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Fluoride emissions from Pidgeon process for magnesium production
School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
2012 (English)Conference paper, Presentation (Refereed)
Abstract [en]

Primary magnesium is nowadays produced in China via Pidgeon process. An important reaction in the process is silicothermic reduction of MgO from dolime near 1200ºC under pressure of 2-10 Pa to generate Mg vapor. Fluorite, ranging 2-3% (mass fraction), is usually mixed with the raw materials to catalyze the reaction. Under the process conditions, CaF2 in the fluorite may form some fluorides to vaporize, thus polluting air. The fluorides remaining in the solid process waste, the Mg slag, may be dissolved to cause water pollution.In the present study, experiments were performed by using retorts of pilot scale in a maffle furnace to simulate the Pidgeon process for primary Mg production. The test materials, briquettes of 5.6-10 kg made of dolime, ferrosilicon and fluorite, were charged in the retorts and heated under conditions similar to the industry operation. Fluoride minerals in the Mg slag from the simulation experiments were identified by XRD and SEM-EDS techniques. Quantities of some F-containing phases formed in the process under equilibrium condition were calculated by FactSage 6.2 thermodynamic package. Fluoride distributions were determined to establish an F-balance among the input and output materials. Besides, slag samples from a magnesium plant were also characterized, including leaching test according to EN 12457-2.Based on these results, fluoride impacts on the environment were evaluated and discussed. Suggestions were also presented to minimize the environmental impacts from primary Mg production using the Pidgeon process.

Place, publisher, year, edition, pages
Keyword [en]
Chemistry - Environmental chemistry
Keyword [sv]
Kemi - Miljökemi
Research subject
Process Metallurgy
URN: urn:nbn:se:ltu:diva-40024Local ID: efe27882-9b63-437b-ab20-912f8ed0fe32OAI: diva2:1013546
International Conference on Solid Waste Technology and Management : 11/03/2012 - 14/03/2012
Godkänd; 2012; 20120410 (yang)Available from: 2016-10-03 Created: 2016-10-03Bibliographically approved

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