process and plant for producing a liquid nitrogen stream, a gaseous nitrogen stream, a helium-rich gaseous stream and a dehydrogenated hydrocarbon stream from a hydrocarbon, nitrogen and helium charge stream

摘要

This process includes the cooling of an introduction stream (72) inside an upstream heat exchanger (28). It includes the introduction of the cooled introduction stream (76) into a fractionating column (50) and the tapping at the bottom portion of the column (50) of the denitrided stream of hydrocarbons. It also includes the introduction of a stream (106) rich in nitrogen obtained from the head portion of the column (50) into a separation container (60) and the recovery of the head gaseous stream from the separation container (60) in order to form the stream (20) which is rich in helium. The liquid stream (110) is obtained from the bottom of the first separation container (60) is separated into a liquid nitrogen stream (18) and a first reflux stream (114) which is introduced as reflux into the head of the fractionating column (50).