Study on the decomposition characteristics of ammonium bisulfate and fly ash blend deposition during the heating process

Abstract

AbstractAmmonium bisulfate (ABS; NH4HSO4) and ash blend deposition endanger the boiler's safety by blocking and corroding air preheater in coal‐fired power plants. In this work, a self‐heating probe was used to investigate the decomposition characteristics of ABS and fly ash blend deposition after heating at 365°C for 5, 15, and 30 min. The results showed that after heating for 15 min, ash deposition was peeled off from the probe surface. When it came to 30 min, the metal surface of the probe could be seen. Scanning electron microscope (SEM) results showed that extending the heating time could alleviate the agglomeration of ash particles. After the deposition stage, the stable relative heat flux density was about 0.868, and it increased after heating. When the heating time was 5, 15, and 30 min, it was 0.954, 0.978, and 0.989, respectively. According to X‐ray diffraction (XRD) results, the main minerals in the deposition were quartz, mullite, tschermigite (NH4Al(SO4)2·12H2O), CaSO4, ammonium sulfate (AS; (NH4)2SO4), ABS, (NH4)3Al(SO4)3, and godovikovite (NH4Al(SO4)2). The thermal gravimetric analyzer (TGA) results indicated that after heating, the total content of ABS and AS in cases 1 ~ 4 was 2.03%, 1.33%, 0.75%, and 0.70%, respectively. This work can assist in air preheater design and ash deposition removal.