| Nitrogen oxide (NOX, Nitre) is one of the main atmospheric pollutants recognized around the world, and The NOX account of coal-fired emissions is around 60%.Flue gas denitration technology of NH3 selective catalytic reduction (SCR) is the most effective way to removal NOX in flue gas by now. Catalysts in operation process are decorated in high temperature region, they will inevitably encounter substances (including alkali, alkaline earth metals and heavy metals) in the fly ash and cause poisoning deactivation. Parsing poisoning mechanism can not only guide the improvement of catalyst, and can guide the operation. In literatures, not only studies of alkali earth metals poisoning is less, and most studies don’t consider the influences of SO2, CO2 in flue gas and water vapor. Therefore, this article made CaCl2, MgCl2 and CaO as representatives of alkaline earth metals, studied influences of SO2, CO2 on alkaline earth metals poisoning of the catalyst. In addition, because of the large amount of coal-fired boiler dust in China, plate type catalyst is more suitable for the characteristics of high ash, this paper studied the plate vanadium titanium base denitration catalyst preparation. So it can give attention to both activity and strength, which can limit your chances of poisoning, extend the life of the catalyst. The main conclusions are shown as follows:1. With the increasing of CaCl2 loadings, the degree of its poisoning to catalyst is greater. SO2 can alleviate the poisoning of alkaline earth metal to catalyst:it can be oxidated to SO42- under the condition of water by O2 in the atmosphere, although SO42- can react with Ca2+ to generate CaSO4 causing the catalyst blocking, but it increases surface acidity of catalyst to adsorb more NH3 which is of advantage to the SCR reaction.2. CO2 has no effect on CaCl2 poisoning of catalyst, but can weaken MgCl2 poisoning. For poisoning of MgCl2 to catalyst, CO2 can significantly increase the ratio of reactive oxygen, making V3+ oxidated into V4+ and V5+, and can release TiO2 interacting with V3+, thus making the denitration catalyst activity increased. For any atmosphere conditions, the poisoning of CaCl2 to catalyst is stronger than MgCl2.The stronger basicity of alkaline earth metal is, the greater the degree of catalyst poisoning is.3. Under the condition of the same Ca/V ratio, CaCl2 on catalyst poisoning effect is stronger than CaO. Both can lead to decline B acid sites and the oxidation ability of V, but CaCl2 catalyst is stronger, Cl- can interact with dispersed phase Ⅴ on catalyst surface, leading to loss of catalyst activity. For poisoning of CaCl2 to catalyst, the toxicity of impregnation method of is stronger than method of aerosol.4. Water content of sludge has a great influence on the strength of the catalyst,32.72% is advisable to water content; with glass fiber length increasing from 0.038 mm to 3 mm, the strength of the catalyst increases. But for denitration activity, the four are almost same; For 10 nm of titanium powder particle size, the strength of the catalyst is best, and also the denitration activity is better than the other two. |
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