IMPROVEMENTS IN THE MANUFACTURE OF IRON AND STEEL, AND IN FURNACES AND APPARATUS CONNECTED THEREWITH, PART OF WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO THE CALCINING, REDUCING, AND BURNING OF ORES AND GRANULAR SUBSTANCES GENERALLY
Year: 1868

page_text: LETTERS PATENT to Charles William Siemens, of No. 3, Great
George Street, Westminster, in the County of Middlesex, for the
Invention of "IMPROVEMENTS IN THE MANUFACTURE OF IRON AND STEEL,
AND IN FURNACES AND APPARATUS CONNECTED THEREWITH, PART OF WHICH
IMPROVEMENTS ARE ALSO APPLICABLE TO THE CALCINING, REDUCING, AND
BURNING OF ORES AND GRANULAR SUBSTANCES GENERALLY."
Sealed the 22nd May 1869, and dated the 24th November 1868.
PROVISIONAL SPECIFICATION left by the said Charles William
Siemens at the Office of the Commissioners of Patents, with his.
Petition, on the 24th November 1868.
I, CHARLES WILLIAM SIEMENS, of No. 3, Great George Street,.
Westminster, in the County of Middlesex, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF IRON
AND STEEL AND IN FURNACES AND APPARATUS CONNECTED THEREWITH, PART
OF WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO THE CALCINING, REDUCING,

page_text: AND BURNING OF ORES AND GRANULAR SUBSTANCES GENERALLY, to be as
follows:-
My Invention has reference chiefly to certain processes by which iron
ores are purified and converted into metallic iron or steel, including the
process of puddling, but part of these improvements are applicable also
to the calcining, roasting, and burning of other ores and of granular
substances generally. If iron or other metallic ores contain water of
hydration, carbonic acid, sulphur, or other volatile constituents, they are
generally roasted or calcined in kilns, or upon the bed of a long
reverberatory furnace. The calcining kiln has the advantage of greater
simplicity, but is only applicable to ore in pieces of such size that the
flame can circulate between them, whereas the calcining furnace has to
be resorted to in dealing with ores of small grain or of a friable nature.
The latter process has the advantage that no residual matter resulting
from the combustion of solid fuel is mixed with the ore and that the
temperature and time of operation can be varied at will, but on the
other hand it involves a considerable amount of attention and manual
labour in turning the ore.
The first part of my Invention consists in effecting the calcination of
metallic ores, and also the burning of such substances as cement, lime,
or plaster of Paris in a drum or cylinder of iron lined with fire-brick
which is mounted upon rollers and is made to rotate round its horizontal
axis. The ores or substances to be burnt are introduced in the axis at
one extremity of the rotating drum, and being worked forward by the
rotation they finally drop in a continuous manner from the other open
extremity into a stationary receiver or chamber whence they can be
removed at pleasure. A smoke box communicating with a chimney is
fitted to the extremity of the cylinder where the ores enter, and a
current of air is induced by the chimney to pass through an outer jacket
of the smoke box and through longitudinal channels in the lining of the
drum itself to the ore receiving chamber, where it is met in a heated
condition by a current or currents of combustible gas which has also
been previously heated by passing through a jacket surrounding the
receiving chamber. The flame thus resulting at or near the extremity
of exit of the rotating drum passes through the same, heating the ore,
and thence through the smoke box to the chimney, being thoroughly
deprived of heat by the cold incoming ore and the incoming air in the
smoke box jacket. The combustible gases employed may be derived
from a blast furnace or from a gas producer, such as described in the

page_text: Specifications to my former Patents No. 167, of 1861, and No. 3018, of
1864. If the volatile substance to be removed from the ore or other
substance is carbonic acid or moisture a sufficient supply of gas must be
admitted to raise its temperature near the exit to the requisite degree,
but the supply of gas may be very much reduced and may even be
stopped entirely if sulphur is emitted from the ore in considerable
quantity. The sulphurous acid produced in that case may be condensed
or utilized by passing the products of combustion through a scrubber or
through lead chambers on their way to the chimney or to an exhausting
apparatus, or a jet of water may be introduced at the bottom of the
smoke box for condensing the gases. By leading the combustible gas
forward through a pipe into the rotating drum the combustion may be
conveniently made to take place at a point at some distance from the
exit end of the drum in order to expose the calcined ore finally to the.
chemical action of the uncombined oxygen of the air passing in and to
impart additional heat to the air and gas before entering into combustion.
By the accumulative action thus set up the maximum temperature
within the rotating drum may be raised even to a white heat. If the
ores contain such foreign substances as may be rendered volatile or
soluble by the chemical reaction of another substance under the influence
of heat, such other substance may be charged in with the ore in the
requisite proportion. Thus for instance, if the iron ore under treatment
contains copper common salt may be added, and the chloride of copper
produced may be separated by levigating the calcined ore, or if the iron
ore contains sulphur this may be converted into sulphate of iron by
oxidation and then removed by levigation. The calcined ores may be
made to fall through a spout from the revolving drum into a cistern
filled with water, whence they are raised by a Jacob's ladder to the plat-
form or hopper of the smelting furnace, being at the same time subjected
to the action of a shower bath of fresh water for removing therefrom all
soluble matter. In cases where the calcined ores have not to be washed,
but are intended to be smelted or reduced into the metallic state, I prefer
to place the calcining cylinder above the smelting or reducing furnace.
in order to save the heat residing in the calcined ore for the succeeding
operation. Thus these calciners may be placed on the top of a blast
furnace or over the receiving hopper of the ore reducing apparatus
described in the Specification to my Patent No. 1892, of 1868, for the
manufacture of cast steel from the ore. If I want to produce pulverulent
metallic iron, I combine the calciner above described with the rotating

page_text: ore reducing apparatus described in my former Patent just alluded to,
the reduced ore being made to fall into a closed metallic chamber which
is cooled externally by currents of water or gases, and which is provided
with doors at the lower extremity for the removal of the pulverulent
iron after it has had time to cool to prevent its taking fire when brought
into contact with the atmospheric air. Such cold pulverulent iron I
sometimes require for changing rapidly the temper of a bath of liquid
cast steel, but its chief application for the objects of my present
Invention consists in using it for making the bottom and sides of the
liquid metallic bath of cast steel upon the open hearth of a regenerative
gas furnace or of a puddling furnace. For this purpose I mix say
100 parts by weight of pulverulent metallic iron with from say 15 to 25
parts of ground fire-clay. This mixture may be effected dry under a
pair of edge runners or other mixing apparatus, or it may be effected by
mixing the ground clay with oil or tar to the consistency of a liquid
paste, and by mixing the pulverulent iron into this paste until a uniform
doughy substance is produced which can be laid aside for use. In
making up the bottom and sides of a steel melting furnace the dry
mixture will be preferable, which
of the furnace (in melting the G
metallic iron), but in puddling ir
e consolidated purely by the heat
cervening between the particles of
prefer the use of the wet or doughy
compound. The form of puddling furnace which I prefer to employ is the
regenerative puddling furnace with horizontal regenerators similar to the
one described in the Specification to my Patent No. 1172, of 1868, but
instead of a single furnace I prefer a double furnace, that is to say, a
furnace of double the usual capacity, with two working doors opposite
to each other, whereby the relative extent of lining surface required is
considerably decreased. At the back of this furnace I provide a
chamber through which a portion of the flame is made to circulate, and
which serves to heat the pig iron to redness before it is charged into
the puddling chamber.
Two such double furnaces are conveniently
arranged back to back. Instead of constructing the puddling pan of
plates of iron fitted into a frame with sides through which water is
generally made to circulate I prefer to make the puddling pan of mild
cast steel of considerable thickness, and to expose its exterior surface
only to a circulating current of air, cast steel being of such a tough
and infusible nature as to resist the action of the internal heat even
though no protecting lining or fettling were employed. Nevertheless, I
prefer to employ a lining of pulverulent metallic iron mixed with clay

page_text: as above described, which is not acted upon by the materials employed
in puddling to anything like the same extent as the "bulldog" or
roasted tap cinder usually employed for this purpose, and which I
consider exercises a deleterious influence upon the quality of the iron
produced owing to the sulphur and phosphorus which it generally
contains. In a scientific paper read by me before the British Association
of 1868, I have shown that the active oxydising agent in the process of
puddling does not reside in the flame as is generally supposed, but rather
in the oxides of iron which are invariably employed for fettling. Guided
by these views I discard the use of peroxides such as red ore finely
ground, which is expensive, and bulldog, which contains all the
impurities extracted from the puddled iron in previous operations, and I
employ comparatively pure and fusible protoxides or proto-peroxides,
such as hammer and roll slag and ores, in the proportion (say from 15
to 20 per cent) indicated by theory according to the amount of carbon,
silicon, sulphur, or phosphorus to be removed from the pig iron, and I
add such other oxydising and basic agents as will produce fluid cinder
poor in iron but capable of holding the impurities referred to. At the
same time I effect a great saving of manual labour by putting these
re-agents in such a form as to produce a violent commotion of the liquid
mass of metal and oxides. This I effect by filling a hollow cylinder
of lead with nitrate of soda, potash, salammoniac, ferrocyanide of
potassium, or any other salt which in its decomposition by heat gives
rise to a great development of gases, and which I mix previously with
oxides of iron, peroxide of manganese, or other oxydising agent. Or
I enclose these materials between discs of metallic lead or of lead and
iron combined. These cylinders, canisters, or discs are introduced into
the molten mass shortly before the "boil" would otherwise commence,
and being heavy (owing to the great specific gravity of the lead) they
sink to the bottom and cause a violent commotion of the mass
accompanied by energetic chemical action. The lead itself in melting
and combining with oxygen and with the cinder exercises a purifying
influence upon the metal produced, which is balled, hammered, and
rolled in the usual way. A metal of great purity and toughness is thus
produced and a considerable saving of materials and labour is effected.