The ash formation and attrition characteristics of an Indonesia lignite coal ash for a 550 MWe ultra supercritical CFB boiler

The Samcheok CFBC (circulating fluidized bed combustion) power generation plant, the world largest, consists of 4 units of 550 MWe USC (ultra-supercritical) CFB boilers, started operation since the end of 2016. The years’ operation proves that there lacks circulating material and low solid hold-up in the upper furnace when burning Indonesia coal with low ash content of 4.5%. To solve this problem, the present study studied the mass balance of the Samcheok CFB boiler by investigating the ash formation and attrition characteristics of the feed coal in the lab. The ash formation PSD (particle size distribution) proves that the burnout-produced fly ash and fragmentation-produced fly ash are not the main sources of the production of fly ash. The heterogeneity of specific chemical compositions of particles in terms of particle sizes is proved to be one of the key factors for determining the attrition rate. For large particles, SiO2 and Al2O3 compositions dominate and results in low attrition rate, while for small particles, Fe2O3 and CaO compositions dominate and results in high attrition rate. The fine particles produced due to attrition have very high Fe2O3 contents, indicating that the heterogeneity of chemical composition is enhanced due to attrition. These findings show good agreement with the phenomenon of the high content of Fe2O3 in fly ash in the CFB boiler.