880

THE COLLIERY GUARDIAN.

October 29, 1915.

CURRENT SCIENCE

Power in the Montana Copper Region.

Among ithe most gigantic undertakings in the world
is the elaborate system by wrhich the Montana
copper mines are supplied with power. The power is
derived in the first instance from the Great Falls and
other water sources on the Missouri, Madison, Big Hole,
and Clark’s Fork rivers, the reservoirs in service and
under construction having a total area of nearly 34,000
acres, and the total capacity of 23,275,000,000 cu. ft. The
transmission system embraces 1,463 miles of lines,
ranging up to 100,000 volts. Butte, the largest power-
conserving centre in the state, is supplied by four sets
of transmission lines from independent sources, all of
which are in duplicate. At the Butte sub-station, the
present equipment comprises four 3,000 kw. banka of
single-phase transformers, all windings delta-connected,
and arranged to step down from 102,000 volts to 2,500
volts. From the sub-station a high pressure line extends
22 miles to Anaconda for the huge Washoe smelter.

The maximum load on the system at present is
61,000 kw., and the output in kilowatt hours for 1914
was 402,663,369, the load factor being 75 per cent.;
65 per cent, of this power is used for mining and
smelting. A power factor of nearly unity is maintained
on the generating plant switchboards, since the line
capacity about neutralises the lagging characteristics of
the induction motor load, while the synchronous
machines at the Anaconda compressor plant and else-
where can be adjusted to preserve the balance closely.

This compressor plant supplies air at 90 lb. gauge
pressure, for operating the hoists of a number of mines
in the neighbourhood. Westinghouse, 1,200-horse
power, 2,300 volt, synchronous motors, are direct con-
nected to three Nordberg constant speed, variable
capacity, air compressors, with cylinders 30 in. and
50 in. by 48 in. stroke, and five of the constant capacity
type, each having a capacity at 75 revolutions per
minute and normal pressure of 7,500 cu. ft. per minute.
With fields over-excited at 120 amps., direct current,
these machines are ordinarily operated at unity power
factor. The air is stored as compressed in a series of
huge steel tanks 10 ft. in diameter and 57 ft. in height.
Part of these receivers are located at the bottom of the
hill, while 200 ft. above them an open water tank is
connected to the system, so that a constant pressure of
about 90 lb. is maintained on the receivers, the water
flowing down to take the place of the air, as the latter
is used for hoisting. Excess air is discharged by an
automatic relief valve into the “ mine system,” from
which drills and other apparatus are operated. Each
compressor handles 7,500 cu. ft. of free air per minute.

The mine hoists, operated by compressed air instead
of steam, average 2,000 to 3,500-horse power on nominal
rating. The present compressor plant is supplying 21
Nordberg hoists, the majority of which have air cylinders
23 in. and 23 in. by 60 in. stroke. In addition, the plant
furnishes air to the mine drill system through a 14-in.
pipe. As successive workings in the mines are
exhausted of ore they are back filled for support and for
disposal of the waste rock. The lowering of this material
into the mines allows the hoist cylinders to be used in
compressing air for return to the system, thus contri-
buting to its net efficiency.

Conserving the Heat Value of Coal.

According to the Queensland Government Mining
Journal, the name Thermosod, meaning “ heat saver,”
has been given to a furnace and boiler of new design,
which has shown itself capable of extracting very remark-
able heat values from the lowest grades of coal. Mr.
L. F. Chew, a Denver man, has devoted the past six-
years to the development of the device, during which
time a number of machines have been built and put
through a long series of tests. Essentially, the aim of
Mr. Chew has been to produce a power plant in which
the rate of combustion is in nearly exact proportion to
the load carried. This he does by insulating the heat
generator or furnace, and heat absorber or boiler, from
each other, confining the heat content of each separately,
and putting the generator in response to the absorber by
automatic means, in such a manner that combustion
cannot take place except when steam is first used, and
then only to transfer from the fuel to the water the
exact amount of heat required to replace the steam
used.

In seeking this end, it was necessary, first, to accom-
plish complete combustion, and, second, complete
absorption, as nearly as possible. The first of these has
been so fully attained that the poorest slack and screen-
ings from the smokiest bituminous coals are burned abso-
lutely without smoke and without “ ashes ” of the ordi-
nary sort. No chimney is required, only an outlet pipe
being provided for the burnt gases. When the furnace
is in operation, nothing can be seen coming from this
except a faint dust, which, if collected for a time, is
found to be a grey powder, the actual ash content of the
coal. As to how nearly the second of these aims has
been accomplished, it is perhaps enough to state that the
products of combustion leave the boiler at a temperature
of 200 or 300 degs. below that of the steam delivered,
instead of 200 or 300 degs. above it, as with other boilers.

On the generator side of the system, the principle is
that of converting the fuel into combustible gas with a
measured volume of air, then burning the gas with a
measured volume of air, in order to give to the products
of combustion the highest initial temperature. The two
volumes of air are maintained at a constant ratio, auto-
matically, regardless of the rate of supply, so that
analyses of the flue gases show carbon dioxide ranging
close to 17 per cent, in average service, which is nearly
the theoretical limit. A constant mass of fuel is auto-
matically maintained, at uniform temperature, sufficient-
in mass to carry the peak load, its heat content is con-
fined, and the air supply is made to equal the demand

AND TECHNOLOGY.

for heat at each instant. No air can find entrance to
the fuel, except as purposely pumped in, and substanti-
ally no heat can escape from the fuel, except as pur-
posely transferred to the water to produce steam.

On the absorber side of the system, the principle is
that of bringing the products of combustion into contact
with progressively cooler surfaces, in order to give to
them the lowest final temperature. Just sufficient water
is supplied to the boiler to absorb the heat supplied, the
rate of feed being determined by the temperature of the
steam delivered. A governor of simple construction is
easily adjusted for any temperature, so that steam may
be delivered at any desired degree of superheat, regard-
less of the pressure. Also, the pressure governor may
be instantly adjusted to maintain steam at any desired
working pressure. The supply of fuel is placed in a
hopper, from which it is automatically drawn, as needed,
depending on the depth of the mass in the retort.

The result of this system is an unlimited supply of
steam at uniform pressure and temperature, available at
a moment’s notice, with no appreciable combustion of
fuel when there is no demand for steam, and with an
efficiency about 80 per cent, under varying demand, from
light load to full load. This result is the more impor-
tant, since it is obtained with fuel which is at many
mines an unsaleable product.

Coal Tar Products Used in Making Explosives.

Mr. C. G. Storm, in Technical Paper 89 issued by the
U.S. Bureau of Mines, says :—Mononitrobenzene, com-
monly known as “ oil of mirbane,” is little used in the
explosives industry because of its volatility, although it
is sometimes used as a minor constituent of certain low-
freezing dynamites and other types of explosives. It is
used much more extensively in soaps, lubricating greases,
etc., mainly for the purpose of imparting a more or less
agreeable odour. Furthermore, it forms an intermediate
product in the preparation of aniline and its many
derivatives.

Among the aniline derivatives of importance are
tetranitroaniline and tetranitromethylaniline, both of
which have in the past few years assumed prominence
as detonating explosives for projectiles, mines, and
torpedoes. Many other derivatives of aniline have been
found to be applicable as stabilisers or as gelatinising
agents in nitrocellulose smokeless powders. Among such
substances are methyl or ethyl phenyl urea, phenyl
benzyl ether, phenylacetanilide, formanilide, and
diphenylamine. The latter is, however, the only one
which has been used in this country.

The nitrotoluenes are more extensively used in the
explosives industry than any other nitro-substitution com-
pounds, being employed chiefly for sensitising certain
types of ammonium-nitrate explosives and for lowering
the freezing point of the low-freezing dynamites.

In the absence of exact statistics, a rough estimate
places the amount of the various grades of nitrotoluenes
used in the low-freezing dynamites manufactured in the
United States in 1913 at about 2,000,0001b., while in the
“ permissible ” explosives employed in coal mining pro-
bably 250,0001b. of the same materials were used during
the same year.

Pure crystalline trinitrotoluene has proved one of the
most efficient explosives for use in explosive shells,
torpedoes, and mines, and is extensively used by almost
every important military service, including that of
the United States. In recent years it has also come
into use as a substitute for a large proportion of the
mercury fulminate in detonators (blasting caps) and as
a charge for detonating fuse.

The nitronaphthalenes are used to some extent, chiefly
as sensitisers, in the ‘‘short-flame ” permissible explo-
sives of the ammonium-nitrate type. Certain deriva-
tives of these compounds, the alkaline salts of nitro-
naphthalene sulphonic acids, produce, when mixed with
sodium nitrate and other ingredients, explosives suitable
for coal mining.

Picric acid (trinitrophenol) and certain of the picrates
are highly important as military shell explosives; the
acid is also employed in surgical dressings for burns and
wounds. The manufacture of these compounds depends
entirely on phenol (carbolic acid) as a raw material.

The possibilities of the use of the nitro-derivatives of
coal tar products in explosives are far greater than is
indicated by the above brief summary. Much investi-
gative work on such compounds is being carried on in
the United States, as well as other places abroad, from
which important developments in the explosives art may
result. The U.S. Bureau of Mines has instituted a
systematic research into the preparations and properties
of these nitro-substitution compounds, with a view to
studying their possibilities in the explosives industry.

The Production and Manufacture of Oils.

The Journal of the Royal Society of Arts lias now
published the Cantor lectures recently delivered by Dr.
F. M. Perkin on the production and manufacture of oils.
Dealing in the first place with petroleum, the variation
in quality of mineral oils was described, and the methods
of obtaining crude oil were explained. Crude oil is
fractionated by distillation, and there has been a com-
plete reversal in the commercial value of the various
fractions. Petrol, at one time almost valueless in com-
parison with kerosene, has now assumed the premier
position, kerosene being almost a drug in the market by
comparison with the fuel oil used in motor engines and
oil engines of the Diesel type. In dealing with the shale
oil industry, Dr. Perkin recalled the early experiments
of Dr. James Young on the distillation of coal. In 1850
he took out a patent for obtaining paraffin oil from the
Boghead coal of West Lothian, leading to the establish-
ment of the Bathgate Oil Works. The exhaustion, in
about 12 years, of the Torbanehill shale deposits then
led to the working of the shales of Linlithgow and Mid-
Lothian, and, on the expiry of Young’s patents in 1864,

there was a great expansion in the Scottish oil industry,
which, after some vicissitudes, has successfully outlived
the competition of petroleum. Although there are now
only seven oil companies in Scotland, the output of shale
oil has increased, over 3,000,000 tons of shale being now
treated annually, with the production of over 70,000,000
gals, of oil, yielding products exceeding J-2,000,000 in
annual value. The method of manufacture of shale oil
products is described in considerable detail. It is pointed
out that shale itself does not contain oil as such, but has
a constituent called kerogen, which yields oil on distil-
lation. Dr. Perkin then passes to low temperature car-
bonisation, examples of which are found in the Coalite,
Del Monte, and Tarless Fuel Syndicate processes, each
of which is discussed in turn. Finally, Dr. Perkin
described the process of “ cracking,” the history of
which is traced from the early experiments of Vohl in
1850 to the present day. The chemistry of “ cracking ”
is described in detail, and the various processes are dis-
cussed. The difficulties encountered in “ cracking ” oils
have been numerous, but gradually they have been over-
come. The production of light oils by ‘‘ cracking,” how-
ever, does not end the business, for these always require
some amount of refining before they can be used success-
fully in internal combustion engines.

Determining the Steam Consumption of a Twin-Cylinder
Winding Engine.

The twin-cylinder engine has latterly been growing in
popularity for coal winding, being simpler in construc-
tion than the compound, and consuming very little more
steam when used in combination with a superheater.
Trials have recently been made by the Dortmund Boiler
Inspection Association with an engine of this kind, at the
Concordia Collinery, Oberhausen, having the following
dimensions :—Cylinder diameter, 37 in.; stroke, 70 in.;
and diameter of driving pulley, 23 ft. The engine duty
is to raise a useful load of 96 cwt. in eight tubs from a
depth of 450 yds., at a minimum velocity of 50 ft. per
second, with a steam pressure of 103-132 lb. (superheat,
300 degs. Cent.) at the admission valve, both with free
exhaust, and when connected with an exhaust steam
plant producing a back pressure of 4| lb. The tappet
valve gear is controlled by a speed governor and a steam
operated device, so that the admission is automatically
adjusted according to the load for the time being. The
driver, however, is not deprived of control, and can
even reverse the engine when the governors are in the
highest position. The split driving pulley has a wide
grooved elm rim for the rope, which is lapped several
times round the pulley. A hand and steam brake arc
provided, the latter having a pressure regulator. Thu
speed controller of the overwinding device shuts off
steam in the final period of the wind, so that the cage
velocity decreases progressively as it nears the bank.
The following results were obtained in a five hours run :
Mean steam pressure at engine, 140 1b.; mean steam
temperature at engine, 253 degs. Cent. (290 degs. in
engine room main); total condensation, 4’16 tons, or
2-83 tons per hour; duration of a wind, 46 seconds, or,
including deckings, two minutes; mean rope velocity,
29| ft. per second; total weight lifted, 1,234 tons, tare
519 tons, net load, 714 tons; effective shaft horse-power,
223-3; steam consumption per shaft horse-power hour,
281b. (guaranteed steam consumption, 36| lb.); steam
consumption of brake and reversing gear, 2-9 per cent, of
total consumption.

THE GERMAN AND AUSTRIAN COAL
AND IRON TRADES.

We give below further extracts from German
periodicals that have reached us, showing the course of
the coal and iron trades in Germany and Austria :—

The Brown Coal Market of Mid-Germany in September.

The Brown Coal Industry Association reports that
during September business was generally active, and
on a par with the previous month. Owing to the pro-
gressive scarcity of labour, the output in some districts
showed a decrease. In the latter half of the month
the shortage of railway wagons hampered delivery con-
siderably. In spite of overtime and the employment
of female labour, it was impossible in many instances
to meet the demand. Wages were again raised, and
war bonuses granted to meet the increased cost of
living.

Steel Union Report for September.

The total deliveries in weight of raw steel amounted to
246,840 tons (250,080 tons in August), 67,220 tons being
semi-manufactured products, 117,426 tons railway
superstructural material, and 62,194 tons sections.

German Pig Iron Production in September.

The Association of German Iron and Steel Makers
reports that the output of pig iron in the German
Customs Union in September amounted to 1,033,078
tons (1,056,610 tons in August), or 34,436 tons (33,890
tons), per working day. Of this total, 188,121 tons were
foundry pig, 17,699 tons Bessemer pig, 638,431 tons
basic pig, 170,602 tons steel-iron and spegeleisen, and
18,225 tons puddling pig. Rhenish-Westphalia pro-
duced 462,393 tons, Siegerland, Wetzlar and Hesse -
Nassau, 66,115 tons; Silesia, 64,559 tons: North
Germany, 20,262 tons; Mid-Germany, 32,261 tons:
South Germany and Thuringia, 18,658 tons; the Saar
district, 69,418 tons; Lothringen, 159,213 tons; and
Luxemburg, 140,199 tons.

Increased Screw Prices in Germany.

Prices for most grades of screws and nuts have l>een
advanced from 1 to 4 per cent., by reducing the
discounts.

New Mining Leases.

The A. G. Vereinigte Stahlwerk van der Zyphen und
Wissener Eisenhutten has acquired a mining property
with an area of 109,937 sq. metres, at Hovel and Nachen
(Altenkirchen), to be worked for iron and copper ores.