A high pressure combustion turbine (109) is integrated with a double column cryogenic air separation system by cooling (111,113) and purifying (115) a portion (11) of the compressed air (6) from the combustion turbine compressor (105), work expanding (118) a first portion (17) of the resulting cooled air (15), and introducing the expanded air (19) into the lower pressure column (119). A second portion (21) of the resulting cooled air (15) is further cooled (117), throttled (121), and introduced (23) into the high pressure column. A nitrogen product stream (35) is returned to the turbine combustor (101), and a portion (41) of the nitrogen product stream optionally is cooled (143,117), throttled (133), and recycled (31) into the higher pressure column (123). Preferably the higher pressure column operates at an absolute pressure which is 20% to 85% of the absolute pressure of the compressed air from the combustion turbine air compressor. Optionally oxygen-rich liquid (33) or nitrogen-rich liquid (45) withdrawn from the higher pressure column (123) during a period of low nitrogen product demand is stored, and withdrawn from storage to supplement feed to the lower pressure column (119) during periods of high nitrogen product demand. Alternatively, high purity liquid oxygen (51) is withdrawn from the lower pressure column (119) during a period of low oxygen product, stored, and withdrawn from storage during periods of high oxygen product demand to supplement oxygen product withdrawn from the higher pressure column.