Feasibility of Producing Pellet Grade Concentrate by Beneficiation of Iron Ore Slime in India

Abstract

Beneficiation of low grade iron ore slime from Chitradurga, India was studied with a view to produce pellet grade fines. The slime sample had a feed grade of 49.86% total Fe, 7.93% Al₂O₃, and 10.19% SiO₂. Kaolinite and quartz was found to be the main gangue minerals and they formed porous and friable oxide and hydroxide of iron. Over 54% of the materials in the slime were less than 20 micron and this size fraction contained higher percentage of gangue minerals. Liberation of free gangue minerals was observed to be substantial in all size classes. Beneficiation studies indicated that excellent rejection of silica and alumina could be obtained through physical separation. The low grade slime could be enriched to 66.36% Fe with 1.75% silica, and 1.44% alumina.     

Effect of mineral geology, mineral size and settling time on selective dispersion and separation process for recovering iron value from iron ultra fines

The dispersion study was conducted on ultra fines of iron ore collected from two locations, Joda and Noamundi slime ponds in the states of Orissa and Jharkhand (India) respectively using sodium hexametaphosphate as a dispersing agent. The Joda slime has been separated into two parts by using hydro cyclone to identify the effect of particle size on selective dispersion and separation of iron ore slimes. Among the gangue minerals present in the slimes, zeolite is more selective towards separation through dispersion process. Under a particular settling condition, a high grade concentrate containing 67.9 wt.% Fe, 1.2 wt.% Al₂O₃ and 1.25 wt.% SiO₂ with 58% iron recovery is achievable using off grade iron ultra fines containing 57.8 wt.% Fe, 7.55 wt.% Al₂O₃ and 7.15 wt.% SiO₂.The efficiency of selective dispersion process strongly depends on mineral geology and particle size. The iron ore ultra fines collected from the Joda slime pond have better selectivity towards dispersion resulting in better separation of gangue minerals in comparison to iron ore ultra fines collected from Noamundi slime pond. This can be attributed to better liberation of Joda slime and difference in nature of the mineral content in Noamundi slime.     

Utilization of Iron Ore Slimes: A Future Prospective

In India, iron ores processing industries play a vital role in the Indian economy. During the washing and processing of iron ores, slimes less than 0.15 mm are generated and discarded into the tailing pond. These slimes need processing as they cannot be used directly in blast furnaces. In the present investigation, a typical iron ore slime sample containing 59.22% Fe, 4.76% SiO₂, and 4.57% Al₂O₃ was taken. The desliming operation was carried out by using 2” Mozley hydrocyclone. The process variables used to attain the optimum condition of desliming include the spigot opening, the feed pressure, and the diameter of the vortex finder maintaining the pulp density at 10% solid. The deslimed sample was treated by different techniques including an enhanced gravity separator to achieve iron concentrate with 65% Fe so that it can be used for steel making through pelletization. The yield of the magnetic concentrate is about 46.8% with 65% Fe. To improve the yield, the overflow from 2” hydrocyclone and the rejects from magnetic separation were deslimed and processed to recover the iron values. The final concentrate is 74% yield with 64.8% Fe, 1.76% SiO₂, and 1.8% Al₂O_3.     

Integrated experimental phase equilibria study and thermodynamic modelling of the binary ZnO–Al2O3, ZnO–SiO2, Al2O3–SiO2 and ternary ZnO–Al2O3–SiO2 systems

Phase equilibria of the ZnO–SiO₂, Al₂O₃–SiO₂ and ZnO–Al₂O₃–SiO₂ systems at liquidus were characterized at 1340–1740 °C in air. The ZnO–Al₂O₃ subsolidus phase equilibria were derived from the experiments with the SiO₂- and CaO + SiO₂-containing slags. High-temperature equilibration on silica or platinum substrates, followed by quenching and direct measurement of Zn, Al, Si and Ca concentrations in the phases with the electron probe X-ray microanalysis (EPMA) was used to accurately characterize the system. Special attention was given to zincite phase that was shown to consist of two separate ranges of compositions: round-shaped low-Al zincite (<2 mol.% AlO_1.5) and platy high-Al zincite (4–11 mol.% AlO_1.5). A technique was developed for more accurate measurement of the ZnO solubility in the low-ZnO phases (corundum, mullite, tridymite and cristobalite) surrounded by the ZnO-containing slag, using l-line for Zn instead of K-line, avoiding the interference of secondary X-ray fluorescence. Solubility of ZnO was found to be below 0.03 mol.% in corundum and cristobalite, and below 0.3 mol.% in mullite. Present experimental data were used to obtain a self-consistent set of parameters of the thermodynamic models for all phases in this system using FactSage computer package. The modified quasichemical model with two sublattices (Zn²⁺, Al³⁺, Si⁴⁺) (O^2?) was used for the liquid slag phase; the compound energy formalism was used for the spinel (Zn²⁺,Al³⁺)[Zn²⁺,Al³⁺,Va]₂O^2-₄ and mullite Al³⁺₂(Al³⁺,Si⁴⁺) (O^2?,Va)₅ phases; the Bragg-Williams formalism was used for the zincite (ZnO, Al₂O₃); other solid phases (tridymite and cristobalite SiO₂, corundum Al₂O₃, and willemite Zn₂SiO₄) were described as stoichiometric. Present study is a part of the research program on the characterization of the multicomponent Pb–Zn–Cu–Fe–Ca–Si–O–S–Al–Mg–Cr–As–Sn–Sb–Bi–Ag–Au–Ni system.     

Studies on removal of lead ions from aqueous solutions using iron ore slimes as adsorbent

Iron ore slimes, a waste material generated during iron ore mining have been employed for the removal of lead ions from aqueous solutions by a batch adsorption technique. The slime sample contains 45.8% Fe, 13.6% SiO₂, and 13.9% Al₂O₃. It is characterized by X-ray diffraction (XRD) and optical microscopy to determine the presence of different phases such as hematite, goethite, limonite, quartz and kaolinite. It is assumed that the adsorption of lead ions is mainly due to the presence of pores and cavities in goethite mineral. The FTIR studies showed the presence of Si-OH and Fe-OH sites responsible for adsorption. Furthermore, the point of zero charge (pzc) of iron ore slime is shifted from 6.2 to 5.8 due to the adsorption of lead ions. Batch adsorption experiments have been conducted to study the sorption behavior of lead ions on iron ore slime. The effects of agitation time, concentration of lead ions, adsorbent doses, solution pH, other metal ions and temperature on the amount of lead ions adsorbed have been investigated. Lead ion adsorption is fast, and equilibrium could be achieved within 15 minutes of time. The adsorption increased with increase in temperature suggesting an endothermic adsorption. Under the conditions, it is possible to remove 95% lead from an aqueous solution bearing ∼20 mg/l at pH∼5.1. The equilibrium adsorption isotherm data fitted very well to both Langmuir and Freundlich adsorption models.     

EQUILIBRIUM STUDIES IN THE SYSTEM FeO-AI2O3,-SiO2*

Equilibrium relationships on the liquidus surface in the system Fe0-Al₂O₃SiO₂ have been established by a modified quenching procedure. The crystal phases which separate from melts heated in iron crucibles are fayalite (2FeO·SO₂), hercynite (FeO·Al₂O₃), tridymite and cristobalite (SiO₂), mullite (3Al₂O₃·2SiO₂), corundum (Al₂O₃), and wastite (approximately FeO). A considerable portion of this system is liquid at 1400°C. Diagrams show the isotherms and the index of refraction of the glasses formed. Two quintuple points have been established in this investigation. One point is at the composition, SiO₂ 42% by weight, Al₂O₃13%, and FeO 45%, and is a eutectic involving the phases fayalite, hercynite, and tridymite at 970°C. ± 200C. The preferred composition of the second quintuple point is 48% of SO₂, 23% of Al₂O₃, and 29% of FeO; it is a peritectic, and the crystal phases are mullite, hercynite, and tridyrnite. Crystallization from this melt without a change in the weight composition calls for the resorption of mullite at a temperature of 1100°C. ±20°C.     

Optimal Recovery of Iron Values from a Low Grade Iron Ore using Reduction Roasting and Magnetic Separation

A low grade iron ore containing 51.6% Fe, 17.6% SiO₂, 4.3% Al₂O₃, and 3.8% LOI was subjected to reduction roasting followed by low intensity magnetic separation studies. The phase transformation of hematite into magnetite and fayalite due to reduction roasting was investigated using reflected microscope and X-ray diffraction (XRD) techniques. The effects of reduction variables such as reduction time (40?175 min), temperature (750?1000°C), and reductant dosage (3?11%) using activated charcoal were studied. The process was optimized by using central composite rotatable design (CCRD) and response surface methodology. Iron grade from 59?66% with recovery of 9.5?87% was achieved using CCRD experiments. Model equations were developed both for Fe grade and recovery and then optimized within the bounds of experimental conditions. The program predicted 63.3% Fe with 79% recovery with the following optimum conditions: temperature: 950°C, time: 53.04 min, and reductant: 3%.     

Beneficiation routes for upgrading iron ore tailings with a teetered bed separator

The aim of this study was to investigate the possibility of producing sinter/pellet grade concentrate from iron ore tails. Two different wet flow sheets were considered. The first consists of a teetered bed separator (TBS) followed by a gravity concentration resulting in a product quality with 65.54% Fe, 4.96% SiO₂ and 1.50% Al₂O₃ content ensuring 68.52% iron recovery. In the second option, the iron ore tail is treated in a similar approach, but the gravity concentration replaced by magnetic separation results in a product quality with 65.34% Fe, 3.70% SiO₂ and 1.00% Al₂O₃ with 70.91% of iron recovery.     

Experimental phase equilibria study and thermodynamic modelling of the PbO-“FeO”-SiO2-ZnO,PbO-“FeO”-SiO2-Al2O3 and PbO-“FeO”-SiO2-MgO systems in equilibrium with metallic Pb and Fe

Phase equilibria of the PbO-“FeO”-SiO₂-ZnO, PbO-“FeO”-SiO₂-Al₂O₃ and PbO-“FeO”-SiO₂-MgO slags with liquid Pb metal, solid or liquid Fe metal and solid oxides (cristobalite and tridymite SiO₂, willemite (Zn,Fe)₂SiO₄, wustite (Fe,Al)O_1+x, spinel (Fe,Al)₃O₄, olivine Fe₂SiO₄, corundum (Al,Fe)₂O₃, mullite Al₆Si₂O₁₃ and pyroxene (Mg,Fe)SiO₃) were investigated at 1125–1670 °C. These conditions correspond to the minimum solubility of PbO in slag in presence of Pb and Fe metals at reducing conditions and represent the limit of lead smelting and slag cleaning process. High-temperature equilibration on silica, corundum or iron foil substrates, followed by quenching and direct measurement of Pb, Fe, Si, Zn, Al and Mg concentrations in the liquid and solid phases with the electron probe X-ray microanalysis (EPMA) was used. Present data can be used to improve the thermodynamic models for all phases in this system.     

Determination of fluoride in cement and related materials

This paper describes the determination of fluoride in cement and cement-related materials using a fluoride ion selective electrode. Different sample preparation methods and complexing buffers were investigated. It was concluded that the fluoride electrode offers a rapid and accurate method for fluoride determination in cement and cement-related materials when a suitable buffer medium capable of complexing Si, Al, and Fe in the solution is used. Sintering with Na₂CO₃6ZnO is preferable to LiBO₂ fusion for decomposing materials high in SiO₂, Al₂O₃ and Fe₂O₃. However, the latter method is more rapid and gives the same results as the former method for samples with relatively low SiO₂, Al₂O₃ and Fe₂O₃ contents.     

EQUILIBRIUM RELATIONSHIPS ON THE LIQUIDUS SURFACE IN PART OF THE MnO-Al2O3-SiO2 SYSTEM*

The minerals found to have a stability range on the liquidus surface in the system MnO-Al₂O₃-SiO₂ are cristobalite and tridymite, SiO₂; mullite, 3Al₂O₃. 2SiO₂; corundum, Al₂O₃; rhodonite, MnO.SiO₂; tephroite, 2MnO.SiO₂; galaxite, MnO.Al₂O₃; spessartite, 3MnO.Al₂O₃.3SiO₂; and a new compound, 2MnO.2Al₂O₃.5SiO₂. The quintuple points and boundary lines found in that part of the MnO.Al₂O₃.SiO₂ system bounded by the systems 3MnO.Al₂O₃.3SiO₂-SiO₂, 3MnO.Al₂O₃.3SiO₂-Al₂O₃, and Al₂O₃-SiO₂have been determined. Quintuple points and boundary lines involving the area inclosed by the systems 2MnO . SiO₂-3MnO . Al₂O₃ . 3SiO₂, 3MnO . Al₂O₃ . 3SiO₂-SiO₂, and 2MnO.-SiO₂-SiO₂ are indicated. Isotherms and isofracts (lines of equal refractive index) are given for the portion of the system investigated. X-ray data show that crystals of the compound 3MnO.Al₂O₃.3SiO₂ have the same structure as the garnet mineral spessartite (manganese garnet). The compound 2MnO. 2Al₂O₃ . 5SiO₂, which is shown by X-ray data to have a basic structure similar to cordierite, 2MgO.2Al₂O₃.5SiO₂, seldom crystallizes from the glass, but a third substance which has a high extinction angle crystallizes readily from the reheated glass. These high extinction angle crystals are replaced by 2MnO .2Al₂O₃.5SiO₂ when a proper heating cycle is employed, and they are not found again until the product is melted and crystallization is repeated.     

Upgrading a rutile concentrate produced from Athabasca oil sands tailings

A rutile concentrate recently produced by Lakefield Research Ltd and Syncrude Canada Ltd from athabasca oil sands tailings was characterized and attempts were made to upgrade it to market-grade. The rutile concentrate contained 75.5% TiO₂, 18.7% Fe₂O₃, 1.03% Al₂O₃, 1.94% SiO₂, and 563 ppm Th+U. The amount of rutile (anatase) in the concentrate was estimated to be about 10-17%, and the remaining TiO₂ came from ilmenite in various altered forms. Magnetic separation could remove the Fe from the concentrate but it increased the SiO₂ content from 1.94 to 6.01%. A reverse flotation process was developed to remove the SiO₂. Although the fine dissemination of SiO₂ in the rutile matrix limited the removal of SiO₂, the upgraded rutile concentrate, containing 87-89% TiO₂, could be used as a feedstock to the chloride titanium pigment processes.     

Formation and transition of calcium aluminate and calcium silicate compounds from pre-synthesized mullite in low-calcium system by solid-state reaction

The formation and transition of calcium aluminate and calcium silicate compounds from pre-synthesized mullite in low-calcium system were systematically studied by solid-state reaction at 1350–1500 °C using XRF, XRD, FTIR, SEM and PSD methods. Ca₃Al₂O₆, Ca₁₂Al₁₄O₃₃, CaAl₂O₄, Ca₂SiO₄ and Ca₂Al₂SiO₇ can form via direct reaction of mullite with CaO at the beginning of the reactions, then Ca₁₂Al₁₄O₃₃ and Ca₃Al₂O₆ react with mullite to form CaAl₂O₄ and Ca₂SiO₄, and finally Ca₂Al₂SiO₇ reacts with CaO to generate Ca₂SiO₄ and calcium aluminate compounds as the sintering process proceeds. Elevating the sintering temperature is in favor of the formation of Ca₁₂Al₁₄O₃₃, Ca₃Al₂O₆ and Ca₂Al₂SiO₇ at the initial reaction stage, but Ca₂Al₂SiO₇ cannot totally transform to calcium silicate and calcium aluminate compounds in the low-calcium system, which deteriorates the pulverization performance of the final products. Increasing the calcium dosage accelerates the transformation of Ca₂Al₂SiO₇ to Ca₁₂Al₁₄O₃₃, CaAl₂O₄ and Ca₂SiO₄, which enhances the pulverization performance. If the CaO/Al₂O₃ molar ratio exceeds 1.4, Ca₃Al₂O₆ will generate by the reactions of pre-formed CaAl₂O₄ and Ca₁₂Al₁₄O₃₃ with excessive CaO.     

Low thermal conductivity in porous SiC–SiO2–Al2O3–TiO2 ceramics induced by multiphase thermal resistance

The introduction of multiple heterogeneous interfaces in a ceramic is an efficient way to increase its thermal resistance. Novel porous SiC–SiO₂–Al₂O₃–TiO₂ (SSAT) ceramics were fabricated to achieve multiple heterogeneous interfaces by sintering equal volumes of SiC, SiO₂, Al₂O₃, and TiO₂ compacted powders with polysiloxane as a bonding phase and carbon as a template at 600 °C in air. The porosity could be controlled between 66% and 74% by adjusting the amounts of polysiloxane and the carbon template. The lowest thermal conductivity (0.059 W/(m·K) at 74% porosity) obtained in this study is an order of magnitude lower than those (0.2–1.3 W/(m·K)) of porous monolithic SiC, SiO₂, Al₂O₃, and TiO₂ ceramics at an equivalent porosity. The typical specific compressive strength value of the porous SSAT ceramics at 74% porosity was 3.2 MPa cm³/g.     

Recycling of waste lubricant oil into chemical feedstock or fuel oil over supported iron oxide catalysts

The recycling of waste lubricant oil from automobile industry was found to be best alternative to incineration. Silica (SiO₂), alumina (Al₂O₃), silica-alumina (SiO₂-Al₂O₃) supported iron oxide (10 wt% Fe) catalysts were prepared by wet impregnation method and used for the desulphurisation of waste lubricant oil into fuel oil. The extent of sulphur removal increases in the sequence of Fe/SiO₂-Al₂O₃<Fe/Al₂O₃<Fe/SiO₂ and this might be due to the presence of smaller crystalline size (7.4 nm) of Fe₂O₃ in Fe/SiO₂ catalyst. X-ray diffraction results suggest the presence of iron sulphide in the used catalyst. Gas chromatography with thermal conductivity detector analysis confirms the presence of H₂S in gaseous products. In addition, Fe/SiO₂ catalyst facilitated the formation of lower hydrocarbons by cracking higher hydrocarbons (≈C₄₀) present in waste lubricant oil.     

Corrosion behavior of Monofrax K-3 refractory in borosilicate-based model low activity waste glass melts

Owing to its good chemical and thermal durabilities at high temperatures, Monofrax K-3 refractory is widely used in nuclear waste vitrification as a lining material in melting vessels. However, the corrosion of K-3 refractory during the vitrification of nuclear waste is a serious problem because it affects the melter's safety, performance, and lifetime. Therefore, in the present study, we have focused on unearthing the impact of glass network formers, such as SiO₂, B₂O₃, and Al₂O₃, in a model nuclear waste glass composition on the corrosion of Monofrax K-3 refractory. The corrosion tests have been performed per ASTM C621 at 1150°C for 5 days. The dimensional measurements on corroded K-3 refractory suggest that Al₂O₃ and SiO₂ tend to reduce the refractory corrosion (neck loss), with the effect of Al₂O₃ being significant. A corroded region on the K-3 refractory at the melt–refractory interface is observed. The corrosion occurs via a coupling of the melt infiltration induced by a capillary effect and the dissolution of Al, Mg, and Fe components from K-3 into the melt through chemical reactions. A Cr-rich layer is retained on the glass contact surface of the corroded K-3 refractory.     

EPI-type zeolite synthesis from Greek sulphocalcic fly ashes promoted by H2O2 solutions

EPI-type zeolite was synthesised from Greek sulphocalcic lignite fly ashes. They consist mainly of SiO₂, CaO and Al₂O₃, while the SiO₂/Al₂O₃ ratio was found to be 2.74. The activation was performed by 30% H₂O₂ in an open system. Zeolite formation was observed only when activated products aged at 95 °C. The resulting materials were characterised by means of PXRD, FT-IR and SEM-EDS. PXRD and FT-IR results are in good agreement, confirming the zeolite formation. The role of H₂O₂ as a dominant factor in the zeolite synthesis is attributed to the oxidation of Fe(II) to Fe(III) and to the oxidative action on the unburned organic mater of the fly ash to prevent the reduction of Fe(III) to Fe(II). Fe(III) is proposed to participate in the reaction with Si-OH and HO-Al groups in the preliminary steps, resulting to the formation of an intermediate group [Fe-(H⁺)O(O-Si)-Al] which then gives Si-O-Al groups and Si-O-Fe groups to a lesser extent, both of which lead to a zeolite structure. Formation of the latter group explains the presence of Fe(III) in the zeolite crystal structure.     

Mixture Design and Response Surface Analysis of Densification of Silicon Carbide Ceramics with (SiO2–Dy2O3–Al2O3) Additives

Statistical mixture designs are used to systematically study the densification properties of silicon carbide (SiC) ceramics sintered with SiO₂, Dy₂O₃, and Al₂O₃. Mixture models for percentage theoretical density and SiC weight loss as a function of the SiO₂, Dy₂O₃, and Al₂O₃ oxide proportions have been determined and validated by analysis of variance. The results indicate a region confined by about 0–20 mol% silica, 50–65 mol% dysprosia, and 40–65 mol% alumina, with all samples containing 10% by volume of additives, and simultaneously maximization of density values and minimization of weight loss during SiC-based ceramic sintering.     

Effect of alkali roasting and sulfatization on the extraction of different metal oxides from waste alum sludge

Water treatment plants (WTP) generate a significant amount of sludge as byproducts with environmentally harmful elements. Thus, this work focused on the recycling of alum sludge through the extraction of different metal oxides, i.e., Al₂O₃, Fe₂O₃ and SiO₂, for use in different applications, such as ceramics, cement, and agriculture. The extraction of Al₂O₃, Fe₂O₃, and SiO₂ from alum sludge was performed using sulfatization and roasting to compare which of the two processes could produce the metal oxides of the highest purity. Precipitated powders were calcined at 700°, 900° and 1100 °C. Moreover, the obtained prepared and calcined powders were characterized by studying their phase compositions, microstructure, particle size, and surface area. Results indicated that roasting achieved the highest yield of alumina. Iron oxide was extracted mostly in maghemite form through roasting after calcination at 1100 °C. Further, silica was obtained in cristobalite and quartz phases after calcination at 1100 °C for the samples prepared through sulfatization. However, these phases of silica were combined with albite and obtained after calcination at 1100 °C for the samples prepared through roasting method.     

Synthesis and characterization of calcium aluminate compounds from gehlenite by high-temperature solid-state reaction

The mineral transition mechanism and self-pulverization property of the sintered products in the Ca₂Al₂SiO₇-CaO system were systematically studied using pre-synthesized gehlenite determined by XRD, SEM, FTIR and particle size analyses. The minerals of Ca₁₂Al₁₄O₃₃, CaAl₂O₄, Ca₃SiO₅ and Ca₂SiO₄ are formed by the direct reactions of Ca₂Al₂SiO₇ with CaO. CaAl₂O₄ reacts with CaO to form Ca₁₂Al₁₄O₃₃ or Ca₃Al₂O₆, while Ca₃SiO₅ reacts with Ca₂Al₂SiO₇ to form Ca₂SiO₄ and calcium aluminate compounds. The sintered products mainly contain CaAl₂O₄, Ca₁₂Al₁₄O₃₃ and Ca₂SiO₄ at 1350?°C or above 1500?°C when the molar ratio of CaO to Al₂O₃ is 1.0. Increasing the sintering duration or the CaO consumption promotes the transition of Ca₂Al₂SiO₇ to Ca₂SiO₄ and calcium aluminate compounds when sintered at 1350?°C, which accordingly improves the self-pulverization property of the sintered products. The formed minerals of Ca₁₂Al₁₄O₃₃, CaAl₂O₄ and Ca₂SiO₄ transform into Ca₂Al₂SiO₇ again when the sintering temperature is between 1400?°C and 1450?°C, and the corresponding self-pulverization property of the sintered products deteriorates sharply.