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AssigneeOutotec Oyj
InventorsBror Nyman, Stig-Erik Hultholm, Juhani Salmi, Jarmo Sivonen
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The invention relates to a method for the removal of metals from their aqueous solution with lime precipitation, in conditions where a precipitate of metal hydroxide and gypsum is formed, which settles well and is easy to filter. The metals are precipitated from their aqueous solutions at a high pH value and the slurry is recirculated several times in the precipitation space, whereby the gypsum is precipitated as separate crystals instead of a solid layer. The method is particularly suitable for neutralization of the aqueous solution from the pickling of refined steel. Using this method enables the removal of metals and fluoride from the water in question.
A method for the removal of metals from their aqueous solution as metallic hydroxides and gypsum using lime precipitation, comprising introducing a lime compound and a majority of a feed solution containing nickel, iron and chrome into a first neutralization stage to form a metallic hydroxide-gypsum slurry having a pH at least 10.5, feeding the balance of the feed solution and the slurry from the first neutralization stage in its entirety to a second neutralization stage where the pH of the slurry is adjusted to at least 9.5 and a precipitate forms;
Dependencies are inferred from the claim text.