Influence of coal quality on the tendency for slagging formation on a spreader stoker boiler

Abstract

ABSTRACT During the combustion of solid fuels in power generation systems, one of the biggest problems related to ash is the surface deposition and accumulation of molten or sintered slag, commonly known as slagging. This research evaluated the influence of coal quality on the tendency for slagging based on the evaluation of practical criteria for industry, such as traditional indices, ash load, and coal granulometry. The indices were evaluated from standardized analyses of the composition and fusibility temperatures of the ash of eight bituminous coals. Ash fusibility tests were performed in both oxidizing and reducing atmospheres. Under oxidizing conditions, iron had a dominant influence on the formation characteristics of slagging, resulting in higher melting temperatures. Coals with low frequencies of hard deposit formation, as determined by their ash composition, contributed significantly to deposition problems due to their high ash load and granulometry. Furthermore, large coal particles require more time to burn, which can lead to caking or slag and increased carbon loss in ash. Therefore, when using empirical indices to assess the tendency for slagging, it is essential to consider ash content and ensure an appropriate distribution of coal sizes for combustion.