the heating
surfaces than in the former case.

Smoke may be diminished by employing a baffle arrangement which gives
the gases a fairly long travel under heated brickwork and by introducing
air above the fire. In many cases, however, special furnaces for smoke
reduction are installed at the expense of capacity and economy.

From the standpoint of smokelessness, undoubtedly the best results are
obtained with a good stoker, properly operated. As stated above, the
best stoker will cause smoke under certain conditions. Intelligently
handled, however, under ordinary operating conditions, stoker-fired
furnaces are much more nearly smokeless than those which are hand fired,
and are, to all intents and purposes, smokeless. In practically all
stoker installations there enters the element of time for combustion,
the volatile gases as they are distilled being acted upon by ignition or
other arches before they strike the heating surfaces. In many instances
too, stokers are installed with an extension beyond the boiler front,
which gives an added length of travel during which, the gases are acted
upon by the radiant heat from the ignition or supplementary arches, and
here again we see the long travel giving time for the volatile gases to
be properly consumed.

To repeat, it must be emphatically borne in mind that the question of
smokelessness is largely one of degree, and dependent to an extent much
greater than is ordinarily appreciated upon the handling of the fuel and
the furnaces by the operators, be these furnaces hand fired or
automatically fired.

[Illustration: 3520 Horse-power Installation of Babcock & Wilcox Boilers
at the Portland Railway, Light and Power Co., Portland, Ore. These
Boilers are Equipped with Wood Refuse Extension Furnaces at the Front
and Oil Burning Furnaces at the Mud Drum End]

SOLID FUELS OTHER THAN COAL AND THEIR COMBUSTION

Wood--Wood is vegetable tissue which has undergone no geological change.
Usually the term is used to designate those compact substances
familiarly known as tree trunks and limbs. When newly cut, wood contains
moisture varying from 30 per cent to 50 per cent. When dried for a
period of about a year in the atmosphere, the moisture content will be
reduced to 18 or 20 per cent.

TABLE 41

ULTIMATE ANALYSES AND CALORIFIC VALUES OF DRY WOOD (GOTTLIEB)

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