Low-temperature, low-pressure separation of gases

Claim 1

A METHOD FOR DEMETHANIZING A FEED GAS COMPRISING METHANE, ETHYLENE, ETHANE, PROPLYENE AND HYDROGEN, COMPRISING CHILLING SAID FEED GAS IN A FIRST INDIRECT HEAT EXCHANGING ZONE TO A TEMPERATURE SUFFICIENTLY LOW TO CONDENSE A MAJOR PORTION OF THE C2+ HYDROCARBON CONTAINED IN SAID FEED GAS AT A SUPERATMOSPHERIC PRESSURE AND THEREBY PRODUCE A FIRST UNCONDENSED GAS STREAM AND A FIRST LIQUID CONDENSATE STREAM; PASSING SAID FIRST LIQUID CONDENSATE STREAM INTO A FRACTIONATION ZONE; PASSING SAID FIRST UNCONDENSED GAS STREAM THROUGH SECOND, THIRD AND FOURTH INDIRECT HEAT EXCHANGING ZONES IN SERIES AND THEREIN CHILLING SAID FIRST UNCONDENSED GAS STREAM TO A TEMPERATURE SUFFI-CIENTLY LOW TO CONDENSE SUBSTANTIALLY ALL OF THE C2+ HYDROCARBONS CONTAINED IN SAID FIRST UNCONDENSED GAS STREAM AND THEREBY PRODUCE A SECOND UNCONDENSED GAS STREAM AND A SECOND LIQUID CONDENSATE STREAM, PASSING SAID SECOND UNCONDENSED GAS STREAM THROUGH SAID SECOND INDIRECT HEAT EXCHANGING ZONE IN DIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM; PASSING SAID SECOND LIQUID CONDENSATE STREAM INTO SAID FRACTIONATION ZONE; WITHDRAWING AN OVERHEAD VAPOR STREAM FROM SAID FRACTIONATION ZONE; ADMIXING A FIRST HEATED FLUID WITH SAID OVERHEAD VAPOR STREAM TO FORM A FIRST COMBINED STREAM; PASSING SAID COMBINED STREAM THROUGH A FIFTH INDIRECT HEAT EXCHANGING ZONE WHEREIN SAID COMBINED STREAM IS HEATED; COMPRESSING THE THUS HEATED FIRST COMBINED STREAM IN A FIRST COMPRESSING ZONE; ADMIXING WITH THE THUS COMPRESSED HEATED FIRST COMBINED STREAM A SECOND HEATED FLUID TO FORM A SECOND COMBINED STREAM; COMPRESSING SAID SECOND COMBINED STREAM IN A SECOND COMPRESSING ZONE; PASSING THE THUS COMPRESSED SECOND COMBINED STREAM IN INDIRECT HEAT EXCHANGE WITH COOLING WATER AND THEN THROUGH SAID FIFTH INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST COMBINED STREAM THEREBY CHILLING SAID COMPRESSED SECOND COMBINED STREAM; WITHDRAWING A BOTTOMS STREAM FROM SAID FRACTIONATION ZONE, PASSING AT LEAST A PORTION OF SAID BOTTOMS STREAM IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH THE THUS CHILLED COMPRESSED SECOND COMBINED STREAM TO FURTHER COOL SAID THUS CHILLED COMPRESSED SECOND COMBINED STREAM; FLASHING THE THUS FURTHER COOLED COMPRESSED SECOND COMBINED STREAM TO PRODUCE A THIRD UNCONDENSED GASSTREAM AND A THIRD LIQUID CONDENSATE STREAM; PASSING A FIRST PORTION OF SAID THIRD LIQUID CONDENSATE STREAM THROUGH SAID THIRD INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM; ADMIXING THE THUS WARMED FIRST PORTION OF SAID THIRD LIQUID CONDENSATE STREAM WITH A FIRST PORTION OF SAID THIRD UNCONDENSED GAS STREAM TO FORM A THIRD COMBINED STREAM; PASSING SAID THIRD COMBINED STREAM THROUGH SAID FIFTH INDIRECT HEAT EXHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST COMBINED STREAM AND TO THE STEP OF ADMIXING WITH THE THUS COMPRESSED HEATED FIRST COMBINED STREAM A SECOND HEATED FLUID IN THE SOURCE OF SAID SECOND HEATED FLUID; FLASHING A SECOND PORTION OF SAID THIRD LIQUID CONDENSATE STREAM; PASSING THE THUS FLASHED SECOND PORTION THROUGH SAID FOURTH INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM AND THEN TO THE STEP OF ADMIXING A FIRST HEATED FLUID WITH SAID OVERHEAD VAPOR STREAM AS THE SOURCE OF SAID FIRST HEATED FLUID; FLASHING A THIRD PORTION OF SAID THIRD LIQUID CONDENSATE STREAM; PASSING THE THUS FLASHED THIRD PORTION INTO SAID FRACTIONATION ZONE AS REFLUX THEREFOR; PASSING A SECOND PORTION OF SAID THIRD UNCONDENSED GAS STREAM THROUGH SAID SECOND INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM; EXPANDING THE THUS HEATED SECOND PORTION OF SAID THIRD UNCONDENSED GAS STREAM; PASSING THE THUS EXPANDED HEATED SECOND PORTION OF SAID THIRD UNCONDENSED GAS STREAM THROUGH SAID SECOND INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM; SAID BUTTONS STREAM COMPRISING SUBSTANTIALLY ALL OF THE C2+ HYDROCARBONS INTRODUCED INTO SAID FRACTIONATION ZONE; AND SAID THIRD UNCONDENSED GAS STREAM CONTAINING SUBSTANTIALLY ALL OF THE METHANE INTRODUCED INTO SAID FRACTIONATION ZONE.

Claim 2

A METHOD FOR DEMETHANIZING A FEED GAS COMPRISING METHANE, ETHYLENE, ETHANE, PROPLYENE AND HYDROGEN, COMPRISING CHILLING SAID FEED GAS IN A FIRST INDIRECT HEAT EXCHANGING ZONE TO A TEMPERATURE SUFFICIENTLY LOW TO CONDENSE A MAJOR PORTION OF THE C2+ HYDROCARBON CONTAINED IN SAID FEED GAS AT A SUPERATMOSPHERIC PRESSURE AND THEREBY PRODUCE A FIRST UNCONDENSED GAS STREAM AND A FIRST LIQUID CONDENSATE STREAM; PASSING SAID FIRST LIQUID CONDENSATE STREAM INTO A FRACTIONATION ZONE; PASSING SAID FIRST UNCONDENSED GAS STREAM THROUGH SECOND, THIRD AND FOURTH INDIRECT HEAT EXCHANGING ZONES IN SERIES AND THEREIN CHILLING SAID FIRST UNCONDENSED GAS STREAM TO A TEMPERATURE SUFFI-CIENTLY LOW TO CONDENSE SUBSTANTIALLY ALL OF THE C2+ HYDROCARBONS CONTAINED IN SAID FIRST UNCONDENSED GAS STREAM AND THEREBY PRODUCE A SECOND UNCONDENSED GAS STREAM AND A SECOND LIQUID CONDENSATE STREAM, PASSING SAID SECOND UNCONDENSED GAS STREAM THROUGH SAID SECOND INDIRECT HEAT EXCHANGING ZONE IN DIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM; PASSING SAID SECOND LIQUID CONDENSATE STREAM INTO SAID FRACTIONATION ZONE; WITHDRAWING AN OVERHEAD VAPOR STREAM FROM SAID FRACTIONATION ZONE; ADMIXING A FIRST HEATED FLUID WITH SAID OVERHEAD VAPOR STREAM TO FORM A FIRST COMBINED STREAM; PASSING SAID COMBINED STREAM THROUGH A FIFTH INDIRECT HEAT EXCHANGING ZONE WHEREIN SAID COMBINED STREAM IS HEATED; COMPRESSING THE THUS HEATED FIRST COMBINED STREAM IN A FIRST COMPRESSING ZONE; ADMIXING WITH THE THUS COMPRESSED HEATED FIRST COMBINED STREAM A SECOND HEATED FLUID TO FORM A SECOND COMBINED STREAM; COMPRESSING SAID SECOND COMBINED STREAM IN A SECOND COMPRESSING ZONE; PASSING THE THUS COMPRESSED SECOND COMBINED STREAM IN INDIRECT HEAT EXCHANGE WITH COOLING WATER AND THEN THROUGH SAID FIFTH INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST COMBINED STREAM THEREBY CHILLING SAID COMPRESSED SECOND COMBINED STREAM; WITHDRAWING A BOTTOMS STREAM FROM SAID FRACTIONATION ZONE, PASSING AT LEAST A PORTION OF SAID BOTTOMS STREAM IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH THE THUS CHILLED COMPRESSED SECOND COMBINED STREAM TO FURTHER COOL SAID THUS CHILLED COMPRESSED SECOND COMBINED STREAM; FLASHING THE THUS FURTHER COOLED COMPRESSED SECOND COMBINED STREAM TO PRODUCE A THIRD UNCONDENSED GASSTREAM AND A THIRD LIQUID CONDENSATE STREAM; PASSING A FIRST PORTION OF SAID THIRD LIQUID CONDENSATE STREAM THROUGH SAID THIRD INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM; ADMIXING THE THUS WARMED FIRST PORTION OF SAID THIRD LIQUID CONDENSATE STREAM WITH A FIRST PORTION OF SAID THIRD UNCONDENSED GAS STREAM TO FORM A THIRD COMBINED STREAM; PASSING SAID THIRD COMBINED STREAM THROUGH SAID FIFTH INDIRECT HEAT EXHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST COMBINED STREAM AND TO THE STEP OF ADMIXING WITH THE THUS COMPRESSED HEATED FIRST COMBINED STREAM A SECOND HEATED FLUID IN THE SOURCE OF SAID SECOND HEATED FLUID; FLASHING A SECOND PORTION OF SAID THIRD LIQUID CONDENSATE STREAM; PASSING THE THUS FLASHED SECOND PORTION THROUGH SAID FOURTH INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM AND THEN TO THE STEP OF ADMIXING A FIRST HEATED FLUID WITH SAID OVERHEAD VAPOR STREAM AS THE SOURCE OF SAID FIRST HEATED FLUID; FLASHING A THIRD PORTION OF SAID THIRD LIQUID CONDENSATE STREAM; PASSING THE THUS FLASHED THIRD PORTION INTO SAID FRACTIONATION ZONE AS REFLUX THEREFOR; PASSING A SECOND PORTION OF SAID THIRD UNCONDENSED GAS STREAM THROUGH SAID SECOND INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM; EXPANDING THE THUS HEATED SECOND PORTION OF SAID THIRD UNCONDENSED GAS STREAM; PASSING THE THUS EXPANDED HEATED SECOND PORTION OF SAID THIRD UNCONDENSED GAS STREAM THROUGH SAID SECOND INDIRECT HEAT EXCHANGING ZONE IN INDIRECT HEAT EXCHANGING RELATIONSHIP WITH SAID FIRST UNCONDENSED GAS STREAM; SAID BUTTONS STREAM COMPRISING SUBSTANTIALLY ALL OF THE C2+ HYDROCARBONS INTRODUCED INTO SAID FRACTIONATION ZONE; AND SAID THIRD UNCONDENSED GAS STREAM CONTAINING SUBSTANTIALLY ALL OF THE METHANE INTRODUCED INTO SAID FRACTIONATION ZONE.