Title: Enabling chloride salts for thermal energy storage: implications of salt purity

Abstract

Molten salts for use as heat transfer fluids in concentrated solar or nuclear power plants have experienced a resurgence over the past decade with a special focus on chloride-based salt mixtures, particularly for use in concentrating solar power and fast-spectrum nuclear reactors. Salt purification, specifically oxide removal, is required even for high purity commercial salts and can be achieved using many different methods. Carbochlorination, however, proves most effective according to thermodynamics and produces a gaseous byproduct easily removed from the salt. A variety of carbochlorinating reagents and reagent combinations were evaluated for thermodynamic favorability in the removal of common impurities in MgCl₂-based feedstock or coverage gases used in industrial systems. Carbon tetrachloride exhibited superior purification thermodynamics above the melting point of common MgCl₂-based salt compositions. Salt with composition of 68 : 32 mol% KCl : MgCl₂ was purified on the kilogram scale by sparging with carbon tetrachloride, reducing dissolved oxide to trace levels (42 mmol MgO/kg salt). Interestingly, the lower purity salts exhibited magnesium and oxygen presence along grain boundaries in the corrosion layers while the purified salts did not, highlighting the need for decreased oxide content. The lessened corrosivity of the highly purified salt suggests a proper salt treatmentmore » may reduce dependence on specialized materials for use with molten salts.« less

Authors:

Kurley, J. Matthew  ^[1];

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Halstenberg, Phillip W.  ^[1];

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McAlister, Abbey  ^[1];

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Raiman, Stephen  ^[2];

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Dai, Sheng  ^[3];

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• Search DOE PAGES for ORCID "0000-0002-8046-3931"
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Mayes, Richard T.  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-7457-3261"
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+ Show Author Affiliations

1. Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, USA
2. Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, USA
3. Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, USA, Department of Chemistry

Publication Date:

2019-08-15

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Molten Salts in Extreme Environments (MSEE); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1557370

Alternate Identifier(s):

OSTI ID: 1558546

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Published Article

Journal Name:

RSC Advances

Additional Journal Information:

Journal Name: RSC Advances Journal Volume: 9 Journal Issue: 44; Journal ID: ISSN 2046-2069

Publisher:

Royal Society of Chemistry

Country of Publication:

United Kingdom

Language:

English

Subject:

25 ENERGY STORAGE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE