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Defined purge gas composition stabilizes molten nitrate salt - Experimental prove and thermodynamic calculations

Sötz, Veronika and Bonk, Alexander and Steinbrecher, Julian and Bauer, Thomas (2020) Defined purge gas composition stabilizes molten nitrate salt - Experimental prove and thermodynamic calculations. Solar Energy, 211, pp. 453-462. Elsevier. DOI: 10.1016/j.solener.2020.09.041 ISSN 0038-092X

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Official URL: https://www.sciencedirect.com/science/article/abs/pii/S0038092X20309889

Abstract

Thermal energy storage systems are integrated in concentrating solar power plants to improve the flexibility of the electricity generation. Commonly, the liquid storage material Solar Salt, a nitrate salt mixture, is applied to transport and store solar thermal energy. The lifetime and the temperature range of Solar Salt in the storage units are restricted by decomposition reactions of the material. Oxide ion formation is one of the fundamental issues. So far, it has not been proven if oxide ion formation can be prevented by addition of gaseous reaction products to the gas atmosphere. Also, a reliable reaction equation for the oxide ion formation is missing. In the presented experiments, molten salt at 600 and 620 °C is purged with a gas mixture of nitrogen, oxygen, and nitrous gases. Post-analysis of salt samples reveals stabilizing effects, depending on the purge gas compositions. Chemical equilibrium of the oxide ion forming reaction is demonstrated. It is proven that oxide ion formation can be controlled and suppressed. Reaction equations are evaluated and selected in order to quantify the reaction thermodynamics. The results contribute to recommendations for operating conditions and gas handling in storage systems of solar thermal power plants, which finally ensure reliable and constant material properties for extended lifetime and high temperatures.

Item URL in elib:https://elib.dlr.de/137741/
Document Type:Article
Title:Defined purge gas composition stabilizes molten nitrate salt - Experimental prove and thermodynamic calculations
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Sötz, VeronikaVeronika.Soetz (at) dlr.dehttps://orcid.org/0000-0002-8309-6612
Bonk, AlexanderAlexander.Bonk (at) dlr.dehttps://orcid.org/0000-0002-0676-7267
Steinbrecher, JulianJulian.Steinbrecher (at) dlr.deUNSPECIFIED
Bauer, ThomasThomas.Bauer (at) dlr.dehttps://orcid.org/0000-0003-4080-7944
Date:November 2020
Journal or Publication Title:Solar Energy
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:211
DOI :10.1016/j.solener.2020.09.041
Page Range:pp. 453-462
Publisher:Elsevier
ISSN:0038-092X
Status:Published
Keywords:Thermal energy storage, Solar Salt, Salt decomposition, Oxide ion formation, Chemical equilibrium, Reaction thermodynamics
HGF - Research field:Energy
HGF - Program:Storage and Cross-linked Infrastructures
HGF - Program Themes:Thermal Energy Storage
DLR - Research area:Energy
DLR - Program:E SP - Energy Storage
DLR - Research theme (Project):E - Thermochemical Processes (Storage)
Location: Köln-Porz
Institutes and Institutions:Institute of Engineering Thermodynamics > Thermal Process Technology
Deposited By: Sötz, Veronika
Deposited On:07 Dec 2020 12:07
Last Modified:07 Dec 2020 12:07

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