ANALYSIS OF POLLUTANT CHEMISTRY IN COMBUSTION BY IN-SITU PULSED PHOTOACOUSTIC LASER DIAGNOSTICS

A technique for gas analysis based on pulsed-laser-induced photoacoust ic spectroscopy in the UV and the visible is presented. The laser-base d technique and the associated analysis probe have been developed for the analysis of pollutant chemistry in fluidized beds and other combus tion environments with limited or no optical access. The photoacoustic -absorption spectrum of the analyzed gas is measured in a test cell lo cated at the end of a tubular probe. This test cell is subject to the prevailing temperature and pressure in the combustion process. The ins trument response has been calibrated for N2O, NO, NO2, NH3, SO2, and H 2S at atmospheric pressure between 20 and 910 degrees C. The response of the probe was found to increase with pressure for N2O, NO, NH3, and NO2 up to 1.2 MPa pressure. The method and the probe have been used f or detection and ranging of gas concentrations in a premixed methane f lame. Some preliminary tests in a large 12-MW circulating bed boiler h ave also been done. (C) 1995 Optical Society of America