| 摘要 |
In the method and device, nitrogen is obtained by two-stage rectification of air in a double column. Double column contains a high-pressure column and a medium-pressure column that are in a heat-exchange relationship with each other. Entering air is compressed, purified, cooled in a main heat exchanger against separation products, and fed to rectification. At least one nitrogen product fraction is taken from high-pressure column. A nitrogen gas fraction from double column is heated, expanded, and brought into indirect heat exchange with an oxygen-enriched liquid from the lower region of medium-pressure column. In this way, the nitrogen gas fraction is at least partially condensed and the oxygen-enriched liquid is at least partially evaporated. The condensate formed in the indirect heat exchange is at least partially fed to medium-pressure column. The nitrogen gas fraction is heated upstream of expansion to an intermediate temperature that is between the temperatures at the cold end and the warm end of main heat exchanger.
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