Producing synthetic quartz glass granules, comprises vitrifying pourable silicon dioxide granules made of porous granules that is obtained by granulating pyrogenically produced silicic acid, in rotary kiln

摘要

Producing synthetic quartz glass granules, comprises vitrifying pourable silicon dioxide granules made of porous granules that is obtained by granulating pyrogenically produced silicic acid, in a rotary kiln having a mullite-containing ceramic rotary tube, which is produced by applying a starting powder (103) comprising silicon dioxide and aluminum dioxide with a molar proportion of at least 70%, on a mold core (105) by thermal powder spraying method forming a mullite containing layer (108), and removing the mold core. Producing synthetic quartz glass granules, comprises vitrifying pourable silicon dioxide granules made of porous granules that is obtained by granulating pyrogenically produced silicic acid, in a rotary kiln having a mullite-containing ceramic rotary tube, which is produced by applying a starting powder (103) comprising silicon dioxide and aluminum dioxide with a molar proportion of at least 70%, on a mold core (105) by thermal powder spraying method forming a mullite containing layer (108), and removing the mold core. The ceramic rotary tube is flooded with a treating gas or rinsed with treating gas comprising helium and/or hydrogen (at least 30 vol.%).