Experimental verification of gas spectra calculated for high temperatures using the HITRAN/HITEMP database

The knowledge of absorption coefficients of the gases CO, CO2 and H2O at high temperatures is important for the in situ determination of the concentration of these gases in combustion system. These coefficients can be calculated using molecular data form the HITRAN database. The 1996 edition of this database contains a special high temperature database for CO, CO2 and H2O. Based on these data absorption coefficients and spectra of CO, CO2 and H2O have been calculated for different concentrations and temperatures. Additionally, measurements were carried out using a high temperature calibration gas cell and in situ Fourier transform infrared spectroscopy absorption spectroscopy. A comparison between the spectra calculated and measured showed a good agreement. At temperatures of 1100°C large deviations between these results of theory and experiment could be found for certain spectral regions of CO2. Based on these results the measuring system was used for the quantitative analysis of the combustion gases in a pilot-scale horizontally moving grate furnace as well as in a laboratory scale furnace using wood chips, waste wood and fibreboard as fuels.