Chromite Ore Research Articles

The use of raw materials of Western Kazakhstan for the production of acid-resistant

The results of studies of acid-resistant materials obtained from unenriched kaolin clay, chamotte fired from this clay at 1200 o C, and sludge tailings of chromite ore enrichment fired at 800 o C are presented. Studies have shown that it is impossible to obtain acid-resistant tiles from non-enriched kaolin clay without thinners that meet the technical requirements of the standard at 1300 o C. However, such tiles can be obtained by introducing 40 % chamotte into their composition. The use of burnt sludge tails in acid-resistant tiles in an amount of 40 % significantly increases the technical performance of acid-resistant tiles at a firing temperature of 1350 o C. The introduction of burnt sludge promotes the formation of refractory minerals: magnochromite, chromite, alumomagnesial spinel and forsterite. Ill. 4. Ref. 23. Tab. 7.

Efficient pre-reduction of chromite ore with biochar under microwave irradiation

Pre-reduction of chromite ore is crucial for producing ferrochromium alloy by submerged arc furnace (SAF) smelting. In this study, an efficient method for low-temperature pre-reduction of chromite ore using biochar under microwave irradiation was explored to produce good burden for subsequent SAF smelting. The thermodynamic analysis proved the feasibility of the easy decomposition of the main phase in the ore, FeCr2O4 to Cr2O3, and finally to ferrochromium, mainly (Fe,Cr)7C3, in the commonly examined temperature range for pre-reduction. The characterizations of electromagnetic properties, microwave absorption capabilities, and temperature rising behaviors of the main raw materials and their mixtures showed that microwave heating could greatly improve the carbothermic reduction of chromite ore. Under the condition of C/O molar ratio of 1.2, addition of 2 wt% Na2B4O7, pre-reduction temperature of 1100 °C, and dwell time of 3 h, the chromite ore-biochar composite briquettes had efficient pre-reduction, producing pre-reduced briquettes with (Fe,Cr)7C3 as the main alloy phase. The iron and chromium metallization degrees (ηFe and ηCr) reached 98.1% and 86.8%, respectively. Compared with the conventional pre-reduction, they were increased by 15.9% and 51.7%, respectively. The results proved the feasibility of using microwave for efficent pre-reduction of chromite ore.

Dissolution Behavior of Chromite Ore in CaO‐SiO2 System

Numerous investigations proposed that the dissolution of chromite ore is the rate‐controlling step for the smelting reduction of chromite ore. The mechanism of chromite ore dissolution in the binary CaO‐SiO2 system is presented. The effect of basicity, temperature, and reducing conditions on chromite ore dissolution is elaborated. The solubility of chromite ore increases considerably when the basicity increases from 0.56 to 0.65. However, the solubility of chromite ore decreases when the basicity further increases from 0.65 to 0.74. The positive effect of reducing conditions on the solubility of chromite ore is evident. The maximum dissolved Cr2O3 in slag under reducing conditions by using a graphite crucible reaches 2.6 wt% after 15 min of dissolution. The element diffusion behavior at the chromite/slag interface is elaborated through SEM‐EDS technology. The analysis suggests that the rate‐controlling step in the early stage is the interface dissolution reaction. After a certain time, the rate‐controlling step becomes the mass transfer of Cr2O3 from the chromite ore to the chromite/slag interface. The activation energy of the dissolution reaction is = 285.29 kJ mol−1.

Efficient reduction of Cr(VI) and recovery of Fe from chromite ore processing residue by waste biomass

The traditional chromite ore processing residue (COPR) detoxification process is carried out in strong acid or anoxic high-temperature condition, which not only has a high input cost but leading difficulties for resource utilization of treated COPR. This study first reported the efficient reduction of Cr(VI) and recovery of Fe from COPR by waste molasses-assisted hydrothermal treatment. Under optimal conditions (i.e., the Na2CO3 dosing of 0.5 mol/L, the molasses/COPR mass ratio of 10%, hydrothermal treatment at 140 °C for 150 min), the Cr(VI) reduction efficiency reached 99.96 ± 0.01%, and the leaching toxicity of total Cr met the USEPA regulatory limit of 5 mg/L. Moreover, Fe was recycled in the form of magnetic magnesioferrite with Fe2O3 grade of 52.58 ± 0.90%, which can be used as raw material in steel industry. The Cr(VI) reduction reaction conforms to a pseudo-first-order kinetic model, and the reaction rate constants increase with increasing temperature (120 ∼160 °C). As a potential mechanism of the reaction, the Mg-Al hydrotalcite (LDHs) structure collapses in the presence of Na2CO3 during the hydrothermal treatment, and the embedded Cr(VI) is released, which is then reduced to Cr(OH)3 by reducing substances such as fructose, sucrose, and glucose in waste molasses. From the standpoint of a circular economy, this study may provide a potential strategy for minimizing resource input and waste/emission production by harmless disposal and resource utilization of COPR and waste molasses.

Chromite ore addition to serpentinized magnesite mining wastes for the production of refractory products following thermal treatment

Taking a circular approach to mining facilities requires the further exploitation of produced solid wastes, which are now considered as potential raw materials. This research aims to the re-utilization of specific mining wastes, containing mainly geologically degraded serpentinized minerals, produced during the minerals’ enrichment process of extractive magnesite industry, combined with the addition of chromite ore, aiming to the upgrading of refractory properties of the product, by applying the appropriate thermal treatment. A representative sample examined, corresponding to the proper blending of different mineral waste samples from several waste piles of mining area, combined with various chromite ore’s content, followed by the investigation of optimum thermal treatment, considering the applied temperature and time. The scope was to maximize the (desired) forsterite mineral phase in the product and, hence, to improve its refractory properties. The optimum results (e.g., considering the firing shrinkage level and the mechanical strength) achieved by the application of thermal treatment at 1300 °C and after heating time for 120–240 min. The refractory properties generally improved after mixing of examined mining wastes and chromite ore, due to the achievement of the best molar ratio of constituents [MgO]/[SiO2] = 2.2, regarding the additive, enhancing the formation of forsterite, whereas the application of heating temperatures over 1300 °C led to the melting of enstatite mineral phase, resulting to the degradation of product. The obtained results reveal that the produced sintered products can exhibit better refractory properties, and can be used as refractory raw materials for relevant applications up to 1300 °C.

Influence of Slag Chemistry on the Dissolution of FeCr<sub>2</sub>O<sub>4</sub> in CaO–SiO<sub>2</sub>–Al<sub>2</sub>O<sub>3</sub>–MgO Slag with Graphite Crucible

The effect of Al2O3 and SiO2 content and basicity (w(CaO) + w(MgO)/w(SiO2) + w(Al2O3)) on the chromite ore dissolution in CaO–SiO2–Al2O3–MgO slag system was studied under the condition of 1550°C. The results show that the increase of basicity (R = 0.54, 0.67, 0.82) results in the reduction of the dissolved amount and dissolution rate of chromite ore in the slag. The dissolved amount of Cr in lower basicity slag (R = 0.54) is about 1.5 to 2 times higher than that in higher basicity slag (R = 0.67, R = 0.82). The dissolved amount of Cr tends to increase when the Al2O3 mass content decreases from 20% to 15%. While as the Al2O3 mass fraction continues to decrease from 15% to 10%, the dissolved amount begins to decrease. This may be related to the viscosity of the slag. The spinel phase tends to form on the surface of the unreacted FeCr2O4, thus hindering the further dissolution of FeCr2O4. After starting to dissolve, the FeCr2O4 decomposes into FeO and Cr2O3 dissolving in the slag. The FeO in the slag is preferentially reduced to metal iron attached to the surface of the FeCr2O4. The main forms of Cr element in the slag are CrO and Cr2O3, and the proportion of these two depends on the composition of the slag and the experimental environment. The proportion of CrO in the slag with lower basicity is larger. In the experiment, the maximum solubility of FeCr2O4 in 60 min was obtained in the slag system with 45% SiO2, 15% CaO, 20% Al2O3 and 20% MgO.

Understanding and eliminating the reductant interference on Chromium VI measurement with USEPA method 3060A

Excessive reductants are used in engineering to ensure a reliable remediation effect of chromite ore processing residue (COPR), however, re-yellowing phenomenon of remediated COPR occurs after some time though the Cr(VI) content meets regulatory requirements after curing period. This problem is due to a negative bias on Cr(VI) determination using USEPA method 3060A. To address this issue, this study tried to reveal the interference mechanisms and proposed two methods to amend the bias. Results of ion concentrations, UV–Vis spectrum, XRD, and XPS together showed that Cr(VI) was reduced by ions (Fe2+, S52−) in the digestion stage of USEPA method 3060A, and as a result, method 7196A would not reflect the true Cr(VI) concentration. The interference on Cr(VI) determination generated by excess reductants mainly occurs during the curing period of remediated COPR, but it decreases over time as reductants being oxidized gradually by the air. Compared with the thermal oxidation, the chemical oxidation with K2S2O8 prior to alkaline digestion performs better to eliminate the masking effect brought by excess reductants. This study provides an approach on how to accurately determine the Cr(VI) concentration in the remediated COPR. It might be helpful to reduce the occurrence possibility of re-yellowing phenomenon.

Reduction of Carbon Footprint Through Hybrid Sintering of Low-Grade Limonitic Nickel Laterite and Chromite Ore

Reduction of Carbon Footprint Through Hybrid Sintering of Low-Grade Limonitic Nickel Laterite and Chromite Ore

Co-treatment of chromite ore processing residue and pyrolusite for simultaneous detoxification and resource utilization

Efficient and low-cost recovery of metals from pyrolusite and Chromite Ore Processing Residue (COPR) is of great significance for environmental protection and sustainable development of metal resources. This study proposes a new method for the simultaneous recovery of Cr and Mn from COPR and pyrolusite, to realize COPR and pyrolusite resource utilization and detoxification. Under the optimal conditions (i.e., the temperature of 150 ℃, the holding time of 1.5 h, the H2SO4 concentration of 3 M, the mass ratio of COPR to pyrolusite of 1:1, and the solid-liquid ratio of 1:20), the leaching efficiency of Cr and Mn reached 99.56% and 85.34% respectively. The Toxicity Characteristic Leaching Procedure (TCLP) total Cr concentration of the detoxified slag was 0.26 mg/L meeting the EPA standard (＜5 mg/L). The reaction mechanism was elucidated based on thermodynamics, kinetics, and mineral characterization. In addition, a high-quality utilization strategy was proposed, leaching solution to prepare manganese carbonate and sodium chromate, and the detoxified slag can be used for steel smelting. In brief, this method has good economic benefits and provides a new reference for the resource utilization of hazardous waste.

Automated and Quantitative Mineralogy Applied to Chromite Ore Characterization and Beneficiation

A characterization study of chromite ore from South Africa was conducted using bulk assays, X-ray diffraction, optical, scanning electron microscopy (SEM), automated electron probe microanalysis (EPMA) and quantitative evaluation of mineral by scanning electron microscopy (QEMSCAN) mineralogical techniques, and quantitative EPMA. The aim was to identify all major gangue impurities, the degree of chromite liberation, and possible beneficiation options. The bulk material assayed 40.5% Cr2O3 with the major impurities being Al2O3 (13.2%), MgO (12.1%), and SiO2 (7.5%). Quantitative mineral phase analysis showed that the sample mineralogy was dominated by a chrome-rich spinel phase with an average chemical composition (in wt.%) of: Cr2O3—47.8; FeO—26.0; Al2O3—15.4; and MgO—11.0. Contaminant phases included siliceous minerals enstatite, anorthite-rich plagioclase (bytownite), Cr-rich diopside (containing 1–2 wt.% Cr2O3), and phlogopite mica. QEMSCAN analysis of sized fractions indicated that (a) most silicate gangue species were in the +850 μm fractions, (b) the chrome-rich spinel in all fractions was >80% liberated, and (c) the most common mineral association for chromite was with enstatite. Based on the results, upgrading test work demonstrated that stage crushing followed by wet gravity concentration produced a chemical–metallurgical-grade ‘chromite’ product containing >46% Cr2O3 and <1% SiO2.

Prospecting for ophiolite-type chromite deposit in Sartohay, West Junggar (NW China): Constraints from geological and geophysical data

Chromite is a critical mineral that is of great significance for the development of metallurgical, chemical, and other industries. In order to study the deep ore prospecting methods of ophiolite-type chromitite, we have carried out plane-profile geological and mineral surveys, as well as high-precision gravity, magnetic, and controlled source audio-frequency magnetotelluric (CSAMT) measurements in the Sartohay, West Junggar. Based on the analysis, interpretation, and inference of multi-source geological information, a three-dimensional (3D) geological model of the typical mining area in Sartohay District was established. The results show that Sartohay ophiolite was occurred in the form of rootless tectonic blocks and generally displayed deformation and metamorphism (e.g., oblique thrust, transverse extrusion, and lateral strike slip). Sartohay ophiolite is in tectonic contact with surrounding strata. Several northwest dipping high-angle thrust faults are developed at the contact sites and inside the ophiolite rock mass, showing a thrust imbricated structure. Meanwhile, ophiolite in the modeling area is a NW-trending monoclinic rock mass. The base surface of the ophiolite is obliquely distributed in an “N-like” shape, and the chromitite bearing lithofacies zones also have a NW-trending distribution. Geophysical data reveal that the studied mining area is characterized by a layered electrical structure in the vertical direction. The upper layer displays a high-resistivity agglomerate and a low-resistivity band distributed alternately, while the lower layer is a complete high-resistivity block. Combined with the deposit characteristics in Sartohay, it is considered that the morphological occurrence, geological structure, lithology, and lithofacies of ophiolite control the spatial distribution of related chromitites. The dunite-harzburgite lithofacies belts, highly strain zones, and strong tectonic alteration belts of the ophiolite rock mass are significant sites for the chromite ore bodies/groups occurrence. This study provides approaches for researching on the production laws of ophiolite-type chromitite and supplys a prospecting pattern for deep concealed orebodies.

Modeling of Knelson Concentrator Operating Parameters by Using Application of Box–Behnken Experimental Design for Chromite Ore

Modeling of Knelson Concentrator Operating Parameters by Using Application of Box–Behnken Experimental Design for Chromite Ore

MagWasteVal Project—Towards Sustainability of Mining Waste

In the direction of sustainable mining solid waste management and eventually zero-waste production, the MagWasteVal research program aimed to achieve the proper handling of massive quantities of extractive mining waste originating from the magnesite mines after the enrichment process of useful ore. The main objectives of this project were both the investigation of geochemical variables affecting the serpentinization process (degradation) and the respected exploitation and further valorization of stocked-pilled solid (inert) wastes in the mining area. The study of thermal treatment (considering the heating duration and heating temperature) and the addition of various additives (alumina, chromite ore, run of mine, iron oxide, and magnesia) showed that the optimum upgrade for the mining waste samples occurs when a combination of magnesia (according to the optimum defined molar ratio: [MgO] + [FeO])/[SiO2] = 2) and iron oxide of approximately 2.5% is applied at both 1300 and 1600 °C for 120 min. The final products of the MagWasteVal project may have various potential applications, even on a large scale, for the production of alternative refractory materials/services, substituting other raw materials, and presenting both economic and environmental benefits.

Paragenetic Association of Platinum and Gold Minerals in Placers of the Anabar River in the Northeast of the Siberian Platform

Areal placers of diamond and precious metals (platinum and gold) of unknown origin are widespread in the Anabar River basin on the northeastern part of the Siberian Platform. This article discusses the typomorphic features of palladium gold (porpezite) and ferroan platinum, which, in addition to fragmented individual grains, sometimes form close growths, which indicates their obvious genetic relationship. This can be used to delimit the primary sources of commercial components of complex placers by their genetic types. The composition of minerals was determined on a Camebax-Micro (Cameca, France) microprobe analyzer, and their microstructural relationships were studied using the scanning microscope JSM-6480LV JEOL. Determination of the structure and parameters of elementary lattices of minerals was carried out on the D8 Discover diffractometer. According to microprobe analysis, the Pd content in porpezite ranges from 0.73% to 12.83%, Ag does not exceed 2.75% and Cu reaches 3–4%. Considering the composition, such a gold–platinum mineral association from placers of the Anabar river is close to precious metals from placers of the Gulinsky massif, as well as Au–PGE ore occurrences related to ultramafic–mafic intrusions of other regions of the world. Complex gold–platinum-metal mineralizations are usually closely related to parent rocks and are often observed in sulfide and chromite ores of layered ultramafic–mafic intrusions with complex metasomatic and hydrothermal transformations. It is shown that in such cases gold and platinum form a magmatogenic paragenesis of minerals that coexist until the separation of hydrothermal solutions from magma, which, as a rule, transports Au and Ag with a small fraction of PGE from the fluid-ore-magmatic system in accordance with the model of the formation of gold–porphyry deposits. Within the Anabar diamond-bearing region, according to modern geophysical data, a significant number of local gravimagnetic anomalies associated with the presence of intrusive massifs of basic and alkaline-ultrabasic rocks in the cover and within the basement have been identified. This allows us to assume that the buried parent rocks of the Anabar Au–Pt placers may be located in both the Precambrian and Phanerozoic strata.

INVESTIGATION OF CHROMITE ORE BENEFICIATION POSSIBILITIES WITH DIFFERENT GRAVITY CONCENTRATORS

The rapid development of industry increases the demand and importance of chromium. In this study, beneficiation possibilities of the representative chromite ore taken from the Tokat Province with a laboratory type jig, spiral concentrator, shaking table and multi gravity separator (MGS) were investigated. Appropriate particle size fractions were fed into each beneficiation device. Experimental studies were shown as a flow chart. The shaking table gave the best results for chromite beneficiation and a concentrate of 47.02% Cr2O3 grade and 94.29% recovery were obtained by using a -0.3+0.106 mm particle size fraction. It was observed that concentrates with saleable grade could be obtained as a result of the beneficiation of chromite ore with a spiral concentrator. The tailings obtained from the jig, spiral concentrator and shaking table were blended and scavenger experiments were carried out with an MGS to recover the remaining chromite in the tailings. 93.55% of the chromite in this blended sample was recovered with a grade of 34.96% Cr2O3. Hence, MGS seems to be the promising equipment for the beneficiation of tailings.

Collaborative resource utilization of hazardous chromium ore processing residue (COPR) and C-bearing dust during limonitic laterite sintering process

Much chromite ore processing residue (COPR), which is defined as hazardous solid waste due to virulent Cr (Ⅵ), is produced from chromium salt industry. C-bearing dust from steel industry is a kind of typically solid waste with poor surface activity. The iron ore sintering process has the potential on large-scale harmless utilization of COPR and C-bearing dust. This study proposes a new approach of co-utilizing COPR and C-bearing dust during limonitic laterite sintering process. The negative influence of COPR and C-bearing dust on permeability was offset by the fuel attribute of extra C from C-bearing dust. The results indicate that, while 6% COPR and 8% C-bearing dust were added, the tumble index and yield of the sinters were basically equal to those of the blank samples. The toxic Cr (Ⅵ) was reduced to Cr (Ⅲ) which was concentrated in high alumina spinel phases during the sintering process. The obtained sinters were identified as nontoxic, and no secondary waste was generated throughout the clean utilization process.

The Strategies of Chromite Terrace in Sukinda Valley, India: An Appraisal

Iron chrome oxide (FeCr 2O4), is a commercially viable and major ingredient of stainless steel. The Odisha state in India possesses 98% of the pre-Cambrian India’s Chromite ore deposits in Sukinda valley, Jajpur District. To meet the present escalating demand for chromium in steel industries, it is urged to extract more chrome ore to satiate domestic needs. The depletion of chrome deposits, rise in demand, fewer chrome mines, and less conversion from tailings increase of more toxic hexavalent chrome ion level in the geo-bio hydrosphere, shall aggravate health concerns for the people, fauna, and flora in Sukinda Ultramafic Complex (SUC).
 The present quest is a collection of chromite ores and tailings. A chemical study is done by using the X-ray fluorescent spectrometer. An insitu/GIS study of the Sukinda ultramafic complex by using Arc-GIS, and ERADAS software has been done to originate hydrology, aspect, and hill-shade map of the valley. The literature, and as an inhabitant of the area helped in preparing the strategic plan through Environmental Impact Assessment and Environmental Management Plan. 
 CR (III) is a dietary requirement. The anthropogenic activities and atmospheric exposure have converted Cr (III) to Cr (VI) in SUC and have surpassed the recommended values. The noxious Cr (VI) in the geo-bio-hydrosphere shall invite health and environmental concerns in the future. The aboriginals of SUC are economically burdened with food insecurity, poor livelihood, health, and of formal societal values. The Sukinda Valley ore samples contain 50% chromite ore is economic. But the >7% of CR (III) ore in the tailings and overburden shall warrant the future expected exorbitant Cr (VI) in the geo-bio-hydro environment of Sukinda valley.

Resource Intensity Trends in the South African Ferrochrome Industry from 2007 to 2020

Processing resource requirements in mineral extractive industries tend to increase over time as ore grades decrease, which consequently increases the environmental footprint of operations and products. This phenomenon may be alleviated by cleaner production interventions. South Africa is the largest global supplier of chromium. This study investigates the impact of cleaner production process improvements on selected resource intensities of the South African ferrochrome industry. Sustainability data, available since the start of regular sustainability reporting in 2007, were used to compile resource intensity trends. This was followed by a review of industry capital projects relating to resource-use optimisation, interrogated in interviews with industry experts, to ascertain their effect on resource intensities. The emergence of a symbiotic relationship with the platinum-group metals industry was identified as a major development, with chromite ore intensity decreasing from 2.54 to 1.98 kg per kg ferrochrome. Electrical energy intensity was observed to decrease from 3.47 to 2.86 kWh per ton ferrochrome, mainly as a result of cleaner smelting technology, though cogeneration fired by furnace off-gases also contributed significantly. The introduction of cleaner production interventions in the South African ferrochrome industry was thus documented to have resulted in decreased resource use intensities.

Mineralogical studies and optimization of tabling parameters of low grade chromite ore by box behnken design of experiments

Chromite ore is geologically associated with gangue materials which have lower density compared to pure chromite (FeO.Cr2O3). Gravity separation techniques are very suitable for beneficiation of low grade chromite ore. In the present study mineralogical analysis of the sample has been carried out by using Wavelength dispersive x-ray fluorescence (WDXRF), X-ray powder diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX). The beneficiation of low grade (Cr2O3% 26.88) chromite ore has been investigated using wilfley table. Optimization has been carried out using box-behnken statistical design (BBD). The experimental parameters selected are: tilt angle, water flow rate and pre-heat treatment of the chromite ore. It is observed that percentage recovery of Cr2O3 depends upon tilt angle, water flow rate and pre-heat treatment of chromite ore. Pre-heat treatment of chromite ore plays a vital role in gravity separation. The optimized tabling conditions suggested by BBD are 8° tilt angle, 4 L∙min-1 water flow rate and temperature for pre-heat treatment of raw chromite ore at 443.72℃. After tabling under optimized conditions, chromite concentrate contained 1.91 Cr/Fe ratio, 46.02% of Cr2O3 with 65.95% recovery.

Size reduction performance evaluation of HPGR/ball mill and HPGR/stirred mill for PGE bearing chromite ore

In the present study, size reduction experiments were performed on High-Pressure Grinding Rolls (HPGR), ball mill and stirred mill of PGE bearing chromite ore. The performance of HPGR was evaluated in two stages of size reduction to reduce energy consumption. In the first stage of HPGR, the effect of operating variables such as the gap between the rolls, roll speed, and specific pressing force on product size (P80) and energy consumption (ECS) was investigated. The process to get the smallest product size was optimized within the experimental range of investigation. The crushed product of HPGR was subjected to grinding in the second stage in a ball mill and stirred mill. The effect of mill speed, grinding time, and ball size on the performance of the ball mill was investigated and the product was further investigated in the second stage. A comparative analysis of the ball mill and stirred mill performance and energy consumption at different grinding time intervals was also performed. It was found that the ball mill consumed 54.67 kWh/t energy to reduce the F80 feed size of 722.2 µm to P80 product size of 275.4 µm while stirred mill consumed 32.45 kWh/t of energy to produce the product size of 235.6 µm. It also showed that stirred mill produced finer product than the ball mill at around 40% lesser consumption of energy. It can be concluded that the HPGR-Stirred mill combination was a more energy-efficient grinding circuit than the HPGR-Ball mill combination for PGE bearing chromite ore.