| abstract |
A method for producing fumed silica and a fluorine-containing product from a source of silica in solid form and a solid material containing fluorine, the solid material selected from the group consisting of sodium aluminum tetrafluoride, cryolite, aluminum fluosilicate, ammonium bifluoride, sodium aluminum silicofluoride, and sodium flurosiliate. The method comprises the steps of digesting the silica in solid form and the solid material selected from the group consisting of sodium aluminum tetrafloride, cryolite, aluminum fluosilicate, ammonium bifluoride, sodium aluminum silicofluoride, and sodium flurosiliate in a sulfuric acid digester. The digesting step produces a first gas component comprised of silicon tetrafluoride, hydrogen fluoride and water vapor. The first gas component is removed from the digester. The gas component recovered from the digester is heated to a temperature sufficiently high to convert the silicon tetrafluoride to fumed silica in the presence of the hydrogen fluoride and the fumed silica is separated from the hydrogen fluoride. |