Process for separating off nitrogen

Abstract

A process is described for separating off a nitrogen-rich fraction from a feed fraction containing essentially nitrogen and hydrocarbons, wherein the feed fraction is separated by rectification into a nitrogen-rich fraction and a methane-rich fraction, the methane-rich fraction, for the purpose of cold generation at a pressure as high as possible, is vaporized against the feed fraction which is to be cooled and superheated and the nitrogen-rich fraction is compressed at least occasionally and/or at least in part and is fed to the rectification as reflux stream. According to the invention at least occasionally at least a substream (16) of the compressed (C) nitrogen-rich fraction (9′) is expanded (f) after condensation (E1) thereof and, for the purpose of cold generation, is at least in part, preferably completely, vaporized (E1).

Dependencies are inferred from the claim text.