Phase change energy storage material and preparation method thereof

Abstract

The invention discloses a phase change energy storage material and a preparation method thereof, and belongs to the field of building materials. The phase change energy storage material is mainly formed by compounding a phase change microcapsule and modified ardealite, wherein the phase change microcapsule comprises a phase change energy storage core serving as an inner core and a calcium carbonate shell serving as an inorganic shell. According to the invention, industrial waste ardealite can be effectively utilized, a material which has certain heat storage capacity and can be used as a building material can be formed in a more economical, environment-friendly and low-carbon manner, and the material can be used for regulating and controlling the internal temperature of a building.

Description

Technical Field

[0001] This application belongs to the field of building materials, and in particular, this application relates to a phase change energy storage material and its preparation method. Background Technology

[0002] Phospholipid gypsum (PG) originated from phosphate mining and is a byproduct of the phosphate fertilizer industry, produced during the production of phosphoric acid from phosphate rock. It contains approximately 80%–95% calcium sulfate dihydrate (CaSO4·2H2O) and less than 5% toxic and harmful substances. The indiscriminate dumping and accumulation of phospholipid gypsum will severely damage the ecological environment, polluting groundwater resources and wasting land resources.

[0003] Currently, the resource utilization of phosphogypsum is mainly concentrated in building materials, chemicals, agriculture, external sales, and mine backfilling. Although there are many utilization pathways, the comprehensive utilization rate is low, and the effects are not very significant. Therefore, developing methods and technologies for further processing and large-scale application of phosphogypsum remains an important issue that urgently needs to be addressed in the industry. Summary of the Invention

[0004] The purpose of this application is to provide a phase change energy storage material with temperature regulation function and the ability to turn waste into treasure, and a method for its preparation.

[0005] The solution presented in this application is implemented through the following steps.

[0006] In one aspect, this application discloses a phase change energy storage material.

[0007] The phase change energy storage material is mainly composed of phase change microcapsules and modified phosphogypsum. The phase change microcapsules include a phase change energy storage core as the inner core and a calcium carbonate shell as an inorganic outer shell.

[0008] Optionally, the phase change energy storage core is composed of paraffin.

[0009] Optionally, the paraffin and calcium carbonate in the phase change microcapsules are present in a 1:1 mass ratio.

[0010] Alternatively, modified phosphogypsum is β-hemihydrate gypsum formed by modifying phosphogypsum.

[0011] Optionally, phase change energy storage materials may also include reinforcing agents.

[0012] Optionally, the reinforcing agent includes glass fiber.

[0013] On the other hand, this application discloses a method for preparing a phase change energy storage material. The preparation method includes: thoroughly mixing phase change microcapsules and modified phosphogypsum, wherein the phase change microcapsules include a phase change energy storage core as the core and a calcium carbonate shell as an inorganic outer shell.

[0014] Optionally, methods for preparing phase change microcapsules include: Paraffin wax is mixed with an emulsifier in a solvent, and then calcium salts and carbonates soluble in the solvent are added.

[0015] Alternatively, the emulsifier is prepared by mixing styrene-maleic anhydride copolymer and sodium hydroxide with water, and then adjusting the pH to 8-9 with citric acid solution and sodium hydroxide solution.

[0016] Optionally, the calcium salt and carbonate are added sequentially in different steps, and vigorous stirring is performed after each addition.

[0017] Optionally, methods for modifying phosphogypsum include: The phosphogypsum powder is washed with water to remove water-soluble impurities, and then calcined to convert the phosphogypsum into β-hemihydrate gypsum.

[0018] In another aspect, this application discloses a method for preparing a phase change energy storage material; the preparation method includes: (i) A phase change microcapsule with paraffin as the core and CaCO3 as the shell was prepared by in-situ precipitation and self-assembly. Preparation of emulsifiers: Mix 3-5 parts of styrene-maleic anhydride copolymer, 0.5-1 parts of sodium hydroxide and 80-100 parts of deionized water and stir at 80-90℃ for 100-120 min. Adjust the pH to 8-9 with citric acid solution and sodium hydroxide solution. Use the resulting solution as an emulsifier. Preparation of CaCO3 phase change microcapsules: Mix 8-10 parts of paraffin wax with the prepared emulsifier and deionized water, and then shear with a high-speed shearing machine (8000-10000rpm) for 8-10 minutes to obtain an oil-in-water emulsion. Dissolve 8-10 parts of CaCl2 in 70-80 parts of deionized water, add it dropwise to the above oil-in-water emulsion, and stir at 300-1200 rpm for 3-4 hours in an oil bath at 55-65℃. Dissolve 8-10 parts of NaCO3 in 70-80 parts of deionized water, add the solution dropwise to the above solution, and stir continuously at 500-700 r / min for 3-4 hours in an oil bath at 55-65℃. After the reaction was completed, the obtained sample was washed repeatedly with deionized water and 50% ethanol aqueous solution 4-6 times, and dried in a freeze dryer for 48 hours to obtain phase change microcapsules; (II) Pretreatment of phosphogypsum: The lumpy phosphogypsum was crushed into phosphogypsum powder, and then the phosphogypsum was washed with distilled water to remove water-soluble impurities. The washed and dried phosphogypsum was then calcined in a muffle furnace at 170°C for 2 hours. (III) Preparation of phosphogypsum-based phase change composite materials: The self-made phase change microcapsules, glass fiber, and calcined modified phosphogypsum were mixed and stirred evenly according to the given ratio. Then, the retarder was dissolved in distilled water and poured into the mixture of phase change microcapsules and modified phosphogypsum, and stirred and mixed evenly.

[0019] This invention relates to a phase change energy storage material that combines phase change microcapsules with modified phosphogypsum; the phase change microcapsules include a calcium carbonate shell as an inorganic outer shell. Therefore, the phase change microcapsules can fully integrate with the modified phosphogypsum to form a stable, durable, and high-performance material. Attached Figure Description

[0020] To illustrate this more clearly, the accompanying drawings used in the description will be briefly introduced below.

[0021] Figure 1 This is a flowchart of the preparation process described in Example 1 of the present invention; Figure 2 The differential thermal comparison diagram shows the phase change microcapsules prepared in step (1) of Example 1 of the present invention and the phase change microcapsules prepared by replacing NaCO3 with Na2SO4 as a comparison. Figure 3 These are differential thermal experimental data at different stirring speeds in Comparative Examples 2-1, 2-2, and Example 1 of the present invention; Figure 4 The data are based on Example 1, but with different stirring temperatures in steps (1-3) of Comparative Examples 2-3, 2-4, and the phase change microcapsules of Example 1, and are different from those in Example 1. Figure 5 Differential thermal experimental data for the preparation of phase change microcapsules with different core-to-wall ratios of paraffin and CaCO3 in Comparative Examples 2-5, 2-6, 2-7, and Example 1 of the present invention. Detailed Implementation

[0022] The building sector consumes a significant amount of energy and emits a large amount of carbon dioxide; therefore, developing green and energy-efficient building materials is of great strategic importance. Thermal energy storage (TES) has attracted considerable attention because it can effectively address energy supply and demand issues, improve energy efficiency, and protect the environment.

[0023] Phase change materials (PCMs) are the core of thermal energy storage systems. During a phase change process, they can release and store a large amount of latent heat while maintaining a relatively constant temperature.

[0024] However, most current phase change materials suffer from drawbacks such as leakage and low thermal conductivity.

[0025] In this application example, microencapsulation technology is used to encapsulate PCMs in organic or inorganic shells (forming microencapsulated phase change materials MPCMs) to overcome the inherent shortcomings of PCMs, thereby greatly expanding their application areas.

[0026] Furthermore, this application also combines microencapsulated phase change materials (MPCMs) with treated phosphogypsum (modified phosphogypsum) to prepare phosphogypsum-based phase change composite materials for use in the construction field, giving them not only the functions of ordinary gypsum such as lightweight humidity regulation, but also adding the ability to store energy and regulate temperature.

[0027] Research on phosphogypsum-based phase change composite materials can not only solve the problem of excessive accumulation of phosphogypsum, but also reduce the energy consumption of buildings, realize energy conservation and emission reduction in the construction field, and help solve the problem of energy shortage, thus having important application value.

[0028] Previously, physical doping of microcapsules with organic phase change materials such as paraffin and fatty acids as core materials and polymethyl methacrylate (PMMA), silica, or polyurea as wall materials was employed in combination with phosphogypsum. The applicant recognized that although such microcapsules could endow materials with heat storage / release functions, their incorporation resulted in poor mechanical properties.

[0029] Therefore, to address the aforementioned issues, the applicant has developed a novel phosphogypsum-based phase change energy storage composite material. This material possesses both excellent physical and mechanical properties and energy storage performance. It enables large-scale resource utilization of phosphogypsum while also meeting the requirements for application in building structures, providing a feasible solution for achieving low-energy buildings.

[0030] Based on the above understanding, the phase change energy storage material disclosed in the example is mainly composed of phase change microcapsules and modified phosphogypsum. The phase change microcapsules include a phase change energy storage core as the inner core and a calcium carbonate shell as the inorganic outer shell. The calcium carbonate shell coating technology can prevent paraffin leakage and also has good compatibility with phosphogypsum—because the main component of phosphogypsum is calcium sulfate, and calcium ions and sulfate ions have better compatibility with calcium carbonate.

[0031] As an alternative, the phase change energy storage core may be composed of paraffin, for example; and the modified phosphogypsum may be β-hemihydrate gypsum formed by modifying phosphogypsum.

[0032] Furthermore, in some applications, to improve the strength of the material, reinforcing agents can be added to the phase change energy storage material. For example, the reinforcing agent may include glass fiber.

[0033] Furthermore, based on practical experience, the applicant has found that controlling the ratio of paraffin to calcium carbonate in microcapsule phase change materials can yield positive results—such as improved energy storage performance. Therefore, in some examples, the ratio of paraffin to calcium carbonate in the phase change microcapsules is limited to a 1:1 mass ratio.

[0034] To facilitate the implementation of this solution, a method for preparing phase change energy storage materials is also disclosed in the embodiments. Exemplarily, and briefly, the preparation method includes: thoroughly mixing phase change microcapsules and modified phosphogypsum.

[0035] The phase change microcapsules can be pre-made or prepared on-site. Methods for preparing phase change microcapsules may include, for example, mixing paraffin wax with an emulsifier in a solvent, and then adding calcium salts and carbonates soluble in the solvent. The emulsifier can be prepared by mixing styrene-maleic anhydride copolymer and sodium hydroxide with water, and then adjusting the pH to 8-9 (weakly alkaline) with citric acid and sodium hydroxide solutions.

[0036] Unexpectedly, the applicant also noted that the method of adding calcium salts and carbonates in the above-described preparation process of phase change microcapsules significantly affects the quality of the prepared phase change microcapsules. Specifically, in a preferred embodiment, calcium salts and carbonates are added sequentially in different steps, and vigorous stirring is performed after each addition.

[0037] In addition, the method for modifying phosphogypsum in the example may include: washing phosphogypsum powder with water to remove water-soluble impurities, and then calcining it to convert the phosphogypsum into β-hemihydrate gypsum.

[0038] Therefore, in the example of this application, a phase change energy storage microcapsule with paraffin as the core and CaCO3 as the shell was realized, which was then mixed with modified β-hemihydrate phosphogypsum and cured to obtain a composite energy storage material. This application uses CaCO3 to microencapsulate paraffin wax, and then combines it with modified phosphogypsum. This effectively prevents paraffin wax leakage, improves its compatibility with phosphogypsum, and increases the thermal conductivity of paraffin wax, thereby comprehensively improving the stability, durability, and energy storage performance of the resulting composite energy storage material.

[0039] Furthermore, by adjusting the component ratio and proportion of modified phosphogypsum, the mass ratio of modified phosphogypsum to phase change energy storage microcapsules, and the curing time, the resulting composite energy storage material can possess excellent physical and mechanical properties.

[0040] The above methods not only effectively utilize industrial waste, but also enable buildings to have a certain heat storage capacity in a more economical, environmentally friendly and low-carbon way, thereby effectively regulating the internal temperature of the building.

[0041] To facilitate understanding and implementation of the scheme of this application, the following provides optional examples of more specific preparation methods.

[0042] See Figure 1 The preparation methods of phase change energy storage materials include: (i) A phase change microcapsule with paraffin as the core and CaCO3 as the shell was prepared by in-situ precipitation and self-assembly. (1-1-1) Preparation of emulsifier: Mix 3-5 parts of styrene-maleic anhydride copolymer, 0.5-1 parts of sodium hydroxide and 80-100 parts of deionized water and stir at 80-90℃ for 100-120 min. Adjust the pH to 8-9 with citric acid solution and sodium hydroxide solution. Use the resulting solution as an emulsifier and transfer it to a three-necked flask. (1-1-2) Preparation of CaCO3 phase change microcapsules: Mix 8-10 parts of paraffin wax with the emulsifier prepared in step (1-1-1) and deionized water, then shear using a high-speed shear mill (8000-10000 rpm) for 8-10 minutes to obtain an oil-in-water emulsion, which is then transferred to a three-necked flask. The shearing speed of the high-speed shear mill can also be 8000-14000 rpm, such as 8000 rpm, 10000 rpm, 12000 rpm, or 14000 rpm, but is not limited to the listed values; other values ​​not listed within the above range are also applicable. The shearing time is 8-14 minutes, such as 8 minutes, 10 minutes, 12 minutes, or 14 minutes, but is not limited to the listed values; other values ​​not listed within the above range and any range formed by any two values ​​are also applicable.

[0043] (1-2) Dissolve 8-10 parts of CaCl2 in 70-80 parts of deionized water and add it dropwise to the solution in the three-necked flask above. Stir at 300-1200 rpm for 3-4 hours in an oil bath at 55-65℃. The reaction temperature is, for example, 50℃, 55℃, 60℃ or 65℃, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0044] (1-3) Dissolve 8-10 parts of NaCO3 in 70-80 parts of deionized water, and add it dropwise to the above solution. Stir continuously for 3-4 hours at 500-700 r / min in an oil bath at 55-65℃ (this stage is the complexation stage). The reaction temperature is, for example, 50℃, 55℃, 60℃ or 65℃, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] After the reaction, the obtained sample is washed repeatedly with deionized water and 50% ethanol aqueous solution 4-6 times, and then dried in a freeze dryer for 24-48 hours to obtain phase change microcapsules. The freeze drying time can also be limited to 1-7 days, such as 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, or 7 days, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0046] During the reaction of adding CaCl2 and NaCO3, the core-to-wall ratio is (4~1):1, such as 1:1, 2:1, 3:1, or 4:1, but is not limited to the listed values; other values ​​within the above range are also applicable. The stirring speed is 600~1200 rpm, such as 600 rpm, 800 rpm, 1000 rpm, or 1200 rpm, but is not limited to the listed values; other values ​​within the above range are also applicable. The stirring time is 3~6 hours, such as 3 hours, 4 hours, 5 hours, or 6 hours, but is not limited to the listed values; other values ​​within the above range are also applicable.

[0047] (II) Pretreatment of phosphogypsum First, the lumpy phosphogypsum is crushed into phosphogypsum powder using a pulverizer. Then, the phosphogypsum is washed with distilled water to remove water-soluble impurities. After washing and drying, the phosphogypsum is calcined in a muffle furnace at 170°C for 2 hours. Finally, the calcined phosphogypsum is packed into self-sealing bags for later use. (III) Preparation of phosphogypsum-based phase change composite materials: A certain proportion of self-made phase change microcapsules, glass fiber, and calcined modified phosphogypsum were mixed and stirred evenly. Simultaneously, a certain amount of retarder was dissolved in an appropriate amount of distilled water and then poured into the mixture of phase change microcapsules and modified phosphogypsum, and stirred thoroughly until homogeneous. If the specific gravity of the phase change microcapsules is too high, it will affect the compressive strength of the material; if the specific gravity is too low, the energy storage performance will be insufficient. In the subsequent comparative examples, the specific gravity of the phase change microcapsules was 40%, 50%, and 60% wt, respectively.

[0048] In the above process, some process parameters and conditions can be optimized to achieve better product performance and better process implementation.

[0049] For example, in the emulsifier preparation step, the stirring temperature is limited to 90°C, the stirring time is 120 min, and the emulsifier concentration is 0.032 g / ml. The emulsifier concentration can also be 0.016~0.04 g / ml, such as 0.016 g / ml, 0.024 g / ml, 0.032 g / ml, or 0.04 g / ml, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0050] In the preparation steps of phase change microcapsules, the mass ratio of emulsified paraffin to emulsifier is, for example, 80:1; the mass ratio of paraffin to calcium carbonate is (1~3):1. In the manufacturing process of phase change microcapsules, the oil-in-water emulsion obtained after the emulsification reaction needs to be allowed to stand for 5-10 minutes before the next encapsulation step.

[0051] In short, the preparation method includes the following steps: (1) Preparation of phase change energy storage microcapsules with paraffin as the core and CaCO3 as the shell; (2) After washing and drying the phosphogypsum, place it in a muffle furnace at 170 degrees Celsius and calcine for 2 hours. (3) Set the water-cement ratio to (0.5, 0.6, 0.7):1, add 40~60%wt of the phase change energy storage microcapsules described in step (1), and add (0.05%~0.15%) boric acid and (0.05%~0.15%) glass fiber. After mixing evenly, the mixture is successively molded, compacted and air removed, and then cured at 35~45℃ for at least 24h to obtain phosphogypsum-based composite phase change energy storage material.

[0052] Steps (1) and (2) can be performed sequentially or in reverse order, or they can be performed simultaneously. This application does not restrict this.

[0053] The water-cement ratio refers to the amount of distilled water and the mass of solid mixture used in the preparation of phosphogypsum-based phase change composite materials.

[0054] In addition, in step (3), water, the phase change energy storage microcapsules described in step (1), and the pretreated phosphogypsum described in step (2) can be mixed evenly in a mass ratio of (0.4~0.8):(0.05~0.5):(0.5~0.95).

[0055] For example, the ratio of the three components can be 0.4:0.5:0.5, 0.6:0.5:0.5, 0.7:0.5:0.5, 0.8:0.5:0.5, 0.5:0.05:0.95, 0.5:0.1:0.9, 0.5:0.15:0.85, 0.5:0.2:0.8, 0.5:0.25:0.75, 0.5:0.3:0.7, 0.5:0.4:0.6, 0.5:0.5:0.5, etc., but it is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0056] Furthermore, the specific length of the curing time described in this invention can be selected by those skilled in the art based on the actual situation. Generally, the longer the curing time, the better the solidification effect, but at least the mechanical properties of the resulting composite energy storage material should meet the actual use requirements. It should be noted that step (3) should be carried out at 35~45℃, such as 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃ or 45℃, for at least 1 day, such as 1 day, 3 days, 6 days, 9 days, 12 days, 15 days, 18 days, 21 days, 24 days, 27 days or 30 days, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0057] This invention uses in-situ precipitation and self-assembly to coat paraffin with an inorganic CaCO3 shell to form microcapsules. Compared with organic shell microcapsules, the inorganic shell microcapsules of this application have better compatibility and higher thermal conductivity when combined with phosphogypsum (the high thermal conductivity of the calcium carbonate shell is beneficial to the phase change of paraffin). The stability and durability of the resulting composite energy storage material are improved.

[0058] With the support of this good compatibility, the modified phosphogypsum significantly improves the thermal conductivity, which is conducive to the full utilization of the energy storage performance of phase change microcapsules, effectively improves the phase change heat utilization rate, and ultimately makes the obtained composite energy storage material have excellent heat absorption and heat storage capabilities. This invention further adjusts the composition ratio of modified phosphogypsum, boric acid, and glass fiber, as well as the mass ratio of modified phosphogypsum to phase change energy storage microcapsules and the curing time, to obtain composite energy storage materials with excellent physical and mechanical properties. This enables them to be effectively applied in buildings, giving buildings a certain heat storage capacity and effectively controlling the internal temperature of buildings.

[0059] Furthermore, the preparation method of this invention is simple to operate, has low production cost, and is easy to implement. It can significantly improve the economy and safety of thermal storage, while effectively utilizing phosphogypsum as a waste industrial resource, meeting environmental protection and low-carbon requirements, and greatly increasing the added value of secondary resources.

[0060] A phosphogypsum-based composite phase change energy storage material is prepared by configuring phosphogypsum, CaCO3 phase change microcapsules, boric acid and glass fiber in a certain proportion. The phosphogypsum is converted into β-hemihydrate phosphogypsum by calcination, and the retarder boric acid and glass fiber are added to improve its gelling properties and compressive strength.

[0061] Adjusting the mass ratio of modified phosphogypsum to phase change energy storage microcapsules can balance the physical strength and phase change thermal storage performance of the resulting modified phosphogypsum-based composite phase change energy storage material. When the amount of phase change thermal storage microcapsules is too large, the mechanical strength of the material will be reduced, and when the amount is too small, the thermal storage density of the material will be reduced.

[0062] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0063] Example 1 This embodiment provides a method for preparing a modified phosphogypsum-based organic phase change composite thermal storage material, the preparation method comprising the following steps: (1) Preparation of phase change energy storage microcapsules with paraffin as the core and CaCO3 as the shell, the specific preparation steps include: (1-1) Weigh 3.2g of styrene-maleic anhydride copolymer and 0.64g of NaOH, add them to 100ml of deionized water, stir at 90℃ for 120min, and adjust the pH to 8-9 to obtain an emulsifier solution. Then weigh 8g of paraffin wax and 25ml of the emulsifier solution, add them to 100ml of deionized water, melt them in a 70℃ water bath, and then shear them at 10000rpm for 10min using a high-speed shearing machine to obtain an oil-in-water emulsion. (1-2) Prepare a CaCl2 aqueous solution with a mass ratio of 1:1 to paraffin, slowly add the CaCl2 aqueous solution dropwise, and then set the stirring speed to 600 rpm and the temperature to 55℃, and stir for 3 hours; (1-3) Prepare an aqueous solution of NaCO3 with a mass ratio of 1:1 with paraffin. Slowly add the aqueous solution of NaCO3 to the solution obtained in step (1-2). Then set the stirring speed to 600 rpm and the temperature to 55℃ and stir for 3 hours to obtain a suspension. After filtration, washing and freeze drying for 24 hours, phase change energy storage microcapsules are obtained.

[0064] The latent heat of fusion of the phase change energy storage microcapsules with paraffin as the core and CaCO3 as the shell prepared in step (1) above is 116.17 J / g, and the coating rate is 53.13%. In comparison, when the NaCO3 aqueous solution is replaced with Na2SO4, the latent heat of fusion of the phase change energy storage microcapsules with paraffin as the core and CaSO4 as the shell is 15.13438 J / g, and the coating rate is 6.84%. This shows that CaCO3 can achieve an ideal coating effect, while CaSO4 cannot achieve a good coating effect. That is, in the composition of phase change energy storage microcapsules, the choice of inorganic coating shell components has a substantial and significant impact on the successful preparation of phase change energy storage microcapsules. The differential scanning calorimetry data of the inorganic salt-coated microcapsule phase change materials (PCM-CaCO3 and PCM-CaSO4) prepared under the two process conditions are compared as follows: Figure 2 As shown.

[0065] (2) After washing the phosphogypsum with water and drying it, calcined it in a muffle furnace at 170°C for 2 hours to obtain the modified β-hemihydrate phosphogypsum.

[0066] (3) The phase change energy storage microcapsules from step (1) were mixed with 40%wt of water and 0.1% boric acid (as a retarder) and 0.1% glass fiber according to a water-cement ratio of 0.5:1. After being mixed evenly, the mixture was molded, compacted and air removed, and then cured at 40°C for 24 hours to obtain phosphogypsum-based composite phase change energy storage material.

[0067] Comparative Examples 1-1 to 1-6 Based on Example 1, the only difference between Comparative Example 1-1 and Example 1 is that the retarder in step (3) is citric acid.

[0068] Based on Example 1, the only difference between Comparative Examples 1-2 and Example 1 is that sodium citrate is selected as the retarder in step (3).

[0069] Based on Example 1, the only difference between Comparative Examples 1-3 and Example 1 is that the water-cement ratio in step (3) is 0.6:1.

[0070] Based on Example 1, the only difference between Comparative Examples 1-4 and Example 1 is that the water-cement ratio in step (3) is 0.7:1.

[0071] Based on Example 1, the only difference between Comparative Examples 1-5 and Example 1 is that the amount of phase change microcapsules in step (3) is 50%wt.

[0072] Based on Example 1, the only difference between Comparative Examples 1-6 and Example 1 is that the amount of phase change microcapsules in step (3) is 60%wt.

[0073] Performance testing The latent heat of molten metal (after coating), thermal conductivity and compressive strength of the materials prepared in Example 1 and Comparative Examples 1-1 to 1-6 were tested, and the results are shown in Table 1. Thermal performance: The latent heat of fusion, phase transition temperature, and peak temperature of the specimens were tested using a differential scanning calorimeter. The specimens were crushed into powder and placed in a pure aluminum sealed crucible for testing. The gas atmosphere was N2, the heating rate was 5℃ / min, and the temperature range was 0-90℃. The latent heat of fusion was calculated according to the formula:

[0074] In the formula, ΔH (J / g) is the enthalpy of fusion or crystallization of the sample; ΔHs (J / g) is the enthalpy of fusion or crystallization of the standard sample; A (mm2) is the peak area of ​​the sample; As (mm 2W(mg) is the peak area of ​​the standard sample; Ws(mg) is the mass of the sample; T(mW / mm) is the sensitivity Δ of the sample on the Y-axis; Ts(mW / mm) is the sensitivity of the standard sample on the Y-axis; B(s / mm) is the sensitivity of the sample on the X-axis; Bs(s / mm) is the sensitivity of the standard sample on the X-axis. The results are shown in Table 1.

[0075] Thermal conductivity test: The thermal conductivity of the phosphogypsum-based phase change composite material was measured using a thermal conductivity meter with a transient planar source method. Each group of specimens was tested three times, and the average value was taken, ensuring the relative error of the test was within 3%. The calculation formula is as follows:

[0076] In the formula λ(W·m) -1 ·K -1 ) represents the thermal conductivity of the specimen, Q(W) represents the heat flux, d(m) represents the average thickness of the specimen, and A(m) represents the thermal conductivity of the specimen. 2 The area is denoted by T1 (°C) and T2 (°C), which are the hot and cold surface temperatures of the specimen, respectively. The results are shown in Table 1.

[0077] Compressive strength test: Referring to the test method for compressive strength of gypsum in GB / T17669.3-1999, the compressive strength of the prepared phosphogypsum and phosphogypsum-based phase change composite materials was tested using a fully automatic cement strength testing machine. Each group of specimens was tested three times, and the average value was taken, ensuring that the relative error of the test was within 3%. The formula for calculating compressive strength is:

[0078] In the formula, R is the compressive strength of the specimen, P is the maximum failure load of the specimen, and S is the stress area of ​​the specimen. The results are shown in Table 1. The latent heat of fusion is the latent heat of the phase change microcapsules after coating.

[0079] Table 1

[0080] As shown in Table 1, the technical solution provided by the present invention has good mechanical properties, as well as good thermal insulation and heat storage properties, which can achieve the purpose of reducing building energy consumption.

[0081] The compressive strength of the materials in Comparative Examples 1-1 and 1-2 is lower than that in Example 1 because different retarders reduce the setting speed of gypsum at different rates, affecting its fluidity and thus having some impact on the mechanical properties of gypsum. The thermal conductivity of the materials in Comparative Examples 1-3 and 1-4 is lower than that in Example 1, and the compressive strength of Comparative Examples 1-4 is also lower. This is because the water-cement ratio of Comparative Examples 1-3 and 1-4 is higher, which affects the thermal conductivity and compressive strength. The materials in Comparative Examples 1-5 and 1-6 have higher latent heat of fusion because of the different amounts of phase change microcapsules added. As the proportion of phase change microcapsules increases, the latent heat of fusion increases accordingly, but the compressive strength decreases accordingly.

[0082] Therefore, the raw materials selected in this invention will affect the performance of the phosphogypsum-based wall material, and the raw materials need to be combined with each other to obtain the phase change phosphogypsum-based building insulation wall material described in this invention.

[0083] The above comparative analysis shows that the present invention, by forming inorganic shell microcapsules from paraffin wax and combining them with modified phosphogypsum, results in a composite phase change energy storage material with good compatibility. This facilitates the full utilization of the phase change microcapsule's thermal storage performance, effectively improving the phase change heat utilization rate. Ultimately, the resulting composite thermal storage material possesses excellent heat absorption and storage capabilities as well as thermal conductivity. By adjusting the water-cement ratio, the mass ratio of modified phosphogypsum to phase change thermal storage microcapsules, the type and proportion of retarder, and the proportion of glass fiber, the resulting composite phase change energy storage material can exhibit excellent physical and mechanical properties.

[0084] Experiment 2 Comparative Examples 2-1 and 2-2 are experimental examples based on Example 1, but the stirring speeds in steps (1-3) are different to prepare phase change microcapsules.

[0085] Comparative Examples 2-3 and 2-4 are experimental examples based on Example 1, but the stirring temperature in steps (1-3) is different to prepare phase change microcapsules.

[0086] Comparative Examples 2-5, 2-6, and 2-7 are experimental examples based on Example 1, but with different core-to-wall ratios of paraffin and CaCO3 in steps (1-3) to prepare phase change microcapsules; the core-to-wall ratio of Comparative Example 2-5 is 1:2, the core-to-wall ratio of Comparative Example 2-6 is 2:1, and the core-to-wall ratio of Comparative Example 2-7 is 3:1. The core-to-wall ratio in Example 1 is 1:1.

[0087] The test data of the phase change microcapsule materials prepared in the above experimental examples are shown in Table 2, where the latent heat of melting is the latent heat data of the unencapsulated microcapsules.

[0088] Table 2

[0089] Differential thermal analysis data of phase change microcapsules in Comparative Examples 2-1, 2-2 and Example 1 are as follows: Figure 3 .

[0090] Comparative Examples 2-3 and 2-4 are based on Example 1, but the stirring temperatures in steps (1-3) are different. The differential thermal analysis data for the phase change microcapsules are as follows: Figure 4 .

[0091] Differential thermal analysis data for the preparation of phase change microcapsules with different core-to-wall ratios of paraffin and CaCO3 in Comparative Examples 2-5, 2-6, 2-7, and Example 1 are as follows: Figure 5 .

[0092] The embodiments shown above illustrate the structure, features, and effects of this application in detail. The above are only preferred embodiments of this application. Any changes made in accordance with the concept of this application, or modifications to equivalent embodiments with equivalent variations, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of this application.

Claims

1. A phase change energy storage material, characterized in that, The phase change energy storage material is mainly composed of phase change microcapsules and modified phosphogypsum. The phase change microcapsules include a phase change energy storage core as the inner core and a calcium carbonate shell as an inorganic outer shell.

2. The phase change energy storage material according to claim 1, characterized in that, The phase change energy storage core is composed of paraffin.

3. The phase change energy storage material according to claim 2, characterized in that, Paraffin and calcium carbonate in the phase change microcapsules exist in a 1:1 mass ratio.

4. The phase change energy storage material according to claim 1, characterized in that, The modified phosphogypsum is a β-hemihydrate gypsum formed by modifying phosphogypsum.

5. The phase change energy storage material according to claim 1, characterized in that, The phase change energy storage material also includes a reinforcing agent; Optionally, the reinforcing agent comprises glass fiber.

6. A method for preparing a phase change energy storage material, characterized in that, The preparation method includes: thoroughly mixing phase change microcapsules and modified phosphogypsum, wherein the phase change microcapsules include a phase change energy storage core as the core and a calcium carbonate shell as an inorganic outer shell.

7. The preparation method according to claim 6, characterized in that, Methods for preparing phase change microcapsules include: Paraffin wax is mixed with an emulsifier in a solvent, and then calcium salts and carbonates soluble in the solvent are added to it. Optionally, the emulsifier is prepared by mixing styrene-maleic anhydride copolymer and sodium hydroxide with water, and then adjusting the pH to 8-9 with citric acid solution and sodium hydroxide solution.

8. The preparation method according to claim 7, characterized in that, Calcium salts and carbonates are added sequentially in different steps, and vigorous stirring is performed after each addition.

9. The preparation method according to claim 7 or 8, characterized in that, The method for modifying phosphogypsum includes: The phosphogypsum powder is washed with water to remove water-soluble impurities, and then calcined to convert the phosphogypsum into β-hemihydrate gypsum.

10. A method for preparing a phase change energy storage material, characterized in that, The preparation method includes: (i) A phase change microcapsule with paraffin as the core and CaCO3 as the shell was prepared by in-situ precipitation and self-assembly. Preparation of emulsifiers: Mix 3-5 parts of styrene-maleic anhydride copolymer, 0.5-1 parts of sodium hydroxide and 80-100 parts of deionized water and stir at 80-90℃ for 100-120 min. Adjust the pH to 8-9 with citric acid solution and sodium hydroxide solution. Use the resulting solution as an emulsifier. Preparation of CaCO3 phase change microcapsules: Mix 8-10 parts of paraffin wax with the prepared emulsifier and deionized water, and then shear with a high-speed shearing machine (8000-10000rpm) for 8-10 minutes to obtain an oil-in-water emulsion. Dissolve 8-10 parts of CaCl2 in 70-80 parts of deionized water, add it dropwise to the above oil-in-water emulsion, and stir at 300-1200 rpm for 3-4 hours in an oil bath at 55-65℃. Dissolve 8-10 parts of NaCO3 in 70-80 parts of deionized water, add the solution dropwise to the above solution, and stir continuously at 500-700 r / min for 3-4 hours in an oil bath at 55-65℃. After the reaction was completed, the obtained sample was washed repeatedly with deionized water and 50% ethanol aqueous solution 4-6 times, and dried in a freeze dryer for 48 hours to obtain phase change microcapsules; (II) Pretreatment of phosphogypsum: The lumpy phosphogypsum was crushed into phosphogypsum powder, and then the phosphogypsum was washed with distilled water to remove water-soluble impurities. The washed and dried phosphogypsum was then calcined in a muffle furnace at 170°C for 2 hours. (III) Preparation of phosphogypsum-based phase change composite materials: The self-made phase change microcapsules, glass fiber, and calcined modified phosphogypsum were mixed and stirred evenly according to the given ratio. Then, the retarder was dissolved in distilled water and poured into the mixture of phase change microcapsules and modified phosphogypsum, and stirred and mixed evenly.

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