Page 146 - Boiler plant and distribution system optimization manual
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Over 100 Ways to Improve Efficiency 131
the magnitude of the force involved. When the are, or how fancy the trim system, the burner will
wind is driven into the outside vents boiler room ultimately control the level of excess air that can
pressure can rise, when on the sheltered side of be achieved. Older burners may not have been
a building a partial vacuum can form. This con- designed with low excess air in mind or they may
dition can cause burner adjustment problems. have worn out to a point where low excess air
The simple solution is to be aware of the poten- levels are no longer possible. The solution is to
tial problem and protect the boiler room from this install a burner which has been designed for low
wind effect or set the excess air high enough to excess air operation, or to repair or refurbish the
stay out of the smoking zone. This may seem like one you have so that it is capable of dependable
a small thing, but when low excess air levels are low excess air operation.
to be achieved a condition like this can become a
big challenge. Advantages/Disadvantages
High cost and redesign of boilers to accom-
modate these new burners may be a problem.
12. VENT CAPS ON STACKS
However, low excess air operation may not be
Cost possible without burner conversion.
Low
Savings 14. OxYGEN ENRICHMENT
Low to Moderate
Cost
Description
Varies
Something as simple as a vent cap on the
stack is not an obvious candidate for fuel savings.
Savings
A strong wind and a bent or damaged stack cover
Moderate to small
can produce some wild draft effects. These draft
effects will change the air/fuel ratio and cause
Description
large swings towards excess air conditions and
Substitution of oxygen for combustion air,
possibly cause smoking.
which contains only 20.9% O reduces the vol-
With the lack of good draft control, excess air 2
ume of heat absorbing nitrogen flowing through
adjustments must be made to compensate for this
the combustion process and therefore reduces
effect which can be excessive causing wasted fuel.
flue gas loss. Energy savings must be measured
It has always been a mystery as to just how vent
against the cost of oxygen and the cost involved
covers get bent and pushed over to one side, but
in additional safety precautions.
they have been known to deflect air into the boiler
The usual oxygen enriching practice in in-
or furnace in a good wind and cause serious prob-
dustrial heating is to increase the oxygen in the
lems and can even back smoke into a building.
combustion air from its normal 21% to 25% or
30%. It is preferable to premix it with the combus-
13. LOW ExCESS AIR BURNER tion air, but lances are sometimes used. Economic
justification of the use of oxygen is often marginal
Cost unless the user has oxygen facilities with spare
Moderate to High capacity.
Potential Savings
Advantages/Disadvantages
Moderate to High
Good energy savings are possible but safety
Description will be a paramount factor in mixing oxygen with
It doesn’t matter how good your controls fuel oil.
