Patent ID: 8991209
Filing Date: 2015-03-31
Classification: F25J

Abstract:
1. A process for producing high pressure nitrogen, the process comprising: cooling feed air to substantially the dew-point thereof; introducing at least a portion of said feed air at a base of a high pressure column; removing an oxygen enriched liquid from the base of said high pressure column; reducing the pressure of said oxygen enriched liquid in a first valve to a medium pressure; wherein said medium pressure is between said high pressure and atmospheric pressure; introducing said oxygen enriched liquid at an intermediate place of a medium pressure column; reducing the pressure of at least a part of a liquid removed from the base of said medium pressure column in a second valve to a low pressure to cool a top condenser of said medium pressure column and to form a waste vapor stream; compressing a vapor stream removed form the medium pressure column in a cold compressor, cooling said vapor stream, and introducing the vapor stream into the base of the high pressure column; heating said waste vapor stream, and expanding said waste vapor stream in an expander to produce power, withdrawing a top liquid from the top of said medium pressure column; pumping said top liquid to said high pressure and injecting it at the top of the high pressure column; and withdrawing product nitrogen from the top of the high pressure column.