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  • Chimney anticorrosion construction scheme and precautions
  • Author / arrangement: YueShun chimney corrosion protection Co., Ltd. release time: May 24, 2020
  •  Chimney brick anti-corrosion

    According to the corrosion situation of the inner and outer walls of the chimney, the anticorrosive mat of the smoke map can be divided into five main corrosion areas, namely, the original flue gas corrosion area, the warm flue gas mat corrosion area, the dry and wet interface corrosion area of the C1 flue gas, the corrosion area in the absorption tower and the corrosion area of the clean flue gas. The flue gas from the kiln usually has a temperature of about 180C 600C, and some will be higher. The relative humidity in the flue gas is 3%. It contains ash and various corrosive components, such as SO2, HCl, NO2 and salt spray. In the desulfurization process, it has the characteristics of alternating acid-base value, so the equipment is seriously corroded and the anti-corrosion conditions are demanding. The smoke anticorrosive coating for the inner wall of chimney flue contains silicon inorganic polymer modified organic polymer. The coating can arrange several copolymers alternately to form a dimensional network structure in the coating space and form a point labyrinth. The ultra-fine powder oxide objects in the coating form a dense interface transition layer in the coating, effectively preventing acid and alkali from invading the matrix under the joint action.

    Although the content of sulfur dioxide in flue gas is greatly reduced after desulfurization, the effect of washing method on removing a small amount of sulfur trioxide in flue gas is not good. Due to the wet desulfurization, the humidity of flue gas increases and the temperature decreases, and the flue gas is easy to condense on the inner wall of the chimney. After the residual sulfur trioxide in the flue gas is dissolved, the corrosive dilute sulfuric acid solution is formed. The flue gas in the desulfurization chimney has the following characteristics:

    1) the humidity of flue gas is high, and the corrosive medium contained in the saturated wet flue gas is easy to be corroded under the dual effect of flue gas pressure and humidity, which affects the structure durability.

    2) the corrosion of dilute sulfuric acid solution with low concentration is stronger than that with high concentration.

    3) when the temperature of the acid solution is between 40 ℃ and 80 ℃, it is particularly corrosive to the structural materials. Taking steel as an example, the corrosion rate at 40 ℃ - 80 ℃ is about 3-8 times higher than that at other temperatures.

    We should pay attention to the following aspects in chimney construction:

    1. The construction site should be clean and tidy with ventilation measures, and the content of harmful gas should not exceed the specified requirements. Except for the paint used in chimney anti-corrosion, inflammable materials are strictly prohibited to be stored on the construction site. That is to say, pay attention to some environmental safety and clean up the site.

    2. Smoking is prohibited in the site. Welding or open fire operation is not allowed within 10 meters. Explosion proof lighting equipment shall be used in construction. Construction operators should be equipped with necessary protective equipment, and should take turns to work in containers, and take good ventilation facilities. There should be anti-skid measures, and the operators should fasten the safety belt.

    3. When using high-pressure airless spray gun, the spray gun should be grounded to avoid fire and explosion caused by electrostatic sparks. If you use airless spraying equipment under extremely high pressure, do not put the spray gun hole on the human body and palm, in order to avoid personal injury.

    4. After the anti-corrosion construction of the chimney is completed, it is not allowed to dump the waste solvent in the tools and containers at will, and it should be handled properly. If something unexpected happens, it should be placed in the prescribed place.

    Anticorrosion construction scheme for chimney inner wall: technical measures

    (1) Construction process Construction preparation (inspection of materials, tools and machines, staff education and training, construction scaffolding, etc.) → inner wall treatment (base cleaning, high-pressure pump water flushing, polymer acid fast drying mortar repair, grinding, etc.) → brushing Fuchen VEGF-1 (or other brand resin) heat-resistant resin primer with uniform and no missing coating → drying for 6-10 hours until it does not stick to hands → coating resin and lining glass Cloth (aeration and compaction) → drying for 10 hours → surface treatment, painting evenly and without leakage → coating resin again according to the above process to the required number of layers → drying at room temperature for more than 12 hours → surface treatment, brushing resin on the surface layer once (drying for 12 ~ 24 hours each time) → fine completion → completion acceptance.

    A. Base treatment of cloth sticking position: Iron drill rod, shovel blade and other tools are used to remove the corrosion layer at the construction site, high-pressure pump is used to wash with water, and then the uneven parts on the surface are cleaned, polished and repaired with polymer mortar by using electric grinder, planer blade, wire brush, chisel and other tools, so as to make the surface of base layer meet the following requirements after cleaning:

    (1) after treatment, the surface should be clean and flat, free of oil and chemical corrosive substances adhesion, penetration, condensation and crystallization.

    (2) the surface shall be free of corner drop, pit, hole, crack, bulge, honeycomb and pitted surface, loose pulverization and other damages (surface cracks and holes shall be smoothed with polymer repair mortar, and the corresponding drainage slope of flue shall be made).

    (3) rough surface.

    (4) the water content of the surface should be less than 6% after treatment. If the drying degree is not reached, spray lamp can be used for drying.

    B. The quality of the paint preparation should be strictly in accordance with the following requirements in the preparation process.

    (1) the full-time staff should be responsible for the mixing and mixing, and the mixing should be carried out according to the specification;

    (2) can opening: the brand, variety, color, batch number, etc. of the coating shall be confirmed before opening the can, and the record shall be made. If the identification is fuzzy, it shall be checked carefully. The oil-based and oil modified coatings may have crusts after opening the can, so the crusts should be carefully removed. If it is found that the paint or glue is out of date, it should be identified and confirmed that its quality is reliable before construction. In case of deterioration of paint or glue, it should be discarded.

    (3) mixing: some pigments in the coating are dense and easy to precipitate, and the color of top coat is easy to float. All these phenomena need to be mechanically stirred to make the coating uniform.

    (4) filtration: in order to remove the large particles and crusts or other foreign matters in the coating, it must be filtered. The more standard way is to pour it into another empty barrel through the filter screen.

    C. Apply Fuchen heat-resistant and acid resistant resin primer

    According to the requirements of the product manual, the primer shall be prepared in strict accordance with the coating ratio, and shall be applied after full mixing. The painting shall be carried out in sequence. The corner, joint, hemp hole and unevenness shall be applied at first, and then the sealing primer shall be applied uniformly and carefully in the whole sequence, so as to make the whole base surface penetrate the primer without omission, pinhole bubble, etc Membrane defects.

    D. Interlining

    (1) according to the product manual, and referring to the batching method and proportion of the construction scheme, mix and mix the lining material, and then brush the prepared rubber evenly on the surface of the base course. When applying the rubber compound, brush it carefully, quickly and crisscross each time to prevent leakage (the width of the brush depends on the width of the pasted cloth). When brushing, dip the glue properly, not too much or too little. After brushing, roll the glass cloth along the place where the glue is applied.

    (2) the glass cloth should be vertically lined. Generally, the upper part should be protected from the lower part, and the wall should be first followed by the bottom.

    (3) when the glass cloth is pasted and lined, it shall not be pulled too tightly, so that the glass cloth is basically straight, and there shall be no concave convex phenomenon on both sides.

    (4) after the lining is flat, brush and compact it evenly with a brush (or roller) immediately. Remove the air bubbles from the center of the cloth to both sides. The glass cloth must be pasted tightly without bubbles and folds.

    (5) the glass cloth must be soaked by the rubber material to make the glue penetrate through the hole of the glass cloth. The upper, lower, left and right of each layer of glass cloth shall be overlapped at least by 30-50 mm. The glass cloth shall be separated from each other in the lap joint of each layer and shall not overlap. The glass cloth shall be cut at the fillet, and the glass cloth shall be cut at the flange edge, and then the glass cloth shall be pasted on the flange edge and flattened with a plate.

    (6) the first layer of glass cloth to be pasted and lined shall be naturally dried until it is preliminarily solidified for trimming. The burr, protruding edge and air hole shall be repaired and checked to be qualified before further construction In other words, according to the above procedures, other layers of glass cloth are continuously pasted on the same part (the lining part is continuously completed), that is, the fish scale overlay method of multi-layer continuous lining is adopted, that is, after the first pair of cloth is paved, the second pair is 3 / 4 of the width of the previous cloth with a half range, so that the multi-layer glass cloth can be continuously pasted at one time. When multi-layer continuous lining is applied, the operation should be careful Do not scrape the previous layer of cloth with wrinkles and bubbles. The lap joint should be compacted carefully (the thickness of anti-corrosion coating at each part should be constructed according to the requirements of the bidding document).

    E. Application of Fuchen high temperature resin topcoat

    The last layer of glass cloth shall be pasted and lined, and the finishing coat shall be applied after finishing. The finish coat shall have good corrosion resistance and wear resistance, and the surface shall be smooth and clean. Then, the mixture shall be prepared in strict accordance with the proportion specified in the product manual. The filler shall be added as little as possible, and the paint shall be applied evenly after full mixing and ripening. Generally, the paint shall be evenly applied from top to bottom, first from wall to bottom, first difficult to easy, and then three layers of high-temperature topcoat shall be applied in sequence, and there shall be no pinhole, missed coating, sagging and other film defects.

    F. Carefully inspect the unqualified parts until they meet the technical requirements.

    G. Local glass fiber cloth (MAT) reinforcement

    Glass fiber cloth (MAT) reinforcement (three cloth and seven oil) should be used in corner area of each node, inner surface of nozzle and flange sealing end face. The bonding material for laying glass fiber cloth (felt) shall be prepared with the same resin as the scale lining mortar.

    H. Pay attention to the problem

    The first layer of lining should be pasted continuously after construction, and the lining layer should be pasted continuously after construction;

    All lining layers attached to the lining shall be compacted by gas driving, and it is not allowed to drive and compact at one time after the completion of multi-layer construction;

    During the continuous lining construction, it is necessary to avoid wrinkling the previous layer and causing bubbles when brushing the mortar.

    1. Quality standard of sticking cloth

    (1) Coating quality standard

    1) Surface quality: each coating should be uniform and flat, with consistent color, without obvious looseness, wrinkle, sagging, pinhole and bubble; there should be no leakage and peeling.

    2) Coating thickness: the coating times and the thickness of each coating shall meet the technical requirements of the specified coating. The allowable deviation of dry film thickness per pass is - 5um, and the allowable deviation of total dry film thickness of coating is - 25um.

    3) The type, number of layers, color, mark and thickness of the paint shall meet the relevant requirements in the design documents.

    4) Adhesion: the coating adhesion shall be tested in accordance with gb9286-88 "cross cut test for paints, varnishes and film" or GB 1720-88 "determination method for adhesion of paint film".

    (2) Coating quality inspection

    1) Detection of wet film thickness: the wet film thickness gauge shall be used for detection immediately after construction, because if it is not carried out in time, the volatilization of solvent will affect the reading; the detection of wet film thickness gauge can reflect the inspection of paint dosage, and help to control the specified dry film thickness and reflect the solid content of paint.

    2) Dry film thickness detection: dry film thickness gauge shall be used. After each coating is completed and fully cured, the quantity shall be carried out according to different conditions, because different designs of coated structures need to be considered.

    3) Testing of adhesion and interlayer adhesion: the adhesion and interlaminar adhesion of coating system is destructive and usually only complaints occur. The quality approval test acts on the designated reference area, which is not a routine test. The fracture of interlayer adhesion occurs between coating and substrate or between separate coating and coating.

    4) Detection of pores and pinholes: the pinhole detector can detect unacceptable coating faults.

    Summary of chimney anticorrosion:

    There are high requirements for the selected anticorrosive materials for chimney corrosion protection. It requires high temperature resistance, acid and alkali resistance, water and moisture resistance, wear resistance, impact resistance, smooth surface, not easy to grow cracks, good expansion coefficient, not easy to fall off and other performance requirements. In the desulfurization process, it has the characteristics of alternating acid-base value, so the equipment is seriously corroded and the anti-corrosion conditions are demanding.

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Tel: 0515-88266009; mobile phone: 15351551158; 13705105077, manager; address: room 208, Party mass service center, Sanzao village, Xinxing Town, Yancheng City