April 19, 1918.

THE COLLIERY GUARDIAN.

795

plant is that it has been so designed that, should it
subsequently be found necessary to wash the coal before
coking—either owing to deterioration in quality or
inferior coals having to be resorted to—washing appa-
ratus can be added, and plant converted into a proper
coal washery with drainage bunkers. Each compartment
of the storage bunker is fitted with drainage arrangements
for this purpose, and also for draining any wet crushed
coal that may be purchased instead of the dry coal.

The 600-tons crushed coal bunker (fig. 3) is fitted
with a series of shoots and slides on the underside for

series where the benzol is extracted from the gas by the
creosote or wash-oil constantly circulated through the
scrubbers. The gas then passes on to the burners under
the ovens, for combustion in the heating flues, the coal
being carbonised by the combustion of its own gases,
whilst the benzolised wash-oil is collected in a low-level
tank From this it is pumped to an overhead feed tank,
which serves a continuous crude benzol still, in which
the benzol vapours are driven off and condensed by
means of a constant circulation of cool water in a con-
denser. In the base of this condenser is a separating

MINING INSTITUTE OF SCOTLAND.

At the meeting of the Mining Institute of Scotland,
held on April 6 in Glasgow, the following discussion
took place on the paper contributed by the president,
Mr. D. M. Mowat, on

Capital Charges Considered Along With Current Expenses.

Mr. Archibald Russell (Bacares) wrote that the
equipment of a colliery was usually more easily decided,
owing to more data being available, than a field of

■FLAN.

PART FRONT AND PART SECTIONAL, ELEVATION,

Fig. 3.

Fig. 2.



filling, at one operation, the three hoppers of the
electrically-drivvn coal charging lorry which travels on
the top of the ovens and loads, also in one operation,
each oven with coal as required. The coal is simul-
taneously levelled in the oven by means of the mechanical
leveller attached to the coke ram. A feature of this
installation is, that the coke is not handled by manual
labour from the moment of discharge from the ovens
until it is placed into the blastfurnace charging barrows,
being pushed out of the ovens by an electrically-driven
coke ram, through a mechanical quencher, on to a
sloping bench (fig. 5). It is then delivered into a
conveyor placed at the foot, wfiich in turn delivers it
to the coke screens and thence direct to the coke
storage bunkers behind the blastfurnaces. From these
bunkers it is drawn through the bottom doors into the
charging barrows, ready for taking
up the hoist and tipping into the
furnace.

The by-product plant is designed
on the latest Otto system of direct
recovery. The gas given off in the
carbonising of the coal in the ovens
passes up the ascension pipes into
the hydraulic main common to all
the ovens, then along the gas-suction
main, through the air coolers' for
regulating the temperature of the
gas, thence it traverses the tar sprays,
where the tar‘ is extracted, and, sub-

sequently passes into the saturator

where the ammonia in the gas combines with the sul-
phuric acid in the bath, and sulphate of ammonia is
formed. The exhauster then draws the hot gas through
one of the Otto patent naphthalene scrubbers, where,
by means of sprays of water acting counter-current
to the gas, it is chilled suddenly, causing the
naphthalene to be precipitated and carried away
with the water into a collecting tank, where it is separ-
ated and recovered. Aftei’ leaving the exhauster the
gas is then forced through two benzol scrubbers in

| niuB stebl cover for gerriHg

STAUe,

OPENINGS IN DtWI £ ON WALLS FORGArWrli

DISCHARGE CONVEYORS*

□ND .SECTIONAL ELEVATION.

Fig. 4.



chamber in which the steam coming over from the still
with the benzol vapour and condensing into water is
automatically separated from the benzol, after which
the latter is decanted and conveyed into storage tanks
ready for delivery to purchasers. With these regenera-
tive Otto ovens there is stated to be more than fifty
per cent, of surplus gas over and above that required
for the heating of the coke ovens ; and this surplus at
the Thornaby Ironworks is utilised for firing ore kilns'
and steam boilers.

other mineral where, although a sufficient quantity of
ore is proved to warrant expenditure or sinking shafts,
the possibilities were to a great extent unknown. Mr.
Mowat did not mention one important point, namely,
that unless in exceptional cases it was always advisable,
from a financial point of view, that the profit be won
in as short a space of time as possible, although to
some investors a longer life might appeal more strongly.
In these days, when such large amounts were spent in
sinking and equipment, the interest on capital was a
very important matter. There was no doubt that the
saving in fixed charges was a great feature in deter-
mining increased output, whilst pumping was in itself
an important factor. Each case must be treated on
its own merits, and certainly in coal mining the pro-
position was complicated by conditions of leases, as the
field was not usually purchased outright. A somewhat
allied problem was the relative advantage of centralis-
ing or concentrating output from a large coal field by
two shafts, or sinking, say, three pairs of shafts suit-
ably placed and conveying output to a central cleaning
and washing plant. In the past, when workings were
comparatively shallow, this was the best scheme in
many cases. Now, however, with the large expendi-
ture involved in sinking, especially through wet strata,
the problem was not so easy to solve, whilst the ton-
nage locked up in shaft pillars at a depth of 2,000 ft.
was considerable.

Mr. James Hamilton (Glasgow) said that on the
general question dealt with by the author he con-
sidered that provision should be made for doing every-
thing essential at the outset in the equipment of a
colliery, because experience had shown that such a
provision was more satisfactory in the end. Members
would know of instances where a judicious expenditure
in the early stages of operations had been repaid many
times over.

Mr. Robert McLaren said that in starting a colliery
first of all one had to ascertain the quantity of minerals
to be worked, the probable life of the colliery, and the