JP6964692B2 - Method of manufacturing metallic iron - Google Patents

Description

The present invention belongs to the field of metallurgical technology, and specifically relates to a method for producing metallic iron.

The conventional method for producing directly reduced iron is, for example, the Midrex method, in which iron ore or pellets containing iron oxide are directly reduced with a reducing gas to obtain reduced iron. In such a method for producing directly reduced iron, a reduced gas made of natural gas or the like is forcibly flowed into the vertical furnace from the bottom of the vertical furnace to reduce iron oxide to obtain sponge iron.

In countries and regions where natural gas is scarce, the method of producing reduced iron is to use a carbonaceous material such as coal to replace natural gas, to use coal as a reducing agent, and to use already known rotary furnaces, rotary kilns, etc. As described above, pellets made of calcined iron ore are heated and reduced to obtain sponge iron. After that, Japan developed a method called ITMK3, which obtains metallic iron in one step by direct reduction based on coal, based on the method of direct reduction in a rotary furnace. The directly reduced iron produced by such a method does not contain the gangue component in the slag, has a high purity of metallic iron, does not require a melt, and can be used directly in electric furnace or converter steelmaking. Steelmaking costs can be significantly reduced.

However, when metallic iron is produced by using this method, there are the following problems. The amount of reducing gas generated in the final stage of the reduction reaction in the reduction furnace is reduced, and the concentrations of water as exhaust gas and oxidizing gas such as carbon dioxide generated by combustion of the heating raw material in the burner are relative. The reduced metallic iron is reoxidized, and especially in the final stage of reduction, the more the reduction of the reduced iron progresses sufficiently, the easier it becomes to be reoxidized. Therefore, in some cases, the reduced iron does not sufficiently carburize and melt, which affects the quality of the product and the metal yield.

The embodiments of the present invention can at least partially solve the shortcomings of the prior art with respect to the method for producing metallic iron.

An embodiment of the present invention relates to a method for producing metallic iron, which is obtained by placing a mass containing iron oxide and a carbonaceous reducing material in a reduction furnace, heating the mass to reduce and melt the iron oxide, and heating the mass. The metallic iron is cooled, the already cooled metallic iron is discharged from the reduction furnace, the already cooled metallic iron is recovered, and the iron oxide is heated in a state where the air is shut off.

As one of the examples, the amount of the carbonaceous reducing material added is 1.05 to 2 times the amount of the carbonaceous reducing material added to reduce the iron oxide.

As one of the examples, the carbonaceous reducing material contains at least one of anthracite, lignite and coke flour.

As one of the examples, the reduction and melting temperature of iron oxide in the reduction furnace is 1350 to 1500 ° C.

As one of the examples, the particle size of the carbonaceous reducing material is in the range of 0.3 to 3 mm.

As one of the examples, the lump is obtained by lumping at least one of iron ore powder, metallurgical dust-removed iron powder, and red mud.

As one of the examples, at least one of calcium carbonate, slaked lime, molasses, and wheat flour is used as the binder used for mass formation.

The embodiments of the present invention have at least the following effective advantages. Since the reduction reaction and the melting reaction are carried out with the air shut off, there is no air and fuel to assist the combustion entering the reduction furnace, the atmosphere inside the reduction furnace is a reducing atmosphere, and the iron oxide is heated. Effectively suppresses the reoxidation of iron in the process of reduction and melting, thereby suppressing the increase in FeO content in vein stones, reducing the sulfur content in metallic iron, and reducing the content of metallic iron as a product. At the same time as improving the quality, the fireproof material of the reduction furnace was protected.

In order to clearly explain the embodiment of the present invention or the technical solution method in the prior art, the drawings that need to be used in the embodiment or the prior art description will be briefly described below. Obviously, the drawings in the description below are examples of the present invention, and engineers in the art can obtain other drawings based on these drawings without any creative effort. ..

FIG. 1 is a schematic fabric diagram of pellets and a carbonaceous reducing agent according to Example 2 of the present invention. FIG. 2 is a schematic fabric diagram of pellets and a carbonaceous reducing agent according to Example 3 of the present invention.

The following will clearly and completely explain the technical solution method of the examples of the present invention with reference to the drawings of the examples of the present invention, and of course, the described examples are some examples of the present invention. , Not all examples. All other examples obtained by engineers in the art based on the examples in the present invention without any creative effort are included in the scope of protection of the present invention.

Example 1
An embodiment of the present invention provides a method for producing metallic iron, in which a mass containing iron oxide and a carbonaceous reducing material are placed in a reduction furnace, and the mass is heated to reduce and melt the iron oxide, and then heated. This includes cooling the obtained metallic iron, discharging the already cooled metallic iron from the reduction furnace, and recovering the already cooled metallic iron. Among them, iron oxide is heated with the air shut off.

The principle of the present invention is roughly as follows. In the process of heating the iron oxide and carbonaceous reduction material, the iron oxide undergoes a reduction reaction to _{generate CO 2} (FeO + CO = Fe + CO ₂ ), and the produced CO ₂ is the carbonaceous reduction material and boule at high temperature. The reaction is carried out _{to generate CO (C + CO 2} = 2CO), a reduction reaction is carried out with the iron oxide, and the process is continued until the iron oxide is reduced to iron. Heating continues, the pellets melt and the iron separates from the gangue. Since the reduction reaction and the melting reaction are carried out with the air shut off, there is no air and fuel to assist the combustion entering the reduction furnace, the atmosphere inside the reduction furnace is a reducing atmosphere, and the iron oxide is heated. Effectively suppresses the reoxidation of iron in the process of reduction and melting, thereby suppressing the increase in FeO content in vein stones, reducing the sulfur content in metallic iron, and reducing the content of metallic iron as a product. At the same time as improving the quality, the fireproof material of the reduction furnace was protected.

More preferably, in the above method, the dose of the carbon-containing reducing substance adopts an excess amount of the carbonaceous reducing material, and specifically, the amount of the carbonaceous reducing material added is for reducing the iron oxide. It is 1.05 to 2 times the amount of the required carbonaceous reduction material added. When an excess amount of carbonaceous reduction material is adopted and CO ₂ is generated in the process of iron oxide reduction reaction, the carbonaceous reduction material is excessive, so the excess carbonaceous reduction material and the boule reaction (Boolean reaction). ) To generate CO, which guarantees the absence of oxide gas in the furnace and effectively suppresses iron reoxidation in the process of heating, reducing and melting iron oxide.

In the above method, preferably, the temperature inside the reduction furnace is raised to 1300 ° C. to 1500 ° C. by heating the outside of the reduction furnace. Roughly present in the process of heating, reducing and melting iron oxide as the temperature in the reduction furnace rises. Specifically, when an external heat source heats the reduction furnace, the iron oxide-containing mass and the carbonaceous reduction material are heated by conduction heat transfer between the furnace wall, the mass and the carbonaceous reduction material of the reduction furnace. When the temperature in the reduction furnace reaches about 900 ° C., the carbonaceous reducing material _{begins to gasify (C + CO 2} = 2CO) and the iron oxide begins to be reduced (FeO + CO = Fe + CO ₂ ). Since the inside of the reduction furnace is in a reducing atmosphere, the metallic iron obtained by reduction is not oxidized again. The temperature of the reduced metallic iron rises further, and during the heating process, it continuously carburizes with the carbonaceous reducing material in close contact with the surroundings. After the temperature in the reduction furnace reaches the reflow temperature of gangue and gangue (1300 ° C to 1500 ° C), the gangue and gangue begin to melt and aggregate separately, and the gangue and gangue Achieve the purpose of separation and realize the production of metallic iron.

Following the above method, the iron oxide-containing lump is obtained by lumping at least one of the iron-containing materials such as conventional iron ore powder, metallurgical dust-removing iron powder, and red mud. The mass-forming method may be to press the ball through a rollerball machine, or to make a ball through a disc pelletizer. This is a conventional technique in this field, and description thereof will be omitted here. In general, binders and / or auxiliaries can be added as needed in the process of making the balls. In this example, at least one of calcium carbonate, slaked lime, molasses, and wheat flour can be preferably used as the binder used for mass formation, and ideal pellet strength can be obtained. In the ingot formation process, it may be selected to add or not add a carbonaceous reducing agent according to the production demand. Addition of a carbonaceous reducing agent accelerates the reduction reaction rate, and metal iron produced without addition is accelerated. Can increase the cleanliness of. The size of the pellet can be selected according to the actual production conditions, and the diameter of the pellet is preferably 15 to 35 mm.

In this embodiment, a specific composition of a mass containing an iron oxide is as follows.

The mass contains the following parts by weight of components:
58 to 65 parts of TFe, of which FeO is 1 to 2.5 parts.
3.5-5 parts of CaO.
0.6 to 0.85 parts of Al ₂ O ₃ .
4 to 6.5 parts of SiO ₂ .
0.05 to 1.15 parts of MgO.

The mass containing the above components has a relatively high iron grade, can guarantee the smooth progress of the subsequent reduction and melting reaction in the reduction furnace, and guarantees the quality of the product metallic iron.

Following the above method, in the present embodiment, the carbonaceous reducing material contains at least one of anthracite, montan, and coke powder, among which the reducing effect obtained by using anthracite or coke powder and metallic iron. The carburizing effect is particularly preferred. Further, preferably, the particle size of the carbonaceous reducing material is suppressed to the range of 0 to 3 mm. If the particle size is too small, the carbonaceous reducing material is blown up with the furnace gas and easily enters the furnace, which increases the amount of dust removed and the amount of coal consumed. If the particle size is too large, the vaporization rate will be slow and the production efficiency will be affected.

Following the above method, the metallic iron obtained from the reduction furnace is discharged from the reduction furnace, cooled, and then the carbonaceous material is separated by sieving or magnetic separation to obtain metallic iron. The obtained carbonaceous material can be recovered as the carbonaceous reducing material.

As a preferred embodiment, the reduction furnace can adopt the following configuration.
a. The reduction furnace is an annular furnace, the axial direction of the reduction furnace is vertical and rotatable around its own axis, and the mass and the carbonaceous reduction material are laid at the bottom of the reduction furnace. A heat source is used to heat the lower end of the bottom of the reduction furnace.
b. The production process is carried out in a coal-based vertical furnace, the coal-based vertical furnace includes a combustion chamber, and at least a part of the reduction furnace is located in the combustion chamber, and the reduction furnace is provided through the combustion chamber. Supply heat to. Further, heat can be supplied from the same combustion chamber by using a plurality of reduction furnaces.

The method for producing metallic iron will be further described below with specific examples.

Example 2
The present embodiment provides a method for producing metallic iron, and specifically includes the following.

First, pellets 200 containing iron oxide are made, and the method of making balls is to press the balls with a rollerball machine. The binder used is slaked lime, the proportion of the binder used is 3%, and the particle size of the pellet 200 is 18 mm.

The components of pellet 200 are as shown in the table below.

[Table 1] Pellet components

The pellet 200 produced is dried so that the water content is 1% or less.

Next, the carbonaceous reducing agent 300 is selected, the carbonaceous reducing agent 300 to be used is lignite, the average particle size is 0.8 mm, and the carbonaceous reducing agent 300 components to be used are as shown in the table below. Is.

[Table 2] Ingredients of carbonaceous reducing agent

The dried pellets 200 and the carbonaceous reducing agent 300 are mixed evenly and then charged into the reduction furnace 100. The reduction furnace 100 is a mobile annular reduction furnace, and the bottom portion is heated by using a heat source, that is, the reduction furnace 100 provided with the a portion in the above-mentioned Example 1 is adopted. As shown in FIG. 1, a layer of pellets 200 and a carbonaceous reducing agent 300 is laid at the bottom of the reduction furnace 100, and the pellets 200 are tightly surrounded by the carbonaceous reducing agent 300. The temperature in the reduction furnace 100 is raised to about 1380 ° C., and the time for the pellets 200 and the carbonaceous reducing agent 300 to stay in the reduction furnace 100 is about 50 minutes.

When the temperature in the reduction furnace 100 reaches about 900 ° C., the carbonaceous reducing material _{begins to gasify (C + CO 2} = 2CO) and the iron oxide begins to be reduced (FeO + CO = Fe + CO ₂ ). Since the inside of the reduction furnace 100 is in a reducing atmosphere, the metallic iron obtained by reduction is not oxidized again.

The temperature of the reduced metallic iron rises further, and during the heating process, it is continuously carburized with the carbonaceous reducing material in close contact with the surroundings. After the temperature in the reduction furnace 100 reaches the reflow temperature of the metal iron and the metal iron, the metal iron and the metal iron begin to melt and aggregate separately, reaching the purpose of separating the metal iron and the metal iron. It realizes the production of metallic iron and effectively controls the problem of reoxidation of metallic iron in the reduction furnace 100.

Example 3
The present embodiment provides a method for producing metallic iron, and specifically includes the following.

First, the method of making pellets 20 containing iron oxide and making balls is to make balls with a disc pelletizer. The binder used is slaked lime, and at the same time, coal powder is added into the pellet 20, the ratio of adding the coal powder is 10% of the mass of 20 pellets, the ratio of the binder used is 3%, and the pellets. The 20 particle size is 15 mm.

The components of pellet 20 are as shown in the table below.

[Table 3] Pellet components

The pellet 20 produced is dried so that the water content is 1% or less.

Next, the carbonaceous reducing agent 30 is selected, the carbonaceous reducing agent 30 used is anthracite, the average particle size is 1 mm, and the carbonaceous reducing agent 30 used is as shown in the table below.

[Table 4] Ingredients of carbonaceous reducing agent

The dried pellets 20 and the carbonaceous reducing agent 30 are mixed evenly, and then charged into the reduction furnace 10. The reduction furnace 10 is a vertical reduction furnace 10, the center line in the height direction of the reduction furnace 10 is perpendicular to the ground, and a heat source is used to heat the reduction furnace 10 from around the reduction furnace 10, that is, the above-mentioned Example 1. The reduction furnace 10 provided with the b portion inside is adopted. As shown in FIG. 2, the pellet 20 and the carbonaceous reducing agent 30 are added into the reduction furnace 10, and the pellet 20 is closely surrounded by the carbonaceous reducing agent 30. The temperature in the reduction furnace 10 is raised to about 1400 ° C., and the time for the pellets 20 and the carbonaceous reducing agent 30 to stay in the reduction furnace 10 is 3 hours.

When the temperature in the reduction furnace 10 reaches about 900 ° C., the carbonaceous reducing material _{begins to gasify (C + CO 2} = 2CO) and the iron oxide begins to be reduced (FeO + CO = Fe + CO ₂ ). Since the inside of the reduction furnace 10 is in a reducing atmosphere, the metallic iron obtained by reduction is not oxidized again. The temperature of the reduced metallic iron rises further, and during the heating process, it is continuously carburized with the carbonaceous reducing material in close contact with the surroundings. After the temperature in the reduction furnace 10 reaches the reflow temperature of the metal iron and the metal iron, the metal iron and the metal iron begin to melt and aggregate separately, reaching the purpose of separating the metal iron and the metal iron. It realizes the production of metallic iron and effectively controls the problem of reoxidation of metallic iron in the reduction furnace 10.

The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the invention are all within the scope of the invention.

(Additional note)
(Appendix 1)
A mass containing iron oxide and a carbonaceous reducing material are placed in a reduction furnace, and the mass is heated to reduce and melt the iron oxide, and the metallic iron obtained by heating is cooled, and the metallic iron that has already been cooled is cooled. Is discharged from the reduction furnace, the already cooled metallic iron is recovered, and the iron oxide is heated here with the air shut off.
A method for producing metallic iron, which is characterized by the fact that.

(Appendix 2)
The amount of the carbonaceous reducing material added is 1.05 to 2 times the amount of the carbonaceous reducing material required to reduce the iron oxide.
The method for producing metallic iron according to Appendix 1, wherein the method is characterized by the above.

(Appendix 3)
The carbonaceous reducing material contains at least one of anthracite, lignite and coke flour.
The method for producing metallic iron according to Appendix 1 or 2, wherein the method is characterized by the above.

(Appendix 4)
The reduction and melting temperature of iron oxide in the reduction furnace is 1350 to 1500 ° C.
The method for producing metallic iron according to Appendix 1, wherein the method is characterized by the above.

(Appendix 5)
The particle size of the carbonaceous reducing material is in the range of 0.3 to 3 mm.
The method for producing metallic iron according to Appendix 1, wherein the method is characterized by the above.

(Appendix 6)
The lump is obtained by lumping from at least one of iron ore powder, metallurgical dust-removed iron powder, and red mud.
The method for producing metallic iron according to Appendix 1, wherein the method is characterized by the above.

(Appendix 7)
The binder used for mass formation is at least one of calcium carbonate, slaked lime, molasses, and wheat flour.
The method for producing metallic iron according to Appendix 6, wherein the method is characterized by the above.

Claims (6)

The mass and a carbonaceous reducing material containing iron oxide placed in the reduction furnace, the mass heated to reducing and melting the iron oxide, metallic iron obtained by heating and cooling, and already cooled the metallic iron discharged from the reducing furnace, to recover the metal iron previously cooled, wherein the heating of the iron oxide are performed by the state of blocking the air,
The amount of the carbonaceous reducing material added is 1.05 to 2 times the amount of the carbonaceous reducing material added to reduce the iron oxide.
The mass contains the following parts by weight (1) to (5).
A method for producing metallic iron, which is characterized by the fact that.
(1) 58 to 65 parts of TFe, of which FeO is 1 to 2.5 parts.
(2) 3.5 to 5 parts of CaO.
(3) 0.6 to 0.85 parts of Al ₂ O ₃ .
(4) 4 to 6.5 parts of SiO ₂ .
(5) 0.05 to 1.15 parts of MgO. The carbonaceous reducing material contains at least one of anthracite, lignite and coke flour.
The method for producing metallic iron according to claim 1. Reduction and melting temperature of the iron oxide of the reduction furnace are 1,350 to 1500 ° C.,
The method for producing metallic iron according to claim 1. The particle size of the carbonaceous reducing material is in the range of 0.3 to 3 mm.
The method for producing metallic iron according to claim 1. The lump is obtained by lumping from at least one of iron ore powder, metallurgical dust-removed iron powder, and red mud.
The method for producing metallic iron according to claim 1. The binder used for the ingot is at least one of calcium carbonate, slaked lime, molasses, and wheat flour.
The method for producing metallic iron according to claim 5.

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