Pig iron production method

Abstract

A pig iron manufacturing method of one embodiment of the present application is a pig iron manufacturing method for manufacturing pig iron using a blast furnace having a tuyere, in which a process of alternately stacking a first layer containing a raw material of ore and a second layer containing coke in the blast furnace is included; a process of blowing auxiliary fuel into the blast furnace by hot air blown from the tuyere and reducing and melting the raw material of ore of the first layer; and a process of mixing aggregate for making the hot air flow to the center of the blast furnace in the first layer, the aggregate containing a reduced iron compact obtained by compression molding reduced iron.

Description

TECHNICAL FIELD

[0001] The present application relates to a pig iron production method. BACKGROUND

[0002] A known method of producing pig iron is to alternately stack a first layer containing a raw material of ore and a second layer containing coke in a blast furnace, while reducing the raw material of ore and melting it by blowing auxiliary fuel into the blast furnace through hot air blown from a tuyere. At this time, the coke serves the roles of: a heat source for melting the raw material of ore; a reducing material for the raw material of ore; a carburizer for permeating into molten iron to lower the melting point; and a spacer for ensuring permeability in the blast furnace. The use of the coke to maintain permeability enables stable discharge of the charge and stable operation of the blast furnace.

[0003] In the operation of a blast furnace, it is desirable to reduce the proportion of coke from the viewpoint of cost reduction. However, if the proportion of coke is reduced, the roles of the coke described above are also reduced. As a method of reducing the proportion of coke, i.e., increasing the proportion of the raw material of ore, a method of operating a blast furnace in which small-diameter reduced iron is charged in the peripheral portion of the blast furnace is proposed (see Japanese Patent Application Publication No. 11-315308). In the method of operating a blast furnace described above, it is considered that by charging reduced iron that does not need to be reduced in the peripheral portion of the furnace, the proportion of the raw material of ore can be increased while maintaining the roles of the coke in the central portion of the furnace as a heat source, a reducing material, a carburizer, and a spacer.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 11-315308 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] Recently, from the requirement of reducing the amount of CO2 emission, it is required to further reduce the amount of coke used in the operation of a blast furnace. In the method of operating a blast furnace described above, the coke serves the roles of a heat source, a reducing material, and a carburizer, which can be replaced by auxiliary fuel blown from a tuyere. On the other hand, the coke only serves the role of a spacer. In the method of operating a blast furnace described above, the position where reduced iron is charged is limited to the peripheral portion of the furnace. In addition, the amount of coke used is reduced in relation to the charging of reduced iron. Therefore, in the method of operating a blast furnace described above, there is a limitation in reducing the amount of coke used, and it is not possible to sufficiently respond to the recent requirement of reducing CO2.

[0009] The present application is made in view of the circumstances described above, and aims to provide a method of producing pig iron that can maintain stable operation of a blast furnace and reduce the amount of coke used.

[0010] Means for solving the problem

[0011] The pig iron manufacturing method of one embodiment of the present application is a pig iron manufacturing method for manufacturing pig iron using a blast furnace having a tuyere, including: a step of alternately stacking a first layer containing a raw material of ore and a second layer containing coke in the blast furnace; and a step of reducing and melting the raw material of ore of the first layer while blowing auxiliary fuel into the blast furnace using hot air blown from the tuyere, the aggregate for making the hot air flow to the center of the blast furnace being mixed in the first layer, the aggregate including a reduced iron compact obtained by compression molding of reduced iron.

[0012] In the pig iron manufacturing method, the first layer containing the raw material of ore includes the reduced iron compact obtained by compression molding of reduced iron as the aggregate. With the reduced iron compact, the hot air easily passes through when the first layer is softened and melted in the melting step, and thus the amount of coke used for ensuring the permeability in the pig iron manufacturing method can be reduced. Therefore, by using the pig iron manufacturing method, it is possible to reduce the amount of coke used while maintaining stable operation of the blast furnace.

[0013] Here, the "center portion" of the blast furnace refers to a region having a distance of 0.2R or less from the center when the radius of the mouth portion is R.

[0014] The amount of the reduced iron compact to be charged is 100 kg or more per 1 ton of pig iron, the ratio of the average particle diameter of the reduced iron compact to the average particle diameter of the raw material of ore is 1.3 or more, and the air permeability resistance index of the reduced iron compact after the drum rotation test is 0.1 or less. By making the amount of the reduced iron compact to be charged be the lower limit or more, making the ratio of the average particle diameter of the reduced iron compact be the lower limit or more, and making the air permeability resistance index of the reduced iron compact be the upper limit or less, it is possible to reliably make the hot air flow to the center portion of the blast furnace. Therefore, it is possible to reduce the amount of coke used.

[0015] Here, the "air permeability resistance index of the reduced iron compact after the drum rotation test" is calculated in the following manner. First, a drum rotation test is performed in accordance with the drum strength measurement method for iron ores (JIS-M 8712:2000) to obtain the particle size distribution of the reduced iron compact after the drum rotation test. In the particle size distribution, the representative particle diameter (median) between the screen openings through which the particles are classified is expressed as d i [cm], and the weight fraction of the reduced iron compact having the representative particle diameter d i is expressed as w i . Using the particle size distribution, the harmonic mean diameter D p [cm] and the particle size composition index I sp are calculated according to the following formula 1. In addition, the gravity conversion coefficient g c[9.807 (g-cm) / (G-sec 2 )], the permeation resistance index K is calculated from the following equation 1. Also, the rotation condition of the drum in the drum rotation test described above is to rotate at 24 ± 1 rpm for 600 rotations.

[0016]

Equation 1

[0017] D p = 1 / (∑w i / d i )

[0018]

[0019] Here, I s = D p 2 x ∑w i x (1 / d i - 1 / D p ) 2

[0020] I p = 1 / D p 2 x ∑w i x (d i - D p ) 2 ··· 1

[0021]

[0022] Here, n = 0.47, C = 0.55

[0023] The basicity of the reduced iron shaped body described above is 0.9 or more. When the basicity of the reduced iron shaped body is made to be the lower limit described above or more as such, the shrinkage start temperature of the reduced iron shaped body is made high, and thus the shrinkage amount of the first layer can be suppressed. Therefore, the permeability of the softening zone is improved, and the hot air described above can be made to flow surely to the central portion of the blast furnace. Therefore, the amount of coke used can be reduced.

[0024] Here, the "basicity" means the proportion of the mass of CaO with respect to the mass of SiO2.

[0025] The reduced iron shaped body described above contains alumina, and the content of the alumina in the reduced iron shaped body described above is 1.5 mass% or less. Alumina makes the viscosity of the slag rise, and deteriorates the dripping property of the slag. Therefore, when the content of the alumina in the reduced iron shaped body is made to be the upper limit described above or less, the increase in the amount of coke used can be suppressed.

[0026] The content of the reduced iron formed body in the first layer is preferably 30% by mass or less. Since the reduced iron formed body is larger than the ore raw material, the specific weight is large, and if it is charged into the blast furnace together with the ore raw material, segregation is likely to occur. By making the content of the reduced iron formed body be 30% by mass or less, segregation and separation can be suppressed. Therefore, since the reduced iron formed body is present relatively uniformly up to the center of the blast furnace, the aggregate effect can be exerted in the softening zone, and the hot blast can be made to flow to the center of the blast furnace. Therefore, the amount of coke used can be reduced.

[0027] The ore raw material can be an iron ore pellet in which the porosity of the coarse open pores having a pore diameter of 4 μm or more is 21% or more. By including the iron ore pellet in which the porosity of the coarse open pores having a pore diameter of 4 μm or more is 21% or more in the ore raw material, the reduction rate of the ore raw material can be increased, and therefore the amount of coke used can be further reduced.

[0028] Here, the "porosity of the coarse open pores having a pore diameter of 4 μm or more" is the volume ratio of the coarse open pores having a pore diameter of 4 μm or more with respect to the apparent volume of the iron ore pellet, and is calculated from the open porosity of the iron ore pellet, ε0 [%], the total pore volume per unit weight of the iron ore pellet, A [cm3 / g], and the total pore volume per unit weight of the iron ore pellet having a pore diameter of 4 μm or more, A 3 [cm +4 [cm 3 / g], as A +4 / A [%]. Also, the open pore is a pore that opens to the outside of the iron ore pellet, and the closed pore is a pore that is closed in the inside of the iron ore pellet.

[0029] The method can include a step of charging a mixture of coke and reduced iron formed bodies into the center of the blast furnace, and in the reduced iron formed bodies in the mixture, the proportion of the reduced iron formed bodies having a particle diameter of 5 mm or more is 90% by mass or more, and the content of the reduced iron formed bodies in the mixture is 75% by mass or less. If the hot blast reaches the center of the blast furnace, the center is raised. By including the reduced iron formed bodies having a large particle diameter in the center in an amount of 75% by mass or less, the hot blast can flow without being hindered, and the sensible heat can be effectively used. Therefore, the amount of coke used can be further reduced.

[0030] The powder from the reduced iron compact is micronized together with the coal, and the micronized powder of the reduced iron compact and the coal is blown from the tuyere to be used as the auxiliary fuel, so that the reduced iron compact can be effectively utilized, and the permeability in the blast furnace can be improved.

[0031] Effects of the Invention

[0032] As explained above, the pig iron manufacturing method of the present application can maintain stable operation of the blast furnace, and can reduce the amount of coke used. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a flowchart showing a pig iron manufacturing method according to one embodiment of the present application.

[0034] Figure 2 is a schematic diagram showing the inside of a blast furnace used in the pig iron manufacturing method of Figure 1

[0035] Figure 3 is a schematic partial enlarged view from the softening zone to the vicinity of the drop zone of Figure 2

[0036] Figure 4 is a flowchart showing a pig iron manufacturing method according to another embodiment of the present application, which is different from Figure 1

[0037] Figure 5 is a schematic diagram showing the inside of a blast furnace used in the pig iron manufacturing method of Figure 4

[0038] Figure 6 is a flowchart showing a pig iron manufacturing method according to still another embodiment of the present application, which is different from Figure 1 and Figure 4

[0039] Figure 7 is a diagram schematically showing the treatment performed at the tuyere in the melting step of Figure 6

[0040] Figure 8 is a schematic sectional view showing the structure of a large-scale load reduction test furnace used in the example.

[0041] ​​​​​​Figure 9 is a graph showing the temperature distribution of the heated sample packing layer in the example of investigation of the maximum pressure loss. Figures 11-14

[0042] Figure 10 is a graph showing the temperature distribution of the heated sample packing layer in the example of investigation of the maximum pressure loss. Figures 11-14

[0043] Figure 11 is a graph showing the relationship between the HBI packing amount and the maximum pressure loss in the example.

[0044] Figure 12

[0045] Figure 13

[0046] Figure 14

[0047] Figure 15 is a schematic diagram showing the structure of the blast furnace packing distribution test apparatus used in the example.

[0048] Figure 16 is a graph showing the relationship between the HBI content and the ore packing inclination angle θ in the example when the size of the iron plate was 20 x 7 x 4 mm.

[0049] Figure 17 is a graph showing the relationship between the HBI content and the ore packing inclination angle θ in the example when the size of the iron plate was 10 x 7 x 4 mm.

[0050] Figure 18 is a graph showing the temperature distribution of the heated sample packing layer in the example of investigation of the reduction rate.

[0051] Figure 19 is a graph showing the relationship between the temperature of the sample packing layer and the supplied gas flow rate in the example of investigation of the reduction rate.

[0052] Figure 20

[0053] Figure 21

[0054] Figure 22 ​​​​​​​is a graph showing the relationship between the amount of HBI blown and the amount of pressure loss change for the embodiment. DETAILED DESCRIPTION

[0055] Hereinafter, a pig iron manufacturing method for each embodiment of the present application will be described.

[0056] [1st Embodiment]

[0057] Figure 1 The pig iron manufacturing method shown is a pig iron manufacturing method for manufacturing pig iron using a blast furnace 1. Figure 2 The pig iron manufacturing method shown is a pig iron manufacturing method for manufacturing pig iron using a blast furnace 1.

[0058] <BLAST FURNACE>

[0059] The blast furnace 1, as shown in Figure 2 has a tuyere la provided at the lower portion of the furnace and a tap hole lb. The tuyere la is usually provided with a plurality of tuyeres. The blast furnace 1 is a shaft furnace of a solid-gas countercurrent type, and hot air with high temperature or normal temperature oxygen added as needed is blown into the furnace from the tuyere la, so that a series of reactions such as reduction and melting of the ore raw material 11 described later can be performed, and pig iron is taken out from the tap hole lb. In addition, in the blast furnace 1, a raw material charging device 2 of a bell-skirt type is provided. The raw material charging device 2 will be described later.

[0060] <LAYING-UP PROCESS>

[0061] In the laying-up process S1, as shown in Figure 2 the first layer 10 and the second layer 20 are alternately laid up in the blast furnace 1. In other words, the number of layers of the first layer 10 and the second layer 20 is two or more, respectively.

[0062] (First Layer)

[0063] The first layer 10 contains the ore raw material 11. In addition, in the first layer 10, the aggregate 12 is mixed.

[0064] The ore raw material 11 refers to a mineral ore as an iron raw material, and mainly contains iron ore. As the ore raw material 11, sintered ore (iron ore pellets, sinter), lump ore, carbon-in-pulp ore, metal, and the like can be listed. The ore raw material 11 is reduced by being heated by the hot air blown from the tuyere la in the melting process S2 to become molten iron. Also, the reduced iron compact contained in the aggregate 12 described later can also be used as an iron raw material, but in the present specification, the reduced iron compact is not included in the ore raw material 11.

[0065] In the first layer 10, in addition to the ore raw material 11, auxiliary raw materials such as limestone, dolomite, and silica can also be charged together.

[0066] Aggregate 12 is used to improve the permeability of the softening zone D described later, so that the hot air can circulate to the center of blast furnace 1. Aggregate 12 contains reduced iron shaped bodies (HBI, Hot Briquette Iron) obtained by compressing reduced iron.

[0067] HBI is formed from hot-formed reduced iron (DRI). DRI has the disadvantage of high porosity and exothermic oxidation during sea transport and outdoor storage. In contrast, HBI has low porosity and is difficult to re-oxidize. After ensuring the permeability of the first layer 10, aggregate 12 functions as a metal, becoming molten iron. Due to its high metallization rate, aggregate 12 does not require reduction, so minimal reduction materials are needed when forming this molten iron. Therefore, CO2 emissions can be reduced. Furthermore, the term "metallization rate" refers to the proportion of metallic iron to total iron [mass %].

[0068] As a lower limit for the amount of reduced iron shaped body charged, it is 100 kg per ton of pig iron, more preferably 150 kg. If the amount of reduced iron shaped body charged is lower than the lower limit, the permeability assurance function of the aggregate 12 in the softening zone D may not be fully realized in the melting process S2. On the other hand, the upper limit for the amount of reduced iron shaped body charged is appropriately determined within a range that will not result in excessive aggregate and reduced aggregate effect. For example, the upper limit for the amount of reduced iron shaped body charged is 700 kg per ton of pig iron 1.

[0069] The lower limit for the ratio of the average particle size of the reduced iron shaped body to the average particle size of the ore raw material 11 is 1.3, more preferably 1.4. Figure 3 As shown, a portion of the ore raw material 11 in the first layer 10 melts and moves to the bottom of the blast furnace 1 as dripping slag 13. Even when the ore raw material 11 softens and shrinks, the high-melting-point reduced iron shaped body does not soften. If the reduced iron shaped body, which is significantly larger than the ore raw material 11, is mixed as aggregate 12, the aggregate effect of the reduced iron shaped body is easily manifested, suppressing overall layer shrinkage in the first layer 10. Therefore, by ensuring that the average particle size ratio is above the aforementioned lower limit, it is possible to ensure... Figure 3 The hot air flow path indicated by the arrow improves the permeability in the melting process S2. On the other hand, the upper limit of the aforementioned average particle size ratio is preferably 10, more preferably 5. If the average particle size ratio is higher than this upper limit, it becomes difficult to uniformly mix the reduced iron molded body in the first layer 10, and segregation may increase.

[0070] The upper limit of the permeability resistance index of the reduced iron compact after the drum rotation test described above is 0.1, and more preferably 0.08. The reduced iron compact described above is generally manufactured at a factory different from a factory where it is used and is transported. If the reduced iron compact in which the particle size distribution has changed due to volume damage occurs during the transportation is used, the permeability of the lump zone E described later can be reduced in the blast furnace operation. In view of this, by using the reduced iron compact in which the permeability resistance index is ensured to be below a certain value even after the drum rotation test described above, volume damage can be suppressed, and thus the permeability of the lump zone E can be ensured. On the other hand, the lower limit of the permeability resistance index described above is not particularly limited and can be a value close to the theoretical limit value 0 defined, but is generally about 0.03. Note that, by using the reduced iron compact having the permeability resistance index described above of a value below a certain value, it does not mean that the drum rotation test needs to be performed in the pig iron manufacturing method.

[0071] Further, by setting the amount of the reduced iron compact described above to be charged to be above the lower limit described above, setting the ratio of the average particle diameter of the reduced iron compact described above to be above the lower limit described above, and setting the permeability resistance index of the reduced iron compact described above to be below the upper limit described above, the permeability of the lump zone E and the softening zone D can be improved, and the hot blast can be surely circulated to the central portion of the blast furnace 1. Thus, the amount of the coke used can be reduced.

[0072] The lower limit of the basicity of the reduced iron compact described above is 0.9, and more preferably 1.0. By setting the basicity of the reduced iron compact described above to be above the lower limit described above, the shrinkage start temperature of the reduced iron compact described above is high, and thus the shrinkage amount of the first layer 10 can be suppressed. Thus, the permeability of the softening zone D in the melting step S2 is improved, and the hot blast can be surely circulated to the central portion of the blast furnace 1. Thus, the amount of the coke used can be reduced. On the other hand, the upper limit of the basicity of the reduced iron compact described above is preferably 1.4, and more preferably 1.3. If the basicity of the reduced iron compact described above is higher than the upper limit described above, the strength of the reduced iron compact described above can be reduced. Further, the basicity of the reduced iron compact described above can be adjusted by adding auxiliary raw materials such as limestone at the time of manufacturing the reduced iron compact.

[0073] Further, the above-mentioned reduced iron formed body contains alumina. As an upper limit of the content of the above-mentioned alumina in the above-mentioned reduced iron formed body, 1.5 mass% is preferable, and 1.3 mass% is more preferable. If the content of the above-mentioned alumina is higher than the above-mentioned upper limit, the permeability of the lower portion of the furnace can not be ensured due to the increase in the melting point and the viscosity of the slag. Therefore, by making the content of the alumina in the reduced iron formed body be equal to or lower than the above-mentioned upper limit, the increase in the amount of the coke used can be suppressed. Further, the content of the above-mentioned alumina can be higher than 0 mass%, but as a lower limit of the content of the above-mentioned alumina, 0.5 mass% is more preferable. If the content of the above-mentioned alumina is lower than the above-mentioned lower limit, the reduced iron formed body can be expensive, and the manufacturing cost of the pig iron can be increased.

[0074] (2nd layer)

[0075] The 2nd layer 20 contains the coke 21.

[0076] The coke 21 functions as a heat source for melting the ore raw material 11, a reducing material CO gas required for the reduction of the ore raw material 11, a carburizing agent for carburizing into the molten iron to reduce the melting point, and a spacer for ensuring the permeability in the blast furnace 1.

[0077] (Stacking method)

[0078] The method of alternately stacking the 1st layer 10 and the 2nd layer 20 can be performed using various methods. Here, the method will be described with reference to the blast furnace 1 equipped with the bell and the shield shown in FIG. 2 (hereinafter, also referred to simply as "the blast furnace 1"). Figure 2

[0079] The raw material charging device 2 is located at the top of the furnace. In other words, the 1st layer 10 and the 2nd layer 20 are charged from the top of the furnace. The raw material charging device 2, as shown in FIG. 2, has a bell cup 2a, a lower bell 2b, and a shield 2c. Figure 2

[0080] The bell cup 2a is a portion where the charged raw material is filled. When the 1st layer 10 is charged, the raw material constituting the 1st layer 10 is filled into the bell cup 2a, and when the 2nd layer 20 is charged, the raw material constituting the 2nd layer 20 is filled.

[0081] The lower bell 2b is a conical shape that expands downward and is disposed inside the bell cup 2a. The lower bell 2b is movable up and down (indicated by a solid line in FIG. 2 to show the state of moving upward and by a dashed line to show the case of moving downward). The lower bell 2b is configured to close the lower portion of the bell cup 2a when moved upward and to form a gap on the extension of the side wall of the bell cup 2a when moved downward. Figure 2

[0082] ​​​The guard plate 2c is located below the charging bell 2b and is disposed on the furnace wall of the blast furnace 1. When the charging bell 2b is moved downward, the raw material falls through the aforementioned gap, but the guard plate 2c is a rebound plate used to bounce the falling raw material. In addition, the guard plate 2c is configured to move in and out toward the interior (center) of the blast furnace 1.

[0083] Using this material, the first layer 10 can be stacked in the following manner. The same applies to the second layer 20. Furthermore, the stacking of the first layer 10 and the second layer 20 is performed alternately.

[0084] First, with the feed bell 2b positioned at the top, the raw material of the first layer 10 is loaded into the feed bell cup 2a. With the feed bell 2b at the top, the lower part of the feed bell cup 2a is sealed, thus the aforementioned raw material is filled into the feed bell cup 2a. Furthermore, the filling amount is the same as the layer stacking amount.

[0085] Next, the feeding bell 2b is moved downwards. This creates a gap between the feeding bell and the feeding cup 2a, allowing the raw material to fall through this gap towards the furnace wall and collide with the guard plate 2c. The raw material, after colliding with the guard plate 2c and rebounding, is loaded into the furnace. Because of the rebound from the guard plate 2c, the raw material falls while moving towards the furnace, flowing in and accumulating towards the center of the furnace from its falling position. The guard plate 2c is configured to move forward and backward towards the center; therefore, the falling position of the raw material can be adjusted by moving the guard plate 2c forward and backward. This adjustment allows the first layer 10 to accumulate into a desired shape.

[0086] <Melting Process>

[0087] In the melting process S2, auxiliary fuel is blown into the blast furnace using hot air blown from the tuyeres 1a, while the first layer 10 of the stacked ore raw material 11 is reduced and melted. Furthermore, the blast furnace operation is continuous, and the melting process S2 is carried out continuously. On the other hand, the stacking process S1 is carried out intermittently, and based on the reduction and melting status of the first layer 10 and the second layer 20 in the melting process S2, additional layers 10 and 20 that should be processed by the melting process S2 are added.

[0088] Figure 2 This indicates the state in melting process S2. For example... Figure 2 As shown, under the influence of hot air from tuyeres 1a, a tuyeres circulation zone A is formed near tuyeres 1a. This zone is a cavity where coke 21 swirls and exists in a significantly sparse state. The temperature of this tuyeres circulation zone A within the blast furnace 1 reaches a maximum of approximately 2000°C. Adjacent to the tuyeres circulation zone A, inside the blast furnace 1, there exists a furnace core B, which serves as a pseudo-stagnant zone for coke. Furthermore, from furnace core B upwards, in sequence, there exists a dripping zone C, a softening zone D, and a blocky zone E.

[0089] The temperature in the blast furnace 1 rises from the top toward the tuyere circulation zone A. In other words, the temperature rises in the order of the lump zone E, the softening zone D, and the dripping zone C, for example, to a degree of 20°C or higher and 1200°C or lower in the lump zone E, and to a degree of 1200°C or higher and 1600°C or lower in the core B. Also, the temperature of the core B differs in the radial direction, and there are cases where the center portion of the core B is lower in temperature than the dripping zone C. Also, by causing the hot blast to flow stably in the center portion of the furnace, a softening zone D in the shape of an inverted V in cross section is formed, and the permeability and the reducing property in the furnace are ensured.

[0090] In the blast furnace 1, the iron ore raw material 11 is first subjected to temperature rise reduction in the lump zone E. In the softening zone D, the ore that has been reduced in the lump zone E softens and shrinks. The ore that has softened and shrunk descends to become a dripping molten slag and moves to the dripping zone C. In the melting step S2, the reduction of the ore raw material 11 mainly occurs in the lump zone E, and the melting of the ore raw material 11 mainly occurs in the dripping zone C. Also, in the dripping zone C and the core B, direct reduction in which the liquid iron oxide FeO that has descended directly reacts with the carbon of the coke 21 occurs.

[0091] The aggregate 12 containing the reduced iron compact exerts an aggregate effect in the softening zone D. In other words, even in the state where the ore softens and shrinks, the above-mentioned reduced iron compact, which has a high melting point, does not soften, and the air passage through which the above-mentioned hot blast flows surely to the center portion of the blast furnace 1 is ensured.

[0092] Also, in the hearth portion, molten iron F obtained by melting the reduced iron is stacked, and molten slag G is stacked on the upper portion of the molten iron F. This molten iron F and molten slag G can be taken out from the tap hole lb.

[0093] As the auxiliary fuel to be blown in from the tuyere la, there are, for example, fine coal obtained by finely pulverizing coal to a particle diameter of about 50 μm, heavy oil, natural gas, and the like. The above-mentioned auxiliary fuel exerts a function as a heat source, a reducing material, and a carbon additive. In other words, it assumes a role other than that of the spacer among the roles assumed by the coke 21.

[0094] <Advantages>

[0095] In the pig iron production method, the first layer 10 containing the ore raw material 11 includes a reduced iron compact obtained by compression molding of reduced iron as the aggregate 12. By using this reduced iron compact, the hot blast easily passes through the first layer 10 at the time of softening and melting in the melting step S2, and therefore in the pig iron production method, the amount of the coke 21 for ensuring the permeability can be small. Therefore, by using the pig iron production method, it is possible to maintain stable operation of the blast furnace and reduce the amount of the coke 21 used.

[0096] [Second Embodiment]

[0097] Figure 3The shown pig iron manufacturing method is to use a blast furnace 1 having Figure 4 The shown pig iron manufacturing method of the blast furnace 1 of the tuyere 1a, wherein there is provided the following process: a process (layering process S1) of alternately layering the first layer 10 containing the ore raw material 11 and the second layer 20 containing the coke 21 in the blast furnace 1; a process (melting process S2) of reducing and melting the ore raw material 11 of the layered first layer 10 while blowing auxiliary fuel into the blast furnace 1 by hot air blown from the tuyere 1a, for mixing the aggregate 12 for allowing the hot air to flow to the center portion of the blast furnace 1 in the first layer 10, the aggregate 12 containing a reduced iron molded body obtained by compression molding of reduced iron. In addition, the pig iron manufacturing method has a center portion loading process S3.

[0098] <BLAST FURNACE>

[0099] Since the blast furnace 1 is the same as the blast furnace 1 of the first embodiment, the same structure is added with the same number and the description is omitted.

[0100] <Layering Process>

[0101] (First Layer)

[0102] The ore raw material 11 can contain an iron ore pellet having a porosity of 21% or more of a large open pore having a pore diameter of 4 μm or more. The so-called iron ore pellet is made by using a pellet feed, an iron ore powder, and an auxiliary raw material as needed, and improving the quality according to the properties suitable for a blast furnace (e.g., size, strength, reducibility, etc.).

[0103] The iron ore pellet is mainly composed of coarse particles as a pellet feed and a powder as an iron ore crushed raw material, and a large number of pores are formed inside. As described above, the iron ore pellet can also contain an auxiliary raw material. As such an auxiliary raw material, limestone, dolomite, etc. can be listed.

[0104] The inventors have found that the iron ore pellet having a porosity of 21% or more of a large open pore having a pore diameter of 4 μm or more in the ore raw material 11 can improve the reduction rate of the ore raw material. The inclusion of the above-described iron ore pellet in the ore raw material 11 can further reduce the amount of coke used. Also, as a lower limit of the porosity of the above-described large open pore, 23% is more preferable, and 25% is further preferable.

[0105] As a lower limit of the compressive strength of the above-described iron ore pellet, 180 kg / P is preferable, 190 kg / P is more preferable, and 200 kg / P is further preferable. If the compressive strength is lower than the above-described lower limit, the iron ore pellet 1 is easily pulverized in the blast furnace, and the blast furnace operation can be difficult.

[0106] The above iron ore pellets preferably have a coagulated structure of fine powder. With such a coagulated structure of fine powder, both the porosity of the coarse open pores having a pore diameter of 4 μm or more and the compressive strength can be improved. Here, the "coagulated structure" refers to a state in which a plurality of fine powders are aggregated to form secondary particles, and specifically refers to a state in which 5 or more, preferably 10 or more, fine powders are in contact with each other. Also, the "fine powder" refers to a particle having a spherical diameter (particle diameter) of 0.5 mm or less in terms of volume.

[0107] Also, the same effect can be obtained by using a carbon block ore instead of the above iron ore pellets, or together with the above iron ore pellets.

[0108] As an upper limit of the content of the above reduced iron compact in the first layer 10, 30% by mass is preferable, and 25% by mass is more preferable. Since the reduced iron compact is larger than the ore material 11 and has a large single weight, if the reduced iron compact is charged into the blast furnace 1 together with the ore material 11, it is separated from the ore material 11 and easily segregates. By making the content of the reduced iron compact be equal to or less than the above upper limit, the separation and segregation can be suppressed, and the ore accumulation inclination angle is stabilized at a low level. Therefore, the reduced iron compact can be made to exist relatively uniformly in the first layer 10, and the above hot blast can be made to flow surely to the central portion of the blast furnace 1. Therefore, the amount of the coke 21 used can be reduced. Also, the instability of the first layer 10 due to the segregation of the reduced iron compact can be avoided, and thus the layer collapse can be suppressed when the upper layer descends during the melting step S2. Also, the "ore accumulation inclination angle" refers to the angle of the inclined surface of the ore accumulation layer (the first layer 10, etc.) from the horizontal.

[0109] As a lower limit of the amount of the above reduced iron compact to be charged, 100 kg per 1 ton of pig iron is preferable, and 150 kg is more preferable. If the amount of the above reduced iron compact to be charged is less than the above lower limit, the function of the aggregate 12 in the softening zone D to ensure the permeability can not be sufficiently exerted during the melting step S2.

[0110] As a lower limit of the ratio of the average particle diameter of the above reduced iron compact to the average particle diameter of the ore material 11, 1.3 is preferable, and 1.4 is more preferable. If the above ratio of the average particle diameters is less than the above lower limit, the aggregate effect of the above reduced iron compact can easily be exhibited, and the permeability of the softening zone D can possibly decrease.

[0111] As an upper limit of the permeation resistance index of the above reduced iron compact after the drum rotation test, 0.1 is preferable, and 0.08 is more preferable. If the above permeation resistance index is higher than the above upper limit, the permeability of the lump zone E can possibly decrease.

[0112] As a lower limit of the basicity of the above-mentioned reduced iron formed body, 0.9 is preferable, and 1.0 is more preferable. If the basicity of the above-mentioned reduced iron formed body is lower than the above-mentioned lower limit, the shrinkage starting temperature of the above-mentioned reduced iron formed body is lowered, and thus the shrinkage of the first layer 10 of the softening zone D easily occurs, and the permeability of the lower portion of the furnace can possibly be lowered.

[0113] The above-mentioned reduced iron formed body can also contain alumina. When the above-mentioned reduced iron formed body contains alumina, as an upper limit of the above-mentioned alumina content in the above-mentioned reduced iron formed body, 1.5 mass% is preferable, and 1.3 mass% is more preferable. If the content of the above-mentioned alumina is higher than the above-mentioned upper limit, the permeability of the lower portion of the furnace can possibly be lowered due to the high temperature of the melting point and the increase of the viscosity of the slag.

[0114] (Second Layer)

[0115] The second layer 20 of the second embodiment is configured in the same manner as the second layer 20 of the first embodiment, and thus the detailed description is omitted.

[0116] (Layer Stacking Method)

[0117] As the method of alternately stacking the first layer 10 and the second layer 20, the same method as that described in the first embodiment can be used, and thus the detailed description is omitted.

[0118] <Center Portion Filling Step>

[0119] In the center portion filling step S3, a mixture of the coke 31 and the reduced iron formed body 32 is filled in the center portion of the blast furnace 1. By the filling of this mixture, the center layer 30 is formed as shown in FIG. 1. Figure 5

[0120] (Center Layer)

[0121] ​The proportion of the reduced iron formed bodies 32 having a particle size of 5 mm or more in the above mixture is preferably 90% by mass or more, and more preferably 95% by mass or more. The hot air blown from the tuyere 1a in the melting step S2 warms the central layer 30 when it reaches the central portion of the blast furnace 1. When the central layer 30 contains the reduced iron formed bodies having a particle size of 5 mm or more of the above lower limit or more, the sensible heat of the high-temperature gas can be recovered without hindering the flow of the above hot air. In addition, the reduced iron formed bodies 32 having a small particle size are easily reoxidized. Since the reduced iron formed bodies 32 that are reoxidized require re-reduction, the temperature of the central portion of the blast furnace 1, which is preferably high, is lowered. In addition, the reduced iron formed bodies 32 that are reoxidized react with the coke of the central layer 30 and the hearth B, and deteriorate the coke. According to the above, by containing the reduced iron formed bodies having a particle size of 5 mm or more that are difficult to reoxidize of the above lower limit or more, the sensible heat can be effectively utilized. Therefore, the amount of the coke 21 used can be further reduced. Also, the upper limit of the particle size of the reduced iron formed bodies 32 is not particularly limited, and can be, for example, 100 mm.

[0122] The content of the reduced iron formed bodies 32 in the above mixture is preferably as much as possible from the viewpoint of reducing the amount of the coke 31 used, but the upper limit of the above content is preferably 75% by mass, and more preferably 70% by mass. If the above content is higher than the above upper limit, the permeability of the central layer 30 can be reduced.

[0123] (Layering method)

[0124] The layering of the central layer 30 can be performed using various methods, and can be performed using the material charging device 2 in the bell-dish method, as in the first layer 10 and the second layer 20. Specifically, a portion of the central layer 30 (a thickness corresponding to the thickness of the second layer 20 or the first layer 10 to be layered thereafter) can be layered in the central portion of the blast furnace 1 using the material charging device 2 between the layering of the first layer 10 and the second layer 20, in other words, before the layering of the second layer 20 after the layering of the first layer 10, and before the layering of the first layer 10 after the layering of the second layer 20. In other words, the layering step S1 is performed simultaneously with the central portion charging step S3.

[0125] <Melting step>

[0126] The melting step S2 can be the same as the melting step S2 of the first embodiment, and a detailed description thereof is omitted.

[0127] <Advantages>

[0128] In this pig iron manufacturing method, because the content of reduced iron shaped bodies in the first layer 10 is 30% by mass or less, the segregation and fragmentation of reduced iron shaped bodies around the blast furnace periphery can be suppressed. Therefore, the reduced iron shaped bodies exist relatively uniformly all the way to the center of the blast furnace 1, thus enabling them to function as aggregates in the softening zone D and ensuring that the hot air from the melting process S2 flows reliably to the center of the blast furnace 1.

[0129] Furthermore, this pig iron manufacturing method includes a step of charging a mixture of coke 31 and reduced iron shaped pieces 32 into the center of the blast furnace 1, such that the proportion of reduced iron shaped pieces with a particle size of 5 mm or more in the mixture is 90% by mass or more, and the content of reduced iron shaped pieces in the mixture is 75% by mass or less. By including large-particle-size reduced iron shaped pieces in the center at a content below the aforementioned upper limit, sensible heat can be effectively utilized without hindering the flow of hot blast.

[0130] Based on the above, this pig iron manufacturing method can reduce the amount of coke used.

[0131] [Third Implementation]

[0132] Figure 6 The method of producing pig iron shown is to use a method with Figure 1 The blast furnace 1 with tuyeres 1a shown is used in a pig iron manufacturing method, which includes the following steps: alternatingly layering a first layer 10 containing ore raw material 11 and a second layer 20 containing coke 21 within the blast furnace 1 (layering step S1); reducing and melting the ore raw material 11 in the first layer 10 while blowing auxiliary fuel into the blast furnace 1 using hot air blown from tuyeres 1a (melting step S2); and mixing aggregate 12, which is used to circulate the hot air to the center of the blast furnace 1, into the first layer 10. The aggregate 12 contains reduced iron shaped bodies obtained by compressing reduced iron. Furthermore, this pig iron manufacturing method includes a micro-pulverization step S4.

[0133] <Blast Furnace>

[0134] Blast furnace 1 is the same as blast furnace 1 in the first embodiment, so detailed description is omitted.

[0135] <Layering Process>

[0136] The lamination process S1 is performed in the same manner as the lamination process S1 in the first embodiment, so detailed description is omitted.

[0137] <Micronization process>

[0138] In the micro-pulverization process S4, the powder and coal from the reduced iron molten body are micro-pulverized.

[0139] The reduced iron shaped body is partially broken into powder due to the handling process. Because of its large specific surface area, this powder is re-oxidized from metallic iron into iron oxide. The re-oxidized reduced iron powder also reduces the permeability inside blast furnace 1, and therefore is not suitable for use in the first layer 10. In the micro-pulverization process S4, the reduced iron shaped body that is not used in the first layer 10 is utilized.

[0140] The upper limit of the particle size of the reduced iron shaped body pulverized in the micro-pulverization step S4 is preferably 3 mm, more preferably 1 mm. If the particle size is higher than the upper limit, the degree of re-oxidation is small and the metallization rate is high, so it may not be able to fully function as a flux for improving the permeability of bird's nests.

[0141] Micronization can be performed using roller mills, ball mills, etc. The maximum particle size of the micronized reduced iron pellet and the coal is preferably below 500 μm, and the average particle size is preferably below 100 μm.

[0142] <Melting Process>

[0143] The melting process S2 is the same as the melting process S2 in the first embodiment, except that it includes the micronized powder 41 obtained in the micronization process S4 as auxiliary fuel. Hereinafter, the inclusion of micronized powder 41 as auxiliary fuel will be explained, and other descriptions will be omitted.

[0144] like Figure 7 As shown, a cylindrical auxiliary fuel inlet 1c connected to a tuyer 1a is provided on the blast furnace 1, through which the fine powder 41 is blown into the tuyer 1a. The fine powder 41 comprises reduced iron shaped body (fine reduced iron 41a) obtained in the micro-pulverization process S4 and coal (fine coal 41b). The auxiliary fuel inlet 1c is configured such that the auxiliary fuel blows the fine powder 41 into the tuyer circulation zone A along with the airflow of hot air H blown in from the tuyer 1a, with this outlet facing the downstream side of the hot air H.

[0145] As described above, the air circulation zone A is a cavity portion in which the coke 21 swirls and exists in a significantly sparse state relative to the surrounding area filled with coke 21 (see reference). Figure 7 The auxiliary fuel blown in is mainly directed towards the coke 21 within the tuyeres circulation zone A. This results in an increase in acidic slag from the molten ash of the fine coal 41b within the tuyeres circulation zone A. The increased viscosity and melting point of this slag form a stagnant (restricted) slag layer, known as the "bird's nest" slag J. If the bird's nest slag J grows, the permeability of the lower part of the furnace near the tuyeres circulation zone A of blast furnace 1 deteriorates.

[0146] Here, the fine powder 41 contains the reduced iron compact as described above, which is reoxidized. If the auxiliary fuel containing the oxidized iron is blown from the tuyere la, it is heated and melted in the tuyere circulation zone A, assimilated and slagged with the nest-shaped slag J formed up to this point, and rapidly dripped as the dripped slag 13. As a result, the nest-shaped slag J is difficult to grow, and the permeability can be maintained. If the permeability is maintained, the hot blast H is easily circulated to the central portion of the blast furnace 1, and as a result, the amount of the coke 21 used can be reduced.

[0147] As the lower limit of the amount of the reduced iron compact contained in the fine powder 41 to be blown, 3 kg per 1 ton of pig iron is preferable, and 5 kg is more preferable. If the amount to be blown is less than the lower limit, the permeability improvement effect can be insufficient.

[0148] <Advantages>

[0149] In the pig iron production method, by performing the fine pulverization of the powder from the reduced iron compact and using it as the auxiliary fuel to be blown from the tuyere la, the effective use of the reduced iron compact can be achieved, and the permeability in the blast furnace 1 can be improved.

[0150] [Other Embodiments]

[0151] Further, the present application is not limited to the above-described embodiments.

[0152] In the above-described first embodiment, the cases where (1) the amount of the reduced iron compact to be charged is 100 kg or more per 1 ton of pig iron, the ratio of the average particle diameter of the reduced iron compact to the average particle diameter of the ore raw material is 1.3 or more, and the permeability resistance index after the drum rotation test of the reduced iron compact is 0.1 or less, (2) the basicity of the reduced iron compact is 0.9 or more, and (3) the reduced iron compact contains alumina and the content of the alumina in the reduced iron compact is 1.5 mass% or less are described, but the conditions of the above-described (1) to (3) do not all have to be satisfied, and the pig iron production method in which only two of the above-described three conditions are satisfied or only one of the above-described three conditions is satisfied is also the intention of the present application. By satisfying any one of the above-described three conditions, the permeability of the softening zone can be improved, the central gas flow can be strengthened, and thus the amount of the coke used can be reduced. Further, in the above-described conditions, in the case where the condition (3) is not included, the reduced iron compact does not necessarily have to contain alumina.

[0153] In the above-described second embodiment, the case where the pig iron production method has the central portion charging step is described, but the central portion charging step is not a necessary step and can be omitted. Even if the central portion charging step is omitted, the amount of the coke used can be reduced.

[0154] Further, the above-described central portion charging step can be provided in the pig iron production method of the first embodiment.

[0155] In the layering process of the first embodiment and the second embodiment described above, and the center portion loading process of the second embodiment described above, the case where the bell-dish and apron method is used as the layering method or the loading method is described, but other methods can be used. As such other methods, the bell-less method can be cited. In the bell-less method, a rotary chute can be used, and layering or loading is performed while adjusting the angle thereof.

[0156] Further, in the second embodiment described above, the case where layering of the first layer and the second layer, and loading of the center layer are performed separately is described, but the layering described above and the loading described above can be performed at once with the same device. For example, in the bell-less method described above, the first layer or the second layer can be layered while adjusting the angle of the rotary chute, and loading into the center portion can be performed with this chute.

[0157] In the third embodiment described above, the case where a micro-pulverization process is added to the first embodiment is described, but a micro-pulverization process can be added to the second embodiment.

[0158] Example

[0159] Hereinafter, the present application will be described in more detail by examples, but the present application is not limited by these examples.

[0160] [Particle diameter ratio]

[0161] A large-scale load reduction experiment simulating the peripheral portion of a blast furnace was performed, and the influence of the ratio of the average particle diameter of the reduced iron molded body to the average particle diameter of the ore raw material (hereinafter, also referred to as "HBI particle diameter ratio") on the permeability was investigated.

[0162] Figure 8 In the experiment, a large-scale load reduction experiment furnace 7 used for this experiment is shown. The inner diameter of the graphite crucible 71 filled with the test material was φ75 mm. The test material filling layer 72 was composed of an upper coke layer 72a (height 20 mm), an ore layer 72b (height 110 mm), and a lower coke layer 72c (height 40 mm) from top to bottom. The ore layer 72b corresponds to the first layer 10 of the present application, and the upper coke layer 72a and the lower coke layer 72c correspond to the second layer 20.

[0163] Ore layer 72b is a mixture of reduced iron briquettes (HBI), sinter (particle size 11.2–13.2 mm), iron ore pellets (particle size 8.0–11.2 mm), and lump ore (particle size 11.2–13.2 mm). Ore layer 72b maintains a constant total iron content (T.Fe). Furthermore, by varying the particle size of the HBI, the ratio of the average particle size of the HBI to the average particle size of the ore raw material is varied. Specifically, three types of HBI are prepared: (1) with a particle size of 8.0–11.2 mm, (2) with a particle size of 11.2–13.2 mm, and (3) with a particle size of 13.2–16.0 mm. The chemical properties of the HBI used are shown in Table 1. In addition, the amount of HBI charged is 400 kg per ton of pig iron.

[0164] Table 1

[0165]

[0166] For this sample filling layer 72, an electric furnace 73 was used, while pressing... Figure 9 The temperature distribution shown is used for heating, while supplying... Figure 10 The gas (reducing gas) shown is supplied from a gas supply pipe 74 located at the bottom of the large-scale load reduction experimental furnace 7 and discharged from an exhaust pipe 75 located at the top. The total gas supply rate is 40 NL / min, and temperature control is achieved by two thermocouples 76. Additionally, the load applied to the sample packing layer 72 is 1 kgf / cm². 2 The load is added by adding the weight of the hammer 78 via the loading bar 77.

[0167] The pressure loss of the sample filler layer 72 was continuously measured under the above conditions, and its maximum value (maximum pressure loss) was recorded. A larger maximum pressure loss indicates lower air permeability. The results show... Figure 11 middle.

[0168] Depend on Figure 11 The results show that by making the HBI particle size ratio above 1.3, the aggregate effect (when the ore raw material layer softens and shrinks, M.Fe is the main component, and the high-melting-point HBI will not soften and will function as an aggregate to inhibit layer shrinkage. As a result, voids are generated around HBI, which have the effect of gas flow in these voids) is easily manifested.

[0169] [Loading Amount]

[0170] A large-scale load reduction experiment was conducted to simulate the periphery of a blast furnace to investigate the effect of HBI per ton of pig iron charge on permeability.

[0171] In the above-described particle size ratio example, the particle size of the HBI was fixed at 13.2 to 16.0 mm (HBI particle size ratio = 1.6), the HBI charging amount per ton of pig iron was changed, and the same experiment was performed. The results are shown in Table 4. Figure 12

[0172] From the results of Table 4, it was found that by making the HBI charging amount per ton of pig iron 100 kg or more, the aggregate effect easily appears. Figure 12

[0173] 〔Basicity〕

[0174] A large-scale load reduction experiment simulating the peripheral portion of a blast furnace was performed, and the effect of the basicity of the HBI on the permeability was investigated.

[0175] As the HBI, two kinds containing T.Fe and Al203 in the following contents were prepared.

[0176] case (1): T.Fe = 74.2 to 80.4 mass%, and

[0177] Al203 = 1.99 to 2.20 mass%

[0178] case (2): T.Fe = 89.9 to 91.7 mass%, and

[0179] Al203 = 0.66 to 1.31 mass%

[0180] For the two kinds of the above-described HBI, the particle size of the HBI was made 13.2 to 16.0 mm (HBI particle size ratio = 1.6), the HBI charging amount per ton of pig iron was made 250 kg, and the maximum pressure loss was measured while changing the basicity. The adjustment of the basicity was performed by changing the amount of the auxiliary raw material such as limestone and the kind of the iron ore. Also, the other conditions were the same as in the above-described particle size ratio example. The results are shown in Table 5. Figure 13

[0181] From the results of Table 5, it was found that regardless of the kind of the HBI, by making the basicity 0.9 or more, the aggregate effect easily appears. Also, if compared at the same basicity, case (2) in which T.Fe is high (amount of molten slag is low) and the Al203 content is low has a low maximum pressure loss. Figure 13

[0182] 〔Alumina content〕

[0183] A large-scale load reduction experiment simulating the peripheral portion of a blast furnace was performed, and the effect of the basicity of the HBI on the permeability was investigated.

[0184] ​​​​As the HBI, one having a T.Fe = 87.6 to 92.0 mass%, basicity = 0.04 to 0.56, and different contents of Al203was prepared. Also, according to the results shown in FIG. 2, it can be considered that, among the contents of T.Fe described above, when the basicity is in the range of 0.56 or less, the maximum pressure loss is difficult to be affected by the basicity. Figure 13

[0185] In addition to using the HBI described above, the maximum pressure loss was measured under the same conditions as the examples of the particle size ratio described above. The results are shown in FIG. 3. Figure 14

[0186] From the results shown in FIG. 2, it can be considered that, among the contents of T.Fe described above, when the basicity is in the range of 0.56 or less, the maximum pressure loss is difficult to be affected by the basicity. Figure 14

[0187] [Content]

[0188] A blast furnace burden distribution experiment of a simulated bell / damper type raw material charging device was performed, and the effect of the content of the HBI in the first layer 10 on the permeability was investigated.

[0189] Figure 15 In FIG. 1, a blast furnace burden distribution experiment device 8 used for this experiment is shown. Figure 15 The blast furnace burden distribution experiment device 8 shown in FIG. 1 is a two-dimensional sliced cold model that simulates a bell / damper type raw material charging device at a scale of 1 / 10.7. The size of the blast furnace burden distribution experiment device 8 is a height of 1450 mm (length of L1 in FIG. 2), a width of 580 mm (length of L2 in FIG. 2), and a depth of 100 mm (length in the direction perpendicular to the paper in FIG. 2). Figure 15 Figure 15 Figure 15

[0190] Each of the constituent elements of the blast furnace burden distribution experiment device 8 is assigned the same number as the constituent element of the bell / damper type raw material charging device 2 in FIG. 1 that corresponds to the same function. Since the functions are the same, detailed descriptions are omitted. In addition, the blast furnace burden distribution experiment device 8, as shown in FIG. 2, has a center charging chute 8a for charging coke that simulates center charging. Figure 2 Figure 15

[0191] ​​​​​​​​In the blast furnace charge distribution experimental apparatus 8, after sequentially loading the bottom layer of coke 81, the center layer of coke 82, and the ore layer 83, the experimental layer 84 as the ore layer is loaded, and the ore stacking tilt angle θ is measured. Compared with roasted ore (sintered ore and iron ore pellets) and lump ore, HBI has a higher metallization rate (lower proportion of oxides) and lower porosity, resulting in a higher apparent density. In addition, the larger size of each particle also results in a larger mass. Therefore, if HBI is loaded into the blast furnace together with roasted ore and lump ore, separation and segregation are likely to occur. If separation and segregation occur, local segregation may occur at the periphery, causing the gas flow to move along the periphery, potentially increasing the reducing material ratio due to increased equipment wear and heat loss.

[0192] The raw materials used for loading experimental layer 84 were sintered ore (particle size 2.8–4.0 mm) simulating sintered ore and lump ore, alumina balls (φ2 mm) simulating iron ore pellets, coke lumps (particle size 8.0–9.5 mm) simulating lump coke, and iron plates (20×7×4 mm, 10×7×4 mm) simulating HBI. The raw material ratio was 2 / 11.2.

[0193] As a ratio of sinter to alumina balls (sinter / alumina balls), three ratios were prepared: 70 / 30, 40 / 60, and 0 / 100. The HBI content was varied while the ore stacking tilt angle θ was measured. The results for simulating HBI with an iron plate size of 20×7×4mm are shown... Figure 16 The results for a size of 10×7×4mm are shown in the image. Figure 17 middle.

[0194] Depend on Figure 16 and Figure 17 The results show that regardless of the size of the iron plate simulating HBI, by keeping the HBI content below 30% by mass, the ore stacking tilt angle θ remains stable at a low level. On the other hand, if the HBI content is higher than 40% by mass, the ore stacking tilt angle θ increases, and the segregation of HBI to the upper part of experimental layer 84 becomes significant.

[0195] [Open porosity of iron ore pellets]

[0196] A large-scale load reduction experiment simulating the periphery of a blast furnace was conducted to investigate the effect of the open porosity of iron ore pellets contained as ore raw materials on reducibility.

[0197] use Figure 8A large-scale load reduction test furnace 7 is shown. The inner diameter of a graphite crucible 71 filled with a test material is φ 85 mm. The test material filling layer 72 is composed of an upper coke layer 72a (height 20 mm), an ore layer 72b (height 150 mm), and a lower coke layer 72c (height 40 mm) from top to bottom. The ore layer 72b is a mixture of sinter (particle size 16 to 19 mm), the above-mentioned iron ore pellets (particle size 11.2 to 13.2 mm), and iron blocks (30 mm square cubes x 2) simulating HBI.

[0198] To this test material filling layer 72, an electric furnace 73 is used to heat while supplying a gas (reducing gas) of the composition shown in Figure 18 at the temperature distribution shown in Figure 19 The above-mentioned gas is supplied from a gas supply pipe 74 provided at the lower portion of the large-scale load reduction test furnace 7 and discharged from an exhaust pipe 75 provided at the upper portion. The total supply amount of the above-mentioned gas is 58.4 NL / min before the test material temperature reaches 200°C and 50.4 NL / min from 200°C to 1250°C, and temperature management is performed by two thermocouples 76. In addition, the load applied to the test material filling layer 72 is 1 kgf / cm 2 . This load is added via a load rod 77 to the weight of a weight 78.

[0199] The temperature of the test material filling layer 72 under the above-mentioned conditions reaches 1250°C, at which time the temperature increase is ended, and the supply of the gas is stopped, and the reduction rate is calculated from the difference between the weight before reduction and the weight after reduction of the test material filling layer 72.

[0200] Three kinds of iron ore pellets having different open porosities were used to measure the reduction rate. The measurement was performed twice for the iron ore pellet having the lowest open porosity and once for each of the other two kinds of iron ore pellets. The results are shown in Figure 20 In the graph in Figure 20 , for the two kinds of measurement, the results are indicated by bars and the average values are indicated by dots. From the results in Figure 20 , it is known that the reduction rate is improved by using an iron ore pellet having a porosity of 21% and a large open porosity of 4 μm or more.

[0201] [Content of HBI in center layer]

[0202] A large-scale load reduction test simulating the center portion of a blast furnace was performed to investigate the influence of the center layer on permeability.

[0203] In Figure 8In a large-scale loaded reduction experimental furnace 7, a sample packing layer 72 consisting of a mixed layer (150 mm high) of HBI (particle size 11.2–13.2 mm) and coke (particle size 10.0–13.2 mm) with the chemical properties shown in Table 1 was used. The HBI content was varied, and the maximum pressure loss was measured. Furthermore, the heating rate was fixed at 5 °C / min, and the gas composition was CO / N2 = 50 / 50% by volume, with a total gas supply of 40 NL / min. Other conditions were the same as in the example with the particle size ratio described above. The results showed… Figure 21 middle.

[0204] Depend on Figure 21 The results show that by keeping the HBI content in the center layer below 75% by mass, breathability does not deteriorate. On the other hand, if the HBI content in the center layer is higher than 75% by mass, the maximum pressure loss increases, and breathability deteriorates.

[0205] [Addition of micronized powders to auxiliary fuels]

[0206] Powder from reduced iron shaped bodies was finely pulverized together with coal, and the resulting fine powder was included in auxiliary fuel. The effect was verified by simulation.

[0207] In the above simulation, the average particle size of the powder from the reduced iron briquettes was 50 μm, and the amount of fine coal pulverized in the powder was fixed at 226 kg per ton of pig iron. Under these conditions, the amount of HBI pulverized was varied, and the melting rate of the powder, the viscosity of the slag, the dripping velocity, and the amount of resistance were calculated using known methods. Based on these results, the change in pressure loss was calculated.

[0208] Depend on Figure 22 The results show that even a small amount of HBI containing micronized powder reduces the pressure loss in the lower part of the furnace. Furthermore, it is shown that blowing in more than 3 kg of HBI containing micronized powder per ton of pig iron significantly improves permeability.

[0209] Industrial availability

[0210] The pig iron manufacturing method of the present invention can maintain the stable operation of the blast furnace and reduce the amount of coke used.

[0211] Symbol Explanation

[0212] 1 Blast Furnace

[0213] 1a Wind Entrance

[0214] 1b Iron tapping hole

[0215] 1c Auxiliary fuel inlet

[0216] 2 Raw material loading device

[0217] 2a charging cup

[0218] 2b lower charging cup

[0219] 2c shield

[0220] 10 first layer

[0221] 11 ore material

[0222] 12 bone material

[0223] 13 dripped slag

[0224] 20 second layer

[0225] 21 coke

[0226] 30 center layer

[0227] 31 coke

[0228] 32 reduced iron compact

[0229] 41 fine powder

[0230] 41a fine powder reduced iron

[0231] 41b fine powder coal

[0232] 7 large-scale load reduction test furnace

[0233] 71 graphite crucible

[0234] 72 test material filling layer

[0235] 72a upper coke layer

[0236] 72b ore layer

[0237] 72c lower coke layer

[0238] 73 electric furnace

[0239] 74 gas supply pipe

[0240] 75 gas exhaust pipe

[0241] 76 thermocouple

[0242] 77 load rod

[0243] 78 hammer

[0244] 8 blast furnace charge distribution test apparatus

[0245] 8a center charge chute

[0246] 81 coke layer

[0247] 82 central coke layer

[0248] 83 ore layer

[0249] 84 experimental layer

[0250] A tuyere circulation zone

[0251] B hearth

[0252] C drip zone

[0253] D softening zone

[0254] E cohesive zone

[0255] F molten iron

[0256] G molten slag

[0257] H hot blast

[0258] J bird's nest slag

Claims

1. A pig iron production method of producing pig iron using a blast furnace having a tuyere, wherein, having the steps of: a step of alternately stacking a first layer containing an ore raw material and a second layer containing coke in the blast furnace; a step of blowing auxiliary fuel into the blast furnace by hot air blown from the tuyere, and reducing and melting the ore raw material of the stacked first layer, a bone material for making the hot air flow to the center part of the blast furnace is mixed in the first layer, the bone material contains a reduced iron molded body obtained by compression molding of reduced iron, the reduced iron molded body has a basicity of 0.9 or more and 1.4 or less, the center part of the blast furnace refers to a region having a distance of 0.2R or less from the center when the radius of the mouth part is R.

2. A pig iron production method of producing pig iron using a blast furnace having a tuyere, wherein having the steps of: a step of alternately stacking a first layer containing an ore raw material and a second layer containing coke in the blast furnace; a step of blowing auxiliary fuel into the blast furnace by hot air blown from the tuyere, and reducing and melting the ore raw material of the stacked first layer, a bone material for making the hot air flow to the center part of the blast furnace is mixed in the first layer, the bone material contains a reduced iron molded body obtained by compression molding of reduced iron, the reduced iron molded body has a loading amount of 100 kg or more per 1 ton of pig iron, a ratio of an average particle diameter of the reduced iron molded body to an average particle diameter of the ore raw material is 1.3 or more, a permeation resistance index after a drum rotation test of the reduced iron molded body is 0.1 or less, The air permeation resistance index is calculated in the following manner: a drum rotation test is performed in accordance with the drum strength measurement method for iron ores JIS-M 8712:2000, using reduced iron compact bodies obtained by sieving, with the median value of the representative particle diameter between the sieves being d i , the weight fraction of the reduced iron compact bodies that are representative of the particle size distribution of d i is w i , the harmonic mean diameter D p , the particle size composition index I sp are calculated in accordance with the following formula 1, and the air permeation resistance index K is obtained using the gravitational conversion coefficient g c , where the units of d i , D p are cm, and g c is 9.807 (g-cm) / (G-sec 2 ), the center part of the blast furnace refers to a region having a distance of 0.2R or less from the center when the radius of the mouth part is R.

3. A pig iron production method of producing pig iron using a blast furnace having a tuyere, wherein having the steps of: a step of alternately stacking a first layer containing an ore raw material and a second layer containing coke in the blast furnace; a step of blowing auxiliary fuel into the blast furnace by hot air blown from the tuyere, and reducing and melting the ore raw material of the stacked first layer, a bone material for making the hot air flow to the center part of the blast furnace is mixed in the first layer, the bone material contains a reduced iron molded body obtained by compression molding of reduced iron, the reduced iron molded body contains alumina, a content of the alumina in the reduced iron molded body is 1.5 mass% or less, the center part of the blast furnace refers to a region having a distance of 0.2R or less from the center when the radius of the mouth part is R.

4. A pig iron production method of producing pig iron using a blast furnace having a tuyere, wherein having the steps of: a step of alternately stacking a first layer containing an ore raw material and a second layer containing coke in the blast furnace; a step of blowing auxiliary fuel into the blast furnace by hot air blown from the tuyere, and reducing and melting the ore raw material of the stacked first layer, a bone material for making the hot air flow to the center part of the blast furnace is mixed in the first layer, the bone material contains a reduced iron molded body obtained by compression molding of reduced iron, the ore raw material contains an iron ore pellet having a porosity of 21% or more and a compressive strength of 180 kg / P or more, and a coarse open pore having a pore diameter of 4 μm or more, the center part of the blast furnace refers to a region having a distance of 0.2R or less from the center when the radius of the mouth part is R.

5. A pig iron production method of producing pig iron using a blast furnace having a tuyere, wherein having the steps of: a step of alternately stacking a first layer containing an ore raw material and a second layer containing coke in the blast furnace; a step of blowing auxiliary fuel into the blast furnace by hot air blown from the tuyere, and reducing and melting the ore raw material of the stacked first layer, a step of charging a mixture of coke and reduced iron compact in a central portion of the blast furnace; a step of blowing auxiliary fuel into the blast furnace by hot air blown from the tuyere and reducing and melting the ore material of the stacked first layer, the aggregate for making the hot air flow to the central portion of the blast furnace is mixed in the first layer, the aggregate contains reduced iron compacts obtained by compression molding of reduced iron, of the reduced iron compacts in the mixture, the proportion of reduced iron compacts having a particle size of 5 mm or more is 90% by mass or more, the content of the reduced iron compacts in the mixture is 75% by mass or less, the central portion of the blast furnace refers to a region having a distance of 0.2R or less from the center when the radius of the mouth portion is R.

6. A pig iron production method of producing pig iron using a blast furnace having a tuyere, wherein a step of: stacking a first layer containing an ore material and a second layer containing coke alternately in the blast furnace; a step of blowing auxiliary fuel into the blast furnace by hot air blown from the tuyere and reducing and melting the ore material of the stacked first layer; a step of finely pulverizing a powder from a reduced iron compact and coal, the aggregate for making the hot air flow to the central portion of the blast furnace is mixed in the first layer, the aggregate contains reduced iron compacts obtained by compression molding of reduced iron, in the pulverization step, the particle size of the pulverized reduced iron compact is 3 mm or less, and the average particle size of the reduced iron compact after fine pulverization is 100 μm or less, contains a fine powder obtained in the fine pulverization step as the auxiliary fuel, the central portion of the blast furnace refers to a region having a distance of 0.2R or less from the center when the radius of the mouth portion is R.

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