Patent GB-805242-A (GB)
Title: Cracking heavy hydrocarbon oils in a two-stage process
IPC: C10G9/32
Filed: 1955-10-26
Abstract: A heavy hydrocarbon oil is cracked by contacting the oil with a fluidized bed of inert solid particles at a temperature in the range of 850 DEG  to 1200 DEG  F., whereby a substantial proportion of the oil is converted into vapours which contain gas oil and naphtha; the particles coated with residual oil are withdrawn from the fluidized bed and are passed rapidly through a <PICT:0805242/III/1> transfer line in admixture with freshly-heated particles so that a temperature above 1200 DEG  F. (preferably in the range of 1200-1600 DEG  F.) is attained and ethylene and propylene and coke are produced. Petroleum residua, coal tars, shale oils and asphalts may be used as feedstocks for the process.  The apparatus shown comprises reaction vessel 10, transfer line reactor 20, and burner 30. Vessel 10 contains a bed of coke particles (average size 250 m ), at a temperature of about 950 DEG  F., fluidized by steam introduced through line 2.  A vacuum residuum is injected into vessel 10 via line 1; and about 60 per cent of this feed is converted into vapours, which are withdrawn via cyclone 3, quenched with heavy oil in scrubber 4, and taken through line 8 to a fractionation system.  Gas oil forms the main constituent of this product.  The heavy oil withdrawn from the scrubber is in part introduced into vessel 10, the remainder being returned to the top of the scrubber via heat-exchanger 6.  Coke particles coated with unconverted oil are transferred from vessel 10 via line 9 to the inlet of transfer line 20; and very hot particles from burner 30 are added through line 22 so as to raise the temperature of the mixture to about 1300 DEG  F.  The mixture is carried up the transfer line by steam admitted through line 11, the residence-time being about 1 second; and about 30 per cent of the residual oil is converted into hydrocarbon gases while fresh coke is deposited on the particles. The gases are separated from the coke particles in cyclone 12, cooled by heavy oil introduced through line 14, and removed from the system via line 13.  These gases contain ethylene and propylene.  The coke particles withdrawn from cyclone 12 are passed to vessel 16 where they are fluidized with steam, introduced through line 17, in order to remove occluded hydrocarbons.  These hydrocarbons are led via line 18 into the top of vessel 10.  A major proportion of the stripped coke particles are transferred from the stripped via line 19 and steam generator 28 to the fluidized bed in vessel 10.  The remainder of the particles are transferred via line 21 to burner 30, where they are reheated by fluidization and partial combustion in air supplied via line 24.  The temperature of the particles is raised to about 1650 DEG  F. in the burner.  Flue gases are vented via line 26.  Some of the reheated coke particles are passed via line 22 to transfer line 20; and excess coke is removed from the system through line 27.ALSO:A heavy hydrocarbon oil is cracked by contacting the oil with a fluidized bed of inert solid particles at a temperature in the range of 850 DEG  to 1200 DEG  F. whereby a substantial proportion of the oil is converted into vapours which contain <PICT:0805242/IV (b)/1> gas oil and naphtha; the particles coated with residual oil are withdrawn from the fluidized bed and are passed rapidly through a transfer line in admixture with freshly-heated particles so that a temperature above 1200 DEG  F. (preferably in the range of 1200-1600 DEG  F.) is attained and ethylene and propylene and coke are produced.  Petroleum residua, coal tars, shale oils and asphalts may be used as feedstocks for the process.  The apparatus shown comprises reaction vessel 10, transfer line reactor 20, and burner 30.  Vessel 10 contains a bed of coke particles (average size 250 m ) at a temperature of about 950 DEG  F., fluidized by steam introduced through line 2.  A vacuum residuum is injected into vessel 10 via line 1; and about 60 per cent of this feed is converted into vapours, which are withdrawn via cyclone 3, quenched with heavy oil in scrubber 4, and taken through line 8 to a fractionation system.  Gas oil forms the main constituent of this product.  The heavy oil withdrawn from the scrubber is in part introduced into vessel 10, the remainder being returned to the top of the scrubber via heat-exchanger 6.  Coke particles coated with unconverted oil are transferred from vessel 10 via line 9 to the inlet of transfer line 20; and very hot particles from burner 30 are added through line 22 so as to raise the temperature of the mixture to about 1300 DEG  F. The mixture is carried up the transfer line by steam admitted through line 11, the residence-time being about 1 second; and about 30 per cent of the residual oil is converted into hydrocarbon gases while fresh coke is deposited on the particles.  The gases are separated from the coke particles in cyclone 12, cooled by heavy oil introduced through line 14, and removed from the system via line 13.  These gases contain ethylene and propylene.  The coke particles withdrawn from cyclone 12 are passed to vessel 16 where they are fluidized with steam, introduced through line 17, in order to remove occluded hydrocarbons.  These hydrocarbons are led via line 18 into the top of vessel 10.  A major proportion of the stripped coke particles are transferred from the stripper via line 19 and steam generator 28 to the fluidized bed in vessel 10.  The remainder of the particles are transferred via line 21 to burner 30, where they are reheated by fluidization and partial combustion in air supplied via line 24.  The temperature of the particles is raised to about 1650 DEG  F. in the burner.  Flue gases are vented via line 26.  Some of the re-heated coke particles are passed via line 22 to transfer line 20; and excess coke is removed from the system through line 27.