抄録
The calculation expressions for the emissivity spectra of powdery coal ashes have been derived by fitting the measured emissivity spectra to improve the accuracy with which the radiative heat transfer rate can be estimated with a calculation tool for pulverized coal-fired boilers. The expressions are defined in three bands. First, in band 1, which corresponds to wavelengths ranging from 2 to 4 micrometers, and in band 3, which corresponds to wavelengths ranging from 8 to 16 micrometers, the expressions are formulated into the linear function of the weight ratio of five chemical compositions, which correspond to silica, alumina, calcium oxide, ferric oxide and magnesia, and the temperature of the coal ash and the wavelengths. Second, the expression in band 2, with the wavelengths ranging from 4 to 8 micrometers, is formulated into the cubic function of the wavelength. The expression predicts the emissivity spectra of powdery coal ash, whose raw coals range from 0.6 to 2.4 (-) in a fuel ratio (=mass ratio of fixed carbon to volatile matter in coal), with 0.050 (-) to 0.170 (-) predictability. The proposed expression has widespread predictability of powdery coal ashes that range from 2 to 16 micrometers in wavelength.
