May 30, 1913.

THE COLLIERY GUARDIAN.

1115

one loading position. Under normal conditions the
outputs from conveyor faces in thin seams are between
60 and 120 tons per day, and such quantities are within
the capacity of any of the traveller or carriage types
described. It is neither necessary nor desirable that a
conveyor discharging this quantity should be in con-
tinuous operation; if it were, there would be more
breakage and grinding of the coal, and incessant noises
with some types, and, with all, extravagance of power.
Within the above-mentioned limits the question as
between the types of conveyors is not one of conveying
capacity but of mode of operation.

Continuity of discharge implies unremitting activity
of the fillers and perfect regularity in the service of
trams. These conditions are not in fact fulfilled. The
periods of filling the traveller type, however, cover brief
irregularities in the haulage traffic and give time for
marshalling the trams at the loading position, so that
the coal is promptly delivered, and the conveyor
returned to the fillers.

As a matter of experience the output per filler,
under corresponding conditions, is not greater with
the continuously - discharging type than with the
traveller type in dealing with machine-cut coal. On
hand-worked faces the traveller type affords more room
for the men to work at the face, but the full-length
conveyor has the countervailing advantage that the men
may promptly get rid of the coal, and are not hampered
by accumulations.

The examples given in figs. 1 and 2 illustrate graphi-
cally what actually occurs under normal conditions in
the regular course of working, where conveying is well
established. The number, duration, distribution, and
causes of the stoppages are clearly presented, and the
examples are fairly representative of the performance
of conveyors, in operation. It will be noted that even
with conveyors which have been in use for a number of
years, delays in the service of trams are responsible for
the greatest number of stoppages.

These diagrams not only detect the existence of
defects in equipment or organisation; they are also
valuable aids to diagnosis of the defects.

It will be seen that in practice the “ continuously-
discharging ” conveyor does not conform to its descrip-
tion. Its operation is intermittent and usually extremely
erratic, being governed by the tram traffic. This, of
course, is no fault of the conveyor, but it illustrates
the conditions under which conveyors are operated.

Fig. 3 is plotted from observations of the number of
trams filled in periods of 15 minutes during six hours of
the shift represented by fig. 2 L. The rate of discharge
in this case was exceptionally regular, yet the extent of
the variations observed in the 15-minute periods is
40 per cent. Comparison of the diagrams warrants the
conclusion that the variation in rate of filling the more
spasmodically operated conveyors is much greater. This
factor must, however, be partly governed by the time
required to break out the coal for filling, and to gob
dirt where bands are contained in the seam.

If the analyses of a working shift were carried further,
and the time occupied in filling each tram from con-
tinuously discharging conveyors were recorded, it would
be found that the rate of filling while the conveyor is
in motion is very irregular.

The “ flitting ” system is most in vogue where the
coal produced by an undercut requires more than one
day for its removal. There is little doubt, however,
that in the thinner seams where “flitting” of coal-
cutters is practised there is considerable scope for con-
veyors. For such service the carriage conveyor appears
to have special advantages in that it can convey from
either side of a loading road without regard to the
other side of the road.

In seams where the use of explosives of any kind is
inadmissible, the prompt carrying forward of the
loading road is a matter of considerable difficulty. By
arranging the loading road in the middle of a face 160
to 200 yards long a carriage conveyor can strip the two
sides of the face on alternate days, and two days are
thus allowed to carry forward the road ripping.

(To be continued.}

Hull Coal Export!.—The official return of the exports of
coal from Hull for the week ending Tuesday, May 20,1913,
is as follows :—Antwerp, 495 tons ; Amsterdam, 2,071;
Algiers, 287; Buenos Ayres, 6 067; Bremen, 3.436 ; Cron-
stadt, 22,761; Christiania, 369; Copenhagen, 198; Dront-
heim, 230; Fiume, 5,505; Ghent, 460; Gothenburg, 686;
Harburg, 2,902; Harlingen, 1,521; Hamburg, 8,729; Jersey,
302 ; Landscrona, 1,476; Konigsberg, 1,950; Kalvid, 726;
Kampen, 108; Karlshamn, 541; Libau, 405; Leghorn, 309 ;
Malmo, 2,340; Nexo, 412; Naples, 512; Oporto, 1,316;
Pernau, 4,331; Port Said, 5,050; Riga, 3,334; Rotterdam,
8,712; Rendsburg, 329; Ronne, 791; Rouen, 3,635; Ron-
neby, 1,119; Reval, 1,667; Stettin, 331 ; Svend*borg, 322 ;
St. Petersburg, 2,467; Stockholm, 744; Trieste, 475;
Venice, 507; Wasa, 1,176; total, 101,094 tons. Corre-
sponding period last year, 100,265 tons.

THE DETERMINATION OF WATER IN COAL *

By P. Litherland Teed.

At first sight, the determination of water in coal
would appear to be one of the simplest operations that
the assayer is called upon to perform, and, because of
its simplicity, one in which the accuracy of the opera-
tion is likely to be great. However, the author of this
paper makes it his object:—

First, to show that in the simple drying method
universally employed for determining the percentage of
moisture in a fuel, reactions other than the simple
volatilisation of the water take place which may
materially affect the accuracy of the result; and,

Secondly, to describe an accurate and rapid, though
more complex, process for determining the percentage
of moisture in fuel.

The Inaccuracy of the Simple Drying Method.

The method universally employed of taking a
weighed quantity (generally 2 grammes) of 80-mesh
coal, drying the same in a steam oven, and recording
the loss in weight, was tested in the cases of lignite and
a bituminous coal; in each case the percentage loss in
weight was determined from time to time and plotted
on a time base, as is shown in figs. 1 and 2.

On looking at these graphs, it will be seen that an
increase in weight takes place after a certain time, and
that a variation in weight continues for a long period.

The fact that an increase in weight took place after a
certain time, led the author to suppose that at this stage

c 6*3
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True

•'Perce itage H?

O = 6 45

6*3

66

6 5

£ 6-5

V>
° 6-4

I	4	6	8	/0	/3 HOURS

Analysis : Ash-, 14’45 % ; Sulphur, 4’4 % ; Coke, 73-4 % ; Water, 6’45 % ;

Cal. Power, 11’38.

64

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/		_	-*—			
/	True	Percent	age H?O	« 6*45	
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6 5

6 0

5*5

30	5 0	70	90 HO MIN.

Analysis: Ash, 14*45 % ; Sulphur, 4’4 % ; Coke, 73’4 % ; Water, 6’45 % ;
Cal. Power, 11’38.

Fig. 3.—Bituminous Coal: Drying in Vacuo at 100° C.

a io

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True

Percentage H?O

= IO-2O3

HOURS

IO

II

13

12

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Analysis : Ash, 7’60 % ; Sulphur, 2’73 % : Coke,49’07 % ; Water, 10’203 %.
Fig. 2.—Lignite; Drying in Air at 100° C.

oxidation was the most pronounced reaction going on;
therefore, samples of the same coals were dried in vacuo
at 100 degs. Cent., the loss in weight being determined
from time to time and plotted on a time base, as shown
in figs. 3 and 4.

Examination of these graphs shows that with drying
out of contact with air there was at no time an increase
in weight, but a gradually decreasing loss in weight,
thus proving that the increase in weight shown in figs. 1
and 2 was, as supposed, due to oxidation, while the
variation in weight in all four cases over a long period
of time must be attributed to volatilisation, of matter
contained in the coal.

The fact having been established that reaction with
increase in weight takes place between the coal and the
air when drying at 100 degs. Cent.' led to some investi-
gation as to the behaviour of pyrites unassociated with
coal under these conditions.

A weighed quantity of pyrites was placed in a boat in
a steam jacketed tube through which dry carbon-dioxide-
free, air was slowly drawn, and after contact with the
pyrites passed through baryta water. After four hours
it was found that the baryta water was perfectly free
from turbidity, thus showing that no sulphur dioxide
had been evolved, while the weight of the pyrites in the
boat in the steam jacketed tube had undergone no
change.

However, on passing moist air over the pyrites under

* A paper read before the Institution of Mining and
Metallurgy, May 22, 1913.

these conditions, traces of sulphur dioxide were evolved,
and, on re-drying the pyrites, its weight was found to
have materially increased, leading to the conclusion
that the increase in weight, recorded in figs. 1 and 2,
was due to the oxidation of the pyrites, being then the
most pronounced reaction taking place.

Having established the fact that, even at the relatively
low temperature of 100 degs. 0., reaction was taking
place between the moist air and pyrites, the author
determined to investigate if there were any reaction
between air and the organic portion of the coal, con-
sequently a weighed quantity of anthracite was placed
in a pressure flask and a vacuum created, the outcoming
gas being passed through baryta water, which remained
perfectly clear, thus showing that the coal itself was
entirely free from occluded carbon dioxide.

The anthracite was then placed in a steam jacketed
tube and dry carbon-dioxide-free air passed over the
coal for two hours, and then through baryta water,
which became turbid with barium carbonate, thus
proving the evolution of carbon dioxide. The amount
of carbon dioxide was estimated by Pettenkofer’s
method and found to be equal in weight to 0*0076 per
cent, of the anthracite employed; however, to be
absolutely certain that this carbon dioxide was the
result of reaction between the air and coal, the anthracite
was removed from the apparatus and a series of blank
experiments performed under exactly the same condi-
tions, when it was found that the baryta water showed
not the slightest trace of carbon dioxide. Thus from

* 9-5
0.

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* 10-5

					
					
		z*			
	True I	Percent	age HgO	« IO-2O3	
	I				
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no

10-5

10-0

9*5

20	30	40	50	60 MIN.

Analysis: Ash, 7’60 % ; Sulphur, 2*73 % ; Coke, 49’0 % ;
Water, 10’203 %.

Fig. 4.—Lignite: Drying in Vacuo at 100° C.

the above it will be seen that in the simple method of
drying in air, sources of inaccuracy exist due to the
following reactions:—

(a)	Oxidation of pyrites making the result too low;
and

(b)	Volatilisation of matter contained in the coal
making the result too high ; and

(c)	Oxidation of the coal itself making the result too
high.

A Rapid Method for the Determination of Water
in Coal.

Having determined the sources of error in the
lengthy but simple drying method, the author gave his
attention to the evolution of a process devoid of these
errors, and, if possible, somewhat more rapid in its
operation. After a great number of unsuccessful
attempts, the following method was by gradual stages
evolved; and though requiring careful manipulation
and apparatus, not at the disposal of all assayers, yet,
since it gives a high degree of accuracy, is quick in
operation and employable in many cases where simple
drying would be impossible, the author hopes that the
publication of this method will be of use on occasions
where the above conditions are required.

The apparatus, which is ‘ illustrated in fig. 5, consists
of a 100 cubic centimetres pressure flask, a U tube of
about J in. bore and a sulphuric acid drying tube, all of
which must be capable of withstanding atmospheric
pressure; besides these, sound rubber corks and some
form of vacuum pump are necessary; with regard to