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Heavy Anti-corrosion Brick Lining Of Power Plant Flue And Chimn

Jun 12, 2020

Brick board linings are mostly used in heavy corrosion environments and have special requirements on pressure bearing and wear resistance. Compared with FRP lining anti-corrosion and mortar lining anti-corrosion, the cost is higher. But as I said before, every anti-corrosion method has its reason. There are occasions where it is applicable. In some occasions, brick lining must be applied. The temperature resistance, corrosion resistance, wear resistance, pressure bearing, and slow heat transfer of the brick lining are all its advantages; insufficient toughness, poor impact resistance, poor application of jointing materials, easy to leak, and adhesive material of the isolation layer Improper use can easily cause the brick to fall off.

       During this time, I met a lot of friends with brick lining, some made raw materials and some did construction. The communication is fragmented. Here, I have to briefly summarize the main points of attention of the brick lining. When I give you a popularization, it is not something esoteric. The technical essay I wrote with my interest.

    The main raw materials of brick lining are divided into two parts: one is brick and board; the other is binder material. The most commonly used bricks and boards are: acid-resistant ceramic materials (including boards and bricks of various sizes), cast stone slabs (using green limestone, basalt, industrial slag, etc.), acid-resistant bricks of various sizes, Natural acid resistant stone (mainly granite), thermosetting resin impregnated graphite material, water glass impregnated graphite material. Among them, acid-resistant bricks, industrial ceramics, and granite are the most suitable. In some special fields, other brick board materials are also used. Almost all brick materials are not resistant to hydrofluoric acid and other fluoric acids.


     The bonding material mainly refers to glue, which is mainly used for jointing, squeezing, bonding, and sometimes directly used as an isolation layer. Here are mainly: water glass cement is silicate cement (KPI is currently used more, potassium water glass performance is better), phenolic cement (not much actual use), furan cement (to be matched with epoxy primer Use), epoxy mastic (used a lot), unsaturated resin mastic (used a lot), vinyl ester resin mastic (used a lot), etc. It should be pointed out here that the choice of bonding material has a lot to do with the final lining application environment: temperature resistance, acid resistance, alkali resistance, etc., and it is also related to other factors such as substrates: bonding strength, toughness, shrinkage margin, etc. In addition to considering the performance at room temperature, it is more necessary to consider the brick lining at a high temperature or a certain temperature (it is definitely used at a certain temperature or a high temperature, otherwise why use a brick lining such a high-cost solution), Whether the bonding material can maintain very good strength, toughness, acid and alkali corrosion resistance, penetration resistance and so on. This is what most people in the industry have not seriously considered.

    Another thing that everyone often misses is: I think that the formula of the clay is very simple, and the configuration is also very simple. Just mix it on the spot. This is wrong. Of course, I am not saying that this is not possible at all, but that the quality of this kind is definitely not enough. The vacuum-dispersed pre-made cement is good for jointing.

    Let's talk about the setting of the isolation layer again. In addition to the joints and squeezes, the glue often continues to be an isolation layer. The choice of isolation layer is very particular. If the heat transfer is required to be fast, most of them are made of metal materials, which is very expensive; rubber materials are also very common; glass fiber reinforced plastic is more common In addition, the adhesion is good, and the choice of resin changes is large.

    In short, the surface of the brick lining is like the wall of a house in our country. In fact, it is in-depth and there are many details that need to be paid attention to. In particular, the laying of corners and other non-planar special cases requires special attention.

    Sui Xing wrote so much. I hope that friends who make brick linings in the jars can talk more about some of their construction experiences and take out the sun drying experience.

Here are some differences between OM coating and vinyl ester resin glass flake cement (FC-flake compoung):

A Composition difference: OM is pure organic, FC is organic-inorganic composite; after curing, the coefficient of thermal expansion and contraction (linear expansion coefficient) of FC is closer to the substrate (refractory brick, brick , Metal substrate), which determines the following aspects of performance;

B. The difference between the bonding ability of bricks: FC is much better than OM;

   Bonding ability with metal substrate: FC is much better than OM;

   Especially after the periodic high-temperature and low-temperature changes, the difference in bonding ability is more obvious.

The effective anti-corrosion thickness of C FC is much thicker than OM, and the cost is much higher. Before 2005, OM was used in domestic flues and chimneys for anti-corrosion. Since 2005, especially after companies such as SGL Wuhan and Jingjiang Prince in Japan introduced FC technology to wet desulfurization in Chinese power plants, the use of OM There are fewer and fewer, and there are more and more application cases of FC. It is not that there are cases where FC does not have problems. There are also cases, but relatively speaking, on the market, Party A and engineering units are more easily accepted by FC or FC deep processing. The plan (brick board lined with FC cement joint).

D Temperature resistance and sudden temperature change, FC is far superior to OM;

E. In terms of impermeability, FC far exceeds OM;

F FC is far superior to OM in terms of wear resistance and erosion resistance.

Let's talk about flue first, then chimney.

The flue, the situation mentioned by the friends, the flue is immersed in the desulfurized water for a long time with a high moisture content, and the pH is 2 in the acidic wet flue gas environment. The water droplets in the flue gas condensation layer below the dew point corrode the inner wall of the flue It is very terrible. The corrosive effect of the acid concentration in the local acidic water drops is far beyond the corrosive performance of acid gas with PH=2, and its permeability is extremely strong. It is a little difficult to use OM coating. As for what other options to use, a few points must be considered before choosing:

1 Acid resistance; 2 Impermeability; 3 Temperature-resistant type; 4 Adhesion to the substrate; 5 Abrasion resistance.

At present, in this market, under these circumstances, the choice of vinyl ester resin glass flake cement or this kind of cement glued joint and then brick lining accounted for most of the two options. There are also people who choose KPI to bond the joints and make bricks, but compared with vinyl ester resin glass flake cement, KPI glue has corrosion resistance, impermeability, temperature sudden change, and adhesion performance at a certain temperature. Wait, not as good as the latter.

Just choose the cement and when you need the glue to make the brick board. This is related to the impurity particle composition in the flue gas and the flue gas speed. After all, the lining of the brick board is much better than the lining of the clay. Of course, the cost is also much higher, which depends on the design life and the investment of Party A.

As for how to do it, please pay more attention to other posts in the thermosetting resin section, which have detailed instructions.

Besides the chimney

There are a lot of chimneys. If FGD is not running, run directly into the chimneys. This temperature is very high, especially the inlet temperature may be as high as 200 degrees or more, of course, it is dry. In this case, whether the metal inner tube is a whole glass fiber reinforced plastic or refractory brick is then lined, the temperature resistance of the material selected for the entrance must be higher. Because the chimney situation mentioned by the friends here is only the chimney of the A3 metal inner tube, we will not discuss the chimney in other cases, otherwise the scope will be too wide. Regarding the anti-corrosion of the chimney, you can find related posts in this section. If you take a closer look, you will know which solutions are used in the current domestic market.

In the current situation, friends of the altar are doing OM coatings. Obviously, they cannot be solved. Even if there is no problem for a short period of one or two years, the probability of a problem is very large if it exceeds two years. The smoke of 60 degrees, the temperature is not high. I think the same impermeability, abrasion resistance, corrosion resistance, these requirements, just like vinyl ester resin glass flake mortar lining.

The key point needs to be considered: the difference between the linear expansion coefficients of metal materials and cement. Therefore, it is necessary to make some slight improvements in the formula of the clay, and it is not that the thicker the better.

Checked the APC hybrid polymer coating information for everyone to encourage.

APC hybrid polymer coating material properties:

A. The APC hybrid polymer structure layer uses organic-inorganic hybrid polymer material, which is a high cross-linking density three-dimensional space structure anti-corrosion material.

B. Temperature resistance of APC hybrid polymer structure layer: -40 ~ 260 ℃, can maintain material properties at high temperature;

C. High corrosion resistance, high wear resistance, and very good flexibility are new stages following the different development stages of phenolic resin, epoxy resin, and vinyl ester resin;

D. APC hybrid polymer structure layer adopts nano-pore sealing technology, which has excellent impermeability;

E. Due to the structural characteristics of the material, it has flame retardant properties after curing and molding;

F. Because the structure after curing does not contain breakable bonds, it takes a lot of energy to break the bonds, so its resistance to strong corrosion and aging is one grade higher than the general organic value.

APC hybrid polymer coating process performance:

A. Good workability, not limited by the shape of the structure surface, and can be cured at room temperature;

B. Good wettability and very good wettability with carbon steel, concrete and brick board, high bonding strength;

C. Mechanized construction, high construction efficiency, high overall structure controllability, avoiding inconsistencies caused by manual construction;

D. The construction period is short, the impact on production operation is small, the flexibility is good, and the temperature change is small.

Advantages of APC hybrid polymer coating technology:

A. "CIS" performance: it has independent structural strength, high-strength connection performance attached to the substrate, and at the same time it has integrity;

B. Seamless: As the anticorrosion layer on the steel structure, brickwork and concrete, the overall structure has no gaps. The combined effect of this structure and the nano-sealing layer ensures excellent anti-seepage and anti-seepage performance;

C. Not limited by the surface shape of the substrate, it can be constructed arbitrarily. Defects such as staggers, gaps, and pores of the substrate do not affect normal operation. The moisture content of the substrate is not high, but the strength of the substrate must be guaranteed.

      Proof that there should be no loose phenomena such as loosening and powdering;

D. It has the advantages of high temperature resistance, non-combustibility and high corrosion resistance of inorganic elements, and the advantages of high elasticity and high ductility of organic materials;

E. The thickness of one-time construction can be up to 5mm thick. It can form most of the chimneys and flues at one time. The construction efficiency is high and the construction period can be greatly shortened.

Typical application of APC hybrid polymer coating (power plant):

A. High-speed flue gas wear-resistant and anti-scouring area (lower part of chimney)

 B. Chimney body and top

   C. The connection between the flue and the chimney

   D. Corbel expansion joints

 E. Ash deposit platform and drainage holes

Application case of APC hybrid polymer coating in power plant chimney:

The United States has: 800MW unit chimney and flue of Sasol II Power Plant, 700MW unit chimney of ELKRAFT Power System Company

Domestic: no

There are applications in the field of domestic non-power plant chimneys:

(1) Applied to the atmospheric and vacuum distillation unit and neutralization tank of CNOOC Fuel Oil Company.

(2) The oil production casing of Liaohe Oilfield, the corrosive medium is 10 MPa, 120-180 ℃ oil vapor, acid vapor (sulfuric acid, carbonic acid, chloride ion), wear mud, and after high temperature alkaline washing.

(3) The blower-type ring seals of Shenyang Blower Factory are used for sealing and corrosion protection. The corrosion environment is: 150-200℃, H2S steam, strong oxidizing acid steam and water vapor.

(4) On the stainless steel drying equipment of Shenyang Activated Carbon Factory, the corrosive environment is: 140-160℃, HCl and H2S vapor.

(5) The anticorrosion of the solder tail of Lianhuashan Drilling Tools Co., Ltd. is used in mining in Australia. The corrosive environment is: 80-200 ℃, high concentration of chloride ions and sulfuric acid vapor.

The aging resistance of APC hybrid polymer coating is much higher than that of organic materials, but worse than that of titanium steel.

Performance index of APC hybrid polymer structure layer (3.0mm)

No. Project name Test value Test standard

1 Tensile strength 62MPa ASTMD638

2 Tensile modulus 2.8GPa ASTMD638

3 Elongation 4.8% ASTMD638

4 Flexural strength 108MPa ASTMD790

5 Flexural modulus 2.8MPa ASTMD790

6 Thermal denaturation temperature 136℃ ASTMD648

7 Bus hardness 35 ASTMD2583

8 Minimum Oxygen Index 25 ASTMD2863

APC hybrid polymer coating chimney anticorrosion layer requirements index

1 Bonding strength with steel plate ≥10MPa

2 Bonding strength with concrete ≥12MPa

3 Tensile strength ≥80MPa

4 Bending strength ≥100MPa

5 Wear resistance (CS-17W-1000g) ≤50mg

6 High temperature elastic modulus (180℃) ≥5GPa

7 Heat resistance, (230℃) 2h, no cracking

8 Thermal shock resistance (placed in 100°C boiling water and 0°C water for 1 hour each) ≥100 times without cracking

9 High thermal shock resistance (2 hours at 200℃, 2 hours at 20℃) ≥30 times, no cracking

10 Resistance to 5% hydrochloric acid + 10% sulfuric acid (60℃, 480h)

11 Resistant to 3% sulfuric acid gas (150℃, 240h), no foaming and falling off