Performance analysis of mixed sodium waste salts applied in a thermal storage field

doi:10.19799/j.cnki.2095-4239.2023.0684

Abstract

Abstract:

The accumulation of industrial waste salts has significantly increased in recent years, resulting in several environmental problems. This study proposes a method to deal with industrial waste salts using NaCl and Na₂SO₄ as the main components (mainly including calcium, magnesium, and potassium impurity ions) and analyzes their thermal properties. These elements comprise sodium-based waste salt as a heat storage material, and its thermal properties are influenced by the existence of several impurity ions, which were discovered through molecular dynamics methods. In addition, binary sodium-based eutectic salts, NaCl-Na₂SO₄ were prepared using a two-step high-temperature melting method with 1% and 5% of KCl added to resemble the waste salts. These results indicated that K⁺ ion enhance the thermal performance of these sodium-based salts. Compared with the latent heat of phase change of binary sodium-based eutectic salts, the latent heat values of mixed molten salts increased by 64% (1%KCl) and 60% (5%KCl). Furthermore, the thermal conductivities of the mixed molten salts were increased by 2—3 times. The results also showd that the presence of K⁺ ions could improve the thermal performance of sodium waste salts, providing a means to reutilize this type of resource.

Key words: industrial waste salt, sodium-based salt, resource recycling, molten salt heat storage, thermal performance

CLC Number:

TB 33

Ziou YUAN, Feng WANG, Xingzhao QI, Qi ZHANG, Rui MA. Performance analysis of mixed sodium waste salts applied in a thermal storage field[J]. Energy Storage Science and Technology, 2023, 12(12): 3616-3626.

Figures/Tables 26

Table 1

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Table 2

Simulated/measured value of density and their fitting formulas of mixed salts"

样品	拟合公式	计算值/(g/cm³)	实测值/(g/cm³)
NS	$y 1 = 4.7 × 10 - 5 x - 3 × 10 - 7 x 2 + 2.5476$	2.548	2.478
1 KNS	$y 2 = - 8 × 10 - 5 x - 7.5 × 10 - 8 x 2 + 2.4105$	2.408	2.338
5 KNS	$y 3 = - 7.975 × 10 - 5 x - 1.0625 × 10 - 7 x 2 + 2.38645$	2.389	2.313

Table 2

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Table 3

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Table 6

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样品	Na/ (mg/cm³)	Cl/ (mg/cm³)	K/ (mg/cm³)	Ca/ (mg/cm³)	Mg/ (mg/cm³)	Fe/ (mg/cm³)
1#废盐	4.23×10³	8.17×10³	3.91×10²	6.77×10²	4.64×10²	4.11×10¹
2#废盐	9.81×10³	2.10×10⁴	1.42×10²	—	3.47×10²	—
3#废盐	9.65×10³	1.62×10⁴	4.88×10²	5.55×10²	—	—

样品	熔点/℃	纯度/%	规格	生产厂家
NaCl	801	≥99	分析纯	麦克林
Na₂SO₄	884	≥99	分析纯	麦克林
KCl	770	≥99	分析纯	麦克林

名称	熔融起始温度/℃	熔化潜热/(kJ/kg)
NS	623	133.2
1 KNS	624	218.5
5 KNS	598	212.9

样品	分解温度/℃	700 ℃质量/%	800 ℃质量/%	900 ℃质量/%	1000 ℃质量/%	1100 ℃质量/%	质量差/%
NS	756	99.00	95.68	88.30	71.10	58.80	41.20
1 KNS	873	99.55	97.01	96.18	83.12	66.37	33.63
5 KNS	884	99.67	99.18	95.52	85.75	70.90	29.10

样品	模拟比热容/ [J/(g·℃)]	平均比热容/[J/(g·℃)]	模拟导热系数/ [W/(m·K)]	平均导热系数/[W/(m·K)]
NS	2.18	0.72	0.71	0.56
1 KNS	2.89	1.43	1.68	1.54
5 KNS	2.73	1.26	1.24	1.17