126

THE COLLIERY GUARDIAN.

January 19,; 1917.

CURRENT SCIENCE

Pulverised Coal.

In a paper read before the American Society of
Mechanical Engineers, New "York (abstracted in Engi-
neering), Mr. J. E. Muhlfeld reports that as a result of
his investigations, any solid fuel having, in a dry pul-
verised form, two-thirds of its content combustible, can
be used’for generating steam. Anthracite, bituminous
and semi-bituminous coals, lignite and peat, anthracite
culm, dust and slush, bituminous and lignite slack,
screenings and dust, are all suitable for burning in pul-
verised form. The best results are obtained when'these
fuels are mechanically dried and crushed, their dryness
and fineness being comparable to those of Portland
cement, the moisture not exceeding 1 per cent., 95 per
cent, of the total passing through a 100-mesh screen,
and 85 per cent, of the total passing through a 200-mesh
screen. For a railway coaling station of average capa-
city the total cost of preparing suitable pulverised fuel
is estimated at about Is. per ton; the pulverised coal
fuel should be handled with the same care as oil fuel.
The fuel in its pulverised .form is supplied to the tender .
from overhead storage bins, at the rate of 15 torus in
three or four minutes, without exposing the fuel to the
atmosphere during its conveyance.

The prepared fuel gravitates from the enclosed fuel
bunker on the tender to conveyor screws, which carry it
to the fuel and pressure air feeders, where it thoroughly
commingles with the pressure air, and is carried
by it through connecting hose to the fuel and pressure
air nozzles, and blown into the fuel and' air mixers.
Additional induced air is supplied in the fuel' and air
mixers, and this mixture, then in combustible form, is
drawn into the furnace by the smokebox draught. The
flame produced at the time the combustible mixture
enters the furnace obtains its average maximum tem-
perature—from 2,'500 to 2,900degs. Fahr,—at the for-
ward combustion zone under the main arch; at this
point auxiliary air is induced by the smokebox draught
to finally complete the combustion process. The liquid
ash runs down the underside of the main arch and the
front and sides of the forward combustion zone of the
furnace, falling into the self-clearing slag pan, where it
accumulates, and is air-cooled and solidified into a
button of slag which can readily, be dumped. Each of
the fuel and pressure air feeders has a capacity range
of from 500 to 3,0001b. of pulverised fuel per hour; as
from one to five of these can easily be applied to the
ordinary tender, there is no difficulty in meeting any
desired boiler and superheater capacity. The steam
can be maintained’ within a variation of 21b. of the
maximum allowable pressure, without blowing off.

For firing-up the engine, the steam blower is turned
on in the stack, a piece of lighted waste is introduced
through the firebox door and placed on the furnace floor
just ahead of the primary arch, after which the pressure
fan and one of the fuel and pressure air feederis are
started. It takes from 45 to 60 minutes to get up a
2001b. steam pressure from boiler water at 40 degs.
Fahr. After firing-up, the fuel and air supply are
adjusted to suit the requirements '; the stack blower is
operated only when the engine is not using steam.

The use of pulverised fuel, besides eliminating smoke
and the other disadvantages'above alluded to, is stated
to increase the drawbar horse-power hour per unit of
weight, to improve the thermal efficiency of the loco-
motive as a whole, to reduce the non-productive time alt-
terminals, to utilise otherwise unsuitable or waste fuels,
to reduce labour, and to provide greater continuity of
service, and produce more effective and economical
operation and maintenance.

Figures are given relating to -a 10-wheel type of goods
locomotive, rated, at 31,0001b. of cylinder tractive
power, with driving wheels 69 in. in diameter, when
used on fast through goods service, on runs of from 91
to 138 miles in length, for the purpose of testing various
fuels under identical adjustment conditions.

The engine was worked at its maximum capacity on
all trips, about 10 per cent, more tonnage being hauled
than usual for like engines burning coal on grates and
at practically fast freight schedule speed. The exhaust
nozzle opening was about 25 per cent, larger than the
maximum for hand-firing. The general' results were
excellent, particularly as regards tonnage, speed, com-
bustion, and steam pressure, the latter', being main-
tained at full speed with the injector supplying the
maximum amount of water to the boiler. With the
highest sulphur coal and the highest ash coal there was
less than leu. ft. of slag in the slag box at the end of
each run, and practically no collection of ash or soot on
the flue or firebox sheets. In fact, with the latter fuel
there was less than .two handfuls of slag, ash, and soot
collected on each trip.

From tests made with pulverised lignite, having an
analysis of about 1'8 per cent, of moisture, 47 per cent,
of- volatile matter, 41 per cent, of fixed, carbon, 9-5 per
cent, of ash, and 0’75 per cent, of sulphur, with a heat-
ing value of 10,900 B.T.U. per lb.., in regular passenger
locomotive service, the same satisfactory results were
obtained as with bituminous, coals, the combustion and
operating being entirely smokeless, sparkless, and
cinderless, and the steam pressure ' being fully main-
tained.

The same question-also formed the subject of a paper
read before the American Iron and Steel Institute by
Mr. J. W. Fuller, who stated that probably the
greatest recent development in this direction was its
application to open-hearth furnaces. Pulverised, coal
had been applied very satisfactorily within the last few
years to various, kinds of metallurgical heating furnaces
and to soaking pits. In regard to open-hearth furnace
practice, observations had shown that pulverised coal
gave a more regular supply of heat than producer gas;
they had demonstrated, further, that it was much easier

AND TECHNOLOGY.

to burn powdered fuel to. gas than to gasify coal in the
ordinary gas producer. The gas was of a more even
chemical composition, and a direct result was a greater
number of yields per week. Open-hearth furnaces were
in operation to-day,. using powdered fuel, having a very
low fuel consumption, equal to the best producer gas
practice, and much better than the average of the older
producer gas plants. Coal could be pulverised and
delivered to the furnace at a little more than half the
cost of that required for gas producers, and the substi-
tution of pulverised coal for producer gas gave, in most
instances, an increase in output which might amount to
between 10 and 40 per cent., according to the nature of
the practice and plant. Another advantage was that a
pulverised coal installation cost less than one of gas pro-
ducers. It was believed further—and this is important
from a steel maker’s standpoint—that there would be
from 1 to 2 per cent, less oxidation in pig iron and scrap
in melting down a heat from the cold state. The best
coal for the purpose was a bituminous coal as high in
volatile matter as possible, and preferably low in ash.
A coal having 0*64 per cent, of moisture, 35 per cent,
of volatile matter, 50 per cent, of carbon, 5 per cent, of
ash, and 1’36 per cent, of sulphur gave excellent results.
A coal of this analysis had a heating value of 14,200
B.T.U. The difficulty in .the case of pulverised fuel in
open-hearth practice appears to be the ash problem.
Ash was not found to deposit on the slag in any great
quantities, but a large quantity' of ash was formed, and
this had to be dealt, with. The discussion on this paper
revealed the important fact that the use of pulverised
coal demanded the- provision of suitably designed
checkers and slag pockets. In regard to the economy of
the system, this was confirmed, actual experience having
shown that with the use of pulverised coal a furnace
used from 100 to 1501b. of coal less than the producer
gas furnace per ton of ingots cast. There was no appre-
ciable difference in the life of the two types of furnace,
and the average time of heats, using pulverised coal,
was from 14 to 2 hours shorter than when using pro-
ducer gas.

Mr. Fuller also dealt with the construction of the open-
hearth furnace and with the preparation of the pulverised
fuel. This latter is kept in dust-tight bins. It is essen-
tial that the feed of the coal to the burner be under the
absolute control of the furnace operator, and be positive
at all times, for if the feed to the burner were not abso-
lutely regular and positive, the -efficiency of combustion
would be materially lowered, and puffing at the furnace
would take place..

Hydrocarbons in Coal.

A communication (says Gas World) presented to the
French Academy of Sciences by MM. Ame Pictet, L.
Ramseyer, and Q. Kaiser, on certain hydrocarbons pre-
sent in coal, states that, after having found .that the
distillation of coal under reduced pressure gave a special
tar consisting mostly of the hydro-aromatic series, the
authors applied themselves to finding out whether these
substances existed as such in the coal, or whether they
are the products of a decomposition occasioned by heat.
The only means of solving this question was the use of
neutral solvents. Much work has already been done in
this direction, from the time of Commines.de Marcilly
(1862) to the recent work of Vignon, Wahl, F. Fischer,
and Glund. But the aim of these investigators was, in
the main, to ascertain the solvent power of the different
solvents, and no definite substance has been extracted
by this means.

The coal used was a bituminous coal from the Sarre
(Maybach), and thanks to MM. Hoffmann, La Roche
et Cie., Basle, Switzerland, the authors have been able
to work on a pretty large -scale. Five and a half tons of
this coal were extracted with boiling benzol in the
research laboratory of this firm, in Soxhlet extractors.
The coal was broken down to the size of peas, and boiled
with the benzol for four days; the solution was reduced
to 20 litres by distillation, and was then mixed with 100
litres of petroleum ether. A precipitate was thus
formed, which was a clear brown amorphous powder
(2'7 kilogs.). The solvent was evaporated from the
remaining liquid: there remained a brownish liquid, very
mobile, 10'6 kilogs. . The yield is thus very small, 4 per
cent.; this can be slightly raised by powdering the coal,
but the subsequent operations are rendered difficult by
this.,	.	•	'

The liquid extract closely resembles vacuum tar; it
has the same smell, the same specific gravity, and a very
similar chemical composition. Its composition is -J- per
cent, of basic substances, 2 per cent, of oxygenated
hydrocarbons (alcohols), the remainder being one-fourth
saturated and three-fourths unsaturated hydrocarbons.
To separate thes-e components, the method adopted'was
exactly the same as that employed with vacuum tar, by
successive treatment with ’ hydrochloric acid, with
sodium, and with liquid sulphurous, anhydride. The
hydrocarbons were then fractionally distilled in frac-
tions at 2 degs. Cent, difference of temperature. The
fractions had their molecular weights, their densities,
and their refractive indices determined; and the follow-
ing hydrocarbons were identified among them

C^H, 0, dihydro-toluene; C8Hj 9, dihydro-metaxylene;
G9H^, dihydro-mesitylene; CJ0H1P, dihydro-prehnesol
(?); CnH]6; C14H1fi; C]3H12, solid, dihydro-fluorene (?);
C8H1G (saturated); C9H18, C10H20, CnH22, C12H24,
c;„h2c, c3Oh,0.

Are the hydrocarbons extracted from coal at 80 degs.
Cent, the same-as those found in vacuum tar produced
at 450degs. Cent.? The enquiry is not yet completed
as regards the non-saturated hydrocarbons, those found
in vacuum tar not having yet been fully ascertained.
But as regards the saturated hydrocarbons, or, at any
rate, some of them, there is more information. The

first three fractions appear to contain a slight admixture
of hydrocarbons Cn Hsn + 2 ; but the C1XH22, the C12H24,
and the CX3Hnc are identical with those found in vacuum
tar, which, in their turn, are the same as those found by
Mabery in Canadian petroleum. The solid hydrocarbon
C30Hro is also identical in all respects with melene, found
in vacuum tar, and also in Galician petroleum. There-
fore, a large part, at any rate of the hydrocarbons pre-
sent in vacuum tar is already present in the coal : dis-
tillation in a vacuum separates them by simple volatili-
sation without there being any pyrogenic decomposition.
Coal, 'therefore, has to be considered as a solid hydro-
carbonaceous material impregnated with a liquid chemi-
cally very nearly resembling petroleum.

This latter point of view is confirmed in a striking
manner by the circumstances that this liquid portion of
the coal has, like most petroleums, an optical rotatory
power. It is slightly laevorotatory (index for D line at
20degs. Cent. = —0-08degs.); but after taking out the
alcohols by means of sodium it is dextrorotatory (index
= +0*27 degs.). Once the fractions are separated by
treatment with liquid SO2 and fractional distillation, it
is found that none of the non-saturated fractions have
any action upon polarised light; and none of the
saturated fractions up to 180 degs. Cent, have any effect.
The rotatory power only appears among the higher
saturated fractions; but then it changes its sign from
one fraction to another. Thus the fraction 215 degs.
— 216 degs. Gent. (C12H24) has a deviation —0’53 deg.,
while the fraction 227 degs. —229 degs. Cent. (CX3H26)
has a deviation +1’56 degs. Absolutely similar pheno-
mena are known (Engler and Steinkopf) to occur in
petroleum.

The authors have not, however, ever found any optical
activity in any fraction of the vacuum tar, We may
conclude that exposure to a temperature of 450 degs.
Cent, is sufficient to “ racemise ” or render inactive the
optically active substances contained in coal. It also
indicates that the material, the coal, from which the
vacuum tar had been formed, had itself never at any
time been exposed to a temperature of 450 degs.

THE GERMAN 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 :—

Siegerland Ore and Iron Market.

Conditions in 'the ore market are firm. The Ironstone
Association recently threw open the placing of contracts
for the first quarter of 1917, the prices being raised as
follow :—In view of the increased cost of production
and the scarcity of manganese ore : Roasted spathic ore,
330 mk.; raw spathic, 230 mk.; and brown ironstone,
244 mk. These are basis prices per 10 tons, ex loading
stations, and represent, in the first-named case, a rise
of 7 mk. per ton. The small available quantities are
being taken up readily by the iron works at these rates,
the production being in arrear of the demand. There
is practically no Hesse-Nassau or Wetzlar ore on the
market, the whole of the 1917 output having been con-
tracted for a long time back. The military 'authorities
have fixed the maximum price' of 45 per cent, red iron-
stone at 25 mk. per ton ex mine station; but it is not
known whether any of the ore has changed hands at this
rate. The scarcity of railway wagons is greatly imped- .
ing delivery. Little business has been done i'n Lor-
raine-Luxemburg ores, and that only in calciferous
minette; and no ores of any other kind are to' be found
on the market.	>

The pig iron market has also kept very firm, with a
considerable advance in the prices of foundry pig, cast
iron for rolling, Bessemer iron,, puddled iron, steel iron,
and spiegeleisen. The Pig Iron Union has been unable
to accept all the orders sent in, especially for mangani-
ferouis marks; and stocks are more attenuated than ever..
Gold blast pig is particularly scarce, and prices have risen
to about 150 mk. per ton ex works. Most makers are
sold right up into the second quarter of the year, and are
requiring several weeks to deliver when specifications are
received.	i

In the scrap market the tumultuous upward course of
prices for free material has given way to a quieter tone,
sellers and consumers having entered into agreements
by which prices have been regulated.

The previous tension in the semi-products market has
become intensified, the works being quite unable to
satisfy the demand for crude ingots and slabs, so that
consumers are hard put to it to obtain the requisite
supplies from other districts. Little is obtainable from,
the works in the Steel Union, as they are all busy on
army work. There has been no change in the official
prices of the union, but local steel works easily obtain
considerably higher rates for the small surplus they have
for disposal.

The difficulties of makers of fine and medium plate
have greatly increased, and they, are quite unable to
meet customers’ requirements, even for army purposes,
and no stated time for delivery can be guaranteed. There
is little disposition to accept new orders, there being
sufficient in hand to last w^ll into' the spring; and,
moreover, the future prospect of being able to obtain
semis is very obscure. Prices for the home market
remain about the same, and though. higher rates are
quoted for export to neutrals, little business is done, in
view of national requirements. In the heavy plate
market the conditions are more simple, and show little '
change. Sales for the first quarter of the year are con-
ducted at old rates, with the reservation, that any
increase fixed will have to be paid. The works are busy,
on army orders exclusively, and the demand for black
and galvanised plate keeps ahead of the supply.

The bar iron market is practically closed, the output
being almost entirely for army purposes, so that no