Urea Injection System (SNCR)
Nitrogen Oxides (NOx) is a generic term for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts. NOx forms when fuel is burned at high temperatures, as in the combustion of coal at the J. B. Sims Plant (Sims). NOx is one of three ingredients involved in the formation of ground-level smog. The other two are sunlight and volatile organic carbons (primarily from automobile exhaust).
Sims is allocated a specific number of NOx credits by the Environmental Protection Agency (EPA), which corresponds to the number of tons the facility can emit during a given calendar year. In the past, if the Sims plant used more credits than it was allocated, additional NOx credits were purchased from the open market at a substantial cost to the facility.
In an effort to reduce NOx emissions at the source and to reduce the dependency on purchasing credits, the facility chose to install a Selective Non-Catalytic Reduction System or, as we call it, the “Urea Injection System.”
Urea is a solid white crystalline material that has many uses, including:
- A component of animal feed, providing a source of nitrogen to promote growth.
- A non-corroding alternative to rock salt, for road de-icing, and the resurfacing of snowboarding half-pipes and terrain parks.
- A flavor-enhancing additive for cigarettes.
- A main ingredient in hair removers such as Nair.
- A browning agent in factory-produced pretzels.
- A nitrogen release fertilizer.
In addition, it is used to control NOx. When dissolved in water and injected into our boiler, the combustion of urea releases ammonia. Ammonia chemically reacts with NOx to form nitrogen (78% occurring naturally in the air) and water, thereby reducing the emission of NOx from the boiler.
Installation of the urea system was completed in spring 2010 and operation began in July 2010. Once the performance of the system was optimized, NOx reduction ranged from 30% to 45%, depending on the load requirements placed on the boiler.