Sunflower seed husk biochar / stearic acid composite phase change material and preparation method thereof
By combining sunflower seed shell biochar with stearic acid, a fixed composite phase change material was prepared, which solved the problems of low thermal conductivity of existing phase change materials and easy leakage during phase change processes, and achieved efficient heat storage and simplified process effects.
Patent Information
- Application Number
- CN202411833596.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-05-06
AI Technical Summary
The existing phase change materials have low thermal conductivity and easy leakage in the phase change process. The method of preparing composite phase change materials uses a large number of chemical reagents and cumbersome processes, resulting in low loading.
Sunflower seed shell biochar is used as the support material and stearic acid as the phase change energy storage material. Biochar is obtained by pyrolysis and composited with stearic acid, and is pressed by magnetic stirring and hydraulic press to prepare a fixed composite phase change material.
The thermal conductivity and heat storage performance of phase change materials are improved, the leakage and deformation of the phase change process is avoided, the preparation process is simplified, and the cost is reduced.
Smart Images
Figure CN119931606A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of phase change energy storage materials, and in particular to a sunflower seed shell biochar / stearic acid composite phase change material and a preparation method thereof. Background Art
[0002] Phase change energy storage materials store and release energy through the phase change process, which can effectively solve the contradiction of energy supply and demand mismatch in time and space, improve energy utilization efficiency, and are energy-saving and environmentally friendly materials. There are many types of phase change materials, among which solid-liquid phase change materials have always attracted widespread attention due to their superior properties such as high energy storage density, uniform melting, less supercooling, stable chemical properties, constant phase change temperature and low price. They have great application prospects in energy-saving fields such as building refrigeration and solar energy. However, common phase change materials such as paraffin and palmitic acid have disadvantages such as low thermal conductivity and easy leakage during the phase change process, which limits their practical application in thermal energy storage. Many researchers combine phase change materials with carriers with porous structures, such as activated carbon, SiO2, kaolin, fly ash, diatomaceous earth, etc., and absorb phase change materials into micropores through capillary force to prepare shape-stable composite phase change materials (CPCMs). This method not only improves the heat storage capacity of phase change materials but also effectively prevents leakage of materials. However, materials such as activated carbon, SiO2 and kaolin not only have complicated preparation processes, but also cause certain pollution to the environment, thus reducing their application potential.
[0003] Since some mineral-based materials such as fly ash and diatomaceous earth have low thermal conductivity, fillers such as expanded graphite, carbon nanotubes, and metal foams can be added to increase their thermal conductivity during the preparation of composite phase change materials. However, carbon nanofibers, graphene, and metal foams are expensive, have complex preparation processes, and produce toxic substances, which greatly hinders their large-scale application in industrial production. Therefore, it is still a huge challenge to prepare high thermal conductivity support materials using low-cost and easily available materials.
[0004] Biochar is a porous material with rich pore structure processed from agricultural byproducts and renewable plant resources. Its advantages are renewable, low cost and wide source. Making waste biomass into biochar can turn waste into treasure, and its developed pore structure helps to shape solid-liquid phase change materials. At present, many researchers have used biochar as a thermal conductive additive and supporting skeleton for phase change materials, but some are limited to enhancing the thermal conductivity of CPCMs and cannot solve the leakage problem of phase change materials. In the process of preparing some composite phase change materials, a large amount of chemical reagents are added, and the process flow is cumbersome.
[0005] Based on the current status of phase change heat storage technology, it is necessary to provide a composite phase change heat storage material with a simple preparation process and environmental protection, while expanding the application temperature range of biochar-based composite phase change materials and improving their heat storage performance, ensuring that the phase change process does not leak or deform. Summary of the invention
[0006] In order to solve the problems in the prior art of low thermal conductivity of phase change materials, leakage during phase change, the use of a large amount of chemical reagents in the method for preparing composite phase change materials, complicated preparation process and low loading amount of phase change materials, the present invention provides a sunflower seed shell biochar / stearic acid composite phase change material and a preparation method.
[0007] The present invention is implemented by the following technical solutions:
[0008] A sunflower seed shell biochar / stearic acid composite phase change material uses sunflower seed shell biochar as its supporting material and stearic acid as its phase change energy storage material, the mass percentage of biochar is 15-25%, and the mass percentage of phase change energy storage material is 75-85%.
[0009] The sunflower seed shell biochar / stearic acid composite phase change material preferably has the mass percentages of sunflower seed shell biochar being 15wt%, 20wt% and 25wt%, respectively, and the mass percentages of stearic acid being 85%, 80% and 75%, respectively.
[0010] The method for preparing a sunflower seed shell biochar / stearic acid composite phase change material is as follows: Figure 1 As shown, the steps are as follows:
[0011] (1) After washing, drying, crushing, and sieving through a 60-80 mesh sieve, the sunflower seed shells are placed in a pyrolysis furnace, heated to 600-1000° C. at a heating rate of 2-10° C. / min and kept at this temperature for 1-2 hours to obtain sunflower seed shell biochar;
[0012] (2) placing the biochar in a completely melted stearic acid phase change material and stirring it thoroughly with a magnetic heating stirrer;
[0013] (3) pouring the mixture into a silicone mold to cool, and then grinding it thoroughly in a grinding mortar;
[0014] (4) Finally, the ground mixture is pressed into shape using a hydraulic press at a pressure of 6 to 12 MPa to obtain a shaped composite phase change material.
[0015] The beneficial positive effects of the present invention are:
[0016] 1. The present invention provides a method for preparing a sunflower seed shell biochar / stearic acid composite phase change material, wherein the biochar obtained by pyrolysis has a plurality of active functional groups on its surface, such as Figure 2 shown.
[0017] 2. The present invention provides a method for preparing a sunflower seed shell biochar / stearic acid composite phase change material, wherein the biochar obtained by pyrolysis has an irregular three-dimensional porous structure, such as Figure 3 As shown, the structure provides a large amount of adsorption space for the phase change material, thereby increasing the loading rate of the phase change material.
[0018] 3. The present invention provides a method for preparing a sunflower seed shell biochar / stearic acid composite phase change material, wherein the biochar obtained by pyrolysis has a graphitized two-dimensional sheet structure, such as Figure 4 As shown, the thermal conductivity of the phase change process increases significantly.
[0019] 4. The present invention provides a method for preparing a sunflower seed shell biochar / stearic acid composite phase change material, and the obtained composite phase change material has good shape stability and high phase change latent heat. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 This is a flow chart for preparing a sunflower seed shell biochar / stearic acid composite phase change material according to the present invention; Figure 2 This is the FTIR spectrum of sunflower seed shell biochar; Figure 3 This is the SEM image of sunflower seed shell biochar; Figure 4 This is the TEM image of sunflower seed shell biochar; Figure 5 The appearance diagram of the shaped composite phase change material before and after the solid-liquid phase change of Example 1-3; Figure 6 The appearance diagrams of stearic acid in comparative example 1 and shaped composite phase change materials in comparative examples 2-3 before and after solid-liquid phase change; Figure 7 The appearance of the shaped composite phase change material of Example 1-3 before and after 200 thermal cycles; Figure 8 This is a curve diagram of the DSC test of the shaped composite phase change material in Example 1; Fig. 9 It is a curve chart of DSC test of the shaped composite phase change material in Example 2; Fig.10 This is a curve diagram of the DSC test of the shaped composite phase change material of Example 3; DETAILED DESCRIPTION
[0021] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.
[0022] Embodiment 1
[0023] In this embodiment, the preparation method of the sunflower seed shell biochar / stearic acid composite phase change material is as follows:
[0024] (1) After the sunflower seed shells were washed, dried, crushed, and sieved through a 60-mesh sieve, they were placed in a pyrolysis furnace, heated to 600° C. at a heating rate of 2° C. / min and kept at this temperature for 1 hour to obtain sunflower seed shell biochar;
[0025] (2) placing 15 g of the above biochar into 85 g of completely melted stearic acid phase change material and stirring thoroughly with a magnetic heating stirrer;
[0026] (3) pouring the mixture into a silicone mold to cool, and then grinding it thoroughly in a grinding mortar;
[0027] (4) Finally, the ground mixture is pressed into shape using a hydraulic press at a pressure of 6 MPa to obtain a shaped composite phase change material.
[0028] Embodiment 2
[0029] In this embodiment, the preparation method of the sunflower seed shell biochar / stearic acid composite phase change material is as follows:
[0030] (1) After washing, drying, crushing, and sieving through a 60-mesh sieve, the sunflower seed shells were placed in a pyrolysis furnace, heated to 800° C. at a heating rate of 6° C. / min and kept at this temperature for 1 hour to obtain sunflower seed shell biochar;
[0031] (2) placing 20 g of the above biochar into 80 g of completely melted stearic acid phase change material and stirring thoroughly with a magnetic heating stirrer;
[0032] (3) pouring the mixture into a silicone mold to cool, and then grinding it thoroughly in a grinding mortar;
[0033] (4) Finally, the ground mixture is pressed into shape using a hydraulic press at a pressure of 8 MPa to obtain a shaped composite phase change material.
[0034] Embodiment 3
[0035] In this embodiment, the preparation method of the sunflower seed shell biochar / stearic acid composite phase change material is as follows:
[0036] (1) After washing, drying, crushing, and sieving through an 80-mesh sieve, the sunflower seed shells were placed in a pyrolysis furnace, heated to 1000° C. at a heating rate of 10° C. / min and kept at this temperature for 2 hours to obtain sunflower seed shell biochar;
[0037] (2) placing 25 g of the above biochar into 75 g of completely melted stearic acid phase change material and stirring thoroughly with a magnetic heating stirrer;
[0038] (3) pouring the mixture into a silicone mold to cool, and then grinding it thoroughly in a grinding mortar;
[0039] (4) Finally, the ground mixture is pressed into shape using a hydraulic press at a pressure of 12 MPa to obtain a shaped composite phase change material.
[0040] Comparative Example 1
[0041] 20g of stearic acid, without adding sunflower seed shell biochar, was pressed into shape using a hydraulic press at a pressure of 6MPa to obtain a shaped phase change material.
[0042] Comparative Example 2
[0043] In this comparative example, the preparation method of the sunflower seed shell biochar / stearic acid composite phase change material is as follows:
[0044] (1) After washing, drying, crushing, and sieving through a 60-mesh sieve, the sunflower seed shells were placed in a pyrolysis furnace, heated to 800° C. at a heating rate of 6° C. / min and kept at this temperature for 1 hour to obtain sunflower seed shell biochar;
[0045] (2) placing 5 g of the above biochar into 95 g of completely melted stearic acid phase change material and stirring thoroughly with a magnetic heating stirrer;
[0046] (3) pouring the mixture into a silicone mold to cool, and then grinding it thoroughly in a grinding mortar;
[0047] (4) Finally, the ground mixture is pressed into shape using a hydraulic press at a pressure of 8 MPa to obtain a shaped composite phase change material.
[0048] Comparative Example 3
[0049] In this comparative example, the preparation method of the sunflower seed shell biochar / stearic acid composite phase change material is as follows:
[0050] (1) After washing, drying, crushing, and sieving through an 80-mesh sieve, the sunflower seed shells were placed in a pyrolysis furnace, heated to 1000° C. at a heating rate of 10° C. / min and kept at this temperature for 2 hours to obtain sunflower seed shell biochar;
[0051] (2) placing 10 g of the above biochar into 90 g of completely melted stearic acid phase change material and stirring thoroughly with a magnetic heating stirrer;
[0052] (3) pouring the mixture into a silicone mold to cool, and then grinding it thoroughly in a grinding mortar;
[0053] (4) Finally, the ground mixture is pressed into shape using a hydraulic press at a pressure of 12 MPa to obtain a shaped composite phase change material.
[0054] The heat leakage performance test of the shaped composite phase change material obtained in Examples 1-3 was carried out. The results are as follows: Figure 5 After being heated to a solid-liquid phase transition, it exhibits good packaging performance, with no deformation or leakage.
[0055] The heat leakage performance test was conducted on the stearic acid in Comparative Example 1 and the shaped composite phase change materials in Comparative Examples 2-3. The results are as follows: Figure 6 As shown. After being heated to the solid-liquid phase transition, they all deformed and leaked.
[0056] The shaped composite phase change materials obtained in Examples 1-3 were subjected to 200 heating-cooling cycles (each cycle was heated to 80° C. and then cooled to room temperature). The results are as follows: Figure 7 As shown. After 200 thermal cycles, the composite phase change thermal storage material did not deform or crack, showing excellent structural stability.
[0057] The shaped composite phase change materials obtained in Examples 1-3 were subjected to DSC testing, and the results were as follows: Figure 8-10 shown.
[0058] Various performance tests were performed on the shaped composite phase change materials obtained in Examples 1-3 and the samples in Comparative Examples 1-3.
[0059] Compared with Comparative Example 1 (pure stearic acid), the latent heat of phase change of Examples 1-3 is reduced by 16.02%, 21.65% and 25.66%, respectively, and is only 1.2%, 2.07% and 0.88% lower than the corresponding theoretical values. Compared with Comparative Example 1, the thermal conductivity of Examples 1-3 is increased by 217.78%, 255.35% and 287.22%, respectively, wherein the thermal conductivity of Example 3 is 3.87 times that of pure stearic acid. After 200 cycles, the latent heat loss of phase change of Examples 1-3 is 6.93%, 5.48% and 7.19%, respectively, having excellent thermal cycling performance.
[0060] Comparative Example 1-3 has a higher latent heat of phase change than Example 1-3, but a lower thermal conductivity and poorer support for stearic acid. Figure 6 shown.
[0061] The above implementation modes are only used to illustrate the present invention and are not limited to the technical solutions described in the present invention. However, the present invention is not limited to the above specific implementation modes. Any modification or equivalent replacement of the present invention and any device and solution similar to the basic principle of the present invention are within the protection scope of the present invention.
Claims
1. A sunflower seed shell biochar / stearic acid composite phase change material, characterized in that: Sunflower seed shell biochar is used as its supporting material and stearic acid is used as its phase change energy storage material. The mass percentage of biochar is 15~25%, and the mass percentage of phase change energy storage material is 75~85%.
2. The method for preparing a sunflower seed shell biochar / stearic acid composite phase change material according to claim 1, characterized in that: Preferably, the mass percentages of sunflower seed shell biochar are 15wt%, 20wt% and 25wt%, respectively, and the mass percentages of stearic acid are 85%, 80% and 75%, respectively.
3. The method for preparing a sunflower seed shell biochar / stearic acid composite phase change material according to claim 1, characterized in that: The steps include: (1) After washing, drying, crushing, and sieving through a 60-80 mesh sieve, the sunflower seed shells were placed in a pyrolysis furnace, heated to 600-1000°C at a heating rate of 2-10°C / min and kept at this temperature for 1-2 hours to obtain sunflower seed shell biochar; (2) placing the above biochar in a completely melted stearic acid phase change material and stirring it thoroughly with a magnetic heating stirrer; (3) Pour the above mixture into a silicone mold and cool it, then put it into a grinding mortar and grind it thoroughly; (4) Finally, the ground mixture is pressed into shape using a hydraulic press at a pressure of 6 to 12 MPa to obtain a shaped composite phase change material.