Behavior of Pulverized Coal Particles During Early Stages of Combustion. HTGL Topical Report T-251

摘要

The behavior of pulverized coal particles during the early stages of combustion has been investigated through experiments and modeling. The combustion experiments have been performed with a flow-tube reactor while maintaining a simple environment, but at the same time systematically controlling the major reaction parameters, i.e., gas temperature, oxygen concentration, and particle size. Diagnostic features include gaseous product measurements, particle luminosity detection, and the collection and analysis of intermediate combustion products. Experimental results are discussed in terms of the mechanisms which a coal particle would undergo during combustion; in particular, transient particle heating, pyrolysis in an oxidizing environment, and the oxidation of released volatiles. The parametric variation of reaction environments and extensive diagnostic features make it possible to assess the significance of the reaction variables in each of the submechanisms. The particle heating phase, which determines the onset of fast mass release, is controlled by the particle mass and the ambient gas temperature. The overall oxidation of pulverized coal particles undergoing simultaneous devolatilization and combustion is found to vary with the oxygen concentration and particle size, as well as the ambient gas temperature. Radiative energy transfer is shown to be important in the transient particle heating and in the volatile cloud formation stage. The STaR cloud model is proposed to describe the heat transfer behavior of a particle surrounded by a volatile cloud. 93 refs., 80 figs., 10 tabs. (ERA citation 11:015600)