Effects of ash formation during co-firing refuse-derived fuel with coal on initial superheater material degradation

Refuse-derived fuel (RDF) has significant potential as a co-firing fuel in power plants. However, its different characteristics from coal, particularly the high chlorine (Cl) concentration in the ash deposits, can degrade metal elements during combustion. This study aims to investigate the effect of adding RDF to coal on the initial degradation of materials caused by ash deposits during combustion. This research is conducted on a laboratory scale using a drop tube furnace to simulate pulverized coal boiler conditions, analyzying ash deposits, mineral transformations, and evaluating the microstructure of the probe material. The results show that the chlorine content in the R-10 at 0.035 wt% substantially affects the initial degradation of 18Cr-Ni during combustion. The oxide layer begins to degrade in the second hour due to ash deposits, reaching 2.38 μm. The presence of Ca (1.11%), K (1.66%), Na (4.46%), and Cl (0.42%) increases to 1.12% on the metal surface, gradually attacking the substrate area and forming cavities. Degradation increases linearly up to probe-8, resulting in a thickness loss of 3.81 μm and a significant reduction in chromium content, which decreases by 12.54%. These findings highlight the importance of understanding the impact of chlorine levels in RDF, which can aggressively attack and corrode metals.