TWI473764B

TWI473764B - Molten salt composition

Info

Publication number: TWI473764B
Application number: TW101144439A
Authority: TW
Inventors: Ching Cheng Lin; Li Hua Wang; Tien Heng Huang
Original assignee: Ind Tech Res Inst
Priority date: 2012-11-28
Filing date: 2012-11-28
Publication date: 2015-02-21
Also published as: CN103849358B; TW201420504A; CN103849358A

Description

熔鹽組合物Molten salt composition

本發明係關於熔鹽組合物，更特別關於熔鹽組合物於太陽能熱能發電的應用。This invention relates to molten salt compositions, and more particularly to the use of molten salt compositions for solar thermal power generation.

太陽熱能發電系統需大量熔鹽，以作為熱能介質。熔鹽成本占熱儲存系統的40~50%。換言之，若能提昇熔鹽性質如降低其熔點、增加其比熱、及增加其穩定性，則可降低發電成本。The solar thermal power generation system requires a large amount of molten salt to serve as a thermal energy medium. Molten salt costs 40 to 50% of the thermal storage system. In other words, if the molten salt properties can be improved, such as lowering the melting point, increasing its specific heat, and increasing its stability, the power generation cost can be reduced.

目前市售熔鹽包括硝酸鹽組合物Hitec^® ，包含60wt%的NaNO₃ 與40wt%的KNO₃ ，其熔點為220℃，25℃的比熱(熱容量)為1.3398 J/gK，而350℃的比熱為1.55J/gK。市售熔鹽如Dow所售之硝酸鹽組合物，包含53wt%的KNO₃ 、7wt%的NaNO₃ 、與40wt%的NaNO₂ ，其熔點為142℃。市售熔鹽如Dow所售之硝酸鹽組合物，包含45wt%的KNO₄ 、7wt%的NaNO₃ 、與48wt%的Ca(NO₃ )₂ ，其熔點為120℃。Currently commercially available molten salts include the nitrate composition Hitec ^® , which contains 60 wt% of NaNO ₃ and 40 wt% of KNO ₃ , having a melting point of 220 ° C, a specific heat (heat capacity) of 25 ° C of 1.3398 J/gK, and a specific heat of 350 ° C. It is 1.55J/gK. Commercially sold by Dow as molten salt of nitrate composition comprises 53wt% of KNO _3, 7wt% of NaNO _3, and 40wt% of NaNO _2, a melting point of 142 ℃. A commercially available molten salt such as the nitrate composition sold by Dow comprises 45 wt% KNO ₄ , 7 wt% NaNO ₃ , and 48 wt% Ca(NO ₃ ) ₂ having a melting point of 120 °C.

美國專利7,588,694揭露之硝酸鹽組合物包含13wt%至21wt%的LiNO₃ 、9wt%至18wt%的NaNO₃ 、40wt%至52wt%的KNO₃ 、及20wt%至27wt%的Ca(NO₃ )₂ ，其熔點<100℃，熱穩定性>500℃。美國專利7,922,931揭露之亞硝酸鹽和硝酸鹽組合物包含LiNO₃ 、NaNO₃ 、KNO₃ 、NaNO₂ 、及KNO₂ ，其中Li占20mol%至33.5mol%，Na占18.6mol%至40mol%，K占40mol%至50.3mol%，NO₃ 占36mol%至50mol%，而NO₂ 占50mol%至62.5mol%，其熔點介於70℃ 至80℃之間。U.S. Patent No. 7,588,694 discloses a composition comprising a nitrate of 13wt% to 21wt% of LiNO _3, 9wt% to 18wt% of NaNO _3, 40wt% to 52wt% of KNO _3, and 20wt% to 27wt% of Ca (NO ₃₎ ₂ , its melting point <100 ° C, thermal stability >500 ° C. The nitrite and nitrate compositions disclosed in U.S. Patent No. 7,922,931 comprise LiNO ₃ , NaNO ₃ , KNO ₃ , NaNO ₂ , and KNO ₂ , wherein Li accounts for 20 mol% to 33.5 mol%, and Na accounts for 18.6 mol% to 40 mol%, K. From 40 mol% to 50.3 mol%, NO ₃ accounts for 36 mol% to 50 mol%, and NO ₂ accounts for 50 mol% to 62.5 mol%, and its melting point is between 70 ° C and 80 ° C.

綜上所述，目前熔鹽的開發多以降低熔點與提高熱穩定性為重點。然而在太陽熱能發電的應用中，熔鹽的比熱(熱容量)比熔點更重要。舉例來說，若能使熔鹽比熱加倍，則相同用量的熔鹽所能儲存的熱能亦加倍，可大幅降低太陽熱能發電的成本。換言之，目前亟需高比熱的熔鹽組成。In summary, the development of molten salt is currently focused on lowering the melting point and improving thermal stability. However, in solar thermal power generation applications, the specific heat (heat capacity) of the molten salt is more important than the melting point. For example, if the molten salt is doubled than the heat, the same amount of molten salt can be stored to double the heat energy, which can greatly reduce the cost of solar thermal power generation. In other words, there is a need for a molten salt composition of high specific heat.

本發明一實施例提供一種熔鹽組合物，包括：15wt%至26wt%的LiNO₃ ；12wt%至21wt%的NaNO₃ ；43wt%至53wt%的KNO₃ ；以及3wt%至29wt%的Ba(NO₃ )₂ 或2wt%至10wt%的CsNO₃ 。An embodiment of the present invention provides a molten salt composition comprising: 15 wt% to 26 wt% of LiNO ₃ ; 12 wt% to 21 wt% of NaNO ₃ ; 43 wt% to 53 wt% of KNO ₃ ; and 3 wt% to 29 wt% of Ba ( NO ₃ ) ₂ or 2 wt% to 10 wt% of CsNO ₃ .

本發明一實施例提供之熔鹽組合物，包括：15wt%至26wt%的LiNO₃ ；12wt%至21wt%的NaNO₃ ；43wt%至53wt%的KNO₃ ；以及3wt%至29wt%的Ba(NO₃ )₂ 或2wt%至10wt%的CsNO₃ ，也就是(1)LiNO₃ 、NaNO₃ 、KNO₃ 、與Ba(NO₃ )₂ 的組合物；以及(2)LiNO₃ 、NaNO₃ 、KNO₃ 、與CsNO₃ 的組合物。上述熔鹽組成物具有高比熱(>1.5J/gK)與寬廣的流體範圍(熔點為約110℃至130℃，熱穩定溫度高達550℃至570℃)，適於作為熱傳介質與熱儲存介質，以應用於太陽熱能發電，或搭配傳統發電如火力發電或核能發電等，請參考Hybrid Solar Thermal Power Plant(資料出處：the World Bank)。值得注意的是，若熔鹽組合物中某一鹽類的比例超出上述範圍，即可能劣化熔鹽組合物的物性，比如降低比熱或縮減流體範圍。A molten salt composition according to an embodiment of the present invention comprises: 15 wt% to 26 wt% of LiNO ₃ ; 12 wt% to 21 wt% of NaNO ₃ ; 43 wt% to 53 wt% of KNO ₃ ; and 3 wt% to 29 wt% of Ba ( NO ₃ ) ₂ or 2 wt% to 10 wt% of CsNO ₃ , that is, (1) a combination of LiNO ₃ , NaNO ₃ , KNO ₃ , and Ba(NO ₃ ) ₂ ; and (2) LiNO ₃ , NaNO ₃ , KNO _3. A composition with CsNO ₃ . The above molten salt composition has high specific heat (>1.5 J/gK) and a wide fluid range (melting point of about 110 ° C to 130 ° C, heat stable temperature up to 550 ° C to 570 ° C), suitable for heat transfer medium and heat storage. Medium for solar thermal power generation, or with conventional power generation such as thermal power or nuclear power generation, please refer to the Hybrid Solar Thermal Power Plant (source: the World Bank). It is to be noted that if the proportion of a certain salt in the molten salt composition is outside the above range, the physical properties of the molten salt composition may be deteriorated, such as lowering the specific heat or reducing the range of the fluid.

為了讓本發明之上述和其他目的、特徵、和優點能更明顯易懂，下文特舉數實施例配合所附圖示，作詳細說明如下：The above and other objects, features, and advantages of the present invention will become more apparent and understood.

【實施例】[Examples]

下述LiNO₃ 、NaNO₃ 、KNO₃ 、Ba(NO₃ )₂ 、與CsNO₃ 係購自J.T.Baker Chemicals。依化學計量比，秤取上述鹽類置於加熱爐中，以電熱器加熱至150℃後維持4小時以去除熔鹽組合物中的水份，再加熱至400℃後維持8小時使其均勻混合。至此即得熔鹽組合物，在室溫下的外觀為透明無色或不透明白色，在高溫下(>140℃)的外觀則為透明無色。以目視觀察加熱的熔鹽具良好流動性，所以黏度並未明顯增加。The following LiNO ₃ , NaNO ₃ , KNO ₃ , Ba(NO ₃ ) ₂ , and CsNO ₃ were purchased from JT Baker Chemicals. According to the stoichiometric ratio, the above salt is placed in a heating furnace, heated to 150 ° C by an electric heater and maintained for 4 hours to remove water in the molten salt composition, and then heated to 400 ° C for 8 hours to make it uniform. mixing. Thus, the molten salt composition has a transparent, colorless or opaque white appearance at room temperature, and is transparent and colorless at high temperatures (>140 ° C). The heated molten salt was visually observed to have good fluidity, so the viscosity did not increase significantly.

熱電偶可用以量測熔鹽組合物的熔點。加熱過程中的熔鹽由固態完全轉變為液態的溫度即所謂的熔點，而在冷卻過程中開始出現固態的溫度即所謂的凝固點。A thermocouple can be used to measure the melting point of the molten salt composition. The temperature at which the molten salt is completely converted from a solid state to a liquid state during heating is a so-called melting point, and a solid temperature, a so-called freezing point, begins to appear during the cooling process.

熱重分析儀(TGA,model Labsys of Setarm Instrumentation)可用以量測熔鹽組合物之熱穩定溫度。在控制氣氛下加熱熔鹽，連續量測熔鹽的重量。在超過熱穩定溫度時，熔鹽將分解成氣相物而減輕重量。A thermolabile analyzer (TGA, model Labsys of Setarm Instrumentation) can be used to measure the heat stable temperature of the molten salt composition. The molten salt is heated under a controlled atmosphere, and the weight of the molten salt is continuously measured. When the heat stable temperature is exceeded, the molten salt will decompose into a gas phase to reduce the weight.

示差掃描量熱儀(DSC,model Q20 of TA Instruments)可用以量測熔鹽組合物之比熱。依據ASTM-E1269規範(Standard Test Method for Determining Specific Heat Capacity by Differential Scanning Calorimetry)量測熔鹽組合物的比熱。A differential scanning calorimeter (DSC, model Q20 of TA Instruments) can be used to measure the specific heat of the molten salt composition. According to ASTM-E1269 (Standard Test Method for Determining Specific Heat Capacity by Differential Scanning Calorimetry) The specific heat of the molten salt composition was measured.

實施例1Example 1

取16wt%的LiNO₃ 、13wt%的NaNO₃ 、43mol%的KNO₃ 、與28wt% Ba(NO₃ )₂ 混合後，加熱至150℃後維持4小時以去除熔鹽組合物中的水份，再加熱至400℃後維持8小時使其均勻混合。上述熔鹽混合物之熔點、凝固點、熱穩定溫度、比熱(在150℃)如第1表所示。16 wt% of LiNO ₃ , 13 wt% of NaNO ₃ , 43 mol% of KNO ₃ , and 28 wt% of Ba(NO ₃ ) _{2 were} mixed, and then heated to 150 ° C for 4 hours to remove water in the molten salt composition. After heating to 400 ° C, it was maintained for 8 hours to make it uniformly mixed. The melting point, freezing point, heat stable temperature, and specific heat (at 150 ° C) of the above molten salt mixture are shown in Table 1.

實施例2Example 2

取26wt%的LiNO₃ 、20wt%的NaNO₃ 、51wt%的KNO₃ 、與3wt% Ba(NO₃ )₂ 混合後，加熱至150℃後維持4小時以去除熔鹽組合物中的水份，再加熱至400℃後維持8小時使其均勻混合。上述熔鹽混合物之熔點、凝固點、熱穩定溫度、比熱(在150℃)如第1表所示。26 wt% of LiNO ₃ , 20 wt% of NaNO ₃ , 51 wt% of KNO ₃ , and 3 wt% of Ba(NO ₃ ) _{2 were} mixed, and then heated to 150 ° C for 4 hours to remove water in the molten salt composition. After heating to 400 ° C, it was maintained for 8 hours to make it uniformly mixed. The melting point, freezing point, heat stable temperature, and specific heat (at 150 ° C) of the above molten salt mixture are shown in Table 1.

實施例3Example 3

取22wt%的LiNO₃ 、18wt%的NaNO₃ 、50wt%的KNO₃ 、與10wt% Ba(NO₃ )₂ 混合後，加熱至150℃後維持4小時以去除熔鹽組合物中的水份，再加熱至400℃後維持8小時使其均勻混合。上述熔鹽混合物之熔點、凝固點、熱穩定溫度、比熱(在150℃)如第1表所示。22 wt% of LiNO ₃ , 18 wt% of NaNO ₃ , 50 wt% of KNO ₃ , and 10 wt% of Ba(NO ₃ ) _{2 were} mixed, and then heated to 150 ° C for 4 hours to remove water in the molten salt composition. After heating to 400 ° C, it was maintained for 8 hours to make it uniformly mixed. The melting point, freezing point, heat stable temperature, and specific heat (at 150 ° C) of the above molten salt mixture are shown in Table 1.

實施例4Example 4

取26wt%的LiNO₃ 、20wt%的NaNO₃ 、52wt%的KNO₃ 、與2wt% CsNO₃ 混合後，加熱至150℃後維持4小時以去除熔鹽組合物中的水份，再加熱至400℃後維持8小時使其均勻混合。上述熔鹽混合物之熔點、凝固點、熱穩定溫度、比熱(在150℃)如第1表所示。26 wt% of LiNO ₃ , 20 wt% of NaNO ₃ , 52 wt% of KNO ₃ , and 2 wt% of CsNO _{3 were} mixed, and then heated to 150 ° C for 4 hours to remove water in the molten salt composition, and then heated to 400. After °C, it was maintained for 8 hours to make it evenly mixed. The melting point, freezing point, heat stable temperature, and specific heat (at 150 ° C) of the above molten salt mixture are shown in Table 1.

實施例5Example 5

取26wt%的LiNO₃ 、16wt%的NaNO₃ 、48wt%的KNO₃ 、與10wt% CsNO₃ 混合後，加熱至150℃後維持4小時以去除熔鹽組合物中的水份，再加熱至400℃後維持8小時使其均勻混合。上述熔鹽混合物之熔點、凝固點、熱穩定溫度、比熱(在150℃)如第1表所示。26 wt% of LiNO ₃ , 16 wt% of NaNO ₃ , 48 wt% of KNO ₃ , and 10 wt% of CsNO _{3 were} mixed, and then heated to 150 ° C for 4 hours to remove water in the molten salt composition, and then heated to 400. After °C, it was maintained for 8 hours to make it evenly mixed. The melting point, freezing point, heat stable temperature, and specific heat (at 150 ° C) of the above molten salt mixture are shown in Table 1.

由第1表可知，本發明實施例中的熔鹽組成物具有高比熱(>1.5 J/gK)與寬廣的流體範圍(熔點為約110℃至130℃，熱穩定溫度高達550℃至570℃)，適於作為熱傳介質與熱儲存介質。As is apparent from the first table, the molten salt composition in the examples of the present invention has a high specific heat (>1.5 J/gK) and a wide fluid range (melting point is about 110 ° C to 130 ° C, and heat stable temperature is as high as 550 ° C to 570 ° C). ), suitable as a heat transfer medium and a heat storage medium.

雖然本發明已以數個較佳實施例揭露如上，然其並非用以限定本發明，任何熟習此技藝者，在不脫離本發明之精神和範圍內，當可作任意之更動與潤飾，因此本發明之保護範圍當視後附之申請專利範圍所界定者為準。While the invention has been described above in terms of several preferred embodiments, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

Claims

一種熔鹽組合物，包括：15wt%至26wt%的LiNO₃ ；12wt%至21wt%的NaNO₃ ；43wt%至53wt%的KNO₃ ；以及3wt%至29wt%的Ba(NO₃ )₂ 或2wt%至10wt%的CsNO₃ 。A molten salt composition comprising: 15 wt% to 26 wt% of LiNO ₃ ; 12 wt% to 21 wt% of NaNO ₃ ; 43 wt% to 53 wt% of KNO ₃ ; and 3 wt% to 29 wt% of Ba(NO ₃ ) ₂ or 2 wt % to 10 wt% of CsNO ₃ .

如申請專利範圍第1項所述之熔鹽組合物，包括16wt%的LiNO₃ 、13wt%的NaNO₃ 、43wt%的KNO₃ 、與28wt%Ba(NO₃ )₂ 。The molten salt composition as described in claim 1, comprising 16 wt% of LiNO ₃ , 13 wt% of NaNO ₃ , 43 wt% of KNO ₃ , and 28 wt% of Ba(NO ₃ ) ₂ .

如申請專利範圍第1項所述之熔鹽組合物，包括26wt%的LiNO₃ 、20wt%的NaNO₃ 、51wt%的KNO₃ 、與3wt%Ba(NO₃ )₂ 。The molten salt composition as described in claim 1, comprising 26 wt% of LiNO ₃ , 20 wt% of NaNO ₃ , 51 wt% of KNO ₃ , and 3 wt% of Ba(NO ₃ ) ₂ .

如申請專利範圍第1項所述之熔鹽組合物，包括22wt%的LiNO₃ 、18wt%的NaNO₃ 、50wt%的KNO₃ 、與10wt%Ba(NO₃ )₂ 。The molten salt composition according to claim 1, comprising 22% by weight of LiNO ₃ , 18% by weight of NaNO ₃ , 50% by weight of KNO ₃ , and 10% by weight of Ba(NO ₃ ) ₂ .

如申請專利範圍第1項所述之熔鹽組合物，包括26wt%的LiNO₃ 、20wt%的NaNO₃ 、52wt%的KNO₃ 、與2wt%CsNO₃ 。The molten salt composition as described in claim 1, comprising 26 wt% of LiNO ₃ , 20 wt% of NaNO ₃ , 52 wt% of KNO ₃ , and 2 wt% of CsNO ₃ .

如申請專利範圍第1項所述之熔鹽組合物，包括26wt%的LiNO₃ 、16wt%的NaNO₃ 、48wt%的KNO₃ 、與10wt%CsNO₃ 。The molten salt composition as described in claim 1, comprising 26 wt% of LiNO ₃ , 16 wt% of NaNO ₃ , 48 wt% of KNO ₃ , and 10 wt% of CsNO ₃ .

如申請專利範圍第1項所述之熔鹽組合物，係一太陽熱能發電裝置的熱傳介質或熱儲存介質。 The molten salt composition according to claim 1 is a heat transfer medium or a heat storage medium of a solar thermal power generation device.