Denitration equipment | the influence factors of denitration SCR exhaust system have?
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Nitrogen oxide is an important atmospheric pollutant. At present, the air pollution caused by it is increasingly serious, both the environment and human health are threatened. In order to reduce pollution, the state comprehensively promotes NOx emission control, and the related industries that cause nitrogen oxide emissions are required to rectify emissions. Coal-fired thermal power plants, power stations, generators, kilns, boilers, transportation and other industries that discharge the most NOx shall carry out emission control treatment.
I. Basic principle of SCR denitration system
The selective catalytic reduction process of nitrogen oxides (NOx) is to convert NOx into nitrogen (N2) and water (H2O) in the air by using NH3 or urea at a certain temperature and under the action of a catalyst. As NH3 preferentially reduces NOx and is not oxidized by oxygen (O2), it is called "selective catalytic reduction".
Ii. Several key factors affecting the denitrification performance of SCR:
1. Activity of catalyst
Catalyst is the main component of SCR system, and the composition, structure, life and related parameters of catalyst directly affect the denitrification efficiency and operation status of SCR. The reaction activity of the catalyst is affected by the reaction temperature, the reaction temperature is different, affect the reaction speed, if the reaction temperature is higher, the catalyst activity is higher, the denitrification efficiency will be higher.
2. Flue gas temperature
Flue gas temperature not only determines the reaction speed of catalyst, but also determines the activity of catalyst.
When the flue gas temperature is higher, the catalyst activity is higher. When the flue gas temperature is higher, the injected reducing agent NH3 reacts with O2 to produce NOx, which cancelling the denitrification efficiency.
3. NH3 ammonia escapes
In the SCR system, the catalyst is arranged in layers, and the NH leakage is caused by uneven distribution. In the reaction process of SCR, there will be excess NH and S03 participating in the reaction. Under the action of water steam, NH4HSO4 is produced, which has a strong adsorbability and leads to blockage. Excess NH3 leads to higher operating costs and lower availability. In order to control the maximum denitration efficiency of SCR and the minimum ammonia escape, it is necessary to precisely adjust and control the inlet flue gas velocity distribution of SCR reactor.
For the excess NH3, a certain proportion of ammonia escape catalyst (ASC) is coated on the end of SCR carrier to ensure that NH3 reacts with O2 to produce N2 and H2O, avoiding the secondary pollution caused by NH3 leakage.