JPH10291816A - Production method of iron carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deposition of soot from a metallized ion oxide- containing material and to stably produce a low-sulfur iron carbide. SOLUTION: At the time of producing iron carbide by carbonizing after reducing an iron oxide-containing material, the iron oxide-containing material is reduced by a sulfur-containing reductive gas in which [S]/([H2 ]+[CO], a sulfur molarity ratio to the sum of a molarity ration of H2 and CO, is made to 0.05 times to less than 1 times of the sulfur molarity ratio at the time of Fe/FeS equilibrium to produce a preliminary reduced material having less than the 20 mass% iron carbide and a >=60% metallized ratio and the iron carbide is produced by carbonizing the preliminary reduced material with a carbonizing gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of a method for producing reduced iron, in which iron oxide (Fe _x C _y ; x / y = 1 to
6) relates to a method for producing it stably.

[0002]

2. Description of the Related Art Conventionally, HyL 1 using a fixed bed (for example, JP-A-52-194) and HyL3 using a shaft furnace have been used.
(E.g., JP 54-99705 A) and Midrex (e.g. JP 62-263910 A), etc., to produce metallic iron from iron ore, and in a cooling step, carbon content in the product by carbonizing gas in a cooling process. The method of adjusting is widely known. However, due to the precipitation of free carbon during the production of iron carbide, almost no iron carbide can be produced.

[0003] As a conventional method for producing iron carbide, (1) Stelling in which fine iron ore is reduced and carbonized at 400 to 900 ° C with a CO-containing gas.
Method (US Patent No. 2780537), (2) iron ore in a fluidized bed 59
The IronCarbide method of reducing with H ₂ gas at 5 to 705 ° C. and simultaneously carburizing (carbonizing) with a carbon-containing material (for example, US Pat.
No. 1) and (3) a method of performing reduction carbonization with a gas obtained by adding a sulfur compound to CO-H2 (Japanese Patent Application No. 7-54687, Japanese Patent Application Laid-Open No. 8-198613) and the like.

In these processes, iron oxide is reduced and carbonized in the same reactor to produce iron carbide, thereby minimizing the formation of an intermediate product, metallic iron, to prevent sticking during operation in fluidized bed reduction. Prevents ignition of the product. However, on the other hand, it is known that free carbon is generated as an impurity during carbonization. In the (2) Iron Carbide method, the deposition of free carbon is prevented by reducing the driving force of the reaction using an introduced gas having a composition close to the Fe / FeO / Fe ₃ C equilibrium.

[0005] However, the reduction carbonization takes about 10 hours and the productivity is poor. Therefore, in the method (3), a sulfur compound that does not generate iron sulfide is added to the gas to suppress the precipitation of free carbon, and the productivity is improved by using a gas having a strong carbonization property.

[0006]

Since the formation of free carbon prevents the carbonization reaction in the carbonization process after metallizing the iron oxide, the carbonization rate (percentage of iron converted to carbide relative to the total iron mass) is reduced. It could not be more than 90%.

[0007] Further, the sulfur concentration produced by iron sulfide (FeS) depends on the type and concentration of the reducing gas and the reaction temperature, and decreases as the amount of the carbonizing gas (CO or hydrocarbon) is increased or the reaction temperature is decreased. I do. Therefore, in the method of adding a sulfur compound to prevent the precipitation of free carbon, it is necessary to reduce the concentration of sulfur in the product by suppressing the formation of iron sulfide under conditions with a large amount of carbonizing gas or at low temperatures. It is necessary to reduce the supply of sulfur compound gas, and as a result, there is a problem that free carbon increases.

An object of the present invention is to provide a method for producing iron carbide by reducing and carbonizing an iron oxide-containing substance, thereby efficiently producing iron carbide in a short time by preventing the formation of free carbon without increasing the sulfur concentration in the product. Another object of the present invention is to provide a method for increasing gas utilization and improving productivity.

[0009]

The present invention SUMMARY OF] has been made in order to solve the above problems, (1) after the reduction of iron oxide-containing material, in producing iron carbide by carbonizing, H ₂ And CO
The molar ratio of sulfur to the sum of the molar concentrations of ([S] / ([H ₂ ] + [C
O])) is reduced to 0.05 to less than 1 times the molar ratio of sulfur at the time of Fe / FeS equilibrium to reduce the iron oxide-containing substance with a reducing gas containing S, and metallization is performed when the iron carbide is less than 20 mass%. The method is characterized in that a pre-reduced product having a rate of 60% or more is produced, and the pre-reduced product is carbonized with a carbonizing gas to produce iron carbide.

(2) In (1), the temperature is obtained by the equation (1) depending on the reduction temperature and the molar concentration of each component in the reduction gas.
{[S] / ([H ₂ ] + [CO])} _e is the ratio of the sulfur molarity to the sum of the molar concentrations of H ₂ and CO in the Fe / FeS equilibrium.

[0011]

(Equation 3)

Here, t: reduction temperature (° C.), [i]: molar concentration of the i component.

(3) In (1) and (2), a reducing gas having a CO molar concentration of not more than H2 molar concentration is used,
It is characterized in that it is reduced at 50 ° C. (4) In (1) and (2), using a reducing gas containing CO less than the CO partial pressure that satisfies the relational expression (2) with the partial pressures of H ₂ , H ₂ O, and CO ₂ at 750 ° C. 3. The method for producing iron carbide according to claim 1, wherein the reduction is performed at a temperature exceeding 1000 ° C. or lower.

[0014]

(Equation 4)

Here, p (i): partial pressure (atm) of the i component, t: reduction temperature (° C.).

(5) In (1) to (4), CH ₄ and C
It is characterized in that carbonization is performed using a carbonizable gas having a sum of O and a molar concentration of 50% or more. (6) In (1) to (5), when the sum of H ₂ and CO is 10% or more in molar concentration and S is less than the molar ratio of sulfur to the sum of the molar concentrations of H ₂ and CO in Fe / FeS equilibrium, It is characterized by carbonizing with a carbonizing gas containing.

Here, the iron oxide-containing substance refers to iron ore such as hematite, magnetite, limonite, dust containing iron oxide, and the like. Incidentally, cementite Fe ₃ C in normal carbonization step, excessive iron carbide _{(χ-Fe 5 C 2,} η-Fe 23 C, ε-Fe 2 C) or the like, the general formula Fe _x C
Iron carbides represented by _y (x / y = 1 to 6) are obtained, and in the present invention, these are collectively referred to as iron carbide.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Iron carbide, iron oxide such as iron ore coal gas (H ₂ -CO-CO ₂
) Or natural gas (H ₂ -CH ₄ ), etc., and is obtained by reduction carbonization. Here, it is known that the reduction reaction can be expressed by equation (3) and the carbonization reaction can be expressed by equations (4) to (6). (a) Reduction reaction:

[0019]

(Equation 5)

(B) Carbonization reaction:

[0021]

(Equation 6)

[0022]

(Equation 7)

[0023]

(Equation 8)

C in the formulas (4) to (6) is carbon dissolved in metallic iron, and the carbon generated in the formula (4) is dissolved and diffused to be subjected to a carbonization reaction. In the reaction involving the CO gas in the reaction of the formula (4), the reaction proceeds at lower temperatures and higher pressures. In the decomposition reaction of methane of the formula (5), the reaction proceeds at higher temperature and lower pressure. In these reactions, metallic iron serves as a catalyst. In the reducing gas mainly composed of H2 and CO, carbonization occurs when the concentrations of the carbonizable gases CO and CH4 are high.

From the reaction of formula (6), iron percarbide (χ
-Fe ₅ C ₂ , η-Fe ₂₃ C, ε-Fe ₂₃ C), and other general formulas Fe _x C _y (x / y = 1
Iron carbides represented by ~ 6) are also obtained. Iron carbide Fe _x C _y including cementite Fe ₃ C, which is the most stable, is a metastable substance, and is decomposed by the next so-called graphitization reaction to deposit graphite, that is, free carbon.

(C) Reverse reaction (graphitization reaction):

[0027]

(Equation 9)

In the conventional method for producing iron carbide, if the carbon concentration in the gas is increased in order to promote the reduction carbonization reaction,
In the formulas (4) and (5), there is a problem that carbon does not form a solid solution but precipitates as soot (free carbon). When sulfur is present in the reducing carbonized gas, it is adsorbed on the surface of reduced iron or iron carbide and stabilizes the iron carbide. Therefore, the reaction of the formula (6) is promoted, and at the same time, the graphitization reaction of the formula (8) is suppressed, and the precipitation of free carbon is reduced, so that the yield of iron carbide is improved.

When iron oxide is simultaneously reduced and carbonized as in the prior art, particularly at a reaction temperature of 750 ° C. or less, carbonization is
O, requires a reducing carbon gas containing 50 mol% or more of CH ₄ ,
Sulfur requirements also increase. However, when the amount of sulfur is increased at a low temperature, there is a possibility that a part of the metallic iron after reduction may be sulfided, so that the required amount of sulfur cannot be added, and precipitation of free carbon cannot be avoided.

The present inventors have proposed that the reduction reaction depends on the reaction temperature.
(a), since the gas composition suitable for each of the carbonization reaction (b) is different, the iron carbide production process is divided into a pre-reduction process and a carbonization process, and iron sulfide is not generated in the pre-reduction process. By reducing the iron oxide-containing substance with a reducing gas containing sulfur having a sulfur concentration lower than the sulfur concentration, and by sufficiently adsorbing sulfur on the metallic iron surface and carbonizing, the concentration of the carbonizable gas is increased at 750 ° C. or lower. In addition, the present inventors have found that the precipitation of free carbon can be sufficiently suppressed, and the productivity of iron carbide can be improved.

Hereinafter, the reasons for limiting the numerical values of the present invention will be described in detail. Using a fixed bed, Experiments 2 to 5 were performed by pre-reducing hematite ore (S: 0.003 mass%), which is an iron oxide-containing substance, at 700 ° C.
Carbonized at 700 ° C. Pre-reduction uses H ₂ gas, carbonization 30% H ₂ -7
Using 0% CO gas, H ₂ S was added to each of these gases so as to have a predetermined sulfur concentration. The ratio of sulfur molar concentration to the sum of H ₂ and CO molar concentration of Fe / FeS equilibrium [S] /
([H ₂ ] + [CO]) is 940 ppm when the reducing gas is 100% H ₂ and 304 ppm when the carbonizing gas is 30% H ₂ -70% CO.

FIG. 1 shows the change in the product after carbonization due to the difference in the pre-reduction. The carbonization rate (%), the free carbon concentration (mass%), and the sulfur concentration (mass %). Table 1 shows the amount of H ₂ S added in the preliminary reduction and carbonization steps in each experiment.

[0033]

[Table 1]

First, hematite ore (S: 0.003 mass%), which is an iron oxide-containing substance, was simultaneously reduced and carbonized without preliminary reduction as in the conventional method (Experiment 1). From Fig. 1, the carbonization rate is 90% with a carbonizing gas containing 70 mol% of CO at 700 ° C for about 1 hour.
Exceeded. However, since no sulfur was added to the reduced carbonized gas, more than 40% of free carbon was precipitated, resulting in poor iron carbide production efficiency.

Experiment 2 is an example in which iron carbide was produced at the same reaction temperature as in Experiments 3 and 4 by dividing into pre-reduction and carbonization steps, but sulfur was not added to the reducing gas and the carbonizing gas. In addition, the carbonization rate does not exceed 60%, and free carbon is deposited near 50% by mass. This condition is considered to be close to the method of adjusting the amount of free carbon in the product using the carbonizing gas in the cooling process.However, a detailed examination revealed that a large amount of free carbon was deposited upstream of the gas and the inside of the layer and the gas It was found that carbonization was significantly inhibited on the downstream side of.

It was also found that when carbonized large-diameter pellets or dense iron ore, under the conditions as in Experiments 1 and 2, soot was clogged in the pores and carbonization stopped at about 50%.
From the above, it can be seen that when sulfur is not added, a large amount of soot is generated, so that a gas containing a large amount of CO cannot be used.

Experiment 5 is an example of a method of carbonizing after preliminary reduction. However, unlike the present invention, the sulfur concentration at the time of reduction was set to 1034 ppm at which iron sulfide was stable. Therefore, although the precipitation of free carbon is suppressed, the sulfur concentration is high. It is not desulfurized even during carbonization and exceeds the desulfurization limit of steelmaking, and is 0.1 mass% or more. Therefore, the sulfur concentration in the reducing gas must be lower than the region where iron sulfide is stable.

Experiment 6 is an example in which sulfur was added to the reducing carbonization gas and the iron oxide-containing substance was reduced and carbonized at 700 ° C. when reduction and carbonization were performed simultaneously.
It could only be suppressed to about ss%.

Experiments 3 and 4 are examples of the method of the present invention in which carbonization is performed after pre-reduction. As a result of adding 94 mol ppm of sulfur to the reducing gas during the preliminary reduction, the precipitation of free carbon could be suppressed to less than 5 mass%, which is the allowable range of impurities. As a result of suppressing the precipitation of free carbon, carbonization gas was sufficiently supplied inside the iron oxide-containing substance and downstream of the gas, and the carbonization rate reached 90% or more. The same was true for large pellets and dense ore. When sulfur was added during carbonization as in Experiment 4, free carbon could be further reduced to about 1 mass%. In both Experiments 3 and 4, the sulfur concentration in iron carbide was 0.05 mass% or less, which is the desulfurization limit in steelmaking.

The concentration of sulfur in the gas at the iron sulfide / metallic iron (FeS / Fe) equilibrium is determined by the ratio of the molar concentration of sulfur to the sum of the molar concentrations of H ₂ and CO in the reducing gas [S] / ([ H ₂ ] + [CO]). As shown in FIG. 2, the concentration of sulfur in the gas at the FeS / Fe equilibrium depends on the type, concentration, and temperature of the reducing gas, and is higher as the temperature increases. When completely equilibrated, sulfur
On average at 400-900 ° C

[0041]

(Equation 10)

H ₂ S and COS are distributed so as to satisfy the following. Figure
Using the [COS] / [CO] relationship at the time of FeS / Fe equilibrium shown in Fig. 2, the reducing gas CO, H ₂
The sulfur concentration (mole ppm) with respect to is approximately expressed by equation (1).

[0043]

[Equation 11]

Here, t: reduction temperature (° C.), [i]: molar concentration of the i component.

The sulfur adsorbed on the metallic iron suppresses the solid solution carbon from precipitating as free carbon, so-called soot, so that the carbonization reaction by the carbonizable gas proceeds uniformly. About half of the adsorbed sulfur is desorbed with the progress of carbonization. It was found that the sulfur remaining about half of the iron carbide suppressed the graphitization of the iron carbide, so that iron carbide could be produced stably. Furthermore, it was found that if sulfur was added to the carbonizing gas, the desorption of sulfur could be suppressed, and the precipitation of soot could be avoided.

Here, when the sulfur concentration in the reducing gas is about 0.05 times or more of the concentration specified by the equation (1), the sulfur ions are saturatedly adsorbed (or segregated) on the surface of metallic iron as sulfide ions, and the amount thereof is Although it is small, the inside of the pores of the ore is uniformly adsorbed similarly to the outer surface, so that the generation of free carbon can be suppressed in the carbonization step. If the sulfur concentration in the reducing gas exceeds the specified value of the formula (1), part of the metallic iron is sulfided, and the sulfur concentration in the iron carbide is increased by one digit, which is not preferable.

If the product immediately after reduction contains iron oxide or iron carbide, the amount of adsorbed sulfur and the affinity for iron are reduced. However, it was found that there was no problem if iron carbide was less than 20 mass% and the metallization ratio was 60% or more. In actual operation, reducing gas is C
O is contained, but at that time, metallic iron is carburized and γ
At temperatures above 730 ° C where iron is formed, γ-iron may decompose during cooling, producing up to 20 mass% of iron carbide. However, there is no problem as long as carbon is dissolved in the solution at the time of reduction. However, if the carbonization rate is as high as the reduction reaction, the reduction rate and the carbonization rate cannot be controlled.

When the metallization rate required for adsorbing sulfur in the reduction step was examined, it was found that when the metallization rate was 60% or more, the sulfur required to suppress the deposition of free carbon on the reduced iron surface could be adsorbed. If the conversion is less than 60%, the adsorption of sulfur is not sufficient, which is not preferable. When the iron oxide-containing material is pre-reduced with a reducing gas containing S under the above conditions, the reduction temperature is
At 400 to 750 ° C., the CO molar concentration in the reducing gas must be H ₂ molar concentration or less. CO molar concentration in the reducing gas is H ₂
If it exceeds the molar concentration, free carbon is generated during the reduction, which is not preferable. When the reduction treatment is performed at a reduction temperature of more than 750 ° C. and 1,000 ° C. or less, the equilibrium constant of the next gas shift reaction is about 1 at a temperature of 750 to 1000 ° C.

[0049]

(Equation 12)

The equilibrium constant of the equation (4) is represented by the following equation.

[0051]

(Equation 13)

When the following equilibrium constant K of the water gas shift reaction is used between the two equilibrium constants K _B and K _{H in} the equation (10), the relationship of K _B = K · K _H is established.

[0053]

[Equation 14]

In the case of a mixed gas, when the water gas shift reaction proceeds completely, the oxygen concentration in the gas is distributed between CO ₂ and H ₂ O so as to satisfy the equation (11). In particular, since the equilibrium constant K approaches 1 at a temperature of 750 to 1000 ° C., the carbon potential of the gas is determined by the ratio of the partial pressures, p (CO) (p (CO) + p (H ₂ )) / (p (CO ₂ ) + p (H ₂ O))
(atm). Therefore, the equilibrium constants K _B and K _H in the carburizing reaction (4) can be approximated by the same formula (2).

Carbonization of the pre-reduced product reduced under the above conditions and sufficiently adsorbing sulfur is carbonized using a carbonizing gas in which the sum of CH ₄ and CO is 50% or more in molar concentration. If the sum of CH ₄ and CO is less than 50% in molar concentration, it is not preferable because the carbon source becomes insufficient and the production rate of iron carbide decreases. C at low temperature of 400 ~ 750 ℃
Carbonization proceeds in a region containing 50 mol% or more of O and CH ₄ .

Further, in addition to the above conditions, a carbonizing gas
With H ₂ and the sum of CO molar concentration of 10% or more, generation of free carbon during carbonization reaction by adding S less than the sulfur molar ratio to the sum of the molar concentrations of H ₂ and CO in the Fe / FeS equilibrium Is particularly preferable since the above can be further suppressed.

The reducing gas and the carbonizing gas are produced using natural gas, coal, solid carbon such as coke and char, or liquid hydrocarbon such as petroleum as a raw material. These substances thiol (-SH), sulfide (-S-), disulfide (-S ₂
Organic compounds having functional groups such as-), thiophene (-CSH) and thiocyan (-CSN), and sulfur compounds in the form of metal sulfides.

Further, a substance containing sulfur and iron, such as iron ore, iron sulfide, dust having a high sulfur concentration, and a product obtained by calcining a substance containing these sulfides, can be used by mixing with an iron oxide-containing substance. . These are S ₂ , COS, H ₂ S, CS ₂ , H
₂ S _2, are known (NH _{4) 2} S, while decomposed into SO _x other sulfur compounds gases generally be adsorbed (or segregation) on the surface of metallic iron as sulfide ions. When the sulfur molar concentration of the reaction gas is low, it can be adjusted by adding at least one of the above sulfur compounds to increase the sulfur molar concentration.

Further, a material containing sulfur and iron or a carbon material such as coal may be mixed with the raw material so as to have such a gas composition,
You may decorate in pellets. Conversely, CaO, CaCO ₃ , Ca (OH)
_2, dolomite, fluorite, or the addition of a desulfurizing agent such as metal calcium, be adjusted to reduce the sulfur molar concentration of sulfur in the reaction gas by the addition of gas containing no sulfur (carbonization or reducing gas is desirable) Can be.

In summary, in the conventional iron carbide production method in which reduction and carbonization are performed simultaneously, reduction and carbonization occur simultaneously in the ore particles. Therefore, the carbonization reaction on the surface of the metallic iron in which sulfur is not sufficiently adsorbed after the reduction proceeds, so that the precipitation of free carbon cannot be suppressed. However, if the reduction time is separated from the carbonization and the reduction time is sufficient, sulfur is sufficiently adsorbed on the reduced metal surface, so that the precipitation of free carbon in the carbonization step is suppressed. Further, the present invention is more advantageous in that the applicable range of the gas composition, operating temperature, ore particle size, bed height, and the like during reduction and carbonization can be expanded as compared with the case where reduction and carbonization are performed simultaneously.

[0061]

EXAMPLE The ore having a particle size of 0.05 to 15 mm was preliminarily reduced by a high-speed circulating fluidized bed and then carbonized in a bubble fluidized bed. Table 2 shows the operating conditions, the carbonization rate (%) of the product, and the free carbon concentration (mass%).
Example 1 is an example in which gases having the same composition are used in the reduction step and the carbonization step. When the reduction is performed at a high temperature of 900 ° C., the reduction time can be reduced. However, as described above, since the molar ratio of sulfur generated by iron sulfide is high at high temperatures but lower at low temperatures, the supply amount of sulfur is increased in the high-temperature reduction step, and is decreased in the low-temperature carbonization step (or Desulfurization). In the carbonization process, the temperature was lowered to 600 ° C,
This is because the carbonization gas is mainly composed of CO, and at high temperatures, the carbonization reaction rate decreases.

Embodiment 2 is an example in which the exhaust gas from the reduction step is used in the carbonization step. When CO is used as the carbonizing agent, the gas with reduced reducing power can be used as the carbonization gas at a low temperature. Can be improved.

Embodiments 3 and 4 are examples in which a gas containing a large amount of H ₂ is used in the reduction step and a gas containing a large amount of CO is used in the carbonization step. Can be gasified into carbonized gas.

Embodiments 5 and 6 are examples in which the reforming of natural gas or coal dry distillation gas is performed in a carbonization furnace. This is effective because even a large amount of sulfur having a poisoning effect on the gas reforming catalyst can be reformed.

[0065]

[Table 2]

In this embodiment, a fluidized bed is used for the reduction step and the carbonization step. However, even when pellets or lump ore is used, a product whose carbonization rate reaches 90% without soot clogging in the pores is obtained. Therefore, it can be used without limitation in a process using a shaft furnace, a rotary kiln, or the like, and is not limited to a fluidized bed.

[0067]

According to the present invention, it is possible to stably produce high-grade iron carbide having a low sulfur content and a small amount of free carbon even at a low reaction temperature at which conventional operation has been difficult and a large amount of carbonizing gas. Furthermore, by dividing the process into a reduction process and a carbonization process, the reduced gas can be reused for carbonization,
Since the gas can be reformed in the carbonization step by utilizing the catalytic reaction of metallic iron, the gas utilization rate can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between pre-reduction conditions and carbonization rates, free carbon and sulfur concentrations.

FIG. 2 is a graph showing the relationship between the sulfur concentration in the reducing gas and the temperature in the FeS / Fe equilibrium.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Shoji Hayashi 8-2 Okuda Keiyocho, Inazawa, Aichi Prefecture (72) Inventor Kazuya Kunitomo 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Satoshi Sawai 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division

Claims (6)

[Claims] When the iron oxide-containing substance is reduced and then carbonized to produce iron carbide, the molar ratio of sulfur to the sum of the molar concentrations of H ₂ and CO ([S] / ([H ₂ ] + [ CO])) was reduced to a content of 0.05 to less than 1 times the molar ratio of sulfur at the time of Fe / FeS equilibrium to reduce the iron oxide-containing substance with a reducing gas containing S.
Produces a pre-reduced product with a metallization rate of less than 60% by mass,
A method for producing iron carbide, comprising producing iron carbide by carbonizing the pre-reduced product with a carbonizing gas. 2. The method according to claim 1, wherein {[S] / ([H ₂ ] + [CO])} _e obtained by the equation (1) is represented by Fe /
_{2. The} method for producing iron carbide according to claim 1, wherein the ratio of the molar concentration of sulfur to the total molar concentration of H2 and CO in FeS equilibrium is set. (Equation 1) Here, t: reduction temperature (° C.), [i]: molar concentration of the i component. 3. The method for producing iron carbide according to claim 1, wherein the reduction is performed at 400 to 750 ° C. using a reducing gas having a CO molar concentration of H ₂ molar concentration or less. 4. Relational expression (2) with each partial pressure of H ₂ , H ₂ O and CO ₂
3. The method for producing iron carbide according to claim 1, wherein the reduction is performed at a temperature higher than 750 ° C. and equal to or lower than 1000 ° C. using a reducing gas containing CO having a CO partial pressure less than a partial pressure satisfying the following. (Equation 2) Here, p (i): partial pressure of the i component (atm), t: reduction temperature (° C.). 5. The carbonization using a carbonizing gas in which the sum of CH ₄ and CO is 50% or more in molar concentration.
The method for producing iron carbide according to any one of the above. 6. The method according to claim 1, wherein the molar concentration of H ₂ and CO is 10% or more, and Fe /
Method for producing iron carbide according to claim 1, characterized in that the carbonized in carbonizing gas containing S less than the sulfur molar ratio to the sum of the molar concentrations of H ₂ and CO in the FeS equilibrium.