Boiler Blog | Nationwide Boiler Inc.

Given today’s awareness to the advantages of minimizing energy usage and carbon footprint, boiler operators and plant managers are always on the lookout for ways to improve boiler efficiency and ensure emissions compliance. With improved efficiency, fuel usage is minimized which in turn reduces the carbon footprint (i.e. reduces CO2 emissions from the boiler) and reduces issues around emissions compliance. One way to increase boiler efficiency is to use oxygen trimming, or O2 Trim, at the stack.

A typical burner will operate from 3 to 4% O2 at 50% boiler load and higher. This stack O2 concentration corresponds to the amount of excess air at the burner, and excess air is required for burner operation to assure complete combustion of the fuel.  For example, for natural gas firing, 3% O2 corresponds to 15% excess air. During commissioning, the burner service engineer will set the fuel / air ratio so that there is always excess air over the firing range of the burner.  The service engineer must also keep in mind that ambient conditions (mainly air temperature changes) will affect air density which will affect the burner fan air flow output.  On cold days the fan will flow more air due to a higher air density, and on hotter days the flow will be less. Varying air flow conditions can adversely affect burner operation.

Boiler efficiency is affected by the excess air concentration in the flue gas. The rule of thumb is that for every 5% more excess air, boiler efficiency decreases by 0.5%. If not adjusted, the boiler stack can vary by at least 2% O2 (i.e., if normal operation is 3% O2, it can increase to 5% O2 on a cold day). That corresponds to about 1% boiler efficiency loss. Saving 1% efficiency over a year operation can save big on fuel costs. If the normal fuel bill is $10,000,000 per year, you would save $100,000. Adding an O2 Trim system would cost a fraction of that amount (assuming a 150,000 lb/hr steam boiler or smaller), providing a quick and worthwhile ROI. So, what exactly is an O2 Trim System?

Many burners use a control system where the fan air flow does not vary based on air temperature.  As explained above, the air flow can vary based on ambient conditions causing the stack O2 to vary; this can be solved by adding O2 Trim to the control system. O2 Trim is an air flow trimming system where stack O2 is measured (using an O2 probe) and the air flow is adjusted (trimmed) based on the reading. It’s a closed loop control system since changes in air flow will directly affect the stack O2 reading (assuming fuel flow is the same). By maintaining a consistent air flow rate, O2 trim reduces fuel usage in turn increasing boiler efficiency.

In addition to increased boiler efficiency, utilizing O2 Trim will ensure stable and safe O2 levels. On hot days with reduced fan air flow, the stack O2 level can drop to dangerously low levels and boiler emissions can go out of compliance. With O2 monitoring, alarms can be created to alert the boiler operator to either reduce fuel flow or increase air flow, to return to safe operating conditions.  

O2 Trim isn’t ideal for every boiler, though. Due to the residence time in the boiler and ducting, it takes time for the changes in burner fan flow to reach the stack. This causes a time delay with an O2 Trim system, which works well for boilers with slow load changes. However, for systems with rapid boiler load changes, the O2 Trim system typically can’t keep up easily and it is often “hunting” for the optimum air flow.

If you are interested in learning more about whether an O2 Trim System will benefit your operations, reach out to one of our qualified parts specialists or call 800-227-1966. Check out other articles on Nationwide’s Boiler Blog for more tips and tricks for improved boiler efficiency, routine maintenance, and more!

At Nationwide Boiler, we’ve spent more than four decades helping industries meet demanding emissions requirements with solutions that deliver reliability, performance, and proven results. Our CataStak™ Selective Catalytic Reduction (SCR) System is one of those solutions—engineered to achieve ultra-low, single-digit NOx emissions on package boilers and a wide range of fired equipment. As air-quality regulations continue to tighten, understanding NOx and the importance of emissions control is more critical than ever.

What Is NOx?

NOx, or nitrogen oxides, represents a group of highly reactive gases formed when nitrogen and oxygen combine during high-temperature combustion. These emissions are common in industrial boilers and fired equipment, including:

• Package boilers
• Fired heaters
• Gas turbines
• Heat recovery steam generators

The amount of NOx produced depends on several operational factors:

• Fuel type
• Burner design
• Peak combustion temperature
• System configuration
• Use of emissions-control technology such as an SCR

Why Reducing NOx Emissions Matters

Once released into the atmosphere, NOx contributes to a series of reactions that impact both environmental quality and human health. Even at low concentrations, these gases can significantly affect regional air quality.

• Ground-Level Ozone (Smog)
  NOx reacts with volatile organic compounds (VOCs) in the presence of sunlight to form ground-level ozone—a major component of smog. Unlike the protective ozone layer, this type of ozone is harmful, contributing to crop damage, reduced visibility, and stressed vegetation. 

• Acid Rain Formation
  When NOx combines with moisture in the atmosphere, it forms nitric acid, a leading cause of acid rain. Acid rain can accelerate the deterioration of buildings, deplete soil nutrients, and disrupt lakes and streams.

• Water Quality Concerns
  Nitrogen compounds from NOx emissions can wash into waterways, fueling algae growth. These algal blooms reduce oxygen levels, harm aquatic life, and create lasting ecological imbalances.

• Climate Influence
  While NOx itself is not a greenhouse gas, it contributes indirectly to climate change by forming ground-level ozone, which is considered a greenhouse gas. Reducing NOx helps minimize an operation’s overall environmental footprint.

• Human Health Considerations
  Exposure to NOx can irritate the respiratory system and worsen existing lung conditions. Elevated levels may increase asthma attacks, aggravate bronchitis, and reduce overall lung function. Children, older adults, and individuals with respiratory sensitivities face the greatest risk.

Nationwide Boiler’s Role in Emissions Compliance

Since the early days of federal emissions legislation, Nationwide Boiler has been a trusted partner in helping facilities meet—and exceed—air-quality requirements. Our team provides engineered solutions tailored to each application, supporting reliable performance and long-term compliance.

For operations that require deeper emissions reduction or consistent performance across a wide operating range, our CataStak™ SCR System delivers emissions compliance without compromise. The CataStak has been proven across hundreds of installations on boilers and fired equipment in demanding industrial environments. Its modular design supports both ammonia and urea-based reagent systems, allowing facilities to choose the solution that best aligns with their operational and safety requirements. With horizontal and vertical configurations, the CataStak can be engineered to fit a wide variety of system layouts, space constraints, and performance needs. Regardless of the application, the result is the same: reliable, near-zero NOx emissions and a system built for long-term, cost-effective operation.

Ultra-low NOx burners are another viable option, designed to minimize NOx formation at the source by optimizing air–fuel mixing and reducing peak combustion temperatures. These burners have consistently demonstrated the ability to achieve ultra low NOx emissions, as low as 5 ppm in many firetube boiler applications. Through ongoing research and development, we’ve also seen promising results at even lower levels in select operating conditions—particularly on smaller firetube boiler systems. While these advancements continue to be refined, they highlight the potential for future solutions that push emissions performance even further.

And lastly, for facilities looking to eliminate combustion-related emissions entirely, electric steam boilers offer a viable, zero-emissions-at-the-source alternative. Because they operate without fossil fuels, electric boilers do not produce NOx, CO, or greenhouse gases at the point of use. While they are not the right fit for every application—particularly where high steam capacities are required—they can be an effective option in regions with clean, reliable electricity or for processes with strict emissions or permitting requirements.

 Nationwide Boiler remains committed to helping facilities operate cleaner, more efficiently, and more sustainably. Our decades of experience—and the proven performance of our environmental solutions—ensure that your operation can meet today’s air-quality standards and future requirements with confidence.

Originally posted in July 2017, this blog has been updated to reflect current information and evolving air-quality regulations.

Nationwide Boiler, established in 1967, has built a strong standing reputation by offering reliable rental boilers to assist industrial companies in both scheduled outages and unforeseen emergencies.

Featuring a diverse inventory of more than 100 boilers across various U.S locations, our equipment spans in size from 50 HP to 200,000 lb/hr and includes mobile package watertube boilers, fully equipped mobile boiler rooms, and skid mounted systems. Over the years, our company has expanded our capabilities, evolving into more than just a world-class rental boiler company. We are a stocking distributor, a UL-certified control panel design and manufacturing facility, and we provide sustainable solutions such as electric boilers, hydrogen blended fuel firing capabilities, and our CataStak™ Selective Catalytic Reduction (SCR) System.

As our company continues to evolve, we adjust to the changing times by providing environmentally friendly alternatives within the boiler industry. This involves the utilization of SCR and ultra-low NOx burners to manage NOx emissions, along with the integration of heat pumps and alternative fuel choices for the purpose of decarbonization.

Ultra-low NOx Solutions

Our journey into sustainable solutions commenced in the 1990’s with the introduction of the CataStak SCR to the market. The CataStak is an established solution for lowering NOx and CO emissions to single-digit levels, tailored for applications with package boilers, fired heaters, gas turbines, and other fired equipment. Equipment utilizing a CataStak SCR system has yielded source test results as low as 1 ppm NOx.

Recognizing that SCR technology may not be suitable for every application demanding ultra-low NOx performance, we serve as a supplier and user providing other options like ultra-low NOx burners. Several of our mobile boiler rooms and package firetube boilers incorporate these burners to comply with emissions standards in various regions of California and Texas. Therefore, we also deliver ultra-low NOx burners for permanent requirements when the application aligns better with burner technology.

Alternative Fuels for Decarbonization

Exploring alternatives to fossil fuels offers an additional avenue for sustainable steam and energy production. These alternatives encompass hydrogen, biofuels, and electricity, preferably sourced from renewable sources.

A preferred electric approach for high-pressure steam generation involves the use of electric boilers. Leveraging electricity as a clean, efficient, and easily controllable fuel, every unit of energy input into the boiler is converted to steam with an efficiency of 99%. Numerous industrial facilities possess the required power infrastructure to support an electric boiler, rendering it an optimal zero-emissions solution. Nationwide Boiler’s in-stock electric boiler packages are available for both rental and permanent applications.

Heat pumps are also a favored option for electric heating in comfort applications and, with ongoing technological advancements, are now being applied in industrial settings. Although heat pumps may not currently produce high-pressure steam, they can contribute to industrial processes by providing heat up to 240°F. Also, a heat pump is significantly more energy-efficient, utilizing only about one-third of the energy compared to traditional electric or fossil fuel heat-generating equipment for achieving the same temperature increase.

Lastly, hydrogen and biofuels are now being utilized more frequently as an environmentally friendly alternative to the prevalent use of natural gas or fuel oil in steam boilers. Hydrogen, a proven and low-emission fuel in the boiler industry for several years, offers virtually no carbon emissions. With experience and expertise in hydrogen and biofuels, our engineering group has confirmed that Nationwide Boiler’s existing fleet of package watertube rental boilers can effectively use blended fuels containing up to 20% hydrogen, with no need for system modifications. Originally designed to accommodate natural gas firing, this adaptability is made possible by our strict rental boiler construction standards, which integrate high-quality and robust components such as valving, fuel trains, burners, and more.

Drawing from our extensive history and the collective years of industry experience, our team is dedicated to providing trustworthy temporary rental boilers, sustainable solutions for steam generation, and more, all guided by the principles of "Integrity, Dependability, and Real Customer Service."

To learn more, please explore our website or reach out to us at (800) 227-1966.

The EPA today proposed a new reporting ruling that would require large, direct emitters of greenhouse gases to comply with new reporting requirements. These would include energy intensive sectors such as cement production, iron and steel production and electricity generation.

EPA Administrator Lisa P. Jackson realizes the importance of gathering critical data in order to better understand climate change for a healthier future.  She notes that this proposed requirement will not affect small businesses, but is rather aimed at large businesses, those that have emissions equal to or greater than a threshold of 25,000 metric tons per year.

"Our efforts to confront climate change must be guided by the best possible information. Through this new reporting, we will have comprehensive and accurate data about the production of greenhouse gases. This is a critical step toward helping us better protect our health and environment - all without placing an onerous burden on our nation's small businesses."

The EPA estimates that the expected cost to comply with the reporting requirements to the private sector would be $160 million for the first year. In subsequent years, the annualized costs for the private sector would be $127 million. This rule is being developed under the authority of the Clean Air Act and the proposed rule will be open for public comment for 60 days after publication in the Federal Register. Two public hearings will be held during the comment period.

Nationwide Boiler's low NOx solutions are developed for companies, large and small, who want to do their part in combating climate change. We have upgraded our fleet of rental boilers with Low NOx equipment in order to easily meet emissions requirements in any part of the county. For those customers wanting even lower emissions our CataStak SCR systems have been proven to reduce NOx emissions below 5 ppm in over 50 installations and that list continues to grow.

Nationwide Boiler is ready to help your facility meet your "green" goals. Contact us today and let us know how we can help.

Click here for more information on the proposed rule.