The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 12, 2011
Filed:
Aug. 21, 2007
Hanns Wochner, Burghausen, DE;
Christian Gossmann, Emmerting, DE;
Wolfgang Stoiber, Eggenfelden, DE;
Hanns Wochner, Burghausen, DE;
Christian Gossmann, Emmerting, DE;
Wolfgang Stoiber, Eggenfelden, DE;
Wacker Chemie AG, Munich, DE;
Abstract
In a method for recovering acid from an aqueous etching mixture containing HF, HNO, HSiFand HNOwhich 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.