Main factors affecting the selection of anti-corrosion coatings for flues and chimneys

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The anti-corrosion of flues and chimneys has the characteristics of complex corrosive environment, high working temperature, harsh construction environment, and many safety hazards in high-altitude operations. The selection of anti-corrosion materials has become difficult. How to choose the right materials and the right technology for flue and chimney anti-corrosion? one. The selection of anti-corrosion materials for flues and chimneys is inseparable from the analysis of actual working conditions. Articles on the analysis of the corrosive environment of flues and chimneys can be found everywhere, and I will not go into details here. However, special reminders should be made of details that are easily overlooked.: Fuel composition, dust particle size and flow rate, drag reduction of chimney flue, temperature change range under special working conditions, etc. fuel composition: At present, most large boilers in my country still use coal as fuel. Coal is produced in different places and types, and its components, especially the media components that affect anti-corrosion, are also different. For example, some coal in Guizhou contains fluoride ions, and the corrosion of fluoride ions is currently one of the most difficult problems to solve with coatings. ； Dust particle size and flow rate: Although most flue gas is currently discharged from flues and chimneys after desulfurization, denitrification and dust removal, both untreated flue gas and treated flue gas contain a certain amount of dust. The particle size, appearance shape, material properties, flow speed, etc. of the dust will affect the anti-corrosion life of anti-corrosion coatings. The abrasive intensity of small particles moving at high speed cannot be ignored. ； Drag reduction of chimney flue: The smoothness of flue gas emission has been taken into consideration when designing the chimney flue. However, as the service life of the chimney flue increases, multiple repairs and structural adjustments based on actual working conditions may destroy the smoothness of the original design, causing structural resistance to the emission of flue gas, increasing erosion and abrasion, and increasing the concentration of unsmooth local flue gas, which is prone to concentration corrosion. ； Temperature change range under special working conditions: When abnormal conditions occur during the production process, the exhaust gas temperature will fluctuate in a wide range, and the maximum temperature sometimes reaches more than 700°C. At the same time, the working conditions of the chimneys in the northwest and northeast regions in winter should also be considered. The natural environment temperature is low, and the insulation condition of the chimney flue will determine the exhaust temperature of the rear section. In this environment, acid dew point corrosion should be considered. two. The selection of flue and chimney anti-corrosion materials is inseparable from the construction performance analysis. Flue construction is a closed space construction with poor ventilation, slow drying speed of paint, and blocked sight. In terms of construction safety, if good ventilation is not ensured during construction in this space, workers may be easily suffocated when working for a long time. If the solvent content in the air is too high, there is a risk of deflagration or explosion when encountering open flames or static sparks. Chimneys are generally designed to be 60m, 80m, 120m or even higher. Regardless of the safety measures of hanging baskets or scaffolding, the safe construction space is still not large enough, so the anti-corrosion construction of chimneys should be: High-risk high-altitude confined space operations. The risk factor is directly proportional to the time spent in the dangerous area. It is not difficult to see that the more complex the construction process and the longer the construction period, the smaller the construction safety factor. The ideal construction properties of anti-corrosion materials should have the following characteristics: There are few processes, the construction method requires less worker activity, the simple construction operations do not affect the anti-corrosion effect of the final anti-corrosion layer, the simple construction tools do not increase the load-bearing load of the scaffolding or hanging basket, etc. The following is the construction period statistics of conventional flue and chimney anti-corrosion construction: Chimney material, anti-corrosion measures, construction period, composite titanium plate\90 days for steel inner cylinder, Bingode foam bricks, 60 days for laying vitrified bricks, 60 days for applying anti-corrosion paint, 25 days for concrete, acid-resistant cement, 70 days for applying anti-corrosion paint, 30 days for laying Bingode bricks 70 days to lay vitrified bricks 70 days to lay vitrified bricks 70 days ZS-1041 flue gas anti-corrosion coating series does not require thick coating and no interlining. Therefore, compared with ordinary coatings such as OM, glass flake cement, etc., it requires 3 fewer processes, and the construction period is shortened by about 5 days. three. The selection of anti-corrosion materials for flues and chimneys is inseparable from the reliability analysis of anti-corrosion performance. Anti-corrosion materials for flues and chimneys should have the characteristics due to the working conditions.: Heavy duty anti-corrosion, extreme high temperature resistance, permeability resistance, flexibility, thermal shock resistance, resistance to sudden stress changes, adhesion at high temperatures, etc. After possessing the above characteristics, designers pay more attention to the three key points of anti-corrosion, anti-seepage and anti-shedding. The 51 anti-corrosion forum objectively evaluated the currently commonly used glass flake cement (author Ouyang Ziqiang). The evaluation concluded that the performance in terms of flexibility and anti-falling is poor, mainly because: A. Glass flake cement has poor toughness and is prone to brittleness. Especially under sudden changes in temperature, the bonding performance between the cement primer layer and the substrate is insufficient and it is easy to fall off. When the substrate is not properly treated, it is more likely to fall off. ； B. When the temperature changes suddenly, the stress caused by local stress is subsequently released in a concentrated manner, and the resistance to stress changes is insufficient. This is a fundamental problem that the glass flake cement lining solution cannot solve. ； C. After the final anti-corrosion layer of glass flake cement is cured, the linear expansion coefficient is greatly different from that of the base material. The inconsistency in thermal expansion and contraction is more obvious at extremely high temperatures. The temperature difference stress causes coating peeling and cracking. ； D. The polar bond in the glass flake cement resin is hydroxyl group, which has poor adhesion with the substrate. ； E. Glass flake cement has high requirements for pre-treatment of the base material during construction. In actual construction, the ideality of pre-treatment is often ignored due to various reasons. The characteristics and practical application of ZS-1041 flue gas anti-corrosion coating show that the coating has: 1. ZS-1041 flue gas chimney anti-corrosion coating has excellent chemical corrosion resistance and the ability to resist condensed sulfuric acid corrosion. ； 2. ZS-1041 flue gas chimney anti-corrosion coating has very high resistance to water vapor penetration ； 3. ZS-1041 flue gas chimney anti-corrosion coating has excellent high temperature resistance and resistance to sudden temperature changes. It can meet the long-term operating temperature fluctuation between 45--600℃, short-term operating temperature 800℃, and protection action temperature 850℃℃ ； 4. ZS-1041 flue gas chimney anti-corrosion coating also has high resistance to deflection and thermal expansion, and can resist the inevitable vibration in operation of steel chimneys despite reinforcement. ； 5. ZS-1041 flue gas chimney anti-corrosion paint can effectively protect for more than 10 years. When used in conjunction with ZS-1042 desulfurization special anti-corrosion paint, the anti-corrosion paint can last up to more than 30 years. Four. The selection of anti-corrosion materials for flues and chimneys is inseparable from the convenience of subsequent maintenance. The inspection and maintenance of flues and chimneys must be stopped, and the price paid is huge. For example, the longer the maintenance period, the greater the losses. Once the lining material is damaged or falls off, it will fall off in large pieces. It is extremely difficult to deal with the failed coating and substrate during repair. The repair process is also relatively complicated and the construction period is long. ZS-1041 flue gas chimney anti-corrosion coating is relatively simple: After degreasing and local grinding, repairs can be carried out by brushing or roller coating. The damaged area will not spread, the repair area is extremely small, and the construction period is short. five. In summary, this article does not conduct corresponding analysis on material cost, construction cost, maintenance cost, subsequent use value, etc. The above factors must also be considered when selecting materials. I believe that through telephone communication, price consultation and comparison, the comprehensive costs and benefits will be clear at a glance. The author believes that various influencing factors should be fully considered when selecting anti-corrosion materials for flues and chimneys, and the anti-corrosion materials with the best cost performance should be selected after careful comparison.