THE COLLIERY GUARDIAN

AND

JOURNAL OF THE COAL AND IRON TRADER

Vol. CIX.

THURSDAY, APRIL 1, 1915.

No. 2831.

Briquette Manufacture.

The term “ briquette ” is usually understood to
signify a block of different materials, which, after
suitable preparation, are filled or pressed into a mould,
and then subjected to a heavy compression, by which
they are solidified sufficiently for the purpose for which
they are required. Generally speaking, they may be
classed as for the following purposes:—•

1.	Heating.—1 hese can be produced from any suitable
combustible materials, but are chiefly composed of
small coal, agglomerated with pitch. In South Wales,
where the largest works for this purpose are situated,
the product is usually termed “ patent fuel.”

2.	Smelting.—These are produced from iron or other
ores, which already contain either suffi dent siliceous or

briquetting for heating purposes. Small coke, sawdust,
town refuse, palm nut shells, and other materials of a
combustible nature, have also been made into briquettes
on a limited scale. The general modus operandi is the
same, with variations in the different parts of the
preparing machinery to suit the different materials
treated.

By far the largest proportion of coal used in commerce
is of the bituminous or semi-bituminous quality, and to
convert this small into briquettes, some agglomerant
must be used for the purpose of binding the small
particles of coal together. Various ingredients have
been tried for this purpose, but, so far, pitch is by far
the best binding agent, as it alone helps the three

to the action of superheated steam, of a suitable temper-
ature, by means of which the pitch becomes plastic and
adhesive. This heater is fixed over the briquette press
which is fitted with a vertical mould plate with inter-
mittent motion, having usually eight moulds in it. At
each stroke of the machine the plastic material is
pushed by a horizontal ram into one of the moulds.
When the full mould reaches the opposite side the
material is powerfully compressed from both sides
simultaneously by two rams working horizontally. A
fourth ram pushes out the finished compressed blocks,
which are then conveyed to the stacking yard or loaded
into trucks. When properly made and cold, the
briquettes are as dense and hard as the large coal itself.

This double compression — i.e., pressure of the
briquettes from both sides simultaneously—has been
found to be a great improvement on the single pressure

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Big. 1.—Two 100-ton Briquette Presses, Polmaise Colliery,
Stirling.

Each of these machines produces briquettes weighing 12 lb. each, at the rate of
about 10 tons per hour.



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Pig. 2.—View of Smaller Plant, Polmaise Colliery, showing
Mixer, Briquette Press and Elevator.

Produces briquettes for household purposes, weighing about 3 lb. each, at the
rate of 3 tons per hour.

other binding material, or have lime or clay added to
them as the agglomerant.

There are a few other minor purposes for which
briquettes, or powerfully compressed blocks, are used-
but the above comprises almost all the products which
are classed under the term “briquette.”

The different kinds of machinery required for suitably
mixing, grinding, and heating the materials vary
according to the ingredients used, and the purpose for
which the briquettes are intended when made.

In the mining of coal there is always a large
proportion of small produced, which, when clean, is of
the same quality as the large, but which, on account of
its size, can be sold only at a much lower price per ton.
It is this small coal which is used principally for

following advantages :—(a) it helps the coal to burn,
(&) it adds practically no ash; and (c) the briquettes
agglomerated with it are very hard and quite weather
proof. This pitch is produced from the distillation of
gas tar, and is also one of the by-products of iron
smelting where coal is used instead of coke. The best
quality is medium, and should contain only 0'25 to
0'5 per cent, of ash. The pitch is broken small in a
pitch cracker, and then fed, along with the coal into a
mixer for measuring accurately the proper pro-
portions of the two materials, which then fall into
a disintegrator, where they are ground together to the
proper fineness. This ground material (coal or pitch) is
then elevated and delivered into a vertical heater, where,
in its downward passage through the same, it is subjected

from one side only, the briquettes being of a more
regular density throughout. The moulds are shaped to
produce briquettes with rounded corners, and with the
system of double compression another important
improvement has been introduced with these presses by
which the edges on both faces of the briquettes are also
rounded, thus largely minimising breakage in transit.
The briquette presses exert a minimum pressure of
2 tons per square inch on the surface of the briquettes.
This enormous pressure is obtained by an ingenious
application of compound levers and a heavy flywheel,
the horse-power required for driving the press being
less than half that used in other machines where the
compression is from one side only. It also effects a
considerable saving in ft e percentage of pitch required