1350

THE COLLIERY GUARDIAN.

December 27, 1918.

like destructive distillation, to differentiate between
primary actions and secondary reactions. There was
in the first place the evolution of certain products
from the coal as the coal was heated, and, in the
second place, there was a complete transformation, in
some cases, of these primary products at higher tem-
peratures, either in contact with the walls of the
retort or in contact with the heated carbon of the
retort. These were problems which it was very diffi-
cult to solve, and he would like to ask if Dr. Perkin
had any information to give in relation to the effect
of temperature primarily on the bituminous sub-
stance, i.e., whether it made any difference if the coal
was dropped straight into the retort at 500 degs. or
whether it was dropped on to the hot surface at 800
or 1,000 degs. He was referring to comparatively small
masses of coal. There were one or two interesting
processes which had not been described in the paper.
Probably some of them were familiar with the interest-
ing process of McLaurin, of Glasgow, in which a
highly heated producer gas was passed through the
carbonising retort, and in that way some oils were
obtained which were very different from anything pre-
viously described in the literature; oils which were
almost wholly soluble in caustic soda. That brought
him to an interesting point in connection with cannel
oils and other oils from coal, viz., the oxygen-contain-
ing compounds. Many low temperature tars yielded
an enormous amount of soluble phenols, of which pro-
bably 30 per cent, was soluble in caustic soda ; but that
did not remove all the oxygen-containing substances.
Tn addition to that, as Winmill had shown in a paper
on the distillation oh cannel coals in vacua, phenolic
ethers were present which were not removed by caustic
soda, but they could be removed by strong sulphuric
acid. Of course, these phenolic ethers might or might
not be substances which would have to be removed
from the oils in order to give us products which were
suitable for certain purposes; by that he meant suit-
able for use in internal combustion engines. It was
well known that certain oils gave a great deal of
trouble in internal combustion engines by carbonisa-
tion, pitting, etc., and no one could say at the present
time the cause of the trouble. Very little apparently
was known of the effect of some of these oxygenated
compounds. They had a big influence on the behaviour
of these oils and the preparation of fuel oils for use
in internal combustion engines would undoubtedly be
one of the most important phases of this new industry.
Another process had recently been developed in
America. The coal was first carbonised at a tempera-
ture of 450 degs., and as large a quantity as possible
of the low temperature oils was obtained. Then it
was suggested that the residual coke should be bri-
quetted with pitch, and that these briquetted mass?s
should then be further retorted, in that way recover-
ing a further quantity of heavy oils. It was claimed
that by this process, no matter what the. original
material might be, it gave a good material suitable for
domestic fuel.

Dr. Dunstan said he was particularly pleased with
Dr. Perkin’s crusade apropos of the claims in connec-
tion with the formation of benzol and toluol in low
temperature processes. It was perfectly obvious that a
temperature of 700 degs. Cent, was about the minimum
for the formation of these products. There was a
good deal of misapprehension as to the production of
these valuable hydrocarbons. In common parlance
coal tar was referred to as the source of these
materials, but in point of fact it was the stripping of
the gas that yielded them. He would like to empha-
sise the extreme importance of a thorough research on
the composition of coal and of the different types of
coal. A valuable monograph had recently been pub-
lished by Drs. Wheeler and M. Stopes on the constitu-
tion of coal,. which brought the subject well up to
date, but the extraordinary discrepancy between the
results of these two investigators and Pictet and
Bouvier showed perfectly clearly that the material
which the observers worked with was very different.
There were similar discrepancies between the work of
other observers; but it was gratifying that the pioneer
work on the constitution of coal was entirely British.
The investigations to which he had referred, and also
those of Bedson, suggested that although coal was
usually described as being a form of carbon, it was
possible that it was a complicated hydrocarbon. The
crux of low and high temperature distillation was con-
cerned with this curious fact, that at about 700 degs.
cent, there was a marked difference in the products.
Below that temperature practically a mineral oil was
obtained, whilst above it a large evolution of hydrogen
took place, and the well known aromatic hydrocar-
bons were obtained. Parr had subjected a number
of American coals to low temperature distillation,
and, apropos of Prof. Brame’s remark, he had also
found this tar acid was about 30 per cent, of the total
oil. Parr stated that the semi-coke, which contained
18 per cent, of volatile matter, worked well in a suc-
tion gas producer plant, and was equal, or nearly so,
to anthracite. The volatile matter also rendered it an
admirable domestic fuel. The tar was rich in light
oils, the pitch was low in carbon content, and the tar
acid was admirable from the point of view of a wood
preservative. Furthermore, 10 per cent, of the dis-
tillate of the low temperature oil was free from acids,
and could be used directly in internal combustion
engines. The impressive point about Parr’s work was
the suggestion that these low temperature oils, as
distinct from coal tar oils, offered a new field of re-
search altogether, but it was rather suggested by Dr.
Perkin that these oils were no use for synthetic pur-
poses. He hoped that Dr. Perkin would be very much
mistaken, and that in low temperature carbonisation
products there would be found bodies which would
be of extreme importance in physical chemistry. With
regard to the occurrence of ammonia, which was
highly important in connection with the technology
of the process, it had been shown by Cobb that at
800 degs. in the presence of steam it was possible to
obtain practically the whole content of nitrogen as
ammonia. Therefore the possibility of obtaining the

maximum amount of ammonia must be borne in mind
in considering these processes.

Sir Boverton Redwood said he wished to emphasise
the fact that they were now in the position to do
what could not be done last February, viz., to lay
the foundations of a permanent industry. In
connection with that he felt very strongly that they
ought to have as soon as possible investigations with
the object of having the low temperature distillation
process placed on a commercial basis within a year or
two. He confessed he was a little surprised to hear
Dr. Perkin refer to the treatment of Scottish shale
for obtaining oil as one of low temperature distilla-
tion. When one took into consideration the diameter
of the Scottish type of retort, it must be perfectly
evident that in order that the centre of the charge
should be raised to a temperature sufficiently high to
effect that separation, even at the lowest available
temperature, the exterior portion of the charge in
contact with the walls of the retort must of neces-
sity become over-heated, and that occurred long
before the shale travelled down from the upper
portion of the retort, in which the oil was supposed
to be separated, into the lower and much more highly
heated section where the ammonia was obtained ; and
that the result was comparatively unsatisfactory from
the oil point of view was, he ventured to submit,
definitely shown by comparing the yield of oil, both
in quantity and quality, with that obtained in a true
low temperature system of distillation. It was quite
evident that there was over-heating of the charge,
and what we mainly wanted at the present moment
was practical testimony, based upon large-scale com-
mercial tests with a true low-temperature distillation
of materials, which the lecturer had shown were
largely unutilised and might be made a source of great
quantities of oil. The committee appointed by the
institution had drawn attention to the very important
result which would accrue from the simple change of
substituting the shovel for the work in the mining of
coal. He had had his attention drawn to the fact
that a ballot of the Leicestershire miners showed more
than a two-thirds majority in favour of a strike to
enforce the filling of coal with shovels instead of
forks. This had been a vexed question for some years.
This clearly showed that the miners recognised the
force of the point brought out in the interim report
of the Institution Committee.

Dr. Ormand y said that we would have to recognise
that, whereas hitherto we had been about the largest
exporters of sulphate of ammonia, we were now faced
with the fact that America was a large producer,
China was starting to produce and was putting up
by-product recovery ovens, Japan was now a larger
producer, and Germany was making more than one
million tons of sulphate of ammonia from the nitro-
gen of the atmosphere. That suggested that we were
going to be up against a very serious situation as
regards the value of ammonia compounds, although
we had not used ammonia fertilisers as we should
have done. We did not use one-sixth of the amount
used in France and Belgium. With regard to lignite,
that had been distilled in Austria for very many
years, and he had once visited a works there which
had 70 by-product recovery ovens into which brown
coal, dug in open workings, taken out by a grab and
put into wagons, was dropped straight into the
retorts at a cost of 4d. per ton. The residue left after
distillation was ground, and the pitch and tar pro-
duced from the distillation was used to briquette the
carbonised lignite. These products were largely used
on the Austrian railways. They also had a system
of dealing with the gases which was unique. The
gases coming away from the coke ovens were carried
through hydraulic mains which were jacketed with
magnesia, as also was the main pipe leading to the
washers. The gases containing tars and oils were
cooled in fractional washers, so that in the first washer
the heavy tar was produced, in the second light tar,
in the third heavy oil, and from the fourth washer
there was a constant stream of pale yellow oil which
was sold locally in competition with Russian and other
petroleums for lighting without any further refining.
It was the utilisation of the Fell principle which
must be adopted some time or other instead of the
stupid arrangement so common to-day, whereby we
distilled the various products, condensing them into
a sticky mass, and then heated them up again and
caused a large number of secondary changes involving
the expenditure of a large amount of fuel. With
regard to the lignites on the south coast, Nature
seemed to have placed them there intentionally. They
were furthest away from the coal fields, but if a cheap
supply of fuel could be obtained there was no reason
why the congested Potteries district should not be
transplanted to Devonshire and Dorsetshire and the
industry developed on new lines where lignite could
be worked profitably. They would then be able to
obtain considerable quantities of mineral wax, the
pockets containing which could be sent to the ex-
tractors and would be found to contain from 10 to
27 per cent, of wax. In getting to the lower beds
of lignite, it was necessary to pass through 300 to
400 ft. of clays of all degrees of purity, many of them
of the highest quality but not hitherto used for the
pottery trade because they were mixed with some fine
sand which rendered them insufficiently plastic. If,
however, supplies of cheap power were available by
the burning of lignite in producers for the production
of electricity, the electric method for the purifica-
tion of clay could be worked, and there was no reason
why a healthy pottery industry should not be de-

Demobilisation of Miners.—The Controller of Coal Mines
announces that coal miners are being demobilised under
special arrangements come to between the various Services
and the Coal Mines Department. Colliery proprietors who
seek the return of their former employees need take only
such action as the Controller from time to time asks them
to take.

REINFORCED CONCRETE IN
COLLIERIES.

At the meeting of the Manchester Association of
Engineers held on December 14, a paper was read by
Mr. B. Taylor upon the “ Development of Reinforced
Concrete.” He said the use of reinforced concrete
as a building material had made rapid strides since
its introduction about 25 years ago. It was now
recognised as one of the standard and best materials
for various classes of construction. The Government
departments had adopted it for important works, and
encouraged others to use it, especially during the war,
when the shortage of steel was felt. This gave it a
great impetus.

After dealing with technical matters, the author
explained in detail, with the help of lantern slides,
many cases in which reinforced concrete had been used
successfully. Pit head gear, he said, could be very
economically and satisfactorily constructed by this
method. The advantages over timber construction were
seen in its fireproof qualities. .In fact, he believed the
Board of Trade did not permit timber headgears in
constructing new shafts at the present time.

In steel work, the constant scraping and painting
was an important item on headgears of large size, and
this was dispensed with by the employment of rein-
forced concrete. It could be constructed more econo-
mically ; it was heavier, and therefore steadier, than
steel or timber. This was seen to be an important
point when it was considered that the cage was guided
by ropes, and any movement of the sheaves at the
head while the cage was in motion was a serious draw-
back.

Reinforced concrete pit props had been used for
the mainways of colliery workings for some time, and
they were so satisfactory that he doubted very much
whether the colliery people would return to using
timber, even if it became cheap again. He did not
recommend reinforced concrete for the coal face
because the men there wanted to saw a few inches off
when convenient, and it was not an easy operation to
do this with concrete. But in the main ways when
the mine was established such props were ideal. A
great advantage was the longer life. The mine he
was referring to was very damp, and the life of the
timber props was about six months; but reinforced con-
crete props, which were put in three or four years ago,
were still standing; they had not been touched.

The aim had been to make the concrete prop the
same strength, or as near as possible, as the corre-
sponding timber prop. It was found by testing that
by a 5 in. timber prop the breaking load was in the
neighbourhood of 25 tons. A 4| in. concrete prop re-
inforced by 4f in. bars and hoops had a breaking load
in the neighbourhood of 25 tons. He was glad to see
that the miners themselves were beginning to appre-
ciate the advantages of these props. They were so
designed that the top was the weakest portion, and
when that gave way the prop could be taken out, the
concrete chipped away, the bar sawn off, and the prop,
although reduced in size, could be used again. One
prop was used three times over in this way. When it
was first tested it carried 25 tons or thereabouts. The
top was cut off, the bar trimmed up, and the second
time the prop carried a little more. The third time
it carried 25 tons or thereabouts. Sometimes a squeeze
came on, and whatever was put in could not resist that
squeeze—something must go. In that case the top of
the prop would go and the prop could then be taken
out and used somewhere else after the top had been
cut off.

Another example of this method was the bunkers
erected at Dalmarnock for the Glasgow Corporation
for the storage of coke. The coke was carried from the
retort house by an overhead electric runway, tipped
into a hopper, which delivered it into a revolving srceen
fixed on the top of the bunkers, and arranged so that
the various gradings of the coke in their passage down
the screen would fall into the various compartments of
the bunker.

In preparing the calculation for the design the coke
was taken as weighing 351b. per cu. ft., and having
an angle of repose of 40 degs.

The type of design adopted was to have a tie beam
running from wall to wall at a height which would
allow the top portion to be cantilevered, and keep the
same area of steel as in the lower portion, which would
be taken as a beam fixed at the bottom and by the
tie beam near the top.

These vertical beams, with a corresponding slab,
took the full pressure of the coke, and by arranging
the ribs on the outside, the advantage of slab forming
the compressional side of the beam was obtained. By
adopting this method fairly straightforward form of
design was obtained.

Owing to the number of columns underneath on one
front having to be a minimum to permit of railway
trucks, carts, etc., passing underneath without diffi-
culty, the supporting beams running parallel to the
hoppers were naturally very large, having to carry a
very big proportion of the load.

A difficulty that arose was that the ground was very
poor, having been filled in for a very considerable
depth, too deep to think of excavating: before resort-
ing to piling a test was made to see the carrying
capacity, and it was found that with a load of one ton
per sq. ft. there should be no fear of uneven settle-
ment. It was, therefore, decided to adopt a raft form
of construction under each line of columns, having
inverted arches between the columns, as shown on
slide. This was deemed preferable to putting a raft
over the whole site, as the variation between the loads
on the columns was very considerable, the corner
columns only having a load of 67 tons, whilst some of
the internal columns had a load as much as 417 tons.

After the bunkers had been in use for some time, it
was found that the movement of the coke downwards
had bent some of the tie beams, and the conclusion
arrived at was that the coke being in large pieces in
this particular bin was bridging itself between the tie
beams, which were only 10 ft. apart. It was decided