High-Temperature Studies of Metallurgical Processes: Part I. The Thermal Reduction of Magnesium Oxide With Silicon

Abstract

The rate of reaction ( a ) has been studied over the temperature range 1140-1460' C, by following the loss in weight of the reactants in high vacuum.( a T h e loss in weight of the reactants was found to be greater than that which can be accounted for by the above reaction. The excess weight loss was found to be due to a brownish, glassy deposit which appeared outside the reaction zone. This material was analyzed by X-ray diffraction and found to be an intimate mixture of Mg?SiOs and Si. Experiments conducted showed that both of these materials are not appreciably volatile a t 1350' C. This transfer of silicon and silicate is postulated to occur by the formation of gaseous SiO formed from thc reaction mixture. Based on this assumption a possible mechanism for this reaction is postulated.

High-Temperature Studies of Metallurgical Processes: Part Ii. The Thermal Reduction of Calcined Dolomite With Silicon

“…SiO gas is stable a t these temperatures according to a number of investigators (23,24). In a previous publication (16), it was shown that SiO is distilled froill the reaction inixture of lMgO + Si a t temperatures above 1300" C. In the present work,…”

“…The esperilnental procedure adopted for the determination of the reaction rate has been previously described (16). Briefly, the method consisted of deterlnining the weight loss with time of a briquetted reaction mixture due to the evolution of magnesium, by means of a calibrated helical steel \\lire spring suspended in a vacuum furnace.…”

“…without a binder. The \\eight of each briquette was approximately 17 g. Three briquettes \\,ere ~~s e d for each experiment and these were arranged as prel iously described (16).…”

Global warming impact of the magnesium produced in China using the Pidgeon process

“…This process (Pidgeon and Alexander, 1944)-later known as the Pidgeon process-is based on reducing oxide of magnesium using silicon by supplying the thermal energy required for the reaction (Toguri and Pidgeon, 1961) as shown by the following equation:…”

Solar Aluminum Production by Vacuum Carbothermal Reduction of Alumina—Thermodynamic and Experimental Analyses

“…[7] The silicothermic reduction of CaOMgO in the industrial Pidgeon process for magnesium was achieved by reacting CaO-MgO with ferrosilicon in evacuated retorts at 1450 K to 1800 K (1177°C to 1527°C) and less than 1.33 9 10 À4 bar. [8][9][10] The production of Si by vacuum carbothermal reduction of SiO 2 in the range 1997 K to 2263 K (1724°C to 1990°C) at 3 9 10 À3 bar yielded Si/SiO 2 mixtures condensed from the gas phase, with 79 wt pct Si content. [11] As will be shown in the following analysis, reaction [1] is highly endothermic (DH 298 K = 1344 kJ/mol) and proceeds at higher than approximately 1500 K (1227°C) when operating at 10 À4 bar.…”