ULTRASENSITIVE IN-SITU DETECTION OF TOXIC FLUE EMISSION

THE 1990 CLEAN AIR ACT AMENDMENTS LIST NEARLY TWO HUNDRED TOXIC MATERIALS THAT MUST BE REGULATED. AMONG THESE ARE POLYCYCLIC AROMATIC HYDROCARBONS (PAHS), CARCINOGENS THAT ARE ASSOCIATED WITH INCOMPLETE COMBUSTION AND FINE PARTICULATES. THERE IS THEREFORE A NEED FOR NEW TECHNOLOGY TO MEASURE VERY LOW CONCENTRATIONS OF SUCH SPECIES AT SITES ADJACENT TO COAL-FIRED UTILITIES, WHICH ARE SOURCES OF PAHS. EXTRACTIVE METHODS, IN WHICH A SEALED SAMPLE OF AIR IS ANALYZED IN A LABORATORY, ARE EXPENSIVE AND ARE INAPPLICABLE TO CONTINUOUS, IN-SITU MONITORING OF THE CONCENTRATIONS OF THESE TOXIC EMISSIONS. THIS PROJECT WILL STUDY THE DEVELOPMENT OF AN INSTRUMENT CALLED A TUNABLE PULSED ABSORPTION DIFFRACTOMETER (TPAD) TO FILL THIS NEED. THE BASIS OF THIS INSTRUMENT IS THE DETECTION OF A TRANSIENT, VOLUMETRIC DIFFRACTION GRATING THAT IS FORMED AFTER A PULSED LASER BEAM IS ABSORBED BY TOXIC EMISSIONS PRESENT IN THE ILLUMINATED REGION. AN INSTRUMENT THAT UTILIZES A TUNABLE, PULSED INFRARED LASER CAN BE TUNED THROUGH THE NEAR-INFRARED ABSORPTION SPECTRUM OF PAHS TO DETERMINE THEIR CONCETRATION IN THE PRESENCE OF OTHER ABSORPTIVE SPECIES. A TPAD WILL BE SENSITIVE TO A CONCENTRATION OF A PART-PER-TRILLON TOXIC GAS CONCENTRATIONS, ORDERS OF MAGNITUDE BETTER THAN INSTRUMENTS BASED ON OTHER APPROACHES TO DETECT SUCH TOXIC SPECIES. THE PHASE I FEASIBILITY STUDY WILL BE FOLLOWED BY A PROOF-OF-PRINCIPLE PHASE II DEMONSTRATION. THE CONSTRUCTION AND TESTING OF A PROTOTYPE INSTRUMENT WILL TAKE PLACE IN PHASE III.