Nitrogen rejection from natural gas with co.sub.2 and variable n.sub.2 content

Abstract From the Canadian patent

A process is described which uses a modified double distillation cycle for rejecting nitrogen from a natural gas stream containing varying amounts of nitrogen methane, carbon dioxide and ethane-plus hydrocarbons. The natural gas stream is fractionally distilled in the high pressure distillation stage of the double distillation cycle to provide a nitrogen overhead and a bottoms comprising carbon dioxide and ethane-plus hydrocarbons. A sidestream consisting essentially of nitrogen and methane is withdrawn from the high pressure distillation stage as intermediate level feed to the low pressure distillation stage of the double distillation cycle. The nitrogen overhead from the high pressure …