Free Access
Issue
Metall. Res. Technol.
Volume 116, Number 6, 2019
Article Number 611
Number of page(s) 10
DOI https://doi.org/10.1051/metal/2019039
Published online 30 August 2019

© EDP Sciences, 2019

1 Introduction

The availability of untouched, abundant, banded type’s iron ores such as banded hematite quartzite (BHQ) is categorized as waste resources in many parts of the world, especially in India due to their low-grade nature [1]. However, because of the depletion and increasing demand for high-grade iron ores in steel making industries, the focus has been shifted towards utilization of such resources progressively. It is expected that proper utilization of such resources could potentially eradicate the crises of desirable high-grade iron ore, particularly for the production of pellet, feeds to target required steel production in the forthcoming years. The nature of banded iron ore is very complex and is presumed to be a sedimentary rock either initiated from a chemical or biochemical precipitates of Precambrian origin [2]. In the Indian context, BHQ iron ores contain Fe content around 30–40%, along with major associated mineral impurities such as 40–50% SiO2, and 0.5–2.5% Al2O3 [1]. Comparing with the Fe% of high-grade iron ores which is normally above 64%, the Fe% in BHQ is found to be lower by almost 20–25% which requires appropriate beneficiation prior to its industrial utilization.

Normally, the response of low-grade BHQ iron ore is poor towards the conventional beneficiation process due to its complex mineralogical characteristics. In some cases, the desired Fe grade up to 64% can be obtained from BHQ ore by conventional beneficiation process, however, with a lower percentage of yield and recovery which is not economically viable. This is attributed to the wide dissemination of mineral impurities in the banded hematite matrix of iron ore in the form of quartz, gibbsite, and kaolinite mineral phase, making the conventional process challenging. Unlike high-grade iron ore which can be directly used in steel-making process, the low-grade BHQ iron ore requires comminution for the liberation of desired mineral impurities at finer size. During the conventional beneficiation process, comminution (or fine grinding) of BHQ iron ore is done to liberate the iron phase minerals from gangue followed by various unit operations including high-intensity magnetic separation to separate magnetic concentrates from non-magnetic materials. Flotation stage may be introduced to enrich the purity of magnetic concentrates further [1,3,4]. The final magnetic concentrates generated are mixed with a binder for the preparation of pellet for steel-making process [5]. The lower yield and recovery of the process particularly for low-grade iron ores and requirements of large numbers of unit operations are the major disadvantages of the conventional beneficiation process.

Considering the above-mentioned challenges, an alternative technique needs to be implemented in order to overcome such limitations. One of the potential alternatives to such problems could be the implementation of reduction roasting process on BHQ iron ore followed by magnetic separation using a low-intensity magnetic separator (LIMS) [1]. Unlike conventional beneficiation process, the reduction roasting process does not require large numbers of unit operations, especially comminution prior to beneficiation for the liberation of minerals at finer size from BHQ iron ore, and hence considered to be the more economical and less energy intensive than conventional beneficiation process. For reduction roasting process, the nominal size fraction of feed required is below 10 mm, whereas the feed size required for the conventional process is at the micron level. Moreover, reduction roasting process can deliver higher yield and recovery than the conventional process even for the low-grade ores with fewer requirements of unit operations. This has attracted many researchers globally in exploring the feasibility of the process for different types of low-grade iron ore resources. In the past decades, researchers have reported about the production of magnetite concentrates of the desired grade by maximizing the product recovery and yield by reduction roasting followed by magnetic separation using various types of reductants [6,7]. Some authors have also reported that the reduction roasting process can be used to convert weakly magnetic minerals to magnetic minerals by roasting in a reduced atmosphere at elevated temperature, i.e., ≥ 600 °C. It is also undesirable to roast iron ore at a higher temperature as it could potentially result in the infusion of particles or in some cases could lead to the formation of paramagnetic wustite [810]. In general, the phase transformation of iron ore begins with the removal of free moisture at around 120–140 °C, while the moisture (3–4.5%) that remains at the matrix of iron ore vaporizes at about 1000 °C. Subsequently, the phase change of hematite from goethite takes place through de-hydroxylation during reduction roasting at 200–400 °C, resulting in expansion and crack formation up to 20% of the particle diameter. In the case of hydro-hematite heat treatment, the formation of maghemite takes place between 200 to 280 °C first and later convert to hematite in the temperature ranges of 370–600 °C. Researchers have also reported that, during the reduction process, three types of phase changes occur which includes: (a) the reduction of hematite to magnetite in the temperature range of 200–250 °C; (b) followed by reduction of magnetite to wustite in the temperature range of 500–900 °C and (c) lastly the reduction of wustite to iron metal in the temperature range of 900–1300 °C [1113].

The reduction mechanism of hematite and growth of iron granules can be divided into three stages which include nucleation stage, reaction stage, and particle coarsening stage. The reduction of iron ore in the presence of a reducing agent such as coal involves stepwise reactions as: (a) reducing gas diffusion across the boundary layer; (b) reducing gas interface by means of intra-particle diffusion; (c) migration of Fe2+ and electrons to the iron nucleus; (d) oxidized gas interface by means of intra-particle diffusion and (e) oxidizing gas diffusion across the boundary layer. The reduction reactions involved during the roasting process of iron ore in the presence of solid carbon may be represented as: (1) Where, x = 1, 2, or 3, (2)Where, y = 1, 3, or 4, (3)

Finally, the overall phase transformation reaction of hematite to magnetite by reduction roasting using as a reducing agent (C or CO) may be represented as follows: (4)

The available literature itself shows that the reduction roasting process has great potential, particularly for the utilization of low-and lean-grade iron ores. Despite literature, there are still some research gaps in Indian context in terms of effective utilization of BHQ iron ores. Considering this points, the present paper aims to investigate the feasibility of reduction roasting process on one of the BHQ iron ore sample for the production of magnetic concentrates which could act as potential feed materials for the iron pellet plant. The magnetic concentrate generated from BHQ by this process could also replace the requirement of natural high-grade magnetite ores in pellet making.

2 Raw material

2.1 Feed characterization

For the present investigation, the BHQ iron ore was obtained from Barbil region of Odisha, India. The head sample was prepared by crushing below 10 mm size using a laboratory jaw crusher. Subsequently, coning and quartering method was adopted on the head sample to collect the representative sample for measuring the particles size distribution by wet screening method. The chemical composition of the head sample was done by the standard wet chemical method, and the obtained results are presented in Table 1.

It can be seen in Table 1 that the head sample consisted of total iron content, i.e., Fe of 47.15% mostly in association with other mineral impurities such as 28.31% SiO2 and 1.65% Al2O3. These impurities together constitute about 30% of the total head sample along with other trace impurities such as Na2O, TiO2, CaO, K2O, etc. The presence of 1.36% loss on ignition (LOI) was also observed which is attributed to the presence of matrix moisture in gibbsite and kaolinite. The particles size analysis was performed on the representative head sample in the range of +6 mm to −45 μm as shown in Figure 1a. The size analysis data shows that the head sample contains approximately 13.52% of particle fractions below 45 μm, whereas 62.09% particles fractions above 1 mm. An even distribution of the Fe% was also observed in all the factions of the head sample as shown in Figure 1a.

Further to understand the mineralogy of BHQ head sample, the mineralogical characterization was done by XRD (X’pert Pro; PANalytical) and Optical Microscope (DM2500 P, Leica). Using XRD technique, the crystalline phases, both qualitatively and quantitatively, were investigated. Qualitative XRD analysis shows that the mineral phases present in the BHQ head sample were hematite, gibbsite, quartz, goethite, and kaolinite as shown in Figure 1b. For the quantitative analysis of mineral phases, a riveted refinement technique was applied on the XRD data which indicates that the individual mineral phase percentages present in BHQ head sample were 63, 7, 27, 1.5 and 1.5% for hematite (H), goethite (Go), quartz (Q), gibbsite (Gi), and kaolinite (K), respectively. Both these qualitative and quantitative analysis confirms a complex and composite mineralogical structure of BHQ head sample which makes the beneficiation process difficult by conventional methods. Optical microscopic study of BHQ head sample shown in Figures 1c and 1d further reveals the presence of hematite (H), goethite (Go), kaolinite (K), quartz (Q), and gibbsite (Gi). In Figure 1c, the BHQ head sample indicates well-distributed hematite grains all over its surface, whereas in Figure 1d, the fraction of the BHQ head sample indicates the composite of hematite grains mixed with goethite and other impurities such as quartz, kaolinite, and gibbsite.

Table 1

Chemical composition of raw BHQ iron ore head sample (−10 mm size).

thumbnail Fig. 1

Feed characterization of BHQ iron ore head sample. a: size distributional analysis; b: XRD analysis of head sample; c,d: optical microscopic study of the head sample.

2.2 Non-coking coal as a reductant for BHQ iron ore reduction roasting

In the batch-wise reduction roasting process, non-coking coal of Indian origin was used as the reducing agent throughout the experiments. Non-coking coals were considered in the present work as a replacement for high-grade coals due to its large availability and low cost in India [1417]. Different coal samples were obtained from various locations in India, and their proximate analysis data are presented in Table 2. For the present work, coal C1 has been used as a main reductant for the reduction roasting process throughout the experiments, whereas coal C2 to C5 have been used to compare the results obtained using coal C1 in terms of process recovery, yield and grade under varying fixed carbon content. The size range of all the reductant (C1 to C5) used in the reduction roasting process was maintained in the range of −6 + 3 mm.

Table 2

Proximate analysis of different types of non-coking coal samples.

3 Experimental method

Reduction roasting experiments were studied using BHQ head sample under varying parameters (such as roasting temperature, reductant dosage, roasting time and fixed carbon) for the determination of optimum conditions based on the recovery, yield, and grade. The iron phase transformations were also investigated for a better understanding of phase conversions taking place under different conditions. The head sample of −10 mm fraction and non-coking coal of −6 + 3 mm size were mixed thoroughly and placed in a refractory crucible by covering with a lid. The prepared refectory crucible was then kept in an airtight muffle furnace under varying roasting temperature and time. After cooling of the crucible to room temperature, the roasted sample was separated from the burnt coal ash physically by a hand magnet. Then the obtained roasted sample was ground to below −45 microns using wet milling in a laboratory ball mill. Subsequently, the ground sample was passed through a low-intensity magnetic separator (1100–1500 Gauss) for the separation of magnetic concentrates from non-magnetic portions. The grade of the magnetic concentrates was then analyzed to determine the extent of recovery, yield, and grade under different experimental conditions. The roasted and final magnetic concentrate samples were analyzed using XRD, Fe analysis, and optical microscopy, respectively. The schematic flow diagram of the reduction roasting process of BHQ iron ore is shown in Figure 2.

thumbnail Fig. 2

Schematic flow diagram of reduction roasting process followed by low-intensity magnetic separation of low-grade BHQ iron ore.

4 Results and discussion

4.1 Effect of various parameters on reduction roasting

In order to optimize the reduction roasting process, various experiments were conducted using BHQ head sample under varying operational parameters such as roasting temperature, reductant dosage, roasting time and fixed carbon content. The results of the roasting experiments at different conditions are discussed in the subsequent sections.

4.1.1 Effects of varying roasting temperature

Roasting temperature plays a vital role in improving recovery, yield and grade of the final magnetic concentrates during the roasting process. In the present investigation, the roasting temperature was varied between 700 to 1100 °C with a temperature interval difference of 50 °C for each batch of experiments. The sample was prepared by mixing 100 gm of BHQ head sample with 60 gm of non-coking coal maintaining the head sample to reductant ratio of 10:6. The sample was then introduced into a muffle furnace for reduction roasting at varying temperatures for 15 min roasting time. After roasting process, the roasted samples were subjected to magnetic separation using hand magnet to remove the burnt ash of the coal attached to the roasted sample, and further ground to below 45 μm by wet milling followed by low-intensity magnetic separation. The results in terms of recovery, yield, and grade of the final magnetite concentrates are provided in Figure 3a. It can be seen in Figure 3a that, with an increase in the roasting temperature, the magnetite concentrate recovery and yield increases from an initial value of 45.71 to 93.53% and 39.45 to 72.08%, respectively. However, grade of the magnetite concentrates obtained in each case almost remains consistent throughout the experiments achieving total Fe grade greater than 64.0%. This grade of magnetite concentrates is highly suitable for the preparation of pellet feed material for steel making. It was also observed that, at the initial roasting temperature of 700 °C, the recovery and the yield percentage are almost negligible due to the insufficient temperature required for the conversion of hematite to magnetite phase. However, with increasing roasting temperature above 700 °C, an increase in the conversion of hematite to magnetite phase was observed. The optimum roasting temperature was found to be 1100 °C providing maximum recovery, yield, and grade of the magnetic concentrate. This is because of the enhancement in the surface crack at 1100 °C which allows sufficient reductant gas to penetrate inside the BHQ ore for the possible conversion of hematite to magnetite. However, at the elevated temperature, i.e., above 1100 °C, excess iron was found in the tailing stream which is clearly attributed to wustite formation caused by over reduction of the sample during the roasting process.

thumbnail Fig. 3

Effect of a: roasting temperature; b: reductant dosage; c: roasting time; d: fixed carbon content on product recovery, yield, and grade of reduction roasting process.

4.1.2 Effects of varying reductant dosage

To understand the effect of reductant dosage on recovery, yield and grade of magnetic concentrates, varying proportions of the reductant dosage were used. The non-coking coal (coal C1) was used as a reductant in different amounts (15, 30, 45, and 60%) with respect to the head sample, maintaining the overall weight of BHQ-coal mixture as 100%. The experiments were conducted at roasting temperature of 1100 °C and roasting time of 15 min to observe the effects of varying reductant dosage on the overall efficiency of the process. The effects of reductant dosage on the recovery, yield, and grade of magnetite concentrates are shown in Figure 3b. As observed in Figure 3b, the grade of total Fe% in the magnetite concentrate is greater than 64% which clearly indicates that the desired quality of products is suitable for the pellet making. When the ratio of head sample to non-coking coal was 10:6, the optimum recovery, yield and grade of 93.53, 2.08, and 66.42% were obtained. The better efficiency under the optimum reductant dosage corresponds to the mineral phase conversion from hematite to magnetite mineral phase due to the penetration of adequate amount of reductant gas through surface crack formed under 1100 °C roasting temperature, which finally removes the matrix oxygen from the hematite and results in higher reduction of hematite to magnetite phase.

4.1.3 Effects of varying roasting time

The effect of roasting time on recovery, yield, and grade of magnetite concentrates was investigated under the optimized roasting temperature and head sample to reductant ratio. The experiments were conducted at roasting temperature of 1100 °C and head sample to reductant (coal C1) ratio of 10:6 to understand the effects of varying reduction time on reduction roasting process. The effects of roasting time on the recovery, yield, metallization, and grade of magnetite concentrates are shown in Figure 3c. As shown in Figure 3c, there is a linear increase in the Fe metallization with respect to increasing roasting time. This metallization stage is undesired for the present purpose as the objective of the present study is to obtain magnetite concentrates only for the preparation of pellet feed materials rather than obtaining Fe metal. Moreover, when the roasting time is greater than 30 min, the results show a decrease in recovery of magnetite concentrates possibly due to the formation of iron silicates and iron aluminates. Considering the above-mentioned observations, the optimized roasting time for the desired conversion of hematite to magnetite concentrate may be considered as 15 min beyond which metallization and lower recovery of the roasting process are predominant. Under the optimized roasting time, maximum recovery and yield of magnetite concentrates were found to be 93.53 and 72.08%, respectively, with a product grade of 66.42%.

4.1.4 Effects of fixed carbon value of different coal

The experiments were performed using different types of Indian coals having varying fixed carbon and volatile matter as shown in Table 2. The experimental conditions maintained were at a roasting temperature of 1100 °C, roasting time of 15 min and head sample to reductant (coal C1) ratio of 10:6. After the roasting experiments at the pre-defined conditions, the roasted samples were subjected to magnetic separation using hand magnet to remove the burnt ash of the coal, and further ground to below 45 μm by wet milling followed by low-intensity magnetic separation. In Figure 3d, it can be seen that the recovery, yield, and grade of the magnetite concentrates changed with varying fixed carbon content of coal samples during the roasting process. For coal C1 sample, recovery and yield of the magnetite concentrates were found lower as compared to the other coal samples (C2 to C5) possibly due to the low fixed carbon value of the coal C1. With increasing fixed carbon of coal C1 to C5, the recovery and yield of the magnetite concentrate increase significantly. This is attributed to the fact that, those hematite phases which remain unconverted during the roasting process using coal C1 may have converted further from hematite to magnetite phase with increasing fixed carbon values.

4.2 Characterization of roasted samples

4.2.1 XRD analysis

The XRD study for the roasted samples was conducted to understand the phase transformations of hematite to magnetite at different temperatures. The reduction roasting experiments were performed at a different roasting temperature ranging from 700 to 1100 °C, maintaining roasting time of 15 min, and head sample to reductant (coal C1) ratio of 10:6.

The XRD patterns in Figure 4a indicate the phase transformations of hematite to magnetite at different temperatures with respect to the head sample. Initially, the XRD pattern of head sample confirms the presence of both hematite and goethite mineral phases along with other associated impurities such as quartz, gibbsite, and kaolinite. The presence of goethite, kaolinite, and gibbsite countered in XRD pattern of the head sample is responsible for the contribution of 1.36% LOI in the head sample as observed in chemical analysis results (Tab. 1). However, with increasing roasting temperature, a decrease in LOI% can be observed. This can be confirmed from the reduction of goethite, kaolinite and gibbsite peaks of roasted samples as shown in Figure 4a due to the release of matrix moisture. Furthermore, with an increase in the roasting temperature above 700 °C, the XRD patterns shows a decline in intensity of hematite peaks and a corresponding rise in intensity of the magnetite peaks. Noteworthy to mention in Figure 4a that maximum phase conversion of hematite to magnetite was observed when roasted at 1100 °C temperature. It is expected that roasting the head sample beyond 1100 °C could results in further phase conversion of magnetite to wustite due to over-reduction and potentially hampers the recovery and yield of the roasting process. To further understand the mineral phase transformation during the roasting process at different temperature ranges, the XRD data was quantitatively analyzed, and results are presented in Figure 4b. The mineral phase quantification shown in Figure 4b gives a clear picture of the phase transformations taking place at different heating conditions. With increasing temperature, it can be seen that the abundance of hematite phase declined from 63 to 4.7%, while there is a steep increase in magnetite phase from non-detectable limit to 63.2% during the heating process.

thumbnail Fig. 4

XRD analysis of reduction roasting samples with temperature variations in terms of (a) qualitative and (b) quantitative mineral phase analysis.

4.2.2 Optical microscopic analysis

In this section, the effects of temperature on the phase transformations of BHQ iron ore were studied under an optical microscope to visualize the phase transformations occurred under varying roasting temperatures.

The obtained photomicrographs of roasted BHQ iron ore samples at different temperatures are provided in Figure 5. It can be seen that in Figure 5a, at 700 °C roasting temperature, initiation in the formation of hematite (H) from goethite occurred. This is attributed to the release of −OH groups which initiated the phase transformation due to progressive alteration of the crystalline structure. Predominant hexagonal hematite (H) with cracking fissures on the surface of the roasted sample was also developed at 700 °C as confirmed in Figure 5b. Figures 5c and 5d further shows the initiation of magnetite formations at 800 °C from hematite (H), and progressive magnetite (M) formation thereafter at 900 °C, respectively. Upon heating the BHQ iron ore sample at 950 and 1000 °C, a transformation of hematite (H) to magnetite (M) with the development of wide cracks was observed as shown in Figures 5e and 5f, respectively. Figure 5g further show the transformation of hematite crystals to magnetite (M) with numerous star like cracks due to intense heating effect at 1000 °C. On increasing temperature above 1000 °C, the formation of magnetite (M) from hematite (H) phase along with large cracks was observed which can be confirmed in Figures 5h and 5g, respectively.

thumbnail Fig. 5

Optical microscopic study at different temperatures ranging from 700 to 1100 °C. The results in Figures 5a5i shows the gradual phase transformation from hematite (H) to magnetite (M) phase till the complete phase transformation.

4.3 XRD analysis of concentrated and tailings of roasted samples

In order to understand the degree of phase transformation during reduction roasting process, XRD analysis was carried out both quantitatively and qualitatively on various concentrates and tailings products obtained after the low-intensity magnetic separation of roasted samples. Initially, the roasted samples were prepared under varying roasting temperature ranging between 700 to 1100 °C at roasting time of 15 min and head sample to reductant (coal C1) ratio of 10:6. The roasted samples were then ground below 45 μm by wet ball milling and subsequently subjected to a low-intensity magnetic separator for the separation of magnetite concentrates and tailings. The XRD patterns of magnetite concentrates and tailings are shown in Figure 6a. In Figure 6a, it can be observed qualitatively that there is a decrease in the intensity of hematite peaks and a simultaneous increase in the intensity of magnetite peaks due to progressive heating effect with increasing temperature. The quantitative analysis of the XRD patterns shown in Figure 6a is presented in Figure 6b. Figure 6b shows that, above 750 °C, the transformation of hematite declined from 76 to 59% during the progressive rise of the heat effect, and simultaneous steep increment in the magnetite from 20.5 to 80.54%. This indicates adequate conversion of the hematite and goethite phases into the magnetite phase at a higher temperature. Finally, at 1100 °C roasting temperature, maximum phase transformation of hematite to magnetite occurred, resulting in the enhancement of recovery, yield, and grade of magnetite concentrates. Evaluation of the mineral phases present in the tailings was also conducted by the XRD analysis as shown in Figure 6c. The mineral phases that exist in the tailings are majorly quartz followed by minor quantities of hematite and magnetite. The XRD patterns of tailings samples in Figure 6c qualitatively shows that, with increasing temperatures, there is an increase in quartz peaks and a subsequent decrease in hematite and magnetite peaks as well. In the XRD patterns of tailing samples, decrease in hematite and magnetite peaks is attributed to the increasing conversion of hematite phase into magnetite phase with respect to temperature increment which is reflected in the magnetite concentrates after low-intensity magnetic separation. On the other hand, increase in the quartz peaks of tailings samples corresponds to the enrichment in magnetic concentrates with increasing temperature and efficient separation of magnetite concentrates during low-intensity magnetic separation. Quantitatively, it can be seen in Figure 6d that, quartz is the predominant mineral impurities present in the tailings, which has increased from 28 to 95.8% with increasing roasting temperature. A minor quantity of iron content (both hematite and magnetite concentrates) can be seen in all the tailings either due to inadequate conversion of hematite into magnetite or inefficient separation of magnetite concentrates during magnetic separation because of their fine distribution with impurities.

thumbnail Fig. 6

XRD analysis of products obtained after magnetic separation of roasted samples. (a) qualitatively and (b) quantitative XRD analysis of magnetite concentrate; (c) qualitatively and (d) quantitative XRD analysis of tailings samples.

5 Conclusion

In the present study, the reduction roasting process of an Indian low-grade BHQ ore was reported. The effect of various roasting parameters such as roasting temperature, reductant dosage, roasting time and fixed carbon on reduction roasting process were studied. The roasting conditions required for the optimum phase conversion of hematite to magnetite were found to be: roasting temperature of 1100 °C, roasting time of 15 min and head sample to reductant (coal C1) ratio of 10:6. At these optimum conditions, maximum recovery of 93.53%, the yield of 72.08% and grade of 66.42% were found for the final magnetite concentrates. Quantitative XRD analysis reveals that the tailings obtained under the optimum conditions contain Fe grade of 11.85% only. This is very important from an economic point of view as the desired Fe% in the tailings must be lower preferably below 30% in Indian context. It is expected that the reduction roasting process would play a vital role in the future as this technique has a great potential towards the utilizing low-and lean-grade iron ore resources. Furthermore, the magnetite concentrates obtained from the reduction roasting process could act as a potential feedstock for pelletization process and simultaneously conserve the natural magnetite ores for future generation.

Acknowledgements

The authors would like to thank Director, CSIR-IMMT Bhubaneswar for giving his permission to communicate this work.

References

  1. S.S. Rath, H. Sahoo, S.K. Das, B. Das, B.K. Mishra, Influence of band thickness of banded hematite quartzite (BHQ) ore in flotation, Int. J Miner. Process. 130, 48–55 (2014). DOI: 10.1016/j.minpro.2014.05.006 [Google Scholar]
  2. I. Koehler, K. Konhauser, A. Kappler, Role of microorganisms in banded iron formations, in: L.L. Barton, M. Mandl, A. Loy (Eds.), Geomicrobiology: Molecular and environmental perspective, Springer, Dordrecht, Netherlands, 2010, pp. 309–324. DOI: 10.1007/978-90-481-9204-5_14 [CrossRef] [Google Scholar]
  3. J.J. Carlson, S.K. Kawatra, Factors affecting zeta potential of iron oxides, Miner. Process. Extr. Metall. Rev. 34, 269–303 (2013). DOI: 10.1080/08827508.2011.604697 [CrossRef] [Google Scholar]
  4. F. Nakhaei, M. Irannajad, Reagents types in flotation of iron oxide minerals: A review, Miner. Process. Extr. Metall. Rev. 39, 89–124 (2018). DOI: 10.1080/08827508.2017.1391245 [CrossRef] [Google Scholar]
  5. S.K. Kawatra, J.A. Halt, Binding effects in hematite and magnetite concentrates, Int. J. Miner. Process. 99, 39–42 (2011). DOI: 10.1016/j.minpro.2011.03.001 [Google Scholar]
  6. S.S. Rath, D.S. Rao, B.K. Mishra, A novel approach for reduction roasting of iron ore slime using cow dung, Int. J. Miner. Process. 157, 216–226 (2016). DOI: 10.1016/j.minpro.2016.11.015 [Google Scholar]
  7. S.S. Rath, H. Sahoo, N. Dhawan, D.S. Rao, B. Das, B.K. Mishra, Optimal recovery of iron values from a low grade iron ore using reduction roasting and magnetic separation, Sep. Sci. Technol. 49, 1927–1936 (2014). DOI: 10.1080/01496395.2014.903280 [Google Scholar]
  8. B. Anameric, S.K. Kawatra, Direct iron smelting reduction processes, Miner. Process. Extr. Metall. Rev. 30, 1–51 (2008). DOI: 10.1080/08827500802043490 [CrossRef] [Google Scholar]
  9. Y. Sun, Y. Han, P. Gao, Z. Wang, D. Ren, Recovery of iron from high phosphorus oolitic iron ore using coal-based reduction followed by magnetic separation, Int. J. Miner. Metall. Mater. 20, 411–419 (2013). DOI: 10.1007/s12613-013-0744-1 [CrossRef] [Google Scholar]
  10. J. Kou, T. Sun, D. Tao, Y. Cao, C. Xu, Coal-based direct reduction and magnetic separation of lump hematite ore, Miner. Metall. Process. 31, 150–161 (2014) [Google Scholar]
  11. S.S. Rath, N. Dhawan, D.S. Rao, B. Das, B.K. Mishra, Beneficiation studies of a difficult to treat iron ore using conventional and microwave roasting, Powder Technol. 301, 1016–1024 (2016). DOI: 10.1016/j.powtec.2016.07.044 [Google Scholar]
  12. I. Iwasaki, M.S. Prasad, Processing techniques for difficult-to-treat ores by combining chemical metallurgy and mineral processing, Miner. Process. Extr. Metall. Rev. 4, 241–276 (1989). DOI: 10.1080/08827508908952639 [CrossRef] [Google Scholar]
  13. F.M. Stephens, B. Langston, A.C. Richardson, The reduction-oxidation process for the treatment of taconites, JOM. 5, 780–785 (1953). DOI: 10.1007/BF03397539 [CrossRef] [Google Scholar]
  14. S.D. Barma, R. Sathish, P.K. Baskey, S.K. Biswal, Chemical beneficiation of high-ash indian non-coking coal by alkali leaching under low-frequency ultrasonication, Energy Fuels 32, 1309–1319 (2018). DOI: 10.1021/acs.energyfuels.7b03291 [Google Scholar]
  15. S.D. Barma, R. Sathish, P.K. Baskey, Ultrasonic-assisted cleaning of Indian low-grade coal for clean and sustainable energy, J. Clean. Prod. 195, 1203–1213 (2018). DOI: 10.1016/j.jclepro.2018.06.030 [Google Scholar]
  16. S.D. Barma, Ultrasonic-assisted coal beneficiation: A review, Ultrason. Sonochem. 50, 15–35 (2019). DOI: 10.1016/j.ultsonch.2018.08.016 [CrossRef] [PubMed] [Google Scholar]
  17. S.D. Barma, S.S. Praneeth Tej, B. Ramya, R. Sathish, Ultrasound–promoter pretreatment for enhancing the yield and combustible matter recovery of high-ash oxidized coal flotation, Energy Fuels (2019). DOI: 10.1021/acs.energyfuels.9b01543 [PubMed] [Google Scholar]

Cite this article as: Sachida Nanda Sahu, Karamjith Sharma, Santosh Deb Barma, Prachiprava Pradhan, Bijaya K. Nayak, Surendra K. Biswal , Utilization of low-grade BHQ iron ore by reduction roasting followed by magnetic separation for the production of magnetite-based pellet feed, Metall. Res. Technol. 116, 611 (2019)

All Tables

Table 1

Chemical composition of raw BHQ iron ore head sample (−10 mm size).

Table 2

Proximate analysis of different types of non-coking coal samples.

All Figures

thumbnail Fig. 1

Feed characterization of BHQ iron ore head sample. a: size distributional analysis; b: XRD analysis of head sample; c,d: optical microscopic study of the head sample.

In the text
thumbnail Fig. 2

Schematic flow diagram of reduction roasting process followed by low-intensity magnetic separation of low-grade BHQ iron ore.

In the text
thumbnail Fig. 3

Effect of a: roasting temperature; b: reductant dosage; c: roasting time; d: fixed carbon content on product recovery, yield, and grade of reduction roasting process.

In the text
thumbnail Fig. 4

XRD analysis of reduction roasting samples with temperature variations in terms of (a) qualitative and (b) quantitative mineral phase analysis.

In the text
thumbnail Fig. 5

Optical microscopic study at different temperatures ranging from 700 to 1100 °C. The results in Figures 5a5i shows the gradual phase transformation from hematite (H) to magnetite (M) phase till the complete phase transformation.

In the text
thumbnail Fig. 6

XRD analysis of products obtained after magnetic separation of roasted samples. (a) qualitatively and (b) quantitative XRD analysis of magnetite concentrate; (c) qualitatively and (d) quantitative XRD analysis of tailings samples.

In the text

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