Calcium-based thermochemical heat storage material and preparation method thereof

Abstract

The application discloses a calcium-based thermochemical heat storage material and a preparation method thereof, and belongs to the technical field of thermochemical heat storage materials. ‑ or CO3 2‑ The preparation method of the calcium-based thermochemical heat storage material comprises the following steps: mixing a soluble calcium salt and a solvent A to prepare a solution A; mixing a precipitant and a solvent B to prepare a solution B; the precipitant comprises a soluble compound containing OH ‑ or CO3 2‑ ; dispersing a modifier C3N4 into the solution A or the solution B, then mixing, reacting and solid-liquid separating the solution A and the solution B to obtain a solid product; and calcining the solid product to prepare a modified calcium-based material. The CaO obtained by the application has a smaller particle size, the uniformity of the product is improved, the particle size and the morphology of the CaO particles are changed, and the heat storage process can be more easily carried out at a low temperature.

Description

Technical Field

[0001] This invention belongs to the field of thermochemical thermal storage materials technology, specifically relating to a calcium-based thermochemical thermal storage material and its preparation method. Background Technology

[0002] Traditional power systems are gradually transitioning to new energy power systems, represented by renewable energy sources. However, the instability of new energy sources limits current energy development. Energy storage technology has the advantage of solving the problem of heat supply and demand mismatch, and has the potential to improve the grid system's capacity to accept new energy power and the flexibility of peak-shaving in summer. Therefore, researching and developing efficient, stable, and low-cost energy storage technologies is a key focus of current energy development.

[0003] Based on different energy storage principles, thermal energy storage systems are classified into three types: sensible heat storage, latent heat storage, and thermochemical heat storage. Compared with the other two types of thermal energy storage systems, thermochemical heat storage has advantages such as being environmentally friendly, producing non-corrosive products, and having a wide reaction temperature range, making it a highly promising method for thermal energy storage.

[0004] Among numerous thermochemical energy storage systems, inorganic hydroxide systems have advantages such as good safety, high energy density, low cost, fast reaction rate, and good reversibility, and are therefore widely used. However, the relatively high reaction temperatures of these systems currently significantly limit the reduction of overall system costs.

[0005] To meet the demands of industrialization and accelerate the development of new large-scale thermal (cold) storage technologies that span long time scales across seasons and wide spatial ranges, it is urgent to find a method for preparing new thermochemical energy storage materials with high energy density and low operating temperature to better cope with the seasonal fluctuations in renewable energy and energy consumption. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the inorganic hydroxide heat storage and release material system in the prior art, which has a large reaction peak temperature and a high total system cost, thus limiting its large-scale application, and to provide a calcium-based thermochemical heat storage material and its preparation method.

[0007] To this end, the present invention provides the following technical solution.

[0008] In a first aspect, the present invention provides a method for preparing a calcium-based thermochemical heat storage material, comprising the following steps:

[0009] A solution A is prepared by mixing a soluble calcium salt with solvent A.

[0010] Solution B is prepared by mixing a precipitant with solvent B; the precipitant includes solvents containing OH-. - or CO3 2- Soluble compounds;

[0011] The modifier C3N4 is dispersed in solution A or solution B, and then solution A and solution B are mixed, reacted, and separated into solid and liquid components to obtain a solid product. The solid product is then calcined to obtain a modified calcium-based material.

[0012] Furthermore, the solid product comprises, by mass percentage, 45% to 95% C3N, with the balance being Ca(OH)2 and / or CaCO3;

[0013] Preferably, the C3N4 content is 20% to 50%; more preferably, the C3N4 content is 20%.

[0014] Furthermore, the soluble calcium salt includes at least one of calcium chloride, calcium bromide, calcium iodide, calcium nitrate, calcium chlorate, calcium perchlorate, calcium bicarbonate, and calcium dihydrogen phosphate.

[0015] Furthermore, the precipitant includes at least one of sodium hydroxide, potassium hydroxide, NH3·H2O, sodium carbonate, or potassium carbonate.

[0016] Furthermore, the preparation method of C3N4 includes: calcining the modifier precursor to obtain C3N4;

[0017] Preferably, the modifier precursor includes one or more of urea and melamine;

[0018] Preferably, the calcination conditions for the modifier precursor are: calcination at 400–700°C for 1–3 hours.

[0019] Furthermore, when the precipitant is an OH-containing... - When dealing with soluble compounds, the calcination conditions for the solid product are: calcination at 750–1200°C for 1–2 hours;

[0020] Furthermore, when the precipitant contains CO3... 2- When dealing with soluble compounds, the calcination conditions for the solid product are: calcination at 900–1200°C for 1–2 hours.

[0021] Furthermore, the steps of dispersing C3N4 into solution A or solution B include:

[0022] C3N4 is dispersed in solvent C to obtain a dispersion, which is then mixed with solution A or solution B.

[0023] Preferably, the conditions for dispersing C3N4 in solvent C are: ultrasonic frequency of 10-50 kHz and ultrasonic treatment time of 15-45 min.

[0024] Furthermore, solvent A includes one or more of deionized water and anhydrous ethanol;

[0025] Furthermore, the solvent B includes one or more of deionized water and anhydrous ethanol;

[0026] Furthermore, the solvent C includes one or more of deionized water and anhydrous ethanol;

[0027] Preferably, solvent A, solvent B, and solvent C are the same.

[0028] Furthermore, after solid-liquid separation, the solid product is washed with water, dried, and then calcined.

[0029] Optionally, the drying conditions are drying at a temperature of 80℃ to 100℃ for 0.5 to 1 hour.

[0030] Secondly, the present invention provides a calcium-based thermochemical heat storage material prepared according to the above method.

[0031] The particle size of the thermochemical thermal storage material is 0.1 μm to 100 μm.

[0032] Dispersion includes, but is not limited to, the use of ultrasonic dispersion cleaners.

[0033] Stirring includes, but is not limited to, using a magnetic stirrer.

[0034] Calcination includes, but is not limited to, the use of a muffle furnace.

[0035] The technical solution of this invention has the following advantages:

[0036] The preparation method of the calcium-based thermochemical heat storage material of the present invention includes the following steps: mixing a soluble calcium salt with solvent A to obtain solution A; mixing a precipitant with solvent B to obtain solution B; dispersing a modifier C3N4 into solution A or solution B; then mixing solution A and solution B, reacting, and separating the solid and liquid to obtain a solid product; calcining the solid product to obtain the modified calcium-based material.

[0037] Thermochemical thermal energy storage materials store thermal energy in the form of chemical energy and release it when needed, thereby improving the utilization rate of off-peak electricity. This invention incorporates C3N4 during the formation of calcium hydroxide and / or calcium carbonate. By doping C3N4 with calcium hydroxide and / or calcium carbonate through a solution method, the generated calcium hydroxide and / or calcium carbonate can be more dispersed, resulting in smaller CaO particles after calcination. This not only improves the uniformity of the product but also alters the particle size and morphology of CaO, thus changing the properties of CaO and making the thermal energy storage process easier to carry out at low temperatures.

[0038] The Ca(OH)2 / CaO thermal storage material system of this invention has a narrow reaction temperature range and a low reaction peak temperature. Compared with existing thermal storage material systems, it has a higher thermal storage density and a lower reaction temperature, which can effectively reduce the cost of thermal storage systems and provide a technical solution for the practical application of calcium-based hydroxides.

[0039] The energy storage density of the thermochemical thermal storage material of this invention reaches 1236.67 kJ / kg, which is about 7.3% higher than that of unmodified Ca(OH)₂. Furthermore, the novel thermal storage material obtained by this invention has a small average particle size, high specific surface area, and high porosity, thus exhibiting a lower reaction temperature. The peak reaction temperature of the thermal storage material of this invention is 17.93 °C lower than that of unmodified Ca(OH)₂. Attached Figure Description

[0040] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 The TG and DSC curves of the thermochemical thermal storage material prepared in Example 1 are shown.

[0042] Figure 2 The TG curve and DSC curve of the thermochemical thermal storage material prepared in Example 2 are shown.

[0043] Figure 3 The TG and DSC curves of the unmodified thermochemical thermal storage material in Comparative Example 1 are shown.

[0044] Figure 4 The XRD patterns of the thermochemical thermal storage materials in Example 1 and Comparative Example 1 are shown in the comparison diagram.

[0045] Figure 5 This is a morphological feature diagram of the thermochemical thermal storage material in Example 1;

[0046] Figure 6 This is a morphological feature diagram of the thermochemical thermal storage material in Comparative Example 1;

[0047] Figure 7 This is a comparison diagram of the particle size of the thermochemical thermal storage materials in Example 1 and Comparative Example 1. Detailed Implementation

[0048] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0049] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0050] The method for preparing calcium-based thermochemical heat storage material of the present invention includes:

[0051] S1. The precursor of the modifier is calcined at high temperature to obtain C3N4. C3N4 is then dispersed in deionized water to obtain a C3N4 dispersion.

[0052] S2, dissolve the soluble calcium salt in deionized water to obtain a calcium salt solution.

[0053] S3, dissolve the precipitant in deionized water to obtain a precipitant solution.

[0054] S4 involves mixing C3N4 dispersion, calcium salt solution, and precipitant solution, reacting them, separating the solid and liquid phases to obtain a precipitate, washing and drying the precipitate, and then subjecting it to high-temperature calcination to obtain a modified calcium-based material.

[0055] In S1, high-temperature calcination includes: placing the modifier precursor in a square ceramic boat, covering it with another ceramic boat of the same size, and calcining it in a muffle furnace at 400℃~700℃ for 1~3 hours; the modifier precursor includes one or more of urea and melamine.

[0056] In S1, dispersion includes: using an ultrasonic dispersion cleaner, C3N4 is added to deionized water and then ultrasonically treated at an ultrasonic frequency of 10kHz to 50kHz for 10 to 45 minutes.

[0057] In S2, the soluble calcium salt includes at least one of calcium chloride, calcium bromide, calcium iodide, calcium nitrate, calcium chlorate, calcium perchlorate, calcium bicarbonate, and calcium dihydrogen phosphate.

[0058] In S3, the precipitant includes at least one of sodium hydroxide, potassium hydroxide, NH3·H2O, sodium carbonate, or potassium carbonate.

[0059] In S4, the reaction after mixing C3N4 dispersion, calcium salt solution and alkaline solution includes: adding calcium salt solution to C3N4 dispersion, stirring thoroughly and evenly, mixing evenly with precipitant solution, and then letting stand for 30-60 minutes to allow for complete reaction and formation of solid precipitate.

[0060] In S4, solid-liquid separation includes separating the precipitate from the mixed reaction system using filter paper or other porous materials.

[0061] In S4, drying includes drying at a temperature of 80℃~100℃ for 0.5~1 hour.

[0062] The urea used in this embodiment of the invention was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; all raw materials used, unless otherwise specified, were of analytical grade.

[0063] Example 1

[0064] This embodiment provides a method for preparing a calcium-based thermochemical heat storage material, including the following steps:

[0065] S1. Weigh 100g of urea and place it in a square porcelain boat. Cover the boat with another porcelain boat of the same size and place it in a muffle furnace. Heat the furnace to 500℃ at a rate of 10℃ / min and keep it at that temperature for 1 hour. Cool the furnace to room temperature to obtain graphitic carbon nitride with a yield of about 5% (5g).

[0066] Weigh 4g of yellow carbon nitride powder and disperse it in a container containing 1L of deionized water. Use an ultrasonic disperser and ultrasonically treat the solution at an ultrasonic frequency of 50kHz for 30 minutes to obtain a carbon nitride dispersion.

[0067] S2. Weigh 31.78g of calcium chloride dihydrate, dissolve it in 0.5L of deionized water to prepare a calcium chloride solution, and slowly add it to the carbon nitride dispersion to obtain a mixed solution. Stir well.

[0068] S3. Weigh 17.30g of sodium hydroxide and dissolve it in 0.5L of deionized water to obtain a sodium hydroxide solution.

[0069] S4. Add the sodium hydroxide solution prepared in S3 to the mixed solution obtained in S2, mix well and react for half an hour, then filter to obtain a light yellow precipitate.

[0070] The light yellow precipitate was washed with water and dried at 100°C for 0.5 h to obtain a calcium hydroxide-carbon nitride composite with a carbon nitride mass fraction of 20%. The dried calcium hydroxide-carbon nitride composite was thoroughly ground into powder using an agate mortar and calcined in a muffle furnace at 1000°C in air atmosphere for 2 h to obtain a modified calcium-based material.

[0071] Example 2

[0072] This embodiment provides a method for preparing a calcium-based thermochemical heat storage material, including the following steps:

[0073] S1. Weigh 100g of urea and place it in a square porcelain boat. Cover the boat with another porcelain boat of the same size and place it in a muffle furnace. Heat the furnace to 500℃ at a rate of 10℃ / min and keep it at that temperature for 1 hour. Cool the furnace to room temperature to obtain graphitic carbon nitride with a yield of about 5% (5g).

[0074] Weigh 2g of yellow carbon nitride powder and disperse it in a container containing 1L of deionized water. Use an ultrasonic disperser and ultrasonically treat the solution at an ultrasonic frequency of 50kHz for 30 minutes to obtain a carbon nitride dispersion.

[0075] S2. Weigh 35.76g of calcium chloride dihydrate, dissolve it in 0.5L of deionized water, and slowly add it to the carbon nitride dispersion to obtain a mixed solution. Stir well.

[0076] S3. Weigh 19.46g of sodium hydroxide and dissolve it in 0.5L of deionized water to obtain a sodium hydroxide solution.

[0077] S4. Add the sodium hydroxide solution prepared in S3 to the mixed solution obtained in S2. After reacting for half an hour, filter to obtain a light yellow precipitate.

[0078] The light yellow precipitate was washed and dried at 80°C for 1 hour to obtain a calcium hydroxide-carbon nitride composite with a carbon nitride mass fraction of 10%. The dried calcium hydroxide-carbon nitride composite was thoroughly ground into powder using an agate mortar and calcined in a muffle furnace at 1000°C in air atmosphere for 2 hours to obtain a modified calcium-based material.

[0079] Example 3

[0080] This embodiment provides a method for preparing a calcium-based thermochemical heat storage material, including the following steps:

[0081] S1. Weigh 200g of urea and place it in a square porcelain boat. Cover the boat with another porcelain boat of the same size and place it in a muffle furnace. Heat the furnace to 550℃ at a rate of 10℃ / min and keep it at that temperature for 1 hour. Cool the furnace to room temperature to obtain graphitic carbon nitride with a yield of about 5% (10g).

[0082] Weigh 7g of yellow carbon nitride powder and disperse it in a container containing 1L of deionized water. Use an ultrasonic disperser and ultrasonic cleaner at a frequency of 50kHz to sonicate the solution for 30 minutes to obtain a carbon nitride solution.

[0083] S2. Weigh 25.872g of calcium chloride dihydrate, dissolve it in 0.5L of deionized water, and slowly add it to the carbon nitride dispersion solution to obtain a mixed solution. Stir well.

[0084] S3. Weigh 14.08g of sodium hydroxide and dissolve it in 0.5L of deionized water to obtain a sodium hydroxide solution.

[0085] S4. Add the sodium hydroxide solution prepared in S3 to the mixed solution obtained in S2. After reacting for half an hour, filter to obtain a light yellow precipitate.

[0086] The light yellow precipitate was washed and dried at 100°C for 0.5 h to obtain a calcium hydroxide-carbon nitride composite with a carbon nitride mass fraction of 35%. The dried calcium hydroxide-carbon nitride composite was thoroughly ground into powder using an agate mortar and placed in a muffle furnace and calcined at a constant temperature of 1000°C in air atmosphere for 2 h to obtain the modified calcium-based material.

[0087] Example 4

[0088] This embodiment provides a method for preparing a calcium-based thermochemical heat storage material, including the following steps:

[0089] S1. Weigh 300g of urea and place it in a square porcelain boat. Cover the boat with another porcelain boat of the same size and place it in a muffle furnace. Heat the furnace to 550℃ at a rate of 10℃ / min and hold for 1 hour. Cool the furnace to room temperature to obtain graphitic carbon nitride with a yield of about 5% (15g).

[0090] Weigh 10g of yellow carbon nitride powder and disperse it in a container containing 1L of deionized water. Use an ultrasonic disperser and ultrasonic cleaner at a frequency of 50kHz to sonicate the solution for 30 minutes to obtain a carbon nitride solution.

[0091] S2. Weigh 19.845g of calcium chloride dihydrate, dissolve it in 0.5L of deionized water, and slowly add it to the carbon nitride dispersion solution to obtain a mixed solution. Stir well.

[0092] S3. Weigh 10.8g of sodium hydroxide and dissolve it in 0.5L of deionized water to obtain a sodium hydroxide solution.

[0093] S4. Add the sodium hydroxide solution prepared in S3 to the mixed solution obtained in S2. After reacting for half an hour, filter to obtain a light yellow precipitate.

[0094] The light yellow precipitate was washed and dried at 100°C for 0.5 h to obtain a calcium hydroxide-carbon nitride composite with a carbon nitride mass fraction of 50%. The dried calcium hydroxide-carbon nitride composite was thoroughly ground into powder using an agate mortar and placed in a muffle furnace and calcined at a constant temperature of 1000°C in air atmosphere for 2 h to obtain a modified calcium-based material.

[0095] Example 5

[0096] This embodiment provides a method for preparing a calcium-based thermochemical heat storage material, including the following steps:

[0097] S1. Weigh 300g of urea and place it in a square porcelain boat. Cover the boat with another porcelain boat of the same size and place it in a muffle furnace. Heat the furnace to 550℃ at a rate of 10℃ / min and hold for 1 hour. Cool the furnace to room temperature to obtain graphitic carbon nitride with a yield of about 5% (15g).

[0098] Weigh 14g of yellow carbon nitride powder and disperse it in a container containing 1L of deionized water. Use an ultrasonic disperser and ultrasonic cleaner at a frequency of 50kHz to sonicate the solution for 30 minutes to obtain a carbon nitride solution.

[0099] S2. Weigh 11.907g of calcium chloride dihydrate, dissolve it in 0.5L of deionized water, and slowly add it to the carbon nitride dispersion solution to obtain a mixed solution. Stir well.

[0100] S3. Weigh 6.48g of sodium hydroxide and dissolve it in 0.5L of deionized water to obtain a sodium hydroxide solution.

[0101] S4. Slowly add the sodium hydroxide solution prepared in S3 to the mixed solution obtained in S2. After reacting for half an hour, filter to obtain a light yellow precipitate.

[0102] The light yellow precipitate was washed and dried at 100°C for 0.5 h to obtain a calcium hydroxide-carbon nitride composite with a carbon nitride mass fraction of 70%. The dried calcium hydroxide-carbon nitride composite was thoroughly ground into powder using an agate mortar and placed in a muffle furnace and calcined at a constant temperature of 1000°C in air atmosphere for 2 h to obtain a modified calcium-based material.

[0103] Other calcium hydroxide-carbon nitride complexes with different carbon nitride mass fractions were prepared by increasing or decreasing the amounts of calcium chloride, sodium hydroxide, and carbon nitride in proportion.

[0104] Comparative Example 1

[0105] This comparative example provides a method for preparing a calcium-based thermochemical thermal storage material, including the following steps:

[0106] S1. Weigh 31.78g of calcium chloride dihydrate and dissolve it in 0.5L of deionized water to obtain a calcium chloride solution.

[0107] S2. Weigh 17.30g of sodium hydroxide and dissolve it in 0.5L of deionized water to obtain a sodium hydroxide solution.

[0108] S3. Add sodium hydroxide solution to calcium chloride solution, react for half an hour, and then filter to obtain precipitate.

[0109] The precipitate was washed with water and dried at 100°C for 0.5 h. The dried product was then ground into powder using an agate mortar and placed in a muffle furnace and calcined at 1000°C in air for 2 h to obtain unmodified calcium-based material.

[0110] Test case

[0111] 1) The thermal storage performance of the calcium-based thermochemical thermal storage materials prepared in the examples and comparative examples was tested using a Setsys Evo simultaneous thermal analyzer manufactured by Setram GmbH, France.

[0112] Since the energy storage density is obtained by measuring the heat of reaction of calcium hydroxide during the endothermic decomposition process, it is necessary to first introduce water vapor to convert the prepared calcium oxide into calcium hydroxide before measurement. The energy storage density of the thermochemical thermal storage material is measured by thermogravimetric analysis (TG). Approximately 20 mg of the thermochemical thermal storage material is placed in a 50 μL alumina crucible. The temperature control program involves heating from room temperature to 600 °C and then directly cooling back to room temperature at a rate of 5 °C / min. The argon flow rate is 50 mL / min. Based on the TG analysis, differential scanning calorimetry (DSC) is used to study the temperature change during the calcium hydroxide thermal storage process. The test results are shown in Table 1 and... Figures 1-3 .

[0113] Table 1 Thermal storage performance

[0114]

[0115]

[0116] As shown in Table 1, the energy storage density of the unmodified calcium-based thermochemical thermal storage material in Comparative Example 1 is 1152.68 kJ / kg; the energy storage density of the calcium-based thermochemical thermal storage material in Example 1 can reach 1236.67 kJ / kg, which is about 7.3% higher than that of Comparative Example 1; the energy storage density of the calcium-based thermochemical thermal storage material in Example 2 can reach 1174.50 kJ / kg, which is about 1.9% higher than that of Comparative Example 1. The calcium-based thermochemical thermal storage material of Example 3 has an energy storage density of 1213.41 kJ / kg, which is about 5.3% higher than that of Comparative Example 1; the calcium-based thermochemical thermal storage material of Example 4 has an energy storage density of 1210.52 kJ / kg, which is about 5.0% higher than that of Comparative Example 1; and the calcium-based thermochemical thermal storage material of Example 5 has an energy storage density of 1162.90 kJ / kg, which is about 0.89% higher than that of Comparative Example 1. The energy storage density of the calcium-based thermochemical thermal storage material prepared by this invention is improved.

[0117] Furthermore, the peak reaction temperature of Comparative Example 1 was 447.94℃, while the peak reaction temperature of the thermochemical thermal storage material prepared in Example 1 was 430.01℃, representing a decrease of 17.93℃ in the reaction temperature of the modified calcium-based thermochemical thermal storage material; the peak reaction temperature of the thermochemical thermal storage material prepared in Example 2 was 438.80℃, a decrease of 9.14℃ compared to Comparative Example 1; the peak reaction temperature of the thermochemical thermal storage material prepared in Example 3 was 433.13℃, a decrease of 14.81℃ in the reaction temperature of the modified calcium-based thermochemical thermal storage material; the peak reaction temperature of the thermochemical thermal storage material prepared in Example 4 was 437.48℃, a decrease of 10.46℃ in the reaction temperature of the modified calcium-based thermochemical thermal storage material; and the peak reaction temperature of the thermochemical thermal storage material prepared in Example 5 was 442.49℃, a decrease of 5.45℃ in the reaction temperature of the modified calcium-based thermochemical thermal storage material. The peak reaction temperature of the calcium-based thermochemical thermal storage material prepared in this invention is significantly lower than that of existing calcium-based thermochemical thermal storage materials.

[0118] The extrapolated starting point of the reaction temperature in Comparative Example 1 was 383.88℃, and the extrapolated ending point was 466.93℃, with a temperature range of 83.05℃. The extrapolated starting points for Examples 1 to 5 were 371.80℃, 373.54℃, 373.64℃, 376.94℃, and 375.65℃, respectively; and the extrapolated ending points were 442.17℃, 452.54℃, 445.63℃, 451.94℃, and 454.90℃, respectively. The temperature range of the five examples was between 70.37℃ and 79.25℃. It can be seen that compared with the Comparative Example, the temperature range was narrowed to varying degrees, which is more conducive to reaction control and system design.

[0119] 2) The phase composition of the thermochemical thermal storage materials prepared in the examples and comparative examples was analyzed by X-ray diffraction (XRD) using an AL-2700 X-ray diffractometer manufactured by Dandong Aolong Company at room temperature. The test results are as follows: Figure 4 As shown.

[0120] from Figure 4 It can be seen that the calcined thermochemical heat storage material powder has only one crystalline phase, CaO.

[0121] Using C3N4 as a modifier can shift the characteristic peaks of CaO to the left, with a maximum shift of 2θ = 0.06°. According to Bragg's law, the crystal structure of CaO changes after modification, the interplanar spacing increases, and the exothermic reaction proceeds more easily.

[0122] 3) Scanning electron microscopy (SEM) was performed using an Evo-18 scanning electron microscope manufactured by Zeiss to observe the microstructure changes of the thermochemical heat storage materials prepared in the examples and comparative examples. The test results are as follows: Figure 5 , Figure 6 As shown.

[0123] Depend on Figure 5 , Figure 6 It can be seen that the thermochemical thermal storage material prepared in Comparative Example 1 is prone to agglomeration and forming particle clusters, while the CaO prepared by adding the modifier C3N4 in the preparation process of Example 1 has more obvious particle dispersion, and its morphological characteristics show more obvious particle characteristics.

[0124] 4) The particle size of the thermochemical thermal storage materials prepared in the examples and comparative examples was tested using a Mastersizer laser particle size analyzer. The test results are shown in [Figure number missing]. Figure 7 .

[0125] Depend on Figure 7 It can be seen that the thermochemical thermal storage material prepared in Example 1 has smaller particle size and a narrower particle size distribution. Using C3N4 as a modifier can significantly reduce the particle size of CaO particles and narrow the particle size range, resulting in CaO particles with a more concentrated particle size distribution.

[0126] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a calcium-based thermochemical heat storage material, characterized in that, Includes the following steps: A solution A is prepared by mixing a soluble calcium salt with solvent A. Solution B is prepared by mixing a precipitant with solvent B; the precipitant includes solvents containing OH-. - or CO3 2- Soluble compounds; The modifier C3N4 is dispersed in solution A or solution B, and then solution A and solution B are mixed, reacted, and separated into solid and liquid components to obtain a solid product. The solid product was calcined to obtain a modified calcium-based material. The solid product comprises, by mass percentage, 45% to 95% C3N, with the balance being Ca(OH)2 and / or CaCO3.

2. The method for preparing calcium-based thermochemical heat storage material according to claim 1, characterized in that, The solid product comprises, by mass percentage, 20% to 50% C3N4, with the balance being Ca(OH)2 and / or CaCO3.

3. The method for preparing calcium-based thermochemical heat storage material according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The soluble calcium salt includes at least one of calcium chloride, calcium bromide, calcium iodide, calcium nitrate, calcium chlorate, calcium perchlorate, calcium bicarbonate, and calcium dihydrogen phosphate; (2) The precipitant includes at least one of sodium hydroxide, potassium hydroxide, NH3·H2O, sodium carbonate or potassium carbonate.

4. The method for preparing calcium-based thermochemical heat storage material according to claim 1, characterized in that, The preparation of C3N4 includes: calcining the modifier precursor to obtain C3N4.

5. The method for preparing calcium-based thermochemical heat storage material according to claim 4, characterized in that, The preparation of C3N4 satisfies at least one of the following conditions: (1) The precursor of the modifier includes one or more of urea and melamine; (2) The calcination conditions for the modifier precursor are: calcination at 400~700℃ for 1~3 hours.

6. The method for preparing calcium-based thermochemical heat storage material according to claim 1, characterized in that, The precipitant is a precipitant containing OH. - For soluble compounds, the calcination conditions for the solid product are: calcination at 750~1200℃ for 1~2 hours.

7. The method for preparing calcium-based thermochemical heat storage material according to claim 1, characterized in that, The precipitant contains CO3. 2- For soluble compounds, the calcination conditions for the solid product are: calcination at 900~1200℃ for 1~2 hours.

8. The method for preparing calcium-based thermochemical heat storage material according to claim 1, characterized in that, After solid-liquid separation, the solid product is washed with water, dried, and then calcined.

9. A calcium-based thermochemical thermal storage material prepared by the method according to any one of claims 1-8.

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