Non-equilibrium thermodynamics approach for the coupled heat and mass transfer in microwave drying of compressed lignite sphere

Fu, B.A.; Chen, Meiqian; Li, Q.H.

doi:10.1016/j.applthermaleng.2018.01.036

Cited by 25 publications

(13 citation statements)

References 27 publications

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“…The content of Ce 4+ in the roasted ore was analyzed by the method of ferrous ammonium sulfate titration without the addition of perchloric acid. 15 The decomposition rate of the bastnasite concentrate is determined by the following leaching method and is expressed by the leaching efficiency of rare earths. The leaching process was carried out under the conditions of initial hydrochloric acid concentration of 9.0 mol/L, liquid–solid ratio of 20:1, leaching temperature of 90 °C, leaching time of 60 min, and stirring rate of 300 rpm.…”

Section: Methodsmentioning

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: Methodsmentioning

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 amounts of Ce 4+ in roasted ore were determined by titration with ferrous ammonium sulfate without the addition of perchloric acid. 28 DRBC were expressed by hydrochloric acid leaching experiments carried out under the condition that is 9.0 mol/L HCl, temperature 90 °C, time 60 min, liquid–solid 20:1, and stirring rate 300 rpm. 13 DRBC (μ) and ORC (φ) were calculated with the following equations where μ and φ are DRBC and ORC, respectively; m 1 is the mass of the roasted ore, m 2 is the mass of the bastnasite concentrate; ω 1 is the mass fraction of Ce in the bastnasite concentrate, ω 2 is the mass fraction of Ce 4+ in the roasted ore; C 1 represents the concentration of REEs in leaching filtrate, C 2 represents the concentration of REEs in roasted ore; S is the mass of roasted ore, and L is the volume of hydrochloric acid solution.…”

Section: Experimental Sectionmentioning

confidence: 99%

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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“…Based on the non-equilibrium thermodynamics, the established mass and energy conservation equations from the former publication [4] can be derived as below and the details can be found in the previous research [10].…”

Section: Governing Equationsmentioning

confidence: 99%

“…The physical model, initial and boundary conditions and parameters in the simulation are listed in ref [10], the mathematic and physical models related to coupling mechanism between the heat and mass transfer, and the molecular polarization in a lignite thin layer were developed as above. The governing equations and boundary conditions would be solved by the finite element commercial software COMSOL Multiphysics.…”

Section: Physical Model and Initial And Boundary Conditionsmentioning

confidence: 99%

LNT microwave-multiphase transport model for the microwave drying of lignite thin layer

Chen

Li³

2018

Proceedings of 21th International Drying Symposium

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The LNT microwave-multiphase transport model has been applied to the microwave drying of lignite thin layer. Microwave energy, temperature and moisture distribution were obtained to gain a comprehensive understanding on the heat and mass transfer mechanism of the drying process. The required drying time of experiments decreased by 50, 63, 67, and 83%, respectively, with the power level rising from 119 to 700 W, while that decreased by 60, 72, 76 and 86%, respectively, for simulation results. The temperature values of the corner and edge of the lignite thin layer were higher than that of the center region, which corresponded to the microwave energy distribution. The moisture ratio profiles, temperature profiles and temperature distribution indicated good agreement between the experimental and simulation results, providing conﬁdence in the modeling approach, which made it possible to obtain the moisture distribution successfully via simulation method.Keywords: microwave; lignite; thin layer.

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Non-equilibrium thermodynamics approach for the coupled heat and mass transfer in microwave drying of compressed lignite sphere

Cited by 25 publications

References 27 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

LNT microwave-multiphase transport model for the microwave drying of lignite thin layer

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