Low-temperature process for fractional distillation of nitrogen from air

摘要

The process uses a fractionating column (8) which receives air (1) which has passed through a compressor (2) beforehand where the pressure of the air is raised to between 2.5 and 3.5 bar. Gas at the top of the column passes through a condenser, and the nitrogen is removed from the resulting condensate. A single-column (8) cryogenic fractional distillation process and assembly extracts nitrogen from air. In the first stage, air (1) is surrendered to a compressor (2) which raises it to a pressure P1 (pref. 2.5 to 3.5 bar) for release into the column (8). Gas (15) at the column head (8) is liquefied in a condenser (14). The resulting condensate (16) is partially (17) returned to the column (8). The nitrogen product (19, 20) is removed from the column (8). A portion (21) of the nitrogen is allowed to expand (10), doing work. The air pressure is raised to a first pressure P1 in the compressor (2) which is essentially the same as the column (8) operational pressure.