Improvements in Processes and Appliances for the Manufacture of Iron and Steel.
Year: 1891

page_text: Date of Application, 11th Mar., 1891
Complete Specification Left, 10th Dec., 1891-Accepted, 16th Jan., 1892
PROVISIONAL SPECIFICATION.
Improvements in Processes and Appliances for the Manufacture of
Iron and Steel.
I, JOSEF VON EURENWERTH, Professor at the Mining Academy at Leoben, in
the Austro-Hungarian Empire, do hereby declare the nature of my invention to be
as follows:-
In carrying out my direct process for the production of various grades of fluid
carburetted iron as described by the Specification of my Patent No. 4386 of 1890,
it is sometimes advantageous, to subject the iron ores to a preliminary reduction,
before they are introduced into the smelting hearth, because in this case the
carburation of the metal bath may be limited to the amount necessary for obtaining
that portion of the iron, which has not been reduced by the preliminary reduction,
and to that part which has been re-oxidised by the cooling of the spongy iron in
an oxidising atmosphere, or by the oxidising effect of the Hame during the process
of smelting.
The preliminary reduction may take place in the smelting hearth itself, because
if a loose mixture of carbon and ore, eventually with the addition of a suitable flux,
is introduced into the smelting hearth in alternate layers, a portion of the iron is
always reduced from the ores before the smelting commences.
If, however, the pre-reduction is effected outside the smelting hearth, I employ
vertical furnaces or ovens constructed and worked in the manner hereinafter
described.
Fig. 1 of the accompanying drawings (first arrangement) represents a reducing
furnace for use with any suitable reducing gases, such as retort-gases (also called
coal-gas), natural gases, and producer gases, and with internal heating. Gare
canals or nozzles for the admission of gas, l, L are inlets or nozzles for the air which
supports combustion. Each kind or set of inlets can either be situated in a
horizontal plane, or arranged in several zones, as shown by the drawing for the gas
inlets.
Instead of admitting the gases at the circumference, I may introduce them
through an axial tube R, (indicated by dotted lines) which is open at the bottom
and may also have lateral outlets.
The top of the furnace is closed in a suitable manner, preferably by means of a feed
cone and two covers, so as to form a double packing.
If the gases at disposal have not the required temperature, they are heated in a
special heating apparatus.
To promote the reduction, solid carbon may be added to the ore, which carbon
may be introduced with the ore at the top, but preferably at a lower level, for
instance through the axial tube R or through the gas nozzles.
The gases produced by the reduction are employed for the preliminary heating
This air
of the ores, by burning them with the air admitted through the canals 2.
of combustion may likewise be admitted through an axial tube.
The working of the furnace is very simple. After the lower stratum of ores has
been reduced, and eventually carburetted, it is drawn off, thus allowing a higher
stratum to drop into its place and be reduced, while another part is subjected to
preliminary heating and the furnace may be filled up again.
Figs.
and 3 (second arrangement) represent a reducing furnace built as a
double vertical furnace with alternating or reversible gas currents.
Two shafts I and II are connected at the top with each other by a flue C, and
at the bottom, by means of flues m, with heating appliances, such as regenerators,
for the purpose of heating the reducing gas (such as generator gas, retort gas, or

page_text: At
natural gas), the said appliances being as usual provided with means for reversing
the current, or for conducting the currents of fresh gases and of waste gases.
the bottom both shafts are connected with a chimney flue E by means of flues n
and suitable valves e g, and also with the direct gas supply canal G, while the upper
part of the furnace contains the inlet for the air of combustion, which is situated in
the partition near L and always provided with a regulating valve.
If the gases resulting from the reduction in one shaft do not supply sufficient
heat for the pre-heating of the other shaft, a special gas inlet may be provided in
the upper part of the shaft, for instance at G, or G₂ (indicated by dotted lines),
through which heating gas may be supplied according to requirements.
With the exception of the canals a, a, the canals shown at the top may be
placed at the bottom, and those at the bottom inay be placed at the top.
In some cases, for instance, when hot reducing gases are at disposal, the
regenerators may be omitted and the gases conducted directly to the shafts.
This furnace works as follows:-
I suppose, that one half, namely furnace II, together with its charge of
ores, is
hot, and thus prepared for the reduction, and that the other shaft I is filled. The
gas current is now conducted through the hot regenerator R, and the shaft II,
where it has a reducing or decarburetting effect, to the shaft I, and air is admitted
to the latter through L for burning the unconsumed portion of the gases, thus
heating the shaft I.
The waste gases from I, as long as they escape at a low temperature, are
conducted through e¹ and E directly to the chimney, but when their temperature is
high, they are first conducted through the regenerator R.
When the reduction in II is sufficiently advanced, the gas current through the
regenerator is cut off, the contents of II are drawn off hot, or after cool gases have
been admitted to II through g, and thereby its contents cooled down, and after
the removal of its contents, they are replaced by fresh ores.
When the charge in I has become sufficiently hot, the current is reversed,
I receives hot reducing gases, and may subsequently receive cooling gas, while the
shaft is subjected to preliminary heating, and so on.
If the reduced ores are used directly, the direct gas supply y may be omitted,
although its use is always advantageous.
Instead of reducing and preheating the ores in the same shaft, as in Fig. 1, or in
two shafts placed side by side, as in Fig. 2, these operations may be distributed
over two or more shafts, which are placed at different level and connected with
each other, so that the upper shaft, or the upper shafts, are heated by the waste
gases of the lower shaft or shafts, if necessary with the aid of specially supplied
heating gases, for the combustion of which a corresponding quantity of air is
admitted through nozzles, or by other suitable means.
In this case (third arrangement) the shafts are arranged in such a manner, that
the preheated ores can be transferred to the lower reduction stratum, either
immediately through a canalisation, or through the top by means of suitable
receptacles.
As in all preceding cases, solid carbon may be added to the ores, while retaining
the use of gas in other respects, the said addition taking place in the lower shafts,
partly for promoting the reduction, and partly for increasing the looseness of the
column of ore.
In this case, however, the smelting of the reduced material may be effected in
the lower part of the shaft itself, with the aid of gases serving as fuel, thus
producing immediately fluid metal of any desired carburation, which metal is then
converted into the desired kind of malleable metal in an open hearth furnace.
Fig. 4 represents a reducing shaft furnace built as a retort furnace and shows the
4th arrangement herein described.
The shaft proper receives ores and reducing material, such as, charcoal, coke,
coal or other solid carbon, or residues of petroleum refineries, or various kinds of
reducing gases.

page_text: It gases are employed for the reduction, they are introduced IT TO CO
of the furnace through canals G, g.
The gases resulting from the reduction are led off at the top of the reducing
shaft through canals G', and conducted downward through canals d, in order to
burn them in the annular space V surrounding the inner shaft, by means of air
which is admitted to this space through canals L, l, thus heating the retort shaft
from the outside.
For heating the inner or retort shaft I may, however, utilize also producer gases,
or waste gases from smelting hearths, in which case the said gases are conducted into
the annular space V at the bottom (through G).
It is evident, that several of the retorts described may be built into the same
heating chamber.
The method of operation is also evident.
Fig. 5 represents also a retort furnace (fifth arrangement), in which the gases
resulting from the reduction are employed for heating the retorts, either alone or in
conjunction with other heating gases. In this case, however, the admission of gases
to the annular combustion space V takes place at the bottom through the canals g,
while the air for combustion is admitted through L.
In order to compensate for loss of heating gases, fresh heating gases are admitted
at the circumference through G, or through a central tube, G¹ or simultaneously at
both places.
These gases pass on their way to the space V through ores, thereby taking up
heat and at the same time cooling the ores, or if the gas current is hot, they serve
to reduce the ores. This arrangement is therefore specially suitable for the
production of spongy iron to be used at a later stage of the process.
The letters a, a denote draw-off canals, one of which (a) may lead directly into
the smelting hearth or into a cooling chamber, or into the open air. E designates
the flue leading to the chimney.
All the reducing furnaces described above serve the same purpose, namely the
reduction of iron from ores, and possess the feature in common, that the waste
gases from the reduction, with the addition of air of combustion, and eventually in
conjunction with fresh heating gases, serve for preheating the ores which are to be
reduced, or in the case of retort furnaces, for heating these retorts, and, in the case
of double shaft furnaces, also for heating the regenerators.
The retort furnaces are designed for the treatment of very small pieces of ore,
such as granular or sandy ores, the arrangement No. II serving more especially to
produce hot iron-sponge and the arrangement No. V more especially to produce
cold iron-sponge; but the arrangements I and II are designed for the treatment of
larger pieces or blocks, I being chiefly used where hot gases are at disposal, and
arrangement II chiefly where the gases are cool, and must therefore be first heated.
The arrangement No. III with separate shafts situated at different levels, is
chiefly intended for the case, where a product more or less rich in carbon is
required, eventually in a fluid condition.
If the ores to be treated are rich in mineral matter which produce slags, it is
advantageous, to remove these admixtures as far as possible, which may be done by
adding to the ores (previously crushed, if necessary) fluxes adapted to combine
with the mineral matter such as silica which would otherwise produce slag from the
iron, the said flux forming with the mineral matter a slag which is already fluid at
the temperature of reduction, and can thus be drawn off the reduced iron. For the
removal of this slag, the hearth of the furnace is provided with a suitable discharge
canal or a tap hole.
Such additions or fluxes are lime, alkalies, alkaline compounds, and many
metallic oxides.
The reducing furnaces described above may be built independently and used for
the manufacture of reduced iron, also called spongy iron, which subsequently serves
for the production of fluid iron in open hearth furnaces.
However, as spongy iron is liable to re-oxidation, which may be counteracted by

page_text: avoiding its contact with air and using it when still hot, it is advisable, to place the
reducing furnace close to the smelting furnace, so that the product of the former
may be immediately introduced into the latter, or that it drops into the same.
For this purpose, the reducing furnaces may be placed at the circumference of
the smelting furnace, for instance at the two narrow ends of the same, or on one of
its long sides, or above the smelting furnace, and connected with the latter by
canals, or they may be built into a recess of the sinelting furnace.
These canals may serve not only for carrying the product of the reduction into
the smelting furnace, but also for conducting gases from the smelting hearth or
from its gas producers into the reducing furnace.
For separating the reducing furnaces from the smelting hearth, when required,
the said connecting canals or Hlues are provided with dampers, slides, or valves.
It is known that carbon, produced by the decomposition of gases, is absorbed by iron
ores in quantities depending on the duration of the process. Consequently, if the
preliminary reduction is continued long, the ores will already contain a portion of
the carbon necessary for highly carburetting the metal bath, that is to say, the use
of such ores may render it unnecessary to recarburet the metal bath by other means.
The performance of the process in conjunction with the preliminary reduction of
the ores would therefore in this case be a modification of the process described in
my Patent No. 4386 of 1890.
However, as the carbon contained in the pre-reduced ores will rarely suffice for
completing the reduction, the recarburation of the metal bath by solid carbon must
in most cases take place in the same manner, as described in my Patent No. 4386
of 1890, that is to say, by the formation of a highly carburetted metal bath, in
which case it is advisable to cover the floor of the hearth with charcoal before the
introduction of the spongy iron, and the spongy iron when being introduced into
the smelting hearth, should be immediately covered with charcoal-or if the spongy
iron is to be used in a cold state, it should be formed into bricks or blocks by means
of a carbonaceous binding substance.
Alternately or simultaneously the fluid iron would be carburetted and used for
the reduction of the iron contained as an oxide on the smelting hearth, and of the
pre-reduced ores which have just been introduced, a large portion of the metallic
iron already contained in the latter being then dissolved in the metal bath.
In this case, the carbon of the metal bath only serves to complete the reduction,
or to compensate for the re-oxidation of the reduced metal in the process of
smelting.
Dated this 9th day of March 1891.
FAIRFAX & WETTER,
433, Strand, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Processes and Appliances for the Manufacture of
Iron and Steel.
I, JOSEF VON EHRENWERTH, Professor at the Mining Academy at Leoben, in
the Austro-Hungarian Empire, do hereby declare the nature of my invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :--
In carrying out my direct process for the production of various grades of fluid
carburetted iron, as described by the Specification of my Patent No. 4386 of 1890,
it is sometimes advantageous, to subject the iron ores to a preliminary reduction,
before they are introduced into the smelting hearth, because in this case the
carburation of the metal bath may be limited to the amount necessary for obtaining
that portion of the iron, which has not been reduced by the preliminary reduction,
and to that part which has been re-oxidised by the cooling of the spongy iron in

page_text: an oxidising atmosphere, or by the oxidising effect of the flame during the process
of melting.
The preliminary reduction may take place in the smelting hearth itself, because
if a loose mixture of carbon and ore, eventually with the addition of a suitable
flux, is introduced into the smelting hearth in alternate layers, a portion of the
iron is always reduced from the ores before the smelting commences.
If, however, the pre-reduction is effected outside the smelting hearth, I employ
vertical furnaces or ovens constructed and worked in the manner hereinafter
described.
Fig. 1 of the drawings filed with the Provisional Specification, (first arrangement)
represents a reducing furnace for use with any suitable reducing gases, such as
retort-gases (also called coal-gas), natural gases, and producer gases, and with internal
heating. G are canals or nozzles for the admission of gas, l, L are inlets or
nozzles for the air which supports combustion. Each kind or set of inlets can
either be situated in a horizontal plane, or arranged in several zones, as shown by
the drawing for the gas inlets.
Instead of admitting the gases at the circumference, I may introduce them
through an axial tube R, (indicated by dotted lines) which is open at the bottom
and may also have lateral outlets.
The top of the furnace is closed in a suitable manner, preferably by means of a
feed cone and two covers, so as to form a double packing.
If the gases at disposal have not the required temperature, they are heated in a
special heating apparatus.
To promote the reduction, solid carbon may be added to the ore, which carbon
may be introduced with the ore at the top, but preferably at a lower level, for
instance through the axial tube R or through the gas nozzles.
The gases produced by the reduction are employed for the preliminary heating
of the ores, by burning them with the air admitted through the canals. This air
of combustion may likewise be admitted through an axial tube.
The working of the furnace is very simple. After the lower stratum of ores has
been reduced, and eventually carburetted, it is drawn off, thus allowing a higher
stratum to drop into its place and be reduced, while another part is subjected to
preliminary heating and the furnace may be filled up again.
Figs. 2 and 3 (second arrangement) represent a reducing furnace built as a
double vertical furnace with alternating or reversible gas currents.
At
Two shafts I and II are connected at the top with each other by a flue C, and
at the bottom, by means of flues m, with heating appliances, such as regenerators,
for the purpose of heating the reducing gas (such as generator gas, retort gas, or
natural gas), the said appliances being as usual provided with means for reversing
the current, or for conducting the currents of fresh gases and of waste gases.
the bottom both shafts are connected with a chimney flue E by means of flues 72
and suitable valves e g, and also with the direct gas supply canal G, while the
upper part of the furnace contains the inlet for the air of combustion, which is
situated in the partition near L and always provided with a regulating valve.
If the gases resulting from the reduction in one shaft do not supply sufficient
heat for the pre-heating of the other shaft, a special gas inlet may be provided in
the upper part of the shaft, for instance at G, or G₂ (indicated by dotted lines),
through which heating gas may be supplied according to requirements.
With the exception of the canals a', a², the canals shown at the top may be
placed at the bottom, and those at the bottom may be placed at the top.
In some cases, for instance, when hot reducing gases are at disposal, the
regenerators may be omitted and the gases conducted directly to the shafts.
This furnace works as follows:-
I suppose, that one half, namely furnace I I, together with its charge of ores, is
hot, and thus prepared for the reduction, and that the other shaft is filled. The
gas current is now conducted through the hot regenerator R, and the shaft I I,

page_text: where it has a reducing or decarburetting effect, to the shaft I, and air is admitted
to the latter through L for burning the unconsumed portion of the gases, thus
heating the shaft 1.
The waste gases from I, as long as they escape at a low temperature, are con-
ducted through e¹ and E directly to the chimney, but when their temperature is
high, they are first conducted through the regenerator R'.
When the reduction in II is sufficiently advanced, the gas current through the
regenerator is cut off, the contents of II are drawn off hot, or after cool gases
have been admitted to II through g2, and thereby its contents cooled down, and
after the removal of its contents, they are replaced by fresh ores.
When the charge in 1 has become sufficiently hot, the current is reversed,
I receives hot reducing gases, and may subsequently receive cooling gas, while the
shaft II is subjected to preliminary heating, and so on.
If the reduced ores are used directly, the direct gas supply g may be omitted,
although its use is always advantageous.
Instead of reducing and preheating the ores in the same shaft, as in Fig. 1, or
in two shafts placed side by side, as in Fig. 2, these operations may be distributed
over two or more shafts, which are placed at different levels and connected with
each other, so that the upper shaft, or the upper shafts, are heated by the waste
gases of the lower shaft or shafts, if necessary with the aid of specially supplied
heating gases, for the combustion of which a corresponding quantity of air is
admitted through nozzles, or by other suitable means.
In this case (third arrangement) the shafts are arranged in such a manner, that the
preheated ores can be transferred to the lower reduction stratum, either immediately
through a canalisation, or through the top by means of suitable receptacles.
As in all preceding cases, solid carbon may be added to the ores, while retaining
the use of gas in other respects, the said addition taking place in the lower shafts,
partly for promoting the reduction, and partly for increasing the looseness of the
column of ore.
In this case, however, the smelting of the reduced material may be effected in
the lower part of the shaft itself, with the aid of gases serving as fuel, thus
producing immediately fluid metal of any desired carburation, which metal is then
converted into the desired kind of malleable metal in an open hearth furnace.
Fig. 4 represents a reducing shaft furnace built as a retort furnace and shows
the 4th arrangement herein described.
The shaft proper receives ores and reducing material, such as charcoal, coke,
coal or other solid carbon, or residues of petroleum refineries, or various kinds of
reducing gases.
If gases are employed for the reduction, they are introduced into the lower zones
of the furnace through canals G, g.
The gases resulting from the reduction are led off at the top of the reducing
shaft through canals G₁, and conducted downward through canals d, in order to
burn them in the annular space V surrounding the inner shaft, by means of air
which is admitted to this space through canals L, l, thus heating the retort shaft
from the outside.
For heating the inuer or retort shaft, may, however, utilize also producer
gases, or waste gases from smelting hearths, in which case the said gases are
conducted into the annular space V at the bottom (through G).
It is evident, that several of the retorts described may be built into the same
heating chamber.
The method of operation is also evident.
Fig. 5 represents also a retort furnace (fifth arrangement) in which the gases
resulting from the reduction are employed for heating the retorts, either alone or
in conjunction with other heating gases. In this case, however, the admission of
gases to the annular combustion space V takes place at the bottom through.the
canals g, while the air for combustion is admitted. through L.

page_text: In order to compensate for loss of heating gases, fresh heating gases are admitted
at the circumference through G, or through a central tube G', or simultaneously at
both places.
These gases pass on their way to the space V through ores, thereby taking up
heat and at the same time cooling the ores, or if the gas current is hot, they serve
to reduce the ores. This arrangement is therefore specially suitable for the
production of spongy iron to be used at a later stage of the process.
The letters a, a denote draw-off canals, one of which (a') may lead directly into
the smelting hearth or into a cooling chamber, or into the open air. E designates
the flue leading to the chimney.
All the reducing furnaces described above serve the same purpose, namely the
reduction of iron from ores and possess the feature in common, that the waste
gases from the reduction, with the addition of fresh air of combustion, and
eventually in conjunction with fresh heating gases, serve for preheating the ores
which are to be reduced, or, in the case of retort furnaces, for heating these
retorts, and, in the case of double shaft furnaces, also for heating the regenerators.
The retort furnaces are designed for the treatment of very small pieces of ore,
such as granular or sandy ores, the arrangement No. II serving more especially
to produce hot iron sponge and the arrangement No. V more especially to produce
cold iron sponge; but the arrangements I and II are designed for the treatment of
larger pieces or blocks, I being chiefly used where hot gases are at disposal, and
arrangement II chiefly where the gases are cool, and must therefore be first
heated. The arrangement No. III with separate shafts situated at different levels,
is chiefly intended for the case, where a product more or less rich in carbon is
required, eventually in a fluid condition.
If the ores to be treated are rich in mineral matter which produces slags, it is
advantageous, to remove these admixtures as far as possible, which may be done by
adding to the ores (previously crushed, if necessary) fluxes adapted to combine with
the mineral matter, such as silica, which would otherwise produce slag from. the
iron, the said flux forming with the mineral matter a slag which is already fluid at
the temperature of reduction, and can thus be drawn off the reduced iron. For
the removal of this slag, the hearth of the furnace is provided with a suitable
discharge canal or a tap hole.
Such additions or fluxes are lime, alkalies, alkaline compounds, and many
metallic oxides.
The reducing furnaces described above may be built independently and used for
the manufacture of reduced iron, also called spongy iron, which subsequently serves
for the production of fluid iron in open hearth furnaces.
However, as spongy iron is liable to re-oxidation, which may be counteracted
by avoiding its contact with air and using it, when still hot, it is advisable, to place
the reducing furnace close to the smelting furnace, so that the product of the
former may be immediately introduced into the latter, or that it drops into the
same.
For this purpose, the reducing furnaces may be placed at the circumference of
the smelting furnace, for instance at the two narrow ends of the same, or on one of
its long sides, or above the smelting furnace, and connected with the latter by
canals, or they may be built into a recess of the smelting furnace.
These canals may serve not only for carrying the product of the reduction into
the smelting furnace, but also for conducting gases from the smelting hearth or
from its gas producers into the reducing furnace.
For separating the reducing furnaces from the smelting hearth, when required,
the said connecting canals or flues are provided with dampers, slides, or valves.
It is known, that carbon produced by the decomposition of gases, is absorbed
by iron ores in quantities depending on the duration of the process. Consequently,
if the preliminary reduction is continued long enough, the ores will already contain
a portion of the carbon necessary for highly carburetting the metal bath, that is to
say, the use of such ores may render it unnecessary, to recarburize the inetal bath

page_text: by other means. The performance of the process in conjunction with the
preliminary reduction of the ores would therefore in this case be a modification
of the process described in my Patent No. 4386 of 1890.
However, as the carbon contained in the pre-reduced ores will rarely suffice for
completing the reduction, the recarburation of the metal bath by solid carbon must
in most cases take place in the same manner, as described in my Patent No. 4386
of 1890, that is to say, by the formation of a highly carburetted metal bath, in
which case it is advisable to cover the floor of the hearth with charcoal, before the
introduction of the spongy iron, and the spongy iron when being introduced into
the smelting hearth, should be immediately covered with charcoal or if the spongy
iron is to be used in a cold state, it should be formed into bricks or blocks by means
of a carbonaceous binding substance.
Alternately or simultaneously the fluid iron would be carburetted and used for
the reduction of the iron contained as an oxide on the smelting hearth, and of the
pre-reduced ores which have just been introduced, a large portion of the metallic
iron already contained in the latter being then dissolved in the metal bath.
In this case, the carbon of the metal bath only serves to complete the reduction,
or to compensate for the re-oxidation of the reduced metal in the process of
smelting.
If the spongy iron is to be compressed, which will be specially advantageous, if
it is not required for immediate use, but allowed to cool, the presses are conveniently
placed in close proximity to the furnace, and may communicate with a gas canal,
so that the sponge enters the presses when still hot and in an atmosphere of gas, and
is pressed in this condition.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. The reduction of iron ores in gas heated vertical furnaces with internal (direct)
or external (indirect) heating (retort furnaces), and with the exclusive or partial
use of gases as reducing agents, in such a manner, that the gases resulting from the
reduction are utilized, by their combination with specially supplied air, for directly
pre-heating the ores to be reduced, and that in the case of duplex vertical furnaces,
they serve furthermore for heating the gas heaters (gas regenerators), or in the.
case of retort furnaces, for heating the retort, substantially as described.
2. The method of using the cres (spongy iron) reduced as specified above, for
obtaining various kinds or grades of iron in a fluid condition, which consists in
smelting them over a carbonaceous iron bath, which is constantly being charged
with fresh quantities of carbon, by bringing it into contact with solid carbon,
either alternately or simultaneously with its use for reacting on prereduced ores,
substantially as described.
Dated this 10th day of December 1891.
J. VON EHREN WERTH,
By Fairfax & Wetter,
433, Strand, London, Agents.