Patent GB-734111-A (GB)
Title: Improvements in or relating to conversion of hydrocarbon materials and apparatus therefor
Inventor: KILPATRICK MYRON ODEN
IPC: C07C4/02
Filed: 1951-01-12
Abstract: <PICT:0734111/IV (b)/1> <PICT:0734111/IV (b)/2> In a process for converting hydrocarbons, particularly cracking light paraffinic hydrocarbons to obtain olefines, wherein hydrocarbon vapours are contacted with a flowing compact mass of pebbles made of refractory material, which are heated to a high temperature before they enter the conversion zone, the heat-input required for the process and the extent of the conversion are controlled in response to the specific gravity of the vaporous conversion products, by varying the temperature of the pebbles introduced into the conversion zone, and/or by varying the rate of flow of the pebbles.  The specific gravity of the conversion products is preferably determined with respect to air.  Pebbles made of alumina, beryllia, silicon carbide, stellite, periclase, zirconia and mullite, may be used; a preferred size being 3/8 inch.  In Fig. 1, the pebbles flow through heater 11, throat 13, and reactor 12; and are then recirculated to the top of the heater by elevator 18.  The pebbles are heated, as they pass down the heater, by direct contact with combustion gases passing upwards. These combustion gases are generated at burner 21, which is supplied with fuel and air through lines 22 and 23 respectively; the gases leave the heater through stack 25. Hydrocarbon gas is introduced into reactor 12 through line 26. The hydrocarbon gas may, if necessary, be mixed with steam, introduced through lines 61 and 29.  The converted hydrocarbon gas is discharged from the reactor through line 33 into tank 34, where it is quenched with water.  The product is withdrawn from tank 34 through line 39.  Temperature-controller 56, which is in communication with line 39, controls valve 37 in water-supply line 36, so as to reduce the temperature of the product to between 60 DEG and 200 DEG  F., depending on the particular conversion process. Controller 57 admits an emergency supply of water through line 59 when the usual supply in line 36 fails.  Gravitometer 76, which is in communication with line 39 and with valve 77 in fuel-line 22, is responsive to variations in the specific gravity of the cooled product stream, so that when the gravity rises above that corresponding to the desired product, the amount of fuel supplied to heater 11 is increased.  The air admitted through line 23 is varied, in response to the amount of fuel supplied through line 22, by controller 79 which regulates valve 81 admitting steam for operating air-blower 24.  In order to prevent overheating of the pebbles and of the lining of the heater, instrument 83, which is an overcontrol of instrument 76, is set at the maximum allowable temperature, so that if for any reason the temperature in the heater tends to exceed the limit, instrument 83 takes over the control of valve 77.  The flow of gases from reactor 12 at throat 13 and at the pebble-exit conduit 16 is prevented by using steam, supplied through pipes 61, 62 and 65, as a blocking-gas.  A suitable pressure-differential between heater 11 and reactor 12 is maintained by control 84, which operates damper 85 in stack 25. In order to prevent air leakage into the system, the suction-pressure on product line 39 is maintained at a constant value, at least as great as atmospheric, by turbo-blower 41 which is operated by steam supplied through line 44.  The speed of the blower is automatically regulated by control 42 which is connected to steamvalve 43.  When the speed of the blower has been reduced to its minimum operational limit, pressure-controller 45 opens valve 46 in line 47, thereby permitting part of the hydrocarbon effluent to be returned to line 39.  Under extreme conditions when both blower 41 and line 47 are unable to maintain the pressure in line 39, controller 48 operates valve 49 in line 51 to admit maintenance gas into line 39.  The various control instruments are operated by compressed air, each being connected to air supply line 91.  Heater 11 has a refractory lining 101 (Fig. 2), and a perforated arch 103 for supporting the pebbles. Below the arch is an annular combustion space 104.  Reactor 12 also has a refractory lining 106.  The pebbles in the reactor pass downwards over hydrocarbon gas distributers comprising a series of inverted troughs 108 supported at different levels on tubes 109 attached to funnel 111, the neck of which extends into pebble withdrawal conduit 16.  Fig. 2 provides for a different control of the heat input to that shown in Fig. 1.  Pyrometer 113 regulates fuel-valve 77 so as to maintain a uniform predetermined temperature in the pebble stream as it enters reactor 12; and gravitometer 76 regulates the speed of motor 115, which communicates through speed-reducer 116 with the shaft of pebble-feeder 17, so that any deviation in specific gravity of the product is reflected in the rate of flow of pebbles through the unit.  In an example, a gas mixture containing 74.5 per cent of propane and 21.6 per cent of ethane is cracked at a temperature of 1700 DEG  F. and a pressure of 4.2 p.s.i.g., using 5/16 inch alumina pebbles.  The temperature of the product is lowered to about 140 DEG  F. by two water-quenching stages, to yield a product of specific gravity 0.7.  This product contains 36.5 per cent of ethylene and 9.4 per cent of propylene. Reaction temperatures between 1500 DEG  and 3500 DEG  F. are also referred to; and operating pressures between atmospheric and about 10 p.s.i.g. are preferred. Specifications 734,125 and 734,176, [both in Group III], are referred to.ALSO:<PICT:0734111/III/1> <PICT:0734111/III/2> In a process for converting hydrocarbons, particularly cracking light paraffinic hydrocarbons to obtain olefins, wherein hydrocarbon vapours are contacted with a flowing compact mass of pebbles made of refractory material, which are heated to a high temperature before they enter the conversion zone, the heat-input required for the process and the extent of the conversion are controlled in response to the specific gravity of the vaporour conversion products by varying the temperature of the pebbles introduced into the conversion zone, and/or by varying the rate of flow of the pebbles.  The specific gravity of the conversion products is preferably determined with respect to air.  Pebbles made of alumina, beryllia, silicon carbide, stellite, periclase, zirconia and mullite may be used, a preferred size being 3/8 inch.  In Fig. 1 the pebbles flow down through heater 11, throat 13 and reactor 12, and are then recirculated to the top of the heater by elevator 18.  The pebbles are heated, as they pass down the heater, by direct contact with combustion gases passing upwards.  These combustion gases are generated at burner 21, which is supplied with fuel and air through lines 22 and 23 respectively; the gases leave the heater through stack 25. Hydrocarbon gas is introduced into reactor 12 through line 26. The hydrocarbon gas may, if necessary, be admixed with steam, introduced through lines 61 and 29.  The converted hydrocarbon gas is discharged from the reactor through line 33 into tank 34, where it is quenched with water.  The product is withdrawn from tank 34 through line 39 at a temperature between 60 DEG  and 200 DEG  F., depending on the particular conversion process.  Gravitometer 76, which is in communication with line 39 and with valve 77 in fuel-line 22, is responsive to variations in the specific gravity of the cooled product stream, so that when the gravity rises above that corresponding to the desired product, the amount of fuel supplied to heater 11 is increased.  The air admitted through line 23 is varied, in response to the amount of fuel supplied through line 22, by controller 79 which regulates the valve 81 admitting steam for operating air-blower 24.  In order to prevent overheating of the pebbles and of the lining of the heater, instrument 83, which is an over-control of instrument 76, is set at the maximum allowable temperature, so that if for any reason the temperature in the heater tends to exceed the limit, instrument 83 takes over the control of valve 77.  The flow of gases from reactor 12 at throat 13 and at the pebble-exit conduit 16 is prevented by using steam, supplied through pipes 61, 62 and 65, as a blocking-gas.  A suitable pressure-differential between heater 11 and reactor 12 is maintained by control 84, which operates damper 85 in stack 25.  In order to prevent air leakage into the system, the pressure in product line 39 is maintained at a constant value at least as great as atmospheric, by turbo-blower 41 which is operated by steam supplied through line 44.  The speed of the blower is automatically regulated by control 42 which is connected to steam-valve 43.  When the speed of the blower has been reduced to its minimum operational limit, pressure-controller 45 opens valve 46 in line 47, thereby permitting part of the hydrocarbon effluent to be returned to line 39.  Under extreme conditions, when blower 41 and return-line 47 are unable to maintain the pressure in line 39, controller 48 operates valve 49 in line 51 to admit maintenance gas into line 39.  The various control instruments are operated by compressed air, each being connected to air supply line 91.  Heater 11 has a refractory lining 101 (Fig. 2) and a perforated arch 103 for supporting the pebbles.  Below the arch is an annular combustion space 104. Reactor 12 also has a refractory lining 106.  The pebbles in the reactor pass downwards over hydrocarbon gas distributers comprising a series of inverted troughs 108 supported at different levels on tubes 109 attached to funnel 111, the neck of which extends into pebble withdrawal conduit 16. Fig. 2 provides for a different control of the heat input to that shown in Fig. 1. Pyrometer 113 regulates fuel-valve 77 so as to maintain a uniform predetermined temperature in the pebble stream as it enters reactor 12; and gravitometer 76 regulates the speed o