Understanding corrosion in coal-biomass co-firing with biomass ratio through embedded corrosion tests

Co-firing biomass with coal in power plants is an effective way to reduce CO2 emissions and dependence on fossil fuels. However, biomass contains corrosive elements such as chlorine (Cl2) and alkaline chlorides (KCl and NaCl) which can accelerate the corrosion rate during combustion. This study aims to determine the corrosion behavior and analyze the effect of fly ash from Stoker, Pulverized Coal (PC), Circulating Fluidized Bed (CFB), and 2-5% biomass. The corrosion testing method used in this study was the embedded test (ISO 17248) with fly ash and biomass powder. The mass gain of samples was measured every 20-hour cycle. Scanning Electron Microscopy-Energy Dispersion X-ray (SEM-EDS) and X-ray Diffraction (XRD) characterizations were performed to determine the morphology, distribution of elements, and the phases formed on the sample surface after the corrosion test. The results showed that the fly ash stoker had a higher corrosion mass gain than fly ash PC and CFB. Also, more biomass addition led to an increase in the corrosion products formed on the sample surfaces, shown by 5 wt.% biomass addition with the corrosion mass gain of 7.39?mg/cm2. The oxide scales (Fe2O3) and metallic chloride (FeCl2) phase are formed on the sample surface, indicating the influence of chlorine and alkali chloride contained in the biomass leading to the accelerated corrosion process and rapid degradation of materials.