1 research outputs found
Rinse water regeneration in stainless steel pickling
Since stainless steel must be rinsed with water after pickling operation with mixtures of nitric and hydrofluoric
acids, the present investigation was undertaken to define a major step towards the close loop circulation of water in
steel plant. This can be done by a new procedure for removing also nitrates from rinse water in such a way that
clean water can be recycled back to rinsing use. The concentrated part of used rinse water will be fed to pickling
acid regeneration plant, where nitric and hydrofluoric acids can be separate and recycled back to the pickling use.
The tests were carried out mainly in one of Outokumpu鈥檚 production plants in Sweden. 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. Since the composition
of permeate is not applicable for direct reusage in the rinsing zone, post-treatment methods were examined. Amberlite
IRA67 ion exchange resin was tested for treatment of reverse osmosis filtrate (pH adjustment). For the recovery of
the mixed acids, the concentrate of reverse osmosis was further treated with electrodialysis. On the basis of these
results, a regeneration concept was developed, in order to close the rinse water loop. The proposed rinse water
recycling concept reduces the overall usage of water.Authors wished to thank to the Research Fund
for Coal and Steel for contract 7210-PR/301
(01.E/06).Peer reviewe