Molten chloride salts for next generation CSP plants: Electrolytical salt purification for reducing corrosive impurity level

Journal Article · Sun Sep 01 00:00:00 EDT 2019 · Solar Energy Materials and Solar Cells

DOI:https://doi.org/10.1016/j.solmat.2019.04.021· OSTI ID:1543119

Ding, Wenjin ^[1]; Gomez-Vidal, Judith ^[2]; Bonk, Alexander ^[1]; Bauer, Thomas ^[3]

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1. German Aerospace Center (DLR), Inst. of Engineering Thermodynamics, Stuttgart (Germany)
2. National Renewable Energy Lab. (NREL), Golder, CO (United States). Building and Thermal Sciences Center
3. German Aerospace Center (DLR), Cologne (Germany). Inst. of Engineering Thermodynamics

In this study, electrolysis with a Mg anode is presented to purify the molten chloride salt (MgCl₂/KCl/NaCl 60/20/20 mol.%) for reducing its corrosivity. Using a Mg anode, the production of toxic gases like Cl₂ on an inert anode (e.g., tungsten) can be avoided. Moreover, compared to an inert anode, a lower over-potential is required to remove the corrosive impurity MgOH⁺ in the molten salt due to the high reactivity of Mg. In order to evaluate the effect of the salt purification, the cyclic voltammetry (CV) method developed in our previous work is used to in-situ measure the concentration of the corrosive MgOH⁺ impurity in the molten salt. The CV measurements indicate that the corrosive impurity is efficiently removed by electrolysis. For decreasing the cathode inactivation due to produced MgO on the surface, a pulsed potential applied on the tungsten cathode during electrolysis shows to be promising. This electrochemical salt purification method has shown to be promising by efficiently controlling the corrosivity of the molten chloride salt. The potentiodynamic polarization (PDP) measurements on a commercial high-temperature alloy (Incoloy 800 H) immersed in the molten salt indicate that the corrosion rate of the alloy is significantly reduced due to the salt purification. It could also lead to a reduction of the cost of the conventional salt purification step, structural container materials, and piping in next generation concentrated solar power (Gen3 CSP) plants.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: AC36-08GO28308; AC36-08-GO28308
• OSTI ID: 1543119
• Alternate ID(s): OSTI ID: 1636908
• Report Number(s): NREL/JA-5500-74320
• Journal Information: Solar Energy Materials and Solar Cells, Vol. 199, Issue C; ISSN 0927-0248
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
47 OTHER INSTRUMENTATION
concentrated solar power (CSP)
corrosion control
corrosive impurity
cyclic voltammetry (CV)
electrolysis
potentiodynamic polarization (PDP)