MEMBRANE MODULE DEVELOPMENT FOR A NATURAL GAS DEHYDRATION PROCESS

VIRTUALLY ALL NATURAL GAS MUST B DEHYDRATED BEFORE ENTERING THE PIPELINE. CURRENTLY, GLYCOL ABSORPTION DEHYDRATORS ARE WIDELY USED. HOWEVER, THESE UNITS COEXTRACT BENZENE, A KNOWN CARCINOGEN, AND RELEASE THE BENZENE TO THE ATMOSPHERE. IN ADDITION, GLYCOL DEHYDRATORS ARE NOT WELL SUITED FOR USE ON SMALL GAS STREAMS OR ON OFFSHORE PLATFORMS, INCREASINGLY COMMON SOURCES OF NATURAL GAS. MEMBRANE PROCESSES ARE AN ALTERNATIVE APPROACH TO NATURAL GAS DEHYDRATION. THE COSTS ARE LIKELY TO BE COMPARABLE TO THOSE OF THE GLYCOL PROCESS FOR LOW THROUGHPUT APPLICATIONS, BUT BENZENE EMISSIONS ARE ELIMINATED. THE SUITABILITY OF THE MEMBRANE PROCESS FOR USE ON ISOLATED SMALL GAS STREAMS AND ON OFFSHORE PLATFORMS IS AN ADVANTAGE LIKELY TO ENCOURAGE INDUSTRY USE. MEMBRANES WITH THE REQUIRED SELECTIVITY AND FLUX FOR A TECHNICALLY VIABLE MEMBRANE DEHYDRATION PROCESS HAVE ALREADY BEEN IDENTIFIED. SMALL MODULES INCORPORATING THESE MEMBRANES SUCCESSFULLY DEHYDRATE SYNTHETIC NATURAL GAS AT PRESSURES UP TO 950 PSIG. HOWEVER, THE MEMBRANE MODULE DESIGN MUST BE SIGNIFICANTLY IMPROVED TO REDUCE OR ELIMINATE CONCENTRATION POLARIZATION EFFECTS. CONCENTRATION POLARIZATION ARISES FROM THE FORMATION OF A STAGNANT GAS LAYER ADJACENT TO THE MEMBRANE, AND DECREASES THE MODULE SEPARATION PERFORMANCE BELOW ACCEPTABLE LEVELS. IN PHASE I, THE MODULE DESIGN WILL BE OPTIMIZED TO MITIGATE THE EFFECTS OF CONCENTRATION POLARIZATION AND TO MAXIMIZE THE SEPARATION ACHIEVED. IN PHASE II, THE PROCESS WILL BE SCALED UP TO THE PILOT DEMONSTRATION SCALE. A FOUR-MODULE PILOT SYSTEM WILL BE CONSTRUCTED AND EQUIPPED WITH COMMERCIAL-SCALE MODULES. THE ABILITY OF THE SYSTEM TO DEHYDRATE NATURAL GAS STREAMS WILL BE EVALUATED OVER A PERIOD OF 3-6 MONTHS. PRELIMINARY OFFERS FOR PHASE II FIELD SITES HAVE BEEN OBTAINED FROM BOTH A MAJOR GAS FIELD OPERATOR AND A SUPPLIER OF GAS PROCESSING EQUIPMENT.