In the coal-fired power plant denitration system, SCR denitration reactor is generally high fly ash disposed, which is to say the SCR reactor placed before the dust removal equipment like ESP., between economizer and air preheater, with the temperature window of 300~450°C. Tungsten trioxide denitration catalyst plays an excellent NOx purification efficiency and sulfur dioxide anti-poisoning in the temperature range. However, in practical applications, flue gas denitration catalyst due to the deposition of fly ash which contains alkali metals K, Na and alkaline earth metals Ca, Mg, etc., leading to poisoning and deactivation eventually; wherein K has the deepest toxic effects. Studies have shown that adding 1% of potassium oxide can lead to the activity of vanadium pentoxide-tungsten trioxide/titania catalyst completely lost under the 250 ~ 400°C.

 

So, how to improve the performance of alkali metal anti-poisoning of tungsten trioxide denitration catalyst? An important reason that alkali metal cause vanadium-based catalyst poisoned is due to the chemical or physical action covered to cause the reduction of activity and active sites lost of vanadium oxide, and the activity of catalyst oxidizing NO to nitrogen dioxide decreased. Therefore, the appropriately increasing of vanadium pentoxide can enhance alkali metal anti-poisoning of the catalyst to some extent. However, the higher vanadium catalyst loaded content will bring out the nitrogen selectivity decreased and the amount of generated nitrogen dioxide increased; besides, vanadium itself is expensive, the more leads the costs increased and resource wasted. Therefore, the amount of increasing vanadium pentoxide should be controlled within a certain extent.

 

Tungsten trioxide as an additive added to the W-Ti-V-based SCR denitration catalyst, can significantly improve the activity and stability of the catalyst. The introduction of tungsten changes the surroundings of vanadium pentoxide in the catalyst, and the synergy between the two improves the catalyst activity. Therefore, under the same load of vanadium, increasing the loading content of tungsten can enhance SCR activity and the alkali metal anti-poisoning.