Advantages of Ammonia Systems for Power Plant SCR Systems
NOx Emission Control
NOx emissions are the product of every air-fed combustion process and are known to contribute to acid rain, forest and vegetation decline, changes to the ozone layer and greenhouse gases. The EPA and other governing agencies mandate the reduction and control of NOx emissions through permitting.
Ammonia is used in a de-nitrification process converting NOx into free nitrogen and water vapor through catalytic (SCR) and non-catalytic (SNCR) applications.
SCR - Selective Catalytic Reduction
- Ammonia or a compound of ammonia is used as the reducing agent that is injected into the flue gas stream, passing over a catalyst. NOx emission reductions of 80-90% are achieved.
- The efficiency of SCR process reactions relies on a very close and effective reagent injection-control, based on the feedback from measured NOx emissions in the flue gas at the economizer outlet.
- The catalyst composition can consist of many active metals and support materials to meet specific requirements in each SCR installation.
- An online control of process exhaust data or injection mapping functions is typically implemented to prevent "ammonia slip".
- The SCR technology has been applied to utility and industrial boilers, process heaters, gas turbines, internal combustion engines, chemical plants and steel mills.
SNCR - Selective Non-Catalytic Reduction
- Ammonia is used as a reducing agent that is injected into hot flue gas reacting with the NOx at high temperatures. NOx emission reductions of 30-70% are achieved.
- The efficiency of SNCR process reactions relies on the careful injection of the ammonia reagent into regions of the furnace or other sources where proper conditions such as, temperature, residence time and concentration exist for the reaction to occur while preventing "ammonia slip"
- SNCR systems are suitable for use on low capacity factor units, units with short service lives and for seasonal control.