A heat insulation protective sleeve for high-temperature blast hole in coal mine fire area

Abstract

The present application relates to the technical fields of coal mine fire area blasting, and discloses a kind of explosives heat-insulating protective sleeve for coal mine fire area high temperature blast hole, from outside to inside sequentially include metal reflecting layer, first thermal expansion transition layer, aerogel heat-insulating layer, second thermal expansion transition layer, phase change endothermic layer and cartridge containment cavity.The thermal expansion coefficient of first transition layer is between metal reflecting layer and aerogel layer, second transition layer is between aerogel layer and phase change layer, and transition layer has moderate elastic modulus;The present application is through two layers of thermal expansion transition layer, the interface thermal mechanical shear stress generated by the order of magnitude difference of thermal expansion coefficient of multilayer structure is decomposed into multiple smaller gradient stress steps, and the thermal strain energy is dissipated by using the elastic deformation of transition layer, so as to inhibit the interface peeling and contact thermal resistance dynamic deterioration, solve the problem that the heat-insulating performance of existing heat-insulating protective sleeve is nonlinearly attenuated due to thermal expansion mismatch, improve the durability of multilayer heat-insulating structure under repeated thermal shock.

Description

Technical Field

[0001] This invention relates to the field of blasting technology in coal mine fire zones, and in particular to a heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones. Background Technology

[0002] In blasting operations at high-temperature boreholes in coal mine fire zones, existing technologies typically employ multi-layer composite thermal insulation protective sleeves to ensure the thermal safety of explosives. These sleeves consist of a metal reflective layer, a low thermal conductivity insulation layer, and a phase change heat absorption layer, arranged sequentially from the outside to the inside. These layers achieve thermal protection by reflecting thermal radiation, impeding heat conduction, and absorbing latent heat, respectively. This type of multi-layer structure demonstrates good thermal insulation performance in laboratory settings or under short-term static high temperatures and has become the current mainstream technology.

[0003] In recent years, in order to further improve thermal insulation performance, researchers have introduced novel high-performance materials such as nano-aerogel felt and paraffin-graphene composite phase change materials into multi-layer thermal insulation structures. For example, Chinese patent application with publication number CN120947440A discloses a multi-layer thermal insulation charging device for high-temperature blasting boreholes in open-pit mines. It adopts a three-level synergistic structure of a metal reflective layer, an aerogel thermal insulation layer and a phase change heat absorption layer, which can maintain the safe temperature of the charge cartridge for several hours in a 600℃ borehole environment.

[0004] However, the paper "Hypocrystalline ceramic aerogels for thermal insulation at extreme conditions" published by Jingran Guo et al. in Nature reveals that porous thermal insulation materials are at risk of structural degradation and interface delamination under long-term high-temperature exposure or severe temperature gradients. Under the unsteady thermal shock and repeated temperature rise and fall cycles of high-temperature blast holes in coal mine fire zones, there are orders of magnitude differences in the coefficients of thermal expansion between the metal reflective layer, aerogel thermal insulation layer and phase change heat absorption layer in multi-layer thermal insulation protective sleeves. This thermal expansion mismatch causes the interlayer interface to bear huge alternating shear stress in each thermal cycle. After long-term service, this will lead to physical delamination of the interface, dynamic deterioration of contact thermal resistance, and even local failure of the thermal insulation structure, thereby causing nonlinear decay of the overall thermal insulation performance and seriously threatening the safety and reliability of blasting operations. Summary of the Invention The technical problem to be solved by this invention is that in the multi-layer heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones, the thermal expansion coefficients of different heat insulation layer materials are mismatched. Under the conditions of unsteady thermal shock and long-term high-temperature service of the blast hole, the interlayer interface peeling and dynamic deterioration of contact thermal resistance are caused, resulting in local failure of the heat insulation structure and nonlinear decay of the overall heat insulation performance. To this end, we propose an explosive heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones.

[0005] To achieve the above objectives, this application adopts the following technical solution: a heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones, comprising, from the outside to the inside, a metal reflective layer, a first thermal expansion transition layer, an aerogel heat insulation layer, a second thermal expansion transition layer, a phase change heat absorption layer, and an innermost explosive cartridge receiving cavity; the thermal expansion coefficient of the first thermal expansion transition layer is between the thermal expansion coefficient of the metal reflective layer and the thermal expansion coefficient of the aerogel heat insulation layer, and the thermal expansion coefficient of the second thermal expansion transition layer is between the thermal expansion coefficient of the aerogel heat insulation layer and the thermal expansion coefficient of the phase change heat absorption layer; the elastic modulus of both the first and second thermal expansion transition layers is 100-500 MPa, and adjacent layers are bonded together by an inorganic adhesive.

[0006] Preferably, the metal reflective layer is one of aluminum foil, aluminized polyester film, tin foil, copper foil or stainless steel foil, with a thickness of 0.03-0.10 mm.

[0007] Preferably, the first thermal expansion transition layer is selected from one of ceramic fiber paper, pre-oxidized polyacrylonitrile fiber felt, carbon fiber paper or aluminum silicate fiber felt, with a thermal expansion coefficient of 4×10-6-15×10-6 / ℃ and a thickness of 0.5-2mm.

[0008] Preferably, the aerogel insulation layer is one of fiber-reinforced silica aerogel felt, alumina aerogel felt, or carbon aerogel felt, with a thickness of 8-15 mm and a density of 150-350 kg / m³. 3 .

[0009] Preferably, the second thermal expansion transition layer is selected from graphite paper, expanded graphite / polymer composite gasket, etc. A type of foamed copper or foamed nickel, with a coefficient of thermal expansion of 20 × 10⁻⁶. -6 -80×10 -6 The temperature is ℃, the thermal conductivity is 10-50W / (m·K), and the thickness is 0.5-2mm.

[0010] Preferably, the phase change heat absorption layer is composed of a phase change material and its encapsulation structure. The phase change material is paraffin, fatty acid, polyol or inorganic hydrated salt, and at least one of graphite powder, expanded graphite, graphene, carbon nanotube or metal powder is added as a thermally conductive filler.

[0011] Preferably, the packaging structure is a high-density polyethylene film bag, an aluminum-plastic composite film bag, or a porous carrier absorbent, and the thickness of the packaging is generally 3-8 mm.

[0012] Preferably, the explosive is an industrial explosive suitable for blasting operations in coal mine fire zones, and is selected from one of emulsion explosives, permitted ammonium nitrate oil explosives for coal mines, and heat-resistant ammonium nitrate oil explosives.

[0013] Preferably, the inorganic adhesive is selected from one of aluminum dihydrogen phosphate, sodium silicate, and silica sol.

[0014] Preferably, the protective cover further includes a moisture-proof and breathable layer, an antistatic layer, a temperature indicator layer, and a mechanically reinforced auxiliary layer.

[0015] The technical effects and advantages of this invention are as follows: This invention creates a gradient transition in the thermal expansion coefficients between adjacent functional layers by setting a first thermal expansion transition layer between the metal reflective layer and the aerogel insulation layer, and a second thermal expansion transition layer between the aerogel insulation layer and the phase change heat absorption layer. This decomposes the interfacial thermomechanical shear stress caused by the difference in thermal expansion coefficients in traditional multilayer structures into multiple smaller gradient stress steps. Furthermore, the moderate elastic modulus of the transition layer itself absorbs and dissipates heat strain energy, thus suppressing the mechanism of interlayer delamination and dynamic degradation of contact thermal resistance from the stress transmission path. From the perspective of thermodynamic matching of multilayer heterogeneous materials, this invention provides a technical path different from simple material stacking to solve the problem of insufficient durability of thermal insulation structures under high-temperature unsteady thermal cycling conditions, constituting an improvement in the design of multilayer thermal insulation protective sleeve structures. Attached Figure Description

[0016] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts: Figure 1 This is a line graph showing the rate of thermal insulation performance degradation of the present invention. Figure 2 This is a SEM image of the interface of the fiber-reinforced aerogel felt of Embodiment 1 of the present invention after 50 thermal cycles. Figure 3 This is a SEM image of the interface of the fiber-reinforced aerogel felt of Comparative Example 1 of the present invention after 30 thermal cycles. Figure 4 The images are SEM images of the fiber-reinforced aerogel felt in Embodiment 1 of the present invention under different temperature heat treatments. Detailed Implementation

[0017] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0018] This invention provides a heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones. Its structure, from the outside to the inside, includes a metal reflective layer, a first thermal expansion transition layer, an aerogel heat insulation layer, a second thermal expansion transition layer, a phase change heat absorption layer, and an innermost explosive cartridge receiving cavity. The material composition and parameters of each layer are as follows.

[0019] The metal reflective layer is composed of a high-reflectivity, high-temperature resistant metal foil, selected from aluminum foil, aluminized polyester film, tin foil, copper foil, or stainless steel foil; preferably aluminum foil, which has high reflectivity, low cost, good ductility, and is not prone to oxidation and peeling at high temperatures; the thickness of the metal reflective layer is 0.03-0.10 mm. If the thickness is too thin, the reflective layer is easily damaged during loading and transportation; if the thickness is too thick, it will increase the overall rigidity and weight of the protective sleeve, which is not conducive to fitting the borehole wall and increases costs; in order to enhance the bonding force between the metal reflective layer and the adjacent first thermal expansion transition layer, the inner surface of the metal reflective layer can be subjected to corona treatment, plasma activation, or pretreatment with a coupling agent.

[0020] The first thermal expansion transition layer is selected from one of ceramic fiber paper, polyacrylonitrile pre-oxidized fiber, carbon fiber paper, or aluminosilicate fiber felt, and its coefficient of thermal expansion should be between the coefficient of thermal expansion of the metal reflective layer and the coefficient of thermal expansion of the aerogel insulation layer, preferably 4×10. -6 -15×10 -6 / ℃; at the same time, the transition layer should have a moderate elastic modulus, preferably 100-500MPa, which can absorb part of the thermal strain difference through its own compression or shear deformation; the thickness is 0.5-2mm.

[0021] The aerogel material is selected from one of silica aerogel, alumina aerogel, carbon aerogel, and fiber-reinforced aerogel mat, preferably fiber-reinforced aerogel mat, which has quartz fibers, glass fibers, or ceramic fibers uniformly dispersed inside to prevent the aerogel from breaking under pressure; the thickness of the aerogel insulation layer is 8-15mm. If the thickness is too low, the insulation effect will be insufficient; if it is too high, it will occupy the radial space of the borehole and increase the risk of jamming; the density of the aerogel insulation layer is usually controlled between 150-350kg / m³. 3 Within the specified range, if the density is too low, the mechanical strength is poor and it is easy to pulverize during loading vibration; if the density is too high, the thermal conductivity increases and the heat insulation performance decreases.

[0022] The second thermal expansion transition layer is selected from one of the following: graphite paper, expanded graphite and rubber or resin polymer composite gasket, copper foam, nickel foam, or thermally conductive silicone gasket. Its coefficient of thermal expansion should be between the coefficient of thermal expansion of the aerogel insulation layer and the coefficient of thermal expansion of the phase change heat absorption layer, preferably 20 × 10⁻⁶. -6 -80×10 -6 / ℃; In addition, the transition layer should have a certain thermal conductivity, preferably 10-50W / (m·K), to allow sufficient heat to pass through the transition layer and be absorbed by the phase change material, and the thickness of the second transition layer is preferably 0.5-2mm.

[0023] The phase change heat absorption layer is composed of a phase change material and its encapsulation structure, selected from paraffin wax, fatty acids, polyols, and inorganic hydrated salts. To improve the thermal conductivity and thermal response speed of the phase change material, a high thermal conductivity filler, such as graphite powder, expanded graphite, graphene, carbon nanotubes, metal powder, or a mixture of the above fillers, is added to the phase change material. Preferably, it is a paraffin wax and graphene composite material, wherein the mass fraction of graphene is 1-10% and paraffin wax is the balance. The phase change enthalpy of this composite material can reach 150-220 J / g, and the phase change temperature can be adjusted according to the grade of paraffin wax. To prevent the phase change material from flowing and escaping in the molten state.

[0024] The encapsulation method involves filling the phase change material into a sealed bag made of high-density polyethylene or aluminum-plastic composite film; blending the phase change material with a polymer matrix and then injection molding it into a sheet; or adsorbing the phase change material into a porous carrier and then encapsulating it. The thickness of the encapsulation is generally 3-8 mm, and the encapsulation body should have good flexibility to adapt to the bending or deformation of the borehole.

[0025] The inorganic adhesive is selected from one of aluminum dihydrogen phosphate, sodium silicate (water glass), and silica sol.

[0026] The explosive is an industrial explosive suitable for blasting operations in coal mine fire zones, and is selected from one of the following: emulsion explosives, permitted ammonium nitrate oil explosives for coal mines, and heat-resistant ammonium nitrate oil explosives.

[0027] Based on the above material selection and structural design, the functional layers of this invention work together according to their physical mechanisms to achieve thermal protection of explosives. The working principle of each layer and its functional positioning in the overall thermal insulation system are described below.

[0028] The metal reflective layer is located on the outermost side of the protective sleeve and is in direct contact with the high-temperature environment or high-temperature rock wall inside the borehole. Its main function is to reflect the heat radiation from the rock wall and high-temperature gas inside the borehole, thereby reducing the heat entering the protective sleeve from the source. At the same time, the metal reflective layer also plays a certain role in structural support and moisture protection.

[0029] The aerogel insulation layer, located inside the metal reflective layer, is the first major heat conduction barrier layer. Aerogel materials possess extremely high porosity and ultra-low thermal conductivity; their nanoscale three-dimensional network structure effectively inhibits convective heat transfer from gas molecules and thermal conduction through the solid framework, thereby slowing the rate of heat transfer inwards.

[0030] The phase change heat absorption layer is located inside the aerogel insulation layer and is the last thermal protection barrier. Its main function is to absorb the residual heat after penetrating the first two layers. It absorbs a large amount of latent heat when the phase change material undergoes a solid-liquid phase change, stabilizing the temperature of the explosive environment near the phase change temperature, thereby providing sufficient safety window time for blasting operations.

[0031] The function of the thermal expansion transition layer is to alleviate the thermal stress caused by the difference in thermal expansion coefficients between adjacent materials, and to prevent the interlayer interface from peeling or cracking during repeated thermal cycling, thereby maintaining the stability of contact thermal conductivity and the durability of thermal insulation performance. The transition layer can be in the form of sheet, felt, paper, or coating. If a coating is used, it can be directly applied to the surface of the adjacent layer by spraying, brushing, or roller coating, and then dried or cured to form the transition layer. The coating formulation can be prepared by mixing inorganic high-temperature adhesives such as silica sol and alumina sol with fillers such as quartz powder, alumina powder, and expanded graphite. Its thermal expansion coefficient can be customized by adjusting the type and proportion of fillers.

[0032] In traditional structures without a transition layer, the metal reflective layer and the aerogel insulation layer are directly bonded. Due to the mismatch in their coefficients of thermal expansion (CTE), high-amplitude thermomechanical shear stresses are generated at the interface during temperature fluctuations, which can easily induce interface delamination failure. After introducing the first transition layer, the originally large single CTE difference is decomposed into two smaller gradient differences: approximately 10-15×10-6 / ℃ at the metal layer / first transition layer interface and approximately 5-10×10-6 / ℃ at the first transition layer / aerogel layer interface. At the same time, the transition layer itself has a low elastic modulus, which can act as a stress buffer, effectively dissipating most of the thermal strain energy through compression or shear deformation. Similarly, the second transition layer decomposes the originally high CTE jump of 200×10-6 / ℃ between the aerogel layer and the phase change material layer into two progressively transitioning steps, thereby avoiding direct impact on the brittle aerogel surface caused by the drastic volume change of the phase change material.

[0033] In addition to the essential functional layers mentioned above, the heat-insulating protective sleeve of the present invention may also include the following auxiliary layers: A moisture-proof and breathable layer is set on the outside of the metal reflective layer. It is made of microporous polytetrafluoroethylene (PTFE) membrane or hydrophobic non-woven fabric. It is used to prevent groundwater or moisture from entering the interior of the protective cover, while allowing water vapor to escape, thus avoiding structural damage caused by water vapor expansion at high temperatures.

[0034] An antistatic layer is applied to the inner side of the phase change heat absorption layer or the surface of the explosive cartridge receiving cavity to prevent static sparks from being generated by friction during the loading process.

[0035] The temperature indicator layer is located on the outer surface of the metal reflective layer and is composed of an irreversible color-changing temperature-indicating coating. When the ambient temperature of the borehole reaches or exceeds a preset threshold, the coating color undergoes a permanent and irreversible change. Specifically, when the temperature is below the preset threshold, the coating retains its initial color; when the temperature reaches or exceeds the preset threshold, the coating changes from its initial color to the set warning color. For example, when 65℃ is selected as the warning threshold, the coating can change from the initial yellow to red; when 80℃ is selected as the warning threshold, it can change from the initial red to black; and when 100℃ is selected as the warning threshold, it can change from the initial colorless to red or from gray to bright red.

[0036] The mechanical reinforcement layer adds a layer of metal wire mesh or plastic mesh to the outside or inside of the aerogel insulation layer to improve the protective sleeve's resistance to radial compression and prevent it from being flattened by rock fragments inside the borehole.

[0037] Includes the following steps: S1: Cut the metal reflective layer into rectangular sheets or roll it into a cylindrical shape according to the design dimensions, and curl or glue the edges to form a basic cylindrical shape; cut the first transition layer into a sheet or arc-shaped sheet with the same dimensions as the inner surface of the metal reflective layer; cut the aerogel insulation layer as needed; cut the second transition layer into a sheet with the same dimensions as the inner surface of the aerogel insulation layer; heat the phase change heat absorption layer to a molten state, encapsulate, seal and cool to solidify, and make a bag with uniform thickness.

[0038] S2: Stack the above layers in the order of metal reflective layer, first transition layer, aerogel heat insulation layer, second transition layer and phase change heat absorption layer; apply or spray a layer of high temperature resistant inorganic adhesive between adjacent layers, align the layers after applying the adhesive and apply a pressure of 0.1-1.0 MPa, and cure at room temperature or 50-100℃ for 2-24 hours; if a winding structure is adopted, stack the materials of each layer in sequence and wind them around the core rod that serves as the drug cartridge cavity, and fix the outer edge with high temperature resistant tape or buckles after winding.

[0039] S3: Place the assembled composite structure in a mold and keep it at 80-120℃ for 0.5-2 hours to cool to room temperature; cut the protective sleeve to the required length according to the borehole diameter and explosive cartridge size, usually 300-1000mm, and seal both ends with high-temperature resistant tape or sealing rings.

[0040] S4: Conduct an appearance inspection on the completed heat insulation protective sleeve, perform a sealing test on the phase change heat absorption layer, and package and store it.

[0041] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art should understand that various modifications and changes can be made to the present invention without departing from the technical principles of the present invention, and these modifications and changes should also fall within the scope of protection of the present invention.

[0042] Example 1 S1: Select commercially available 0.05mm thick aluminum foil as the metal reflective layer; cut the aluminum foil into rectangular sheets of 500mm×250mm, with the length direction being the axis of the protective sleeve and the width direction being the perimeter. Evenly coat the inner surface of the aluminum foil with a layer of aluminum dihydrogen phosphate inorganic adhesive that is resistant to 600℃. Before use, dilute it with water at a mass ratio of 1:1. The adhesive layer thickness is about 0.1mm.

[0043] S2: Commercially available ceramic fiber paper is selected as the first thermal expansion transition layer, with a thickness of 1.0 mm and a coefficient of thermal expansion of 4.5 × 10⁻⁶. -6 / ℃, with an elastic modulus of approximately 200MPa. The main component of this ceramic fiber paper is aluminum silicate fiber, which also contains a small amount of inorganic binder. The ceramic fiber paper is cut into sheets with dimensions comparable to the inner surface of the aluminum foil, aligned and laid on the coated surface of the aluminum foil, gently pressed, and left at room temperature for 2 hours to allow the adhesive to initially cure.

[0044] S3: Apply the diluted aluminum dihydrogen phosphate adhesive again to the free surface of the ceramic fiber paper, and then select fiber-reinforced silica aerogel felt as the aerogel insulation layer, with a thickness of 10 mm and a density of 220 kg / m³. 3 Cut the aerogel felt as needed and lay it on the adhesive-coated surface, then compact it again and cure it at room temperature for 2 hours.

[0045] S4: Apply the above adhesive to the inner side of the aerogel felt, and then select an expanded graphite / polymer composite gasket as the second thermal expansion transition layer with a thickness of 1.2 mm and a coefficient of thermal expansion of 35 × 10⁻⁶. -6 The gasket has an elastic modulus of approximately 150 MPa and a thermal conductivity of approximately 25 W / (m·K). It is made by high-temperature pressing of expanded graphite powder and a small amount of fluororubber. The gasket is cut into sheets with dimensions equivalent to the inner surface of the aerogel felt, laid on the adhesive-coated surface, and compacted and cured.

[0046] S5: Select paraffin wax with a phase change temperature of 85℃ and multilayer graphene powder with an average number of layers ≤10 and an average sheet diameter of 5-10μm. Weigh out 5% graphene and 95% paraffin wax by mass percentage. Heat the paraffin wax to 95℃ to melt it and add graphene. Stir and disperse at high speed for 30 minutes and cool to room temperature to obtain a paraffin wax and graphene composite phase change material. Heat the composite phase change material to 90℃ to melt it and pour it into a sealed bag made of high-density polyethylene (HDPE) film. After sealing, allow it to cool and solidify naturally to obtain a phase change heat absorption layer. Apply adhesive to the inside of the expanded graphite gasket, lay the pre-prepared phase change heat absorption layer on it, gently press it, and cure it at 50℃ for 4 hours.

[0047] S6: The above five-layer composite structure is wound along the width direction onto a round rod with a diameter of 60mm. During winding, ensure that each layer fits tightly and does not produce wrinkles. After winding, fix the seam with high-temperature resistant tape. Place the round rod and the wound protective sleeve into an 80℃ oven for 1 hour, then take it out and let it cool naturally to room temperature. Pull out the round rod to obtain a cylindrical heat insulation protective sleeve with an inner diameter of about 60mm and a wall thickness of about 16.2mm.

[0048] S7: Cut the protective sleeve into 400mm long finished products and seal both ends with high-temperature resistant silicone rubber sealing rings to prevent leakage of phase change material when it melts.

[0049] Example 2 This embodiment provides a heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones. The difference from Embodiment 1 is that the first thermal expansion transition layer is replaced with pre-oxidized polyacrylonitrile fiber, with a thickness of 1.2 mm and a thermal expansion coefficient of 10 × 10⁻⁶. -6 / ℃, elastic modulus approximately 180MPa, temperature resistance 300℃. Due to the slightly lower temperature resistance of polyacrylonitrile pre-oxidized fiber, this embodiment is suitable for scenarios where the borehole temperature does not exceed 400℃; the second thermal expansion transition layer is replaced with foamed copper, with a porosity of 85%, a thickness of 1.0mm, and a coefficient of thermal expansion of approximately 18×10. -6 / ℃, the composite with thermally conductive silicone, the specific preparation method is as follows: a small amount of thermally conductive silicone is coated on both sides of the foam copper, and then it is laminated with the adjacent layer. Other materials and preparation steps are the same as in Example 1.

[0050] Comparative Example 1 This comparative example provides a heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones. The difference from Example 1 is that only one thermal expansion transition layer is provided. That is, only the first transition layer is provided between the metal reflective layer and the aerogel heat insulation layer, while the aerogel heat insulation layer is in direct contact with the phase change heat absorption layer. No second transition layer is provided. The remaining materials and preparation steps are the same as in Example 1.

[0051] Comparative Example 2 This comparative example provides a heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones. The difference between this comparative example and Example 1 is that this comparative example adopts a typical three-layer structure in the prior art, without setting any thermal expansion transition layer. The remaining materials and preparation steps are the same as in Example 1.

[0052] Comparative Example 3 This comparative example provides a heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones. The difference from Example 1 is that a thicker, flexible silicone rubber gasket, 2 mm thick, with a temperature resistance of 250°C and a coefficient of thermal expansion of approximately 200 × 10⁻⁶, is placed between the metal reflective layer and the aerogel layer. -6 At / ℃, no transition layer is set between the aerogel layer and the phase change layer, and the remaining materials and preparation steps are the same as in Example 1.

[0053] Comparative Example 4 This comparative example provides a heat insulation protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones. The difference from Example 1 is that the thickness of the heat insulation layer is increased without setting a transition layer, the thickness of the aerogel layer is changed to 20mm, and the other materials are the same as in Example 1.

[0054] To verify the technical effect of the present invention, the performance of the heat insulation protective sleeves prepared in Examples 1-2 and Comparative Examples 1-4 were tested according to the following methods, and the test results are as follows.

[0055] Experimental Example 1 Take composite structure specimens without assembled phase change layers from each embodiment and comparative example, with a length of 100 mm and a width of 25 mm, fix them in the high-temperature fixture of the universal testing machine, apply a shear force parallel to the interlayer interface at a rate of 1 mm / min at a temperature of 500 °C, record the maximum load when the interface fails, divide it by the bonding area to obtain the interlayer shear strength, test three locations for each specimen, and take the arithmetic mean. The results are shown in Table 1.

[0056]

[0057] As can be seen from Table 1, when ceramic fiber paper is used as the first transition layer, the shear strength of the aluminum foil / transition layer interface is higher than that of the aluminum foil / aerogel directly bonded; in Comparative Example 1, the shear strength of the aerogel / phase change layer interface is lower than that of Examples 1 and 2 with transition layers because there is no transition layer.

[0058] Experimental Example 2 The thermal insulation sleeve sample was placed in a programmable high-temperature muffle furnace and subjected to thermal cycling between room temperature and 500°C. The temperature was increased to 500°C at a rate of 10°C / min, held for 1 hour, and then allowed to cool naturally to room temperature. This cycle was repeated 10-50 times. After completion, the sample was removed, radially sectioned, and examined using a scanning electron microscope for peeling, cracks, or voids. The results are as follows: Figure 2-3 As shown.

[0059] from Figure 2-3 It can be seen that after 50 cycles in Example 1, the interfaces of each layer are tightly bonded, with only a small number of microcracks at the interface between the ceramic fiber paper and the aerogel layer. The width of the microcracks is less than 5 μm, and no obvious peeling or voids are found. After 30 cycles in Example 2, a slight delamination of about 5% of the area appears at the interface between the metal reflective layer and the pre-oxidized polyacrylonitrile fiber, while the other interfaces remain intact. After 50 cycles in Comparative Example 1, a large area of ​​interface peeling occurs between the aerogel layer and the phase change heat absorption layer, with a peeling area of ​​about 60% and an interface gap width of 50-100 μm. Some of the phase change material penetrates into the pores of the aerogel layer. After 30 cycles in Comparative Example 2, the peeling area of ​​the aluminum foil / aerogel interface is about 80%, the aerogel / phase change layer interface is completely separated, and a large amount of phase change material flows out. After 30 cycles in Comparative Example 3, the silicone rubber gasket hardens and cracks, the aluminum foil / silicone rubber interface is completely debonded, and the peeling area of ​​the silicone rubber / aerogel interface is 100%. After 30 cycles in Comparative Example 4, the peeling area of ​​the aluminum foil / aerogel interface is about 75%, and the aerogel / phase change layer is completely separated.

[0060] The above observations indicate that Examples 1 and 2 can effectively suppress interface peeling caused by high-temperature thermal cycling; Comparative Example 1 can protect the aluminum foil / aerogel interface, but cannot prevent the failure of the aerogel / phase change layer interface; without a transition layer or with a CTE mismatch flexible layer, severe peeling occurs at the interface after fewer thermal cycles.

[0061] Experimental Example 3 Thermocouples were attached to the inner surface of the phase change heat-absorbing layer. The entire thermal insulation sleeve was then placed in a test furnace preheated to 500°C. The time required for the inner surface temperature to rise from room temperature to 100°C was recorded. The same protective sleeve, after 50 thermal cycles, was tested again for the same temperature rise. The results are shown in Table 2 and... Figure 1 As shown, the attenuation rate formula is as follows:

[0062] Where η is the decay rate; T0 is the initial safe time; and T1 is the safe time after the cycle.

[0063]

[0064] As can be seen from Table 2, Example 1 has the lowest attenuation rate, indicating that its thermal insulation performance remains good after 50 thermal cycles. The attenuation rate of Example 2 is slightly higher than that of Example 1, but still lower than that of the comparative example. The attenuation rate of Comparative Example 1 is higher than that of Examples 1 and 2, but lower than that of Comparative Examples 2-4. The attenuation rates of Comparative Examples 2-4 all exceed 68%, indicating that their thermal insulation performance has deteriorated after 30 thermal cycles. Although Comparative Example 3 has the longest initial safety time, its attenuation rate after thermal cycles is as high as 73.0%, and its excessive wall thickness causes jamming during loading.

[0065] Experiment Example 4 In a safety test area of ​​a certain mining area, according to the actual blasting process, each heat-insulating protective sleeve containing emulsion explosive cartridges was lowered into simulated blast holes at temperatures of 200℃, 400℃, and 600℃, respectively, and maintained for 2 hours and 4 hours. The structural integrity of the protective sleeves, the surface temperature of the explosives, and the presence of abnormal smoke, combustion, or premature detonation were then checked. Each condition was repeated three times, and the results were observed using a scanning electron microscope. The results are shown in Table 3. Figure 4 As shown.

[0066]

[0067] From Table 3 and Figure 4 It can be seen that under temperature conditions of 400℃ and below, Examples 1 and 2 can both guarantee 4 hours of safe operation time; under the condition of 600℃×2h, Example 1 can still maintain the explosive temperature below 90℃ and there is no premature detonation; Comparative Example 1 shows leakage of phase change material and increase of explosive temperature at 600℃, indicating that the structure is at risk of failure at extreme temperatures when the second transition layer is missing; Comparative Examples 2-3 show structural failure and explosive overheating at 400℃; Comparative Example 4 cannot meet the on-site construction requirements due to excessive wall thickness.

[0068] Based on the test data from Experiments 1-4, the following conclusions can be drawn regarding the role of the transition layer in enhancing interfacial bonding strength: When ceramic fiber paper is used as the first transition layer, the interfacial shear strength of aluminum foil / ceramic fiber paper is approximately 3.4 times that of direct bonding of aluminum foil / aerogel. This indicates that the transition layer effectively reduces the thermomechanical stress concentration at the interface by matching the coefficient of thermal expansion and providing a suitable elastic modulus. After 30-50 thermal cycles, the thermal insulation performance degradation rate of Example 1 is 9.2%, while that of Comparative Example 1 is 48.3% and that of Comparative Example 2 is 73.1%. The data show that the dual transition layer structure can reduce the thermal insulation performance degradation rate to about 1 / 8 of that of the structure without a transition layer, while Comparative Example 1 results in a degradation rate more than 5 times that of the dual transition layer structure. Example 1 showed a degradation rate after 50 thermal cycles at 500℃. The attenuation rate was 9.2% in Example 2 and 14.8% in Example 3 after 30 thermal cycles at 400°C. Both were better than the comparative example, but Example 1 had better high-temperature durability, which is related to the lower upper limit of the temperature resistance of the polyacrylonitrile pre-oxidized fiber. Although Comparative Example 4 had the best initial thermal insulation performance, its attenuation rate after thermal cycling was as high as 73.0%, and the excessive wall thickness caused construction jamming. This result shows that increasing the thickness cannot solve the interface failure problem, but instead brings the side effect of reduced workability. Comparative Example 3 used a silicone rubber gasket, whose coefficient of thermal expansion was not only not between that of aluminum foil and aerogel, but was much higher than both, which led to increased interfacial thermal stress. The interfacial shear strength of this sample was the lowest, and it completely debonded after thermal cycling. This, in turn, proves that the limitation of the range of the coefficient of thermal expansion of the transition layer in this invention is necessary and effective.

[0069] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones, characterized in that, The device comprises, from the outside to the inside, a metal reflective layer, a first thermal expansion transition layer, an aerogel insulation layer, a second thermal expansion transition layer, a phase change heat absorption layer, and a drug cartridge receiving cavity located at the innermost side; the thermal expansion coefficient of the first thermal expansion transition layer is between that of the metal reflective layer and the aerogel insulation layer, and the thermal expansion coefficient of the second thermal expansion transition layer is between that of the aerogel insulation layer and the phase change heat absorption layer; the elastic modulus of both the first and second thermal expansion transition layers is 100-500 MPa, and adjacent layers are bonded together by an inorganic adhesive.

2. The explosive heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones according to claim 1, characterized in that: The metal reflective layer is one of aluminum foil, aluminized polyester film, tin foil, copper foil or stainless steel foil, with a thickness of 0.03-0.10 mm.

3. The explosive heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones according to claim 1, characterized in that: The first thermal expansion transition layer is selected from one of ceramic fiber paper, polyacrylonitrile pre-oxidized fiber, carbon fiber paper, or aluminosilicate fiber felt, with a thermal expansion coefficient of 4×10. -6 -15×10 -6 / ℃, thickness is 0.5-2mm.

4. The explosive heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones according to claim 1, characterized in that: The aerogel insulation layer is one of fiber-reinforced silica aerogel felt, alumina aerogel felt, or carbon aerogel felt, with a thickness of 8-15 mm and a density of 150-350 kg / m³.

5. The explosive heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones according to claim 1, characterized in that: The second thermal expansion transition layer is selected from one of graphite paper, expanded graphite / polymer composite gasket, copper foam, or nickel foam, with a coefficient of thermal expansion of 20 × 10⁻⁶. -6 -80×10 -6 The temperature is ℃, the thermal conductivity is 10-50W / (m·K), and the thickness is 0.5-2mm.

6. The explosive heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones according to claim 1, characterized in that: The phase change heat absorption layer is composed of a phase change material and its encapsulation structure. The phase change material is paraffin, fatty acid, polyol or inorganic hydrated salt, and at least one of graphite powder, expanded graphite, graphene, carbon nanotube or metal powder is added as a thermally conductive filler.

7. The explosive heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones according to claim 6, characterized in that: The packaging structure is a high-density polyethylene film bag, an aluminum-plastic composite film bag, or a porous carrier absorbent, and the thickness of the packaging is generally 3-8mm.

8. The explosive heat insulation protective sleeve for high-temperature blast holes in coal mine fire zones according to claim 1, characterized in that: The explosive is an industrial explosive suitable for blasting operations in coal mine fire zones, and is selected from one of the following: emulsion explosives, permitted ammonium nitrate oil explosives for coal mines, and heat-resistant ammonium nitrate oil explosives.

9. A heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones according to claim 1, characterized in that: The inorganic adhesive is selected from one of aluminum dihydrogen phosphate, sodium silicate, and silica sol.

10. A heat-insulating protective sleeve for explosives used in high-temperature blast holes in coal mine fire zones according to claim 1, characterized in that: The protective cover also includes a moisture-proof and breathable layer, an anti-static layer, a temperature indicator layer, and a mechanically reinforced auxiliary layer.

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