Research on heat storage performance of chloride composite molten salt based on phase diagram analysis

doi:10.11949/0438-1157.20240631

Abstract

Abstract:

Molten salt heat storage technology is widely utilized in solar thermal power generation, power peak regulation, and the consumption of renewable energy, and the key is molten salts. Based on phase diagram thermodynamic calculation, this paper designs NaCl-KCl-ZnCl₂ and NaCl-KCl-CaCl₂ molten salts. The melting point of the designed NaCl-KCl-ZnCl₂ molten salt is 36.6℃ lower than that of the current commercial Solar Salt. The limit operating temperature of NaCl-KCl-CaCl₂ molten salt is 747.5℃, which is greater than the minimum operating temperature of molten salt required for the next generation of solar thermal power generation. The effect of carbonized loofah sponge fragments (CLSF) on the thermal transient response performance of NaCl-KCl-CaCl₂ molten salt is analyzed by combining infrared imaging and digital image processing technology. Compared with the ternary molten salt NaCl-KCl-CaCl₂, the maximum melting enthalpy of NaCl-KCl-CaCl₂/CLSF molten salt is decreased by 27.09%, the maximum thermal conductivity increased by 60.03%, and the heating time and cooling time in the same temperature range decreased by 62.50% and 39.13% respectively. Efficient heat conduction channel inside the composite molten salt is formed by CLSF, resulting in significantly improved the heat storage performance of the composite molten salt. The phase transition behavior and thermal stability of the ternary molten salt are not affected. It can be concluded that NaCl-KCl-CaCl₂/CLSF composite molten salt has good thermal conductivity, thermal stability and heat storage performance, and broad application prospects.

Key words: phase change, composites, renewable energy, enthalpy, heat conduction, molten salt heat storage

摘要：

熔盐储热技术广泛应用于太阳能光热发电、电力调峰、可再生能源消纳等领域，其关键是熔盐。基于相图热力学计算设计NaCl-KCl-ZnCl₂、NaCl-KCl-CaCl₂熔盐，所设计NaCl-KCl-ZnCl₂熔盐熔点比目前商用Solar Salt盐的熔点低了36.6℃，NaCl-KCl-CaCl₂熔盐最高工作温度达747.5℃，超过下一代光热发电所需熔盐最低工作温度。结合红外成像技术与数字图像处理技术分析丝瓜络碳材料（CLSF）对NaCl-KCl-CaCl₂熔盐瞬态热响应性能的影响。与三元熔盐相比，NaCl-KCl-CaCl₂/CLSF复合熔盐熔化焓最大降幅为27.09%，热导率最大增幅为60.03%，相同温度范围内加热时间和冷却时间分别最大减少了62.50%和39.13%。CLSF在复合熔盐内部形成了高效导热通道，显著提升复合熔盐储热性能，未影响三元熔盐的相变行为和热稳定性。可见，NaCl-KCl-CaCl₂/CLSF复合熔盐具有良好导热性能、热稳定性和储热性能，具有广阔的应用前景。

关键词: 相变, 复合材料, 可再生能源, 焓, 热传导, 熔盐储热

CLC Number:

TK 02

Junbing XIAO, Bo ZOU, Jiandi REN, Changhui LIU, Chuankun JIA. Research on heat storage performance of chloride composite molten salt based on phase diagram analysis[J]. CIESC Journal, 2025, 76(3): 963-974.

肖俊兵, 邹博, 任建地, 刘昌会, 贾传坤. 基于相图分析的氯化物复合熔盐储热性能研究[J]. 化工学报, 2025, 76(3): 963-974.

Figures/Tables 14

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样品	熔点/℃	熔化焓测量值/(J/g)	熔化焓计算值/(J/g)	偏差/%
NaCl-KCl-CaCl₂	491.7	132.5	132.5	—
NaCl-KCl-CaCl₂/CLSF_0.1	491.9	115.0	119.3	3.6
NaCl-KCl-CaCl₂/CLSF_0.15	490.7	107.0	112.6	5.0
NaCl-KCl-CaCl₂/CLSF_0.2	489.9	96.6	106	8.9
NaCl-KCl-CaCl₂/CLSF_0.25	490.5	91.8	99.4	7.6
NaCl-KCl-CaCl₂/CLSF_0.3	486.1	89.5	92.8	3.4

样品	熔点/℃	熔化焓测量值/(J/g)	熔化焓计算值/(J/g)	偏差/%
NaCl-KCl-CaCl₂	491.7	132.5	132.5	—
NaCl-KCl-CaCl₂/CLSF_0.1	491.9	115.0	119.3	3.6
NaCl-KCl-CaCl₂/CLSF_0.15	490.7	107.0	112.6	5.0
NaCl-KCl-CaCl₂/CLSF_0.2	489.9	96.6	106	8.9
NaCl-KCl-CaCl₂/CLSF_0.25	490.5	91.8	99.4	7.6
NaCl-KCl-CaCl₂/CLSF_0.3	486.1	89.5	92.8	3.4

样品组成	分解温度/℃	质量损失/%
NaCl-KCl-CaCl₂	747.50	1.0
NaCl-KCl-CaCl₂/CLSF_0.1	745.23	1.6
NaCl-KCl-CaCl₂/CLSF_0.15	742.37	1.2
NaCl-KCl-CaCl₂/CLSF_0.2	748.41	1.4
NaCl-KCl-CaCl₂/CLSF_0.25	742.49	1.8
NaCl-KCl-CaCl₂/CLSF_0.3	746.89	2.1

样品组成	分解温度/℃	质量损失/%
NaCl-KCl-CaCl₂	747.50	1.0
NaCl-KCl-CaCl₂/CLSF_0.1	745.23	1.6
NaCl-KCl-CaCl₂/CLSF_0.15	742.37	1.2
NaCl-KCl-CaCl₂/CLSF_0.2	748.41	1.4
NaCl-KCl-CaCl₂/CLSF_0.25	742.49	1.8
NaCl-KCl-CaCl₂/CLSF_0.3	746.89	2.1

复合材料	添加剂质量分数/%	热导率/(W/(m·K))	热导率增加分数/%	文献
NaCl-KCl-MgCl₂/Al₂O₃	0.7	—	62.59	[28]
NaNO₃-NaNO₂-KNO₂-LiNO₃/MgO	40	0.41	—	[29]
NaCl-KCl-MgCl₂/CuO	0.2	0.340	15.85	[12]
	0.7	0.385	31.40
	2	0.409	39.55
NaCl-KCl-LiCl/CuO	1	0.483	3.20	[13]
	3	0.529	13.03
	5	0.571	22.01
NaNO₃-KNO₃/MgO	0.125	0.851	9.24	[30]
	0.25	0.883	13.36
	0.5	0.853	9.57
	1	0.858	10.19
	2	0.872	11.99
NaNO₃/SiC	20	1.16	50	[31]
LiNO₃-NaNO₃-KNO₃-Ca(NO₃)₂/CaSiO₃	20	1.177	—	[32]
NaCl-Na₂CO₃-Na₂SO₄/graphene nanoplatelets	0.2	1.21	11.53	[33]
	0.5	1.13	3.69
	1	1.38	27.02
	2	1.44	32.02
NaNO₃-KNO₃/EG	20	—	71.31	[34]
lauric acid/modified BN	21.8	0.563	124.30	[35]
diglycidyl ether of bisphenol A/BN	20	0.61	—	[36]
polyimide/BN	30	0.696	—	[37]
poly (tetradecyl acrylate)/BN	5	0.33	13.7	[38]
	10	0.41	41.4
	15	0.46	58.6
	20	0.62	113.8
NaCl-KCl-CaCl₂/CLSF	10	0.3611	2.73	本文
	15	0.3937	12.01
	20	0.4207	19.69
	25	0.4603	30.95
	30	0.5625	60.03