74

THE COLLIERY GUARDIAN.

January 11, 1918.

CURRENT SCIENCE

Percentage of Nitrogen in Oxidised Coal.

Mahler (Comptes JRendus) gives the percentage of
nitrogen in coal as between 0*70 and 2-50 per cent.,
the higher percentage being often found in coals of
the stephanian series. This nitrogen content must be
taken into account in studying the formation, altera-
tion, and chemical composition of coal. The principal
effect of the action of air on coal is to oxidise and
de-hydrogenise the organic matter, with formation of
ulmic substances and loss of nitrogen. The author
has conducted experiments on the changes in the
nitrogen percentage, provoked by this decomposition,
in various specimens of coal from the Decazeville
mines. This coal is reputed to burn rapidly under
the action of oxygen, and even to be capable of spon-
taneous combustion. In the vicinity of an intrusion
of sandstone at Combes, coal is found in all stages of
oxidation. The test pieces included specimens vary-
ing from the practically intact coal, with a heating
value of 8,000 calories and 36 per cent, volatile matter,
to the materially altered portions with a heat value of
5,200 calories and 52 per cent, of volatile matter.

The following table of comparative analyses gives the
result of the experiments: —

Analyses of Decazeville Coal Mined at Combes.

Pl O 42	fl  fl &uo o	fl  fl  o	•  03 £ fl a fl a fl,fl
O	?	s	O ®fl
Per	Per	Per	Per
cent.	cent.	cent.	cent.
81’40 ..,	. 5’30 ...	1’70	... 11’60
80’20 ...	. 5’00 ...	1’65	... 13’15
73’00 ...	. 3’90 ...	1’60	... 21’50
72’60 ..	. 3’60 ...	1’70	... 22’10
—	—	1’70	—
—	—	1’80	—
—	—	1’90	—
64’90	' 3’00	2’50	29’60

11	rfl  m
	
S	u
Per	Per
cent.	cent.
0’5 .	.. 4’3
1’0 .	.. 3’7
5’0 .	..10’1
30’0 .	.. 2’80
50’0 .	..18’4
60’0 .	. 21’0
65’0 .	.. 9’90
70 0 .	. 11’50

Per
cent.

... 3’9
... 4 2
...14’0
...12’0
...19’0
...15’1
...15’0
...15’0

Utilising Petroleum Residues.

According to a report by Mr. T. H. Norton, United
States Commercial Agent, the Rittman process, origi-
nated in, and elaborated as an industrial method by,
the United States Bureau of Mines, has now issued
from the experimental stage, and become a recognised
industrial asset in the -national cycle of productive
activity. By its aid, vast quantities of petroleum
waste, hitherto available for little beyond fuel pur-
poses, can be transformed either into gasoline for
motor engines, or into benzene and toluene, which con-
stitutes the crude material for the manufacture of
picric acid and trinitrotoluene, and forming also the
starting points for the synthesis of dyestuffs, etc.

Apprehension has been felt that at an early date the
supply of gasoline from crude petroleum, or of benzene
and toluene from the distillation of coal, may fall far
behind the world’s demand for motor fuel. The Ritt-
man process promises to relieve this anxiety. The
process, as now perfected, makes it possible to produce
gasoline at a cost of 6c. (3d.) per gal., as compared with
22c. (lid.) per gal. for gasoline obtained directly from
petroleunr refineries.

Ignition Temperature of Gaseous Mixtures.

Mr. J. W, McDavid (Journal of the Chemical
Society), by mixing the gas, hydrogen, or other gases
or vapour with air in a bottle, and blowing a soap
bubble of the cold mixture, obtains, with an electric
igniter, an ignition temperature which is the tempera-
ture to which the cold gaseous mixture must be heated
by the application of a “hot body” so, as to cause
instantaneous ignition. Various hot bodies were used,
including a thin-walled silica tube wound with plati-
num wire, 0-025 cm. in diameter, and containing a
thermo-couple of platinum-rhodium. When the milli-
voltmeter in circuit with the couple was steady, the
hot body was brought near the bubble still adhering
to the pipe; ignition, accompanied by a slight explo-
sion, was instantaneous, when the body was sufficiently
hot. Rotherham coal gas ignited when the tempera-
ture of the coil reached 800 degs. Cent., but not at
795 degs. or less. In order to study the influences of
various factors, the wall thickness of the tube was
varied between 0 055 cm. and 0-0225 cm., the internal
diameter between 0-157 cm. and 0-065 cm., the length
between 6 cm. and 4 cm. The thinner and smaller
tubes gave the higher ignition temperatures, ranging,
in the case of hydrogen, from 712 to 758 degs. With
a winding of eureka wire, instead of platinum, the
’corresponding temperatures were 682 and 735 degs.,
indicating a strong catalytic effect, favouring combina-
tion. Finally, the hot body was made of platinum
wire wound round two notched strips of mica, 3 cm. in
length and 0-3 cm. wide, the couple being between the
strips. It was found that when the bubbles were
larger than the usual size, 3-7 cm. diameter, the igni-
tion temperature was lowered, and the ignition slightly
retarded. The following ignition temperatures (in
degs. Cent.) were obtained:—Hydrogen-air, 747;
carbon monoxide-air, 931; ethylene-air, 1,000;
methane-air1 above, 1,000; petrol (fraction 0 to 80
degs.)-air, 995; benzene-air, 1,062; ether-air, 1,033.

The Waste Gas from Iron Furnaces.

The question of gas efficiency for the iron works
owner is discussed in a recent article in Engineering.
It can be taken for granted that of the heat generated
in a blast furnace 50 per cent, is consumed by the
process of making iron, and that the other 50 per cent,
is recovered in the blast furnace gas. If we assume
one ton of coke to be used per ton of iron, and the
value of blast furnace coke to be 18s. per ton, 9s. per
ton of iron is represented by the calorific value of the
gas. Part of this gas must be used for heating the
blast, but by far the greater part is available for the
gas-fired boilers, gas engines, and the like. If the
stoves consume 30 per cent, of the surplus gas, and if
10 per cent, be allowed for losses through bell lower-

AND TECHNOLOGY.

ing, 60 per cent, is available for boiler firing, so that
this portion of the gas with which we are chiefly con-
cerned represents a value of nearly 5s. 6d. per ton of
coke. If the value of steam at iron works is 2s. per
ton, w'hich corresponds to a coal price of 12s., and an
evaporation of 6 lb. of steam per pound of coal, we
obtain 6s. 3d. worth of steam per ton of coke. In
order to realise the economical importance of the whole
question, let us assume the case of an iron works with
four furnaces, using on an average 3,000 tons of coke
per week. The value of the coke for boiler firing pur-
poses is in their case £48,750 per year, and each 1 per
cent, difference in efficiency means a difference of no
less than £487. Scarcely any iron works obtains a
boiler efficiency of more than 50 per cent., and
many get an efficiency much lower than this, so we see
that small iron works as described above are losing 30
per cent, of £48,750, or £14,610 worth of steam a year
which could easily be recovered. The question of gas
economy is thus seen to play a most important part in
the financial prospects of iron works. Returning
again to the case of the iron works described, the loss
per ton of coke is at least Is. lid. when assuming an
efficiency of 50 per cent. As efficiencies are frequently
as low as 40 per cent., the actual losses sustained are
often over 2s. 7d. per ton of coke. The manufacture
of pig iron in Great Britain was some 10,000,000 tons a
year before the war, so that if the average loss is only
2s. per ton, the formidable sum of £1,000,000 a year
is sent up the stacks of the iron works of Great Britain.

Calorific Values of Russian Coal.

The anthracite of the Donetz basin (says a writer in
Russia) has an average calorific value of about 8,400
calories, that of the Urals (Egorshinsky) is given as
8,428 calories, while the figure for the anthracite in
the Kuznetz coal of Siberia is also in the neighbour-
hood of 8,400 calories.

Among semi-anthracites, that of the Donetz basin
runs about 8,600 to 8,700 calories; the Suchansky
deposit, near Vladivostock, gives the high figure of
9,276 calories; the Kuznetz semi-anthracite, 8,710
calories, as compared with 9,060 calories for Cardiff
semi-anthracite.

The coking coals of the Donetz basin yield from
8,400 to 8,750 calories.

The Kemerovsky nut coals have a calorific value
reckoned at 8,500, the Eutchenkovsky 8,290, and the
Makievsky 8,294.

Among gas coals, the determinations are as follow:
Irminsky, 7,930; Turkestan (Karatansk), 6,300; Kol-
chugino (Kuznetz basin), 8,270; Golubovsky, 7,660.

The respective figures for dry, long flame coals are :
Dombrova (Poland), 7,520; Lisichansk (Donetz basin),
7,500; Tkvibuli (Caucasus), 7,525; Kizelovsky (Urals),
8,103.

The boghead coal of the Muraevinsky yields 8,485
caloriqs, w’hile the brown co.als of the Kiev district and
the Cheliabinsk region yield 7,000 to 7,080 calories
respectively.

Light Oils from Coke Oven Gas.

According to a paper (abstracted in Gas Journal) on
“ The Recovery of Light Oil from By-products Coke
Oven Gas,” submitted by Mr. W. H. Wright to the
American Gas Institute, there are in the States about
43 plants for recovering light oils; only one installa-
tion of any size being in existence which does not pro-
duce these oils. For the year 1913, the output in
America was estimated at 10,000,000 gals. ; while the
recovery for 1917 it is thought will approximate
110,000,000 gals.

The industry seems to be pretty well standardised
in the matter of type of scrubbers, which are in the
form of tow’ers from 6 ft. to 24 ft. in diameter, and
from 40 ft. to 90 ft. high. They are uniformly filled
with wood grids, and the lower 8 ft. to 10 ft. is made
to serve in most cases as a reservoir for the wash oil
in circulation. The wash oil is admitted by means of
a series of sprays; and there are normally two or three
of these tow^ers in a series, the wash oil being circu-
lated in counter-current to the gas. Experience has
unquestionably pointed to the desirability of having
not less than three towers in a series. The quantity
of wash oils should be such as to give a saturation of
the benzolised oil not in excess of 4 per cent. From
2 to 3 per cent, is a better figure. The temperature of
the gas and oil are, of course, the important factors in
determining the permissible maximum. While in
Europe heavy tar oils have been used as the aborbent,
in the United States the industry has uniformly
adopted high boiling petroleum oils (known to the
trade as “ straw oil ” or “ spindle oil ”).

So far, there is no.general practice in the matter of
discarding or replacing the wash oil. Some plants
discard only the boiler still residue obtained in the
subsequent treatment of the light oil, and replace the
wash oil merely as this and other losses make it neces-
sary. At other plants, a regular routine of wash oil
renewal is followed. In one case reported upon, this
routine provides for complete renewal every three
months. Plants at which still temperatures of around
135 degs. Cent, are obtained show better wash oil
results than plants distilling at lower temperatures.
The benzol scrubbers in use are of such size as to give
a velocity of from 1| ft. to 4 ft. per second, when
reckoning that one-half of the gross area of the
scrubbers is available for gas flow, and the time of
contact of the gas with the oil from 40 to 160 seconds.
The contact in the majority of plants runs from 70 to
100 seconds. The absorbing power of the wash oil
starts to drop off very rapidly at about 25 degs. Cent. ;
so that it is important to maintain the temperature of
the gas and wash oil at or below this point, in order to
ensure good efficiency. The question of the sequence
°f the heat exchangers is determined by various con-
siderations. In European plants using tar wash oils,
the sequence for the benzolised oil is first through the
oil-to-oil heat exchanger, and then through the vapour-

to-oil exchanger; while in America, where petroleum
wash oils are used, this sequence is generally reversed.
The majority of the plants in the United States do not
use superheated steam in their light oil operations ;
but experience has fully demonstrated the desirability
of doing so.

The‘cooling of the wash oil has been accomplished in
one type of American plant by means of direct mixing
of the debenzolised wash oil and the cooling water;
and this worked out fairly satisfactorily where the
still temperatures were high enough to ensure a very
good removal of naphthalene from the wash oil. Mr.
Wright approves the tendency manifested to use the
single* pipe refrigeration ammonia cooler for cooling
the wash oil. It is his opinion that the cooling should
be brought about with the wash oil inside the tubes,
and the water outside, down to about 40 degs. Fahr.,
and the remainder of the cooling with the oil outside
the tubes and the water inside. Practically all the
light oil condensers have been of the worm type. There
seems now, however, to be a tendency to utilise the
standard double-pipe ammonia condenser of the
refrigeration type for condensers and heat exchangers;
and it is remarked that this apparatus will give
greater efficiency.

THE GERMAN COAL AND IRON
TRADES.

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

Coal Syndicate Settling Prices.

The Syndicate has decided to leave the settling prices
unchanged for the first quarter of the current year;
but briquettes are to be raised in conformity with the
higher cost of pitch.

Krupp Profits.

The report for 1916-17 gives the total surplus from
all the works as 89,065,407 mk. (95.928,938 mk. the
previous year), together with an income of 6,930,585
mk. (3,783,333 mk.) from investments, and 7,895,604
mk. (3,670,964 mk.) from other sources. Taxes, includ-
ing war tax reserve, amounted to 30,899,115 in.
(28,649,922 mk.); expenditure on workmen’s and staff
insurance, 8,303,855 ink. (6,935,117 mk.); and for bene-
volent purposes, 23,712,170 mk. (18,140,886 mk.). War
assistance funds absorbed 10,438,370 mk., including the
5,000,000 mk. voted last year for this purpose, and a
sum of 6,000,000 mk. is set aside for the same purpose
during the current year. After deducting the total
outgoings, 62,915,139 mk. (53,725,926 mk.), there
remains a net profit of 51,978,577 mk. (59,634,986 mk.),
including the balance of 11,002,121 mk. (9,977,678 mk.)
from old account. A sum of 2,048,823 mk. (2,482,865
mk.) is placed to reserve, 5,000,000 mk. (2,000,000 mk.)
to special reserve, and 5,000,000 mk. (as last year) to
special depreciation and renewal fund. A dividend of
10 per cent. (12 per cent.), equivalent to 25,000,000 mk.
(30,000,000 mk.), will be paid, 250,000 mk. (150,000
mk.) allotted to the board, and 14,679,754 mk. carried
forward.

The Siegerland Iron Market.

The fuel question is not quite so acute as it was.
provision having latterly been made to keep
the blast furnaces well supplied with coke; but in the
case of other works the measures taken by the coal con-
trolling department have not proved satisfactory,
especially as regards distribution. In consequence, a
number of rolling mills, forges, etc., have had to go
on short time, whilst others are only obtaining hand-
to-mouth supplies. There has been small improvement
in the supply of raihvay wagons, and the repeated
stoppage of goods traffic has caused great inconveni-
ence, which has not been lessened by the delays
experienced in obtaining forwarding permits from the
military authorities.

As regards prices, the investigation committee has
again refused permission for any advance, except in
the case of Siegerland spathic ironstone and brown
ironstone, the prices of which are to be raised, from
the 1st inst., in accordance with the higher cost of pro-
duction and the greater selling value of iron and steel.
This is expected to stimulate production, although the
traffic difficulties and the shortage of suitable -labour
still combine to prevent the ore producers from fullv
meeting the requirements of iron works. Of all the
mines forming part of the Siegerland Ironstone Asso-
ciation that have changed hands during the past year,
all but one have passed into the possession of iron
masters, and the transfer of this one is only a question
of time. Nd alteration has taken place in the situation
of the mines in the Lahn and Dill valleys and in Hesse.
There has been no recent change in the basis prices for
red and brown haematite ore, and the traffic difficulties
have not improved; but there is not any very great
demand for the ores from these mines, though a few-
parcels have been sold at maximum prices for the first
three to six months of the new' year. This trade is
pushed into the background by the far more pressino-
demand for manganiferous ores; and, similarly, the
consignments of minette ore from Luxemburg’ and
Lorraine have not been very extensive.

The pig iron market remains firm, with a heavy
demand for all grades. The recent lull in production
and delivery was entirely due to the shortage of coke
for smelting; but of late the conditions in this respect
have been improved. Nevertheless, the makers are not
able to meet the demand for pig, though every effort
is being made to do so. It is anticipated that prices
will shortly be advanced, in view of the increase
granted for local ore. This, however, w ill only affect
manganiferous grades, the others being mainly pro-
duced from ores, which remain at the old prices. The
demand for cold blast pig continues heavy, and in
excess of the quantity available.

Scrap iron prices remain at the maximum, except
for a recent small additional charge to consumers and
are consequently no longer in right proportion to those