Process for the purification of granular silicon dioxide

US4956059A · kind A · utility

Assignee

• Heraeus Quarzschmelze GmbH · DE

Inventors

• Wolfgang Englisch · Kelkheim, DE
• Helmut Leber · Hanau, DE
• Klaus Reimann · Eindhoven, NL
• Fritz Simmat · Gelnhausen, DE

Key dates

• Filing date: Sep 21, 1989
• Grant date: Sep 11, 1990
• Expiry date: Sep 21, 2009

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/80
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Granular silicon dioxide is placed in a treatment chamber which is heated to a temperature ranging from 700.degree. to 1300.degree. C. The chamber is then rotated for a prescribed period of time to mix the grains while a gaseous atmosphere of chlorine and/or hydrogen chloride is passed through the treatment chamber. The mixing period is followed by a resting period which is at least ten times longer than the mixing time. During the resting period the grains are exposed to a constant electric field having a strength of 600 to 1350 V/cm applied across the chamber. The foregoing cycle is repeated several times. For working the process a device is used which includes a quartz glass rotary tube into which hollow silicon carbide electrodes extend.