Patent ID: 9139916
Filing Date: 2015-09-22
Classification: C23G

Abstract:
1. A method for recycling stainless steel pickling baths, including the associated rinsing baths and air washers, having the following steps: a) converting the free acids present in the liquid waste streams to be treated into the metal salt form before recycling, b) separating water from the largely acid-free metal salt solution obtained in order to obtain a concentrated metal salt solution, and c) supplying the concentrated metal salt solution to a thermal method to obtain metal oxides and free acids, and d) separating the waste stream from the pickling baths to be recycled in a suitable separating system into a first partial stream having the metal salts to be recycled and a second partial stream having free acids, wherein the second partial stream is conducted from the separating system back into the pickling bath, while the first partial stream is collected for further treatment according to steps a) to c), wherein the residues of free acids existing in the first partial stream are converted into metal salts according to step a) using metal hydroxides, oxides, or carbonates of the metals used in the pickling bath, wherein the first partial stream is mixed before step a) with the acid waste stream from the rinsing baths/air washers, wherein the treated first partial stream having metal salts is converted in a system for separating water, according to step b), into a concentrated metal salt solution near the solubility limit of the metal salts.