|
Zinc smelting is the process of converting zinc concentrates (ores that contain zinc) into pure zinc. Zinc smelting has historically been more difficult than the smelting of other metals, e.g. iron, because in contrast, zinc has a low boiling point. At temperatures typically used for smelting metals, zinc is a gas that will escape from a furnace with the flue gas and be lost, unless specific measures are taken to prevent it. The most common zinc concentrate processed is zinc sulfide,〔.〕 which is obtained by concentrating sphalerite using the froth flotation method. Secondary (recycled) zinc material, such as zinc oxide, is also processed with the zinc sulfide.〔.〕 Approximately 30% of all zinc produced is from recycled sources.〔.〕 There are two methods of smelting zinc: the pyrometallurgical process and the electrolysis process.〔 Both methods are still used.〔〔.〕 Both of these processes share the same first step: roasting. ==Roasting== (詳細は: : Approximately 90% of zinc in concentrates are oxidized to zinc oxide. However, at the roasting temperatures around 10% of the zinc reacts with the iron impurities of the zinc sulfide concentrates to form zinc ferrite. A byproduct of roasting is sulfur dioxide, which is further processed into sulfuric acid, a commodity.〔 The linked refinery flow sheet shows a schematic of Noranda's eastern Canadian zinc roasting operation〔Noranda's zinc roasting operation illustrated http://www.norandaincomefund.com/pdfs/refinery_flowsheet.pdf〕 The process of roasting varies based on the type of roaster used. There are three types of roasters: multiple-hearth, suspension, and fluidized-bed.〔 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「zinc smelting」の詳細全文を読む スポンサード リンク
|