Patent GB-462632-A (GB)
Title: Improvements in the manufacture of alkali metal salts
IPC: C01B7/03
Filed: 1936-04-28
Abstract: <PICT:0462632/III/1> <PICT:0462632/III/2> In obtaining alkali metal silicates, zincates, ferrites, manganates, aluminates, borates or phosphates by reacting an alkali metal chloride, aqueous vapour with or without air, and the corresponding solid oxide (e.g. silica), the reaction is effected by introducing a charge of the oxide, if desired mixed with an alkali metal chloride, into a furnace chamber so as to form a partition wall or walls dividing the chamber into two gas-filled compartments and by introducing a mixture of alkali metal chloride vapour and aqueous vapour (with or without air) into one of the compartments above the level of the resulting liquid layer of the product of the reaction, the said vapour mixture passing through the partition wall or walls at a temperature of about 1100 DEG  C. or more.  Any alkali metal chloride vapour which escapes reaction is condensed from the resulting hydrogen chloride in a part of the furnace kept at a temperature of about the melting point of the chloride, the condensed liquid chloride being returned for revaporization.  As shown in Fig. 2, a furnace, electrically heated by resistances E, E1 and E2, is divided by two charge walls C, supported by latticework partition walls D and D1, into chambers A and B.  Chamber A is kept at 1100 DEG  C. and chamber B at 850 DEG C.  The charge C consists of a mixture of sand and salt and a molten laver of sodium silicate upon which floats a molten layer of salt forms at the bottom of the furnace.  Aqueous vapour is introduced through a pipe G and mixes with salt vapour, the mixed vapours passing through the charge walls.  Unreacted salt vapour condenses in the chamber B, while unreacted steam and hydrochloric acid pass out through an opening H.  The molten silicate discharges continuously through a liquid seal I.  If desired the system may be reversed, steam being introduced through the tube G1 and leaving through the tube H.  According to a modification, Fig. 7, the furnace is divided into two chambers A and B by a perforated arch D which supports the charge.  The metallic heating resistances E and E1 are immersed in a bath of molten silicate except for the parts extending outside the furnace which are cooled in two water-filled containers M and O respectively.  These containers serve as boilers producing steam for the process.  The steam is introduced through openings G, the gaseous products of the reaction leave through an opening H, and the molten silicate leaves through a discharge trough formed in the container O. Further modifications are described in which the charge forms heaps in front of intermediate beams depending from the upper part of the furnace, in which the charge rests partly on arches or supports of ceramic material and partly on the molten salt on the bottom of the furnace, and in which the charge wall is made to assume a horizontal position in the furnace, for example, by being supported by one or more grates, or by reason of the furnace tapering downwardly.  The furnace may also be built in the shape of an annulus.