Process and apparatus for liquefying low-boiling gases

Claim 1

A REFRIGERATION PROCESS FOR LIQUEFYING FEED GAS BY HEAT EXCHANGE WITH A REFRIGERANT GAS, SAID FEED GAS AND SAID REFRIGRANT GAS BOTH HAVING BOILING POINTS BELOW -80*C. AT ATMOSPHERIC PRESSURE, COMPRISING THE STEPS OF PROVIDING SAID FEED GAS AND COMPRESSING SUCH GAS TO A PRESSURE OF AT LEAST 70 P.S.I.G.; PARTIALLY COOLING SAID FEED GAS IN A FIRST COOLING STEP; FURTHER COOLING SAID FEED GAS IN A SECOND COOLING STEP; LIQUEFYING AND SUBCOOLING SAID FEEDGAS AND WITHDRAWING THE LIQUID FROM SUCH LIQUEFACTION STEP AS A LIQUID PRODUCT; PROVIDIGN AND COMPRESSING SAID REFRIGERANT GAS TO A PRESSURE OF AT LEAST 70 P.S.I.G.; AFTER COOLING THE COMPRESSED REFRIGERANT GAS TO A TEMPERATURE BELOW ABOUT 40*C.; WORK EXPANDING THE COMPRESSED AND AFTERCOOLED REFRIGERANT GAS TO SUFFICIENTLY LOW PRESSURE TO DEVELOP POWER AND COOL THE GAS TO A TEMPERATURE BELOW THE CONDENSATION TEMPERATURE OF SAID FEED GAS; PASSING THE WORK EXPANDED REFRIGERANT GAS CONSECUTIVELY THROUGH TEH LIQUEFACTION, FURTHER COOLING, AND FIRST COOLING STEPS IN COUNTER-CURRENT HEAT EXCHANGE WITH THE FEED STREAM TO EFFECT SUCH COOLIGN AND LIQUEFACTION THEREOF; WITHDRAWING THE WARMED REFRIGERANT GAS FROM THE WARM END OF THE FIRST COOLING STEP AND RECIRCULATING SUCH REFRIGERANT GAS TO THE REFRIGERANT COMPRESSION STEP.