MODELING OF COMPLETE COMBUSTION HISTORY OF A COAL PARTICLE WITH HIGH ASH CONTENT IN A QUIESCENT ATMOSPHERE
Pankaj P. Ekbote*
Indian Coals have high percentage of Ash which affects the coal combustion in many ways. This work studies the combustion of spherical coal particle, with high ash content, placed in a hot ambient. The heating up, devolatilization, combustion of volatiles, char combustion – the complete combustion history of the particle has been studied. Transient model with temperature and component dependant properties for gas phase & ash layer and constant properties for solid phase have been assumed. Conservation equations for mass, energy and species have been written. Equations have been non-dimensionalised and solved using numerical methods. The combustion of particle proceeds by shell progressive mechanism. As the combustion front progresses it divides particle into two parts: the shell, formed by ash without any carbon and the core, formed by original coal char. The results with compared with results of non-ash layer forming particle. The peak temperatures in the gas phase in ash layer forming particles are found to be higher. Large particles are likely to get overheated as the ash layer gets thicker. The peak temperatures in smaller range of particles reduce with reduction in diameter. The combustion time increases rapidly with increase in diameters of particles. Particles with higher ash content are likely to burn faster but lower peak temperature.
*Mr.Pankaj P.Ekbote is presently working as Sr.Manager in Power Management Institute of NTPC. His communication address is – Power Management Institute, NTPC, Sector-16 A, Noida (U.P.) – 201301.