阅读说明：本技术 一种熔融盐基复合相变储热大胶囊的制备方法与应用 (Preparation method and application of fused salt-based composite phase-change heat storage large capsule ) 是由 盛楠 朱春宇 曾令虓 郭云琪 饶中浩 于 2021-09-10 设计创作，主要内容包括：本发明公开一种熔融盐基复合相变储热大胶囊的制备方法与应用。首先将熔融盐与高导热多孔填料混合压制成球形核芯,然后在球形核芯表面包裹一层碳层作为中间层,经干燥、压制、热处理之后再包裹一层陶瓷外壳,再经干燥、压制、热处理后制得复合熔融盐基相变储热大胶囊。本发明制得的储热大胶囊可有效地解决熔融盐在高温融化后泄露的问题,并且提高熔融盐的导热性能,可应用于中高温领域的太阳能以及工业余热的储热。(The invention discloses a preparation method and application of a fused salt-based composite phase-change heat storage large capsule. Firstly, mixing molten salt and high-thermal-conductivity porous filler to be pressed into a spherical core, then wrapping a layer of carbon layer on the surface of the spherical core to be used as a middle layer, drying, pressing and thermally treating the spherical core, then wrapping a layer of ceramic shell, and drying, pressing and thermally treating the ceramic shell to obtain the composite molten salt-based phase-change heat storage macro-capsule. The heat storage large capsule prepared by the invention can effectively solve the problem of leakage of molten salt after melting at high temperature, improves the heat conduction performance of the molten salt, and can be applied to heat storage of solar energy and industrial waste heat in the medium-high temperature field.)

1. A preparation method of a fused salt-based composite phase-change heat storage big capsule is characterized by comprising the following steps:

(1) mixing the molten salt with the heat-conducting filler, stirring and mixing the mixture with an organic adhesive solution according to a certain proportion, uniformly mixing the mixture to prepare a spherical core blank, and drying the spherical core blank to prepare the molten salt/heat-conducting filler spherical core.

(2) And (2) stirring and mixing the carbon material powder and the organic binder solution according to a certain proportion, uniformly mixing, wrapping the mixture on the surface of the spherical core blank prepared in the step (1), drying, pressing by using an isostatic press and other methods to compact the spherical core blank, heating to the temperature of 300-500 ℃ in the air or oxygen atmosphere, sintering for a plurality of hours, removing the organic binder in the sphere, and preparing the carbon shell-coated molten salt/heat-conducting filler composite sphere.

(3) Stirring and mixing the ceramic powder and the organic binder solution according to a certain proportion, uniformly mixing, wrapping the ceramic powder and the organic binder solution on the surface of the composite sphere prepared in the step (2) to form a layer of ceramic shell, drying, pressing by using an isostatic press and other methods, and then carrying out two-stage heat treatment on the composite sphere: 1) heating to 300-500 ℃ in air or oxygen atmosphere, pre-burning for 1-24 hours, and removing the organic binder in the spheres; 2) after pre-sintering, heating to 500-1500 ℃ in an oxygen-free environment, carrying out high-temperature heat treatment for 1-48 hours, and cooling to room temperature to obtain the fused salt-based composite phase-change heat storage large capsule.

2. The method of claim 1, wherein the heat storage macro-capsule has a diameter of 2.5-250mm, and comprises an outer inorganic shell layer, an intermediate carbon layer, and an inner molten salt/heat conductive filler mixed core. The diameter of the internal molten salt/heat-conducting filler mixed core material sphere is 0.5-190mm, the thickness of the intermediate carbon layer is 0.5-10mm, and the thickness of the external inorganic shell layer is 0.5-20 mm.

3. The method for preparing a fused salt-based composite phase-change heat storage macro-capsule as claimed in claim 1, wherein the fused salt in step (1) is selected from hydroxide (alkali) and nitrateOne of carbonate, chloride, fluoride, bromide and sulfate and mixed molten salt formed by two or more of the above. I.e. LiOH, NaOH, KOH, LiNO₃、NaNO₃、NaNO₂、KNO₃、CsNO₃、Mg(NO₃)₂、Ca(NO₃)₂、Sr(NO₃)₂、Ba(NO₃)₂、Na₂CO₃、Li₂CO₃、K₂CO₃、MgCO₃、CaCO₃、SrCO₃、BaCO₃、Cs₂CO₃、LiCl、NaCl、KCl、MgCl₂、BaCl₂、CaCl₂、SrCl₂、CsCl、ZnCl₂、MnCl₂、AlCl₃、LiF、NaF、KF、MgF₂、CaF₂、BaF₂、SrF₂、AlF₃、LiBr、NaBr、KBr、MgBr₂、CaBr₂、SrBr₂、Li₂SO₄、Na₂SO₄、K₂SO₄、MgSO₄、CaSO₄And a mixed molten salt formed from two or more thereof.

4. The method as claimed in claim 1, wherein the heat conductive filler is selected from one or more of carbon-based materials, artificial inorganic compounds and mineral materials, and the mass ratio of the heat conductive filler is 0.5-50%. Carbon-based materials such as graphite, carbon nanotubes, graphene, expanded graphite, carbon black, and the like; inorganic compounds, e.g. Al₂O₃、MgO、SiO₂、SiC、AlN、Si₃N₄BN, etc.; the mineral is selected from kaolin, diatomaceous earth, mullite, clay, expanded perlite, attapulgite, expanded vermiculite, etc.

5. The method of claim 1, wherein the carbon powder used in the intermediate layer is selected from one or more of graphite, expanded graphite, carbon fiber, carbon nanotube, and graphene.

6. The method of claim 1, wherein the organic binder is selected from one or more of sodium carboxymethyl cellulose (CMC), chitosan, starch, polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethyl methacrylate (PMMA).

7. The method as claimed in claim 1, wherein the ceramic shell powder is selected from Al₂O₃、SiO₂、MgO、Si₃N₄One or more of SiC, BN, AlN, kaolin, mullite, feldspar and clay. The grain diameter of the ceramic powder is 5nm-500 mu m.

8. The method as claimed in claim 1, wherein the organic binder solution is prepared by dissolving an organic binder in a solvent, and the mass fraction of the organic binder (the ratio of the organic binder to the total weight of the ceramic powder) is 0.5-20%.

9. The method for preparing a fused salt-based composite phase-change heat storage macro-capsule as claimed in claim 1, wherein in the step (1), the mass ratio of the fused salt/heat conductive filler mixture to the organic binder is 99.5: 0.5-50: 50; in the step (2), the mass ratio of the carbon material powder to the organic binder is 99.5: 0.5-50: 50; in the step (3), the mass ratio of the ceramic powder to the organic binder is 99.5: 0.5-50: 50.

10. The molten salt-based composite phase-change heat storage macro-capsule as claimed in claims 1 to 9, which is applied to the fields of heat storage systems, industrial waste heat recycling and solar heat storage.

Technical Field

The invention belongs to the technical field of heat storage, relates to a preparation method of a phase-change heat storage large capsule, and particularly relates to a preparation method and application of a fused salt-based composite phase-change heat storage large capsule.

Background

China is a big country for energy production and consumption, the total quantity of industrial waste heat generated along with the energy production and consumption is widely distributed every year, and in addition, the vigorous development of renewable energy sources such as solar energy and the like is also an important measure for ensuring the energy safety of China. The efficient energy storage technology is an effective means for solving the problems of low energy utilization efficiency, mismatching of energy distribution in time and space and the like at present. The heat storage technology as an efficient energy storage technology plays an important role in the fields of solar photo-thermal utilization, industrial waste heat recycling and the like.

The heat storage material may be classified into a sensible heat storage material, a thermochemical heat storage material and a latent heat storage material according to a heat storage manner. Thermochemical heat storage technology has the advantage of high heat storage density as an emerging technology, but the heat storage mode has the defects of complex system and high price, and is still in the laboratory research stage at present. Thermochemical heat storage technology is difficult to popularize at present, and latent heat storage and sensible heat storage are already applied. The latent heat storage based on the phase-change material has higher heat storage density and good stability. The fused salt is a potential medium-high temperature phase change heat storage material, and has low price and good heat storage performance. However, since molten salt has problems of low thermal conductivity, liquid leakage after high-temperature melting, corrosion of a container, and the like, and thus, it is very important to develop a technology for improving the thermal conductivity of molten salt and preventing leakage corrosion of molten salt during high-temperature melting.

Disclosure of Invention

The invention aims to provide a preparation method of a leakage-proof fused salt-based composite phase change heat storage large capsule with high heat conduction characteristic, which is characterized in that fused salt and a heat conduction filler are mixed to prepare a sphere, the fused salt is wrapped in a double-layer shell formed by a carbon middle layer and a ceramic shell through a capsule packaging technology, the fused salt can be effectively prevented from leaking during melting phase change, and the heat conduction performance of the fused salt is improved.

The invention also aims to provide the application of the large molten salt phase capsules prepared by the method in the field of high-temperature heat storage.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a preparation method of a fused salt-based composite phase-change heat storage big capsule for high-temperature heat storage application comprises the following steps:

(1) mixing the molten salt with the heat-conducting filler, stirring and mixing the mixture with an organic adhesive solution according to a certain proportion, uniformly mixing the mixture to prepare a spherical core blank, and drying the spherical core blank to prepare the molten salt/heat-conducting filler spherical core.

(2) And (2) stirring and mixing the carbon material powder and the organic binder solution according to a certain proportion, uniformly mixing, wrapping the mixture on the surface of the spherical core blank prepared in the step (1), drying, pressing by using an isostatic press to compact the blank, heating to the temperature of 300 DEG and 500 ℃ in the air or oxygen atmosphere, sintering for a plurality of hours, removing the organic binder in the sphere, and preparing the carbon shell-coated molten salt/heat-conducting filler composite sphere.

(3) Stirring and mixing ceramic powder and an organic adhesive solution according to a certain proportion, uniformly mixing, wrapping the mixture on the surface of the carbon shell coated molten salt/heat-conducting filler composite sphere prepared in the step (2) to form a layer of ceramic shell, drying, pressing by using an isostatic press and other methods, and then carrying out two-stage heat treatment on the composite sphere: 1) heating to 300-500 ℃ in air or oxygen atmosphere, pre-burning for 1-24 hours, and removing the organic binder in the spheres; 2) after pre-sintering, heating to 500-1500 ℃ in an oxygen-free environment, carrying out high-temperature heat treatment for 1-48 hours, and cooling to room temperature to obtain the fused salt-based composite phase-change heat storage large capsule.

The invention also provides a molten salt-based phase-change heat storage large capsule which is prepared by the method and contains the carbon intermediate layer and the ceramic shell, and the molten salt-based phase-change heat storage large capsule is characterized in that the diameter of the heat storage large capsule is 2.5-250mm, and the heat storage large capsule structurally comprises an external inorganic ceramic shell layer, an intermediate carbon layer and an internal molten salt/heat-conducting filler mixed core material. The diameter of the internal molten salt/heat-conducting filler mixed core material sphere is 0.5-190mm, the thickness of the intermediate carbon layer is 0.5-10mm, and the thickness of the external inorganic shell layer is 0.5-20 mm.

Preferably, the molten salt in step (1) is selected from one of hydroxide (alkali), nitrate, carbonate, chloride, fluoride, bromide and sulfate and a mixed molten salt formed by two or more of the above. I.e. LiOH, NaOH, KOH, LiNO₃、NaNO₃、NaNO₂、KNO₃、CsNO₃、Mg(NO₃)₂、Ca(NO₃)₂、Sr(NO₃)₂、Ba(NO₃)₂、Na₂CO₃、Li₂CO₃、K₂CO₃、MgCO₃、CaCO₃、SrCO₃、BaCO₃、Cs₂CO₃、LiCl、NaCl、KCl、MgCl₂、BaCl₂、CaCl₂、SrCl₂、CsCl、ZnCl₂、MnCl₂、AlCl₃、LiF、NaF、KF、MgF₂、CaF₂、BaF₂、SrF₂、AlF₃、LiBr、NaBr、KBr、MgBr₂、CaBr₂、SrBr₂、Li₂SO₄、Na₂SO₄、K₂SO₄、MgSO₄、CaSO₄And a mixed molten salt formed from two or more thereof.

Preferably, the heat conducting filler is selected from one or more of carbon-based materials, artificial inorganic compounds and mineral materials, and the adding mass ratio of the heat conducting filler is 0.5-50%. Carbon-based materials such as graphite, carbon nanotubes, graphene, expanded graphite, carbon black, and the like; inorganic compounds, e.g. Al₂O₃、MgO、SiO₂、SiC、AlN、Si₃N₄BN, etc.; the mineral is selected from kaolin, diatomaceous earth, mullite, clay, expanded perlite, attapulgite, expanded vermiculite, etc. The particle size of the heat-conducting filler is 5nm-500 mu m.

Preferably, the organic binder is selected from one or more of sodium carboxymethylcellulose (CMC), chitosan, starch, polyvinylpyrrolidone (PVP), polyvinyl butyral (PVB), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), and polymethyl methacrylate (PMMA).

Preferably, the carbon material powder for the intermediate layer is selected from one or more of graphite, expanded graphite, carbon fiber, carbon nanotube, and graphene.

Preferably, the powder raw material of the ceramic shell is selected from Al₂O₃、SiO₂、MgO、Si₃N₄One or more of SiC, BN, AlN, kaolin, mullite, feldspar and clay. The grain diameter of the ceramic powder is 5nm-500 mu m.

Preferably, in the step (1), the step (2) and the step (3), the organic binder solution is prepared by dissolving an organic binder in a corresponding solvent, and the mass fraction of the organic binder (the ratio of the organic binder to the total weight of the ceramic powder) is 0.5-20%.

Preferably, in the step (1), the mass ratio of the mixture of the molten salt and the high thermal conductive material to the organic binder is 99.5: 0.5-50: 50; in the step (2), the mass ratio of the carbon powder material to the organic adhesive is 99.5: 0.5-50: 50; in the step (3), the mass ratio of the ceramic powder to the organic binder is 99.5: 0.5-50: 50.

The invention also provides application of the double-shell-wrapped fused salt-based composite phase-change heat storage ball in a phase-change heat storage system, medium-high temperature industrial waste heat recycling and solar heat storage system.

Compared with the prior art, the invention has the following beneficial effects:

the invention prepares the fused salt-based heat storage capsule ball, encapsulates the mixed spherical core of the fused salt and the heat conducting filler in the double-layer shell formed by the carbon layer and the ceramic shell, and prepares the compound capsule heat storage material with the leakage-proof characteristic and good heat conducting property through the working procedures of drying, multi-stage sintering and the like. The heat conducting filler is added into the molten salt of the core material, so that the heat conducting performance of the molten salt can be improved, and the flowing leakage of the molten salt liquid after melting can be prevented to a certain extent. The carbon layer is wrapped outside the molten salt core material to serve as the middle layer, the molten salt liquid after melting can be prevented from leaking outwards due to the fact that surface tension between the carbon layer and the molten salt liquid is large, the inorganic ceramic shell has high stability, the capsule can be formed more easily, and the capsule ball manufactured after firing has better stability and circulation durability. The invention has the advantages of low preparation cost, green and pollution-free product and the like, and the preparation process is simple and easy to operate.

Drawings

Fig. 1 is a schematic structural diagram of a phase-change heat storage capsule ball of the present invention, in which 1 represents a ceramic shell, 2 represents a carbon layer, 3 represents heat conductive filler particles, and 4 represents molten salt.

FIG. 2(a) is a drawingNa₂CO₃+Li₂CO₃A physical diagram of a core blank of a mixture of eutectic molten salt and expanded graphite heat-conducting filler; (b) coating Na on the carbon layer₂CO₃+Li₂CO₃A physical diagram of a sphere of the eutectic molten salt/heat-conducting filler composite capsule; (c) na wrapped by ceramic shell and carbon interlayer₂CO₃+Li₂CO₃A physical diagram of a composite phase change heat storage large capsule blank of eutectic molten salt-heat conducting filler; (d) a final product object diagram of the fused salt composite phase change heat storage large capsule sintered at 600 ℃; (e) and (5) a real object diagram of the cut large capsule product.

Fig. 3 shows the capsule after repeated melting-solidification phase change cycle test.

FIG. 4 shows the composite phase change core (Na) of the macrocapsule product₂CO₃+Li₂CO₃Mixed with 10% expanded graphite) eutectic molten salt.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

The invention provides a fused salt-based composite phase change heat storage large capsule for high-temperature heat storage, as shown in figure 1, the diameter of the heat storage large capsule is 2.5-250mm, and the heat storage large capsule structurally comprises an external inorganic shell layer, an intermediate carbon layer and an internal fused salt/heat conducting filler mixed core material. The diameter of the internal molten salt/heat-conducting filler mixed core material sphere is 0.5-190mm, the thickness of the intermediate carbon layer is 0.5-10mm, and the thickness of the external inorganic shell layer is 0.5-20 mm.

Example 1: preparing spherical Na containing an expanded graphite carbon interlayer and coating a kaolin ceramic shell₂CO₃+Li₂CO₃The expanded graphite composite phase change heat storage big capsule.

(1) Using eutectic molten salt Na₂CO₃+Li₂CO₃(the mass ratio is 57:43) and high-thermal-conductivity filler expanded graphite are used as raw materials of the heat storage core and are uniformly mixed according to the mass ratio of 9: 1; completely dissolving polyvinylpyrrolidone (PVP) adhesive and absolute ethyl alcohol according to the mass ratio of 0.04: 1; according to the PVP adhesive and the core blank raw materialWeighing Na according to the mass ratio of 1:9₂CO₃+Li₂CO₃Adding the expanded graphite mixture into the binder solution, stirring, mixing, making into spherical blank with diameter of 5mm, drying at 40 deg.C for 12 hr, and making into Na₂CO₃+Li₂CO₃Expanded graphite spherical core, shown in FIG. 2 (a).

(2) Taking expanded graphite powder as a carbon powder raw material, similarly, completely dissolving a PVP (polyvinyl pyrrolidone) adhesive and absolute ethyl alcohol according to the mass ratio of 0.04:1, then weighing the expanded graphite powder according to the mass ratio of 1:9 of the adhesive to the expanded graphite powder, adding the weighed expanded graphite powder into the adhesive solution, stirring and mixing, uniformly mixing, coating the mixture on the surface of the spherical core blank prepared in the step (1) to prepare a carbon-layer-coated spherical blank with the diameter of 8mm, and drying at 40 ℃ for 12 hours to prepare a composite spherical capsule of the carbon-shell-coated molten salt/expanded graphite heat-conducting filler, wherein the material is shown in fig. 2 (b).

(3) The carbon shell coated fused salt/heat conducting filler composite sphere is used as a raw material, a rubber glove is sleeved outside a blank body, then air in the glove is dried and knotted for sealing, and then the blank body is placed in an isostatic press to be pressed for 5min under the pressure of 20 MPa. And taking out the pressed composite sphere, heating to 450 ℃ at the heating rate of 3 ℃ per minute in the air atmosphere, carrying out heat treatment for 4h, and removing the organic adhesive in the blank.

(4) Using kaolin with the particle size of 2.5um as a ceramic powder raw material, completely dissolving a sodium carboxymethylcellulose (CMC) binder and deionized water according to the mass ratio of 1:9, then weighing the kaolin powder according to the mass ratio of 1:9 of the CMC binder to the dry powder of the ceramic powder, adding the kaolin powder into the binder solution, stirring and mixing, uniformly mixing, wrapping the kaolin powder on the surface of the composite sphere prepared in the step (3) to prepare a double-shell large capsule blank with the diameter of 10mm, drying at 70 ℃ for 24h, and then pressing by using an isostatic press under 150MPa to obtain the capsule ball, wherein the real object of the obtained capsule ball is shown in figure 2 (c).

(5) Carrying out the following two heat treatment processes on the large capsule blank prepared in the step (4): 1) heating to 400 ℃ at the temperature rise rate of 10 ℃ per minute in the air atmosphere, pre-sintering for 1h, and removing the organic binder in the green body through the combustion process; 2) heating to 600 ℃ at the temperature rising rate of 10 ℃ per minute in an oxygen-free environment, and carrying out high-temperature heat treatment for 2 hours to prepare the fused salt composite phase change heat storage large capsule. As shown in FIG. 2(d), the actual form of the macrocapsule product obtained in this case was good, and there was no leakage of the molten salt of the core material. The cut macrocapsule object is shown in fig. 2(e), which shows a core sphere surrounded by an outermost ceramic shell and an intermediate carbon layer.

(6) The prepared heat storage large capsule product is subjected to repeated melting-solidification phase change heat storage circulation experiments at the temperature of 450-540 ℃, and a capsule object after 50 times of circulation is shown in figure 3. It can be seen that the capsules after the cycling experiment remained intact with no rupture or leakage. FIG. 4 shows the DSC test result of the prepared fused salt material of the capsule core material, and it can be known that the latent heat of fusion of the core material phase-change composite is 276.5J/g, and the melting temperature is 501.9 ℃. The good heat storage performance and the cycle experiment test result show that the phase-change heat storage large capsule can be used as a core heat storage material to be applied to various heat storage systems and equipment and used in the fields of industrial waste heat recycling and solar heat storage.

Example 2: preparation of graphite carbon interlayer, Al₂O₃LiF/Al coated with ceramic shell₂O₃A composite phase-change heat storage big capsule.

(1) Using molten salt LiF and heat-conducting filler Al₂O₃Uniformly mixing raw materials of a heat storage core according to a mass ratio of 99.5:0.5, completely dissolving a chitosan adhesive and deionized water according to a mass ratio of 0.5:99.5, and weighing LiF/Al according to a mass ratio of the adhesive to heat storage core powder of 0.5:99.5₂O₃Adding the mixture into the adhesive solution, stirring and mixing, uniformly mixing to prepare a spherical blank with the diameter of 0.5mm, and then drying at 80 ℃ for 1h to prepare LiF/Al₂O₃A spherical core.

(2) Taking graphite powder as a raw material of a carbon intermediate layer, completely dissolving a chitosan adhesive and deionized water according to the mass ratio of 0.5:99.5, then weighing the graphite powder according to the mass ratio of 0.5:99.5 of the adhesive to the carbon powder, adding the graphite powder into the adhesive solution, stirring and mixing, uniformly coating a layer of carbon shell on the surface of the spherical core prepared in the step (1), preparing a carbon shell-coated composite spherical blank with the diameter of 1.5mm, and drying at 40 ℃ for 12 hours. And then putting the blank into a mould for pressing, heating to 500 ℃ at a heating rate of 10 ℃ per minute in an air atmosphere, sintering for 4h, and removing the organic adhesive.

(3) Al with a particle size of 2.5um₂O₃The preparation method comprises the steps of completely dissolving a chitosan adhesive and deionized water according to the mass ratio of 0.5:99.5 as a ceramic powder raw material, weighing the ceramic powder according to the mass ratio of 0.5:99.5, adding the ceramic powder into the adhesive solution, stirring and mixing, and uniformly coating a layer of Al on the surface of the prepared carbon shell-coated composite sphere after uniform mixing₂O₃And (3) coating the shell, preparing a heat storage ball blank with the diameter of 2.5mm, and drying at 70 ℃ for 24 h.

(4) The dried capsule blank is subjected to the following two heat treatment processes: 1) heating to 300 ℃ at the temperature rise rate of 10 ℃ per minute in the air atmosphere, pre-sintering for 1h, and removing the organic adhesive in the green body; 2) and after pre-sintering, continuously heating to 900 ℃ at the heating rate of 10 ℃ per minute in the nitrogen atmosphere, and carrying out high-temperature heat treatment for 48 hours to prepare the fused salt-based composite phase-change heat storage large capsule.

Example 3: preparing a carbon fiber carbon intermediate layer and a SiC ceramic shell coated spherical KCl/diatomite phase change heat storage large capsule.

(1) The method comprises the steps of taking molten salt KCl and diatomite as high-thermal-conductivity fillers as raw materials of a heat storage core body, uniformly mixing the raw materials according to a mass ratio of 95:5, completely dissolving a PVB adhesive and deionized water according to a mass ratio of 5:95, weighing a KCl/diatomite mixture according to a ratio of the adhesive to heat storage core powder of 5:95, adding the KCl/diatomite mixture into the adhesive solution, stirring and mixing the mixture, preparing a spherical body with the diameter of 190mm after uniformly mixing, and drying the spherical body at 40 ℃ for 12 hours to prepare the KCl/diatomite spherical core.

(2) The preparation method comprises the steps of taking carbon fiber powder as a carbon interlayer raw material, completely dissolving a PVB adhesive and deionized water according to the mass ratio of 5:95, weighing the carbon fiber powder according to the mass ratio of 5:95, adding the carbon fiber powder into the adhesive solution, stirring and mixing, uniformly coating a layer of carbon shell on the surface of a prepared spherical core after uniform mixing, preparing a carbon shell-coated composite spherical blank body with the diameter of 200mm, and drying at 40 ℃ for 12 hours. The composite spherical embryo body is then pressed in an isostatic press at 50MPa for 30 min. And (3) carrying out the following heat treatment on the pressed composite ball blank: heating to 450 ℃ at the heating rate of 10 ℃ per minute in the air atmosphere, pre-sintering for 4h, and removing the organic binder in the blank.

(3) SiC with the particle size of 10 mu m is used as a ceramic powder raw material, a PVB adhesive and deionized water are completely dissolved according to the mass ratio of 5:95, then the ceramic powder is weighed according to the ratio of 5:95 of the adhesive to the ceramic powder, the ceramic powder is added into the adhesive solution, stirred and mixed, after uniform mixing, a layer of SiC shell is uniformly coated on the surface of the prepared carbon shell-coated KCl/diatomite composite sphere, a heat storage sphere blank body with the diameter of 250mm is prepared, and then the heat storage sphere blank body is dried at 70 ℃ for 24 hours.

(4) The dried large capsule blank is taken as a raw material to carry out the following two-stage heat treatment processes: 1) heating to 400 ℃ at the temperature rise rate of 10 ℃ per minute in the air atmosphere, and pre-sintering for 1 h; 2) and continuously heating to 800 ℃ at the temperature rising rate of 10 ℃ per minute under the argon atmosphere, and carrying out high-temperature heat treatment for 2 hours to prepare the fused salt-based composite phase-change heat storage large capsule.

Example 4: preparation of carbon nanotube carbon layer and mullite ceramic shell coated spherical MgSO₄Phase-change heat storage large capsule of expanded perlite

(1) In molten salt MgSO₄Uniformly mixing the raw materials with high-thermal-conductivity filler expanded perlite as a heat storage core according to the mass ratio of 50:50, completely dissolving a starch adhesive and deionized water according to the mass ratio of 20:80, and weighing MgSO (MgSO) (MgSO) according to the mass ratio of the adhesive to heat storage core powder of 50:50₄Adding the expanded perlite mixture into the adhesive solution, stirring and mixing, and preparing the mixture into the mixture with the diameter of 10 after uniform mixing0mm spherical body, then drying at 70 deg.C for 12h to make MgSO₄Expanded perlite spherical core.

(2) Taking graphite powder as a carbon interlayer raw material, completely dissolving a starch adhesive and deionized water according to the mass ratio of 20:80, weighing the graphite powder according to the adhesive-to-carbon powder ratio of 10:90, adding the graphite powder into the adhesive solution, stirring and mixing, uniformly mixing, and adding the mixture into prepared MgSO (MgSO) powder)₄The surface of the spherical core of the expanded perlite is uniformly coated with a layer of carbon shell to prepare a composite spherical embryo body coated with the carbon shell with the diameter of 110mm, and then the composite spherical embryo body is dried for 12 hours at the temperature of 40 ℃. And then putting the composite spherical blank into a mold for pressing, heating to 450 ℃ at a heating rate of 10 ℃ per minute in an air atmosphere, sintering for 4h, and removing the organic adhesive.

(3) The method comprises the steps of taking mullite with the particle size of 2.5um as a ceramic powder raw material, completely dissolving a starch adhesive and deionized water according to the mass ratio of 20:80, weighing the ceramic powder according to the adhesive-ceramic powder ratio of 50:50, adding the ceramic powder into the adhesive solution, stirring and mixing, uniformly mixing, and adding MgSO coated with a prepared carbon shell₄The surface of the expanded perlite composite ball is uniformly coated with a layer of mullite shell to prepare a heat storage ball blank with the diameter of 130mm, and then the heat storage ball blank is dried for 24 hours at 70 ℃ and then pressed by a grinding tool.

(4) Carrying out two-stage heat treatment on the dried and pressed heat storage large capsule blank: 1) heating to 400 ℃ at the temperature rise rate of 10 ℃ per minute in the air atmosphere, pre-sintering for 1h, and removing the organic binder contained in the green body through the combustion process; 2) and continuously heating to 1200 ℃ at the heating rate of 10 ℃ per minute in the nitrogen atmosphere, and carrying out high-temperature heat treatment for 12 hours to prepare the fused salt-based composite phase-change heat storage large capsule.

Example 5: preparing graphene carbon layer and SiO₂Ceramic case coated spherical Ba (NO)₃)₂Phase-change heat storage/SiC big capsule

(1) With molten salt Ba (NO)₃)₂Uniformly mixing the raw materials with high heat conduction filler SiC as a raw material of a heat storage core blank according to the mass ratio of 90:10, and adding a PAA adhesiveCompletely dissolving the powder in deionized water according to the mass ratio of 10:90, and weighing Ba (NO) according to the mass ratio of 10:90 of the adhesive to the heat storage core powder₃)₂Adding the/SiC mixture into the adhesive solution, stirring and mixing, uniformly mixing to prepare a spherical blank with the diameter of 5mm, and drying at 80 ℃ for 1h to prepare Ba (NO)₃)₂A spherical core of SiC.

(2) Taking graphene powder as a carbon interlayer raw material, completely dissolving a PAA adhesive and deionized water according to a mass ratio of 10:90, weighing the graphene powder according to a ratio of 10:90 of the adhesive to the carbon powder, adding the graphene powder into the adhesive solution, stirring and mixing, and after uniformly mixing, adding prepared Ba (NO) into the prepared Ba₃)₂Uniformly coating a layer of carbon shell on the surface of the/SiC spherical core to prepare a carbon shell-coated composite spherical blank body with the diameter of 8mm, and then drying at 40 ℃ for 12 h. And then pressing the blank in an isostatic press at 50MPa for 10min, heating to 300 ℃ at the heating rate of 10 ℃ per minute in the air atmosphere, sintering for 4h, and removing the organic binder.

(3) SiO with a particle size of 2.5um₂The preparation method comprises the steps of completely dissolving a PAA adhesive and deionized water according to a mass ratio of 10:90 for ceramic powder raw materials, weighing the ceramic powder according to a ratio of 10:90, adding the ceramic powder into the adhesive solution, stirring and mixing, and after uniform mixing, coating Ba (NO) coated with a prepared carbon shell₃)₂The surface of the/SiC composite ball is uniformly coated with a layer of SiO₂And (3) covering the shell, preparing a heat storage ball blank with the diameter of 10mm, and drying at 70 ℃ for 24 h.

(4) The dried heat storage large capsule blank is used as a raw material to carry out two-stage heat treatment processes: 1) heating to 400 ℃ at the temperature rise rate of 10 ℃ per minute in the air atmosphere, pre-sintering for 1h, and removing the organic binder contained in the green body through the combustion process; 2) and continuously heating to 500 ℃ at the heating rate of 10 ℃ per minute in the argon atmosphere, and carrying out high-temperature heat treatment for 2 hours to prepare the fused salt-based composite phase-change heat storage large capsule.