IM- PROVEMENTS IN FURNACES USED IN THE MANUFACTURE OF STEEL AND IRON, AND IN THE MANUFACTURE OF REFRACTORY BASIC MATERIALS
Year: 1878

page_text: LETTERS PATENT to Sidney Gilchrist Thomas, of 3, Queen's Road Villas,
Queen's Road, Battersea, in the County of Surrey, for the Invention of "IM-
PROVEMENTS IN FURNACES USED IN THE MANUFACTURE OF STEEL AND IRON,
AND IN THE MANUFACTURE OF REFRACTORY BASIC MATERIALS."
Scaled the 11th February 1879, and dated the 9th October 1878.
PROVISIONAL SPECIFICATION left by the said Sidney Gilchrist Thomas at
the Office of the Commissioners of Patents on the 9th October 1878.
SIDNEY GILCHRIST THOMAS, of 3, Queen's Road Villas, Queen's Road, Battersea,
in the County of Surrey. "IMPROVEMENTS IN FURNACES USED IN THE MANU-
FACTURE OF STEEL AND IRON, AND IN THE MANUFACTURE OF REFRACTORY BASIC
MATERIALS."
In carrying out the improvements in the manufacture of iron and steel detailed in
my Specifications No. 4422, in the year 1877, and Nos. 289 and 908, in the present
year, I find that silico-aluminous magnesian linestone, containing preferably not
less than about five per cent. silica and alumina, may be advantageously used as a
refractory basic material in blocks prepared by previous firing at a very high tempe-
rature. If magnesian limestone is not obtainable an aluminous non-magnesian
limestone may be used, but it is inferior to the magnesian stone. Hewn quarried
blocks, which should preferably be approximately square in shape and of moderate
dimensions, are exposed after drying at a low temperature to an intense white heat
(considerably higher than that at which fire-clay bricks are fired) in a kiln till all
the silica and alumina has entered into combination. A strong refractory basic
block is thus formed, which may be used with a basic cement, either with or without
subsequent dressing, in lining the Bessemer converter or open-hearth steel furnaces,
such as the Siemens, Pernot, and Ponsard furnaces. By their use the formation of
a basic slag is facilitated. These highly-fired blocks may also be used instead of
silica or fire-clay bricks in all furnaces in which a refractory basic lining material is
desirable, and for the manufacture of crucibles for steel melting, which may be cut
out of the blocks before or after firing.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sidney Gilchrist Thomas in the Great Seal Patent Office on the
5th April 1879.
SIDNEY GILCHRIST THOMAS, of 3, Queen's Road Villas, Queen's Road, Buttersea,
in the County of Surrey. "IMPROVEMENTS IN FURNACES USED IN THE MANU-
FACTURES OF STEEL AND IRON, AND IN THE MANUFACTURE OF REFRACTORY BASIC
MATERIALS."
In carrying out the improvements in the manufacture of iron and steel detailed
in my Specifications No. 289 and No. 908, in the year 1878,"
I find that silico-aluminous magnesian limestone, containing not less than about
five per cent. of silica and alumina together, may be advantageously used as a
refractory basic furnace-lining material in blocks prepared by previous firing at a
very intense temperature.
If magnesian limestone is not obtainable an aluminous non-magnesian limestone
may be used, but it is very inferior to the magnesian stone.
The composition I find it most advantageous for the stone to have is: silica, five
(5) to seven (7) per cent.; alumina, one and a half (1) to three (3) per cent.;
oxide of iron, one (1) to three (3) per cent.
The silica should not exceed twice the amount of the alumina and oxide of iron
together, nor should it in any case exceed ten (10) per cent., nor be less than three
(3) per cent.
As alumina and oxide of iron in presence of each other have a tendency to
diminish refractoriness, if there is much alumina there should be little oxide of iron,
and vice versa; thus if there is three (3) per cent. of alumina, it is well not to have
more than two (2) per cent. of oxide of iron. The more magnesia there is present
the better.
It should be present in the proportion of as nearly as possible two (2) parts of
magnesia to three (3) parts of lime to produce the best results.
The blocks for firing should not be very thin, and should be of moderate
dimensions, such as ten (10) to twelve (12) inches x six (6); or seven (7) inches x
three (3) or four (4) inches. The thickness of the blocks may conveniently be from
one-third (+) to one-fourth (+) of their length.
They should of course be of even structure and composition. They are burnt in
a kiln in which the heat can be raised to a very high temperature. The kiln may
be lined with lime bricks or good silica bricks, and must have a down draft. The
draft should be equally spread over the bottom of the kiln by making a false bottom
of lime bricks or blocks, or, if these are not obtainable, of limestone blocks, between
which are left a number of flue channels leading to the main flues, which are
preferably carried round three (3) sides of the kiln.
The false bottom is laid on a nine (9) to twelve (12) inch bottom of ground lime-
stone.
pre-
The fire-places should be of such aroa as to enable a heat at least equal, and
ferably superior, to that used in burning silica bricks to be used, as ordinary kiln
temperatures, such as generally used for burning fire-bricks, are of no use.
I prefer not to stack the blocks in the kiln to a greater height than four feet.
The firing must be continued till the blocks assume a dense, compact, hard, shrunk
structure, the whole of the silica and alumina, &c., entering into combination with
the lime and magnesia. The blocks should first be dried at a very gentle black heat,
and the temperature is then gradually raised for twenty-four (24) to forty-eight
(48) hours, according to the size of the kiln. The kiln must then be kept at an
intense white heat for from forty-eight (48) to ninety-six (96) hours, according to
its size, till the heat has penetrated thoroughly through the whole mass of the
blocks. The kiln is then cooled down very gradually, preferably at first by merely
slackening the supply of fuel to the fire-places. Throughout the burning great care

page_text: must be taken to prevent any cold air striking the blocks, for which reason the fire-
place should be divided from the body of the kiln by a partition wall, through or
over which the flame passes; or gas firing with heated air may be used. A strong
compact basic block is thus formed, which may be used with a basic cement, either
with or without subsequent dressing, in lining furnaces, particularly iron and steel.
furnaces. They are specially useful in lining Bessemer converters and open-hearth
steel furnaces, such as the Siemens, Ponsard, or Pernot furnaces, or other furnaces
where basic slags are required to be produced.
The blocks should be kept very dry, and preferably in a hot room till they are
used.
These shrunk highly-fired blocks may also be used for grinding up with liquids
to forin basic cements or ramming material (especially for converter bottoms).
When intended for this purpose the blocks are not of course dressed, but fired in
rather small rough blocks.
I do not claim the mere use of blocks of limestone as a furnace lining, but-
I claim the manufacture and use of hard, shrunk, compact basic blocks made
from limestone of substantially the composition herein described, the blocks being
prepared by firing them at a very intense temperature in the manner described.
In witness whereof, I, the said Sidney Gilchrist Thomas, have hereunto set
my hand and seal, this Third day of April, in the year of our Lord One
thousand eight hundred and seventy-nine.
ATVTRY 21 NTAT
SIDNEY G. THOMAS. (L.S.)