Evaluation of different classes of additives on ash melting characteristics of garden grass waste

Abstract

In this work, the ash melting characteristics of crude garden grass waste (GGW) and its additive modulated mixtures were evaluated in a laboratory scale furnace by combusting the samples. For the purpose of understanding and rationalising the complex ash transformation characteristics of crude and additive modulated GGW samples in high-temperature thermochemical units, comprehensive theoretical knowledge and compositional ternary phase diagrams have been utilised in conjunction with the visual evaluation of the sintering degree of ash residues, coupled with their morphology and microchemistry results determined by the SEM–EDX and XRD analysis. This work proved that both raw and calcined eggshells can be utilised as Ca-rich anti-sintering additives as a substitute for commercially available additives such as lime and limestone for the enhancement of melting characteristics of low-melting garden grass ash. Kaolin exhibited the best anti-sintering characteristics for the elimination of ash melting of garden grass waste among all the additive mixtures tested, while no synergistic effects were observed in the Ca-rich and P-rich additive mixtures compared to their pure steams.