24

THE COLLIERY GUARDIAN.

July 3, 1914.

alkaline earth waters produced by weathering rocks, and
that the carbon monoxide has been absorbed and oxidised
by metallic oxides?* Gas thus obtained from carbonis-
ing lignite, for example, by removal of CO2 and CO would
be practically identical with natural gas. Thus, calcu-
lating out the C02 and CO from the gas obtained in heat-
ing lignites at low temperatures, we have left a gas con-
taining principally methane, i.e., a typical natural gas.

Classification of Coals.

Now that we understand the nature of coals as different
residues in the progressive decomposition of wood into
graphite, we are in a position to classify them. Rejecting
accidental impurities, such as ash and sulphur, and
using the pure coal basis, coals may be classified in
several ways. Five important differences are suggested
on the following chart as bases of classification; for
example, moisture, volatile, oxygen content, calorific
value, and finally, initial decomposition temperature.
Specific gravity, total carbon, oxygen content, and other
characteristics might also be given, all of which indicate
the same progressive change in characteristics.

Unfortunately it is necessary to call attention to the
lack of uniformity in methods of determining moisture
and volatile matter in coals, since much of the data given
in the tables presented depends in paiticular upon con-
sistent results in the determination of the figures.

An atmosphere standing over a calcium chloride solu-

The classification, however, of coals on the basis of
temperature required to decompose, is rational, as is
strikingly shown from a study of coal deposits every-
where. In Washington State there are coals of all types
from lignite to graphite, and, under different conditions,
all types may be found in what appears to be the same
geological horizon. When the seam is horizontal the
coal is lignite; when somewhat disturbed and oblique the
coal is generally a gas or smokeless coking coal; when
folded it becomes anthracite, and finally, when pierced
by igneous rock, we have graphite.

Cokability.

In commercial work for our purposes coking coals have
also to be classified as to cokability. In the following
manner, which really is based upon oxygen content,
though not requiring the tedious ultimate analysis
necessary to give oxygen content, we have classified
coals as to cokability, using as a basis the calorific value
of the volatile matter contained. This, for coals of the
same percentage volatile content, fairly represents
cokability in actual coke oven practice.

On the previous chart, fig. 1, the range of possible
coking coals was indicated. Now, by deducting the
calorific value due to fixed carbon (calculated) from the
total calorific value, and dividing by the amount of vola-
tile matter, all on the pure basis, we get a series of coals
of increasing cementing or coking tendencies. As

Commercial Manufacture of Coke and By-Products.

The conversion of bituminous coking coal to its
anthracite-graphite equivalent, coke, has become of
extreme commercial importance, and particularly when
this is done with the recovery of the by-products. A ton
of average coking coal will produce in the modern by-
product oven :—

1,500 pounds coke.

18 to 26 pounds sulphate of ammonia.

6 to 10 gallons tar.

1| to 2| gallons mixed light oils (benzole, toluole,
xylole).

1| pounds ferrocyanid.

By further elaboration, from these light oils and tar
practically all the compounds mentioned in Beilstein
may be produced.

On fig. 3, is indicated the influence of temperature
upon the yields and character of the by-products obtained
from an everage coking coal. The temperatures given
represent the hottest part of the retort at the beginning
and end of the carbonising period. The average tem-
perature would be considerably lower. On this chart
the yield of light oil is not given, but our experiments
indicate a maximum yield of this material at about
500 degs. to 550 degs. Cent.

a

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w

3OO

4OO

200

100

30

6o

40

50

20

10

8o

70

c< LOK

a.a>

w

<u w

C/2

E 2

<y

<u <u

,4500

6500

5500

95ooa

8500

7500

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rt
O

nJ
O

al
<u

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rt
M 00

X aJ
£ o

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KA* »£or COA7. f» Cl AU

Fig. 1.







3 11500

12500

12000

10500

11000

10000

TT1

<3

9000

8500

8000

9500

Table showing calorific value of volatile matter for typical coals of
the United States.

Fig. 2.

tion containing 35*5 per cent, anhydrous chloride will
show a test at any ordinary temperature of 50 per cent,
relative humidity. Likewise atmosphere in equilibrium
with calcium chloride solutions will have the following
relative humidities :—

Calcium chloride.	Humidity,

f Per cent.	Per cent.

26	  60

12	  40

20	  50

30’5	  30

35*5........................... 70

41	  90

45	  80

A coal in such an atmosphere will, like any other
hygroscopic material, take up and hold a definite amount
of moisture according to its position among the types of
fuels shown on the chart, fig. 1.

Volatile tests can be made with much satisfaction
by use of the Meker burner, but perhaps for strict com-
parison standardised conditions in a muffle furnace are
better. Evidently as we progress in the series volatile
matter, oxygen and moisture go down, while calorific
values and temperatures of decomposition go up. As
decomposition progresses, the specific gravity also goes
up.

I am not aware that the decomposition temperatures
of coal types have ever before been studied, but since,
as we have assumed, coals are residues representing
the different steps in nature’s carbonising process under
progressively severer conditions, it 'is only natural that
they should have different, and, as we go up the scale,
increasing temperatures at which they begin (again) to
decompose. That these decomposition temperatures are
progressively higher is a further strong indication that
coals really are just such residues as has been assumed.

Low grade coals contain much moisture. They are in
fact hygroscopic, and will, like other hygroscopic
materials, when dried take up again moisture from
moist air in proportion to its relative humidity. As
has sometimes been assumed, high volatile coals
are not geologically new coals, nor are smokeless
coals of an older geological formation, as is evident from
the wide variations in volatile found in coals from the
same geological seam. For example, the Pocahontas
coals vary in volatile from, say, 16 per cent, in the true
Pocahontas district, to above 30 per cent, in the equiva-
lent geological New River district north of Meadow
River, W. Va.

Though coals were formed from vegetation at the
beginning of the carboniferous era, in the presence of
more carbon dioxide in the air than later coals, this
does not seem to have been the cause of any real differ-
ence in their character.

* It is well-known that CO in the presence of hydrogen
can be oxidised to CO2 without attacking the hydrogen by
passing over metallic oxides. This selective oxidation is
possible with ferric oxide and with copper oxide. Tempera-
tures as low as 250 degs. Cent, are sufficient.

10

20

15

14000

13000

12000

11000

10000

6000

9000

8000

7000

4 >00

r.OOO

400

500

IOOO

IIOO

2 7

2.;

3-1

x-5

•3:400

•7

500

too

700

Gas
yield
cu. ft.

Fig. 3.

1.9 800

.’rt
r

600	700	800	900

TEMPERATURE 0 C.

tr I « , •
o Rr

I IM

shown on fig. 2, this variation in calorific value of the
volatile matter has been found to represent results in
actual coking practice.

As the calorific value of the volatile matter increases
the cokability increases up to the point where the actual
amount of volatile matter becomes insufficient to cement
and hold the mass together. For example, semi-anthra-
cite coals and anthracite, as to cokability, are beyond
the limiting factor of insufficient cementing volatile
material.

Cannel coal is unusual in that the calorific value of its
volatile matter is higher than for any other coal with
volatile so high. By the Ralston method of classifying
and plotting it falls well above the usual curve.

Coals also differ as to the amount of materials con-
tained capable of solution in caustic, pyridine, benzene
and other solvents, and may be classified accordingly.
So the residues from artificial carbonisation at low tem-
peratures give different amounts of matter soluable in
the various solvents.

Finally, on exposure to moist atmosphere, coals decay.
They become oxidised and go back in the series. For
example, by taking up oxygen and water a good coking
coal takes on the character of a poor sub-bituminous
coal or the non-coking lignite.

Coals and their by-products are therefore not such
mysterious materials. They are merely intermediate
bodies resulting from the decomposition of ancient vege-
tation, just as a multitude of substances may be obtained
by violent or gradual decomposition with heat of any
simple organic compound.

Hull Coal Exports.—The official return of the exports of
coal from Hull for the week ending Tuesday, June 23, 1914,
is as follows Abo, 1,394 tons; Antwerp, 133; Amsterdam,
503; Bremen, 850; Christiania, 1,459; Copenhagen, 401;
Cronstadt, 22,070; Drontheim, 255; Dunkirk, 205; Dram-
men, 452; Dahlsbruk, 1,534; Gefle, 3,943; Ghent, 619;
Hamburg, 1,058; Harlingen, 589; Harburg, 3,066; Kirke-
haven, 20; Libau, 403; Leghorn, 748; Malmo, 1,319; New-
fairwater, 575; Novorossisk, 1,495; Naples, 461; Nordstrand,
143; Pernau, 8,036; Riga, 6,409; Rotterdam, 584; Rouen,
12,320; Reval, 2,546; Rendsburg, 101; Stockholm, 647; St.
Malo, 211; St. Petersburg, 4,645; St. Nazaire, 2,310;
Stettin, 359; Trieste, 262; Zeebrugge, 54—total, 82,179 tons.
Corresponding period, June 1913—total, 99,317 tons.

“ P.P.” Safety Shot-Firing Appliance.—We have been
favoured with copies of reports of the working of the “ P.P.”
safety shot-firing appliance at the mines of the Albion Steam
Coal Co. Limited, and the Glamorgan Coal Co. Limited.
Mr. H. H. Evans, agent of the former company,
reports that there has not been a single case of miss-fire
where the “ P.P.” appliance was used, and that he is
. informed by the shot-firers that the claim that by the “ P.P.”
method increased safety is obtained is quite borne out by
actual experience. Mr. Christmas R. Evans, manager,
Glamorgan Coal Company Limited, writes that with an
average of 120 to 150 shots per day fired there has been no
miss-fire or accident in six months with the “ P.P.”
appliance; further, that the appliance has been used under
all the most trying conditions, and has been found thoroughly
satisfactory. Prior to the introduction of the “ P.P.”
method, it is stated that the number of miss-fires was, on an
average, two per week.