Patent GB-734176-A (GB)
Title: Improvements in or relating to conversion of hydrocarbon materials and apparatus therefor
Inventor: KILPATRICK MYRON ODEN
IPC: B01J8/12
Filed: 1951-01-12
Abstract: <PICT:0734176/III/1> In a process for the conversion of hydrocarbons, such as the cracking of light paraffinic hydrocarbons to obtain olefins, wherein the hydrocarbon vapours are contacted with a flowing compact mass of heat-refractory pebbles which have been heated to a high temperature before they enter the conversion zone, by contact with hot combustion gases in a heating zone, the conversion product vapours withdrawn from the conversion zone are quenched by direct contact with a stream of cooling fluid such as water, and the rate of flow of the quenching fluid is automatically regulated in response to deviations from a predetermined temperature so as to maintain relatively uniform product temperature.  Pebbles made of alumina, beryllia, silicon carbide, stellite, periclase, zirconia and mullite, may be used; a preferred size being 3/8 inch.  In the Figure, 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, which are generated at burner 21 supplied with fuel and air through lines 22 and 23 respectively. Hydrocarbon gas is introduced into reactor 12 through line 26. The converted hydrocarbon gas is discharged from the reactor through line 33 into tank 34, where it is quenched with water; and the quenched product is withdrawn from the tank through line 39. Temperature-controller 56, which is in communication with line 39 just downstream of tank 34, controls valve 37 in water-supply line 36 to regulate the amount of water admitted to the tank, so as to maintain a constant temperature in the quenched product stream. The temperature in line 39 may suitably be maintained anywhere between 60 DEG  and 200 DEG  F. depending upon the particular conversion process.  Pressure controller 57 admits an emergency supply of p  water through line 59 if the usual supply in line 36 fails. Gravitometer 76, which is in communication with line 39, is responsive to variations in the specific gravity of the cooled product stream, and controls the amount of heat supplied to the reactor and the extent of the conversion, as claimed in Specification No. 734,111.  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.  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 effluent from the reactor is given a fast primary quench with water to a temperature of about 600 DEG  F. A secondary quench with water at atmospheric temperature reduces the temperature of the effluent stream to about 140 DEG  F.  The specific gravity of the cooled product, with respect to air, is maintained at 0.7.  This product contains 36.5 per cent of ethylene and 9.4 per cent of propylene.  Apparatus for automatically purging the reactor when emergency conditions arise, is described in Specification 734,125.