硝酸熔盐储能材料的制备及热物性研究
发布时间：2018-08-24 07:23
【摘要】：Solar Salt熔盐(60%Na NO_3-40%KNO_3)因其使用温度范围宽、热稳定性好、腐蚀性弱、储热性能好、价格低廉等优点,在太阳能光热发电领域得到广泛应用,其使用温度范围为300~550℃,比较适合作为中高温储能材料,目前制备Solar Salt熔盐的原料纯度不同,制备的产品热物性有所差异。青海地区盐湖钠钾镁资源丰富,利用氯化钾、芒硝和水氯镁石制备硝酸盐,对硝酸熔盐中的杂质离子进行调控,结合青海丰富的太阳能资源,将高纯硝酸熔盐应用于太阳能光热发电系统,既可以综合利用盐湖钠镁钾资源,又可以促进硝酸熔盐储热技术的发展。本文以Solar Salt熔盐为基础,首先探究了杂质离子对Solar Salt熔盐热物性、结构及腐蚀性的影响,其次通过添加低熔点Mg(NO_3)_2.6H_2O,制备了低熔点Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐储能材料,开展了低熔点硝酸熔盐制备工艺优化及热物性变化规律研究,获得了制备硝酸盐最佳工艺及参数,并探究纯度对Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐储能材料热物性影响。本文主要内容总结如下:(1)高纯硝酸盐制备及其杂质离子调控利用重结晶法对工业级Na NO_3、KNO_3进行提纯,制备了高纯Na NO_3、KNO_3,产品纯度大于99.9%;利用盐湖丰产的水氯镁石为原料,采用离子交换法制备了Mg(NO_3)_2.6H_2O,产品纯度大于99.0%。制备的高纯硝酸盐中杂质离子含量得到了有效控制,更加适合制备光热发电所需储能材料。(2)Cl~-和SO_4~(2-)对Solar Salt熔盐热物性、结构及腐蚀性的影响通过探究杂质离子Cl~-和SO_4~(2-)及其含量对Solar Salt熔盐热物性、结构及腐蚀性的影响,获得了杂质离子Cl~-和SO_4~(2-)对Solar Salt熔盐热物性等的影响规律。随着Solar Salt熔盐中Cl~-和SO_4~(2-)含量(0.25%~1.0%)的升高,熔盐熔点和相变潜热有所波动,分解温度有所降低,熔盐稳定性变差。Solar Salt熔盐500℃循环烧制576h后,当Solar Salt熔盐中Cl~-含量小于0.75%(SO_4~(2-)含量小于1.0%)时,Cl~-(SO_4~(2-))对熔盐热腐蚀性影响较小。(3)低熔点Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐制备及热物性研究以Solar Salt二元熔盐为基础,采用熔融共混法,通过添加Mg(NO_3)_2.6H_2O制备了低熔点Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐,优化了制备工艺,获得了最佳工艺参数及条件,获得了三元熔盐热物性变化规律,确定了其配比为49.5%Na NO_3-33%KNO_3-17.5%Mg(NO_3)_2,烧制条件为250℃,2 h;300℃,18 h。三元熔盐熔点为157.4℃,相变潜热为74 J/g,分解温度为451.7℃。(4)纯度对Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐热物性的影响以工业级和高纯Na NO_3、KNO_3和Mg(NO_3)_2.6H_2O为原料,分别制备工业级和高纯Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐。探究了纯度对Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐熔点、相变潜热、分解温度、密度、黏度和导热系数等的影响。与工业级Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐相比,高纯Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐熔点降低,相变潜热增大,分解温度升高;在不同温度下循环烧制30 h后,高纯Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐热失重较小,热稳定性较好;在相同循环时间及温度下,高纯Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐质量损失减小,表明提纯可以增加Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐的热稳定性。通过阿基米德法、旋转法、差示扫描量热法和激光闪光法分别测得Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐的密度、黏度、比热容和导热系数,并对数据进行分析及拟合,获得了密度等性质随温度的变化关系,高纯Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐与工业级Na NO_3-KNO_3-Mg(NO_3)_2三元熔盐相比,密度增大,黏度降低,比热容降低,高温条件下导热系数有所降低,具有较好的热物性。
[Abstract]:Solar Salt molten salt (60% Na NO_3-40% KNO_3) is widely used in solar photothermal power generation because of its wide temperature range, good thermal stability, weak corrosiveness, good thermal storage performance and low price. Its temperature range is 300-550, which is suitable for medium-high temperature energy storage materials. At present, the raw material purity of Solar Salt molten salt is prepared. The Salt Lake in Qinghai is rich in sodium, potassium and magnesium resources. Nitrate is prepared from potassium chloride, mirabilite and brucite hydrochloride. The impurity ions in the molten nitrate are controlled. Combined with the abundant solar energy resources in Qinghai, the high purity molten nitrate is applied to solar photothermal power generation system, which can be utilized comprehensively. Salt lake sodium magnesium potassium resources can also promote the development of nitrate molten salt heat storage technology. Based on the Solar Salt molten salt, this paper first explored the influence of impurity ions on the thermal properties, structure and corrosion of Solar Salt molten salt, and then prepared low melting point Na NO_3-KNO_3-Mg (NO_3) _2 ternary molten salt energy storage materials by adding low melting point Mg (NO_3) _2.6H_2O. The preparation process optimization and thermophysical properties of low melting point molten nitrate were studied. The optimum preparation process and parameters were obtained. The effect of purity on Thermophysical Properties of Na NO_3-KNO_3-Mg (NO_3) _2 ternary molten salt energy storage materials was investigated. High purity Na NO_3 and KNO_3 were prepared by crystallization method, and the purity of the product was more than 99.9%. Mg(NO_3)_2.6H_2O was prepared by ion exchange method from high yield brucite in salt lake, and the purity of the product was more than 99.0%. The impurity ion content in the prepared high purity nitrate was effectively controlled, which was more suitable for preparation. (2) The effects of Cl~ - and SO_4~ (2-) on the thermophysical properties, structure and corrosiveness of Solar Salt molten salt were investigated. The effects of impurity ions Cl~ - and SO_4~ (2-) and their contents on the thermophysical properties, structure and corrosiveness of Solar Salt molten salt were investigated. With the increase of Cl~ - and SO_4~ (2-) content (0.25%~1.0%) in Solar Salt molten salt, the melting point and latent heat of phase transformation fluctuate, the decomposition temperature decreases, and the stability of the molten salt becomes worse. (3) Preparation and thermophysical properties of ternary molten salt Na NO_3-KNO_3-Mg(NO_3)_2 with low melting point were studied. Based on Solar Salt Binary Molten salt, low melting point Na NO_3-KNO_3-Mg(NO_3)_2 ternary molten salt was prepared by adding Mg(NO_3)_2.6H_2O by melt blending method. The preparation process was optimized and the optimum technological parameters and conditions were obtained. The thermophysical properties of ternary molten salts were studied. The effects of the ratio of 49.5% Na NO_3-33% KNO_3-17.5% Mg(NO_3)_2, firing conditions at 250 C for 2 h, 300 C for 18 h, melting point at 157.4 c, latent heat of phase transformation at 74 J/g and decomposition temperature at 451.7 (4) on the thermophysical properties of ternary molten salts were determined. The effects of purity on the melting point, phase change latent heat, decomposition temperature, density, viscosity and thermal conductivity of the ternary molten salt Na NO_3-KNO_3-Mg (NO_3) _2 were investigated. The melting point of the ternary molten salt NO_3-KNO_3-Mg(NO_3)_2 decreases, the latent heat of phase transformation increases, and the decomposition temperature rises. After 30 hours of cyclic firing at different temperatures, the high-purity ternary molten salt Na NO_3-KNO_3-Mg(NO_3)_2 has smaller thermal weight loss and better thermal stability, and the mass loss of the high-purity ternary molten salt Na NO_3-KNO_3-Mg(NO_3)_2 decreases at the same cycle time and temperature. The density, viscosity, specific heat capacity and thermal conductivity of Na NO_3-KNO_3-Mg(NO_3)_2 ternary molten salt were measured by Archimedes method, rotational method, differential scanning calorimetry and laser flash method, respectively. Compared with industrial grade Na NO_3-KNO_3-Mg(NO_3)_2 ternary molten salt, high purity Na NO_3-KNO_3-Mg(NO_3)_2 ternary molten salt has higher density, lower viscosity, lower specific heat capacity and lower thermal conductivity at high temperature.
【学位授予单位】：中国科学院大学(中国科学院青海盐湖研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34
本文编号：2200050
[Abstract]:Solar Salt molten salt (60% Na NO_3-40% KNO_3) is widely used in solar photothermal power generation because of its wide temperature range, good thermal stability, weak corrosiveness, good thermal storage performance and low price. Its temperature range is 300-550, which is suitable for medium-high temperature energy storage materials. At present, the raw material purity of Solar Salt molten salt is prepared. The Salt Lake in Qinghai is rich in sodium, potassium and magnesium resources. Nitrate is prepared from potassium chloride, mirabilite and brucite hydrochloride. The impurity ions in the molten nitrate are controlled. Combined with the abundant solar energy resources in Qinghai, the high purity molten nitrate is applied to solar photothermal power generation system, which can be utilized comprehensively. Salt lake sodium magnesium potassium resources can also promote the development of nitrate molten salt heat storage technology. Based on the Solar Salt molten salt, this paper first explored the influence of impurity ions on the thermal properties, structure and corrosion of Solar Salt molten salt, and then prepared low melting point Na NO_3-KNO_3-Mg (NO_3) _2 ternary molten salt energy storage materials by adding low melting point Mg (NO_3) _2.6H_2O. The preparation process optimization and thermophysical properties of low melting point molten nitrate were studied. The optimum preparation process and parameters were obtained. The effect of purity on Thermophysical Properties of Na NO_3-KNO_3-Mg (NO_3) _2 ternary molten salt energy storage materials was investigated. High purity Na NO_3 and KNO_3 were prepared by crystallization method, and the purity of the product was more than 99.9%. Mg(NO_3)_2.6H_2O was prepared by ion exchange method from high yield brucite in salt lake, and the purity of the product was more than 99.0%. The impurity ion content in the prepared high purity nitrate was effectively controlled, which was more suitable for preparation. (2) The effects of Cl~ - and SO_4~ (2-) on the thermophysical properties, structure and corrosiveness of Solar Salt molten salt were investigated. The effects of impurity ions Cl~ - and SO_4~ (2-) and their contents on the thermophysical properties, structure and corrosiveness of Solar Salt molten salt were investigated. With the increase of Cl~ - and SO_4~ (2-) content (0.25%~1.0%) in Solar Salt molten salt, the melting point and latent heat of phase transformation fluctuate, the decomposition temperature decreases, and the stability of the molten salt becomes worse. (3) Preparation and thermophysical properties of ternary molten salt Na NO_3-KNO_3-Mg(NO_3)_2 with low melting point were studied. Based on Solar Salt Binary Molten salt, low melting point Na NO_3-KNO_3-Mg(NO_3)_2 ternary molten salt was prepared by adding Mg(NO_3)_2.6H_2O by melt blending method. The preparation process was optimized and the optimum technological parameters and conditions were obtained. The thermophysical properties of ternary molten salts were studied. The effects of the ratio of 49.5% Na NO_3-33% KNO_3-17.5% Mg(NO_3)_2, firing conditions at 250 C for 2 h, 300 C for 18 h, melting point at 157.4 c, latent heat of phase transformation at 74 J/g and decomposition temperature at 451.7 (4) on the thermophysical properties of ternary molten salts were determined. The effects of purity on the melting point, phase change latent heat, decomposition temperature, density, viscosity and thermal conductivity of the ternary molten salt Na NO_3-KNO_3-Mg (NO_3) _2 were investigated. The melting point of the ternary molten salt NO_3-KNO_3-Mg(NO_3)_2 decreases, the latent heat of phase transformation increases, and the decomposition temperature rises. After 30 hours of cyclic firing at different temperatures, the high-purity ternary molten salt Na NO_3-KNO_3-Mg(NO_3)_2 has smaller thermal weight loss and better thermal stability, and the mass loss of the high-purity ternary molten salt Na NO_3-KNO_3-Mg(NO_3)_2 decreases at the same cycle time and temperature. The density, viscosity, specific heat capacity and thermal conductivity of Na NO_3-KNO_3-Mg(NO_3)_2 ternary molten salt were measured by Archimedes method, rotational method, differential scanning calorimetry and laser flash method, respectively. Compared with industrial grade Na NO_3-KNO_3-Mg(NO_3)_2 ternary molten salt, high purity Na NO_3-KNO_3-Mg(NO_3)_2 ternary molten salt has higher density, lower viscosity, lower specific heat capacity and lower thermal conductivity at high temperature.
【学位授予单位】：中国科学院大学(中国科学院青海盐湖研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34
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