| 摘要 |
<p>PURPOSE: To produce a high purity nitrogen vapor product by rectifying air using a two stage air separation unit comprising high and low pressure columns operatively associated with one another by a condenser-reboiler and to reduce construction cost by simplifying assembling work of the low pressure column. CONSTITUTION: Air flow 12 is compressed, at first, through a compressor 14 and rectified through a preliminary rectification unit 18 after compression heat is removed therefrom by means of an aftercooler 16. Subsequently, the air flow 12 is cooled through a main heat exchanger 20 and introduced sequentially into a high pressure column 24 and a low pressure column 26 constituting an air separation unit 22. In this regard, high purity nitrogen condensed through a condenser-reboiler 28 is branched into a plurality of auxiliary flows 30, 32. One auxiliary flow 32 is supercooled through a supercooler 34 and fed to a head condenser 42 after temperature is lowered through expansion in a Joule- Thomson valve 36. Furthermore, a rough oxygen flow 38 taken out from the bottom part of the high pressure column 24 is supercooled through the supercooler 34 and the pressure thereof is lowered down to the pressure level of the low pressure column 26 through another Joule-Thomson valve 40.</p> |
