or use
under boilers or in gas engines, that is, approximately 8500 pounds of
gas per ton of pig iron produced. In a modern blast furnace plant, the
gas serves ordinarily as the only fuel required. Table 49 gives the
analyses of several samples of blast furnace gas.

TABLE 49

TYPICAL ANALYSES OF BLAST FURNACE GAS

+----------------------------------------------------------------+
|+-----------------------+------+----+-----+----+------+--------+|
|| |CO_{2}| O | CO | H |CH_{4}| N ||
|+-----------------------+------+----+-----+----+------+--------+|
||Bessemer Furnace | 9.85|0.36|32.73|3.14| .. |53.92 ||
||Bessemer Furnace | 11.4 | .. |27.7 |1.9 | 0.3 |58.7 ||
||Bessemer Furnace | 10.0 | .. |26.2 |3.1 | 0.2 |60.5 ||
||Bessemer Furnace | 9.1 | .. |28.7 |2.7 | 0.2 |59.3 ||
||Bessemer Furnace | 13.5 | .. |25.2 |1.43| .. |59.87 ||
||Bessemer Furnace[47] | 10.9 | .. |27.8 |2.8 | 0.2 |58.3 ||
||Ferro Manganese Furnace| 7.1 | .. |30.1 | .. | .. |62.8[48]||
||Basic Ore Furnace | 16.0 |0.2 |23.6 | .. | .. |60.2[48]||
|+-----------------------+------+----+-----+----+------+--------+|
+----------------------------------------------------------------+

Until recently, the important consideration in the burning of blast
furnace gas has been the capacity that can be developed with practically
no attention given to the aspect of efficiency. This phase of the
question is now drawing attention and furnaces especially designed for
good efficiency with this class of fuel are demanded. The essential
feature is ample combustion space, in which the combustion of gases may
be practically completed before striking the heating surfaces. The gases
have the power of burning out completely after striking the heating
surfaces, provided the initial temperature is sufficiently high, but
where the combustion is completed before such time, the results secured
are more satisfactory. A furnace volume of approximately 1 to 1.5 cubic
feet per rated boiler horse power will give a combustion space that is
ample.

Where there is the possibility of a failure of the gas supply, or where
steam is required when the blast furnace is shut down, coal fired grates
of sufficient size to get the required capacity should be installed.
Where grates of full size are not required, ignition grates should be
installed, which need