GB353276A - Improvements in or relating to the cracking of hydrocarbon oils - Google Patents

Abstract

Liquid residual oil from a liquid phase cracking operation is fractionated to give (a) a light fraction, (b) an intermediary fraction, (c) a heavy fraction, (d) and a liquid residuum, the intermediary fraction and the residuum being blended to give a fuel oil while the heavy fraction is returned to the cracking zone. Oil is delivered by a pump 15 to a cracking plant comprising heating coil 10, reaction drum 11, fractionating tower 12, condenser 13 and separator 14, the residues in the tower 12 being returned by the pipe 19 to the middle of the cracking coil 10. The residual oil from the drum 11 is passed through a pipe 20 with reduction of pressure at a valve 21a into an expansion chamber 23 and the vapours evolved are fractionated in a tower 28 into a light fraction passing off through a line 29 and condenser 30 to a receiver 31, an intermediary fraction withdrawn through lines 33, 34, and a heavy fraction withdrawn through a line 32 for recircu <PICT:0353276/III/1> tion to the cracking zone by a pump 49. The residuum from the chamber 23 may be further stripped in a chamber 24 with the aid of steam introduced through a jet 26 the pressure being preferably reduced below atmospheric. The vapours pass to a tower 36 comprising upper and lower zones 36a, 36b, vapours not condensing below 212 DEG F. in the upper zone being withdrawn with the steam and washed with water in the lower zone. The residuum from the chambers 23, 24 is withdrawn and mixed by a pump 48 with the condensate withdrawn through the lines 33, 34, the blended oils being stored in a tank 56 and having characteristics suitable as fuel oils.