January 30, 1914.

THE OOELlEBt GUAEDIAU'.

245

These advantages, together with the greater ease in
handling and opening out the smaller engines for
examination or repairs, makes their adoption more
serviceable for colliery work. For a colliery requiring
the provision for a maximum of, say, 3,000-horse power,
it will probably be found preferable to adopt 10 300-
horse power units, or six 500-horse power units rather
than three 1,000-horse power or larger units, but for
installations of 10,000-horse power or over the unit may
be increased to 1,000-horse power with advantage. The
adoption of a horizontal form appears to offer more
advantages than a vertical form.

The economical limit of size of the cylinder of a gas
engine may be put at about 25 in. diameter. Beyond
that the strength of the engine parts must be increased
to a degree out of proportion to the horse-power
developed. For the smaller sizes of the engines
mentioned above—viz.: 300 B.H.P. to 500 B.H.P.—it
would be better to adopt two cylinders in each engine,
arranged in tandem, giving one impulse per revolution
of the crank as an average of the two four-cycle
cylinders; and the 1,000-horse power engines should
have two pairs of tandem cylinders giving two impulses
per revolution.

A point of considerable importance to gas engine
users, and which, unfortunately, has not so far been
appreciated, is the standardisation of dimensions and
quality of material used in the building of gas engines.
This difficulty might easily be removed, if, recognising
the help it would be to colliery owners, this institute
could appoint a committee to consider the best type and
most suitable construction of gas engines for use in
collieries, and prepare a specification for the materials
used and a scale of dimensions of the important parts,
with rules for testing—all on broad and safe lines. A
board of control might be appointed, which would
arrange and maintain the necessary organisation for the
inspection of engines built by the makers who were
willing to work to this specification, and they would
appoint competent engineers to inspect the engines at
the makers’ works and certify that they had been built
in accordance with the specification and rules for testing
as laid down. A certificate of quality and efficiency
would be granted with each approved engine, and such
certificate would be handed to the buyer when the
engine was sold. A register of approved engines sold
might be kept for reference, and the history of such
engines written up, as in the case of Lloyd’s register of
ships. After deciding upon the engine most suited to
the purpose, the colliery engineer should give still more
careful consideration to the gas arrangements, especially
as it is necessary to deal with two gases so widely
different in their quality as coke-oven gas, with a
thermal value of 500 British thermal units, and a
producer-gas with a thermal value of 150 British
thermal units, or less.

For use in colliery gas engines, regularity in the
composition of the gas is more important than its high
thermal value, and it would be necessary either to
allocate a separate power system to each of these gases,
or to blend them in fixed proportions by means of
gasometers. A colliery which equips itself to generate
power in large quantities for sale as an industrial
investment would probably adopt the latter course. A
battery of 100 modern regenerative coke ovens will
carbonise approximately 150.000 tons of coal per annum,
with a gross yield of 10,000 cubic feet of gas per ton,
which would allow about 5,000 cubic feet per ton avail-
able for the generation of power. If the mean lower
calorific value be taken as 400 B.T.U. per cubic foot,
this would develop approximately 5,000-horse power
continuously during a year of 300 working days. This
would require augmenting by 15,000 continuous horse-
power generated by a mixture of slack, with as much
batt and other colliery waste as may be available, all of
which would be gasified in a power-producer. The
average thermal value of this mixed gas would be about
225 B.T.U. Gas generated from colliery waste will
contain more sulphur than that obtained from good
coal, owing to the decomposition of the pyrites which is
always present in the waste ; therefore gas obtained
from this source and also from coke ovens should be
purified from sulphur (the recovery of which will always
pay for the operation).

It is fair to assume that the value of the coke and
ammonium sulphate will pay for the cost of coking the
coal and allow a sufficient margin of profit on that
operation without placing a specific value on the
recovered gases. With such a combination the total
cost of producing power, harnessing it, and converting it
into electrical current, including wages, stores, repairs,
and all dead charges, with an allowance for the added
fuel as shown below, should result in the generation of
electric power at the exceedingly low case of approxi-
mately 018 of a penny per B.O.T. unit. Assuming that
only 100 tons per day of batt, bituminous shale, and
other waste is available, and that its average ash
contents is 40 per cent., this would produce a gas
volume equivalent to that from 60 tons of coal, and this
100 tons of refuse may be considered to have a value
of Is. per ton. The additional fuel required for the
balance of the 15,000-horse power would have to be
supplied by using 108 tons per day of slack at say 5s.
per ton, making a daily cost of £27 5s. for the slack,
and £5 for the waste, to produce the required 15,000-horse
power per hour, which added to the 5,000-horse power
per hour from the coke oven gases would be equivalent
to the production of 20,000-horse power per hour with
an actual expenditure in fuel of 0‘016 of a penny per
horse power per hour, an amount which ought to be
practically extinguished by the profit on the additional
1,500 tons of ammonium-sulphate recovered from the
solid fuel and which would have a market value of
£18,000 compared with the value of £9,675 placed upon
the fuel and waste from which it would be extracted.

The cost of converting the gas into power by means
of gas engines and transforming it into electrical

energy should be approximately (without taking into
account the additional profit on the ammonium sulphate)
as follows :—

Estimated ost of Producing 20,000-horse power per
Hour by Gas Engines and Transforming it into
Electrical Energy.

Per B.O.T. unit.

d.

Coal................................. 0016

Oil, &c.............................. 0-01

Wages ............................... 0 04

Repairs .............................. 008

Standing charges including interest and
depreciation ...................... 0 02

Management and sundry expenses ...... 0 02

0186

It does not require much argument to prove that the
cost of conveying this energy through electric leads is
less than the cost of carrying an equivalent of fuel,
especially when solid fuel must be transported for the
whole of the power generated. These considerations
appear to establish the unassailable position which a
colliery occupies for supplying electric energy to outside
sources of consumption. The advantage to a colliery
owner can be summed up by saying that his fuel cost
can be reduced to one-tenth of that at any public
generating works.

The ambitions at the majority of collieries may not
reach quite so far as this, but the advantage of utilising
the products of coking coal has ceased to be a debatable
subject, the only question of interest at the present
time being a consideration of the most satisfactory way
of doing this, having regard to the efficiency and
simplicity of the plant and the capital expenditure it
requires.

The system adopted for recovering the ammonia and
liquid hydrocarbons, leaves the gas in a suitable state
for use in gas engines. The heating value of this gas is
subject to rather high variations under its present
method of production. This and the unusually high
percentage of hydrogen which it contains necessitates
special arrangements for its use. The excess of
hydrogen means sensitiveness to pre-ignition by com-
pression, and when gas so rich in hydrogen as this is
mixed with the full quantity of air required for its
complete combustion, the safety point of compression
for the mixture would probably be reached at a little
under 100 lb. per square inch. Under such conditions
there would be an appreciable loss of power. The
danger of pre-ignition has been most successfully over-
come by Dr. Dugald Clerk, F.B.S., in a very simple
arrangement, which consists in introducing into the air-
inlet pipe, at atmospheric pressure, about 10 to 20 per
cent, by volume of cooled exhaust gases from the
exhaust chamber of the engine. This reduces the
amount of free oxygen, replacing an equivalent of air
by a mixture of carbonic acid and nitrogen, which has
the effect of entirely suppressing all pre-ignition, and
the inert gas added reduces the inflammability both by
diminishing the oxygen contents and by the diluting
effect of the carbonic acid gas and nitrogen without
reducing the total mass of the charge. With this device,
considerable over-loads are quite permissible without
danger. Nevertheless, a gas engine for this purpose
should be of very rigid construction and great strength,
built from as simple a design as possible, but with
ample provision for scavenging. Where small units of
power are required, say up to 1,000-brake horse
power, the simplest, cheapest, and most efficient
way of generating gas is by a suction producer.
The “ Cambridge ” suction-gas-producer, which has
recently been put upon the market, works well with
bituminous coal as well as with anthracite or coke, and
it is especially serviceable with waste fuels of any
description. The producer works are on the down-
draught principle. The generator, which is rectangular
in shape, is provided with an air jacket and fitted with
auxiliary air ports. When the plant is working, warm
air is drawn from the jacket to the top of the producer.
The heat at this part of the producer disengages
volatile products—acting, in fact, almost like a coke
oven—‘and these are drawn down through the fuel.
The auxiliary air ports, which are placed at various
distances down the generator, can be opened or closed
at will, and these also draw warm air from the jacket.
The air entering at these points creates a secondary
combustion zone, having a very high temperature, and
the tarry vapours in the gas given off in the distilling
zone above are drawn through an intensely hot zone,
where they undergo decomposition and become con-
verted into fixed gases, which go to enrich the main gas.
The fuel below the auxiliary air ports is in a completely
carbonised form, and at this point the reactions which
take place are exactly the same as those which take
place in the ordinary suction producer—that is, the
carbon after burning to carbon dioxide passes through
an excess of incandescent carbon which reduces it to
carbon monoxide, which is the chief constituent of the
gas. A central air pipe is also used to increase the
temperature at the centre of the fire. The generating
base is provided with rotating firebars of special
design to crush clinker or large mineral residue. The
cooler which is placed between the generator and the
scrubbers, supplies the necessary steam, which is
admitted with the air into the apparatus. The gas is
led from the generator to coke scrubbers, where it is
further washed and cooled, finally passing through saw-
dust scrubbers which dry it before passing it to the
engine. The plant has been designed to use almost any
class of bituminous fuel which is reasonably non-
caking, and is made in units up to 1,000-horse power.

In larger power installations a pressure plant, such as
the Mond gas producer should be adopted to use waste
colliery fuel to its full advantage, and wlu n the power
required exceeds 1,500 brake-horse power the profitable
recovery of ammonia and other by-products adds

another advantage to the adoption of a gas process for
generating colliery power.

Of the several means now available to a colliery
engineer for reducing the cost of his fuel consumption
both by the generation of power from waste products
and by the adoption of more perfect machines for
utilising his source of energy, probably the most
interesting problem for his consideration at the present
time is the most efficient means of utilising the gases
produced in regenerative coke-ovens. The advantages
obtained by employing gas engines for developing this
power have now been demonstrated by many colliery
owners, and such installations as those at Powell Duffryn
and at Wharncliffe Silkstone Colliery have shown the
possibilities in this direction.

The paper contains a description of some suitable
types of gas engine.

MlWma AM OTHER MTES.

A meeting of the honorary committee of experts in
connection with the Shipping, Engineering and Machinery
Exhibition, to be held at Olympia this year, was held at the
Connaught Rooms, Queen-street, London, on Thursday of
last week. It was proposed that Sir Archibald Denny, Bart,
should be asked to become chairman of the committee.
Mr. A. Boyle, Consultative Branch of the Board of Trade,
was elected vice-chairman. Mr. Charles H. Luke, A.M.S.E.,
was unanimously elected secretary of the committee.

At a recent conference of representatives of a number of
Liverpool associations to consider proposed new strike
expenses clauses in bills of lading, it was unanimousiy
resolved :—1. That the clauses proposed for insertion by the
International Shipping Federation are highly objectionable,
and can under no circumstances be accepted. 2. That each
association do circularise its members, urging them to
protect their interests by instructing their bankers not to
accept any draft to which a bill of lading containing the
said objectionable clauses is attached, and to notify their
various correspondents abroad to the same effect. It was
also decided that each association should notify their
kindred London, provincial, and Continental associations of
the passing of these resolutions.

It is understood that the Navy. Department of the United
States Government intends constructingall future warships
with a view to the exclusive use of oil fuel, and the Govern-
ment are now negotiating for the control of oil lands. The
Standard Oil Trust owns most of the oil-bearing land
in the United States, but fresh wells have been discovered
*n Oklahoma and several other parts of the Union, which,
although at present operated by the Trust, can be acquired
by the Government.

An alcohol motor fuel committee has been formed by the
Imperial Motor Transport Council, in accordance with the
unanimous desire of upwards of 200 delegates from all parts
of the empire, who attended the Imperial Motor Transport
conference in July last. Its meetings will be held at the
Royal Automobile Club. The members include Mr. Bertram
Blount, F.I.C., consulting chemist to the Crown Agents for
the Colonies ; Mr. J. Sidney Critchley, M.I.Mech.E., M.I.A.E.,
president of the Institution of Automobile Engineers; Mr.
S. F. Edge, president of the Society of Motor Manufacturers
and Traders; Mr. S. Glover, M.Inst.C.E., F.R.M.S., gas
engineer to the Corporation of St. Helens ; Dr. H. S. Hele-
Shaw, D.Sc., LL.D., F.R.S.; Prof. Vivian B. Lewes, F.I.C.*
F.C.S., Greenwich; Dr. W. R. Ormandy, D.Sc., M.I.A.E.;
Sir BovertonRedwood, Bart., D.Sc.; and Mr. Horace Wyatt,
B A. (hon. secretary.)

The late Mr. Joseph Reay, of Gateshead, fitter to the
Pelton Collieries, has left estate valued at £147,057.

Messrs. Humphreys-Davies and Co., of 5, Laurence
Pountney-lane, Cannon-street, London, E.C., inform us that
they have entirely severed their connection with the
Machinery Users’ Association (Incorporated), and no
longer act as its surveyors or are in any way responsible for
its proceedings or management. The firm have accepted
the appointment of surveyors to the Manufacturers’ Associa-
tion Limited, which has recently been formed for the
purpose of advising users of machinery upon all questions
connected with the rating of tenants’ machine tools and
assessments upon mills and factory property for imperial
and local purposes.

At an ordinary meeting of the Institution of Civil
Engineers on Tuesday, February 3, at 8 p.m, a paper will
be read on “ The Problem of the Thrust Bearing, ” by Henry
Thornton Newbigin, Assoc.M Inst.C.E.

Hull Coal Exports.- The official return of the exports of
coal from Hull for the week ending Tuesday, January 20
1914, is as follows :—Amsterdam, 1,078 tons ; Antwerp, 308 ;
Alexandria, 2,618; Abo, 1,003; Ahus, 1,635; Boulogne,
1,417 ; Bordeaux, 2,144 ; Bremen, 4,163 ; Copenhagen, 542 ;
Christiania, 3,273 ; Dieppe, 1,442; Drontheim, 104; Gothen-
burg, 198; Ghent, 1,056; Hamburg, 5,173; Harlingen,
1,007; Harburg, 2,360; Horten, 245 ; Libau, 849; Naples,
1,001; Nyborg, 350; Norrkoping, 272; Port Said, 3,624;
Rouen, 6,970; Rendsburg, 150; Rotterdam, 352; Stock-
holm, 302; Stettin, 2,964 ; Reval, 6,004; Riga, 2,566;
Sperzin, 2,363; Trieste, 147 ; Tonsberg, 684 ; Warberg, 942;
Wyk, 85 ; Ystad, 13,113—total, 60,934 tons. Corresponding
period January 1913, total 70,869 tons.