Abstract
Hot dilute acidic pre-hydrolysis biorefining is a pre-treatment technology recently developed for converting raw biomass materials into sugar streams and other valuable intermediate chemicals at elevated temperatures. However, corrosion database of steels and alloys in hot dilute acidic solutions are very limited, resulting in the cost-effective selection of materials of construction difficult. Corrosion studies were thus performed to identify suitable alloys of construction and advance the understanding of how alloying elements (e.g., Cr and Mo) present in steels and alloys affect the formation and properties of surface oxides. In this paper, the corrosion performance of three alloys (UNS S31603, UNS S32101 and UNS N06625) in hot dilute sulfuric acids are introduced. The alloys exhibited active general corrosion and even pitting in the hot acidic solutions. Alloy 625 has better resistance to the hot dilute acid compared to SS 316L and duplex 2101. This may be attributed to the higher contents of Mo in the alloy. Long-term tests indicate that their corrosion rates are gradually increased with time. The introduction of 100 ppm Cl- from raw biomass feedstocks into the acid solution only has marginal effect on corrosion.
