Hydrothermal liquefaction (HTL) is seen as a promising thermochemical approach to convert wet and waste biomass feedstocks into biocrude oils and other valuable chemicals. One of the critical technical barriers that must be addressed for the industrial deployment of HTL technology is the corrosion of process core equipment, especially the refining reactors, due to the presence of the hot-compressed water medium, applied alkali catalyst, and aggressive intermediate and final products (such as aggressive sulfur and/or chlorinated compounds, organic acids) generated during the conversion. In this study, the corrosion performance of two candidate alloys (UNS N06625 and UNS R20033) was investigated in a batch reactor containing hot-compressed water, 5 wt.% K2CO3 catalyst and cellulose (a typical model compound of lignocellulosic biomass). Certain amounts of organic acids and phenolic compounds were present in the produced oil, implying the change of environmental pH (from mild basic to near neutral) during the conversion. The two tested alloys experienced general oxidation associated with localized oxide peel-off or nodular oxidation. Due to its higher Cr content, UNS R20033 had a lower corrosion rate compared to UNS N06625 under the HTL of cellulose.

Subject
Test methods, Water, Corrosion rate, Oils, Metal surfaces, Reactors, Molybdenum alloys, Metal coupons, Descaling, Biomass, Cellulose, Corrosion products, Alloys
Keywords:
hydrothermal liquefaction, cellulose, Ni-based alloy, corrosion
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2022
Association for Materials Protection and Performance (AMPP)
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