Microwave strengthens decomposition of mixed rare earth concentrate: Microwave absorption characteristics

Huang, Yukun; Zhang, Ting‐an; Zhang, Dou; Lv, Guozhi; Han, Gaorong; Peng, Weijun

doi:10.1016/j.jre.2018.08.010

Cited by 24 publications

(9 citation statements)

References 31 publications

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“…The heating curve shown in Figure 1 is consistent with the results reported by other research groups. 16 We chose such a high roasting temperature because we can take full advantage of the rapid internal heating of microwave radiation, 14 and the highest microwave roasting temperature that the ore can reach is 1100 °C. The decomposition reaction of the bastnasite concentrate is an endothermic reaction, which is more favorable for promoting the decomposition of the bastnasite concentrate at a high temperature.…”

Section: Results and Discussionmentioning

confidence: 99%

Nonoxidative Microwave Radiation Roasting of Bastnasite Concentrate and Kinetics of Hydrochloric Acid Leaching Process

Zheng

Cui

et al. 2020

ACS Omega

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Herein, a new clean extraction technology for the decomposition of bastnasite concentrate by utilizing the microwave radiation is proposed, which prevented Ce(III) from being oxidized to its tetravalent form. The process includes microwave radiation roasting to nonoxidatively decompose the bastnasite concentrate, mechanism analysis of Ce(III) not being oxidized to Ce(IV), hydrochloric acid leaching of the nonoxidative roasted ore, and kinetics analysis of the leaching process. The experiments were carried out concentrating on the effect of roasting temperature and holding time on the decomposition rate of the bastnasite concentrate and the oxidation rate of cerium and the effect of acidity, liquid–solid ratio, leaching temperature, and stirring rate on the leaching kinetics of the nonoxidative roasting ore. When the roasting temperature is 1100 °C, the holding time is 20 min, and the m (C)/ m (REFCO 3 ) ratio is 0.2, the results show that the leaching efficiency of rare earths can reach 85.45% under the conditions 3 mol/L HCl, 90 °C, 60 min, 9 mL/g liquid–solid ratio, and 300 rpm stirring rate. The X-ray diffraction and scanning electron microscopy analyses of the samples before and after acid leaching show that the rare earth oxides were completely leached and Ce(III) was not oxidized to its tetravalent form. The apparent activation energies of leaching rare earths were calculated as 14.326 kJ/mol, and the HCl leaching process can be described by a new variant of the shrinking-core model, in which both the interfacial transfer and the diffusion through the product layer influenced the reaction rate. Furthermore, a semiempirical rate equation was created to describe the leaching process of the nonoxidative roasted ore.

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Section: Results and Discussionmentioning

confidence: 99%

Nonoxidative Microwave Radiation Roasting of Bastnasite Concentrate and Kinetics of Hydrochloric Acid Leaching Process

Zheng

Cui

et al. 2020

ACS Omega

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“…The temperature rise curves are similar to those reported by other researchers. 7 It is generally accepted that a higher holding temperature helps to accelerate the decomposition reaction of the bastnasite concentrate. 13 Therefore, the optimal holding temperature was set to 1100 °C.…”

Section: Resultsmentioning

confidence: 99%

“…This is because the absorbing properties of the bastnasite concentrate change with the temperature and the nature of the bastnasite concentrate. 7 …”

Section: Resultsmentioning

confidence: 99%

“…Microwave irradiation heating, as an efficient heating method, has been applied in metallurgy and has become a new type of green metallurgy method. , However, the dielectric properties of bastnasite concentrate and of the mixture of bastnasite concentrate and activated carbon in the microwave field have not been investigated. Dielectric properties are the critical factors that determine how microwave energy is transmitted, reflected, and absorbed.…”

Section: Introductionmentioning

confidence: 99%

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Process Optimization and Modeling of Microwave Roasting of Bastnasite Concentrate Using Response Surface Methodology

Zheng

et al. 2021

ACS Omega

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The investigation of the dielectric properties of bastnasite concentrate has critical directing centrality for the microwave roasting process of bastnasite concentrate. The dielectric properties are correlated with information such as thermogravimetry–differential scanning calorimetry and temperature rise curves. This combination permits a targeted study of the mechanism of the microwave roasting process, providing new evidence about the unique conditions of this microwave roasting process. This work also explores the response surface methodology based on a central composite design to optimize the microwave non-oxidative roasting process. Single-factor tests were conducted to determine the suitable range of factors such as the content of activated carbon, holding time, and roasting temperature. The interactions between parameters were investigated through the analysis of variance method. It was indicated that the models are available to navigate the design space. Also, the optimal roasting temperature, content of activated carbon, and holding time were 1100 °C, 20%, and 21.5 min, respectively. Under these conditions, the decomposition rate of bastnasite concentrate (hereinafter to be referred as DRBC) and the oxidation rate of cerium (hereinafter to be referred as ORC) was 99.8% and less than 0.3%, respectively. The new non-oxidizing roasting method significantly shortens the roasting time, reduces the energy consumption, and has great significance for industrial applications.

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“…The parameter reflecting the relationship between the microwave energy absorbed by the medium and microwave penetration depth is called as the microwave absorption index 27 . It can be expressed in terms of ε ', ε '', and D p as follows 28 :

A = \frac{2 \sqrt{2 ()(, \sqrt{{ε^{'}}^{2} + {ε^{″}}^{2}} + ε^{'})}}{D_{p} ()(, \sqrt{{ε^{'}}^{2} + {ε^{″}}^{2}} + \sqrt{2 ()(, \sqrt{{ε^{'}}^{2} + {ε^{″}}^{2}} + ε^{'}) + 1})}

…”

Section: Methodsmentioning

confidence: 99%

Influence of dielectric property of organic sulfur compounds on coal microwave desulfurization

Tao

Yang

2020

Asia-Pacific J Chem Eng

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The present study aims to reveal the influence mechanism of organic sulfur structures and microwave frequency on its dielectric property and establish the relationship between the dielectric properties of organic sulfur components in coal and the efficiency of microwave desulfurization. Results showed that the different polarization mechanisms of organic sulfur compounds lead to the real part of complex permittivity decreased initially and then increased with increasing frequency. At the same time, the real parts of the complex permittivity of mercaptan and thioether compounds were higher than that of thiophene, which were caused by their different structures. As the frequency increased, the loss tangent, microwave penetration depth, and absorption index showed decline in oscillation. The loss tangent was mainly related to the polarization mechanism; both polarization mechanism and microwave wavelength had effect on the changes of microwave penetration depth and absorption index. Mercaptan and thioether compounds were more effective at converting microwave energy into heat energy. After microwave processing, the relative content of mercaptan (thioether) in GZ, CQ, and SX coals decreased from 37.38%, 36.93%, and 40.02% to 27.34%, 29.26%, and 26.67% and of thiophene increased from 47.61%, 53.35%, and 49.54% to 58.76%, 59.09%, and 60.38%.

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Microwave strengthens decomposition of mixed rare earth concentrate: Microwave absorption characteristics

Cited by 24 publications

References 31 publications

Nonoxidative Microwave Radiation Roasting of Bastnasite Concentrate and Kinetics of Hydrochloric Acid Leaching Process

Nonoxidative Microwave Radiation Roasting of Bastnasite Concentrate and Kinetics of Hydrochloric Acid Leaching Process

Process Optimization and Modeling of Microwave Roasting of Bastnasite Concentrate Using Response Surface Methodology

Influence of dielectric property of organic sulfur compounds on coal microwave desulfurization

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