December 15, 1916.

THE COLLIERY GUARDIAN.

1163

to be treated with a large quantity of water, which would
probably have to be boiled out. That meant the use of
a great deal more coal, and it was this fact probably
which had held back the bulk of the experiments which
a lot of people would like to make in preparing the clays,
as they got them from the deep mines, into the condition
in which they used to get them just for the asking by
digging holes in their own back yards. Certainly it was
that particular question which had caused people to con-
sider that Stourbridge clay was not nearly as good as it
used to be. They had exhausted the outcrop, and were
now getting clay which had to be treated in order to
bring it up to the original standard.

COMBINED COAL AND GAS FIRING.

An interesting example of the mechanical firing of
boiler furnaces with gas and coal is afforded by an instal-
lation in operation at the South Staffordshire Mond Gas
(Power and Heating) Company’s Works, Dudley Port,
Tipton. The plant comprises eight producers, each
capable of gasifying 20 tons of fuel per day of 24 hours,
and generating sufficient gas to drive gas engines of

1
.t

7

$ ‘ ■

9

B8 -X

’ Sfc. V ■ ■■ ■ :•

Fig. 1.—Boiler Plant with Combined Coal and Gas Firing.



after superheating, 332 degs. Cent.; test of flue gases—
CO2 13 per cent., O2 5 per cent.; volume of air supplied
per 100 cu. ft. of gas burnt, 158'6 cu. ft.; losses to
chimney stack (after superheaters and economisers), 11'4
per cent.

The steam from the boilers is led to the various parts
of the plant by ring mains, so that each steam-driven
machine can be supplied through at least two separate
lines of main.

The Lancashire bailers measure 9 ft. by 30 ft., are
fitted with extended flues, and work at 120 lb. pressure.
They aire also fitted with superheaters, the gases dis-
charging into an economiser containing 4,000 sq. ft. of
heating surface. The total grate area of each boiler is
about 57 sq. ft.

A guarantee was given by the stoker makers that the
evaporation of each boiler should not be less than
12,0001b. of water per hour, with an overload evapora-
tion of 15,0001b. per hour, when desired, for short
periods, and an efficiency of 72 per cent, was also con-
ceded. This has not only been borne out in the tests
carried on by the staff of the South Staffordshire Mond
Gas Company, but also appreciably exceeded. For
instance, an overload evaporation of 17,0001b. of water



MINING INSTITUTE OF SCOTLAND.

A meeting of the Mining Institute of Scotland was
held on Saturday, 9th inst., in the Royal Technical
College, Glasgow, Mr. D. M. Mowat, the president of
the institute, occupying the chair. There was a parti-
cularly large attendance of members.

New Members.

The following gentlemen were admitted to member-
ship :—Messrs. Frank Owen, mining superintendent,
Dishergarh, Bengal, India; George Park, mining engi-
neer, 58, Bath-street, Glasgow; Wm. L. Brown, elec-
trical engineer, Muirhead, Chryston, Glasgow; R. D.
Taylor, civil and mining engineer, Pollokshields,
Glasgow; Robert McCulloch, under-manager, New-
mains, Lanarkshire; and John E. Brown, mining
student, Hamilton.

The linking and Equipment of a Circular Shaft.

Discussion was resumed on the paper read at a
previous meeting of the institute by Mr. James Nisbet
on “ The Sinking and Equipment of a Circular Shaft.”

Mr. James Curley, East Kirkby, Notts, in the course
of a written contribution, said he observed from the
discussion that Mr. G. L. Kerr had never heard of so
small a space between the cages as 6 in.; but he him-
self had had several circular shafts under his charge,
one, in particular, winding from a depth of 766 yds.,
and fitted with two three-deck cages, with two tubs on
each deck, end to end, and running in flexible con-
ductors, three on the outside of each cage, with two
dummy or rubbing ropes between. The cages had 2 in.
wooden rubbers fitted on the inside. The distance
between the rubbers on each cage was 2f in., viz., | in.
clearance between rubber and rubbing rope, If in. rubber
rope, and J in. clearance between rubber rope and rubber
of other cage. When winding coal, the engineer ran
at full speed past the meeting, but, of course, when
raising and lowering men, the speed was a bit reduced,
and at the change of the shift, one going in when the
other was coming out, he had 72 men in the shaft at one
time (36 on each cage). There had never been any
mishap to the cages to cause them to stop for more than
a few minutes. In deep winding, with a high shaft
speed and a large volume of air passing, it was essen-
tial that the sides of the cages should be perforated as
much as possible, so as to lessen the air pressure on the
sides of the cages, and prevent them from colliding at
the meeting. Twisting of the winding rope had to be
guarded against to prevent the (inside) ends of the cages
from striking. In his opinion, there was nothing to
beat flexible conductors of the lock-coil type for deep
shafts, both as regards first cost and smoothness in
running. Besides, the life of a flexible conductor was
equal to that of the rail type. He disagreed with Mr.
Kirkby (East Wemyss) that cages could be run closer
together with rail conductors than with rope guides.
In his opinion, the most practical and economical method
of installing rail conductors was to have the bearers or
buntons fixed in the centre of the shaft—not the sides—
and to use four rails, two on each side of the buriton.

2,000 horse-power continuously. The total capacity of
the present section is thus equal to 16,000 horse-power.

The rail- or waterborne fuel is loaded by hand into
bunkers, and thence fed automatically into two con-
veyors, each having a capacity of 40 tons per hour,
which distribute the fuel Into the storage bunkers over
each set of producers. Each bunker holds 40 tons, i.e.,
sufficient to keep the producer working for two days.

The gas from the producers is thoroughly washed in
mechanical washers, passed through ammonia recovery
and gas cooling towers, purified by large centrifugal
fans, and passed through scrubbers and the meters before
being compressed and sent through the mains for distri-
bution.

Since for each ton of coal gasified more than two tons
of steam have to be supplied with the blast entering the
firegrate of the producer, a considerable amount of
steam has to be provided, although more than half the
total required is obtained from the system of recupera-
tion by circulating water in the Mond producer plant.
The steam for this purpose is raised at a pressure of
120 lb. per sq. in., and after passing through the various
engines and pumps where it does work, the exhaust
steam is collected and mixed with the air supply to the
producers.

It being necessary, for equalising the station load, to
fire with gas alone during part of the day, and to employ
coal in addition during the time when consumers’
demand for gas is high, the Lancashire boilers have
been fitted with Bennis “ Sprinkler ” stokers for this
purpose, as illustrated in fig. 1. The method of com-
bining the two systems of firing can be gathered from
fig. 2, which .shows the gas ducts let into the top flange
of the stoker front, and secured by means of a gastight
joint. The baffler plates, which are situated behind the
front, are arranged with a passage, the outlet being
over the grate; the gas thus passes from the ducts to the
furnace. There are two duets to each flue, i.e., four to
each boiler, each pair containing a breeches pipe placed
immediately behind the hopper, and passing thence to
the ga-s supply, constituting an extremely simple and
satisfactory arrangement. It being essential that air
should have access to the gas, a valve is placed on the
furnace front with an adjustable cover, to regulate the
amount of air supply. The air is conveyed into the fur-
nace through a separate air duct, and does not mix with
the gas until it reaches the inside of the flue, where
ignition takes place.

A test lasting 40 hours with gas firing alone has shown
a heat efficiency, as between calorific value of gas and
heat in steam generated, of 79'1 per cent. Other
interesting figures from this test ar© the following :—
Steam pressure, 841b. per sq. in.; temperature of steam

%-7/Zz
w

I ig. 2.—Sectional Views of Boiler Fitted for Combined Firing.

per hour from each boiler, instead of 15,000 lb. per hour,
was obtained.

Prior to the installation, much inconvenience had
been experienced owing to the fact that steam was
required to be kept both during the night and from
midday Saturday until Monday morning, when it was
desirable that labour duties should stand at a minimum;
but since the introduction of the- combined system of
firing, the desired flexibility has been attained. A
thermal efficiency of 73 per cent, has been obtained
during a six months’ run under all conditions and vari-
ations of load, including times when parts of the plant
were off for cleaning and inspection. The average quan-
tity of water evaporated per boiler per hour for a month’s
run was 14,8801b., during which period the boilers were
fired with slack during the day, and gas-fired during
nights and week-ends.

Grimsby Coal Exports.—The official returns for the week
ending December 8 show that 6,207 tons of coal have been
exported. The total for the corresponding week of last year
was 9,760 tons foreign.

The distance this method required between the cages
was 18 in. That was 6 in. for each rail and shoe, and
6 in. for the steel bunton. He (Mr. Curley) thought
Mr. James Black was on correct lines in expressing him-
self favourable to four guide ropes to each cage, with
two rubbing ropes between for deep shafts. Over two
years a,go he (Mr. Curley) deepened a. shaft from 766 to
916 yds. A distance of 39 yds. was for sump, conductor,
weights, and balance wheel, the winding being from a
depth of 877 yds. The cages were each fitted to run in
four lock-coil conductors, with rubber ropes between,
also lock-coil. The diameter of the conductors was
If in., and these were made of special plough steel, .with
a factor of safety of 6. The weights on the conductors
were six tons. The details in respect of the rope® in the
above shaft were as under : Winding ropes, two, each
1,060 yds. long, lock-coil, 5| in. circumference, weight
(25 1b. per yd.), 11 tons 17 cwt.; breaking strain, 194
tons; net load on rope, 23-8 tons; factor, 8. Conductors,
eight, each 990 yds., 5 in. circumference, lock-coil;
weight (18|lb. per yd.)-, 8'3 tons; on each conductor
cast iron weights of 6 tons; breaking strain, 85 tons;
factor, 6. Rubbing rods or ropes, two, lock-coil, each