Patent GB-723466-A (GB)
Title: Apparatus for and method of operating a pneumatic lift used to transport granular solids
IPC: B01J8/00
Filed: 1952-08-12
Abstract: <PICT:0723466/III/1> <PICT:0723466/III/2> Apparatus for lifting granular solids, such as contact material for carrying out a hydrocarbon conversion process, through a vertical pipe by means of gas, is provided with means in the upper two-thirds of the pipe for measuring continuously the static pressure therein and with means for adjusting the flow rate of the gas admitted to the feeding zone surrounding the bottom of the pipe in accordance with changes in the static pressure in the pipe.  The apparatus may be used for processes such as catalytic cracking, isomerization, hydrogenation, dehydrogenation, reforming, hydroforming, aromatization, alkylation, cyclicization treatment or desulphurization of petroleum fractions, coking of hydrocarbons in the presence of granular coke or refractory solids, viscosity reducing of petroleum residuums at elevated temperatures and pyrolytic conversion processes such as the conversion of propane and ethane to unsaturaaed hydrocarbons and of methane to acetylene.  In catalytic hydrocarbon systems the catalyst may be natural or treated clays, bauxites, inert or active carriers impregnated with catalytically active metals, or synthetic associations of silica, aluminal, magnesia, chromia, molybdenum oxide or compounds thereof to which may be added small amounts of other compounds usually metallic, for specific purposes.  When the contact material is used principally for heat carrying purposes as in pyrolytic conversion processes, it may be fused alumina, mullite, carborundum, zirconium oxide or charcoal. In coking processes the material may consist of a low activity clay catalyst, petroleum coke, pumice or similar <PICT:0723466/III/3> materials.  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.  Contact material is raised from the tank 34, Fig. 1, to the separator 36 through a pipe 25 by air, steam or other inert gas admitted to the tank by pipes 38, 43.  Contact material passes from the separator through a pipe 11 to the reactor 10 from whence it passes to the regenerator 15 through pipes 14.  The regenerator is connected to the tank by pipes 32, 33.  The lifting gas is drawn through a pipe 50 by a blower 51 driven by a motor 57 and is forced through a heater 52 to the pipe 53 which feeds the pipes 38, 43.  The pipe 38 enters the bottom of the tank and terminates below the bottom of the pipe 25.  The pipes 43 are distributed about the wall of the tank.  The pressure of the gas delivered by the blower is maintained substantially constant by a controller 56 which regulates automatically the speed of the motor 57.  The total flow of gas is measured by a meter 60 on the pipe 50.  A flow regulating controller 61 is operatively connected to the meter 60 and to a valve 62 in the pipe 38.  A pressure regulating controller 58 is operatively connected to a pressure tap 5 at the bottom of the lift and to a valve 59 in the pipe 54 through which air passes to the pipes 43.  A pressure tap 70 inserted in the upper two-thirds of the pipe 25 is connected to an indicator 79.  In operation the controls are first set so that the gas flow is above the refluxing rate, i.e. the rate at which violent surging or refluxing occurs in the pipe 25 with sudden changes of pressure and a rapid increase in attrition of the contact material.  The flow is then reduced gradually by adjusting the controller 61 until the pressure registered on the indicator 79 shows a magnitude of fluctuation of about one hundred per cent.  This is known as the threshold refluxing rate and it is stated that attrition will then be at a minimum value.  In a modification the valve 62 is by-passed by a pipe containing a valve which is actuated by a pressure controller connected to the pressure tap 70.  The valve 62 is first adjusted to cause a flow rate slightly below optimum and the valve on the by-pass is then controlled automatically to maintain the velocity at the maximum and the attrition at a minimum.  Pressure fluctuations are removed by a dampener inserted in the pipe between the pressure controller and the tap 70.  In another modification, Fig. 3, the pressure tap 70 is connected to a limit controller 80 which is designed to control the width of the pressure band between maximum and minimum ranges.  The controller is connected to a valve 81 in a small pipe 82 leading from the pipe 38.  Gas is admitted to, or withdrawn from, the pipe 38 as the pressure varies.  In a further modification, Fig. 4, the valve 66 is operated automatically by a flow controller 83 to maintain a constant flow through the pipe 25. The controller is connected by pressure lines 86, 87 to points on the inlet pipe 50 on each side of a meter 60, and these lines are connected by a line 88 containing a valve 89 which normally is closed but is opened automatically when the valve 73 is actuated.  The limit controller 84 may act directly on the controller 83 to reset the flow meter to a new control point whenever the flow through the line 85 is increased or diminished.