Role of Al-Based Additives in Controlling Ash Adhesion

In combustion plants, ash particles adhere to the plant walls because of liquid bridging induced by the melting of alkali-metal compounds. The presence of adhered ash particles can hinder the efficient and stable operation of the plant. Therefore, adopting appropriate adhesion control methods that suit the combustion conditions is critical. Additives, which are one method to deal with ash adhesion, increase the slag formation temperature and prevent the formation of liquid bridges by changing the composition of the ash. However, with the recent expansion of biomass utilization, various types of ash are generated, and additives that are effective irrespective of the ash composition are desirable. This study aims to investigate the effect of three different Al salts on adhesion reduction using synthetic ashes that exhibit high-temperature adhesion caused by the melting of Na and K components. The study revealed the influence of the counteranions of the Al salts on the adhesion of ash particles. The results indicate that the pyrolysis temperature for the Al salts and the reactivity of the heat treatment intermediates play critical roles in controlling adhesion.