Boiler SCR Technology: A Pivotal Step Towards Environmental Sustainability

Nationwide Boiler developed the CataStak™ SCR to address stringent emissions regulations specifically for their fleet of package watertube rental boilers and eventually, they applied the technology to firetube boilers, gas turbines, and other fired equipment applications.

The CataStak is a post-combustion, selective catalytic reduction system proven to achieve ultra-low, single-digit NOx performance. The CataStak provides both economical and practical benefits to users through improved operating efficiency and lower emissions, it provides a reasonable return on investment, and it often exceeds emission limits beyond what is required. With the ability to reduce NOx, CO, and VOC, the CataStak was a pivotal step towards sustainable steam solutions for the boiler industry.

Larry Day, Nationwide Boiler’s current President & CEO, drove the integration of such back-end solutions into the company’s fleet of rental boilers. The objective was clear: to develop an SCR system that would reliably meet and exceed current and future emission limits without compromising critical boiler functionalities. Nationwide Boiler started off as a user operating these SCR’s across their fleet of rental boilers. The CataStak was proven to offer dependable performance through experience, testing as low as 1 ppm NOx time and time again, before it was ever applied to permanent applications.

In one case study, the CataStak reduced NOx emissions to less than 1 ppm NOx and resulted in an Energy Efficiency Rebate of almost $300,000 for a prominent Food Processing facility in California. The end-user purchased a new Babcock and Wilcox 50,000 lb/hr, 275 psi boiler equipped with a standard 30 ppm low NOx burner, a CataStak SCR system, an EconoStak fuel economizer, and a condensing economizer. Once installed and commissioned, it was certified to operate at better than 95% fuel-to-steam efficiency with less than 1 ppm NOx emissions.

Rather than what was available at the time—a more expensive and complex ultra-low NOx burner with an oversized FD fan—the CataStak proved to be the ideal solution for reducing NOx emissions economically, efficiently and with minimal operator intervention.

With more than 250 installations across the country, the CataStak was an early innovation and just one step towards a more sustainable future for steam production.

NOx Reduction Today

In addition to SCR technology, now there are more reliable, ultra-low NOx burners that address single-digit NOx limits as low as 2 ½ ppmvd at 3% O2. Some of these burners utilize flue gas recirculation (FGR) and higher gas delivery pressures, while others achieve 2 ½ ppm with lower residual O2, normal gas delivery pressures, and no need for FGR. The 2 ½ ppm burner solution is currently only available for firetube boiler applications.

Technologies Reapplied for Decarbonization

With today’s focus geared toward the reduction of carbon and other greenhouse gas emissions, there are numerous proven technologies that are being reapplied for decarbonization efforts. Fossil fuel alternatives provide one sustainable approach to steam and energy production, and this presents options, like hydrogen, biofuels, and electricity sourced from renewable outlets.

Burners have been successfully fired on hydrogen and biofuels for more than 50 years, and these fuels are proven to be viable, carbonless options for industrial steam production. The limiting factor, however, is hydrogen supply and the production of green hydrogen. Green hydrogen hubs, or networks of hydrogen producers, consumers, and local infrastructure, are currently being developed and are intended to accelerate the use of hydrogen as a clean energy carrier. Once these hubs are in place and hydrogen is more readily available, it will likely gain even more traction in industrial boiler applications. One challenge of hydrogen firing is the increase in NOx production but, as covered previously, an SCR can be installed to reduce the increase of NOx output.

Leveraging electricity as an alternative, electric boilers offer a clean, controllable, and highly efficient means of generating high-pressure steam, boasting an impressive 99% conversion of energy input. This method showcases zero emissions, which is especially advantageous for industrial sites with the necessary electricity infrastructure required to support such boilers. Electric boilers have been around for decades and, most notably, can be found in locations like Quebec, Ontario, and British Columbia due to an electrical grid based mostly on hydro, nuclear, or other non-fossil fuel energy sources.

Lastly, we have heat pumps as a sustainable option that supports steam production. While initially geared for HVAC, heat pumps are gaining traction in industrial applications as technology advances. Prepackaged heat pumps are not currently capable of producing high-pressure steam, but they can contribute to industrial processes by providing heat up to 240°F. Driven by electricity, it is a carbonless solution with the added benefit of energy efficiency. A heat pump uses approximately one-third of the energy compared to traditional electric or fossil fuel heat-generating equipment for the same temperature increase. In fact, a heat pump can typically move three to four times the amount of energy it consumes.

A Continued Focus on Sustainability

As emission reductions and decarbonization continue to be an important part of our global sustainability efforts, the industry needs reliable products that not only ensure compliance but also drive sustainability and operational efficiency. Innovations, like the CataStak and ultra-low NOx burners, as well as proven technologies, like hydrogen firing and heat pumps, reflect a forward-thinking approach. This aligns with the industry’s pursuit of efficient, sustainable, and economically viable solutions.