Hydrated salt thermochemical composite heat storage particle with imitated compound eye structure as well as preparation method and application of hydrated salt thermochemical composite heat storage particle
Hydrated salt thermochemical composite heat storage particles with a compound eye structure were prepared by liquid nitrogen rotary directional freezing method, which solved the problems of low adsorption capacity and poor cycle stability of existing hydrated salt thermochemical heat storage materials, achieved efficient solar energy absorption and heat storage performance, and promoted its application in the fields of solar thermal energy and industrial energy conservation.
Patent Information
- Application Number
- CN202511032168.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-25
- Publication Date
- 2025-10-10
AI Technical Summary
Existing hydrated salt thermochemical heat storage materials have disadvantages such as low adsorption capacity, poor cyclic stability, slow reaction kinetics, and weak solar energy absorption, which limit their application in solar thermal and industrial energy conservation fields.
The liquid nitrogen rotary directional freezing method is used to prepare hydrated salt thermochemical composite heat storage particles with a compound eye structure. By simulating the hierarchical porous and radial channel characteristics of insect compound eyes, a directional pore structure is constructed, combined with chemical bonding to form a stable interface, thereby improving the salt loading capacity and solar light absorption capacity.
It achieves high salt loading, excellent water absorption capacity and heat storage density, improves the cycle life and heat storage efficiency of the material, and is suitable for large-scale preparation and environmentally friendly high-performance thermochemical heat storage materials.
Smart Images
Figure CN120758233A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of hydrated salt thermo-chemical heat storage, and relates to a hydrated salt thermo-chemical heat storage composite material, a preparation method and application thereof, and the application relates to a heat storage and release process of a hydrated salt thermo-chemical heat storage fixed bed. TECHNICAL BACKGROUND
[0002] With the continuous growth of global energy demand and the promotion of the "double carbon" target, efficient energy storage technology has become a key support for energy transformation. Thermo-chemical heat storage, as a technology that realizes heat storage and release through reversible chemical reactions, has shown significant advantages in solar thermal utilization, industrial waste heat recovery, building energy saving and other fields due to its high heat storage density, long-term storage capacity and adjustable temperature range, and is regarded as one of the core directions of the next generation of energy storage technology. The essence of hydrated salt thermo-chemical heat storage is to realize heat storage and release through reversible "dehydration-hydration" chemical reactions: dehydration reaction occurs at the high temperature end (such as solar heat collection or industrial waste heat), absorbs heat and stores chemical energy; at the low temperature end (such as when heat is needed), it absorbs environmental heat or water to re-hydrate and release stored chemical energy. Compared with sensible heat storage and phase change heat storage, hydrated salt thermo-chemical heat storage materials have become a research hotspot due to their wide raw material sources, mild reaction conditions and high theoretical heat storage density. Although hydrated salt thermo-chemical heat storage has significant advantages, its actual application still faces the problems of low adsorption capacity, poor cycle stability, slow reaction kinetics and weak solar energy absorption. SUMMARY
[0003] The present application aims to provide a high-performance hydrated salt thermo-chemical composite heat storage particle with an artificial compound eye structure, and a preparation method for the hydrated salt thermo-chemical composite heat storage particle. The method can prepare a composite thermo-chemical heat storage material with high salt loading capacity, high water absorption capacity, high heat storage density and high light absorption capacity, and can improve the shortcomings of existing hydrated salt thermo-chemical heat storage materials, such as low adsorption capacity, poor cycle stability, slow reaction kinetics and weak solar energy absorption. The last purpose of the present application is to provide the application of the hydrated salt thermo-chemical composite heat storage particle with an artificial compound eye structure in the field of solar thermal or industrial energy saving.
[0004] Technical solution: The preparation method of the hydrated salt thermo-chemical composite heat storage particle with an artificial compound eye structure according to the present application is prepared by using a "liquid nitrogen rotation directional freezing method", which comprises the following steps:
[0005] (1) mixing and stirring polyimide acid powder with water, then adding triethylamine dropwise and stirring to dissolve, obtaining a polyimide acid salt aqueous solution, then slowly adding biomass starch in several portions, stirring to completely hydrate and dissolve, obtaining a viscous precursor aqueous solution;
[0006] (2) adding hydrated salt to the precursor aqueous solution, stirring to dissolve, and allowing to stand to remove bubbles to obtain a gel-like mixed solution;
[0007] (3) The gel-like mixed solution is slowly dripped into liquid nitrogen drop by drop, and the droplets are rotated and shaped on the surface of the liquid nitrogen and frozen to form spherical particles;
[0008] (4) vacuum freeze-drying the spherical particles to obtain a polyimide-based porous carbon sphere precursor;
[0009] (5) The polyimide-based porous carbon sphere precursor is first subjected to polyimide amidation at a relatively low temperature and then subjected to high-temperature carbonization to obtain hydrated salt thermochemical composite heat storage particles with a compound eye structure.
[0010] Furthermore, the liquid nitrogen rotational directional freezing method refers to a method in which liquid droplets are dropped into liquid nitrogen at room temperature. After the liquid droplets come into contact with liquid nitrogen, the liquid nitrogen evaporates rapidly due to the temperature difference. The nitrogen gas produced by the volatilization causes the droplets to suspend on the liquid nitrogen surface and rapidly rotate to form spherical particles. The ice crystals produced by the freezing grow directionally from the outside of the droplet to the inside, thereby producing a directional bionic structure.
[0011] Furthermore, in step (1), the mass ratio of polyimide acid to triethylamine is 1:(0.3-0.6), and the concentration of polyimide acid in the polyimide salt aqueous solution is 3-7wt%. The biomass starch is one or more of chitosan, xanthan gum, and guar gum. The mass ratio of the polyimide salt aqueous solution to the biomass starch is 100:(0.5-1.5); the stirring speed is 500-900 rpm, and the stirring time is 8-12 hours. In step (2), the hydrated salt is one or more of strontium chloride hexahydrate, calcium chloride hexahydrate, and magnesium chloride hexahydrate. The mass ratio of the hydrated salt to the precursor aqueous solution is less than 25:100, preferably the mass ratio of the hydrated salt to the precursor aqueous solution is (15-25):100; the stirring speed is 800-1200 rpm, the stirring time is 6-10 hours, and the solution is statically defoamed for 8-12 hours. In step (3), the precursor aqueous solution is slowly dripped into liquid nitrogen drop by drop using a syringe. The needle of the syringe is a stainless steel flat needle with a model of 18G-22G optional. The inner diameter of the needle is 0.40-0.86mm. The height of the droplet at the outlet of the syringe from the liquid nitrogen level of the insulation barrel is 20-60cm. The dripping speed is such that the droplet falling interval is greater than 1s. In step (4), the temperature of the vacuum freeze drying is below -10°C, and the time of the vacuum freeze drying is 2-3 days. In step (5), the polyimide amidation is carried out in an inert gas atmosphere by heating to 200-400°C at 3-6°C / min and keeping warm for more than 3h, and then heating to 500-700°C at 2-5°C / min and keeping warm for more than 3h for carbonization.
[0012] The application also comprises the hydrated salt thermo-chemical composite heat storage particles with the compound eye structure prepared by the preparation method.
[0013] The application of the hydrated salt thermo-chemical composite heat storage particles with the compound eye structure in the field of solar light and heat or industrial energy saving.
[0014] The application can realize mass production through only three key steps of liquid nitrogen rotating directional freezing, freeze-drying and cross-linking carbonization. The prepared porous thermo-chemical composite heat storage particles have a compound eye directional structure, which is constructed by simulating the characteristics of the hierarchical porous and radial channel of the compound eye of insects, and has a directional pore structure with a gradient distribution from outside to inside. The directional pore channel can limit the water-absorbing salt (increase the salt load), and the radial communication channel can strengthen the absorption of sunlight and the internal heat and mass transfer. Meanwhile, the particle skeleton and the hydrated salt form a stable interface through chemical bonding, effectively inhibiting the problems of phase separation and pulverization in the cycle process, and significantly improving the cycle life and heat storage efficiency of the material. The structure realizes high-quality anchoring of the water-absorbing salt, increases the salt load, and strengthens the absorption of sunlight and the internal heat and mass transfer. The application is expected to provide a new technical path for the development of high-performance thermo-chemical heat storage materials and promote their large-scale application in the fields of solar light and heat, industrial energy saving and the like.
[0015] Advantages: Compared with the prior art, the application has the following significant advantages: (1) The high-performance compound eye hydrated salt thermo-chemical composite heat storage particles prepared by the liquid nitrogen rotating directional freezing method have controllable particle size, high spheroidization rate, high salt content, highly directional and ordered pore structure, high average light absorption rate, large water absorption and large heat storage density. (2) The preparation method is simple, environment-friendly and low in energy consumption. The prepared compound eye hydrated salt thermo-chemical composite heat storage particles have high spheroidization rate, adjustable particle size, can be prepared on a large scale, and have significant advantages in resource utilization and environmental protection, in line with the concept of sustainable development. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 It is a preparation flowchart of the compound eye hydrated salt thermo-chemical composite heat storage particles.
[0017] Figure 2 It is a comparison chart of the appearance shape of the precursor after freeze-drying and the final carbonized particles of Example 1, Example 2, Example 3, Example 4 and Comparative Example 1.
[0018] Figure 3 It is an SEM diagram of the overall appearance of the compound eye hydrated salt thermo-chemical composite heat storage particles prepared in Example 3.
[0019] Figure 4SEM image of the hydrated salt thermo-chemical composite heat storage particle with the structure of compound eye prepared in Example 3 under 10 μm;
[0020] Figure 5 SEM image of the cross section of the hydrated salt thermo-chemical composite heat storage particle with the structure of compound eye prepared in Example 3 under 20 μm;
[0021] Figure 6 Water absorption performance chart of the hydrated salt thermo-chemical composite heat storage particle prepared in Example 2, Example 3, Example 4 and the pure carbon ball prepared in Comparative Example 1;
[0022] Figure 7 UV-Vis absorption performance chart of the hydrated salt thermo-chemical composite heat storage particle prepared in Example 1, Example 2, Example 3, Example 4 and the pure carbon ball prepared in Comparative Example 1;
[0023] Figure 8 DSC-TG curve of the hydrated salt thermo-chemical composite heat storage particle with the structure of compound eye prepared in Example 3;
[0024] Figure 9 Heat release performance test chart of the hydrated salt thermo-chemical composite heat storage particle with the structure of compound eye prepared in Example 3 in the adsorption process based on a laboratory scale adsorption heat pool. DETAILED DESCRIPTION
[0025] The technical solutions of the present application are further described below in combination with examples.
[0026] Example 1
[0027] (1) Polyimide acid powder and water were mixed according to the mass ratio of 5:95, and then triethylamine was added according to the mass ratio of polyimide acid powder and triethylamine of 1:0.48, and the solution was stirred and dissolved at a speed of 500 rmp for 12 h to obtain a 5% wt polyimide acid salt aqueous solution; then according to the mass ratio of polyimide acid salt aqueous solution and guar gum of 100:1, guar gum powder was slowly added to the polyimide acid salt aqueous solution in several times, and the solution was stirred at a speed of 800 rmp for 10 h to completely hydrate and dissolve, and then a viscous precursor aqueous solution was obtained;
[0028] (2) According to the mass ratio of the precursor aqueous solution and strontium chloride hexahydrate of 100:15, strontium chloride hexahydrate was added to the viscous precursor aqueous solution, and then the solution was stirred at a speed of 1000 rmp for 12 h, and then the solution was left to stand at room temperature for 12 h or more to remove bubbles, and a gel-like mixed solution was obtained;
[0029] (3) The gel-like mixed solution was slowly dropped into the cryogenic barrel containing liquid nitrogen through a stainless steel flat needle (21G, inner diameter 0.5mm) controlled by a precision injection pump, the dropping speed was controlled at 1 drop / s, the distance between the drop and the liquid nitrogen surface was 40cm, and the drop formed a spherical particle on the liquid nitrogen surface;
[0030] (4) After a period of time, the spherical particle product was separated and placed in a vacuum freeze dryer at -10℃ for 2-3 days to obtain a hydrated salt thermo-chemical composite heat storage particle precursor with an ommatidium structure;
[0031] (5) The polyimide-based porous particle precursor was placed in a tube furnace at room temperature, and heated to 300℃ at 5℃ / min under N2 atmosphere, and kept for 3h to complete the amidation of the polyimide acid, and then heated to 600℃ at 5℃ / min, and kept for 3h to complete the carbonization of the particle, and thus an ommatidium structure hydrated salt thermo-chemical composite heat storage particle was obtained. The whole preparation process is shown in Figure 1 .
[0032] Example 2
[0033] The experimental process was the same as that of Example 1, and on the basis of Example 1, the mass ratio of the precursor aqueous solution to strontium chloride hexahydrate in step (2) was 100:20, and other conditions were unchanged.
[0034] Example 3
[0035] The experimental process was the same as that of Example 1, and on the basis of Example 1, the mass ratio of the precursor aqueous solution to strontium chloride hexahydrate in step (2) was 100:25, and other conditions were unchanged.
[0036] Example 4
[0037] The experimental process was the same as that of Example 1, and on the basis of Example 1, the mass ratio of the precursor aqueous solution to strontium chloride hexahydrate in step (2) was 100:30, and other conditions were unchanged.
[0038] Comparative Example 1
[0039] The experimental process was the same as that of Example 1, and on the basis of Example 1, the mass ratio of the precursor aqueous solution to strontium chloride hexahydrate in step (2) was 100:0, i.e. no strontium chloride hexahydrate was added, and a pure carbon ball without salt was prepared, and other conditions were unchanged.
[0040] Structure characterization
[0041] The appearance and shape of the hydrated salt thermochemical composite heat storage particle precursor prepared in Example 1, Example 2, Example 3, Example 4 and Comparative Example 1 after freeze-drying in step (4) and the hydrated salt thermochemical composite heat storage particle with compound eye structure after final carbonization were compared. The results are as follows: Figure 2 .Depend on Figure 2 As can be seen, both Examples 1-3 and Comparative Example 1 successfully prepared regular, complete spherical particles. Compared with Examples 1-3, the pure carbon spheres prepared in Comparative Example 1 had smaller particle sizes. Furthermore, in Example 4, due to the excessively high mass ratio of strontium chloride hexahydrate, the prepared hydrated salt thermochemical composite heat storage particle precursor and the final carbonized composite heat storage particles exhibited cracking.
[0042] The hydrated salt thermochemical composite heat storage particles with compound eye structure prepared in Example 3 were characterized by scanning electron microscopy. Figure 3 、 4 , 5. Figure 3 It can be seen that the spherical structure of the prepared hydrated salt thermochemical composite heat storage particles with compound eye-like structure is complete and regular.
[0043] Depend on Figure 4 and 5 It can be seen that the surface of the spherical particles has a neatly and regularly arranged micro-nanopore structure, and the interior has an ordered directional pore structure, which is similar to the compound eye structure of a butterfly.
[0044] Performance Testing
[0045] The water absorption performance of the hydrated salt thermochemical composite heat storage particles with compound eye structure prepared in Example 1, Example 2, Example 3 and Comparative Example 1 was tested in the test environment of 25°C and 80% RH. The water absorption performance of the above materials was as follows: Figure 6 .
[0046] Depend on Figure 6 It can be obtained that the salt-free pure carbon balls prepared in Comparative Example 1 have a very low water absorption capacity. After adsorption for 5 hours at 25°C and 80% RH, the water absorption capacity is only 152 g / g; the water absorption capacity of the hydrated salt thermochemical composite heat storage particles with a compound eye structure prepared in Example 1, Example 2, and Example 3 under the same adsorption conditions are 1833 g / g, 1933 g / g, and 2030 g / g, respectively.
[0047] The UV-visible light absorption performance test was conducted on the hydrated salt thermochemical composite heat storage particles with compound eye structure prepared in Example 1, Example 2, Example 3, Example 4 and Comparative Example 1. Figure 7 .
[0048] Depend on Figure 7 It can be seen that the prepared particles all have a high average light absorption rate, among which the average light absorption rate of the pure carbon spheres without salt in Comparative Example 1 is the lowest.
[0049] The DSC-TG performance test was performed on the hydrated salt thermochemical composite heat storage particles with compound eye structure prepared in Example 3. Before the test, the composite heat storage particles were adsorbed in an environment of 25°C and 80% RH for 6 hours, and then the DSC-TG performance was tested. The test conditions were heating to 200°C at a heating rate of 5°C / min. The DSC-TG curve of the above material was as follows: Figure 8 .
[0050] Depend on Figure 8 It can be seen that when the temperature of the composite heat storage particles rises to 200°C, the dehydration rate of the material reaches 59.6% and the desorption heat is 1375 J / g.
[0051] A laboratory-scale adsorption heat cell was constructed based on the hydrated salt thermochemical composite heat storage particles with compound eye structure prepared in Example 3 to test the heat release performance of the hydrated salt thermochemical composite heat storage particles during the adsorption process. Experimental conditions: The composite heat storage particles were first heat treated at 150°C for 3 hours, and then adsorbed at a humidity of 80% RH. The temperature and humidity changes of the inlet and outlet gases were recorded during the adsorption process. The experimental results are shown in Figure 2. Figure 9 shown.
[0052] By Figure 9 It can be found that the hydrated salt thermochemical composite heat storage particles with compound eye-like structure have excellent heat release performance. The outlet temperature can rise to 27.2℃ within 1 hour, and the maximum temperature rise is 9.16℃.
Claims
1. A method for preparing hydrated salt thermochemical composite heat storage particles with a compound eye structure, characterized in that: The steps include: (1) Mixing polyimide acid powder with water and stirring, then adding triethylamine dropwise and stirring thoroughly to dissolve, to obtain a polyimide salt aqueous solution, then slowly adding biomass starch in portions, stirring to completely hydrate and dissolve, to obtain a viscous precursor aqueous solution; (2) adding hydrated salt to the precursor aqueous solution, stirring to dissolve, and allowing to stand to remove bubbles to obtain a gel-like mixed solution; (3) The gel-like mixed solution is slowly dripped into liquid nitrogen drop by drop, and the droplets are rotated and shaped on the surface of the liquid nitrogen and frozen to form spherical particles; (4) vacuum freeze-drying the spherical particles to obtain a polyimide-based porous carbon sphere precursor; (5) The polyimide-based porous carbon sphere precursor is first subjected to polyimide amidation at a relatively low temperature and then subjected to high-temperature carbonization to obtain hydrated salt thermochemical composite heat storage particles with a compound eye structure.
2. The preparation method according to claim 1, characterized in that In step (1), the mass ratio of polyimide acid to triethylamine is 1:(0.3-0.6), and the concentration of polyimide acid in the polyimide salt aqueous solution is 3-7 wt %.
3. The preparation method according to claim 1, characterized in that In step (1), the biomass starch is one or more of chitosan, xanthan gum, and guar gum.
4. The preparation method according to claim 1, characterized in that In step (1), the mass ratio of the polyimide salt aqueous solution to the biomass starch is 100:(0.5-1.5); the stirring speed is 500-900 rpm, and the stirring time is 8-12 hours.
5. The preparation method according to claim 1, characterized in that In step (2), the hydrated salt is one or more of strontium chloride hexahydrate, calcium chloride hexahydrate, and magnesium chloride hexahydrate.
6. The preparation method according to claim 1, characterized in that In step (2), the mass ratio of the hydrated salt to the precursor aqueous solution is less than 25:100; the stirring speed is 800-1200 rpm, the stirring time is 6-10 hours, and the static defoaming is 8-12 hours.
7. The preparation method according to claim 1, characterized in that In step (3), the precursor aqueous solution is slowly dripped into the liquid nitrogen drop by drop using a syringe. The needle of the syringe is a stainless steel flat needle with optional models of 18G-22G. The inner diameter of the needle is 0.40-0.86mm. The height of the droplet at the outlet of the syringe from the liquid nitrogen level in the insulation barrel is 20-60cm, and the dripping speed is such that the droplet falling interval is >1s.
8. The preparation method according to claim 1, characterized in that In step (4), the vacuum freeze drying temperature is below -10°C, and the vacuum freeze drying time is 2 to 3 days; in step (5), the polyimide is amidated by heating the polyimide to 200-400°C at 3-6°C / min and keeping the temperature for more than 3 hours under an inert gas atmosphere, and then heating the polyimide to 500-700°C at 2-5°C / min and keeping the temperature for more than 3 hours for carbonization.
9. Hydrated salt thermochemical composite heat storage particles with a compound eye-like structure obtained by the preparation method according to any one of claims 1 to 8.
10. Application of the hydrated salt thermochemical composite heat storage particles with compound eye-like structure as claimed in claim 9 in the field of solar thermal energy or industrial energy conservation.