A review of the beneficiation of low-grade manganese ores by magnetic separation

ABSTRACT

Magnetic separation is an effective strategy for the upgrading of a variety of lean ores, including the beneficiation of low-grade manganese ores. This work reviews 24 studies on the magnetic separation of manganese ores; 6 of these studies report both a sufficiently high Mn grade (>44% Mn) and Mn/Fe ratio (>7.5) in the concentrate as to be suitable for use as high-grade feed materials in the production of ferromanganese. Of these 24 studies, the most efficient separation and enrichment was generally achieved by the reduction roasting of the ore prior to magnetic separation, rather than the direct separation of the ore. In both cases there was sufficient evidence for correlation, depending on the mineralogy, between the Mn and Fe grades of the ore and the final concentrate grade and Mn/Fe ratio. To yield a concentrate suitable for use in ferromanganese production, it is recommended that the ore contain a minimum initial concentration of ～25% Mn and ～10% Fe.     

铁锰矿和贫锰矿的合理利用

本文通过生产实践得出,含 Mn18—28％,(Mn Fe)38—48％的铁锰矿都可在高炉中生产富锰渣。利用高磷高铁的铁锰矿和低磷高硅贫锰矿进行配矿入炉,采用自然碱度酸性渣操作,控制渣中SiO_2含量在24—30％,可以炼出低磷低铁优质富锰渣。     

Effect of temperature on magnetizing reduction of agbaja iron ore

Agbaja oolitic iron ore, which has not been responsive to such beneficiation processes as froth flotation, gravity concentration, magnetic separation, and electrostatic separation, has been concentrated to 60 pct Fe grade and 87.3 pet Fe recovery (starting from a crude assaying 45.6 pct Fe) by the magnetizing reduction technique. The main parameter investigated was the effect of temperature on the magnetizing reduction process, and 600 °C was established as the optimum temperature for the reduction step. X-ray diffraction studies of the reduction products showed that the iron oxides were converted to magnetite, to wustite, or to metallic iron, depending on the temperature of reduction. The results from the subsequent magnetic concentration step were, in the main, dependent on the observed reduction products.     

Effect of temperature on magnetizing reduction of agbaja iron ore

Agbaja oolitic iron ore, which has not been responsive to such beneficiation processes as froth flotation, gravity concentration, magnetic separation, and electrostatic separation, has been concentrated to 60 pct Fe grade and 87.3 pet Fe recovery (starting from a crude assaying 45.6 pct Fe) by the magnetizing reduction technique. The main parameter investigated was the effect of temperature on the magnetizing reduction process, and 600 °C was established as the optimum temperature for the reduction step. X-ray diffraction studies of the reduction products showed that the iron oxides were converted to magnetite, to wustite, or to metallic iron, depending on the temperature of reduction. The results from the subsequent magnetic concentration step were, in the main, dependent on the observed reduction products.     

Direct Reduction of Mixtures of Manganese Ore and Iron Ore

This paper presents recent results of direct reduction investigation of different combination of blends of manganese ore, iron ore and coal at the Department of Ferrous Metallurgy (IEHK) of RWTH Aachen University. A mixture of iron and manganese ore in a ratio of 75/25 is a good raw material for steelmaking of high Mn‐alloyed grades. The experimental studies consisting of reduction of (a) fine material and (b) agglomerated material (briquettes) were carried out in the range of 1273 to 1673 K. The behaviour of combined reduction of manganese ore and iron ore and the employment in the direct reduction on a coal and gas basis for production of steels with high Mn content were investigated. It was found that a high metallization degree for Mn can be reached at 1273 K with the reduction of manganese ore by hydrogen‐containing gas. Addition of carbon monoxide to the reducing gas retarded the reduction process. The addition of coal to manganese ore and iron ore blends increased the degree of reduction. The results of carbothermic reduction of briquettes consisting of a mixture of manganese ore and iron ore combined with coal as reducing agent show that a high temperature, a low Mn/Fe ratio and a high Fe₂O₃ content have a favourable effect on the degree of reduction. In order to obtain a high degree of metallization, the temperature should be higher than 1473 K. The reduction of briquettes at higher temperatures (up 1573 K) has shown a molten phase and the separation of slag and metal.     

Structure and mechanical properties of tempered martensite and lower bainite in Fe−Ni−Mn−C steels

The structure and mechanical properties of tempered martensite and lower bainite were investigated in a series of high purity 0.25 pct C steels with varying amounts of nickel and manganese. The martensites in 0.25 C-5 Ni?Fe and 0.25 C-3 Mn?Fe alloys were mainly untwinned, while those in 0.25 C-5 Ni-7 Mn?Fe and 0.25 C-7 Mn?Fe alloys were heavily twinned. Manganese appears to promote carbide precipitation along the lath boundaries in tempered martensite. At equivalent yield and ultimate tensile strength levels, the tempered martensite of lower manganese steels showed better impact toughness than the tempered martensite of higher manganese steels. The impact toughness (compared at similar strength levels) of untwinned tempered martensite of 0.25 pct C steel with Widmanstatten precipitation of carbide was higher than that of lower bainite, which showed unidirectional carbides. The reasons for the difference in impact toughness between the alloys, and also between the structures are rationalized in terms of internal twinning, grain boundary precipitation and carbide morphology together with other microstructural features.     

由软锰矿,闪锌矿,铁屑直接制取锰锌铁氧体软磁材料新工艺研究

本文结合磁性材料工艺和锰矿技术特点，创造性地提出由软锰矿、闪锌矿制备锰锌铁氧体材料，克服了锰矿、闪锌矿处理过程的Ｍｎ－Ｚｎ、Ｍｎ－Ｆｅ、Ｚｎ－Ｆｅ分离难题，大大降低了磁性材料生产成本，由于磁性材料产品附加值高，从而为我国丰富的贫锰矿利用找到了一条有效的途径     

Behaviour of manganese oxides during magnetising reduction of Baharia iron ore by CO–CO2 gas mixture

Abstract

High manganese containing iron ore samples were isothermally reduced with a CO–CO₂ gas mixture at 600–1000°C. The course of reduction was followed by a weight loss technique. The influence of reducing gas composition and temperature on the reduction kinetics was investigated. The different phases formed during reduction were identified by X-ray phase analysis, while their structures were microscopically examined. The reduced samples were magnetically tested by means of a Davis tube tester. The effect of grain size, drum speed, and cleaning conditions on the efficiency of magnetic separation was studied using a Box-Mag wet low intensity magnetic separator. The separation efficiency was determined by analysing total iron, manganese, and acid insoluble contents in both magnetic and non-magnetic fractions. Best testing results were obtained on separation of the sample reduced with 80CO–20CO₂ (vol.-%) at 800°C. The optimum grain size for magnetic separation is below 0·15 mm while that of the drum speed is 100 rev min^-1 . The cleaning of the magnetic fraction increases the iron content and decreases the manganese and acid insoluble contents.     

Acidithiobacillus ferrooxidans对软锰矿浸出的影响

利用循环伏安、交流阻抗谱和极化曲线研究了Acidithiobacillus ferrooxidans对软锰矿在模拟浸出溶液(9K基础培养基, A.ferrooxidans, Fe (Ⅲ), A.ferrooxidans+Fe (Ⅲ))中电化学腐蚀行为的影响; 利用模拟有菌/无菌浸出溶液中钝化膜的Mott-Schottky理论比较了有无细菌存在情况下形成的钝化膜的优劣性.结果表明, A.ferrooxidans促进MnO₂/Mn2+氧化还原转化, 催化MnO₂/Mn (OH)₂电极反应; 加速软锰矿/溶液界面电子交换, 无铁存在时A.ferrooxidans使电荷转移内阻降低34%, 比含Fe (Ⅲ)无菌体系低11%;引起软锰矿电极极化, 增强其氧化活性; 加速MnO₂向MnO·OH转化及其产物扩散.A.ferrooxidans与软锰矿作用更倾向于间接作用机理.在选取的各模拟电解液(pH值为2.0)中, 0.2~0.4 V区间内软锰矿形成耗尽层, 在模拟浸出溶液中形成的钝化膜都表现出p-n-p-n型半导体性能.在选取的0.2 V极化电位下, 无铁时引入A.ferrooxidans使膜中的施主/受主密度减少, 细菌含有多种基团参与半导体/溶液界面电子转移反应, 接受界面间自由电子或填充空穴, 促使软锰矿与溶液界面物质交换变频繁; 含铁溶液中加入A.ferrooxidans使得钝化膜受主/施主密度增大, A.ferrooxidans降低了膜的耐腐蚀性, 因而促进软锰矿浸出.      

Consolidation Behavior of High-Fe Manganese Ore Sinters with Natural Basicity

High-iron content manganese ore resources are becoming the mainstream raw ores for manganese extraction due to the depletion of high-grade manganese ores. Our previous research has reported the optimization parameters for the sintering of high-Fe manganese ore (abbr. high-Fe Mn-ore) fines. This study further investigated the consolidation behavior of high-Fe Mn-ore sinters with natural basicity. Sintering pot tests showed that the high-Fe Mn-ore sintering required high coke breeze dosage (about 9.9 wt.%). The CO content of the outlet flue gas (7.5 vol.%~8.0 vol.%) in the high-Fe Mn-ore sintering was higher than that in the ordinary iron ore sintering (1.0 vol.%~2.2 vol.%). XRD and SEM-EDS analyses indicated that the major mineral phases in the sinters included Fe-Mn oxides (Fe_xMn_3-xO₄), ferrotephroite ((Fe,Mn)₂SiO₄), Ca-,Al-,Mn-,Fe- bearing silicate melts, and a small quantity of hausmannite (Mn₃O₄) and free quartz (SiO₂). Optical microstructure and SEM images showed that the Fe-Mn oxides, Ca-, Al-, Mn-, Fe- bearing silicate melts and ferrotephroite particles are closely interconnected with one another. The formation of Fe-Mn oxides and ferrotephroite were beneficial to the sinter strength. Thermodynamic and phase diagram analyses further demonstrated that the major bonding phases of Fe-Mn oxides and ferrotephroite were easily formed under the strong reductive sintering atmosphere of high-Fe Mn-ores.     

Replacement of Ni by Mn in High-Ni-Containing Austenitic Cast Steels used for Turbo-Charger Application

High-temperature tensile properties of austenitic cast steels fabricated by replacing Ni by Mn in a 20 wt pct Ni-containing steel were investigated. In a steel where 8 wt pct Ni was replaced by 9.2 wt pct of Mn, 17.4 and 9.8 pct of ferrite existed in equilibrium phase diagrams and actual microstructures, respectively, because a role of Mn as an austenite stabilizer decreased, and led to deterioration of high-temperature properties. When 2 to 6 wt pct Ni was replaced by 2.3 to 6.9 wt pct Mn, high-temperature properties were comparable to those of the 20 wt pct Ni-containing steel because ferrites were absent, which indicated the successful replacement of 6 wt pct Ni by Mn, with cost reduction of 27 pct.     

熔融制样-X射线荧光光谱法测定铝矿、铁矿、钙矿、镁矿和锰矿中主要组分

熔融制样-X射线荧光光谱法(XRF)被应用到很多种类矿物样品中的主次组分的测试,但地矿实验室需要测试的矿物种类较多,单一的矿物种类测试很难满足测试需求。实验采用熔融制样法,以多种矿物标样及其混合标样为基础,建立了一种可用于多种类型矿物主要组分的X射线荧光光谱分析方法。实验确定熔融条件为样品量0.400 0 g,助熔剂为7.000 0 g四硼酸锂,加入4滴150 g/L溴化锂溶液为脱模剂,0.500 0 g硝酸锂氧化剂和0.400 0 g氟化锂流化剂。结果表明样品基体效应对测试结果影响不大。精密度考察发现:铝矿中主成分Al₂O₃、铁矿中主成分Fe、钙矿中主成分CaO、镁矿中主成分MgO、锰矿中主成分Mn的相对标准偏差(RSD,n=6)分别为0.49%、0.37%、0.64%、0.38%、0.85%。正确度考察发现:5种矿物样品中SiO₂、Al₂O₃、Ca、MgO、Mn、Fe的测定值与其他方法测定值相吻合。方法采用一套标准样品可测试多种矿物样品中主要组分,适用于地矿实验室矿物样品分析。     

CaO对海滨钛磁铁矿精矿直接还原?磁选工艺中还原气氛的影响

以铁品位为58.58%、TiO₂品位为12.04%的海滨钛磁铁矿精矿为试样,进行煤基直接还原–磁选试验。从反应产生的CO和CO₂气体组成、总反应的气化速率、CO分压值、金属化率、矿物组成等角度进行分析,查明了CaO在海滨钛磁铁矿精矿直接还原?磁选工艺中的作用机理。研究结果表明,CaO可以提高还原剂的气化速率,促进钛磁铁矿的还原,增加CO₂气体的产生量,从而降低CO分压值。同时发现CaO可以参与固固反应,降低含钛矿物中的FeO含量,也有利于钛、铁组分的迁移和富集,促进金属铁颗粒的聚集长大。因此,添加CaO有利于通过磨矿?磁选促进钛铁分离与回收。      

Solid-State Metalized Reduction of Magnesium-Rich Low-Nickel Oxide Ores Using Coal as the Reductant Based on Thermodynamic Analysis

The solid-state metalized reduction of magnesium-rich low-nickel oxide ore using coal as a reductant was studied based on thermodynamic analysis. The major constituent minerals of the ore were silicates and goethite. The former was the main nickel-bearing mineral, and the latter was the main iron-bearing mineral. Single factor tests were conducted to investigate the effects of reduction temperature, duration, and coal dosage on the beneficiation of nickel and iron such that optimal conditions were achieved. Considering the low recoveries of nickel and iron (Ni, 13.9 pct; Fe, 30.3 pct) under the obtained optimal conditions, an improved process, adding CaF₂ before the reaction, was proposed to modify the solid-state metalized process. The results showed that the recoveries of nickel and iron reached to 96.5 and 73.4 pct, respectively, and that the grades of nickel and iron in the concentrate increased from 2.5 and 62.6 wt pct to 6.9 and 71.4 wt pct, respectively. Nickel and iron in the absence of CaF₂ were metalized; nevertheless, the size of ferronickel particles was only 1 μm. Furthermore, alloys in the presence of CaF₂ aggregated and exhibited bands with a length greater than 200 µm. These observations suggested that CaF₂ could effectively reduce the surface tension of the newly generated alloy interface and promote the migration and polymerization of the alloy particles, which improves the beneficiation of nickel and iron by magnetic separation.     

Magnetic properties of low-grade hematite ore after magnetizing reduction and reoxidation using a fluidized bed

Magnetizing roasting via a fluidized bed,which was recognized as an efficient method for beneficiation of low-grade iron ores,has attracted much attention in China recently due to the fluctuation of the international iron ore market.In order to examine the effects of magnetic properties on the separability and to optimize the operating parameters,magnetic susceptibility and coercivity of a low-grade hematite after magnetizing reduction and reoxidation under different conditions were investigated.It was found that the magnetic susceptibility of roasted ore increased with reduction degree and particle diameter to different degrees.The magnetite was re-oxidized to maghemite when the temperature was below 400℃,and the magnetic susceptibility decreased slightly.The recovery efficiency decreased notably with the particle size for very fine grains although no significant change was found in magnetic susceptibility.The coercivity and remanence of roasted ores decreased with increasing roasting temperature.The scanning electron microscope(SEM) study showed that more cracks were produced by the reoxidation of reduced ores,which could possibly favor the intergranular fracturing and the liberation for further treatment.     

原位硫酸焙烧浸出低品位软锰矿及元素分离

研究了一种低品位软锰矿焙烧-水浸提锰的新方法。以锰和铁的提取率为指标,通过正交试验,确定了焙烧工艺的最合适条件为酸矿比2∶1,焙烧温度650 ℃,水酸比0.2∶1,焙烧时间4 h。进一步研究溶出温度、溶出时间、溶出液固比等因素对锰、铁提取率的影响,确定了溶出试验的最合适条件为搅拌速度300 r/min,溶出温度90 ℃,溶出时间50 min,溶出液固比6∶1,此条件下锰的提取率可达98.16%,铁的提取率约为0.87%,实现了低品位软锰矿中锰元素的高效提取以及锰与铁、硅元素的有效分离。     

某难选锰矿选矿工艺试验研究

本文针对陕西某低品位难选碳酸锰矿开展选矿工艺试验研究,并分别进行了两种不同品位矿样的选矿试验。结果表明,对于品位8.87%的低品位贫矿,采用磁选可获得锰品位14.35%,回收率89.59%的锰精矿;对于锰品位10.68%的混合样,磁选可获得品位16.02%,回收率88.61%的锰精矿,选别指标较好。     

Recovery Improvement of Fine Magnetic Particles by Floc Magnetic Separation

The performance of floc magnetic separation (FMS) has been compared with wet high-intensity magnetic separator (WHIMS). This study was performed on low-grade iron ore slime contained 59.58% Fe with 4.57% silica and 3.78% alumina. Detailed characterization data indicated that a substantial amount of the slime was below 20 µm in size. Beneficiation studies indicated that the FMS process is effective to recover fine hematite and goethite particles, compared with the conventional magnetic separation. In conventional magnetic separation, the extent of the fluid drag force exceeds the magnetic force exerted on ultrafine particles. Thus, ultrafine magnetic particles were usually not recovered effectively by magnetic separators, resulting in the loss of valuable ultrafine slime particles. The FMS process significantly increases the magnetic force on the ultrafine iron ore in the form of hydrophobic flocs in a magnetic field, thus the ultrafine particles can be picked up effectively as magnetic concentrates. The FMS process improved the Fe recovery from 37.35% to 79.60%.     

Dissolution behaviour of manganese ore in basic oxygen furnace type slag

In order to improve manganese yield during the reduction process of manganese ore in blowing practices employing less slag at BOF, the dissolution behaviour of manganese ore in slag has been studied in an experimental scale. The effect of temperature, slag composition, addition of CaF₂, and pre-treatment of manganese ore was examined for the dissolution behaviour of manganese ore into BOF type slags. The precipitation of (Fe,Mn)O phase in slag was observed during the addition of manganese ore. The dissolution rate of manganese ore into molten slag increased with temperature, and also increased with the initial contents of FeO, MgO and MnO. However, the effect of slag basicity was not evident on the dissolution rate of manganese ore into slag. The addition of CaF₂ and pre-treatment of Mn ore were very effective to promote the dissolution of manganese ore into slag.     

电感耦合等离子体发射光谱法测定矿产品中微量硫的研究

研究了利用电感耦合等离子体发射光谱法（ＩＣＰ－ＡＥＳ）测定铁矿、锰矿、水泥等矿产品中微量硫的溶样方法、工作条件的选择和结果的准确性。实验表明,王水溶样方法可靠,Ｓ１８０．７３１ｎｍ分析线可避免大量存在的Ｍｎ、Ｆｅ等基体元素的干扰,测定结果相对标准偏差小于２％,与国际方法无显著性差异。该法简便快速,稳定可靠,重现性好,可应用于进出口铁矿、锰矿、金属锰粉和水泥等产品的检验中。