The thermal radiation properties are studied for a cloud of coal char and ash particles. The monochromatic absorption of the sample particles dispersed in liquid paraffin wax is measured spectroscopically at an atmospheric state by using FT-IR. The effect of the particles number density in the cloud and the thickness of the dispersion layer on the spectrum of absorption could be expressed in the property of the extinction efficiency. The spectral distribution of the extinction efficiency is dependent of wavelength in the near infrared region of 0.8 to 2.2 micrometers. The extinction efficiency is influenced significantly so as to rise with increasing the carbon content in the char, and is correlated by a 2nd order polynomial function of the content. The contribution of scattering by ash particles can be ignored, or the forward scattering dominates the particle scattering in the radiative heat transfer in the cloud.
