JP2020020010A - Reduction method of high-phosphorus iron ore - Google Patents

Abstract

To obtain metal iron having low phosphorus content by reducing high-phosphorus iron ore.SOLUTION: Provided is a reduction method of a high-phosphorus iron ore having a phosphorus compound. By using a gas, the phosphorus compound in the high-phosphorus iron ore is reduced and vaporized to remove the gaseous phosphorus. The iron oxide is subsequently reduced. The temperature and composition of the gas are within a Pgas equilibrium region and a FeO equilibrium region of a CO gas reduction equilibrium diagram of iron oxide and diphosphorus pentaoxide, a Hgas reduction equilibrium diagram of iron oxide and diphosphorus pentaoxide and/or a CO-Hgas mixture reduction equilibrium diagram of iron oxide and diphosphorus pentaoxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for reducing high-phosphorous ore containing a large amount of phosphorus.

  Conventionally, iron ore containing high phosphorus (0.06 mass% or more) (high iron phosphate ore) has hardly been used as a raw material for ironmaking. It is starting to be used as a raw material. However, since high-phosphorous ore contains a large amount of phosphorus, it is technically difficult to efficiently dephosphorize to a required level in a normal ironmaking and steelmaking process. The amount is limited.

  Under such circumstances, several techniques for effectively using high-phosphate iron ore as a raw material for ironmaking have been proposed.

  Patent Literature 1 discloses a process in which iron ore having a phosphorus concentration of 0.06 wt% or more as a part or all of an iron source is charged into a blast furnace, and desiliconization with tapping from the blast furnace or after tapping from the blast furnace. A step of obtaining hot metal having a silicon concentration of 0.20 wt% or less through the treatment, a step of dephosphorizing the low silicon hot metal that has passed through the step, and a step of decarburizing the hot metal that has passed through the dephosphorization step. And a method for producing steel using high-phosphorus ore as a raw material, characterized by at least the following.

  However, since the iron ore having a phosphorus concentration of 0.06% by weight or more is used as a part or all of the iron making raw material in the steel manufacturing method of Patent Document 1, the dephosphorization cost in the steel making process becomes excessive, and the steel is not practically used. There are issues.

Patent Literature 2 discloses that the proportion of the Al ₂ O ₃ content in a high-phosphorous ore having a P content of more than 0.1% by mass and contained in a fine powder portion of 0.25 mm or less in the high-phosphorous ore is 2. An ore for a sintering raw material characterized by being 2% by mass or less, and a method for producing a sinter using the ore for the sintering raw material have been proposed.

  In the production method of Patent Document 2, high-phosphate iron ore can be used in a large amount as an ore for a sintering raw material. However, since the dephosphorization treatment is performed in the steelmaking process as before, the dephosphorization cost becomes excessively large and is not practical. Absent.

Phosphorus present in iron ore can be any of (a) phosphate minerals such as apatite, (b) derived from rare earths, (c) dissolved in Fe ₂ O ₃ , and (d) adsorbed on FeOOH. It is classified into crab. In (c) and (d), since Fe and P coexist, it is impossible to physically separate P (for example, by a beneficiation method). Conventionally, P is leached with acid or alkali. It is separated or reduced to magnetite (Fe ₃ O ₄ ) and then separated by weak magnetic selection.

Non-Patent Document 1 reports that high-phosphate iron ore is reduced in a hydrogen-steam atmosphere to directly remove phosphorus from the high-phosphate iron ore. However, according to the report of Non-Patent Document 1, the vaporized phosphorus is absorbed by the metallic iron generated by the reduction, and Fe ₂ P, which is a source of phosphorus in the hot metal, is generated, and the metallization rate is about 30%. Incidentally, the dephosphorization rate is saturated and is as low as about 10%. Therefore, the non-patent literature dephosphorization is not practical.

JP 2001-049320 A JP 2006-104516 A

Iron and Steel (Jakube et al., “Direct Dephosphorization from High Phosphorus Iron Ore”), Vol.100 (2014) No.2, pp.217-222

  When high-phosphate iron ore is used as a raw material for ironmaking, even if reduction treatment is performed on the high-phosphate iron ore, the dephosphorization rate does not improve, and a large cost is required for the dephosphorization treatment in the steelmaking process, which is economically disadvantageous. In view of the above, the present inventor aims to obtain metallic iron having a low phosphorus content in the reduction of high-phosphate iron ore, and to provide a method for reducing high-phosphate iron ore that solves the problem. Aim.

  The present inventors diligently studied a technique for solving the above-described problem based on the report of Non-Patent Document 1.

As a result, when reducing high-phosphate iron ore, the reduction is divided into two stages, and in the first stage, the phosphorus compound (mainly phosphoric acid [P ₂ O ₅ ]) in the ore is reduced under reducing conditions in which metallic iron is not generated. If the iron oxide in the ore is reduced to metallic iron in the second stage, the vaporized phosphorus and metallic iron do not come into contact with each other, so that re-absorption of phosphorus into metallic iron is prevented. Thus, it was found that the generation of Fe ₂ P, which is a source of phosphorus in the hot metal, was suppressed, and the dephosphorization rate was improved.

  In addition, if the high-phosphate iron ore is subjected to one or more of a washing treatment, a dehydration treatment, and a beneficiation treatment before subjecting the high-phosphate iron ore to the reduction treatment of the phosphorus compound, the dephosphorization rate is further improved. There was found.

  The present invention has been made based on the above findings, and the gist is as follows.

(1) A method for reducing high-phosphate iron ore containing a phosphorus compound,
Temperature and composition, CO gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, H ₂ gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, and / or, of iron oxide and phosphorus pentoxide CO-H ₂ Gases in the P ₂ gas equilibrium region and the FeO equilibrium region of the mixed gas reduction equilibrium diagram are used to reduce and vaporize phosphorus compounds in high-phosphate iron ore, remove vaporized phosphorus, and then reduce iron oxide. Characteristic method for reducing high phosphate iron ore.

  (2) The high-phosphate iron ore containing the phosphorus compound is subjected to one or more of a dehydration treatment, a water washing treatment, and a beneficiation treatment before the reduction treatment for reducing the phosphorus compound is performed. The method for reducing high-phosphate iron ore according to (1).

  (3) The method for reducing high-phosphate iron ore according to (2), wherein the dehydration treatment is performed by heating the high-phosphate iron ore to 400 ° C or more and less than 800 ° C.

  (4) In the beneficiation treatment, the ore enriched in goethite is recovered from the high phosphate iron ore containing a phosphorus compound, and the ore enriched in goethite is subjected to a reduction treatment. ) Or (3).

  (5) The gas generated in the step of reducing iron oxide in the high phosphate iron ore is reformed in a reforming furnace and used as part or all of the gas for reducing the phosphorus compound in the high phosphate iron ore. The method for reducing high phosphate iron ore according to any one of the above (1) to (4).

According to the present invention, when performing a dephosphorization treatment at the ore stage on a high-phosphorous iron ore, the generation of Fe ₂ P as a source of phosphorus in the hot metal is suppressed, and the dephosphorization rate is increased more than before. be able to.

It is a figure which shows the basic aspect of a phosphorus removal and iron reduction process. It is a figure which shows another aspect of a phosphorus removal and iron reduction process. It is a figure which shows another aspect of a phosphorus removal and iron reduction process. It is a figure which shows another aspect of a phosphorus removal and iron reduction process. It is a figure which shows another aspect of a phosphorus removal and iron reduction process. It is a CO gas reduction equilibrium figure of iron oxide and diphosphorus pentoxide. FIG. 3 is an H ₂ gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide. A CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide. (A) is a CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide when the dephosphorized gas is 20% CO-80% H ₂ , and (b) is 40% dephosphorized gas. FIG. 3 is a CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide in the case of% CO-60% H ₂ . A CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide. (A) is a CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide when the dephosphorized gas is 60% CO-40% H ₂ , and (b) is a dephosphorized gas of 80%. FIG. 4 is a CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide in the case of% CO-20% H ₂ .

The method for reducing high phosphate iron ore of the present invention (hereinafter sometimes referred to as the “reduction method of the present invention”) is a method for reducing high phosphate iron ore containing a phosphorus compound,
Temperature and composition, CO gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, H ₂ gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, and / or, of iron oxide and phosphorus pentoxide CO-H ₂ Gases in the P ₂ gas equilibrium region and the FeO equilibrium region of the mixed gas reduction equilibrium diagram (hereinafter sometimes referred to as “dephosphorized gas”) are used to reduce and vaporize phosphorus compounds in high phosphate iron ore (hereinafter referred to as “dephosphorized gas”). Phosphorous step "), removes vaporized phosphorus, and then reduces iron oxide (hereinafter sometimes referred to as" iron reducing step ").
It is characterized by the following.

  In the reduction method of the present invention, a dehydration treatment, a water washing treatment, and a reduction treatment are performed on the high-phosphate iron ore containing the phosphorus compound before the reduction treatment for reducing the phosphorus compound (hereinafter, may be referred to as “dephosphorization treatment”). And one or more of the beneficiation processes.

  The reduction method of the present invention is characterized in that the dehydration treatment is performed by heating the high phosphate iron ore to 400 ° C. or more and less than 800 ° C.

  The reduction method of the present invention is characterized in that, in the beneficiation treatment, ore enriched in goethite is recovered from high phosphate iron ore containing a phosphorus compound, and the ore enriched in goethite is subjected to a reduction treatment. .

  In the reduction method of the present invention, the gas generated in the step of reducing iron oxide in the high phosphate iron ore is reformed in a reforming furnace, and the gas (phosphorus removal gas) for reducing the phosphorus compound in the high phosphate iron ore is reduced. It is characterized in that it is used as part or all.

  Hereinafter, the reduction method of the present invention will be described with reference to the drawings.

  FIG. 1 shows a basic mode of the phosphorus removal / iron reduction step.

As shown in FIG. 1, high phosphate iron ore having a required particle size is charged into a dephosphorization furnace 1, and a dephosphorization gas is supplied to the dephosphorization furnace 1 to remove a phosphorus compound in the high phosphate iron ore. Reduce and vaporize. The vaporized phosphorus is sent to the phosphorus recovery device 1a and collected. Dephosphorization gas temperature and composition, CO gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, H ₂ gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, and / or iron oxide and diphosphorus pentoxide Is a reducing gas in the P ₂ gas equilibrium region and the FeO equilibrium region of the CO—H ₂ mixed gas reduction equilibrium diagram of FIG. The temperature and composition of the dephosphorizing gas will be described later.

  Table 1 shows, as an example of the high-phosphorous ore to be treated, the component composition of the high-phosphorus Brockmann ore produced in Australia.

The high phosphate iron ore shown in Table 1 contains 0.12% by mass of phosphorus. In the reduction method of the present invention, a high-phosphorous ore as shown in Table 1 is first (first stage) reduced in temperature and composition in a reducing gas (dephosphorization) in the P ₂ gas equilibrium region and the FeO equilibrium region. Gas). By this reduction, the iron oxide is not reduced, and only the phosphorus compound (mainly the phosphorous oxide [P ₂ O ₅ ]) in the high phosphate iron ore is reduced.

  The iron ore from which phosphorus has been removed in the dephosphorization furnace 1 is fed to a reduction furnace 2 and reduced by a gas having a potential of reducing iron oxide to metallic iron (hereinafter sometimes referred to as “iron reducing gas”). To produce reduced iron (metallic iron).

  As described above, in the reduction method of the present invention, the reduction of high phosphate iron ore is divided into two stages, and in the first stage, only the phosphorus compound in the high phosphate iron ore is reduced to remove phosphorus (dephosphorization step). In the second stage, the iron oxide in the iron ore after the dephosphorization is reduced (iron reduction step). This is the basic concept of the reduction method of the present invention. The first stage dephosphorization treatment will be described later.

  The gas discharged from the reduction furnace 2 (hereinafter sometimes referred to as “off gas”) is reformed in the reforming furnace 3 by, for example, reacting with natural gas, and is supplied to the dephosphorization furnace 1. It may be used as part or all of the phosphorus gas. This point will also be described later.

  FIG. 2 shows another embodiment of the phosphorus removal / iron reduction step. In the dephosphorization / iron reduction step shown in FIG. 2, a dehydration step of removing water of crystallization of high-phosphate iron ore is arranged as a step before the dephosphorization step. The dephosphorization / iron reduction step shown in FIG. 2 is the same as the dephosphorization / iron reduction step shown in FIG. 1 after the dephosphorization step, and the same steps as those shown in FIG. Are indicated by the same reference numerals.

<Dehydration step>
Before performing the dephosphorization treatment on the high-phosphate iron ore, the high-phosphate iron ore is heated to 400 ° C. or more and less than 800 ° C., and subjected to a dehydration treatment (decrystallization water treatment) for removing water of crystallization in the ore. When the water of crystallization is removed from the high-phosphate iron ore, the production of low-melting-point compounds is suppressed in the reduction reaction, and the dephosphorization rate is improved.

Phosphorus in the goethite in the main component of high phosphorus iron ore, Strange catcher site: Fe (PO ₄₎ · 2H present at ₂ O forms. Strengite has a low melting point (eutectic point) of 968 ° C., and if the reaction temperature with the dephosphorizing gas is higher than the melting point (eutectic point), the reaction with the reducing gas becomes a gas-liquid reaction. Rapidly decreases, and the dephosphorization rate decreases.

When the strengite is subjected to a dehydration treatment at a temperature lower than its melting point for a predetermined time, water of crystallization is removed, and at the same time, it reacts with hematite existing in the surroundings, and is Fe ₂ O ₃ rich, high melting point iron phosphoric acid: 3Fe ₂ O ₃ · P ₂ O ₅ is produced.
Fe ₂ O ₃ · P ₂ O ₅ + 2Fe ₂ O ₃ → 3Fe ₂ O ₃ · P ₂ O ₅

Further, 2FeO · P ₂ O ₅ and 3FeO · P ₂ O ₅ to produce by reducing _{Fe 2 O 3 · P 2 O} 5 is also a low melting point, similarly, inhibits dephosphorization reaction, once, high forming a _{3Fe 2 O 3 · P 2 O} 5 of melting and reducing _{3Fe 2 O 3 · P 2 O} 5 , since also increases the melting point of the reduction product, and dephosphorization reaction is promoted, the dephosphorization rate improves.

  FIG. 3 shows another embodiment of the phosphorus removal / iron reduction step. In the phosphorus removal / iron reduction step shown in FIG. 3, a water washing step or a water washing step and a dehydration step are arranged as a step before the phosphorus removal step.

<Washing process>
Prior to the dephosphorization step or prior to the dehydration step, the high-phosphate iron ore is washed with water to wash away the -20 to 45 μm clay mineral adhering to the ore surface. When the clay mineral adhering to the ore surface is removed, the dephosphorized gas easily diffuses into the iron ore, the reduction of the phosphorus compound is promoted, and the dephosphorization rate is improved.

  The high-phosphorous ore washed in the washing machine 4 is sent to the dephosphorization furnace 1 or sent to the dehydration furnace 5 and then sent to the dephosphorization furnace 1. The dephosphorization furnace 1 and subsequent steps are as described in FIG. The washing machine 4 is not limited to a particular washing machine as long as it can wash iron ore with water. For example, a drum type scrubber, a washing sieve and the like are preferable.

  FIG. 4 shows another embodiment of the phosphorus removal / iron reduction step. In the dephosphorization / iron reduction step shown in FIG. 4, high-phosphate iron ore subjected to a water-washing treatment is supplied to a beneficiation step.

<Mineral processing>
In the beneficiation process, high-phosphorous ore is beneficiated by the beneficiator 6 to recover the goethite-enriched portion.

  When classification was performed in two stages according to the specific gravity, the hematite-enriched portion having the highest specific gravity (hereinafter sometimes referred to as “hematite-rich ore”) was first recovered, and then the goethite was enriched. A portion (hereinafter sometimes referred to as “gecite rich ore”) is recovered, and finally, a portion enriched in gangue (hereinafter sometimes referred to as “gangue-rich ore”) as tailings is recovered. Is done.

  Then, the goethite-rich ore is subjected to a dephosphorization step. The gangue-rich ore is discarded, and the hematite-rich ore is agglomerated by the agglomerator 7 and provided to the iron reduction step.

  For example, P in Australian high-phosphate iron ore is abundant in goethite contained in the ore in an amount of about 35 to 50 mass, and hardly exists in other hematite or gangue.

  Table 2 shows the distribution of phosphorus in the high phosphate iron ore.

  As shown in Table 2, since phosphorus is abundant in goethite, high-phosphate iron ore is separated into goethite-rich ore, hematite-rich ore, and gangue-rich ore before being subjected to the dephosphorization treatment. Only the site rich ore is subjected to dephosphorization. By subjecting the high-phosphorous ore to a beneficiation process, the throughput in the dephosphorization step is reduced, and the dephosphorization furnace can be simplified.

  High-phosphate iron ore is classified by about 3 mm, and the ore-sorting of iron ore on the sieve is performed by JIG sorting (jig sorting) or heavy liquid sorting, and the ore-sorting of iron ore under the sieve is spiral sorting, UCC It is preferable to carry out the separation (Up-Current Classifier [ascent water type specific gravity separation]), WHIMS selection (Wet High Intensity Magnetic Separation [wet type strong magnetic separation]), or heavy liquid separation.

  The reason why the classification particle size is set to 3 mm is that the particle size range in which the ore can be efficiently sorted by JIG is 3.0 mm or more, and the particle size range in which the orifice can be efficiently classified is 3.0 mm or less.

  FIG. 5 shows another embodiment of the phosphorus removal / iron reduction step. In the dephosphorization / iron reduction step shown in FIG. 5, the goethite-rich ore separated in the ore separator 6 is subjected to a dehydration treatment (decrystallization water treatment) in the dehydration furnace 5 to be subjected to the dephosphorization step.

  When the crystallization water is removed from the goethite, the tissue becomes porous, and the reactivity with the dephosphorization gas is improved. The lower the dehydration temperature is, the more porous it is. Therefore, the lower the dehydration temperature in the dehydration furnace 5 is, the more preferable it is. When dehydration treatment is applied to a goethite-rich ore, the formation of a low melting point mineral phase is suppressed, and the iron ore becomes porous, and the dephosphorization reaction in a dephosphorization furnace and the reduction reaction in a reduction furnace (metallic iron) Formation reaction) is promoted, and the dephosphorization rate and the metallization rate are improved.

  In the dephosphorization / iron reduction step shown in FIGS. 4 and 5, a beneficiation step is arranged after the water-washing step. However, the water-washing step may be omitted, and the high-phosphorous iron ore may be directly supplied to the beneficiation step. .

  Next, the first stage dephosphorization treatment of the reduction method of the present invention will be described.

<Dephosphorization treatment>
As described above, in the present invention reduction method, temperature and composition, CO gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, H ₂ gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, and / or, Reduction of phosphorus compounds in high iron ore with reducing gas (dephosphorization gas) in the P ₂ gas equilibrium region and FeO equilibrium region of the CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide , Vaporized and the vaporized phosphorus is removed.

Since the reducing compound in the P ₂ gas equilibrium region and the FeO equilibrium region reduces the phosphorus compound in the high phosphate iron ore, the oxide in the high phosphate iron ore is not reduced and no metallic iron is generated.

(Temperature and composition)
Figure 6 shows the CO gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, in FIG. 7 shows the H ₂ gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide. In FIG. 6, the reduction potential on the vertical axis: ηCO is CO ₂ / (CO + CO ₂ ), and in FIG. 7, the reduction potential on the vertical axis: ηH ₂ is H ₂ O / (H ₂ + H ₂ O). It is. 6 and 7, the solid line is a reduction equilibrium curve of iron oxide, and the dotted line is a reduction equilibrium curve of P ₂ O ₅ (diphosphorus pentoxide).

The reduction equilibrium curve of P ₂ O ₅ (diphosphorus pentoxide)
1 / 5P ₂ O _{5 (s)} + 5CO _(g) = 1 / 5P _{2 (g)} + CO ₂
ΔG ^O /J=38168.64-20.7T
_{1 / 5P 2 O 5 (s} ) + 5H 2 (g) = 1 / 5P 2 (g) + H 2 O
ΔG ^O /J=11182.92-50.442T
(See Kashiwaya et al .: Iron and Steel, 100 (2014) 302).

When a CO gas is used as the dephosphorizing gas, a reducing gas having a temperature and a composition in a hatched region in FIG. 6, that is, a P ₂ gas equilibrium region and a FeO equilibrium region is used, and H ₂ gas is used as the dephosphorizing gas. When used, reducing gas in the shaded region in FIG. 7, that is, the P ₂ gas equilibrium region and the FeO equilibrium region is used.

In other words, the shaded regions in FIGS. 6 and 7 are regions in which P ₂ gas is generated by reducing the phosphorus compound, but which has an affinity for phosphorus and does not generate metallic iron (Fe) that adsorbs P ₂ gas. It is. FeO is generated in the shaded region, but does not adsorb P ₂ gas because FeO has a low affinity for phosphorus.

In the case of using a mixed gas of CO and H ₂ as the dephosphorizing gas, CO—CO ₂ and H ₂ —H ₂ O each satisfy the hatched area in FIG. 5 and the hatched area in FIG. Next, the temperature and composition of the dephosphorization gas are adjusted.

FIG. 8 and FIG. 9 show equilibrium diagrams of CO-H ₂ mixed gas reduction of iron oxide and diphosphorus pentoxide when a mixed gas of CO and H ₂ is used as the dephosphorizing gas.

FIG. 8A shows a CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide when the dephosphorizing gas is 20% CO-80% H ₂ , and FIG. FIG. 3 shows a CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide when the dephosphorization gas is 40% CO-60% H ₂ .

FIG. 9A shows a CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide when the dephosphorization is 60% CO-40% H ₂ , and FIG. FIG. 3 shows a CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide when the phosphorus gas is 80% CO-20% H ₂ .

8 (a), 8 (b), 9 (a), and 9 (b), the hatched region in the CO-H ₂ mixed gas reduction equilibrium diagram of iron oxide and diphosphorus pentoxide is shown. , P ₂ gas equilibrium region and FeO equilibrium region.

<Production of dephosphorized gas>
Dephosphorization gas, the temperature and composition, CO gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, H ₂ gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, and / or iron oxide and diphosphorus pentoxide Is a gas adjusted so as to be in the P ₂ gas equilibrium region and the FeO equilibrium region of the CO—H ₂ mixed gas reduction equilibrium diagram of FIG. ₂ , but in actuality, the fuel gas (natural gas, coal gasification gas, converter gas, Blast furnace gas, hydrogen, etc.) are produced by mixing a gas (H ₂ O, CO ₂ , or a mixed gas of both) obtained by partially burning or partially reforming and an off-gas discharged in the iron reduction step.

  The above-mentioned mixed gas is preferable in that the exhaust gas from the iron reduction furnace can be effectively used to reduce the total required energy.

Table 3 shows a production example of the dephosphorized gas when natural gas is used as the fuel gas. 70 vol% of offgas with ηH ₂ = 0.42 and ηCO = 0.47 discharged from the iron reduction furnace and 30 vol% of natural gas are mixed, and the mixed gas is mixed with air of 25 vol% of the mixed gas. By partial combustion, dephosphorized gas (partial combustion gas) was produced.

(Dephosphorization furnace)
As shown in FIGS. 1 to 4, the dephosphorization treatment is performed in a dephosphorization furnace 1. The dephosphorization furnace 1 may be any furnace that can perform dephosphorization, and is not limited to a specific furnace. Furnaces are preferred.

Since phosphorus in high-phosphate iron ore is mainly present in goethite, it is difficult to agglomerate by granulation, and when agglomeration by sintering, phosphorus and CaO combine to form P _Since a stable phase of ₂ O ₅ .CaO is formed and it is difficult to vaporize and remove phosphorus, it is necessary to treat high-phosphate iron ore in a powdery state. A fluidized bed furnace is suitable for efficiently bringing the powdery iron ore into contact with a high-temperature dephosphorization gas to cause a reaction and to efficiently perform dephosphorization.

  Next, the iron reduction process of the iron ore subjected to the dephosphorization treatment in the dephosphorization furnace will be described.

<Iron reduction process>
As shown in FIGS. 1 to 4, in a dephosphorization furnace 1, an iron ore from which phosphorus has been removed by reducing a phosphorus compound with a reducing gas that does not produce metallic iron (see FIGS. 5 to 8) is reduced. To reduce the iron oxide to obtain metallic iron (reduced iron). Metallic iron (reduced iron) may be supplied to a smelting reduction furnace (not shown) following the reduction furnace.

The iron reducing gas blown into the reduction furnace 2 is not limited to a specific reducing gas, but a gas obtained by reforming natural gas with H ₂ O (see the following reaction formula) is preferable in that it has a sufficient reducing ability. .
CH ₄ + H ₂ O = 3H ₂ + CO

  Next, an example of the present invention will be described. The conditions in the example are one condition example adopted to confirm the operability and effects of the present invention, and the present invention is based on this one condition example. It is not limited. The present invention can employ various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example 1)
The high-phosphorous ore whose component composition is shown in Table 4 was subjected to a dephosphorization treatment and an iron reduction treatment in accordance with the dephosphorization / iron reduction step shown in FIG. The dephosphorization treatment was performed for 120 minutes using a dephosphorization gas (see a hatched area in FIG. 6) at a temperature of 1200 ° C. and ηCO: 30%.

  The iron reduction treatment was performed for 60 minutes using a reducing gas having a temperature of 1000 ° C. and ηCO of 0%. Table 3 also shows the component composition of the iron ore after the dephosphorization treatment and the component composition of the reduced iron (metallic iron) after the reduction treatment.

  From Table 4, it can be confirmed that the dephosphorization rate of the metallic iron after the iron reduction treatment is substantially the same as the dephosphorization rate achieved by the dephosphorization treatment, and that there is no adsorption of phosphorus to the metallic iron. That is, the effect of performing the phosphorus removal treatment prior to the reduction treatment can be confirmed.

(Example 2)
The high-phosphate iron ore having the required component composition is heated to 400 to 500 ° C. to perform a dehydration treatment (decrystallization water treatment), and the dephosphorization treatment is performed on the high-phosphate iron ore after the dehydration treatment under the conditions shown in Example 1. The dephosphorization rate was compared with the dephosphorization rate without dehydration treatment. Table 5 shows the results.

  Table 5 shows that the dephosphorization rate increases when dehydration treatment (decrystallization water treatment) is performed on the high phosphate iron ore.

(Example 3)
The high phosphate iron ore having the component composition shown in Table 6 (before washing) was washed with a wet sieving and sorting machine. Table 6 also shows the component composition of the high-phosphate iron ore after washing with water. From Table 6, it can be seen that the amount of SiO ₂ and Al ₂ O ₃ , which are the main components of the clay mineral of −20 to 45 μm, adhering to the surface of the high phosphate ore is reduced by the water washing.

Under the conditions of Example 1, the dephosphorization treatment and the reduction treatment were performed on the high-phosphate iron ore before and after the washing. The dephosphorization rate of the high phosphate iron ore after the water washing was 61%, which is 16% higher than the 45% dephosphorization rate of the high phosphate iron before the water washing. This increase in the dephosphorization rate is attributable to the fact that the amounts of SiO ₂ and Al ₂ O ₃ , which are the main components of the clay mineral having a size of −20 to 45 μm, were reduced by the water washing treatment.

(Example 4)
The high-phosphate iron ore was subjected to a beneficiation treatment using a UCC apparatus, and separated into goethite-rich ore, hematite-rich ore, and gangue-rich ore. Table 7 shows the mass ratio, phosphorus concentration, and phosphorus distribution ratio of the core ore after the beneficiation. From Table 7, it can be seen that phosphorus is concentrated in the goethite-rich ore.

  The phosphorus-enriched goethite-rich ore was subjected to a dephosphorization treatment under the conditions of Example 1. The dephosphorization rate was 40 to 60%.

As described above, according to the present invention, when dephosphorizing a high-phosphorous ore at the ore stage, the production of Fe ₂ P, which is a source of phosphorus in the hot metal, is suppressed, and the dephosphorization rate is reduced. Can be increased more than before. Therefore, the present invention has high applicability in the steel industry.

DESCRIPTION OF SYMBOLS 1 Dephosphorization furnace 1a Phosphorus recovery apparatus 2 Reduction furnace 3 Reforming furnace 4 Washing machine 5 Dehydration furnace 6 Mineral mill 7

Claims (5)

A method for reducing high-phosphate iron ore containing a phosphorus compound, comprising:
Temperature and composition, CO gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, H ₂ gas reduction equilibrium diagram of iron oxide and phosphorus pentoxide, and / or, of iron oxide and phosphorus pentoxide CO-H ₂ Gases in the P ₂ gas equilibrium region and the FeO equilibrium region of the mixed gas reduction equilibrium diagram are used to reduce and vaporize phosphorus compounds in high-phosphate iron ore, remove vaporized phosphorus, and then reduce iron oxide. Characteristic method for reducing high phosphate iron ore.   The high-phosphate iron ore containing the phosphorus compound is subjected to one or more of a dehydration treatment, a water washing treatment, and a beneficiation treatment before the reduction treatment for reducing the phosphorus compound is performed. The method for reducing high-phosphate iron ore described above.   The method of reducing high phosphate iron ore according to claim 2, wherein the dehydration treatment is performed by heating the high phosphate iron ore to 400 ° C or more and less than 800 ° C.   The ore treatment according to claim 2 or 3, wherein the ore enriched in goethite is recovered from the high phosphate iron ore containing the phosphorus compound, and the ore enriched in goethite is subjected to a reduction treatment. The method for reducing high-phosphate iron ore described above.   The gas generated in the step of reducing iron oxide in the high phosphate iron ore is reformed in a reforming furnace, and is used as a part or all of the gas for reducing the phosphorus compound in the high phosphate iron ore. The method for reducing high-phosphate iron ore according to claim 1.

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