The nitrogen oxides produced by coal combustion as a pollutant will affect human health.
The most harmful is NO2, which mainly affects the respiratory system of human beings, and can cause bronchitis and emphysema.
SCR selective catalytic reduction technology has become the most widely used and most effective flue gas denitrification technology in the world. It has the advantages of low reaction temperature, high purification rate, reliable operation and small two pollution. After its catalysis, the main non-toxic and non polluting N2 and H2O are produced.
In the SCR soot denitrification technology selective catalytic reduction system, it is generally composed of ammonia storage system, ammonia and air mixing system, ammonia injection system, reactor system and monitoring control system, the thermal power plant, SCR reactor is usually installed in the boiler economizer and air preheater, here for the high dust temperature arrangement, smoke temperature in this region for SCR denitrification reaction, ammonia injection in the appropriate position in the flue between economizer and SCR reactor, and the flue gas mixture after the reaction with NOx catalyst in the reactor. The catalyst is placed in a solid reactor. The catalyst unit is usually vertically arranged and the flue gas flows up and down.
Catalyst is one of the core of SCR technology, its cost is about 20%~40% of the total cost of SCR system, and the performance of catalyst has a direct impact on the removal efficiency of NOx. For SCR systems, the three main commercial catalysts are noble metal catalysts, metal oxide catalysts, and molecular sieve catalysts. At present, metal oxide catalysts are the most widely used in industry because they are the cheapest. In the past, vanadium titanium catalyst is the main catalyst for selective catalytic reduction system of SCR in China. But in recent years, scientists have found that titanium tungsten vanadium catalysts are more active, selective, antioxidant and anti toxic, and they are expected to be the first choice of catalysts.
Some scholars use imported V2O5 - WO3/TiO2 catalyst to test the effect of SCR, with the help of tungsten trioxide, SCR denitration ratio reached 100%, compared with the traditional vanadium and titanium powder, the effect increased by 30%, the effect is very obvious, but the cost has also increased a lot. For some enterprises, environmental protection measures are only a move, and raising environmental costs is tantamount to their lives, which is the biggest obstacle to the commercial popularization of titanium tungsten vanadium SCR catalyst.
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