AN OFF-LINE-LOCKED LASER DIODE SENSOR (OLDS)

SECONDARY WASTE STREAM MONITORING REQUIRES REALTIME/CONTINUOUS MEASUREMENTS OF HAZARDOUS GAS SPECIES. ALTHOUGH BASELINE TECHNIQUES USING GAS FILTER CORRELATION AND ION-SELECTIVE ELECTRODES HAVE BEEN DEMONSTRATED FOR MONITORING HYDROGEN CHLORIDE OFF-GAS AT A HAZARDOUS WASTE INCINERATOR, NONE OF THESE TECHNIQUES ARE SUITABLE FOR MONITORING CORROSIVE OR REACTIVE GASES SUCH AS HYDROGEN FLUORIDE. AN OFF-LINE-LOCKED LASER DIODE SENSOR WHICH WILL PROVIDE AUTOMATIC, UNATTENDED, REAL-TIME, IN-SITU MONITORING OF SELECTED TOXIC GASES WILL BE DEVELOPED IN PHASE I. THE INSTRUMENT EXTENDS CURRENT LASER ABSORPTION TECHNOLOGY TO THE MEASUREMENT OF UNSTABLE GAS SPECIES IN HARSH STACK CONDITIONS. THE TECHNIQUE PROVIDES ACTIVE CONTROL OF THE LASER EMISSION WITHOUT USE OF A SAMPLE MOLECULE FOR REFERENCE, WHICH CAN BE CHEMICALLY UNSTABLE AND PHYSICALLY UNSAFE FOR THE INSTRUMENT OPERATION. THIS WILL PROVIDE PERFORMANCE AND COST ADVANTAGES IN THE DETECTION OF A LARGE NUMBER OF TOXIC SPECIES, INCLUDING HYDROGEN FLUORIDE, HYDROGEN CHLORIDE, HYDROGEN BROMIDE, CARBON DIOXIDE, CARBON MONOXIDE, NITROGEN DIOXIDE, HYDROGEN CYANIDE, AND HYDROGEN SULFIDE AT CONCENTRATIONS RANGING FROM BELOW THE THRESHOLD LEVEL TO WELL ABOVE THE ACUTE DAMAGE LEVEL.