GB686794A - Improvements in or relating to a process for recovering silica - Google Patents

Abstract

<PICT:0686794/III/1> Amorphous light-coloured silica in spherical particles substantially entirely less than 44 microns diameter is produced by reacting siliceous material and carbon at at least 1200 DEG C, e.g. 1200-1750 DEG C, in an electrically heated reaction zone to form gaseous products which are mixed in a confined space with volumes of air sufficiently large to rapidly oxidize and to cool the oxidized products, e.g. 1800-4000 cu. ft. per lb. of silica, simultaneously rapidly removing the products from the reaction zone and flowing them in an enclosed path to a filtering zone, and filtering to recover silica. A charge of iron, silica, and carbon, e.g. coal, coke, or graphite is fused in the hearth 1 of an electric arc furnace having carbon electrodes 4 and hood 5 Air flows in at 6, 7 and oxidizes the fume of SiO and CO to SiO2 and CO2, the heat from oxidizing CO to CO2 serving to maintain the SiO in vapour state until completely oxidized. The gaseous products flow through conduit 9, which may have secondary cooling air inlets 10 or a water-cooled heat-exchanger, to surge chamber 11. The silica-containing gases at 49 DEG C pass to filtering chamber 15 where the silica is collected in filter bags 14, e.g. wool, cotton, nylon, or sateen, and is periodically shaken into hopper 18 for removal. The waste gases pass out at 21 to pump F which maintains the rapid flow of gases in the system. At least two filter chambers should be used so that one is collecting while the bags in the other are being shaken. Ferrosilicon formed is withdrawn as necessary through taphole 3.