GB1234499A - - Google Patents

Abstract

1,234,499. Steam cracking to produce olefins. INSTITUT FRANCAIS DU PETROLE DES CARBURANTS ET LUBRIFIANTS. 3 Sept., 1969 [4 Sept., 1968], No. 43554/69. Heading C5E. Olefins, particularly ethylene, are produced by thermal or catalytic cracking of hydrocarcarbon feedstocks in the presence of steam, the gaseous cracked product being treated as follows: (a) it is mixed with first and second relatively cool streams of recycled liquid hydrocarbons to decrease the temperature and to cause partial condensation; (b) the resulting liquid fraction is separated from the remaining gaseous fraction and is utilized, after cooling by passage through an indirect heat exchange zone, as the first recycle stream of (a); (c) the gaseous fraction from (b) is admixed with a third relatively cool stream of recycled liquid hydrocarbons to cause further condensation; (d) the liquid fraction resulting from (c) is utilized, after cooling by passage through an indirect heat exchange zone, as the second and third recycle streams in (a) and (c) respectively; and (e) the residual gaseous fraction from (d) is withdrawn as the product containing desired olefins. The two streams in (a) may be added either separately or together to the cracked gaseous product, and step (a) may be conducted in several devices in parallel. The indirect heat exchange zone in (b) may be used to generate moderate pressure steam which may be used in the cracking process.