| 摘要 |
Finely divided, e.g., 5-400 mm , silicon dioxide is produced by treating silicon or a silicon alloy, e.g. silicon iron at an elevated temperature, say 650 DEG C., with dry hydrochloric acid to form chlorine-containing silicon compounds, such as silicon tetrachloride, or silicon chloroform, and free hydrogen, and hydrolyzing the silicon compounds in gaseous form to produce silica, and hydrochloric acid. The silicon compounds may be hydrolyzed by direct introduction of water vapour or by water vapor formed by combustion of the free hydrogen with added oxygen. The very pure hydrochloric acid may be reused in the treatment of silicon or alloy, or in part added to the gaseous reaction products before hydrolysis, or absorbed and recovered as concentrated acid. Chlorine may be added in the first stage to control the temperature and permit the use of higher temperatures say 1050 DEG C. Any iron chloride may be condensed from the gases before hydrolysis and the silica is recovered in a dust separator. |
