1. Field of the Invention
The present invention relates to a process for treating dust containing zinc and lead derived from a gas-cleaning installation in an iron or steel making process. In particular the treatment process involves a flotation separation treatment.
2. Description of the Prior Art
A process of this general type is already known, for example from Dutch Published Patent application No. 76 00876 (JA published applications Nos. 51-125603 and 52-066805, DE No. 2 603 096). This represents one of many attempts to separate all the zinc and lead individually by means of flotation in a flotation process. To date, such attempts have hitherto always failed, and for this reason the use of flotation processes for treating this type of waste gas dust has remained unsuccessful. In practice, where the zinc and lead-bearing dust is processed, this is achieved mainly by a thermal treatment in which the zinc and lead are removed selectively from the dust. The direct separation of zinc and lead from the dust-bearing gas by leaching has also been suggested.
Thermal processing of the dust entails considerable investment and high running costs, primarily energy costs. For this reason, physical/chemical processing methods, which can be considerably cheaper than thermal processes are currently being sought.
It has also been suggested that a hydrocyclone treatment is used to separate a zinc and lead rich fraction and a fraction containing little zinc and lead. However, this method also entails high investment costs and is in addition susceptible to malfunctioning.