应用于储热领域的混合钠基废盐热物性分析

doi:10.19799/j.cnki.2095-4239.2023.0684

摘要/Abstract

摘要：

近年来工业废盐的堆积量剧增引发一系列环境问题。废盐的处置方法已成为制约废盐资源化利用的瓶颈。针对以NaCl和Na₂SO₄为主要成分的工业废盐(杂质离子包含钙、镁、钾等金属离子)，本工作提出利用钠基废盐作为储热材料的处置思路并对其热性能进行分析。采用分子动力学方法，分析废盐中主要杂质对钠基盐体系热物性影响。进一步通过高温熔融法制备二元钠基共晶盐NaCl-Na₂SO₄，分别添加质量分数为1%和5%的KCl模拟含有微量K⁺废盐，研究其对混合盐热物性影响。结果表明K⁺对钠基盐的热物性有显著提升，含有1%和5% KCl的混合钠基盐相比二元钠基共晶盐的相变潜热分别提高了64%和60%，导热系数提高了2～3倍。K⁺的存在有利于废盐热物性改善，为该类固废资源化利用提供了途径。

关键词: 工业废盐, 钠基盐, 资源化, 熔盐储热, 热物性

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

中图分类号:

TB 33

袁子鸥, 王峰, 祁星朝, 张琦, 马瑞. 应用于储热领域的混合钠基废盐热物性分析[J]. 储能科学与技术, 2023, 12(12): 3616-3626.

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.

图/表 26

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表2

混合熔盐密度计算值与实测值(30 ℃)"

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

表2

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表3

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表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