Air is rectified in a rectification system comprising a higher pressure rectification column 14, an intermediate pressure rectification column 16, and a lower pressure rectification column 18. A first reboiler-condenser 20 provides liquid nitrogen reflux for the higher pressure rectification column 14 and for the lower pressure rectification column 18 and also reboils the intermediate pressure rectification column 16. Another reboiler-condenser 53 provides liquid nitrogen reflux for the intermediate pressure rectification column 16 and reboils the lower pressure rectification column 18. Air is fed to the higher pressure rectification column 14 through inlets 12 and 26. A first oxygen product is withdrawn from the intermediate pressure rectification column 16 by pump 58. Gaseous nitrogen products are withdrawn from the intermediate and lower pressure rectification columns 16 and 18 through outlets 46 and 74 respectively. <IMAGE>
