Investitionsvorhaben Beizsaeureaufbereitung Abschlussbericht

A very severe drawback of metal construction parts made of iron and steel is their susceptibility to corrosion. There are a number of processes for attaining long-term material protection. In the case of hot-dip galvanisation the parts are coated with negatively electric metals, chiefly zinc. The surface of the metal being subjected to this process must be bright. To achieve this the parts are first pickled in a hydrochloric acid bath. In the course of time the hydrochloric acid used for the pickling becomes spent as rust, hammer scales, iron and so on are deposited in the solution. This waste mixture has to be disposed of. In the techniques most commonly used up to now (oil-emulsion separation, CP units) the waste mixture is neutralized/precipitated and subsequently deposited on an special dump. The HYC-process recovers from the waste mixture valuable raw materials (iron chloride and zinc chloride) which can then be reintegrated in the processing cycle. A multiphase process removes the secondary constituents fouling the product or interfering with the separation process. The liquid is passed through an activated charcoal adsorption unit to remove the grease, inhibitors etc. from it. In a two-phase carburizing process heavy metals introduced through the steel being galvanized and the zinc used for this purpose are precipitated. The core of the unit consists of a zinc specific liquid-liquid extraction in which the iron chloride and zinc chloride are separated from one another. After passing through several re-treatment phases in an evaporation unit both the FeCl_2 and the ZnCl_2 solutions have reached the concentration desired. (orig.)SIGLEAvailable from TIB Hannover: RO 2148(6024) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekUmweltbundesamt, Berlin (Germany)DEGerman