Low temperature purification of an impurity-containing gas

Claim 1

A PROCESS FOR THE LOW-TEMPERATURE PURIFICATION OF A LOW-BOILING IMPURITY-CONTAINING COMPRESSED GAS STREAM COMPRISING THE STEPS OF PROVIDING A GAS STREAM AT THE WARM END OF A REVERSIBLE HEAT EXCHANGE ZONE; AS A GAS CLEANUP STROKE, PASSING AT LEAST PART OF THE INLET GAS STREAM ALTERNATELY THROUGH FIRST AND SECOND REVERSING PASSAGEWAYS IN SUCH ZONE AND COOLING SUCH STREAM TO A TEMPERATURE BELOW THE DEPOSITION POINT OF THE LOW-BOILING IMPURITIES THEREBY DEPOSITING SUCH STREAM TO A TEMPERATURE SAGEWAYS; PROVIDING A COLD PURGE GAS STREAM AT THE COLD END OF THE HEAT EXCHANGE ZONE; AS A GAS EXHAUST STROKE, DRAWING THE COLD PURGE STREAM AT SUB-ATMOSPHERIC PRESSURE THROUGH THE REVERSING PASSAGEWAY VACATED BY THE INLET GAS STREAM AND IN OPPOSITE FLOW DIRECTION THERETO SO AS TO EVAPORATE THE PREVIOUSLY DEPOSITED LOW-BOILING IMPURITIES THEREIN FOR REMOVAL FROM THE HEAT EXCHANGE ZONE; PERIODICALLY SWITCHING THE INLET GAS AND PURGE GAS FLOWS BETWEEN THE FIRST AND SECOND REVERSING PASSAGEWAYS; PROVIDING A COLD PRODUCT STREAM OF AT LEAST ATMOSPHERIC PRESSURE AT THE COLD END OF THE HEAT EXCHANGE ZONE, SAID COLD PRODUCT STREAM BEING DERIVIDED FROM THE COOLED AND CLEANED INLET GAS STREAM AND CONSTITUTING MORE THAN ABOUT 50% BY VOLUME OF THE INLET GAS STREAM; PASSING SUCH PRODUCT STREAM THROUGH THE ZONE IN INDIRECT COUNTERCURRENT HEAT EXCHANGE RELATION WITH THE INLET GAS STREAM TO COOL SUCH STREAM; DISCHARGING THE WARMED PRODUCT STREAM FROM THE WARM END OF SAID ZONE IN THE IMPURITY FREE STATTE.