Production of Magnesium Metal from Turkish Calcined Dolomite using Vacuum Silicothermic Reduction Method Onuralp Yücel a , Selen Yiğit b and Bora Derin c Istanbul Technical University, Department of Metallurgical and Materials Engineering, Istanbul, 34469, TURKEY a yucel@itu.edu.tr, b selenyigit@hotmail.com, c bderin@itu.edu.tr Keywords: calcined dolomite, silicothermic reduction, FeSi, Abstract. In the present study, the production of magnesium metal from Turkish calcined dolomite containing 43.20 % MgO and 47.46 % CaO via Pidgeon process was studied under the pressure of 1 mbar. In the experiments, Turkish ferrosilicon containing 75 % Si and 24 % Fe was used as reducing agent. Effects of FeSi addition (90-150 % of stoichiometric requirement of silicon) and time (60-240 min.) were investigated on recovering of metallic magnesium from calcined dolomite (dolime) at the temperature of 1200 °C. Effects of fluxing additive (CaF 2 ), calcined magnesite and different temperatures on Mg recoveries and concentrations were also studied using with 100 % of stoichiometric requirement of silicon for 180 min. It was found that magnesium recovery increases with increasing FeSi addition, temperature, time, CaF 2 addition and decreases with increasing calcined magnesite additions under the pressure of 1 mbar. Introduction Magnesium is a light weight material and it finds wide applications in many fields such as aircraft, rockets and automobile industry, the desulphurisation and nodularization of iron and steel, corrosion applications, production of Al-Mg alloys and some chemical applications [1, 2]. Although there are considerable amount of dolomite and magnesite reserves [3], magnesium metal is not being produced in Turkey, yet. The present work aims to investigate the parameters affecting the silicothermic reduction of calcined dolomite using Turkish ores and FeSi sources. In the experiments, charge composition, amount of reducing and fluxing additives, time and temperature were taken as variables in order to obtain high recovery efficiencies. Theoretical investigations ∆G°-T diagram for oxide formation indicates that MgO reduction with silicon is only possible beyond 2140 °C. In order to obtain magnesium metal at lower temperatures for Eq. 1, partial pressure of the magnesium vapour and/or activity of SiO 2 should be lowered. For this aim, vacuum technique and additions of lime for formation of a basic slag (Ca 2 SiO 4 ) are needed. In practice the lime is added in the form of calcined dolomite (dolime, MgO.CaO) and silicon is added as reducing agent in the form of ferrosilicon alloys [4-7]. 2 MgO + Si = 2 Mg (g) + SiO 2 (1) By using the FactSage 5.2 thermodynamic program [8], the Eq. 2 was simulated for different temperatures under 1 mbar of vacuum atmosphere. As can be seen in Fig. 1, reduction of magnesium oxide starts at 1000 °C and it totally reduced to metallic Mg in gas form at 1300 °C. 2MgO.CaO + FeSi (75% Si) = 2Mg (g) + Ca 2 SiO 4 + Fe (2) Materials Science Forum Vols. 488-489 (2005) pp 39-42 Online available since 2005/Jul/15 at www.scientific.net © (2005) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/MSF.488-489.39 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 128.250.144.144, University of Melbourne, Melbourne, Australia-14/09/14,11:46:46)