Spectral Emissivity Measurements of Single Mineral Phases and Ash Deposits Available to Purchase

The spectral and total emissivity of particulate ash deposits of different chemical composition which originate from lignite and hard coal fired boilers from Alstom Power and RWE Power were investigated with a spectral radiometer. Furthermore the emittance of all major single phases present in ashes and slag have been determined. The single phases under consideration were SiO₂, Al₂O₃, FeO, Fe₂O₃, CaO and MgO. The results on SiO₂, Al₂O₃ and MgO have already been presented by Linka in 2003 [6] and therefore the focus is on FeO, Fe₂O₃ and CaO in the current paper. A spectral radiometer measures the emittance as a function of temperature and wavelength. The temperature varies from 600 to 1200°C in steps of 50K. The wavelength range from 1 to 15 μm has been examined. The measurements confirm the dependency of the spectral emittance on the chemical composition. Especially the content of either FeO or Fe₂O₃ or CaO influences the emittance of ashes and slag. The single phase samples of FeO and Fe₂O₃ show a temperature dependence of the emittance in the wavelength range between 1 and 6 μm. The same character of emittance appears in samples with high fractions of FeO or Fe₂O₃. CaO shows no temperature dependency in the complete range of wavelengths.