Patented NOx Emissions Reduction System (SCR)
With the help of Michael MacDonald, retired partner at R.F. MacDonald Co., and the Boiler Special Projects Group, R.F. MacDonald has invented and patented the safest NOx emissions reduction process for boilers and fired vessels. This innovative process uses direct urea injection with Selective Catalytic Reduction (SCR).
U.S. Patent and Trademark
In November 2020, the U.S. Patent and Trademark Office granted R.F. MacDonald Co. a patent for the safest and simplest NOx-reduction process for packaged boilers. The patent covers a “process for direct urea injection with selective catalytic reduction (SCR) for NOx reduction in hot gas streams and related systems and assemblies.”
The Safest Ammonia-Based Reagent: Urea
SCR typically requires the use and storage of ammonia-based reagents, which can vary in risk levels. The R.F. MacDonald Co. patent specifically uses urea, the safest ammonia-based reagent available. According to the Hazardous Materials Identification Systems (HMIS), urea presents only a minor health hazard, such as “possible irritation.” This urea solution is identical to Diesel Exhaust Fluid (DEF), which is widely available in automotive stores for use in diesel vehicles.
As illustrated below, urea is injected into the boiler at each injection point. When NOx and urea pass through the NOx Reduction Catalyst, the NOx is broken down into two harmless elements: Nitrogen (N2) and water (H2O).
There are three types of ammonia-based reagents: anhydrous, aqueous, and urea. Both anhydrous and aqueous ammonia carry higher risks and stricter regulatory requirements compared to urea, as shown in the chart below. While R.F. MacDonald Co. offers SCR installation and service for all types of ammonia-based reagents, direct urea injection with SCR is recommended for institutions housing people, such as hospitals and universities, due to urea’s non-hazardous classification. Hospitals use boilers to produce steam for sanitation, and universities use them to provide hot water for amenities.
As restrictions on NOx emissions and air pollutants tighten, industrial and institutional facilities are increasingly investing in SCR technology for their boiler systems. SCR has proven to achieve the lowest NOx emissions levels while maintaining boiler efficiency.
R.F. MacDonald Co.’s newly patented SCR technology meets every emissions limit in California, including those set by the strictest district in the nation: The San Joaquin Valley Air Pollution Control District. California has 35 local air districts responsible for regional air quality, planning, monitoring, and facility permitting. Visit the California Air Resources Board for more information.
California Air Districts by RFMCO Office Location
- Bay Area Air Quality Management District (BAAQMD):BAAQMD Rules and Compliance
- Sacramento Metropolitan Air Quality Management District (SacMetro AQMD):Rules and Regulations
- San Diego Air Pollution Control District (SDAPCD):Rules and Regulations
- San Joaquin Valley Air Pollution Control District (SJVAPCD):Rules List
- Southern California Air Quality Management District (SCAQMD):SCAQMD Rule Book
R.F. MacDonald Co.’s history with low NOx began in the late 1970s after the California Air Resources Board (CARB) began mandating new low NOx rules and compliance deadlines. At that time, R.F. MacDonald Co. poised itself to be the low NOx solutions provider in California and began retrofitting and installing flue gas recirculation and ultra-low NOx burners.
Selection of the appropriate emissions control system requires a detailed evaluation of environmental, technical, safety and economic factors. Solutions currently available to meet emissions regulations include burner installation, burner retrofit and SCR installation.
