Application of waterborne epoxy emulsion mortar in corrosion prevention of inner wall of wet desulphurization concrete chimney

Abstract

The invention relates to application of water-based epoxy emulsion mortar to corrosion prevention of the inner wall of a wet desulphurization concrete chimney, which effectively solves the problem of erosion of a flue gas corrosive medium by adopting the water-based epoxy emulsion mortar as a main anti-corrosion layer and combining a metal net reinforcing structure and a closed coating protection system. The method has excellent acid resistance and temperature change resistance, is simple and convenient to construct, is green and environment-friendly, and is suitable for long-term anti-corrosion protection of desulfurization chimneys in the industries of electric power, chemical engineering and the like.

Description

Technical Field

[0001] This invention relates to the field of industrial chimney corrosion protection technology, specifically to the application of water-based epoxy emulsion mortar in the corrosion protection of the inner wall of wet desulfurization concrete chimneys. Background Technology

[0002] Currently, most coal-fired power plants employ wet desulfurization methods, with the desulfurized flue gas emitted through chimneys. While wet desulfurization significantly reduces the sulfur dioxide content in the flue gas (SO2, SO3, and HCl), it is less effective at removing small amounts of sulfur trioxide. Due to the increased humidity and decreased temperature of the flue gas after wet desulfurization, condensation easily forms on the inner wall of the chimney. The residual SO3 dissolves, forming highly corrosive dilute sulfuric acid. The strong permeability of this highly humid, dilute acid creates a harsh, corrosive environment that is difficult to prevent, severely damaging the chimney structure.

[0003] The temperature of the flue gas after desulfurization is generally between 40 and 60°C (around 80°C after being heated by the GGH heater). In this low-temperature, high-humidity flue gas environment, corrosive compounds such as SOx and NOx react with water to form a highly corrosive acid solution that adheres to the inner surface of the chimney. The corrosiveness of this acid solution is extremely high at temperatures between 40°C and 80°C, with a corrosion rate approximately 3-8 times higher than at room temperature. Furthermore, the inner surface of the chimney is also subject to flue gas pressure, making the inner wall of the chimney highly susceptible to corrosion and damage.

[0004] As the temperature of the imported flue gas decreases, the humidity increases, and the density of the flue gas increases, the chimney's self-extraction capacity decreases, the positive pressure range expands, and the permeability of the flue gas increases, accelerating and amplifying its corrosive effect.

[0005] During heating operation, various factors cause repeated temperature changes, resulting in significant fluctuations in humidity and acidity. Rapid cooling and heating can lead to stress damage.

[0006] The lining of concrete chimneys is typically constructed using red bricks or firebricks, with cement mortar as the building material. Corrosive media can easily penetrate this structure, causing the concrete joints to become porous. Further corrosion will then seep into the chimney's interior, leading to chimney corrosion. The reasons for concrete corrosion damage are as follows:

[0007] The flue gas contains SOx, an acidic medium. Sulfides penetrate into the concrete and react with free Ca(OH) to form CaSO4. They can also react with hydrated calcium aluminate to form hydrated calcium sulfoaluminate, which has a lower solubility. The calcium sulfate and hydrated calcium aluminate produced by the reaction are much larger in volume than the original compounds, causing the concrete joints to expand and become loose.

[0008] When the joints between concrete bricks become loose, sulfides continue to seep in, directly exposing the chimney concrete to corrosive media. This also causes the chimney concrete to become loose, reduces the alkalinity of the concrete, damages the protective film on the reinforcing bars, and leads to steel bar corrosion. After corrosion, the steel bars expand in volume and lose strength, affecting their use.

[0009] In conclusion, it can be seen that the operation of the chimney becomes very complex after the addition of a wet desulfurization device, which seriously threatens the safe operation of the reinforced concrete chimney. In order to ensure the long-term good and safe operation of the chimney, the selection of anti-corrosion materials and the construction quality are particularly important.

[0010] Currently, there are many anti-corrosion measures for the inner wall of concrete flue gas desulfurization chimneys, which can be commonly summarized as: brick lining series, mortar and adhesive series, fiberglass lining series, and chimney anti-corrosion coating series. Brick lining series mostly uses high-temperature silicone rubber to bond vitrified ceramic bricks or foam glass bricks, which is relatively expensive. Mortar and adhesive series currently use JS polymer mortar and silica-based anti-corrosion mortar. JS polymer mortar has poor anti-corrosion performance, while silica-based anti-corrosion mortar has high shrinkage and poor water and acid resistance. Fiberglass and chimney anti-corrosion coatings have relatively short service lives in terms of chimney corrosion protection. Summary of the Invention

[0011] The purpose of this invention is to provide the application of water-based epoxy emulsion mortar in the corrosion protection of the inner wall of a wet desulfurization concrete chimney. To achieve the above objective, this invention is implemented through the following technical solution: the application of water-based epoxy emulsion mortar in the corrosion protection of the inner wall of a wet desulfurization concrete chimney.

[0012] A water-based epoxy emulsion mortar is used to construct the main anti-corrosion layer of the chimney's inner wall, combined with a hot-dip galvanized metal mesh reinforcement structure, and then coated with a high-temperature resistant sealing coating. This combined system, through multi-layer synergy, forms a protective layer that combines high strength, impermeability, and weather resistance, effectively isolating corrosive media in the flue gas after wet desulfurization. Material environmental friendliness: The water-based system has no solvent evaporation, and the VOC content is lower than environmental standards, avoiding construction pollution; Structural stability: The metal mesh improves crack resistance, and the sealing coating enhances surface wear resistance, adapting to chimney vibration and dust erosion; Long-term protection: Laboratory tests show that the corrosion rate is less than 0.05 mm / s over a 15-year period.

[0013] It will meet the durability requirements of the power industry within a year.

[0014] Furthermore, the water-based epoxy emulsion mortar boasts a compressive strength ≥30MPa, a flexural strength ≥4.5MPa, a permeability grade ≥1.5MPa, and high-temperature resistance up to 150℃, ensuring its mechanical reliability under complex working conditions. Its compressive strength is improved by 230% compared to traditional silica mortar, enabling it to withstand localized chimney loads and temperature stresses; its superior permeability resistance, with a microporous ratio of less than 5%, blocks sulfuric acid penetration and prevents substrate carbonization; and its adaptability to construction, with rapid curing at low temperatures (above 5℃), shortening the construction period by 60%, making it suitable for emergency repairs.

[0015] Furthermore, the construction steps include substrate treatment, high-pressure water washing, mortar application, metal mesh embedding, and sealing coating spraying. Each step is carried out progressively to ensure the integrity of the coating. Substrate cleanliness: High-pressure water gun (spray pressure ≥20Mpa) is used to wash the surface until there is no oil, dirt, desulfurization crystals, or loose or unstable surface (refer to high-pressure water spraying Wa2 grade), with moderate roughness to improve bonding strength; Metal mesh reinforcement: Galvanized iron wire mesh (φ≥1mm, mesh ≤30mm×30mm) is tightly bonded to the mortar to inhibit shrinkage cracks; Joint optimization: Sloping joint is reserved (sloping joint slope 45°) and used with joint adhesive to eliminate the risk of cracks and adapt to on-site construction errors.

[0016] Furthermore, the metal mesh uses hot-dip galvanized iron wire welded mesh with a diameter of φ≥1mm and a mesh spacing of ≤30mm×30mm, balancing strength and economy. Corrosion resistance: The galvanized layer withstands over 2000 hours of salt spray testing, preventing electrochemical corrosion; Mechanical synergy: The tensile strength of the iron wire is ≥47MPa, forming a "rigid-flexible" structure with the water-based epoxy emulsion mortar; Convenient construction: The modular mesh design improves splicing efficiency, and the anchor nail pull-out force is ≥1.2kN.

[0017] Furthermore, the mortar layer is applied in multiple layers with a pre-dip joint, and adhesive is pre-applied at the joint before construction to ensure continuity between layers. Stress relief: The diagonal joint design reduces shrinkage stress concentration and avoids drying shrinkage cracks; Interface strengthening: Water-based epoxy latex penetration depth ≥2mm, bond strength >3MPa; Improved sealing: Water absorption rate at the joint <0.1%, superior to conventional joints (water absorption rate ≤0.5%).

[0018] Furthermore, the sealing coating must meet the requirements of temperature resistance ≥180℃ and dust erosion resistance, and adopt a two-component phenolic vinyl resin system. High temperature adaptability: heat distortion temperature >180℃, resisting the temperature shock during chimney start-up and shutdown; enhanced abrasion resistance: abrasion amount in sand drop test <0.02g / cm2, adapting to fly ash erosion; flame retardancy meets standards: smoke toxicity reaches AQ1 level, meeting the fire protection standards of the power industry.

[0019] Furthermore, after construction, the surface flatness, density, and metal mesh coverage must be tested to ensure coating uniformity. Flatness control: the maximum gap of a 2m straightedge ≤5mm, unevenness <3mm, to improve appearance quality; Defect detection: ultrasonic testing (UT) sensitivity up to 0.5mm, to prevent hidden holes; Coverage verification: the penetrant method confirms that the metal mesh coverage is ≥95%, eliminating exposed substrate.

[0020] Furthermore, component A (water-based epoxy emulsion) and component B (powder) are mixed in a mixer at a mass ratio of 1:5 to ensure reactivity and the application window. Compatibility: controllable gel time (8-12 hours at 25℃); Environmental adaptability: suitable for winter (freezing point -10℃); Green attributes: free formaldehyde <0.05%, meeting the HJ 2537-2014 low VOC standard.

[0021] Furthermore, the total thickness of the anti-corrosion layer is ≥22mm (including the metal mesh and sealing layer), and a gradient design is adopted to optimize stress distribution. Protection redundancy: 25%-50% higher than traditional solutions (15-20mm), extending service life; Gradual thickness: 1:10 slope at the tapered end reduces edge stress concentration; Economic balance: Unit area cost increases by <15%, but service life is extended by more than 3 times.

[0022] Furthermore, the method is applicable to the corrosion protection of the inner wall of chimneys in coal-fired power plants under operating conditions of 40-80℃ after wet desulfurization, and is particularly suitable for high-humidity environments during GGH failures. It has broad operating condition coverage: meeting the operating parameters of 90% of domestic coal-fired power units; extreme environmental tolerance: corrosion rate <0.1mm / year under Cl- concentration environment; cost-effectiveness: the retrofit cost for a single 600MW unit is approximately 6 million yuan, a 40% reduction compared to imported solutions.

[0023] This invention provides the application of water-based epoxy emulsion mortar in the corrosion protection of the inner wall of wet desulfurization concrete chimneys, which has the following beneficial effects:

[0024] The compressive strength is ≥41MPa, which is 230% higher than that of silica mortar. The flexural strength is ≥6.5MPa. It meets the requirements of chimney vibration conditions; the impermeability grade reaches P15>1.5MPa, and there are no abnormalities in the 72-hour acid immersion stability test, effectively blocking sulfuric acid penetration; the volatile organic compound (VOC) content is <5g / L, which meets the requirements of the "Green Building Evaluation Standard" GB / T 50378-2019.

[0025] Embedded galvanized metal mesh with a diameter of φ≥1mm and a mesh spacing of ≤30mm×30mm increases the tensile strength of the coating by 40% and effectively inhibits cracking caused by temperature stress; 20mm thick water-based epoxy mortar + 150μm sealing coating form a "rigid skeleton + flexible seal" composite system, which adapts to the periodic thermal expansion and contraction of the chimney (thermal deformation coefficient matching degree >90%).

[0026] High-pressure water jet (6kg / cm2) rinsing achieves a surface cleanliness level of Wa2, and combined with pre-reserved oblique joint technology, ensures interlayer bonding strength >2.5MPa.

[0027] The overall cost per unit area is reduced by 45% compared to brick lining, and the service life is ≥15 years; the maintenance cycle is extended to more than 8 years, reducing the frequency of downtime for maintenance, resulting in significant overall economic benefits. Detailed Implementation

[0028] Example 1: Corrosion Protection Project for a New 60-meter-high Coal-fired Power Plant Chimney

[0029] A newly built 60-meter-high wet desulfurization chimney of a coal-fired power plant has an inlet flue gas temperature of 60-80℃, an SO2 concentration of 3500mg / m3, and a Cl- concentration of 180mg / m3. The following process was adopted: mechanical grinding to remove the carbonized layer of concrete to a depth of 5mm; high-pressure water gun (spray pressure 20MPA) rinsing until the substrate absorbs 0.3L / (min·m2); mixing mortar with water-based epoxy emulsion and powder in a ratio of 1:5, applying it in 2-3 layers to a thickness of 22mm, embedding φ1.2mm galvanized steel wire mesh (grid size 25mm×25mm, with a 1:5 slope reserved at the joint and pre-coated with epoxy emulsion); spraying a two-component phenolic vinyl resin anti-corrosion coating (80% solids content) in 3 coats, with a total dry film thickness of 180μm; 28-day compressive strength of 45MPa, impermeability grade P15, 5-year measured corrosion rate of 0.03mm / year, meeting the DL / T 5193-2014 standard.

[0030] Example 2: Repair Project for Old Chimneys (GGH Failure Condition)

[0031] A 15-year-old chimney experienced flue gas temperature fluctuations (40-95℃) due to a GGH malfunction, resulting in internal wall leakage. The following repair plan was adopted: The damaged coating was removed down to the substrate; the chimney was rinsed with a high-pressure water gun (6 kg / cm²) and then dried; a 25mm thick layer of water-based epoxy mortar (including φ1.5mm galvanized mesh, 20mm×20mm grid) was applied, with a curing period of 14 days; a 200℃ high-temperature resistant vinyl resin coating (200μm thickness) was sprayed at a 75° angle; after a 2-year follow-up, the leakage disappeared, the coating showed no cracking, and the impact resistance reached 50 kg·cm / cm².

[0032] Example 3: Corrosion Prevention of Chimneys in Coastal Power Plants with High Chloride Ion Levels

[0033] The chimney of a power plant in the southern coastal area (Cl- concentration 450mg / m3) adopts the following anti-corrosion design: sandblasting to Sa3 level, applying epoxy primer (penetration depth 3mm); applying 28mm thick water-based epoxy mortar (including double-layer galvanized mesh, 15mm×15mm mesh), steam curing after final setting; spraying fluorocarbon coating, artificial accelerated aging test (xenon lamp irradiation for 1000h) gloss retention rate >80%; no rust in 1500-hour salt spray test, chloride ion penetration resistance coefficient <5×10-13cm / s.

[0034] Example 4: Emergency Repair Project in Cold Regions during Winter

[0035] A power plant in Northeast China needed urgent repairs for a chimney that had been perforated due to corrosion (ambient temperature -10℃). The chimney was mechanically sprayed to a thickness of 18mm and cured with infrared heating. An antifreeze agent (10% ethylene glycol content) was added to the sealing coating, and the adhesion strength retention rate was >80% at -25℃. The chimney cured for 48 hours and underwent a 72-hour freeze-thaw cycle (-20℃ / 20℃) without any quality loss, allowing it to be put into operation 10 days ahead of schedule.

[0036] Example 5: Corrosion Protection Treatment for Irregularly Shaped Flue Interfaces

[0037] Corrosion protection for the irregular interface (curvature radius 0.5m) between a power plant chimney and a GGH: a silicone soft mold is used to fit the curved surface, with a 5% shrinkage allowance; a 12mm layer of fiber-reinforced mortar (containing 0.2% carbon fiber) is applied as the base layer, followed by a 10mm layer of ordinary mortar, and the metal mesh density is increased to 100mm×100mm; the bending strength is ≥8MPa, and the bonding strength after thermal cycling (80℃ / 20℃×50 times) is >3.5MPa.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. The application of water-based epoxy emulsion mortar in the corrosion protection of the inner wall of wet desulfurization concrete chimneys, characterized by: Water-based epoxy emulsion mortar is used as the main anti-corrosion layer, combined with a hot-dip galvanized metal mesh reinforcement structure, and supplemented with a high-temperature resistant sealing coating.

2. The application of the water-based epoxy emulsion mortar according to claim 1 in the corrosion protection of the inner wall of a wet desulfurization concrete chimney, characterized in that: The water-based epoxy emulsion mortar has a compressive strength ≥30MPa, a flexural strength ≥4.5MPa, a permeability grade ≥1.5MPa, and a high temperature resistance of 150℃.

3. The application of the water-based epoxy emulsion mortar according to claim 1 in the corrosion protection of the inner wall of a wet desulfurization concrete chimney, characterized in that: The anti-corrosion construction steps include: The surface is chiseled and polished until it is free of dirt and loose substrate; High-pressure water gun is used to rinse the inner wall, with a water jet pressure ≥20Mpa; Apply a ≥20mm thick layer of water-based epoxy emulsion mortar, with an embedded φ≥1@30 hot-dip galvanized metal mesh; Spray a high-temperature resistant sealing coating with a dry film thickness ≥150μm.

4. The application of the water-based epoxy emulsion mortar according to claim 3 in the corrosion protection of the inner wall of wet desulfurization concrete chimneys, characterized in that: The metal mesh is made of hot-dip galvanized iron wire welded mesh with a diameter of φ≥1mm and a mesh spacing of ≤30mm×30mm.

5. The application of the water-based epoxy emulsion mortar according to claim 3 in the corrosion protection of the inner wall of a wet desulfurization concrete chimney, characterized in that: When applying mortar layers in multiple stages, a sloping joint should be left, and adhesive should be pre-applied to the joint before plastering.

6. The application of the water-based epoxy emulsion mortar according to claim 1 in the corrosion protection of the inner wall of a wet desulfurization concrete chimney, characterized in that: The sealing coating must meet the requirements of temperature resistance ≥180℃ and dust erosion resistance.

7. The application of the water-based epoxy emulsion mortar according to claim 1 in the corrosion protection of the inner wall of a wet desulfurization concrete chimney, characterized in that: After construction, surface flatness, density, and metal mesh coverage must be tested.

8. The application of the water-based epoxy emulsion mortar according to claim 1 in the corrosion protection of the inner wall of a wet desulfurization concrete chimney, characterized in that: The waterborne epoxy emulsion mortar is made by mixing component A (waterborne epoxy emulsion) and component B (powder) in a mass ratio of 1:5 using a mixer.

9. The application of the water-based epoxy emulsion mortar according to claim 1 in the corrosion protection of the inner wall of a wet desulfurization concrete chimney, characterized in that: The total thickness of the anti-corrosion layer is ≥22mm, including the metal mesh and the sealing layer.

10. The application of the water-based epoxy emulsion mortar according to claim 1 in the corrosion protection of the inner wall of a wet desulfurization concrete chimney, characterized in that: The method is applicable to the corrosion protection of the inner wall of chimneys in coal-fired power plants under operating conditions of 40-80℃ after wet desulfurization.