Method and device for efficiently recycling waste heat and packaging high-temperature phase-change material through coal cinder

Abstract

The invention discloses a coal cinder packaging high-temperature phase change material method for efficient waste heat recovery, which comprises the following steps: adding a fluxing agent into liquid slag, and reheating until the liquid slag is completely molten, so that the liquid temperature of the slag is higher than the phase change temperature of the phase change material; and the metal phase change particles are evenly wrapped with the liquid slag, the metal phase change particles wrapped with the slag are subjected to heat exchange with cooling water, the particles release heat and are cooled and solidified, and the packaging structure is formed. The invention further discloses a coal cinder packaging high-temperature phase change material device for efficient waste heat recovery. According to the invention, the high-temperature metal phase-change material is used as a core, and the industrial solid waste slag is used as a packaging shell, so that a unique macroscopic packaging structure is formed; the high-temperature characteristic of the liquid slag generated in the industrial process can be fully utilized, and the liquid slag is used as a heat source in the sintering process, so that heat energy is recycled.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change heat storage packaging, and in particular to a method and device for packaging high-temperature phase change materials with coal slag for efficient waste heat recovery. Background Art

[0002] In high-temperature industrial applications, the effective storage of thermal energy is the key to achieving efficient energy utilization. In high-temperature processes such as steel smelting and glass manufacturing, a large amount of waste heat is often generated. If this waste heat is not properly utilized, it will be lost as waste heat. The application of advanced thermal energy storage technology can not only efficiently collect this waste heat, but also store it for subsequent heating, power generation or other industrial processes, significantly improving the overall efficiency of energy utilization. In addition, by reducing dependence on fossil fuels, high-temperature thermal energy storage technology plays an important role in reducing greenhouse gas emissions and other environmental pollution, and has a positive impact on promoting sustainable environmental development.

[0003] However, when faced with extreme high temperature environments, traditional thermal energy storage solutions may encounter challenges with material stability and heat loss. In order to meet these challenges, high-temperature thermal energy storage technology uses specially designed packaging materials and structures to adapt to extreme temperature conditions and ensure efficient storage and stable transmission of thermal energy. In the selection of high-temperature phase change thermal storage materials, inorganic salts, metals, and alloys have been widely studied due to their characteristics at high temperatures. Inorganic salt materials have limitations in thermal conductivity and chemical stability, especially at high temperatures, they may exhibit strong corrosiveness. Metal or alloy materials stand out for their excellent thermal conductivity, low vapor pressure, and small thermal expansion coefficient. It is worth noting that high-temperature metal phase change materials may cause chemical corrosion to storage containers or face the risk of high-temperature oxidation in actual applications. Therefore, developing effective packaging technology to prevent direct contact between materials and containers and the environment is the key to ensuring their long-term stable operation.

[0004] In the daily operation of coal-fired power plants, the slag discharge of the slag furnace is a key link. Liquid slag discharge technology is particularly suitable for treating combustion residues with a melting temperature below 1450°C, and is an efficient high-temperature ash treatment solution. The processing flow of this technology is as follows: after the liquid slag flows out of the slag outlet, it quickly enters the granulation water tank. Under the action of rapid cooling, the molten slag quickly solidifies and cracks to form glassy solid slag particles. Subsequently, these solid slag particles are discharged from the furnace regularly or continuously through professional slag removal equipment, ensuring the efficiency and safety of the slag discharge process. However, behind this efficient slag discharge technology, the accompanying large amount of high-quality heat energy loss cannot be ignored. The heat energy released by the liquid slag during the cooling and solidification process will be a huge waste of energy if it is not effectively recovered and utilized. Therefore, there is still significant room for improvement and optimization in the field of heat recovery and utilization. By developing and applying more advanced heat recovery technologies, not only can the energy utilization efficiency be improved, but also economic benefits can be brought to power plants, while also responding to the environmental protection requirements of energy conservation and emission reduction.

[0005] At present, in the field of high-temperature heat storage technology, the packaging method of phase change materials is still under development and has not yet fully matured. Packaging technology is mainly divided into two strategies: micro packaging and macro packaging. Micro packaging technology involves the use of physical and chemical methods to encapsulate metal or alloy materials in a shell material with corrosion resistance and high melting point characteristics. Although this method has significant advantages in material protection, its process flow is relatively complicated, and the packaging shell needs to undergo high-temperature thermal oxidation treatment, which not only increases the production cost, but also fails to completely eliminate the risk of material leakage; such as a preparation method for a double-layer packaged phase change heat storage ball provided in the patent application document with publication number CN111808575A. Macro packaging technology uses a high-temperature refractory container to encapsulate the phase change material. Achieving a completely closed package of a refractory container is a challenging technical problem. Improper packaging may cause the phase change material to leak from an open structure; such as a phase change material packaging structure and a heat storage tank provided in the patent application document with publication number CN210374746U. In addition, another implementation method of macro packaging is to mix metal powder with a powder skeleton support material with high corrosion resistance and melting point and a sintering agent, followed by extrusion molding and sintering at high temperature to form a block structure with stable shape. In this process, the sintering temperature is usually set to be higher than the phase change temperature of the material so that the phase change material can liquefy and adhere to the skeleton through surface tension and capillary forces. However, even so, after multiple cycles of use, the phase change material may still precipitate from the surface, and the thermal oxidation of the metal and potential leakage problems may also lead to a decrease in the cyclic stability of the phase change material.

[0006] Therefore, in order to improve the maturity of high-temperature phase change material packaging technology, future research needs to focus on developing more efficient packaging materials, optimizing process flows, and at the same time enhancing the integrity and reliability of the packaging structure to ensure the long-term stability and cyclic performance of phase change materials in high-temperature environments.

[0007] At present, although many technologies of macro packaging and micro packaging have been disclosed in the low-temperature field, these technologies still face many challenges in high-temperature application scenarios. The packaging skeleton support material is prone to thermal decomposition, thermal oxidation and thermal corrosion at high temperatures. These problems seriously limit the application and promotion of packaging technology in the field of high-temperature heat storage. In addition, most of the existing packaging technologies for high-temperature phase change materials require a high-temperature sintering step to achieve the solidification and molding of the material. This process itself consumes a lot of heat energy. Therefore, it is particularly important to develop a high-temperature phase change material packaging technology that is both energy-saving and efficient. This technology should be able to reduce energy consumption and improve the overall energy efficiency of the system while ensuring the packaging effect. Summary of the invention

[0008] Based on the current technical principles and research background, the present invention proposes a method for encapsulating high-temperature phase change materials with coal slag for efficient waste heat recovery, which is specifically aimed at the packaging needs of high-temperature metal phase change materials. This method takes high-temperature metal phase change materials as the core and uses industrial solid waste slag as the packaging shell to form a unique macro packaging structure.

[0009] The specific technical solution adopted by the present invention is as follows:

[0010] A method for encapsulating high-temperature phase change materials with coal slag for efficient waste heat recovery comprises: adding a flux to liquid slag for reheating until it is completely melted, so that the liquid temperature of the slag is higher than the phase change temperature of the phase change material; uniformly encapsulating the liquid slag on metal phase change particles, and the metal phase change particles encapsulated by the slag release heat and cool and solidify through heat exchange with cooling water to form an encapsulation structure.

[0011] The present invention is aimed at the leakage and oxidation problems of high-temperature metal phase change materials in practical applications, as well as the current situation that the waste heat of industrial by-product coal slag is not fully utilized; an innovative solution is proposed to improve the performance of heat storage materials and optimize the waste heat recovery process.

[0012] By adopting the method of the present invention, the slag forms a dense shape during the liquid solidification process and exhibits excellent mechanical properties. Using it as a shell not only provides the necessary protection to prevent leakage of the phase change material, but also can effectively isolate the external environment and extend the service life of the material. More importantly, the present invention can make full use of the high temperature characteristics of the liquid slag generated in the industrial process and use it as a heat source in the sintering process, thereby realizing the recovery and reuse of heat energy. It not only saves a lot of heat energy and reduces energy consumption, but also provides a new idea for the resource utilization of industrial solid waste.

[0013] Preferably, the slag is derived from a liquid slag discharge furnace of a coal-fired power plant, and the added flux makes the melting point of the slag higher than the phase change temperature of the phase change material.

[0014] Preferably, the phase change material is a metal or alloy with a melting point higher than 1000°C, and the metal or alloy material has a thermal conductivity exceeding 100W / (m·°C); the chemical composition of the slag mainly includes 40-50% silicon dioxide, 30-35% aluminum oxide, 4-20% iron oxide, 1-5% calcium oxide, as well as magnesium, sulfur and carbon.

[0015] Preferably, the flux is one or a mixture of two or more of lime, dolomite, silica, iron oxide, sodium carbonate, potassium carbonate, borax, calcium fluoride, phosphate and sulfate.

[0016] The present invention also discloses a coal slag encapsulated high temperature phase change material device with high efficiency waste heat recovery, comprising a melting furnace, a phase change particle rotating drum and a particle cooling tank;

[0017] The melting furnace is used for reheating liquid slag;

[0018] The phase-change particle drum comprises a drum wall and a rotating shaft with a spiral; a liquid slag inlet is distributed on the peripheral surface of the drum wall; metal phase-change particles are input from one end of the phase-change particle drum, and the liquid slag entering through the liquid slag inlet on the peripheral surface of the drum wall uniformly wraps the metal phase-change particles;

[0019] The particle cooling tank is used to cool the metal phase change particles wrapped by slag to form a packaging structure.

[0020] Preferably, a slag drum is wrapped around the middle of the drum wall, a slag conveyor belt is provided between the melting furnace and the slag drum, and the reheated liquid slag is conveyed into the slag drum through the slag conveyor belt.

[0021] Preferably, the openings on the drum wall at corresponding positions of the slag drum serve as the liquid slag inlets, and the liquid slag infiltrates into the phase change particle drum through the openings.

[0022] Preferably, one end of the slag drum is the slag drum inlet, the other end is the slag drum outlet, and the interior of the slag drum is provided with a guide thread around the drum wall.

[0023] Preferably, a slag recovery tank is provided at the outlet of the slag drum for recovering the slag discharged from the outlet of the slag drum.

[0024] The present invention develops a novel "core-shell" high-temperature metal phase change heat storage material, which takes the high-temperature metal phase change material as the core and utilizes the industrial solid waste slag as the packaging shell to form a unique macro packaging structure; the slag forms a dense shape during the liquid solidification process and exhibits excellent mechanical properties; using it as the shell not only provides the necessary protection to prevent the leakage of the phase change material, but also can effectively isolate the external environment and extend the service life of the material; more importantly, this technology can make full use of the high-temperature characteristics of the liquid slag generated in the industrial process and use it as a heat source in the sintering process, thereby realizing the recovery and reuse of thermal energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural diagram of the coal slag encapsulated high temperature phase change material device in the present invention.

[0026] In the figure: 1. metal phase change particles; 2. phase change particle conveyor belt; 3. slag conveyor belt; 4. slag; 5. melting furnace; 6. phase change particle drum; 7. rotating shaft; 8. opening; 9. slag drum; 10. slag recovery tank; 11. water cooling pipe; 11-1. water cooling pipe inlet; 11-2. water cooling pipe outlet; 12. particle cooling tank; 13. slag drum inlet; 14. slag drum outlet; 15. phase change particle drum inlet; 16. phase change particle drum outlet; 17. shaped particle cooling tank inlet; 18. shaped particle cooling tank outlet; 19. shaped particle storage tank. DETAILED DESCRIPTION

[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0029] The present embodiment provides a method for encapsulating high-temperature phase change materials with coal slag for efficient waste heat recovery, comprising: adding a flux to liquid slag and reheating it until it is completely melted, so that the liquid temperature of the slag is higher than the phase change temperature of the phase change material; uniformly encapsulating the liquid slag on metal phase change particles, and the metal phase change particles encapsulated by the slag release heat and cool and solidify through heat exchange with cooling water to form an encapsulation structure.

[0030] The core part of the present invention is a high-temperature metal phase change material, which has the characteristics of high latent heat, excellent thermal conductivity and high melting point. The material is chemically stable at the preset working temperature, and the volume change is small during the phase change process, ensuring long-term and reliable heat storage performance.

[0031] The shell of the present invention uses slag, an industrial byproduct, which comes from the liquid slag furnace of a coal-fired power plant. The melting point of the slag varies depending on the composition of the coal, and is usually below 1450°C. Through scientific formula adjustments, such as adding flux, the melting point of the slag can be effectively controlled to ensure that it is higher than the phase change temperature of the core phase change material, thereby forming a stable protective layer during the packaging process.

[0032] In another preferred embodiment, the slag comes from the liquid slag discharge furnace of a coal-fired power plant, and the flux is added to make the melting point of the slag higher than the phase change temperature of the phase change material, so that within the application temperature range of the heat storage material, the phase change material is liquefied, while the slag is still solid, playing a packaging role. Specifically, the flux is one or a mixture of two or more of lime, dolomite, silica, iron oxide, sodium carbonate, potassium carbonate, borax, calcium fluoride, phosphate and sulfate.

[0033] Phase change materials are metals or alloys with a melting point higher than 1000°C, such as copper (Cu) and aluminum-copper (Al-Cu) alloys with a melting point higher than 1000°C. They not only have a high melting point but also have a specific shape advantage, such as a spherical shape.

[0034] The chemical composition of slag is mainly composed of 40-50% silicon dioxide (SiO2), 30-35% aluminum oxide (Al2O3), 4-20% iron oxide (Fe2O3), 1-5% calcium oxide (CaO) and a small amount of magnesium, sulfur, carbon, etc. These components give the slag specific physical and chemical properties, making it an ideal packaging material.

[0035] In this embodiment, the slag shell forms a specific shape consistent with the phase change material after solidification, such as a spherical shape, which not only helps to improve the mechanical strength of the package, but also facilitates industrial production and application.

[0036] like Figure 1As shown, another embodiment of the present application also provides a slag-encapsulated high-temperature phase change material device with efficient waste heat recovery, including a melting furnace 5, a phase change particle drum 6 and a particle cooling tank 12; the melting furnace 5 is used for reheating treatment of liquid slag; the phase change particle drum 6 includes a drum wall and a spiral shaft 7; a liquid slag inlet is distributed on the circumferential surface of the drum wall; the metal phase change particles 1 are input from one end of the phase change particle drum, and the liquid slag 4 entering through the liquid slag inlet on the circumferential surface of the drum wall uniformly wraps the metal phase change particles; the particle cooling tank 12 is used to cool the metal phase change particles wrapped by the slag to form a packaging structure.

[0037] A slag drum 9 is wrapped around the middle of the drum wall. A slag conveyor belt is provided between the melting furnace 5 and the slag drum 9. The liquid slag after reheating is conveyed into the slag drum 9 through the slag conveyor belt.

[0038] The opening 8 on the wall of the slag drum 9 at the corresponding position is the inlet of the liquid slag, and the liquid slag 4 penetrates into the phase change particle drum 6 through the opening 8. One end of the slag drum 9 is the slag drum inlet 13, and the other end is the slag drum outlet 14, and the inside of the slag drum 9 is provided with a guide thread around the drum wall. The inside of the slag drum has a thread design and is in a rotation mode, so that the slag inside that has not yet penetrated into the phase change particle drum can be pulled out of the slag recovery tank by the thread.

[0039] A slag recovery tank 10 is provided at the outlet of the slag drum 9 for recovering the slag discharged from the outlet of the slag drum. The slag recovery tank has high temperature resistance and heat preservation effects.

[0040] The following is combined with Figure 1 The specific process of the coal slag encapsulation high temperature phase change material device in this embodiment is further described:

[0041] Step 1: Slag pretreatment. After the liquid slag is discharged from the slag discharge furnace, in order to solve the problem of possible incompletely burned carbon particles or high melting point components, the slag is transported to the melting furnace 5 through the slag conveyor belt 3, and appropriate flux is added for reheating. The purpose of this key step is to effectively reduce the overall melting point of the slag and ensure its complete melting. By controlling the content and composition of the flux, the liquid temperature of the slag is made higher than the phase change temperature of the phase change material by 50-100°C, while avoiding excessively high temperatures to prevent the phase change material from melting rapidly, thereby ensuring the performance and stability of the material.

[0042] Step 2: Material transportation. The low-temperature spherical phase change material (metal phase change particles 1) smoothly enters the phase change particle drum 6 through the phase change particle conveyor belt 2. At the same time, the liquid slag 4 also enters the slag drum 9 through a dedicated conveyor belt. This step ensures the synchronous feeding of the two materials, laying the foundation for the subsequent packaging process.

[0043] Step 3: Slag encapsulation and molding. In the continuously rotating slag drum 9 and phase change particle drum 6, the slag is evenly encapsulated on the rotating phase change particles through the precise openings 8 on the phase change particle drum 9. This dynamic encapsulation process not only realizes the effective combination of slag and phase change material, but also transports the encapsulated particles to the outlet through the rotation of the shaft 7, realizing an automated encapsulation operation. At the same time, the excess slag in the slag drum 9 is pushed to the slag drum outlet 14 through the threaded structure and drips back into the slag recovery tank 10.

[0044] Step 4: Cooling and energy recovery. The phase-change particles wrapped in slag then enter the particle cooling tank 12. Through heat exchange with cooling water, the particles release heat and cool and solidify to form a stable "core-shell" structure, and enter the shaped particle storage tank through the particle cooling tank outlet. In this process, the water in the water cooling pipe absorbs heat and is converted into steam, which can flow out of the water cooling pipe outlet and be reused, achieving efficient energy recovery.

[0045] In this embodiment, the melting furnace 5 used can reach a high temperature of more than 1500°C and is suitable for solid, liquid or gaseous fuels, including but not limited to coal, oil and natural gas. The selection of flux includes lime, dolomite, silica, iron oxide, sodium carbonate, potassium carbonate, borax, calcium fluoride, phosphate and sulfate, etc. These fluxes can significantly reduce the melting point and optimize the melting process.

[0046] The phase change particle conveyor belt 2 and the slag conveyor belt 3 have the characteristics of high temperature resistance, and the slag conveyed to the slag conveyor belt has been completely liquefied. The conveyor belt can be made of special materials such as ceramic fiber, carbon fiber, graphite material, special alloy mesh belt, multi-layer composite refractory material, aluminum silicate fiber blanket and alumina fiber.

[0047] The openings on the phase change particle drum 9 are kept at a moderate size, such as 5-20 mm, and should not be too large to avoid causing a large amount of slag in the slag drum to penetrate into the phase change particle drum, thereby causing the slag to wrap the phase change particles unevenly and causing the phase change particles to melt due to excessive heat.

[0048] The shaft inside the phase change particle drum also has threads, which facilitates the slag to wrap the phase change particles evenly and to transport the wrapped particles out. The recovered slag can be re-entered into the melting furnace to achieve the recycling of materials and energy.

[0049] The device of this embodiment not only achieves efficient packaging of high-temperature metal phase change materials, but also realizes the recycling of slag and waste heat and the additional output of steam, greatly improving the energy efficiency and environmental performance of the entire process.

[0050] Compared with the prior art, the technical solution of the present invention has the following innovations and beneficial effects:

[0051] High-temperature heat storage capacity: This invention is specially designed for the field of high-temperature heat storage, and can withstand a maximum heat storage temperature of more than 1200°C, which provides a solid guarantee for energy storage in extreme high-temperature environments. By simultaneously utilizing the latent heat and sensible heat of the material, the heat storage density is significantly improved, which plays a vital role in improving the energy efficiency of the heat storage system. In addition, the metal or alloy material used has a thermal conductivity of more than 100W / (m·℃). This excellent thermal conductivity greatly accelerates the heat charging and discharging rate of the heat storage device and optimizes the efficiency of heat energy transfer.

[0052] Resource utilization and cost-effectiveness: The present invention provides a low-cost, environmentally friendly and technically simple energy storage solution by innovatively utilizing the slag produced by the liquid slag removal furnace. This method not only promotes the resource utilization of industrial by-products, but also effectively reduces production costs, achieving a dual improvement in economic and environmental benefits.

[0053] Innovation in packaging technology: The innovative packaging technology used in this invention successfully solves the leakage problem that may occur during the application of high-temperature metal phase change materials, ensures the safety and reliability of the entire heat storage system, and lays a solid foundation for the commercial application of high-temperature phase change heat storage technology.

[0054] Efficient conversion and utilization of thermal energy: The present invention cleverly utilizes the heat of the slag in the liquid slag removal furnace to provide the necessary energy for the sintering process. At the same time, during the cooling process of the phase change particles, the secondary recovery of thermal energy is achieved, and the efficient conversion and utilization of energy is achieved by producing steam, further improving the overall energy efficiency of the system.

[0055] The above description is only an example of a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for efficiently recovering waste heat by encapsulating high-temperature phase change materials with coal slag, characterized in that: include: Flux is added to the liquid slag and reheated until it is completely melted, so that the liquid temperature of the slag is higher than the phase change temperature of the phase change material; the liquid slag is evenly wrapped on the metal phase change particles, and the metal phase change particles wrapped by the slag release heat and cool and solidify through heat exchange with cooling water to form a packaging structure.

2. The method for encapsulating high-temperature phase change materials with slag for efficient waste heat recovery according to claim 1 is characterized in that: The slag is derived from a liquid slag discharge furnace of a coal-fired power plant, and the added flux makes the melting point of the slag higher than the phase change temperature of the phase change material.

3. The method for encapsulating high-temperature phase change materials with slag for efficient waste heat recovery according to claim 1 is characterized in that: The phase change material is a metal or alloy with a melting point higher than 1000°C, and the metal or alloy material has a thermal conductivity of more than 100W / (m·°C); The chemical composition of the slag mainly includes 40-50% silicon dioxide, 30-35% aluminum oxide, 4-20% iron oxide, 1-5% calcium oxide, magnesium, sulfur and carbon.

4. The method for encapsulating high-temperature phase change materials with slag for efficient waste heat recovery according to claim 1 is characterized in that: The flux is one or a mixture of two or more of lime, dolomite, silica, iron oxide, sodium carbonate, potassium carbonate, borax, calcium fluoride, phosphate and sulfate.

5. The method for encapsulating high-temperature phase change materials with slag for efficient waste heat recovery according to claim 1 is characterized in that: The metal phase-change particles are spherical.

6. A cinder-encapsulated high-temperature phase change material device for efficient waste heat recovery, characterized in that: It includes a melting furnace, a phase change pellet drum and a pellet cooling tank; The melting furnace is used for reheating liquid slag; The phase-change particle drum comprises a drum wall and a rotating shaft with a spiral; a liquid slag inlet is distributed on the peripheral surface of the drum wall; metal phase-change particles are input from one end of the phase-change particle drum, and the liquid slag entering through the liquid slag inlet on the peripheral surface of the drum wall uniformly wraps the metal phase-change particles; The particle cooling tank is used to cool the metal phase change particles wrapped by slag to form a packaging structure.

7. The slag encapsulated high temperature phase change material device for efficient waste heat recovery according to claim 6 is characterized in that: A slag drum is wrapped around the middle of the drum wall, and a slag conveyor belt is arranged between the melting furnace and the slag drum. The liquid slag that has been heated is conveyed into the slag drum through the slag conveyor belt.

8. The slag encapsulated high temperature phase change material device for efficient waste heat recovery according to claim 7 is characterized in that: The openings on the drum wall at corresponding positions of the slag drum serve as the liquid slag inlets, and the liquid slag infiltrates into the phase change particle drum through the openings.

9. The slag encapsulated high temperature phase change material device for efficient waste heat recovery according to claim 7, characterized in that: One end of the slag drum is the slag drum inlet, and the other end is the slag drum outlet, and the interior of the slag drum is provided with a guide thread around the drum wall.

10. The slag encapsulated high temperature phase change material device for efficient waste heat recovery according to claim 9, characterized in that: A slag recovery tank is provided at the outlet of the slag drum for recovering the slag discharged from the outlet of the slag drum.

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