For many years, Zhisheng Weihua anti-corrosion coating personnel found that a 670t/h thermal power boiler has a gas flow rate of 20-50m/s in the furnace. The iron oxide is washed away by high-speed flue gas, and the newly exposed metal surface is oxidized again. Being washed, the wall of the pipe is gradually thinned, jeopardizing the life of the pipe.
The Xunda Aluminum Foil Tape is a cold applied coating system designed for the corrosion protection water, oil gas underground or aboveground pipelines, protecting insulation coatings ,UV resistance and waterproofing for the windows,roofs ,wall and other building joints.
l Excellent resistance to UV.
l Excellent resistance to soil stress
l Excellent resistance to vapor transmission.
l Good conformability and consistent uniform thickness.
l Waterproof for the basement, bridges ,roofs etc.
l Adhesion to metal .concrete.brick.slate.tile painted wood.glass.rigid plastics
l Meets ASTM D 1000 .EN 12068.AWWA C214 and other international standard
The water wall is the main heated part of the boiler. The main heat receiving surface is composed of several rows of steel pipes, which are distributed around the boiler furnace and then transferred to the heated fluid. Its interior is flowing water or steam, and the outside receives the heat of the flame of the boiler furnace.
The water-cooled pipe wall is in the boiler, and the furnace pipe is placed in the irradiation of the flame of the furnace cavity. Generally, the heating temperature of the combustion radiation is above 1000 °C, and the outer side of the furnace tube is subjected to high temperature, oxidation and corrosion, and the iron oxide is relatively loose. For many years, Zhisheng Weihua anti-corrosion coating personnel found that a 670t/h thermal power boiler has a gas flow rate of 20-50m/s in the furnace. The iron oxide is washed away by high-speed flue gas, and the newly exposed metal surface is oxidized again. Being washed, the wall of the pipe is gradually thinned, jeopardizing the life of the pipe.
The water-cooled pipe wall forms a relatively loose iron oxide under the irradiation of high-temperature gas. The slightly ash in the flue gas gradually adheres to the surface of the iron oxide in the wall of the water-cooled pipe under the action of the temperature difference in the furnace, and the metal oxide vapor (sodium oxide, etc.) condenses in the above-mentioned ash to form the first layer of the water-cooled pipe wall. The ash layer is chemically reacted with S02 in the flue gas to form a metal sulphate with a lower melting point. The ash layer on the heated surface increases with the increase of the thickness, and the thermal efficiency of the boiler decreases. The surface temperature of the layer is increased, so that the sulfate of the scale is melted, and a large cohesive force is generated, and a large amount of fly ash is collected in the flue gas, so that the heat exchange of the furnace tube enters a vicious cycle state, which is slagging. The slag layer is relatively loose, SO2 in the flue gas can penetrate, and when the slag melts, SO2 is invaded into the steel pipe, and the reaction products K3Fe (S04) 3 and Na3Fe (S04) 3 melt at 584 ° C, and then decompose into sulfate. The inner wall of the deep layer is corroded. As a result, the annual corrosion of the boiler water-cooled pipe wall is 1.5-2.5 mm/a, which is a serious problem that has been widespread so far. It causes the boiler thermal efficiency to decrease with time, which shortens the life of the boiler equipment and collapses.
In order to solve the heat exchange tubes, heat exchange sheets, heat pipes, high temperature molds, cracking tubes, heaters, heat sinks and other equipment on the boiler equipment, it is necessary to have good heat transfer in high temperature acid-base medium. Heat. Zhisheng Weihua Company of Dongtieying, Fengtai District [010-51185868] The R&D personnel developed ZS-722 acid-resistant and heat-conductive anti-corrosion coating with high temperature resistance, acid and alkali resistance and high thermal conductivity based on high thermal conductivity and infrared thermal radiation of coating coating. .
The main types of high temperature gas corrosion on high temperature boiler equipment are: high temperature oxidation, vulcanization, nitriding, carbonization, etc.; high temperature corrosion in liquid environment: molten salt corrosion and high temperature liquid metal corrosion, as well as hot corrosion, vanadium corrosion, etc. High temperature corrosion caused by depositing salts. ZS-722 acid-resistant heat-conducting anti-corrosion coating film-forming material: an inorganic-organic high-temperature film-forming solution grafted by Zhisheng Weihua, which is chelated by silicone resin and passivated aluminum sol. The film forming solution has high temperature resistance and temperature resistance up to 750 ° C. It can fully withstand the temperature resistance of the water wall, has good film forming property, high adhesion and good heat conduction, and overcomes the shortcomings of low thermal conductivity of the polymer film forming solution. ZS-722 acid-resistant heat-conducting anti-corrosion coating consists of ceramic functional fillers composed of various components, which synergistically impart excellent wear resistance and thermal shock resistance to the coating, and can resist cavitation erosion and powder friction for a long time. ZS-722 acid-resistant and heat-conductive anti-corrosion coating can greatly increase the heat exchange, improve the heat energy utilization rate and heat loss, shorten the heating time of the object, reduce the accumulation of heat, and improve the working efficiency of the heating element.
The boiler tube is generally made of No. 20 boiler steel tube. The infrared radiation coefficient (black body coefficient) of the metal surface is very low, generally only about 0.1, the reflection coefficient is very close to 0.9 high temperature, due to surface oxidation, the emissivity is about 0.5, according to the base. Erfurt's law, the absorption rate of the infrared radiation of the furnace furnace surface absorption furnace is also only about 0.5, and the radiant heat exchange efficiency is low. If the ZS-722 acid-resistant and heat-conductive anti-corrosion coating increases the emissivity of the surface of the tube to 0.9, the heat exchange efficiency of the working fluid (such as water) and the furnace flame in the furnace tube can be increased by about 8%, which greatly increases energy efficiency and improves productivity.
Assuming that the water vapor content of the boiler water wall is 10% and the sulfuric acid content is 20 ppm, then the dew point temperature is based on the two states of H20 and H2SO4. It can be known that the combustion temperature is 1400 ° C. If the exhaust gas temperature is close to or lower than 140 ° C, sulfuric acid will be produced. The dew point is attached to the metal surface of the water wall to cause pitting corrosion, which causes the equipment to be perforated and scrapped. Therefore, the coating of Zhisheng Weihua ZS-722 acid-proof and heat-resistant anti-corrosion coating, strong acid and alkali resistance, excellent wear resistance and thermal shock resistance usually have to exceed the dew point temperature, which reduces the thermal efficiency of the boiler. , wasted energy. However, the dew point of the flue gas is not a fixed number, it changes with the content of water vapor content SO2, SO3 in the flue gas, even if the exhaust gas temperature is increased, it is difficult to completely avoid the problem of dew point corrosion. Therefore, Zhisheng Weihua Company proposes to adopt a new method to protect the equipment from dew point corrosion, improve the heat exchange capacity of the furnace tube, and reduce the exhaust gas temperature and heat efficiency.
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Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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