Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a process of making molt-
en iron while simultaneously obtaining a gas mixture which can be
used for the prereduction of the employed iron ore.
Undertakings have been going on for quite some time to re-
place the blast furnace process and the ore dressing processes, i.e.
coking and subsequent refining as required in a blast furnace pro-
cess, by other direct procedures. Within the framework of these
efforts many suggestions have been made of which however only vari-
ous direct reduction processes have been used in the actual practice.
All propositions to make liquid steel of a desired composition in a
single process step from iron ore by means of the so-called melt re-
duetion proeesses have so far not had a satisfactory and industrial-
ly useful result.
One of the prior art proposals has been to obtain molten
steel in a single process step by reacting iron ore in a reduction
chamber with a reducing gas and melting the product of the reduction
in an adjoining chamber which acts as the melting and gas generating
part of the installation. The reduction gas in this process is pro-
dueed in the gas generating part of the apparatus by introducing a
suitable fuel such as coal or a liquid or gaseous hydrocarbon through
a nozzle together with technically pure oxygen. By ad]usting the
fuel and oxygen supply passing into the nozzle the composition of
the reduction gas could be controlled so as to cause it to have a
redueing aetion on the iron ore. The heat neeessary for the melt-
ing of the preredueed produet was usually obtained from a separate
heating installation at the reaetion ehamber.
The earbon earrier passed into the burner accordingly is
used essentially for generating the reduetion gas by an ineomplete
oxidation with oxygen. Under the aspeet of the desired direet steel
manufaeture it has however not been possible to eontrol the eomposi-
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tion of the bath resulting from the molten prereduced material to
the extent necessary. Particularly the possibility to cause the
fuel to act on the composition of the melt could not be fully ex-
ploited.
It is therefore an object of the present invention in the
melting of a prereduced material, upon simultaneous recovery of a
reduction gas for the ore and upon employment of low priced fuels,
to control the reaction process taking place in the bath in a manner
that a crude iron melt of desired carbon contents is obtained.
This object is met by
(a) introducing a carbon precursor together with a reactive
medium adapted to dissociate in the course of the reaction into a
first zone, acting as carburization zone, of a main reaction chamber,
the introduction being effeeted beneath the surface of a bath formed
by the molten ore or iron so as to eause the earbon of a bath formed
by the molten ore or iron so as to eause the earbon to eombine with
the iron and to supersaturate the melt with earbon;
(b) blowing oxygen into an adjoining seeond zone, acting
as eombustion zone, of the main reaction chamber and below the sur-
faee of the bath while eontinuously agitating the bath so as to con-
vert the excess carbon introdueed into said first zone to carbonmonoxide, the ore continuing to be melted by the thus produced ex-
othermic reaetion in said second zone;
(e) recycling the flue gases generated in the melt cham-
ber into a reduetion chamber so as to subject the ore to an at least
partial prereduetion;
(d) passing the ore from said prereduction chamber into
the second zone of the main reaction chamber at a point close to the
point where the oxygen is blown into the bath, and
(e) withdrawing the formed molten crude iron from the
bath.
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The invention also comprises an apparatus for carryingout the process wherein two lances extend into the reaction chamber,
one lance having an internal channel into which the reactive mixture
and, suspended therein, the carbon precursor may be passed below the
surface of the intended bath and the second lance having an internal
channel for introduction of the ore and another channel, preferably
arranged coaxially around said first channel for introducing oxygen
below the surface of the bath.
The single FIGURE of the drawing illustrates in diagramma-
1- tic form an apparatus for practicing the invention.
The carbon precursor or carrier may be any kind of fossil
fuel. Particularly solid fuels may be used such as coal which is
not suited for coking, anthracite or lignite, and these materials
can be used without expensive preliminary preparation, that is in
their unmodified condition in bulk form.
In a preferred embodiment the fuel is blown into the bath
in the form of a fine grained or dust-like state suspended in the -
likewise introduced reactive medium which may be hydrogen, carbon
dioxide or a fuel gas having a high contents of carbon dioxide or
also a hydrocarbon material. This causes the carbon to pass into
the bath and to combine with the iron to an extent that the carbon
contents of the iron is at least 3~ while the volatile components
of the carbon are dissociated and together with the dissociation-
and reaction products of the reactive medium pass into the flow of
the fuel gases.
~ Technical oxygen is then blown into the bath in a carbon
; combustion zone which adjoins the carburization zone with a flow en-
ergy to cause at least the penetration of the slag layer on the iron.
This again causes a portion of the carbon, which is combined with
the iron in an amount depending on the oxygen introduction, to be
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converted into carbon oxide. By adjusting the carbon and oxygen
supply the carbon contents of the molten product can be controlled
to obtain a preconceived value in lines with the values for crude or
pig iron.
The gases formed in the reaction chamber predominatly are
composed of the hydrogen formed in the carburization zone and of
the carbon oxide formed in the zone where the oxygen is blown in.
These gases which are generated in the amounts necessary for the
reduction of the ore are then passed on a path as direct as possible
into an ore-direct reduction installation. It is preferred to con-
tinuously check the composition of the reduction gases in order to
maintain the desired C0/H2 ratio by adjusting the supply of carbon
hydrogen and oxygen. This ratio preferably should not be larger
than 3 expressed in volume percent.
The ore which is prereduced by the action of the still
hot CO/H2 mixture is then in turn introduced into the melting and ;~
gas generating reaction chamber. This introduction is effected di-
rectly into the zone where the ozygen is blown in or to the immed-
iate neighborhood of such zone since in this zone excess heat for
melting is available. The charge of the ore can for instance be
effected by a lance which is provided with several coaxially ar-
ranged inlet tubes and is subject to continuous cooling. Thus,
through the same lance the oxygen can also be blown into the bath.
The iron oxide which is still present in the partially
prereduced product and may also additionally be formed during the
blowing in of the oxygen is then largely reduced in the agitated
bath by the carbon dissolved in the bath. A sufficient intermixing
of the melt can in amny cases be obtained by the mere kinetic ener-
gy of the media which are blow into the bath through the lances
arranged at an angle. Additional mixing devices such as an induc-
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1049792
tion coil at the melt and gas generating vessel may be used particu-
larly where nozzles are provided in the masonry of the reaction cham-
ber for introducing the gaseous media.
The control of the carbon contents of the molten product
is effected by adjustment of the fuel and oxygen supply so as to
obtain the conventional amounts of carbon contents for pig iron.
For this reason it is possible to keep the temperature in the melt-
ing chamber at a comparatively low level. Thus, no problems will
arise regarding the durability of the refractory walls of the reac-
tion chamber as this is the case in all processes for the directmanufacture of steel from ore or prereduced products.
Because of the vigorous mixing the molten carbon contain-
ing crude iron is mixed in the bath with slag which may be separated
in a separator vessel which may for instance have the form of a
forehearth of the furnace. The crude iron that remains in the re-
action chamber serves simultaneously as heat storage material, as `
heat transmission agent, and as reaction promoter.
A further advanctage of the invention is the possibilityto reduce the sulfur contents of the bath in case even of the use
of inferior coal having a high sulfur contents. This can be affect-
ed by adding finely ground slag forming constitutents for combining
with the sulfur. The sulfur can thus be reduced to a point where
the crude iron can be further processed into steel without any sub-
sequent desulfurization. If fuels are used of a high ash contents,
it is preferred however to effect a partial desulfurization in the
i separator vessel in view of the volume of slag which will be present
in the reaction chamber.
The process of the invention is particularly suited for
continuous operation. The introduction of the raw materials as well
as the tapping of the melt and of the slag or the emulsion thereof
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accordingly are preferably carried out without interruption as a
continuous process.
From this description it will be understood that the in-
vention creates optimum reaction conditions by employing different
reaction zones and by the temporary formation of a carbon excess in
the bath. Thus, it is on one hand possible to obtain a valuable re-
ducing gas in spite of the employment of inexpensive and inferior
fuels and gas forming materials. On the other hand an iron melt is
formed with a preconceived carbon contents because of the immediate
passing or for further processing of the gases obtained by the re-
duction of the ore by the reaction gas. The working temperature
can be maintained at a low level compared with melt redcution pro-
cesses and this will keep the wear on the refractory all materials
of the furnace within reasonable limits.
With particular reference to the drawing which illustrates
an apparatus for carrying out the process of the invention it will
be noted that 1 indicates a melt furnace which is connected with a
eonventional direct reduction installation. The refractory wall 2
of the smelting furnace 1 surrounds a hearth 3 for receiving the
melt product and a cover which is connected with a gas outlet 5.
The starting products are introduced for instance through
lanees into the reaetion ehamber.
A frist water-eooled lance 70 penetrates the lateral wall
of the hearth 2 and extends directly below the surface of the bath.
This lance is arranged at a slant in order to cause the introduced
materials to have a motion component which is directed towards the
overflow tap hole 6. The height of the lance ban be adapted to the
variations of the bath level by changing the depth of immersion of
the lance.
In the exterior annular channel 71 cooling water for the
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lance circulates. In addition this lance serves to introduce the
carbon containing material and the reactive medium which preferably
consists of a flue gas mixture composed of carbon monoxide, carbon
dioxide and hydrogen. The finely divided coal is obtained from a
storage bin 73 and is passed across a bucket wheel 74 into the cen-
tral portion 72 of the lance. The bucket wheel is adjustable by a
variable adjustment device in regards to its performance. The re-
active medium in the preferred form of a flue gas is introduced
through an extension 75 of the central channel 72. The flue gas
will entrain the carbon particles and cause both components to pene- --
trate the bath at a sufficient depth.
A second lance 80 which is also water-cooled passes through
the cover 4 of the furnace and extends into the bath in an area be-
tween the lance 70 and the tapping hole 6.
The prereduced material is introduced through a drop pipe
83 provided in the lance 80. The pipe is adapted to the granulomet-
ery of the prereduced material (Fe/FeO). The drop pipe is provided
directly or via a separate storage with the hot ore material. An
intermediate annular channel or jacket 82 is provided between the
central pipe 83 and the outer cooling jacket 81. The oxygen is pass-
ed through this intermeidate channel at a sufficiently great force
into the bath to penetrate below its surface.
It is also possible to add for instance lime from a stor-
age funnel 84 to combine with the coal ash and the sulfur or also
to add an ore concentrate in order to modify the temperatureO All
this can be done in a continuous or discontinuous operation.
Both lances 70 and 80 are adjustable as to their height
and preferably are sealed against the wall portion of the furnace
by gas seals.
The portion of the melt which flows from the carbon in-
1049792
troduction or carburization area into the area where the oxygen is
blown in is subject in that second area to the action of the oxygen
and thus the excess portion of dissolved carbon will be converted
to carbon monoxide which can then escape in gaseous form.
The introduced prereduced material melts in the zone where
the oxygen is blown in because of the excess heat present in that
zone and the melt then mixes with the remainder of the bath.
Any unreduced iron oxide that may still be present in the
charge passes into the bath and is exposed to the contact with the
carbon dissolved in the bath and will thus be subject to direct re-
duction.
The carbon containing iron is discharged from the lower
portion of the melt through an overflow drain 6. This discharge
is effected to the extent that new melt forms so that the volume
will continuously remain constant. As required by the fuel employ-
ed and the developing reaction the iron may also be subjected to a
desulfurization in a forehearth or mixer~type vessel. It can there
also be completely separated from the slag. The slag may then be
immediately granulated while the pig iron is continuously or period-
; 20 ically passed for further processing.
The gas which forms in the reaction chamber will predomin-
antly consist of a CO/H2 mixture. It is passed via an outlet 5 di-
rectly into a direct reduction installation which is not further
shown in the drawing. If desired there may be a compensatory con-
trol in the gas outlet of the volume of gas and temperature.
The flue gases formed in the prereduction or obtained from
any other suitable operation can be recycled into the main reaction
chamber where the melting and gas generation takes place. If de-
sired there may be a CO2 and/or H2O scrubbing device interposed.
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