At present, NOx accounts for more than 90% of the total amount of no in the combustion flue gas, and nitrogen oxide (NOx) is one of the main sources of air pollution. With the development of reform and opening up and the improvement of people's living standards, the awareness of environmental protection is increasing, and environmental protection has been paid attention to.
1、 Main hazards of nitrogen oxides:
1) Impact on the environment:
NOx is one of the main reasons for the formation of acid rain and acid mist;
NOx and hydrocarbons form photochemical smoke;
NOx breaks the ozone layer quickly;
2) Harm to animals and human body:
In the NOx environment, the respiratory system of any animal is affected, causing bronchitis, emphysema and other symptoms.
2、 Main governance methods
Selective catalytic reduction:
Under the action of a certain temperature and catalyst, NOx is reduced to harmless NOx and other substances without nitrogen. In the purification process, according to whether the reductant reacts with O2 in the gas, it can be divided into selective catalytic reduction method and selective non catalytic reduction method. Selective catalytic reduction method is to control NOx in diesel engine exhaust, using NH3 or urea as reducing substance under certain temperature and catalysis. NH3 is used to reduce NOx to N2 and H2O. NH3 selectively preferentially reduces NOx without reacting with O2 first.