How to Reduce NOx

How to Reduce NOx: A Guide to Low Emission Boilers

Across the United States, there are over 60,000 industrial boilers, and virtually everyone wants to know how to reduce NOx. Whether you have a large utility boiler or industrial boilers, it's important to have a significant focus on NOx reduction. Continue reading to learn more about innovative ways of how to reduce NOx.

How Is Nitrogen Oxide NOx Produced by Boilers?

Before delving into how to reduce NOx, it's important to have an understanding of how nitrogen oxide is produced. Boiler burners use combustion to produce heat to make hot water or steam. In the process, nitrous oxide or NOx is produced as a byproduct of combustion. This pollutant can have harmful effects on the environment and is a large contributor to particulate matter, ozone, and acid rain.

In general, NOx has three main sources:

  • Thermal NOx
  • Prompt NOx
  • Fuel-bound NOx

The majority of NOx emissions are the result of nitrogen in the fuels used or from nitrogen in the combustion air, which is thermal NOx. For oil-fired boilers and natural gas-fired boilers, thermal NOx comprises most NOx produced by industrial boilers.

Thermal NOx emissions will increase as peak flames temperatures increase. At the same time, NOx emissions are affected by the availability of oxygen in the boiler combustion zone.

How to Reduce NOx

When you are considering how to reduce NOx emissions, the most important step is to choose a qualified consultant, service provider, or vendor. This expert will help you conduct a boiler characterization and choose the right boiler or NOx reduction measure. However, the most common methods taken to reduce NOx are listed below.

Low NOx & Ultra Low NOx Burners

Undoubtedly, one of the most effective ways to reduce NOx is through Low NOx and Ultra Low NOx burners. Low NOx burners can reduce your NOx emissions to 30 pm. This equipment uses FGR and can maintain 3 to 5% excess O2 with strong controls. Low NOx burners offer good flame stability and turndowns that are less than the ratio of 8 to 1.

With Ultra Low NOx burners, you can achieve emissions anywhere between 7 to 15 ppm. These burners use adjusted fuel/air ratios, FGR, as well as staging to achieve exceptionally low emissions. Some Ultra Low NOx burner designs may have:

  • Larger combustion air fans, which require a 15% to 50% step up in HP
  • Anywhere from 5 to 9% higher O2 emissions
  • Flame stability and reduced turndown ratio of either 4:1 or 3:1

The Ultra Low NOx technology is continually improving with more conventional designs aimed at achieving greater efficiency.

Burner System Modifications and Tune-Ups

If you are not in the market for a new Low or Ultra Low Nox burner, the most prudent NOx reduction measures will start with a boiler tune-up. This maintenance solution includes the verification and optimization of the current operating parameters of the boiler.

By fine tuning the fuel content and oxygen in the combustion zone, you can reduce NOx emissions and improve efficiency. After performing simple tune-ups, systems can be utilized to automatically trim and monitor fuels and oxygen for optimum performance.

However, it's imperative any and all of these procedures are performed by a qualified and factory-trained service professional. Failure to do so can result in serious hazards and injuries.

Burners out of Service

Burners out of Service or BOOS is another technique for how to reduce NOx. This technique can be used for boilers with multiple burners. It includes taking one or more than one of the burners out of service, which reduces the peak flame temperature. As a result, NOx emissions can be significantly reduced by several mechanisms of combustion.

Boiler De-Rating

In some cases, a facility's steam needs and demands drop. The changing needs could be because of the implementation of more energy efficient processes or because of phased-out equipment. In either case, a boiler can be de-rated, which means it will fire at lower loads. Under these conditions, NOx emissions will be reduced by effectively lowering the firing rate.

Low Excess Air

For boilers that use spud or ring burners, a number of modifications can be made to:

  • Delay combustion
  • Control flame length
  • Reduce peak flame temperature
  • And delay fuel/air mixing.

These measures are effective at reducing NOx emissions. In some instances, air registers around the burner can be adjusted to help minimize NOx emissions.

Stage Combustion

Typically, stage combustion is only achievable in boilers with large furnace volumes. Stage combustion promotes fuel and air reactions in multiple stages or zones instead of all at once. As a result, stage combustion produces combustion properties, such as lower peak flame temperatures, that are much more conducive for low NOX emissions.

Contact Applied Technologies of New York

At Applied Technologies of New York, we help educational facilities, pharmaceutical firms, multi-residential apartments, as well as hospitals and medical facilities achieve greater efficiency and performance. We partner with the top boiler and combustion related manufacturers in the world. Simply put, we will help your facility learn how to reduce NOx and achieve greater performance out of your equipment.

Contact Applied Technologies of New York today for an innovative and cost-effective solution.

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