The effect of CaO on the recovery of Fe and Ni in a vacuum carbothermal reduction of garnierite

Wang, Q; Qu, Tao; X.-P., Gu; Shi, Lei; Yang, Bin; Dai, Yongnian

doi:10.2298/jmmb190213035w

Cited by 4 publications

(5 citation statements)

References 22 publications

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“…However, the recovery of Si and the removal rate of Mg showed the opposite trend, this becomes a contradiction point for recovering garnierite comprehensively. Previously, we used this method to recover Ni, Fe, Si, and Mg with CaO as an additive, achieved some good experiment results, especially for the removal rate of Mg [29]. Subsequently, we could consider the mixture of CaF 2 -CaO as an additive to solve the contradiction of Si and Mg, and achieve the purpose of comprehensive recovery of valuable metals from garnierite.…”

Section: Discussionmentioning

confidence: 99%

“…This become a contradiction point for recovering of garnierite comprehensively, therefore, the recovery of Si and Mg will not be ideal if only adding CaF 2 . Our previous research [29] has proved that CaO can greatly enhance the recovery of Si and Mg. We could consider the mixture of CaF 2 -CaO as an additive to achieve the purpose of comprehensive recovery of valuable metals from garnierite. Figures 17 and 18 show that the main phases of the Fe-Ni-rich residue were forsterite, spinel, and FeSi, as well as a small amount of CaSiO 3 and low-melting-point compounds (FeF 2 , NiF 2 , and MgF 2 ).…”

Section: Analysis Of the Reduction Processmentioning

confidence: 99%

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Mechanism of CaF2 under Vacuum Carbothermal Conditions for Recovering Nickel, Iron, and Magnesium from Garnierite

Wang

et al. 2020

Metals

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Nickel laterite ore is divided into three layers and the garnierite examined in this study belongs to the third layer. Garnierite is characterized by high magnesium and silicon contents. The main contents of garnierite are silicates, and nickel, iron, and magnesium exist in silicates in the form of lattice exchange. Silicate minerals are difficult to destroy so are suitable for smelting using high-temperature pyrometallurgy. To solve the problem of the large amounts of slag produced and the inability to recycle the magnesium in the traditional pyrometallurgical process, we propose a vacuum carbothermal reduction and magnetic separation process to recover nickel, iron, and magnesium from garnierite, and the behavior of the additive CaF2 in the reduction process was investigated. Experiments were conducted under pressures ranging from 10 to 50 Pa with different proportions of CaF2 at different temperatures. The experimental data were obtained by various methods, such as thermogravimetry, differential scanning calorimetry, scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and inductively coupled plasma atomic emission spectroscopy. The analysis results indicate that CaF2 directly reacted with Mg2SiO4, MgSiO3, Ni2SiO4, and Fe2SiO4, which were isolated from the bearing minerals, to produce low-melting-point compounds (FeF2, MgF2, NiF2, etc.) at 1315 and 1400 K. This promoted the conversion of the raw materials from a solid–solid reaction to a liquid–liquid reaction, accelerating the mass transfer and the heat transfer of Fe–Ni particles, and formed Si–Ni–Fe alloy particles with diameters of approximately of 20 mm. The smelting materials appeared stratified, hindering the reduction of magnesium. The results of the experiments indicate that at 1723 K, the molar ratio of ore/C was 1:1.2, the addition of CaF2 was 3%, the recovery of Fe and Ni reached 82.97% and 98.21% in the vacuum carbothermal reduction–magnetic separation process, respectively, and the enrichment ratios of Fe and Ni were maximized, reaching 3.18 and 9.35, respectively.

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Section: Discussionmentioning

confidence: 99%

Section: Analysis Of the Reduction Processmentioning

confidence: 99%

Mechanism of CaF2 under Vacuum Carbothermal Conditions for Recovering Nickel, Iron, and Magnesium from Garnierite

Wang

et al. 2020

Metals

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“…Zeng et al [13] developed a process using garnierite and red mud which is mainly composed of CaO, Al 2 O 3 , and Fe, and cast iron composed of 1.5-2 wt% Ni and 0.7-0.8 wt% was produced. Further, Wang et al [14] studied the effect of CaO on the recovery rates of iron and nickel from garnierite by carbothermal reduction in vacuum, which reached 84.33% and 97.00%, respectively. According to the literature, the purpose of these pyrometallurgical processes is to extract iron and nickel from garnierite; in other words, it is difficult to make use of the magnesium in saprolite and garnierite.…”

Section: Introductionmentioning

confidence: 99%

“…According to the literature, the purpose of these pyrometallurgical processes is to extract iron and nickel from garnierite; in other words, it is difficult to make use of the magnesium in saprolite and garnierite. Qu et al [14,15] analyzed the value of magnesium in garnierite and determined it to be approximately three times that of nickel; therefore, the abandonment of magnesium will make it difficult to maximize the value of garnierite.…”

Section: Introductionmentioning

confidence: 99%

Extraction of magnesium from garnierite by carbothermal reduction in vacuum

Shi

et al. 2020

Mater. Res. Express

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The aim of the traditional pyrometallurgical processes is to extract nickel and iron in garnierite, but it is difficult to extract magnesium of higher value in minerals. Aimed at solving this problem, the extraction of magnesium from garnierite is proposed and studied in this study. The effects of different reduction temperatures, different reduction times and dosage of CaO additions in experiments were investigated. The experimental results indicate that the extraction rate of magnesium can reach 93.23% when the mass ratio of mineral/reductant is 100:28.3, system pressure is 50 Pa, reduction temperature is 1823 K, and reduction time is 120 min, and, at the same time, the purity of metal magnesium in the condensate can be up to 91.88%. Under these conditions, the extraction rate of magnesium can increase to 99.45% by adding 25 wt% CaO, and the purity of the metal magnesium in the condensate exceeds 90%. CaO as the additive can effectively improve the extraction rate of magnesium and promote the recovery and utilization of magnesium. The mechanism is that CaO replaces -O-Mgin the -O-Mg−O-Si−Ostructure to form free MgO, which is reduced to Mg vapor by carbon and condensed into magnesium metal in the condensation zone to achieve the purpose of removing and collecting Mg from the garnierite. At the same time, the reduced slag is rich in Ni and Fe, which can be used for the extraction of Ni and Fe. Compared with the traditional pyrometallurgical process, the process can extract magnesium from garnierite, and the process is short and its operation is simple, which is a potential technology.

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“…The vacuum metallurgy team of Kunming University of Science and Technology, based on the vacuum carbothermal reduction principle, proved that nickel and iron in the reduced slag can be recovered by magnetic separation process under the vacuum condition of extracting magnesium from the garnierite [5,6] . Qu Tao, Wang Qiang, et al adopted this principle to make the removal rate of magnesium in minerals reach 99% or more, and the recovery rate of nickel and iron in reducing slag reached 97.27% and 92.54%, respectively [7,8] ; Luo Qi et al analyzed the promoting factors of minerals in carbothermal reduction by studying the behavior of silicon, magnesium and other substances in minerals under vacuum [9,10] . However, the above studies did not elaborate the behavior of magnesium in the process of carbothermal reduction in vacuum of the garnierite from the kinetic point of view.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Magnesium Removal from Garnierite by Carbothermal Reduction in Vacuum

Zhang

et al. 2020

MSF

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The removal of magnesium from garnierite in Yuanjiang area of Yunnan was performed by carbothermal reduction in vacuum. The effects of reduction temperature and reduction time on the removal rate of magnesium were investigated. The kinetics of the removal of magnesium by carbothermal reduction in vacuum was studied. The thermodynamic calculation results show that it is feasible to remove magnesium from garnierite by carbothermal reduction in vacuum. The experimental results show that the removal rate of magnesium in garnierite can reach 93.23% under the conditions of 1823K for 120min. The reduction process conforms to the chemical reaction kinetics model, which indicated that the reduction process is controlled by chemical reaction and whose expression is 1-(1-α)1/3=(-22850.1/T+2.6296) t, the apparent activation energy (Ea) and the pre-exponential factor (A) are 189.97 kJ/mol and 13.87 s-1, respectively. The results of XRD and SEM analysis show that the condensate obtained by carbothermal reduction in vacuum of the garnierite is magnesium, which is mainly obtained by the reduction reaction between magnesium silicate produced by the decomposition of serpentine in minerals and coal. At the same time, it is proved that it is feasible to directly extract magnesium metal from the garnierite.

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The effect of CaO on the recovery of Fe and Ni in a vacuum carbothermal reduction of garnierite

Cited by 4 publications

References 22 publications

Mechanism of CaF2 under Vacuum Carbothermal Conditions for Recovering Nickel, Iron, and Magnesium from Garnierite

Mechanism of CaF2 under Vacuum Carbothermal Conditions for Recovering Nickel, Iron, and Magnesium from Garnierite

Extraction of magnesium from garnierite by carbothermal reduction in vacuum

Kinetics of Magnesium Removal from Garnierite by Carbothermal Reduction in Vacuum

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