Kinetcis of silicothermic reduction of clacined dolomite in flowing argon atmosphere
The magnesium vapour extracted is removed using vacuum condition to condense as a dense metal. Thermodynamic analysis of this process has been carried out in the past to predict the distribution of the metal impurities in condensed magnesium. The results suggested that a number of impurities in different phases formed in the region between reaction zone and condenser. The thermodynamic results only are not sufficient to describe the process, and the knowledge of the kinetics of the Pidgeon process is required. Kinetics plays important role to give more insight to the process such as for process design and control.
Producing Pure Magnesium Through Silicothermic Under the Atmospheric Pressure
The majority of pure magnesium produced worldwide is made by using silicothermic method (Pidgeon process). However, the Pidgeon process suffers poor efficiency, low industrial concentration, and intermittent production. The main reason is that Pidgeon process requires to keep the reaction chamber in a vacuum state during the entire reduction process. By analyzing the thermodynamic reaction principle, we reveal that it is the low magnesium partial pressure instead of vacuum that is necessary for the silicothermic process. Based on this understanding, we develop a new technique that can produce pure magnesium under the atmospheric pressure by using silicothermic method. Flowing argon is used to carry away the magnesium vapor around the reactants, which reduces the local magnesium partial pressure. The magnesium production efficiency reaches 82.36% that is comparable to the widely used Pidgeon method, and high purity of magnesium with 99.97 wt% after melting is produced directly. The industrialized application of this exciting technique is expected to help the silicothermic to realize high efficiency, automated, and continuous production while at the same time completely change the poor production conditions, and reduce energy consumption and pollution.
HIGH-TEMPERATURE STUDIES OF METALLURGICAL PROCESSES: PART II. THE THERMAL REDUCTION OF CALCINED DOLOMITE WITH SILICON
The production of magnesium by the following reaction has been studied:The rate of reaction (a) was followed by continuous weight loss measurements of the reactants. Keeping the particle size of the reactants and size and shape of the charge constant, the following factors which affect the yield of magnesium were investigated: (1) temperature, from 1050–1560 °C; (2) pressure, from less than 1 µ to 261 mm of Hg; (3) catalysts, CaF2, BaF2, and MgF2; and (4) ferrosilicon grade, from 18.7% to 96.7% Si.It was found that the yield increased by a factor 1.55 for a 50° increase in temperature over the temperature range investigated. At temperatures below 1300 °C the yield falls linearly with increase in pressure, while at temperatures above 1300 °C the yield remains relatively constant until the pressure exceeds the equilibrium magnesium pressure. All fluoride additions were found to increase the yield, CaF2 being the most effective. The rate of the reaction was also found to have a direct relationship with the s...