Extraction method for valuable elements of low-grade vanadia–titania magnetite

Gao, Zixian; Yang, Shuren; Xue, Xiangxin; He, Yang; Cheng, Gongjin

doi:10.1016/j.jclepro.2019.119451

“…The comparisons of the evolution of each crystalline phase at each temperature and H2 gas concentration is shown in Figure 5. 13 , where the x-axis is normalized time (t/τ). As with the flow rate comparison, most of the phase concentration curves are seen to be highly similar across all of the studied H2 gas concentrations and temperatures.…”

Section: Figure 512-(a) the Effect Of H2 Gas Concentration On The Production Of Metallic Fe During Reduction Of Pre-oxidised Pellets At Amentioning

confidence: 99%

“…Equation 7. 13 gives a constant value as 0 = 0.26. In equation 7.14, the ratio can be calculated from the concentration of each phase measured from ND at each condition.…”

mentioning

confidence: 99%

Reduction of New Zealand Titanomagnetite Ironsand pellets in H2 Gas at High Temperatures

Zhang¹

2021

Preprint

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To reduce the emission of carbon dioxide (CO2) from industrial ironmaking in New Zealand (NZ), it is proposed to perform direct reduction (DR) of NZ titanomagnetite ironsand pellets using H2 gas. In this thesis, the H2 reduction behaviour of pellets made from the NZ ironsand are examined. The aim of the thesis is to understand the reduction mechanism, and develop an analytical kinetic model to describe the reduction progress with time. This has been addressed through a series of reduction experiments in H2 gas. The overall reduction kinetics are examined in a Thermogravimetric analysis system (TGA); the phase evolution during reduction is measured by an in-situ neutron diffraction (ND) method; and the evolution of pellet- and particle-scale morphologies are analysed by scanning electron microscopy (SEM) of quenched samples. Based on the analysis of results from these experiments, the mechanism of the reduction is found to be adequately described by a single interface shrinking core model (SCM). Two different types of pellet are considered in this work: Ar-sintered pellets were sintered in an inert atmosphere to produce pellets containing mainly titanomagnetite (TTM). Pre-oxidised pellets were sintered in air to produce pellets containing mainly titanohematite (TTH). The reduction rate of both types of pellets is found to increase with reduction temperature, H2 gas flow rate, and H2 gas concentration. Above 1143 K, it is found that both types of pellets present a similar reduction rate, while below 1143 K, the reduction of pre-oxidised pellets is much faster than that of Ar-sintered pellets. For both pellets, the maximum reduction degree can reach ~97%. After complete reduction, metallic Fe coexists with other unreduced Fe-Ti-O phases (FeTiO3, TiO2 or pseudobrookite (PSB)/ferro-PSB), which is consistent with the observed reduction degree of < 100%. During reduction of both types of pellets, any TTH present is rapidly reduced first. After this step, TTM is then reduced to FeO, with Ti becoming enriched in the remaining unreduced TTM. FeO is further reduced to metallic Fe, which makes up to ~90% reduction degree. Eventually Ti-enrichment of the TTM leads to a change in the reduction pathway and it instead directly converts to metallic Fe and FeTiO3. Above ~90% reduction degree, reduction of the remaining Fe-Ti-O phases occurs (leading to the formation of TiO2 or PSB/ferro-PSB). The enrichment of Ti in TTM which accompanies the generation of FeO is substantially different from conventional non-titaniferous ores. This enrichment is confirmed by EDS-maps of the particles and stoichiometric calculations of the molar fraction Ti within the TTM phase. This enrichment effect changes the morphology of FeO in the particles, leading to the formation of FeO channels surrounded by Ti-enriched TTM. At the pellet-scale, both types of pellets present a single interface shrinking core phenomenon at higher temperatures. Metallic Fe is generated from pellet surface with a reaction interface moving inwards. However, at lower temperatures this pellet-scale interface becomes less defined in the pellets. Instead, particle-scale reaction fronts are observed. A single interface shrinking core model (SCM) is shown to successfully describe the reduction of pellets for reduction degrees < ~90% at all temperatures studied. However, at reduction degrees > ~90% this model fails. This is attributed to the change in reaction mechanism required to reduce the residual Fe-Ti-O phases that remain dispersed throughout the whole pellet at this stage of the reaction. The single interface SCM indicates that the reduction rate of the Ar-sintered pellets is controlled by the interfacial chemical reaction rate. However, two different temperature regimes are identified. Above 1193 K, the activation energy is calculated to be 41 ± 1 kJ/mol, but below 1193 K the calculated activation energy increases to 89 ± 5 kJ/mol. This change in activation energy appears to be associated with the change of the rate-limiting reaction from FeO → metallic Fe to TTM → FeO. By contrast, the pre-oxidised pellets exhibit mixed control at 1043 K, where a role is played by both the interfacial chemical reaction rate and the diffusion rate through the outer product layer. However, at temperatures of 1143 K and above, the pre-oxidised pellets also exhibit interfacial chemical reaction control, with a single activation energy of 31 ± 1 kJ/mol, which again seems to be consistent the rate-limiting reaction being FeO → metallic Fe. In summary, the findings in this thesis contribute to understanding of the reduction of NZ ironsand pellets in H2 gas, and establish a kinetic model to describe this process. In the future, this information will be applied to develop a prototype H2-DRI shaft reactor for NZ ironsand pellets.

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“…These are not conducive to the treatment and utilization of VTMT on a large scale. Thus, it is preferred to extract further valuable metals such as iron, titanium, vanadium and scandium from the VTMT by means of advanced metallurgical and mineral processing techniques (Xiao et al, 2021), similar to those used in raw vanadiferous titanomagnetite ore (Gao et al, 2020;Han et al, 2021;Li et al, 2022b;Sukmara et al, 2022). Meanwhile, whether directly preparing new materials or extracting valuable elements from VTMT, a detailed process mineralogical analysis is an important prerequisite and an effective method to improve the availability of VTMT (Baum, 2014;Brough et al, 2013;Kelvin et al, 2022;Xu et al, 2021;Zhang et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the potential of recovering various valuable elements from a vanadiferous titanomagnetite tailing based on chemical and process mineralogical characterization

Liu

¹

,

Xing

²

,

Liu

³

et al. 2023

Environ Sci Pollut Res

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In order to evaluate the potential of recovering various valuable elements from vanadiferous titanomagnetite tailing (VTMT), the chemical and process mineralogical characterization of VTMT were investigated in this study by various analytical techniques such as XRF, XRD, optical microscope, SEM, EDS and AMICS et al. It was found that VTMT is coarser powder in general, about 50% of the particle size is greater than 54.30 µm. The total iron content of the VTMT was 22.40 wt.%, and its TiO 2 grade is 14.45 wt.%, even higher than those found in natural ilmenite ores. The majority of iron and titanium were located in ilmenite and hematite, 62.84% of hematite and 90.27% of ilmenite were present in monomeric form. However, there is still a portion of ilmenite and hematite embedded in gangue such as anorthite, diopside, and serpentite et al. For the recovery of valuable fractions such as Fe and TiO 2 from VTMT, a treatment process including ball milling -high-intensity magnetic separation -one roughing and three re ning otation was proposed. Finally, a concentrate with TiO 2 grade of 47.31% and TFe grade of 35.44% was produced, TiO 2 and TFe had recovery rates of 57.71% and 28.23%, respectively. The recovered product is absolutely adequate as a raw material for the production of rutile. This study provides a reference and a new research direction for the recycling and comprehensive utilization of VTMT.

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“…The mining and utilisation of the ironsand not only directly contributes to New Zealand's GDP, but also helps the local economy by creating jobs [11], [12]. Finally, there is also possible value in co-production of TiO2 and V2O5 minerals found within the titanomagnetite ironsand [13], [14].…”

Section: Background Of the Studymentioning

confidence: 99%

“…In this table, some selected titanomagnetite ores from around the world are also presented for comparison [13], [40]- [43]. As can be seen, the titanomagnetite ores from international deposits have quite different chemical compositions to NZ ironsand.…”

Section: An Introduction To Nz Titanomagnetite Ironsandmentioning

confidence: 99%

Reduction of New Zealand Titanomagnetite Ironsand pellets in H2 Gas at High Temperatures

Zhang¹

0

View full text Add to dashboard Cite

To reduce the emission of carbon dioxide (CO2) from industrial ironmaking in New Zealand (NZ), it is proposed to perform direct reduction (DR) of NZ titanomagnetite ironsand pellets using H2 gas. In this thesis, the H2 reduction behaviour of pellets made from the NZ ironsand are examined. The aim of the thesis is to understand the reduction mechanism, and develop an analytical kinetic model to describe the reduction progress with time. This has been addressed through a series of reduction experiments in H2 gas. The overall reduction kinetics are examined in a Thermogravimetric analysis system (TGA); the phase evolution during reduction is measured by an in-situ neutron diffraction (ND) method; and the evolution of pellet- and particle-scale morphologies are analysed by scanning electron microscopy (SEM) of quenched samples. Based on the analysis of results from these experiments, the mechanism of the reduction is found to be adequately described by a single interface shrinking core model (SCM). Two different types of pellet are considered in this work: Ar-sintered pellets were sintered in an inert atmosphere to produce pellets containing mainly titanomagnetite (TTM). Pre-oxidised pellets were sintered in air to produce pellets containing mainly titanohematite (TTH). The reduction rate of both types of pellets is found to increase with reduction temperature, H2 gas flow rate, and H2 gas concentration. Above 1143 K, it is found that both types of pellets present a similar reduction rate, while below 1143 K, the reduction of pre-oxidised pellets is much faster than that of Ar-sintered pellets. For both pellets, the maximum reduction degree can reach ~97%. After complete reduction, metallic Fe coexists with other unreduced Fe-Ti-O phases (FeTiO3, TiO2 or pseudobrookite (PSB)/ferro-PSB), which is consistent with the observed reduction degree of < 100%. During reduction of both types of pellets, any TTH present is rapidly reduced first. After this step, TTM is then reduced to FeO, with Ti becoming enriched in the remaining unreduced TTM. FeO is further reduced to metallic Fe, which makes up to ~90% reduction degree. Eventually Ti-enrichment of the TTM leads to a change in the reduction pathway and it instead directly converts to metallic Fe and FeTiO3. Above ~90% reduction degree, reduction of the remaining Fe-Ti-O phases occurs (leading to the formation of TiO2 or PSB/ferro-PSB). The enrichment of Ti in TTM which accompanies the generation of FeO is substantially different from conventional non-titaniferous ores. This enrichment is confirmed by EDS-maps of the particles and stoichiometric calculations of the molar fraction Ti within the TTM phase. This enrichment effect changes the morphology of FeO in the particles, leading to the formation of FeO channels surrounded by Ti-enriched TTM. At the pellet-scale, both types of pellets present a single interface shrinking core phenomenon at higher temperatures. Metallic Fe is generated from pellet surface with a reaction interface moving inwards. However, at lower temperatures this pellet-scale interface becomes less defined in the pellets. Instead, particle-scale reaction fronts are observed. A single interface shrinking core model (SCM) is shown to successfully describe the reduction of pellets for reduction degrees < ~90% at all temperatures studied. However, at reduction degrees > ~90% this model fails. This is attributed to the change in reaction mechanism required to reduce the residual Fe-Ti-O phases that remain dispersed throughout the whole pellet at this stage of the reaction. The single interface SCM indicates that the reduction rate of the Ar-sintered pellets is controlled by the interfacial chemical reaction rate. However, two different temperature regimes are identified. Above 1193 K, the activation energy is calculated to be 41 ± 1 kJ/mol, but below 1193 K the calculated activation energy increases to 89 ± 5 kJ/mol. This change in activation energy appears to be associated with the change of the rate-limiting reaction from FeO → metallic Fe to TTM → FeO. By contrast, the pre-oxidised pellets exhibit mixed control at 1043 K, where a role is played by both the interfacial chemical reaction rate and the diffusion rate through the outer product layer. However, at temperatures of 1143 K and above, the pre-oxidised pellets also exhibit interfacial chemical reaction control, with a single activation energy of 31 ± 1 kJ/mol, which again seems to be consistent the rate-limiting reaction being FeO → metallic Fe. In summary, the findings in this thesis contribute to understanding of the reduction of NZ ironsand pellets in H2 gas, and establish a kinetic model to describe this process. In the future, this information will be applied to develop a prototype H2-DRI shaft reactor for NZ ironsand pellets.

show abstract

Extraction method for valuable elements of low-grade vanadia–titania magnetite

Cited by 9 publications

References 26 publications

Reduction of New Zealand Titanomagnetite Ironsand pellets in H2 Gas at High Temperatures

Reduction of New Zealand Titanomagnetite Ironsand pellets in H2 Gas at High Temperatures

Evaluation of the potential of recovering various valuable elements from a vanadiferous titanomagnetite tailing based on chemical and process mineralogical characterization

Reduction of New Zealand Titanomagnetite Ironsand pellets in H2 Gas at High Temperatures

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