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Tttfi COLLIERY GVaWMAN.

July 31, 1914.

a revolving stirrer C driven by the motor D. The motor
drives also a scraper conveyor E, which brings the coal
from the hopper into the funnel F. The funnel con-
ducts the- coal into the space between a belt G and the
channel wheel H. This is of pulley shape, but the
groove on its periphery forms, when in contact with the
belt G, a large channel, and the coal is thus laid on the
belt G in a certain shape. By the great speed of the
belt the coal is thrown off from the bottom pulley I,
over which the belt returns, and the force is so great
that the coal is carried 30 ft. wide. To ensure an even
filling on the ovens, an iron channel K is introduced
through the levelling door into the oven, and guides the
coal to the opposite end. As the retort is filled this
channel is gradually withdrawn by the man in charge
operating the motor and winch work L, until the oven
is completely filled. Although these machines work
excellently in gas works, their introduction on coke
oven plants has met with difficulties which the makers,
as far as the writer learns, have not altogether been
able to remove. While in gas works the coal is prac-
tically dry, and contains a certain amount of lumps,,
on coke oven plants the coal is evenly ground to fine-
ness, and mostly contains between 10 and 13 per cent,
of water. The coal thus forms a cake on the belt, if the
moisture is too high, and is not thrown far enough into
the ovens.

A machine similar in appearance, but working on an
entirely different principle, is the one by Messrs. Grono
and Stoecker, of Oberhausen, in Germany, shown in
fig. 23. The fig. 23 shows the arrangement combined
with a pushing machine. The inventors claim with
this construction the abandonment of all smoke while
charging. While the machine fig. 22 commences
charging on the coke bench side, this machine begins
charging behind the machine side door. Encased in
an all round closed channel runs a conveyor with open-
ing on the bottom on the end introduced into the oven,
and opening on top on the opposite end. The top part
of the machine forms a bunker with inclined side walls
uniting on the bottom in a row of small hoppers with
bottom doors. The top opening of the conveyor on the
end furthest from the oven is provided with a vertical
branch which, by a catch, automatically opens the
bottom doors of the hoppers while passing. The capa-
city of the hopper corresponds exactly with the con-
tents of an oven. In the machine the conveyor case is
conducted over a number of carrying rolls. When
introduced into the ovens the openings in the oven
doors are such that the conveyor casing fits tightly in
the oven door, so that no gas can escape. The motor
moves the casing along, thereby opening the hopper
slide furthest from the oven. As the first hopper com-
partment gets empty a proportional part of the oven is
filled to the top, and the casing is moved further, open-
ing the next slide, and so on until the hopper is empty
and the oven filled. The arrangement offers the advan-
tage that the conveyor case, when in the oven any dis-
tance, is supported by the coal charge underneath it,
and is further provided by the charge underneath the
conveyor with a comparatively cool space, so that it
does not suffer by the heat; in any case not more than a
levelling rod. Another suggestion is to let a row of
bricks project under the crown of the retort arches in
both walls opposite each other, and let the casing by
means of two rolls move on those.

Charging machines are introducing themselves
rapidly in this country now, and newdy-built batteries
are nearly in all cases provided with electrically-driven
cars if a compression of the coal is not needed.

FUEL: CASEOUS, LIQUID, AND SOLID.

A discussion on the above subject took place recently
before the Birmingham section of the Society of
Chemical Industry. Prof. John W. Cobb (Leeds), in
opening the discussion, said that coal was not simply a
potential source of so many heat units, but was a
chemical substance capable of yielding other chemical
substances of considerable commercial value on its way
to carbon dioxide and water if the process were con-
trolled. This was the reason for the existence of many
fuel problems, and particularly modern fuel problems.
The existence of the smoke nuisance might be said
briefly to be due to the particular fact that, though dis-
tillation and oxidation of coal could both go on at low
temperatures, the distillation reached a high velocity at
a comparatively low temperature, at which combustion
was very slow. Another problem arose from the diffi-
culty of using large quantities of fine coal dust. Bust
firing for boilers and furnaces was fortunately making
some headway. A practical method of dealing with the
smoke problem was to effect the combustion of coal in
more than one stage—in one, the coal was gasified; in
the other, the gas was burned. A blast of air used
below a deep layer of glowing coal half-burned it to
what was known as producer gas, which could be taken
away and burned completely where desired. It con-
tained the nitrogen of the air blast, and so was called
low-grade gas. If the coal were only heated without
contact with air, as in gas retorts or coke ovens, the gas
contained very little nitrogen, and was a high-grade gas.
The advantage of producer gas was made obvious to
certain industries by the introduction of the important
principle (for fuel users) of regeneration. The process
of regeneration was necessary for high temperatures
with producer gas, but ceased to be of the same
importance with high-grade gas. There was also the
difficulty in applying the regenerative principle to small
furnaces, that the expense of construction would be
prohibitive, and the cost of renewal of complicated
working parts too great. The possibilities of producer

gas were much increased as soon as another disadvan-
tage was removed. For delicate work there should be
a proper control of the flow of gas and air; and the
regenerators, ports and passages should remain unfused,
and be free from dust. A considerable step was made
in the development of producer gas engineering and
furnaces when it became economical, on a large scale,
to wash producer gas. This was effected successfully
by the introduction of a plant, the primary purpose of
which was the recovery of ammonia. A claim had
recently been made that the same high ammonia results
could be obtained with a smaller quantity of steam in
the blast essentially by water jacketing the top of the
producer. But he thought that those who had had
much to do with the ammonia recovery process would
require a stricter and narrower definition of the claim
made before accepting its probable validity. Ammonia
recovery introduced a new problem, since ammonia,
when it was recovered in producer gas, coal gas, or
coke oven practice as ammonium sulphate, required
that sulphuric acid should be brought to it, and this had
to be bought or made. Interest, therefore, attached to
any process which would do away with the necessity
of providing sulphuric acid, especially in plants erected
in somewhat inaccessible places abroad. The sulphur
was in the coal. The ammonium sulphide was in the
gas, and by the simple addition of oxygen one got
ammonium sulphate. The addition of the oxygen was
not a process as simple as it appeared, but several
processes were on trial for doing it. If no oxygen were
used in gasifying coal, most of the carbon remained as
coke; the rest going forward with other constituents
as permanent gas, and as vapours. Modern develop-
ments were tending to unify the science and practice of
carbonisation to this extent—that it would be more
necessary in the future carefully to consider local con-
ditions and markets, and decide what modification of
plants, or what combination of them, was most
effective. The old horizontal retort was being, to some
extent, replaced by the vertical retort, in which gravita-
tion was used to save labour; and continuous vertical
retorts were another development. Processes were
also being tried and worked in which the temperature
and the conditions of carbonisation were even further
altered from the normal. One object was to make a
coke which ignited easily and burned cheerfully. A
disadvantage of low7 temperature coke was that it was
rather soft for carriage; and there was a difficulty in
controlling the distribution of temperature in a retort
working at low temperatures. It was apt to be
irregular. In low temperature carbonisation it was not
only the coke which was altered, but the gas was richer,
and the tars and oils which came out and condensed
were lighter. This was now a point of great importance,
because of the large and increasing use of motor traffic
and internal combustion engines generally. The
demand had arisen for an increased supply of an oil or
spirit which was easily and completely volatilised in a
current of cool air, and could be used in a carburettor.
One way of meeting the difficulty was to design a new
carburettor working on a less volatile oil. Another way
was to work out a process by which a mixture of oils of
different densities, such as a crude petroleum, could be
altered in chemical nature so as to contain a much
higher proportion of volatile oils. Work in both these
directions was being prosecuted vigorously. A third
way which would increase the supply, although not to
the extent sometimes stated, was to carbonise coal so
as to yield a large supply of light oils. In the coalite
process this was done by using a lower temperature;
but processes were also being tried using higher and
lower pressures. It was not, of course, correct to say
that high benzene yields resulted from low tempera-
tures; as a matter of fact, the volatile oils produced
were more like petrol itself.

Whether coke or gas’, or both, were burned, we should
be freed from the smoke nuisance. But the gas indus-
try was handicapped by a system of selling gas at a
price' too far above that of its manufacture and distri-
bution. This policy had been defended as a definite
means of indirect municipal taxation. It was a tax
placed upon the home manufactured article; and the
competitor, raw coal, was out of reach of the imposer.
In effect, it placed a premium upon the wasteful use
of fuel and the pollution of the atmosphere.

Dr. W. B. Davidson said he was strongly in agree-
ment with Professor Cobb in suggesting that coal should
be brought into disuse as much as possible, in favour
of coke and gas. He was glad that Professor Cobb
hit out against municipalities who contributed to the
rates from the gas profits. It was a great mistake not
to reduce the price of gas to the lowest point. There
was, he added, a tremendous wastage of fuel even in
gas works where huge quantities of coal w’ere dealt with.
In Birmingham the amount required in heating the
retorts was 100,000 tons; and this amount could be cut
down by the simple device of controlling the primary
air, as by Brooke’s air regulator. At one of the city
gas works the fuel consumed had been reduced from
25,000 tons to 16,000 tons per annum—a saving of
9,000 tons, or an equivalent of £5,000. If this were
done in the whole of the Birmingham gas works there
would be a saving of 35,000 tons, or nearly £20,000 per
annum.

Mr. Cooper stated that the production of metallurgical
coke was about 11 million tons per annum, of which
not more than 65 to 70 per cent, was produced in a
scientific way. He was very sceptical as to the claims
made in relation to the results of low temperature
carbonisation. An interesting development of this
system of carbonisation which w7as to be worked on a
Yorkshire colliery was a combination of the coalite
process with gasification of the resulting coke in gas
producers. The company working this scheme had
realised the difficulty they might be faced with when
it came to- getting rid of the smokeless fuel; and they
had, therefore, adopted the idea of gasifying this in

producers and recovering the ammonia. The surplus
gas w'as to be sold to an electric power company for the
production of electricity. On a coke oven plant the
surplus gas was used for boiler firing purposes, and in
some cases in gas engines. Its value on the colliery
for boiler firing purposes as compared with coal, on the
calorific value basis, was about 2d. per 1,000 cu. ft.

Mr. H. T. Pinnock pointed out that it was the
application of the regenerative and recuperative
principle that brought prominence and position to
producer gas. The principle was easily applied, and it
was this circumstance which made it possible for pro-
ducer gas to compete with higher power calorific gas
for high temperature furnace use. Finality had not
been reached in regard to producer gas; and he thought
it was likely to develop to this end on the lines of
reduced steam consumption for making ammonia. He
thought there would be difficulty, if it was a producer
of large size—of from 10 ft. to 11 ft. diameter—to cool
the interior of it sufficiently, merely by outside water
jacketing. Another way in which producer plants
might be expected to improve was in the more
centralised extraction of tar.

Mr. W. J. Rees was of opinion that progress must
be along the lines of the recovery of the by-products,
particularly in gas producer work. The serious question
presented was the immense capital expenditure neces-
sary in laying down recovery plants with works using
large quantities of coal. It was also necessary to aim
at the further removal of dust and of sulphur from
producer gas; and if this could be economically achieved
without resort to by-product recovery, the advantage
would be considerable to many industries, and to the
glass industry in particular. With some fuels it was
possible to keep some of the sulphur out of the pro-
ducer gas by sprinkling the fuel with milk of lime;
but this method was not really satisfactory in any way.
As to the coal dust problem, it was possible that much
of the dust could be used by mixing with tar, and
using in briquetted form.

Mr. E. W. Smith said it was startling to hear that
coal gas could be produced even at a colliery at 2d. per
1,000 cu. ft. No doubt it could be made in the retort
house at this figure; but then all the charges for
carriage, coal handling, and purifying the gas, and for
distribution, must be added. He had no faith in the
claims made for ‘ ‘ surface combustion ’ ’ at high tem-
perature, nor with the results obtained. Although he
had seen large apparatus working under the so-called
new process, he had seen nothing, either in boilers or
furnaces, practicable, or likely, efficiently, to last. The
scientific explanations given with regard to surface
combustion—in which there was nothing new either
in the forni of combustion or the type of furnace
employed — were unnecessary and unsatisfactory.
Interest would centre on an experiment shortly to be
made, on the lines of low temperature carbonisation,
by a large firm of continuous vertical retort makers.
They were about to instal a plant in the Midlands for
experiments on these lines mainly with a view to
producing hard coke and large volatile oil yields. In
the Birmingham gas works fuel was being used in what
appeared to be an ideal way. The volatile matter was
first driven off from the coal; and the coke was then
put into producers and gasified, and gas was made from
this product with which the retorts were heated. This
method gave the further advantage of enabling them to
obtain by-products in sulphate. A drawback in the use
of producer gas for industrial purposes lay in the fact
that it contained a large amount of sulphur compounds.
This was an almost insuperable stumbing block in many
processes. In the new corporation plant experience
showed that the tar was materially reduced by the
centrifugal extractors before the saw’dust scrubbers were
reached. He did not see why it should not be possible
to use coal dust when low in ash in coke ovens com-
pressed with water. The coke w’ould be useful for small
furnace work if the ash content was not too high. A
coke of high porosity burned much more easily than
ordinary gas coke, and ignited immediately from chips.
By co-operation w’ith the local gas officials experiments
were to be made on making “ producer ” gas from the
dried sludge with recovery of the nitrogen as ammonium
sulphate.

Professor Cobb, in reply, said as regards tar extraction
and ammonia recovery in producer gas plant, centralisa-
tion would simplify the cooling process; but he was
doubtful as to air condensers being applicable to large
plants. The difficulty of cooling depended upon the
fact that the thermal capacity was so enormously
increased by the latent heat of the steam present.
Calculations he had made on surface cooling gave dis-
couraging results for a plant of any size. One difficulty
of using coke oven gas in regenerative furnaces was the
considerable loss in actual heating power, when the gas
passed through the regenerator, on account of the
decomposition of hydrocarbons. Mixing with blast
furnace gas was reported to be successful. He agreed
that the coke oven process might deal satisfactorily with
dust of certain qualities. Ash could not be determined
accurately without very careful sampling, because so
much was concentrated in the smaller coal, and particu-
larly the dust. He agreed that the question of
purchasing coal, on standardised lines, would assume
greater importance in the future.

Winding Signals.—Messrs. John Davis and Son (Derby)
Limited, of All Saints Works, Derby, inform us that they
have designed a non-cumulative indicator, which indicates
“ men," and the second signal of “ 1 ” or “ 2 ” separately
on the same dial, and both remain visible until the signal
is complied with. Although their original design had the
sanction of the Home Office, colliery managers and winding
enginemen desired an entirely non-cumulative indicator.
Messrs. John Davis and Son have effected this with an
addition of one wire only to the existing electrical or
mechanical wires.