METHOD FOR PRODUCING SYNTHETIC QUARTZ GLASS GRANULES

摘要

The production of quartz glass granules comprises the granulation of pyrogenically produced silicic acid and the formation of a SiO2 granulate (9), the drying and cleaning of the SiO2 granulate (9) by heating in an atmosphere containing halogen, and the vitrification of the SiO2 granulate (9) under a treatment gas which contains at least 30% by volume of helium and/or hydrogen. This process is time-consuming and expensive. In order to provide a method which, starting from a porous SiO2 granulate (9), allows the cost-effective production of dense, synthetic quartz glass granules suitable for melting bubble-free components of quartz glass, the invention proposes that the cleaning and vitrification of the SiO2 granulate (9) and a post-treatment of the vitrified quartz glass granules are carried out in each case in a rotary tube (6) of a rotary kiln (1), said rotary tube rotating about a central axis (7), wherein the rotary tube (6) comprises an inner wall made of a ceramic material during vitrification, and wherein the vitrified quartz glass granules are subjected to a post-treatment during a treatment period of at least 10 minutes in an atmosphere which contains less than 20% of helium or hydrogen at a treatment temperature of 300° C. or more.

主权项

1. A method for producing synthetic quartz glass granules by vitrifying a free-flowing SiO2 granulate, the method comprising:
granulating pyrogenically produced silicic acid so as to form the SiO2 granulate of porous granulate particles, drying the SiO2 granulate, cleaning the SiO2 granulate by heating in a halogen-containing atmosphere, vitrifying the cleaned SiO2 granulate in a treatment gas containing at least 30% by vol. of helium, hydrogen or a mixture of helium and hydrogen so as to form vitrified quartz glass granules, and subjecting the vitrified quartz glass granules to a post-treatment in an atmosphere containing helium or hydrogen in an amount less than 20%, and at a treatment temperature of 300° C. or more for a treatment period of at least 10 minutes, wherein the cleaning and the vitrifying of the SiO2 granulate and the post-treatment of the vitrified quartz-glass granules are each carried out in a rotary tube of a rotary kiln rotating about a central axis, and wherein, during said vitrifying, the rotary tube comprises an inner wall consisting of a ceramic material.