Patent GB-824495-A (GB)
Title: Two-stage hydrocarbon-cracking process
Filed: 1956-11-08
Abstract: <PICT:0824495/III/1> A combined coking and cracking process of the type wherein a heavy hydrocarbon oil is converted to coke, low-molecular weight normally gaseous unsaturated hydrocarbons, and small quantities of aromatic unsaturated low-boiling normally liquid hydrocarbons comprises contacting the oil with a dense turbulent fluidized bed of catalytically inert particulate solids in a reaction zone at 900 DEG  to 1150 DEG  F. to evolve lighter hydrocarbon vapours and deposit carbonaceous residue on the solids, and then passing the vapours withdrawn from the dense bed reaction zone without substantial cooling to a transfer line where they are contacted at 1200 DEG  to 1600 DEG  F. with a fluidized suspension of hot inert particulate solids coming from a heating zone to effect further cracking. Reduced crudes, vacuum bottoms, pitch asphalt and other heavy hydrocarbon residua may be cracked by the process.  A typical feed yielded 22% of a C5-475 DEG  F. fraction, 10% hydrocarbons boiling between 475 DEG  and 650 DEG  F., 8% of tar boiling over 650 DEG  F. and 17% coke.  The remainder comprised C6 and lower hydrocarbons and hydrogen, principally ethylene (12%) and propylene (10%). Preheated heavy oil from line 1 is introduced into a fluid coking reactor through manifold 2.  The coker contains a bed of inert particulate solids, e.g. coke or sand of particle size up to 1000 microns, which is fluidized by a gas, e.g. steam, entering via line 3 at velocities of 0.1 to 5 F.S. and which is maintained at 900 DEG  to 1150 DEG  F.  Relatively cool solids with deposits of fresh coke are stripped of occluded hydrocarbons in stripping zone 10a and are withdrawn via line 5 to a reheater, from which they are returned to the coker via line 6 at temperatures above the coking temperature, e.g. 1400 DEG  F.  The vaporous effluent from coker 10 is transferred via line 4 to a transfer line 20 where they are mixed with a fluidized suspension of particulate solids heated to 1300-1800 DEG F. in amounts which yield a reaction temperature of 1200 DEG  to 1600 DEG  F.  The reaction products are separated in cyclonic separator 11, the solids passing through line 13 to a reheater which may be the same one as is used for solids from coker 10 or which may be independent.  The gaseous products leave the cyclone by line 14 where they are cooled to below 900 DEG  F. by a quench from line 15 comprising, for example, water, cool oils, cool coke particles, cool hydrocarbon gases or steam.  Suitable fluidizing gases for reactor 20 are steam, light hydrocarbon gases, nitrogen or flue gases, in amounts sufficient to produce a solids velocity of at least 10 F.S. The products may be further processed, e.g. by fractionation, absorption, crystallization, extractive or azeotropic distillation or polymerization.ALSO:<PICT:0824495/IV (b)/1> A combined coking and cracking process of the type wherein a heavy hydrocarbon oil is converted to coke, low-molecular weight normally gaseous unsaturated hydrocarbons, and small quantities of aromatic unsaturated low-boiling normally liquid hydrocarbons comprises contacting the oil with a dense turbulent fluidized bed of catalytically inert particulate solids in a reaction zone at 900 DEG  to 1150 DEG  F. to evolve lighter hydrocarbon vapours and deposit carbonaceous residue on the solids, and then passing the vapours withdrawn from the dense bed reaction zone without substantial cooling to a transfer line where they are contacted at 1200 DEG  to 1600 DEG  F. with a fluidized suspension of hot inert particulate solids coming from a heating zone to effect further cracking. Reduced crudes, vacuum bottoms, pitch asphalt, and other heavy hydrocarbon residua may be cracked by the process.  A typical feed yielded 22% of a C5-475 DEG F. fraction, 10% hydrocarbons boiling between 475 DEG  and 650 DEG F., 8% of tar boiling over 650 DEG  F. and 17% coke.  The remainder comprised C6 and lower hydrocarbons and hydrogen, principally ethylene (12%) and propylene (10%).  Preheated heavy oil from line 1 is introduced into a fluid coking reactor through manifold 2.  The coker contains a bed of inert particulate solids, e.g. coke or sand of particle size up to 1000 microns, which is fluidized by a gas, e.g. steam, entering via line 3 at velocities of 0.1 to 5 f.s., and which is maintained at 900 DEG  to 1150 DEG  F.  Relatively cool solids with deposits of fresh coke are stripped of occluded hydrocarbons in stripping zone 10a  and are withdrawn via line 5 to a reheater, from which they are returned to the coker via line 6 at temperatures above the coking temperature, e.g. 1400 DEG  F.  The vaporous effluent from coker 10 is transferred via line 4 to a transfer line 20 where they are mixed with a fluidised suspension of particulate solids heated to 1300-1800 DEG  F. in amounts which yield a reaction temperature of 1200 DEG  to 1600 DEG  F.  The reaction products are separated in cyclonic separator 11, the solids passing through line 13 to a reheater which may be the same one as is used for solids from coker 10 or which may be independent.  The gaseous products leave the cyclone by line 14 where they are cooled to below 900 DEG  F. by a quench from line 15 comprising, for example, water, cool oils, cool coke particles, cool hydrocarbon gases or steam. Suitable fluidizing gases for reactor 20 are steam, light hydrocarbon gases, nitrogen or flue gases, in amounts sufficient to produce a solids velocity of at least 10 f.s.  The products may be further processed, e.g. by fractionation, absorption, crystallization, extractive or azeotropic distillation or polymerization.