CN106867466B - Method for synthesizing inorganic phase change energy storage material by using fly ash and hydrated inorganic salt - Google Patents
Method for synthesizing inorganic phase change energy storage material by using fly ash and hydrated inorganic salt Download PDFInfo
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Abstract
A method for synthesizing an inorganic phase change energy storage material by utilizing fly ash and hydrated inorganic salt belongs to the technical field of synthesis of inorganic non-metallic materials, and the composition of the fly ash and a composite phase change material is characterized by 30-40% of the fly ash and 60-70% of the composite phase change material by mass percent. The composite phase change material comprises 49-58% of sodium sulfate decahydrate, 21-36% of sodium hydrogen phosphate dodecahydrate, 3-4% of borax and 11-18% of water. First, sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax are prepared into saturated solution, and then the porous property of the fly ash is utilized for adsorption, so that the composite phase change material capable of adjusting room temperature is prepared. The invention has the advantages that: the raw materials completely belong to inorganic materials, the source is wide, and the cost is low; the solid waste fly ash is utilized, and the problem of combination with building materials is not worried about; the synthesis method is simple, the phase transition temperature is in the room temperature range, and the indoor temperature is convenient to adjust; the composite phase change heat storage material is not layered, the supercooling degree is relieved, the performance is stable, the repeatability is good, the service life is prolonged, and the composite phase change heat storage material can be better applied to actual building energy-saving engineering.
Description
Technical Field
The invention relates to the technical field of synthesis of inorganic nonmetallic materials, in particular to a method for synthesizing an inorganic composite energy storage phase change material by using solid waste (fly ash), sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax as raw materials.
Background
In recent years, as the problem of energy shortage has become more remarkable, countries have been working on the development of renewable energy sources and the recovery of waste heat, such as the utilization of solar energy, wind energy, geothermal energy, and the like. The heat storage technology (Thermal energy storage) can be used for solving the contradiction that the energy supply and demand are not matched in time and space, is an effective means for improving the energy utilization efficiency and protecting the environment, has wide application prospect in the fields of solar energy utilization, peak load shifting of electric power, recycling of waste heat and waste heat, energy conservation of heating and air conditioning of industrial and civil buildings and the like, and has become a research hotspot in the world. Phase Change Materials (PCMs) have great potential as core materials of phase change energy storage technology in terms of solar energy storage and waste heat utilization, etc., PCM can store more heat per unit volume than general storage materials such as water or rock, etc., and another key advantage is that PCM heat storage and recovery occur isothermally, which makes them very suitable for space heating or cooling.
The current methods for bonding PCMs materials to building materials mainly include direct incorporation, impregnation, encapsulation, and sizing of phase change materials, etc. The direct incorporation and impregnation are to combine the phase change material and the building material directly, although relatively simple, there are problems of leakage and material incompatibility. The encapsulation is divided into macro encapsulation and micro encapsulation, wherein macro encapsulation refers to encapsulating the phase change material into a specific container (such as a tubular container, a spherical container and a plate container), and micro encapsulation (microcapsule technology) refers to encapsulating the phase change material into a micro high molecular polymer and then mixing the micro high molecular polymer into the building material.
The fixed phase change material is formed by dispersing the phase change material in another support material (such as high-density polyethylene, styrene butadiene rubber and the like) to form a composite material. Because such composite materials generally have a large heat capacity, a suitable thermal conductivity, a good fixed phase change material, and a good thermal cycle stability, attention is getting higher and higher. In addition, the adoption of inorganic porous materials for adsorbing phase change materials is also a shaping packaging technology which is widely researched at present, and the porous materials which are applied at present are as follows: expanded perlite, expanded graphite, sepiolite, montmorillonite, ceramic, and the like. The fly ash is a typical solid waste, and is an ideal choice for adsorbing the phase change material for building energy conservation due to the large specific surface area and the porous property of the fly ash and the good binding capacity of the fly ash and cement.
At present, most of the researches on the shaped phase-change materials at home and abroad mainly focus on organic phase-change materials, which belong to organic-organic types (most of microcapsule technologies, melamine formaldehyde resin-n-dodecanol, polyurea-butyl stearate and the like) or inorganic-organic types (most of shaped phase-change materials, partial microcapsule technologies, kaolin-paraffin, diatomite-polyethylene glycol, expanded graphite-palmitic acid and the like). The inorganic phase change material, especially the inorganic hydrated salt, has the advantages of large heat density, high heat conductivity coefficient, low cost and the like compared with the organic phase change material, and although the supercooling and phase separation problems restrict the development of the inorganic phase change material, researches show that the phase separation problem after micropore adsorption can be solved, and the supercooling degree can be relieved to a certain extent. Therefore, in recent years, more and more researches are made on the shaping and packaging of inorganic phase change materials, and at present, the adsorption of expanded graphite on the inorganic phase change materials is mostly researched, but the expanded graphite is higher in cost, energy is consumed for self pretreatment, particularly, the compression strength of building materials is reduced due to the combination of the expanded graphite and cement and the like, compared with the expanded graphite, although the specific surface area of fly ash is relatively small, the fly ash is solid waste, the cost of an adsorbent can be greatly reduced by utilizing the adsorption of the fly ash, the solid waste is eliminated, the key point is that the components of the fly ash and the cement are very close, and part of the fly ash can be added in the cement production, so the problem of incompatibility of the materials is not considered, the synthesis method is simple, and the pretreatment is not needed. The phase change energy storage material is completely synthesized by inorganic materials, belongs to inorganic-inorganic composite phase change materials, and has the advantages of high energy density, low cost, high safety coefficient and the like compared with other organic-organic and organic-inorganic phase change energy storage materials; the solid waste fly ash is used as an adsorption carrier, and the phase change is also completed at room temperature, so that the method has a wide development prospect in the field of building energy storage.
Disclosure of Invention
The invention aims to provide a method for synthesizing an inorganic composite energy storage phase change material by using fly ash, sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax as raw materials. All raw materials for synthesis are inorganic materials, wherein the fly ash belongs to solid waste. The invention only adopts a simple mixed adsorption method, and the phase change occurs at room temperature, and all the performances reach the expected targets, so the invention can be used for adjusting the indoor temperature, has wide application prospect in the field of building energy conservation in the future, and has higher economic value and environmental significance.
The invention discloses a method for synthesizing an inorganic phase change energy storage material by utilizing fly ash and hydrated inorganic salt, which is characterized in that the fly ash, sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax are used as raw materials, and the synthesis method comprises the following steps:
(1) preparing raw materials: drying the fly ash in a 60 ℃ oven for 10-15 hours, selecting two inorganic hydrated salts of sodium sulfate decahydrate and sodium hydrogen phosphate dodecahydrate as phase change materials, and selecting borax as a nucleating agent;
(2) preparing an inorganic composite phase-change material: controlling the mass ratio of sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax, mixing 49-58% of sodium sulfate decahydrate, 21-36% of sodium hydrogen phosphate dodecahydrate, 3-4% of borax and 11-18% of water according to mass percentage, and putting the mixture into an oven at 55-65 ℃ until the solids in the oven are completely melted to form a saturated solution;
(3) adsorption of fly ash: the weight percentage ratio is as follows: 30-40% of fly ash and 60-70% of inorganic composite phase-change material, adding the weighed fly ash into the saturated solution, stirring for 0.5-1.5 hours at a rotation speed of 500-800 rpm by using a magnetic stirrer at 55-65 ℃ to uniformly disperse the fly ash into the saturated solution of the composite phase-change material, and then putting the mixture into an oven at 55-65 ℃ for 10-15 hours to ensure that the fly ash is completely adsorbed;
(4) low-temperature evaporation: and (3) drying the completely adsorbed fly ash phase-change material for 10-15 hours in a constant temperature environment of 10-20 ℃, and evaporating excessive water.
The invention has the advantages that: the inorganic composite energy storage phase change material is synthesized by using solid wastes of fly ash, sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax as raw materials, the prepared raw materials are the fly ash, the solid wastes are consumed, the sodium sulfate decahydrate also belongs to mineral substances with rich reserves, the cost is low, and the sodium phosphate dodecahydrate and the borax are easily obtained as additives. In addition, the synthesis method is simple, the fly ash does not need additional pretreatment, and the fly ash and the inorganic phase change material can be completed only by a simple adsorption mode, the initial heat value of the obtained composite phase change material reaches 100-110 coke/g, the initial melting temperature is 23-25 ℃, the weight loss within 60 ℃ is within 5%, and the heat value can still be kept above 80 coke/g after 100 times of cold-heat circulation. The method not only solves the problem of environmental pollution caused by the accumulation of a large amount of solid wastes, but also has a long-term application in building energy-saving utilization in the future, and conforms to the industrial policy of circular economy advocated by the state.
Drawings
FIG. 1 is a flow chart of preparation of a fly ash composite phase change material.
FIG. 2 is a differential scanning calorimetry diagram of the fly ash composite phase change material.
FIG. 3 is an X-ray diffraction pattern of the fly ash composite phase change material.
FIG. 4 shows the microstructure of the fly ash composite phase change material.
FIG. 5 is a thermogravimetric image of a fly ash composite phase change material.
FIG. 6 shows the results of a cycle experiment of the fly ash composite phase change material.
Detailed Description
Fly ash, sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax are used as raw materials to synthesize the inorganic composite energy storage phase change material, and the formula is shown in table 1. The preparation process is shown in figure 1. The synthesized samples were subjected to X-ray diffraction, SEM, thermogravimetric analysis, and differential scanning calorimetry.
TABLE 1 raw material ratio for preparing fly ash composite phase change material
FIG. 2 shows the results of differential scanning calorimetry tests on the fly ash composite phase-change material, and as shown in the figure, the initial melting temperature of the sample is 23 degrees Celsius, the melting heat is 109.0 joules/gram, the initial solidification temperature is 15 degrees Celsius, and the solidification heat is 72.2 joules/gram. Fig. 3 and 4 are X-ray diffraction and SEM results of the fly ash composite phase change material, and fig. 3 shows that the phases in the composite phase change material are hydrates of sodium sulfate and sodium phosphate except for main components (silica and mullite) of fly ash, fig. 4 shows the morphology of fly ash before and after adsorption, a shows the morphology of fly ash before adsorption, and b shows the morphology of fly ash after adsorption. Fig. 5 shows the thermogravimetric test result of the fly ash composite phase change material, and it can be seen that the weight loss of the sample in the working temperature (in 60 ℃) range is not more than 5%. Fig. 6 is a sample cycle test result, and the heat value of the material is still kept above 80 coke/g after 100 cycles of cold and heat.
Claims (1)
1. A method for synthesizing an inorganic phase change energy storage material by utilizing fly ash and hydrated inorganic salt is characterized in that the fly ash, sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax are used as raw materials, and the synthesis method comprises the following steps:
(1) preparing raw materials: drying the fly ash in a 60 ℃ oven for 10-15 hours, selecting two inorganic hydrated salts of sodium sulfate decahydrate and sodium hydrogen phosphate dodecahydrate as phase change materials, and selecting borax as a nucleating agent;
(2) preparing an inorganic composite phase-change material: controlling the mass ratio of sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate and borax, mixing 49-58% of sodium sulfate decahydrate, 21-36% of sodium hydrogen phosphate dodecahydrate, 3-4% of borax and 11-18% of water according to the mass ratio, and putting the mixture into an oven at the temperature of 55-65 ℃ until the solids in the mixture are completely melted to form a saturated solution;
(3) adsorption of fly ash: the weight percentage ratio is as follows: 30-40% of fly ash and 60-70% of inorganic composite phase-change material, adding the weighed fly ash into the saturated solution, stirring for 0.5-1.5 hours at a rotation speed of 500-800 rpm by using a magnetic stirrer at 55-65 ℃ to uniformly disperse the fly ash into the saturated solution of the composite phase-change material, and then putting the mixture into an oven at 55-65 ℃ for 10-15 hours to ensure that the fly ash is completely adsorbed;
(4) low-temperature evaporation: drying the completely adsorbed fly ash phase-change material for 10-15 hours in a constant temperature environment of 10-20 ℃, and evaporating excessive water;
the initial heat value of the obtained composite phase change material reaches 100-110 coke/g, the initial melting temperature is 23-25 ℃, the weight loss within 60 ℃ is within 5%, and the heat value can still be kept above 80 coke/g after 100 times of cold and heat cycles.
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| CN109337654B (en) * | 2018-11-23 | 2021-03-16 | 辽宁科技学院 | Fly ash composite phase change energy storage material and preparation method thereof |
| CN110295028B (en) * | 2019-07-19 | 2021-02-02 | 华北电力大学 | High-temperature shaping phase-change heat storage material and preparation method thereof |
| CN111978922B (en) * | 2020-07-31 | 2021-04-23 | 西安交通大学 | Hydrated salt-based medium-low temperature chemical heat storage material and preparation method thereof |
| CN113214796B (en) * | 2021-04-12 | 2022-02-22 | 东南大学 | Composite inorganic salt phase change cold storage agent and preparation method thereof |
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