Typical Iron Ore Research Articles

Effect of iron ore type on the reduction behavior at multi-stage reduction by H2

Effect of iron ore type on the reduction behavior at multi-stage reduction by H₂

Migration behavior of iron and phosphorus during gas-based reduction for high-phosphorus iron ore

With the depletion of high-grade iron ore, it is necessary to develop low-quality high-phosphorus iron ore through economical and sustainable solutions. In this study, we presented simultaneous enrichment of iron (Fe) and phosphorus (P) to recover P from high-phosphorus iron ore and clarified the migration of P from the original apatite to reduced iron during the direct reduction process. To capture the migration route, gas-based reduction at a relatively slow rate was conducted on two typical iron ores samples (low-grade and high-grade) at different temperatures and times. Results indicate that there are concentration gradients for P and Fe of reaction products in the low-grade iron ore at 1400 °C. The P content continuously increased in the sequence from metallic iron (Fe), wustite (FeO), and fayalite (Fe2SiO4), to apatite (Ca3(PO4)3F). Conversely, the content of Fe gradually decreased. During this process, P dissolved from apatite entered and formed P-bearing fayalite. For the high-grade iron ore, P-bearing fayalite with a metastable structure disappeared as the reduction progressed, and P was released and then reduced to a gaseous state, finally absorbed by metallic iron. Furthermore, when metallic iron was not formed in the initial 60 min at 1300 °C, the P migrated from the apatite to the fayalite and gas phase. As the reduction time increased from 60 min to 240 min, the formed metallic iron provided a site for gasified P, which inhibited the volatilization of P and contributed to Fe and P enrichment.

Feasibility of Estimating Type and Abundance of Iron Ore Using Field Hyperspectral Radiometry and Spectral Transformation in Precambrian Banded Iron Formations of North Odisha, India

Feasibility of Estimating Type and Abundance of Iron Ore Using Field Hyperspectral Radiometry and Spectral Transformation in Precambrian Banded Iron Formations of North Odisha, India

Experimental analysis of the melt fraction - mechanical strength relationship for iron ore sinter analogues

This study examined the strength of sinter analogue tablets for different types of iron ore under varying sintering conditions. A steel tamper was designed to quantify strength based on the percentage of 1 mm retained size after a drop weight test. The study found a linear relationship between total melt fraction M and strength index S quantified by mass fraction of the +1 mm retained size: S=0.88M. Importantly, a relationship was found between the total melt and a combined F factor incorporating the thermodynamic liquid fraction (α, representing sintering conditions) and the mineralogical factor loss on ignition (LOI ratio, β, representing ore types), where F=6.5α+β−1. This factor F was found well correlated the total melt via an asymptotic exponential relationship as M=1−2.6e−F. The results also suggested that, to achieve an acceptable strength of 80% +1 mm for a typical basicity B = 2, a sintering temperature range between 1273 and 1370 °C is required for the LOI range between 1.6% to 10.7% respectively. Finally, an analogous analysis was also carried out which proposed a similar trend between sinter yield obtained in a kilogram-scale by lab-scale studies and the present 0.6-g analogue scale.

Shear zone-hosted hypogene high-grade iron deposit: The Cuité case study

The Cuité iron ore deposit consists of high-grade schistose lenses (>60 wt% Fe) hosted in a tectonic sliver of iron formation associated to mica schist (Serra da Serpentina Group). It is located at the southeastern border of the São Francisco Craton, enclosed by sheared Sthaterian granitoids (Borrachudos Suite), Neoarchean ortogneiss (Guanhães Complex), quartz and pegmatite veins. The iron formation encloses schistose to massive high-grade ore lenses, with a pervasively, continuous to anastomosed schistosity defined by millimetric elongated hematite plates and quartz grains enclosing hematite granoblastic domains. Kenomagnetite/maghemite and martite pseudomorphs (after magnetite) overgrow the foliation and intergrow with granoblastic hematite. Three high-grade iron ore types are identified, according to the fabric and mineralogy of the main iron oxides: lamellar-granular hematitic (LGO), magnetitic (MO), and granular hematitic ore (GO). Intrusive pegmatite bodies related to the swarms of the Eastern Brazilian Province (late Ediacaran to early Cambrian) and to post-collisional Cambrian vents of the Brasiliano Orogeny caused extensive hydrothermal alteration in the country rocks, encompassing recrystallization of the detrital zircon grains from the associated psammopelitic units, which yielded Cambrian ages, formation of kaolinite-rich lenses, and generation of granoblastic ore bodies. The association of intense stretching along foliation and circulation of hydrothermal fluids from pegmatite intrusion is responsible for the ore formation.

Grinding of Australian and Brazilian Iron Ore Fines for Low-Carbon Production of High-Quality Oxidised Pellets

Oxidised pellets have become an indispensable high-quality charge for blast furnaces. Nevertheless, high-quality pellet feeds are becoming scarcer and scarcer. To broaden the range of sources of pellet feeds and reduce the production cost of pellets, more steel mills are predicted to use coarse iron ore fines with a relatively low iron grade and low impurities for the preparation of desirable pellet feeds through a typical wet grinding–settling–filtering process. In this work, the grinding, settling and filtering behaviour of Brazilian and Australian iron ore fines are studied and compared, with the aim of discovering the internal relationship between the mineralogical characteristics of different iron ore types and their grinding–settling–filtering performance. Additionally, the effects of ore blending on pellet preparation were investigated. The results show that, usually, the higher the hardness of the iron ore, the more grinding energy is required. Australian and Brazilian ore fines exhibit good grindability, with a Bond work index of about 10–15 kW·h/t. Furthermore, ore blending can reduce grinding energy consumption and improve settling and filtration rates, and the addition of finely ground Australian ores improves the balling performance of pellet mixtures. At the same bentonite content, the ball drop strength of the three blends with added Australian ore is significantly higher than that of the base blend, and the fired pellets obtained from Blend 1, Blend 2 and Blend 3 blends exhibit good metallurgical properties.

The Geochemical Characteristics of Trace Elements in the Magnetite and Fe Isotope Geochemistry of the Makeng Iron Deposit in Southwest Fujian and Their Significance in Ore Genesis

The Makeng iron deposit in southwest Fujian is a significant iron polymetallic deposit containing various types of iron ore, including garnet magnetite, diopside magnetite, and quartz magnetite. The metallogenetic type of the deposit has been a subject of debate, particularly in relation to the genesis of magnetite and the source of iron. In situ microanalysis of trace elements in magnetite from different ores shows relatively low levels of V, Ti, Cu, and Zn, with higher concentrations of Ca and Si, indicating the characteristics of a skarn type deposit. The δ57Fe values of the magnetite range from −0.091‰ to 0.317‰. Combining these data, whole-rock iron isotope analyses, including Juzhou and Dayang granites, diabase, and the Lower Carboniferous Lindi Formation sandstone, suggest that Fe in the magnetite primarily originates from granitic pluton, with potential contributions from diabase and the Lower Carboniferous Lindi Formation sandstone. Combined with field work, these results indicate that Makeng iron deposit is a skarn-type magnetite deposit associated with Yanshanian granitic intrusions. Therefore, the initial ore-forming fluid is postulated to be a high-temperature magmatic hydrothermal fluid with high oxygen fugacity. This fluid infiltrates spaces such as interlayer fracture zones between the Upper Carboniferous Jingshe Formation–Middle Permian Qixia Formation carbonate rocks and the Lower Carboniferous Lindi Formation sandstone, resulting in diverse magnetite ores due to metasomatism. The mineralization process of the Makeng iron deposit is basically the same, as it is composed of typical skarn deposits. Magnetite was mainly formed during calcic skarn formation stage, and this process persisted until the initial phase of the retrograde alteration of skarns. In contrast, sulfide minerals, including molybdenite, sphalerite, and galena, precipitated during the quartz–sulfide stage.

Use of backscattering ultrasound parameters for iron ore varieties recognition

Purpose. Development of the method for recognizing the main mineral-technological varieties of iron ore in the deposits being developed by selecting an analytical model for the spectral characteristics of the received ultrasonic echo signals and quantitative assessment of their parameters. Methodology. The work uses methods for modeling the processes of propagation of ultrasonic waves in a randomly heterogeneous medium. The process of backscattering of ultrasound in mineral structures formed by inclusions of iron ore of various varieties and associated rock was considered. The estimated parameters of the spectral characteristics of the inversely scattered probing ultrasound pulse were studied. Findings. A method for recognizing the main mineral and technological varieties of iron ore of the deposit being developed, based on the parameters of the propagation of ultrasonic waves in the studied samples, was proposed. This is achieved by selecting an analytical model for the spectral characteristics of the received echo signals and quantifying their parameters. The amplitude of the echo signal and its spectral properties depends on the size and concentration of the scatterers, i.e., the structural and textural features of the iron ore sample under study. Taking into account these factors, the extracted parameters of the model were used to identify the main mineralogical and technological varieties of iron ore of the studied deposit. Originality. The proposed method for recognizing mineral-technological varieties of iron ore differs from the known ones in that the amplitude, central frequency, and bandwidth of the amplitude spectrum of the Gaussian parametric model of the measured echo signals are used as evaluation parameters. Practical value. The proposed scientific and technical solution allows for operational non-destructive control of the main mineralogical and technological types of iron ore in the process of its extraction and processing.

Large-scale Mesoproterozoic iron formations in northwestern China

Iron formations (IFs) represent an economically important iron-rich rock type in the Precambrian geologic record. It is generally assumed that after ca. 1.85 Ga, large-scale IFs were not deposited for approximately 1.1 Gy. However, substantial IFs, including over 15 large- to small-scale iron deposits, have been identified recently in Northwest China, and they would constitute the largest Mesoproterozoic IFs globally if their Mesoproterozoic ages can be confirmed. Field observations reveal that these iron deposits are dominantly stratiform and stratoid within the thick clastic-carbonate and volcanic-sedimentary succession. The ores mainly comprise Fe-rich (specularite, hematite, and siderite) and Si-rich (jasper and quartz) minerals with banded or massive structures. Geochemical investigations of typical iron ores show high SiO2 and TFe2O3 and relatively low Al2O3 and TiO2 contents, indicating that they are primary chemical sediments with high hydrothermal and low detrital contributions. These features suggest that these iron deposits in the NQOB are typical IFs, which resemble the Archean and Paleoproterozoic IFs worldwide. New zircon U-Pb dating and lithostratigraphic correlations indicate that these IFs were deposited at ca. 1.1 Ga. The sizable ore reserves and Mesoproterozoic ages confirm that these IFs are the largest reported IFs for the billion years between 1.8 and 0.8 Ga. The large-scale Mesoproterozoic-aged IFs help fill the longest gap in Earth history where the IFs were thought absent from the geologic record and provide an unusual perspective to understand the reappearance mechanism of Precambrian IFs.

Genesis of submarine volcanic iron deposits in the Central Asian Orogenic Belt: Insights from the texture and chemical composition of magnetite from the Langwashan iron deposit in the Beishan orogenic belt, NW China

Carboniferous submarine volcanic rocks hosting iron deposits are widely distributed in the Tianshan and Beishan orogenic belts. However, the genesis of these deposits remains unresolved, with contrasting magmatic and magmatic-hydrothermal models being proposed. The Langwashan iron deposit (83.18 Mt @ 37% Fe) is one of the largest iron deposits in the Beishan orogenic belt. In this paper, we present detailed textural and trace-elemental properties of magnetite from the Langwashan iron deposit to elucidate the genesis and evolution of iron mineralization hosted in Lower Carboniferous submarine volcanic rocks. The Langwashan iron deposit has various types of iron ore that are closely associated with skarn minerals, including garnet and epidote. Magnetite in these samples can be classified into two distinct types, early-stage mushketovite (Mag1) and late-stage granular magnetite (Mag2), both of which show oscillatory zoning, with low Ti (mean of 0.03–0.07 wt%) and V (mean of 0.03–0.04 wt%) contents, and variable Si contents (mean of 0.74–6.50 wt%). These textural and compositional data classify the Langwashan deposit as a typical Fe-skarn deposit. Results also reveal that iron oxides in the Langwashan deposit underwent a complex evolution comprising three episodes: (1) early-stage influx of low-oxygen-fugacity, calcium-rich hydrothermal fluids, causing the transformation of original hematite to mushketovite (Mag1-1) and the formation of scheelite inclusions; (2) subsequent dissolution–reprecipitation between high-temperature magmatic-hydrothermal fluids and Mag1-1, generating trace-element-rich mushketovite (Mag1-2) and the precipitation of trace-element-rich granular magnetite (Mag2-1) from magmatic-hydrothermal fluids; and (3) final multiple fluid metasomatism under the influence of trace-element-poor hydrothermal fluids, involving dissolution–reprecipitation that produced trace-element-deficient Mag1-3, Mag2-2, and Mag2-3. Results also highlight that the submarine volcanic iron deposits from both the Tianshan and the Beishan orogenic belts were probably formed in a similar geological setting, with similar timing of formation, mechanism of mineralization, and evolution, and they are likely Fe-skarn deposits.

Geology and Fe-Skarn Mineralization in Lolo Prospect, Solok West Sumatra, Indonesia

The study area is situated in Lolo village, Pantai Cermin district, Solok regency, West Sumatra province, Indonesia. Several mining companies have been operated for skarn-related iron ore type in this area and its vicinity. Although the study area has been explored, the detailed geology and Fe skarn characteristics remain unclear. This paper therefore, is dealing with the geological framework and characteristics of skarn mineralogy employing some laboratory analyses such as petrography, ore microscopy, X-Ray Diffraction, micro-XRF and AMICS, ICP-AES and ICP-MS analyses. The geological framework of the prospect was defined by a surface geological mapping and observation. Skarn alteration of limestone host-rock is typified by the presence of prograde minerals such as garnet, clinopyroxene, and wollastonite. The retrograde mineral is peculiarly not found in the limestone wall-rock, but in altered causative intrusion i.e. granodiorite. The altered granodiorite is composed of some key propylitic minerals such as chlorite, epidote, and a few clay minerals. Fe skarn mineralization is represented in magnetite, hematite, goethite and limonite which are associated with several sulphide minerals such as covellite, pyrite, and chalcopyrite. Mass balance analysis on limestone indicates a mass gain of 0.16%, whereas mass balance analysis on granodiorite indicating mass loss of 3.36%. Ore mineralization and skarn alteration are strongly controlled by NW-SE and NE-SW trending faults and the distribution of limestone. Follow-up subsurface exploration is needed to define the Fe skarn orebody.

Rudomain Iron Ore Treatment by High-Temperature Reduction

The purpose of this study was to conduct experiments comprising the high-temperature reduction treatment of commercially produced iron ore fines and lumps aimed at increasing the use value of the ore. The analysed ore was Ukrainian iron ore sold under the Rudomain commercial name, mined from a bed located in the southern part of the Saksagan region (Kryvyi Rih, Ukraine). The study describes in detail the basic physical, chemical, and physico-chemical properties of the analysed ore, and it comprised a thermodynamic analysis, which is typically used as the basis for defining reduction conditions. The Ukrainian ore—Rudomain—exhibited a lower total Fe content (58.20 wt%) and, by contrast, the highest SiO2 content (13.40 wt%), whereas SiO2 is present in this type of ore not only in form of silica (SiO2) but also in form of hydrated iron silicate (Fe3Si2O5(OH)4), i.e., the form of iron that is the most difficult to reduce. In the study, tests of thermal stability and thermal shock stability were carried out in various conditions, while the hardened pellets were thermally stable up to temperatures of 950 °C. The results of the performed experiments in high-temperature reduction of Rudomain iron ore were then compared with the results obtained with two other types of iron ores, in particular Krivbas and Carajas. Krivbas and Carajas ores show higher degrees of reduction and degrees of metallization than Rudomain ore. High-temperature experiments in thermal stability and carbothermic reduction have brought favourable information that is useful for the treatment of lower-grade ores with higher contents of SiO2, while Rudomain iron ore exhibited a rather good potential for effective metallisation.

Mineral Liberation Properties of Iron Ores with Different Grain Sizes by Particle-Bed Breakage and Traditional Grinding

ABSTRACT More efficient liberation of valuable minerals from gangue would bring enormous benefits to the comminution process and the downstream beneficiation processes. However, whether particle-bed breakage can improve liberation compared with traditional grinding has been controversial. In this study, three types of iron ores with 3–0.425 mm were comminuted to −0.425 mm via the piston-die compression unit or the dry ball mill at essentially the same grinding degrees. Liberation analysis was performed using Mineral Liberation Analyzer (MLA) for each breakage method and the size fraction product. Statistical methods based on bootstrap resampling and standardized mean differences (SMD) were used to quantitatively analyze the significance of differences in the liberation distribution of iron oxide minerals with different breakage methods. MLA tests showed that the particle-bed breakage did not significantly improve the liberation degree compared to the ball mill grinding; the maximum difference of the proportion of 80–100% liberated iron oxide mineral in a certain size fraction with the two breakage methods was only 5%. The SMD was less than 1.2 in most size/composition classes, which indicated that the difference in the liberation distribution of iron oxide minerals between the two breakage methods was not statistically significant in most size/composition classes. The particle-bed breakage slightly improved the liberation of iron oxide minerals compared to ball mill grinding at the particle size of the products close to the grain size of the iron oxide minerals in the feeds.

Study of technological properties of the sample ethiopian iron ore of the arabian-nubian shield. Part 2. Microscopic analysis of ore samples with a thickness of +40.0+5.0 mm

As a result of the research, the mineral composition of the mineralogical and petrological varieties of material of the 10-20 mm and 20-40 mm size classes of the studied ore sample was specified. Transparent and polished sections of the above-mentioned granulometric samples were prepared. Microscopic examination was carried out using a transmitted and reflected light microscope «Carl Zeiss Jena NU-2 Microscope». A description of the discovered minerals was completed. It was found that the main ore minerals of the studied ore are dispersed hematite and hydrohematite, and their amount is about 54.0% of the total volume. Microscopic analysis also revealed hydrohematite spherulites, including in the intergranular space in quartz aggregates. It is shown that secondary ore minerals in the studied raw materials are goethite and hydrogoethite. Microscopic analysis showed their content at the level of 4.0 %. The color of goethite and hydrogethite, which are represented by iron hydroxides of yellow, brown, brown and black color and their form in the form of nodular aggregates, spherulites of crusts, and nest-like aggregates, is also determined. It was found that the main non-metallic mineral in the studied raw material is quartz, the content of which is on average 30 %. This mineral in the sample of the studied ore is characterized by a variety of morphological features and a wide range of grain sizes – from several micrometers to several centimeters. Microscopic examination of quartz showed that it is represented by xenomorphic grains with a complex nature of fusions with other minerals, rounded and acute-angled grains, chalcedony (agat) grains and thin-prismatic crystals. The presence of a secondary non-ore mineral, which has clay properties and is represented by kaolinite, is also shown. An additional study was carried out, in which chalcopyrite – an additional component of iron ore raw materials – was analyzed. The conducted microscopic studies made it possible to draw a conclusion about the mineral and petrological characteristics of the raw material. It is shown that the type of iron ore of the Arabian-Nubian shield is similar to ores of volcanic-sedimentary origin and brown iron ores

Are iron ore microparticles toxic for the European clam Ruditapes decussatus? Response elements from biomarker activities and in silico modeling

Inevitably, high concentrations of iron, the most widely produced ore globally, can be found in aquatic environments. To assess the toxicity of iron on aquatic organisms, Ruditapes decussatus specimens were subjected to microparticles derived from two types of iron ore (hematite and magnetite) at four different concentrations (0.5, 1, 1.5, and 5 g/L). The findings revealed that both types of iron ore were absorbed by clams in a concentration-dependent manner. Biomarkers analysis demonstrated significant and organ-specific impacts on the health of the clams caused by these microparticles, which was further supported by computational analyses on bioavailability. Within seven days of exposure, changes were observed in the activities of several enzymes, including catalase, acetylcholinesterase, and glutathione S-transferases, as well as in the rate of lipid peroxidation in both the digestive gland and gills. This study provides an environmental perspective on the toxicological effects of iron ore microparticles.

Modeling the Liberation of Iron Ores with Different Grain Sizes Considering Intergranular Fracture

ABSTRACT Predicting the liberation distribution of minerals in comminuted ore particles is one of the fundamental problems in mineral processing. However, there is still no widely accepted liberation model due to the complexity of the mineral fracture mechanism. In this study, the shape constants of the cumulative beta distribution were further optimized based on the investigation of the liberation distribution and fracture mechanism of iron oxide minerals in three types of iron ores with different grain sizes by locked-cycle grinding and batch grinding to model the liberation distribution of iron oxide minerals with different grinding methods. The results showed that the liberation distribution of iron oxide minerals in the three types of iron ores with locked-cycle grinding and batch grinding was related to intergranular fracture proportion and the closeness of ore particle size and mineral grain size. By relating the shape constants of cumulative beta distribution to ore particle size, mineral grain size, and the proportion of intergranular fracture, the developed liberation model well predicted the liberation distribution of iron oxide minerals with different grinding methods and its coefficient of determination (R2) was between 0.85–0.93.

Chronolgy and Geochemistry of the Sijiaying Iron Deposit in Eastern Hebei Province, North China Craton: Implications for the Genesis of High-Grade Iron Ores

The Sijiaying iron deposit is located in the Eastern Hebei area of the southern section of the northern margin of the North China Craton (NCC) and is the largest single iron deposit in China. The deposit contains many banded iron formations (BIFs) and was proven to have more than 3 million tons of high-grade iron ore resources. This study carried out geochemistry and zircon U–Pb analysis of normal-grade iron ore, high-grade iron ore, and wall rock (biotite–leptynite, chlorite–sericite schist) in the Sijiaying deposit and discussed the genesis and metallogenic age of high-grade iron ore. BIFs have low concentrations of Al2O3 and TiO2 and high field strength element (HFSE) depletion, indicating almost no contamination via terrestrial debris. The standardized post-Archean Australian shale (PAAS) rare earth element (REE) distribution pattern indicates that the iron formation exhibits positive Eu, Y, and heavy rare earth element (HREE) anomalies and lacks negative Ce anomalies, indicating that the Sijiaying BIF was enriched with iron sources via high-temperature hydrothermal fluids from the seabed and deposited in an anoxic ancient marine environment. In addition, geological field work identified two types of high-grade iron ore in the mining area: primitive sedimentary and hydrothermally altered high-grade iron ore. Further ore geochemical research showed that the primitive sedimentary-type iron ore is similar in geochemistry to the BIF. In addition to low Eu/Eu* values, the hydrothermally altered high-grade iron ore shows geochemical characteristics similar to those of the BIF, suggesting that they share the same iron source but did not form at the same time. The total large ion lithophile element (LILE) (Sr, Ba, Pb) contents in primitive sedimentary-type high-grade iron ore are higher than those in hydrothermally altered high-grade iron ore, indicating that LILEs are carried away via fluids during the hydrothermal alteration process in normal-grade iron ore. The geochemical characteristics of biotite–leptynite and chlorite–sericite schist include high contents of SiO2 and Al2O3, light rare earth elements (LREEs), LILE enrichment (Rb, Ba, Sr, Zr), and HFSE depletion (Nb, Ta, P, Ti), characteristics that are similar to island arc volcanic rocks. The reconstruction of the original rock indicates that the wall rock is a product of volcanic sedimentary cycles in an island arc setting. Zircon cathodoluminescence images and LA–ICP–MS zircon U–Pb dating can be divided into four age groups (3283 Ma, 2547 Ma, 2500 Ma, and 2407 Ma), which correspond to the earliest volcanic activity in eastern Hebei, the main mineralization age of the Sijiaying BIF (the mineralization age of primitive sedimentary high-grade iron ore), a regional tectonic–metamorphic event, and the occurrence of migmatization (the mineralization age of hydrothermally altered high-grade iron ore), respectively. Therefore, the Sijiaying BIF and primitive sedimentary high-grade iron ores were deposited and mineralized at 2547 Ma, and the iron orebody was later altered via the hydrothermal solution at 2407 Ma, forming large-scale high-grade iron ores.

Formation and distribution of dioxins in agglomerated products and emitted dust during iron ore sintering

This study investigated the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in sintered products and emitted dust samples. Four types of iron ores were used in this study and tested in a sinter pot grate. The PCDD/F analysis showed that the PCDD concentrations (0.175–1.415, pg/g, 0.028–0.087 pg WHO-TEQ/g) were higher than the PCDFs (0.105–0.327 pg/g, 0.006–0.032 pg WHO-TEQ/g) in sinter. In dust samples, three of the four test experiments showed PCDDs < PCDFs in their measured concentrations. Although PCDD/F concentrations were different in sinter and dust samples, the PCBs presented similar behavior in both solid samples. The PCB analysis (pg WHO-TEQ/g) showed that non-ortho PCBs were higher in concentration than the mono-ortho PCBs. The statistical analysis showed significant correlations between low chlorinated PCDD/F congeners and high chlorinated PCDD/F congeners, as well as strong correlations between non-ortho PCBs and mono-ortho PCBs in both sinter and dust samples. However, the dust samples presented stronger and more positive correlations among the PCDD/F and PCB congeners in comparison to corresponding data in sinter samples. The differences in PCDD/F profiles and correlation matrix in sinter and dust samples suggest the dioxin formation during sintering undergos different mechanisms in the sinter and dust samples.

Studies on characterization of properties of low-grade hematite iron ores and their fired pellets

ABSTRACT In this study, pellets were made from iron ores of Ramallakota and Veldurthi mines, Andhra Pradesh, by the addition of 1.5 to 4.5 wt.% of bentonite and molasses binders. Dried iron ore pellets were fired at 1173, 1373 and 1573K for 1, 2 and 3h. The aim has been to determine the effects of type of iron ore and binder, and firing conditions on the properties of resulting fired pellets. Chemical compositions and XRD patterns of studied iron ores revealed them to be of low- grade hematite iron ores having 27–46% Fe. Drop number of dried pellets got increased with an increase in their binder contents. Both the types of fired iron ore pellets exhibited an increase in their crushing strengths and decrease in apparent porosity with rise of firing temperature and time due to an increase in the extent of sintering of particles, as revealed by SEM micrographs.

Investigation of Liberation Properties and Mineral Fracture Mechanisms of Iron Ores with Different Mineral Grain Sizes at Different Grinding Degrees

ABSTRACT Understanding the liberation properties of minerals in ores with different grinding degrees is very important for establishing liberation models. However, a detailed study of the effect of grinding degree on the liberation properties of minerals in ores is still highly desirable. In this study, three types of iron ores with different mineral grain sizes were ground to different particle size distributions by locked-cycle grinding and batch grinding. The liberation properties of iron oxide minerals and quartz in each grinding method and the size fraction product were analyzed using Mineral Liberation Analyzer (MLA). Statistical methods were used to quantify the extent of the difference in liberation properties between the two grinding methods. Furthermore, the fracture mechanisms of iron oxide minerals and quartz were investigated. It was found that the liberation degrees of the products were higher in locked-cycle grinding with a lower grinding degree. For fine-grained iron oxide minerals, the iron oxide minerals distribution of 80–100% composition class differed by 22% at −75 + 53 μm size fraction with the two grinding methods, and its corresponding standardized mean differences (SMD) was 20.5, indicating that the difference was statistically significant. The significant change in the percentage of intergranular fracture with different grinding degrees is the reason for the obvious difference in the liberation properties of the products.