WO2000012431A1

WO2000012431A1 - Process for producing iron carbide

Info

Publication number: WO2000012431A1
Application number: PCT/JP1998/003868
Authority: WO
Inventors: Torakatsu Miyashita; Takeshi Nagahama; Teruyuki Nakazawa; Akio Nio
Original assignee: Kawasaki Jukogyo Kabushiki Kaisha; Mitsubishi Corporation
Priority date: 1997-02-28
Filing date: 1998-08-27
Publication date: 2000-03-09
Also published as: ZA987851B; AU8887498A

Abstract

A process for producing iron carbide by efficiently converting iron-containing starting material into iron carbide, which comprises reducing and carbonizing a mixture of an iron-containing starting material having a high reduction rate and an iron-containing starting material having a low reduction rate.

Description

Description Manufacturing method of iron carbide [Technical field]

The present invention steel to iron Carbide de the (F e ₃ C) as main components, a raw material for steelmaking, for example, a method of manufacturing a suitable iron force one by de steelmaking raw material used in the electric furnace or the like. (Background technology)

In general, steel production consists of converting iron ore to pig iron using a blast furnace, and then converting pig iron to steel using a furnace or a converter. Such traditional manufacturing methods require large amounts of energy, equipment, and cost.Therefore, for small-scale steelmaking, iron ore is conventionally converted to raw material for steelmaking furnaces by direct steelmaking. A method has been adopted which consists of converting steelmaking furnace raw materials into steel using an electric furnace or the like. In such direct steelmaking, there is a direct reduction method that converts iron ore to reduced iron.However, the reduced iron produced by this method has strong reaction activity and generates heat by reacting with oxygen in the atmosphere. In this case, it is necessary to provide a treatment such as sealing with an inert gas. For this reason, iron carbide containing a relatively high percentage of iron (Fe), which has a low reaction activity, can be easily transported and stored, and has a relatively high percentage of iron (Fe) has recently been used as a steelmaking raw material for electric furnaces and the like. is there.

In addition, steel raw materials mainly composed of iron carbide are not only easy to transport and store, but also carbon combined with iron atoms can be used as a fuel source for iron or steelmaking furnaces. In this case, there is also an advantage that it is a source of fine bubbles that promote the reaction. Due to these forces, raw materials for steelmaking and steelmaking mainly composed of iron carbide Attention has been paid.

Conventionally, such a method of producing iron carbide is a method in which iron ore is powdered and charged into a fluidized bed reactor or the like, and a mixed gas of a reducing gas (hydrogen gas) and a carbonizing gas (for example, methane gas) is used. At a predetermined temperature, as shown in the following reaction equations ((1), (2), (3), (4)), the iron oxide (hematite (Fe) ₂ 0 _3), with a magnetic Thailand preparative (F e ₃ 〇 ₄₎ refers to Usutai bets (F e O)) is carried out by introducing a reducing and carbonizing gases simultaneously in a single operation (in one reactor operation) It is to be reduced and carbonized.

3 F e ₂ 0 ₃ + H ₂ → 2 F e ₃ 0 ₄ + H ₂ 0 (1)

_{_{_{F e 3 0 4 + H 2}}} → 3 F e O + H 2 〇 - - - (2)

F e O + H ₂ → F e + H ₂ 0

3 F e + C H4 → F e _{: i} C + 2 H ₂ ··· (4) As this kind of prior art, see, for example, Japanese Patent Application Laid-Open No. 6-5019803. Some are listed.

However, when using an iron-containing raw material having a uniform reduction rate at which the start of iron carbide conversion is performed uniformly, the reaction time until the completion of iron carbide conversion may be long. This is because, as shown in the above equations (1) to (3), when iron oxide is reduced, H ₂₀ is generated in the reaction system 、, and particularly, a large amount of H is generated in the initial stage of the reduction. ₂₀ occurs. On the other hand, the partial pressure of H ₂ O in the reaction system must be reduced in order to start Fe ₃ C conversion. H ₂ 0 partial pressure because higher Ri sweet when F e ₃ C reduction is inhibited. That is, when an iron-containing raw material having a uniform reduction rate is used as a raw material, the formation of Fe ₃ C is easily inhibited by H ₂₀ generated as a result of the reduction reaction. In particular, when the reduction rate is relatively low iron-containing raw material as a raw material, a large amount of H ₂ 0 since occurs, the more F e ₃ C reduction is inhibited. For this reason, when iron-containing raw materials with a uniform reduction rate are used as raw materials, iron carbide In some cases, the reaction time until the completion of the reaction becomes longer.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a method of manufacturing an iron carbide capable of efficiently promoting the conversion of iron-containing raw materials to iron carbide. It is to provide [Disclosure of the Invention]

To accomplish the above object, by a different ferrous raw materials of reduced rate as a raw material, the density in the system of H ₂ O to inhibit iron Carbide de reduction is not uniform, the density of H ₂ 0 Since the thin and dark portions are mixed, the formation of iron carbide is promoted as compared with the case where the iron-containing raw material having a uniform reduction rate is used as the raw material.

That is, the present invention relates to a method for producing a raw material for iron and steel making mainly composed of iron carbide by reducing and carbonizing an iron-containing raw material mainly containing iron oxides and iron hydroxides. Further, the iron-containing raw material is characterized by being a mixture of an iron-containing raw material having a high reduction rate and a iron-containing raw material having a low reduction rate.

For the reasons described below, it is preferable to proceed with the second reaction operation for performing the remaining reduction reaction and the carbonization reaction after the first reaction operation for performing a part of the reduction reaction of the iron-containing raw material for iron making.

According to the good urchin constructed present invention, by different containing iron raw materials having reducing ratio as the raw material, the density in the system of H ₂ O to inhibit iron Carbide de reduction is not uniform, H ₂ Starting from the iron-containing raw material portion with a low density of 0 and a high reduction ratio, iron carbide is promoted. In addition, if the reaction is divided into a first reaction operation that performs part of the reduction reaction and a second reaction operation that performs the remaining reduction reaction and carbonization reaction, the gas used in the first reaction operation can be reduced to only the reduction reaction. And the gas used in the second reaction operation is reduced to the rest. Since the composition can be optimized for the reaction and the carbonization reaction, the reaction rate is higher than that of the iron carbide production method in which reduction and carbonization are performed in a single operation using a mixed gas of a reducing gas and a carbonized gas. The time (time required to convert iron-containing raw materials to iron carbide) can be reduced.

The present invention is configured as described above, and has the following effects.

Since the conversion to iron carbide proceeds efficiently, the reaction time can be reduced, and if the same production volume is sufficient, the size of the reactor can be reduced. By changing the mixing ratio of the reduction ratio of the iron-containing raw material, the reaction operation conditions can be made flexible. By mixing iron-containing raw materials with an appropriate reduction rate, it is possible to suppress excessive consumption of the reaction gas (hydrogen, methane). According to the invention described in claim 2, the reaction time can be further reduced.

[Brief description of drawings]

Fig. 1 is a diagram showing a comparison of the progress of iron carbide conversion due to differences in the reduction rates of iron-containing raw materials.

FIG. 2 is a diagram showing an embodiment of a method of mixing iron-containing raw materials having different reduction ratios to form iron carbide in the case of one fluidized bed reactor.

FIG. 3 is a diagram showing another embodiment of a method of mixing iron-containing raw materials having different reduction rates to form iron carbide when one fluidized bed reactor is used.

FIG. 4 is a view showing still another embodiment of a method of mixing iron-containing raw materials having different reduction ratios to form iron carbide in the case where one fluidized bed reactor is used.

Fig. 5 shows a case where a hobber is provided separately from one fluidized bed reactor. FIG. 3 is a view showing one embodiment of a method of mixing iron-containing raw materials having different reduction rates to form iron carbide.

FIG. 6 is a view showing an embodiment of a method of mixing iron-containing raw materials having different reduction rates to form iron carbide when two fluidized bed reactors are used.

FIG. 7 is a diagram showing another embodiment of a method of mixing iron-containing raw materials having different reduction rates to form iron carbide when two fluidized bed reactors are used.

FIG. 8 is a diagram showing still another embodiment of a method of mixing iron-containing raw materials having different reduction rates to form iron carbide when two fluidized bed reactors are used.

FIG. 9 is a view showing still another embodiment of a method of mixing iron-containing raw materials having different reduction rates to form iron carbide when two fluidized bed reactors are used.

FIG. 10 is a view showing one embodiment of a method of mixing iron-containing raw materials having different reduction rates to form iron carbide when a hopper is provided separately from two fluidized bed reactors.

[Best mode for carrying out the invention]

^Following: lower, it will be described with reference to the embodiment of the present invention with reference to the accompanying drawings. In Fig. 1, the reaction time (hr) is plotted on the horizontal axis, and the vertical axis is Fe ₃ C (weight ⁰ / o) in the product. The meaning of each symbol in Fig. 1 is as follows.

Iron-containing raw material with 50% reduction of hematite powder

△ = Iron-containing raw material obtained by reducing hematite powder by 53%

X = Iron-containing raw material reduced by 76% of hematite powder

〇 = As shown in Table 1 below, iron-containing raw materials mixed with various reduction rates of hematite powder, the overall reduction rate is 55% What is

Mouth = As shown in Table 1 below, an iron-containing raw material mixed with various reduction rates of hematite powder, with an overall reduction rate of 56%

【table 1 】

As is evident from Fig. 1, iron carbide raw materials with a relatively low reduction rate and a uniform reduction rate (▽, △) have an iron carbide conversion rate of 90% or more. It takes about 5 hours to get the product. However, a mixture of iron-containing raw materials with different reduction rates (〇, □) can obtain an iron carbide product with the same conversion rate in about 4 hours. It is possible to carbonize in the same short time as when carbonizing.

Hereinafter, a specific method for obtaining a raw material for iron making containing iron carbide as a main component by using a mixture of iron-containing raw materials having different reduction rates as a raw material will be described with reference to the drawings.

(a) When there is one reactor

① As shown in Fig. 2, the lower part of the fluidized bed reactor 1 is divided into three sections 1a, lb, 1c, and a pipe through which the reaction gas (reducing gas and carbon gas) flows into the bottom of the reactor 1. Line 2 is connected, and a line 3 for discharging the same reaction gas is connected to the top of the reactor 1. An iron-containing raw material is charged into the reaction furnace 1 and a predetermined reduction and carbonization reaction is performed in the reaction furnace 1, and then a raw material for iron making mainly composed of iron carbide is discharged from a pipe 5. In this method, the iron-containing raw material having a low reduction rate in the section 1a near the inlet of the reactor 1 is added to and mixed with the iron-containing raw material having a high reduction rate in the section 1c near the outlet.

② In this method, as shown in Fig. 3, contrary to Fig. 2, the iron-containing raw material with a high reduction rate in section 1c near the outlet of reactor 1 is reduced in section 1a near the inlet. This is a method of adding and mixing iron-containing raw materials with a low rate.

③ In this method, as shown in Fig. 4, the iron-containing raw material with a high reduction rate in Section 1c near the outlet of Reactor 1 is replaced with a reduction rate in Section 1b located in the center of Reactor 1. Is a method of adding and mixing with a medium iron-containing raw material.

(b) When there is a separate hopper from the reactor

In this method, as shown in FIG. 5, a hopper 6 is provided above the fluidized bed reactor 1, and the hopper 6 is connected to the vicinity of the center of the top of the reactor 1 via a pipe 7. This is a method in which a low (or unreduced) iron-containing raw material is added to and mixed with the iron-containing raw material in the section 1b having a moderate reduction rate. In this case, the pipe 7 can be connected to a position corresponding to the upper part of the section 1c.

(c) Two reactors

① As shown in Fig. 6, another fluidized bed reactor 8 is arranged behind the lower part of the fluidized bed reactor 1, and the lower part of the reactor 8 is partitioned into three sections 8a, 8b, 8c. At the bottom of the reaction furnace 8, a pipe 9 through which a reaction gas (reducing gas and carbonizing gas) flows is connected in the same manner as the reaction furnace 1, and at the top of the reaction furnace 8, a pipe 10 through which the reaction gas is discharged is connected. Connect. In this case, the reaction gas flowing from the pipe 2 to the bottom of the reactor 1 is mainly a reducing gas, and a part of the reduction reaction is performed in the reactor 1. In the reactor 8, the remaining reduction reaction and carbonization reaction are performed. Then, the pipeline 5 for discharging the iron-containing raw material having a high reduction rate in the section 1c near the outlet of the reactor 1 and the pipeline 11 for discharging the iron-containing raw material having a medium reduction rate in the section 1b are connected. A mixture of these iron-containing raw materials having different reduction rates is supplied to a reaction furnace 8 via a pipe 12, and a predetermined reduction reaction and a carbonization reaction are performed in the reaction furnace 8. The raw materials for iron making, mainly composed of iron carbide, are discharged. In this method, the mixing ratio of the iron-containing raw materials having different reduction rates can be changed by adjusting the opening degrees of the valves 14 and 15.

② In this method, as shown in Fig. 7, the iron-containing raw material with a low reduction rate (or unreduced) sent through pipe line 16 (reduction and carbonization) in section 8b of reactor 8 is used. This is a method of adding and mixing with iron-containing raw materials. In this case, the pipeline 16 can be connected to the section 8c. To change the mixing ratio of the iron-containing raw material in this method, the opening of the valve 17 may be adjusted.

③ In this method, as shown in Fig. 8, the iron-containing raw material in section 1b of fluidized-bed reactor 1 is added to and mixed with the iron-containing raw material in section 8b of reactor 8 through line 11. It is. In this case, the pipeline 11 can be connected to the section 8c.

は This embodiment is a modification of FIG. 6, and as shown in FIG. 9, the pipeline 5 for feeding the iron-containing raw material having a relatively high reduction rate in the section 1 c of the reactor 1 and the section 1 b in the section 1 b. In this method, the pipeline 11 for discharging the iron-containing raw material having a slightly lower reduction rate is directly connected to the section 8 a of the reactor 8.

方法 In this method, as shown in FIG. 10, a hopper 18 is provided above the fluidized bed reactor 8, and the hopper 18 and the vicinity of the center of the top of the reactor 8 are connected by a pipe 19. In this method, the iron-containing raw material having a low reduction rate (or unreduced) in the hopper 18 is added to and mixed with the iron-containing raw material in the section 8b. In this case, pipeline 19 corresponds to above section 8c It can be connected to a different position.

As described above, there are many methods of mixing iron-containing raw materials having different reduction rates, reducing and carbonizing the iron-containing raw materials to obtain iron-based steelmaking raw materials mainly composed of iron carbide. By the way, the reaction when carbonized iron-containing raw material (iron oxide) that has been reduced to a certain extent by methane can be expressed by the following equation (5).

3 F e O x + CH ₄ → F e ₃ C + 2 H ₂ O · · · (5) And the value of X in the above equation is 2 3. That is, (2 Z 3) O atoms are bonded to the Fe atom of the iron oxide. Since the iron oxide before reduction is hematite (F e ₂ 〇 ₃ ), there are 3/2 O atoms bonded to the F e 1 atom. If this is expressed in terms of the reduction rate, then one-one (2Z3) / (3Z2) = about 0.56. That is, when an iron oxide having a reduction ratio of about 56% is used as a raw material, the carbonization reaction proceeds according to the stoichiometry according to the above equation (5), and an iron carbide product of a predetermined grade can be obtained. However, when using iron oxides with a reduction ratio of less than 56% as raw materials, it is necessary to increase the supply of reducing gas (hydrogen) in order to promote reduction. On the other hand, when iron oxide having a reduction ratio of more than 56% is used as a raw material, excess hydrogen is released in the circulation gas because X in equation (5) is smaller than 2Z3 by an amount smaller than 2Z3. There is a need to. However, the circulating gas contains not only hydrogen but also methane, so it is necessary to release methane at the same time as hydrogen. As described above, when iron oxide having a reduction ratio of more than 56% is carbonized as a raw material, not only methane required for carbonization but also circulating gas to maintain a reaction gas composition is released. A considerable amount of methane is produced, and the consumption of methane increases because the surplus portion of the hydrogen consumed in the reduction and the hydrogen produced in the carbonization reaction is removed outside the circulation gas system. However, according to the present invention, the reduction rate of the iron oxide was 60 By adjusting the content to the range of not more than%, the consumption of the reaction gas such as methane can be suppressed.

If the number of sections in the fluidized bed reactor is too small, the reduction rate of the product discharged from the first fluidized bed reactor (1 in Fig. 6) becomes too low, and the second fluidized bed reactor ( The burden of reference numeral 8) in Fig. 6 becomes too large. That is, the processing efficiency as a whole decreases. On the other hand, if the number of sections in the reactor becomes too large, the reduction rate will be made uniform, so that even if the method of the present invention is applied, the effect cannot be expected. Therefore, the number of sections of the fluidized bed reactor is preferably 3 to 4.

[Possibility of industrial use]

Since the present invention is configured as described above, the present invention is suitable as an iron carbide manufacturing apparatus capable of efficiently promoting the conversion of iron-containing raw materials to iron carbide.

Claims

Scope of the request This is a method of reducing and carbonizing an iron-containing raw material containing iron oxides and iron hydroxides as a main component to produce a raw material for iron and steel making mainly containing iron carbide. A method for producing an iron carbide, wherein the iron-containing raw material is a mixture of a high reduction iron-containing raw material and a low reduction iron-containing raw material.

2. The iron according to claim 1, wherein after the first reaction operation for partially performing the reduction reaction of the iron-containing raw material for iron making, a second reaction operation for performing the remaining reduction reaction and the carbonization reaction is performed. Carbide manufacturing method.