Pidgeon process

Thermal magnesium, i.e., magnesium produced by the Pidgeon process earlier and by the magnefherm process at present, constitutes only 30% of the total magnesium production. The rest is produced electrolytically in which the leading examples are (i) the Dow electrolytic reduction process, and (ii) Norsk hydro process. 

Silicothermic reduction is also an important technique for the production of ferroalloys. The production of low-carbon ferrochrome and of ferrovanadium are carried out by this technique. The overall reaction for the reduction of vanadium pentoxide by ferrosilicon to yield ferrovanadium can be represented as 

Examples of metals which are prepared by the metallothermic reduction of oxides include manganese, chromium, vanadium, zirconium, and niobium. In a manner similar to the production of magnesium by the Pidgeon process, some of the rare earth metals have been produced by the metallothermic reduction-distillation process. 

The metallothermic reduction of oxides is essentially a reaction involving only condensed phases. It follows therefore, that the entropy changes in these reactions are small and that the differences in the heats of formation of the pertinent compounds determine the feasibility of a given reaction. Among the metallic reductants, calcium forms the oxide whose heat of formation is the most negative. As a first approximation, calcium may be considered to be the most effective reducing agent for metal oxides. 

One of the early applications of calcium as a reducing agent has been in the preparation of vanadium metal from vanadium pentoxide  

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Three basic processes exist for the thermal reduction of magnesium oxide the Pidgeon process, the Magnetherm process, and the BoKano process. 

A vacuum-retort process (Pidgeon process) was used during World War II for the production of magnesium and calcium. SiHcon, in the form of ferrosihcon, was used as the reducing agent instead of carbon to avoid the problem of cooling magnesium vapor in the presence of carbon dioxide ... 

An industrial example of the reduction of stable oxides to form a metallic element as a vapour, is the Pidgeon process for the production of magnesium. 

In the Pidgeon process discussed above, a secondary side reaction occurs between the CaO and Si02 forming dicalcium silicate ... 

PIDGEON PROCESS. Also referred to as ferrosilicon process or silicothermic process. Process for the production of high-purity magnesium... 

Derivation (1) Electrolysis of fused magnesium chloride (Dow seawater process) (2) reduction of magnesium oxide with ferrosilicon (Pidgeon process). 

In the thermal reduction process, reaction (14.4), magnesium oxide (as a component of dolime) reacts with a metal such as silicon, which is present in ferrosilicon, to produce magnesium metal. The two thermal methods in operation today are the Pidgeon and Magnetherm processes. The Pidgeon process is a batch process in which dolime and silicon (usually ferrosilicon) are briquetted and fed into a gas-fired or electrical heat retorts. The retort is... 

Electrolysis must be developed and optimized to be able to compete with thermal routes such as the Pidgeon process. Better control of the levels of dissolved oxygen and hydrogen containing species is of cmcial importance for achieving a high current efficiency. The cell life and especially the service life of the anodes must be increased. 

Magnesium production (Pidgeon process) retorts llOO C oxidation... 

Pidgeon process A process used for the production of magnesium developed by Canadian scientist Lloyd Montgomery Pidgeon (1903-99) in 1941. It involves the high tempera-mre reaction of silicon and magnesia to form silica and magnesium ... 

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