Optimization of low-NO{sub x} overfire air systems to improve boiler performance
- Fossil Energy Research Corporation, Laguna Hills, CA (United States)
Overfire air (OFA) is a common post-retrofit NO{sub x} control measure that can adversely impact coal-fired utility boiler performance if not properly implemented. Some utilities have experienced a significant increase in fly ash carbon content, difficulty in maintaining efficient operating O{sub 2} levels, and changes in furnace heat absorption as the result of installing OFA systems. Although staged combustion conditions and coal properties have often been cited as reasons for increased fly ash carbon content and LOI, the importance of optimizing OFA system performance during post-retrofit commissioning and warranty testing has not been adequately recognized. This paper outlines combustion diagnostic and analysis techniques that have been successfully used to evaluate OFA mixing, penetration and combustion uniformity on typical coal-fired utility boilers. Field test data is provided illustrating the results of combustion diagnostic testing on several units where the distribution of air flow to the OFA ports was not well balanced or the OFA penetration and mixing, were not sufficient to achieve uniform combustion. The paper includes a discussion of instrumentation used to adjust OFA parameters to optimize both NO{sub x} emissions and boiler performance. OFA tuning at one 250 MW tangentially-fired unit reduced the O{sub 2} level where CO emissions were first encountered from 4.25 percent O{sub 2} to less than three percent O{sub 2} at the economizer exit.
- Research Organization:
- Electric Power Research Inst. (EPRI), Palo Alto, CA (United States); Encor-America, Inc., Mountain View, CA (United States)
- OSTI ID:
- 269598
- Report Number(s):
- EPRI-TR-106529; CONF-960524-; TRN: 96:003583-0011
- Resource Relation:
- Conference: Heat-rate improvement conference, Dallas, TX (United States), 22-24 May 1996; Other Information: PBD: May 1996; Related Information: Is Part Of Proceedings: 1996 heat rate improvement conference; Diaz-Tous, I.A. [ed.] [Encor-America, Inc., Mountain View, CA (United States)]; PB: 568 p.
- Country of Publication:
- United States
- Language:
- English
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