User Manual

Near ideal comBuStioN
This is When we burn pure hydro- gen
intheair.Ouratmosphereis20.9%oxygen with
theremaining79.1%nitrogen.
This is nearly as desirable as the example for ideal
combustion with the only added loss being the
heat that is carried away from your target with
thenitrogen.Becausenitrogenisn’tpartof the
combustion process, it enters the combustion
chamber at the inlet temperature and leaves
with some of the heat created by the combus- tion.
Ifthisisn’trecoveredattheheatexchangeritis lost
up the flue.
The main problem with this example is again the
availability and cost of pure hydrogen.
BeSt of the real world
Natural gas is a
readily available fuel, and our atmosphere
contains sufficient oxygen. When this is
usedasafuelwegetthereaction;shown
in figure 3.
Now the other added outputs are CO2
and hot nitrogen compared to the Ideal
World situation. In addition to this we
haveaddedtheoutputExcessAir.
ExcessAirisexactlywhatthename
implies, air that is in excess of what is
needed to burn all of the fuel. The
reason for this is more related to the
ability to mix all of the fuel and O2 for
complete combustion. Without some
amount of excess air not all of the fuel
would burn completely, and this leads to
the formation of CO instead of CO2.
Other fuels all contain the basic ingre-
dients for combustion, but also may
include other components such as
sulfur, fuel bound nitrogen, soot and
ash and water. These either react with
the oxygen to form other pollutants or
contribute to
additional losses.
Wet Loss
Dry Loss
figure 3
Carbon Monoxide is formed from incomplete combustion (partial oxidation of carbon in
the fuel). Typical causes are incomplete mixing of fuel and air, low combustion temperatures,
or not enough excess air.
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