硝酸熔鹽儲(chǔ)能材料的制備及熱物性研究
發(fā)布時(shí)間：2018-08-24 07:23
【摘要】：Solar Salt熔鹽(60%Na NO_3-40%KNO_3)因其使用溫度范圍寬、熱穩(wěn)定性好、腐蝕性弱、儲(chǔ)熱性能好、價(jià)格低廉等優(yōu)點(diǎn),在太陽能光熱發(fā)電領(lǐng)域得到廣泛應(yīng)用,其使用溫度范圍為300~550℃,比較適合作為中高溫儲(chǔ)能材料,目前制備Solar Salt熔鹽的原料純度不同,制備的產(chǎn)品熱物性有所差異。青海地區(qū)鹽湖鈉鉀鎂資源豐富,利用氯化鉀、芒硝和水氯鎂石制備硝酸鹽,對硝酸熔鹽中的雜質(zhì)離子進(jìn)行調(diào)控,結(jié)合青海豐富的太陽能資源,將高純硝酸熔鹽應(yīng)用于太陽能光熱發(fā)電系統(tǒng),既可以綜合利用鹽湖鈉鎂鉀資源,又可以促進(jìn)硝酸熔鹽儲(chǔ)熱技術(shù)的發(fā)展。本文以Solar Salt熔鹽為基礎(chǔ),首先探究了雜質(zhì)離子對Solar Salt熔鹽熱物性、結(jié)構(gòu)及腐蝕性的影響,其次通過添加低熔點(diǎn)Mg(NO_3)_2.6H_2O,制備了低熔點(diǎn)Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽儲(chǔ)能材料,開展了低熔點(diǎn)硝酸熔鹽制備工藝優(yōu)化及熱物性變化規(guī)律研究,獲得了制備硝酸鹽最佳工藝及參數(shù),并探究純度對Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽儲(chǔ)能材料熱物性影響。本文主要內(nèi)容總結(jié)如下:(1)高純硝酸鹽制備及其雜質(zhì)離子調(diào)控利用重結(jié)晶法對工業(yè)級Na NO_3、KNO_3進(jìn)行提純,制備了高純Na NO_3、KNO_3,產(chǎn)品純度大于99.9%;利用鹽湖豐產(chǎn)的水氯鎂石為原料,采用離子交換法制備了Mg(NO_3)_2.6H_2O,產(chǎn)品純度大于99.0%。制備的高純硝酸鹽中雜質(zhì)離子含量得到了有效控制,更加適合制備光熱發(fā)電所需儲(chǔ)能材料。(2)Cl~-和SO_4~(2-)對Solar Salt熔鹽熱物性、結(jié)構(gòu)及腐蝕性的影響通過探究雜質(zhì)離子Cl~-和SO_4~(2-)及其含量對Solar Salt熔鹽熱物性、結(jié)構(gòu)及腐蝕性的影響,獲得了雜質(zhì)離子Cl~-和SO_4~(2-)對Solar Salt熔鹽熱物性等的影響規(guī)律。隨著Solar Salt熔鹽中Cl~-和SO_4~(2-)含量(0.25%~1.0%)的升高,熔鹽熔點(diǎn)和相變潛熱有所波動(dòng),分解溫度有所降低,熔鹽穩(wěn)定性變差。Solar Salt熔鹽500℃循環(huán)燒制576h后,當(dāng)Solar Salt熔鹽中Cl~-含量小于0.75%(SO_4~(2-)含量小于1.0%)時(shí),Cl~-(SO_4~(2-))對熔鹽熱腐蝕性影響較小。(3)低熔點(diǎn)Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽制備及熱物性研究以Solar Salt二元熔鹽為基礎(chǔ),采用熔融共混法,通過添加Mg(NO_3)_2.6H_2O制備了低熔點(diǎn)Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽,優(yōu)化了制備工藝,獲得了最佳工藝參數(shù)及條件,獲得了三元熔鹽熱物性變化規(guī)律,確定了其配比為49.5%Na NO_3-33%KNO_3-17.5%Mg(NO_3)_2,燒制條件為250℃,2 h;300℃,18 h。三元熔鹽熔點(diǎn)為157.4℃,相變潛熱為74 J/g,分解溫度為451.7℃。(4)純度對Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽熱物性的影響以工業(yè)級和高純Na NO_3、KNO_3和Mg(NO_3)_2.6H_2O為原料,分別制備工業(yè)級和高純Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽。探究了純度對Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽熔點(diǎn)、相變潛熱、分解溫度、密度、黏度和導(dǎo)熱系數(shù)等的影響。與工業(yè)級Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽相比,高純Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽熔點(diǎn)降低,相變潛熱增大,分解溫度升高;在不同溫度下循環(huán)燒制30 h后,高純Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽熱失重較小,熱穩(wěn)定性較好;在相同循環(huán)時(shí)間及溫度下,高純Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽質(zhì)量損失減小,表明提純可以增加Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽的熱穩(wěn)定性。通過阿基米德法、旋轉(zhuǎn)法、差示掃描量熱法和激光閃光法分別測得Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽的密度、黏度、比熱容和導(dǎo)熱系數(shù),并對數(shù)據(jù)進(jìn)行分析及擬合,獲得了密度等性質(zhì)隨溫度的變化關(guān)系,高純Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽與工業(yè)級Na NO_3-KNO_3-Mg(NO_3)_2三元熔鹽相比,密度增大,黏度降低,比熱容降低,高溫條件下導(dǎo)熱系數(shù)有所降低,具有較好的熱物性。
[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.
【學(xué)位授予單位】：中國科學(xué)院大學(xué)(中國科學(xué)院青海鹽湖研究所)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB34
本文編號(hào)：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.
【學(xué)位授予單位】：中國科學(xué)院大學(xué)(中國科學(xué)院青海鹽湖研究所)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB34
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