Improve Your Boiler's Combustion Efficiency: Office of Industrial Technologies (OIT) Steam Energy Tips No.4
Operating your boiler with an optimum amount of excess air will minimize heat loss up the stack and improve combustion efficiency. Combustion efficiency is a measure of how effectively the heat content of a fuel is transferred into usable heat. The stack temperature and flue gas oxygen (or carbon dioxide) concentrations are primary indicators of combustion efficiency. Given complete mixing, a precise or stoichiometric amount of air is required to completely react with a given quantity of fuel. In practice, combustion conditions are never ideal, and additional or ''excess'' air must be supplied to completely burn the fuel. The correct amount of excess air is determined from analyzing flue gas oxygen or carbon dioxide concentrations. Inadequate excess air results in unburned combustibles (fuel, soot, smoke, and carbon monoxide) while too much results in heat lost due to the increased flue gas flow--thus lowering the overall boiler fuel-to-steam efficiency. The table relates stack readings to boiler performance. On well-designed natural gas-fired systems, an excess air level of 10% is attainable. An often stated rule of thumb is that boiler efficiency can be increased by 1% for each 15% reduction in excess air or 40 F reduction in stack gas temperature.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC36-99-GO10337
- OSTI ID:
- 15000229
- Report Number(s):
- DOE/GO-102002-1506; TRN: US200325%%124
- Resource Relation:
- Other Information: PBD: 1 Mar 2002
- Country of Publication:
- United States
- Language:
- English
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