Utilization Of Low-grade Iron Ores Research Articles

Making quality agglomerates using lean iron ores for sustainable iron-making

For sustainable iron making and hassle-free operation of large blast furnaces (BF) and direct reduced iron (DRI) units, a more prepared burden in the form of good quality agglomerates is required. However, the situation is becoming more and more challenging owing to the faster depletion of high-grade iron ore, increased fines generation due to mechanized mining, wide variations in chemistry & mineral characteristics, high content of gangue minerals, and poor liberation characteristics. The growing demand for steel vis-à-vis iron ores has necessitated the utilizationof low-grade iron ores for steel production. The challenges lie in the economic extraction of lean ores and their conversion into quality agglomerates for use in iron making. The utilization of low-grade iron ores has assumed greater significance for the optimal utilization of natural resources and the sustainability of the steel industry. Thebeneficiated concentrate of BHQ iron ore from the Sandur Schist belt is used for the pellets. Green green pellets with 1.21 kg/pellet GCS and drop strength of 12 drop number were producedat an optimum binder of 1.2% and moisture of 9.5%. Induration of green pellets at a firing temperature of 1300 °C has resulted in adequate pellet properties of 237 kg/pellet of CCS, 91.87% TI, 7.41% RDI, and 22.56% porosity. An attempt is made to produce pellets suitable for iron making by optimizing various raw materials and operating parameters.This will reduce dependency on high-grade ores and effectively utilize low-grade iron ore to produce good-qualityiron-making pellets.

Predictive study of drying process for limonite pellets using MLP artificial neural network model

Due to the decline in high-grade iron ore production, the utilization of low-grade iron ore, such as limonite, has become necessary. Limonite contains a significant amount of bound water, which requires a drying process prior to use. Excessive heat stress caused by the evaporation of bound and free water during the drying of limonite pellets can lead to pellet disintegration and adversely affect gas-solid reactions. In recent years, artificial neural network (ANN) has been developing continuously in the fields of modeling and intelligent control, and has been widely used. Many predecessors used artificial neural network model to study the drying process of natural organic matter, and analyzed the factors affecting the drying rate of organic matter. In this study, we employed big data analysis, specifically Multilayer Perceptron (MLP) artificial neural networks, to analyze the drying process of limonite pellets and successfully established a predictive drying model applicable to limonite pellets. The MLP artificial neural network demonstrated excellent fitting between predicted and experimental values, with a maxi-mum R2 value of 0.999. The artificial neural network for drying developed in this study provides technical guidance for industrial material drying, reduces the workload of manual measurements, and minimizes energy consumption.

Separation characteristics of dry high-intensity drum magnetic separator

Dry high-intensity drum magnetic separator (DHIDMS) has been effectively used for the utilization of low-grade iron ores, thus an in-depth investigation on the separation characteristics of the DHIDMS separator would contribute to its design and practical operation. A numerical model was established to describe the particles motion in the DHIDMS process, on which the motion trajectories of siderite and quartz particles were simulated in the high and low magnetic field areas above the magnet surface, to reveal their dynamic behaviors; and the effects of two dominant operating parameters affecting the trajectory of particles, i.e., particle size and drum rotation speed, on the separation performance of a pilot-scale DHIDMS separator were investigated for a siderite ore. Simulation analysis indicates that the motion trajectories of the siderite and quartz particles are obviously different from each other in the high magnetic field area, but they generate negligible diversities in the low magnetic field area. In addition, in the high magnetic field area, the particle size and drum rotation speed significantly affect the distance between the motion trajectories of siderite and quartz particles, thereby affecting the separation selectivity of the DHIDMS separator. Experimental investigations indicate that, the feed particle size and drum rotation speed have definitely significant effects on the separation selectivity of the separator in the high magnetic field area; meanwhile, there is no separation selectivity for iron minerals in the low magnetic field area, thus deteriorating the recovery rate of iron concentrate. These results are basically consistent with the simulation analysis. This investigation has provided a general reference for the optimum design and operation of DHIDMS separator.

Improved iron recovery from low-grade iron ore by efficient suspension magnetization roasting and magnetic separation

Considering the decreasing reserves of high-grade iron ores, the utilization of low-grade iron ores is of great significance to the steel industry; however, improving iron recovery from low-grade iron ores is challenging. In this study, to improve iron recovery from low-grade iron ores, preconcentration was performed, followed by two separation processes, namely, reverse flotation (RF) and suspension magnetization roasting-magnetic separation (SRM), which were selected for comparing their effects on Fe grade and Fe recovery. The results showed that the iron grade and iron recovery rate of the concentrate obtained under the optimized RF conditions were 64.76% and 64.83%, respectively, and those under the optimized SRM conditions (500 °C roasting temperature, 20 min roasting time, 20% CO concentration, and 200 mL/min gas flow rate) were 69.60% and 99.18%, respectively. The analysis of the roasted products obtained by suspension magnetization roasting through X-ray diffraction, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy and by using a vibrating sample magnetometer showed that most hematite in the roasting feed was reduced to magnetite, which significantly enhanced the saturation magnetization of the roasted product and effectively facilitated the subsequent magnetic separation. Multiple cracks were formed in the roasted product, unlike the roasting feed (which had a smooth surface); the crack formation resulted in the acceleration of the magnetization reaction in the iron ore.

Novel Technology for Comprehensive Utilization of Low-Grade Iron Ore

In this study, a novel technology for the comprehensive utilization of low-grade iron ore is presented. For the iron ore with a Fe content of 24.91%, a pilot-scale study of pre-concentration, suspension magnetization roasting, grinding, and low-intensity magnetic separation was conducted, and an iron concentrate with a grade of 62.21% and a recovery of 85.72% was obtained. The products were analysed using chemical elemental analysis, particle size analysis, X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. The results indicated that hematite was reduced by CO and H2 mixture and transformed into ferrimagnetic magnetite in the suspension magnetization roasting, which was easily recovered in the subsequent magnetic separation. Additionally, a pre-concentration tailing with a SiO2 content of 81.55% and a magnetic tailing of the roasted ore with a SiO2 content of 79.57% were obtained, which can be used as building materials. This presents significant implications for the comprehensive utilization of low-grade iron ore.

Roles of MgO and Al2O3 in Viscous and Structural Behavior of Blast Furnace Primary Slag with C/S = 1.4

Permeability is crucial for stable operation and strengthening of smelting in blast furnace ironmaking, especially for the current utilization of low-grade iron ore. The viscosity of the primary slag is an important factor affecting permeability. In this study, the roles of MgO and Al2O3 in the viscous and structural behavior of CaO-MgO-Al2O3-SiO2-10 mass pct FeO (CaO/SiO2 weight ratio of 1.4) primary slag were investigated. The results showed that slag viscosity initially decreased and subsequently increased when Al2O3 content was increased from 6 to 16 mass pct, having the lowest value at 10 mass pct Al2O3. The reduction in viscosity with increase in Al2O3 content from 6 to 10 mass pct was attributed to the effect of solid crystals dissolving into the liquid phase caused by the decrease in the liquidus temperature, while the increase in viscosity at higher Al2O3 contents up to 16 mass pct was caused by the network-forming role of Al2O3 owing to its acidic nature. The viscosity fluctuated with increase in MgO content from 6 to 16 mass pct, which was related to the variation in the equilibrated primary phase field. The MgO and Al2O3 in the molten slag network structure functioned as network modifier and network former, respectively, to change the silicate network, as verified by Fourier transform infrared (FTIR) and Raman spectroscopy.

Recovery of Iron Values from Discarded Iron Ore Slimes

The ever-increasing demand for steel and the subsequent depletion of high-grade ores requires the massive utilization of low-grade iron ores. In the present study, an iron ore slime sample containing 56.1% Fe was investigated using physical beneficiation, carbothermal reduction, and a microwave-assisted process; however, physical beneficiation and microwave exposure were found to be inefficient as they yielded lower iron recovery. Using coconut shell as an alternative reductant was found to be promising and does not lead to the formation of higher iron oxides, such as fayalite and wustite phases. The microwave-assisted carbothermal reduction was found at par with conventional reduction, saving time and heating. The optimum magnetic concentrate obtained in both carbothermal reduction routes (microwave and muffle furnace: Fe grade, Fe recovery, and yield of 64.3, 97, and 84%, and 67, 99, and 83%, respectively) are suitable for alternative iron-making or blast furnace units.

Production of pig iron nugget from low-grade iron ore and pyrolyzed oil-palm-empty-fruit-bunch composites

Utilization of low-grade iron ore and pyrolyzed oil palm empty fruit bunch (EFB) is an effective way as the solution to deal with the depletion of iron reserves and administer of empty fruit bunch waste. This study was aimed to analyze the pig iron that is produced by carbothermic reduction of low-grade iron ore with pyrolyzed palm oil EFB as a reductant. The ore from Lampung was reduced at temperature 1400°C and 1450°C for holding time 40 minutes with inert condition (N2 atmosphere). The structures of pig iron were studied by using X-Ray diffraction (XRD), and the microstructures and chemical composition were analyzed by using Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS). It was found that iron nugget that was reduced at 1450°C for 40 minutes that was wholly separated from its slag, with reduction degree 98.5%, metallization degree 99.2%. The microstructure has metallic iron as a base with some pores. On the other hand, the other iron nuggets that are not separated from its slag consist of two prominent phases, metallic iron and lamellar fayalite (Fe2SiO4).

Sulphide Capacity of CaO–SiO<sub>2</sub>–Al<sub>2</sub>O<sub>3</sub>–MgO System Relevant to Low MgO Blast Furnace Slags

Desulphurization has been of more importance to control the quality of hot metal in blast furnace (BF) with increasing utilization of low-grade iron ores and poor-quality fuels as well as reducing the slag volume by decreasing MgO concentration. To improve performance with better understanding the desulphurization in BFs, sulphide capacities of CaO-SiO -Al O -MgO system relevant to BF slags were experimentally determined using gas-slag equilibration technique. The results show that sulphide capacity increases with the increase in temperature, CaO/SiO weight ratio and MgO at fixed Al O concentration. The experimental results were further compared with sulphide capacity obtained from available models in open literature. In addition, the equilibrium sulphur partition ratio between slag and hot metal was calculated from sulphide capacity with oxygen activity in the melt, which is also compared with industrial data and the laboratory experiments of kinetic desulphurization of hot metal.

Utilization of Low-grade Iron Ore in Ammonia Decomposition

Due to its cleanliness, fast energy cycle, and convenience of energy conversion, hydrogen has been regarded as the new energy source. Conventional process to produce hydrogen yield large amount of CO as byproduct. Moreover, the hydrogen storage and transportation have become the drawbacks in hydrogen economy. Thus, there has been increased interest in the hydrogen transportation medium as alternatives from the conventional process to produce and transport hydrogen. Ammonia has drawn worldwide attention as the most reliable hydrogen transportation medium. Through the decomposition of ammonia, hydrogen and nitrogen gas were produces as the byproduct without any CO or CO2 emission. In this experiment, the ore were introduced as the medium for ammonia decomposition. The ore were put into quartz tube reactor and were dehydrated at 400°C for 1 hour, then hydrogen reduced for 2hours before and undergone ammonia decomposition at 500-700°C for 3hours. The effects of temperature to the % conversion of ammonia decomposition were also studied. Ammonia decomposition at higher temperature gives higher conversion. As seen in the results, the NH3 conversion decreased with increasing time and the value after 3hours of reaction increased in the sequence of 500°C<600°C< 700°C. During ammonia decomposition, nitriding of iron occurred. The relation between temperature and the nitriding potential, KN is also investigated. The purpose of this study is to investigate the utilization of low-grade ore as medium for ammonia decomposition to produce hydrogen.

Iron Ore Recovery from Low Grade by using Advance Methods

With increasing global demand of iron ores due to the huge requirement of steel all over the world, important iron ore producing countries have increased their production by initiating steps to utilize the low-grade iron ores, fines and slimes. The main difficulty in processing and utilization of low-grade iron ores primarily stems from their mineralogical characteristics as well as the soft nature of some ores and their high silica content. Thus, beneficiating the low-grade iron ores to remove the gangue minerals and enhancing their grade is an attractive proposition today. Among the known iron deposits in Karnataka, many are of low-grade which require beneficiation to produce an acceptable feed for steel making plants.

Catalytic coal-tar decomposition to enhance reactivity of low-grade iron ore

Effective utilization of low-grade iron ore and coal can be one of the solutions for avoiding the high cost of raw materials and solving the problem of resource shortages in the steelmaking industry. This paper describes the behavior of reduction reaction during tar decomposition over low-grade iron ore. Pisolite ore, containing 5.9mass% of combined water, was dehydrated at 450°C to obtain porous ore. Tar vapor and pyrolysis gas of low-grade coal were introduced to porous ore for tar decomposition and carbon deposition. The iron ore effectively decomposed 22.1mass% of tar component into gas product and deposited carbon at 600°C. Besides tar decomposition, the ore was also reduced to magnetite and wustite by gas product which was produced from coal pyrolysis and tar decomposition. The reactivity of deposited carbon within ore was evaluated by reduction reaction using thermogravimetry method. The reduction of the carbon-deposited ore began at 750°C, while that of the reference mixture of Fe3O4 and coke began at 1100°C. The carbon-deposited iron ore was more reactive because nanoscale contact between iron ore and carbon enhanced reaction rate. These results revealed attractive utilization and reduction process of low-grade iron ore with coal tar decomposition.