FT-IR emission/transmission tomography of a coal flame

Abstract

Fourier Transform Infrared (FT-IR) Emission/Transmission (E/T) spectroscopy has recently been shown to be a versatile technique for coal combustion diagnostics by allowing for measurements of particle concentrations and temperatures, and gas compositions, concentrations, and temperatures. These measurements are for the ensemble of particles and gases along a line-of-sight in the flame. In this paper, tomographic reconstruction techniques have been applied to line-of-sight FT-IR E/T measurements to derive spectra that correspond to small volumes within a coal flame. From these spectra, spatially resolved point values for species temperature and relative concentrations can be determined. The technique was used to study the combustion of Montana Rosebud subbituminous coal burned in a transparent wall reactor. The coal is injected into the center of an up-flowing preheated air stream to create a stable flame. Values for particle temperature, relative particle density, relative soot concentration, the fraction of ignited particles, the relative radiance intensity, the relative CO2 concentration and the CO2 temperature have been obtained as functions of distance from the flame axis and height above the coal injector nozzle. The spectroscopic data are in good agreement with visual observations and thermocouple measurements. The data present a picture of the coal burning in a shrinking region which collapses to the center at the tip of the flame. The highest CO2 temperatures are 2200 to 2600 K. The highest particle temperatures are 1900 to 2000 K, with occasional temperatures up to 2400 K.