LOW NITROGEN OXIDES (NOx) BURNERS FOR REDUCTION OF NOx EMISSIONS IN INDUSTRIAL BOILERS
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| Overview: | Low NOx burners (LNB) reduce the formation of
NOx by staging the combustion process by producing fuel rich and fuel lean zones within
the flame. The fuel rich zone is the primary combustion zone and prevents the formation of
thermal NOx (formation of NOx caused by high flame temperatures) resulting from low oxygen
concentration. The cooler, fuel lean zone prevents thermal and fuel NOx (formation of NOx
resulting from the oxidation of fuel bound nitrogen). LNBs can reduce NOx emissions by as
much as 60 percent. NOx represents nitric oxide (NO) and nitrogen dioxide (NO2). It is a pollutant that causes many health problems, leads to the formation of ozone and smog, is one of the causes of acid rain (nitric acid), and reduces visibility due to the formation of aerosols. By replacing existing burners with burners designed to reduce the formation of NOx, reductions in NOx emissions of between 20 and 60 percent can be achieved. Department of Defense (DoD) installations have large numbers of small single burner water and fire tube boilers. These units range in size from 0.4 million Btu per hour (MMBtu/hr) to 250 MMBtu/hr, with the majority under 50 MMBtu/hr. Older units are generally exempt from emission control regulations. Commercial off-the-shelf LNBs are available to control emissions produced in these boilers, however they often require extensive retrofitting and the installation of additional equipment and controls. They normally require very little additional maintenance other than more frequent tip cleaning. |
| Compliance Benefit: |
The use of LNB decreases the amount of NOx formation at the facility and therefore may
help facilities meet state air pollution control requirements (40 CFR 52).
Additionally, this technology may help facilities meet the standards of performance for
industrial-commercial-institutional steam generating units found in 40 CFR 60. A
decrease in a facility's NOx emissions may decrease the possibility that the facility
will meet the NOx emission threshold for an air permit under 40 CFR 70 and 71. The compliance benefits listed here are only meant to be used as general guidelines and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g., the amount of workload involved. |
| Materials Compatibility: |
No materials compatibility issues were identified. Any change in boiler configuration or
operation should be checked to ensure that no flame impingement or other adverse change in
operations occurs. |
| Safety and Health: |
No significant changes in safety or health issues should result from the installation and
implementation of LNBs. Consult your local industrial health specialist, your local health
and safety personnel, and the appropriate material safety data sheet (MSDS) prior to
implementing this technology. |
| Benefits: |
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| Disadvantages: |
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| Economic Analysis: |
In an effort to provide for the use of lower cost fuel, two 8.37 MM Btu/hr package boilers
at the Naval Consolidated Brig Marine Corps Air Station (MCAS) were retrofitted as
dual fuel LNBs (lower cost natural gas and oil), incorporating FGR and other changes. The cost of retrofitting a single boiler with a LNB was estimated
at $24,000 (1992 dollars). The new system replaced an external FGR module with one that is
integral to the boiler front. No operating or maintenance problems have been identified.
FGR maintenance costs were reduced significantly and boiler shutdowns were almost
eliminated. While each boiler will manifest its own operating characteristics, turndown ratios are often lessened with LNBs. Boilers of the same size and same equipment may have different operating requirements and combustion properties, therefore, each boiler should be economically evaluated for LNB on an individual basis. Economic Analysis Summary:
The Capital Cost for Equipment/Process: $24,000 |
| NSN/MSDS: | None identified. |
| Approving Authority: |
Appropriate authority for making process changes should always be sought and obtained prior to procuring or implementing any of the technology identified herein. |
| Points of Contact: | For more information |
| Vendors: | This is not meant to be a complete list, as there
may be other manufacturers of this type of equipment. Coen Company, Inc.
Babcock Power Environmental, Inc. |
| Related Links: | None. |
| Sources: | Evaluation of Air
Pollution Control Technologies for Industrial Boilers, prepared by HSC/YAL, December 1995. Steam: Its Generation and Use, The Babcock & Wilcox Company, 40th edition, 1992. Vendor information from Coen, Inc., Combustion Specialties, Inc., and Tampella Power Corporation. NOx Control Technology Data Source Book, EPA-600/2-91-029, NTIS PB91-217364. Evaluation and Costing of NOx Controls for Existing Utility Boilers, EPA-453/2-92-010. |