The joint project "Copper slags" developed a method to avoid metal losses in metallurgical slag based on the example of copper recovery. The majority of metals produced in the world today are extracted by smelting. The slags formed in the process still contain a share of the valuable metals, which means these slags represent an important source of secondary raw materials. Their potential can be better exploited by targeted separation and concentration of the valuable elements in marketable product phases.
The project partners developed an efficient and flexible treatment process for slags from primary metal production, which maximises the total output of valuable metallic components like copper compared to conventional processes.
The innovative part of this method is the combination of a conventional electric furnace with a downstream stir reactor, whose magnetic field helps to achieve a better mixture and then to separate the metals from the slag tank. Adding reducing agents in parallel causes the reduction of oxidised, chemically bound metals.
The innovative combination of processes results in increased flexibility and improved process quality. Besides increasing the output of valuable metals, the co-product iron silicate stone is also produced. Due to its low heavy metal content, this can be used for constructing roads and hydraulic engineering applications.
The process conserves natural resources because both ore concentrates and natural rock can be substituted. The process combination can also optimize output in other slag systems. Furthermore, slag heaps can also be treated using this method in the sense of "urban mining".