| 摘要 |
<p>A stream of compressed air has water and carbon dioxide removed therefrom in a purification apparatus 4 and is then cooled in heat exchanger 6 to a temperature suitable for its separation by rectification. The rectification is performed in a dephlegmator 8 that takes the form of a plate fin heat exchanger having four distinct sets of passages 10a, 10b, 10c and 10d. The rectification of the air takes place in passages 10a, and oxygen-enriched liquid passes from the bottom thereof upwardly through the passages 10b in which it is sub-cooled. The sub-cooled liquid oxygen is passed through expansion valve 30 and then flows downwardly through the passages 10c providing the necessary cooling to condense gas in the passages 10a and thus provide a reflux flow for the rectification of the air. The oxygen-rich fluid passing out of the passages 10c flows back through the heat exchanger 6 and is taken as product. Nitrogen is taken from the top of the passages 10a and is passed downwardly through the passages 10d and is thereby superheated. The superheated nitrogen is warmed in the heat exchanger 6, withdrawn at intermediate temperature therefrom, expanded in turbine 44 to meet the refrigeration requirements of the process and then passed through the heat exchanger 6 from its cold to its warm end. <IMAGE></p> |
