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A microwave plasma continuous emissions monitor has been successfully demonstrated for sensitive (< 1 ppb), real time measurements of trace metals in furnace exhaust. The instrument uses a robust, up to 1.5 kW, 2.45 GHz microwave plasma sustained in a portion of the undiluted furnace exhaust flow for atomic emission spectroscopy. The waveguide device is constructed of refractory materials compatible with high temperature environments (>500 *C) and is flange mountable into the inside of the furnace exhaust duct. Fused quartz fiber optics in close proximity to the plasma flame transmit the UV through visible emission (190-690 nm) to three spectrometers for simultaneous monitoring of several metals. This instrument has been used for continuous monitoring for a 49 hour period with 0.5 second time resolution on a dc graphite electrode arc furnace during a soil vitrification test. Results are presented for chromium, manganese, and iron emissions during soil loading operations.

A 135 GHz heterodyne receiver with a rotatable graphite waveguide/mirror system has been implemented on a waste remediation DC arc furnace for internal surface temperature measurements. The linear temperature measurement range extends from <10 to approximately 15,000*C relative to ambient with a simultaneous capability to monitor surface reflectivity with the local oscillator leakage. Reliable and robust operation on a continuous 24 hour basis in a smoky, dirty furnace environment is demonstrated for a total of 5 furnace runs reaching a maximum temperature of 2200*C. Complete temperature profile measurements with approximately 5 cm spatial resolution clearly documented thermal gradients on the slag melt surface and refractory walls and ceiling for all operating regimes of the furnace. The unique active probing capability of this instrument provided additional real time information on melt surface turbulence, changing furnace wall emissivity, and millimeter-wave optic losses inside the furnace.1

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