What is NOx?

Nitrogen oxides (NOx) includes nitric oxide (NO) and nitrogen dioxide (NO2). It’s a family of poisonous, highly reactive gases. They form when fuel is burned at high temperatures.

What are NOx emissions made up of?

Nitric oxide (NO):

  • This is non-toxic in small quantities. NO is naturally found in your body and expands blood vessels, increasing blood flow.
  • When excess oxygen is present in the combustion chamber of an engine, nitric oxide is oxidised into nitrogen dioxide.

Nitrogen dioxide (NO2):

  • A major pollutant and component of smog.
  • Breathing air with particularly high concentrations of NO2 can cause irritation of the airways leading to symptoms such as wheezing, coughing and difficulty breathing. Longer exposures can contribute to the development of asthma.
Why is NOx so bad?

It plays a major role in atmospheric reactions with volatile organic compounds (VOC). VOCs are another by-product from burning fossil fuels. Sunlight causes a chemical reaction between VOCs and NOx, which leads to ozone formation. Ground-level ozone is the main ingredient of smog. You’ll often see it present itself on hot summer days.

How can we reduce NOx emissions?

The MCP Directive has a NOx limit of 190mg/Nm3@15%O2 for all combustion plant/generators in the 1-50MWth range.

The non-road mobile machinery regulations impose a limit of 10.4g/kWh of NOx.

IPU’s SCR systems can reduce these emissions by 99.8%.