Refrigeration process

Claim 1

A PROCESS FOR RECOVERING A MIXTURE COMPRISING ETHANE AND PROPANE FROM NATURAL GAS, WHICH PROCESS COMPRISES, IN COMBINATION, THE STEPS OF: A. COOLING SAID NATURAL GAS PARTIALLY TO LIQUEFY SAID NATURAL GAS; B. DISTILLING SAID PARTIALLY LIQUEFIED GAS FROM STEP (A) IN A FIRST DISTILLATION ZONE TO RECOVER AN OVERHEAD STREAM COMPRISING METHANE, ETHANE, AND PROPANE, AND TO RECOVER FROM A FIRST REBOILER ZONE OF SAID FIRST DISTILLATION ZONE A BOTTOMS STREAM COMPRISING SOME PROPANE AND HIGHER BOILING HYDROCARBONS; C. PARTIALLY CONDENSING SAID OVERHEAD STREAM FROM STEP (B); D. IN A SECOND DISTILLATION ZONE, DISTILLING A FEED, AS OBTAINED BELOW, TO RECOVER FROM SAID SECOND DISTILLATION ZONE AN OVERHEAD STREAM COMPRISING METHANE WHICH OVERHEAD STREAM IS THEN COMBINED WITH SAID OVERHEAD STREAM FROM STEP (B) AND PASSED TO A COMMON ACCUMULATOR TO FORM A MIXTURE; E. REMOVING A STEAM COMPRISING METHANE FROM SAID COMMON ACCUMULATOR ZONE; F. RETURNING A FIRST PORTION OF SAID ACCUMULATOR MIXTURE TO SAID FIRST DISTILLATION ZONE AS REFLUX TO THE FIRST DISTALLATION ZONE; G. PASSING A SECOND PORTION OF SID ACCUMULATOR MIXTURE CONTROLLED IN ACCORDANCE WITH THE LIQUID LEVEL IN SAID REBOILER REGION OF THE SECOND DISTILLATION ZONE TO THE SECOND DISTILLATION ZONE AS FEED TO SAID SECOND DISTILLATION ZONE; H. RECOVERING A BOTTOMS STEAM COMPRISING ETHANE AND PROPANE, AS A PRODUCT OF THE PROCESS, FROM A SECOND REBOILER ZONE IN SAID SECOND DISTILLATION ZONE, SAID SECOND REBOILER ZONE HEATED BY INDIRECT HEAT EXCHANGE WITH LIQUID FROM SAID FIRST REBOILER ZONE SAID LIQUID FLOW CONTROLLED IN ACCORDANCE WITH THE TEMPERATURE IN SAID SECOND REBOILER ZONE; AND I. CONTROLLING THE AMOUNT OF HEAT SUPPLIED TO SAID FIRST REBOILER ZONE IN ACCORDANCE WITH THE LEVEL IN THE COMMON ACCUMULATOR ZONE SO AS TO MAINTAIN A DESIRED LEVEL IN SAID COMMON ACCUMULATOR ZONE.