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Kinetics and mechanism of natural wolframite interactions with sodium carbonate

International Journal of Minerals,Metallurgy and Materials 2019年第11期26卷 1364-1371页

作者： evgeniy nikolaevich selivanov Kirill Vladimirovich Pikulin Lyudmila Ivanovna Galkova Roza Iosifovna Gulyaeva Sofia Aleksandrovna Petrova Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences

The kinetics and mechanism of natural wolframite interactions with sodium carbonate during air heating were studied.X-ray phase and X-ray microanalysis were used to establish that the initial monocrystalline wolframite consists of Fe0.5 Mn0.5 WO4 and Fe0.3 Mn0.7 *** thermal analysis showed that the interaction of wolframite with sodium carbonate begins above 450°C with the formation of tungstate,sodium ferrite,iron oxides,and *** experiments on sintering with the subsequent removal of water-soluble compounds(leaching)tracked the change in the structure of *** atomic ratio of Fe/Mn in wolframite does not change up to 600°C,and subsequently decreases to 0.2 during heating,which allows the mechanism of the process to be identified and indicates the greater reactivity of wolframites with an increased proportion of *** analysis with data processing using non-isothermal kinetics established that the interaction of wolframite with sodium carbonate in an air stream proceeds via a two-stage mechanism,wherein the first stage is limited by diffusion(activation energy,E=243 kJ/mol)and the second stage is limited by autocatalysis(activation energy,E=212 k J/mol)due to the formation of a Na2 WO4–Na2 CO3 eutectic.

关键词： wolframite structure sodium carbonate sintering thermal analysis kinetics

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Thermal state calculation of chamber in small thrust liquid rocket engine for steady state pulsed mode

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Chinese Journal of Aeronautics 2019年第2期32卷 253-262页

作者： Alexey Gennadievich VOROBYEV Svatlana Sergeevna VOROBYEVA Lihui ZHANG evgeniy nikolaevich BELIAEV Department of Rocket Engines Moscow Aviation Institute School of Astronautics Beihang University

This paper presents a method of thermal state calculation of combustion chamber in small thrust liquid rocket engine. The goal is to predict the thermal state of chamber wall by using basic parameters of engine: thrust level, propellants, chamber pressure, injection pattern, film cooling parameters, material of wall and their coating, etc. The difficulties in modeling the startup and shutdown processes of thrusters lie in the fact that there are the conjugated physical processes occurring at various parameters for non-design conditions. A mathematical model to predict the thermal state of the combustion chamber for different engine operation modes is developed. To simulate the startup and shutdown processes, a quasi-steady approach is applied by replacing the transient process with time-variant operating parameters of steady-state processes. The mathematical model is based on several principles and data commonly used for heat transfer modeling: geometry of flow part, gas dynamics of flow, thermodynamics of propellants and combustion spices, convective and radiation heat flows, conjugated heat transfer between hot gas and wall, and transient approach for calculation of thermal state of construction. Calculations of the thermal state of the combustion chamber in single-turn-on mode show good convergence with the experimental results. The results of pulsed modes indicate a large temperature gradient on the internal wall surface of the chamber between pulses and the thermal state of the wall strongly depends on the pulse duration and the interval.

关键词： Combustion chamber Film cooling Mathematical model Nonstationary thermal mode Small thrust liquid rocket engine Steady pulse mode Thermal state

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Kinetics and mechanism of oxidation for nickel-containing pyrrhotite tailings

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International Journal of Minerals,Metallurgy and Materials 2021年第9期28卷 1469-1477页

作者： Alexander M.Klyushnikov Rosa I.Gulyaeva evgeniy N.selivanov Sergey M.Pikalov Institute of Metallurgy of the Ural branch of the Russian Academy of Sciences Yekaterinburg 620016Russia

X-ray powder diffraction,scanning electron microscopy,energy dispersive spectroscopy,thermogravimetry,differential scanning calorimetry,and mass spectrometry have been used to study the products of nickel-containing pyrrhotite tailings oxidation by oxygen in the *** kinetic triplets of oxidation,namely,activation energy(E_(a)),pre-exponential factor(A),and reaction model(f(α))being a function of the conversion degree(α),were adjusted by regression *** case of a two-stage process representation,the first step proceeds under autocatalysis control and ends atα=*** kinetic triplet in the first step is E_(a)=262.2 kJ/mol,lg A=14.53 s^(−1),and f(α)=(1-α)^(4.11)(1+1.51×10^(-4)α).For the second step,the process is controlled by the two-dimensional diffusion of the reactants in the layer of oxidation *** kinetic triplet in the second step isЕa=215.0 kJ/mol,lg A=10.28 s^(−1),and f(α)=(-ln(1-α))^(-1).The obtained empirical formulae for the rate of pyrrhotite tailings oxidation reliably describe the macro-mechanism of the process and can be used to design automatization systems for roast-ing these materials.

关键词： pyrrhotite tailings oxidation thermogravimetry kinetics mechanism

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