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The Submerged-arc furnace for phosphorus production is a particular sub-type of electric arc furnace used to produce phosphorus and other products. Submerged arc furnaces are mainly used for the production of ferroalloys. The nomenclature ''submerged'' means that the furnace's electrodes are buried deep in the furnace ''burden''. A reduction reaction takes place near the tip of the electrodes to facilitate the furnace's process. == Main reaction == Large-scale production of phosphorus uses the Wöhler process.〔 〕 In this process, apatites (nearly always fluorapatite) are reduced in the presence of carbon (coke) and silica (gravel). This is performed in a submerged-arc furnace at temperatures of between 1150 and 1400C. The main internal reaction is described below: :Ca10(PO4)6F2 + 15C + 9SiO2 → 3P2(g) + 9() + CaF2 + 15CO(g) This main reaction produces a liquid calcium silicates slag, carbon monoxide gas and the desired product, phosphorus gas. This process also has intermediate reactions, and as such, the phosphate rock created has impurities. One such impurity—and the most important one—is iron oxide. Iron oxide impurities are reduced and form iron phosphides. The resulting second liquid product is called ferrophosphorus. Iron is considered an impurity and undesirable because it requires additional carbon and power for reduction. Thus, it locks up a certain percentage of the phosphorus. Another impurity is alumina - this increases the slag bulk but reduces the melting point. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Submerged-arc furnace for phosphorus production」の詳細全文を読む スポンサード リンク
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