IMPROVED TEMPERATURE-MEASUREMENTS OF BURNING CHAR AND COAL PARTICLES USING AN FT-IR SPECTROMETER

A novel method for temperature measurements on individual burning char and coal particles with an FT-IR spectrometer has been developed. The technique is demonstrated for monitoring emission spectra of individu al moving particles that require a few milliseconds to pass the field of view of a conventional scanning FT-IR spectrometer. The accurate pa rticle surface temperature is calculated from a best match of the meas ured emission spectrum to a detailed physical radiance model spectrum. The technique is applied to measure the surface temperature of 90-125 mu m particles with temperatures from 1000 to 2200 K in an entrained now reactor. A one-temperature calibration of the FT-IR spectrometer i s sufficient for accurate measurements throughout a broad temperature range. Background radiation and a fluctuating particle feeding rate ar e handled by subtraction of two successive measurements. The single-pa rticle emission spectra are useful for testing the assumptions about p article emissivity as a function of wavelength. The findings. in the p resent work justify the graybody assumption for the burning char parti cles as well as the burning coal particles. Under sooting conditions p article temperature errors of about 300 K were observed. The burn-off for four coal samples is analyzed and compared with particle temperatu res at 1, 3, 6, 12, and 21 vol % oxygen. In addition to giving importa nt information on the modeling of the combustion process, the particle temperature measurements and the burn-off give information that can b e used for ranking of coal samples with respect to reactivity.