GB815155A - Cracking heavy hydrocarbon oils by means of a fluidized bed of hot inert-solid particles - Google Patents

Abstract

In a process for cracking heavy hydrocarbon oils, such as residual oils, by introducing the oil into a fluidized bed of hot inert-solid particles, the product-vapours issuing from the reactor are scrubbed with a heavy hydrocarbon oil in order to remove entrained solid particles and those oil components boiling above 1000 DEG F., the vapours are then scrubbed with a lighter <PICT:0815155/III/1> hydrocarbon oil to remove heavy gas oil having an initial boiling point within the range 800-950 DEG F., and the scrubbed vapours are fractionated whereby gas oil, suitable for catalytic cracking, is obtained. The liquid withdrawn from the first scrubbing zone is introduced into the fluidized bed. The liquid withdrawn from the second scrubbing zone is partially vaporized to remove lighter gas oil components, and the liquid-residue is recycled to the fluidized bed. In an example, a residual oil having an initial boiling point of 1000 DEG C. is injected through manifold 2 into a fluidized bed of coke particles maintained at a temperature of 950 DEG F., whereby 75 per cent of the feed is converted to products boiling below 1000 DEG F., and coke is deposited on the particles. The vapours pass through cyclone 8; and are introduced into the lower section of scrubbing tower 10, where they are contacted with a recycle bottoms fraction, having an initial boiling point of 1075 DEG F. and an inlet temperature of 600 DEG F., supplied through line 11 in an amount sufficient to condense all material boiling above 1030 DEG F. The scrubbing liquid and the condensate collects in the base of tower 10; a portion of this liquid is recycled via heat-exchanger 13 to line 11, and the remainder is introduced via line 16 into the lower part of the fluidized bed. The vapours leave the first scrubbing zone through plate 17, and are then scrubbed with recycled heavy gas oil, boiling within the range 800-950 DEG F. and having an inlet temperature of 500 DEG F., supplied through line 18 in amount sufficient to condense all material boiling above 950 DEG F. The liquid which collects on plate 17 is in part recycled via heatexchanger 21 to line 18, while the remainder is passed through line 20 to the uppermost portion of the fluidized bed where gas oil is vaporized with substantially no cracking and the heavier components are deposited on the particles. Alternatively, the liquid in line 20 may be passed to an external vaporization zone, such as a fluidized bed or a transfer line zone where it is contacted with solid particles at a temperature of 600-800 DEG F. The vapours can then be returned directly to the second scrubbing zone, while the particles, charged with liquid deposit, are passed to the cracking reactor. In another alternative, the feed oil is subjected to initial topping to remove gas oil in a vacuum tower; and the liquid withdrawn from the second scrubbing zone is also passed to the vacuum tower.