BOILER PLANT BURNER PERFORMANCE
ISSUE:
For optimum boiler efficiency, the burner should be adjusted so that the
flue gas excess air, as measured by percent oxygen, is as low as possible without
generating excessive quantities of carbon monoxide.
DISCUSSION:
Based on experience with many modern package-type boiler/burners, the
recommended excess air has been listed in VA Master Specifications for
fire tube and water tube steam boilers.
These recommendations are:
Steam loads below 20% of max: 15% excess air min. (2.7% oxygen).
Steam loads 20% to 40% of max: 15 35% excess air (2.7 5.2% oxygen).
Steam loads 40% and above: 15 25% excess air (2.7- 4.0% oxygen).
On oil firing, maximum excess air can be 5 percentage points higher.
Carbon monoxide in the flue gas should not exceed 200 parts per million (ppm).
An improvement in boiler efficiency of approximately one percent can be achieved
by reducing the excess air by 15 percentage points, which is roughly equivalent to
1.5% oxygen.
On larger water tube package boilers, low excess air burners have occasionally
been applied. These burners can have excess air as low as 5%. Refer to Master
Specification Section 15624, Par. 2.3.C.3.
RECOMMENDATIONS:
If possible, burners should be tuned to obtain the recommended performance.
Some older installations with field-erected boilers may not be capable of this.
LINKS TO FM TECHNICAL INFORMATION LIBRARY (TIL):
See VA Master Specifications Section 15622, Fire Tube Steam Boilers and
Accessories, and Section 15624, Water Tube Steam Boilers and Accessories.
http://www.va.gov/facmgt/standard
FOR ADDITIONAL INFORMATION:
Contact Jim Shoemaker, at 202-565-5176, in the Consulting Support Service (183A);
james.shoemaker@hq.med.va.gov
16 JANUARY 2002
FM-181A-DA-110
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