Influence of temperature and time on reduction behavior in iron ore–coal composite pellets

Man, Yi; Feng, Jie; Li, F.J.; Ge, Qiang; Chen, Y.M.; Zhou, Jianmin

doi:10.1016/j.powtec.2014.02.039

Cited by 97 publications

(31 citation statements)

References 20 publications

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“…The high iron content and low oxygen content imply that spherulites are pure iron; therefore, pure iron was formed by melting above 1300 °C. Many experiments and production processes have demonstrated the reduction of iron oxides by carbon (Man et al, 2014). Graphite was found in the experimental products and in the natural principal slip zone of the 2008 Wenchuan rupture (Kuo et al, 2014); therefore, carbon could be the reductant in the thermal reduction of ferric oxides.…”

Section: Discussionmentioning

confidence: 96%

Metallic iron formed by melting: A new mechanism for magnetic highs in pseudotachylyte

Zhang

Sun

et al. 2018

Geology

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Previous studies of rock magnetism in fault rocks imply frictional heating temperatures from ~300 °C to ~700 °C, which are far below the temperatures needed to form pseudotachylyte. Here, heating experiments were performed at elevated temperatures (as high as 1750 °C) on cataclasites from the Wenchuan Earthquake Fault Scientific Drilling borehole 2 (WFSD-2) cores, Longmen Shan thrust belt, China. Based on microstructural, geochemical, and rock magnetic analyses, the main conclusions are as follows. The melting occurred at 1100 °C. The newly formed magnetite generated by the thermal decomposition of paramagnetic minerals contributed to the high magnetic susceptibility values of samples below 1100 °C. Above 1300 °C, many circular metallic iron spherulites were formed by the reducing action of Fe-bearing minerals at elevated temperatures. As the temperature increased, metallic iron content and magnetic susceptibility increased, indicating that the newly formed metallic iron was responsible for the high magnetic susceptibility values. Therefore, in addition to the newly formed magnetite, the metallic iron is another factor contributing to the magnetic highs of pseudotachylytes. The frictional melting temperature reached 1300 °C during ancient earthquakes in the Longmen Shan thrust belt, indicating that metallic iron might be responsible for the strong magnetic highs in pseudotachylyte.

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Section: Discussionmentioning

confidence: 96%

Metallic iron formed by melting: A new mechanism for magnetic highs in pseudotachylyte

Zhang

Sun

et al. 2018

Geology

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“…Thus the reduction reaction process of the particles in the carbon-containing pellet can be described via the shrinking unreacted core model, as shown in Figure 10. The carbothermal reduction process includes the following: It is generally recognized that the diffusion of CO/CO2 through the gas phase boundary layer is too fast to become the restrictive link of the reduction rate at a high temperature [12]. To discuss the kinetics of the reduction reaction, we assumed that (1) the pellet was isotropic, and that the ore particles and the carbon particles uniformly distributed; (2) the temperature gradient and gas phase concentration gradient were negligible; and (3) the temperature change of the pellets at the initial stage (~300 s) was insignificant.…”

Section: Kinetic Analysis Of Reduction Reactionmentioning

confidence: 99%

“…As shown in Figure 11, the data of −ln(1 − f ), 1 − (1 − f ) 1/3 and 1− 2/3f − (1 − f ) 2/3 at different times in the roasting process was calculated according to Equations (10)- (12) in Table 4 and then linearly fitted, and the rate constant k, equal to the slope of the fitted line, was obtained. The rate constant k and the correlation coefficient R 2 of the linear fitting are listed in Table 5.…”

Section: Kinetic Analysis Of Reduction Reactionmentioning

confidence: 99%

Reduction Characteristics of Carbon-Containing REE–Nb–Fe Ore Pellets

Zhang

Fan

Liu

et al. 2018

Metals

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Abstract:To separate and recover the valuable metals from low-grade REE (rare earth elements)-Nb-Fe ore in China, the reduction characteristics of carbon-containing REE-Nb-Fe ore pellets, including mineral phase variation, reduction degree, and reaction kinetics, were observed based on thermogravimetry experiments. The results showed that the reduction and separation efficiency of valuable metals in the carbon-containing pellets were superior to the ones in the previous non-compact mixture. After the reduction roasting of the pellets at 1100 • C and a subsequent magnetic separation, the iron powder with a grade of 91.7 wt % was separated, and in magnetic separation tailings the grades of Nb 2 O 5 and (REE)O were beneficiated to approximately twice the grades in the REE-Nb-Fe ore. The reaction rate of the reduction of the carbon-containing pellets was jointly controlled by the carbon gasification reaction and the diffusion of CO in the product layer with an activation energy of 139.26-152.40 kJ·mol −1 . Corresponding measures were proposed to further improve the kinetics condition.

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“…The reaction behavior of CCB can be of fundamental importance because it is closely related to the changes of ore reduction and of coke gasification in the upper part of a BF. Most studies on CCB reaction behavior have been carried out under simulated BF in-furnace conditions [18][19][20]. However, the high-pressure environment in a BF was generally overlooked in these studies.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigation of Reaction Behavior of Carbon Composite Briquette in Blast Furnace

Tang

Sun

2019

Metals

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The application of carbon composite briquette (CCB) is considered to be an efficient method for achieving low-energy and low-CO2-emission blast furnace (BF) operations. In this research, a combined experimental and numerical study was conducted on the CCB reaction behavior in BF. The CCB used in this study had a composition of 20.10 wt.% carbon, 29.70 wt.% magnetite, 39.70 wt.% wüstite, and 1.57 wt.% metallic iron. Using the prepared CCB samples, isotherm reduction tests under a simulated BF atmosphere (CO-CO2-N2) were conducted and a reaction model was developed. Subsequently, the reaction behavior of CCB along the mid-radial solid descending path in an actual BF of 2500 m3 was analyzed by numerical simulations based on the experimental findings and the previous results of comprehensive BF modeling. The results of the experiments showed that the CCB model predictions agreed well with the experimental measurements. With respect to the BF, the results of the numerical simulations indicated that, along the path, before the CCB temperature reached 1000 K, the CCB was reduced by CO in the BF gas; when its temperature was in the range from 1000 to 1130 K, it underwent self-reduction and contributed both CO and CO2 to the BF gas; when its temperature was above 1130 K, it only presented carbon gasification. Moreover, these results also revealed that the reduction of iron oxide and the gasification of carbon inside the CCB proceeded under an uneven mode. The uneven radial distribution of the local reduction fraction and local carbon conversion were evident in the self-reducing stage of the CCB.

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Influence of temperature and time on reduction behavior in iron ore–coal composite pellets

Cited by 97 publications

References 20 publications

Metallic iron formed by melting: A new mechanism for magnetic highs in pseudotachylyte

Metallic iron formed by melting: A new mechanism for magnetic highs in pseudotachylyte

Reduction Characteristics of Carbon-Containing REE–Nb–Fe Ore Pellets

Experimental and Numerical Investigation of Reaction Behavior of Carbon Composite Briquette in Blast Furnace

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