A type of high-temperature refractory mortar

Abstract

This invention relates to the field of refractory materials technology, specifically to a high-temperature refractory mortar. By weight, it comprises the following components: 15-25 parts clay binder, 30-40 parts high-alumina powder, 30-40 parts calcined coal gangue mullite, 4-8 parts kyanite, and 2-7 parts composite additives. The composite additives include 1-3 parts CMC and 1-4 parts solid aluminum dihydrogen phosphate. The calcined coal gangue mullite consists of mullite particles generated in situ from high-temperature calcination of coal gangue, exhibiting irregular angular shapes, rough surfaces, and a micron-sized shallow microporous structure. This invention significantly improves the material's density and mechanical strength through a triple synergistic innovation: a customized rigid framework of microporous interlocking crystal network based on coal gangue; a time-sequential iron component secondary mineralization enhancement mechanism across the entire temperature range; and a kyanite phase transformation symbiotic crystal phase and dynamic expansion compensation system. This approach balances practicality in construction with long-term industrial service performance.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, specifically to a high-temperature refractory mortar. Background Technology

[0002] High-temperature refractory mortar is a core cementing material for the construction and repair of refractory linings in high-temperature industrial kilns and thermal equipment. It is widely used in high-temperature industries such as metallurgy, building materials, chemicals, and power generation, primarily playing a crucial role in bonding refractory masonry, filling gaps, sealing and protecting the structure, and balancing furnace stress. The workability, room-temperature bonding performance, high-temperature mechanical stability, thermal shock resistance, and sintering density of the refractory mortar directly determine the overall integrity, sealing and seepage prevention capabilities, and long-term safe service life of the refractory masonry.

[0003] Currently, most mainstream high-temperature refractory mortars on the market are simply compounded from clay, high-alumina powder, conventional refractory aggregates, and a small amount of additives. The formulation structure is relatively traditional, and the overall technology exhibits significant homogenization. The refractory aggregates used in conventional refractory mortars are mostly industrially produced general-purpose powders, with standard particle morphology and size distribution. The selection and combination of raw materials are relatively simple. Under conventional preparation processes, the powders rely solely on simple physical mixing, resulting in insufficient powder-level formulation rationality, limited packing density, and a high proportion of porosity within the formed blank, making it difficult to further improve the overall sintering density. Due to limitations in raw material characteristics and formulation systems, the overall bonding stability is insufficient. During long-term high-temperature service, problems such as structural loosening, joint cracking, and sealing failure easily occur, affecting the overall performance of the masonry. In terms of raw material selection, metallic impurities are generally considered unfavorable components in refractory materials. Conventional industry solutions tend to use high-purity, low-impurity refractory raw materials to avoid the refractory performance degradation caused by the formation of low-melting-point phases at high temperatures. While this approach ensures the basic refractory temperature of the material, it also introduces significant performance limitations. High-purity, low-impurity raw material systems have relatively simple chemical activity, resulting in a relatively gradual phase evolution during high-temperature sintering. This makes it difficult to achieve continuous strengthening of the sintered structure based on its own composition, leading to performance fluctuations in the refractory slurry within the intermediate-temperature transition range, poor strength stability, and a clear performance weakness. This makes it difficult to adapt to complex service environments with large temperature ranges and frequent operational fluctuations.

[0004] In summary, existing conventional high-temperature refractory mortars generally suffer from common industry problems such as traditional solidification of formulation systems, poor powder compaction, limited bonding stability, large performance fluctuations in temperature range, significant high-temperature sintering shrinkage, and insufficient thermal shock resistance. They are difficult to simultaneously achieve excellent construction performance, structural stability across the entire temperature range, and long-term service reliability, and cannot fully meet the long-term, low-consumption, and highly stable usage requirements of modern large-scale high-temperature industrial equipment. Summary of the Invention

[0005] This invention provides a high-temperature refractory mortar to solve the technical problems of existing refractory mortars, such as limited bonding stability, large performance fluctuations in the temperature range, significant high-temperature sintering shrinkage, and insufficient thermal shock resistance.

[0006] To solve the above problems, the present invention provides a high-temperature refractory mortar using the following technical solution: By weight, it includes the following components: 15-25 parts clay binder, 30-40 parts high alumina powder, 30-40 parts calcined coal gangue mullite, 4-8 parts kyanite, and 2-7 parts composite additives.

[0007] The composite additives include 1-3 parts of CMC and 1-4 parts of solid aluminum dihydrogen phosphate.

[0008] The coal gangue calcined mullite is mullite particles generated in situ by high-temperature calcination of coal gangue. The particles are irregularly angular, have a rough surface, and have a micron-level shallow microporous structure.

[0009] Furthermore, the particle size of the calcined mullite from the coal gangue is 180–325 mesh, with a median diameter D50 of 40–70 μm; the particle size of the high-alumina powder is 250–325 mesh, with a median diameter D50 of 20–45 μm; and the particle size of the clay binder is ≥300 mesh, with a median diameter D50 of 10–25 μm.

[0010] The kyanite has a particle size of 150-250 mesh and a median diameter D50 of 40-80 μm; both the CMC and solid aluminum dihydrogen phosphate are ultrafine powders of 300 mesh or above.

[0011] Furthermore, each powder forms a multi-level continuous gradation structure of coarse, medium, and fine particles, and the overall particle packing porosity of the system is ≤18%.

[0012] Furthermore, the high-alumina powder contains 55%-65% aluminum and 1.2%-1.8% iron.

[0013] Furthermore, the aspect ratio of the calcined coal gangue mullite particles is 1.2 to 2.0, the micropore diameter on the particle surface is 1 to 10 μm, and the closed-pore porosity of the particles is 3% to 8%.

[0014] Furthermore, the mullite crystal phase content in the calcined coal gangue mullite is ≥90wt%, and the mullite is a needle-like and columnar interlocking crystal with a crystal length of 5-30μm, forming an interlocking mullite crystal network structure inside the particles.

[0015] Furthermore, during high-temperature service, the kyanite undergoes a phase transformation to generate secondary mullite in situ. The secondary mullite crystals have a grain size of 3–15 μm and form a symbiotic composite crystal phase structure with the calcined mullite from coal gangue.

[0016] The high-temperature service temperature is 1000~1350℃.

[0017] Furthermore, by controlling the high-temperature firing temperature of 1000–1350°C, solid aluminum dihydrogen phosphate reacts with the alumina components in the high-alumina powder and coal gangue calcined mullite within the system to generate needle-like and rod-shaped high-temperature resistant aluminum phosphate crystals. The crystal length of the aluminum phosphate crystals is 2–15 μm, the aspect ratio is 3–8, and the main phase is a stable aluminum phosphate multiphase.

[0018] The needle-shaped aluminophosphate crystals are randomly interspersed and bridged between the rigid mullite crystal network and the silicate sintered phase formed by clay sintering, filling the microscopic gaps in the system and crosslinking the matrix phases to form a dense, interlocking, multi-element interlocking three-dimensional composite network.

[0019] Furthermore, after the refractory slurry is dried and formed, the overall average pore size is ≤2μm, the total porosity is 12%~20%, and there are no interconnected pores with a pore size greater than 10μm.

[0020] The beneficial effects of the high-temperature refractory mortar provided by this invention are: 1. This invention utilizes a proprietary gradient rapid calcination process to customize and obtain coal gangue mullite aggregate with rough edges, surface micropores, and a three-dimensional needle-like interlocking crystal network, distinguishing it from traditional smooth, spherical, non-porous, dense mullite. This unique microstructure can form a mechanical anchoring and interlocking effect with the matrix, significantly improving the powder packing density and interfacial bonding strength. It effectively inhibits high-temperature sintering shrinkage, porosity defects, and crack initiation, significantly improving the room-temperature bonding performance, high-temperature mechanical strength, dimensional stability, and re-softening temperature of refractory mortar. This solves the technical problems of weak interfacial bonding, easy high-temperature shrinkage and cracking, and poor structural stability of traditional refractory mortar.

[0021] 2. This invention abandons the conventional understanding in the field of pursuing low-iron, high-purity raw materials, creatively limiting the iron content of high-alumina powder to a precise range of 1.2%–1.8%, and establishing a time-series control system of "first calcining to shape the mullite crystal network, then secondary mineralization of the iron component during the firing stage." This avoids the defects of premature high-temperature calcination of the iron component to generate a low-melting-point glass phase, iron-aluminum spinel leading to crystal network damage, and crystal spheroidization; by utilizing the secondary synergistic induction effect of the iron component during the firing stage, it precisely promotes the growth of needle-like aluminophosphate crystals, achieving interfacial cross-linking, crystal growth, and micro-defect repair, constructing a complete three-dimensional inorganic bonding network, eliminating the drawbacks of traditional refractory slurry such as mid-temperature strength discontinuity and loose structure, and achieving stable and excellent mechanical properties across the entire temperature range.

[0022] 3. This invention introduces kyanite as a functional component, leveraging its high-temperature phase transformation properties to generate secondary mullite in situ. This secondary mullite forms a symbiotic composite crystalline phase with the primary mullite, strengthening the rigidity of the matrix framework. Simultaneously, it utilizes the moderate volume expansion generated by the phase transformation to dynamically compensate for the sintering shrinkage of the system, fundamentally suppressing the initiation and propagation of high-temperature microcracks. This effectively solves the core problems of traditional refractory mortars, such as lack of shrinkage compensation, poor thermal shock stability, and large high-temperature dimensional deviations. It significantly improves the service life of the material under cyclic temperature change conditions and the sealing accuracy of the masonry, making it suitable for various complex high-temperature industrial kiln construction and repair scenarios. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.

[0024] The principles and spirit of the present invention will be explained in detail below with reference to several representative embodiments.

[0025] Example 1 of a high-temperature refractory mortar provided by the present invention: By weight, it includes the following components: 20 parts clay binder, 35 parts high alumina powder, 35 parts calcined coal gangue mullite, 6 parts kyanite, and 4 parts composite additives; of which 2 parts are CMC and 2 parts are solid aluminum dihydrogen phosphate.

[0026] Among them, coal gangue calcined mullite is mullite particles generated in situ by high-temperature calcination of coal gangue. The particles are irregularly angular, have a rough surface, and have a micron-level shallow microporous structure.

[0027] Specifically, the calcined mullite from coal gangue is 180–325 mesh, with a D50 of 55 μm, an aspect ratio of 1.6, surface micropores of 3–6 μm, closed-cell porosity of 5%, and a mullite crystalline phase content of 92%. The mullite consists of needle-like and columnar interlocking crystals with a crystal length of 5–30 μm, forming an interlocking mullite crystal network structure within the particles. The high-alumina powder is 250–325 mesh, with a D50 of 30 μm, an alumina content of 59%, and an iron content of 1.5%. The clay binder is ≥300 mesh, with a D50 of 18 μm. The kyanite is 150–250 mesh, with a D50 of 60 μm (40–80 μm). CMC and solid aluminum dihydrogen phosphate are both 300 mesh ultrafine powders. All powders form a multi-level continuous gradation structure of coarse, medium, and fine particles, with an overall particle packing porosity of 16%.

[0028] In this embodiment, after the refractory mortar is fired at 1000–1350℃ for 2 hours, kyanite undergoes a phase transformation to generate secondary mullite with a particle size of 3–15 μm in situ, forming a symbiotic composite crystalline structure with calcined coal gangue mullite. Within the system, solid aluminum dihydrogen phosphate reacts with the alumina components of high-alumina powder and coal gangue mullite to generate needle-like and rod-shaped stable aluminum phosphate multiphase crystals with a length of 2–15 μm and an aspect ratio of 3–8. Alumina phosphate crystals randomly interweave and bridge between the rigid mullite crystalline network and the sintered clay silicate phase, filling microscopic gaps and crosslinking the matrix phases to form a multi-element interlocking three-dimensional composite network. The finished refractory mortar has an overall average pore size ≤2 μm and no interconnected pores larger than 10 μm.

[0029] In this embodiment, coal gangue is used in conjunction with a dedicated gradient rapid calcination process to prepare needle-like / columnar interwoven crystalline network mullite in situ. The specific steps are as follows: (1) Raw material pretreatment: Select raw coal gangue solid waste, and only process it by crushing, grinding and screening, without deep magnetic separation to remove impurities, so as to completely retain the original trace mineralized impurities of coal gangue; (2) Spreading treatment: Loosely spread the coal gangue powder to ensure uniform heating during calcination; (3) Gradient rapid heating: The temperature is increased at a constant rate from room temperature to 1100℃. The heating rate in the key crystallization range of 1100℃ to 1450℃ is controlled at 8 to 12℃ / min to break the isotropic growth balance of the crystal. (4) Low temperature short-time crystallization: keep warm at 1400~1500℃ for 1~1.5h to avoid the crystal spheroidization defect of high temperature overheating; in this temperature range, the 0.5% Fe iron powder introduced and the original impurities of coal gangue are synergistically mineralized, reducing the activation energy of specific crystal faces of mullite, inducing the crystals to preferentially grow into high aspect ratio needle-shaped and columnar morphologies, and spontaneously overlapping to form a three-dimensional interlocking crystal network; (5) Gradient cooling lock-in: In the crystal form stabilization range of 1450 ℃~800 ℃, the cooling rate is controlled at 6~10 ℃ / min. Rapid cooling locks in the needle-like columnar crystal network, micron-level micropores on the surface and rough edge microstructure, preventing the crystals from slowly rearranging and spheroidizing in the high-temperature range; in the range below 800 ℃, the furnace is naturally and slowly cooled to gradually release the internal thermal stress of the material and avoid cracking defects in the powder. (6) Screening and grading: control the finished mullite to 180-325 mesh, D50=55μm, and the mullite crystal phase content to 92%, and set aside for later use.

[0030] Mix all the powders together evenly, and add 32%-40% water to form a slurry before use.

[0031] Example 2 of a high-temperature refractory mortar provided by the present invention: The difference between this embodiment and Embodiment 1 is that, by weight, it includes the following components: 15 parts clay binder, 40 parts high alumina powder, 30 parts calcined coal gangue mullite, 4 parts kyanite, and 2 parts composite additives; of which 1 part CMC and 1 part solid aluminum dihydrogen phosphate.

[0032] Example 3 of a high-temperature refractory mortar provided by the present invention: The difference between this embodiment and Embodiment 1 is that, by weight, it includes the following components: 25 parts clay binder, 30 parts high alumina powder, 40 parts calcined coal gangue mullite, 8 parts kyanite, and 7 parts composite additives; of which 3 parts are CMC and 4 parts are solid aluminum dihydrogen phosphate.

[0033] Comparative Example 1 The difference between this comparative example and Example 1 is that the angular coal gangue-based mullite with micron-sized pores on its surface is replaced with smooth, spherical, non-porous mullite prepared from the same particle size, crystal phase content, and source material.

[0034] The coal gangue calcined mullite in this comparative example was produced using conventional process steps: 1. Take coal gangue solid waste of the same origin as the sample in Example 1 as the base raw material, and perform impurity removal treatment on the coal gangue powder to remove mineralized impurities such as Fe and Ti in the system, so that the iron content of the raw material is reduced to below 0.5%.

[0035] 2. High-pressure compact forming reduces internal pores.

[0036] 3. Low-speed, uniform heating throughout the entire calcination process. A low-speed, uniform heating regime is employed throughout, with the overall heating rate controlled at 3–5 °C / min. There is no rapid thermal shock, resulting in uniform growth rates across all crystal faces, no preferred orientation, and no formation of oriented columnar / acicular crystals.

[0037] 4. Ultra-high temperature and long-term heat preservation. The calcination temperature is raised to 1550-1650℃ and held at a constant temperature for 2-4 hours. Through ultra-high temperature and long-term heat preservation, the particles are fully sintered and densified, while the initial fine needle-like microcrystals are melted, agglomerated, and spheroidized to form regular and rounded discrete granular crystals.

[0038] 5. Slow natural cooling in the furnace. After calcination, the entire furnace is slowly cooled, allowing the crystal lattice to become regular and the interfaces to become smooth, ultimately forming isolated granular mullite particles with smooth surfaces and dense structures.

[0039] 6. Crushing, shaping, and sieving. After cooling, the material is crushed, shaped, and sieved to obtain conventional granular mullite powder with uniform particle size and a dense, smooth surface.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that the active high-alumina powder with an iron content of 1.2%-1.8% is replaced with conventional high-purity high-alumina powder with the same particle size, the same alumina matrix, and an Fe content of ≤0.7%.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that kyanite is replaced with an equal amount of quartz powder.

[0042] Standard tests were conducted on the products from Examples 1-3 and Comparative Examples 1-3.

[0043] The samples were uniformly prepared as standard 40mm×40mm×160mm specimens, naturally cured for 24 hours, dried at 110℃ for 2 hours, and fired at 1000~1350℃ for 2 hours. The bonding strength at room temperature, flexural strength after firing at 1300℃, linear change rate at 1350℃, apparent porosity, number of thermal shock cycles, re-softening temperature, and construction grade were uniformly tested.

[0044] The softening temperature was tested under a national standard load of 0.6 MPa. Specific performance data are shown in the table below. Example 1 1.85 4.25 -0.28 15.6 ≥38 1380 excellent Example 2 1.52 4.51 -0.22 14.8 32 1410 excellent Example 3 2.12 4.2 -0.32 17.2 42 1350 excellent Comparative Example 1 1.42 2.76 -0.72 23.8 19 1220 good Comparative Example 2 1.63 3.35 -0.56 18.9 25 1300 excellent Comparative Example 3 1.48 2.94 -0.91 21.5 20 1230 good Combined with data analysis: 1. Comparative Example 1 was replaced with conventional smooth spherical non-porous mullite of the same origin, particle size, and crystalline phase content, and the core characteristics of "1.2–2.0 particle aspect ratio, 1–10 μm surface micropores, 3%–8% closed-cell porosity, and needle-like interlocking crystalline network structure" specified in this application were removed. Experimental results showed that Comparative Example 1 exhibited significant decreases in room temperature bond strength, high-temperature flexural strength, thermal shock stability, and softening temperature, while high-temperature sintering linear shrinkage and apparent porosity increased significantly.

[0045] Analysis reveals that conventional spheroidized mullite particles have smooth surfaces, lack anchoring micropores, and lack a three-dimensional interlocking crystalline framework. Relying solely on simple physical stacking, they cannot form a mechanically anchored structure with the slurry, resulting in weak interfacial bonding. Simultaneously, the particle packing porosity significantly exceeds the standard, leading to a deterioration of the microporous structure within the molded body. Numerous interconnected macropores form stress concentration sources, and the lack of framework constraint during high-temperature sintering results in severe shrinkage cracking.

[0046] 2. Comparative Example 2 used low-iron, high-purity, high-alumina powder (Fe≤0.7%) instead of the iron-containing active high-alumina powder specified in this application, only lacking the limiting iron content mineralization activity variable. Experimental results showed that Comparative Example 2 exhibited significantly inferior mechanical properties at room temperature and high temperature, high-temperature dimensional stability, and thermal shock resistance compared to Example 1.

[0047] The mechanism is as follows: In Comparative Example 1, high-alumina powder with an iron content of 1.2%–1.8% can achieve precise secondary mineralization activation within the sintering range of 1000–1350℃, inducing the system to generate sufficient needle-like and rod-shaped aluminophosphate multiphase crystals with an aspect ratio of 3–8. These crystals randomly interweave and crosslink with the mullite crystal network and the silicate sintered phase, constructing a continuous and dense three-dimensional bonded network. Low-iron high-alumina powder lacks sufficient mineralization induction activity, resulting in sparse, short, and discontinuous phosphate crystal development. This makes it impossible to achieve interface defect repair and phase interface bonding enhancement, leading to a large number of microstructural defects in the system.

[0048] In addition, the iron component in the high-alumina powder acts as a secondary synergistic induction source in the later stage, which only acts on the slurry during the firing stage at 1000-1350℃. It specifically achieves interfacial cross-linking, crystal growth, and micro-defect repair, and has a boosting effect of activating, strengthening, and densifying the already formed mullite crystal network.

[0049] 3. Comparative Example 3 replaced kyanite with an equal amount of quartz powder, eliminating the phase transformation expansion compensation and secondary mullite symbiotic structure. Experimental results showed that Comparative Example 3 exhibited a significantly increased high-temperature linear shrinkage rate, a substantial decrease in the number of thermal shock cycles, and a marked reduction in high-temperature strength and re-softening temperature, making it the group with the most significant performance degradation among the three comparative examples.

[0050] The principle is as follows: In Example 1, kyanite can undergo an in-situ phase transformation during high-temperature service to generate 3-15μm secondary mullite, forming a primary-secondary composite symbiotic crystalline phase with the main acicular mullite, thus strengthening the overall framework rigidity. Simultaneously, the moderate volume expansion generated during the phase transformation process precisely offsets the volume shrinkage caused by clay and powder sintering, inhibiting the initiation and propagation of microcracks at their source. After replacing the inert quartz powder, the system completely loses the dual effects of dynamic shrinkage compensation and crystalline phase symbiotic reinforcement, leading to a concentrated outbreak of sintering defects.

[0051] In summary, 1. This invention significantly improves the density, mechanical strength, and high-temperature stability of mud structure through a proprietary angular microporous crystalline network mullite structure. Compared to the smooth, spherical, non-porous mullite used in Comparative Example 1, the coal gangue calcined mullite specified in this invention possesses an aspect ratio of 1.2–2.0, surface micropores of 1–10 μm, and a three-dimensional needle-like interlocking crystalline network structure, which can form a mechanical anchoring and interlocking effect with the bonding system.

[0052] Experimental data show that, compared with Comparative Example 1, Example 1 exhibits the following improvements: room temperature bond strength increased from 1.42 MPa to 1.85 MPa; flexural strength after burning at 1300℃ increased from 2.76 MPa to 4.25 MPa; apparent porosity decreased from 23.8% to 15.6%; high-temperature linear shrinkage was optimized from -0.72% to -0.28%; re-softening temperature increased by 160℃; and thermal shock cycle performance was more than doubled.

[0053] This invention demonstrates that the customized mullite microstructure can significantly optimize powder packing density, strengthen interfacial bonding strength, suppress high-temperature sintering shrinkage and pore defect formation, and fundamentally improve the material's mechanical properties and high-temperature structural stability.

[0054] 2. By limiting the active range of high alumina powder to 1.2% to 1.8% iron content, this invention ensures sufficient mineralization reaction of the system and achieves stable performance across the entire temperature range.

[0055] Comparative Example 2 used low-iron, high-purity, high-alumina powder (Fe≤0.7%), lacking the appropriate iron mineralization and activation effect, resulting in insufficient development of aluminophosphate crystals and an incomplete cross-linking network. Comparative experimental data shows that Example 1 exhibits significantly better mechanical strength, dimensional stability, and thermal shock resistance at both ambient and high temperatures than Comparative Example 2. Specifically, the flexural strength after firing increased by 26.9%, and high-temperature linear shrinkage and porosity defects were significantly improved. This invention overcomes the technical inertia of solely pursuing low-iron, high-purity raw materials. By precisely defining the active range of iron content, it stably induces a high-temperature solid-state reaction to generate needle-like aluminophosphate multiphase crystals, constructing a continuous inorganic cross-linking network. This eliminates the defects of traditional refractory slurries, such as temperature strength discontinuities and structural looseness, ensuring continuous and stable mechanical properties of the material across the entire temperature range.

[0056] 3. This invention effectively suppresses sintering shrinkage and significantly improves thermal shock stability and high-temperature dimensional accuracy through the kyanite phase transformation symbiosis and expansion compensation mechanism.

[0057] Comparative Example 3, which uses quartz powder instead of kyanite, loses the high-temperature phase transformation expansion compensation and the symbiotic reinforcement effect of secondary mullite, resulting in the most significant performance degradation. Data shows that Comparative Example 3 has a high-temperature linear shrinkage rate as high as -0.91%, an apparent porosity of 21.5%, and only 20 thermal shock cycles, with all core performance characteristics far inferior to Example 1. This invention generates 3-15μm secondary mullite through a high-temperature in-situ phase transformation of kyanite, forming a symbiotic composite crystalline phase with the primary mullite, strengthening the rigid framework of the matrix. Simultaneously, the moderate volume expansion generated by the phase transformation precisely offsets the sintering shrinkage of the system, effectively inhibiting the initiation and propagation of microcracks, significantly improving the high-temperature dimensional stability and thermal shock fatigue resistance of the slurry, making it suitable for long-term cyclic temperature-varying service conditions in kilns.

[0058] Those skilled in the art will understand that the embodiments described below are only some, not all, of the embodiments disclosed herein. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

Claims

1. A high-temperature refractory mortar, characterized in that, By weight, it includes the following components: 15-25 parts clay binder, 30-40 parts high alumina powder, 30-40 parts calcined coal gangue mullite, 4-8 parts kyanite, and 2-7 parts composite additives. The composite additive includes 1-3 parts of CMC and 1-4 parts of solid aluminum dihydrogen phosphate; The coal gangue calcined mullite is mullite particles generated in situ by high-temperature calcination of coal gangue. The particles are irregularly angular, have a rough surface, and have a micron-level shallow microporous structure.

2. The high-temperature refractory mortar according to claim 1, characterized in that, The calcined mullite from the coal gangue has a particle size of 180–325 mesh and a median diameter D50 of 40–70 μm; the high-alumina powder has a particle size of 250–325 mesh and a median diameter D50 of 20–45 μm; and the clay binder has a particle size ≥300 mesh and a median diameter D50 of 10–25 μm. The kyanite has a particle size of 150-250 mesh and a median diameter D50 of 40-80 μm; both the CMC and solid aluminum dihydrogen phosphate are ultrafine powders of 300 mesh or above.

3. The high-temperature refractory mortar according to claim 2, characterized in that, Each powder forms a multi-level continuous gradation structure of coarse, medium and fine particles, and the overall particle packing porosity of the system is ≤18%.

4. The high-temperature refractory mortar according to claim 2, characterized in that, The high-alumina powder contains 55%-65% aluminum and 1.2%-1.8% iron.

5. The high-temperature refractory mortar according to claim 1, characterized in that, The coal gangue calcined mullite particles have an aspect ratio of 1.2 to 2.0, a micropore diameter of 1 to 10 μm on the particle surface, and a closed-pore porosity of 3% to 8%.

6. The high-temperature refractory mortar according to claim 5, characterized in that, The calcined mullite from the coal gangue contains ≥90wt% mullite crystal phase, and the mullite is a needle-like and columnar interlocking crystal with a crystal length of 5-30μm. The particles form an interlocking mullite crystal network structure.

7. The high-temperature refractory mortar according to claim 6, characterized in that, During high-temperature service, the kyanite undergoes a phase transformation to generate secondary mullite in situ. The secondary mullite crystals have a grain size of 3–15 μm and form a symbiotic composite crystal phase structure with the calcined mullite from coal gangue.

8. The high-temperature refractory mortar according to claim 7, characterized in that, By controlling the high-temperature firing temperature of 1000-1350℃, solid aluminum dihydrogen phosphate reacts with the alumina component in the high-alumina powder and coal gangue calcined mullite in the system to generate needle-shaped and rod-shaped high-temperature resistant aluminum phosphate crystals. The crystal length of the aluminum phosphate crystals is 2-15 μm and the aspect ratio is 3-8. The main phase is a stable aluminum phosphate multiphase. The needle-shaped aluminophosphate crystals are randomly interspersed and bridged between the rigid mullite crystal network and the silicate sintered phase formed by clay sintering, filling the microscopic gaps in the system and crosslinking the matrix phases to form a dense, interlocking, multi-element interlocking three-dimensional composite network.

9. The high-temperature refractory mortar according to claim 1, characterized in that, After drying and molding, the refractory slurry has an overall average pore size of ≤2μm, a total porosity of 12% to 20%, and no interconnected pores with a pore size greater than 10μm.