R.F. MacDonald Co. has patented a process for direct injection of urea in flue gas streams on boilers; urea is regarded as the safest reagent for use in the SCR process
On Tuesday, Nov. 24, 2020 the U.S. Patent and Trademark Office issued the safest and simplest NOx-reduction process patent for packaged boilers. The patent was granted to R.F. MacDonald Co. for inventing a “process for direct urea injection with selective catalytic reduction (SCR) for NOx reduction in hot gas streams and related systems and assemblies.”
SCR requires the use and storage of ammonia-based reagents, which range from high risk to low risk. The R.F. MacDonald Co. patent specifies urea, which is the lowest risk ammonia-based reagent. The only health hazard associated with urea is “possible irritation” as indicated by the Hazardous Materials Identification System (HMIS). The urea solution is identical to Diesel Exhaust Fluid (DEF), which is sold worldwide in automotive retail stores for use in diesel motor vehicles.
As shown in the graphic below, urea is injected at each Injection Point into the boiler. As NOx and urea pass through the NOx Reduction Catalyst, NOx is separated into two non-harmful 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 risk and regulatory issues compared to urea as shown in the chart below. R.F. MacDonald Co. provides SCR installation and service for each type of ammonia-based reagent. However, direct urea injection with SCR is recommended for institutions housing people, such as hospitals and universities, because urea is classified as non-hazardous. Hospitals use boilers to produce steam for sanitation and universities use boilers to produce hot water for amenities.
As restrictions on NOx emissions and air pollutants increase, industrial and institutional facilities are investing in SCR technology for their boiler systems because SCR has been proven to reach the lowest NOx emissions levels while maintaining boiler efficiency.
R.F. MacDonald Co.’s newly patented SCR technology complies with every emissions limit in California, including 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.
Examples of California Air Districts by RFMCO Office Location
- Bay Area Air Quality Management District (BAAQMD)
- Sacramento Metropolitan Air Quality Management District (SacMetro AQMD)
- San Diego Air Pollution Control District (SDAPCD)
- San Joaquin Valley Air Pollution Control District (SJVAPCD)
- Southern California Air Quality Management District (SCAQMD)
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.
Since 2006, R.F. MacDonald Co. has installed multiple SCR systems each year for the various industries within California and Nevada, including hospitals, universities, manufacturing facilities, power plants, food processors and more. Loma Linda University Health achieves sub 5 PPM NOx using Direct Urea Injection with SCR.
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. Contact us to help guide you through the process or learn more about SCR packaged systems here.
Director of Engineering
Publication No.: US 2018/02588814 A1
Patent No.: US 10,844,763 B2
Applicant: R.F. MacDonald Co., Modesto, CA
Issued and Approved: Nov. 24, 2020
PDF: Patent Abstract