Zinkframställning

Zinkframställning refers to the industrial processes used to extract and refine zinc metal from its ores. The primary zinc ore is sphalerite, also known as zinc blende, which is a zinc sulfide mineral. Other zinc-bearing minerals like smithsonite and hemimorphite are also used.

The process typically begins with the mining of zinc ores. These ores are then concentrated through physical methods such as froth flotation to increase the zinc content and remove impurities like iron and lead. The concentrated ore is then subjected to roasting, where it is heated in the presence of air. This converts the zinc sulfide into zinc oxide, releasing sulfur dioxide, which is often captured and used to produce sulfuric acid.

Following roasting, zinc oxide is then smelted to produce metallic zinc. Two main methods are employed for this smelting: pyrometallurgy and hydrometallurgy. The pyrometallurgical route, known as the horizontal retort process or the vertical retort process, involves heating the zinc oxide with carbon at high temperatures to reduce it to zinc vapor, which is then condensed into molten zinc. The hydrometallurgical route, which is more common today, involves leaching the zinc oxide with sulfuric acid to form a zinc sulfate solution. This solution is then purified to remove impurities, and the zinc is recovered through electrolysis. In this electrolytic process, an electric current is passed through the purified zinc sulfate solution, causing zinc metal to deposit onto cathodes. The deposited zinc is then melted and cast into ingots.

The resulting zinc metal can be used in various applications, including galvanizing steel to prevent corrosion, in alloys like brass, and in the production of zinc oxide for rubber and chemical industries.