Analysis of pulverized coal particles (10–100 μm) for Fe, S, Ca, Si and Al on a particle-by-particle basis

Abstract

A computer controlled scanning electron microscope fitted with soft X-ray fluorescence analysed thousands of pulverized coal particles in the size range 10 to 100 μm for amounts of Al, Si, Ca, S and Fe in each of the particles. Two coals were used, namely, subbituminous C, Comanche-Wyoming and subbituminous B, Rosebud-Montana. In pulverized coal combustion Rosebud coal has a bad slagging record not predictable from conventional slagging indices based on the elemental analyses of the total coal ash. The coal particles were placed into one of four groups: little mineral matter; low melting point inorganic composition; high melting point compositions; and large amounts of iron or pyrite. On this basis, Rosebud coal had 47% of its mineral matter in groups likely to cause slagging compared with 12% for Comanche coal, in agreement with the slagging record. It is concluded that although the particle-by-particle analysis technique used here is in a crude state of development, it can give a correct indication of the possible slagging behaviour of a pulverized coal in cases where conventional slagging indices based on the analysis of the total mean coal ash fail to give the correct indication.