| 摘要 |
<p>PROBLEM TO BE SOLVED: To absorb and remove impurities in air thus assuring a stable running of a device even in summer by cooling raw material air with an air cooling system in a nitrogen gas production method which feeds the raw material air in a cold box and carries out cooling, liquefying, rectifying and separation of the raw material air with a liquefied nitrogen. SOLUTION: Raw material air compressed by a raw material air compressor 1 is cooled by an air cooling through an indirect heat exchange caused between the raw material air and atmospheric air blown off from a fan 21a in an air-cooled aftercooler 21. A condensate produced by the heat exchange is separated by a drain separator 22 and is fed to a refrigeration dryer 30 and flows into an absorber 4 by way of an air-cooled refrigeration dryer 30. Accordingly, impurities such as moisture and carbon dioxide contained in air is absorbed and removed so that the raw material air is refined. The raw material air which temperature is elevated by the absorption heat is cooled by an air cooling by means of an air-cooled cooler 23 and then is fed to a cold box 5. Subsequently, the raw material air is cooled down to an approximately liquefying temperature by a heat exchange in the main heat exchanger 6 with a return gas and is fed to a lower portion of a rectifying column 7 where the raw material air is separated into nitrogen and oxygen-rich liquefied air.</p> |
