A process for producing liquid nitrogen utilizes a distillation system comprising higher-pressure and lower-pressure columns, a first condenser in the lower-pressure column bottom, and a second condenser disposed on top of the lower-pressure column. Feed air is compressed in a main air compressor above 15 bar(a) and cooled in a main heat exchanger. A first cooled air portion is expanded in a cold turbine before separation in the higher-pressure column. A second cooled air portion is liquefied before entering the higher-pressure column. Liquid nitrogen streams condensed by both the first and second condensers are combined to yield the final product. Another feature involves warming and expanding a lost air stream (e.g., from the cold turbine outlet and/or higher-pressure column) to below 2 bar(a) in a warm turbine.