AU2022215174A1 - Process for smelting a metalliferous feedstock - Google Patents
Process for smelting a metalliferous feedstock Download PDFInfo
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- AU2022215174A1 AU2022215174A1 AU2022215174A AU2022215174A AU2022215174A1 AU 2022215174 A1 AU2022215174 A1 AU 2022215174A1 AU 2022215174 A AU2022215174 A AU 2022215174A AU 2022215174 A AU2022215174 A AU 2022215174A AU 2022215174 A1 AU2022215174 A1 AU 2022215174A1
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- gas
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- carbon monoxide
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B19/00—Combinations of furnaces of kinds not covered by a single preceding main group
- F27B19/04—Combinations of furnaces of kinds not covered by a single preceding main group arranged for associated working
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0006—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0006—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state
- C21B13/0013—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state introduction of iron oxide into a bath of molten iron containing a carbon reductant
- C21B13/002—Reduction of iron ores by passing through a heated column of carbon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0073—Selection or treatment of the reducing gases
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/008—Use of special additives or fluxing agents
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/10—Making spongy iron or liquid steel, by direct processes in hearth-type furnaces
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/12—Making spongy iron or liquid steel, by direct processes in electric furnaces
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/14—Multi-stage processes processes carried out in different vessels or furnaces
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/14—Multi-stage processes processes carried out in different vessels or furnaces
- C21B13/143—Injection of partially reduced ore into a molten bath
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
- F27D17/001—Extraction of waste gases, collection of fumes and hoods used therefor
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/40—Gas purification of exhaust gases to be recirculated or used in other metallurgical processes
- C21B2100/44—Removing particles, e.g. by scrubbing, dedusting
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/60—Process control or energy utilisation in the manufacture of iron or steel
- C21B2100/62—Energy conversion other than by heat exchange, e.g. by use of exhaust gas in energy production
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/60—Process control or energy utilisation in the manufacture of iron or steel
- C21B2100/64—Controlling the physical properties of the gas, e.g. pressure or temperature
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/122—Reduction of greenhouse gas [GHG] emissions by capturing or storing CO2
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Manufacture Of Iron (AREA)
- Vertical, Hearth, Or Arc Furnaces (AREA)
Abstract
The invention pertains to a smelting process. The process includes the steps of: (i)
feeding agglomerates which include fine metalliferous feedstock particles and fine
reductant particles to a melting furnace to form a packed bed of agglomerates; (ii)
passing a first portion of a carbon monoxide (CO) off-gas through the packed bed of
agglomerates to partially reduce the fine metalliferous feedstock particles; (iii)
combusting a second portion of the carbon monoxide (CO) off-gas, as a fuel gas and
by means of a burner, to heat the agglomerates in the melting furnace to a temperature
exceeding 1000°C and to thereby melt the agglomerates in the melting furnace to form
a molten product; (iv) feeding the molten product to the reduction furnace; and (v)
smelting the molten product to form a liquid metal product, a liquid slag product and
the carbon monoxide (CO) off-gas which is fed to the melting furnace.
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FIGURE 1
Description
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FIGURE 1
Australian Patents Act 1990
Invention Title Process for smelting a metalliferous feedstock
The following statement is a full description of this invention, including the best method of performing it known to me/us:-
The invention pertains to a process for smelting a metalliferous feedstock. More
particularly, the invention pertains to a process for smelting a metalliferous feedstock
by using a carbon monoxide (CO) off-gas of a reduction furnace as a reducing gas
and as a fuel gas.
A metal is typically extracted from its ore by means of a smelting process. During a
smelting process, heat together with a chemical reducing agent reduces a metal oxide
in the ore to release oxygen bound to the metal. The oxygen that is released from the
metal oxide binds to carbon to form a carbon monoxide (CO) off-gas.
The carbon monoxide (CO) off-gas is often burned in a flare stack and released to the
atmosphere as carbon dioxide (C02). In such an instance, all the energy that is
associated with the carbon monoxide (CO) off-gas is lost.
Efforts have been made to use the energy that is associated with a carbon monoxide
(CO) off-gas. As an example, a carbon monoxide (CO) off-gas has been used for
general plant heating functions and for power generation. However, both of the
aforesaid uses have a relatively low thermal efficiency and much of the energy that is
associated with a carbon monoxide (CO) off-gas is still lost.
Metallurgical processes or methods by which a carbon monoxide (CO) off-gas is used
to pre-heat feed materials are also known. However, these processes and methods do not use the energy that is associated with a carbon monoxide (CO) off-gas optimally.
A first example of such a process is described in international publication number WO
2017/089651 Al. The invention described in this publication relates to a method for
pre-heating and smelting manganese ore sinter. The method includes a step of
combusting a carbon monoxide (CO) off-gas that emanates from a submerged electric
arc furnace to form a carbon dioxide (CO2) gas. The carbon dioxide (CO2) gas is then
fed to a pre-treatment silo to heat a feed mixture that contains the manganese ore
sinter, prior to feeding said feed mixture to the submerged arc furnace. The method
also includes a step of adjusting the temperature of the carbon dioxide (CO2) gas to a
temperature below the melting temperatures of the calcite manganese ore sinters
described in examples 1 to 4 of the publication. Thus, in the method described in this
publication, a carbon monoxide (CO) off-gas of the submerged electrical arc furnace
is combusted to form a carbon dioxide (CO2) gas to pre-heat, but not melt, the calcite
manganese ore sinters.
The above-described method has been used by Outokumpu Oyj to pre-heat, but not
melt, sintered ferrochrome ore pellets in a pre-heating silo to a temperature of 7000 C.
This resulted in a 6 to 8% reduction in the electric energy required to melt and reduce
the ferrochrome pellets in an electric arc furnace. Thus, whilst this method utilises the
carbon monoxide (CO) off-gas to provide for a more energy efficient process for the
smelting of ores, it does not optimally use the energy associated with the carbon
monoxide (CO) off-gas.
A second example of a process wherein a carbon monoxide (CO) off-gas is used to
increase the energy efficiency of a process is described in a European patent
application published under publication number EP 2,937,429 Al. This publication
describes an invention whereby a carbon monoxide (CO) off-gas from a melting
furnace is partially combusted and passed through a pre-heating furnace to heat, but
not melt, steel scrap that are fed to the pre-heating furnace. Having passed through
the steel scrap, some of the carbon monoxide (CO) off-gas is fed to a reducing furnace
where it is combusted in a reducing atmosphere to partially reduce low grade iron
oxide scales at temperatures between 800 and 1300°C; i.e., temperatures below the
melting temperatures of iron oxide scales. Therefore, in the reduction furnace, the
low-grade iron oxide scales are heated and partially reduced in a solid state. The
partially reduced low-grade iron oxide scales are then fed to the melting furnace where
it is melted and reduced further by means of electrical energy. Although the invention
described in this application does use some of the energy associated with a carbon
monoxide (CO) off-gas, it is unsuitable for the melting and reduction of metalliferous
ores. The invention described in this publication is suitable only for melting steel scrap
and reducing low-grade iron oxide scales.
A third example of a method that uses a carbon monoxide (CO) off-gas to increase
the energy efficiency of the method is described in United States patent number
3,186,830. The invention described in this patent pertains to a method of continuously
melting cast iron. The apparatus used to perform the method includes a vertical shaft
furnace that is connected to a forehearth. The method includes the step of feeding
metal-solid lump fuel to the vertical shaft furnace and melting said metal-solid lump
fuel by utilising energy obtained from combusting coke in the shaft furnace. A carbon monoxide (CO) off-gas is combusted in the forehearth to heat the liquid metal that locates in the forehearth to a pouring temperature. Again, whilst this method does use some of the energy associated with a carbon monoxide (CO) off-gas, it does not use such energy optimally.
From the above it is apparent that there remains a need for the better utilisation of the
energy that is associated with a carbon monoxide (CO) off-gas.
It is an object of the present invention to provide a process for smelting a metalliferous
feedstock by using a carbon monoxide (CO) off-gas of a reduction furnace, with which
the applicant believes the energy that is associated with a carbon monoxide (CO) off
gas may be better utilised than in known smelting processes and systems, or which
would provide a useful alternative use of the energy that is associated with a carbon
monoxide (CO) off-gas.
According to a first aspect of the invention, there is provided a process for smelting a
metalliferous feedstock, the process including the steps of:
- feeding agglomerates comprising fine metalliferous feedstock particles, fine
reductant particles and fine flux particles to a melting furnace to form a packed
bed of agglomerates in the melting furnace;
- feeding a carbon monoxide (CO) off-gas of a reduction furnace to a burner of the
melting furnace;
- passing a first portion of the carbon monoxide (CO) off-gas through the packed
bed of agglomerates to partially reduce at least some of the fine metalliferous
feedstock particles;
- feeding a source of oxygen (02) gas to the burner of the melting furnace;
- combusting a second portion of the carbon monoxide (CO) off-gas, as a fuel gas
and by means of the burner of the melting furnace, to heat the agglomerates in
the melting furnace to a temperature exceeding 1000°C and to thereby melt the
agglomerates in the melting furnace to form a molten product;
- feeding the molten product to the reduction furnace; and
- smelting the molten product to form a liquid metal product, a liquid slag product
and the carbon monoxide (CO) off-gas which is fed to the burner of the melting
furnace.
The fine metalliferous feedstock particles may be fine ore particles or fine metal oxide
particles.
The agglomerate may take the form of a briquet, a pellet or an extrusion.
It will be appreciated that the term "fine" means, as per the metallurgy industry
standard, very small particles which, when agglomerated, will allow intimate contact
between said particles. The particles typically have a diameter of 0.1mm or less.
In an embodiment where the reductant particles are fed separately from the
agglomerates to the melting furnace, the reductant particles may typically have a
diameter of 6 mm or less.
It will be appreciated by those skilled in the art that an off-gas is a gas which is emitted
as a by-product of a chemical process.
The process may include the additional step of feeding reductants independently from
the agglomerates to the melting furnace. The reductants may be one selected from
the group comprising: anthracite, coal, coke and combinations thereof
The process may include the additional step of controlling the volume (i.e., flow rate)
of the source of oxygen (02) gas which is fed to the burner of the melting furnace in
order to ensure that oxygen (02) is a limiting reactant in a combustion reaction with
the carbon monoxide (CO) off-gas which is fed to the burner.
The source of oxygen (02) gas may be pre-heated prior to it being fed to the burner.
The source of oxygen (02) gas may be pre-heated to a temperature of 8000 C. The
source of oxygen (02) gas is typically combustion air.
As an alternative to or in combination with combustion air, substantially pure oxygen
(02) may be fed to the burner of the melting furnace for combusting the oxygen (02) gas together with the second portion of the carbon monoxide (CO) off-gas of the reduction furnace in the melting furnace.
The fine metalliferous feedstock particles in the agglomerates may be partially reduced
in the solid state in the melting furnace.
The molten product which is formed in the melting furnace may contain solids that are
entrained in a liquid. Furthermore, the molten product may comprise a metalliferous
feedstock constituent, a partially reduced metalliferous feedstock constituent, an
unreacted reductant constituent and a flux constituent.
The reduction furnace may be any one selected from the group consisting of a DC
brush-arc furnace, an AC brush arc furnace and a DC-arc furnace.
A brush-arc furnace is an electrical furnace whose electrodes are arcing on top of the
furnace contents with a short arc length, typically not longer than 100 mm.
The process may include the additional step of feeding reductants to the reduction
furnace. The reductants may be one selected from the group comprising: anthracite,
coal, coke and combinations thereof.
The melting furnace may be a gas-fired cupola furnace (i.e., a coke-less cupola
furnace). Alternatively, the melting furnace may be a shaft furnace.
The process may include the additional step of removing particulate matter from the
carbon monoxide (CO) off-gas of the reduction furnace in a wet scrubber prior to
feeding it as a reducing gas and as a fuel gas to the burner of the melting furnace.
According to a second aspect of the present invention, there is provided a process for
smelting a metalliferous feedstock, the process including the steps of:
- feeding agglomerates comprising fine metalliferous feedstock particles, fine
reductant particles and fine flux particles to a melting furnace to form a packed
bed of agglomerates in the melting furnace;
- feeding a carbon monoxide (CO) off-gas of a reduction furnace to the melting
furnace;
- passing a first portion of the carbon monoxide (CO) off-gas through the packed
bed of agglomerates to partially reduce at least some of the fine metalliferous
feedstock particles;
- feeding a source of oxygen (02) gas to a burner of the melting furnace;
- combusting a second portion of the carbon monoxide (CO) off-gas, as a fuel gas
and by means of the burner of the melting furnace, to heat the agglomerates in
the melting furnace to a temperature exceeding 1000 0C and to thereby melt the
agglomerates in the melting furnace to form a molten product;
- feeding the molten product to the reduction furnace; and
- smelting the molten product to form a liquid metal product, a liquid slag product
and the carbon monoxide (CO) off-gas which is fed to the melting furnace.
According to a third aspect of the present invention, there is provided a process for
smelting a metalliferous feedstock, the process including the steps of:
- feeding agglomerates comprising fine metalliferous feedstock particles, fine
reductant particles and fine flux particles to a melting furnace to form a packed
bed of agglomerates in the melting furnace;
- feeding a first portion of a carbon monoxide (CO) off-gas of a reduction furnace
to the melting furnace;
- passing the first portion of the carbon monoxide (CO) off-gas through the packed
bed of agglomerates to partially reduce at least some of the fine metalliferous
feedstock particles;
- feeding a source of oxygen (02) gas to a burner of the melting furnace;
- feeding a second portion of the carbon monoxide (CO) off-gas of the reduction
furnace the burner of the melting furnace;
- combusting the second portion of the carbon monoxide (CO) off-gas, as a fuel
gas and by means of the burner of the melting furnace, to heat the agglomerates
in the melting furnace to a temperature exceeding 1000 0 C and to thereby melt
the agglomerates in the melting furnace to form a molten product;
- feeding the molten product to the reduction furnace; and
- smelting the molten product to form a liquid metal product, a liquid slag product
and the carbon monoxide (CO) off-gas which is fed to the melting furnace and
burner of the melting furnace, respectively.
figure 1 is a schematic diagram of a system of the invention by which the process
of the invention is implemented.
With reference to figure 1, a system for smelting a metalliferous feedstock according
to the process of the invention is generally indicated by reference numeral 10.
The system 10 includes a melting furnace 20 which has a burner 22. The system 10
also includes a reduction furnace 30. A conduit 40 extends between the reduction
furnace 30 and the burner 22 of the melting furnace 20 for feeding a carbon monoxide
(CO) off-gas of the reduction furnace 30, as a reducing gas and as a fuel gas, to the
burner 22 of the melting furnace 20.
Agglomerates (not shown) comprising fine metalliferous feedstock particles, fine
reductant particles and fine flux particles are fed to the melting furnace 20 to form a
packed bed of agglomerates (not shown) in the melting furnace 20. The agglomerates
are typically fed to the melting furnace 20 via a sluice (not shown). Process stream (I)
in figure 1 indicates the step of feeding the agglomerates to the melting furnace 20.
The flux serves to promote the melting of the fine metalliferous feedstock particles in
the agglomerates. An agglomerate that is fed to the melting furnace 20 typically takes
the form of a briquet, a pellet or an extrusion.
The particles of the agglomerates typically have a diameter of 0.1 mm or less.
Reductants are also fed independently from the agglomerates to the melting furnace
20. The reductants are typically coke, coal or anthracite.
The reductants typically have a diameter of 6 mm or less.
The fine metalliferous feedstock particles are typically fine ore particles or fine metal
oxide particles.
The packed bed of agglomerates typically locates on top of a bed of refractory
materials (not shown). The bed of refractory materials, in turn, locates on top of a
water-cooled grate 24 of the melting furnace 20. The water-cooled grate 24 is covered
with refractory material to reduce heat loss and to protect the water-cooled 24 grate.
A combustion chamber 26 of the melting furnace 20 locates beneath the water-cooled
grate 24 which is covered with refractory material. The burner 22 is arranged to
combust a second portion of the carbon monoxide (CO) off-gas of the reduction
furnace 30 together with combustion air in the combustion chamber 26 of the melting
furnace 20 to heat the agglomerates to a temperature exceeding 1000 0C and to
thereby melt the agglomerates to form a molten product. The combustion air is fed to
the burner 22 of the melting furnace 20, as indicated by process stream (II) in figure
1. The combustion air is typically pre-heated in a pre-heater 70 prior to it being fed to
the burner 22 of the melting furnace 20. The combustion air is typically heated to a
temperature of 800 0C in the pre-heater 70. As an alternative to combustion air or in combination with combustion air, oxygen may be fed to the burner 22 of the melting furnace 20.
As a further alternative or in any combination with the aforementioned, where
additional external energy is required to achieve a desired temperature and to maintain
a reducing atmosphere inside the smelting furnace 22, external fuel gas in the form of
syngas or natural gas may be provided to the burner 22 from a source 72. It has been
found that such external fuel gas may be required where the agglomerates comprise
ferrochrome.
Such external fuel gas may also assist during a start-up phase of the process.
A first portion of the carbon monoxide (CO) off-gas of the reduction furnace 30 is
passed through the packed bed of agglomerates to partially reduce at least some of
the fine metalliferous feedstock particles of the agglomerates in the solid state.
Therefore, the fine metalliferous feedstock particles in the agglomerates are first
partially reduced in the solid state in the melting furnace 20 and then melted to form
the molten product. The molten product comprises a metalliferous feedstock
constituent, a partially reduced metalliferous feedstock constituent, an unreacted
reductant constituent and a flux constituent
A valve arrangement 90 is provided to control the flow rate of combustion air or oxygen
(02) gas to the burner 22 of the melting furnace 20. The flow rate of combustion air or
oxygen (02) gas to the burner 22 is controlled to ensure that oxygen (02)is a limiting reactant in the combustion reaction of the second portion of the carbon monoxide (CO) off-gas. That is, the flow of combustion air or oxygen (02) is controlled to be below the stoichiometric ratio required for the complete combustion of the carbon monoxide
(CO) off-gas which is fed from the reduction furnace 30 to the melting furnace 20.
An outlet (not shown) is provided at an operatively top region of the melting furnace
for extracting an off-gas which is formed in the melting furnace 20 from the melting
furnace 20. The step of extracting an off-gas which is formed in the melting furnace
from the melting furnace 20 is indicated by process stream (VI) in figure 1. An off
gas which is formed in and extracted from the melting furnace 20 is typically carbon
dioxide (C02). The carbon dioxide (C02) off-gas which is formed in and extracted from
the melting furnace 20 is passed through a bag filter 60 to remove particulate matter
therefrom prior to the off-gas being released to the atmosphere.
The melting furnace 20 is in fluid flow communication with the reduction furnace 30 by
means of a conduit 50. The conduit 50 typically extends between an operatively
bottom region of the melting furnace 30 (e.g., a tap region and tap hole of the melting
furnace 20) to the reduction furnace 30. The conduit 50 serves to convey the molten
product (not shown) which is formed in the melting furnace 20 to the reduction furnace
30. The molten product comprises a metalliferous feedstock constituent, a partially
reduced metalliferous feedstock constituent, an unreacted reductant constituent and
a flux constituent. The conduit 50 is typically a closed conduit and insulated to prevent
heat losses when the molten product is conveyed from the melting furnace 20 to the
reduction furnace 30.
The reduction furnace 30 may be any one of a DC brush-arc furnace, an AC brush
arc furnace or a DC-arc furnace. A brush-arc furnace is an electrical furnace whose
electrodes are arcing on top of the furnace contents with a short arc length, typically
not longer than 100 mm. Exemplary embodiments of a brush-arc furnace are provided
in international patent application number PCT/IB2011/052428, South African patent
number 2012/04751 and South African provisional patent application number
2019/07850. The contents of these three documents are incorporated herein by
reference.
In figure 1, the reduction furnace 30 takes the form of a brush-arc furnace having two
electrodes 32a and 32b which extends from or through a roof 31 of the reduction
furnace 30. The electrodes 32a and 32b are arranged to arc 33a and 33b on top of
the furnace contents 34. Reductants (not shown), for the reduction of the partially
reduced fine metalliferous feedstock particles in the molten product, are fed to the
reduction furnace 30, as indicated by process stream (III) in figure 1. The reductants
are typically anthracite, coal, coke or a combination of the afore.
The furnace contents 34 comprise a liquid slag product 34a and a liquid metal product
34b. The furnace contents 34 are formed by means of a smelting reaction. During
the smelting reaction the partially reduced fine metalliferous feedstock constituent of
the molten product is reduced to form the liquid slag product 34a and the liquid metal
product 34b. A carbon monoxide (CO) off-gas is emitted during the smelting reaction.
A tap hole (not shown) is provided in the reduction furnace 30 to convey the liquid slag
product 34a out of the reduction furnace 30 as indicated by process stream (IV) in figure 1. A further tap hole (not shown) is provided in the reduction furnace 30 to convey the metal liquid product 34b out of the reduction furnace 30 as indicated by process stream (V) in figure 1.
As already described, a conduit 40 extends between the reduction furnace 30 and the
burner 22 of the melting furnace 20 for feeding the carbon monoxide (CO) off-gas of
the reduction furnace 30 as a fuel gas and as a reduction gas to the melting furnace
20. The carbon monoxide (CO) off-gas may be fed directly to the burner 22 of the
melting furnace 20. More specifically, the conduit 40 extends between an operatively
top region of the reduction furnace 30 and the burner 22 of the melting furnace 20.
That is, the conduit 40 has an opening in the reduction furnace 30 which locates above
the contents 34 of the reduction furnace 30.
Alternatively, a first portion of the carbon monoxide (CO) off-gas may be fed to the
melting furnace 20 and a second portion of the carbon monoxide (CO) off-gas may be
fed to the burner 22 of the melting furnace 20.
As shown in figure 1, a wet scrubber 80 is provided for removing pollutants from the
carbon monoxide (CO) off-gas of the reduction furnace 30. In particular, the wet
scrubber 80 serves to remove particulate matter from the carbon monoxide (CO) off
gas of the reduction furnace 30 prior to feeding it as a fuel gas to the burner 22 of the
melting furnace 20.
In use, agglomerates (not shown) comprising fine metalliferous feedstock particles,
fine reductant particles and fine flux particles are fed to the melting furnace 20 via the sluice (not shown). This step is indicated by process stream (I) in figure 1. The agglomerates are fed to the melting furnace 20 to form a packed bed of agglomerates on a packed bed of refractory materials (not shown). The packed bed of refractory materials is supported on a refractory covered water-cooled grate 24 of the melting furnace 20.
The scrubbed carbon monoxide (CO) off-gas of the reduction furnace 30 is fed as a
fuel gas and a reducing gas to the melting furnace 20 via the conduit 40.
A first portion of the carbon monoxide (CO) off-gas is passed through the packed bed
of agglomerates to partially reduce at least some of the fine metalliferous feedstock
particles in the solid state.
Pre-heated combustion air is fed to the burner 22 of the melting furnace 20, as
indicated by process stream (II) in figure 1. The burner 22 of the melting furnace 20
combusts a second portion of the carbon monoxide (CO) off-gas and the combustion
air to heat the packed bed of refractory materials in the melting furnace 20. The
refractory materials, in turn, heat the agglomerates to a temperature exceeding
1000 0C to thereby melt the agglomerates in the melting furnace 20 so as to form a
molten product (not shown). The molten product comprises a metalliferous feedstock
constituent, a partially reduced metalliferous feedstock constituent, an unreacted
reductant constituent and a flux constituent
During the combustion reaction, a carbon dioxide (CO2) off-gas is formed. The carbon
dioxide (CO2) off-gas is extracted from the melting furnace 20, as indicated by process stream (VI). The extracted carbon dioxide (C02) off-gas is passed through the bag filter 60 to remove particulate matter therefrom prior to it being released to the atmosphere.
The molten product trickles down and through the packed bed of refractory materials
and refractory covered water-cooled grate 24, where after it is conveyed to the
reduction furnace 30 by means of the conduit 50.
The molten product locates in the reduction furnace 30 and electrical energy is
continually added to the reduction furnace 30 and its contents 34 by means of the
electrodes 32a and 32b. The electrodes 32a and 32b are arranged to arc 33a and
33b on top of the furnace contents 34. Reductant (not shown) is also continually added
to the reduction furnace 30, as indicated by process stream (III) in figure 1.
As electrical energy and reductants are continuously added to the reduction furnace
and its contents 34, the partially reduced fine metalliferous feedstock particles and
fine metalliferous feedstock particles that were not partially reduced in the melting
furnace 20, are smelted to form a liquid metal product 34b and a slag 34a. The liquid
metal product 34b is tapped periodically or continuously from the reduction furnace 30
via a tap hole (not shown), as indicated by process stream (V) in figure 1. The slag
34a is tapped periodically or continuously from the reduction furnace 30 via tap hole
(not shown), as indicated by process stream (IV) in figure 1.
During the smelting reaction, an off-gas consisting of mainly carbon monoxide (CO) is
emitted. The carbon monoxide (CO) off-gas is extracted from the reduction furnace via the conduit 40 and fed to the wet scrubber 80. Pollutants and particulate material are removed from the carbon monoxide (CO) off-gas of the reduction furnace in the wet scrubber 80. The scrubbed carbon monoxide (CO) off-gas of the reduction furnace 30 is then fed as a fuel gas and as a reducing gas to the melting furnace 20.
It will be appreciated by those skilled in the art that the carbon monoxide (CO) off-gas
of the reduction furnace 30 can form a constituent of a fuel gas which is fed to the
burner 22 of the melting furnace 30.
The process of the present invention provides for the energy efficient use of energy
that is associated with a carbon monoxide (CO) off-gas of reduction furnace. By using
the carbon monoxide (CO) off-gas of a reduction furnace as a fuel gas for a burner of
a melting furnace and a reducing gas, the applicant has found that the processing
capacity of the reduction furnace can be doubled. Alternatively, by using the carbon
monoxide (CO) off-gas of a reduction furnace as a fuel gas for a burner of a melting
furnace and a reducing gas, the applicant has found that the electric energy
requirements of the reduction furnace can be reduced substantially.
Mass and energy balances exemplifying the advantages of the present invention
Below follows a comparison between two smelting processes:
(i) a first conventional smelting process that uses an electric brush arc furnace; and
(ii) a second smelting process that uses the process and system 10 of the present
invention.
First conventional smelting process that uses an electric brush arc furnace:
The first conventional process is a smelting process that utilises an electric brush arc
furnace to smelt agglomerates. The agglomerates take the form of fluxed pellets and
comprise, by weight percentage, approximately:
- 32.5% Cr203;
- 22.6% FeO;
- 13.4% A1203;
- 12.7% CaO;
- 8.1% MgO; and
- 5.5% Si02.
The agglomerates are fed to the electric brush arc furnace at a rate of 21.3 metric tons
per hour. Reductants are also fed to the electric brush arc furnace at a rate of 3.6
metric tons per hour. 30 megawatt is supplied to the electric brush arc furnace so as
to provide the energy required to smelt the metal oxides that locate in the
agglomerates.
The electric brush arc furnace smelts the agglomerates to form an alloy liquid product
and a slag liquid product.
Alloy liquid product is tapped from the electric brush arc furnace at a temperature of
1550 0C and at a rate of 7.7 metric tons per hour. The alloy liquid product comprises,
by weight percentage, approximately:
- 50.3% Cr;
- 38.9% Fe;
- 6.5% C; and
- 4.0% Si.
The slag liquid product is tapped from the electric brush arc furnace at a temperature
of 1650C and at a rate of 10.7 metric tons per hour. The slag liquid product
comprises, by weight percentage, approximately:
- 11.6% Cr203;
- 9.0% FeO;
- 28.4% A1203;
- 25.3% CaO;
- 16.2 MgO; and
- 7.4% SiO 2 .
An off-gas is extracted from the electric brush arc furnace at flow rate of 8173 normal
cubic meters per hour and 10 metric tons per hour. The off-gas has a temperature of
1200 0C and comprises, by weight percentage, approximately:
- 51.4% CO;
- 7.9% C02;
- 26.5% N2;
- 2.7% H2;
- 0.1% S02; and
- 11.4% H20.
The electric brush arc furnace has an operating factor of 0.92. 4 megawatts are lost
from the electric brush arc furnace due to heat losses.
The brush arc furnace of this first convention smelting process has a specific electric
consumption of 3.81 megawatts hour per metric ton hot metal.
Second smelting process that uses the process and system of the present invention:
The second process is a smelting process that utilises the process and system 10 of
the present invention to smelt agglomerates. The agglomerates take the form of fluxed
pellets and comprise, by weight percentage, approximately:
- 32.5% Cr203;
- 22.6% FeO;
- 13.4% A1203;
- 12.7% CaO;
- 8.1% MgO; and
- 5.5% SiO 2 .
The agglomerates are fed to the melting furnace 20 at a rate of 36.5 metric tons per
hour. The agglomerates form a packed bed of agglomerates in the melting furnace
20. Reductants are also fed to the melting furnace at a rate of 0.6 metric tons per
hour.
An off-gas from the reduction furnace 30, which takes the form of an electric brush arc
furnace, is passed through a wet scrubber 80 and fed at a temperature of 500 C and at a rate of 10.88 metric tons per hour to the melting furnace 20. The off-gas from the electric brush arc furnace 30 comprises, by weight percentage, approximately:
- 58.5% CO;
- 27.1% N2;
- 13.6% H2;
- 0.1% SO2; and
- 0.7% H20.
Combustion air is pre-heated to a temperature of 800 0C and fed at a rate of 69.2 metric
tons per hour to the burner 22 of the melting furnace 20.
A first portion of the carbon monoxide (CO) off-gas is passed through the packed bed
of agglomerates to partially reduce at least some of the fine metalliferous feedstock
particles.
A second portion of the carbon monoxide (CO) in the off-gas is combusted by means
of the burner 22 and the packed bed of agglomerates is heated to a temperature of
1500 0C in the melting furnace 20 to form a molten product and a melting furnace off
gas. The molten product has a temperature of 1500 0C and is conveyed out of the
melting furnace 20 into the electric brush arc furnace 30 at a rate of 33.8 metric tons
per hour. The molten product contains 50% solids and comprise, by weight
percentage, approximately:
- 35.2% Cr203;
- 7.3%% FeO;
- 13.3% Fe;
- 14.6% A1203;
- 13.7% CaO;
- 8.8% MgO; and
- 6% SiO2.
The melting furnace off-gas is extracted from the melting furnace 20 at a flow rate of
34233 normal cubic meters per hour and 47.4 metric tons per hour. The melting
furnace off-gas is extracted from the melting furnace 20 at a temperature of 5000 C and
comprise, by weight percentage, approximately:
- 21.7% C02;
- 4.8% 02;
- 66.5N2; and
- 6.9% H20.
As already described, the molten product is conveyed from the melting furnace 20 to
the electric brush arc furnace 30 at a rate of 33.8 metric tons per hour. Reductants
are also fed to the electric brush arc furnace 30 at a rate of 6.3 metric tons per hour.
megawatt is supplied to the electric brush arc furnace 30 so as to provide the
energy required to smelt the metal oxides that locate in the molten product.
The electric brush arc furnace 30 smelts the molten product to form an alloy liquid
product and a slag liquid product.
Alloy liquid product is tapped from the electric brush arc furnace 30 at a temperature
of 1550C and at a rate of 14.2 metric tons per hour. The alloy liquid product
comprises, by weight percentage, approximately:
- 50.3% Cr;
- 40.5% Fe;
- 8% C; and
- 1% Si.
The slag liquid product is tapped from the electric brush arc furnace 30 at a
temperature of 1650C and at a rate of 17.8 metric tons per hour. The slag liquid
product comprises, by weight percentage, approximately:
- 8% Cr203;
- 5% FeO;
- 29.5% A1203;
- 26.1% CaO;
- 16.7% MgO; and
- 12.6% SiO2.
An off-gas is extracted from the electric brush arc furnace 30 at a flow rate of 12460
normal cubic meters per hour and 13.6 metric tons per hour. The off-gas has a
temperature of 1400 0C and comprises, by weight percentage, approximately:
- 58.5% CO;
- 27.1% N2;
- 13.6% H2;
- 0.1% S02; and
- 0.7% H20.
% by weight of the off-gas of the electric brush arc furnace 30 is fed, as a fuel gas
and a reducing gas, to the melting furnace 20 where it is used as described above.
The electric brush arc furnace 30 has an operating factor of 0.92. 4 megawatts are
lost from the electric brush arc furnace 30 due to heat losses.
The electric brush arc furnace 30, of the system 10, has a specific electric consumption
of 2.07 megawatts hour per metric ton hot metal.
It will be appreciated by the person skilled in the art that a reduction in specific electric
consumption of an electric brush arc furnace from 3.81 megawatts hour per metric ton
hot metal to 2.07 megawatts hour per metric ton hot metal is significant. This
significant reduction is a direct consequence of the present invention's novel and
inventive use of the energy that is associated with a carbon monoxide (CO) off-gas of
a reduction furnace.
It will be appreciated by those skilled in the art that the invention is not limited to the
precise details as described herein and that many variations are possible without
departing from the scope of the invention. As such, the present invention extends to
all functionally equivalent processes, methods and uses that are within its scope.
The description is presented by way of example only in the cause of providing what is
believed to be the most useful and readily understood description of the principles and
conceptual aspects of the invention. In this regard, no attempt is made to show more detail than is necessary for a fundamental understanding of the invention. The words which have been used herein are words of description and illustration, rather than words of limitation.
Throughout this specification and the claims which follow, unless the context requires
otherwise, the word "comprise", and variations such as "comprises" and "comprising",
will be understood to imply the inclusion of a stated integer or step or group of integers
or steps but not the exclusion of any other integer or step or group of integers or steps.
The reference in this specification to any prior publication (or information derived from
it), or to any matter which is known, is not, and should not be taken as an
acknowledgment or admission or any form of suggestion that that prior publication (or
information derived from it) or known matter forms part of the common general
knowledge in the field of endeavor to which this specification relates.
Claims (17)
1. A process for smelting a metalliferous feedstock, the process including the steps
of:
- feeding agglomerates comprising fine metalliferous feedstock particles, fine
reductant particles and fine flux particles to a melting furnace to form a
packed bed of agglomerates in the melting furnace;
- feeding a carbon monoxide (CO) off-gas of a reduction furnace to a burner
of the melting furnace;
- passing a first portion of the carbon monoxide (CO) off-gas through the
packed bed of agglomerates to partially reduce at least some of the fine
metalliferous feedstock particles;
- feeding a source of oxygen (02) gas to the burner of the melting furnace;
- combusting a second portion of the carbon monoxide (CO) off-gas, as a
fuel gas and by means of the burner of the melting furnace, to heat the
agglomerates in the melting furnace to a temperature exceeding 10000 C
and to thereby melt the agglomerates in the melting furnace to form a
molten product;
- feeding the molten product to the reduction furnace; and
- smelting the molten product to form a liquid metal product, a liquid slag
product and the carbon monoxide (CO) off-gas which is fed to the burner of
the melting furnace.
2. The process of claim 1, wherein the fine metalliferous feedstock particles are fine
ore particles.
3. The process of claim 1, wherein the fine metalliferous feedstock particles are fine
metal oxide particles.
4. The process of any one of the preceding claims, wherein the agglomerate is
selected from the group consisting of a briquet, a pellet and an extrusion.
5. The process of any one of the preceding claims, wherein the process includes
the additional step of feeding reductants independently from the agglomerates to
the melting furnace.
6. The process of any one of the preceding claims, wherein the fine metalliferous
feedstock particles are partially reduced in the solid state in the melting furnace.
7. The process of any one of the preceding claims, wherein the process includes
the additional step of controlling the volume of the source of oxygen (02) gas
which is fed to the burner of the melting furnace so as to ensure that oxygen (02)
is a limiting reactant in a combustion reaction with the carbon monoxide (CO) off
gas which is fed to the burner.
8. The process of any one of the preceding claims, wherein the source of oxygen
(02) gas is pre-heated prior to it being fed to the burner of the melting furnace.
9. The process of claim 8, wherein the source of oxygen (02) gas is pre-heated to
a temperature of 8000 C.
10. The process of any one of the preceding claims, wherein the reduction furnace
is any one selected from the group consisting of a DC brush-arc furnace, an AC
brush arc furnace and a DC-arc furnace.
11. The process of any one of the preceding claims, wherein the process includes
the additional step of feeding reductants to the reduction furnace.
12. The process of claim 11, wherein the reductants are selected from the group
consisting of anthracite, coal, coke and combinations thereof.
13. The process of any one of claims 1 to 12, wherein the melting furnace is a gas
fired cupola furnace.
14. The process of any one of claims 1 to 12, wherein the melting furnace is a shaft
furnace.
15. The process of any one of the preceding claims, wherein the process includes
the additional step of removing particulate matter from the carbon monoxide (CO)
off-gas of the reduction furnace in a wet scrubber prior to feeding it to the burner
of the melting furnace.
16. A process for smelting a metalliferous feedstock, the process including the steps
of:
- feeding agglomerates comprising fine metalliferous feedstock particles, fine
reductant particles and fine flux particles to a melting furnace to form a
packed bed of agglomerates in the melting furnace;
- feeding a carbon monoxide (CO) off-gas of a reduction furnace to the
melting furnace;
- passing a first portion of the carbon monoxide (CO) off-gas through the
packed bed of agglomerates to partially reduce at least some of the fine
metalliferous feedstock particles;
- feeding a source of oxygen (02) gas to a burner of the melting furnace;
- combusting a second portion of the carbon monoxide (CO) off-gas, as a
fuel gas and by means of the burner of the melting furnace, to heat the
agglomerates in the melting furnace to a temperature exceeding 10000 C
and to thereby melt the agglomerates in the melting furnace to form a
molten product;
- feeding the molten product to the reduction furnace; and
- smelting the molten product to form a liquid metal product, a liquid slag
product and the carbon monoxide (CO) off-gas which is fed to the melting
furnace.
17. A process for smelting a metalliferous feedstock, the process including the steps
of:
- feeding agglomerates comprising fine metalliferous feedstock particles, fine
reductant particles and fine flux particles to a melting furnace to form a
packed bed of agglomerates in the melting furnace;
- feeding a first portion of a carbon monoxide (CO) off-gas of a reduction
furnace to the melting furnace;
- passing the first portion of the carbon monoxide (CO) off-gas through the
packed bed of agglomerates to partially reduce at least some of the fine
metalliferous feedstock particles;
- feeding a source of oxygen (02) gas to a burner of the melting furnace;
- feeding a second portion of the carbon monoxide (CO) off-gas of the
reduction furnace the burner of the melting furnace;
- combusting the second portion of the carbon monoxide (CO) off-gas, as a
fuel gas and by means of the burner of the melting furnace, to heat the
agglomerates in the melting furnace to a temperature exceeding 10000 C
and to thereby melt the agglomerates in the melting furnace to form a
molten product;
- feeding the molten product to the reduction furnace; and
- smelting the molten product to form a liquid metal product, a liquid slag
product and the carbon monoxide (CO) off-gas which is fed to the melting
furnace and the burner of the melting furnace, respectively.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2029142 | 2021-09-07 | ||
| NL2029142A NL2029142B1 (en) | 2021-09-07 | 2021-09-07 | Process for smelting a metalliferous feedstock |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| AU2022215174A1 true AU2022215174A1 (en) | 2023-03-23 |
Family
ID=78135064
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| AU2022215174A Pending AU2022215174A1 (en) | 2021-09-07 | 2022-08-09 | Process for smelting a metalliferous feedstock |
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| Country | Link |
|---|---|
| CN (1) | CN115584372A (en) |
| AU (1) | AU2022215174A1 (en) |
| NL (1) | NL2029142B1 (en) |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3186830A (en) | 1963-05-20 | 1965-06-01 | William H Moore | Melting process |
| US3734716A (en) * | 1971-11-18 | 1973-05-22 | Fmc Corp | Steelmaking process |
| CA1057960A (en) * | 1975-02-26 | 1979-07-10 | Westinghouse Electric Corporation | Method of ore reduction with an arc heater |
| GB2026548B (en) * | 1978-07-26 | 1983-03-30 | Cons Natural Gas Svc | Production of intermediate hot metal for steemaking |
| US4434003A (en) * | 1980-12-15 | 1984-02-28 | Geskin Ernest S | Steel making method |
| AT406482B (en) * | 1995-07-19 | 2000-05-25 | Voest Alpine Ind Anlagen | METHOD FOR THE PRODUCTION OF LIQUID PIPE IRON OR STEEL PRE-PRODUCTS AND SYSTEM FOR IMPLEMENTING THE METHOD |
| AUPO426096A0 (en) * | 1996-12-18 | 1997-01-23 | Technological Resources Pty Limited | Method and apparatus for producing metals and metal alloys |
| US6685761B1 (en) * | 1998-10-30 | 2004-02-03 | Midrex International B.V. Rotterdam, Zurich Branch | Method for producing beneficiated titanium oxides |
| AU2039201A (en) * | 1999-09-14 | 2001-04-17 | Danieli Technology, Inc. | High temperature premelting apparatus |
| MY133537A (en) * | 2002-01-24 | 2007-11-30 | Kobe Steel Ltd | Method for making molten iron |
| WO2011052428A1 (en) | 2009-10-28 | 2011-05-05 | Ｎｅｃエナジーデバイス株式会社 | Nonaqueous electrolyte solution and device comprising same |
| WO2014031801A1 (en) * | 2012-08-22 | 2014-02-27 | Hoffman Glenn E | Production of pig iron |
| KR101406503B1 (en) | 2012-12-21 | 2014-06-13 | 주식회사 포스코 | Fixed type electric arc furnace and molten steel manufacturing method |
| FI127451B (en) * | 2015-11-24 | 2018-06-15 | Outotec Finland Oy | Method and apparatus for preheating and smelting manganese ore sinter |
| CN205313650U (en) * | 2016-01-11 | 2016-06-15 | 长沙有色冶金设计研究院有限公司 | Device that laterite -nickel ore ore deposit obtained ferronickel is smelted in molten bath |
| KR102231655B1 (en) * | 2018-12-18 | 2021-03-23 | 주식회사 포스코 | Manufacturing apparatus of molten iron and manufacturing method of molten iron |
-
2021
- 2021-09-07 NL NL2029142A patent/NL2029142B1/en active
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2022
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| CN115584372A (en) | 2023-01-10 |
| NL2029142B1 (en) | 2023-03-21 |
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