PROCESS TO PRODUCE NITROGEN USING A DOUBLE COLUMN PLUS AN AUXILIARY LOW PRESSURE SEPARATION ZONE

摘要

A process is set forth for the cryogenic distillation of an air feed to producenitrogen, particularly high pressure nitrogen of various purity, varying from low purity (upto 98% nitrogen) to ultra-high purity (less than 1 part per billion of oxygen). Thenitrogen may be produced at two different pressures and two different purities. Theprocess uses an auxiliary low pressure separation zone in addition to the conventionalhigh pressure column and low pressure column. The auxiliary low pressure separationzone, which is operated at the same pressure as the low pressure column and which isheat integrated with the top of the high pressure column by means of its bottomreboiler/condenser, pretreats the crude liquid oxygen from the bottom of the highpressure column.