Understanding the Mechanism of Particle Adhesion in High-Temperature Combustion Induced by Sodium and Potassium: Use of a Synthetic Ash Strategy

During high-temperature combustion of coal, biomass, and municipal waste, ash particles can agglomerate and adhere to the internal surfaces of the plant under high-temperature conditions, resulting in a decrease in operating efficiency. It is known that the presence of small amounts of Na and K in the ash can facilitate adhesion; however, mechanistic details of the process are unclear. In this paper, a synthetic ash strategy consisting of a base material of SiO2 involving controlled additions of simple chemical components is proposed as a novel and convenient way to investigate adhesion. The synthetic ash consisted of SiO2 as the base material, and trace amounts of Na or K were added as target elements to examine their potential role in facilitating the adhesion process. It became clear that small amounts of Na and K increased the propensity for adhesiveness at high temperatures. The effect of the addition of Al2O3 nanoparticles to the synthetic ashes, which was expected to prevent adhesion, was also investigated. Therefore, it was found that the effect of Al2O3 would depend on the elements, which may increase the adhesiveness. It is projected that the present research can contribute to stable operation of many types of combustion plants.