Mechanism of nitrogen oxide production
Nitrogen oxide (NOx) is a compound composed of nitrogen and oxygen elements, the most important of which are NO and NO2. Nitrogen oxides also occur in small amounts in nature, but most of them come from transportation and energy production. In the combustion process, nitrogen oxides can be divided into three categories according to their causes:
1.Thermal NOx: NOx is formed by the oxidation of nitrogen in the air at high temperature during combustion.
2.Rapid NOx: NOx is produced by the reaction between nitrogen in the air and hydrocarbon ions in the fuel during combustion.
3.Fuel NOx: NOx is produced by the thermal decomposition of nitrogen oxides in fuel during combustion.
Common management plan
Low nitrogen emission targets are achieved through technical schemes such as boiler replacement, combustion equipment modification or terminal treatment. There are mainly the following several common governance schemes:
1.Boiler replacement is a technical means to replace the boiler body. The key is to control the initial emission concentration of NOx from boiler flue gas to meet the requirements of low nitrogen emission.
2.The modification of combustion equipment is a pollution prevention technology in the combustion process, which is to meet the requirements of low nitrogen emission by changing low-nitrogen burners or implementing flue gas recycling transformation and other measures. At present, flue gas recycling is the most mature and most widely used. Among them, flue gas internal circulation (FIR) is introduced into the combustion area by means of jet flow in the furnace chamber, and flue gas external circulation (FGR) is introduced into the combustive air or gas, and the flue gas external circulation (FGR) is most widely used.
3.NOx terminal treatment is a post-combustion pollution treatment technology, which refers to the supplementary measures taken when the emission requirements cannot be met only by relying on low nitrogen transformation. Its technical methods mainly include: selective non-catalytic reduction denitration (SNCR), selective catalytic reduction denitration (SCR), snCR-SCR combined denitration, etc..
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