Model of the diffuse reflectivity of fly ash and its application to an optical sensor system for the determination of carbon in fly ash

Fly ash, a fine gray powder, is filtered out of the flue gas in coal-fired power stations. It consists of silicon oxide, metal oxides, and unburned carbon. An optical sensor system for measurement of the carbon content of fly ash is described. Based on a mathematical model, an algorithm is deduced that allows the carbon content to be calculated from two measurements of the diffuse reflectivity of a fly ash sample before and after a surface-grinding process. In this model the fly ash sample is assumed to be composed of three types of cube: light-scattering cubes, soft absorbing cubes (carbon), and hard absorbing cubes (iron oxide).