____________________________________
| | |
| | Degrees |
| | Fahrenheit |
|_________________|__________________|
| | |
| Lignite Dust | 300 |
| Dried Peat | 435 |
| Sulphur | 470 |
| Anthracite Dust | 570 |
| Coal | 600 |
| Coke | Red Heat |
| Anthracite | Red Heat, 750 |
| Carbon Monoxide | Red Heat, 1211 |
| Hydrogen | 1030 or 1290 |
|_________________|__________________|
Combustibles--The principal combustibles in coal and other fuels are
carbon, hydrogen and sulphur, occurring in varying proportions and
combinations.
Carbon is by far the most abundant as is indicated in the chapters on
fuels.
Hydrogen in a free state occurs in small quantities in some fuels, but
is usually found in combination with carbon, in the form of
hydrocarbons. The density of hydrogen is 0.0696 (Air = 1) and its weight
per cubic foot, at 32 degrees Fahrenheit and under atmospheric pressure,
is 0.005621 pounds.
Sulphur is found in most coals and some oils. It is usually present in
combined form, either as sulphide of iron or sulphate of lime; in the
latter form it has no heat value. Its presence in fuel is objectionable
because of its tendency to aid in the formation of clinkers, and the
gases from its combustion, when in the presence of moisture, may cause
corrosion.
Nitrogen is drawn into the furnace with the air. Its density is 0.9673
(Air = 1); its weight, at 32 degrees Fahrenheit and under atmospheric
pressure, is 0.07829 pounds per cubic foot; each pound of air at
atmospheric pressure contains 0.7685 pounds of nitrogen, and one pound
of nitrogen is contained in 1.301 pounds of air.
Nitrogen performs no useful office in combustion and passes through the
furnace without change. It dilutes the air, absorbs heat, reduces the
temperature of the products of combustion, and is the chief source of
heat losses in furnaces.
Calorific Value--Each combustible element of gas will combine with
oxygen in certain definite proportions and will generate a definite
amount of heat, measured in B. t. u. This definite amount of heat per
pound liberated by perfect combustion is termed the calorific value of
that substance. Table 31, gives certain data on the reactions and
results of combustion for elementary combustibles and several compounds.