Hydrate-foamy carbon composite phase change temperature control material and preparation method thereof

Abstract

The invention discloses a hydrate-foamy carbon composite phase change temperature control material and a preparation method thereof. The composite phase change temperature control material is prepared by taking hydrate as a phase change material and carbon foam as a carrier. The preparation process comprises the following steps: firstly, carrying out ultrasonic cleaning on original melamine foam to remove impurities, drying in a drying oven, and calcining in a muffle furnace; a light flexible carbon foam matrix is obtained through the processes of pre-oxidation, carbonization and the like, then the prepared foam carbon is impregnated into a hydrate aqueous solution through a vacuum impregnation method till the material is full of the hydrate aqueous solution, and therefore the green and environment-friendly composite phase change temperature control material is formed. The hydrate composite phase change temperature control material with high enthalpy value and high thermal conductivity is prepared, the preparation process is simple, the stability is good, the method for preparing the hydrate composite phase change temperature control material is provided, and the product can give full play to the advantages of energy storage and temperature control of the hydrate, can be used periodically and can be applied to the fields of refrigeration, cold chain transportation and the like.

Description

Technical Field

[0001] The present invention relates to the field of energy storage composite materials, and more specifically, to a preparation method of a hydrate-carbon foam composite phase change temperature control material. Background Art

[0002] At present, with the further growth of the population and the rapid development of modern industrial technologies, the dependence and consumption of human beings on energy are increasing sharply. The growing energy demand has become an urgent problem to be solved in society. The main current energy sources are still fossil fuels (i.e., coal, oil, and natural gas), and their proportion in energy consumption has reached 85%. Due to the exploitation and use of fossil fuels, the emissions of gases such as CO, NO2, and CO2 have increased. For the sustainable development of society, people must change the energy system dominated by fossil fuels and find low-carbon and safe sustainable energy to gradually replace fossil fuels. As a green energy source, thermal energy has a very wide range of sources and can be obtained from fields such as solar energy, geothermal energy, and industrial waste heat. However, thermal energy has the disadvantage of intermittency, with uncertain factors between supply and demand, resulting in low thermal energy utilization efficiency. Therefore, it is extremely important to solve the imbalance between energy supply and demand through thermal energy storage technology and improve the thermal energy utilization rate.

[0003] Thermal energy storage can be used to store thermochemical energy, sensible heat, latent heat, or a combination of the three. Among them, latent heat thermal energy storage is that phase change materials achieve higher thermal energy storage within a small temperature change. Phase change materials (PCMs) have inherent advantages such as large phase change latent heat, good thermal cycle stability, good chemical durability, and environmental friendliness. Especially solid-liquid PCMs have been widely studied as ideal energy storage media in thermal energy storage systems. PCMs can reversibly store and release energy in the form of latent heat, effectively reducing the imbalance between thermal energy supply and demand. However, the inherent properties of solid-liquid PCMs (including easy leakage in the molten state and low thermal conductivity during use) greatly limit their wide application in various fields.

[0004] In order to overcome the inherent problems of phase change materials, in recent years, a large number of studies on PCM encapsulation technologies have emerged to overcome these disadvantages and difficulties, and have been effectively applied in different fields. Hydrates are a type of phase change material with the advantage of large heat storage density at 0-10°C and are currently a research hotspot in the field of phase change material energy storage temperature control. The present invention provides a hydrate-carbon foam composite material and its preparation method, which not only solves the problem that the hydrate has large fluidity during the phase change process and is easy to leak and affect the container, but also provides a material with large energy storage capacity and good thermal conductivity in the temperature range of 0-10°C. Summary of the Invention

[0005] The primary objective of the present invention is to provide a hydrate-carbon foam composite material with high enthalpy value and high thermal conductivity, which can be used to prepare various types of hydrate energy storage and temperature control materials. The technical solution adopted for the composite material is as follows:

[0006] A hydrate-foam carbon composite phase change temperature control material and its preparation method, characterized by including the following steps:

[0007] (1) Synthesize hydrates, prepare an aqueous solution of hydrates, and then form hydrates. The hydrates are tetrahydrofuran hydrate, tetrabutylammonium bromide hydrate, and tetrabutylammonium chloride hydrate. Among them, the mass ratio of the tetrahydrofuran aqueous solution is 15%-40%, and the preferred range is 15%-20%; the mass ratio of tetrabutylammonium bromide and tetrabutylammonium chloride is about 15%-40%, and the preferred range is 35%-40%.

[0008] (2) Prepare carbon foam. After the melamine foam is subjected to stepwise heating and annealing treatment, take it out and soak it in concentrated sulfuric acid, then wash it with deionized water until neutral, and obtain carbon foam after drying treatment;

[0009] (3) Prepare a hydrate-foam carbon composite phase change temperature control material by impregnating the carbon foam into a vial containing an aqueous solution of hydrates.

[0010] Further, for the hydrate solution in step (1), it is characterized in that: in step (1), the hydrates are tetrahydrofuran hydrate, tetrabutylammonium bromide hydrate, and tetrabutylammonium chloride hydrate.

[0011] Further, for the preparation of the aqueous solution of hydrates in step (1), it is characterized in that: in step (1), the prepared aqueous solution of hydrates needs to be magnetically stirred for 5-10 min.

[0012] Further, for the synthesis of hydrates in step (1), it is characterized in that: in step (1), the circulating water bath temperature required for the synthesis of hydrates is 0-4°C.

[0013] Further, for the preparation of carbon foam in step (2), it is characterized in that: the stepwise heating and annealing treatment process of the melamine foam in step (2) is: rising from room temperature to 120-180°C, holding for 20-60 min; then rising to 350-450°C, holding for 20-60 min; finally rising to 800-900°C, holding for 1-2 h, and then annealing to 300-500°C, holding for 1-2 h.

[0014] Further, for the hydrate-carbon foam composite phase change material in step (3), it is characterized in that: in step (3), the sealed vial needs to be stored in a water bath at 6-12°C for 1-2 hours.

[0015] Further, the hydrate-carbon foam composite phase change material described in step (3) is characterized in that: for the composite material in step (3), the impregnated foam is filtered out through a Buchner funnel, transferred onto a polytetrafluoroethylene sheet, and then frozen in a refrigerator at -15 to -20 °C.

[0016] Compared with the existing technologies, the beneficial effects of the present invention are as follows:

[0017] (1) The present invention uses hydrates as phase change materials and carbon foam as carriers. Compared with organic composite phase change materials, it not only has a high enthalpy value but also higher thermal conductivity, which can ensure a relatively high thermal conductivity coefficient. It has good repeatability, can be reused, and has good prospects and application value.

[0018] (2) The preparation method has a simple process and is easy to operate. Moreover, the raw materials are easily available, the cost is low, and the requirements for equipment are low.

[0019] The present invention prepares a hydrate composite phase change temperature control material with a high enthalpy value and high thermal conductivity. The preparation process is simple and has good stability. A method for preparing a hydrate composite phase change temperature control material is provided. The product can give full play to the advantages of hydrate energy storage and temperature control, and can be used cyclically. It can be applied to fields such as refrigeration and cold chain transportation. Description of the Drawings

[0020] Figure 1 Differential scanning calorimetry curve of tetrahydrofuran hydrate-carbon foam composite phase change material;

[0021] Figure 2 Tetrahydrofuran hydrate-carbon foam composite diagram. Detailed Embodiments

[0022] The embodiments of the present invention will be described in detail below, taking tetrahydrofuran hydrate as an example. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0023] Example 1

[0024] (1) Synthesize hydrate: Weigh 4 g of tetrahydrofuran solution and 16.9864 g of water and add them into a screw-cap glass bottle. Then place it on a magnetic stirrer and stir for 2 min. Turn on the circulating water bath, set the water bath temperature to 1 °C, and place the sample in the circulating water bath for 4 h until its crystallization forms hydrate.

[0025] (2) Prepare carbon foam. After the melamine foam is subjected to stepwise heating and annealing treatment, the specific process is as follows: Heat from room temperature to 180 °C, keep warm for 60 min; then rise to 400 °C, keep warm for 60 min; finally rise to 900 °C, keep warm for 1 h, and then anneal to 400 °C, keep warm for 1 h.

[0026] Take it out and soak it in concentrated sulfuric acid with a mass concentration of 98% for 2 h, then wash it with deionized water until neutral, and obtain carbon foam after drying treatment;

[0027] (3) Take out the prepared tetrahydrofuran hydrate, put it into a sealed vial, and then melt it in a circulating water bath. The water bath temperature is 10 °C. Immerse the carbon foam in the melted tetrahydrofuran hydrate solution for 2 h, then filter out the impregnated foam through a funnel, transfer it to a polytetrafluoroethylene sheet, and then freeze it in a refrigerator at -17 °C. Obtain a tetrahydrofuran hydrate-carbon foam composite phase change material, whose phase change enthalpy value is 187 J / g, the phase change temperature is 1.52 °C, and the differential scanning calorimetry curve is as Figure 1 shown.

[0028] Example 2

[0029] (1) Synthesize hydrate: Weigh 4 g of tetrahydrofuran solution and 10.2857 g of water and add them to a screw-cap glass bottle, then place it on a magnetic stirrer and stir for 2 min. Turn on the circulating water bath, set the water bath temperature to 1 °C, place the sample in the circulating water bath for 4 h, and wait for it to crystallize to form hydrate.

[0030] (2) Prepare carbon foam. After gradually heating and annealing the melamine foam, the specific process is as follows: Raise the temperature from room temperature to 180 °C and keep it warm for 60 min; then raise the temperature to 400 °C and keep it warm for 60 min; finally raise the temperature to 900 °C and keep it warm for 1 h, and then anneal to 400 °C and keep it warm for 1 h.

[0031] Take it out and soak it in concentrated sulfuric acid with a mass concentration of 98% for 2 h, then wash it with deionized water until neutral, and obtain carbon foam after drying treatment;

[0032] (3) Take out the prepared tetrahydrofuran hydrate, put it into a sealed vial, and then melt it in a circulating water bath. The water bath temperature is 10 °C. Immerse the carbon foam in the melted tetrahydrofuran hydrate solution for 2 h, then filter out the impregnated foam through a funnel, transfer it to a polytetrafluoroethylene sheet, and then freeze it in a refrigerator at -17 °C. Obtain a tetrahydrofuran hydrate-carbon foam composite phase change material, whose phase change enthalpy value is 209.65, and the phase change temperature is 2.61 °C.

[0033] Example 3

[0034] (1) Synthesize hydrate: Weigh 4 g of tetrahydrofuran solution and 8.1212 g of water and add them to a screw-cap glass bottle, then place it on a magnetic stirrer and stir for 2 min. Turn on the circulating water bath, set the water bath temperature to 1 °C, place the sample in the circulating water bath for 4 h, and wait for it to crystallize to form hydrate.

[0035] (2) Prepare carbon foam. After gradually heating and annealing the melamine foam, the specific process is as follows: heat from room temperature to 180 °C and keep the temperature for 60 min; then heat to 400 °C and keep the temperature for 60 min; finally heat to 900 °C and keep the temperature for 1 h, and then anneal to 400 °C and keep the temperature for 1 h.

[0036] Take it out and soak it in concentrated sulfuric acid with a mass concentration of 98% for 2 h, then wash it with deionized water until neutral, and obtain carbon foam after drying treatment;

[0037] (3) Take out the prepared tetrahydrofuran hydrate and put it into a sealed vial, then place it in a circulating water bath to melt. The water bath temperature is 10 °C. Immerse the carbon foam in the melted tetrahydrofuran hydrate solution for 2 h, then filter out the immersed foam through a funnel, transfer it to a polytetrafluoroethylene sheet, and then freeze it in a refrigerator at -17 °C. Obtain a tetrahydrofuran hydrate-carbon foam composite phase change material with a phase change enthalpy value of 176.35 J / g and a phase change temperature of 0.39 °C.

[0038] The phase change temperature of the tetrahydrofuran hydrate-carbon foam composite phase change materials prepared in Examples 1-3 of the present invention is 0.39-2.61 °C, and the phase change enthalpy value is 176.35-209.65 J / g. This shows that the present invention: a tetrahydrofuran hydrate-carbon foam composite phase change material provides a material with a large energy storage capacity and good thermal conductivity in the temperature range of 0-10 °C.

Claims

1. A hydrate-foamed carbon composite phase change temperature control material, characterized in that The composite phase change material is composed of a hydrate and carbon foam; the mass ratio of carbon foam in the material is 0.5%-1%, and the rest is hydrate.

2. The material according to claim 1, characterized in that: The hydrate is one or more of tetrahydrofuran hydrate, tetrabutylammonium bromide hydrate, and tetrabutylammonium chloride hydrate.

3. A preparation method of the material according to any one of claims 1-2, characterized in that: (1) Preparation of hydrate: Place one or more of tetrahydrofuran, tetrabutylammonium bromide, and tetrabutylammonium chloride in water to prepare an aqueous solution with a mass concentration of 15%-40%. Form hydrates at a temperature of 0-4°C. (2) Preparation of carbon foam: After gradually heating and annealing melamine foam (also known as melamine foam), Take it out and soak it in concentrated sulfuric acid with a mass concentration of 95%-98% for 1-2 h, then wash it with deionized water until neutral, and obtain carbon foam after drying treatment. The process of gradually heating and annealing the melamine foam is as follows: heat from room temperature to 120-180°C and keep it warm for 20-60 min; then heat to 350-450°C and keep it warm for 20-60 min; finally heat to 800-900°C and keep it warm for 1-2 h; then anneal to 300-500°C and keep it warm for 1-2 h. (3) Preparation of hydrate-foamed carbon composite phase change temperature control material: Immerse the carbon foam in a sealed container containing an aqueous solution of hydrate.

4. The preparation method according to claim 3, characterized in that: In the step (1), the process of preparing the aqueous solution needs to be magnetically stirred for 1-10 min; the mass concentration of tetrahydrofuran in the aqueous solution is preferably 15%-20%; the mass concentration of tetrabutylammonium bromide and / or tetrabutylammonium chloride in the aqueous solution is preferably 35%-40%.

5. The preparation method according to claim 3, characterized in that: In the step (3), the sealed container needs to be stored in a water bath at 6-12°C for 1-2 hours.

6. The preparation method according to claim 1, characterized in that: In the step (3), for the composite material: the impregnated foam is filtered out through a funnel, transferred to a polytetrafluoroethylene sheet, and then frozen in a refrigerator at -15--20°C.

7. A hydrate-carbon foam composite material prepared by the preparation method according to any one of claims 2-6, wherein the hydrate-foamed carbon composite phase change temperature control material uses hydrate as the phase change material and carbon foam as the carrier to prepare a composite phase change temperature control material; The composite material includes tetrahydrofuran aqueous solution, tetrabutylammonium bromide and tetrabutylammonium chloride, and carbon foam as the support, having excellent high enthalpy value and high thermal conductivity.

8. A hydrate-carbon foam composite material prepared by the preparation method according to claim 1 or 7 or any one of claims 2-6 can be used as a phase change temperature control material in the field of refrigeration or cold chain transportation.

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