Reduction Roasting Followed by Pelletization Study of Concentrate Fines of a Low Grade Iron Ore

Bentonite is the traditionally used binder in iron ore pelletization. However, it consists of up to 85% silica and alumina which are undesired acidic gangue in iron-making. In this study, carboxymethyl cellulose, sodium lignosulfonate and cornstarch were used as acidic gangue-free organic alternatives to bentonite in synthesizing iron pellets. Iron ore, water and the corresponding binder were mixed and rolled in a pelletizing disk to form green pellets. The green pellets were dried and subsequently indurated in a furnace at 1200 ℃ to form indurated pellets. To evaluate the effectiveness of the organic binders, the pellets produced were tested on various pellet properties. Known industrial pellet property standards and the bentonite binder were used as references. Carboxymethyl cellulose, sodium lignosulfonate and corn starch produced green pellets with average drop numbers of 7.20 ± 0.84, 5.60 ± 0.89 and 6.00 ± 1.00 respectively, compared to bentonite’s 5.00 ± 0.71. Dry pellets of average compressive strength 5.93 ± 0.09, 5.86 ± 0.03 and 11.52 ± 0.18 kg/pellet were produced by carboxymethyl cellulose, sodium lignosulfonate and corn starch respectively while bentonite’s averaged 5.60 ± 0.08 kg/pellet. For indurated pellets, carboxymethyl cellulose (210.2 ± 1.88 kg/pellet) and sodium lignosulfonate (198.1 ± 2.49 kg/pellet) pellets were weaker than those of bentonite (250.4 ± 2.06 kg/pellet) but satisfied the industrial requirement of 181.4 kg/pellet. A boron oxide additive (0.1 wt. %) was used to boost the strength of carboxymethyl cellulose indurated pellets to 252.6 ± 1.32 kg/pellet, rendering them superior to those of bentonite.

Geochemical and mineralogical evaluation of Libale iron- rich manganese deposit, North-central Nigeria

Abstract The present study focuses on the mineralogical aspects and roasting of iron ore (Fe: 55.4%) fines in both fixed bed and fluidized bed roaster. Goethite is the dominant mineral phase in this low-grade iron ore containing hematite, silica and alumina. Such ore was roasted at a constant temperature of 900°C, with non-coking coal of 20% at residence time ranging from 15 to 60 minutes at intervals 15-minute in the fixed bed and 2 to 8 minutes at intervals 2-minute in the fluidized bed reactor. Non-coking coal was utilized as a reductant in the reduction reaction. A high-grade iron ore concentrate was subsequently extracted using Low Intensity Magnetic Separation (LIMS) from the roasted ore. Phase changes in both cases were different due to the difference in the mechanism of reduction. In the fixed-bed reduction roasting phase, transformation occurs as Goethite – Hematite – Magnetite – Wustite, whereas in a fluidized bed, it has followed Goethite – Hematite – Magnetite – Maghemite route. The maghemite phase formed during the fast reduction process due to reoxidation of the reduced magnetite. The wustite phases are reported in the nonmagnetic fractions during LIMS, lowering the yield. On the other hand, the maghemite phase is reported to the magnetic portions. It has a simple cubic structure like magnetite, which increases the yield in the fast reduction roasting process. The results show that 65.85-grade iron ore can be obtained after 30 minutes of residence time with a recovery of 51.5% from the fixed bed and 62.17-grade iron ore can be obtained after 4 minutes of residence time with a recovery of 53.2 % from the fluidized bed.

Batch scale study on magnetizing roasting of low-grade iron ore tailings using fluidized bed roaster

India is an economically developing country. Country’s development and growth is largely interlinked with iron and steel industry as well as availability of energy and its utilization. Energy sector and iron and steel industry mainly consumes convectional and fossil fuel like coal and gas. Present coal reserves of India will last for about 30-40 years at present consumption rate. Consumption of conventional fuels is not economically feasible and environment friendly. Biomass can be an alternative source of fuel for numerous engineering and scientific applications. The char derived from biomass known as biochar can be utilized in the iron and steel-making processes. It can lessen the coke consumption rate and subsequently reduce pollution as well as cost economics. Utilization of low and lean grade iron ore is need of the hour. Removal of gangue impurities from lean and low-grade iron ore is difficult through convectional beneficiation process. The reduction roasting process can be adopted to counter these challenges. The present study focuses on the reduction behavior of iron ore using three various biochar derived from three biomass, viz; wood dust, sugarcane bagasse and coconut shell. A single factorial Design of Experiment with two levels and three variables was adopted and a first-order regression equation was generated to estimate the degree of reduction. The Student’s T-test and Fisher test were performed to validate the regression equation. The obtained results showed that the biochar can be used as a substitute reductant. However, the residence time and temperature play a vital role in the reduction process. The obtained regression equation also validates the effect of residence time and temperature on the reduction process.

Currently, fossil fuels are still the primary fuel source and reducing agent in the steel industries. The utilization of fossil fuels is strongly associated with CO2 emissions. Therefore, an alternative solution for green steel production is highly recommended, with the use of biomass as a source of fuel and a reducing agent. Biomass’s growth consumes carbon dioxide from the atmosphere, which may be stored for variable amounts of time (carbon dioxide removal, or CDR). The pellets used in this study were prepared from a mixture of low-grade iron ore and palm kernel shells (PKS). The reducing reactivity of the pellets was investigated by combining thermogravimetric analysis (TGA) and laboratory experiments. In the TGA, the heating changes stably from room temperature to 950 °C with 5–15 °C/min heating rate. The laboratory experiments’ temperature and heating rate variations were 600–900 °C and 10–20 °C/min, respectively. Additionally, the reduction mechanism was observed based on the X-ray diffraction analysis of the pellets and the composition of the reduced gas. The study results show that increasing the heating rate will enhance the reduction reactivity comprehensively and shorten the reduction time. The phase change of Fe2O3 → Fe3O4 → FeO → Fe increases sharply starting at 800 °C. The XRD intensities of Fe compounds at a heating rate of 20 °C/min are higher than at 10 °C/min. Analysis of the reduced gas exhibits that carbon gasification begins to enlarge at a temperature of 800 °C, thereby increasing the rate of iron ore reduction. The combination of several analyses carried out shows that the reduction reaction of the mixture iron ore-PKS pellets runs optimally at a heating rate of 20 °C/min. In this heating rate, the reduced gas contains much higher CO than at the heating rate of 10 °C/min at temperatures above 800 °C, which encourages a more significant reduction rate. In addition, the same reduction degree can be achieved in a shorter time and at a lower temperature for a heating rate of 20 °C/min compared to 10 °C/min.

Coal ash induced ring formation in a pilot scale rotary kiln for low-grade iron ore direct reduction process: Characterization and mechanism

This study compares the efficiency of different methods in beneficiation of iron ore from Doğanşehir (Malatya) region. It is a low grade ore with 27.43 % Fe content that requires concentration to meet the specifications of blast furnace feed. The ore mainly contains magnetite, ferro-actinolite and magnesioferrite. The collected samples were classified into different size fractions after size reduction and then subjected to different gravimetric and magnetic separation methods for concentration. The results showed that particle sizes affected the concentrations to a large extend, but wet magnetic separation yielded comparably better results than gravimetric methods. A concentrate assaying 65.66 % Fe and 0.38 % K2O+Na2O was obtained with 78.11 % recovery by wet magnetic separation. It was concluded that concentrates meeting blast furnace specifications could be obtained from this low grade iron ore. It was also concluded that the proposed separation flow sheet can be applied to similar low grade iron ores in the region.

.In the present study a detailed characterization followed by beneficiation of low grade iron ore was studied. The Run of Mine (R.O.M) sample assayed 21.91 % Fe, which is very low grade in nature. The impurities are SiO2 26.25%, MgO 20.48%, CaO 5.85%, Al2O3 1.86% and loss on ignition (LOI) 12.71%. A Davis Tube test was performed for the assessment of the separability of magnetic ores by low intensity magnetic separators. The heavy liquid test was carried out to evaluate the possible response of the sample by the gravity concentration technique. The samples were subjected to jigging, dry low intensity magnetic separation (DLIMS) and shaking table tests. Thus a sufficient concentrate could not be obtained in +1 mm by using jigging and DLIMS. The obtained results show that the a high grade iron concentrate (>65% Fe) with lower recoveries was obtained from shaking table tests by using -1 mm fraction. According to the results a flowsheet was developed. From the developed flowsheet, it is possible to obtain pellet grade concentrate with 65.41% Fe, 2.54% SiO2, 2.79% MgO, 0.70% CaO and 0.32% Al2O3. with 21.42% weight recovery. The overall ganguerejection recovery of the circuit is over 95%.

With the gradual depletion of high grade iron ores, the effective utilization of low grade iron ore resources is currently a subject of concern. ] mm). Effective utilization of these resources is of great benefits to the ironmaking and steelmaking industry in these areas.

This study investigates upgrading of low-grade banded hematite quartzite iron ore (Fe ~31%). Conventional beneficiation was found to be futile. The susceptibility of iron phases to microwave exposure and their selective absorption assists in the liberation of iron values. Microwave exposure of coarse particles at 540 W for 10 min yielded a concentrate with Fe 56.30% and recovery of 50.68%. Conventional carbothermic reduction at 500 °C, 60 min and 9% charcoal yielded a concentrate with Fe 57.6% and iron recovery of 68%. The presence of sufficiently bonded silica leads to an easy formation of a fayalite phase. The microwave reduction design yielded FeG of 57.6%, FeR of 47% and a yield of 24% at an optimal condition of 540 W, 8 min and 6% charcoal. It was found that a small fraction of microwave-irradiated ore-charcoal mixture melted rapidly, and pure ferrite balls were observed within 8 min. An optical micrograph of a ferrite ball reveals the retained austenite and martensite phase.

ABSTRACT To optimise processing/beneficiation procedures a detailed characterisation of goethitic ores is needed, including mineral liberation, association and textural classification. The identification of different iron oxides and oxyhydroxides is already reliably performed by optical image analysis (OIA). Automated OIA identification of different gangue materials, particularly quartz, can be problematic, however. The article demonstrates the capability of OIA software Mineral4/Recognition4 to characterise goethitic iron ores. Characterisation includes identification of the different types of goethite, hydrohematite and gangue materials such as quartz and kaolinite. XRD and XRF analysis results are compared with those from OIA. Correlation of these results and visual comparison shows that optical image analysis can be an effective tool for characterisation of low and medium grade iron ores. The work highlights issues regarding discrimination of aluminous goethite and gangue, micro and nano-porosity and effective density, for further study.

The objective of this research was to investigate the effect of low grade iron ore as catalyst on pyrolysis process of using palm empty fruit bunch. The process was conducted in fixed bed reactor at 450-600 °C. During experiment, the biomass placed within the first stack underwent pyrolysis process was pyrolyzed to produce char, tar and gases. Tar vapor and gases passed through the catalyst bed located within the second stack to conduct catalytic reaction. Furthermore, the vapor left the reactor and entered the cooling system. The catalyst after experiment was weighed to calculate total carbon deposited into catalyst pores. The results showed that the presence of low grade iron ore catalyst increased the gas yield with the yield reduction of liquid fraction. The gas yield was also increased with increasing temperature.

The corrosion behaviors of corundum brick and carbon composite brick used in blast furnace hearth by CaO-SiO2-MgO-Al2O3-Cr2O3(-CaF2) slags were studied in the present work. The degradation of the corundum brick in slag was a result of slag infiltration and brick dissolution, and the corrosion of the brick became more serious with the addition of CaF2 due to the decrease of slag viscosity. The disintegration of carbon composite brick in CaF2-containing slag was caused by the combination of slag penetration, brick dissolution and reaction between slag and brick. By comparing the corrosion behavior in CaF2-containing slag between the corundum brick and carbon composite brick, the corrosion degree of the corundum brick was greater than that of the carbon composite brick. To the blast furnace operation in which a low grade iron ore such as laterite ore and CaF2 containing slag (about 2 wt%) are used, it was found that the carbon composite brick with better slag corrosion resistance can be selected as a hearth refractory so as to improve the operation performance and ensure the longer campaign life of blast furnace.

This study investigates the microwave carbothermal reduction of low-grade banded hematite jasper iron ore (Fe ~ 37%). The susceptibility of iron phases to microwave exposure and their selective absorptions help in the liberation of iron values from impurities. It was found that a small fraction of the microwave-irradiated ore-charcoal mixture was rapidly melted to produce pure ferrite balls with Fe ~ 90%. The ferrite balls were observed within 6-10 min of reduction at 8% and above charcoal at microwave power of 900 W. The iron grade deteriorated over prolonged exposure because of the formation of the fayalite phase. The optical micrograph of the ferrite ball reveals retained austenite and martensitic iron phases with an average hardness value ~ 302 HV and a saturation magnetization of ~ 190.4 emu/g.

Deposits of low grade and high-phosphorus iron ores are spreading globally, however, the usage of this kind of deposits in the manufacturing of steel bounded because of the high-phosphorus content as well as depression of iron in which affect the quality of the produced steel. The Bajrawia iron ore deposit is one of the largest in Sudan but it only contains (35.5% Fe) and undesirable amount of phosphorus (0.37% P). This paper investigated the utilization of reverse anionic flotation (RAF) for the upgrading of iron and dephosphorization. Additionally, the effect of microwave pre-treatment on forth flotation performance on a laboratory scale. Microwave pre-treatment was applied on optimized reverse anionic flotation parameters in an account of iron grade (47.31% Fe), iron recovery (86.43%) and phosphorus content (0.167% P). The findings into the microwave pre-treatment are quite promising. This investigation has revealed that microwave heating improves the flotation response of iron grade to (51.94%) and phosphorus content decreases into (0.127% P) due to increasing the liberation.

ABSTRACT The consumption of iron ore has increased rapidly over the past decade due to the tremendous growth of iron and steel industry. The depletion of high grade iron ore resources make it inevitable to utilize the existing low grade iron ores/ fines/ tailings with effective beneficiation to meet the present specification and demand. Enormous amounts of fines are produced both from the natural geological process as well during the mechanized mining operations which is hitherto in unknown resource present in the form of waste. Beneficiation and utilization of these fines/tailings still remains a challenging task. In order to find out the effective way of utilization of these fines, an in-depth characterization study is essential. A detailed insight into the different mineralogical attributes involving microscopic SEM-EDX, EPMA, XRD, FTIR, TGA, physical and chemical characterization are undertaken on the Barsua iron ores fines. These studies revealed that hematite and goethite are the major iron bearing minerals with gibbsite, kaolinite and quartz present as gangue that makes up the deleterious Al and Si content. Traces of magnetite is also observed along with martite. The liberation size of the sample is found to be below 150 μm. The bulk chemical composition shows around 57.67% Fe, 6.29% Al2O3, 3.52% SiO2 and 6.93% LOI. Based on the detailed characterization, possible routes of beneficiation of the iron ore fines are discussed.

We have succeeded to synthesize the octahedral micro shape of MnFe2O4 through the co-precipation process followed by a ceramic processing method. At the beginning, the Mn3O4 and Fe2O3 nanoparticles were separately synthesized by the co-precipitation method from the low grade manganese ore and iron sand, respectively. Here, effect of the weight ratio of Fe2O3 and Mn3O4 to the crystal and microstructure of MnFe2O4 were investigated. Four cases of weight ratio i.e. 60:40, 70:30, 80:20, and 90:10 were considered. After mixing and compaction process in the cylindrical mould shape, the samples were sintered at 1000 °C and for 6 hours. XRD data showed that a high quality crystal phase of MnFe2O4 can be obtained for both mass ratio of 60:40 and 70:30, while in the case of 80:20 and 90:10 the MnFe2O4 appear together with impurity of α-Fe2O3. The particle shapes are almost octahedral in the micrometer size in the range of 1.2 to 1.5 m. The magnetic property shows a soft-magnetic type with a 27.5 emu/g of saturated magnetization. This will be potential for applications as the electrode materials and the magnetic core.

Due to the depletion of high-grade iron ores and their simultaneous demand, the utilization of low-grade iron ores such as banded hematite quartzite (BHQ) has become a topic of research interest around the globe, particularly in India. These low-grade iron ores are reckoned to be the future feedstock for iron and steel making industries. However, one of the major challenges is to remove associated gangue impurities from such low-grade iron ores by the conventional beneficiation techniques prior to its industrial applications. The reduction roasting process is one of the potential alternatives to overcome such challenges. Herein, we have presented the feasibility study using reduction roasting process on one of the Indian low-grade BHQ iron ore for the preparation of magnetite concentrate-based pellet feed materials. To establish the methodology of the reduction roasting process, different experimental parameters such as roasting temperature, reductant dosage, roasting time and fixed carbon were optimized for obtaining the maximum recovery, yield, and grade of the magnetite products. In the present study, Indian non-coking coals were used as reductant due to its large availability in the country. Using one of the non-coking coals as reductant, the optimum condition were found to be as, roasting temperature: 1100 °C, roasting time: 5 min, and head sample to reductant ratio: 10:6. Under these conditions, maximum grade and recovery of final magnetite concentrates were found to be 66.42 and 93.53%, respectively. It is expected that the large-scale development of reduction roasting process would lead to effective utilization of low and lean grade iron ore resources for the production pellet feed materials in the Indian context and simultaneously conserve the natural magnetite ores for future generation.