Abstract
Especially in the production of MnZn- and NiCuZn-ferrites the purity of applied ferric oxide is of vital importance to achieve high quality products. Usually synthetic iron oxides produced by the spray roasting process of spent pickle liquor in flat carbon steel production are used. Spray roasting plants therefore have to be equipped with a pickle liquor purification process to remove elements like Ti, Al, Cr, P simultaneously by means of precipitation. Colloidal silica is bonded in parallel to a certain degree by means of adsorption on precipitated metal hydroxides. In recent years plenty of new steel grades have been developed requiring more and/or new alloying elements leading to an additional contamination of the pickle liquor and thus pushing the purification system to the limit. In order to overcome possible troubles additional treatment of spent pickle liquor prior to spray roasting has to be considered. In the case of Ni and Cu a removal of the pickle liquor by membrane electrolysis was investigated by operating a small pilot plant. Cu was removed completely and Ni removal was up to 20%. In case of Ni for quantitative removal also organic complex forming agents like Dimethylglyoxime can be applied.
