Vaporized ammonia is used in catalytic and noncatalytic reduction systems for emissions control. Ammonia is injected into the flue gas stream and acts as a reducing agent. It is also used to enhance precipitator efficiency for particulate control. Pure ammonia is stored in a pressure vessel rated for 250 to 300 psig. Aqueous ammonia (70 to 80% water) is stored in a tank rated for 25 to 30 psig. Storage requirements for aqueous ammonia are three to four times that of pure ammonia.
Accidental atmospheric release of pure ammonia vapor can be hazardous, so safety and environmental measures may be required which affect the level control selected.