| 摘要 |
A method for the preparation of a substantially oxygen-free fraction, i.e. not exceeding 20 vols., oxygen per million, from a crude gaseous mixture containing oxygen comprises mixing therewith an amount of hydrogen in excess of that stoichiometrically required to react with the oxygen present, passing the gas mixture so formed over a catalyst adapted to promote the reaction of hydrogen and oxygen to form water and a substantially oxygen-free gaseous product, removing the water formed and partially liquefying the oxygen-free gaseous product to separate a liquid fraction which is substantially free from hydrogen or oxygen, and a gaseous residue containing substantially the whole of the remaining hydrogen. The method may be used for preparing oxygen-free <PICT:0723050/III/1> nitrogen, argon, krypton, neon, or xenon or argon-nitrogen mixtures, or oxygen and nitrogen-free argon from a ternary mixture of these gases. Crude argon containing 1 per cent air enters compressor 1 through line 2 after admixture of a gas containing hydrogen and argon in equal proportions. After compression to say 2.7 atms., the gas passes to catalytic deoxidizer 5, containing, e.g. a supported palladium catalyst, and resulting water is removed in drier 7. The dried gases pass through heat exchanger 9 and cooler 11 to condenser-evaporator 13 of rectification column 14, where they are completely liquefied apart from a small residue of hydrogen, which passes, with some argon and nitrogen through 15 to heat exchanger 16 where most of the argon and all the nitrogen is condensed and returned to condenser 13 through 17. The liquid argon from 13 still containing some nitrogen and traces of hydrogen is passed through pipe 18 to upper section of column 14 where the nitrogen and hydrogen are eliminated and pass out through 20 in a gas comprising argon and nitrogen mixture. The reflux in column 14 is provided by expanding pure liquid argon from the bottom of column 14 through pipe 23 and valve 24 to heat exchanger 16 to cool the hydrogen vent gases, and thence to column condenser 21 through 25. Pure argon vaporized from 21 is withdrawn through 26 and heat exchanger 9, to cool incoming gas, and is recovered at 27. The hydrogen vent gases leaving exchanger 16 pass through pipe 29, where pure hydrogen is added through pipe 33 and flow meter 35, the addition being automatically controlled to ensure that the recycle gas passing out through catharometer 31 and flowmeter 32 to recycle line 3 contains hydrogen and argon in approximately equal proportions. Provided valve 30 is set to give a reading on meter 32 which is more than double that on meter 35 then some hydrogen must be present in the vent gases from exchanger 16 and an excess of hydrogen is maintained. The hydrogen addition should be controlled to maintain the hydrogen content at the upper limit fixed by the condensing pressure and condenser temperature.
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