GB728234A - Improvements in or relating to petroleum distillation - Google Patents

Abstract

<PICT:0728234/III/1> Gasoline is separated from crude petroleum containing a substantial proportion of light ends by a distillation process employing two stages connected in series, the first stage being operated at a pressure greater than atmospheric and at a temperature such that only about half the total gas and gasoline is distilled off therein; the heavy gasoline is obtained as distillate from the second stage which is operated at a higher temperature but at a lower pressure than the first stage. The process is preferably carried out using two fractionating columns and the distillate from the second column may be introduced into the upper section of the first column. Crude oil containing about 2 per cent. gas and about 14.5 per cent. gasoline is pumped through heat exchanger 12, desalting unit 16 and heat exchanger 18 into a flash zone at the lower part of column 14. This column, which has fractionating decks above the feed inlet, is operated at a pressure of 30-50 p.s.i.g., with a bottom temperature of 300 DEG to 400 DEG F. Vapours containing about 90 per cent. of the gas and about 40 per cent of the gasoline in the feed pass overhead through line 20, and are condensed; the condensate being collected in drum 24. Some of the condensate is returned through line 26 to column 14 as reflux. The bottoms from column 14 are withdrawn through line 30, and are passed through heat exchanger 32 to furnace 34, where the temperature is raised to 700 DEG -750 DEG F. The hot oil is then introduced into column 36 which is maintained at a pressure of about 10-15 p.s.i.g. Stripping steam is introduced into column 36 via line 38. The heavy ends of the gasoline are driven overhead from column 36, and are condensed; the condensate being collected in drum 44. Some of the condensate is returned via line 46 to column 36 as reflux. The remainder of the heavy ends of the gasoline is passed through line 48, and is introduced in part via line 48a to the overhead vapours in line 20, and in part via line 48b to the reflux return line 26 of column 14. All the gasoline and gas in the crude is withdrawn from drum 24 via line 28. Side streams moved refrom column 36 account for approximately 43.5 per cent. of the crude; and the bottoms account for the remaining 40 per cent.