Free Access
Issue
Metall. Res. Technol.
Volume 117, Number 2, 2020
Article Number 207
Number of page(s) 10
DOI https://doi.org/10.1051/metal/2020022
Published online 17 April 2020

© EDP Sciences, 2020

Pellets is one of the main burden compositions of blast furnace (BF) [13], it have some favorable properties, such as high iron grade, low gangue content, high compressive strength and uniform particle size, etc. The wide application of pellets contributes to the effective use of fine-sized iron concentrate. Meanwhile, it also promotes energy-saving and reduces dust as well as exhaust gas emissions of the BF [4]. Nowadays, the main raw material of the production of oxidized pellets is magnetite concentrate [5]. But, there is a special type of iron ore containing barite (BaSO4) in China and Egypt. Most of the barite in iron ore is uniformly distributed around quartz and iron oxides, and other small particles of barite is embedded in quartz and iron oxides, which has a great influence on the smelting performance of iron ore [6]. In the past, these ores have mainly been used for sinter production and are not regarded as the raw material source of pellets. With the gradual implementation of Chinese environmental policy, the ores containing barium will be widely used in pellets production in the future. Thus, it is of great practical significance to explore the influence of BaSO4 on the quality of pellets.

In recent years, a large number of studies about the compressive strength and reducibility of pellets have been conducted by many researchers [715]. Zhang et al. [8] studied the influence of alumina on the compressive strength of the pellets. They found that a small amount of Al2O3 could improve the crystallinity of Fe2O3 and thus increase the pellets compressive strength. However, excessive Al2O3 could hinder the oxidation of Fe3O4 and the recrystallization of Fe2O3, leading to the decrease of the compressive strength of pellets. Bi et al. [10] explored the effect of MgO on properties of oxidized pellets and demonstrated that the compressive strength of preheated pellets and roasted pellets decreased significantly as MgO increasing, while the reducibility and reduction degradation index improved. Guo et al. [11] studied the influence of SiO2 on the compressive strength as well as reduction behavior of pellets and reached the conclusion that both the compressive strength and the reduction degree decreased with increasing SiO2 contents in pellets. Most studies focus on the influence of conventional components, such as MgO, Al2O3, SiO2, etc., on compressive strength and reducibility of pellets [1621]. However, the study on the effect of BaSO4 on pellets has not been reported and its effect on the quality of pellets has been a subject of concern to improve the blast furnace operation.

In present study, the influence of BaSO4 on the compressive strength and the reduction behavior of pellets were investigated in present work. The microstructure of roasted pellets and reduced pellets was determined by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS).

1 Experimental

1.1 Raw materials

The materials of pellets in the present study include the magnetite concentrate, bentonite and barium sulfate chemical reagent. The magnetite concentrate and bentonite were taken from one Iron & Steel Company in china. The bentonite was used as binder in pelletizing, and the barium sulfate chemical reagent was added to adjust the BaSO4 content of pellets. The purity of BaSO4 is 99.99%, which enough to assure the accuracy of the experiments. The chemical composition and particle size of the bentonite and magnetite concentrate are listed in Tables 1 and 2. It is observed that the magnetite concentrate has a high Fe grade of 63.16%, the content of FeO and SiO2 is 20.75 and 8.59%, respectively. The content of harmful elements is low. The magnetite and bentonite with particle size less than 74 µm are about 85.04 and 99%, respectively. The particle size of the raw materials meets the requirement for pelletizing.

Table 1

Chemical composition of the raw materials (%).

Table 2

Size distribution of the raw materials (%).

1.2 Experimental methods

1.2.1 The preheating and roasting experiment

The pelletizing experiments were carried out in laboratory. The blend mix proportion of raw materials was shown in Table 3. The bentonite content in mixed pelletizing materials was kept at a constant of 2.0%, and the portions of the BaSO4 content were designed at 0, 1.0, 1.5, 2.0, 3.0, and 5.0%, respectively.

The pelletizing process is displayed in Figure 1. Green pellets were prepared in pelletizing disc with a diameter of 1000 mm. The screened out green pellets with a diameter between 10 mm and 12.5 mm were dried for 5 h at 105 °C.

The details of experiment process are illustrated in Figure 2. The process of preheating and roasting of pellets was conducted in a high temperature resistance furnace. The green pellets were placed in the resistance furnace at 900 °C for 12 min. The temperature inside the furnace was then increased to 1250 °C at a heating rate of 6 °C/min and maintained at 1250 °C for 15 min. Air was allowed to flow through the furnace via the air compressor and control cabinet at a flow rate of 1.5 L/min during the whole process [8]. When the roasting process was completed, the pellets were allowed to cool to room temperature along with the furnace. The compressive strength of pellets was tested using a precision digital compression tester, and each sample was tested for 10 times. The maximum crushing force was obtained by slowly increasing the pressure until the particle was crushed. The strength was evaluated by the average crushing force and the error bar was calculated [22]. The internal structure of roasted pellets was analyzed by SEM-EDS.

Table 3

Mixed ratios of the pelletizing materials (%).

thumbnail Fig. 1

Pelletizing and firing process of pellets.

thumbnail Fig. 2

Preheating and roasting system parameters.

1.2.2 The reduction experiment

The isothermal reduction experiments of pellets were carried out in the reduction furnace, as shown in Figure 3. In reduction experiment, the sample was set in the holder with the inner diameter of 28 mm, and it was set in the furnace. Then, it was heated up to 900 °C at the rate of 10 °C/min. During the whole heating processes, 5 NL/min N2 was introduced into the reduction tube. Subsequently, N2 was changed to a reducing gas (30%CO–70%N2), keeping constant the flow rate of 15 NL/min, and the reduction temperature was 900 °C for 90 min. After the experiment, the reducing gas was replaced by N2 and the reduction tube was taken out of the furnace to cool down to room temperature. The mass loss resulted from the removal of oxygen during reduction as a function of time was continuously recorded by electronic balance. Next, SEM-EDS were used to examine the internal structure of pellets after reduction.

thumbnail Fig. 3

Schematic of the reduction experimental apparatus.

2 Results and discussion

2.1 Thermodynamic analysis of the behaviour of BaSO4

Research by Ren et al. [23] shows that the decomposition temperature of BaSO4 is in the range of 1190–1300 °C. Therefore, the BaSO4 reaching the decomposition temperature is decomposed during the roasting process. The decomposition reaction is shown in formula (1). (1)

Decomposition of BaSO4 produces BaO, SO2 and O2. The SO2 as well as O2 release from the interior of the pellets, and BaO reacts with other phases in the pellets. In order to verification the phase is formed by the reaction of BaO with iron oxide and gangue composition, X-ray diffraction (XRD) analysis was performed on the roasted pellets of sample 1 (BaSO4 = 0%) and sample 6 (BaSO4 = 5.0%). The results are given in Figure 4.

It is observed that BaFe2O4 and BaSiO3 phases are found in the pellets after the addition of BaSO4. This indicates that BaO combines with iron oxide or SiO2 to form BaFe2O4 and BaSiO3 phases. The reaction equations are as follows: (2) (3)

Because the BaSO4 has been decomposed completely in the roasting process, there is no existing undecomposed BaSO4 and no reaction of BaO with the iron oxides as well as the gangue composition in the reduction process.

thumbnail Fig. 4

X-ray pattern of roasted pellets.

2.2 Effect of BaSO4 on compressive strength

Compressive strength of the pellets plays a significant role in the performance of Blast furnace process. Pellets with low strength cannot withstand the handling loads during their shipping and load of burden in the reduction furnace [24]. The compressive strength of preheated pellets and roasted pellets with different BaSO4 content are shown in Figure 5. It is evident that the compressive strength both preheated pellets and roasted pellets with different BaSO4 content meet the requirements of blast furnace ironmaking. The compressive strength of preheated pellets decreases from 534 N to 510 N as the BaSO4 content increases from 0 to 1.5% and then varies slightly, which indicates that BaSO4 has little effect on the compressive strength of the preheated pellets. However, the compressive strength of roasted pellets has a large variation range with increasing BaSO4 content. When the BaSO4 content varies from 0 to 1.5%, the compressive strength increases from 2849 N to 3411 N, whereas the compressive strength drops to 2793 N with the increase of BaSO4 content to 5%. So, it can be concluded that the mechanical strength could be significantly enhanced within a small addition of BaSO4. When further increasing the amount of BaSO4, it has a negative effect on the compressive strength of pellets.

thumbnail Fig. 5

Effect of BaSO4 on compressive strength of pellets.

2.3 Effect of BaSO4 on pore size distribution and porosity

The porosity and pore distribution of roasted pellets with different BaSO4 content were measured using a mercury injection apparatus. Each testing result of porosity was repeated twice and finalized in the arithmetic mean of the two results. The finally results are presented in Figure 6. It can be seen that the porosity increases by 0.8%, the pore size decreases gradually and the structure of the pellets becomes dense with increasing the BaSO4 content from 0 to 1.5%. The pore size mainly distributes between 2–10 um as BaSO4 content is less than 1.5%. However, the porosity of pellets increases by 2.5% and the pore size of pellets mainly distributes between 7–18 um when the BaSO4 content changes from 2.0 to 5.0%.

thumbnail Fig. 6

Effect of BaSO4 on the pore distribution (a) and porosity (b) of pellets.

2.4 The chemical evolution of pellets

The chemical evolution of pellets in roasting and reduction process was tested when the BaSO4 content is constant at 2%, and the results are given in Table 4. As can be seen in Table 4, the content of TFe varies slightly, while the FeO content shows an obvious decreasing trend from 2.69 to 1.74% with increasing roasting time from 3 min to 15 min. The reasons for which are that: on one hand, the magnetite in the pellet is oxidized adequately at high temperature; and on the other hand, the oxygen generated by the decomposition of BaSO4 promotes the oxidation of magnetite. Thus, the magnetite content in the pellet decreases. The FeO content of the pellets is directly proportional to magnetite content. Higher the amount of magnetite in the pellet, the higher amount of FeO content. As far as reduction process is concerned, the content of TFe increases gradually. The FeO content is 5.84% when the reduction time is 10 min and then reaches a peak value of 59.58% at 30 min. This occurs because the reduction from hematite to magnetite takes precedence over other reduction during the first 10 min. The formation amount of FeO increases from the reduction of magnetite with increasing reduction time from 10 min to 30 min. A large amount of FeO is reduced into Fe, the metallic iron (MFe) content gradually increased and the FeO content decreases when reduction time exceeds to 30 min.

Table 4

The chemical evolution of the pellets (%).

2.5 Effect of BaSO4 on the FeO content

The FeO content is an important factor to evaluate the reducibility of pellets. The relationship between FeO content of roasted pellets and BaSO4 content is given in Figure 7. It can be observed that the FeO content drops from 2.33 to 1.62% with changing BaSO4 content from 0 to 3.0%. When the portion of BaSO4 addition is more than 3.0%, the variation range of FeO content is small and it just decreases by 0.05%. The FeO content of the pellets are directly proportional to magnetite content. Higher the amount of magnetite phase in pellets the higher amount of FeO content [24]. As mentioned above, the porosity increases with the addition of BaSO4, which is beneficial to the oxidation of magnetite phase to hematite phase. Accordingly, FeO content in pellets decreases gradually.

thumbnail Fig. 7

Effect of BaSO4 on FeO content of roasted pellets.

2.6 Effect of BaSO4 on reduction degree

The reduction degree indicates the degree of difficulty of removing oxygen from iron oxides in the pellets. The higher the reduction degree, the less coke consumed by pellets in blast furnace and the higher productivity. In this study, the reduction degree (R) of pellets is calculated by the following formula (4): (4) Where m0 is the initial mass of the pellets, g; mt is the mass of pellets at time t during reduction, g; wFeO is the FeO content of the pellets before reduction, %; wFe2O3 is the Fe2O3 content of the pellets before reduction, %.

Figure 8 demonstrates that the effect of BaSO4 content on the reduction degree of pellets. It can be found that the reduction process is improved with adding of BaSO4. The reduction degree is 80.7, 85.2, 88.0, 95.7 and 97.9% by adding BaSO4 content of 0, 1.0, 1.5, 2.0, 3.0, 5.0%, respectively. The main reason is that the pellets contain a small amount of barium ferrite formed by the reaction of BaSO4 and hematite, which is embedded between the hematite particles in granular form and hinders the diffusion of ions within the lattice. The dense internal structure of the pellets is destroyed. The loose inner structure of the pellets makes the reducing gas easy to diffuse during the reduction process. In addition, the decrease of difficult-to-reduction phases, such as fayalite, ferrous, etc., also facilitates the reduction process of pellets.

Previous studies have found that reduction of Fe2O3 strictly follows the process of [25,26], which is exactly the same as the three reduction stages in this study as shown in Figure 8. Stage 1 is the incubation period required for initial heating of pellets after insertion into the hot zone [26]. In this stage, the reduction degree of pellets increases obviously with adding BaSO4. In Stage 2, the reduction of Fe3O4 into FeO takes place at a fast rate. Compared with the content of BaSO4 exceeding 2.0%, the reduction degree of pellets is higher when the content of BaSO4 is between 1.0 and 2.0%. Third stage is a slowing down period due to a local deficiency of CO and CO2 gases [26]. As the content of BaSO4 increases, the reduction degree of pellets improves uniformly.

In order to reveal the reduction process of iron oxide clearly, the schematic diagram of reduction process is displayed in Figure 9.

In the first step, CO initially diffuses and reaches the Fe2O3 layer, and a part of CO reacts with Fe2O3 to generate Fe3O4 and CO2. CO2 diffuses out of the Fe3O4 layer with the opposite direction of CO. In the second step, CO reacts with Fe3O4 to generate FeO and CO2. In the third step, the remaining CO finally attaches to the Fe–FeO layer and reacts with FeO to generate CO2. The Fe content gradually increases as the reaction continues. The reaction equations of three steps are as follows: (5) (6) (7)

thumbnail Fig. 8

Effect of BaSO4 on reduction fraction of pellets.

thumbnail Fig. 9

Schematic diagram of reduction process.

2.7 Effect of BaSO4 on microstructural

2.7.1 Microstructure of roasted pellets

The microstructure of roasted pellets with different BaSO4 content was analysed by SEM-EDS and the results are given in Figure 10. The distribution of the slag system between the hematite particles is uniform and the size of holes is small in Figure 10a. The internal structure of the pellets is loose and the connection between solid particles is bad. The main minerals in pellets are hematite and silicate phase. The results shown in Figures 10b and 10c and Figures 10g–10i indicate that the main minerals do not change when the BaSO4 content increases from 1.0 to 1.5%. The degree of polycrystalline of hematite improves and thus the compressive strength of pellets increases. With increasing BaSO4 content from 1.5 to 5.0%, it can be seen from Figures 10d–10f that the crystallization of hematite decreases and the large size holes whose distribution is uneven increases. The decomposition of BaSO4 produces BaO, which combine with the surrounding hematite and quartz to form barium ferrate (BaO•6Fe2O3) and barium silicate (BaSiO3). The generated BaO•6Fe2O3 consumes some hematite, resulting in crystallization of the remaining hematite decreases. A small amount of undecomposed BaSO4 embeds between the hematite grains, which restrains the recrystallization of hematite. Consequently, the integrity of pellets is destroyed, leading to the compressive strength reduces.

thumbnail Fig. 10

The microstructure of roasted pellets with different BaSO4.

2.7.2 Microstructure of pellets after reduction

Figure 11 shows the SEM-EDS analysis of reduced pellets with different BaSO4 content. The white area is metallic iron (point 1) and the gray area is the wustite (point 2). With increasing BaSO4 content from 0 to 5.0%, it is observed that the wustite reduces and metallic iron increases. The minerals closely connect with each other and their compactness is improved. In addition, a small amount of barium ferrate (point 3) still exists in the pellets and the content of slag phase decreases. It can be concluded that the reduction of pellets can be improved by increasing BaSO4 content. The improvement of the reduction is mainly caused by the increase of the porosity of roasted pellets with adding BaSO4. The cracks and holes in pellets promote the CO diffusion and increase the gas–solid reaction surface area, which results the improvement of reduction and makes the reduction more uniform.

thumbnail Fig. 11

The microstructure of reduced pellets with different BaSO4.

2.8 Mechanism analysis

The oxidation and agglomeration process of pellets is directly related to the quality of pellets. The schematic diagram of pellets preheating and roasting process is shown in Figure 12. During the preheating process, the oxidation of Fe3O4 and recrystallization of Fe2O3 are hindered by the low temperature. The internal structure of the pellets is loose and the connection between solid particles is bad. BaSO4 exists independently in pellets because it does not reach decomposition temperature, and there is no reaction between BaSO4 and other phases. Consequently, BaSO4 has little effect on the compressive strength of preheated pellets.In the roasting process, the dense outer structure of the pellets is formed early, which hinders the diffusion of O2 to the surface of magnetite particles along the pores. Thus, the internal oxygen partial pressure of the pellets is relatively low. The quartz and remnant magnetite form excessive Fe2SiO4, which is a low-melting point compound. These factors act against the formation and recrystallization of hematite. A large number of Fe2SiO4 are located between the solid particles, increasing the distance between the hematite grains. Consequently, the connection between some hematite particles depends on solidification of the liquid phase. Compared with the consolidation strength of hematite particles, the strength of solidification of the liquid phase is clearly low [27]. When a small amount of BaSO4 is added into the pellets, the internal oxygen partial pressure of the pellets increases due to the oxygen produced by the decomposition of BaSO4. The continuous oxidation of magnetite is promoted. Meanwhile, the porosity of the pellets enhances and the diffusion rate of the oxygen from the exterior to the interior of the pellets increases, which is helpful for the process of oxidation reaction of magnetite. The formation and recrystallization of hematite also improve, the internal structure of pellets is dense. However, the porosity and holes clearly increase when the BaSO4 content further increases. The undecomposed BaSO4 is embedded between the hematite particles, which hinders the diffusion of ions within the lattice. The internal structure of the pellets is destroyed. It can be concluded that it is beneficial to improve the compressive strength and reducibility of roasted pellets when the content of BaSO4 is low. With increasing BaSO4 more than 1.5%, the compressive strength of roasted pellets becomes bad.

The reaction between CaO and Fe2O3 weakens with addition of BaSO4 during the isothermal reduction of pellets, thereby suppressing the generation of liquid phase and promoting the recrystallization of Fe2O3. In addition, the BaO produced by the decomposition of BaSO4 reacts with SiO2, decreasing the content of fayalite in the pellets. Fayalite has poor reducibility, and thus the reducing performance of pellets becomes better. Moreover, a small amount of barium ferrite is embedded between the hematite particles. This hinders the diffusion of ions within the lattice, causing the internal structure of the pellets becomes loose. Thus, it is conducive to the diffusion of reducing gas, thereby improving the reducibility of pellets.

thumbnail Fig. 12

Mechanism of action of BaSO4 in pellet.

3 Conclusion

The compressive strength, reduction degree and microstructure of pellets containing with different proportions of BaSO4 were investigated, and the conclusions are as follows:

  1. BaSO4 has little effect on the compressive strength of preheated pellets whereas roasted pellets have a great change when BaSO4 content varies from 0 to 5%.

  2. The generated O2 from BaSO4 decomposition promotes the oxidation process of magnetite. The FeO content gradually decreases and the reducibility improves when BaSO4 content increases from 0 to 5.0%.

  3. The generated BaO from BaSO4 decomposition can combine with the surrounding hematite and quartz to form barium ferrate and barium silicate, etc. The undecomposed BaSO4 embeds between the hematite grains, which restrains the recrystallization of hematite.

  4. In the reduction process, the wustite reduces and metallic iron increases with increasing BaSO4 content from 0 to 5.0%. The minerals are closely connected with each other and their compactness is improved.

  5. A small amount of iron ores containing barite is conducive to improving the quality of pellets when producing industrial pellets, such as compressive strength and reducibility. It is more appropriate to keep the BaSO4 content in green pellets in the range of 1.5–3%.

Acknowledgments

The present work was financially supported by National Nature Science Foundation of China (Grant No. 51604209) and Natural Science Basic Research Program of Shaanxi (Program No. 2019JLP-05).

References

  1. J.K. Tang, L. Guo, Z.C. Guo, et al., Changes of hot compressive strength of iron ore pellets during reduction process and mechanism, Iron Steel 49, 66–71 (2014) [Google Scholar]
  2. P. Ranjan, J. Pal, Salt solution treatment to prevent the low temperature reduction degradation of hematite pellet, Ironmak. Steelmak. 43, 688–696 (2016) [CrossRef] [Google Scholar]
  3. X.D. Xing, J.L. Zhang, Y.R. Liu, et al., Isothermal carbothermal reduction of synthetic FeTiO3–Fe2O3 solid solutions, Chinese J. Eng. 38, 1227–1232 (2016) [Google Scholar]
  4. G.L. Qing, C.D. Wang, E.J. Hou, et al., Compressive strength and metallurgical property of low silicon magnesium pellet, J. Iron Steel Res. 26, 7–12 (2014) [Google Scholar]
  5. H.J. Cho, M. Tang, P.C. Pistorius, Magnetite particle size distribution and pellet oxidation, Metall. Mater. Trans. B 45, 1213–1220 (2014) [CrossRef] [Google Scholar]
  6. X.D. Xing, W.G. Liu, J.T. Ju, et al., Potassium removal capacity of BaO-bearing blast furnace slags, Ironmak. Steelmak., (2019), https://doi.org/10.1080/03019233.2019.1665938 [Google Scholar]
  7. T.K.S. Kumar, N.N. Viswanathan, H. Ahmed, et al., Developing the oxidation kinetic model for magnetite pellet, Metall. Mater. Trans. B 50, 162–172 (2019) [CrossRef] [Google Scholar]
  8. J.L. Zhang, Z.Y. Wang, X.D. Xing, et al., Effect of aluminum oxide on the compressive strength of pellets, Int. J. Miner. Metall. Mater. 21, 339–344 (2014) [CrossRef] [Google Scholar]
  9. G. Wang, Q.G. Xue, Y.X. Zhao, et al., Strength and high temperature behavior of carbon composite pellets containing BOF fine dust, Ironmak. Steelmak. 41, 591–597 (2014) [CrossRef] [Google Scholar]
  10. C.G. Bi, H.M. You, T.J. Chun, et al., Effect of w(MgO) on properties of oxidized pellets, Iron Steel 52, 22–26 (2017) [Google Scholar]
  11. H. Guo, X. Jiang, F.M. Shen, et al., Influence of SiO2 on the compressive strength and reduction-melting of pellets, Metals 9, 852–870 (2019) [Google Scholar]
  12. Q. Gao, X. Jiang, H. Zheng, et al., Induration process of MgO flux pellet, Minerals 8, 389–407 (2018) [CrossRef] [Google Scholar]
  13. E.A. Mousa, A. Babich, D. Senk, Reduction behavior of iron ore pellets with simulated coke oven gas and natural gas, Steel Res. Int. 84, 1085–1097 (2013) [CrossRef] [Google Scholar]
  14. J.W. Chen, W.B. Chen, L. Mi, et al., Kinetic studies on gas-based reduction of vanadium titano-magnetite pellet, Metals 9, 95–108 (2019) [Google Scholar]
  15. G. Qing, K. Wu, Y. Tian, et al., Effect of the firing temperature and the added MgO on the reduction swelling index of the pellet with low SiO2 content, Ironmak. Steelmak. 45, 83–89 (2018) [CrossRef] [Google Scholar]
  16. M. Meraj, S. Pramanik, J. Pal, Role of MgO and its different minerals on properties of iron ore pellet, Trans. Indian Inst. Met. 69, 1141–1153 (2016) [CrossRef] [Google Scholar]
  17. P. Semberg, A. Rutqvist, C. Andersson, et al., Interactions between iron oxides and the additives quartzite, calcite and olivine in magnetite based pellets, ISIJ Int. 51, 173–180 (2011) [CrossRef] [Google Scholar]
  18. X.L. Chen, S. Liu, M. Gan, et al., Roasting behavior and enhancing technology of high-titanium pellets, Chinese J. Eng. 38, 920–929 (2016) [Google Scholar]
  19. Q.J. Gao, Y.S. Shen, X. Jiang, et al., Effects of MgO and TiO2 on comprehensive metallurgical properties of magnesia vanadium titanium pellets, Iron Steel 52, 14–21 (2017) [Google Scholar]
  20. J. Li, C.C. Han, A.M. Yang, et al., Effect of SiO2 on quality of magnesian acid pellets, J. Iron Steel Res. 29, 872–877 (2017) [Google Scholar]
  21. X.D. Xing, Y.F. Chen, Y.R. Liu, Study of the reduction mechanism of ironsands with addition of blast furnace bag dust, Metall. Res. Technol. 115, (2018), https://doi.org/10.1051/metal/2017097 [Google Scholar]
  22. Z.H. Zhang, S. Pi, D.L. He, et al., Investigation of pore-formers to modify extrusion-spheronized CaO-based pellets for CO2 capture, Processes 7, 62–76 (2019) [CrossRef] [Google Scholar]
  23. Y.F. Ren, L. Feng, Mechanism of decomposition of barite in process of sintering Jiuquan barite-containing iron ore concentrate, Acta Metall. Sinica 22, 142–148 (1986) [Google Scholar]
  24. T. Umadevi, N.F. Lobo, S. Desai, et al., Optimization of firing temperature for hematite pellets, ISIJ Int. 53, 1673–1682 (2013) [CrossRef] [Google Scholar]
  25. H. Park, I. Sohn, J. Tsalapatis, et al., Reduction behavior of dolomite-fluxed magnetite: coke composite pellets at 1573 K (1300 °C), Metall. Mater. Trans. B 49, 1109–1118 (2018) [CrossRef] [Google Scholar]
  26. H. Park, V. Sahajwalla, Influence of CaO–SiO2–Al2O3 ternary oxide system on the reduction behavior of carbon composite pellet: Part I. Reaction kinetics, Metall. Mater. Trans. B 44, 1379–1389 (2013) [CrossRef] [Google Scholar]
  27. Y.M. Chen, J. Li, Crystal rule of Fe2O3 in oxidized pellet, J. Cent. South Univ. (Natural Science Edition) 38, 70–73 (2007) [Google Scholar]

Cite this article as: Jiantao Ju, Chenmei Tang, Xiangdong Xing, Shan Ren, Guangheng Ji, Effect of BaSO4 on the compressive strength and reduction behavior of pellets, Metall. Res. Technol. 117, 207 (2020)

All Tables

Table 1

Chemical composition of the raw materials (%).

Table 2

Size distribution of the raw materials (%).

Table 3

Mixed ratios of the pelletizing materials (%).

Table 4

The chemical evolution of the pellets (%).

All Figures

thumbnail Fig. 1

Pelletizing and firing process of pellets.

In the text
thumbnail Fig. 2

Preheating and roasting system parameters.

In the text
thumbnail Fig. 3

Schematic of the reduction experimental apparatus.

In the text
thumbnail Fig. 4

X-ray pattern of roasted pellets.

In the text
thumbnail Fig. 5

Effect of BaSO4 on compressive strength of pellets.

In the text
thumbnail Fig. 6

Effect of BaSO4 on the pore distribution (a) and porosity (b) of pellets.

In the text
thumbnail Fig. 7

Effect of BaSO4 on FeO content of roasted pellets.

In the text
thumbnail Fig. 8

Effect of BaSO4 on reduction fraction of pellets.

In the text
thumbnail Fig. 9

Schematic diagram of reduction process.

In the text
thumbnail Fig. 10

The microstructure of roasted pellets with different BaSO4.

In the text
thumbnail Fig. 11

The microstructure of reduced pellets with different BaSO4.

In the text
thumbnail Fig. 12

Mechanism of action of BaSO4 in pellet.

In the text

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