SCR technology is the most mature denitrification technology in denitrification technology, its NOx removal rate can reach more than 80%. At present, SCR technology has become the mainstream technology of denitration in power plants at home and abroad. SCR denitrification technology using ammonia as a reducing agent, into the temperature of about 280 ~ 420 ℃ flue gas, under the action of the catalyst, the selective reduction of NOx to N2 and H2O. Denitrification catalyst is the core element of SCR technology, decides the denitration performance of the whole technology, so it is very important to keep the activity of denitrification catalyst. However, in the reaction process of SCR, because the catalyst is exposed to the high-temperature flue gas containing pollutants for a long time, the catalytic efficiency will be reduced with the growth of the use time. The reason for the regeneration of denitrification catalyst is as follows:
Three denitrification catalysts
First, the catalyst sintering and blocking ash: high temperature environment can lead to active sintering of the catalyst, increasing the catalyst particles, reducing surface area and reduce its activity. Blocking ash is mainly due to the unavoidable formation of ammonium salts during the SCR reaction and small particles of fly ash in the flue gas to deposit in the pores of the catalyst so that NOx, NH3, and O2 are hard to reach the active surface of the catalyst and cause passivation. To prevent the first block of ash should choose a reasonable catalyst spacing, followed by different flue gas space velocity to choose a different catalyst, you can refer to “Which kind of denitrification catalyst to prevent blocking effect”, select the appropriate catalyst. If the coal contains more than 10% ash, no matter what the size of the catalyst, are required to install sootblowers.
Second, As and Na, K and other alkali metal poisoning: As and alkali metals and other substances will react with the active components on the catalyst, thereby reducing the catalyst denitrification activity.
Third, water and SO3 poisoning: flue gas in the form of water vapor is present, if the water vapor condenses on the catalyst surface, will lead to K, Na and other alkali metal soluble salt dissolved in the catalyst surface, exacerbating the catalyst And when the reaction temperature is raised, the condensed water vapor in the pores of the catalyst will vaporize and swell, damage the fine structure of the catalyst, and eventually lead to the rupture of the catalyst. The formation of SO3 and other substances will react with the active component of the catalyst to produce sulfate material, making the active ingredient of the catalyst failure.
4, Ca poisoning: free CaO in fly ash and the formation of SO3 reaction, adsorption on the catalyst surface to generate CaSO4, will cover the pores of the catalyst, making the reaction difficult to spread to the catalyst surface, thus affecting the catalytic effect of the catalyst.
Some of the reasons we can be avoided, such as the choice of appropriate catalyst to improve anti-blocking effect. From all stages of production to reduce the NOx content of flue gas, reducing the burden on the catalyst to extend its life and improve economic efficiency.