MEASUREMENT OF MERCURY AND OTHER TRACE METALS IN COMBUSTION GASES

IT IS PLANNED TO INVESTIGATE THE APPLICATION OF ACTIVE NITROGEN ENERGY TRANSFER (ANET) FLUORESCENCE EXCITATION TO THE DETECTION OF MERCURY IN EXHAUST STACK EFFLUENTS FROM COAL BURNING POWR PLANTS. THE INNOVATION IS TO APPLY DIELECTRIC-BARRIER DISCHARGE TECHNOLOGY TO GENERATE ACTIVE NITROGEN AT ATMOSPHERIC PRESSURE. MERCURY FLUORESCENCE AT 253.7 NM WILL BE EXCITED BY THE ACTIVE NITROGEN WHEN SMALL SAMPLES CONTAINING MERCURY AT PPB LEVELS ARE INTRODUCED INTO THE ACTIVE NITROGEN DISCHARGE. ACTIVE NITROGEN EXCITATION OF ATOMIC FLUORESCENCE TENDS TO POPULATE ONLY A LIMITED NUMBER OF STATES SO THAT THE RESULTANT FLUORESCENCE SPECTRUM IS SIMPLE AND EASY TO ANALYZE. THUS, A COMPACT INSTRUMENT OF MODEST RESOLUTION WILL SUFFICE TO DETECT THE FLUORESCENCE. IN THE CASE OF MRCURY DETECTION, AN INTERFERENCE FILTER AND PHOTOTUBE SHOULD BE ADEQUATE. THE BASIC TECHNIQUE IS GENERAL AND HAS BEEN DEMONSTRATED TO ALLOW MULTISPECIES DETECTION AT PPB LEVELS. THE USE OF DIELECTRIC-BARRIERDISCHARGE TECHNOLOGY TO GENERATE THE ACTIVE NITROGEN AFFORDS THE OPPORTUNITY TO DEVELOP A LIGHTWEIGHT INSTRUMENT WITH LOW POWER REQUIREMENTS (A 12 V BATTERY) SO THAT A TRULY PORTABLE INSTRUMENT CAN BE CONSTRUCTED. IN ADDITION, THE ACTIVE NITROGEN SOURCE CAN BE MOUNTED ON THE END OF A PROBE ALLOWING DIRECT, REAL-TIME ANALYSIS OF THE FLUE GAS TOXICS. THIS RESEARCH PROJECT IS DIRECTED TOWARD FIRST OPTIMIZING THE PRODUCTION OF ACTIVE NITROGEN IN A DIELECTRIC-BARRIER DISCHARGE TO ACHIEVE MAXIMUM SENSITIVITY FOR MERCURY, AND THEN TO DEVELOP TECHNIQUES TO ALLOW SAMPLES TO BE DRAWN DIRECTLY FROM A COMBUSTER EXHAUST INTO THE ACTIVE NITROGEN SOURCE. THE SECOND COMPONENT OF THE PROGRAM WILL USE AN ENTRAINED-FLOW, HIGH TEMPERATURE COAL COMBUSTION FACILITY. THE GOAL OF THE PHASE I PROJECT IS TO DEMONSTRATE THE SENSITIVITY AND FLXIBILITY OF THIS TECHNIQUE SO THAT A PROTOTYPE INSTRUMENT FOR MONITORING MERCURY IN FLUE GASES CAN BE DESIGNED AND FABRICATED IN A PHASE II PROGRAM.