Method for producing reduced iron

Abstract

Provided is a method for producing reduced iron, whereby the occurrence of agglomeration can be prevented when reduced iron is obtained by reducing a raw material for reduction with a reducing gas using a shaft furnace or a kiln. A method for producing reduced iron in which reduced iron is obtained by reducing a raw material for reduction with a reducing gas using a shaft furnace or a kiln, the raw material for reduction comprising sintered ore, preferably the raw material for reduction comprising 80% by mass or less of sintered ore and the balance of lump ore and / or pellet ore.

Description

Technical Field

[0001] The present invention relates to a method for producing reduced iron, in which a raw material for reduction is reduced by a reducing gas using a shaft furnace or a kiln to obtain reduced iron. Background Art

[0002] Conventionally, various methods for producing reduced iron are known in which a reducing raw material is reduced by a reducing gas using a shaft furnace or a kiln to obtain reduced iron. In the operation of the shaft furnace or the kiln, pellets or agglomerates obtained by granulating and firing powdered ore are mainly used as the reducing raw material (for example, refer to Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 4427295 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, in the reduction method of reduced iron described in Patent Document 1, there is no mention of agglomeration of the reducing raw materials in the reduction furnace, and there is a possibility that the reduced iron cannot be discharged from the furnace.

[0008] In addition, in the existing reduced iron manufacturing using a vertical furnace or a kiln (for example, MIDREX: a registered trademark), hydrogen and carbon monoxide are used as reducing gases. At this time, a method of increasing the hydrogen in the reducing gas to 67 to 100 volume % relative to the usual 60 volume % (called hydrogen reduction ironmaking) has attracted attention because it can reduce CO2 emissions. When the hydrogen in the reducing gas is increased to 67 to 100 volume %, in order to ensure the reaction speed in the vertical furnace or the kiln, the temperature in the furnace is sometimes increased, and it is necessary to more reliably prevent agglomeration.

[0009] The present invention has been made in view of such circumstances, and its object is to propose a method for producing reduced iron that can prevent agglomeration from occurring when reducing a reducing raw material using a reducing gas in a shaft furnace or a kiln to obtain reduced iron.

[0010] Methods used to solve problems

[0011] The present invention is a method for producing reduced iron, which is a method for producing reduced iron by reducing a reducing raw material with a reducing gas using a shaft furnace or a kiln, wherein the reducing raw material includes sintered ore.

[0012] It should be noted that, for the method for producing reduced iron of the present invention configured as above, the following is considered to be a more preferable solution:

[0013] (1) The reducing raw material is composed of 80% by mass or less of sintered ore and the remainder of at least one of lump ore and pellet ore;

[0014] (2) the reducing raw material is composed of 5% to 70% by mass of sintered ore and the remainder of at least one of lump ore and pellet ore;

[0015] (3) the reducing raw material is composed of 15% to 50% by mass of sintered ore and the remainder of at least one of lump ore and pellet ore;

[0016] (4) The RDI of the sintered ore is 54% by mass or less;

[0017] (5) The total iron content of the sintered ore is less than 65% by mass;

[0018] (6) The reducing gas contains more than 60% by volume of hydrogen;

[0019] (7) The reducing gas contains 67% by volume or more of hydrogen.

[0020] Effects of the Invention

[0021] According to the present invention constituted as above, when reducing iron is produced using a shaft furnace or a kiln, by using sintered ore, preferably sintered ore satisfying predetermined conditions as a reducing raw material, it is possible to prevent agglomeration from occurring in the produced reduced iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a diagram for explaining the relationship between the mixing ratio of sintered ore and the contact ratio between sintered ores and between pellets.

[0023] Figure 2 This is a graph showing the relationship between the amount of sintered ore blended and the agglomeration index.

[0024] Figure 3 This is a graph showing the relationship between the RDI and the agglomeration index of sintered ore.

[0025] Figure 4 This is a graph showing the relationship between the total iron content (T.Fe) of sintered ore and the agglomeration index. DETAILED DESCRIPTION

[0026] The following is a detailed description of the embodiments of the present invention. It should be noted that the following embodiments illustrate devices and methods for implementing the technical concept of the present invention, and do not limit the composition to the following content. That is, the technical concept of the present invention can be modified in various ways within the technical scope described in the claims.

[0027] <About the concept of the present invention and the configuration of the present invention for realizing the concept>

[0028] Conventionally, it is known that the higher the iron content of the reducing raw material, the more likely it is to agglomerate. Therefore, it was thought that by adding a sintered ore with a low iron content to the reducing raw material to reduce the iron content of the reducing raw material, agglomeration may be suppressed, and the present invention was achieved.

[0029] That is, sintered ore uses agglomerating materials and lime-based auxiliary materials, so the content of slag components is high and the iron content is low compared to pelletized ore. The low iron content is conducive to agglomeration, but the agglomeration index increases when only sintered ore is used. It is believed that this is because, although the content of the iron component is low, the slag component generates a molten liquid and causes fusion.

[0030] This makes it clear that the main cause of agglomeration is the fusion of iron between pellets, while the fusion of slag between sintered ores, and the mechanism of agglomeration between pellets and sintered ores is different. This suggests that agglomeration is easy to occur in the contact between pellets and sintered ores, but difficult to occur in the contact between pellets and sintered ores.

[0031] The inventors have found that the frequency of contact between a particle and a particle of the same type as the particle is the product of the existence ratio of the particles of the same type and the existence ratio of the particles of the contact object, which is the square of the proportion of the particles of the same type. Therefore, it is thought that by appropriately mixing the sintered ore, it is possible to reduce the overall agglomeration index (see Figure 1 ).

[0032] The method for producing reduced iron of the present invention based on the above concept is a method for producing reduced iron by reducing a raw material for reduction with a reducing gas using a shaft furnace or a kiln, characterized in that the raw material for reduction contains sintered ore. It is preferably characterized in that the raw material for reduction is composed of 80% by mass or less of sintered ore and at least one of the remaining lump ore and pellet ore. It is more preferably characterized in that the raw material for reduction is composed of 5% by mass to 70% by mass of sintered ore and at least one of the remaining lump ore and pellet ore. It is further preferably characterized in that the raw material for reduction is composed of 15% by mass to 50% by mass of sintered ore and at least one of the remaining lump ore and pellet ore. In addition, the method for producing reduced iron of the present invention is characterized in that the RDI of the sintered ore is 54% by mass or less, the total iron content of the sintered ore is less than 65% by mass, and the reducing gas contains more than 60% by volume, and more preferably contains more than 67% by volume of hydrogen.

[0033] Here, "reducing gas contains more than 60% by volume of hydrogen" means the following. That is, when the volume ratio of hydrogen is set to 100% after removing the gas without reducing effect such as nitrogen and CO2 gas from the gas supplied to the vertical furnace or kiln, it is more than 60% by volume. For example, assume that the composition of the gas supplied to the vertical furnace or kiln is 50% by volume of hydrogen, 30% by volume of carbon monoxide gas, 10% by volume of carbon dioxide gas, and 10% by volume of nitrogen. In this case, the reducing gas contains hydrogen volume concentration ÷ (hydrogen volume concentration + carbon monoxide volume concentration) = 50 ÷ (50 + 30) = 62.5% by volume of hydrogen.

[0034] Example

[0035] Hereinafter, embodiments of the present invention will be described in detail.

[0036] First, sintered ore having predetermined properties was produced as described below. The produced sintered ore and pellets were blended by changing the blending amount of the sintered ore, and the reducing raw materials of Examples 1 to 9 and Comparative Examples 1 to 4 were prepared as shown in Table 1 below.

[0037] Then, for the reducing raw materials prepared in Examples 1 to 9 and Comparative Examples 1 to 4, the cluster strength measurement described below was performed to simulate the production of reduced iron from the reducing raw materials, and the agglomeration state was evaluated by the agglomeration index. The results are shown in the following Tables 1 and Figure 2 to Figure 4 middle.

[0038] <About the production of sintered ore>

[0039] For sintered ore, iron ore and auxiliary raw materials are mixed in a manner to meet the specified properties, and then granulated with water using a drum mixer, and manufactured using a cylindrical sintering test pot that simulates a sintering machine. Sintered ore with a diameter of 5 mm or more in the manufactured sintered ore is screened out as a test raw material for cluster strength measurement. In addition, in the present invention, sintered ore with a specified RDI is manufactured by adjusting the suction negative pressure and the condensation material ratio during firing. Furthermore, in the present invention, sintered ore containing a specified amount of iron is manufactured by adjusting the type of iron ore and the amount of auxiliary raw materials. It should be noted that, here, RDI refers to the reduction pulverization index specified in JIS M 8720. However, in the case of hydrogen reduction ironmaking in which the hydrogen supplied to the reducing gas is 67% by volume or more, part or all of the CO gas of the reducing gas specified in JIS M 8720 can be replaced with hydrogen for measurement.

[0040] <About cluster strength measurement>

[0041] 500g of sample was placed in a vertical cylindrical furnace with a diameter of 100mm. The sample was heated to 1000℃ in a vertical cylindrical furnace in a N2 atmosphere. When the sample temperature reached 1000℃, the reducing gas was 24L / min, H2:N2=20:80 (volume %), and the load was 1kg / cm 2 The sample is kept under the conditions of for 3 hours. Then, the sample is cooled in a N2 atmosphere. Next, it is sieved using a sieve with a mesh of 16 mm, which is the maximum size of a single pellet, and the weight (Wa (g)) is measured. Then, the sample on the sieve is placed in a Type I testing machine (cylindrical container (diameter 132 mm, capacity 700 mL)), rotated at 30 rpm for 5 minutes, and then the amount Wb (g) obtained by sieving with a sieve with a mesh of 16 mm is evaluated. According to this test, the proportion of unbroken agglomerates (Wb / Wa) × 100 is evaluated as the agglomeration index.

[0042]

[0043] It should be noted that based on the results in Table 1, Figure 2 The relationship between the amount of sintered ore and the agglomeration index is shown in Figure 3 The relationship between RDI and agglomeration index of sintered ore is shown in Figure 4 The relationship between the total iron content (T.Fe) of the sintered ore and the agglomeration index is shown in FIG.

[0044] according to Figure 2 From the relationship between the amount of sintered ore added and the agglomeration index shown (using the data of Examples 1 to 6 and Comparative Examples 1 to 2), the following about the addition of sintered ore in the raw material for reduction can be known. First, by adding 80% by mass or less of sintered ore to the raw material for reduction, the agglomeration index is reduced (improved) to less than 35. In addition, by adding 5 to 70% by mass of sintered ore to the raw material for reduction, the agglomeration index is further reduced to less than 20. Furthermore, by adding 15 to 50% by mass of sintered ore to the raw material for reduction, the agglomeration index is further reduced to less than 10. From the above, it can be seen that in order to prevent the occurrence of agglomeration, it is effective to add sintered ore to the raw material for reduction, especially to add 80% by mass or less of sintered ore to the raw material for reduction. In addition, it can be seen that regarding the amount of sintered ore added, it is preferred to add 5 to 70% by mass of sintered ore to the raw material for reduction, and it is further preferred to add 15 to 50% by mass of sintered ore to the raw material for reduction.

[0045] according to Figure 3The relationship between the RDI of the sintered ore and the agglomeration index shown (using the data of Examples 5, 7, 8 and Comparative Example 3) assumes that 70% by mass of the sintered ore is mixed in the reducing raw material. In this case, it can be seen that by setting the RDI of the sintered ore to 54% by mass or less, the agglomeration index is further reduced. It can be seen from this that in order to prevent the occurrence of agglomeration, it is preferred to set the RDI of the sintered ore to 54% by mass or less.

[0046] according to Figure 4 The relationship between the total iron content (T.Fe) and the agglomeration index of the sintered ore shown in Figure 1 (using the data of Examples 5, 9 and Comparative Example 4) assumes that 70% by mass of sintered ore with an RDI of 50% by mass is added to the reducing raw material. In this case, it can be seen that by setting the total iron content (T.Fe) of the sintered ore to less than 65% by mass, the agglomeration index is further reduced. It can be seen that in order to prevent the occurrence of agglomeration, it is preferred to set the total iron content (T.Fe) of the sintered ore to less than 65% by mass.

[0047] Industrial Applicability

[0048] The method for producing reduced iron of the present invention can reduce the occurrence of agglomeration when reducing raw materials for reduction by reducing gas using a shaft furnace or a kiln to obtain reduced iron. Therefore, it helps to reduce CO2 and is useful in industry. It is also useful in a method using hydrogen and carbon monoxide as reducing gases, and is particularly useful when used in a method containing 67% by volume or more of hydrogen as reducing gas (called hydrogen reduction ironmaking).

Claims

1. A method for producing reduced iron, wherein a raw material for reduction is reduced by a reducing gas using a shaft furnace or a kiln to obtain reduced iron, wherein: The reducing raw material includes sintered ore.

2. The method for producing reduced iron according to claim 1, characterized in that: The reducing raw material is composed of 80 mass % or less of sintered ore and the remainder of at least one of lump ore and pellet ore.

3. The method for producing reduced iron according to claim 1, characterized in that: The reducing raw material is composed of 5% to 70% by mass of sintered ore and the remainder of at least one of lump ore and pellet ore.

4. The method for producing reduced iron according to claim 1, characterized in that: The reducing raw material is composed of 15% to 50% by mass of sintered ore and the remainder of at least one of lump ore and pellet ore.

5. The method for producing reduced iron according to any one of claims 1 to 4, characterized in that: The RDI of the sintered ore is 54 mass % or less.

6. The method for producing reduced iron according to any one of claims 1 to 5, characterized in that: The total iron content of the sintered ore is less than 65% by mass.

7. The method for producing reduced iron according to any one of claims 1 to 6, characterized in that: The reducing gas contains 60% by volume or more of hydrogen.

8. The method for producing reduced iron according to any one of claims 1 to 6, characterized in that: The reducing gas contains 67% by volume or more of hydrogen.

Images