Ethylene recovery from pyrolysis gas mixts. - by condensation and removal of methane

摘要

Process and appts. are claimed for the sepn. of olefins from pressurised gas mixts. comprising H2, CH4 and olefins. The method comprises (a) cooling the feed mixt. (I) by sequential stages to condense the olefins and part of the CH4 and H2, (b) sepg. at each cooling stage, the condensate from the gaseous residue, (c) demethanising the condensate to obtain pure olefins, and a residual gas mixt. (II) of H2, CH4 and traces of ethylene, (d) cooling (II) to obtain further condensate and using the liquid as a spray in the lemethanising step, (e) introducing the remaining cooled (II) into a first vortex tube to cause expansion and formation of a hot gas stream (III) and a cold gas stream (IV), (f) using (IV) to c cool (II( from step (c), (g) mixing (III) and (IV) and passing the mixt. through a second vortex tube to form a second hot gas stream (V) and a second cold gas stream (VI), (h) subjecting (I) to countercurrent heat exchange with (V), using (VI) to cool first (II) from step (c) and then (I), and (i) collecting olefin product from (c) and venting (II), having a reduced ethylene content, from the process. The process is used for recoving ethylane in yields of 99% or more from naphtha pyrolysis effluents. The appts. is simple in design, contg. no structural elements with moving parts, reliable and adaptable to automatic operation, No additional energy sources are required and in fact total energy demand is reduced.