Dezincification - Zinc Recycling from New Scrap

摘要

In the past three decades automobiles and appliance manufacturers have been continuously increasing the use of galvanized steel. As a result the amount of primary and secondary steel scrap returning to steel producers has increased equally. In the process of manufacturing a car body approximately 40 percent of zinc coated sheet ends up as scrap - the new scrap. In the current project a new, patented process for acid dezincification is introduced in Germany as collaboration between the automotive industry, scrap trade, zinc metallurgy, foundry industry, machine and plant engineering and research facilities. The concept of the new process is to use processing acids from the zinc electrolysis of the zinc smelter for the dezincification of new scrap from automotive industry and to supply the foundry industry with the produced zinc free scrap. Added value for the dezincified steel scrap in the order of 25 EUR per ton of scrap is achieved. Additional benefits arise from the zinc, which is recycled in a parallel loop as zinc sulfate. For example, zinc sulfate can be used as a raw material for the pigment industry. Beside the economic also environmental benefits are enormous. Energy cost can be cut by up to 74% due to the low temperature in the dezincification process and CO_2 emissions can be reduced severely by up to 88% in comparison to the conventional Waelz process. In a pilot plant the dezincification process based on sulfuric acid has been tested and further developed. Due to good results, a demonstration plant is being designed right now for processing zinc coated metal scrap from a renowned auto maker in Germany.