240

THE COLLIERY GUARDIAN.

February 2, 1917.

Prof. Fearnsides referred. With the work of Dr. Mellor,
they were,in some measure familiar. He was glad that
they had someone, not only in Staffordshire, but in
Yorkshire, who was so much au -fait with the problems of
refractory materials, and he thought they might pro-
phesy that Prof. Fearns'ides would very soon become
known in the refractory material world as one whose
opinion was very much to be valued, trusted, and
respected. They had all had their' experiences of
different ooke oven bricks, but in the past they had not
given much scientific thought to the questions, either as
coke oven managers or as makers of refractory materials.
Now that their thoughts had been set running in such
grooves, however, he was sure that they would consider
these matters very much in the future, and he should
look forward with pleasure to a continuation of Prof.
Fearnsides’ remarks.

Mr. W. Green (Manvers Main) said they had that
night laid the foundation of a very good study, which
they could pursue with advantage not only to themselves
but to their companies, in endeavouring to arrive at a
satisfactory solution of the problem of a coke oven brick
which would stand the heating effects that went on in
the ordinary life of an oven, and would also stand the
codling down process which went on when re-lining or
patching became necessary. The question of the admix-
ture of the two refractory materials, in order to obtain
a proper brick, was very important. He thought that
was what was most needed. He thought it was chiefly
in South Yorkshire that they had heard complaints of
oven walls being rotten, and the salt high. They did
not hear the same reports from Durham. Usually, the
trouble was put down to the salt problem, but he thought
that Prof. Fearnsides’ suggestion ais to the admixture of
the' bricks would give them the correct solution. As
Prof. Cobh told them last year, the salt volatilised at a
much lower temperature than its melting point. When
the oven was charged, a cooling-down process occurred,
owing to the liberation of the moisture which was
charged with the coal, and which was often 10 per cent,
and upwards. The salt was then assumed to volatilise,
and pass into the walls through the broken face,.gradu-
ally going further and further into the brick at those low
temperatures. Then, when the oven got up to the
higher temperature, there ensued the fluxing action
which had such disastrous results on the coke oven walls.
As Prof. Fearnsides had put it, they would want to get
a brick which would satisfy their requirements. The
principal thing necessary appeared to be a brick with
such a smooth face that it would readily resist the action
. of the salting process which was presumed to .occur. On
that point, he did not think there was any really defi-
nite information, but Prof. Cobb’s theory was more or
less readily accepted. Attempts had been made to meet
the trouble. Coke oven walls had been washed with
cements, but the cements cracked off in due course. He
believed that one of the latest theories was to face the
brick with a special refractory, but, whilst this had
proved satisfactory during the heating process, it failed
when the cooling down was reached. It remained for
them to go further in this direction.

Even Burning Necessary.

Mr. J. Wilson (Staveley) said he had been very much
struck with the counter-balancing action which Prof.
Fearnsides had described. He thought that put before
'the brickmakers the problem of even burning, which
seemed to him la most difficult thing to accomplish. The
ordinary rectangular kiln, which was used for the pur-
pose of making coke oven bricks, was certainly not
evenly heated. The fires were on each side of it, so
that the bricks nearest to the fires would certainly get
the mos't heat, however carefully matters were arranged
with regard to the draught. He considered that the
failure of certain bricks was probably due to this uneven
burning in the kiln. At the colliery with which he was
connected, they had had batteries of ovens which, as a
whole, had stood very well, but in which there had been
isolated cases of bricks melting out in the flues at tem-
peratures for which they could not blame the gasmen.
They seemed to have collapsed, and then gone through.
The larger the brick, of course, the more readily this
would occur. He thought the makers had a great diffi-
culty before them in this respect.

Mr. J. W. Lee (Grassmoor), in adding his thanks to
Prof. Fearnsides, said he had had a fair number of
years’ experience of ordinary analytical work on bricks,
for the purpose of deciding the composition of the bricks
to be placed in various positions in the gas producer.
This work, he suggested, had been done much more
accurately, and with much more attention, in the gas
industry than in, the coke oven industry proper, and
therefore it seemed to him that if they in their industry
came to something like the same decisions which some
years ago were come to in connection with the gas
industry, they would be wise. Some ten years ago,
enquiries were sent out to all the gas companies and
corporations, asking'for information as to the tempera-
tures of the various parts of their settings at which the
bricks were going to be used. As one who had the work
of providing the information from the Sheffield Gas Com-
pany, he knew with what very great care they obtained
the temperatures of their combustion chambers, of the
tops, bottoms, middles, runners, and all the other parts
of their settings. This information was obtained from
all the gas companies who were willing and able to
supply it, was taken before the Refractory Committee of
the Gas Industry and before the makers of bricks, and
attempts were then made to lay down a specification as
to the bricks which were going to* be used. He knew
that the result had not been, perhaps,, as satisfactory
as one would have hoped, and this was partly due to the
practical difficulty of brick producing which had been
mentioned by Mr. Wilson. It was not an easy matter
to heat the bricks evenly in every part of a kiln, or even
to heat a single brick uniformly. He had seen bricks

which had been .perfectly burned on the outside, but
was black at the core. It seemed to him that their first
business was to lay down the conditions under which
their bricks had to. be used. Having done that, first
for their, own information and later on for the Informa-
tion of the brick people, they would have taken the first
step towards a satisfactory solution of the difficulty of
the working of their bricks. But at present they did
not know this themselves. How many people in the
coking industry were sufficiently well equipped to pro-
vide this information ? He did not say this in criticism
—-he was asking it of himself, as well as of others. How
many of them had any idea of what they wanted? For
that reason, among many others, Prof. Fearnsides had
placed them under an obligation by laying down the
first principles of the reactions which took place when
bricks were heated.’ They had begun to learn. They
asked of Prof. Fearnsides, and the other members of the
' university staff, that they would continue the lessons,
until they had shown the coke oven managers all that
they needed. They would then demand from the brick
makers the things which they needed, and he believed
there were sufficient brick makers of high standing in
the country to- produce these things for them. As one
who had some little experience, and who had attempted
for some years in that university to describe something
of the physical .changes that took place in bricks, know-
ing that chemical analysis was not sufficient to answer
all the problems, lie added bis word of thanks to those
already expressed to Prof. Fearnsides.

Fine v. Coarse Grain.

. Mr. A. R. Fleming (Sil ver wood) -said he had had con-
siderable analytical experience in testing bricks. When
he first began to consider the question of satisfactory
coke oven bricks, and looked round for the requirements
necessary in a good brick, he found there was some con-
fusion in the general ideas of the' coke oven people.
Finally, he managed to evolve a sort of specification
which seemed to meet the case. One of the chief
qualities required was as little expansion or contraction
as possible—none, if practicable; but that could not
always be attained. The bricks must resist change of
temperature. In order to do this, the wall bricks,
which were subjected to the. most severe changes,
should be made as porous as possible, and generally of
rather coarse-grained material. That was the old idea,
before they knew anything about crystal changes or
eutectic curves. Again, they wanted resistance against
chemical attack, by the vapours from the fuel, and so
forth; and they also wanted a smooth upper surf ace,’’and
a capacity for resistance to mechanical friction and
impact. This seemed to contradict, to some extent, the
idea of the coarse-grained structure of the brick, but he
was simply speaking about the upper surface, the sur-
face of the walls. Further, they wanted exact shape of
the bricks, by slow, drying, careful handling, and skilful
burning. Looking into this matter, he discovered, some
years back, that there seemed to be -great discrepancies
between the figures given by various authorities for the
melting point of the bricks, the melting point of silica,
even, and alumina. Kanolt gave the melting point of
kaolin, as 1,735 to 1,740 degs. Cent.; he said that silica
brick melted at 1,700 degs., but he also remarked that
silica began to melt at 1,600 degs. to a very viscous
liquid.—(Prof. Fearnsides: 1,470degs. For making
silica tubes, you do not carry past 1,500 degs.)—In 1910,
,a specification was put ’ before the gas people by the
Institute of Gas Engineers, which said : “A piece of
brick shall show no fusion when heated to a tempera-
ture of 1,630 degs. Cent.’.’ This temperature, however,
was the fusing point of pure silica. The bricks referred
to had to be in an oxidising atmosphere.. The question of
porosity seemed to have some significance. He found
that there were well-known methods for determining
porosity, 'but in the whole range of the literature on the
subject there was no statement as to what was a desir-
able porosity, whether it had to be 5 or 15. As he was
proposing to do some research on the subject, he looked
round for a suitable furnace for heating the samples.
First, he considered the Deville furnace, 'but he was
informed that this was not quite suitable for the pur-
pose, owing, he believed, to the reducing atmosphere
produced, and the difficulty of keeping the heating
chamber at a constant temperature. Then he thought
of an electric furnace, but discovered that none of the
makers could produce one that would go to a sufficiently
high temperature to take a large enough sample to be
of any practical! use. A coke oven brick was of a very
mixed nature, and if they wanted a really practical test,v
they should take a sample of, at any rate, ta quarter of
a brick in size, and heat it to a temperature of at least
1,400 degs. Cent. The curve that Prof. Fearnsides had
given them was interesting indeed. As a rule, they
found that in the centre of the oven the highest tempera-
ture they got was about 900 to 1,000 degs., and in the
walls outside they often got from 1,200 to 1,300 degs.
These figures seemed to lie between the points of 875 and
1,470, the range of temperature which they had to con-
sider. It would certainly seem that there was a great
deal in Prof. Fearnsides’ argument that they should con-
sider whether the brick makers would not be on the right-
track if they tried to so burn their bricks that the change
to tridymite would take place gradually, and counteract
the contraction. -They had alii discovered that there was
a great deal to be learned with regard to this, matter.
They had now to evolve apparatus for testing the bricks
in a proper manner, and to discover how far these
crystalline substances did influence the melting tem-
perature; and ’also the-whole question of the influence of
the impurities on the kaolinite quartz mixture needed
investigation.

Mr. T. H. Riley (Tinsley Park) seconded the Vote of
thanks. He hoped the series of lectures would be con-
tinued, and that, by the time they were finished, the
coke oven managers would be able to get the brick

makers to make them a brick which would stand for
ten years. "	.

The President, in putting the resolution, said the
lecture had been listened to with the greatest possible
interest. If Prof. Fearnsides had done nothing else, he
had at least showjn them that they knew very little- about
the matter. He could foresee a very unpleasant time
for the. brick makers in the near future.

- The resolution/ was cordially adopted.

Action of Salt.

Prof. Fearnsides, in reply, emphasised the fact that
it took ais long to get the expansion out of a brick as to
get it in, and the time allowed for cooling must be equal
to that allowed for heating. The action of salt was a
very complicated matter indeed. Probably its most
important action was that they had the alkalies vola-
tilised. He was not sure that it was always sodium
chloride. He believed that, although very few chemists
were able to find it, they had a very great deal of potash.
He> had. recently had the opportunity to examine a con-
siderable amount of flue dust from coke ovens, and
potash was a thing to be watched. He got some bricks
that had failed by reason of salting, and found that the
mineral which had formed in them was potash felspar.
That was an awful shock. He should not be surprised
if this was important to coke oven users in more ways
than one, and they would find potash salts in some of
their recovery processes. Soda was bad enough by
itself, but soda and potash together brought down the
eutectic temperature further and further. Although
they might make a coke oven brick in which the first
liquid that formed after the water had gone away did
not begin to form till a temperature of 800 degs. Cent,
was reached, yet,, if they got some salt in, some soda,
and some potash, he believed there would be liquid in
the brick at temperatures as low as 600 degs., and pro-
bably 500degs., and that would spoil the refractory pro-
perties altogether. That meant that they must arrange
their brick bases so that the material would not go in.
Mr. Green had spoken of preventing volatilisation into
the cracks. Let them do that as much as possible : thev
would be doing good. Possibly the way to deal with it
was to have a glaze. He had seen the behaviour of coke
oven bricks in kilns which were used for the burning of
silica, and which were- taken up to temperatures far
higher than those reached in coke ovens. The ordinarv
coke oven brick, raised to a high temperature on the
inside, and cold on the outside, maintained its shape in
a very • excellent way, and formed an excellent glaze,
and in consequence of that they got an impervious skin
which was.highly refractory, beyond anything that they
could possibly want. He did not know whether there
was a possibility of glazing coke oven walls by some
surface process within the empty ovens. Probably that
would come. He wondered whether an acetylene blow-
lamp had been tried. That was a suggestion that he
threw out. It might be no good at all, but it would do
something, and would give them a glaze that- would
stick on to .the bricks.—(A member said this had been
tried, and without success.)—If they could not put a
glaze on, the important thing, aS far as he could see,
was to put a glaze in. So long.as they had the expan-
sion, and the quartz grains keeping the others tight,
they would keep the cracks tight; and if thev could stop
the gas going through, it would stop the other materials
penetrating. He was convinced that if they made their
bricks, of porcelain—and he thought they -could with the
material they had, which possessed the essential con-
stituents of porcelain—they would do well. That, he
thought, would, be arranged when they got the expansion
of their silica in big pieces. As far as he could make
out, the successful coke oven bricks of the past had
been those which had got lumps of silica in. These had
kept the kaolin .material in compression all the time.
Therefore, he said, “ use coarse silica, and don’t grind
the things, together too fine.” The success of ithe
Halifax bricks had been mentioned, together with a
figure of 86 per -cent. It was a very fortunate thing that
there were in the Halifax neighbourhood several beds—
one in particular—which happened to come up to that,
by natural selection. He thought it was essential that
these beds should not be used for anything but coke oven
bricks.. But there was trouble, even with them, because
the silica in the clay was exceedingly fine-grained.
There was -a certain quantity of fluxes in the clay, and
as time went on, when the bricks were in use, the silica
was effectively fluxed, until the grains got smaller and
smaller, and finally went, and the life of the bricks then
came to an end. It appeared from experience of which
he had knowledge, that that life, with a non-salty coal,
could often be three or four years. He was certain that
the. Germans had succeeded in balancing the expansion
against the contraction by using eoarsed grog of silica
in a very fine matrix of the other stuff. There was,
where the one met the other, a sticky glaze. Prof.
Fearnsides finished his remarks by discussing the causes
of “ black-hearting ” or “ steaming,” with which he
dealt before- the Midland Institute in December (see
Colliery Guardian, Dec. 15, 1916).

Revised List of Certified Occupations.—The Local Govern-
ment Board has issued a new list of certified occupations.
The chief alteration introduced is the removal from the list
of men classed as Bl (garrison service abroad) who fall
below the age limits stated in previous lists. The age limi rs
for married men have been very generally raised, usually
either from 25 to 27 or from 31 to 33. Larger advances
have been made in a number of cases in many occupations.
The only change directly affecting coal miners is that men
who have entered the mines since August 15, 1915, are no
longer entitled to be treated as in a certified occupation. The
age limit in steel and tin-plate manufacturing has been
raised from 31 to 41.