A wet spraying material special for rotary kiln mouth and a preparation and construction method thereof

Abstract

The present application relates to a kind of wet spraying material of rotary kiln mouth special and its preparation and construction method, wherein the raw material of wet spraying material includes the following components according to mass fraction: aggregate 58-70 parts, matrix 26-36 parts, calcium aluminate cement 5-7 parts, composite modifier 0.3-0.6 parts, polyethylene fiber 0.05-0.06 parts, coagulant 0.2-0.3 parts.The spraying material provided in the present application is specially designed for the special working conditions of rotary kiln mouth 1200-1400 ℃ alternate high temperature, mechanical scouring, cold and hot impact, medium erosion, aggregate is graded and matched, cooperates with superfine powder and composite modifier, improves the plasticity, thermal shock resistance and erosion resistance of spraying material, solves the problems of insufficient high-temperature resistance, thermal shock resistance, wear resistance and erosion resistance of existing general wet spraying material, and low density and bonding force.

Description

Technical Field

[0001] This invention belongs to the technical field of rotary kiln refractory materials, specifically relating to a special wet spray coating for rotary kiln inlet and its preparation and application method. Background Technology

[0002] As the core equipment for cement clinker calcination, metallurgical smelting, and chemical raw material roasting, the rotary kiln has a kiln inlet that is a critical weak point. It is constantly exposed to alternating high-temperature environments of 1200-1400℃, and is subjected to mechanical scouring when materials enter the kiln, frictional wear caused by the rotation of the kiln body, and severe thermal shock caused by the intrusion of cold air. It is also subject to erosion by acidic media and molten materials in the flue gas, which makes the refractory lining of the kiln inlet extremely susceptible to damage such as peeling, cracking, wear, and erosion.

[0003] Currently, the protection of rotary kiln inlets mainly employs two methods: refractory brick lining or castable refractory casting. Refractory brick lining suffers from drawbacks such as long construction periods, numerous joints, poor thermal shock resistance, and difficulty in repairing damage. Furthermore, it is difficult to adapt to the irregular structure of the kiln inlet, requiring prolonged kiln shutdown for repairs, severely impacting production efficiency. Castable refractory casting requires the erection of molds before mixing, transporting, and pouring, resulting in a complex construction process and high labor intensity.

[0004] Dry spray coatings generate a large amount of dust during application, which not only pollutes the environment and harms the health of operators, but also has problems such as high rebound rate (usually 15%-25%), serious material waste, low density of the sprayed layer, and poor bonding strength, resulting in a short service life of the sprayed layer and the need for frequent repairs. Semi-dry spray coatings, on the other hand, have drawbacks such as difficulty in accurately controlling the amount of water added, easy formation of pores and cracks in the sprayed layer, and insufficient erosion resistance, which cannot meet the requirements for long-term stable operation of kilns.

[0005] Compared with dry spraying, wet spraying has significant advantages such as less dust, less spray rebound, higher coating density, higher bonding strength, and higher construction efficiency, and has been gradually applied in the field of kiln refractory protection. However, most existing wet spraying coatings are general-purpose formulas and have not been optimized for the special working conditions of rotary kiln inlets, resulting in the following core defects: First, insufficient high-temperature resistance; in the alternating high-temperature environment of 1200-1400℃ at the kiln inlet, it is prone to softening, sintering deformation, and poor thermal shock resistance, frequently resulting in thermal shock cracking; Second, lack of wear resistance and erosion resistance; unable to resist material erosion and the erosion of flue gas and molten media, resulting in rapid coating wear; Third, poor construction adaptability; difficult material pumping, easy pipe blockage; either too fast setting speed leading to uneven coating, or too slow setting speed affecting construction efficiency, and insufficient bonding strength with the kiln inlet substrate, easily leading to peeling; Fourth, some wet spraying coatings use binders and additives that pose environmental hazards, and the utilization rate of raw materials is low, which does not meet the requirements of green production.

[0006] In existing related technologies, such as: CN107140997A discloses a kiln mouth castable and its production process. The formula is as follows: 8-15% homogenized bauxite with a particle size of 1-8mm, 5-10% calcined bauxite with a particle size of 1-8mm, 20-25% silicon carbide with a particle size of 1-3mm, 10-15% andalusite with a particle size of 1-3mm, 4-10% high-alumina bauxite powder with a particle size of 0.001-0.088mm, 3-5% calcined α-alumina with a particle size of 0-2.5μm, 5-8% silica powder with a particle size of 0-0.15μm, 20-25% white corundum powder with a particle size of 1-4mm, 5-10% calcium aluminate cement, 0.1-0.5% explosion-proof fiber, 5-8% hollow alumina spheres with a particle size of 1-8mm, and 0.2-0.3% composite water-reducing agent. The sum of the contents of the above components is 100%.

[0007] CN113416067A discloses an anti-oxidation and impact-resistant castable for molten iron ladles, its preparation method, and the molten iron ladle itself. The ladle is composed of the following materials in the indicated mass percentages: sintered mullite aggregate: 50-65%, andalusite: 3-8%, silicon carbide: 3-14%, fused mullite fine powder: 10%-30%, zirconium mullite fine powder: 0.01%-5%, alumina micro powder: 0.1%-3%, aluminum powder: 0.05%-0.1%, pure calcium aluminate cement binder: 3-6%, NaHCO3: 0.01%-0.1%, boric acid: 0.02%-0.12%, water glass: 0.01%-0.3%, and water-reducing agent FDN: 0.03%-0.13%.

[0008] CN114873978 A discloses a medium-low temperature, high-strength, wear-resistant wet-process spray coating. The components include: 55-70 parts aggregate; 5-10 parts ultrafine powder of one or more of the following: activated alumina, or dust collected during the production of mullite or corundum; 2-6 parts ultrafine silica powder; 10-30 parts aluminate cement; 0.5-2 parts white mud; 0.03-0.5 parts wear-resistant fiber; and 0.05-0.5 parts pumping admixture. The aggregate is selected from one or more of bauxite, brown corundum, and calcium aluminate titanate. The coating provided by this patent is mainly suitable for medium-low temperature applications below 800℃, and cannot adapt to the high-temperature conditions of 1200-1400℃ at the kiln mouth of a rotary kiln. Furthermore, its wear resistance and erosion resistance are insufficiently optimized for material erosion and media corrosion at the kiln mouth. CN 111574201A discloses a magnesium-carbon wet spray coating. The dry powder of the coating includes 80-90% Wt magnesia, 2-15% Wt carbon materials, 0.5-5% Wt sintering agent, 0.5-5% Wt bentonite, and 0.05-0.3% Wt water-reducing agent. The coating provided by this patent is mainly used for hot repair of steel ladles. Its formulation system is designed for the operating conditions of steel ladles and has poor adaptability to the alternating high temperature, mechanical erosion, and thermal shock conditions of rotary kiln inlets. Furthermore, the introduction of graphite components easily leads to high-temperature oxidation and peeling of the sprayed layer, which cannot meet the long-term protection requirements of rotary kiln inlets.

[0009] Other related technologies: CN120794588A discloses a self-leveling high-temperature resistant wet spray coating for blast furnaces and its preparation method. The coating consists of 20-40 parts of white corundum aggregate with a particle size of 0.5-3mm; 15-25 parts of activated alumina micropowder with a D90 particle size of <10μm; 10-20 parts of high-alumina cement; 8-15 parts of silica sol with a solid content of 30%; 2-5 parts of dehydrated sodium silicate; 1-3 parts of modified bentonite; 0.3-1.0 parts of heat-resistant polymer thickener; 0.05-0.2 parts of defoamer; and 10-25 parts of water. The highest compressive strength at room temperature is 45.1 MPa (Example 2), and the highest strength after cooling is 76.2 MPa (Example 1). CN118439852A discloses a wet spray coating for steel ladle lining and its application method, which is composed of 12-14 wt% bauxite particles, 50-52 wt% tabular corundum particles, 19-23 wt% white corundum fine powder, 4-6 wt% fused magnesia fine powder, 4-6 wt% alumina micro powder, 2-6 wt% binder, and 1-3 wt% sintering accelerator; at the same time, 0.1-0.3 wt% explosion retardant, 0.8-1 wt% coagulation accelerator and 2-4 wt% coagulation accelerator are added. The highest compressive strength is 39.3 MPa, and the maximum number of uses is 45 (Example 2); CN118184305A discloses a self-healing wet spray coating and spraying method for repairing molten iron ladles, wherein the components include 35-45 wt% sapphire or mullite, 20-40 wt% titanium corundum, 6-12 wt% silicon carbide, 6-12 wt% alumina micro powder and 0-6 wt% pumping additives. The cold compressive strength after heat treatment at 110℃ for 3 hours is 40~45 MPa (Example 2); CN106699205B discloses a sol-bonded wet spray coating for blast furnace lining and its preparation method. The raw material composition is as follows: silicon carbide ≤30 parts by weight, high alumina material ≤80 parts by weight, mullite ≤60 parts by weight, fused alumina ≤60 parts by weight, alumina powder 3-20 parts by weight, silica fume 3-20 parts by weight, clay ≤5 parts by weight, resin powder 0.5-5 parts by weight, organic fiber 0.02-1 parts by weight, interface agent ≤1 part by weight, coagulant 0.01-0.2 parts by weight, dispersant 0.02-0.2 parts by weight, sol 8-12 parts by weight.

[0010] The aforementioned coatings are all designed for equipment such as blast furnaces, ladles, and molten iron ladles, and their effectiveness is unlikely to meet the requirements of rotary kiln inlets.

[0011] Therefore, it is necessary to develop a special wet spray coating that can adapt to the special working conditions of rotary kiln inlets, and has excellent high temperature resistance, thermal shock resistance, wear resistance, and erosion resistance, as well as convenient construction, environmental protection and high efficiency, and long service life. At the same time, it is also necessary to develop a matching preparation and construction method to solve the shortcomings of existing technologies. This has become an urgent technical problem to be solved in the field of rotary kiln refractory protection. Summary of the Invention

[0012] To address the shortcomings of existing rotary kiln inlet materials, such as insufficient high-temperature resistance, poor thermal shock resistance, weak wear and erosion resistance, poor construction adaptability, and short service life, this invention provides a special wet spray coating for rotary kiln inlets, along with its preparation and application method. By optimizing the formula components and proportions, improving the preparation process, and standardizing the construction procedure, the coating material is precisely adapted to the working conditions of the rotary kiln inlet, improving the high-temperature stability, wear and erosion resistance, and bonding strength of the spray layer, extending the kiln inlet protection life, reducing construction costs and environmental impact, and ensuring the continuous and stable operation of the rotary kiln.

[0013] The specific technical solution adopted is as follows: A wet spray coating specifically for rotary kiln inlets comprises the following components by weight: 58-70 parts aggregate, 26-36 parts matrix, 5-7 parts calcium aluminate cement, 0.3-0.6 parts composite modifier, 0.05-0.06 parts polyethylene fiber, and 0.2-0.3 parts accelerator.

[0014] Preferably, the raw materials, by mass, include the following components: 60-70 parts aggregate, 26-36 parts matrix, 5-7 parts calcium aluminate cement, 0.3-0.6 parts composite modifier, 0.05-0.06 parts polyethylene fiber, and 0.2-0.3 parts accelerator.

[0015] Further preferred, the raw materials, by mass parts, include the following components: 60-66 parts aggregate, 28-36 parts matrix, 6-7 parts calcium aluminate cement, 0.3-0.4 parts composite modifier, 0.05-0.06 parts polyethylene fiber, and 0.2-0.25 parts accelerator.

[0016] In the above-mentioned spray coatings: The aggregate is a composition of andalusite and silicon carbide, wherein the weight parts of andalusite and silicon carbide in the aggregate are as follows: 10-15 parts and 6-12 parts in the aggregate for 5-3 mm; 6-18 parts and 7-18 parts in the aggregate for 3-1 mm; and 6-10 parts and 8-14 parts in the aggregate for 1 mm or less.

[0017] Preferably, the weight parts of andalusite and silicon carbide in the aggregate are as follows: 12-15 parts and 6-10 parts in the 5-3mm aggregate; 6-18 parts and 7-18 parts in the 3-1mm aggregate; and 8-10 parts and 8 parts in the aggregate not larger than 1mm.

[0018] The matrix is ​​a compound of activated alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of (3-5):(2-4):(1-2) per part of the matrix. Preferably, the weight ratio of the three components per part of the matrix is ​​(3-5):(2-4):1. Most preferably, the weight ratio of the three components is 3:4:1 or 5:2:1.

[0019] The mass percentage of Al2O3 in the calcium aluminate cement is not less than 80%.

[0020] The composite modifier is a compound of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of (2-3):(1-2):(1-2):1.

[0021] Preferably, the weight ratio of the four components in the compound modifier is 2:2:1:1 or 3:2:2:1.

[0022] The coagulant is a lithium hydroxide aqueous solution with a mass percentage concentration of 3-5%.

[0023] The flow value of the wet spray coating material for rotary kiln inlet is 250-300 mm before the addition of the accelerator.

[0024] The second objective of this invention is to provide a method for preparing a wet spray coating specifically for rotary kiln inlets, comprising the following steps: (1) Pre-treated aggregates: andalusite aggregates and silicon carbide aggregates were ball-milled separately with a ball-to-material ratio of 3:1 and a ball-milling time of 30 min. After ball milling, they were screened into three specifications: 5-3 mm, 3-1 mm and no more than 1 mm. (2) Premixing of matrix and composite modifier: The active alumina, zircon powder and silicon oxynitride micro powder in the matrix are mixed in proportion and premixed in a ball mill for 20 min and stored separately; FDN, sodium hexametaphosphate, polyacrylamide and oxalic acid in the composite modifier are mixed in proportion and mixed in a mixer for 30 min and stored separately. (3) Dry material mixing: After the pretreated aggregate, premixed matrix and composite modifier, calcium aluminate cement and polyethylene fiber are mixed in proportion, they are put into a forced mixer. The mixing speed is 10-20 r / min and the mixing time is 10-15 min to ensure that each dry material component is mixed evenly to form a dry material mixture.

[0025] The spray coating prepared by the above method should be sealed in a package to avoid the introduction of impurities and moisture during the packaging process. It should be stored in a dry place for no more than 3 months.

[0026] The third objective of this invention is to provide a method for applying a wet spray coating specifically for rotary kiln inlets, comprising the following steps: (1) Preparation before construction: Clean the rotary kiln inlet substrate, remove floating dust, oil stains, old lining debris and loose debris from the substrate surface, and blow it clean with a high-pressure air gun to ensure that the substrate surface is dry, flat and free of looseness; weld the anchor fasteners firmly; check the spraying equipment to ensure that the spray gun, conveying pipeline and pressure pump are operating normally, the pipeline is free of blockage, and the spray gun outlet pressure is adjusted to 4.5-6.0MPa; (2) Add water to dry material mixture and stir: Pour the dry material mixture into the mixer and add 6-8 parts of water and stir evenly, keeping the flow value of the wet material after adding water at 250-300mm; (3) Spraying construction: Pour the wet material into the hopper of the spraying equipment, start the equipment, and send the wet material to the spray gun through the conveying pipeline by the pressure pump. Add 0.2-0.3 parts of accelerator at the spray gun outlet by pumping. Control the distance between the spray gun and the kiln substrate at 0.8-1.2m. Spray angle is 45°-60°. Move the spray gun at a uniform speed of 0.8-1.2m / min. Use a layered spraying method. The thickness of each layer is 50-100mm. The interval between two adjacent layers is 30-60min until the designed spray thickness (usually 200-300mm) is reached. During the spraying process, adjust the spray gun pressure and spraying speed in real time to ensure that the spray layer is uniform, dense, and free of bubbles, cracks, and missed spraying. (4) Curing treatment: After the spraying is completed, the sprayed layer is naturally cured. The curing environment temperature is 20-30℃, the relative humidity is 60-80%, and the curing time is 24-48h. During the curing period, avoid collisions and vibrations to the sprayed layer and avoid rain washing. After the natural curing is completed, low-temperature baking curing is carried out. The baking temperature is gradually increased from room temperature to 200-250℃, the heating rate is 50-80℃ / h, and the baking time is 3-4h to remove residual moisture in the sprayed layer and improve the strength and stability of the sprayed layer. (5) Heating and commissioning: After the low-temperature baking is completed, the rotary kiln is slowly heated up at a rate of 100-150℃ / h until it reaches the normal operating temperature. During the heating process, the sprayed layer is observed in real time. If slight cracks appear, timely repair spraying is carried out. After the heating is completed, the rotary kiln is put into normal operation. The sprayed layer is inspected regularly, and any damage is repaired in time.

[0027] The rotary kiln inlet-specific wet spray coating provided by this invention has the following advantages: 1. The spray coating provided by this invention is specifically designed for the special working conditions of rotary kiln inlet, such as alternating high temperatures of 1200-1400℃, mechanical erosion, thermal shock, and media erosion. The aggregate adopts graded matching and works synergistically with ultrafine powder and composite modifier to improve the plasticity, thermal shock resistance and erosion resistance of the spray coating. It solves the problems of insufficient high temperature resistance, thermal shock resistance, wear resistance and erosion resistance, as well as low density and bonding strength of existing general-purpose wet spray coatings. It achieves precise adaptation of the spray layer to the working conditions of the kiln inlet and significantly improves the density and long service life of the spray layer.

[0028] Technical solution utilization: The mullite effect of andalusite and the low coefficient of thermal expansion of silicon carbide mean that both andalusite and silicon carbide have good thermal shock resistance and erosion resistance. The matrix components can significantly improve the thermal shock resistance and high temperature stability of the spray coating, and prevent the spray layer from peeling off under alternating hot and cold conditions. Composite modifiers can improve the plasticity and adhesion of spray coatings, reduce cracking of the spray layer, significantly reduce the amount of water added to the spray coating, improve pumping performance, avoid pipe blockage during construction, and regulate the setting speed of the spray coating, taking into account both construction convenience and spray layer strength.

[0029] Accelerators can increase the hardening speed of spray coatings, reduce the sintering temperature of spray coatings, promote the densification of the spray layer, and enhance the spray layer's resistance to alkaline media erosion.

[0030] The accompanying preparation and application methods further ensure the performance of the spray coating.

[0031] 2. The coating material prepared by this invention has a room temperature compressive strength ≥84MPa, a compressive strength after firing at 1100℃ ≥105MPa, a thermal shock resistance (1100℃ water cooling cycle) ≥35 times without cracking or peeling, a wear resistance ≤5cm³, and high bonding strength between the coating material and the kiln substrate.

[0032] Compared to existing dry and semi-dry spray coatings, the service life can be extended from 5 months to more than 8 months, which is more than 60% longer.

[0033] Compared to existing general-purpose wet spray coatings, the above data shows that the service life is extended by more than 40%, which can significantly reduce the number of repairs and lower production costs.

[0034] 3. The spray coating prepared by this invention has excellent pumping performance and no pipe blockage due to optimized raw materials and proportions. The spray rebound rate is ≤5%, and the material utilization rate is high. The dust emission during construction is extremely low, which meets environmental protection requirements. Moreover, the construction efficiency is high. Compared with refractory brick masonry, the construction cycle is shortened by more than 70%. Compared with dry spray coating, the construction efficiency is increased by more than 50%, which can reduce the downtime of rotary kiln and ensure production continuity. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0038] Particle sizes of 5-3mm and 3-1mm are common industry standards. The particles are first passed through a 5mm sieve and then separated by a 3mm sieve.

[0039] Silicon carbide with a particle size of no more than 1 mm is the undersize portion after sieving with a 1 mm sieve.

[0040] Example 1: A wet spray coating specifically for rotary kiln inlets The raw materials used, by weight, include the following components: 12 parts of 5-3mm andalusite, 6 parts of 5-3mm silicon carbide, 6 parts of 3-1mm andalusite, 18 parts of 3-1mm silicon carbide, 10 parts of andalusite no larger than 1mm, 8 parts of silicon carbide no larger than 1mm, 36 parts of matrix, 5 parts of calcium aluminate cement, 0.3 parts of composite modifier, 0.05 parts of polyethylene fiber, and 0.2 parts of accelerator.

[0041] in: The matrix is ​​a compound of activated alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of 3:4:1 in each part of the matrix; The composite modifier is a mixture of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of 2:2:1:1 in each part of the composite modifier; The coagulant is a 5% (w / w) aqueous solution of lithium hydroxide.

[0042] Example 2: A special wet spray coating for rotary kiln inlet The raw materials used, by weight, include the following components: 15 parts of 5-3mm andalusite, 12 parts of 5-3mm silicon carbide, 13 parts of 3-1mm andalusite, 10 parts of 3-1mm silicon carbide, 6 parts of andalusite not larger than 1mm, 14 parts of silicon carbide not larger than 1mm, 26 parts of matrix, 7 parts of calcium aluminate cement, 0.6 parts of composite modifier, 0.06 parts of polyethylene fiber, and 0.3 parts of accelerator.

[0043] in: The matrix is ​​a compound of active alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of 5:2:1 in each part of the matrix; The composite modifier is a mixture of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of 3:1:2:1 in each part of the composite modifier; The coagulant is a 3% (w / w) aqueous solution of lithium hydroxide.

[0044] Example 3: A wet spray coating specifically for rotary kiln inlets The raw materials used, by weight, include the following components: 10 parts of 5-3mm andalusite, 12 parts of 5-3mm silicon carbide, 15 parts of 3-1mm andalusite, 10 parts of 3-1mm silicon carbide, 8 parts of andalusite not larger than 1mm, 8 parts of silicon carbide not larger than 1mm, 32 parts of matrix, 6 parts of calcium aluminate cement, 0.5 parts of composite modifier, 0.05 parts of polyethylene fiber, and 0.2 parts of accelerator.

[0045] in: The matrix is ​​a compound of active alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of 4:3:2 in each part of the matrix; The composite modifier is a mixture of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of 2:1:2:1 in each part of the composite modifier; The coagulant is a 4% (w / w) aqueous solution of lithium hydroxide.

[0046] Example 4: A special wet spray coating for rotary kiln inlet The raw materials used, by weight, include the following components: 15 parts of 5-3mm andalusite, 10 parts of 5-3mm silicon carbide, 18 parts of 3-1mm andalusite, 7 parts of 3-1mm silicon carbide, 8 parts of andalusite not larger than 1mm, 8 parts of silicon carbide not larger than 1mm, 28 parts of matrix, 7 parts of calcium aluminate cement, 0.4 parts of composite modifier, 0.06 parts of polyethylene fiber, and 0.25 parts of accelerator.

[0047] in: The matrix is ​​a compound of active alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of 5:2:1 in each part of the matrix; The composite modifier is a mixture of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of 3:2:2:1 in each part of the composite modifier; The coagulant is a 5% (w / w) aqueous solution of lithium hydroxide.

[0048] Example 5: A special wet spray coating for rotary kiln inlet The raw materials used, by weight, include the following components: 14 parts of 5-3mm andalusite, 6 parts of 5-3mm silicon carbide, 6 parts of 3-1mm andalusite, 18 parts of 3-1mm silicon carbide, 10 parts of andalusite no larger than 1mm, 8 parts of silicon carbide no larger than 1mm, 34 parts of matrix, 6 parts of calcium aluminate cement, 0.5 parts of composite modifier, 0.06 parts of polyethylene fiber, and 0.28 parts of accelerator.

[0049] The matrix contains a compound of activated alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of 3:4:1 in each part of the matrix. The composite modifier is a mixture of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of 2:2:1:1 in each part of the composite modifier; The coagulant is a 3% (w / w) aqueous solution of lithium hydroxide.

[0050] Comparative Example 1: The raw materials used, by weight, include the following components: 18 parts of 5-3mm andalusite, 12 parts of 5-3mm silicon carbide, 10 parts of 3-1mm andalusite, 13 parts of 3-1mm silicon carbide, 10 parts of andalusite not larger than 1mm, 10 parts of silicon carbide not larger than 1mm, 23 parts of matrix, 5 parts of calcium aluminate cement, 0.3 parts of composite modifier, 0.05 parts of polyethylene fiber, and 0.2 parts of accelerator. The matrix is ​​a compound of activated alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of 4:4:1 in each part of the matrix; The composite modifier is a mixture of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of 3:2:1:1 in each part of the composite modifier; The coagulant is a 5% (w / w) aqueous solution of lithium hydroxide.

[0051] Comparative Example 2: The raw materials used, by weight, include the following components: 14 parts of 5-3mm andalusite, 8 parts of 5-3mm silicon carbide, 10 parts of 3-1mm andalusite, 12 parts of 3-1mm silicon carbide, 9 parts of andalusite not larger than 1mm, 12 parts of silicon carbide not larger than 1mm, 27 parts of matrix, 4 parts of calcium aluminate cement, 0.5 parts of composite modifier, 0.06 parts of polyethylene fiber, and 0.1 parts of accelerator.

[0052] in: The matrix is ​​a compound of activated alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of 5:2:2 in each part of the matrix; The composite modifier is a mixture of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of 2:1:1:1 in each part of the composite modifier; The coagulant is a 5% (w / w) aqueous solution of lithium hydroxide.

[0053] Comparative Example 3: The raw materials used, by weight, include the following components: 13 parts of 5-3mm andalusite, 11 parts of 5-3mm silicon carbide, 14 parts of 3-1mm andalusite, 9 parts of 3-1mm silicon carbide, 7 parts of andalusite not larger than 1mm, 9 parts of silicon carbide not larger than 1mm, 38 parts of matrix, 6 parts of calcium aluminate cement, 0.5 parts of composite modifier, 0.06 parts of polyethylene fiber, and 0.3 parts of accelerator.

[0054] in: The matrix is ​​a compound of activated alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of 3:2:1 in each part of the matrix; The composite modifier is a mixture of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid, with a weight ratio of 2:1:2:1 in each part of the composite modifier; The coagulant is a 5% (w / w) aqueous solution of lithium hydroxide.

[0055] Example 6: A method for preparing a special wet spray coating for rotary kiln inlet, comprising the following steps: (1) Pre-treatment of aggregates. Andalusite aggregate and silicon carbide aggregate were ball-milled separately at a ball-to-material ratio of 3:1 for 30 minutes. After ball milling, the aggregates were sieved into three sizes: 5-3 mm, 3-1 mm, and no larger than 1 mm. (2) Premixing of matrix and composite modifier. The active alumina, zircon powder and silicon oxynitride micro powder in the matrix are prepared in proportion and premixed in a ball mill for 20 min and stored separately. The FDN, sodium hexametaphosphate, polyacrylamide and oxalic acid in the composite modifier are prepared in proportion and mixed in a spiral mixer for 30 min and stored separately.

[0056] (3) Dry material mixing. The pretreated aggregate, premixed matrix and composite modifier, calcium aluminate cement and polyethylene fiber are mixed in proportion and then put into a forced mixer. The mixing speed is 20 r / min and the mixing time is 10 min to ensure that each dry material component is mixed evenly to form a dry material mixture; package.

[0057] Seal the dry mixture in a sealed package, avoiding the introduction of impurities and moisture during the packaging process. Store in a dry place for no more than 3 months.

[0058] Example 7: The preparation method of the rotary kiln inlet-specific wet spray coating provided in Example 2 includes the following steps: Same as Example 6, except that: (3) Dry material mixing. The pretreated aggregate, premixed matrix and composite modifier, calcium aluminate cement and polyethylene fiber are mixed in proportion and then put into a forced mixer. The mixing speed is 10 r / min and the mixing time is 15 min to ensure that the dry material components are mixed evenly to form a dry material mixture.

[0059] Example 8: The preparation method of the rotary kiln inlet-specific wet spray coating provided in Example 3 includes the following steps: Same as Example 6, except that: (3) Dry material mixing. The pretreated aggregate, premixed matrix and composite modifier, calcium aluminate cement and polyethylene fiber are mixed in proportion and then put into a forced mixer. The mixing speed is 15 r / min and the mixing time is 12 min to ensure that each dry material component is mixed evenly to form a dry material mixture.

[0060] Example 9: A method for preparing the special wet spray coating for rotary kiln inlet provided in Example 4 or Example 5, comprising the following steps: Same as Example 6, except that: (3) Dry material mixing. The pretreated aggregate, premixed matrix and composite modifier, calcium aluminate cement and polyethylene fiber are mixed in proportion and then put into a forced mixer. The mixing speed is 10-20 r / min and the mixing time is 10-15 min to ensure that the dry material components are mixed evenly to form a dry material mixture.

[0061] Example 10: The application method of the spray coating prepared in Example 6 includes the following steps: (1) Preparation before construction. Clean the rotary kiln inlet substrate, remove floating dust, oil stains, old lining debris and loose debris from the substrate surface, and blow it clean with a high-pressure air gun to ensure that the substrate surface is dry, flat and free of looseness; weld the anchor fasteners firmly; check the spraying equipment to ensure that the spray gun, conveying pipeline and pressure pump are operating normally, the pipeline is not blocked, and the spray gun outlet pressure is adjusted to 6.0MPa; (2) Add water to the dry mixture and stir. Pour the dry mixture into the mixer, add 6 parts of water and stir evenly, keeping the flow value of the wet material after adding water at 300 mm.

[0062] (3) Spraying construction. Pour the wet material into the hopper of the spraying equipment, start the equipment, and use a pressure pump to send the wet material to the spray gun along the conveying pipeline. At the outlet of the spray gun, add 0.2 parts of lithium hydroxide aqueous solution coagulant with a mass percentage concentration of 5% by pump. The distance between the spray gun and the kiln substrate is controlled at 0.8-1.2m, the spraying angle is 45°-60°, the spray gun is moved at a uniform speed of 0.8-1.2m / min, and a layered spraying method is adopted. The thickness of each layer is 50-100mm, and the interval between two adjacent layers is 30-60min until the designed spraying thickness (usually 200-300mm) is reached. During the spraying process, the spray gun pressure and spraying speed are adjusted in real time to ensure that the sprayed layer is uniform, dense, free of bubbles, cracks and missed spraying. (4) Curing treatment. After the spraying is completed, the sprayed layer is naturally cured. The curing environment temperature is 20-30℃, the relative humidity is 60-80%, and the curing time is 24-48h. During the curing period, avoid collisions and vibrations to the sprayed layer and avoid rain washing. After the natural curing is completed, low-temperature baking curing is carried out. The baking temperature is gradually increased from room temperature to 200-250℃, the heating rate is 50-80℃ / h, and the baking time is 3-4h to remove residual moisture in the sprayed layer and improve the strength and stability of the sprayed layer. (5) Heating and commissioning. After the low-temperature baking is completed, the rotary kiln is slowly heated, and the heating rate is controlled at 100-150℃ / h until it reaches the normal working temperature. During the heating process, the sprayed layer status is observed in real time. If slight cracks appear, timely repair spraying is carried out. After the heating is completed, the rotary kiln is put into normal operation. The sprayed layer is inspected regularly, and any damage is repaired in time.

[0063] Example 11: Application method of the spray coating prepared in Example 2 The method is the same as in Example 10, except that: (1) Preparation before construction: Adjust the spray gun outlet pressure to 4.5MPa; (2) Add water to the dry mixture and stir. Pour the dry mixture into the mixer, add 8 parts of water and stir evenly, keeping the flow value of the wet material after adding water at 250 mm.

[0064] (3) Spraying construction. Pour the wet material into the hopper of the spraying equipment, start the equipment, and send the wet material to the spray gun through the conveying pipeline by the pressure pump. At the outlet of the spray gun, add 0.3 parts of lithium hydroxide aqueous solution coagulant with a mass percentage concentration of 3% by pump.

[0065] Example 12: Application method of the spray coating prepared in Example 3 The method is the same as in Example 10, except that: (1) Preparations before construction. Adjust the spray gun outlet pressure to 5.0 MPa; (2) Add water to the dry mixture and stir. Pour the dry mixture into the mixer, add 6 parts of water and stir evenly, keeping the flow value of the wet material after adding water at 280 mm.

[0066] (3) Spraying construction. Pour the wet material into the hopper of the spraying equipment, start the equipment, and send the wet material to the spray gun through the conveying pipeline by the pressure pump. At the outlet of the spray gun, add 0.3 parts of lithium hydroxide aqueous solution coagulant with a mass percentage concentration of 4% by pump.

[0067] Example 13: Application method of the spray coating prepared in Example 4 The method is the same as in Example 10, except that: (1) Preparations before construction. Adjust the spray gun outlet pressure to 5.5 MPa; (2) Add water to the dry mixture and stir. Pour the dry mixture into the mixer, add 6 parts of water and stir evenly, keeping the flow value of the wet material after adding water at 260 mm.

[0068] (3) Spraying construction. Pour the wet material into the hopper of the spraying equipment, start the equipment, and send the wet material to the spray gun through the conveying pipeline by the pressure pump. At the outlet of the spray gun, add 0.3 parts of lithium hydroxide aqueous solution coagulant with a mass percentage concentration of 5% by pump.

[0069] Example 14: Application method of the spray coating prepared in Example 5 The method is the same as in Example 10, except that: (1) Preparations before construction. Adjust the spray gun outlet pressure to 6.0 MPa; (2) Add water to the dry mixture and stir. Pour the dry mixture into the mixer, add 6 parts of water and stir evenly, keeping the flow value of the wet material after adding water at 250 mm.

[0070] (3) Spraying construction. Pour the wet material into the hopper of the spraying equipment, start the equipment, and send the wet material to the spray gun through the conveying pipeline by the pressure pump. At the outlet of the spray gun, add 0.3 parts of lithium hydroxide aqueous solution coagulant with a mass percentage concentration of 3% by pump.

[0071] Experiment Example 1: Performance Evaluation Experiment 1. Samples: The coatings provided in Examples 1, 2, 3, 4, and 5 were prepared according to the method in Example 6 and then applied according to the method in Example 10.

[0072] 2. Detection Method 2.1 Bulk density: Refer to GB / T 4513.6-2017 Unshaped refractories - Part 6: Determination of physical properties.

[0073] 2.2 Flexural strength at room temperature: Refer to GB / T 4513.6-2017 Unshaped refractories - Part 6: Determination of physical properties.

[0074] 2.3 Compressive strength at room temperature: Refer to GB / T 4513.6-2017 Unshaped refractories - Part 6: Determination of physical properties.

[0075] 2.4 Permanent linear change rate upon heating: Refer to GB / T 4513.6-2017 Unshaped refractories - Part 6: Determination of physical properties.

[0076] 2.5 Abrasion resistance at room temperature: Refer to GB / T 18301-2012 Test method for abrasion resistance of refractory materials at room temperature, 1100℃×3h.

[0077] 2.6 Thermal shock resistance: Refer to GB / T 30873-2014 Test method for thermal shock resistance of refractory materials, with a water cooling cycle temperature of 1100℃.

[0078] 3. Test results, see Table 1 Table 1: Performance test results of samples from Examples 1-5

[0079] Table 1 shows that Examples 1-5 performed well, with Examples 1 and 4 showing the best results, while Comparative Examples 1-3 performed poorly. (The effectiveness is mainly judged by wear resistance; lower wear resistance indicates better wear resistance.) Results analysis: In Examples 1-5, the aggregates were graded and matched, and worked synergistically with ultrafine powder and composite modifiers to improve the plasticity, thermal shock resistance and erosion resistance of the spray coating. The high aggregate content (18 parts of 5-3mm andalusite) in Comparative Example 1 resulted in a higher rebound rate of the spray coating during construction, leading to material waste. On the other hand, it also reduced the bonding strength and thermal shock resistance of the spray coating.

[0080] The addition of calcium aluminate cement and accelerator in Comparative Example 2 was relatively low (4 parts and 0.1 parts, respectively), which slowed down the hardening speed of the spray coating during construction. The inability of the spray coating to solidify quickly caused the material to flow and fall off, and the thermal shock resistance was also weakened.

[0081] The matrix content in Comparative Example 3 was relatively high (38 parts). After sintering at high temperature, the material shrank and cracks were easily generated, which reduced the wear resistance and erosion resistance of the spray coating.

[0082] The results show that the material properties are related to the ratio and type of aggregate and matrix, the amount of composite modifier, polyethylene fiber, and accelerator added. The spray coating provided by this invention has strong comprehensive properties such as compressive strength, thermal shock resistance, and erosion resistance.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A wet spray coating material for rotary kiln inlet, the raw materials comprising the following components by mass: 58-70 parts aggregate, 26-36 parts matrix, 5-7 parts calcium aluminate cement, 0.3-0.6 parts composite modifier, 0.05-0.06 parts polyethylene fiber, and 0.2-0.3 parts accelerator.

2. The wet spray coating according to claim 1, characterized in that, Its raw materials, by mass, include the following components: 60-70 parts aggregate, 26-36 parts matrix, 5-7 parts calcium aluminate cement, 0.3-0.6 parts composite modifier, 0.05-0.06 parts polyethylene fiber, and 0.2-0.3 parts accelerator.

3. The wet spray coating according to claim 1, characterized in that, Its raw materials, by mass, include the following components: 60-66 parts aggregate, 28-36 parts matrix, 5-7 parts calcium aluminate cement, 0.3-0.4 parts composite modifier, 0.05-0.06 parts polyethylene fiber, and 0.2-0.25 parts accelerator.

4. The wet spray coating according to claim 1, characterized in that, The aggregate is a composition of andalusite and silicon carbide, wherein the weight parts of andalusite and silicon carbide in the aggregate are as follows: 10-15 parts and 6-12 parts in the 5-3mm size; 6-18 parts and 7-18 parts in the 3-1mm size; and 6-10 parts and 8-14 parts in the size not greater than 1mm. Preferably, the weight parts of andalusite and silicon carbide in the aggregate are as follows: 12-15 parts and 6-10 parts in the 5-3mm size; 6-18 parts and 7-18 parts in the 3-1mm size; and 8-10 parts and 8 parts in the size not greater than 1mm.

5. The wet spray coating according to claim 1, characterized in that, The matrix is ​​a compound of activated alumina, zircon powder, and silicon oxynitride micro powder, with a weight ratio of (3-5):(2-4):(1-2) in each part of the matrix; preferably, the weight ratio of the three components in each part of the matrix is ​​(3-5):(2-4):1; most preferably, the weight ratio of the three components is 3:4:1 or 5:2:

1.

6. The wet spray coating according to claim 1, characterized in that, The composite modifier is a compound of FDN, sodium hexametaphosphate, polyacrylamide, and oxalic acid in a weight ratio of (2-3):(1-2):(1-2):1; preferably, the weight ratio of the four components in the composite modifier is 2:2:1:1 or 3:2:2:

1.

7. The wet spray coating according to claim 1, characterized in that, Before the addition of the accelerator, the flow value of the wet spray coating is 250-300 mm.

8. The wet spray coating according to claim 1, characterized in that, The coagulant is a lithium hydroxide aqueous solution with a mass percentage concentration of 3-5%.

9. A method for preparing a wet spray coating according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Pre-treated aggregates: andalusite aggregates and silicon carbide aggregates were ball-milled separately with a ball-to-material ratio of 3:1 and a ball-milling time of 30 min. After ball milling, they were screened into three specifications: 5-3 mm, 3-1 mm and no more than 1 mm. (2) Premixing of matrix and composite modifier: The active alumina, zircon powder and silicon oxynitride micro powder in the matrix are mixed in proportion and premixed in a ball mill for 20 min and stored separately; FDN, sodium hexametaphosphate, polyacrylamide and oxalic acid in the composite modifier are mixed in proportion and mixed in a mixer for 30 min and stored separately. (3) Dry material mixing: After the pretreated aggregate, premixed matrix and composite modifier, calcium aluminate cement and polyethylene fiber are mixed in proportion, they are put into a forced mixer. The mixing speed is 10-20 r / min and the mixing time is 10-15 min to ensure that each dry material component is mixed evenly to form a dry material mixture.

10. A method for preparing a wet spray coating according to any one of claims 18, characterized in that, Includes the following steps: The construction method includes the following steps: (1) Preparation before construction: Clean the rotary kiln inlet substrate, remove floating dust, oil stains, old lining debris and loose debris from the substrate surface, and blow it clean with a high-pressure air gun to ensure that the substrate surface is dry, flat and free of looseness; weld the anchor fasteners firmly; check the spraying equipment to ensure that the spray gun, conveying pipeline and pressure pump are operating normally, the pipeline is free of blockage, and the spray gun outlet pressure is adjusted to 4.5-6.0MPa; (2) Add water to dry material mixture and stir: Pour the dry material mixture into the mixer and add 6-8 parts of water and stir evenly, keeping the flow value of the wet material after adding water at 250-300mm; (3) Spraying construction: Pour the wet material into the hopper of the spraying equipment, start the equipment, and send the wet material to the spray gun through the conveying pipeline by the pressure pump. Add 0.2-0.3 parts of accelerator at the spray gun outlet by pumping. Control the distance between the spray gun and the kiln substrate at 0.8-1.2m. Spray angle is 45°-60°. Move the spray gun at a uniform speed of 0.8-1.2m / min. Use a layered spraying method. The thickness of each layer is 50-100mm. The interval between two adjacent layers is 30-60min until the designed spray thickness is reached. During the spraying process, adjust the spray gun pressure and spraying speed in real time to ensure that the spray layer is uniform, dense, and free of bubbles, cracks, and missed spraying. (4) Curing treatment: After the spraying is completed, the sprayed layer is naturally cured. The curing environment temperature is 20-30℃, the relative humidity is 60-80%, and the curing time is 24-48h. During the curing period, avoid collisions and vibrations to the sprayed layer and avoid rain washing. After the natural curing is completed, low-temperature baking curing is carried out. The baking temperature is gradually increased from room temperature to 200-250℃, the heating rate is 50-80℃ / h, and the baking time is 3-4h to remove residual moisture in the sprayed layer and improve the strength and stability of the sprayed layer. (5) Heating and commissioning: After the low-temperature baking is completed, the rotary kiln is slowly heated up at a rate of 100-150℃ / h until it reaches the normal operating temperature. During the heating process, the sprayed layer is observed in real time. If slight cracks appear, timely repair spraying is carried out. After the heating is completed, the rotary kiln is put into normal operation. The sprayed layer is inspected regularly, and any damage is repaired in time.

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