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US20090282950A1 - Process for producing metallic iron - Google Patents

Process for producing metallic iron Download PDF

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Publication number
US20090282950A1
US20090282950A1 US12/094,607 US9460706A US2009282950A1 US 20090282950 A1 US20090282950 A1 US 20090282950A1 US 9460706 A US9460706 A US 9460706A US 2009282950 A1 US2009282950 A1 US 2009282950A1
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Prior art keywords
slag
iron
raw material
iron oxide
heating
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Inventor
Akira Uragami
Isao Kobayashi
Mitsutaka Hino
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Kobe Steel Ltd
KAB KAISHA KOBE SEIKO SHO (Kobe Steel Ltd)
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KAB KAISHA KOBE SEIKO SHO (Kobe Steel Ltd)
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Assigned to KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.) reassignment KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.) ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HINO, MITSUTAKA, KOBAYASHI, ISAO, URAGAMI, AKIRA
Publication of US20090282950A1 publication Critical patent/US20090282950A1/en
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/0046—Making spongy iron or liquid steel, by direct processes making metallised agglomerates or iron oxide
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/0066—Preliminary conditioning of the solid carbonaceous reductant
    • 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
    • C21B13/105—Rotary hearth-type furnaces
    • 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
    • Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen

Definitions

  • the present invention relates to an improvement in technique for manufacturing metallic iron by heating and reducing an iron source such as an iron ore using a carbonaceous reducing agent such as coke, and more particularly, the present invention relates to a technique for efficiently manufacturing metallic iron having a predetermined carbon concentration.
  • an iron oxide is reduced and is simultaneously carburized, and metallic iron produced thereby is efficiently separated from slag-forming components which are mixed, for example, in a raw mineral ore as gangue components and the like.
  • Patent Document 1 One of the inventors of the present invention proposed a method disclosed in Patent Document 1 as a new type direct iron-making method, and research for improving the above direct iron-making method has also been carried out thereafter.
  • This method is a technique to produce metallic iron by heating and reducing a raw material mixture containing a carbonaceous reducing agent and iron oxide.
  • the reduction is further advanced in a solid state until the iron oxide is not substantially present inside the metallic iron shell, followed by further continuous heating to make slag, which is produced inside, flow out of the metallic iron shell, so that the metallic iron is separated from the slag.
  • the molten slag present inside the metallic iron shell may be made to flow out thereof.
  • the melting point of the metallic iron shell may be decreased by dissolving carbon derived from a carbonaceous reducing agent present inside the metallic iron shell into metallic iron (this phenomenon may be called “carburization” in some cases).
  • metallic iron solidified in the form of particles may be separated using a magnetic separator or a sieve while the slag is ground, or the solidified metallic iron and the produced slag may be melted by heating, followed by separation using the difference in specific gravity.
  • metallic iron can be obtained having a high purity of 95 mass percent or more or 98 mass percent or more.
  • Patent Document 2 a method for separating granular metallic iron from low-melting point slag containing FeO has been disclosed in which steel mill waste is used as an iron oxide source and is mixed with a carbonaceous reducing agent (hereinafter referred to as a “carbonaceous material” in some cases) and an additional raw material (slag-forming agent) so that a produced slag composition is adjusted to have a CaO/SiO 2 ratio (degree of basicity) in the range of 1.4 to 1.6 on a mass basis, followed by heating to 1,250 to 1,350° C. for reduction to form granular metallic iron.
  • a carbonaceous reducing agent hereinafter referred to as a “carbonaceous material” in some cases
  • slag-forming agent additional raw material
  • this method is a method using steel mill waste as an iron oxide source.
  • adjustment of the degree of basicity of a slag-forming component used in this method is performed when raw materials are mixed together, and behavior of slag produced in heating and reducing and that of iron oxide contained therein have not been sufficiently investigated.
  • Patent Document 3 a method has been disclosed in which the degree of basicity of a slag-forming component in a raw material is controlled in the range of 0.4 to 1.3, and at least one third of the time for heating and reducing performed on a hearth is controlled in the range of 1,200 to 1,350° C. so as to set the reduction degree of iron to 40% to 80%, followed by melting a reduced product.
  • the adjustment of the degree of basicity used in this method is performed by calculation when raw materials are mixed together.
  • influence of unreduced iron oxide contained in a raw material on the production of molten slag, dynamic behavior of iron oxide contained in molten slag, influence of the iron oxide on a meltdown state of metallic iron produced by reduction, and the like have not been investigated at all.
  • Patent Document 4 a technique disclosed in Patent Document 4 was proposed.
  • the basic concept of this invention is that, when metallic iron is manufactured by heating and reducing a raw material mixture containing a carbonaceous reducing agent and iron oxide, by controlling a liquid fraction in a solid-liquid coexisting phase of multi-component slag which is produced in reduction and melting of the raw material mixture and which contains gangue components, carburization and melting of solid metallic iron to be produced are facilitated.
  • the technique is characterized in that besides the control of a meltdown temperature of metallic iron, the carbon content (carbon concentration, hereinafter the same expression as the above will be used) of metallic iron to be produced is controlled.
  • Non-Patent Document 1 In order to understand a carbonization phenomenon of iron in a blast furnace, one of the inventors of the present invention carried out intensive fundamental research on reduction of iron oxide under the presence of molten slag and dynamic behavior of pig iron (Fe—C) which is produced by reduction and which dissolves carbon by carburization, and as a result, the following phenomenon was confirmed and was disclosed in Non-Patent Document 1.
  • This Non-Patent Document 1 relates to reduction of iron oxide in a blast furnace and carburization behavior of reduced iron (metallic iron) produced by the reduction.
  • behavior has been disclosed in which iron oxide (FeO) is reduced in molten slag (S) by a carbonaceous material (G: graphite) and in which produced metallic iron (Fe) is carburized.
  • iron oxide (FeO) in molten slag (S) is reduced and carburized by carbon (C) derived from a carbonaceous reducing agent (that is, carbonaceous material, G) to produce carburized molten iron (Fe—C).
  • the concentration of FeO in slag which is in contact with a carbonaceous material is decreased and becomes different from the concentration of FeO in slag which is in contact with reduced iron.
  • the carburized molten iron (Fe—C) tends to move in a direction apart from the carbonaceous material; hence, it rapidly moves in a direction towards solid reduced iron (S—Fe) and adheres thereto to form an unified body, thereby carburizing the solid reduced iron.
  • Patent Document 1 Japanese Unexamined Patent Application Publication No. 9-256017
  • Patent Document 2 Japanese Unexamined Patent Application Publication No. 10-147806
  • Patent Document 3 Japanese Unexamined Patent Application Publication No. 2000-45008
  • Patent Document 4 Japanese Unexamined Patent Application Publication No. 2005-48197
  • Non-Patent Document 1 ISIJ International, Vol. 44 (2004), No. 12, pp. 2033 to 2039
  • the present invention has been conceived in consideration of the above circumstances, and an object of the present invention is to provide an iron-making method having more excellent operation performance and operation efficiency than that of the direct iron-making method disclosed in the above Patent Document 4 that was developed by the inventors of the present invention.
  • the present invention is a method for manufacturing metallic iron from a raw material mixture containing a carbonaceous reducing agent and an iron oxide-containing material, and the above method has a step of determining a target temperature of initial molten slag formation corresponding to a predetermined target carbon concentration in the metallic iron, the initial molten slag containing a gangue component, an unreduced iron oxide, and an ash component of the carbonaceous reducing agent, and being first produced in the raw material mixture by heating thereof; a step of preparing the raw material mixture producing a composition of the initial molten slag corresponding to the target temperature; and a step of heating the raw material mixture to reduce and melt the raw material mixture and to produce the initial molten slag.
  • FIG. 1 is a schematic view conceptually showing the movement of molten iron oxide and a carbon carrier function of molten iron in molten slag containing carbon, discovered by one of the inventors of the present invention.
  • FIG. 2 is a multi-component phase diagram of CaO, SiO 2 , Al 2 O 3 , and FeO, which are primary components of molten slag.
  • FIG. 3 is graph showing an example of the relationship between the metallization degree and unreduced FeO remaining amount in heating and reducing.
  • FIG. 4 is a graph showing the change in reduction degree (referred to as “metallization degree” some times in this specification) with time for heating and reducing.
  • FIG. 5 is a graph showing the influence of the content of iron oxide (FeO) in slag on an initial molten slag forming temperature and a CO gas generation start temperature.
  • FIG. 6 is a graph showing the influence of the content of iron oxide (FeO) in slag on an initial molten slag forming temperature and a CO gas generation start temperature.
  • FIG. 7 is a graph showing the relationship between an initial molten slag forming temperature and a carbon concentration of meltdown metallic iron (metallic iron product) obtained under the above temperature condition.
  • the most significant feature of the present invention is that when a raw material mixture containing an iron oxide-containing material, such as iron ore, iron oxide, or a partially reduced material thereof, and a carbonaceous reducing agent, such as coke or coal, is heated to manufacture metallic iron by reduction and melting, a “target temperature of initial molten slag formation” corresponding to a predetermined target carbon concentration in metallic iron is determined, and the raw material mixture producing the initial molten slag corresponding to the target temperature is prepared and is then further heated to form the initial molten slag; that is, in other words, by controlling the forming temperature of the initial molten slag, the carbon concentration of obtained metallic iron is controlled.
  • the initial molten slag is slag which is first produced in the raw material mixture and which contains gangue components, unreduced iron oxide, and an ash component in the carbonaceous reducing agent.
  • the inventors of the present invention considered the probability that if the technique disclosed in the above Non-Patent Document 1 is used for direct iron making, when molten reduced iron produced by carburization following reduction using a carbonaceous material in a molten slag moves in a direction towards solid metallic iron in accordance with the above phenomenon and is then unified therewith, the molten reduced iron may be used as a carrier carrying carbon towards the solid metallic iron, and based on this assumption, research was further conducted.
  • the method (disclosed in Patent Document 4) developed by one of the inventors of the present invention is based on new finding at the time that indicates a close relationship between the liquid fraction of by-product slag and the meltdown of metallic iron, and this method is to perform the control using a new concept, that is, the liquid fraction in a solid-liquid coexistence phase of by-product slag, without melting the entire amount of the by-product slag.
  • this method when the liquid fraction is properly controlled, carburization of solid metallic iron produced by heating and reducing can be performed at a lower operation temperature, and as a result, the melting point thereof can be rapidly decreased.
  • meltdown of metallic iron can be performed at a lower temperature by this method, separation from by-product slag can be efficiently performed at a low temperature, and in addition, the carbon concentration of metallic iron, which has a large influence on the quality of a metallic iron product, can also be controlled.
  • a significant technical feature of the above invention filed in the past is that when metallic iron is manufactured by heating, reducing, and melting the above raw material mixture, the fact confirmed from the state of by-product slag, the carburization state of produced metallic iron, and the molten state thereof in a system containing a carbonaceous reducing agent is effectively used. That is, a phenomenon is used in which when a carbonaceous reducing agent is present together with slag in a molten state, molten metallic iron produced from molten slag having fluidity has a carrier-like function, carries carbon, and is then rapidly brought into contact with the surface of solid metallic iron, and thereby carburization of the solid metallic iron is efficiently performed.
  • an effective carburization promotion effect by coexistence of a carbonaceous reducing agent and molten slag is not limited only to the case in which the entire amount of slag is in a molten state, and when the liquid fraction of slag in a solid-liquid coexistence state is properly controlled, the carburization of solid metallic iron is promoted, and the meltdown temperature can be decreased.
  • the liquid fraction indicates a mass fraction of liquid, which is located between a solidus line and a liquidus line under a certain temperature condition, in a solid and a liquid (that is, in two phases, the solid phase and the liquid phase) and is determined by a thermodynamic equilibrium relationship of a multi-component system containing SiO 2 , Al 2 O 3 , CaO, and MgO, which are primarily derived from gauge components contained in raw materials, and FeO as a main component derived from an iron source.
  • This liquid fraction can be quantitatively obtained by observing the behavior of a raw material mixture when it is heated, reduced, and melted using a high-temperature laser microscope, followed by performing image analysis.
  • molten iron oxide FeO
  • carbon or carbon monoxide
  • molten iron which is carburized may be rapidly moved in a molten slag phase in a direction towards solid reduced iron and may then be unified therewith. Accordingly, after the unification with the solid reduced iron, a carbon component at a high concentration which enters the molten iron by carburization rapidly diffuses into the solid reduced iron, and as a result, the carbon concentration of the entire solid reduced iron is increased.
  • the carbon concentration of molten iron can be increased to that at 1,147° C., which is a eutectic point in terms of equilibrium, that is, can be increased to 4.3 mass percent, and also as apparent from the phase diagram described above, up to the eutectic temperature, the carbon concentration is increased as the temperature of the system is decreased.
  • a melt of a slag-forming component containing unreduced iron oxide derived from an iron source be produced at a temperature as low as possible to advance reduction of the iron oxide (formation of reduced iron) and to promote the movement thereof in a direction towards solid metallic iron, and that production of molten iron by carburization be further accelerated.
  • a temperature producing a melt that is, the initial molten slag
  • a slag-forming component including iron oxide which is first produced in a raw material mixture in a heating and reducing step.
  • this slag forming temperature is preferably decreased. In this reduction process, even when the exterior is partly reduced, the above initial molten slag may be produced in some cases.
  • the forming temperature of initial molten slag which triggers off carburization and melting (meltdown) of solid reduced iron at a final stage of reduction of the raw material mixture
  • the forming temperature of multi-component initial molten slag can be obtained from a multi-component thermodynamic phase diagram containing SiO 2 , Al 2 O 3 , CaO, MgO, FeO, and the like. In recent years, it could be obtained from a computer-programmed phase diagram of multi-component slag.
  • FIG. 2 is a phase diagram obtained by synthesizing a SiO 2 —Al 2 O 3 —CaO system and a SiO 2 —Al 2 O 3 —FeO system.
  • the composition of molten slag is a SiO 2 —Al 2 O 3 —CaO system
  • the composition is as shown by a dotted circle A in which Al 2 O 3 is approximately 20% and a CaO/SiO 2 ratio is approximately 5/5
  • the composition is as shown by a dotted circle B in which Al 2 O 3 is approximately 15% and a CaO/SiO 2 ratio is approximately 30/70
  • the melting temperature of the above four-component system slag shows the lowest value.
  • the composition of molten slag is a SiO 2 —Al 2 O 3 —FeO system
  • the composition when the composition is as shown by a thick line C in which a FeO content is in the range of approximately 35% to 50% (more preferably approximately 40%) and a SiO 2 /Al 2 O 3 ratio is approximately 45/55 or 40/60, the melting temperature of the above four-component system slag shows the lowest value.
  • the forming temperature of initial molten slag can be decreased to the lowest temperature.
  • a method may be used in which in accordance with slag-forming components in raw material components (including gangue components in an iron source, an ash component of a carbonaceous material, an inorganic binder component, and the like), additional materials, such as CaO, SiO 2 , or Al 2 O 3 , may be added.
  • additional materials such as CaO, SiO 2 , or Al 2 O 3 .
  • the addition is most generally performed when a raw material mixture is prepared; however, component adjustment may also be performed by additional supply at an early stage of heating and reducing.
  • an iron oxide (FeO) component in slag the amount of iron oxide remaining in unreduced state, which can be controlled by the metallization degree, may be used for the adjustment, the above iron oxide being one of iron oxide sources contained in a raw material mixture.
  • the ratio of metallic iron recovered from iron oxide in a raw material is represented by the metallization degree, and it is judged that as the metallization degree is high, the productivity is superior. Hence, much energy was spent in the past to find a way of increasing the metallization degree. However, it is very difficult to increase the metallization degree to 100% by reducing all of an iron oxide source, the metallization degree obtained under general conditions is approximately up to 90% to 95%, and unreduced iron oxide in an amount of several percent remains.
  • the present invention positively uses unreduced iron oxide which remains in a heating and reducing process. That is, in addition to decrease in forming temperature of initial molten slag by mixing unreduced iron oxide in slag, unreduced iron oxide in a molten state mixed in the slag is reduced and carburized, so as to enable carburized iron thus obtained to function as a carrier carrying carbon in a direction towards solid reduced iron. As a result, the production efficiency of metallic iron can be improved as a whole.
  • the metallization degree (reduction degree of an iron oxide-containing material) of an iron oxide source may be controlled so as to obtain a remaining amount of unreduced iron oxide corresponding to an optimum FeO content.
  • a heating temperature pattern or a reduction potential is adjusted, and in addition, the raw material mixture may be heated.
  • the heating temperature pattern for example, control of temperature, time, or temperature rise rate in heating and reducing may be mentioned.
  • the reduction potential for example, control of the amount of a carbonaceous reducing agent, the amount of a reducing agent used as a hearth protection material, or an in-furnace atmospheric gas may be mentioned.
  • FIG. 3 is a graph showing the result of research on the relationship between the metallization degree and the remaining FeO amount in an iron oxide source, which was obtained when a material produced in South America and supplied by MBR was used as iron oxide source (iron ore), Oak Grove coal produced in North America was used as a carbonaceous material, and heating and reducing were performed at 1,250 to 1,350° C.
  • the relationship described above may vary to a certain extent by the types of iron oxide source and/or carbonaceous material, mixing ratios thereof, heating and reducing conditions, and the like; however, when the relationship therebetween is obtained beforehand by a preliminary experiment, the remaining FeO amount can be adjusted by controlling the metallization degree of a raw material mixture, and as a result, the FeO content in produced slag can be properly obtained.
  • FIG. 4 is a graph showing the changes in temperature and metallization degree (that is, reduction degree) with time, which were obtained in the case in which a target temperature of a heating and reducing furnace was set to 1,400° C., a raw material mixture similar to that described above was supplied thereto, and heating and reducing were then performed.
  • the metallization degree is increased as the heating time passes and is rapidly increased 4 to 5 minutes after the start of heating at a heating temperature used in this case, and the degree of increase in metallization degree is rapidly decreased approximately 9 minutes after the start.
  • the metallization degree reaches approximately 90 mass percent about 8 minutes after the start of heating, and at this stage, the amount of iron oxide remaining in an unreduced state is approximately 10 mass percent.
  • the initial molten slag forming temperature can be controlled to the lowest temperature.
  • FIG. 5 is a graph showing the relationship between the iron oxide (FeO) concentration in slag and the initial molten slag forming temperature (and CO gas generation start temperature), which was obtained when a CaO/SiO 2 mass ratio in slag was maintained constant at 0.38.
  • the initial molten slag forming temperature melting temperature of slag
  • the CO gas generation start temperature is also decreased, the CO gas generation being caused by reduction of molten iron oxide (FeO).
  • FIG. 6 is a graph showing the result of an experiment similar to that described above except that the CaO/SiO 2 mass ratio in slag was changed to 0.92, and although the slag composition was changed, the tendency in which the initial molten slag forming temperature and the CO gas generation start temperature are decreased as the FeO content is increased is the same as that shown in FIG. 5 .
  • FIG. 7 is a graph showing the result obtained when the influence of the initial molten slag forming temperature (slag meltdown temperature) on the carbon concentration (C concentration) in produced molten metallic iron (meltdown metallic iron) was investigated, and from this graph, the tendency can be confirmed in which as the initial molten slag forming temperature (slag meltdown temperature) is decreased, the carbon content in metallic iron, which is a reduced product, is increased.
  • the forming temperature of the initial molten slag composed of a mixture containing slag-forming components (CaO, SiO 2 ) and unreduced iron oxide (FeO), which is produced in a reducing and melting process for a raw material mixture, and the carbon content in molten metallic iron to be produced has a certain relationship, and that when the forming temperature of the initial molten slag is controlled, the carbon content of obtained metallic iron can be controlled.
  • the tendency in which as the forming temperature of the initial molten slag is decreased, the carbon content of meltdown metallic iron is increased indicates that metallic iron having a high carbon content can be efficiently obtained by positively decreasing an operation temperature for metallic iron production, and this tendency is also significantly effective in view of decrease in thermal consumption.
  • the forming temperature of the initial molten slag as described above, based on a multi-component phase diagram (such as that shown in FIG. 2 ), which includes unreduced iron oxide remaining in reduction besides slag-forming components in raw materials (gangue components in an iron source and/or an ash component contained in a carbonaceous material) which are first used to form a raw material mixture, an appropriate amount of a slag-forming component other than the gangue components in the above iron source may be added (hereinafter referred to as “addition of a third slag-forming component” in some cases) at the stage when a raw material mixture is prepared, is charged, or is heated so that a melting temperature of slag having the above mixed composition is further decreased.
  • a multi-component phase diagram such as that shown in FIG. 2
  • an appropriate amount of a slag-forming component other than the gangue components in the above iron source may be added (hereinafter referred to as “addition of a third slag
  • the metallization degree of an iron source in a raw material mixture and the heating temperature pattern may be properly controlled in a metal iron-production process so that a necessary iron oxide content in slag is ensured by iron oxide remaining in an unreduced state.
  • the optimum initial molten slag forming temperature is obtained from the relationship shown in FIG. 7 , and based on a multi-component phase diagram as shown in FIG. 2 , compositions of slag-forming components and an unreduced iron oxide may be adjusted so as to obtain the above optimum initial molten slag forming temperature.
  • the adjustment of the initial molten slag composition in this case may also be performed by addition of a third slag-forming component or by the metallization degree of an ion source in a raw material and the heating temperature pattern.
  • the control of the initial molten slag forming temperature can be adjusted by mixing use of another iron ore in accordance with the composition of gangue components contained in an iron ore and the like used as an iron oxide source so as to obtain an appropriate slag-forming component composition; however, in accordance with a gangue component composition contained in a raw material ore, an additional raw material which can change the initial molten slag forming temperature is preferably added.
  • calcined lime CaO
  • lime stone CaCO 3
  • silica SiO 2
  • serpentine rock MgO+SiO 2
  • Mn ore MnO+FeO
  • bauxite Al 2 O 3
  • a raw material mixture is prepared by mixing an iron oxide source and a carbonaceous reducing agent, plus a binder component whenever necessary, after a melting temperature is obtained from the composition of gangue components contained in raw materials based on a multi-component phase diagram, an appropriate amount of oxide as mentioned above may be mixed as an additional raw material with the raw material mixture so as to obtain a target initial molten slag forming temperature.
  • the carbon concentration of metallic iron after carburization be controlled in the range of 0.5 to 4.3 mass percent, and that, in addition, the initial molten slag forming temperature be controlled in the range of 1,147 to 1,500° C.
  • the carbon concentration of metallic iron after carburization be controlled in the range of 1.5 to 3.5 mass percent, and that, in addition, the initial molten slag forming temperature be controlled in the range of 1,200 to 1,450° C.
  • the carbon concentration of metallic iron after carburization may be adjusted by the amount of a carbonaceous reducing agent to be mixed at a raw material preparation stage, and in particular, as the amount of a carbonaceous reducing agent, the total of a necessary theoretical amount required for reducing an iron oxide source and the above amount necessary for carburization may be used.
  • a carbonaceous reducing agent is partly consumed by an oxidizing gas generated, for example, by burner heating in reduction, when the actual carbonaceous material amount is determined, the amount must be adjusted in consideration of the consumption amount described above.
  • an iron oxide source and a carbonaceous reducing agent are both preferably in the form of powder and are preferably placed in a mixed state for the use.
  • This raw material mixture may be lightly solidified on a hearth with pressure and then be supplied; however, as disclosed in the above Patent Document 1, when the mixture is formed into an agglomerated material having an optional shape such as approximately spheres, briquettes, or pellets and is then supplied, a metallic shell of solid reduced iron is formed around the periphery of the agglomerated material in solid reduction by heating, and a high reduction potential can be maintained inside; hence, the metallization degree can be further efficiently improved, which is preferable.
  • an apparatus may be used in which a circular or a doughnut-shaped rotary hearth is provided; a heating and reducing furnace is used which has a raw material mixture supply zone, a preheating zone, a heating and reducing zone, a metallic iron melting zone, a cooling zone (metallic iron solidification zone), and a discharge zone provided in that order in a rotary direction; and a series of operations including supply of raw materials, heating and reducing, cooling and solidification of produced metallic iron, and recovery can be continuously performed.
  • the composition of slag-forming components in raw materials and the carbon content thereof are determined corresponding to a target carbon concentration by a preliminary experiment, and in addition, the metallization degree is also adjusted to obtain the optimum initial molten slag forming temperature in heating and reducing, so that the content of unreduced iron oxide in the initial molten slag may be ensured.
  • the carbon concentration in metallic iron to be obtained can be optionally controlled.
  • the following secondary effects can also be obtained.
  • the carbon content of metallic iron obtained by the method according to the present invention is increased as the initial molten slag forming temperature is decreased, that is, in other words, since when an operation temperature is decreased, metallic iron having a high carbon content can be obtained, a thermal consumption for heating and reducing can be decreased.
  • molten iron oxide contained in initial molten slag functions as a carbon carrier for solid reduced iron produced by gas reduction, rapidly performs carburization of solid reduced iron (solid metallic iron), and promotes its meltdown; hence, melting of solid reduced iron is significantly accelerated, and as a result, the production efficiently can be significantly improved as a whole.
  • unreduced iron oxide is contained as described above.
  • this iron oxide is reduced to metallic iron, and metallic iron functioning as a carbon carrier moves in molten slag to a solid reduced iron side.
  • the composition of molten slag is changed with time.
  • metallic iron instead of generating temperature of initial molten slag, it is preferable to control a melting point of slag even after metallic iron is produced.
  • a melting temperature that is, slag meltdown temperature
  • metallic iron can be efficiently manufactured.
  • the initial molten slag forming temperature is determined by slag-forming components contained in raw materials and a remaining unreduced iron oxide amount in heating and reducing; however, when the slag-forming components are not appropriate, by additionally adding a material containing a slag-forming component, the initial molten slag forming temperature can be decreased.
  • FIG. 3 is a graph showing the result of research on the influence of a CaO addition amount on the initial molten slag forming temperature.
  • the target carbon concentration of metallic iron to be obtained was set to approximately 3% in Example 1, in order to ensure the initial molten slag forming temperature corresponding to that concentration, lime stone as CaO source was additionally added as a material containing a slab-forming component when a raw material mixture was prepared.
  • the carbonaceous material in both cases, it was understood that when an appropriate amount of CaO was added, the initial molten slag forming temperature could be decreased.
  • the carbon contents of obtained metallic iron were 1.8%, 1.7%, 2.9%, and 3.5% when the CaO addition amounts in Table 3 were 0.3%, 0.4%, 2.0%, and 4.0%, respectively.
  • the initial molten slag forming temperature can be effectively controlled.
  • the initial molten slag forming temperature and/or the remaining unreduced iron oxide amount in heating and reducing can also be controlled.
  • a CaO content is intentionally increased by adding CaO to a carbonaceous material, so that the initial molten slag forming temperature is changed.
  • Table 4 shows the results of research on the change in initial molten slag forming temperature, the results being obtained by adding CaO in amounts shown in Table 4 to the aforementioned 3 types of carbonaceous materials to change the ash content.
  • Table 4 shows the results of research on the change in initial molten slag forming temperature, the results being obtained by adding CaO in amounts shown in Table 4 to the aforementioned 3 types of carbonaceous materials to change the ash content.
  • the initial molten slag forming temperature is apparently decreased.
  • Ca ions in CaO has a catalytic effect as an alkali to enhance reducing capability of a carbonaceous material and also contributes to improve reactivity thereof, it is believed that CaO can also be used to control a remaining unreduced iron oxide amount in heating and reducing.
  • the present invention relates to a method for manufacturing metallic iron from a raw material mixture containing a carbonaceous reducing agent and an iron oxide-containing material, and this method has a step of determining a target temperature of initial molten slag formation corresponding to a predetermined target carbon concentration in the metallic iron, the initial molten slag containing a gangue component, an unreduced iron oxide, and an ash component of the carbonaceous reducing agent, and being first produced in the raw material mixture by heating thereof; a step of preparing the raw material mixture producing a composition of the initial molten slag corresponding to the target temperature; and a step of heating the raw material mixture to reduce and melt the raw material mixture and to produce the initial molten slag.
  • the target temperature of the initial molten slag formation may be a specific temperature or a temperature range having a specific upper and lower limit.
  • the above “specific temperature” may be a “temperature higher than the lowest temperature” in a changeable range of each component composition of a slag-forming component. The same thing can be said for the “upper limit” and the “lower limit” in the above temperature range. Accordingly, metallic iron having a predetermined carbon concentration can be efficiently manufactured.
  • a slag-forming component may be mixed with the iron oxide-containing material.
  • a slag-forming component may be mixed with the carbonaceous reducing agent.
  • the raw material mixture may further contain an additional raw material, and in the preparation step, a slag-forming component may be mixed with the additional raw material.
  • a step of charging an additive containing a slag-forming component may be performed.
  • a slag-forming agent containing a slag-forming component may be added.
  • a flux containing a slag-forming agent may be added, or a slag-forming agent containing a slag-forming component and a flux containing a slag-forming component may be added.
  • the target temperature may be controlled.
  • a necessary slag-forming component can be optionally added into initial molten slag at the stage when a raw material mixture is prepared, is charged, or is heated, and as a result, the initial molten slag can be produced at a target temperature.
  • the target temperature can be determined by a multi-component phase diagram composed of gangue components, unreduced iron oxide remaining in reduction, and an ash component of a carbonaceous reducing agent. Accordingly, when individual component compositions of slag-forming components are adjusted within their changeable ranges, the target temperature which corresponds to the lowest temperature of initial molten slag formation in a target composition range can be easily determined. Alternatively, when the relationship between the forming temperature of initial molten slag and the carbon concentration in metallic iron is investigated beforehand, the target temperature can also be determined by the target carbon concentration in accordance with the above relationship. Accordingly, metallic iron having a target carbon concentration can be stably manufactured.
  • the heating step there may further be provided a step of setting a target content of the unreduced iron oxide in the initial molten slag and calculating a target reduction degree of the iron oxide-containing material corresponding to the target content, and in the heating step, until a reduction degree of the iron oxide-containing material reaches the target reduction degree, a heating temperature pattern or a reduction potential may be adjusted, and simultaneously heating may be performed. Accordingly, unreduced iron oxide, carburized iron, which remains in heating and reducing can be positively used as a carrier carrying carbon in a direction towards solid reduced iron, and as a result, the production efficiency of metallic iron can be improved as a whole.
  • heating may be performed based on a melting point of slag containing unreduced iron oxide in reduction. Accordingly, even when the amount of unreduced iron oxide in molten slag is decreased, since rapid movement of metallic iron in the molten slag can be ensured, even at the stage at which the reduction reaction has proceeded, metallic iron can be effectively manufactured.
  • the present invention compared to the method disclosed in Patent Document 4 developed by the inventor, by controlling the amounts of gangue components in a raw material mixture, an ash component in a carbonaceous reducing agent, and reduced iron oxide remaining in heating and reducing, which is not a small amount, the temperature of initial molten slag formation can be controlled. Accordingly, the carbon concentration in obtained metallic iron can be adjusted, and metallic iron having a desired carbon concentration can be efficiently obtained.
  • the present invention contains subject matter related to Japanese Patent Application No. 2006-008743 filed on Jan. 17, 2006, the entirety of which is incorporated herein by reference.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Manufacture Of Iron (AREA)
US12/094,607 2006-01-17 2006-11-30 Process for producing metallic iron Abandoned US20090282950A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2006-008743 2006-01-17
JP2006008743A JP4981320B2 (ja) 2006-01-17 2006-01-17 金属鉄の製法
PCT/JP2006/323928 WO2007083450A1 (fr) 2006-01-17 2006-11-30 Procédé servant à produire du fer métallique

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JP (1) JP4981320B2 (fr)
CN (1) CN101331239B (fr)
AU (1) AU2006335814B2 (fr)
CA (1) CA2630236C (fr)
RU (1) RU2388830C1 (fr)
TW (1) TWI307365B (fr)
WO (1) WO2007083450A1 (fr)

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JP2010261101A (ja) * 2009-04-07 2010-11-18 Mitsutaka Hino 金属鉄の製法
US20130047787A1 (en) * 2010-03-25 2013-02-28 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Carbon-material-containing iron oxide briquette composition, method for producing the same, and method for producing direct reduced iron using the same
RU2529435C1 (ru) * 2010-08-30 2014-09-27 Кабусики Кайся Кобе Сейко Се Способ получения гранулированного металлического железа
KR101293625B1 (ko) 2011-08-26 2013-08-13 우진 일렉트로나이트(주) 용융 슬래그 중 산화철 측정방법

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CA2630236C (fr) 2012-07-31
AU2006335814A1 (en) 2007-07-26
TWI307365B (en) 2009-03-11
AU2006335814B2 (en) 2011-04-14
RU2008133606A (ru) 2010-02-27
TW200730630A (en) 2007-08-16
CN101331239B (zh) 2012-03-28
CN101331239A (zh) 2008-12-24
JP2007191736A (ja) 2007-08-02
WO2007083450A1 (fr) 2007-07-26
JP4981320B2 (ja) 2012-07-18
CA2630236A1 (fr) 2007-07-26

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