Improvements in or relating to the treatment of hydrocarbon oils by fractional distillation and pyrolytic conversion

摘要

PICT:0469435/III/1 In a process for distilling and cracking oils the charging stock, preheated by hot conversion products of the process, is distilled and fractionated into light, intermediate and heavy fractions, the heavy fractions are cracked cyclically, the cracked products are separated in a separate fractionation zone into a gasoline, an intermediate, and a heavy fraction, which latter is recycled to the conversion stage, the gasoline fraction is stabilized, and gaseous fractions from the fractionation and stabilization stages are absorbed by contact with a portion of the charging stock, the enriched oil being fed to the cracking stage. Crude oil is fed by a pump 3 through a heat-exchanger 6 to a sedimentation tank 9 and passes thence through heat-exchangers 14, 17 and a pipe coil 20 to a fractionating column 24. Gasoline fractions are removed through a line 25 and cooler 27 to a receiver 30 while an intermediate kerosene or naphtha fraction is removed to a reboiler 42 and thence to storage. The heavy fraction is led off through a line 49 and heat-exchangers 14, 6 (1) directly through lines 54, 56 to the fractionating tower 61 of a cracking plant comprising cracking coil 80, reactor 84 and evaporator 87, or (2) first through an absorption tower 59 to which crude oil may be separately supplied by a pump 64 and line 66, the enriched oil passing through the lines 70, 68 to the line 56. The cracked products are separated in the tower 61 into (a) a gasoline fraction removed through a line 113 through a cooler 115 to a receiver 118 where it is separated from gases and then fed by a pump 126 through lines 127, 136 and heat-exchanger 135 to a stabilizing tower 129; (b) an intermediate kerosene fraction which is removed to a reboiler 106 and thence to storage; (c) a heavy fraction which is recycled through lines 75, 78 to the cracking stage. The gasoline in the tower 129 is stabilized by feeding it through a line 138 to a heat-exchanger 140 the vapours evolved being returned to the tower through a line 152 while the stabilized gasoline is removed through lines 154, 156. The heat-exchanger is heated by flowing therethrough part of the heavy recycle stock from the tower 61 which is supplied through a line 141 and returned, with or without passage through a cooler 147, through a line 143. Vapours removed from the stabilizer 129 are condensed in a cooler 160 and separated from gases in a receiver 163. These gases and the gases removed from the receiver 118 are fed through lines 121, 123 to the absorption tower 59. Part of the recycle stock flowing in the line 75 is diverted through a line 92 to flow through the heat-exchanger 17 and thence with or without passage through a cooler 97, through a line 94 into the evaporator 87 or into the tower 61.