Unfired ceramsite, composite phase change energy storage material based on unfired ceramsite and preparation method of composite phase change energy storage material

Abstract

The invention discloses unfired ceramsite, a composite phase change energy storage material based on the unfired ceramsite and a preparation method of the composite phase change energy storage material, and belongs to the technical field of building materials. The unfired ceramsite is prepared from the following raw materials in parts by mass: 40-60 parts of sludge, 10-30 parts of household garbage, 5-15 parts of cement blocks and 6-18 parts of fly ash. The composite phase change energy storage material comprises the following components: a phase change aggregate, a packaging material and a composite phase change material, the phase change aggregate is unfired ceramsite, the packaging material is charcoal cement paste, and the composite phase change material is a mixture of decanoic acid and stearic acid. The sludge and the household garbage are subjected to resource utilization, the unfired ceramsite and the biochar are prepared, the biochar cement paste is used for packaging, the biochar cement paste packaging material can keep proper viscosity, and the difficulty caused by hydrophobicity of a phase change material to'shell making 'is overcome; meanwhile, a mixture of decanoic acid and stearic acid is used as the composite phase change material, and the composite phase change energy storage material with good performance is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to non-fired ceramsite and a composite phase change energy storage material based on non-fired ceramsite and a preparation method thereof. Background Art

[0002] According to statistics, the annual global output of concrete has exceeded 4 billion tons, which is the most widely used type of building material in the world today. In recent years, with the development of China's social economy, there have been more and more infrastructure constructions such as various buildings, structures, expressways, and high-speed railways, and the demand for concrete has also been increasing. The increasing demand for concrete has brought new requirements for its performance and environmental protection.

[0003] Ceramsite is a lightweight aggregate produced by foaming in a rotary kiln. Its biggest feature is that its outer surface is hard, while there are many micropores inside. These micropores endow ceramsite with the characteristics of light weight, and at the same time, it has the characteristics of low density, low thermal conductivity, and high strength, and is widely used in concrete. Compared with ordinary concrete, ceramsite concrete has advantages such as heat preservation, fire resistance, sound insulation, earthquake resistance, high specific strength, good deformation performance, low elastic modulus, and low cost, and is increasingly widely used in new special building structures such as high-rise building structures, long-span bridge projects, earthquake-resistant buildings, and soft soil foundation projects. With the demand for engineering infrastructure construction and the country's strong promotion of strategies such as prefabricated buildings, green energy-saving buildings, and solid waste resource utilization, ceramsite concrete has gradually shifted from the original single pursuit of mechanical property improvement to the development direction of comprehensive performance improvement such as lightweight and high strength, intelligent self-repair, green energy-saving, and heat preservation and sound insulation.

[0004] Phase change materials are a type of latent heat energy storage materials that regulate temperature by absorbing and releasing heat energy by themselves. Phase change ceramsite concrete can effectively reduce the hydration heat of mass concrete and the energy consumption of concrete buildings, which is one of the development directions of new intelligent concrete. However, the phase change temperature of traditional single-phase change materials is single and cannot meet the different temperature requirements of actual projects. Organic composite solid-liquid conversion phase change materials are widely used in building envelopes because of their advantages such as large latent heat, small volume change, and stable performance. However, when the aggregate adsorbed with the composite phase change material is directly mixed and stirred with building materials such as cement, water, sand, and gravel, the composite phase change material is extremely easy to leak out from the aggregate during the phase change process. This will not only greatly affect the thermal efficiency of the composite phase change material, but also affect the overall mechanical properties and durability of the concrete. Therefore, it is necessary to find a suitable encapsulation material to process it; at the same time, due to the existence of a thin layer of phase change material on the surface of the phase change aggregate, it is not conducive to the "shell formation" of the liquid encapsulation and shaping material on the surface of the phase change aggregate, which also poses relatively high requirements for the selection of the encapsulation material; in addition, under the background of the "dual carbon" strategy, how to promote the resource recovery and utilization of biomass wastes such as domestic waste and industrial sludge is also an issue that needs to be concerned about in the development of related industries such as transportation and civil engineering. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention provides non-fired ceramsite and a composite phase change energy storage material based on the non-fired ceramsite and a preparation method thereof, which solve the problems such as difficult surface encapsulation and shaping of the phase change aggregate and poor energy storage performance of the phase change energy storage material.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: to provide a non-fired ceramsite, and the preparation raw materials thereof include the following components in parts by mass: 40-60 parts of sludge, 10-30 parts of domestic waste, 5-15 parts of cement blocks, and 6-18 parts of fly ash.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Further, a preparation method of the non-fired ceramsite includes the following steps: (1) Weigh sludge, domestic waste, cement blocks and fly ash, perform drying and pulverizing and grinding, and then mix them to make material balls; (2) Screen out the material balls with a particle size of 6-10 mm, and dry them at 110-130 °C for 2.5-3.5 h under vacuum conditions; (3) Preheat the material balls treated in step (2) at 400-500 °C, fire them at 1100-1300 °C for 20-30 min, and cool them to room temperature to obtain the non-fired ceramsite.

[0009] Further, in step (1), the particle size of the sludge after pulverizing and grinding is 2-3 mm, the particle size of the domestic waste is 3-4 mm, and the particle size of the cement blocks is 3-4 mm; a granulator is used to prepare the material balls, the rotation speed of the granulator is 60-70 rpm, and the treatment time is 30-40 min; in step (2), the drying temperature is 120 °C and the drying time is 3 h; in step (3), the preheating temperature is 450 °C and the preheating time is 15 min; the firing temperature is 1200 °C and the firing time is 20 min.

[0010] Further, a composite phase change energy storage material based on the non-fired ceramsite includes raw materials of the following components: a phase change aggregate, a packaging material, and a composite phase change material; the phase change aggregate is the above-mentioned non-fired ceramsite, the packaging material is biochar cement slurry, and the composite phase change material is a mixture of capric acid and stearic acid.

[0011] Further, the preparation raw materials of the packaging material include the following components: biochar, cement and water, and the mass ratio of biochar, cement and water is 2-4:6-8:4-6. The packaging material is prepared by the following steps: mix biochar and cement, stir evenly, and then add water and stir evenly to obtain it; The raw materials for preparing the composite phase change material include the following components: capric acid and stearic acid, and the mass ratio of capric acid to stearic acid is 6 - 7:3 - 4. The composite phase change material is prepared by the following steps: stirring and mixing capric acid and stearic acid evenly, and then stirring at 65 - 75 °C for 2.5 - 3.5 h to obtain it.

[0012] Furthermore, the biochar is prepared by the following steps: subjecting industrial sludge and domestic waste to microwave pyrolysis and grinding to obtain biochar with a particle size of 60 - 80 μm; the microwave frequency is 2400 - 2500 MHz, the pyrolysis temperature is 450 - 550 °C, and the pyrolysis time is 1.5 h; the mass ratio of industrial sludge to domestic waste is 3:7, and the moisture content of industrial sludge is 70% - 90%.

[0013] Furthermore, the mass ratio of biochar, cement, and water for preparing the encapsulation material is 3:7:5; the microwave frequency for preparing biochar is 2450 MHz, the pyrolysis temperature is 500 °C, and the particle size of biochar is 70 μm; the mass ratio of capric acid to stearic acid for preparing the composite phase change material is 6:4, the stirring temperature is 70 °C, and the stirring time is 3 h.

[0014] The beneficial effects of the present invention adopting the above further technical solutions are as follows: The role of the phase change aggregate is to provide a storage place for the phase change material. When the organic phase change material undergoes a phase change, it is prone to leakage. Therefore, special technological means are required to encapsulate and shape it. Using sludge and domestic waste as raw materials can recycle sludge and domestic waste, reducing the use of traditional raw materials such as clay and shale for preparing ceramsite. The added fly ash can be used as a pore-forming agent during the preparation of ceramsite. By forming more micropores inside the ceramsite, the weight of the ceramsite can be reduced, and its heat insulation performance can be improved. At the same time, the strength and durability of the ceramsite can be significantly enhanced. The active components in the fly ash react with other components in the ceramsite to form a more solid structure, thereby improving the overall performance of the ceramsite. Cement has excellent adhesion and hardening properties. When combined with ceramsite, it can fill the gaps between ceramsite particles to form a solid whole, thereby enhancing the structural strength and load-bearing capacity of the phase change aggregate. Biochar has the characteristics of being porous and having a high specific surface area. It can effectively adsorb and fix the composite phase change material to prevent leakage during the phase change process. It can also enhance the mechanical strength of the overall material and improve the durability of the material. Biochar also has good thermal conductivity, which can promote the heat transfer of the phase change material during the energy storage and release processes and improve the thermal efficiency of the material. Cement has a strong binding effect and can tightly combine biochar, water, and the phase change aggregate to form a solid overall structure. The encapsulation material made of biochar, cement, and water has comprehensive improvements in terms of structural stability, thermal conductivity, and mechanical strength. Moreover, the encapsulation material can better adapt to the volume change of the phase change material during the phase change process and reduce the leakage risk. The composite phase change material composed of capric acid and stearic acid can store and release a large amount of energy during the phase change process. Applying the phase change material to the construction field, without having a large sensible heat storage structure, a large amount of heat energy can be stored in the building envelope through its phase change process, which has a very important thermal application in the energy storage of buildings. The phase change temperature of capric acid is relatively low, while the phase change temperature of stearic acid is relatively high. Mixing the material with a lower phase change temperature with other materials with a higher phase change temperature can form a binary eutectic system with a temperature lower than that of any pure component, and a phase change material with a wide melting temperature range can be obtained.

[0015] Further, a preparation method of a composite phase change energy storage material based on non-fired ceramsite includes the following steps: (1) Soak the non-fired ceramsite in an acid solution with a concentration of 2.5 - 3.5 mol / L for 2.5 - 3.5 h, then treat it with an alkali solution until it is neutral, and dry it at 110 - 130 °C for 2.5 - 3.5 h under vacuum conditions; then use a vibrating sieve to break the shells and remove dust from the dried non-fired ceramsite; (2) Put the fired clay pellets after the treatment in step (1) into a vacuum defoaming bucket. The vacuum defoaming bucket maintains a negative pressure of -80 kPa to -100 kPa. Add the composite phase change material to submerge the fired clay pellets, adsorb for 60 - 70 minutes, and then immerse the treated fired clay pellets in water for cooling; (3) Add the fired clay pellets after the treatment in step (2) to the encapsulating material. The amount of fired clay pellets added is 15% of the mass of cement in the encapsulating material. Stir at a rotation speed of 90 - 110 rpm for 5 - 8 minutes, then fish out the treated fired clay pellets and dry them in the sun; (4) Repeat the treatment in step (3) once, and then cure the treated fired clay pellets with a concrete surface strengthener at room temperature for 3 days to obtain the product.

[0016] Further, in step (1), the alkali solution is a KOH solution with a concentration of 3 - 5 mol / L; in step (4), the thickness of the concrete surface strengthener sprayed on the fired clay pellets is 1.5 - 3 mm, and it is sprayed and cured 2 - 4 times a day.

[0017] Further, in step (1), the acid solution is a hydrochloric acid solution with a concentration of 3 mol / L, the soaking time is 3 h, and the concentration of the KOH solution is 4 mol / L; the drying temperature is 120 °C and the drying time is 3 h; in step (2), the negative pressure value is -90 kPa and the adsorption time is 60 minutes; in step (3), the stirring rotation speed is 100 rpm and the stirring time is 5 minutes; in step (4), the thickness of the concrete surface strengthener sprayed is 2 mm, and it is sprayed and cured 3 times a day.

[0018] The beneficial effects of the present invention are: (1) The ceramsite is common, easy to obtain, and has a low price, making it very suitable as a phase change carrier; (2) After the fired clay pellets are treated by means of acid-base solutions and vibration sieving, the external pores are opened, the internal pores are enlarged, and the adsorption capacity is greatly improved. Compared with the fired clay pellets not treated by acid-base solutions and vibration sieving, for the composite phase change energy storage material prepared with the fired clay pellets treated by acid-base solutions and vibration sieving, its adsorption rate is increased to 20.2%; (3) The method of secondary encapsulation is adopted to eliminate problems such as incomplete outer shells and broken outer shells during the first encapsulation process. At the same time, curing with a concrete surface strengthener can effectively improve the strength of the biochar cement slurry outer shell. The cylinder compressive strength of the material prepared without the second encapsulation is 8.6 MPa, the strength of the material prepared without the curing process is 7.5 MPa, and the cylinder compressive strength of the material prepared after the second encapsulation and the completion of the curing process is 10.2 MPa; (4) The composite phase change material (a mixture of capric acid and stearic acid) used in the present invention has a relatively high phase change latent heat, which can reach 165.34 J / g, which is greater than the phase change latent heat of commonly used phase change materials, such as neopentyl glycol, which is 114.3 J / g, and polyethylene glycol, which is 124.1 J / g, and can better meet the temperature requirements of actual engineering.

[0019] The present invention provides an unfired ceramsite prepared by using sludge and domestic waste as raw materials, and a composite phase change energy storage material prepared based on the unfired ceramsite; the unfired ceramsite and biochar are prepared by using domestic waste and sludge, which can effectively utilize domestic waste and sludge as resources, and utilize the excellent energy storage and multi-pore characteristics of the unfired ceramsite; utilize the change of the physical state of the composite phase change material to absorb or release heat and perform temperature control; use biochar cement slurry for packaging, the biochar cement slurry packaging material can maintain a suitable viscosity to overcome the difficulties brought by the hydrophobicity of the phase change material to "shell making", and at the same time can also ensure the thermal conductivity of the phase change aggregate. DETAILED DESCRIPTION

[0020] The specific implementation modes of the present invention are described in detail below with reference to the embodiments.

[0021] Example 1 A fire-free ceramsite prepared based on sludge and domestic waste includes the following raw materials by weight: 40 parts of sludge, 10 parts of domestic waste, 5 parts of cement blocks, and 6 parts of fly ash. The preparation method is as follows: (1) Sludge, domestic waste, cement block and fly ash were weighed by weight and dried, and then crushed and ground using a pulverizer. The sludge, domestic waste and cement block were then passed through a sieve to obtain sludge with a particle size of 2-3 mm, domestic waste with a particle size of 3-4 mm and cement block with a particle size of 3-4 mm; (2) adding the materials processed in step (1) into a granulator and mixing them thoroughly to prepare material balls; the speed of the granulator is set to 70 rpm and the processing time is 30 min; (3) Screening out material balls with a particle size of 6 to 10 mm through a sieve, placing the screened material balls in a vacuum drying oven, and drying at 120°C for 3 hours; (4) Place the dried material balls into a high-temperature electric furnace, preheat at 450°C for 15 minutes, then sinter at 1200°C for 20 minutes, and cool naturally to room temperature.

[0022] Example 2 A kind of unburned ceramsite prepared based on sludge and domestic waste comprises the following raw materials in parts by weight: 50 parts of sludge, 20 parts of domestic waste, 10 parts of cement blocks, and 12 parts of fly ash. The preparation method is the same as that in Example 1.

[0023] Example 3 A non-fired ceramsite prepared from sludge and domestic waste, comprising the following raw materials in parts by mass: 60 parts of sludge, 30 parts of domestic waste, 15 parts of cement blocks, and 18 parts of fly ash. The preparation method is the same as that of Example 1.

[0024] Example 4 A composite phase change energy storage material prepared based on non-fired ceramsite. The raw materials for preparing the composite phase change energy storage material include phase change aggregate, encapsulation material, and composite phase change material. The phase change aggregate is the non-fired ceramsite prepared in Example 1, the encapsulation material is biochar cement slurry, and the composite phase change material is a mixture of capric acid and stearic acid; Biochar cement slurry, comprising the following raw materials in parts by mass: 3 parts of biochar, 7 parts of cement, and 5 parts of water; The preparation steps of the biochar cement slurry are as follows: Weigh each raw material according to the ratio, mix the biochar and cement, stir evenly, and then add water and stir evenly to obtain the biochar cement slurry.

[0025] Biochar, comprising the following raw materials in parts by mass: 3 parts of industrial sludge and 7 parts of domestic waste; among them, the water content of the industrial sludge is about 80%, which is obtained by removing metals, plastics and other garbage through a sludge filtering device; the domestic waste is screened by a separator to remove particles with a diameter of less than 5 cm; The preparation steps of the biochar are as follows: Treat the industrial sludge and domestic waste in a high-efficiency microwave heating device. The microwave frequency of the high-efficiency microwave heating device is 2450 MHz, the pyrolysis temperature is about 500 °C, and the pyrolysis time is 1.5 h; then process it by the ball milling method to obtain biochar with a particle diameter of 60 - 80 μm.

[0026] A mixture of capric acid and stearic acid, comprising the following raw materials in parts by mass: 6 parts of capric acid and 3 parts of stearic acid. Both capric acid and stearic acid are refined from kitchen waste oil; The preparation steps of the mixture of capric acid and stearic acid are as follows: Add capric acid and stearic acid to a beaker according to the parts by mass, stir the mixed solution with a glass stirring rod for 8 min, place the mixed solution in a constant temperature water bath and heat it to 70 °C and stir for 3 h to prepare the capric acid-stearic acid composite phase change material.

[0027] The preparation steps of the composite phase change energy storage material are as follows: (1) Soak the non-fired ceramsite in a hydrochloric acid solution with a concentration of 3 mol / L for 3 h, then take it out and place it in a KOH solution with a concentration of 4 mol / L until it is neutral. Wash the treated non-fired ceramsite with pure water and then place it in a vacuum drying oven at 120 °C for 3 h; then use a top-hitting standard vibration pendulum instrument to break the shell and remove dust from the dried non-fired ceramsite by vibrating sieving; the swing stroke of the top-hitting standard vibration pendulum instrument is 25 mm, the number of swings per minute is 185 times, and the number of shockings per minute is 135 times; (2) placing the unfired ceramsite treated in step (1) into a drain basket, and then placing the drain basket into a stainless steel vacuum defoaming barrel, evacuating the vacuum defoaming barrel by a vacuum machine, and maintaining a stable negative pressure of about -90 kPa, and passing the capric acid-stearic acid composite phase change material into the stainless steel vacuum defoaming barrel, ensuring that the liquid level of the capric acid-stearic acid composite phase change material is above 2 cm from the top of the unfired ceramsite, and the adsorption time is counted from the start of the vacuum pump, and the adsorption time is 60 minutes; after the adsorption is completed, the unfired ceramsite after the capric acid-stearic acid composite phase change material is adsorbed is quickly poured into a water cooling barrel, and the liquid phase change material is prevented from flowing out of the unfired ceramsite as much as possible; (3) Immerse the unburned ceramsite treated in step (2) into the biochar cement slurry at a ratio of 15% of the mass of cement in the biochar cement slurry, and then put it into an automatic stirring ball mill. Set the stirring time to 5 min and the speed to 100 rpm. Stir thoroughly so that the surface of the ceramsite adheres to enough biochar cement slurry. Finally, remove the unburned ceramsite from the biochar cement slurry and dry it in the sun. (4) Repeat the process of step (3) to encapsulate the expanded clay for a second time; then use a concrete surface enhancer (Yong'an Gu imported concrete enhancer) to spray and cure the unfired expanded clay after the second encapsulation. The thickness of the concrete surface enhancer sprayed on the unfired expanded clay is 2 mm. The spraying and curing time is 3 days, and the spraying and curing are carried out 3 times a day. The curing is carried out at room temperature.

[0028] Example 5 A composite phase change energy storage material prepared based on unfired ceramsite comprises a phase change aggregate, a packaging material and a composite phase change material, wherein the phase change aggregate is the unfired ceramsite prepared in Example 2, and other materials and steps are the same as those in Example 4.

[0029] Example 6 A composite phase change energy storage material prepared based on unfired ceramsite comprises a phase change aggregate, a packaging material and a composite phase change material, wherein the phase change aggregate is the unfired ceramsite prepared in Example 3, and other materials and steps are the same as those in Example 4.

[0030] Comparative Example 1 A composite phase change energy storage material prepared based on unfired ceramsite, comprising a phase change aggregate, a packaging material and a composite phase change material, wherein the phase change aggregate, the packaging material and the composite phase change material are the same as those in Example 4; The preparation steps of the composite phase change energy storage material are as follows: (1) Put the non-fired ceramsite into a drainage basket, and then place the drainage basket into a stainless-steel vacuum defoaming barrel. Use a vacuum machine to evacuate the vacuum defoaming barrel and maintain a stable negative pressure of about -90 kPa. Introduce the capric acid-stearic acid composite phase change material into the stainless-steel vacuum defoaming barrel, ensuring that the liquid level of the capric acid-stearic acid composite phase change material is more than 2 cm above the top of the non-fired ceramsite. The adsorption time is counted from the start of turning on the vacuum pump, and the adsorption duration is 60 min. After adsorption is completed, quickly pour the non-fired ceramsite adsorbed with the capric acid-stearic acid composite phase change material into a water-cooling barrel, trying to avoid the liquid phase change material flowing out of the non-fired ceramsite as much as possible. (2) Immerse the non-fired ceramsite treated in step (1) into the biochar cement slurry at 15% of the cement mass in the biochar cement slurry, then put it into an automatic stirring ball mill, set the stirring time to 5 min and the rotation speed to 100 rpm, and stir thoroughly to make the surface of the ceramsite adhere to enough biochar cement slurry. Finally, take out the non-fired ceramsite from the biochar cement slurry and dry it in the sun. (3) Repeat the process in step (2) to conduct the second encapsulation of the ceramsite; then use a concrete surface enhancer (Yongan Gu imported concrete enhancer) to spray and cure the non-fired ceramsite after the second encapsulation. The thickness of the concrete surface enhancer sprayed on the non-fired ceramsite is 2 mm, the spraying and curing time is 3 d, and it is sprayed and cured 3 times a day. The curing is carried out at room temperature; thus obtained.

[0031] Comparative Example 2 A composite phase change energy storage material based on non-fired ceramsite, including a phase change aggregate, a packaging material, and a composite phase change material, where the phase change aggregate, the packaging material, and the composite phase change material are the same as in Example 4. The preparation steps of the composite phase change energy storage material are as follows: (1) Immerse the non-fired ceramsite in a hydrochloric acid solution with a concentration of 3 mol / L for 3 h, then take it out and place it in a KOH solution with a concentration of 4 mol / L until it is neutral. Wash the treated non-fired ceramsite with pure water and then place it in a vacuum drying oven at 120 °C for drying for 3 h; then use a top-hitting standard shaking table to break the shell and remove dust from the dried non-fired ceramsite by sieving; the swing stroke of the top-hitting standard shaking table is 25 mm, the number of swings per minute is 185 times, and the number of shocks per minute is 135 times. (2) placing the unfired ceramsite treated in step (1) into a drain basket, and then placing the drain basket into a stainless steel vacuum defoaming barrel, evacuating the vacuum defoaming barrel by a vacuum machine, and maintaining a stable negative pressure of about -90 kPa, and passing the capric acid-stearic acid composite phase change material into the stainless steel vacuum defoaming barrel, ensuring that the liquid level of the capric acid-stearic acid composite phase change material is above 2 cm from the top of the unfired ceramsite, and the adsorption time is counted from the start of the vacuum pump, and the adsorption time is 60 minutes; after the adsorption is completed, the unfired ceramsite after the capric acid-stearic acid composite phase change material is adsorbed is quickly poured into a water cooling barrel, and the liquid phase change material is prevented from flowing out of the unfired ceramsite as much as possible; (3) Immerse the unburned ceramsite treated in step (2) into the biochar cement slurry at a ratio of 15% of the mass of cement in the biochar cement slurry, and then put it into an automatic stirring ball mill. Set the stirring time to 5 min and the speed to 100 rpm. Stir thoroughly so that the surface of the ceramsite adheres to enough biochar cement slurry. Finally, remove the unburned ceramsite from the biochar cement slurry and dry it in the sun. (4) Use concrete surface enhancer (Yong'an Gu imported concrete enhancer) to spray and cure the encapsulated unfired expanded clay. The thickness of the concrete surface enhancer sprayed on the unfired expanded clay is 2 mm. The spraying and curing time is 3 days. Spray and cure 3 times a day. The curing is carried out at room temperature.

[0032] Comparative Example 3 A composite phase change energy storage material prepared based on unfired ceramsite, comprising a phase change aggregate, a packaging material and a composite phase change material, wherein the phase change aggregate, the packaging material and the composite phase change material are the same as those in Example 4; The preparation steps of composite phase change energy storage materials are as follows: (1) Soak the unburned ceramsite in a 3 mol / L hydrochloric acid solution for 3 h, then take it out and treat it in a 4 mol / L KOH solution until it is neutral, wash the treated unburned ceramsite with pure water and place it in a 120°C vacuum drying oven for 3 h; then use a top-impact standard vibrating pendulum instrument to break the shell and remove dust from the dried unburned ceramsite by a vibrating screen; the top-impact standard vibrating pendulum instrument has a swing stroke of 25 mm, 185 swings per minute, and 135 shocks per minute; (2) placing the unfired ceramsite treated in step (1) into a drain basket, and then placing the drain basket into a stainless steel vacuum defoaming barrel, evacuating the vacuum defoaming barrel by a vacuum machine, and maintaining a stable negative pressure of about -90 kPa, and passing the capric acid-stearic acid composite phase change material into the stainless steel vacuum defoaming barrel, ensuring that the liquid level of the capric acid-stearic acid composite phase change material is above 2 cm from the top of the unfired ceramsite, and the adsorption time is counted from the start of the vacuum pump, and the adsorption time is 60 minutes; after the adsorption is completed, the unfired ceramsite after the capric acid-stearic acid composite phase change material is adsorbed is quickly poured into a water cooling barrel, and the liquid phase change material is prevented from flowing out of the unfired ceramsite as much as possible; (3) Immerse the fired clay pellets treated in step (2) into the biochar cement slurry according to 15% of the cement mass in the biochar cement slurry, then put them into an automatic stirring ball mill, set the stirring time to 5 min and the rotation speed to 100 rpm, fully stir to make the surface of the clay pellets adhere to enough biochar cement slurry, and finally fish out the fired clay pellets from the biochar cement slurry and dry them in the sun; (4) Repeat the process in step (3) to perform the second encapsulation on the clay pellets; thus obtained.

[0033] Comparative Example 4 A composite phase change energy storage material based on shale clay pellets, comprising phase change aggregates, encapsulating materials and composite phase change materials, wherein the phase change aggregates are shale clay pellets obtained under ordinary preparation processes; other materials and preparation steps are the same as those in Example 4; The preparation process of shale clay pellets mainly includes stages such as raw material preparation, drying and preheating, roasting and cooling, etc. The following is the detailed preparation process flow: (1) Raw material preparation: The collected shale raw materials first go through a crushing stage, and a jaw crusher is used to crush the raw materials to an appropriate particle size; the crushed shale is screened, and qualified particles (particles with particle sizes of 5 - 10 mm and 10 - 20 mm) are selected as raw materials; (2) Drying and preheating: The raw materials need to be dried before roasting to remove the moisture therein; place the raw materials in a drying oven furnace and slowly heat up to 110 °C, the drying time is 4 h, after the pellets (granules) are dried, they can enter the preheating stage, and the preheating stage temperature is 600 °C; (3) Roasting: The preheated raw materials are sent into a rotary kiln for roasting, the roasting temperature is 1200 °C, and the time is 30 min; during the roasting process, the raw materials are subjected to high-temperature treatment to be fired into clay pellets; a coal injection system is equipped in the rotary kiln to ensure sufficient combustion and temperature control; (4) Cooling: The clay pellets after roasting are immediately cooled to prevent them from continuing to react or deform, thus obtained.

[0034] Comparative Example 5 A composite phase change energy storage material prepared based on fired clay pellets, comprising phase change aggregates, encapsulating materials and composite phase change materials, wherein the encapsulating material is cement slurry; other materials and preparation steps are the same as those in Example 4; The cement slurry comprises the following raw materials in parts by mass: 7 parts of cement and 5 parts of water; The preparation steps of the cement slurry are as follows: Weigh each raw material according to the ratio, mix the cement and water, and stir evenly to obtain the cement slurry.

[0035] Experimental Example The test methods for the adsorption effect, encapsulation effect and compressive strength of the phase change energy storage material are as follows: 1. Adsorption effect evaluation: It is represented by the adsorption rate after the phase change aggregate adsorbs the composite phase change material for 48 hours. A small adsorption rate indicates a poor adsorption effect and a small latent heat of phase change of the composite phase change material. Adsorption rate = (mass of the phase change aggregate after adsorption - mass of the phase change aggregate before adsorption) / (mass of the phase change aggregate before adsorption) × 100%. The vacuum adsorption test was carried out using a DZF-6050 desktop vacuum drying oven produced by Shanghai Jiecheng Experimental Instrument Co., Ltd.

[0036] 2. Encapsulation effect evaluation: (1) Find the center of the filter paper with a ruler, and use a compass to draw a circle with a diameter of 30 mm at the center of the filter paper. Place a phase change aggregate after encapsulation within the drawn circle area; (2) Place the sample to be tested in an electrothermal blast drying oven and heat it at 150 °C for 48 hours; (3) Observe the diffusion degree of the phase change material on the filter paper, and then measure the maximum value of the diameter of the diffusion of the phase change material d max and the minimum value d min , and calculate the average value of the maximum value and the minimum value d 0 ; (4) Calculate the percentage of exudation φ, and the calculation formula is: ; (5) The encapsulation effect evaluation criteria are shown in Table 1: Table 1 Encapsulation effect evaluation criteria

[0037] 3. Compressive strength evaluation: Prepare cement mortar with a ratio of cement:sand:water of 4:11:2, incorporate the composite phase change energy storage material at 15% of the cement mass, and test the compressive strength after curing for 28 days (the formed cement mortar is placed indoors for film curing, usually carried out in an environment with a temperature of 20 ± 3 °C and a relative humidity of 60% - 90%) to observe the effect of encapsulation using biochar cement slurry on the strength. The compressive strength test was carried out on a WAW-1000D microcomputer-controlled electro-hydraulic servo universal testing machine produced by Zhongluchang Universal Testing Machine Co., Ltd.

[0038] 4. The detection of the cylinder compressive strength shall be carried out with reference to the provisions in "Lightweight Aggregates and Their Test Methods" (GB / T 17431-2010), and the specific steps are as follows: (1) The test equipment includes: a pressure cylinder, a universal testing machine, an electronic scale, and a blast drying oven; (2) Loading method: Load at a uniform speed of 300 - 500 N, and record the pressure value when the stamping die is pressed into a depth of 20 mm; (3) Data analysis method: The cylinder compressive strength is calculated according to the formula:

[0039] In the formula, f a is the cylinder compressive strength of coarse aggregate, with the unit of megapascal (MPa); p 1 is the pressure value when the penetration depth is 20 mm, with the unit of newton (N); p 2 is the mass of the stamping die, with the unit of newton (N). In this study, the mass of the stamping die is 1.85 kg; F is the bearing area (in this study, F is 10000 mm 2 ).

[0040] The cylinder compressive strength is the average value of three measurement results. If the difference between the maximum and minimum values among the three measurement results is greater than 15% of the average value, a new sample should be taken for testing.

[0041] The test results of the adsorption effect, encapsulation effect, and compressive strength of the composite phase change energy storage material are shown in Table 2: Table 2 Performance test results of the composite phase change energy storage material

[0042] (1) Comparative example 1 is the unburned ceramsite without being treated by acid-base solution and vibration sieving method. The adsorption rate of the prepared material is 15.6%. While example 4 is the composite phase change energy storage material prepared from unburned ceramsite treated by acid-base solution and vibration sieving method, and its adsorption rate is increased to 20.2%; Comparative example 4 uses shale ceramsite obtained by ordinary preparation process, and its adsorption rate is relatively lower than that of the unburned ceramsite prepared from sludge and domestic waste, and its compressive strength decreases significantly compared with that of the examples; It shows that after the unburned ceramsite is treated by the acid-base solution and vibration sieving method together, the external pores are opened, the internal pores are increased, and the adsorption capacity is greatly improved, and more composite phase change materials can be adsorbed.

[0043] (2) The method of secondary encapsulation is used to eliminate problems such as incomplete outer shell and broken outer shell during the primary encapsulation process. At the same time, using a concrete surface strengthening agent for curing can effectively improve the strength of the biochar cement slurry outer shell. In addition, the use of biochar has a significant effect on the material properties; Using the same encapsulation preparation process, the material prepared with cement slurry as the encapsulation material (Comparative example 5) has a lower cylinder compressive strength of 8.9 MPa compared with the material prepared by secondary encapsulation and completed curing process (Example 4), and the encapsulation effect of the material prepared in Comparative example 5 also shows an obvious decline; The cylinder compressive strength of the material prepared without the second encapsulation (Comparative example 2) is 8.6 MPa, and the strength of the material prepared without the curing process (Comparative example 3) is 7.5 MPa. The cylinder compressive strength of the material prepared by secondary encapsulation and completed curing process (Example 1) is 10.2 MPa.

[0044] (3) The compressive strengths of the materials prepared in Comparative Examples 1, 4, and 5 showed a significant decrease compared with those in Examples 4-5, indicating that the combined treatment of acid-base solution and sieving method, the ceramsite as the phase change aggregate, and the biochar in the encapsulation material are all beneficial to the compressive properties of the composite phase change energy storage material; especially the addition of biochar in the encapsulation material significantly improves the compressive strength.

[0045] (4) The composite phase change material has a high phase change latent heat. The phase change latent heat of the mixture of capric acid and stearic acid prepared in Example 4 reaches 165.34 J / g, which is greater than that of common phase change materials, such as the phase change latent heat of neopentyl glycol is 114.3 J / g and that of polyethylene glycol is 124.1 J / g, and can better meet the temperature requirements of actual engineering.

[0046] The present invention uses domestic waste and sludge to prepare fired clay aggregate and biochar, which can effectively recycle domestic waste and sludge. By using the excellent energy storage and porous characteristics of the fired clay aggregate, and at the same time, using the physical state change of the composite phase change material to absorb or release heat for temperature control, a composite phase change energy storage material with good performance is prepared.

[0047] Although the specific implementation manners of the present invention have been described in detail in combination with the embodiments, it should not be construed as a limitation on the protection scope of this patent. Within the scope described in the claims, various modifications and deformations that can be made by those skilled in the art without creative efforts still fall within the protection scope of this patent.

Claims

1. A kind of unburned ceramsite, characterized in that: The raw materials for preparing the catalyst include the following components in parts by weight: 40-60 parts of sludge, 10-30 parts of domestic garbage, 5-15 parts of cement blocks and 6-18 parts of fly ash.

2. The method for preparing the unfired ceramsite according to claim 1, characterized in that: The following steps are involved: (1) Weigh sludge, domestic waste, cement blocks and fly ash, dry and grind them, and then mix them to form material balls; (2) Screening out material balls with a particle size of 6 to 10 mm, and drying them at 110 to 130 °C under vacuum conditions for 2.5 to 3.5 hours; (3) Preheat the material ball treated in step (2) at 400-500°C, sinter at 1100-1300°C for 20-30 min, and cool to room temperature to obtain the product.

3. The method for preparing unfired ceramsite according to claim 2, characterized in that: In the step (1), the particle size of the sludge after crushing and grinding is 2-3 mm, the particle size of the domestic garbage is 3-4 mm, and the particle size of the cement block is 3-4 mm; the material balls are prepared by a granulator, the rotation speed of the granulator is 60-70 rpm, and the processing time is 30-40 min; in the step (2), the drying temperature is 120° C. and the drying time is 3 h; in the step (3), the preheating temperature is 450° C. and the preheating time is 15 min; the firing temperature is 1200° C. and the firing time is 20 min.

4. A composite phase change energy storage material based on unfired ceramsite, characterized in that: The raw materials include the following components: phase change aggregate, packaging material and composite phase change material; the phase change aggregate is the unburned ceramsite according to claim 1, the packaging material is biochar cement slurry, and the composite phase change material is a mixture of capric acid and stearic acid.

5. The composite phase change energy storage material based on unfired ceramsite according to claim 4, characterized in that: The raw materials for preparing the packaging material include the following components: biochar, cement and water, wherein the mass ratio of the biochar, cement and water is 2-4:6-8:4-6, and the packaging material is prepared by the following steps: mixing the biochar and cement, stirring evenly, and then adding water and stirring evenly; The raw materials for preparing the composite phase change material include the following components: capric acid and stearic acid, the mass ratio of capric acid to stearic acid is 6-7:3-4, and the composite phase change material is prepared by the following steps: capric acid and stearic acid are stirred and mixed evenly, and then stirred at 65-75°C for 2.5-3.5h to obtain the composite phase change material.

6. The composite phase change energy storage material based on unfired ceramsite according to claim 5, characterized in that: The biochar is prepared by the following steps: industrial sludge and domestic waste are subjected to microwave pyrolysis and grinding to obtain biochar with a particle size of 60-80 μm, the microwave frequency is 2400-2500 MHz, the pyrolysis temperature is 450-550° C., and the pyrolysis time is 1.5 h; the mass ratio of the industrial sludge to the domestic waste is 3:7, and the water content of the industrial sludge is 70%-90%.

7. The composite phase change energy storage material based on unfired ceramsite according to claim 6, characterized in that: The mass ratio of biochar, cement and water for preparing the packaging material is 3:7:5; the microwave frequency for preparing the biochar is 2450 MHz, the pyrolysis temperature is 500°C, and the particle size of the biochar is 70 μm; the mass ratio of capric acid and stearic acid for preparing the composite phase change material is 6:4, the stirring temperature is 70°C, and the stirring time is 3 hours.

8. The method for preparing the composite phase change energy storage material based on unfired ceramsite according to any one of claims 4 to 7, characterized in that: The following steps are involved: (1) soaking the unburned ceramsite in an acid solution with a concentration of 2.5-3.5 mol / L for 2.5-3.5 h, then treating it with an alkali solution until it becomes neutral, and drying it at 110-130° C. under vacuum conditions for 2.5-3.5 h; and then using a vibrating screen to break the shell and remove dust from the dried unburned ceramsite; (2) placing the unfired ceramsite treated in step (1) into a vacuum defoaming barrel, maintaining a negative pressure of -80 kPa to -100 kPa, adding the composite phase change material to cover the unfired ceramsite, adsorbing for 60 to 70 minutes, and then immersing the treated unfired ceramsite in water to cool; (3) adding the unburned ceramsite treated in step (2) to the packaging material, wherein the amount of the unburned ceramsite added is 15% of the mass of the cement in the packaging material, stirring at a speed of 90-110 rpm for 5-8 minutes, and removing the treated unburned ceramsite and drying it in the sun; (4) Repeat the treatment of step (3) once, and then use the concrete surface enhancer to cure the treated unburned ceramsite at room temperature for 3 days.

9. The method for preparing a composite phase change energy storage material based on unfired ceramsite according to claim 8, characterized in that: The alkali solution in step (1) is a KOH solution with a concentration of 3-5 mol / L; the thickness of the concrete surface enhancer sprayed on the unfired ceramsite in step (4) is 1.5-3 mm, and the spraying and curing are performed 2-4 times a day.

10. The method for preparing a composite phase change energy storage material based on unfired ceramsite according to claim 9, characterized in that: In the step (1), the acid solution is a hydrochloric acid solution with a concentration of 3 mol / L, the immersion time is 3 h, and the concentration of the KOH solution is 4 mol / L; the drying temperature is 120° C., and the drying time is 3 h; in the step (2), the negative pressure value is -90 kPa, and the adsorption time is 60 min; in the step (3), the stirring speed is 100 rpm, and the stirring time is 5 min; in the step (4), the spraying thickness of the concrete surface enhancer is 2 mm, and the spraying and curing is performed 3 times a day.

Images