Condensation Behavior of Magnesium Metal in Argon Gas
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AS the lightest structural metal in industrial applications,[1,2] magnesium is widely used in metallurgy, mechanical manufacturing, aerospace and other fields.[3] The main method for magnesium extraction is at present the Pidgeon process.[4] The production of magnesium by the Pidgeon process is mainly divided into two parts: calcination and reduction. The calcination process is calcined in a rotary kiln to produce dolime. The calcination temperature is 1150 °C, and the reaction is as follows. CaCO3 MgCO3 ðsÞ ! CaO MgOðsÞ þ CO2 ðgÞ:
½1
JI-BIAO HAN, TING-AN ZHANG, DA-XUE FU, JUN-HUA GUO, ZONG-HUI JI, and ZHI-HE DOU are with the School of Metallurgy, Northeastern University, Shenyang 110819, P.R. China and also with the Key Laboratory of Ecological Metallurgy of Multimetal Intergrown Ores of Ministry of Education, Shenyang 110819, P.R. China. Contact e-mail: [email protected] Manuscript submitted November 26, 2019; accepted September 25, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
The dolime is mixed with ferrosilicon and fluoride, and the following reactions take place in the retorts at 1200 °C vacuum condition. 2ðCaO MgOÞðsÞ þ SiðsÞ ¼ 2MgðgÞ þ 2CaO SiO2 ðsÞ: ½2 Magnesium vapor is produced in the reduction process and moves to the condensation temperature area for condensation and is finally crystalline in the end of the retorts. With the continuous development of the magnesium extraction industry, energy consumption and pollution have been greatly reduced.[5,6] However, the Pidgeon process involves vacuum conditions. After reduction, the vacuum has to be removed and crystalline magnesium and reduction slag removed, with raw materials loaded for further production. The production process is divided into two parts, and the reduction process takes place in vacuum, which makes the vacuum extraction process an intermittent process, with low production efficiency, low automation, high labor intensity and high energy consumption,[7] leading to the restriction of continuous production of magnesium. Therefore, in recent years, achieving a continuous process has become a serious issue in magnesium extraction processing. New technologies and processes for the continuous process of magnesium extraction
have been put forward by experts and scholars. Zhang et al.[8] carried out a one-step silicothermal reduction magnesium extraction study, which combined dolomite decomposition, magnesium reduction processes and kinetic analysis. It was found that a one-step method could reduce the time of calcination and reduction. Fu et al.[9–13] studied the thermodynamics and kinetics of the magnesium reduction process by the silicothermic method and put forward a new process for calcination-reduction-integrated magnesium extraction, which reduces the calcination step and saves energy. However, the above studies have been carried out in vacuum conditions and could not complete the real meaning of a continuous process, as a continuous process cannot be achieved in a vacuum. For continuous processing, it is necessary to smelt at atm
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