Understanding the effect of dolomite additive on corrosion characteristics of straw biomass ash through experiment study and molecular dynamics calculations

Abstract

Experiments and molecular dynamics calculations were conducted to study the corrosion characteristics of straw biomass ash with dolomite as an additive. The results showed that the corrosion of metal by straw ash followed a parabolic law with respect to time, and this corrosion gradually reduced after adding dolomite. At 650 °C, the surface of straw ash almost completely sintered and melted and was composed of SiO2, KCl, K2Si4O9 and K2CrO4. The corrosion layer contained cracks and many acicular Fe–Cr oxides. After adding 5% dolomite, the corrosion rate decreased by 57.74%. The ash layer loosened and was mainly composed of CaMgSi2O6, CaSiO3 and MgSiO3. No evident cracks were observed in the corrosion layer. As the temperature increased, the absolute value of the binding energy of KCl on the Fe2O3 and dolomite surfaces increased. Moreover, stronger chemical interactions were observed between the K+, Cl−, and dolomite. On the same surface, the diffusion coefficient of K+ was higher than that of Cl−. At the same temperature, the diffusion coefficient of K+ and Cl− on the dolomite was greater than on the Fe2O3. KCl was more likely to combine with dolomite than with the metal surface, alleviating the metal corrosion caused by biomass ash.