| 摘要 |
PURPOSE: To produce liquid nitrogen with high yield, by circulating a fraction of heated nitrogen for compression/refrigeration, introducing the compressed/refrigerated nitrogen into a heat exchanger in the lower portion of a column for condensation, then introducing the condensed nitrogen to a position higher than the column or to the upper portion of the column after reducing the pressure thereof. CONSTITUTION: A process for producing nitrogen comprises circulating a fraction of heated nitrogen 14 to compress and cool it, introducing the compressed and cooled nitrogen into a heat exchanger 6 in the lower portion of a column 4 to condense it therein, in some cases extracting a little amount of the condensed nitrogen therefrom to generate liquid nitrogen under high pressure, and introducing the nitrogen into the upper portion of the column 4 after reducing the pressure thereof. That is, the nitrogen 14 is first cooled in a heat exchanger 2, and at least a fraction of it is heat- exchanged with an oxygen-enriched fraction under evaporation process in the heat exchanger 6 in the lower portion of the column 4 to be condensed. Then the flow of the condensed nitrogen is supercooled in a heat exchanger 10 if necessary, reduced in pressure by way of a valve 17, and introduced to the upper portion of the column 4. As a result, the extraction yield of the nitrogen 14 is increased, and a production unit is maintained at a low temperature.
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