Now there are any new anti-corrosion acid and alkali resistant materials, power plant desulfurization system corrosion is very strong, want to inquire about what the latest good anti-corrosion materia

Now there are any new anti-corrosion acid and alkali resistant materials, power plant desulfurization system corrosion is very strong, want to inquire about what the latest good anti-corrosion materials. Send a material to you, I hope to help you. This is a domestic resin-based anti-corrosion experts wrote.

Thermal power plant desulfurization system anticorrosion technology

1 desulfurization system introduction

Figure 1 desulfurization system schematic

Thermal power plant desulfurization system is the main body of the plant from the function, structure, mode of operation are completely different from the relatively independent system, it can be thought that the desulfurization system is the internal of the power plant is a small chemical plant or chemical plant, it is the raw material is from boiler Its raw materials are raw flue gas from the boiler and limestone slurry (or other absorbents), and the products are net flue gas and gypsum (or other products). The reaction principle is as follows:

A Absorption reaction:

SO2+H2O→H2SO3

H2SO3→H++SO3-

B Oxidization reaction:

SO3-+1/2O2→HSO4

HSO4-→H++SO42-

C Neutralization reaction:

Ca2++CO32-+2H++SO42-+H2O→ CaSO4-2H2O+CO2

Total reaction:

SO2+2H2O+1/2O2+CaCO3→CaSO4-2H2O+CO2

2 Desulfurization system corrosive environment

According to the corrosive medium of the different, desulfurization system can be subdivided into the flue gas system, slurry system and the absorption tower.

2.1 flue gas system

From the boiler out of the original flue gas, through the gas heat exchanger (GGH) cooling into the absorption tower, desulfurization of the net flue gas by mist eliminator mist, and then by the GGH warming, through the flue into the chimney for emissions. Any flue and equipment that mainly contact with flue gas can be categorized as flue gas system, including original flue gas flue, baffle door, GGH, mist eliminator, net flue gas flue, chimney and so on.

The original flue gas contains SO2, CO2, NOx, HF and other corrosive gases, before entering the GGH, the original flue gas temperature is high, humidity is small, corrosivity is very small, after the GGH cooling, corrosivity increases, after the absorption tower of the net flue gas humidity, temperature is low, coupled with the residual SO2 and so on, so that the net flue gas corrosivity is the strongest.

2.2 Slurry system

Any piping and equipment in contact with the slurry, including absorbent preparation system and absorption system in contact with the slurry piping and pumps, agitators, filters (screens), slurry tanks (tanks, pools) are all slurry system.

In wet FGD (limestone-gypsum), with the addition of absorbent CaCO3, the absorber tower slurry will reach a certain pH value. A high pH slurry environment favors SO2 absorption, while a low pH facilitates Ca2+ precipitation, the two opposing each other. In a certain range with the absorption tower slurry pH value increases, desulfurization rate is generally on the rise, but when the pH value reaches a certain value (neighboring value), the desulfurization rate will not continue to rise; then raise the pH value, desulfurization rate will instead be reduced, and gypsum slurry in the content of CaCO3 will increase, while the content of CaSO4-2H2O will be reduced, it is clear that at this time, the reaction between SO2 and desulfurization agent is not complete, the reaction is not complete. It wastes limestone and reduces the quality of gypsum. Therefore, choosing the appropriate pH value is crucial for the flue gas desulfurization reaction. The optimal pH value should take into account the anti-scaling, desulfurization efficiency and absorbent CaCO3 utilization. According to process design and experience generally control the pH of the slurry in the absorption tower between 5.0 and 5.4. Therefore, the slurry in the absorption tower is acidic.

In addition, if the desulfurization gypsum is dewatered and stored or transported, the water separated from the gypsum is to be utilized and sent to the absorber preparation system to facilitate the precipitation of Ca2+ in CaCO3.

2.3 Absorption tower

The absorption tower is the heart of the wet FGD system (FGD), the original flue gas in the absorption tower through the limestone slurry spray cleaning, removal of sulfur dioxide, to achieve compliance with the environmental emission standards of the net flue gas.

Absorbent in the slurry and flue gas in the sulfur dioxide in the absorption tower intersection reaction, slurry spray on the tower wall has scouring abrasion, high-temperature flue gas by the spray temperature reduction, there is the impact of the temperature alternation, so the absorption tower is the strongest corrosive effect of the environment.

3 Desulphurization system anti-corrosion technology

3.1 Flue gas system

3.1.1 flue gas

High temperature raw flue gas corrosivity is very low, do not do corrosion. Any flue in contact with the net flue gas and low-temperature flue gas, that is, from the original flue side of the flue gas heat exchanger (GGH) into the elbow up to the chimney of the flue (including the flue within the deflector), should be taken to prevent corrosion measures. For the desulfurization unit without flue gas heat exchanger, anticorrosive measures should be taken from at least 5 meters away from the entrance of the absorption tower.

Anti-corrosion of the flue generally use vinyl ester resin glass scale coating or lined with nickel-based alloy; the deflector plate directly with nickel-based alloy; chimney generally use vinyl ester resin glass scale coating, paste glass brick or lined with nickel-based alloy.

The flue at the entrance of the absorption tower generally adopts vinyl ester resin glass scale coating with tiles or directly with nickel-based alloy.

3.1.2 Equipment

The main equipment of the flue gas system are heat exchanger, baffle gate, mist eliminator.

a Heat exchanger

The corrosion protection of the inner surface of the shell of the heat exchanger is generally vinyl ester resin glass scale coating;

The heat exchanger components are generally coated enamel.

b Baffle door:

The baffle door that needs anti-corrosion is the desulfurization exit baffle door and bypass baffle door.

The frames, blades, shafts, bolts and sealing plates should be made of nickel-based alloy.

c Mist eliminator:

The frame, mist elimination plate, screw locks, flushing hose and nozzles of the mist eliminator can be plastic such as polypropylene.

3.2 Slurry system

Since the water separated from gypsum goes to the slurry preparation system for recycling, all the pipelines and equipments in contact with the slurry, including the pipelines and pumps, agitators, filters (screens), slurry tanks (tanks, pools) in contact with the slurry in the absorber preparation system and the absorption system, which are in the corrosive environment of the acidic liquid medium, should be corrosion-resistant.

3.2.1 Pipeline

a Slurry pipeline:

Slurry pipeline corrosion prevention generally uses carbon steel pipe lined with butyl rubber or polypropylene plastic, or glass fiber reinforced plastic pipe

b Absorption tower internal pipeline:

Internal pipeline of the absorption tower is generally used fiberglass reinforced plastic pipe (FRP).

3.2.2 Equipment

The main equipment of the slurry system are pumps, agitators, filters (screens), slurry tanks (tanks, pools).

a Pump

The shell of the pump in contact with the slurry is generally steel lined with rubber, while the impeller is generally acid-resistant, wear-resistant alloy steel.

b Agitator:

The blades of side-entry agitator can be either alloy steel or steel lined with rubber; the shaft should be alloy steel; and the blades and shaft of the top-entry agitator can both be steel lined with rubber.

c Filter (screen):

The housing of the filter is generally made of steel lined with rubber or vinyl ester resin glass scale coating, while the screen is made of nickel-based alloy.

d Slurry boxes (tanks, pools):

Boxes, tanks, pools for storing slurry, are anticorrosive. Anti-corrosion measures are generally rubber lining or the use of vinyl ester resin glass scale coating.

3.3 Absorption tower

Desulfurization reaction in the absorption tower, both the strongest corrosive medium, but also hot and cold alternation, as well as spray scouring, is the most hostile corrosive environment, therefore, in addition to the requirement of corrosion-resistant anti-corrosion measures, but also requires resistance to hot and cold shock, wear-resistant, is generally the use of vinyl ester resin glass flake coatings, adhesive lining, or the direct use of nickel-based alloy, the slurry in the scouring of the more serious places and the bottom of the slurry tank. More serious places and slurry pool bottom anticorrosion layer should be thickened.

4 XXXX series of flue coatings

4.1 Product Description

Desulfurization system, in addition to equipment, slurry pipeline, the rest of the parts of the anti-corrosion can be used in vinyl ester resin glass scales coating.

Vinyl ester resin is made of epoxy resin reacted with acrylic acid and methacrylic acid, through crosslinking with styrene to form a body structure, the ester group for space protection, with acid, alkali, salt, organic compounds corrosion resistance and outstanding temperature resistance. In addition to alkali resistance is not as good as epoxy resin, resistance to other corrosive media and temperature resistance are better than epoxy resin, adhesion, mechanical and mechanical properties similar to epoxy resin, the disadvantage of curing shrinkage is large, standard vinyl ester resin volume shrinkage after curing is about 6%, phenolic vinyl ester resin up to 11% or so. Improper selection of formulations, construction quality control is not strict easily caused by the coating shrinkage and cracking, and in serious cases, large areas will fall off, which is the quality of these products in the past application of accidents that are likely to occur.

XXX series of flue coatings by adding all kinds of additives, the volume shrinkage rate will be reduced to less than 2%, comparable with epoxy resin products, if you can strictly according to the requirements of the construction process for the construction, can completely avoid the problem of shrinkage cracking. According to the use of different environmental temperatures, the development of XXX-1, XXX-2 two series of products, each series has a primer, (I) type, (II) type, M-type (wear-resistant topcoat) 4 products. XXXX-1 series adopts the standard vinyl ester resins, temperature resistance of 180 ℃ or less, a short period of time can be 220 ℃ (1 hour); XXXX-2 series adopts phenolic type vinyl ester resin, temperature resistance below 180 ℃, short period of time can be 220 ℃ (1 hour); XXXX XXXX-2 series adopts phenolic vinyl ester resin, with temperature resistance below 200℃, short time can be resistant to 260℃ (1 hour), corrosion resistance is also better than XXX-1 series. Product technical indicators are shown in Table 1 and Table 2.

Table 1 XXX-1 desulfurization flue coatings technical requirements

Serial No. Item Indicator XXX-1DXXX-1 (I) XXX-1 (II) XXX -1M1 container in the state of light brown transparent liquid dark gray viscous liquid, no hard lumps, stirred to a uniform state of white viscous liquid, no hard lumps, stirred to a uniform state of black viscous liquid, no hard lumps, stirred to a uniform state of 2 paint film color and appearance colorless or light brown, the paint film is flat dark gray, the paint film dense white, the paint film dense black, the paint film dense 3 density , g/ml1.061.351.151.364 Viscosity, component A, s ≥ 15 ≥ 60 ≥ 60 ≥ 605 Anti-sagging, μm- ≥ 1006 Solids content, component A, wt% ≥ 60 ≥ 807 Drying time (23 ℃), h surface drying time solid drying time ≤ 1 ≤ 24 ≤ 2 ≤ 248 Application period (23 ℃), h1 ≥ 29 Flexibility, mm ≤ 1-10 Abrasion resistance (g,1kg500r) - ≤ 0.06 ≤ 0.06 ≤ 0.0411 Adhesion (pull-apart method), MPa ≥ 5-12 Artificial accelerated aging b-500h does not blister, does not fall off, the No cracking, no chalking 13 water resistance, 72h paint film does not blister, no flaking, no rust spots 14 salt water resistance, 72h paint film does not blister, no flaking, no rust spots 15 immersion in water 24h water absorption ≤ 1% 16 heat resistance 220 ° C ± 5 ° C constant temperature of 1h, cooling the coating is not cracked, blistering, flaking 17 corrosion resistance, 80 ° C, 15d 40% sulfuric acid after immersion, the coating is not cracked, blistering, flaking 18 freeze-thaw cycle resistance, sub-50 ℃ ± 2 ℃ / -23 ℃ ± 2 ℃, each constant temperature 3h, cycle 10 times, the coating is no cracking, blistering, flaking 19 resistance to rapid cooling, rapid heating 220 ℃ ± 5 ℃ / 23 ℃ ± 2 ℃ + blowing, each constant temperature 1h, cycle 5 times, the coating is no cracking, blistering, flaking Note: 1, 13 ~ 19 items coating system for: XXX-1D : 30μm

XXX-1 (I): 800μm

XXX-1 (II): 100μm

XXX-1M: 100μm

The total thickness of about 1,000μm.

2, artificial accelerated aging of the technical specifications for the guaranteed items, not as factory inspection and type inspection items.

Table 2 XXX-2 desulfurization flue coating technical requirements

Serial number item index XXX-2DXXX-2 (I) XXX-2 (II) XXX-2M1 container in the Status light brown transparent liquid dark gray viscous liquid, no hard lumps, stirred to a uniform state white viscous liquid, no hard lumps, stirred to a uniform state black viscous liquid, no hard lumps, stirred to a uniform state 2 paint film color and appearance colorless or light brown, paint film flat dark gray, paint film dense white, paint film dense black, paint film dense 3 Density, g/ml1.061.351.151. 364 Viscosity, component A, s ≥ 15 ≥ 60 ≥ 60 ≥ 605 Anti-sagging, μm- ≥ 1006 Solids content, component A, wt% ≥ 60 ≥ 807 Drying time (23 ℃), h Surface drying time Solid drying time ≤ 1 ≤ 24 ≤ 2 ≤ 248 Suitable for the period of (23 ℃), h1 ≥ 29 Flexibility, mm ≤ 1 -10 abrasion resistance (g,1kg500r) - ≤ 0.06 ≤ 0.06 ≤ 0.0411 artificially accelerated aging b-500h does not blister, does not fall off, does not crack, does not chalking 12 adhesion (pull apart method), MPa ≥ 5-13 Water resistance, 72h paint film does not blister, no flaking, no rust spots14 Salt water resistance, 72h paint film does not blister, no flaking, no rust spots15 Water absorption rate of 24h immersion ≤ 1%16 Heat resistance 250 ℃ ± 5 ℃ constant temperature of 1h, cooling the coating is not cracked, blistering, flaking17 Corrosion resistance, 80 ℃, 15d50% sulfuric acid immersion, the coating is not cracked, blistering, flaking18 Freeze-thaw cycle resistance, time 50 ℃ ± 2 ℃ / -23 ℃ ± 2 ℃, each at a constant temperature of 3h, cycle 10 times, the coating is no cracks, blistering, peeling 19 resistance to rapid cold, rapid heat 250 ℃ ± 5 ℃ / 23 ℃ ± 2 ℃ + blowing, each at a constant temperature of 1h, cycle 5 times, the coating is no cracks, blistering, peeling Note: 1, 13 ~ 19 items of the coating system is: XXX-2D: 30μm

< p>XXX-2 (I): 800μm

XXX-2 (II): 100μm

XXX-2M: 100μm

The total thickness is about 1000μm.

2, artificial accelerated aging specifications for the guarantee project, not as a factory inspection and type test items. The technical specification of artificial accelerated aging is a guarantee item, not as a factory inspection and type inspection item.

4.2 Construction program and process

4.2.1 Construction program

Material selection and thickness according to design requirements.

The middle of the coating is strengthened with 1-2 layers of glass cloth.

4.2.2 Construction process

(1) Environmental requirements

When constructing in winter, heat preservation measures should be taken to prevent condensation; it is recommended to take heating measures to make the ambient temperature above 15℃.

It is not suitable for construction in case of rain, fog, snow, frost, large wind and sand and other weather.

(2) Surface treatment

The steel surface should be sandblasted to the national standard Sa2.5 level or above, and dust and oil pollution should be removed.

(3) XXX-1D, XXX-2D construction

Brush or roll coating, two-component ratio of A: B = 100: 1 ~ 2, according to the applicable period of adjustment of the ratio of A, B, so that the period of application of more than 1 hour, stirring evenly. According to the number of construction personnel and brush coating speed to determine the amount of dosage, required to be used up within the applicable period, it is recommended that each person each time the amount of dosage of 1kg or so appropriate. Primer to wet the substrate to form a continuous film is appropriate, the theoretical coating amount of 35g/m2 (30 μm), the actual coating amount of up to 80 ~ 100g/m2.

Surface drying time: about 1 hour (23 ℃), 24 hours of actual drying. The next coating can be applied after 8 hours of construction.

(4) XXX-1(I), XXX-2(I) construction

Scraping or smearing, two-component ratio A:B = 100:1~2, adjust the ratio of A and B according to the applicable period, so that the applicable period of more than 1 hour, stirring evenly. According to the number of construction personnel and scraping speed to determine the amount of dosage, required to be used up in the application period, it is recommended that each person each time the amount of dosage of about 1kg is appropriate. (I) type viscosity is large, require repeated scraping a few times to drive out the bubble and make the scales spread flat.

In the middle of (I) type, add glass cloth to strengthen.

Theoretical coating volume: 1350g/m2 (1mm), the actual coating volume up to 1400 ~ 1600g/m2.

Surface drying time: about 1 hour (23 ℃), drying 24 hours. The next coating can be applied after 8 hours of construction.

(5) XXX-1 (II), XXX-2 (II) construction

Scraping, brushing, or rolling, two-component ratio A: B = 100: 1 ~ 2, adjust the ratio of A, B according to the applicable period, so that the applicable period of more than 1 hour, stirring evenly . According to the number of construction personnel and brush coating speed to determine the amount of dosage, required to be used up within the application period, it is recommended that each person each time the amount of dosage of about 1kg is appropriate.

Theoretical coating volume: 115g/m2 (100 μm), the actual coating volume can be up to 120-140g/m2.

Surface drying time: about 1 hour (23 ℃), 24 hours of actual drying. It can be put into use after solid drying.

(6) XXX-1M, XXX-2M construction

Scraping, brushing, or rolling, two-component ratio of A: B = 100: 1 ~ 2, adjust the ratio of A, B according to the applicable period, so that the applicable period of more than 1 hour, stirring evenly . According to the number of construction personnel and painting speed to determine the amount of dosage, required to be used up in the application period, it is recommended that each person each time the amount of dosage of about 1kg is appropriate.

Theoretical coating volume: 136g/m2 (100 μ m), the actual coating volume can be up to 140-160g/m2.

Surface drying time: about 1 hour (23 ℃), solid drying 24 hours. It can be put into use after solid drying.

(7) Coating Quality Inspection

Appearance

Flat and dense, no defects such as air holes and flow hanging.

Thickness

Check the thickness of the coating with magnetic thickness gauge, measuring more than 5 points per square meter, the minimum thickness should not be less than 80% of the design thickness, and the average thickness should not be less than the design thickness.

Leakage point

Check the leakage point of coating with EDM scanner. Scanning voltage 5000V, full scanning, the whole coating should not have leakage points.

(8) Repair

For insufficient thickness and leakage points, knock off the top layer with sandpaper, scrape XXX-1(I) or XXX-2(I) to the designed thickness, and then apply top coat. After repairing, it is still necessary to make a comprehensive inspection of the coating until it is qualified.

(9) safety and health

Painting construction, the site should be conspicuous no fire signs, with dry powder fire extinguishers and other fire tools. Smoking and the use of open flame are strictly prohibited.

The construction site should be well ventilated. Construction should wear cloth gloves, wearing overalls, sticky paint on the skin should be promptly wiped off and rinsed with water.

When paint is splashed into eyes and mouth, it should be flushed with water immediately. It is forbidden to take food at the construction site, and you should change your working clothes and wash your hands when you leave the site.

On-site construction workers are not allowed to wear slippers and shoes with nails, but can wear flat rubber shoes, cloth shoes and so on.

The site construction workers are not allowed to wear slippers and shoes with nails.