GB757703A - A method and apparatus for mixing and reacting gaseous fluids - Google Patents

Abstract

<PICT:0757703/III/1> <PICT:0757703/III/2> <PICT:0757703/III/3> In the production of pigmentary metal oxides by mixing and reacting together a volatile metal halide and an oxidizing gas, one of the said reactants is charged to the reaction zone through an inlet or inlets circumferentially arranged in the walls of the reaction zone or discharged radially outwards from a centrally arranged reactant feed pipe, in the form of a sheet stream directly into and in a direction angular to the axis of flow of the other reactant which is separately and simultaneously charged into the reaction zone. Oxides of titanium, zirconium, aluminium, silicon, antimony, zinc and tin for example may be so prepared from their chloride, bromide or iodide employing air, oxygen, moisture enriched air or oxygen, or mixtures thereof with inert gases. As shown in Fig. 1 titanium tetrachloride vapour is charged to a reaction zone 4, through a pipe 12 leading into an annular chamber 11 which communicates with the reaction zone 4 through a slot or slots 7; humified air enters at 2; alternatively as in Fig. 2 the titanium tetrachloride reactant flows into reaction vessel 22 through a tube 19 surrounded by an annular space 20 through which moisture enriched air is fed, and a further quantity of moisture enriched air is passed into the reaction zone 22 as a sheeted stream through slots 16 and 17 from the annular chamber 25. In Fig. 3 one of the reactants is fed through the outer annulus 30 formed between the reactor walls 27 and an inner tube 28 whilst the other reactant is fed through passages 31 to be discharged as a sheeted stream into the other reactant from slots formed between the lower edge 34 of the wall 28 and the upper edge 35 of an element 33 closely adjacent to the end of tube 28. In Fig. 1 the oxidizing gas and titanium tetrachloride both at 350 DEG C. for example may be separately charged in amounts such that the mass velocity of the tetrachloride is 15 to 40 times the mass velocity of the oxidizing medium whereby reaction occurs at 1000 to 1350 DEG C. and the reaction is completed in from 0.1 to 10 seconds. The gasous reaction products are cooled quickly to below 900 and preferably below 600 DEG C. within 0.01 to 10 seconds and preferably within 0.05 to 5 seconds from the time of introduction of the reactants to the reaction zone. Such cooling may be effected by recirculating cooled product gases or by directly dispersing the titanium dioxide suspension, cold inert finely divided refractory solids such as silicon. The reactant injected as a sheeted stream may impinge upon the other reactant stream at from 45 to 135 DEG C. and if desired a swirling motion may be imparted to the sheeted stream by admitting the reactant to the manifold surrounding the slot through one or more tangential inlets. According to Examples (1) air a 865 DEG C. containing 0.95 per cent water by volume was charged to the reactor of Fig. 1 whilst simultaneously injecting a stream of vaporized titanium chloride at 865 DEG C. The reaction products at 1150 DEG C. after a retention time of .13 seconds were cooled in less than 2 seconds to 300 DEG C. by mixing cold chlorine gas therewith. (2) titanium tetrachloride and air containing 0.07 per cent water preheated to 950 DEG C. were introduced into the reactor shown in Fig. 2 which was maintained at a 1000 DEG C. in a furnace. The average retention time was 0.15 seconds and the reaction products were quenched to 300 DEG C. in less than 5 seconds by cold chlorine. Zirconium and aluminium chlorides may be similarly prepared. The effectiveness of the mixing occasioned by the invention is illustrated by feeding air containing about 1 per cent by volume of dry ammonia gas to the reactor shown in Fig. 1 whilst simultaneously feeding dry hydrogen chloride gas through the slot inlet as a sheeted stream into the air/ammonia stream to form a visible ammonium chloride smoke. Complete mixing occurred two inches downstream from the slot.