Process for the selective recovery of the salt constituents from used hardening shop salts which contain nitrite-nitrate
AssigneeDurferrit GmbH Thermotechnik
InventorsMatthias Kremer, Georg Wahl, Eberhard Gock, Stefan Wigger, Jorg Kahler
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Abstract
In order to recover in an environmentally sound and economic manner used hardening shop salts which contain nitrate-nitrite, the salts, comminuted to particle sizes of from 1 to 50 mm, are dissolved in a mixture of nitric acid and hydrogen peroxide without nitrogen oxides arising, and, by evaporation and cooling, potassium nitrate, sodium chloride, and sodium nitrate are obtained sequentially by fractional crystallization.
Claims14
A process for the selective recovery of salt constituents from used salts containing potassium, sodium, nitrates, nitrites chlorides, and hydroxides comprising
- comminuting a solid used salt mixture to a particle size from 1 to 50 mm,
- dissolving said comminuted used salt mixture in an aqueous starting solution comprising nitric acid and hydrogen peroxide at from 40.degree. to 90.degree. C. to form a used salt solution, removing insoluble residue from said used salt solution,
- cooling said used salt solution to from -10.degree. C. to +20.degree. C. to form a potassium nitrate precipitate,
- evaporating water from said solution at from 60.degree. to 120.degree. C. to concentrate said used salt solution and to form a sodium chloride precipitate, and
- adding concentrated nitric acid to said concentrated used salt solution to form a sodium nitrate precipitate.
Dependencies are inferred from the claim text.