GB341882A - Method of and apparatus for treating hydrocarbons - Google Patents

Abstract

<PICT:0341882/III/1> Crude oil is fractionated in a series of stills A, B, the residue from the still B is cracked and the products hydrogenated in the stills C, D by gases such as methane. Oil is preheated at E by the distillate from the stills B, D. The still A is heated by vapours from the still B and by oil residues from the still D. In the example described, with the stills in full operation, all the gasoline is separated in the still A, the oil is heated to 290 DEG C. in still B driving off naphtha and kerosene without cracking. The <PICT:0341882/III/2> <PICT:0341882/III/3> still C is heated to 400 DEG C. and is worked at 4 to 24 kg. per sq. cm. The residue from still C passes to the still D which is heated to 590 DEG C. and worked at normal or high pressure. The still A comprises a cylinder 1 provided with heating jackets 8, 12, a fractionating tower 18a and vapour dome 20. A hollow vertical shaft 48 driven by a motor 34 carries an oil impeller 42, vanes 50, and discs 51 with vanes 52. The discs 51 are arranged between annular drip plates 54 in the tower 18a. Preheated oil together with oil from the base of the tower 18a enter a chamber 3 at the base of the still, rises through the ports 4, 5 into the body of the still and is thrown outwards against the wall by the impeller 42. The speed of the blades 50 is sufficient to maintain the oil in a thin film on the wall of the still and any residue not evaporated escapes at 58 from the trough 15. Vapour from the preheater enters at the top of the still, passes down through the hollow shaft which is perforated at the lower part at 49, and mixes with the vapour generated in the still. The mixed vapours are separated in the tower 18a into heavier and lighter portions by centrifugal force. The heavier portions are condensed on the wall of the tower, flow down over the baffles 54, and meet the rising vapour. A small amount of liquid finally collects in the trough 55 and is returned by pipe 56 to the inlet chamber 3. The lighter portions of the vapour pass to the dome 20 and outlet 26 leading to a condenser, and a portion of the light condensate may be returned to the top of the tower at 60. Gases and steam, lighter than the vapours, collect in the trap 29 and escape at 27. The jacket 8 is heated by vapour from the second still B, and the coil 16 in the jacket 12 is heated by the uncracked oil residue from the still D. The oil residue leaving the still A at 58 is pumped to the still B, Fig. 5. This still is generally similar, but the lower part is heated by furnace gases in the chamber 75, and the tower is provided with a greater number of centrifuging discs 51 and drip plates 54, whilst a number of outlets 85 are provided for different fractions of the distillate. Each outlet is provided with two branches so that the fractions may be passed to separate storage or to a common pipe leading either to the preheater or to common storage. The vapours from the dome 20b pass to the testing jacket 8 of still A and then to a condenser. The cracking and hydrogenating stills C, D are similar to the still B. The still C has fewer discs 51, no outlets 85, and is of heavier construction. Gases rich in hydrogen, such as methane, are drawn either from the condensers of the system or from a separate source and delivered from a compresser to the top end of the stills C, D, and pass down through the hollow shafts. The still C receives the oil residues from the still B, the condensate from the tower flows back at 56 to the inlet, and the residues from the outlet 81, Fig. 5, are pumped to the still D for similar treatment at 590 DEG C. at normal pressure, or under high pressure. The stills B, D have return pipes (not shown) corresponding to the pipe 56, Fig. 2.ALSO:In the treatment of crude oil by cracking to increase the content of gasoline, a gas rich in hydrogen, e.g. methane, is introduced into the vapour space which is surrounded by a film of the oil, so that the methane is bombarded by molecules freshly formed in cracking the oil and combines therewith.