On the combustion parameters of coal, biomass and iron, burning either as isolated particles or in groups of particles

Abstract

In this research, combustion characteristics of pulverized solid fuels, including bituminous coal, various biomass types, and iron, were investigated with experimental methods. Emphasis was placed on obtaining radiative parameters for these fuels, including spectral emissivity, temperature and soot volume fractions. Moreover, the structural development of the chars of bituminous coal and various biomass samples, upon devolatilization, was studied by using experimental data and a numerical model. Such measurements can be used in the development of predictive numerical models for the operation and emissions of furnaces. The experimental methods that were used in this study included three-color pyrometry, spectrometry and highspeed cinematography. The following results were obtained: (i) For single particle combustion of coal and three types of biomasses, all three experimental methods were used to measure the combustion temperatures, spectral emissivities and soot volume fractions. The spectral emissivities of the chars volatile matter flames those fuels were measured, and average peak temperatures and 2D temperature distribution were identified. (ii) For group particles combustion of coal and biomasses, the spectrometer and high-speed camera were used to measure the combustion temperatures, spectral emissivities and soot volume fractions. Average spectral emissivities and mean particle cloud temperatures were measured for two different particle number densities (PNDs) of these fuels in the furnace. (iii) For iron combustion, all three experimental methods were used to measure the combustion temperatures and spectral emissivities for single particle combustion and only the spectrometer and high-speed camera for group combustion. Average spectral emissivities of single particles for different oxygen concentration and groups of iron particles burning in air at different PNDs were measured. Corresponding average temperatures and 2D temperature distribution of single particles and groups combustion of iron were also measured. (iv) The numerical model, which was used in this work, is a kinetic model that was designed for char combustion of biomass which requires an experimental temperature profile. The model was used to determine the size and overall porosity (pore volume) of carbonaceous chars, originating from high-heating rates and hightemperature pyrolysis and/or combustion of biomass. The average char porosities (effective porosities) of several raw and torrefied biomass particles were calculated to be in the range of 92-95%. The average initial dimension of the chars, upon rapid pyrolysis, was in the range of 50-60% mid-value of the mesh size of the sieves used to size-classify their highly irregular parent biomass particles. Finally, this dissertation presents measurements and calculations of multiple critical combustion parameters for different fuels. It provides important information and lays the foundation for subsequent experimental research and applications for those renewable fuels. The combination of spect...