| 0.0042 | --- | --- | _ --- |
Nitrogen......... | 0.1045 | --- | 0.18 | | |
Ash.............. | 0.0540 | --- | --- | | |
+----------+------------+ | | 85.5 |
| | | | | |
Total........... | 1.0000 | 2.572 | --- | | |
9-1/3.lb nitrogen | --- | --- | 118.9 | | |
6 lb. excess of air. | --- | --- | 71.4 | _| |
+----------+------------+--------+------------+
Total cubic feet of | | | | |
products per 1 lb. | | | | |
of coal........... | -- | -- | 226.4 | 100.0 |
---------------------+----------+------------+--------+------------+

The temperature of the furnace not having been determined, we must
calculate it on the supposition, which will be justified later on,
that 50 per cent more air was admitted than was theoretically
necessary to supply the oxygen required for perfect combustion. This
would make 18 lb. of air per 1 lb. of coal; consequently 19 lb. of
gases would be heated by 14,727 units of heat. Hence:

14,727 u.
T = ---------------- = 3,257 deg.
19 lb. x 0.238

above the temperatures of the air, or 3,777 deg. absolute. The temperature
of the smoke, _t_, was 849 deg. absolute; hence the maximum duty would be

3,777 deg. - 849 deg.
--------------- = 0.7752.
3,777 deg.

The specific heat of coal is very nearly that of gases at constant
pressure, and may, without sensible error, be taken as such. The
potential energy of 1 lb. of coal, therefore, with reference to the
oxygen with which it will combine, and calculated from absolute zero,
is:

Units.
19 lb. of coal and air at the temperature
of the air contained 19 lb. x 520 deg. x 0.238 2,350
Heat of combustion 14,727
-------
17,078
Deduct heat expended in displacing atmosphere 151 cubic feet - 422
------
Total potential energy