| 摘要 |
PURPOSE: To recover a part of argon, by introducing a second flow into upper part than the gas-liquid contact surface level of the second column, and producing a fraction softer than the introduced supply material and high in concentration of impurity at the top. CONSTITUTION: Air is introduced into the high-pressure column 4 of a double column 2, and is separated into liquid RL rich in oxygen and liquid PL low in content of oxygen, and RL is taken out of the lower part, is introduced into a low-pressure column 6, and is separated into an oxygen fraction and a nitrogen fraction, and gas oxygen is refined with the first refining column 10 and further with the second refining column 12 so as to manufacture ultras pure oxygen. This second refining column 12 is separated into ultra pure oxygen not containing low boiling point impurities and a fraction large in content of argon, and the content of argon goes higher, according to the rise of steam, and it is returned to the middle stage of the low-pressure column 6 through a condenser 66, and a liquid argon product is extracted through a side column 8 from its bottom. In this way, at least a part of argon can be recovered efficiently.
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