Patent GB-774135-A (GB)
Title: Hydrocarbon cracking process
IPC: C10G49/18
Filed: 1954-09-22
Abstract: A liquid hydrocarbon such as a petroleum residual oil is cracked by introducing it into a hot gas mixture comprising carbon monoxide and hydrogen, and maintaining a temperature of 900 DEG  to 1800 DEG F. and a contact time of 1 to 10 seconds between the oil and the gases whereby the oil is converted <PICT:0774135/III/1> into cracked vapours and solid particles of carbonaceous residue; the linear velocity of the gases and vapours in the cracking zone is adjusted so that the solid particles are entrained therein, and the effluent-product from the cracking zone is passed to a fractionating column from which gasoline and carburetted fuel gas are withdrawn overhead, while a high-boiling fraction, containing the solid particles in suspension, is withdrawn from the base. The hot mixture of CO and H2 required for the cracking zone is made by reacting the bottoms fraction with oxygen and steam at a temperature between 2000 DEG  and 3000 DEG  F.  Residual oil is fed through line 10 and heat-exchanges 12, 13 to furnace 14 where it is raised to about 600 DEG  F.  The preheated oil then passes through line 15 into cracking zone 17, which is a refractory-lined chamber completely free of packing or checkerwork.  A gaseous mixture of CO and H2 at a temperature of about 2500 DEG  F. is introduced into the base of zone 17.  The rate of oil injection is adjusted to maintain a cracking temperature of about 1100 DEG  F. The contact time is about 2 seconds with a linear velocity of the combined gas stream of about 5 feet per second; and coke formation is restricted to particles which remain entrained in the effluent-product from zone 17.  The effluent-product is passed through pipe 18 to heat-exchanger 19, where it is cooled to about 650 DEG  F.; it then enters the lower portion of bubble tower 20, which is provided with reboiler 21.  Gasoline and gases are withdrawn from the head of tower 20 at a temperature of about 450 DEG F.  A sidestream is withdrawn through line 31; this sidestream is pumped through heat-exchanger 13 and cooler 33, and is then returned to the tower as scrubbing liquid.  A slurry of coke particles in heavy oil is discharged from the base of tower 20.  This material is mixed with steam, supplied through pipe 28, and the mixture is passed through pipe 23 to burner-nozzle 24, which is disposed in the base of unobstructed, refractory-lined chamber 25.  Oxygen is supplied to the nozzle through pipe 26. The proportions of oxygen and carbonaceous material fed to chamber 25 are regulated to obtain an atomic-ratio of oxygen to carbon of about 1.5:1, whereby combustion takes place at about 2,500 DEG  F. to yield a gas mixture comprising predominantly CO and H2. This hot mixture passes through constriction 30 into cracking chamber 17.  The pressure in the cracking and gas generation zones is about 450 psig.  A low-carbon residue fraction is withdrawn from the side of tower 20 into stripper 49, the light overhead being returned to tower 20 through line 50.  The stripped material is passed through preheater 52, and is then injected with the fresh feed into zone 17.  Preheater 52 may be employed to preheat the feed to any temperature up to 1000 DEG  F.  All or a portion of the fresh feed, after passing through heat-exchanger 13, may pass through pipe 53 into the lower section of tower 20.  The overhead vapours and gases from tower 20 flow through heat-exchanger 12, and then enter condenser 35.  The condensate passes together with the gases, into decanter 36.  Water is withdrawn through line 37. A portion of the hydrocarbon condensate is passed through pipe 40 to serve as top reflux for tower 20; and the remainder is sent to stabilizer 41. Gasoline is withdrawn through pipe 42, Gaseous hydrocarbons pass through line 43, and are mixed in pipe 44 with the gaseous overhead from decanter 36.  The resulting gas mixture, composed of CO, H2 and gaseous hydrocarbons, is passed through gasoline-recovery system 45 to outlet 46.  The gaseous hydrocarbon include C3 and C4 olefines which may, if desired, be polymerized to gasoline.