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Show temperature measured by the thermocouple. Figure 1 also presents the temperatures determined through the same port as the S R S measurements described above. It is seen that the corrected temperatures obtained by the multi-element thermocouple probe are generally lower than the Raman-inferred temperatures. Because the thermocouples measure the gas temperature in the vicinity of the water-cooled probe and because the furnace's gas flow velocity is low, it m ay be that the lower temperature is due to the water-cooled probe cooling the gas in its vicinity. Fourier-Transform Infrared Spectroscopy Fourier-transform infrared (FTIR) spectroscopy is a versatile, robust technique that is being applied to an ever increasing number of industrial-scale applications.24,7 The entire FTIR infrared spectrum (1.3 to 6 urn) is recorded simultaneously using an interferometer to record an interferogram. Fourier transforming the interferogram yields the entire infrared spectrum over the range of the detector. Because no wavelength scanning is required, it is capable of monitoring transient events. Because the entire spectrum is simultaneously recorded, it is much less susceptible to misinterpretation that can result when the signal intensity in only one wavelength region where several species absorb/emit is monitored. The FTIR spectrometer was located on a tripod and connected to the data acquisition computer using a fiber optic interface. Adjustment of the tripod allowed directing the line of sight of the FTIR optics to the opposite wall of the furnace. The FTIR optical configuration was calibrated against a blackbody source at a temperature of 1000°C at the pathlengths specific to the distances between the FTIR and the opposite wall of the furnace. Spectra were collected at resolutions of 0.5, 4 and 16 c m ' and were comprised of 32 co-added scans. Spectra were corrected for instrument response. The furnace spectra were analyzed for two-color temperature and emissivity using the Planck equation. A curve fitting program was then used to confirm the temperatures over different spectral regions. Spectral contributions from H 2 0 and C 0 2 in the furnace were eliminated prior to analysis. All of the spectra obtained were of similar structure with the molecular transitions from the combustion products C 0 2 and H 2 0 superimposed on blackbody radiation. FTER normally determines gas temperatures by using Maxwell-Boltzmann statistics to model any C O or N O present in the flue gas. The furnace gas composition at all measurement locations investigated did not reveal these molecules; consequently, the temperature profiles across the furnace had to be estimated by FTIR based on the determined surface temperatures (see below). The corresponding results indicate that the furnace was operated at an air-to-fuel stoichiometry in excess of one. SURFACE TEMPERATURE MEASUREMENTS Since the temperature of walls and other surfaces significantly affects the performance of combustion systems, measurement of surface temperatures provides information that can be used to optimize the combustion/process efficiency. A m o n g the techniques D I A L has for measuring surface temperatures are: •Thermal imaging •Multi-wavelength pyrometry •Fourier-transform infrared spectroscopy •Two-color pyrometry •Ratio pyrometry During this campaign, the D I A L thermal imaging, multi-wavelength pyrometry ( M W P ) , and FTIR spectroscopy systems were deployed. Thermal Imaging Thermal images2"4 8 of the furnace walls and tubes were recorded using a black-and-white charge-coupled device ( C C D ) camera equipped with a narrow bandpass filter that transmits radiation in a wavelength region that is free of spectral interferences. The images were stored on a personal computer. The response of the thermal imaging system was calibrated using a standard blackbody radiation source at known temperatures. Data acquisition and analysis of the thermal images was accomplished using software developed at D I A L that provides on-line image capture/display (grey-scale image), near real-time image processing/display (false-color image), storage, as well as offline analysis capabilities. Parameters used in image acquisition are recorded into a dated log file that can be accessed for post-acquisition analysis. Such a capability permits development of a historical library that can be utilized to -4- |