High alumina and silica content in the iron ore affects coke rate, reducibility, and productivity in a blast furnace. Iron ore is being beneficiated all around the world to meet the quality requirement of iron and steel industries. Choosing a beneficiation treatment depends on the nature of the gangue present and its association with the ore structure. The advanced physicochemical methods used for the beneficiation of iron ore are generally unfriendly to the environment. Biobeneficiation is considered to be ecofriendly, promising, and revolutionary solutions to these problems. A characterization study of Salem iron ore indicates that the major iron-bearing minerals are hematite, magnetite, and goethite. Samples on average contains (pct) Fe2O3-84.40, Fe (total)-59.02, Al2O3-7.18, and SiO2-7.53. Penicillium purpurogenum (MTCC 7356) was used for the experiment. It removed 35.22pct alumina and 39.41pct silica in 30days in a shake flask at 10pct pulp density, 308K (35C), and 150rpm. In a bioreactor experiment at 2kg scale using the same organism, it removed 23.33pct alumina and 30.54pct silica in 30days at 300rpm agitation and 2 to 3l/min aeration. Alumina and silica dissolution follow the shrinking core model for both shake flask and bioreactor experiments.
S.N. Groudev, F.N. Genchev, and S.S. Guidarjiev: Metallurgical Applications of Bacterial Leaching and Related Microbiological Phenomena, Eds., L.E. Murr, A.E. Torma, J.A. Bfierley, Academic Press, New York, NY, 1978, pp. 253-73.
D.R. Berry, A. Chmiel, Z. Alobaidi: The British Mycological Symposium Series No. I. Citric Acid Production by Aspergillus Niger, Eds. J.E. Smith, and J.A. Pateman, Academic Press, London, UK, 1977, pp. 410-14.
The authors are genuinely grateful to the Council of Scientific and Industrial Research for its constant financial support. One of the authors would like to acknowledge CSIR for a Senior Research Fellowship.
Mishra, M., Pradhan, M., Sukla, L.B. et al. Microbial Beneficiation of Salem Iron Ore Using Penicillium purpurogenum . Metall Mater Trans B 42, 1319 (2011). https://doi.org/10.1007/s11663-010-9444-7
Iron ore is one of the important raw materials for the production of pig iron and steel in the iron and steel industry. There are many types of iron ore. According to the magnetic properties of the ore, it is mainly divided into strong magnetism and weak magnetism. In order to improve the efficiency and production capacity of ore dressing and meet the smelting production requirements of iron and steel plants, appropriate and technology should be selected according to the different properties of different iron ore during beneficiation to achieve better beneficiation effects.
The composition of iron ore of a single magnetite type is simple, and the proportion of iron minerals is very large. Gangue minerals are mostly quartz and silicate minerals. According to production practice research, weak magnetic separation methods are often used to separate them. In a medium-sized magnetic separation plant, the ore is demagnetized and then enters the crushing and screening workshop to be crushed to a qualified particle size, and then fed to the grinding workshop for grinding operations. If the ore size after grinding is greater than 0.2 mm, one stage of grinding and magnetic separation process is adopted; if it is less than 0.2 mm, two stages of grinding and magnetic separation process are adopted. In order to increase the recovery rate of iron ore as much as possible, the qualified tailings may be scavenged and further recovered. In areas lacking water resources, a magnetic separator can be used for grinding and magnetic separation operations.
Because magnetite is easily depleted under the effect of weathering, such ores are generally sorted by dry magnetic separator to remove part of gangue minerals, and then subjected to grinding and magnetic separation to obtain concentrate.
The magnetite in the polymetallic magnetite is sulfide magnetite, and the gangue mineral contains silicate or carbonate, and is accompanied by cobalt pyrite, chalcopyrite and apatite. This kind of ore generally adopts the combined process of weak magnetic separation and flotation to recover iron and sulfur respectively.
Process flow: the ore is fed into the magnetic separator for weak magnetic separation to obtain magnetite concentrate and weak magnetic separation tailings, and the tailings enter the flotation process to obtain iron and sulfur.
The common process flow in actual production is: the raw ore is fed into the shaft furnace for roasting and magnetization, and after magnetization, it is fed into the magnetic separator for magnetic separation.
Gravity separation and magnetic separation are mainly used to separate coarse-grained and medium-grained weakly magnetic iron ore (20~2 mm). During gravity separation, heavy medium or jigging methods are commonly used for the gravity separation of coarse and very coarse (>20 mm) ores; spiral chutes, shakers and centrifugal concentrators for medium to fine (2~0.2mm) ores, etc. Reselect method.
In magnetic separation, the strong magnetic separator of coarse and medium-grained ore is usually dry-type strong magnetic separator; the fine-grained ore is usually wet-type strong magnetic separator. Because the grade of concentrate obtained by using one beneficiation method alone is not high, a combined process is often used:
Combination of flotation and magnetic separation: the magnetite-hematite ore of qualified particle size is fed into the magnetic separator for weak magnetic separation to obtain strong magnetic iron ore and weak magnetic tailings, and the tailings are fed into the magnetic separator for weak magnetic separation. In strong magnetic separation, strong magnetic separation tailings and concentrate are obtained, and the concentrate is fed to the flotation machine for flotation to obtain flotation iron concentrate tailings.
Combined gravity separation and magnetic separation: similar to the combined flow of flotation and magnetic separation, only the flotation is replaced by gravity separation, and the products are gravity separation concentrate and tailings. These two combined methods can improve the concentrate grade.
The above are mainly the common separation methods and technological processes of strong and weak magnetic iron ore. The composition of natural iron ore is often not so simple, so in actual production, it is necessary to clarify the mineral composition, and use a single sorting method or a joint sorting method according to the corresponding mineral properties. Only in this way can the beneficiation effect be improved.
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The iron ore industries of India are expected to bring new technologies to cater to the need of the tremendous increase in demand for quality ores for steel making. With the high-grade ores depleting very fast, the focus is on the beneficiation of low-grade resources. However, most of these ores do not respond well to the conventional beneficiation techniquesused to achieve a suitable concentrate for steel and other metallurgical industries. The present communication discusses the beneficiation practices in the Indian context and the recent developments in alternative processing technologies such as reduction roasting, microwave-assisted heating, magnetic carrier technology and bio-beneficiation. Besides, the use of new collectors in iron ore flotation is also highlighted.
The present work investigates the microflotation of hematite and quartz using microemulsion and nanoemulsion systems as well as alkyl ether monoamine solutions. This application is based on the ability of such systems to reduce interfacial tension, which favors their application in separation processes. In these systems, the collector was composed by alkyl ether monoamine (Flotigam EDA), n-butyl alcohol, and kerosene. Corn starch with a high degree of purity was the depressant in the process. Results show that the performance of nanoemulsions is higher than those of the microemulsions and alkyl ether monoamine solutions; by simplifying and leading to an improvement of the process.
A biomining approach to process low-grade iron ores has the potential to turn closed mines or uneconomic mineral deposits into economic resources. Microorganisms and their metabolites have been commercially applied in the leaching of metals from medium- and low-grade sulfide minerals for many years. Efforts are now being directed to the application of biomining to oxide ore systems as high-grade ore becomes scarce. This chapter discusses the potential exploitation of microorganisms and their metabolites for the bioleaching of phosphorus from iron ore and as bioreagents for the selective flotation and flocculation of iron ore minerals.
A new modelling technique for simulating hydrocyclone performance has been developed, in which particles in every size fraction of the feed ore are classified based on ore texture type, taking into account that the same ore texture types in every size fraction of the feed ore have similar mineral contents and densities. Mineral tracking by optical image analysis and newly-developed texture classification software was used in this technique to classify the feed ore particles by texture type and to determine the average particle density of each class in every size fraction. Particle density calculations took into account the reduction of porosity with reduction of particle size and the effect of different imaging magnifications for different size fractions. The data obtained about each class in every size fraction was used to create a virtual feed which was input to the hydrocyclone model to simulate the ore processing performance. For model validation, pilot-scale hydrocyclone beneficiation experiments were performed on an iron ore blend, using different hydrocyclone pressures and percent solids in the feed pulp. Model parameters were determined from one set of experimental results and the calibrated model was then used to predict the outcomes of the two subsequent experiments. Comparisons of the model and experimental results are presented and discussed. This new approach enables prediction of the recovery of each mineral and texture type in the products, calculation of the total product iron grade and recovery, and optimisation of the hydrocyclone performance for a given ore.
Microwave-assisted magnetizing roast of a goethite-rich, reject waste stream.Goethite to magnetite conversion occurred at 600C in a 40:60 CO/CO2 gas atmosphere.A+62wt% Fe blast furnace pellet concentrate was produced with>88wt% iron recovery.Higher temperatures caused over-reduction and the generation of reduced Fe phases.
Microwave-assisted reduction roasting of a goethite-rich, reject iron ore waste stream (2 mm) was used to produce a high-grade concentrate. Reduction roast experiments were conducted at 370C, 450C, 600C and 1000C under gas atmospheres of 30:70 and 40:60 CO/CO2, with a soak time of 20min. Goethite was converted to hematite above 370C under both gas mixtures while at the higher roasting temperatures, increasing amounts of magnetite formed. Roasting conditions for the best conversion of goethite to synthetic magnetite were 600C in a gas atmosphere of 40:60 CO/CO2, with a soak time of 20min. Laboratory-based magnetic separations in a Davis tube indicated that a blast furnace grade (+62wt% Fe) pellet concentrate could be produced with an acceptable iron recovery of>88wt%. Under both gas atmospheres, a higher reduction temperature of 1000C achieved a greater conversion of goethite to magnetite but resulted in over-reduction and the generation of wstite, fayalite and Fe-rich spinel phases with different magnetic susceptibilities that are expected to make subsequent beneficiation difficult. Further processing to optimize the microwave-assisted magnetizing roast and the magnetic separation conditions can be expected to maximize the efficiency of upgrading the iron content in low grade goethite-rich iron ores.
Iron ore beneficiation is a multi-stage process that raw iron ore undergoes to purify it prior to the process of smelting, which involves melting the ore to remove the metal content. The process of iron ore beneficiation has two complementary goals and these define the methods used to refine it. The iron content of the ore needs to be increased and gangue, which is native rock and minerals of lesser value within the ore itself, must be separated out. Methods such as screening, crushing, and grinding of iron ore are often used in various ways to purify it, along with several stages of magnetic separation.
The iron ore industry classifies the material by the concentration of the metal that is present after iron ore beneficiation has been completed. High-grade iron ore must have a concentration of 65% iron or higher, and medium grade of 62% to 65%. Low-grade iron ore includes all mixtures below 62% iron concentration, which are not considered to be viable types of ore for use in metallurgy. Several different types of natural iron ore exist, but the two most common types used for metal refining are hematite, Fe2O3, which is usually 70% iron, and magnetite, Fe3O4, which is 72% iron. Low-grade iron ores also exist, such as limonite, which is hematite bonded to water molecules at 50% to 66% iron, and siderite, FeCO3, that is 48% iron.
One of the approaches to iron ore beneficiation first involves a basic screening or filtering of the ore and then crushing it using equipment like a jaw crusher to break up the rock from its natural state down to individual block or rock sizes with dimensions of length or height no greater than 3.3 feet (1 meter). This rock is then further pulverized in medium and fine level cone crushers or fine jaw crushers, and screened down to particle sizes of 0.5 inches (12 millimeters) or less, and is then passed on to a flotation process for separation. Separation involves using low-power magnetic fields to pull the ore with high-metal content away from lower-grade metal particles. The lower-grade ore at this point is cycled back into the rough flotation stage for further refining.
The end product that emerges from crushing and magnetic separation equipment is then ground into a powder-like consistency in a ball mill. This material is then further refined through iron ore beneficiation by using a dehydration tank to remove water content and by applying high-intensity magnetic fields generated by a disc magnetic separator. At this stage, low-grade ore that still contains metal value is placed back at the start of the cycle, and tailings, which are even lower-grade residues, are removed as waste.
Iron ore mining often focuses on looking for hematite deposits known as red iron ore, and magnetite, as they have naturally weak magnetic fields that aid in their purification. Hematite, however, responds better to the flotation process in iron ore beneficiation than magnetite, so it is the preferred type of ore. It responds best to what is known as gravity separation as well and several types of gravity equipment can be used to refine it, including jiggers, centrifugal separators, and shaking tables.
The global industry for iron purification has perfected the methodology for refining hematite as of 2011 more than other types of iron ore, and it therefore offers the highest yield in net iron content of any ore mined to date. Deposits of hematite around the world are considered to be the best form of iron ore available, though it is not clearly understood how such deposits were formed. The deposits are a diminishing natural resource that are believed to have formed on Earth approximately 1,800,000,000 to 1,600,000,000 years ago.