IMPROVEMENTS IN THE PREPARATION OF REFRACTORY MATE- RIALS.
Year: 1879

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for the
Invention of "IMPROVEMENTS IN THE PREPARATION OF REFRACTORY MATE-
RIALS. A communication from abroad by Henri Harmet, of Denain, in the
Republic of France.
"
Sealed the 5th September 1879, and dated the 19th March 1879.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office of
the Commissioners of Patents on the 19th March 1879.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
PREPARATION OF REFRACTORY MATERIALS." [A communication from abroad by
Henri Harmet, of Denain, in the Republic of France.]
Magnesia, when calcined at a red heat, has the well known property of forming
with water a hydrate which, by simple exposure to the air, becomes as hard as
marble.
If lime, graphite, powdered coke, or the like, is added to this magnesia, the
formation of the hydrate embeds all these materials and makes the whole
compact.
This Invention has for its object the application of this property to the
manufacture of basic or carbonaceous bricks for the linings of metallurgical
apparatus.
If carbonate of magnesia cannot be obtained, dolomite (or carbonate of magnesia
and lime), as little silicious as possible, is taken and calcined in large pieces, as is
done with limestone, but to a red heat only without reaching a white, which more
or less destroys the hydraulic property of the magnesia; this is then broken as
small as possible, at the same time adding or not, according to circumstances, a
quantity of lime, graphite, on slow burning coke or other material, avoiding with
great care all silicious matter. Then the mixture, much moistened, is shaped into
bricks, either by hand or with a press; the bricks are left to themselves, and in a
short time they become very hard, unalterable by air or by moisture, and very easy
to use.

page_text: These bricks can, when required, be put into place without other preparation in
a converter, gas furnace, or any other apparatus, in the same way as ordinary bricks,
using a morter made with lime, or, better still, of calcined and broken dolomite,
which is moistened only at the moment of using.
Excellent tuyers for the bottoms of the converters made be formed in this
manner.
If before moistening the calcined dolomite a very large proportion of graphite or
slow burning coke is added, a mixture results, which after being made into bricks
and the formation of the hydrate, gives good results where a basic and carbonaceous
lining is required. Thus the crucibles of blast furnaces, the soles of gas furnaces,
the tuyers, and bottoms of converters and such like made with this mixture, behave
very well.
In place of making bricks the various mixtures may be rammed in place, but in
this case they must not be moistened until the last moment, as is done with hydraulic
lime.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt in the Great Seal Patent Office on the 19th September
1879.
SYDNEY PITT, of Sutton, in the County of Surrey.
"IMPROVEMENTS IN THE
PREPARATION OF REFRACTORY MATERIALS." A communication from abroad by
Henri Harmet, of Denain, in the Republic of France.
Magnesia, when calcined at a red heat, has the well known property of forming
with water a hydrate which, by simple exposure to the air, becomes as hard as
marble.
If lime, graphite, powdered coke, or the like is added to this magnesia, the
formation of the hydrate embeds all these materials, and makes the whole
compact.
This Invention has for its object the application of this property to the
manufacture of basic or carbonaceous bricks for the linings of metallurgical
apparatus.
As carbonate of magnesia cannot usually be obtained I take dolomite (or carbonate
of magnesia and lime), as little silicious as possible, and calcine it in large pieces, as
is done with limestone, but to a red heat only without reaching a white, which
more or less destroys the hydraulic property of the magnesia; this is then broken
as small as possible, at the same time adding or not, according to circumstances, a
quantity of lime, graphite, or slow burning coke or other material, avoiding with
great care all silicious matter. Then the mixture, much moistened, is shaped into
bricks, either by hand or with a press; the bricks are left to themselves, and in a
short time they become very hard, unalterable by air or by moisture, and very easy
to use.
To obtain an essentially basic brick, it is preferable to employ only a natural
dolomite, containing as much magnesia and as little silica as possible; after burning
it is crushed by millstones to a very fine powder without any chalk being added.
It is moistened uniformly under the millstones with the exact amount of water
necessary to form the hydrate, say, about one third of the weight of calcined
dolomite. The matter is then immediately put into brick moulds and moulded
under an ordinary pressure.
In the majority of cases it is well to add to the material under the millstones,
and before moistening it, a tenth part by weight of oxide of iron, or better, of cast
iron borings sifted through a fine sieve. When afterwards the bricks is in use and
is raised to a high temperature, the cast iron fuses and combines with the magnesia,
giving body to the part of the brick which is most highly heated, and which other-
wise would have a tendency to disintegrate.
These bricks can, when required, be put into place without other preparation in
a converter, gas furnace, or any other apparatus, in the same way as ordinary bricks,
using a mortar made with lime, or better still, of calcined and broken dolomite,
which is moistened only at the moment of using.
Excellent tuyeres for the bottoms of converters may be formed in this manner,
making use for moulding the tuyeres of either of the compositions given above, and
moulding them in the manner now practiced when moulding tuyeres.
If before moistening the calcined dolomite a very large proportion of graphite or
slow burning coke is added, a mixture results which, after being made into bricks
and the formation of the hydrate, gives good results where a basic and carbonaceous
lining is required.
When I desire to produce a carbonaceous brick, it is preferred to proceed as
follows:-
To obtain a basic carbonaceous brick, such as is often required in cases where an
energetic reductive action is desired in the presence of a basic slag, I introduce the
desired proportion of carbonaceous matter, coke, graphite, or other generally in

page_text: weight equal to that of the calcined dolomite under the millstones, which should
effect an intimate mixture before the addition of the water. The bricks are
produced and employed as already described. It is also well to add cast iron
borings or oxide of iron to the mixture whilst still dry, about a tenth by weight
of the calcined dolomite.
After moulding the bricks are kept for some time before they are used; until they
are thoroughly hardened. The same mixture of materials is applicable for the
manufacture of other articles; thus the crucibles of blast furnaces, the soles of gas
furnaces, the tuyeres, and bottoms of converters, and such like, made with those
mixtures, behave very well.
In place of making bricks the various mixtures may be rainmed in place, but in
this case they must not be moistened until the last moment, as is done with hydraulic
lime.
Having thus described the nature of the said Invention, and the manner of
performing the same, I would have it understood that I claim, the preparation of
refractory materials, and the moulding the same into bricks, tuyeres, and other
forms, and the production therefrom of furnace linings, substantially as described. ;
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand and
seal, this Eighteenth day of September, in the year of our Lord One thousand
eight hundred and seventy nine.