GB826978A - Improvements in or relating to fluidized bed reaction vessels - Google Patents

Abstract

<PICT:0826978/III/1> <PICT:0826978/III/2> <PICT:0826978/III/3> <PICT:0826978/III/4> <PICT:0826978/III/5> <PICT:0826978/III/6> <PICT:0826978/III/7> A method and apparatus for carrying out a process involving interaction between a gas and a fluidized solid, which may be catalytic, comprises introducing the solid into fluidized bed reaction vessel, which includes a substantially horizontal gas inlet pipe having gas inlet openings all of which are directed downwards, preferably vertically downwards, and a sealing gland through which the pipe enters the vessel and which forms a gas-tight seal between the pipe and the wall of the vessel and which is releasable to enable the pipe to be withdrawn axially from the vessel. If desired, the base of the reaction vessel may be provided with perforations for the admission of further fluidizing gas. Advantageously the drop in the pressure of the gas across the gas inlet openings is approximately equal to the total drop in pressure sustained by the gas during its passage through the particular solid. This ensures that with gas inlet openings of equal area, the rate of flow of gas through each opening is approximately the same and is independent of the position of the opening along the pipe. The size of the gas inlet openings of the, or each, pipe may decrease towards the supply inlet in such way as to cause the rates of flow of gas through the said gas inlet openings to be substantially equal for a particular rate of flow of the gas. This construction provides a way of obtaining an equal rate of flow of gas through each gas inlet opening which is alternative to the method described above in which the pressure drop across each opening is arranged to be approximately equal to the pressure drop across the bed of particular solid. In certain processes such as, for example, when the fluidizing gas or one of the fluidizing gases is corrosive, e.g. chlorine at a high temperature, it is necessary to provide refractory instead of metal gas inlet pipes and to provide watercooling for the glands through which the pipes enter the vessel. The invention may be applied to the process for the oxidation of titanium tetrachloride by allowing it to react with oxygen in a fluidized bed of a suitable heatresistant particulate solid (which may be inert or may catalyse the reaction) as described in Specification 815,891. Thus, the particulate solid is a heat-resisting solid, the fluidizing gas is titanium tetrachloride vapour and oxygen, which are each introduced through a different substantially horizontal gas inlet pipe having downwardly directed gas inlet openings and a releasable sealing gland or through a different set of such pipes, and which are caused to react together in the presence of the particulate solid to form titanium dioxide. If desired, the titanium tetrachloride vapour and the oxygen may be introduced into the particulate solid at different levels. The apparatus enables premixing of the gases before entry to the bed, which could lead to premature reaction between the gases and consequential blocking of the entry tubes, to be avoided. The reaction vessel shown in Figs. 1 and 2 of the drawings has an imperforate circular base 1 and a cylindrical side wall 2. A short distance above the base 1, a straight horizontal gas inlet pipe 3 passes centrally through the vessel and a similar pipe 4 passes horizontally immediately above and at right angles to the pipe 3. The pipes 3 and 4 enter the vessel through gas-tight glands (not shown) and can be withdrawn axially for cleaning or replacement. The reaction vessel shown in Figs. 3 and 4 of the drawings differs from that shown in Figs. 1 and 2 in that it has a square base 1 and rectangular side walls 2, and that the disposition of the gas inlet pipes is different. The reaction vessel shown in Figs. 5 and 6 is larger than those shown in Figs. 1 to 4, and has a circular base 1 and a cylindrical side wall 2. There are two sets of gas inlet pipes, which are situated at the same level. Referring to Fig. 7 of the drawings, one form of water-cooled gland comprises an outer annular water jacket 9 secured centrally to a circular plate 10 having a central circular aperture in which a refractory gas inlet pipe 3 makes a sliding fit. By unscrewing the screw-threaded sleeve 15 from within the outer water jacket 9, the packing rings 12 and 14, and the inner water jacket 17 can be removed. This gives access to the end of the refractory gas inlet pipes 3, which can then be withdrawn axially.