The project "Dezincification of steel scrap" developed a new pre-zincification method which allows the recovery of zinc used to prevent the corrosion of steel. This efficient recycling technology protects primary raw material resources. In addition, the foundry industry is supplied with a high quality raw material in the form of dezinced defined sheet qualities which generate higher sales proceeds. The generated zinc-containing solutions are returned to the primary zinc recovery process using the new method of acid steel dezincification, the so-called bypass pre-dezincification. Thus waste-free zinc recycling is achieved.
In 2010 a plant for acid dezincification was established on a semi-industrial scale. The planning throughput was 24 tons per day. Subsequent reaction-kinetic tests and parameter studies have shown that a maximum throughput of 400 tons per day can be achieved. The costs of the procedure for dezincification of one ton of steel scrap amount to approximately five euros. This process results in sulphuric acid solutions with 120 gram zinc per liter and steel scrap with a more than 98 per cent degree of dezincification. Two international patents "Acidic Dezincification" and "Procedures for Selective Acidic Dezincification of Steel Scrap" were issued for this procedure.
Compared to the standard technology of secondary zinc extraction energy demand is reduced by approximately 75 per cent, less coal and other aggregates are needed. The proces-related zinc application increases from 75 to about 98 per cent and a significant decrease of CO2 emissions compared to the current process chain is achieved.
Implementation of the research results is already foreseeable. Volkswagen AG is currently looking for a suitable site to set up an industrial dezincification plant in an extrusion plant. It is to be put into operation in 2013.