SNCR NOx reduction systems

Selective non catalytic reduction (SNCR) is a technology used to reduce the level of nitrogen oxides (NOx) without the presence of a catalyst. Reagent (Ammonia or Urea) is injected directly into flue gas and reacts with NOx resulting in nitrogen (N2) and water (H2O). 

NO2 + NO + 2 NH3 ↔ 2 N2 + 3 H2O 

4 NO + 4 NH3 + O2 ↔ 4 N2 + 6 H2O 

2 NO2 + 4 NH3 + O2 ↔ 3 N2 + 6 H2O 

Selective non-catalytic reduction (SNCR) is an alternative solution when the operating conditions are not suitable for a catalyst.   

The YARA SNCR system can operate with both Urea or Ammonia and is composed of 3 key modules: the Process Unit (PU) and Control Module Management (CMM) and the injectors 

The PU generates the required quantities of reduction agent for the existing operating condition. It then redirects the flow to each injector individually as well as the Softened water, atomizing and cooling air necessary for proper injections. The PU continuously supervises the injection process and is equipped with the required failed safe control system.  

YARA injectors are manufactured to sustain the harshest conditions. The spraying length, width and the size of the droplets are adjustable. The possibilities of adjustments give a broad flexibility and allows the spraying dose to reach a large area of the ducting. 

Compressed air is used to atomize the droplets. In stand-by operation, the compressed air is used for cooling of the injector. When the system is stopped, the injectors will be purged with softened water to secure that no reduction agent is left in the system. 

The control and management module (CMM) is equipped with PLC and touch screen panels that control, manage, co-ordinate and monitor all process functions. It communicates with the superior control system (DCS) to set and monitor proper performance of the system.  

When is SNCR applicable?

With the proper process conditions, Yara’s SNCR technology can easily reduce NOx emissions between 60% to 90% while maintaining the lowest possible NH3 slip. Some of the recommended conditions are: 

• Temperatures of the flue gas shall be between 800 °C and 1100 °C
• Residence time > 0.5 sec 
• Accessibility for the injectors 

Why choose Yara? 

With over 300 references in green field and retrofits SNCR installation globally, we can meet your needs from design and fabrication to installation and commissioning. YARA SNCR systems are capable to reach the most stringent requirements and are present in all major industries: Cement, Waste to Energy, Biomass and Petrochemicals, Power plants and various industrial applications. 

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