SEPARATION OF NITROGEN FROM NATURAL GAS USING NOVEL MEMBRANES AND MEMBRANE PROCESSES

THIRTEEN PERCENT OF KNOWN U.S. GAS RESERVES, CONTAINING MORE THAN 4% NITROGEN, CANNOT BE EXPLOITED BECAUSE NO ECONOMICAL TECHNOLOGY FOR REMOVING THE NITROGEN EXISTS. MEMBRANE PROCESSESS COULD MAKE THIS GAS AVAILABLE IF MEMBRANES WITH A METHANE/NITROGEN SELECTIVITY OF 6 OR MORE WERE AVAILABLE; A NUMBER OF MATERIALS THAT ARE WITHIN THE RANGE OF THIS SELECTIVITY HAVE BEEN DEVELOPED. ONE POLYMER HAS A SELECTIVITY OF 5.5, THE HIGHEST POLYMER MEMBRANE METHANE/NITROGEN SELECTIVITY KNOWN. THESE METHANE-PERMEABLE MEMBRANES WILL BE INCORPORATED INTO AN INNOVATIVE PROCESS THAT SEPARATES THE RAW GAS INTO THREE STREAMS: A PRODUCT GAS STREAM CONTAINING LESS THAN 4% NITROGEN AT PIPELINE PRESSURE: A CONDENSED, HIGHER HYDROCARBON (GREATER THAN 3 CARBONS) STREAM, WHICH HAS MORE VALUE AS A LIQUID CHEMICAL FEEDSTOCK THAN AS A GASEOUS FUEL; AND A WASTE, NITROGEN-RICH GAS STREAM, WHICH IS USED TO POWER THE PROCESS AND FOR OTHER ON-SITE FUEL USE. THE COST OF PRODUCING PIPELINE GAS BY THE PROCESS IS ESTIMATED TO BE $(.55/THOUSAND STANDARD CUBIC FEET FOR A 1 MILLION CUBIC FEET PER DAY PLANT, WHICH IS VERY COMPETITIVE WITH ALTERNATIVE TECHNOLOGIES. IN THE PHASE I PROGRAM, THE NEW MEMBRANE MATERIALS WILL BE EVALUATED, AND THE OPTIMUM MATERIAL WILL BE SELECTED FOR SCALE-UP IN PHASE II. THE TESTS WILL PROVIDE DATA ON THE EFFECT OF TEMPERATURE ON THE METHANE FLUXES AND METHANE/NITROGEN SELECTIVITIES. THESE DATA WILL THEN BE USED TO PERFORM A TECHNICAL AND ECONOMIC FEASIBILITY ANALYSIS OF A PROCESS THAT INCORPORATES THE MEMBRANES INTO AN ENERGY-EFFICIENT SEPARATION SCHEME THAT ALSO RECOVERS NATURAL GAS LIQUIDS. IF THE RESULTS ARE SUFFICIENTLY ENCOURAGING, A SKID-MOUNTED PROOF-OF-CONCEPT SYSTEM WILL BE CONSTRUCTED IN PHASE II FOR EVALUATION IN THE LABORATORY AND IN A SMALL-SCALE FIELD TEST.