Direct shipping of high grade iron ore, because of depletion or partial depletion of reserves, or high costs of operation has forced operators to use some means of beneficiation to produce an acceptable product with the lower grade iron ore reserves.
Deposits of comparatively lower grade iron ore that remain relatively untouched or by-passed, are now most important because of increase in consumer demands. Deposits of comparatively low grade specular hematite amenable to beneficiation by flotation have produced concentrates superior in grade to direct shipping ores.
Low grade deposits containing specular hematite (Fe2 O3) as the major iron mineral as low as 25% Fe can be treated with Sub-A Flotation to produce concentrates that average better than 62% Fe with less than 9% SiO2 and with a high recovery.
The above flowsheet has been developed to produce a high grade product economically with maximum recovery. Due to the flexibility of Units and especially the Sub-A Flotation Machine, gravity flow can be utilized throughout the mill, thus keeping pumping requirements to a minimum.
Following initial test work for Ford Motors, a Pilot Plant was installed. A fatty acid reagent combination was developed to float the specular hematite in a concentrate assaying over 65% iron. This same procedure and reagents are now being employed in present day operations.
Three stage ore reduction is used with either a grizzly or vibrating screen between each crushing stage. Removing fines before putting the ore through a crusher increased the efficiency of the crusher as it is then only working on material that must be reduced. The fines form a bedding on the conveyor belt, thus increasing its life. Electromagnetic and magnetic head pulleys remove tramp iron from the ore, the former to remove iron near the surface and the magnetic pulley for tramp iron close to the belt.
Increased efficiency of grinding is obtained by using two stage grinding. The Rod Mill reduces the feed to approximately 10 mesh and is in open circuit with the Classifier which overflows at 48 mesh. A Ball Mill operates in closed circuit with the classifier.
A Sub-A Unit Cell will produce an extremely high grade concentrate when operated on the ball mill discharge. A Selective Mineral Jig may also be used on the classifier sands to produce a high grade concentrate. Concentrates removed in the grinding circuit are usually very low in phosphorus and silica.
Reagent costs are cut to a minimum, desliming the 48 mesh material at approximately 20 microns. This is accomplished with a heavy duty Hydroclassifier which also thickens the slurry to approximately 65 % solids for conditioning.
The thickened underflow from the hydroclassifier is metered with a Adjustable Stroke Diaphragm Pump to High Solids Open Type Conditioners. As true of many non-metallics, high solids conditioning is most important. After conditioning, the slurry is diluted to 35% solids for rougher flotation.
Reagents are stage added to the conditioners and unless a unit cell is used or a low phosphorus productis to be made, this is the only point of addition. The most common reagents are red oil high in oleic acid content, petroleum sulfonates, a frother and occasionally some mineral oil. Emulsions of the first two are sometimes helpful. Flotation is carried out in a neutral circuit unless the phosphorus, usually in the form of apatite, is to be depressed. Then cleaners are usually operated with acid pH and sodium fluoride,fuel oil and sulphuric acid are added to the cleaners.
Each flotation circuit consists of a four cell open flow roughing section followed by a two cell scavenger. The scavenger concentrate is returned by gravity to the third rougher cell and the rougher concentrate from the first rougher cell is sufficiently high grade ( + 58% Fe) to combine with the cleaner concentrate which flows by gravity to the recleaners. All cells are supercharged with low pressure air. Double overflow Spitzkasten cells with froth paddles are used to quickly remove the heavy froth as soon as it forms.Typical flotation results are shown in the table below:
The final concentrate flows by gravity to the Heavy Duty Spiral Rake Thickener and is metered to the Disc Filter with a Adjustable Stroke Diaphragm Pump. Due to fast settling characteristics, an agitating mechanism must be placed in the bottom of the filter tank to keep the solids from settling out. The filter is so installed that the tank may be drained by gravity to the thickener. The filtrate is returned to the thickener feed.
The flowsheet is designed for large tonnage operation and parallel circuits which are a necessity on all the low grade, low value iron ore deposits of this type. Flotation offers a very efficient low cost treatment method for beneficiation of these ores.
With the rapid economic development, the iron ore resources of the concentrator are decreasing year by year, and the degree of "lean, fine and heterogeneous" of selected ore is obviously increasing, the supply conditions are becoming more and more demanding, the difficulty of sorting is increasing, and the process flow adapts to changes in the nature of ore The performance has been severely tested, and the trend of rising iron grades in tailings is widespread.
The composition of lean hematite ore is relatively simple and belongs to Anshan-style iron-bearing quartzite. The iron minerals are mainly hematite, false hematite, goethite, magnetite, and a small amount of limonite, siderite, and iron. Dolomite etc. Gangue minerals are mainly quartz, tremolite, actinolite, chlorite and a small amount of clay minerals.
2.Most of the ore structures are belt-like structures, and the structure is relatively simple. The shape of the minerals is relatively complete, with inclusion structure and crystal structure, etc., which affect the separation of the ore content.
3.The particle size of the iron mineral intercalation is about 75m, and the particle size of the gangue mineral intercalation is greater than 100m. This may be the result of sufficient recrystallization in the later stage. The iron mineral content of -10m is low. These characteristics make the content of lean conjoined organisms formed in the ore grinding process low. In summary, the ore is easy to be selected.
Focusing on the production process, that is, the process flow of stage grinding, coarse subdivision, heavy separation strong magnetic anion reverse flotation, in-depth and detailed analysis of the characteristics of the test process and the process parameters that are conducive to improving production indicators. The laboratory continuous selection test results show that under the condition of 24.52% of the original ore grade, the grade of gravity concentrate concentrate is 67%, the flotation concentrate grade is 67.5%, the strong magnetic tailings grade is 11.42%, and the magnetic tailings grade is 7.04%. The flotation tailings grade is 14.43%. The process flow of "stage grinding, coarse subdivision and separation, gravity separationstrong magneticanion reverse flotation" is used to separate poor hematite ore with comprehensive concentrate grade, which has strong adaptability to changes in the nature of the original ore In particular, it has strong adaptability to the status quo of low grade of raw ore and frequent changes in the initial stage of production.
Prominer Shanghai will continue to optimize the beneficiation process, improve process adaptability and provide a basis for stabilizing quality and reducing tails, comprehensively investigate the process flow of lean hematite ore beneficiation, and focus on analyzing the flow of ore materials to determine several major iron minerals in the process Summarize the location and reason of metal loss.
Prominer has been devoted to mineral processing industry for decades and specializes in mineral upgrading and deep processing. With expertise in the fields of mineral project development, mining, test study, engineering, technological processing.
Investigations were carried out, to establish its amenability for physical beneficiation on a low grade siliceous iron ore sample by magnetic separation. Mineralogical studies, with the help of microscope as well as XRD, SEMEDS revealed that the sample consists of magnetite, hematite and goethite as major opaque oxide minerals where as quartz and kaolinite form the gangue minerals in the sample. Processes involving combination of classification, dry magnetic separation and wet magnetic separation were carried out to upgrade the low grade siliceous iron ore sample to make it suitable as a marketable product. The sample was first ground and each closed size sieve fractions were subjected to dry magnetic separation and it was observed that limited upgradation is possible. The ground sample was subjected to different finer sizes and separated by wet low intensity magnetic separator. Dry beneficiation studies by Permaroll separator indicated that it is possible to get a product with 60.2% Fe at 22% weight recovery. It is possible to get an over all concentrate with 54% Fe at 32.4% weight recovery by combination of size reduction followed by LIMS and WHIMS.
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S. Dey, R.P. Bhagat, R.K. Kunwar, D.S. Rao, B. Banerjee, S.C. Maulik, Comparative studies on beneficiation of bauxite samples for application in refractory industry. Metals Mater. Process. 13(1), 18 (2001)
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