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Molten Chloride Salt Technology for Next-Generation CSP Plants: Compatibility of cost-effective Fe-based steels with Mg-purified molten MgCl2-KCl-NaCl at 700°C

Gong, Qing and Ding, Wenjin and Bonk, Alexander and Bauer, Thomas and Shi, Hao and Weisenburger, Alfons and Yu, Rui and Wang, Dihua (2021) Molten Chloride Salt Technology for Next-Generation CSP Plants: Compatibility of cost-effective Fe-based steels with Mg-purified molten MgCl2-KCl-NaCl at 700°C. ICAE2021, Nov. 29-Dec. 5, 2021, Virtual (Thailand).

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Abstract

The next-generation concentrating solar power (CSP) plant can be equipped with a high-temperature thermal energy storage (TES) system and supercritical CO2 (sCO2) Brayton power cycle, whose operating temperatures are higher than 700 °C, for a higher energy conversion efficiency and lower levelized cost of electricity (LCOE). MgCl2-KCl-NaCl is a promising candidate of such high-temperature TES material and heat transfer fluid (HTF) due to its low cost and excellent thermophysical properties. Using Fe-based (Fe: ≥50 wt.%) alloys as the main structural material for the chloride-based TES system is the key to ensuring its cost competitiveness. However, it is universally believed that Fe-based alloys have unacceptably high corrosion rates in unpurified molten MgCl2-KCl-NaCl. Theoretically, purification with Mg metal can reduce the corrosion rates of Fe-based alloys to acceptable low levels (<15 µm/year). In this work, to experimentally verify this theory and prove feasibility of cost-effective Fe-based alloys as the high-temperature structural material for the chloride-based TES, Stainless Steel (SS) 310 and Incoloy (In) 800H were immersed in the Mg-purified molten MgCl2-KCl-NaCl at 700 °C for 2000 hours. The SEM and EDX results show that after immersion, the typical Cr-depleted corrosion layers on the samples are negligibly thin (< 3 µm). Based on mass loss and microstructural analysis results, the corrosion rates of SS 310 and In 800H are only 12.4 and 5.3 µm/year, respectively. Therefore, from the perspective of corrosion, the cost-effective Fe-based alloys possess good compatibility with the Mg-purified molten MgCl2-KCl-NaCl. According to preliminary calculation, the cost of TES using chlorides at >700°C could be potentially reduced close to that using commercial nitrates/nitrites at ≤565°C, leading to a significant reduction of the LCOE of CSP with higher operating temperatures.

Item URL in elib:https://elib.dlr.de/147689/
Document Type:Conference or Workshop Item (Speech)
Title:Molten Chloride Salt Technology for Next-Generation CSP Plants: Compatibility of cost-effective Fe-based steels with Mg-purified molten MgCl2-KCl-NaCl at 700°C
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Gong, QingQing.Gong (at) dlr.deUNSPECIFIED
Ding, WenjinWenjin.Ding (at) dlr.deUNSPECIFIED
Bonk, AlexanderAlexander.Bonk (at) dlr.deUNSPECIFIED
Bauer, ThomasThomas.Bauer (at) dlr.deUNSPECIFIED
Shi, HaoInstitute for Pulsed Power and Microwave Technology, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, GermanyUNSPECIFIED
Weisenburger, AlfonsInstitute for Pulsed Power and Microwave Technology, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, GermanyUNSPECIFIED
Yu, RuiSchool of Resources and Environmental Science, Wuhan University (WHU)UNSPECIFIED
Wang, DihuaSchool of Resources and Environmental Science, Wuhan University (WHU)UNSPECIFIED
Date:4 December 2021
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Concentrating solar power (CSP), Thermal energy storage (TES), Fe-based alloy, Corrosion control, Mg corrosion inhibitor, Cost estimation.
Event Title:ICAE2021
Event Location:Virtual (Thailand)
Event Type:international Conference
Event Dates:Nov. 29-Dec. 5, 2021
Organizer:Journal Applied Energy
HGF - Research field:Energy
HGF - Program:Materials and Technologies for the Energy Transition
HGF - Program Themes:High-Temperature Thermal Technologies
DLR - Research area:Energy
DLR - Program:E SP - Energy Storage
DLR - Research theme (Project):E - Thermochemical Processes
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Thermal Process Technology
Deposited By: Ding, Wenjin
Deposited On:23 Dec 2021 10:36
Last Modified:23 Dec 2021 13:02

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