Chemical composition and size distributions for fly ashes

Inter-particle variations in particle diameter and chemical composition in coal fly ashes are significant, and can be quantitatively studied using currently available microanalytical techniques. One such technique, computer controlled scanning electron microscopy (CCSEM), is now routinely used to determine chemical compositions and diameters of individual fly ash particles, using statistically significant sample sizes. This paper proposes simple mathematical formulae for expressing the inter-particle variations. Additionally, these formulae can be used for economically storing the large amount of data generated by CCSEM. Two apparent limitations of the CCSEM technique are discussed — one relating to the measurement of size distribution, and the other to determining the iron oxide distribution in the ash. These limitations are imposed by statistical considerations, and by artifacts of sample preparation techniques.