Quaternary sulfate molten salt heat storage material, composite heat storage material, and preparation method therefor and use thereof

Abstract

Disclosed in the present application are a quaternary sulfate molten salt heat storage material, a composite heat storage material, and a preparation method therefor and the use thereof. The preparation method for the quaternary sulfate molten salt heat storage material comprises: subjecting first sulfate-type salt lake raw brine to freezing and recrystallization treatments to obtain sodium sulfate decahydrate; subjecting second sulfate-type salt lake raw brine to evaporative crystallization and recrystallization treatments to obtain magnesium sulfate heptahydrate; and mixing the sodium sulfate decahydrate, the magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate, heating the mixture at a first heating rate to a first dehydration temperature for a first heat treatment, then heating at a second heating rate to a second dehydration temperature for a second heat treatment, and then heating at a third heating rate to a molten blending temperature for a third heat treatment, and thereby obtaining the quaternary sulfate molten salt heat storage material. In the present application, a quaternary sulfate molten salt heat storage material is prepared by a one-step method using dehydration and coupling technology. Moreover, the specific heat of the composite heat storage material is improved by adding nanoparticles to the quaternary sulfate molten salt heat storage material.

Description

Quaternary sulfate molten salt thermal storage materials, composite thermal storage materials, their preparation methods and applications

[0001] This application is based on and claims priority to two Chinese patent applications filed on December 26, 2024: application number 202411935355X, entitled "Tertiary Sulfate Molten Salt Thermal Storage Material Based on Salt Lake Resources and Its Preparation Method and Application"; and application number 2024119353579, entitled "High Specific Heat Quaternary Sulfate Molten Salt Composite Thermal Storage Material and Its Preparation Method and Application". Technical Field

[0002] This application belongs to the field of thermal storage materials technology, and relates to a quaternary sulfuric acid molten salt thermal storage material, a composite thermal storage material, and their preparation methods and applications. Background Technology

[0003] As fossil fuels continue to be depleted, environmental and climate problems are becoming increasingly serious. Renewable energy plays a crucial role in mitigating global warming and climate change. Solar energy, being pollution-free and abundant, is considered one of the most promising alternative energy sources, and concentrated solar power (CSP) is one of the main ways to utilize solar energy. Based on the type and efficiency of the thermodynamic cycle, CSP technology can be divided into three generations. The first and second generations of CSP technology both use the Rankine cycle, with peak cycle temperatures below 550℃, utilizing solar salt (NaNO3-KNO3) for heat transfer and storage, achieving an annual power generation efficiency of 10-20%. In the third generation of CSP technology, the Brayton cycle, with a peak cycle temperature >700℃, can further improve the efficiency of solar energy utilization. Currently, the most commonly used heat storage materials in CSP power plants are nitrate (Solar Salt) and nitrite (Hitec). However, their relatively low decomposition temperature (550℃) limits their application in third-generation CSP. Therefore, for third-generation CSP, designing and developing molten salts that can operate stably at high temperatures is crucial.

[0004] Chlorides, carbonates, sulfates, and fluorides are considered potential candidate molten salts for high-temperature heat transfer and have therefore been extensively studied. Tian et al. prepared a NaCl-CaCl2 eutectic salt. Wei et al. developed a ternary chloride molten salt composed of NaCl, CaCl2, and MgCl2. Patange et al. studied a CuCl-KCl-NaCl ternary molten salt. It can be seen that existing molten salts are mostly nitrates, carbonates, and chlorides, and the raw materials used for preparation are mostly industrial-grade or molten salt-grade single salts of nitrates, carbonates, and chlorides. Furthermore, composite thermal storage materials of sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate quaternary molten salts and high specific heat sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate quaternary molten salts have not been reported. Summary of the Invention

[0005] The main objective of this application is to provide a quaternary sulfate molten salt thermal storage material, a composite thermal storage material, and their preparation and application, so as to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted in this application includes:

[0007] This application provides a method for preparing a quaternary sulfuric acid molten salt thermal storage material based on salt lake resources, which includes:

[0008] Sodium sulfate decahydrate was prepared by freezing and recrystallizing the original brine of the first sulfate type salt lake.

[0009] Magnesium sulfate heptahydrate was prepared by evaporation, crystallization and recrystallization of the original brine of the second sulfate type salt lake.

[0010] Furthermore, the sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate are mixed and heated to a first dehydration temperature at a first heating rate for a first heat treatment, then heated to a second dehydration temperature at a second heating rate for a second heat treatment, and finally heated to a melting blending temperature at a third heating rate for a third heat treatment to obtain a quaternary sulfuric acid molten salt thermal storage material.

[0011] This application also provides a quaternary sulfuric acid molten salt thermal storage material based on salt lake resources prepared by the aforementioned preparation method. The quaternary sulfuric acid molten salt thermal storage material has a melting point of 680-700℃ and a decomposition temperature of 1005-1100℃.

[0012] This application also provides a method for preparing a high specific heat quaternary sulfuric acid molten salt composite thermal storage material, which includes:

[0013] A quaternary sulfuric acid molten salt thermal storage material based on salt lake resources was prepared using the aforementioned preparation method.

[0014] Furthermore, the quaternary sulfate molten salt thermal storage material is stirred, ultrasonically mixed, and melt-blended with nano-inorganic materials to obtain a high specific heat quaternary sulfate molten salt composite thermal storage material.

[0015] This application also provides a high specific heat quaternary sulfuric acid molten salt composite thermal storage material prepared by the aforementioned method, wherein the specific heat of the high specific heat quaternary sulfuric acid molten salt composite thermal storage material is 1.42–1.70 J·g. -1 ·℃ -1 .

[0016] This application also provides an energy storage material, which includes at least the aforementioned quaternary sulfuric acid molten salt thermal storage material based on salt lake resources or a high specific heat quaternary sulfuric acid molten salt composite thermal storage material.

[0017] Compared with the prior art, the beneficial effects of this application are as follows:

[0018] (1) This application uses sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate and calcium sulfate, which are abundant in salt lakes, as raw materials. The quaternary sulfate molten salt is prepared in one step by dehydration and coupling technology. This not only makes high-value utilization of sodium, potassium, magnesium and calcium resources in salt lakes, but also reduces the energy consumption of first dehydration and then high-temperature blending to prepare sulfate, simplifies the process and reduces costs.

[0019] (2) This application adds nanoparticles to the quaternary sulfuric acid molten salt thermal storage material to improve the specific heat of the composite thermal storage material. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 is a melting point diagram of the quaternary sulfuric acid molten salt thermal storage material in Example 3 of this application;

[0022] Figure 2 is a diagram showing the decomposition temperature of the quaternary sulfuric acid molten salt thermal storage material in Example 3 of this application. Detailed Implementation

[0023] In view of the deficiencies of the prior art, the applicant, through long-term research and extensive practice, has come up with the technical solution of this application. The technical solution of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Specifically, as one aspect of the technical solution of this application, the preparation method of a quaternary sulfuric acid molten salt thermal storage material based on salt lake resources includes:

[0025] Sodium sulfate decahydrate was prepared by freezing and recrystallizing the original brine of the first sulfate type salt lake.

[0026] Magnesium sulfate heptahydrate was prepared by evaporation, crystallization and recrystallization of the original brine of the second sulfate type salt lake.

[0027] Furthermore, the sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate are mixed and heated to a first dehydration temperature at a first heating rate for a first heat treatment, then heated to a second dehydration temperature at a second heating rate for a second heat treatment, and finally heated to a melting blending temperature at a third heating rate for a third heat treatment to obtain a quaternary sulfuric acid molten salt thermal storage material.

[0028] In some preferred embodiments, the preparation method specifically includes: mixing sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate and calcium sulfate evenly and heating to 50-100°C at a first heating rate of 1-10°C / min for a first heat treatment; heating to 250-350°C at a second heating rate of 1-10°C / min for a second heat treatment; heating to 750-850°C at a third heating rate of 10-20°C / min for a third heat treatment; and finally cooling to room temperature to obtain a quaternary sulfuric acid molten salt thermal storage material.

[0029] In some preferred embodiments, the mass ratio of sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate is 57.6–61.6:25–28:4.4:1–10.

[0030] In some preferred embodiments, the first heat treatment time is 1 to 4 hours.

[0031] In some preferred embodiments, the second heat treatment time is 1 to 4 hours.

[0032] In some preferred embodiments, the third heat treatment lasts for 3 to 6 hours.

[0033] In some preferred embodiments, the preparation method specifically includes:

[0034] The crude sodium sulfate decahydrate product was obtained by freezing the primary sulfate-type brine of the salt lake; wherein the concentration of sodium ions in the primary sulfate-type brine of the salt lake was 10.0-11.0 wt%, the concentration of potassium ions was 0.45-0.51 wt%, the concentration of magnesium ions was 0.25-0.35 wt%, the concentration of chloride ions was 14.5-15.2 wt%, and the concentration of sulfate ions was 3.3-4.0 wt%.

[0035] Furthermore, the crude sodium sulfate decahydrate product is recrystallized to obtain sodium sulfate decahydrate.

[0036] Furthermore, the freezing treatment is performed at a temperature of -20 to 5°C for a duration of 4 to 10 hours.

[0037] Furthermore, the heating temperature used in the recrystallization process is 40–80°C.

[0038] Furthermore, the cooling temperature used during the recrystallization process is -20 to 5°C.

[0039] Furthermore, the purity of the crude sodium sulfate decahydrate product is 85%–95%.

[0040] Furthermore, the purity of the sodium sulfate decahydrate is greater than 99.0%.

[0041] In some preferred embodiments, the preparation method specifically includes:

[0042] The crude magnesium sulfate heptahydrate product was obtained by evaporation and crystallization of the original brine of the second sulfate-type salt lake. The original brine of the second sulfate-type salt lake contained sodium ion concentrations of 6.0–8.0 wt%, potassium ion concentrations of 0.70–0.8 wt%, magnesium ion concentrations of 2.0–2.5 wt%, chloride ion concentrations of 14.5–16.0 wt%, and sulfate ion concentrations of 3.3–5.0 wt%.

[0043] Furthermore, the crude magnesium sulfate heptahydrate product is recrystallized to obtain magnesium sulfate heptahydrate.

[0044] Furthermore, the evaporation crystallization treatment is carried out at a temperature of 20–35°C for a time of 6–12 hours.

[0045] Furthermore, the heating temperature used in the recrystallization process is 40–80°C.

[0046] Furthermore, the cooling temperature used during the recrystallization process is 5–15°C.

[0047] Furthermore, the purity of the crude magnesium sulfate heptahydrate product is 80%–95%.

[0048] Furthermore, the purity of the magnesium sulfate heptahydrate is greater than 99.0%.

[0049] In some more specific embodiments, the preparation method of the quaternary sulfuric acid molten salt thermal storage material based on salt lake resources includes the following steps:

[0050] (1) Using a sulfate-type salt lake brine as raw material, crude sodium sulfate decahydrate is obtained by freezing at a certain temperature. The crude sodium sulfate decahydrate is then recrystallized to obtain sodium sulfate decahydrate with a purity of 99.0%. The sodium ion concentration in the sulfate-type salt lake brine is 10.0%–11.0%, potassium ion concentration is 0.45%–0.51%, magnesium ion concentration is 0.25%–0.35%, chloride ion concentration is 14.5%–15.2%, and sulfate ion concentration is 3.3%–4.0%. The freezing temperature is -20℃ to 5℃; the purity of the crude sodium sulfate decahydrate is 85%–95%; the recrystallization heating temperature is 40℃–80℃, and the recrystallization cooling temperature is -20℃ to 5℃; the purity of the sodium sulfate decahydrate is greater than 99.0%.

[0051] (2) Using a sulfate-type salt lake brine as raw material, crude magnesium sulfate heptahydrate is obtained by evaporation and crystallization at a certain temperature. The crude magnesium sulfate heptahydrate is then recrystallized to obtain 99.0% magnesium sulfate heptahydrate. The sodium ion concentration in the sulfate-type salt lake brine is 6.0%–8%, potassium ion concentration is 0.70%–0.8%, magnesium ion concentration is 2.0%–2.5%, chloride ion concentration is 14.5%–16%, and sulfate ion concentration is 3.3%–5.0%. The evaporation temperature is 20℃–35℃. The purity of the crude magnesium sulfate heptahydrate is 80%–95%. The recrystallization heating temperature is 40℃–80℃, and the recrystallization cooling temperature is 5℃–15℃. The purity of the magnesium sulfate heptahydrate is greater than 99.0%.

[0052] (3) Weigh out 20g of sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate, which are abundant in salt lakes, in a certain proportion, place them in a crucible and mix them evenly. Place the crucible of the mixture in a muffle furnace, heat it to the first dehydration temperature at a certain heating rate and hold it at that temperature for a certain period of time. Then, heat it to the second dehydration temperature at a certain heating rate and hold it at that temperature for a certain period of time. Finally, heat it to the melting and blending temperature at a certain heating rate and hold it at that temperature for a certain period of time. Cool it to room temperature to obtain a quaternary sulfate molten salt thermal storage material. The mixture includes the following components: sodium sulfate decahydrate with a mass fraction of 57.6% to 61.6%, magnesium sulfate heptahydrate with a mass fraction of 25% to 28%, and sulfur... The potassium sulfate mass fraction is 4.4% and the calcium sulfate mass fraction is 1%–10%; the heating rate in the first stage is 1–10℃ / min, the first dehydration temperature is 50–100℃, and the temperature is held for 1–4 hours; the heating rate in the second stage is 1–10℃ / min, the first dehydration temperature is 250–350℃, and the temperature is held for 1–4 hours; the heating rate in the third stage is 10–20℃ / min, the melting and blending temperature is 750–850℃, and the temperature is held for 3–6 hours; the melting point of the sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate quaternary molten salt is 680–700℃, and the decomposition temperature is 1005–1100℃.

[0053] Another aspect of this application provides a quaternary sulfuric acid molten salt thermal storage material based on salt lake resources prepared by the aforementioned preparation method, wherein the quaternary sulfuric acid molten salt thermal storage material has a melting point of 680-700°C and a decomposition temperature of 1005-1100°C.

[0054] Another aspect of this application provides a method for preparing a high specific heat quaternary sulfuric acid molten salt composite thermal storage material, comprising:

[0055] A quaternary sulfuric acid molten salt thermal storage material based on salt lake resources was prepared using the aforementioned preparation method.

[0056] Furthermore, the quaternary sulfate molten salt thermal storage material is stirred, ultrasonically mixed, and melt-blended with nano-inorganic materials to obtain a high specific heat quaternary sulfate molten salt composite thermal storage material.

[0057] In some preferred embodiments, the mass ratio of the quaternary sulfate molten salt thermal storage material to the nano-inorganic material is 100:0.3 to 2.0;

[0058] In some preferred embodiments, the nano-inorganic material includes any one or more combinations of nano-alumina, silicon dioxide, silicon carbide, and boron nitride, but is not limited thereto.

[0059] In some preferred embodiments, the preparation method specifically includes:

[0060] The quaternary sulfate molten salt thermal storage material is stirred and ultrasonically mixed with nano-inorganic materials to form a mixture; wherein the stirring speed is 50-200 rpm, the ultrasonic frequency is 10-50 kHz, and the ultrasonic power is 100-500 W.

[0061] Furthermore, the obtained mixture is heated to 750-850℃ at a heating rate of 10-20℃ / min and melt-blended for 3-6 hours, and then cooled to room temperature to obtain a high specific heat quaternary sulfuric acid molten salt composite thermal storage material.

[0062] In some more specific embodiments, the preparation method of the high specific heat quaternary sulfuric acid molten salt composite thermal storage material includes the following steps:

[0063] (1) Using a sulfate-type salt lake brine as raw material, crude sodium sulfate decahydrate is obtained by freezing at a certain temperature. The crude sodium sulfate decahydrate is then recrystallized to obtain sodium sulfate decahydrate with a purity of 99.0%. The sodium ion concentration in the sulfate-type salt lake brine is 10.0%–11.0%, potassium ion concentration is 0.45%–0.51%, magnesium ion concentration is 0.25%–0.35%, chloride ion concentration is 14.5%–15.2%, and sulfate ion concentration is 3.3%–4.0%. The freezing temperature is -20℃ to 5℃; the purity of the crude sodium sulfate decahydrate is 85%–95%; the recrystallization heating temperature is 40℃–80℃, and the recrystallization cooling temperature is -20℃ to 5℃; the purity of the sodium sulfate decahydrate is greater than 99.0%.

[0064] (2) Using a sulfate-type salt lake brine as raw material, crude magnesium sulfate heptahydrate is obtained by evaporation and crystallization at a certain temperature. The crude magnesium sulfate heptahydrate is then recrystallized to obtain 99.0% magnesium sulfate heptahydrate. The sodium ion concentration in the sulfate-type salt lake brine is 6.0%–8%, potassium ion concentration is 0.70%–0.8%, magnesium ion concentration is 2.0%–2.5%, chloride ion concentration is 14.5%–16%, and sulfate ion concentration is 3.3%–5.0%. The evaporation temperature is 20℃–35℃. The purity of the crude magnesium sulfate heptahydrate is 80%–95%. The recrystallization heating temperature is 40℃–80℃, and the recrystallization cooling temperature is 5℃–15℃. The purity of the magnesium sulfate heptahydrate is greater than 99.0%.

[0065] (3) Weigh out 20g of sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate, which are abundant in the salt lake, in a certain proportion, place them in a crucible and mix them evenly. Place the crucible containing the mixture in a muffle furnace, heat it to the first dehydration temperature at a certain heating rate and hold it at that temperature for a certain period of time. Then, heat it to the second dehydration temperature at a certain heating rate and hold it at that temperature for a certain period of time. Finally, heat it to the melting and blending temperature at a certain heating rate and hold it at that temperature for a certain period of time. Cool it to room temperature to obtain a quaternary sulfate molten salt. The mixture includes the following components: sodium sulfate decahydrate with a mass fraction of 57.6%–61.6%, magnesium sulfate heptahydrate with a mass fraction of 25%–28%, and sulfuric acid... The potassium content is 4.4% by mass, and the calcium sulfate content is 1%–10% by mass. The first stage heating rate is 1–10℃ / min, the first dehydration temperature is 50–100℃, and the temperature is held for 1–4 hours. The second stage heating rate is 1–10℃ / min, the first dehydration temperature is 250–350℃, and the temperature is held for 1–4 hours. The third stage heating rate is 10–20℃ / min, the melting and blending temperature is 750–850℃, and the temperature is held for 3–6 hours. The melting point of the sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate quaternary molten salt is 680–700℃, and the decomposition temperature is 1005–1100℃.

[0066] (4) Weigh 10g of quaternary sulfate molten salt thermal storage material and nano-inorganic material in a certain proportion, put them into a reaction vessel equipped with stirring and ultrasound, heat them to a certain temperature under certain rotation speed and ultrasound conditions, melt and blend for a certain time, and cool to room temperature to obtain a high specific heat quaternary sulfate molten salt composite thermal storage material; the nano-inorganic material is one or two of nano-alumina, silicon dioxide, silicon carbide and boron nitride, and the amount of nano-material added is 0.3%-2.0% of the quaternary sulfate molten salt thermal storage material; the stirring speed is 50-200 rpm; the ultrasonic frequency is 10-50 kHz and the ultrasonic power is 100-500 W; the heating rate is 10-20℃ / min, the melting and blending temperature is 750-850℃, and the temperature is kept constant for 3-6 hours.

[0067] Another aspect of this application provides a high specific heat quaternary sulfate molten salt composite thermal storage material prepared by the aforementioned method, wherein the specific heat of the high specific heat quaternary sulfate molten salt composite thermal storage material is 1.42–1.70 J·g⁻¹. 1 ·℃- 1 .

[0068] Another aspect of this application provides an energy storage material, which includes at least the aforementioned quaternary molten salt sulfate thermal storage material based on salt lake resources or a high specific heat quaternary molten salt sulfate composite thermal storage material.

[0069] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0070] Example 1

[0071] 1) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 10.0% sodium ions, 0.45% potassium ions, 0.25% magnesium ions, 14.5% chloride ions, and 3.3% sulfate ions. Freeze the brine at -20℃ for 4 hours to obtain crude sodium sulfate decahydrate with a purity of 85%. Dissolve the crude sodium sulfate decahydrate at 40℃ and recrystallize it at -20℃ to obtain sodium sulfate decahydrate with a purity of 99.2%.

[0072] 2) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 6% sodium ions, 0.7% potassium ions, 2.0% magnesium ions, 14.5% chloride ions, and 3.3% sulfate ions. Evaporate and crystallize the brine at 20℃ to obtain crude magnesium sulfate heptahydrate with a purity of 80%. Dissolve and evaporate the crude magnesium sulfate heptahydrate at 40℃ for 6 hours, and then crystallize it at 5℃ to obtain magnesium sulfate heptahydrate with a purity of 99.0%.

[0073] 3) Weigh out 20g of the above raw materials in the following proportions: 57.6% sodium sulfate decahydrate, 28% magnesium sulfate heptahydrate, 10% calcium sulfate, and 4.4% potassium sulfate. Place the mixture in a crucible and mix thoroughly. Place the crucible in a muffle furnace and heat it to 50℃ at a heating rate of 1℃ / min. Hold the temperature for 1 hour. Then heat it to 250℃ at a heating rate of 1℃ / min and hold the temperature for 1 hour. Finally, heat it to 750℃ at a heating rate of 10℃ / min and hold the temperature for 3 hours to obtain a sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate quaternary molten salt with a melting point of 680℃ and a decomposition temperature of 1005℃.

[0074] 4) Weigh out 10g of quaternary sulfate molten salt thermal storage material and nano-alumina in a certain proportion, with the nano-material addition amount being 0.3wt% of the quaternary sulfate molten salt thermal storage material. Place them in a reaction vessel equipped with stirring and ultrasound. Heat to 750℃ at a heating rate of 10℃ / min under ultrasonic conditions of stirring at 50rpm, ultrasonic frequency of 10kHz, and ultrasonic power of 100W, and hold at that temperature for 3h. After cooling to room temperature, a high specific heat quaternary sulfate molten salt composite thermal storage material is obtained. The specific heat of the composite material is 1.42J·K. -1 ·g -1 .

[0075] Example 2

[0076] 1) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 11.0% sodium ions, 0.51% potassium ions, 0.35% magnesium ions, 15.2% chloride ions, and 4.0% sulfate ions. Freeze the brine at 5℃ for 10 h to obtain crude sodium sulfate decahydrate with a purity of 95%. Dissolve the crude sodium sulfate decahydrate at 80℃ and recrystallize it at 5℃ to obtain sodium sulfate decahydrate with a purity of 99.0%.

[0077] 2) Weigh 1 kg of raw brine from a sulfate-type salt lake, which has a sodium ion concentration of 8%, a potassium ion concentration of 0.8%, a magnesium ion concentration of 2.5%, a chloride ion concentration of 16%, and a sulfate ion concentration of 5.0%. Evaporate and crystallize the brine at 35℃ to obtain a crude magnesium sulfate heptahydrate product with a purity of 95%. Dissolve and evaporate the crude magnesium sulfate heptahydrate product at 80℃ for 12 hours, and then crystallize it at 15℃ to obtain a magnesium sulfate heptahydrate product with a purity of 99.3%.

[0078] 3) Weigh out 20g of the above raw materials in the proportion of 61.6% sodium sulfate decahydrate, 33% magnesium sulfate heptahydrate, 1% calcium sulfate and 4.4% potassium sulfate, put them into a crucible and mix them evenly. Place the crucible of the mixture in a muffle furnace and heat it to 100℃ at a heating rate of 10℃ / min, hold it at the temperature for 4h, then heat it to 350℃ at a heating rate of 10℃ / min, hold it at the temperature for 4h, and then heat it to 850℃ at a heating rate of 20℃ / min, hold it at the temperature for 6h to obtain a sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate quaternary molten salt with a melting point of 700℃ and a decomposition temperature of 1100℃.

[0079] 4) Weigh 10g of quaternary sulfate molten salt thermal storage material and nano-silica in a certain proportion, with the nanomaterial addition amount being 2.0wt% of the quaternary sulfate molten salt thermal storage material. Place them in a reaction vessel equipped with stirring and ultrasound. Heat to 850℃ at a heating rate of 20℃ / min under the conditions of stirring at 200rpm and ultrasound frequency of 50kHz and ultrasound power of 500W, hold at the temperature for 6h, and cool to room temperature to obtain a high specific heat quaternary sulfate molten salt composite thermal storage material. The specific heat of the composite material is 1.65J·K. -1 ·g -1 .

[0080] Example 3

[0081] 1) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 10.05% sodium ions, 0.48% potassium ions, 0.30% magnesium ions, 15.0% chloride ions, and 3.5% sulfate ions. Freeze the brine at -10℃ for 6 hours to obtain crude sodium sulfate decahydrate with a purity of 90%. Dissolve the crude sodium sulfate decahydrate at 60℃ and recrystallize it at 0℃ to obtain sodium sulfate decahydrate with a purity of 99.3%.

[0082] 2) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 7% sodium ions, 0.75% potassium ions, 2.2% magnesium ions, 15% chloride ions, and 4% sulfate ions. Evaporate and crystallize the brine at 30℃ to obtain crude magnesium sulfate heptahydrate with a purity of 90%. Dissolve and evaporate the crude magnesium sulfate heptahydrate at 60℃ for 8 hours, and then crystallize it at 10℃ to obtain magnesium sulfate heptahydrate with a purity of 99.1%.

[0083] 3) Weigh out 20g of the above raw materials according to the ratio of 59.67% sodium sulfate decahydrate, 30.93% magnesium sulfate heptahydrate, 5% calcium sulfate, and 4.4% potassium sulfate. Place the mixture in a crucible and mix thoroughly. Place the crucible in a muffle furnace and heat to 80℃ at a heating rate of 5℃ / min, hold at that temperature for 3 hours, then heat to 300℃ at a heating rate of 5℃ / min, hold at that temperature for 2 hours, and then heat to 800℃ at a heating rate of 15℃ / min, hold at that temperature for 5 hours. This yields a quaternary molten salt of sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate with a melting point of 686.5℃, a decomposition temperature of 1045.79℃, and a specific heat of 1.32 J·K. -1 ·g -1 The melting point diagram of the quaternary sulfuric acid molten salt thermal storage material is shown in Figure 1, and the decomposition temperature diagram of the quaternary sulfuric acid molten salt thermal storage material is shown in Figure 2.

[0084] 4) Weigh out 10g of quaternary sulfate molten salt thermal storage material, nano-boron carbide, and silicon nitride in a certain proportion. The amount of nanomaterial (where the mass ratio of nano-boron carbide to silicon nitride is 1:1) added is 1.0wt% of the quaternary sulfate molten salt thermal storage material. Place it in a reaction vessel equipped with stirring and ultrasound. Under the conditions of stirring at 100rpm and ultrasound at a frequency of 30kHz and an ultrasonic power of 200W, heat to 800℃ at a heating rate of 15℃ / min, hold at that temperature for 5h, and cool to room temperature to obtain a high specific heat quaternary sulfate molten salt composite thermal storage material. The specific heat of the composite material is 169J·K. -1 ·g -1 .

[0085] Comparative Example 1

[0086] 1) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 10.05% sodium ions, 0.48% potassium ions, 0.30% magnesium ions, 15.0% chloride ions, and 3.5% sulfate ions. Freeze the brine at -10℃ to obtain crude sodium sulfate decahydrate with a purity of 90%. Dissolve the crude sodium sulfate decahydrate at 60℃ and recrystallize it at 0℃ to obtain sodium sulfate decahydrate with a purity of 99.3%.

[0087] 2) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 7% sodium ions, 0.75% potassium ions, 2.2% magnesium ions, 15% chloride ions, and 4% sulfate ions. Evaporate and crystallize the brine at 30℃ to obtain crude magnesium sulfate heptahydrate with a purity of 90%. Dissolve and evaporate the crude magnesium sulfate heptahydrate at 60℃ and crystallize it at 10℃ to obtain magnesium sulfate heptahydrate with a purity of 99.1%.

[0088] 3) Weigh out 20g of the above raw materials in the following proportions: 59.67% sodium sulfate decahydrate, 30.93% magnesium sulfate heptahydrate, 5% calcium sulfate, and 4.4% potassium sulfate. Place the mixture in a crucible and mix thoroughly. Place the crucible in a muffle furnace and heat it to 80℃ at a heating rate of 5℃ / min. Hold the temperature for 3 hours. Then heat it to 300℃ at a heating rate of 5℃ / min and hold the temperature for 2 hours. Finally, heat it to 650℃ at a heating rate of 15℃ / min and hold the temperature for 5 hours. The mixture is not uniform and the quaternary molten salt of sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate has not been formed.

[0089] Comparative Example 2

[0090] 1) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 10.05% sodium ions, 0.48% potassium ions, 0.30% magnesium ions, 15.0% chloride ions, and 3.5% sulfate ions. Freeze the brine at -10℃ to obtain crude sodium sulfate decahydrate with a purity of 90%. Dissolve the crude sodium sulfate decahydrate at 60℃ and recrystallize it at 0℃ to obtain sodium sulfate decahydrate with a purity of 99.3%.

[0091] 2) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 7% sodium ions, 0.75% potassium ions, 2.2% magnesium ions, 15% chloride ions, and 4% sulfate ions. Evaporate and crystallize the brine at 30℃ to obtain crude magnesium sulfate heptahydrate with a purity of 90%. Dissolve and evaporate the crude magnesium sulfate heptahydrate at 60℃ and crystallize it at 10℃ to obtain magnesium sulfate heptahydrate with a purity of 99.1%.

[0092] 3) Weigh out 20g of the above raw materials in the proportion of 15% sodium sulfate decahydrate, 20% magnesium sulfate heptahydrate, 50% calcium sulfate and 15% potassium sulfate, put them into a crucible and mix them evenly. Place the crucible of the mixture in a muffle furnace and heat it to 80℃ at a heating rate of 5℃ / min, hold it at the temperature for 3h, then heat it to 300℃ at a heating rate of 5℃ / min, hold it at the temperature for 2h, and then heat it to 650℃ at a heating rate of 15℃ / min, hold it at the temperature for 5h. No sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate quaternary molten salt is formed.

[0093] Comparative Example 3

[0094] 1) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 10.05% sodium ions, 0.48% potassium ions, 0.30% magnesium ions, 15.0% chloride ions, and 3.5% sulfate ions. Freeze the brine at -10℃ to obtain crude sodium sulfate decahydrate with a purity of 90%. Dissolve the crude sodium sulfate decahydrate at 60℃ and recrystallize it at 0℃ to obtain sodium sulfate decahydrate with a purity of 99.3%.

[0095] 2) Weigh 1 kg of raw brine from a sulfate-type salt lake, which contains 7% sodium ions, 0.75% potassium ions, 2.2% magnesium ions, 15% chloride ions, and 4% sulfate ions. Evaporate and crystallize the brine at 30℃ to obtain crude magnesium sulfate heptahydrate with a purity of 90%. Dissolve and evaporate the crude magnesium sulfate heptahydrate at 60℃ and crystallize it at 10℃ to obtain magnesium sulfate heptahydrate with a purity of 99.1%.

[0096] 3) Weigh out 20g of the above raw materials according to the ratio of 59.67% sodium sulfate decahydrate, 30.93% magnesium sulfate heptahydrate, 5% calcium sulfate, and 4.4% potassium sulfate. Place the mixture in a crucible and mix thoroughly. Place the crucible in a muffle furnace and heat to 80℃ at a heating rate of 5℃ / min, hold at that temperature for 3 hours, then heat to 300℃ at a heating rate of 5℃ / min, hold at that temperature for 2 hours, and then heat to 800℃ at a heating rate of 15℃ / min, hold at that temperature for 5 hours. This yields a sodium sulfate-potassium sulfate-magnesium sulfate-calcium sulfate quaternary molten salt with a melting point of 686.5℃, a decomposition temperature of 1045.79℃, and a specific heat of 1.32 J·K. -1 ·g -1 .

[0097] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0098] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for preparing a quaternary sulfuric acid molten salt thermal storage material based on salt lake resources, characterized in that, include: Sodium sulfate decahydrate was prepared by freezing and recrystallizing the original brine of the first sulfate type salt lake. Magnesium sulfate heptahydrate was prepared by evaporation, crystallization and recrystallization of the original brine of the second sulfate type salt lake. Furthermore, the sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate are mixed and heated to a first dehydration temperature at a first heating rate for a first heat treatment, then heated to a second dehydration temperature at a second heating rate for a second heat treatment, and finally heated to a melting blending temperature at a third heating rate for a third heat treatment to obtain a quaternary sulfuric acid molten salt thermal storage material.

2. The preparation method according to claim 1, characterized in that, Specifically, it includes: Sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate are mixed evenly and heated to 50-100°C at a first heating rate of 1-10°C / min for a first heat treatment. Then, the temperature is raised to 250-350°C at a second heating rate of 1-10°C / min for a second heat treatment. Finally, the temperature is raised to 750-850°C at a third heating rate of 10-20°C / min for a third heat treatment. The mixture is then cooled to room temperature to obtain the quaternary sulfuric acid molten salt thermal storage material.

3. The preparation method according to claim 1 or 2, characterized in that: The mass ratio of sodium sulfate decahydrate, magnesium sulfate heptahydrate, potassium sulfate, and calcium sulfate is 57.6–61.6: 25–28: 4.4: 1–10.

4. The production method according to claim 1 or 2, characterized by: The duration of the first heat treatment is 1 to 4 hours; And / or, the duration of the second heat treatment is 1 to 4 hours; And / or, the duration of the third heat treatment is 3 to 6 hours.

5. The preparation method according to claim 1, characterized in that, Specifically, it includes: The crude sodium sulfate decahydrate product was obtained by freezing the primary sulfate-type brine of the salt lake; wherein the concentration of sodium ions in the primary sulfate-type brine of the salt lake was 10.0-11.0 wt%, the concentration of potassium ions was 0.45-0.51 wt%, the concentration of magnesium ions was 0.25-0.35 wt%, the concentration of chloride ions was 14.5-15.2 wt%, and the concentration of sulfate ions was 3.3-4.0 wt%. Furthermore, the crude sodium sulfate decahydrate product is recrystallized to obtain sodium sulfate decahydrate.

6. The method of claim 5, wherein: The freezing process is carried out at a temperature of -20 to 5°C for 4 to 10 hours. And / or, the heating temperature used during the recrystallization process is 40–80°C; And / or, the cooling temperature used during the recrystallization process is -20 to 5°C; And / or, the purity of the crude sodium sulfate decahydrate product is 85% to 95%; And / or, the purity of the sodium sulfate decahydrate is greater than 99.0%.

7. The preparation method according to claim 1, characterized in that, Specifically, it includes: The crude magnesium sulfate heptahydrate product was obtained by evaporation and crystallization of the original brine of the second sulfate-type salt lake. The original brine of the second sulfate-type salt lake contained sodium ion concentrations of 6.0–8.0 wt%, potassium ion concentrations of 0.70–0.8 wt%, magnesium ion concentrations of 2.0–2.5 wt%, chloride ion concentrations of 14.5–16.0 wt%, and sulfate ion concentrations of 3.3–5.0 wt%. Furthermore, the crude magnesium sulfate heptahydrate product is recrystallized to obtain magnesium sulfate heptahydrate.

8. The method of claim 7, wherein: The evaporation crystallization process is carried out at a temperature of 20–35°C for 6–12 hours. And / or, the heating temperature used during the recrystallization process is 40–80°C; And / or, the cooling temperature used during the recrystallization process is 5 to 15°C; And / or, the purity of the crude magnesium sulfate heptahydrate product is 80% to 95%; And / or, the purity of the magnesium sulfate heptahydrate is greater than 99.0%.

9. The quaternary sulfuric acid molten salt thermal storage material based on salt lake resources prepared by the preparation method according to any one of claims 1-8, characterized in that: The quaternary sulfuric acid molten salt thermal storage material has a melting point of 680–700℃ and a decomposition temperature of 1005–1100℃.

10. A method for preparing a high specific heat quaternary sulfuric acid molten salt composite thermal storage material, characterized in that, include: A quaternary sulfuric acid molten salt thermal storage material based on salt lake resources was prepared by the preparation method according to any one of claims 1-8. Furthermore, the quaternary sulfate molten salt thermal storage material is stirred, ultrasonically mixed, and melt-blended with nano-inorganic materials to obtain a high specific heat quaternary sulfate molten salt composite thermal storage material.

11. The method of claim 10, wherein: The mass ratio of the quaternary sulfate molten salt thermal storage material to the nano-inorganic material is 100:0.3-2.0; And / or, the nano-inorganic material includes any one or more combinations of nano-alumina, silicon dioxide, silicon carbide, and boron nitride.

12. The method of claim 10, wherein, Specifically including The quaternary sulfate molten salt thermal storage material is stirred and ultrasonically mixed with nano-inorganic materials to form a mixture; wherein the stirring speed is 50-200 rpm, the ultrasonic frequency is 10-50 kHz, and the ultrasonic power is 100-500 W. Furthermore, the obtained mixture is heated to 750-850℃ at a heating rate of 10-20℃ / min and melt-blended for 3-6 hours, and then cooled to room temperature to obtain a high specific heat quaternary sulfuric acid molten salt composite thermal storage material.

13. The high specific heat quaternary sulfuric acid molten salt composite thermal storage material prepared by the preparation method according to any one of claims 10-12, characterized in that: The specific heat of the high specific heat quaternary sulfuric acid molten salt composite thermal storage material is 1.42–1.70 J·g. -1 ·℃ -1 .

14. An energy storage material, characterized in that... It includes at least the quaternary sulfuric acid molten salt thermal storage material based on salt lake resources as described in claim 9 or the high specific heat quaternary sulfuric acid molten salt composite thermal storage material as described in claim 13.

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