MIL-HDBK-1003/6
impracticably long residence time and infinite mixing of air and fuel. Firing
of a fuel therefore requires excess air to assure sufficient interaction
between the oxygen in the air and the combustibles in the fuel and to prevent
discharge of excessive combustibles in potentially explosive mixtures of
oxygen and fuel. Excess combustion air is generally in the range shown below:
5.3.1.1
Coal Firing
a)
Underfeed stoker
20 to 50 percent
b)
Vibrating-grate stoker
30 to 60 percent
c)
Traveling-grate stoker
15 to 50 percent
d)
Spreader stoker
30 to 60 percent
e)
Pulverized coal burner
15 to 20 percent
5.3.1.2
Oil Firing
a)
Register type burners
5 to 10 percent
b)
Multifuel burners
10 to 20 percent
5.3.1.3
Natural Gas Firing
a)
Register type burners
5 to 10 percent
b)
Multifuel burners
7 to 12 percent
5.3.1.4
Wood Firing
a)
Stoker
25 to 50 percent
b)
Suspension burning
25 to 50 percent
5.3.1.5
Solid Waste
a)
Mass burning
80 to 100 percent
b)
RDF burning
35 to 60 percent
Combustion Calculations (Example Using Coal). In order to make
5.3.2
combustion calculations, it is necessary to use the molecular weight of any
substance. The molecular weight of carbon is 12, hydrogen is 2, and oxygen is
32; therefore, the molecular weight of carbon dioxide is 12 plus 32 or 44. To
calculate the amount of air required for combustion, the concept of the mol is
used. A molecular weight expressed in pounds is called a pound.mol. For
example, using a bituminous coal of the following analysis (burned at 30
percent excess air), the following information can be calculated:
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