| 摘要 |
<p><PICT:0723629/III/1> Heavy hydrocarbons such as reduced crudes and pitches are cracked in liquid phase to give lower boiling hydrocarbons and coke, the slurry of cracked oil and coke are separated by gravity into a thickened slurry and clarified oil, the thickened slurry is coked in a further coking stage and the clarified oil is catalytically cracked, preferably in a fluidized solid cracker. The thickened slurry is also preferably coked in a fluidized solids bed and vapours from the coking stage passed to the clarified oil cracking stage or to the final product fractionator. As described in an example, heavy oil feed, preferably diluted with lighter oils and mixed with seed coke from a tank 7, containing a slurry of coke in fresh feed, naphtha, kerosene or product bottoms, is fed via line 1 to heating coil 11 (800-850 DEG F.) and soaker 17 where it is maintained above 800 DEG F. and at 1000-3000 p.s.i. pressure for 5 minutes to 2 hours or more. Feed velocity in coil 11 should be sufficiently high (4-10 ft. or more per second) to prevent coke deposition in the coil. In tank 17 the feed is agitated by paddle 19. Cracked products are led by line 21 to settler 25, being cooled below cracking temperature by mixture with cooled clarified oil from line 22. From settler 25 slurry is drawn off to fluidized solids coker 59 and possibly to slurry tank 7. Any quantity of the slurry may be passed through mill 65 to reduce the coke size to a suitable value. Clarified oil is taken off at 27, part recirculated via cooler 30 to the settler 25 and the remainder fed to catalytic cracker 31. From cracker 31 products are fed to product fractionator 35. Overheads from coker 59 may be fed either to cracker 31 or fractionator 35 by line 91. Light or heavy naphtha may be fed from product lines 39, 41 by line 53 to slurry tank 7 to dilute the feed. From coker 59 product coke may be taken off at 77 and part utilized as seed coke for fresh feed. Bottoms from fractionator 35 may be recycled to cracking stage 31 or passed by line 87 to coker 59 or part or all returned to coil 11 by lines 89, 55 and 9. The Specification gives permissible ranges for temperatures, pressures and residence times which are somewhat wider than those specified in the example. Specification 734,509 is referred to.</p> |
