A major problem associated with any power generation process in which coal is burned is the formation of ash and slag from the inorganic constituents of the coal. Ash deposition on heat transfer surfaces in coal-fired reactors is unavoidable and can have a significant effect on the performance and maintenance of boilers and gasifiers. A greater understanding of the thermal properties of coal ash deposits is important in reducing their negative impact. This work presents the development of an experimental method for making in situ measurements of the spectral emittance of coal ash deposits. It also provides measured emittances for two coals under oxidizing and reducing conditions. The experimental procedure consisted of burning coal in a down-fired entrained-flow reactor and collecting ash deposits on a circular probe under controlled conditions. Spectra collected from a Fourier transform infrared (FTIR) spectrometer were combined with an instrument response function to measure the spectral emissive power from the surface of the ash deposit. The spectral emissive power was used to infer the deposit surface temperature. These two measurements were used to calculate the spectral emittance of the deposit. This experimental method was validated by measuring the known temperature and spectral emittance of a blackbody radiator. The experimental method was used to find the spectral emittance of bituminous and subbituminous coals under both oxidizing and reducing conditions. The bituminous coal analyzed was Illinois #6 coal from the Crown III mine and the subbituminous coal analyzed was Wyoming coal from the Corederro mine. The spectral emittance of the subbituminous coal was lower than that of the bituminous coal under both oxidizing and reducing conditions. The emittances of both coals under reducing conditions were greater than those found under oxidizing conditions. A total band emittance was defined and calculated for each coal. The total band emittance as well as theoretical upper and lower total emittance limits were calculated as functions of temperature. There was little temperature dependence in the total emittance estimates.



College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering



Date Submitted


Document Type





coal, ash, deposit, emittance, emissivity