Study on the Influence of Different Particle Sizes of Kaolin Blending with Zhundong Coal Combustion on the Adsorption of Alkali Metal Sodium and Ash Fusion Characteristics

Blending kaolin is an effective method to alleviate fouling and slagging during the combustion of Zhundong coal. The influence of blending kaolin with varying particle sizes on the adsorption behavior of alkali metal sodium and the ash fusion characteristics was studied using sodium capture experiments and ash fusion temperature tests. The results indicate that kaolin particle size is a critical factor influencing sodium retention. As the particle size decreases, the sodium retention rate increases accordingly. In the absence of kaolin, the sodium retention rate was only 28.03%. However, when 75–100 µm particles of kaolin were added, the retention rate increased to 43.49%. Further reducing the particle size to 20–63 µm resulted in an additional increase of 10.51%. Additionally, decreasing the kaolin particle size contributed to the noticeable increase in ash fusion temperatures. After 75–100 µm kaolin was blended, the DT and FT of the ash were 1137 °C and 1161 °C, respectively. With 20–63 µm kaolin, the DT increased by 42 °C, and the FT increased by 36 °C. This trend is attributed to the enhanced decomposition and transformation of sulfates in the ash, which promotes the formation of high-melting-point feldspar minerals such as anorthite and gehlenite. These findings provide important data support for understanding the influence of kaolin particle size on the ash fusion behavior during the combustion of Zhundong coal.