A self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines and its preparation method

Abstract

The present invention discloses a self-repairing thermal insulation spray coating suitable for low-pressure steam pipes, comprising the following raw materials in percentage by mass: 23-37% of modified waste aluminum silicate refractory short fibers, 15-25% of self-repairing composite powder, 10-15% of lightweight floating beads, 5-10% of a coagulant, 25-35% of a binder, 1-3% of a composite water reducer, and 0.05-0.15% of a retarder; the modified waste aluminum silicate refractory short fibers are obtained by ultrasonically vibrating and screening waste aluminum silicate refractory fibers and then surface-modifying them with a polyethylene glycol solution. The spray coating of the present invention has the advantages of excellent thermal insulation performance, self-repairing cracks, long service life, low cost, good waterproofness, and convenient construction. It can effectively solve the problems of structural and material performance degradation, shedding and damage, and large heat loss caused by long-term use of existing steam pipe insulation materials; and the preparation cost involved is low, the environment is friendly, and it is suitable for promotion and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal insulation materials, and in particular relates to a self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines and a preparation method thereof. Background Art

[0002] Steam is one of the most critical energy sources in national pillar industries such as steel, petrochemicals, etc. In particular, steel enterprises generally have more steam generating ends and more dispersed use ends. The steam pipeline network structure is complex, with a wide coverage and long mileage. It is an important energy medium transmission channel.

[0003] At present, the main problems with steam pipeline insulation include: the types of insulation materials and insulation structures are single, and soft insulation materials or hard insulation materials are used. For example, although soft insulation materials such as aluminum silicate needle-punched blankets and rock wool felts have the advantages of good vibration resistance and convenient construction, there is a common problem of loose insulation structure sinking during use. Hard insulation materials such as microporous calcium silicate series products have good strength, are not easy to be compressed, and have little effect on thermal conductivity, but there are problems such as fragility during construction and transportation, difficulty in construction on special-shaped parts, and easy cracking during use; in addition, with the extension of the service cycle, unfavorable factors such as the decline in the thermal insulation performance of the insulation material itself, cracking of the protective layer, and poor waterproof performance of the insulation material are all reasons for excessive heat dissipation in the pipeline.

[0004] To address these issues, patent CN109488838B discloses a steam pipe insulation material and its construction process. This material incorporates multiple insulation materials, including aerogel technology, and employs a multi-layer composite insulation approach to improve the thermal insulation and waterproofing properties of the steam pipe insulation layer. However, this multi-layer wrapping approach results in numerous construction steps, difficult joint handling, and high interlayer thermal resistance. Patent application CN108409200A discloses a method for preparing a high-strength, stable pipe insulation material. This approach uses granite as a raw material to prepare granite fiber, which is then organically treated and composited with aerogel. This approach improves the insulation performance of the insulation material while leveraging the granite fiber's inherent mechanical properties to enhance its strength. However, this approach fails to address the poor waterproofing properties of aerogel nanomaterials.

[0005] To address the problems existing in steam pipe insulation, the use of new low-thermal conductivity aerogel technology and the addition of multi-layer composite insulation structures can improve the insulation performance to a certain extent. However, this cannot effectively solve problems such as the poor waterproof performance of aerogel nanomaterials. An additional waterproof layer is usually required for protection. Once the waterproof layer is damaged, the aerogel nanomaterials in the insulation layer will be damaged. In addition, existing technologies have not yet proposed a solution for the automatic repair of cracks and damage in steam pipe insulation materials during their service life. Summary of the Invention

[0006] The main purpose of the present invention is to provide a self-repairing thermal insulation spray coating suitable for low-pressure steam pipes. The spray coating has the advantages of excellent thermal insulation performance, self-repair of cracks, long service life, low cost, good waterproofness and convenient construction. It can effectively solve the problems of structural and material performance degradation, shedding and breakage, and large heat loss of existing steam pipe insulation materials during long-term use; and the preparation cost involved is low, environmentally friendly, and suitable for promotion and application.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines comprises the following raw materials in percentage by weight: 23-37% of modified waste aluminum silicate refractory short fibers, 15-25% of self-repairing composite powder, 10-15% of lightweight floating beads, 5-10% of a coagulant, 25-35% of a binder, 1-3% of a composite water reducer, and 0.05-0.15% of a retarder; the modified waste aluminum silicate refractory short fibers are obtained by ultrasonically vibrating and screening waste aluminum silicate refractory fibers and performing surface modification using a polyethylene glycol solution; and the modified waste aluminum silicate refractory short fibers come in two sizes: 1-1.5 mm and 3-5 mm.

[0009] Furthermore, the contents of the modified waste aluminum silicate refractory short fibers with sizes of 1 to 1.5 mm and 3 to 5 mm are 8 to 15% and 15 to 22% respectively.

[0010] Preferably, the waste aluminum silicate refractory fibers are taken from industrial waste whose working environment is an oxidizing atmosphere and whose medium- and long-term working temperature is lower than 900°C, or from industrial waste whose working environment is a reducing atmosphere and whose medium- and long-term working temperature is lower than 700°C.

[0011] Furthermore, the vibration screening step includes: shearing the waste aluminum silicate refractory fibers into short fibers of 3 to 5 mm, and then screening them using a vibration screen with an aperture of 3 mm to remove the deteriorated refractory fibers that have become brittle and powdered due to high-temperature crystallization, and taking the part above the sieve to obtain 3 to 5 mm waste aluminum silicate refractory short fibers; then taking part of the obtained 3 to 5 mm waste aluminum silicate refractory short fibers and continuing to shear them into short fibers of 1 to 1.5 mm, and screening them using a vibration screen with an aperture of 1 mm to obtain 1 to 1.5 mm waste aluminum silicate refractory short fibers.

[0012] Furthermore, the vibrating screen is an ultrasonic vibrating screen. When the vibrating screen motor is turned on, the ultrasonic wave generated by the ultrasonic generator is coupled to break and screen out the deteriorated refractory fibers that have become brittle and powdered due to high-temperature crystallization.

[0013] Furthermore, the ultrasonic vibration screen adopts an ultrasonic power of 0.55-1.1 kW, a vibration frequency of 20-30 kHz, an amplitude of 15-20 μm, and a vibration time of 3-5 min.

[0014] Furthermore, the concentration of the polyethylene glycol solution is 0.7-0.8 g / 100 mL.

[0015] Furthermore, the surface modification step includes: sending the waste aluminum silicate refractory short fibers into a closed spray operation chamber through a conveyor belt, a rotary sprayer is provided on the top of the spray operation chamber to spray the polyethylene glycol solution, and a nozzle is provided at the bottom of the conveyor belt. The waste aluminum silicate refractory fibers are blown into the air by spraying compressed air to fully contact with the polyethylene glycol spray. After the spraying is completed, they are sent out of the spray operation chamber through a conveyor belt and left to stand (15 to 20 minutes).

[0016] Furthermore, for a unit amount of waste aluminum silicate refractory fibers (1 kg), the spraying amount of the polyethylene glycol solution is 100 to 150 mL.

[0017] In the above solution, the self-repairing composite powder comprises self-crosslinking acrylic emulsion, medium ammonium polyphosphate, dipentaerythritol, melamine, aluminum silicate powder and water.

[0018] Furthermore, in the self-repairing composite powder, the raw materials and their mass percentages include: 25-40% self-crosslinking acrylic emulsion, 10-20% medium ammonium polyphosphate, 2-5% dipentaerythritol, 5-10% melamine, 15-30% aluminum silicate powder, and 15-25% water.

[0019] In the above scheme, the self-repairing composite powder is obtained by stirring self-crosslinking acrylic emulsion, medium ammonium polyphosphate, dipentaerythritol, melamine, aluminum silicate powder and water in proportion (10-20 minutes), drying (110-130° C.), breaking up and grinding.

[0020] In the above solution, the particle size of the self-repairing composite powder is less than 1200 mesh.

[0021] In the above scheme, the self-crosslinking acrylate emulsion is anionic, the main synthetic monomers are acrylate and methacrylate, the solid content is more than 40%, the average particle size is 0.2-0.4 μm, and the pH value is 6.0-8.0.

[0022] Furthermore, the degree of polymerization of the medium ammonium polyphosphate is 500-800.

[0023] In the above solution, the particle size of the aluminum silicate powder is below 1600 mesh.

[0024] Furthermore, the aluminum silicate powder is obtained by high-energy ball milling of 1-1.5 mm waste aluminum silicate refractory short fibers.

[0025] Furthermore, the high-energy ball milling treatment uses a planetary high-energy ball mill with a rotation speed of 450-550 r / min, a ball milling time of 3-6 hours, a medium filling rate of 0.3-0.45, and a ball-to-material ratio of (3-5):1.

[0026] Furthermore, the high-energy ball milling treatment introduces a grinding aid, the amount of which is 3-6% of the mass percentage of the 1-1.5 mm waste aluminum silicate refractory short fibers; specifically, anhydrous ethanol can be selected.

[0027] Preferably, the particle size of the light floating beads is 80-200 mesh, and the bulk density is ≤0.43g / cm 3 .

[0028] Preferably, the coagulant is sintered magnesia powder with a MgO content of ≥98wt% and a particle size of 300 mesh or less.

[0029] In the above solution, the binder includes silica sol and water-based silicone resin.

[0030] Furthermore, the silica sol has a SiO2 content of 30-40 wt% and a pH value of 9.0-9.5; the water-based organic silicone resin is an ionic water-based organic silicone resin with a temperature resistance of ≥400°C, a solid content of ≥45%, and a pH value of 6.0-8.0.

[0031] Furthermore, the mass ratio of the silica sol to the water-based silicone resin is (4-10):1.

[0032] In the above solution, the composite water reducer includes polycarboxylic acid high-efficiency water reducer and sodium tripolyphosphate.

[0033] Furthermore, the water reduction rate of the polycarboxylic acid high-efficiency water reducer is 30-40%.

[0034] Furthermore, the mass ratio of the polycarboxylate high-efficiency water reducer to sodium tripolyphosphate is 1:(6.5-25).

[0035] Preferably, the retarder is citric acid.

[0036] The present invention also provides a method for preparing a self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines, comprising the following steps:

[0037] 1) Weighing the modified waste aluminum silicate refractory short fibers, self-repairing composite powder, lightweight floating beads, coagulant, binder, composite water reducer and retarder according to the ratio; first adding part of the modified waste aluminum silicate refractory short fibers and the entire amount of lightweight floating beads into the blender, stirring (3 to 5 minutes), then adding the weighed self-repairing composite powder, coagulant and retarder, adding the remaining amount of aluminum silicate refractory short fibers under stirring conditions, stirring (5 to 10 minutes) to obtain a solid mixture;

[0038] 2) The solid mixture and the binder are mixed and stirred evenly (5 to 10 minutes) to obtain the self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines.

[0039] In the above scheme, in step 1), the modified waste aluminum silicate refractory short fibers include modified waste aluminum silicate refractory short fibers with lengths of 3 to 5 mm and 1 to 1.5 mm, respectively. During the feeding process, 2 / 3 of the modified waste aluminum silicate refractory short fibers with a length of 3 to 5 mm and the entire amount of the modified waste aluminum silicate refractory short fibers with a length of 1 to 1.5 mm are added first; and then (after adding the self-healing composite powder, coagulant and retarder) the remaining amount of modified waste aluminum silicate refractory short fibers with a length of 3 to 5 mm is added.

[0040] The self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines prepared according to the above scheme needs to complete the spraying construction within 30 minutes; it is suitable for thermal insulation protection of low-pressure steam pipelines with steam temperatures of 230 to 360°C.

[0041] The principle of the present invention is:

[0042] The present invention improves the thermal insulation performance of the area close to the hot surface of the pipeline through the design of low thermal conductivity self-healing materials, and at the same time forms porous thermal insulation materials through self-expansion to fill and compensate for cracks, thereby realizing automatic repair of the thermal insulation material, and solving the problems of structural and material performance degradation, shedding and breakage, and large heat loss in the long-term use of existing steam pipeline insulation materials: through the design of self-healing materials, aluminum silicate powder is used as the thermal insulation filler, and the combination of ammonium polyphosphate + dipentaerythritol + melamine is used as the foaming expansion agent, and self-cross-linking acrylic ester emulsion is introduced as the bonding agent. Through self-cross-linking polymerization reaction, the thermal insulation filler and the foaming expansion agent are wrapped therein. At the same time, melamine also acts as a cross-linking agent, providing a large number of free radicals, which synergistically promote the interfacial bonding between the self-cross-linking acrylic ester emulsion and the powder particles to form a core-shell structured composite particle self-healing material, thereby improving the stability and waterproofness of the material. When the low-pressure steam pipe is in normal operation (steam temperature 230-360°C), the temperature of the adjacent area in contact with the steam pipe increases (≥200°C). The volume expansion caused by heat foaming forms a porous thermal insulation material. The porous insulation material itself has a low thermal conductivity coefficient and can fill the gaps between the refractory fibers, further improving the thermal insulation performance. In addition, as the service time continues to increase, the thermal insulation material itself will inevitably shrink and crack, and its structure and performance will deteriorate. When cracks appear inside and heat is conducted outward through the gaps, the thermal insulation performance of the insulation layer decreases and the temperature around the cracks increases. When the temperature exceeds 200°C, the self-healing material around the cracks expands due to the heat, forming a porous thermal insulation material to fill and make up for the cracks, realizing the automatic repair of the material during service, thereby improving the overall thermal insulation performance and extending the service life.

[0043] Aluminum silicate refractory fibers discarded from metallurgical furnaces are used as the main raw materials to prepare waste aluminum silicate refractory short fibers and aluminum silicate powder. The raw materials are cheap, easy to obtain, and of high purity. The good thermal insulation ability of the refractory fibers is utilized to improve the thermal insulation performance and tensile strength of the spray coating, while reducing carbon dioxide emissions and environmental pollution. In order to solve the technical problems of performance degradation caused by crystallization, pulverization, hardening, and easy breakage of waste aluminum silicate refractory fibers, the improvement measures adopted are as follows: First, the source of the raw materials is screened. By selecting aluminum silicate refractory fibers used in the thermal insulation layer of metallurgical furnaces, the long-term working temperature in an oxidizing atmosphere is lower than 900°C or the long-term working temperature in a reducing atmosphere is lower than 700°C, which is lower than the significant crystallization temperature of aluminum silicate refractory fibers (950°C in an oxidizing atmosphere and 750°C in a reducing atmosphere), which greatly reduces the crystallization of waste aluminum silicate refractory fibers. The ratio of crystals; secondly, the aluminum silicate refractory fibers are sheared and screened using an ultrasonic vibrating screen. While the vibrating screen motor is turned on, the ultrasonic wave generated by the ultrasonic generator is coupled. Taking advantage of the high density and brittleness of the crystallized fibers compared to the amorphous fibers, the degraded crystallized refractory fibers that have become brittle and powdered due to high temperature crystallization are broken and screened out. At the same time, the degraded slag balls and crystallized particles attached to the surface of the normal refractory fibers that are difficult to screen out using conventional mechanical vibrating screens can also be removed through ultrasonic vibration, further improving the thermal insulation performance and stability of the recycled waste aluminum silicate refractory fibers. Finally, in order to enhance the toughness of the aluminum silicate refractory fibers, improve the interfacial bonding of the refractory fibers and their dispersion in the spray coating, the surface of the waste refractory fibers is spray-modified using a polyethylene glycol aqueous solution with a concentration of 0.7-0.8 g / 100 mL. The efficiency and uniformity of the modification operation are improved by spraying from the top of the spray operation chamber and blowing from the bottom.

[0044] By adding lightweight floating beads and utilizing their typical hollow spherical closed pore microstructure, the number of micron-level closed pores is increased, further reducing the thermal conductivity coefficient. At the same time, the good fluidity of spherical particles is utilized to improve the construction performance of the spray coating.

[0045] By adding sintered magnesia coagulant with a particle size of less than or equal to 300 mesh, and utilizing the physical and chemical effects between magnesium oxide, silica sol and water-based silicone resin, the reaction of anions on the surface of the sol is promoted, the formation and gelation rate of the siloxane group is accelerated, and the coagulation and bonding of the binder are accelerated, which can make the spray coating harden quickly and significantly shorten the curing time (can be shortened to 2 hours), thereby shortening the construction period.

[0046] By using silica sol and water-based silicone resin as composite binders, the pH value can be adjusted to effectively control the curing time of the material to meet construction requirements. At the same time, the silica sol is hydrated and gelled and crystallized inside the material. The large number of micropores generated during molding can further improve the thermal insulation performance. In addition, the water-based silicone resin is coated on the surface of the refractory fiber and powder, and its hydrophobicity is utilized to improve the waterproof performance of the spray coating insulation layer, reduce the impact of rainwater leakage on the insulation layer during the use of the steam pipeline, and increase the service life. The present invention uses a composite binder based on silica sol and water-based silicone resin, which can effectively ensure the mechanical properties and bonding properties of the coating system while controlling costs.

[0047] By adding citric acid retarder, citric acid is reacted with MgO particles in sintered magnesia to form a low-solubility magnesium citrate protective layer, which can control the hydration rate of magnesium oxide, thereby reducing the viscosity of the binder, improving the fluidity of the spray coating, promoting the coagulation and hardening of the matrix, and improving the strength.

[0048] Through the optimized combination of polycarboxylic acid high-efficiency water reducer and sodium tripolyphosphate, the performance shortcomings of a single water reducer are avoided, the construction fluidity of the spray coating is improved, and the amount of binder is reduced, achieving the effect of high water reduction rate without segregation.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] 1) The self-repairing thermal insulation spray coating for low-pressure steam pipes described in the present invention has the advantages of self-repairing cracks, stable thermal insulation performance and long service life. It effectively solves the problem that the thermal insulation performance of existing low-pressure steam pipe insulation materials drops sharply after cracking, shrinking, loosening and settling, and it is impossible to repair them in an online hot state. By exploring the degradation mechanism of the thermal insulation structure of steam pipe insulation materials under long-term service and the temperature distribution law inside the insulation layer after degradation, a self-repairing material suitable for low-pressure steam pipes (steam temperature 230-360°C) was invented, which realizes the automatic repair of the material during service, thereby achieving the purpose of improving the overall thermal insulation performance and extending the service life.

[0051] 2) Compared with the traditional steam pipe insulation process of multi-layer insulation blanket + heat radiation reflection layer + waterproof layer wrapping, the present invention adopts spray construction + hot surface self-expansion fastening + material waterproof component design, which has the advantages of convenient construction, strong integrity, good waterproofness, and high comprehensive thermal insulation performance. While reducing the work intensity, it avoids the problems of air leakage caused by loose wrapping and overlapping seams in the construction of multi-layer insulation blankets.

[0052] 3) The present invention uses discarded aluminum silicate refractory fibers, lightweight floating beads, etc. as main raw materials, combined with the design of self-expanding porous insulation materials during temperature operation, to fully fill the gaps between the refractory fibers. It can effectively overcome the problems of low strength, large shrinkage, and rapid decay of thermal insulation performance of conventional fiber spray coatings, realize high value-added resource utilization of discarded refractory materials, and has the advantages of low preparation cost and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a scanning electron microscope photograph of the self-repairing composite powder in the sample after the self-repairing thermal insulation spray coating for low-pressure steam pipes obtained in Example 1 was heat-treated at 300°C for 3 hours and self-expanded and grew when heated. DETAILED DESCRIPTION

[0054] The following examples and comparative examples clearly and specifically describe the technical solutions adopted in the present invention. The examples and comparative examples are merely examples to illustrate the present invention, do not represent all embodiments, and do not limit the scope of the present invention. The embodiments of the present invention, as well as various changes or modifications made by those skilled in the art based on the present invention, are equivalent to those described in the present invention.

[0055] In the following examples, the waste aluminum silicate refractory fibers are taken from waste aluminum silicate refractory fiber blankets / modules used for cold rolling and annealing furnace linings (oxidizing atmosphere, medium- and long-term operating temperature 700-900° C.).

[0056] The preparation method of the modified waste aluminum silicate refractory fiber adopted comprises the following steps: 1) cutting the recovered waste aluminum silicate refractory fibers into short fibers of 3 to 5 mm, and then screening them with an ultrasonic vibrating screen with an aperture of 3 mm (ultrasonic power 0.55 to 1.1 kW, vibration frequency 20 to 30 kHz, amplitude 15 to 20 um, vibration time 3 to 5 min). When the vibrating screen motor is turned on, the ultrasonic wave generated by the ultrasonic generator is coupled to break and screen out the deteriorated refractory fibers that have become brittle and powdered due to high-temperature crystallization, to obtain 3 to 5 mm waste aluminum silicate refractory short fibers; 2) then taking part of the waste aluminum silicate refractory short fibers and continuing to cut them into short fibers of about 1 to 1.5 mm, and screening them with an ultrasonic vibrating screen with an aperture of 1 mm. The deteriorated slag balls and crystallization particles attached to the surface of the normal refractory fibers that are difficult to be screened out by conventional mechanical vibrating screens are removed by ultrasonic vibration to obtain 1 to 1.5 mm waste fibers. Abandoned aluminum silicate refractory staple fibers; 3) finally, the obtained 3-5mm abandoned aluminum silicate refractory staple fibers and 1-1.5mm abandoned aluminum silicate refractory staple fibers are respectively sent into a closed spray operation chamber through a conveyor belt, and a rotary sprayer is provided on the top of the spray operation chamber to spray polyethylene glycol PEG-4000 aqueous solution (wherein the concentration adopted in Examples 1, 2, and 5 is 0.7g / 100mL, and the spraying amount is 150mL / Kg; the concentration adopted in Examples 3 and 4 is 0.8g / 100mL; the spraying amount is 100mL / Kg), and a nozzle is provided at the lower part of the conveyor belt, and the abandoned aluminum silicate refractory staple fibers are blown into the air by spraying compressed air to fully contact with the polyethylene glycol spray. After the spraying is completed, they are sent out of the spray operation chamber through a conveyor belt and allowed to stand (15-20min) to obtain 3-5mm modified abandoned aluminum silicate refractory staple fibers and 1-1.5mm modified abandoned aluminum silicate refractory staple fibers, respectively.

[0057] In the following examples, the silica sol is provided by Guangdong Huierte Nano Technology Co., Ltd., and its SiO2 content is 40% and the pH value is 9.0-9.5; the water-based silicone resin used is an ionic water-based silicone resin, provided by Shenyang Caiyi Special Coatings Co., Ltd., with a temperature resistance of ≥400°C, a solid content of ≥45%, and a pH value of 6.0-8.0.

[0058] The polycarboxylic acid high-efficiency water-reducing agent used is WSM-M polycarboxylic acid high-efficiency water-reducing agent provided by Hubei Siman New Materials Co., Ltd., and its water reduction rate is ≥35%.

[0059] The self-crosslinking acrylate emulsion used is provided by Kunshan Development Zone Lianle Chemical Trading Co., Ltd., model la-1025, which is anionic, the main synthetic monomers are acrylate and methacrylate, the solid content is ≥40%, the average particle diameter is 0.2~0.4um, and the pH value is 6.0~8.0.

[0060] Example 1

[0061] A self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines, the raw material components and weight percentages of which are as follows:

[0062] Modified waste aluminum silicate refractory staple fibers 28% (3-5mm modified waste aluminum silicate refractory staple fibers 10%, 1-1.5mm modified waste aluminum silicate refractory staple fibers 18%); self-repairing composite powder 22%; 200-mesh lightweight floating beads 11.3%; 300-mesh sintered magnesia powder (MgO content ≥98%) 6%; binder 30% (24% silica sol, 400°C heat-resistant ionic water-based silicone resin 6%); composite water reducer 2.6% (0.1% WSM-M polycarboxylic acid high-efficiency water reducer, 2.5% sodium tripolyphosphate); 0.1% citric acid retarder;

[0063] The self-repairing composite powder used has a particle size of 1200 mesh, and the raw materials and their mass percentages are: 30% self-crosslinking acrylic emulsion, 15% medium ammonium polyphosphate (polymerization degree 800), 4% dipentaerythritol, 6% melamine, 30% aluminum silicate powder (particle size 1600 mesh), and 15% deionized water; the specific preparation steps include: weighing the self-crosslinking acrylic emulsion, medium ammonium polyphosphate, dipentaerythritol, melamine, aluminum silicate powder and deionized water in proportion, mixing and stirring in a blender for 15 minutes, drying at 110°C, breaking up and grinding to obtain the self-repairing composite powder;

[0064] The aluminum silicate powder (1600 mesh particle size) is obtained by high-energy ball milling of 1-1.5 mm waste aluminum silicate refractory short fibers.

[0065] The method for preparing the self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines comprises the following steps:

[0066] 1) The weighed modified waste aluminum silicate refractory fiber, self-repairing composite powder, lightweight floating beads, coagulant, composite water reducer and retarder are added to a blender, first adding two-thirds of the amount of 3-5mm modified waste aluminum silicate refractory short fibers and the entire amount of 1-1.5mm modified waste aluminum silicate refractory short fibers and lightweight floating beads, stirring for 5 minutes, then adding the self-repairing composite powder, coagulant and retarder at one time, and gradually adding the remaining amount of 3-5mm modified waste aluminum silicate refractory short fibers while stirring, and continuing to stir for 10 minutes to obtain a solid mixture, which is packaged in a waterproof sealed package with a shelf life of 6 months;

[0067] 2) Packaging of binder mixture: Weigh silica sol and water-soluble silicone resin according to weight percentage, stir for more than 5 minutes, mix evenly to prepare binder, and package in plastic barrels with a shelf life of 12 months;

[0068] 3) On-site construction of spray coating: Weigh the solid raw materials and binder in proportion, add them into the blender and stir for 6 minutes. After mixing evenly, use special spraying equipment to spray the surface of the steam pipe. The construction should be completed within 30 minutes and solidify within 120 minutes at an ambient temperature of 30°C.

[0069] Example 2

[0070] A self-repairing thermal insulation spray coating suitable for low-pressure steam pipes, the preparation method of which is substantially the same as that of Example 1, except that:

[0071] 1) The raw materials and their mass percentages are as follows: modified waste aluminum silicate refractory short fibers 35% (15% of 3-5 mm modified waste aluminum silicate refractory short fibers, 20% of 1-1.5 mm modified waste aluminum silicate refractory short fibers); self-repairing composite powder 15%; lightweight floating beads with a particle size of 200 mesh 15%; sintered magnesia powder with a particle size of 300 mesh (MgO content ≥98%) 7%; binder 25% (20% of silica sol, 5% of ionic water-based silicone resin with a temperature resistance of 400°C); composite water reducer 2.95% (0.3% of WSM-M polycarboxylic acid high-efficiency water reducer, 2.65% of sodium tripolyphosphate); citric acid retarder 0.05%;

[0072] The self-repairing composite powder used has a particle size of 1200 mesh, and the raw materials and their mass percentages are: 40% self-crosslinking acrylic emulsion, 10% medium ammonium polyphosphate (polymerization degree 800), 2% dipentaerythritol, 5% melamine, 25% aluminum silicate powder (particle size 1600 mesh), and 18% deionized water; the specific preparation steps include: weighing the self-crosslinking acrylic emulsion, medium ammonium polyphosphate, dipentaerythritol, melamine, aluminum silicate powder and deionized water in proportion, mixing and stirring in a blender for 15 minutes, drying at 110°C, breaking up and grinding to obtain the self-repairing composite powder;

[0073] The aluminum silicate powder (1600 mesh particle size) is obtained by high-energy ball milling of 1-1.5 mm waste aluminum silicate refractory short fibers.

[0074] 2) On-site construction of spray coating: Weigh the solid raw materials and binder in proportion, add them into the stirrer and stir for 10 minutes. After mixing evenly, use special spraying equipment to spray the surface of the steam pipe. The construction should be completed within 30 minutes and solidify within 180 minutes at an ambient temperature of 10°C.

[0075] Example 3

[0076] A self-repairing thermal insulation spray coating suitable for low-pressure steam pipes, the preparation method of which is substantially the same as that of Example 1, except that:

[0077] 1) The raw materials and their mass percentages are as follows: 30% modified waste aluminum silicate refractory short fibers (8% modified waste aluminum silicate refractory short fibers of 3-5 mm, 22% modified waste aluminum silicate refractory short fibers of 1-1.5 mm); 20% self-repairing composite powder; 10% lightweight floating beads with a particle size of 80 mesh; 10% sintered magnesia powder with a particle size of 300 mesh (MgO content ≥98%); 28% binder (25% silica sol, 3% heat-resistant 400°C ionic water-based organic silicone resin); 1.95% composite water reducer (0.15% WSM-M polycarboxylic acid high-efficiency water reducer, 1.8% sodium tripolyphosphate); 0.05% citric acid retarder;

[0078] The self-repairing composite powder used has a particle size of 1200 mesh, and the raw materials and their mass percentages are: 25% self-crosslinking acrylic emulsion, 20% medium ammonium polyphosphate (polymerization degree 500), 5% dipentaerythritol, 10% melamine, 15% aluminum silicate powder (particle size 1600 mesh), and 25% deionized water; the specific preparation steps include: weighing the self-crosslinking acrylic emulsion, medium ammonium polyphosphate, dipentaerythritol, melamine, aluminum silicate powder and deionized water in proportion, mixing and stirring in a blender for 15 minutes, drying at 110°C, breaking up and grinding to obtain the self-repairing composite powder;

[0079] The aluminum silicate powder (1600 mesh particle size) is obtained by high-energy ball milling of 1-1.5 mm waste aluminum silicate refractory short fibers.

[0080] 2) On-site construction of spray coating: Weigh the solid raw materials and binder in proportion, add them into the blender and stir for 10 minutes. After mixing evenly, use special spraying equipment to spray the surface of the steam pipe. The construction should be completed within 30 minutes and solidify within 150 minutes at an ambient temperature of 10°C.

[0081] Example 4

[0082] A self-repairing thermal insulation spray coating suitable for low-pressure steam pipes, the preparation method of which is substantially the same as that of Example 1, except that:

[0083] 1) The raw materials and their mass percentages are as follows: 30% modified waste aluminum silicate refractory short fibers (15% 3-5mm modified waste aluminum silicate refractory short fibers, 15% 1-1.5mm modified waste aluminum silicate refractory short fibers); 19% self-repairing composite powder; 15% lightweight floating beads with a particle size of 120 mesh; 5% sintered magnesia powder with a particle size of 300 mesh (MgO content ≥98%); 28% binder (23% silica sol, 5% 400°C heat-resistant ionic water-based organic silicone resin); 2.9% composite water reducer (0.3% WSM-M polycarboxylic acid high-efficiency water reducer, 2.6% sodium tripolyphosphate); 0.1% citric acid retarder;

[0084] The self-repairing composite powder used has a particle size of 1300 mesh, and the raw materials and their mass percentages are: 25% self-crosslinking acrylic emulsion, 20% medium ammonium polyphosphate (polymerization degree 500), 5% dipentaerythritol, 10% melamine, 15% aluminum silicate powder (particle size 1700 mesh), and 25% deionized water; the specific preparation steps include: weighing the self-crosslinking acrylic emulsion, medium ammonium polyphosphate, dipentaerythritol, melamine, aluminum silicate powder and deionized water in proportion, mixing and stirring in a blender for 15 minutes, drying at 110°C, breaking up and grinding to obtain the self-repairing composite powder;

[0085] The aluminum silicate powder (1700 mesh particle size) is obtained by high-energy ball milling of 1-1.5 mm waste aluminum silicate refractory short fibers.

[0086] 2) On-site construction of spray coating: Weigh the solid raw materials and binder in proportion, add them into the stirrer and stir for 10 minutes. After mixing evenly, use special spraying equipment to spray the surface of the steam pipe. The construction should be completed within 30 minutes and solidify within 120 minutes at an ambient temperature of 30°C.

[0087] Example 5

[0088] A self-repairing thermal insulation spray coating suitable for low-pressure steam pipes, the preparation method of which is substantially the same as that of Example 1, except that:

[0089] 1) The raw materials and their mass percentages are as follows: 25% modified waste aluminum silicate refractory fiber (9% modified waste aluminum silicate refractory short fiber of 3-5 mm, 16% modified waste aluminum silicate refractory short fiber of 1-1.5 mm); 25% self-repairing composite powder; 10.7% lightweight floating beads with a particle size of 120 mesh; 5% sintered magnesia powder with a particle size of 400 mesh (MgO content ≥98%); 33% binder (30% silica sol, 3% heat-resistant 400°C ionic water-based organic silicone resin); 1.15% composite water reducer (0.15% WSM-M polycarboxylic acid high-efficiency water reducer, 1% sodium tripolyphosphate); 0.15% citric acid retarder;

[0090] The self-repairing composite powder used has a particle size of 1300 mesh, and the raw materials and their mass percentages are: 25% self-crosslinking acrylic emulsion, 20% medium ammonium polyphosphate (polymerization degree 600), 5% dipentaerythritol, 10% melamine, 15% aluminum silicate powder (particle size 1700 mesh), and 25% deionized water; the specific preparation steps include: weighing the self-crosslinking acrylic emulsion, medium ammonium polyphosphate, dipentaerythritol, melamine, aluminum silicate powder and deionized water in proportion, mixing and stirring in a blender for 15 minutes, drying at 110°C, breaking up and grinding to obtain the self-repairing composite powder;

[0091] The aluminum silicate powder (1700 mesh particle size) is obtained by high-energy ball milling of 1-1.5 mm waste aluminum silicate refractory short fibers.

[0092] 2) On-site construction of spray coating: Weigh the solid raw materials and binder in proportion, add them into the stirrer and stir for 10 minutes. After mixing evenly, use special spraying equipment to spray the surface of the steam pipe. The construction should be completed within 30 minutes and solidify within 120 minutes at an ambient temperature of 30°C.

[0093] Comparative Example 1

[0094] The low-pressure steam pipeline of a steel plant (steam pressure 1.8MPa, temperature 350℃, pipe diameter 325mm) uses rock wool shell and pipe with a thickness of 40mm and a bulk density of 150kg / m 3 , maximum operating temperature 450℃, thermal conductivity 0.081W / m·K (hot surface temperature 300℃).

[0095] Comparative Example 2

[0096] The low-pressure steam pipeline of a steel plant (steam pressure 1.8MPa, temperature 350℃, pipe diameter 325mm) is wrapped with aluminum silicate wool needle-punched blanket with a thickness of 40mm and a bulk density of 128kg / m 3 , maximum operating temperature 1000℃, thermal conductivity 0.087W / m·K (hot surface temperature 300℃).

[0097] According to the self-repairing thermal insulation spray coatings for low-pressure steam pipes of Examples 1 to 5, standard samples were prepared, cured in a natural environment, demoulded after 12 hours, and heat treated at 300°C for 3 hours to test the bulk density, compressive strength and thermal conductivity. The bulk density of each sample was between 0.35 and 0.46 g / cm 3 The compressive strength is between 0.21 and 0.35 MPa, and the thermal conductivity (hot surface temperature 300 ° C) is between 0.08 and 0.10 W / m·K. The scanning electron microscope photo of the self-repairing composite powder in the sample after heat treatment at 300 ° C × 3h for low-pressure steam pipeline self-repairing thermal insulation spray coating in Example 1 after self-expansion growth when heated is shown as follows Figure 1 As shown. Further, according to Examples 1 to 5, a self-repairing thermal insulation spray coating for low-pressure steam pipes was prepared and tested on a low-pressure steam pipe in a steel plant (steam pressure 1.8 MPa, temperature 350°C, pipe diameter 325 mm, insulation layer thickness 40 mm). Compared with Comparative Examples 1 to 2, the material performance indicators and application effects are shown in Table 1. Compared with the existing technology, the self-repairing thermal insulation spray coating has the advantages of excellent thermal insulation performance, crack self-repair, long service life, low cost, good waterproofness, and convenient construction.

[0098] Table 1 Performance indicators and application effects of the embodiments of the present invention and the comparative examples

[0099]

[0100] Comparative Example 3

[0101] A self-repairing thermal insulation spray coating, the preparation method of which is roughly the same as that of Example 1, except that: in the preparation method of the modified waste aluminum silicate refractory fiber adopted, the vibration screening adopts a conventional mechanical vibration screen, wherein the vibration frequency adopted is 20-30kHz, the amplitude is 15-20um, and the vibration time is 3-5min.

[0102] The thermal conductivity of the prepared standard sample was 0.112 (W / m·K) at a hot surface temperature of 300°C, which was greater than the thermal conductivity of Example 1. In addition, after one year of use in an on-site industrial test, the average outer surface temperature of the pipe was 25°C, which was also higher than that of Example 1.

[0103] Comparative Example 4

[0104] A self-repairing thermal insulation spray coating was prepared using a method similar to that used in Example 1, except that the self-crosslinking acrylic emulsion was replaced with a water-based acrylic emulsion produced by Qingdao Enze Chemical Co., Ltd. Because the self-repairing composite powder does not self-crosslink, a crosslinking agent was added during the preparation process. After mixing, the mixture was heated to 150°C and held for 60 minutes. The thermal conductivity of the resulting standard sample was 0.127 (W / m·K) at a hot surface temperature of 300°C, which is greater than that of Example 1.

[0105] Comparative Example 5

[0106] A self-repairing thermal insulation spray coating, the preparation method of which is roughly the same as that of Example 1, except that the mass percentages of the raw materials in the self-repairing composite powder used are as follows: 30% self-crosslinking acrylic emulsion, 15% medium polyammonium phosphate (degree of polymerization 800), 4% dipentaerythritol, 36% aluminum silicate powder (particle size 1600 mesh), and 15% deionized water.

[0107] Using the above-mentioned self-healing composite powder formulation system, the self-crosslinking reaction of the self-crosslinking acrylic emulsion is not sufficient within the same reaction time, and the composition of the prepared self-healing composite powder is uneven; the thermal conductivity of the prepared standard sample is 0.121 (W / m·K) when the hot surface temperature is 300°C, which is greater than the thermal conductivity coefficient of Example 1.

[0108] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed by the present invention, makes equivalent substitutions or changes based on the technical solutions and improved concepts of the present invention shall be covered by the scope of protection of the present invention.

Claims

1. A self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines, characterized in that: The invention comprises the following raw materials in percentage by weight: 23-37% of modified waste aluminum silicate refractory short fibers, 15-25% of self-repairing composite powder, 10-15% of lightweight floating beads, 5-10% of coagulant, 25-35% of binder, 1-3% of composite water reducer, and 0.05-0.15% of retarder; the modified waste aluminum silicate refractory short fibers are obtained by ultrasonically vibrating and screening waste aluminum silicate refractory fibers and surface-modifying them with a polyethylene glycol solution; and the fibers come in two sizes: 1-1.5 mm and 3-5 mm. The raw materials of the self-repairing composite powder include self-crosslinking acrylic emulsion, medium ammonium polyphosphate, dipentaerythritol, melamine, aluminum silicate powder and water; the binder includes silica sol and water-based silicone resin.

2. The self-repairing thermal insulation spray coating according to claim 1, characterized in that: The contents of modified waste aluminum silicate refractory short fibers with sizes of 1~1.5mm and 3~5mm are 8~15% and 15~22%, respectively.

3. The self-repairing thermal insulation spray coating according to claim 1, characterized in that: The vibration screening step includes: shearing the waste aluminum silicate refractory fibers into short fibers of 3 to 5 mm, and then screening them with a vibration screen with an aperture of 3 mm to obtain waste aluminum silicate refractory short fibers of 3 to 5 mm; then taking part of the obtained 3 to 5 mm waste aluminum silicate refractory short fibers and further shearing them into short fibers of 1 to 1.5 mm, and screening them with a vibration screen with an aperture of 1 mm to obtain waste aluminum silicate refractory short fibers of 1 to 1.5 mm.

4. The self-repairing thermal insulation spray coating according to claim 1, characterized in that: The surface modification step comprises spraying a polyethylene glycol solution on the waste aluminum silicate refractory short fibers.

5. The self-repairing thermal insulation spray coating according to claim 1, characterized in that: The self-repairing composite powder comprises the following raw materials and their mass percentages: 25-40% self-crosslinking acrylic emulsion, 10-20% medium ammonium polyphosphate, 2-5% dipentaerythritol, 5-10% melamine, 15-30% aluminum silicate powder, and 15-25% water.

6. The self-repairing thermal insulation spray coating according to claim 1, characterized in that: The composite water reducer comprises polycarboxylic acid high-efficiency water reducer and sodium tripolyphosphate.

7. The self-repairing thermal insulation spray coating according to claim 1, characterized in that: The coagulant is sintered magnesia powder; the retarder is citric acid.

8. The method for preparing the self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines according to any one of claims 1 to 7, characterized in that: The steps include: 1) Weighing the modified waste aluminum silicate refractory short fibers, self-repairing composite powder, lightweight floating beads, coagulant, binder, composite water reducer and retarder according to the ratio; first adding part of the modified waste aluminum silicate refractory short fibers and the entire amount of lightweight floating beads into a blender, stirring, then adding the weighed self-repairing composite powder, coagulant and retarder, adding the remaining amount of aluminum silicate refractory short fibers under stirring, stirring to obtain a solid mixture; 2) The solid mixture and the binder are mixed and stirred evenly to obtain the self-repairing thermal insulation spray coating suitable for low-pressure steam pipelines.

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