Desulfurizing tower and flue anti-corrosion coating process

Abstract

The invention discloses an anti-corrosion coating process for a desulfurizing tower and a flue, relates to the technical field of corrosion prevention, and aims to solve the problems that in the prior art, base material recovery is not thorough, sand blasting is not standard and the like. The process comprises the following steps: S1, carrying out base body receiving (a steel base body weld joint has no defect, and inverted R is greater than or equal to 4.5 mm; the method comprises the steps of S1, surface cleaning, S3, sand blasting (0.5-2.0 mm abrasive materials are used for a steel substrate, RZ is larger than or equal to 60 micrometers, and Sa2.5 level), S4, prime coat (epoxy primer is proportioned according to the ratio of 100: 1.5: 0.8, and a wet film is larger than or equal to 60 micrometers), S5, drying, S6, glass flake plaster trowel scraping (two times, and styrene sensitivity is measured), S7, FRP reinforcing layer / wear-resistant layer construction, S8, surface layer coating (fluorocarbon coating), S9, multi-dimensional detection (electric spark leakage detection and the like) and S10, environment control (5-43 DEG C and humidity is smaller than or equal to 85%). The process is accurate in parameter, adapts to different matrixes, guarantees the anti-corrosion effect, and prolongs the service life of equipment.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection technology, and more specifically, to a corrosion protection coating process for desulfurization towers and flues. Background Technology

[0002] In industrial production, desulfurization towers and flues, as core equipment of desulfurization systems, are exposed to highly corrosive media such as sulfur-containing flue gas and spray slurries (e.g., limestone-gypsum slurry) for extended periods. They also face the effects of temperature fluctuations and airflow erosion, making their substrate (steel or concrete) highly susceptible to corrosion damage. Industry statistics show that desulfurization towers without effective corrosion protection measures have an average service life of only 3-5 years, and the equipment repair and downtime losses caused by corrosion failure result in substantial economic costs for enterprises annually.

[0003] Existing anti-corrosion technologies for desulfurization towers and flues mainly include rubber lining, glass flake mortar, and FRP (fiber reinforced plastic) anti-corrosion. While rubber lining offers good initial protection, it suffers from temperature sensitivity during application (requiring control between 15-30℃) and the mortar layer's tendency to detach due to substrate deformation. Traditional glass flake mortar anti-corrosion processes have several drawbacks: First, substrate acceptance standards are vague; for example, steel substrate welds are only visually inspected, failing to detect internal defects, and the threshold for treating honeycomb pitting on concrete substrates is unclear, easily leaving potential corrosion risks. Second, sandblasting parameters are not strictly controlled; mixed abrasive particle sizes and excessive moisture content result in insufficient surface roughness of the steel substrate (often below RZ50μm), making it difficult to achieve a rust removal grade of Sa2.5, thus affecting the coating. Thirdly, the primer formulation is poorly adapted to the construction environment. In low-temperature environments, the primer viscosity increases sharply, making it prone to sagging and missed areas after application. Furthermore, the content of anti-rust pigments is insufficient (often below 15%), failing to form an effective anti-rust barrier. Fourthly, the material ratios and construction parameters of various coatings, such as glass flake putty, FRP reinforcement layer, and wear-resistant layer, are not standardized. For example, the warp and weft density of fiberglass cloth is too low (often 3×3 threads / cm), and the content of corundum in the wear-resistant layer is insufficient (below 30%), resulting in insufficient structural strength and wear resistance of the coating. Fifthly, the final inspection only focuses on leaks, neglecting the coating thickness and adhesion testing, making it impossible to comprehensively evaluate the anti-corrosion effect.

[0004] Furthermore, existing processes lack sufficient precision in controlling the construction environment. When the temperature is below 5℃ or the relative humidity is above 85%, forced construction leads to poor coating curing, resulting in cracking, blistering, and other problems. To address these shortcomings of existing technologies, there is an urgent need for a desulfurization tower and flue gas duct anti-corrosion coating process that features rigorous process steps, precise parameter control, adaptability to different substrates, comprehensive testing, and suitability for a wide range of environments. Summary of the Invention

[0005] The object of the present invention is to overcome the defects in the existing anti-corrosion coating processes for desulfurization towers and flue ducts, such as incomplete acceptance of the base body, non-standard sandblasting treatment, unreasonable coating ratio, poor adaptability to the construction environment, and incomplete detection. The present invention provides an anti-corrosion coating process for desulfurization towers and flue ducts that can achieve differential and precise treatment for steel base bodies and concrete base bodies, ensure long-term stable anti-corrosion effects through multi-step parametric control and the synergistic effect of multi-level coatings, and has strong construction controllability and a wide adaptation range.

[0006] Technical solution To achieve the above-mentioned invention object, the present invention provides an anti-corrosion coating process for desulfurization towers and flue ducts, and the specific technical solution is as follows: An anti-corrosion coating process for desulfurization towers and flue ducts includes the following steps: S1: Base body acceptance: Conduct a comprehensive inspection on the steel base body or concrete base body of the desulfurization tower and flue duct. Among them, for the steel base body, it is required that the welds are continuous without interruption, all edges and corners are chamfered with an arc transition of R≥4.5mm, the welding slag, welding spatter, etc. are removed cleanly, and the welds have no defects such as pores, cracks, and undercut and are polished smoothly; for the concrete base body, it is required that there are no through cracks, no holes with a size greater than 10mm (length or width) and a depth greater than 5mm, sporadic honeycombing and pitting are allowed, all construction joints, pouring joints, and formwork joints are polished flat without inclusions, and the edges and corners are chamfered with an arc transition of R≥6.0mm.

[0007] S2: Surface purification treatment: Use compressed air (pressure 0.4 - 0.6MPa) to blow the floating ash and sand grains on the surface of the base body. For the parts with attached oil stains, use styrene (purity≥99.5%) to wipe and clean, ensuring that there are no oil stains, floating dust, sand grains and other pollutants on the surface of the base body; at the same time, blow the floating ash and sand on the surface of the scaffolding used in the construction clean with compressed air as well, to avoid pollutants falling onto the surface of the base body during the construction process.

[0008] S3: Sandblasting treatment: For the steel base body, select quartz sand or copper slag with a particle size of 0.5 - 2.0mm, dry and angular as the abrasive; the compressed air needs to be treated by a three-stage oil-water separator to ensure cleanliness and dryness (water content≤0.1%), and the driving pressure is controlled at 0.5 - 0.7MPa. The sandblasting operation follows the order of "starting from the difficult parts, from top to bottom, from the edges to the middle, from the outside to the inside", and the running direction of the spray gun is parallel to the surface of the workpiece. After sandblasting, the surface roughness of the steel base body needs to reach RZ≥60μm, and the sandblasting rust removal grade is not less than Sa2.5 level; if visible rust spots appear on the steel base body before the bottom coating or the rust removal grade < Sa2.5 level, secondary sandblasting needs to be carried out, and after being detected and confirmed to meet the requirements, the subsequent construction can be carried out.

[0009] S4: Primer Application: After sandblasting, the steel surface must be coated with one coat of primer using a brush or roller within 4 hours (to prevent rust re-entry). During application, the coating condition must be checked regularly. Any drips (length exceeding 50mm) or missed areas (area exceeding 5cm²) should be addressed immediately. 2 For any issues such as unevenness, immediately smooth the surface with a roller or brush or apply additional coating. Simultaneously, use a wet film thickness gauge (accuracy ±2μm) to test the wet film thickness in real time, ensuring it is not less than 60μm. For areas with a thickness less than 60μm, promptly apply additional coating until it meets the requirements. The primer material should be prepared according to the weight ratio of "paint:initiator:accelerator = 100:1.5:0.8", or adjusted according to climatic conditions (e.g., in low-temperature environments, the accelerator ratio can be appropriately increased to 1.0%). During preparation, a professional mixing operator should operate the mixing process. First, use a mixer (300-500r / min) to stir the primer for 5-8 minutes until uniform. Then add the initiator and stir for 1 minute, and finally add the accelerator and stir for 1 minute (total stirring time 1-2 minutes). Record the batch number and amount of material used (accurate to 0.1kg).

[0010] S5: Drying: After the primer is applied, allow it to dry. The drying environment should meet the following requirements: temperature 5-43℃, relative humidity ≤85%. The drying time should be adjusted according to the temperature: 4-6 hours at 25-35℃; 8-10 hours at 15-25℃; 12-16 hours at 5-15℃, to ensure that the primer is completely cured (no stickiness to the touch).

[0011] S6: Applying Glass Flake Adhesive: After the primer dries, apply the first coat of glass flake adhesive using a special trowel, with a thickness controlled at 0.8-1.0mm. After the first coat dries (24 hours at 25℃), check for defects such as bubbles, hollow areas, and missed areas. Repair any defects (e.g., bubbles need to be broken and filled with adhesive) until acceptable, then apply the second coat of glass flake adhesive, also with a thickness of 0.8-1.0mm. After the second coat dries, check and repair again. In addition, before applying the base lining, a styrene sensitivity test must be performed on the substrate (primer surface): Cover the substrate surface with cotton wool soaked in styrene, let it stand for 1 hour, and observe. If the substrate shows no softening or wrinkling, the test is passed; if it fails, sandblasting and primer application must be repeated until the test is passed. At the same time, check the curing status of the base layer (no marks when scratched with a fingernail), damage (if the scratch depth exceeds 0.2mm, the base coat needs to be reapplied) and missed areas. After repairing to the acceptable level, remove the dust and impurities from the surface of the base layer, wipe it clean with styrene, and then carry out the base lining construction.

[0012] S7: FRP reinforcement layer construction: Based on the coating structure requirements, there are two construction methods: For FRP-reinforced coating structures: After the second layer of glass flake putty has been inspected, repaired, and dried, first apply a layer of resin (the same resin used for the glass flake putty) to the putty surface, with a thickness of 0.2-0.3mm. Then, lay the fiberglass cloth flat on the resin layer and press it firmly along the warp and weft directions with a scraper to ensure that the fiberglass cloth is fully impregnated with the resin (no white threads) and no air bubbles are generated. After the resin has cured and dried (12 hours at 25℃), repeat the above steps to apply the second layer of resin-lined fiberglass cloth and dry it again.

[0013] For the wear-resistant glass flake coating structure: After the second layer of glass flake putty has been inspected, repaired, and dried, first apply a layer of resin (0.2-0.3mm thick), spread the fiberglass cloth, compact it, and let it dry (dry for 12 hours at 25℃); then apply a layer of wear-resistant coating with a thickness of 0.5-0.8mm by spraying, let it dry (dry for 24 hours at 25℃), then repeat the resin-lined fiberglass cloth construction (one layer), and after drying, apply a second layer of wear-resistant coating with the same thickness of 0.5-0.8mm, and finally dry it (dry for 24 hours at 25℃).

[0014] S8: Topcoat Application: After step S7 is completed and the coating is completely dry, apply the topcoat. Select a suitable topcoat paint according to the corrosion protection requirements, and apply it by spraying or brushing to ensure uniform coverage without defects such as runs, pinholes, or missed areas. After application, allow it to dry and cure under specified conditions.

[0015] S9: Final Inspection and Acceptance: After the topcoat is dried, use an electric spark leak detector (accuracy ±1V) to detect leaks. The leak detection voltage is calculated at 5V / μm (if the topcoat thickness is 40μm, the leak detection voltage is 200V). Move the probe along the coating surface at a speed of 50-100mm / s to ensure there are no leaks (no sparks generated).

[0016] S10: Construction Environment Control: Throughout the construction process, the climate conditions of the work area must be monitored in real time to ensure that the temperature is maintained between 5-43℃ (using a digital thermometer with an accuracy of ±0.5℃, recorded every 2 hours), the relative humidity is ≤85% (using a digital hygrometer with an accuracy of ±2%, recorded every 2 hours), and the substrate surface temperature is more than 3℃ higher than the dew point (using a dew point meter to measure the dew point temperature, comparing the substrate surface temperature with the dew point temperature every 2 hours). If the environmental conditions exceed the range, construction must be suspended, and adjustment measures (such as using a hot air blower for heating and a dehumidifier for dehumidification) must be taken until the requirements are met before construction can continue.

[0017] Furthermore, during the basic acceptance test in step S1, the inspection scope covers all welds to ensure that there are no defects such as porosity, cracks, or slag inclusions inside the welds (defect equivalent ≤ φ2mm); for the honeycomb pitted surface of the concrete substrate, a ruler (accuracy 1mm) and a depth gauge (accuracy 0.1mm) are used for measurement. If the area of ​​a single honeycomb pitted surface is greater than 0.01m², the inspection is considered complete. 2 (e.g., 100mm×100mm) Repair treatment is required first: use an angle grinder to grind the perimeter of the honeycomb surface to a solid base, remove dust, apply an interface agent (epoxy resin: hardener = 5:1), and after the interface agent is surface dry, fill the honeycomb surface with epoxy mortar (epoxy resin: quartz sand: hardener = 1:2:0.2), compact and smooth it, and then inspect it after curing for 72 hours.

[0018] Furthermore, the quartz sand or copper slag abrasive used in step S3 sandblasting must be screened through a 2.5mm mesh screen before use to remove particles larger than 2.5mm in diameter (sampling inspection is required after screening, with a particle pass rate ≥99%). Simultaneously, a Karl Fischer moisture analyzer (accuracy ±0.01%) is used to test the abrasive's moisture content, ensuring it does not exceed 0.5% (if the moisture content exceeds this limit, it must be dried in an oven at 80-100℃ for 2-4 hours and cooled before use). During sandblasting, the distance between the spray gun and the workpiece surface is controlled within 100-300mm using a measuring tape (e.g., 200mm for flat surfaces, 150mm for corners), and the spray angle is controlled between 30°-75° using an angle gauge (e.g., 45° for flat surfaces, 60° for welds). This avoids damage to the substrate due to excessively close distance and incomplete rust removal due to excessively small angle.

[0019] Furthermore, the primer used in step S4 is an epoxy primer, which contains anti-rust pigments (such as zinc chromate yellow). The content of the anti-rust pigments accounts for 20%-30% of the total mass of the primer (determined by gravimetric method: weigh 10g of primer, ignite to constant weight, and calculate the mass percentage of the residue). If the ambient temperature is below 10℃ during primer application, the primer needs to be heat-treated: place the primer bucket in a constant temperature water bath at 30-50℃ (water temperature fluctuation ±2℃), heat for 30-60 minutes, and stir every 10 minutes to ensure uniform primer temperature. After heating, use a viscometer to test the primer viscosity and control it at 500-800mPa・s to ensure the primer's flowability during application and avoid stringing or clumping during brushing.

[0020] Further, in step S6, the preparation ratio of the glass flake putty is a weight ratio of "resin:glass flakes:filler = 100:30-50:20-40" (e.g., 100kg resin, 40kg glass flakes, 30kg filler); wherein, alkali-free glass flakes are selected, with a thickness of 2-5μm (measured using a laser thickness gauge, with 10 sampling points and an average thickness deviation of ±0.5μm), and a diameter-to-thickness ratio of 50-100 (diameter-to-thickness ratio = flake diameter / thickness, with the diameter measured by microscopic observation, taking 10...). The average value of each scale); when troweling the glass flake putty, use a special rubber trowel (150-200mm wide), and control the troweling speed at 0.5-1m / min (timed by a stopwatch, measuring the length troweled within 1 minute). During the troweling process, it is necessary to advance in the same direction to avoid repeated troweling that may cause air bubbles. After troweling, use a strong flashlight to check to ensure that the putty evenly covers the substrate surface and there are no defects such as air bubbles (air bubbles with a diameter ≥1mm need to be broken and filled) or hollow areas (no hollow sound when tapped).

[0021] Furthermore, the fiberglass cloth used in step S7 is alkali-free fiberglass cloth with a warp and weft density of 4×4 threads / cm (observed under a microscope, counting the number of warp and weft yarns within a 1cm×1cm area, with a deviation of ≤1 thread), and a thickness of 0.2-0.3mm (measured with a thickness gauge, sampling 10 points, with an average thickness deviation of ±0.02mm). During the resin-lined fiberglass cloth construction, a layer of resin is first applied to the surface of the glass flake putty, with the application amount controlled at 200-300g / m². 2 (Calculated by weighing method: Weigh the resin bucket before coating, and coat 1m) 2 Weigh it again; the difference is the amount of coating applied. When spreading the fiberglass cloth, ensure that the overlap width between adjacent fiberglass cloths is 50-80mm to avoid gaps. When compacting the fiberglass cloth with a scraper, apply even pressure (5-10N) from the overlap to the edge to ensure that the fiberglass cloth and resin are fully impregnated and free of air bubbles (if air bubbles appear, they need to be punctured with a needle tip and then compacted).

[0022] Furthermore, in step S7, the wear-resistant layer uses a mixture of epoxy resin and corundum. The corundum is selected from brown corundum with a particle size of 0.1-0.3mm (sieved through a standard sieve, with residue ≤5%), and its content accounts for 40%-60% of the total mass of the wear-resistant layer (prepared by weight method: e.g., 100kg epoxy resin, 50kg corundum, mixed evenly). The wear-resistant layer is applied using air spraying, with a spray gun nozzle diameter of 1.5-2.0mm, a spraying pressure of 0.3-0.5MPa, and a spray thickness controlled at 0.5-1mm per coat (monitored in real-time using a wet film thickness gauge). After each coat is applied, it must be dried for at least 24 hours at a temperature of 25℃ and a relative humidity ≤85% (drying time can be adjusted according to temperature: for every 5℃ decrease in temperature, the drying time is extended by 4 hours) to ensure complete curing of the wear-resistant layer before proceeding to the next coat.

[0023] Furthermore, in step S8, the coating used for the topcoat is a fluorocarbon coating, which has excellent corrosion resistance. The topcoat is applied using a high-pressure airless spraying method, with a spray gun nozzle diameter of 0.8-1.2 mm, a spraying pressure of 15-20 MPa, and a coating thickness controlled at 30-50 μm (measured by a dry film thickness gauge, per 1 m). 2 Three testing points were used, with an average thickness deviation of ±3μm. During the spraying process, the spray gun movement speed needed to be controlled at 300-500mm / s, and the spraying distance at 200-300mm to ensure a uniform and smooth coating (surface roughness Ra≤2μm, measured by a roughness tester), free of sagging (sagging length≤10mm) and pinholes (number of pinholes with a diameter ≥0.5mm ≤1 / m). 2 Defects such as ) should be eliminated; after spraying, the coating should be dried for more than 7 days in a standard environment with a temperature of 25℃ and a relative humidity of 60% (if the temperature is higher than 25℃, the drying time can be shortened: for every 5℃ increase in temperature, the drying time should be shortened by 1 day, but not less than 5 days) to ensure that the coating is completely cured (the actual drying time can be judged by the finger touch method, and there should be no marks).

[0024] Furthermore, step S9, the final inspection, includes not only spark leak detection but also coating thickness and adhesion testing. The coating thickness is measured using a magnetic thickness gauge, with testing points spaced every 10m. 2 Detect 1 point (less than 10m) 2 At least one point in the area must be tested to ensure the total coating thickness meets design requirements (e.g., total thickness of FRP reinforced coating structure ≥ 3.0 mm, total thickness of wear-resistant coating structure ≥ 3.5 mm); adhesion testing uses the pull-off method, selecting a standard test column with a diameter of 50 mm. The adhesive between the test column and the coating surface is epoxy adhesive (curing time 24 hours). During testing, the tensile testing machine loading speed is 10 mm / min, and the adhesion is required to be no less than 5 MPa (per 100 m). 2 Detection point 1, less than 100m 2(1 point to be tested); For areas that fail the test (such as insufficient thickness or adhesion <5MPa), repairs are required: if the thickness is insufficient, apply the corresponding coating (if the primer is insufficient, apply the primer; if the putty is insufficient, apply the putty); if the adhesion is unqualified, the coating in that area must be removed (the removal range extends 50mm beyond the unqualified area), and the process steps must be repeated. After repair, the test must be repeated until it is qualified.

[0025] Beneficial effects Precise substrate acceptance: Differentiated acceptance standards are developed for steel and concrete substrates. By combining non-destructive testing and honeycomb surface repair, corrosion risks are eliminated at the source, ensuring that the surface condition of the substrate meets the requirements for subsequent coating construction and improving the bonding stability between the coating and the substrate.

[0026] Standardized sandblasting process: By screening abrasives, controlling moisture content, and precisely setting spray gun parameters (distance, angle), the surface roughness and rust removal level of the steel substrate are ensured to meet the standards, providing a good adhesion base for the primer and avoiding coating peeling due to incomplete sandblasting.

[0027] Improved coating ratio and construction compatibility: The primer uses epoxy primer and optimizes the content of anti-rust pigments. The viscosity is adjusted by heating at low temperature to ensure construction performance. The material ratio and construction parameters of glass flake putty, FRP reinforcement layer, wear-resistant layer and top layer are standardized. The synergistic effect of each coating significantly improves the overall anti-corrosion performance and structural strength.

[0028] Highly controllable construction environment: Real-time monitoring of temperature, relative humidity, and temperature difference between the substrate surface and dew point ensures that the construction environment meets the requirements and avoids defects such as poor coating curing and cracking caused by environmental factors.

[0029] Comprehensive testing guarantee: Covering multiple dimensions such as leaks, thickness, and adhesion, timely detection and repair of substandard parts, ensuring the overall quality of the anti-corrosion coating meets standards, and extending the service life of desulfurization towers and flues. Detailed Implementation

[0030] The following detailed description of the anti-corrosion coating process for desulfurization towers and flues of the present invention, with reference to specific embodiments, is provided. Each embodiment meets the requirements of the Patent Law that the process be "clear, complete, and capable of being implemented by a person skilled in the art".

[0031] Example 1 Construction steps S1, Basic Experience Collection Steel substrate inspection: Visual inspection combined with touch test is used to confirm that the weld is continuous and uninterrupted. The radius of the rounded edges and corners is measured with a radius gauge and is ≥4.5mm (5mm for the rounded corners of the tower flange). Welding flux, slag, and spatter are removed with a wire brush, and the weld is then ground smooth with an angle grinder. The weld is checked for defects such as porosity, cracks, and undercut (no obvious defects are visible).

[0032] Concrete substrate inspection: Visual inspection confirmed the absence of penetrating cracks; holes were measured using a ruler and depth gauge, with the largest hole size being 8mm (length) × 7mm (width) × 4mm (depth), less than 10mm × 10mm × 5mm, meeting the requirements; honeycomb pitting was sporadic (the largest single area was 50mm × 60mm = 0.003m²). 2 Construction joints, pouring joints, and formwork joints should be ground smooth with an angle grinder to remove any impurities. The radius of the rounded edges and corners should be measured with a radius gauge and should be ≥6.0mm (e.g., the radius of the rounded corners of the flue should be 6.5mm).

[0033] S2, Surface Cleaning Treatment Compressed air (treated with oil-water separation) at a pressure of 0.5 MPa was used to blow away loose dust and sand particles from the steel and concrete substrates using a spray gun. The blowing sequence was: top of the tower first, then bottom; inside the flue first, then outside. For locally adhered oil stains on the steel substrate (approximately 2 m²), [further details needed]. 2 Wipe the surface of the scaffolding (bamboo scaffolding, size 2m×0.3m) with degreased cotton soaked in styrene (99.8% purity) three times, until there are no oil stains when wiped with white gauze; the surface dust and sand of the scaffolding (bamboo scaffolding, size 2m×0.3m) should also be blown clean with compressed air, and the blowing time for each scaffolding should not be less than 1 minute.

[0034] S3, Sandblasting treatment (steel substrate only) Abrasive selection: Quartz sand, particle size 0.5-2.0mm, moisture content 0.3%.

[0035] Compressed air: processed by a three-stage oil-water separator, pressure 0.6MPa, water content 0.08%, oil content 0.01mg / m³ 3 .

[0036] Sandblasting operation: First treat the internal support components of the tower, then treat the tower wall plane, start with the top 10m of the tower, then work downwards, start with the flange corners of the tower, then the middle of the tower wall, start with the outer wall of the tower, then the inner wall; the spray gun runs parallel to the surface of the steel substrate, and the spray gun model is QZ-1.

[0037] Quality Inspection: After sandblasting, the surface roughness was measured using a surface roughness meter, with a total of 20 points tested. The average value RZ = 68μm ≥ 60μm. The rust removal grade was assessed according to GB / T8923.1-2011 "Visual assessment of surface cleanliness of steel surfaces before coating - Part 1: Rust grades and treatment grades of uncoated steel surfaces and steel surfaces after complete removal of the original coating", which was Sa2.5 (no visible grease, dirt, scale, rust, paint coating, or other adhering substances on the steel surface; any residual traces should only be slight spots or streaks). Before the base coat was applied (3 hours apart), no visible rust spots were found, and secondary sandblasting was not required.

[0038] S4. Primer application (steel substrate only) Primer material: epoxy primer, initiator is methyl ethyl ketone peroxide, accelerator is cobalt isooctanoate, prepared in a weight ratio of 100:1.5:0.8; operated by a professional batching operator, first use a mixer (400 r / min) to stir the primer for 6 minutes until uniform, add the initiator and stir for 1 minute, then add the accelerator and stir for 1 minute, for a total stirring time of 2 minutes, record the primer batch number, and the amount used is 50 kg.

[0039] Application method: brushing, with the application sequence consistent with the sandblasting sequence; during application, apply every 10m... 2 Upon inspection, two drips (approximately 30mm in length) were found and smoothed out with a brush. One missed area (approximately 3cm in area) was also discovered. 2 Apply the coating until it is uniform; use a wet film thickness gauge (accuracy ±2μm) to measure, a total of 30 points were tested, the minimum wet film thickness was 62μm≥60μm, which meets the requirements.

[0040] S5, Drying Drying environment: temperature 28℃, relative humidity 65% ​​(record every 2 hours with a digital temperature and humidity meter); drying time: let stand and dry for 5 hours, and the surface of the primer should feel non-sticky to confirm complete curing.

[0041] S6: Glass flake putty scraper Both steel and concrete substrates require construction: the glass flake putty uses vinyl ester resin putty (model 901), and the trowel is made of rubber with a width of 180mm.

[0042] First troweling: thickness controlled at 0.9mm, troweling speed 0.8m / min (stopwatch timing, 0.8m troweling per minute); drying time 24 hours (temperature 28℃).

[0043] Inspection and Repair: Using a strong flashlight, three air bubbles (approximately 2mm in diameter) were found on the steel substrate. After being broken, they were filled with putty and compacted. One hollow area (approximately 5cm²) was found on the concrete substrate. 2Remove the old parts and scrape them again; allow them to dry for 12 hours after repair.

[0044] Second troweling: thickness 0.9mm, troweling speed 0.8m / min; after drying for 24 hours, a second inspection showed no defects.

[0045] Styrene sensitivity test: Select 5 test points on both steel and concrete substrates, cover them with cotton wool soaked in styrene for 1 hour, and observe whether the bottom layer softens or wrinkles. If the test is passed, the bottom layer is cured (no mark is left when scratched with a fingernail), and there is no damage or missed coating. Wipe the surface with styrene to remove dust.

[0046] S7. FRP reinforcement layer construction (only within the bottom 3m of the desulfurization tower body, requiring a wear-resistant coating structure). Fiberglass cloth: Alkali-free fiberglass cloth, warp and weft density 4×4 threads / cm, thickness 0.25mm; Resin-lined fiberglass cloth (first coat): Apply vinyl ester resin (same as the resin used in the mortar) to the surface of the second coat of glass flake putty, at a coating weight of 250 g / m². 2 (Weighing method: The resin bucket weighs 10kg before coating, and the coating depth is 40m) 2 The final weight is 2kg, and the coating amount is (10-2) / 40 = 0.2kg / m². 2 =200g / m 2 (Meets requirements); spread the fiberglass cloth with an overlap width of 60mm, and press it firmly along the warp and weft directions with a scraper (applying pressure of 8N), ensuring there are no white threads or air bubbles; dry for 12 hours (temperature 28℃).

[0047] The first wear-resistant layer is made of epoxy resin and corundum, with corundum content of 50% (by weight). It is applied by air spraying with a nozzle diameter of 1.8mm, a pressure of 0.4MPa, and a thickness of 0.7mm. It is dried for 24 hours.

[0048] Resin-lined fiberglass cloth (second coat): Same as the first coat, application rate 250g / m² 2 After spreading and compacting, dry for 12 hours.

[0049] Second wear-resistant layer: Same as the first layer, 0.7mm thick; dry for 24 hours to confirm complete curing.

[0050] S8, Topcoat Topcoat: Fluorocarbon coating, gray in color; Construction method: High-pressure airless spraying, spray gun nozzle diameter 1.0mm, pressure 18MPa, spraying distance 250mm, moving speed 400mm / s.

[0051] Thickness control: Dry film thickness was measured at 40 points, with an average thickness of 42μm (within the range of 30-50μm), which meets the requirements; the coating surface is smooth, without sagging or pinholes (visual inspection showed no obvious defects).

[0052] Drying and curing: Allow to stand and dry for 7 days at a temperature of 25℃ and a relative humidity of 60% to fully cure.

[0053] S9. Final Inspection and Acceptance Spark leak detection: After the surface layer is dried, a spark leak detector is used. The detection voltage is calculated at 5V / μm (surface layer thickness 42μm, detection voltage 210V), the probe moving speed is 80mm / s, and a full 800m test is performed. 2 Area, no sparks generated, no leaks.

[0054] S10, Construction Environment Control Full-process monitoring: Temperature range 25-32℃, relative humidity 55%-75%, substrate surface temperature 5-8℃ higher than dew point temperature (dew point meter measured every 2 hours), all meet the requirements of 5-43℃, relative humidity ≤85%, and substrate surface temperature more than 3℃ higher than dew point, no need to stop construction.

[0055] Example 2 Non-destructive testing of steel substrate welds Testing method: Ultrasonic testing, using a 2.5P13×13K2 probe and machine oil as the coupling agent; Testing range: All circumferential welds (10 in total) and longitudinal welds (2 in total) of the flue, with 100% testing of each weld.

[0056] Inspection results: A 3mm pore (defect equivalent > 2mm) was found in one circumferential weld. The defect was removed by carbon arc gouging. After re-welding, the defect was eliminated and there were no internal defects in the weld.

[0057] Repairing honeycomb and pitted surfaces in concrete substrate Measurement: Using a ruler and depth gauge, three honeycomb-like pitted surfaces with an area greater than 0.01m² were found. 2 The values ​​are 120mm × 110mm = 0.0132m. 2 110mm × 100mm = 0.011m 2 130mm × 100mm = 0.013m 2 .

[0058] Grinding: Use an angle grinder (with a 100mm resin grinding wheel) to grind the area within 50mm around the honeycomb surface until it becomes a solid base surface, and remove dust.

[0059] Interface agent application: Apply one coat of epoxy interface agent (epoxy resin: curing agent = 5:1) with a brush, with a thickness of 0.1mm, and allow it to dry for 1 hour (temperature 25℃).

[0060] Epoxy mortar filling: The epoxy mortar ratio is epoxy resin: quartz sand (particle size 0.1-0.3mm): hardener = 1:2:0.2. Fill the honeycomb surface with a trowel, compact and smooth it, and cure for 72 hours (temperature 25℃, relative humidity 60%).

[0061] Acceptance: After repair, visual inspection reveals no honeycomb or pitted surface, and a light tap with a hammer produces no hollow sound, thus meeting the acceptance requirements.

[0062] Example 3 Abrasive screening and moisture content control Abrasive selection: copper slag, initial particle size 0.3-2.8mm.

[0063] Screening: A sieve with a 2.5mm aperture (made of stainless steel, with a mesh size of 8) was used for screening. After screening, 500g of abrasive was sampled and inspected. Only 2g of particles with a diameter greater than 2.5mm were found. The pass rate was (500-2) / 500×100%=99.6%≥99%, which meets the requirements.

[0064] Moisture content testing: The initial moisture content was measured using a Karl Fischer moisture analyzer. It was 1.2% > 0.5%. After drying in a 90℃ oven for 3 hours and cooling, the moisture content was measured again. The moisture content was 0.3% ≤ 0.5%, which meets the requirements.

[0065] Spray gun parameter control: Spray gun distance: Measured with a tape measure, the distance between the spray gun and the workpiece surface is 200mm on flat surfaces and 150mm on corners. Apply spray gun every 5m. 2 Double-check the distance to ensure it is within the range of 100-300mm.

[0066] Spraying angle: Measured using an angle meter, the spraying angle is 45° for flat areas and 60° for weld areas, applied every 5m. 2 Double-check the angle to ensure it is between 30° and 75°.

[0067] After sandblasting, the surface roughness was tested: a total of 20 points were tested, with an average value of RZ=72μm≥60μm; the rust removal grade was Sa2.5, with no substrate damage (no scratches or dents visible); after subsequent primer application, the adhesion test was 5.8MPa≥5MPa.

[0068] Example 4 Primer type: epoxy primer with added zinc chromate yellow rust-preventive pigment. The gravimetric method was used to determine the content of the rust-preventive pigment: 10g of primer was weighed and ignited in a muffle furnace at 600℃ until constant weight. The residue mass was 2.6g, and the rust-preventive pigment content was 26% (within the range of 20%-30%), which meets the requirements.

[0069] Low temperature heat treatment Heating equipment: constant temperature water bath, temperature set at 40℃ (within the range of 30-50℃), water temperature fluctuation ±2℃.

[0070] Heating process: Place the 50kg primer bucket into a water bath and heat for 45 minutes, stirring once every 10 minutes (300r / min) to ensure uniform temperature.

[0071] Viscosity test: After heating, the viscosity of the primer was tested using a viscometer (at 25°C) and found to be 650 mPa·s (within the range of 500-800 mPa·s). The primer exhibited good flowability during application and showed no stringing or clumping.

[0072] The brushing process was smooth and there were no difficulties in brushing; the wet film thickness was measured at 20 points, with a minimum thickness of 61μm ≥ 60μm; after drying (temperature 8℃, drying time 14 hours), the primer surface was uniform, without cracks or wrinkles, and the adhesion test was 5.5MPa ≥ 5MPa; after heating treatment in a low-temperature environment, the primer's construction performance and quality met the standards, and there were no abnormalities in subsequent coating construction.

[0073] Example 5 Putty preparation: The resin is vinyl ester resin, the glass flakes are alkali-free flakes, and the filler is quartz powder (particle size 0.075mm), which are prepared in a weight ratio of 100:40:30 (resin 30kg, flakes 12kg, filler 9kg).

[0074] Scale inspection: The thickness was measured with a laser thickness gauge, and 10 points were sampled. The average value was 3.2μm (within the range of 2-5μm). The diameter was observed under a microscope. The average diameter of the 10 scales was 250μm, and the diameter-to-thickness ratio was 250 / 3.2≈78 (within the range of 50-100), which meets the requirements.

[0075] Trowel: made of rubber, 180mm wide; trowel speed 0.7m / min (stopwatch timing), advance in the same direction to avoid repeated troweling.

[0076] Quality inspection: When illuminated by a strong flashlight, there are no bubbles or hollow areas; the thickness is measured at 20 points, with the first layer measuring 0.85mm, the second layer measuring 0.85mm, and the total thickness measuring 1.7mm, which meets the design requirements.

[0077] After the putty has cured, the hardness test shows 45HBa, and the impact resistance test (drop ball impact test, 1kg steel ball dropped from a height of 1m) shows no cracks.

[0078] Example 6 Fiberglass cloth: Alkali-free fiberglass cloth. Microscopic observation of warp and weft density shows 4 warp threads and 4 weft threads within a 1cm×1cm area, meeting the requirement of 4×4 threads / cm. Thickness gauge measurements at 10 points show an average thickness of 0.25mm (within the range of 0.2-0.3mm).

[0079] Resin coating: Vinyl ester resin; coating amount controlled by weighing: resin bucket weight 8kg before coating, coating depth 32m. 2 The final weight is 0.8 kg, and the coating amount is (8-0.8) / 32 = 0.225 kg / m². 2 =225g / m 2 (200-300g / m 2 Within the range).

[0080] Fiberglass cloth laying: overlap width 70mm, apply 7N pressure with a scraper, compact along the warp and weft directions, visually inspect for no white threads (if resin is fully impregnated) and no air bubbles (prick one tiny air bubble with a needle tip and then compact).

[0081] Drying: Dry at 25℃ for 12 hours until the resin is fully cured.

[0082] Example 7 Wear-resistant layer material ratio: 10kg epoxy resin (E51), 10kg emery, emery content = 10 / (10+10)×100%=50% (within the range of 40%-60%).

[0083] Carborundum testing: Standard sieve sieving showed that 98% of the particles were 0.1-0.3mm, which meets the requirements.

[0084] Spraying parameters: air spraying, spray gun nozzle diameter 1.7mm, pressure 0.4MPa, first coat thickness 0.6mm, second coat thickness 0.6mm; drying time: temperature 25℃, each coat 24 hours to dry, no sticky feel after drying.

[0085] Example 8 Topcoat type: Fluorocarbon coating; Salt spray test (neutral salt spray, 5% NaCl solution, temperature 35℃) showed no rust after 1000 hours; Accelerated aging test (UVB-313 lamp, irradiance 0.71W / m²) 2 The light loss rate after 2000 hours is 8%≤10%, which meets the requirements.

[0086] Spraying parameters: high-pressure airless spraying, spray gun nozzle diameter 1.0mm, pressure 18MPa, spraying distance 250mm, moving speed 400mm / s; thickness control: dry film thickness gauge detects 30 points, average thickness 40μm (within the range of 30-50μm).

[0087] Visual inspection: No drips or pinholes are visible. The surface roughness tester shows Ra=1.5μm≤2μm, which meets the requirements.

[0088] Drying environment: 25℃, 60% relative humidity, dry for 7 days for complete curing.

[0089] Example 9 Coating thickness inspection: Magnetic thickness gauge is used for inspection; Inspection points are arranged every 10m. 2 One test point was used, and a total of 50 test points were used. The design requirement for the total coating thickness was ≥3.0mm. The test results showed that the minimum thickness was 3.1mm and the maximum thickness was 3.3mm, both of which met the requirements.

[0090] Adhesion testing method: pull-off test, test column diameter 50mm, adhesive is epoxy adhesive (cured for 24 hours), tensile testing machine loading speed 10mm / min; test point layout: every 100m 2 One point was tested, and a total of five points were tested. The adhesion test results were 5.2MPa, 5.5MPa, 5.3MPa, 5.4MPa, and 5.1MPa, respectively. All of them are ≥5MPa and meet the requirements.

[0091] Simulated defects: One area with insufficient thickness (2.8mm) and one area with unacceptable adhesion (4.8MPa) were artificially created.

[0092] Repair treatment: Apply 0.2mm of glass flake putty to areas with insufficient thickness and allow it to dry for 24 hours; remove areas with unacceptable adhesion (exceeding 50mm), re-sandblast, apply primer, apply putty with a trowel, reinforce with FRP, and apply topcoat. Re-inspect after drying.

[0093] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A corrosion-resistant coating process for desulfurization towers and flues, characterized in that, It includes the following steps: S1: Substrate acceptance: Conduct a comprehensive inspection on the steel substrate or concrete substrate of the desulfurization tower and flue, ensuring that the steel substrate welds are continuous without interruption, all edges and corners are chamfered with an arc transition of R≥4.5mm, welding slag, spatter, etc. are removed completely, and there are no defects such as pores, cracks, and undercut in the welds and they are polished smoothly; the concrete substrate has no through cracks, no holes with a size greater than 10mm and a depth greater than 5mm, and sporadic honeycombing and pockmarks are allowed. All construction joints, pouring joints, and formwork joints are polished flat without inclusions, and the edges and corners are chamfered with an arc transition of R≥6.0mm; S2: Surface purification treatment: Use compressed air to blow the floating dust and sand grains on the substrate surface. For the parts with oil stains, wipe and clean them with styrene to ensure that there are no pollutants on the substrate surface; the floating dust and sand on the scaffolding are also blown clean with compressed air; S3: Sandblasting treatment: For the steel substrate, select dry and angular quartz sand or copper slag with a particle size of 0.5 - 2.0mm as the abrasive, and carry out sandblasting operations driven by clean and dry compressed air that has passed through three - stage oil - water separation at 0.5 - 0.7MPa. The sandblasting sequence follows the principles of starting from the difficult parts first, from top to bottom, from the edges to the middle, and from the outside to the inside. The running direction of the spray gun is parallel to the workpiece surface; after sandblasting, the surface roughness of the steel substrate is required to reach RZ≥60μm, and the sandblasting rust - removal grade is not less than Sa2.

5. If there are visible rust spots on the steel substrate before the bottom coating or the rust - removal grade <Sa2.5, secondary sandblasting must be carried out, and subsequent construction can only be carried out after it is confirmed to meet the requirements; S4: Primer construction: Immediately apply a primer to the sandblasted steel surface by brushing or rolling. During the construction process, check at any time. If phenomena such as sagging and missed coating occur, use a roller or brush to press it flat or touch - up. Measure the wet film thickness during the construction process to ensure that the wet film thickness is not less than 60μm, and touch - up the parts with a wet film thickness less than 60μm; the primer material is prepared according to the ratio of paint: initiator: accelerator = 100:1.5:0.8 (weight ratio), or adjusted appropriately according to climatic conditions. The preparation method is to first stir the primer evenly with a mixer, then add the initiator and curing agent and mix and stir for 1 - 2 minutes. The professional batching operator conducts batching and records the batch number and dosage of the materials; S5: Drying: After the primer construction is completed, let it stand still to allow the primer to dry thoroughly; S6: Troweling of glass flake mortar: After drying, trowel the first layer of glass flake mortar. After inspection and repair to be qualified, then trowel the second layer of glass flake mortar and check and repair again; Before the construction of the base lining, conduct a styrene sensitivity test on the bottom layer and make records. For the parts that fail the styrene sensitivity test, re - carry out sandblasting and primer construction until qualified; At the same time, check the curing, damage, and missed coating conditions of the bottom layer. After repair to be qualified, carry out the construction of the base lining and remove the pollutants on the bottom layer surface, and wipe it clean with styrene; S7: FRP Reinforcement Layer Construction: For coating structures requiring FRP reinforcement, after the second layer of glass flake mortar has been inspected and repaired and approved, apply a layer of resin-lined fiberglass cloth, let it dry, then apply another layer of resin-lined fiberglass cloth, and let it dry again; for wear-resistant glass flake coating structures, after the second layer of glass flake mortar has been inspected and repaired and approved, first apply a layer of resin-lined fiberglass cloth and let it dry, then apply a layer of wear-resistant layer, let it dry, then apply another layer of resin-lined fiberglass cloth, then apply the second layer of wear-resistant layer, and let it dry. S8: Topcoat application: After the above steps are completed and dried, the topcoat application is carried out. S9: Final inspection and acceptance: After the topcoat is dried, a spark leak detector is used for final inspection. The leak detection voltage is calculated at 5V / μm to ensure there are no leaks. S10: Construction Environment Control: Throughout the construction process, the climate conditions of the working area should meet the requirements of temperature 5-43℃, relative humidity ≤85%, and the surface temperature of the substrate should be more than 3℃ higher than the dew point.

2. The anti-corrosion coating process for desulfurization towers and flues according to claim 1, characterized in that, During the foundation acceptance in step S1, non-destructive testing methods are used to inspect the welds of the steel substrate to ensure that there are no defects inside the welds; for the honeycomb pitting of the concrete substrate, if the area of ​​a single honeycomb pitting is greater than 0.01m², [further testing is required]. 2 Repairs are required before acceptance.

3. The anti-corrosion coating process for desulfurization towers and flues according to claim 1, characterized in that, The quartz sand or copper slag abrasive used in step S3 for sandblasting must be screened before use to ensure that the abrasive does not contain particles with a diameter greater than 2.5 mm and that the moisture content of the abrasive is not greater than 0.5%. During sandblasting, the distance between the spray gun and the workpiece surface should be controlled within the range of 100-300 mm, and the spray angle should be controlled between 30° and 75°.

4. The anti-corrosion coating process for desulfurization towers and flues according to claim 1, characterized in that, In step S4, the primer used for the base coat application is an epoxy primer. This primer contains anti-rust pigments, and the content of anti-rust pigments accounts for 20%-30% of the total mass of the primer. When the ambient temperature is below 10℃ during the base coat application, the primer needs to be heated. The heating temperature is controlled at 30-50℃ to ensure the application performance of the primer.

5. The anti-corrosion coating process for desulfurization towers and flues according to claim 1, characterized in that, In step S6, the preparation ratio of glass flake putty is resin:glass flakes:filler = 100:30-50:20-40 (by weight), wherein the thickness of the glass flakes is 2-5μm and the aspect ratio is 50-100. When troweling the glass flake putty, a special trowel is used, and the troweling speed is controlled at 0.5-1m / min to ensure that the putty evenly covers the substrate surface without defects such as air bubbles or hollow areas.

6. The anti-corrosion coating process for desulfurization towers and flues according to claim 1, characterized in that, The fiberglass cloth used in step S7 is alkali-free fiberglass cloth with a warp and weft density of 4×4 threads / cm and a thickness of 0.2-0.3mm. During the resin-lined fiberglass cloth construction, first apply a layer of resin to the surface of the glass flake putty, then lay the fiberglass cloth flat on the resin layer and press it firmly with a scraper to ensure that the fiberglass cloth is fully impregnated with the resin without air bubbles. The resin dosage is controlled at 200-300g / m². 2 .

7. The anti-corrosion coating process for desulfurization towers and flues according to claim 1, characterized in that, In step S7, the wear-resistant layer is made of a mixture of epoxy resin and corundum, wherein the corundum has a particle size of 0.1-0.3mm and accounts for 40%-60% of the total mass of the wear-resistant layer. The wear-resistant layer is applied by spraying, with the spray thickness controlled at 0.5-1mm per coat. Each coat must be dried for at least 24 hours before the next coat can be applied.

8. The anti-corrosion coating process for desulfurization towers and flues according to claim 1, characterized in that, In step S8, the coating used for the topcoat is a fluorocarbon coating, which has excellent corrosion resistance and weather resistance. The topcoat is applied by spraying, with the spray thickness controlled at 30-50μm. During the spraying process, it is ensured that the coating is uniform and smooth, without defects such as sagging or pinholes. After spraying, it is dried for more than 7 days in an environment with a temperature of 25℃ and a relative humidity of 60% to allow it to fully cure.

9. The anti-corrosion coating process for desulfurization towers and flues according to claim 1, characterized in that, The final inspection in step S9 also includes coating thickness testing and adhesion testing. Coating thickness testing is performed using a magnetic thickness gauge, measuring every 10 μm. 2 Test one point to ensure that the coating thickness meets the design requirements; the adhesion is not less than 5MPa; for any part that fails the test, it must be repaired and retested until it passes.