SNCR Denitration Technology

SNCR Denitration Technology

Process principles

In the absence of a catalyst role in reducing nitrogen oxides of flue gas to harmless nitrogen and water by reductant . "Selective non-catalytic reduction" ( referred to as SNCR) is a denitrification by free-cataly ,  SNCR technology requires the use of amino reducing agents such as ammonia or urea to selectively reduce NOx in flue gas at higher furnace temperatures (900-1150 ℃) to achieve strong chemical reactivity .

generally speaking,  it is difficult to mix evenly of reducing agents in the furnace or flue, the denitrification efficiency of SNCR will be less than 50% and SNCR that requires a catalyst can reach over 90%.  it has been widely used in coal-fired boilers due to low investment cost, convenient renovation, suitable for collaborative application of other denitrification technologies , especially in the denitrification transformation of old plants.

Chemical principles

The nitrogen oxides of boiler combustion flue gas include NO and NO₂ ,  the denitrification process mainly focuses on removing NO since NO accounts for over 90% of the NOx .

Its chemical equation as following:

CO(NH₂)₂→2NH₂+CO

NH₂+NO→N₂+H₂O

CO+NO→N₂ +CO₂

The general equation as following:

1.1   NO+CO(NH₂)₂+1/2O₂→2N₂+CO₂+2H₂O

1.2  4NH₃+5O₂— 4NO+ 6H₂O

harmless nitrogen, carbon dioxide and water (see Equation 1.1) is produced when NOx react with reducing agent (urea) when appropriate furnace temperature.   urea can be oxidized to NOx when temperature is too high and it  will increase NOx emissions (see formula 1.2)

Process flow diagram

The main function of equipment and process systems

1. Reducing storage and preparation system:  total storage capacity is designed based on the consumption of the boiler SNCR device under BMCR conditions for 5 days .
2.The metering, conveyor systems: filters installed to prevent equipment blockage.
3. Injection system:  the reducing agent injected into the furnace at a suitable temperature through the gun.
4. Electrical control system: complete configuration, independent  instrumentation and control systems.

Technical characteristics

1.Small footprint, suitable for the transformation of the old units。
2.No need to use catalyst.
3.Less Investment , lower operating costs.
4. Insensitive to changes in coal.
5. Short construction period, the construction is simple.
6. No need to replace the induced fan.
7. Use safe urea reductant.
8. Denitration efficiency: 40% to 60%.