Fe基合金の超臨界水環境での腐食に及ぼすCr,AlおよびSiの影響

Abstract

Supercritical water oxidation (SCWO) is a promising and effective method for solving energy problems, similar to the use of biomass. The high solubility for organic compounds and its special physical properties (i.e., density and viscosity) result in a key advantage over standard processes such as saccharification. During sodium chloride (NaCl) oxidation in biomass, severe corrosion attack of most of the materials has been observed as a result of the formation of hydrochloric acid (HCl). While SUS316L is generally considered important for severe service applications, results from laboratory in operation indicate that they will not withstand some aggressive feeds. Moreover, SUS316L is expensive because of containing for Ni and Mo. Therefore, in order to develop and use a Fe-based alloy for the reaction container, the corrosion of the alloy elements in a supercritical water environment must be studied. In this study, corrosion resistance of Fe-Al, Fe-Cr-Al and Fe-Cr-Al-Si alloys was investigated to determine the effects of the added elements on the corrosion characteristics in supercritical water environment. The Fe-30% Cr alloy composed of Cr_2O_3 and Al_2O_3 on the surface with Al content up to 5 mass%, showed high corrosion resistance. Further, the Fe-30% Cr-5% Al alloy, with Si content up to 1 mass%, had a higher corrosion resistance than the Fe-30% Cr-5% Al alloy and also exhibited pitting corrosion resistance. The Fe-30% Cr-5% Al-1% Si alloy showed excellent corrosion resistance comparable to that of SUS316L in a supercritical water environment.