Cascade cycle for liquefaction of natural gas

Claim 1

THE METHOD OF LIQUEFYING A GAS COMPRISING (A) SUPPLYING THE GAS IN A MAIN FEED STREAM AT HIGH PRESSURE AND ESSENTIALLY AMBIENT TEMPERATURE, (B) REMOVING HEAT FROM THE GAS TO COOL THE GAS TO A TEMPERTURE AT WHICH IT IS IN A LIQUID STATE AT SAID HIGH PRESSURE, (C) WITHDRAWING FROM SAID MAIN FEED STREAM A PORTION OF THE LIQUEFIED GAS FROM STEP (B) AND A SIDE STREAM, (D) SUBCOOLING THE REST OF THE GAS IN SAID MAIN STREAM TO A STILL LOWER TEMPERATURE THAN THE GAS IN THE SIDE STREAM, (E) THROTTLING SAID SUBCOOLING LIQUID GAS FROM STEP (D) INTO A FLASH DRUM AT A REDUCED PRESSURE TO FLASH OFF PART OF THE GAS AS A VAPOR AND STILL FURTHER COOL THE RESIDUAL LIQUID GAS, (F) HEAT EXCHANGING LIQUEFIED GAS FROM SAID SIDE STREAM OF STEP (C) WITH THE FLASH VAPOR FRM STEP (E) TO FURTHER SUBCOOL SAID LIQUEFIED SIDE STEAM GAS, (G) THROTTLING SAID LIQUEFIED SUBCOOLED SIDE STREAM GAS OF STEP (F) INTO THE FLASH DRUM TO REJOIN THE MAIN STREAM, (H) THROTTLING THE SUBCOOLED MAIN STREAM LIQUEFIED GAS INTO A STORAGE CONTAINER AS LIQUEFIED GAS AT SUBSTANTIALLY ATMOSPHERIC PRESSURE, (I) WITHDRAWING VAPOR FROM SAID STORAGE CONTAINER TO MAINTAIN THE PRESSURE IN SAID CONTAINER AT SUBSTANTIALLY ATMOSPHERIC PRESSURE, (J) COMPRESSING SAID VAPOR IN MULTI-STAGE COMPRESSION AND COOLING SAID COMPRESSED VAPOR TO AMBIENT TEMPETATURE, (K) WITHDRAWING PART OF SAID COMPRESSED VAPOR FOR USE AS PRODUCT, AND (L) FURTHER COMPRESSING THE REMAINDER OF SAID COMPRESSED VAPOR TO ABOUT THE INITIAL PRESSURE OF THE MAIN FEED STREAM, AND RETURNING IT TO THE ENTRY POINT OF THE MAIN FEED STREAM.

Claim 2

THE METHOD OF LIQUEFYING A GAS COMPRISING (A) SUPPLYING THE GAS IN A MAIN FEED STREAM AT HIGH PRESSURE AND ESSENTIALLY AMBIENT TEMPERATURE, (B) REMOVING HEAT FROM THE GAS TO COOL THE GAS TO A TEMPERTURE AT WHICH IT IS IN A LIQUID STATE AT SAID HIGH PRESSURE, (C) WITHDRAWING FROM SAID MAIN FEED STREAM A PORTION OF THE LIQUEFIED GAS FROM STEP (B) AND A SIDE STREAM, (D) SUBCOOLING THE REST OF THE GAS IN SAID MAIN STREAM TO A STILL LOWER TEMPERATURE THAN THE GAS IN THE SIDE STREAM, (E) THROTTLING SAID SUBCOOLING LIQUID GAS FROM STEP (D) INTO A FLASH DRUM AT A REDUCED PRESSURE TO FLASH OFF PART OF THE GAS AS A VAPOR AND STILL FURTHER COOL THE RESIDUAL LIQUID GAS, (F) HEAT EXCHANGING LIQUEFIED GAS FROM SAID SIDE STREAM OF STEP (C) WITH THE FLASH VAPOR FRM STEP (E) TO FURTHER SUBCOOL SAID LIQUEFIED SIDE STEAM GAS, (G) THROTTLING SAID LIQUEFIED SUBCOOLED SIDE STREAM GAS OF STEP (F) INTO THE FLASH DRUM TO REJOIN THE MAIN STREAM, (H) THROTTLING THE SUBCOOLED MAIN STREAM LIQUEFIED GAS INTO A STORAGE CONTAINER AS LIQUEFIED GAS AT SUBSTANTIALLY ATMOSPHERIC PRESSURE, (I) WITHDRAWING VAPOR FROM SAID STORAGE CONTAINER TO MAINTAIN THE PRESSURE IN SAID CONTAINER AT SUBSTANTIALLY ATMOSPHERIC PRESSURE, (J) COMPRESSING SAID VAPOR IN MULTI-STAGE COMPRESSION AND COOLING SAID COMPRESSED VAPOR TO AMBIENT TEMPETATURE, (K) WITHDRAWING PART OF SAID COMPRESSED VAPOR FOR USE AS PRODUCT, AND (L) FURTHER COMPRESSING THE REMAINDER OF SAID COMPRESSED VAPOR TO ABOUT THE INITIAL PRESSURE OF THE MAIN FEED STREAM, AND RETURNING IT TO THE ENTRY POINT OF THE MAIN FEED STREAM.