Patent GB-860301-A (GB)
Title: Improvements in or relating to exothermic reactions
Inventor: FOULDS JAMES TAYLOR
IPC: C01B13/26
Filed: 1958-03-21
Abstract: For the vapour phase reaction between silicon, titanium, zirconium, aluminium and/or iron halides and oxygen or oxygen-containing gas, a shaft furnace is provided with means for passing gas through a bed and to entrain and lift bed material into the upper part of the shaft furnace constituting the reaction zone, means for admitting halide vapour at a predetermined level above the bed, and means providing a constricted passage for gas, vapour and solid material to flow into the upper part of the shaft furnace and for solid material to fall back to the bed.  A cylindrical shaft furnace 1 has a baffling 3 having a narrowest point or throat located at 4 and having a lower converging conical section 6 above the throat.  The base of the furnace is sealed by a perforated plate 7, on the lower side of which are located plugs 11 through which there are gas pressure-controlling machined <PICT:0860301/III/1> orifices for permitting predetermined supplies of gas from the wind box 12 below to pass upwards into a bed 13.  Titanium tetrachloride vapour, for example, is led through the conduit 15 and oxygen-gases enter through conduit 17 and pass upward through the bed 13.  In operation the bed of material 13 above the perforated plate is fluidized by oxygen gases fed via the conduit 17 and the wind box 12 and thus the sand or sand-like material composing the bed is entrained upwards through the throat 4 to form what may be regarded as a fountain of sand which is shown diagrammatically by the dotted area immediately above the throat, i.e. sweeping in the space 19.  At a height corresponding to a point 20, the velocity of the gases having decreased below the terminal velocity the sand is in a state of settlement and beyond this area virtually cease to contain sand in suspension and thus the gases emerging through the outlet 21 are substantially free from sand.  With these conditions established the titanium tetrachloride vapour at temperatures preferably above 150 DEG  C., but not exceeding 600 DEG  C., is led through the conduit 15 and injected at the point 16 directly through the throat 4 to be preheated and then reacted with oxygen in the space 19 which is pervaded by the sand.  At the level 20 where the reaction is substantially complete and the gases are divested of the sand constituent, the products of reaction which consist in the main of fine precipitated titanium dioxide solid suspended in an atmosphere of substantially chlorine or chlorine-containing gases are conveyed through the outlet 21 onwards through ducting 22 to be further treated, e.g. cooled, collected and/or separated.  There will, however, be some accumulation of titanium oxide on the sand and, in consequence, it will, from time to time, be necessary to purge some of the sand from the bed.  There is accordingly provided a discharge port 24 and an inlet port 25 for fresh sand.  It will also be clear that the process is adapted for making titanium oxide in both the anatase and rutile forms.  The operations may, for instance, be controlled especially in respect of rutilization of the reaction product by the introduction into the oxygen stream of varying proportions of moisture, i.e. from 0.1-5%.  The particle size may also be controlled by the addition of other materials as, for instance, by the addition of 1-5% of silicon tetrachloride.  Other materials which have been found suitable for making variations in the pigment product include the addition of aluminium chloride so as to deposit alumina on the pigment.  Specifications 676,391, 724,193, 761,770, 772,680, 794,666, 813,489 and U.S.A. Specification 2,642,346 are referred to.