The problem as to how the refuse of coal shall be utilized has been
solved in the manufacture from it of an agglomerated artificial
fuel, which is coming more and more into general use on railways and
steamboats, in the industries, and even in domestic heating.
The qualities that a good agglomerating machine should present are as
follows:
1. Very great simplicity, inasmuch as it is called upon to operate in
an atmosphere charged with coal dust, pitch, and steam; and, under such
conditions, it is important that it may be easily got at for cleaning,
and that the changing of its parts (which wear rapidly) may be effected
without, so to speak, interrupting its running.
2. The compression must be powerful, and, that the product may be
homogeneous, must operate progressively and not by shocks. It must
especially act as much as possible upon the entire surface of the
conglomerate, and this is something that most machines fail to do.
3. The removal from the mould must be effected easily, and not depend
upon a play of pistons or springs, which soon become foul, and the
operation of which is very irregular.
The operations embraced in the manufacture of this kind of fuel are as
follows:
The refuse is sifted in order to separate the dust from the grains of
coal. The dust is not submitted to a washing. The grains are classed
into two sizes, after removing the nut size, which is sold separately.
The grains of each size are washed separately. The washed grains are
either drained or dried by a hydro-extractor in order to free them from
the greater part of the water, the presence of this being an obstacle to
their perfect agglomeration. The water, however, should not be entirely
extracted because the combustibles being poor conductors of heat, a
certain amount of dampness must be preserved to obtain an equal division
of heat in the paste when the mixture is warmed.
After being dried the grains are mixed with the coal dust, and broken
coal pitch is added in the proportion of eight to ten per cent. of the
coal. The mixture is then thrown into a crushing machine, where it is
reduced to powder and intimately mixed. It then passes into a pug-mill
into which superheated steam is admitted, and by this means is converted
into a plastic paste. This paste is then led into an agitator for the
double purpose of freeing it from the steam that it contains, and of
distributing it in the moulds of the compressing machine.
[Illustration: IMPROVED MACHINE FOR COMPRESSING REFUSE COAL INTO FUEL.]
Bilan's machine, shown in the accompanying cut, is designed for
manufacturing spherical conglomerates for domestic purposes. It consists
of a cast iron frame supporting four vertical moulding wheels placed at
right angles to each other and tangent to the line of the centers. These
wheels carry on their periphery cavities that have the form of a quarter
of a sphere. They thus form at the point of contact a complete sphere
in which the material is inclosed. The paste is thrown by shovel, or
emptied by buckets and chain, into the hopper fixed at the upper part
of the frame. From here it is taken up by two helices, mounted on a
vertical shaft traversing the hopper, and forced toward the point where
the four moulding wheels meet. The driving pulley of the machine is
keyed upon a horizontal shaft which is provided with two endless screws
that actuate two gear-wheels, and these latter set in motion the four
moulding wheels by means of beveled pinions. The four moulding wheels
being accurately adjusted so that their cavities meet each other at
every revolution, carry along the paste furnished them by the hopper,
compress it powerfully on the four quarters, and, separating by a
further revolution, allow the finished ball to drop out.
The external crown of the wheels carrying the moulds consists of four
segments, which may be taken apart at will to be replaced by others when
worn.
This machine produces about 40 tons per day of this globular artificial
fuel.--_Annales Industrielles_.
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