July 28, 1916.

THE COLLIERY GUARDIAN.

the use of some form of pneumatic dressing machinery,
such as has been erected in several of the Westphalian
collieries. Nothing of the kind seems to have been
attempted in this country, and this valuable article con-
tinues to be thrown away. Here again is a source of
economy, which in some parts of the country would be
decidedly important.

Pillars and Barriers.

Turning next to underground operations, the waste of
coal in the pit may be considered under two heads :
more or less accidental, and more or less deliberate. It
is practically impossible to win the whole of the coal in
any seam; some is always lost, owing to the waste in
undercutting, the crushing of ends and of odd portions
of pillars, and the leaving of barriers and shaft pillars.
The intention is always that a shaft pillar shall be
robbed when the rest of the pit has been worked out,
but it frequently happens that, by that time, much of
the coal in the shaft pillar is so crushed that it cannot
be won.

Barriers are in part left deliberately, whilst in
other cases the intention is ultimately to win them as
far as possible, though here again this cannot always be
accomplished. The waste in undercutting is being
gradually decreased by the use of coal-cutting machines,
owing to the fact that the machine makes a much
narrower cut than is possible with the pick. More might
no doubt be done in the substitution of machines for
hand labour; but the indiscriminate use of coal-cutting
machines is not in all cases to be recommended. Never-
theless, it ought not to be forgotten that our coal reserves
are a national asset, and that the interests of the Nation
at large should receive some consideration as well as the
immediate profit that the colliery owners draw from
their operations.

The crushing and loss of some portions of the seam
areealmost inevitable in any system of working; such
loss is no doubt less when the coal is worked by long-
wall than by bord-and-pillar, but here again the best
system of working any given seam does not depend upon
this consideration alone, though the national aspect is
too often entirely neglected. On the whole, there is no
doubt that the use of the longwall method is extending,
and that loss in working is decidedly less than it was,
say, 50 years ago; and there is every reason to hope that
still further improvements in this respect may be looked
for. Improved methods of stowage, such as the well-
known hydraulic methods, may also be helpful in this
matter.

Afforestation.

An important fact to be borne in mind is that a colliery
is after all not a philanthropic institution, and that no
colliery manager is going to extract small remnants of
coal pillars when the cost of doing so is greater than the
value of the coal; and, further, that his costs depend
largely upon the prices of pit timber, because the
removal of such small portions of coal is rarely possible
except by the lavish use of pit props. That the price of
these has risen lately to formidable figures is well known,
the main reason being that for many years afforesta-
tion has been wholly neglected in this country. What
little has been done has been due to the enterprise of a
few individuals, and it is impossible to acquit of blame
in this respect some semi-public bodies, such as the
Ecclesiastical Commissioners, who hold vast areas of
land. They prefer to get the maximum immediate
revenue out of their lands, say, by letting them as grouse
moors, instead of contenting themselves with a lower
immediate return, and planting timber, which would in
the course of time not only yield a handsome income
for themselves, but prove an important advantage to
the industries of the nation. The need for cheap timber,
if the maximum output is to be obtained from a given
area of coal, may not at first sight be very obvious, but
there is, nevertheless, a very close connection between
them.

Coal a National Asset.

As regards the leaving of barriers between adjoining
properties, this has been, and is still, a very serious
source of loss, though it is to some extent decreasing
owing to the growing tendency of colliery companies to
amalgamate, and for large companies to absorb smaller
ones, so that ever larger areas are being controlled by
one interest. Even so, there is room for much improve-
ment, and possibly legislation on the subject might not
be altogether out of place. Although coal in this country
belongs rightfully to individuals, it constitutes, as a
whole, a national asset, and the nation is entitled to
protect itself against undue waste. As to the proportion
of coal that is left in the ground, 5 per cent, is a rough
estimate, so that the total quantity is formidable enough.
The coal thus left in the ground cannot be looked upon
as a reserve that future generations may be glad to
utilise. On the contrary, coal thus left behind cannot
be won afterwards, and must be regarded as irretriev-
ably lost to the country.

Gob-Fires.

Another source of loss is that due to “ gob-fires,”
which often spread to the coal seam proper; and large
areas of coal have thus at times been lost. The ques-
tion of the best means of preventing such gob-fires is
now' attracting much attention, and excellent work upon
it has been done within the last few years in the Research
Laboratory of the Doncaster Coal Owners. It has been
attacked mainly from the standpoint of the chemist, the
object being, in the first instance, to find out what are
the causes and conditions that' favour the spontaneous
ignition of coal, and in this way to arrive at the proper
remedy to be applied. There are good grounds for say-
ing that the theory of the subject is beginning to be
well understood, and that the colliery manager ought,
in the light of the scientific information thus given, to
be able to keep losses of coal due to gob-fires within very
narrow limits in the near future.

In addition to coal thus accidentally left behind in the
pit, there are many cases in which coal is deliberately
left behind or thrown back into the goaf.

Un worked Coal.

In many parts of the country where non-coking coal
is produced, all small coal is left underground on the
plea that it would cost more to bring it out than it
would fetch in the market. This coal is not mere dust,
for in many cases nut coal is sacrificed in this way; in
parts of Nottinghamshire the author hais seen coal loaded
underground with a fork with IJin. tines, all coal under
in. being thus thrown away, although quite as good
from the point of view of heat production as the coal that
was sent up the shaft, and much of it could have been
used at once for firing boilers. How much coal is lost
in this way it is difficult to say, but there are cases
where the coal thus wasted amounts to over 15 per cent,
of the output.

Again, there are many cases where only the better
portions of the seams are being won, the rest of the coal
being left behind and lost, simply because it is of some-
what inferior quality, though quite capable of being
utilised. Take, for example, a statement from the
Mines Report of 1910, referring to the Barnsley seam,
worked at a number of mines in the Doncaster district :
“ At several of these mines nearly one-half of this fine
seam is left unworked, the ‘ Top-softs,’ about 4 ft. thick,
being left to fall in the goaf. This part of the seam is
not of such high quality as the better portion, and that
is the chief reason for it being left unworked. ... To
lose practically 40 per cent, of this seam is also a
national loss.” A number of analyses of the Barnsley
Hard and of the Barnsley Softs from the Doncaster dis-
trict have recently been published in some of the papers
issued by the Doncaster Coal Owners’ Laboratory, and
these show practically no difference in chemical compo-
sition. It is quite certain that as regards calorific value
there cannot be any serious difference between the two
classes of coal.

In the Barnsley district proper, a certain thickness of
the seam, though rarely amounting here to more than
25 per cent, of the whole—the “ Bags ” as it is locally
called—is very generally left behind in the goaf. In
Fifeshire the Great seam, 6 to 8 ft. thick, consists of
about 2 ft. of ironstone, about as much common coal,
and then about 3 ft. of cannel or Parrot coal. The
latter alone is worked, all the rest of this fine seam being
left behind in the goaf. In Lanarkshire the Ell coal,
about 6 ft. in thickness, is worked, and the Head coal,
about 2 ft. in thickness, left behind in the goaf.

These few examples, taken somewhat at random, will
serve to exemplify the nature of the loss of coal that is
here discussed; in most cases the coal thus left behind
must be looked upon as totally lost; in others it may be
in part recovered. Thus, some of the areas ill Lanark-
shire above referred to are now being worked over again
with the object of recovering as much as possible of the
Head coal previously rejected, but obviously such an
operation can never be a very satisfactory one. In many
districts where there is one particularly good or especially
valuable seam, this is often worked out before any other
seams are touched, without regard to the fact that such
working damages other seams less valuable to-day, but
nevertheless containing coal of quite good quality. The
result of this damage is that a certain proportion, or
possibly in some cases the whole of these other seams
is rendered unworkable, and great loss of coal is thus
brought about.

It is practically impossible to present any figures show-
ing the amount of coal lost to the nation as the result
of this deliberate waste, but it certainly amounts to
enormous quantities in the aggregate. It is not easy to
suggest any remedy for this loss; some authorities
favour legislation, and the imposition of heavy taxes
upon coal left behind has been suggested. This can
hardly be looked upon as a scientific solution of the
problem, and undoubtedly a better remedy would be the
invention or the elaboration of methods of utilising these
inferior coals, which would give them a value sufficient
to make it worth the while of colliery proprietors to work
the whole of their coal. Some of these difficulties are
unquestionably connected with our systems of mineral
ownership, under which two seams within the same
area may be let to different people, each of whom works
for his own interests alone, regardless of the interests
of the neighbour above or below him. The importance
of the question is very great, and it undoubtedly deserves
the fullest possible investigation from every standpoint,
there being probably no portion of the entire subject of
coal economy that promises more valuable results.

Miners’ Safety.

The all-important question of safety is in no wise
involved in the considerations here submitted; in fact,
the reform of most of the sources of wraste indicated must
result in increased safety for the coal miner. The
diminution of gob-fires is obviously a case in point.
Again, if it were possible to turn to good account the
accumulations of fine coal dust, which constitutes such
a grave danger in most collieries owing to the disastrous
explosions to which it may give rise, the removal of this
dust from the workings might readily become a source
of profit instead of a loss as at present. It need hardly
be said that such coal dust could, as pointed out, be
employed directly for firing, and that its cleaning and
subsequent utilisation should present no insoluble diffi-
culties. The coal left behind in the goaf is naturally
also a source of danger to the coal miner, and in this
way- again the successful utilisation of inferior coal
would contribute to the safety of our collieries.

Partnership Dissolved.—Th? London Gazette announces
dissolution of the partnership of W. Picken and A. 0. Picken,
trading as Picken and Son, engineers and wire workers,
Frankfort-street, Birmingham. A. O. Picken continues the
business.

163

— ™ ■■■■ —1 ■

IMPROVEMENTS IN BY-PRODUCT
COKE OVEN PRACTICE.*

By. G. P. Lishman, D.Sc., F.I.C.

Since the introduction of the direct processes, there
has been no great change in coke works practice in this
country. The high wages paid in coke works have led to
numerous labour-saving devices, and it is largely with
items of 'this kind that the present notes are concerned.
Most of these appliances have been in use in odd places
for some years. What may be regarded as ” recent,”
however, is the general adoption of a number of them
in conjunction with each other on recent plants.

Size of Ovens.

The most important advance on these lines is undoubt-
edly the increasing size of ovens, and this involves some
special problems which will have to be faced by all
makers. Since with a larger oven any given output of
coke can be obtained in fewer operations, increased
efficiency certainly lies in this direction. In America
16-ton ovens have been built by the Solvay Company for
some time. These ovens are built of a silica brick, and
are run at a very high temperature, coking in 16 hours.
The largest oven working in England to-day is the Collin
at Middlesbrough, measuring 3-1 x 0’5 x 11 m. The
72 ovens make 3,000 tons of coke per week. The Solvay
Company have also completed a battery of 12-ton ovens
in England, and the Simon-Carves Company have a
battery of 11-ton ovens ready to start. These large
ovens, besides being cheaper to work, involve less capital
outlay, and the quantity of inferior coke on top or ends
is proportionately reduced. It is stated that in Ger-
many an oven 3*5 m. high is now working.

Charging Apparatus.

Where it is not necessary to compress coal, most con-
structional firms are adopting levelling machines and the
electrically-driven coal loading car. This machine con-
sists of a steel under-frame carrying four hoppers which
contain one full oven charge. It runs along the oven
tops on rails in charge of one mas, and enables the whole
laborious process of tub pushing to be dispensed with.
The only drawback is that the collecting must be on
one edge of the battery.

Coke Handling.

The chief mechanical arrangements for this purpose
are :—

(1)	Inclined car discharging into elevated screens, fixed
or shaking. This is probably the cheapest way to load
coke,'but it is sometimes difficult to arrange for storage.

(2)	The inclined bench and coke conveyor, usually a
tray conveyor which rises up an incline at the end of
the battery and delivers to the screens. Coke conveyors
are improving and are becoming more popular than
formerly.

(3)	The Goodall quenching car consists essentially of a
revolving table into which the coke is discharged from
the oven and quenched by a series of sprays fixed over
the table, and also by sprays in the quenching hood
which is part of the car, and through which the coke
passes on its way to the table. When quenching is
complete the coke is discharged over shaking screens
into railway wagons. The ballast and breeze are caught
in special hoppers also forming part of the car, and the
mixture is emptied at intervals into separate trucks. A
useful plant for handling breeze which is carried down
by the quenching water has been put up by Simon-
Carves Limited at one of their recent plants. This con-
sists, as shown in the drawing, of a small telpher, which
elevates special bogies, into which the breeze is filled by
hand, and carries it to a revolving screen. On arriving
at the screen the coke is automatically tipped and the
coke passes through the screen, where it is separated
into three sizes.

(4)	The enclosed type of car as used at Vienna Gas
Works (Hoppers’ gas oven) has not yet been seen in
this country. This is an enclosed chamber running on
rails carrying its own motor and pump. The water is
used over and over again, the pump drawing it through
an 8 in. flexible suction pipe from a trough running along
the battery under the car.

The adaptation of ovens to the supply of lighting gas
has been extended, but not sufficiently. The heating of
ovens by producer or blast-furnace gas can be done quite
satisfactorily, and yet most of our plants consume their
own high-grade gas, many of them taking the -whole of
it. Regeneration plants are still a small minority in
this country, the value of gas as a by-product not being
even yet fully recognised.

Economy has been effected in many plants by means
of door-lifting winches attached to the rams and coke
quenchers, so that raising and lowering doors is carried
out mechanically. In this country they are always
worked from the ram motor, but American practice
works them from an independent motor. It is certainly
undesirable to multiply clutches. This improvement
has been more or less forced on us by the increasing
size and weight of doors required for the newer and larger
ovens. The Collin plant at Middlesbrough has an
arrangement on the hearth side, the travel of the quench-
ing hood and the lifting of the doors being done by a
special electrically-driven machine operated from the
hearth level.

Mechanical ascension pipe cleaners have been intro-
duced lately with some success, and also the split ascen-
sion pipe. The latter is in use at Conset-t. The pipe is
made in two halves, longitudinally, held together by
bolts passing through lugs. Hinges and pins may be
used on one side. The faces have to be machined, but
a narrow fillet is enough for the joint. When the two
sides are separated, the pipe can be cleaned in a few
minutes.

* From a paper read before the Society of Chemical
Industry.