Nitrogen Monoxide (NO) is a colorless, odorless, water soluble gas which reacts rapidly with oxygen to form nitrogen oxides. Nitrogen Dioxide (NO₂) gas has a distinct orange-brown color.  Nitrogen Dioxide is also a water soluble gas with a pungent smell.  NO and NO₂ are often present together in airstreams as oxides of nitrogen, and together combine to form NO_x.

Applications

NO and NO₂ are commonly off gases of industrial manufacturing to include: Nitric acid manufacturing, titanium pickling, stainless steel pickling, aluminum bright dip, metal finishing, precious metals refining, chemical etching, fertilizer production, glass making, industrial boilers, and aqueous chemical production.  NO_x is also a significant source of emissions from coal fired power generation facilities, where processing takes place under high temperatures. NO₂ often enters the atmosphere through the combustion from vehicles, power plants, and boilers, as a result of combustion.

Health and Environmental Effects

NO_x gases play a major role in the formation of ozone smog.   Inhalation of high levels of can lead to respiratory complications. Individuals with asthma are advised to be extremely cautious when NO is in the environment.  NO_x is considered a major constituent in acid rain.

Regulatory Considerations

Due to the effect of NO_x on the environment, NO_x emissions are heavily scrutinized by local and federal agencies.  A common requirement for NO_x control at the state and local level, requires systems to be designed to remove the visible orange-brown plume of NO₂, to a level below 5% opacity.

Control Technologies

NO_x removal can be simple or require multiple stages of wet scrubbing, depending on various factors.  The ratio of NO to NO₂ plays a major factor in determining the control technology.  Single stage scrubbing of NO₂ is accomplished with HEIL Series 730 Counter-current wet scrubber Gas Scrubbing.  Multi stage scrubbers may be required to oxidize NO into NO₂ in the first stage, then remove the NO₂ in the second stage.

HEIL systems can perform at high removal efficiencies, using NON-PROPRIETARY chemicals that are commercially available.  HEIL does not currently offer a product to control NO_x gases from power generation facilities.  Large scale products such as SCR systems are available from other companies to control those applications.