Corrosion behavior of metallic alloys in molten chloride salts for thermal energy storage in concentrated solar power plants: A review

Abstract

Recently, more and more attention is paid on applications of molten chlorides in concentrated solar power (CSP) plants as high-temperature thermal energy storage (TES) and heat transfer fluid (HTF) materials due to their high thermal stability limits and low prices, compared to the commercial TES/HTF materials in CSP-nitrate salt mixtures. A higher TES/HTF operating temperature leads to higher efficiency of thermal to electrical energy conversion of the power block in CSP, however causes additional challenges, particularly increased corrosiveness of metallic alloys used as containers and structural materials. Thus, it is essential to study corrosion behaviors and mechanisms of metallic alloys in molten chlorides at operating temperatures (500-800°C) for realizing the commercial application of molten chlorides in CSP. The results of studies on hot corrosion of metallic alloys in molten chlorides are reviewed to understand their corrosion behaviors and mechanisms under various conditions (e.g., temperature, atmosphere). Emphasis has also been given on salt purification to reduce corrosive impurities in molten chlorides and development of electrochemical techniques to in-situ monitor corrosive impurities in molten chlorides, in order to efficiently control corrosion rates of metallic alloys in molten chlorides to meet the requirements of industrial applications.

Purification strategy and effect of impurities on corrosivity of dehydrated carnallite for thermal solar applications

“…ICP-MS/OES results on non-treated, thermally purified, and thermally/chemically purified DC salts This Unported Licence.been known from literature16,[18][19][20] that intergranular attack of Cr by MgOH + is a common corrosion mechanism in heavily corroded Ni-Fe-Cr alloys such as in the case of the non-treated salt (estimated at >3200 mm per year) and thermally puried salt ($950 mm per year). When an active metal such as Mg is added into the molten chloride, intergranular corrosion can be signicantly reduced, as shown by Ding et al,21 who investigated corrosion of Hastelloy C-276 (C276) at 700 C in a ternary MgCl 2 -KCl-NaCl (60-20-20 mol%) made from commercial NaCl, KCl, and MgCl 2 with 1 wt% of elemental Mg addition.…”

Full loop thermodynamic corrosion inhibition and sensing in molten chloride systems. Final report

“…The potential benefits and drawbacks of different corrosion mitigation schemes are given in Table 12. Chlorinating compounds such as CCl4 and HCl have been employed in previous work to minimize corrosion by eliminating moisture and impurities [8,9]. However, the use of CCl4 may produce extremely toxic phosgene as a byproduct [10].…”

Contributions in renewable energy systems: A perspective from the latest publications of FCSE

“…Cui et al [25] prepared N-doped spherical aggregates of TiO 2 nanosheet for giving a high conversion efficiency for solar energy in dye-sensitized solar cells. By viewing the concentrated solar power (CSP) as a promising system for the utilization of the sun's energy, Ding et al [26] summarized and compared several molten chlorides that could be used as high-temperature thermal energy storage and heat transfer fluid materials in the CSP system. Besides, solar thermochemical processes were regarded as competitive alternatives that may replace fossil fuel-based ones, while an efficient design of solar receivers/reactors was offered by Uddin et al [27] for improving the capacity of green fuels by integrating the solar energy.…”