Distillation: processes – separatory – Distilling to separate or remove only water – From nitric acid
Reexamination Certificate
2011-04-12
2011-04-12
Manoharan, Virginia (Department: 1771)
Distillation: processes, separatory
Distilling to separate or remove only water
From nitric acid
C159SDIG019, C203S015000, C203S071000, C423S341000, C423S394200, C423S483000, C423S488000, C423SDIG010
Reexamination Certificate
active
07922876
ABSTRACT:
In a method for recovering acid from an aqueous etching mixture containing HF, HNO3, H2SiF6and HNO2which has been used for purifying polycrystalline silicon, the used etching mixture is distilled progressively so that approximately from 20 to 50 wt. % of the mixture is distilled off as dilute acid containing more than 90 wt. % of the silicon dissolved as hexafluorosilicic acid in a first fraction, and the water contained in the used etching mixture having been reduced by approximately 10-30 wt. %, this water-depleted mixture is then concentrated by evaporation to a residue of about 1 to 5 wt. % of the initial amount of used etching mixture during which a second fraction is distilled off, and the residue is disposed of.
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Patbase abstract corresponding to DE19852242A1.
Patbase abstract corresponding to JP9-302483.
Patbase Abstract corresponding to FR2659956.
U.S. 5,411,726 corresponding to EP 0 610 748 A1.
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Gossmann Christian
Stoiber Wolfgang
Wochner Hanns
Brooks & Kushman P.C.
Manoharan Virginia
Wacker Chemie AG
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