Patent GB-721958-A (GB)
Title: Method and apparatus for transfer of contact materials
IPC: B01J8/00
Filed: 1952-01-04
Abstract: <PICT:0721958/III/1> <PICT:0721958/III/2> <PICT:0721958/III/3> In a pneumatic elevating system for raising solid material suspended in a lifting gas without excessive attrition of the material, the velocity of the gas flow is controlled within a range in which the pressure drop in the lift is substantially at a minimum, the range being defined on one side by a velocity below which the pressure drop increases rapidly with decreasing gas velocity due principally to refluxing of the material and on the other side by a velocity above which the pressure drop increases rapidly with increasing gas velocity due to factors other than the material.  The process is particularly applicable to the transfer of contact material in cyclic hydrocarbon conversion systems and may be applied to processes such as catalytic cracking, isomerization, hydrogenation, dehydrogenation, reforming, hydroforming, aromatization, alkylation, cyclicizing and the treatment and desulphurization of petroleum fractions.  It may be applied also to the cooking of hydrocarbons in the presence of granular coke or refractory solids, the viscosity reduction of petroleum residuums at high temperatures, the pyrolytic conversion processes such as the conversion of propane and ethane to unsaturated hydrocarbons and of methane to acetylene.  The contact material may range in size from 0.005 to 0.5 inch and may be in the form of pellets, spheres, tablets or pills or may be shaped irregularly.  In catalytic hydrocarbon systems the contact material may be natural or treated clays, bauxites, inert or active carriers impregnated with catalytically active metals or compounds thereof, or synthetic associations of silica, alumina, magnesia, chromia, molybdenum oxide or combinations thereof.  In pyrolytic conversion processes it may be fused alumina, mullite, carborundum, zirconium oxide or charcoal and in coking processes it may be a low activity clay catalyst, petroleum coke, pumice or similar materials.  The catalyst 29, Fig. 2, is conveyed from the feed tank 34 to the separator 36, Fig. 1, through a pipe 25 by air, steam or flue gas supplied through a pipe 38.  The diameter of this pipe increases progressively from the bottom to the top.  The lower end of the pipe 25 is connected to a flared mouthpiece 35, the curvature of which is approximately that of a hyperbolic spiral.  The pipe 38 has a perforated conical roof 201 below which is a series of concentric spaced apart cylinders 200. Rings 202 are attached to the lower ends of these cylinders. Secondary air, &c., supplied from the pipe 42 through pipes 43, 44 to a chamber 41 passes through apertures 48 and below a baffle 47 into the bed of catalyst 29.  The air, &c., is drawn through the pipe 50 into the blower 51 and is forced through a heater 52 and pipe 53 to the pipes 42, 38.  The pressure at the blower is maintained constant by a controller 54 which regulates the speed of the turbine 55 and the rate of secondary air flow can be maintained substantially constant through the actuation of the control valve 60 by the pressure regulating controller 59.  The air supply is maintained at any desired value by the orifice 61, flow regulating controller 62 and control valve 63, these parts ensuring that any increase in the secondary air flow is accompanied automatically by an equal decrease in the primary air flow.  The pipe 25 opens into the chamber 36 above a partition 66 which divides it into a settling chamber 67 and a catalyst surge chamber 69.  Catalyst passes from the upper to the lower chamber through concentric rings of pipes 70, 71, 72.  The lower ends of the pipes in any ring are in a plane which is inclined at the angle of repose of the catalyst and the upper ends of the pipes in all the rings are contained within the sloping surface of a cone.  A ring baffle 170 extends upwards from the partition 66 to just below the top of a ring baffle 73 which depends from the top of the tube 25, the passage between these baffles serving as an overflow when there is too much catalyst on the partition 66.  A sleeve 172 extends from the bottom of the chamber 69 to just above the bottom of the baffle 73.  A baffle 74 suspended in the upper part of the chamber 36 prevents direct flow between the upper end of the tube 25 and the gas outlet 75.  The catalyst passes through a pipe 11 to a reactor 10 from which it passes through two or more pipes 12, 13 and branch pipes 14 to the top of a catalyst regenerator 15.  The catalyst passes from the regenerator through pipes 30, 31 into pipes 32, 33, which are vented at their upper ends and the lower ends of which are disposed in the feed tank 34.  In modifications (1) the upper part of the tube 25 has a greater taper than the lower; (2) the lower part is of uniform cross-section and is surmounted by a tapered upper part; (3) the lower part converges upwardly and the upper part diverges in the same direction; and (4) the pipe consists of two or more uniform sections of different diameters connected by adaptor members and so disposed that any section is immediately below one of larger diameter.  In a modified construction the mixing chamber 101, Fig. 19, is below ground level and catalyst is fed to it by gravity through a conduit 103 which is of sufficient length to provide a head of catalyst greater than the pressure in the chamber.  Concentric nozzles 105, 106, 107 of different diameters and lengths are mounted in the bottom of the chamber and are connected to gas supply pipes 108, 109, 110 respectively, only one of which is in use at any one time.  The lift pipe 100 is of uniform cross-section and in its upper part is in communication with downwardly-sloping pipes 112, 113, 114 which lead to separators 115, 116, 117.  Sufficient gas is withdrawn through one or more of these pipes, which are controlled by valves 130, 132 to maintain the velocity of the catalyst at the desired figure.  Any catalyst entrained with the gas passes back to the conduit 103 through pipes 125, 126, 127.  The separated lift gas passes from the separator 102 through the pipe 150 to a stack or secondary separator.  If lifting is effected by suction instead of by pressure, the lifting gas may be a condensable vapour, e.g. steam, which is passed through the pipe 151 to a barometric condenser 121 in which it is condensed to produce the suction for effecting the elevation.