Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Patent
1997-02-20
1998-07-28
Kilner, Christopher
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
62924, F25J 304
Patent
active
057848998
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an argon separation method in which argon is separated and collected by means of an air liquefying separation method, and to a apparatus employing this argon separation method.
BACKGROUND ART
FIG. 4 shows an example of a conventional argon separation apparatus which employs an air liquefying separation method.
Material air pressurized to approximately 6 kg/cm.sup.2 from which moisture and CO.sub.2 have been removed is cooled to its dew point, and sent from pipe 1 into the lower portion of higher pressure column 3 of double distillation column 2. There, this material air is distilled and separated into liquefied air rich in oxygen, nitrogen gas and liquified nitrogen.
The liquefied nitrogen is withdrawn from the upper portion of higher pressure column 3, passed through pipe 4, supercooler 5, pipe 6, expansion valve 7, and pipe 8, and then introduced as reflux liquid to the upper portion of lower pressure column 9.
The nitrogen gas is effluxed from the upper portion of higher pressure column 3 via pipe 10. Oxygen-enriched liquefied air collects at the bottom of higher pressure column 3, and is withdrawn via pipe 11. The liquefied air withdrawn in this manner is then sent via supercooler 12, pipe 13, expansion valve 14 and pipe 15 to a crude argon condenser 17 located at the top of crude argon column 16. There, a portion of the liquefied air vaporizes, providing cold, after which the liquefied air is introduced to the middle portion of lower pressure column 9 via pipe 18.
The liquid fraction introduced from pipes 8 and 18 flows down through lower pressure column 9 as reflux liquid, and then rises up through lower pressure column 9 after being vaporized at a condensive evaporator 19. Distillation proceeds as a result of contact between the liquid which is coming down and the gas which is rising up through lower pressure column 9. As a result, nitrogen gas is effluxed through pipe 20 from the upper portion of lower pressure column 9, while waste gas is effluxed through pipe 21. Argon material gas which includes mainly oxygen but also argon in the amount of 5 to 15% and trace amounts of nitrogen (argon-containing oxygen gas) is withdrawn from the middle portion of column 9 via pipe 22, and introduced into the lower portion of crude argon column 16.
The argon material gas introduced into crude argon column 16 rises up through column 16, and is liquefied at crude argon condenser 17. A portion of this liquefied argon is removed via pipe 23 as liquefied crude argon, subjected to a deoxidizing process (not shown in the figure), and sent to a pure argon column to be distilled into highly pure argon.
The remaining liquefied crude argon flows down through column 16, comes in contact with the rising gas, collects at the bottom of the column as liquefied oxygen containing a low concentration of argon, and is sent back to lower pressure column 9 via pipe 24.
An immersion-type condenser 25 such as shown in FIG. 5 may be employed for crude argon condenser 17 of crude argon column 16. This immersion-type condenser 25 is designed such that a heat exchanger 27 is disposed inside a liquid collecting portion 26 for holding the liquefied air which is formed at the top of crude argon column 16. This heat exchanger 27 is almost completely immersed in the liquefied air. A straight pipe, plate-fin, or other design may be employed for heat exchanger 27.
However, an immersion-type condenser 25 as described above has the following drawbacks. To begin with, the liquefied air stored in liquid collecting portion 26 contains much component which have higher boiling points above that of the liquefied air inside pipe 15, and is at a temperature which is higher than that of the liquefied air inside pipe 15. Further, because the temperature of the liquefied air on the side at which vaporization is occurring is higher at the bottom portion of condenser 25 due to the liquid air head, the temperature difference between the condensive side and the vaporative side of the condenser is reduced. Moreo
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Honda Hideyuki
Kura Tomio
Nojima Toshiyuki
Kilner Christopher
Nippon Sanso Corporation
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