The Importance Of Industrial and Manufacturing Industries

The Benefits Of Selective Catalytic Reduction For Industrial Boilers

3 October 2018 by Todd Edwards

Nitrogen Oxides (NOx) are a byproduct produced by high temperature fuel combustion. Nitrogen oxides are produced by a variety of sources ranging from internal combustion automobile engines to industrial equipment, including large-scale industrial boilers. Depending on concentration, the various forms of nitrogen oxide produced by the combustion process range from minor irritants to extremely poisonous.

Because these gases are considered to be relatively harmful (or, at a minimum, undesirable) to humans, it is important that their emission is reduced as much as possible. Although regulations vary by region, nitrogen oxide emissions are both monitored and controlled by the EPA and by state environmental agencies.  Selective Catalytic Reduction (SCR) is one common form of nitrogen oxide control and it is widely used in industrial applications as well as the automobile industry.

What is Selective Catalytic Reduction?

Selective Catalytic Reduction is a process by which harmful NOx exhaust gases are converted via chemical reaction into harmless substances before being released to the atmosphere. This process is accomplished by mixing a reductant (a special liquid) into the exhaust stream and allowing a chemical reaction to take place with the aid of a special catalyst. The NOx is converted into nitrogen and water via a reduction reaction. This process is known as a reduction reaction since the NOx is being reduced (it is losing oxygen).

The process was originally developed with ammonia as a reducing agent, but modern systems such as the CataStak SCR systems make use of urea instead. This provides a safer, more environmentally friendly alternative to ammonia. Urea behaves as ammonia in the reaction, allowing for the same efficiency without the difficulties associated with storing and handling ammonia.

Why Use Selective Catalytic Reduction?

Selective Catalytic Reduction is one of the best options available to achieve high levels of NOx reductions. Although more expensive, it can achieve greater overall efficiency than selective non-catalytic reduction as the catalyst allows the unit to operate efficiently within a more reasonable and forgiving temperature. In practice, selective catalytic reduction can achieve reduction efficiencies as high as 90% while still remaining cost effective.

Additionally, selective catalytic reduction systems do not require existing boilers to be altered. The systems operate on the waste gas stream and can be added to existing boilers to meet highly stringent NOx emissions levels without replacing the entire boiler. Non-ammonia based selective catalytic systems are also environmentally friendly and extremely safe, as the urea used as a reductant is not a harmful substance.

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