Genesis and Characteristics of Coal and Biomass Ash

Abstract

The coal ash and biomass ash produced from their respective combustion are widely variable in terms of their physical and chemical properties. Thorough understanding of their properties is a prerequisite for their possible utilization at different sectors. In this chapter we discuss different physical and chemical parameters, viz., particle size distribution, surface area and porosity, major oxide composition, percentage of unburned carbon, and micro-morphology of several ash samples from India. Presence of unburnt carbon, that is, non-combusted or partially combusted organic matter in ash, can cause potential damage when used in concrete structures, as it induces adsorption of air-entraining agents (or AEAs) and thereby limits their role in resisting freeze-and-thaw in concretes. Consequently, knowledge on unburnt carbon, surface area, and porosity of ashes can be critical. Similarly, the chemical composition of the ashes is significantly important, and depending upon their composition, the ashes can be used in relevant sectors. The coal ashes were observed to be marked by higher SiO2 + Fe2O3 + Al2O3 contents, while the biomass ashes were observed to be marked by higher Na2O, K2O, MgO, and P2O5 contents.