| 摘要 |
Process and apparatus are provided for preparing finely-divided silicon dioxide in good yield by reaction of silicon fluoride in the vapor phase with water vapor, combustible gas and free oxygen-containing gas in a flame reaction zone to form hydrogen fluoride and silicon dioxide entrained in a gaseous reaction mixture; withdrawing the gaseous reaction mixture from the flame reaction zone; and then immediately and rapidly cooling the gaseous reaction mixture and entrained silicon dioxide to a temperature below 700 DEG C. by passing the gaseous reaction mixture in a turbulent flow at a Reynolds number above 300 under constraint through a straight narrow passage in alignment with the gas flow, the passage having a diameter within the range from about 20 to about 150 mm and smooth walls constituting a cooling surface.
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