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Savings Potential
If
it were possible to have perfect combustion, the amount of oxygen in the flue
gas stream would be at, or close to, zero.
Because perfect combustion is not practically possible, combustion
equipment is set up to have a small percentage of excess O2
present. The lower the temperature
for a given O2
(or CO2)
reading, the higher is your combustion efficiency as less heat is lost up the
stack. Fine
tuning a boiler’s combustion air and fuel input has a direct impact on the
amount of fuel consumed by a boiler. Unfortunately,
there are too many factors involved to be able to calculate exact savings which
can be achieved. However, there are
several 'rules of thumb' which can roughly estimate savings potentials. For
each 1% decrease in excess air levels introduced into the combustion process,
the boiler’s efficiency increases by 1/4 to 1 of a percent.
While some excess air is necessary to insure complete combustion, flue
gas analysis will verify that excess air is within the manufacturer’s
specifications and optimize efficient operation. In
a Stoichiometric Mix or “perfect” combustion, all of the fuel and oxygen
introduced into the flame combine to generate only heat, water and carbon
dioxide (CO2). In
gas fired appliances, CO is the usual indicator of incomplete combustion.
CO is well known to be a health threat, but also represents unburned fuel
exhausting the appliance. In oil fired appliances, both CO and smoke indicate incomplete combustion. In addition to poor combustion, smoke can deposit soot on heat exchange surfaces which will further reduce efficiency. Also, smoke coming out of the stack can be cause for an air quality violation and potential public relations concerns. |
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