The Locomotive - Lighthouse Survival Blog

108 THE LOCOMOTIVE. [July,
completely burned, and this requires a somewhat long flame-way, because the flame
must not be chilled.
When the coal is finely divided, and delivered uniformly mixed with air, a solid
radiating flame is produced, wdiich at first is full of particles of solid fuel in incandes-
cence. These particles rapidly disappear, leaving the larger portion of the flame com-
posed merely of burning gases. One has only to follow this flame, as the writer has
done, by means of peep-holes arranged in the brick-work of an ordinary boiler setting,
to be impressed with the completeness and ideal character of the combustion. The
flame is that of gas, rather than oil. The fuel appears to be gasified in an intensely hot
atmosphere containing the right proportion of the supporter of combustion.
Different systems handle the pulverization differently. The Germans prefer to
powder the coal in one place and deliver it to the feeding machine in bags, while in this
country the neater and safer process of pulverizing the coal as it is used is generally
followed. A large amount of finely-powdered coal may or may not be dangerous in
storage, but there appears to be a decided advantage in carrying the dust directly
from the pulverizer into the furnace, because this admits of the most perfect aeration,
and this is essential. The power for grinding is applied in various ways, either by belt
driving from a small steam engine or by connecting a steam turbine directly to the grinder.
The grinding is usually in two stages, the first bringing the coal to about the size of split
peas, and the second completing the process. The fine grinding appears to be accomplished
best by attrition in a cylinder filled with rapidly revolving vanes, from which
cylinder a blower takes the dust into the furnace through a tuyere, which is filled with
partitions parallel to the current for the sake of obtaining a uniform mixture, and for
spreading aud concentrating the delivery as desired.— American Engineer and Railroad
Journal. (Quoted in the Journal of the American Society of Naval Engineers.)
[In reprinting the foregoing extract, we do not wish to be understood as either
recommending or opposing the use of pulverized coal as fuel. The matter is still in a
more or less experimental state. The data which have been obtained thus far, some of
which are appended to the original article from which this extract is taken, look prom-
ising; but we are not yet prepared to make any definite statement concerning the
practicability of using pulverized coal in this way.— Editor The Locomotive.]
Superheated Steam.
It often occurs that a mechanical improvement attracts more or less wide attention
for a time and then falls into disuse, even to the point of being almost forgotten, be-
cause of some apparently insurmountable obstacle, to be taken up again at a later date
when the conditions governing its use appear to be more favorable. This seems to be
especially true with the subject of superheated steam, by which we mean the practice of
raising steam, immediately after its generation in the boiler, to a temperature consider-
ably in excess of the saturation point, without greatly increasing its pressure, for the
purpose of working it in a steam engine in this condition.
Considerable attention was given to this subject as far back as the year 1850, when
we find numerous reports of engine tests which show most remarkable gains, ranging
from 30 to 40 per cent, of the work done with a given amount of superheated steam
over that done by the same weight of steam at a temperature corresponding to its pres-
sure. These early experiments seem to have been practically confined to marine practice,
possibly because this was the most active field for developing the steam engine at that
time; and some idea of the thoroughness of the investigation is obtained from the ac-