Hydrogen purification process

Claim 1

A PROCESS FOR OBTAINING SUBSTANTIALLY PURE HYDROGEN FROM A VAPOR FEED STREAM COMPRISING HYDROGEN AND A MIXTURE OF HYDROCARBON COMPOUNDS HAVING FROM 1 TO 10 CARBON ATOMS, THE PROCESS UTILIZING TWO ADSORPTION ZONES PACKED WITH ABSORBENT SELECTED FROM THE GROUP CONSISTING OF ACTIVATED CHARCOAL AND ACTIVATED ALUMINA SELECTIVE FOR HYDROCARBON COMPOUNDS AT THE ADSORPTION TEMPERATURE, THE TWO ZONES BEING ALTERNATELY ON THE ADSORPTION PORTION OF THE CYCLE TO YIELD TO CONTINUOUS PROCESS WHEREIN THE CAPACITY OF THE ABSORBENT DECLINES DUE TO THE ACCUMULATION OF THE MORE DIFFICULTY DESORBABLE HYDROCARBON COMPOUNDS THEREON, THE PROCESS COMPRISING THE STEPS OF FLOWING THE FEED STREAM INTO THE FIRST ZONE IN A POSITIVE FLOW DIRECTION AT A RELATIVELY HIGH ADSORPTION PRESSURE, WITHDRAWING A SUBSTANTIALLY PURE HYDROGEN STREAM THEREFROM, ADSORBING HYDROCARBON COMPOUNDS IN SAID FIRST ZONE, CHANGING THE FLOW OF THE FEED STREAM INTO THE SECOND ZONE AT SAID RELATIVELY HIGH ADSORPTION PRESSURE AT LEAST UPON THE BREAKTHROUGH OF HYDROCARBON COMPOUNDS INTO THE SUBSTANTIALLY PURE HYDROGEN STREAM WITHDRAWN FROM THE FIRST ZONE, THEREBY PUTTING THE SECOND ZONE ON THE ADSORPTION PORTION OF THE CYCLE, DESORBING A PORTION OF THE HYDROCARBON COMPOUNDS FROM THE ADSORBENT IN THE FIRST ZONE BY DEPRESSING SAID FIRST ZONE TO A RELATIVELY LOW DESORPTION PRESSURE AND PURGING SAID FIRST ZONE WITH SAID SUBSTANTIALLY PURE HYDROGEN AT SAID RELATIVELY LOW DESORPTION PRESSURE IN A FLOW DIRECTION OPPOSITE TO THAT OF SAID FEED STREAM WITH A VOLUME OF PURGE OF FROM 0.5 TO 1.5 TIMES THE VOLUMES OF FEED PASSED INTO SAID FIRST ZONE DURING THE ADSORPTION PORTION OF THE CYCLE, REPRESSURING SAID FIRST ZONE TO SUBSTANTIALLY SAID RELATIVELY HIGH ADSORPTION PRESSURE WITH SAID SUBSTANTIALLY PURE HYDROGEN, CONTINUING THE PROCESS IN A CYCLIC MANNER TO OBTAIN A CONTINUOUS FLOW OF SAID SUBSTANTIALLY PURE HYDROGEN PRODUCT EVEN WITH A GRADUAL LOSS IN CAPACITY OF SAID ADSORBENT BY EMPLOYING A VARIABLE CYCLE LENGTH WHEREIN THE FEED RATE INCREASES INVERSELY TO OVERCOME HYDROGEN RECOVERY DECREASE AND THE CYCLE LENGTH GRADUALLY DECREASES UNTIL IT REACHES THE MINIMUM TIME NECESSARY FOR DESORPTION, REGENERATING THE ADSORBENT IN SAID ZONES AT LEAST WHEN CAPACITY OF THE ADSORBENT DECLINES TO THE EXTENT THAT HYDROCARBON COMPOUNDS BREAK THROUGH INTO THE SUBSTANTIALLY PURE HYDROGEN STREAM WITHDRAWN FROM THE ZONE OF THE ADSORPTION PORTION OF THE CYCLE BEFORE THE DESORPTION PORTION OF THE CYCLE CAN BE COMPLETED ON THE OTHER ZONE BY FLOWING AN INERT GAS THROUGH THE ZONES TO HEAT THE ADSORBENT TO A TEMPERATURE OF AT LEAST 600*F. COOLING THE ADSORPTION ZONES TO SUBSTANTIALLY THE ADSORPTION TEMPERATURE AND CONTINUING THE PROCESS BY FLOWING THE FEED STREAM INTO ONE OF THE ADSORPTION ZONES.