GB560195A - Improvements in or relating to the production of olefines by the treatment of hydrocarbon oils at elevated temperatures - Google Patents

Abstract

<PICT:0560195/IV/1> <PICT:0560195/IV/2> Heavy hydrocarbon oils are converted mainly into gaseous unsaturated hydrocarbons, e.g. ethylene, propylene, butadiene, and aromatic hydrocarbons, e.g. toluene, benzene and xylene by vaporising the oil in presence of super-heated steam, separating unvaporised constituents, and passing the vapors and gases through a conversion zone heated to 1200-1300 DEG F., quenching the converted products with a condensate produced later in the process, fractionating the vapors to separate gasoline and gases from a condensate which is used as the quenching oil and further fractionating the gasoline and gases to recover ethylene. Crude oil, e.g. gas oil, is fed through line 10 and preheater 14 into a vaporising coil 18 in a furnace 22 and is mixed with superheated steam in the latter sections of the coil. The mixed vapors and liquid pass to a separating tower 42 where liquids are separated through line 44. Superheated steam may be added at the base of the tower through line 102. The vapors pass overhead through line 48 to the conversion coil 55 and the cracked products are quenched in line 56 and then pass to a combined separator and fractionator 60, 62 where a condensate is collected on a tray 72 and recycled through line 74, 78 as quenching oil. This oil is preferably cooled by passing it through cooler 14 where it preheats the charge and through cooler 32 where it preheats water passing to the superheating coil 37. The condensate may also be cycled (a) through line 47 as reflux to tower 42 (b) through line 68 to the separator 60 (c) through line 96 to tower 62. Vapors and gases passing overhead from tower 62 are collected in separator 112 and subjected to a series of compressions and separations in receivers 126, 142, 154 and compressors 136, 150 to obtain a liquid fraction which is fractionated in tower 174 to recover as bottoms an aromatic gasoline fraction recovered through lines 178, 184 and an over-head which is mixed with gases from receiver 154 compressed in compressor 201 and fractionated in tower 202 to separate ethylene and like gaseous fractions. A combination type furnace for carrying out the various heating operations required comprises (Fig. 2) radiant and convection heating sections 232, 234 heated by roof burners 236, and end burners 240. The oil is first heated in a preheating section 246, and is then divided into two, steam passing through tube banks 242, 244 and uniting in line 264. Steam is superheated and fed through line 252, 260 into the banks at 258, 262.