97% CaO.SiO2, 0.49% Fe2O3, 1.01% Al2O3 and 0.45% LOI at weight % yield of 75.0. The cleaner calcite float assaying 45.6% CaO, 7.20% Fe2O3, 4.21% Al2O3, 5.89% SiO2 and 36.22% LOI may be used as by-product as it meets cement grade.

Optimization of an Iron Ore Washing Plant

The sustainable viability of a mineral enterprise depends on improving the concentrate quality, generating readily salable by-products, improving recovery, throughput, and reduction of unit cost rate and maximize the unit income rate and thereby unit profit rate. Closing down of iron ore mines due to environmental constraints spurred the captive iron ore washing plants to workon a custom plant mode and also recover the values from their slimy tails. This paper enumerates the difficulties faced by a captive iron ore fine washing plant [treating iron ore fines assaying Fe∼58% yielding sands assaying Fe>60%] due to raw material change yielding unsalable sands and discuss the importance of process plant audit for improving the mineral processing plant performance. Based on the base line study, laboratory tests on typical samples followed by short term modifications, retrofitting of downstream slime concentrating wet high intensity magnetic separators and dewatering of products could produce readily salable sinter grade [Fe>60%] and pellet grade[Fe>62.5%] with an overall increase of concentrate yield by 11.5%. Even the previous wash plant tails [which assayed Fe > 45%] may be reprocessed in the retrofitted slime processing VPWHIMS plant. The final tails assayed 38.60% Fe at weight % yield of 28.5. Efforts are on for utilizing the above tails in bricks- tiles manufacture. Also, R&D efforts to concentrate Fe values from above 38.60% Fe tails by Magnetizing roast followed by magnetic separations in bench scale has given encouraging results. Thus auditing not only improved the quality, quantity and rate of production of concentrate but mitigated the problem of tailing disposal. The investments were repaid within a year of operation and unit operating costs reduced by 20% with reference to base line data.

Magnetic Separation and Magnetic Properties of Low-Grade Manganese Carbonate Ore

The relation between the magnetic separation behavior and magnetic properties of a low-grade manganese ore was analyzed before and after treatment by direct reduction with coal. It was found that raw ore with an initial average grade of 10.39% Mn and consisting of diamagnetic and paramagnetic minerals can be concentrated by high-intensity magnetic separation to produce a salable product with a grade of 22.75% Mn and a recovery of 89.88%. In contrast, direct reduction of the ore results in a new Mn-Fe oxide phase formed with a combination of ferromagnetic and paramagnetic properties, thereby increasing the magnetic susceptibilities of the ore by almost two orders of magnitude. The grade of Mn for the roasted ore could only be concentrated to 15.49% with a recovery of 66.67%. Therefore, it is concluded that the low-grade manganese ores with antiferromagnetic and paramagnetic (or diamagnetic, but not strongly ferromagnetic) properties could be efficiently beneficiated via high-intensity magnetic separation.

Beneficiation and Mullitization of Mishdovan Andalusite

The results of mineralogical studies by XRD, XRF and thin section techniques showed that the main minerals of the deposits (Bafgh-Yazd region, containing 5 – 10 percent sillimanite minerals group, with 18 – 20% Al2O3) were quartz, sillimanite, mica (biotite and muscovite), garnet, kyanite, andalusite and some opaque minerals. Mineral processing studies showed that the kyanite concentrate from this ore could be obtained by using different methods such as magnetic separation, vibrating table, and flotation. The results of experiments showed that a concentrate of 42% Al2O3 with 54% recovery was obtained by using a vibrating table. In order to separate iron-bearing minerals (Fe2O3 contents to less than 1%), the concentrate was processed by high-intensity magnetic separation. This increased the Al2O3 content to 62%. Applying the flotation method to the fine fraction of the sample (75 – 150 μm) yielded a concentrate containing 46.3% Al2O3, , with a recovery of 47.56%. The process of mullitization of kyanite concentrate was also studied under different heat-treatment conditions (1400 – 1600°C and 0.5 – 3.5 h) and with different particle sizes (38 – 300 μm). The results of microstructural and phase evolution studies by SEM and XRD showed that complete transformation of kyanite to mullite took place by means of heat treatment in the range 1500 – 1550°C over a period of 2.5 h. At 1550°C, the rates of mullitization and densification were increased as a result of a decrease in the materials’ particle size from 300 to 38 μm.

Experimental study on the beneficiation of low-grade iron ore fines using hydrocyclone desliming, reduction roasting and magnetic separation

Beneficiation of −2 mm low-grade iron ore tailings (50·7%Fe, 10·8%SiO2 and 4·4%Al2O3) from Western Australia was studied. The sample consisted of hydrohaematite, goethite and quartz, with lesser kaolinite and shale. Two processing options were tested, which were wet high-intensity magnetic separation (WHIMS), either using deslimed or untreated feed, and reduction (magnetising) roasting of deslimed feed followed by Davis tube tests (DTT). WHIMS tests using deslimed feed gave a product having 55·4%Fe, 6·1%SiO2 and 2·7%Al2O3, while the iron recovery was 55·7%. The calcined iron grade was 62·1%Fe. Davis tube tests using deslimed feed that had been reduction roasted at 700°C using a 1∶1 mixture of CO/CO2 gave a product with 63·2%Fe, 5·4%SiO2 and 2·9%Al2O3, while the iron recovery was 60·1%. Overall, desliming followed by reduction roasting and DTT produced the highest grade product with the highest iron recovery.

Rejecting phosphorus in hematitic iron ore streams: is flotation the best approach?

It is widely known that steel made from iron ore pellets high in phosphorus is brittle. Removal of phosphorus from iron ores such as hematite has proven to be difficult. The majority of research on phosphorus removal from hematite ores has been focused on flotation. The purpose of this study was to assess phosphorus distribution under current operations at an existing hematite concentrator and determine how efficient the plant is at removing phosphorus. Objectives included: (1) Perform a phosphorus balance at an operating plant to assess phosphorus distribution under current operations; (2) Determine phosphorus removal efficiency of each separating unit and (3) Perform a quantitative liberation analysis to determine max phosphorus removal by physical means. Liberation was quantitatively determined using wet high intensity magnetic separation (WHIMS) to separate iron ore from liberated apatite (and other nonmagnetic compounds). It was observed that 61.2% of the total phosphorus entering Plant F was rejected during current operations. The desliming process was the most efficient step at removing phosphorus (45.1% P removed), whereas the flotation step was much less effective (16.1% P removed). Liberation analyses indicated that the deslime thickener may have been more efficient at removing phosphorus than the flotation circuit due to the greater abundance of liberated phosphorus in the deslime thickener feed. The scavenger returns stream was identified as having a high concentration of phosphorus and a possible point of phosphorus removal. However, liberation analyses indicated that only 32.4% of the total phosphorus in the stream was liberated. Grinding the scavenger returns to 80% passing 5.2 μm increased the amount of liberated phosphorus in the stream to 70.4%.

Development of a process flowsheet for the beneficiation of low-grade iron ore fines from the Bellary-Hospet region of Karnataka, India

It was possible to beneficiate a low-grade iron ore fines sample from Bellary-Hospet, Karnataka, India assaying 56% Fe, 9.1% SiO2 and 5.2% Al2O3 and produce two concentrates, namely, a sinter-grade fines concentrate (43.7% by weight), assaying 63.6% Fe, 2.6% SiO2 and 1.7% Al2O3, and a pellet-grade concentrate (30.7% by weight) assaying 64.7% Fe, 2.9% SiO2 and 1.7%Al2O3. Rejects (25.6% by weight) assayed 32.5% Fe, 27.9% SiO2 and 15.4% Al2O3. The mineralogical characterization indicated that the sample consisted of 69.5% iron-bearing minerals (56% hematite, 7.5% martite and 6% goethite-limonite), 12.5% quartz and 15.2% clay, and the rest were minor minerals. Liberation size was found to be in the size range of 25 to 100 μm. The process flow sheet consists of jigs, spirals, grinding and low- and high-intensity magnetic separation of the deslimed feed.

Separation analysis of dry high intensity induced roll magnetic separator for concentration of hematite fines

In this study, a three level Box–Behnken factorial design combined with response surface methodology was used for modeling and optimization of process parameters of induced roll dry high intensity magnetic separator. The influence of magnetic field intensity, roll speed and feed rate was analyzed for the separation of hematite minerals. Second-order response functions were produced for the grade and recovery of the hematite minerals in the magnetic fraction. Taking advantage of the quadratic programming, optimized levels of the process variables have been determined as optimum levels to achieve the maximum grade of 51.2% Fe, and maximum level of recovery was 97.8% Fe whereas minimum grade of 23.9% SiO2 in the magnetic product was predicted. Further optimization was carried out by targeting the Fe (%) content and recovery of the magnetic product of above 50%. The influence of the process variables of the induced roll high intensity magnetic separator on grade and recovery of the hematite mineral in the magnetic fraction were presented as 3D response surface graphs.

Experimental Study on a Low Grade Sulfide-Oxidized Mixed Copper-Iron Ore in Anhui

The copper-iron ore has grades of 0.58% Cu and 42.14% Fe in Anhui. According to test on raw ore, it has the characteristics of close intergrowth and fine dissemination size, which belongs to a refractory ore. The copper oxide distributes mainly at the perimeter of copper sulfide. According to the characteristics of the structure, a flow sheet of rough grinding and flotation of inter-locked particles is taken. This process can recover copper effectively, leading to the recovery of Cu increase to 70.05%.A combined technological process of high intensity magnetic separation-gravity separation is used to hematite, which achieves an iron grade of 62.34% in the final concentrate and a recovery of 65.49%.

Research on mineral processing for high silica low grade hematite ore in Xinjiang

In order to develop and utilise cheap iron ores with low quality for cost reduction, a hematite ore from Xinjiang province was investigated to determine the iron increase and silicon reduction using ore dressing process experiments. Results showed that iron concentrate with 61%Fe and iron recovery of 66% were achieved through the process flowsheet of grinding, high intensity magnetic separation, regrinding of coarse concentrate, clean concentration by high intensity magnetic separation, roughing reverse floatation and cleaning reverse floatation of the high intensity concentrate, with the tailings from this latter stage fed back into the roughing reverse floatation stage.

Optimisation of magnetic separation: A case study for soil washing at a heavy metals polluted site

Sandy loam soil polluted with heavy metals (As, Cu, Pb and Zn) from an ancient Mediterranean Pb mining and metallurgy site was treated by means of wet high-intensity magnetic separation to remove some of the pollutants therein. The treated fractions were chemically analysed and then subjected to magnetic characterisation, which determined the high-field specific (mass), magnetic susceptibility (κ) and the specific (mass) saturation magnetisation (σS), through isothermal remanent magnetisation (IRM) curves. From the specific values of κ and σS, a new expression to assess the performance of the magnetic separation operation was formulated and verified by comparison with the results obtained by traditional chemical analysis. The magnetic study provided valuable information for the exhaustive explanation of the operation, and the deduced mathematical expression was found to be appropriate to estimate the performance of the separation operation. From these results we determined that magnetic soil washing was effective for the treatment of the contaminated soil, concentrating the majority of the heavy metals and peaking its separation capacity at 60% of the maximum output voltage.

New mega-sized wet high intensity magnetic separator: a cost-effective solution to reclaim iron ore fines from tailing dams

Ten years of continuous research and development have led to a major improvement in the field of iron ore Wet High Intensity Magnetic Separation - WHIMS. With this cutting-edge technology, Gaustec has established a new world record in this class of Magnetic Separators, by providing a sheer feed rate of up to 1400 tph for iron ore fines. Although low-grade iron ore mines will benefit from this new technology, focused on herein is the reclaiming of low-grade iron ore tailing from ponds, having in mind its huge positive environment impact and business opportunity. Based on this newly developed technology, the construction in Brazil of a Concentration Plant started in 2012 for dressing iron ore tailings at 45% Fe grade, at Itaminas Mine. This plant went into operation this year. Based on the good performance of this first unit, the construction of a second Concentration Plant of the same type, to further reduce to 18% Fe in the tailings, is under way, scheduled to be started-up in 2014.

Characterization and beneficiation studies for the removal of iron from a china clay from India

AbstractA china clay sample from Jharkhand State, India, containing 65.0 wt.% SiO2, 22.7% Al2O3, 1.77% Fe2O3and 9.10% LOI was subjected to physical beneficiation and acid leaching studies to improve its quality. The clay was characterized by optical microscopy, XRD, and wet chemical analysis methods. Quartz and goethite are the two major impurities. High intensity magnetic separation removed only 10% of the total iron. Experiments with oxalic acid were carried out to establish the leaching kinetics of iron and the effects of acid concentration, time and temperature on iron leaching were also examined. The study demonstrated that ∼90% of total iron could be removed using 5% oxalic acid. The dissolution of iron from clay is best described by diffusion of ions through the product layer of constant size spherical particles. The activation energy of the leaching process over the temperature range was calculated to be 51.14 kJ/mol.

Iron recovery from the waste generated during the cutting of granite

Metallic iron is present in the waste left when granite blocks are cut. Thus, the purpose of this study was to characterize this waste using chemical and particle size analyses. To achieve this, X-ray diffraction and scanning electron microscopy coupled with electron back-scattered diffraction were used. To find the method with the best metallic iron recovery from the waste of ornamental rock, three distinct methods were examined: magnetic separation, table concentration and cyclone processing. The first method involved three steps: (1) use of a wet high-intensity magnetic separator, where only the equipment’s remaining magnetic field was present; (2) the material from the first step was then submitted to separation again, this time using a magnet for rare earth particles; and (3) this material after two separation processes was finally submitted to ferromagnetic separation. The second method used a concentration table set at various inclinations, oscillation frequencies and wash flow rates. Meanwhile, for the third method, the cyclone tests, only the water pressure was varied. After each test, a chemical analysis was performed to determine the metallic iron present in each sample. The tests revealed that magnetic separation presents the best results. Using this technique, a ferrous concentrate with 93 % metallic iron content and a granite concentrate with only 0.6 % metallic iron were obtained. On the other hand, in the table concentrator tests, the ferrous concentrate only had a metallic concentration of 13.6 %. In separation by the cyclone processing, the product barely contained metallic iron (7.2 % maximum).

Recovery of high grade iron compounds from LD slag by enhanced magnetic separation techniques

A representative sample of LD slag provided from French steel industry was treated by different physical separation techniques especially used in mineral processing. The results of characterisation study show that the LD slag may contain up to 35% of iron compounds. The X-ray diffraction reveals the presence of the following crystallized mineral phases: CaO, MgO, Al2O3, SiO2, MnO, and P2O5. Larnite (Ca2SiO4), di-calcium aluminoferrite (brownmillerite: Ca2Fe2−xAlxO5 with x=0.6) and a solid solution (Fe, Mn, Mg)O structurally close to the wüstite (FeO) and some residual lime (CaO).The results of grinding tests show that the manner of grinding is very important. Soft Grinding (SG) or sequential grinding is most suitable to reduce the particle size of LD slag avoiding the overproduction of fine particles, which hinder the effectiveness of magnetic separation techniques. The combination of Low and High Intensity Magnetic Separation (LIMS and HIMS) of ground LD slag at 63μm in wet process may recover ferromagnetic particles (iron oxides) at LIMS and paramagnetic particles at HIMS, while the non-magnetic fraction contains mostly calcium silicates.From this investigation, two flow-sheets of treatment of LD slag are suggested to recover high grade iron material for recycling in metallurgical processes. Calcium and silicon oxide rich product will be directed to the cement industry.

Experimental Study of Flotation on High Intensity Magnetic Concentrates of Ilmenite

In order to improve the separating index of ilmenite to separate the concentrate by high intensity magnetic separation, the Heishan iron ore in Chengde did some work. Separate the sulfide ore out by flotation under the conditions of concentration by weight in feed 32%, consumption of xanthate 200g/t and 2# oil 40g/t. Use sulfate to adjust the pH of the low sulphur product of flotation, the mixture of EM351-2 and EM351-3 as foaming agent, after one roughinging and four fold concentrating, got the final titanium concentrate, the grade of which is 47.23%, and the recovery is 58.29%. During the procedure of roughing, the consumption of the reagent as follows: sulfate 2kg/t, EM351-3 1kg/t, EM351-2 900g/t. The consumption of sulfate during fourfold concentrating is 1kg/t. The index is more stable when the concentration in feed is 18%~26% during flotation. The index is stable during the continuous 26 work time for the process under this reagent system. The screen analysis of the flotation concentrate indicates that this reagent system has a better effect on the flotation of +0.074mm particles, and a bad effect on the flotation of-0.045mm particles.

Glass Sand Processing Techniques in the Rayong Area, Thailand

This article discusses the beneficiation of glass sand at Rayong province in the eastern part of Thailand . The process consists of revolving screen, hydrocyclone, attrition scrubber, tank classifier, spiral concentrator, wet high intensity magnetic separator and closed loop water recycling system. There are 13 glass sand processing plants in this area with the overall capacity 2 million tons per year and supply glass sand to float glass and flat glass industry, glassware industry, glass packaging industry, ceramic industry and chemical industry in Thailand. Keywords: Glass sand, Revolving screen, Hydrocyclon, Attrition scrubber, Tank classifier, Spiral concentrator, Wet high intensity magnetic separator, Closed loop water recycling system.