Eco-efficient technology for recovering acids and metals from rinse water in stainless steel pickling
The most common pickling liquid for stainless steels is today mixed acid, which is a mixture of nitric and hydrofluoric acid. After pickling stainless steel must be rinsed in order to clean and get rid of all acids on the steel surface. The objective for this project was to take a major step towards the closed loop circulation of water in steel plant. This can be done by using a new method for removing nitrates from rinse water in such a way that clean water can be recycled back for rinsing use. The concentrated part of the used rinse water will be fed to pickling acid regeneration plant, where nitric and hydrofluoric acids can be separated and recycled for pickling use. A membrane technique was used for rinse water treatment. A filtering system based on reverse osmosis was developed to separate the acids and metals from the rinsing water. A pre-filtering method, necessary for reverse osmosis, was tested. The lifetime of membranes was examined. As the composition of permeate is not applicable for direct reusage in the rinsing zone, post-treatment methods were examined. For example, ion-exchange resins were tested for the treatment of reverse osmosis filtrate (pH adjustment). For the recovery of the mixed acids the concentrate of reverse osmosis was additionally treated with electrodialysis. On the basis of these results, a regeneration concept was developed to close the rinse water loop. Investment and operational costs show benefits from the studied production line.
Bibliographic Reference: EUR 21947 EN (2006), 109pp. Euro: 25
Availability: Katalogue Number: KI-NA-21947-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 92-79-00616-9
Record Number: 200618560 / Last updated on: 2006-04-28
Original language: en
Available languages: en