Selenium - an interesting but undervalued by-product of copper production

摘要

Selenium is used in many applications, e.g. for pharmaceutical products, in the electrical and optical industries, as a supplement for animal fodder, in diagnostic radiography and glass production. Selenium is an important trace element as a nutrient in human and animal foodstuffs and an essential element in modern life with many interesting applications. Selenium production, i.e. the recovery of raw selenium as a by-product of the treatment of copper concentrates at Norddeutsche Affmerie AG in Hamburg and the subsequent processing into saleable selenium products at Retorte Ulrich Scharrer GmbH in Nuremberg, has a long tradition at Norddeutsche Affmerie. Since 1936, when processing copper concentrates, selenium has been extracted by treating anode slimes from the copper tankhouse and subsequently processing into a selenium metal or chemicals. Nowadays, crude selenium is produced from anode slimes in the Top Blown Rotary Converter, in which the selenium is oxidised and scrubbed in a wet off-gas system. The selenium is finally precipitated from the scrubber solution by reduction with SO_2. Retorte started selenium production in 1949. In 1974 Retorte was acquired by NA and is still a wholly-owned subsidiary. In 1993 the NA Group's selenium refining and processing activities were concentrated in Nuremberg. Today, Retorte is the leading specialist worldwide for pure selenium and selenium chemicals. Retorte's speciality is a high-grade pure oxygen-free selenium - a product with outstanding electrical properties. Some 90 percent of global selenium output is extracted from copper concentrates. In the last ten years the selenium output of NA's primary smelter has nearly doubled, in particular, due to the expansion of its concentrate processing capacity. In recent years, Retorte has become a well-reputed producer of selenium by-products for other copper smelters as well. Today, Retorte receives crude selenium from copper smelters around the world as its starting material. In 2003 Retorte produced a total of 200 t of selenium metal and 500 t of selenium chemicals of all types and qualities.