The influence of KCL on biomass ash melting behaviour and high-temperature corrosion of low-alloy steel

Abstract

Abstract The main aim of this work was to determine the influence of KCl-rich ash deposits on 10CrMo9-10 steel oxidation rate. Two agricultural biomass samples: oat and rye straw, clean and doped with KCl were tested in this study. The addition of KCl does not decrease the melting temperature of the ash when KCl is not incorporated with mineral matter components. Corrosion experiments were performed at 550\u202f°C and 600\u202f°C, with corrosion coupons covered with real and synthetic biomass ash under oxidising conditions. The nonuniform distribution of KCl in ash affected the results and the effect of potassium concentration on oxidation rate was not observed in all cases. More severe influence of ash rich in KCl was observed at lower temperature, the reason is lower protective oxide scale formation rate and higher influence of ashes on steel material and scale. The temperature increase by 50\xa0°C doubled the corrosion rate. At 550\xa0°C KCl was most aggressive salt, but at 600\xa0°C the influence of eutectic mixture KCl+K2SO4 was the highest. Even at lower temperature thermal decomposition of K2CO3 was observed affecting the results. It might be concluded that temperature and eutectic mixture formation are essential parameters in corrosion prediction.