Patent ID: 6490884
Filing Date: 2002-12-10
Classification: F25J

Abstract:
A process for production of oxygen and nitrogen by low-temperature separation of air in a rectification system which comprises a high-pressure column (4) and a low-pressure column (5), said process comprising:feeding air (1, 3) into a high-pressure column (4), removing an oxygen-containing liquid fraction (8, 10) from said high-pressure column(4) and feeding said oxygen-containing liquid fraction into said low-pressure column (5), at least partially condensing gaseous nitrogen (17) from low-pressure column (5) in a top condenser (7) of said low-pressure column by indirect heat exchange with an evaporating cooling fluid (15), removing a nitrogen product stream (19) from said low-pressure column (5) said pressure column (4), and removing an oxygen product stream (61, 62, 63) in liquid form, gaseous form, or both, from said low-pressure column (5), wherein said cooling fluid for said top condenser (7) of said low-pressure column (5) is formed by an intermediate liquid (15) removed from an intermediate point on said low-pressure column (5), wherein said intermediate point is above the point at which said oxygen-containing liquid fraction (8, 10) from said high-pressure column (4) is introduced into said low-pressure column (5), and said intermediate point is below the point at which said nitrogen product stream (19) is removed from said low-pressure column (5).