METHOD FOR LOADING RAW MATERIAL INTO BLAST FURNACE

Abstract

 A method according to the present invention for charging blast furnace raw material into a blast furnace includes classifying coke into lump coke and small coke and filling furnace top bunkers with the classified coke, classifying ore material into large ore material and small ore material and filling the furnace top bunkers with the classified ore material, and subsequently simultaneously discharging the large ore material when discharging the lump coke and simultaneously discharging the small ore material when discharging the small coke. It is thus possible to ensure gas permeability in the blast furnace, stabilize blast furnace operations, and improve thermal efficiency even when mixing a large amount of coke.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for loading (charging) blast furnace raw material into a blast furnace by charging blast furnace raw material into the furnace with a rotating chute.

BACKGROUND ART

[0002] Generally, ore material such as sintered ore, pellet, lump ore, and the like and coke are charged into a blast furnace from the furnace top in a layer state, and combustion gas is injected through a tuyere to yield pig iron. The coke and ore material that constitute the blast furnace raw material charged into the blast furnace descend from the furnace top to the furnace bottom, the ore reduces, and the temperature of the raw material rises. The ore material layer gradually deforms due to the temperature rise and the load from above while filling the voids between ore materials, and at the bottom of the shaft of the blast furnace, gas permeability resistance grows extremely large, forming a cohesive layer where nearly no gas flows.

[0003] Conventionally, blast furnace raw material is charged into a blast furnace by alternately charging ore material and coke. In the furnace, ore material layers and coke layers form alternately. At the bottom of the blast furnace, in the so-called cohesive zone, ore material layers with a large gas permeability resistance, where ore has softened and cohered, exist along with a coke slit, derived from coke, with a relatively small gas permeability resistance.

[0004] The gas permeability of the cohesive zone greatly affects the gas permeability of the blast furnace as a whole and limits the rate of productivity in the blast furnace.

[0005] In order to improve the gas permeability resistance of the cohesive zone, mixing coke into the ore material layer is known to be effective, and much research has been reported for achieving an appropriate mixing state.

[0006] For example, JP H3-211210 A (PTL 1) discloses charging, in a bell-less blast furnace, coke into an ore hopper that is downstream among the ore hoppers, layering coke onto the ore on a conveyor, and charging the ore and coke into the furnace top bunker and then into the blast furnace via a rotating chute.

[0007] JP 2004-107794 A (PTL 2) discloses separately storing ore and coke in the furnace top bunker and mixing the coke and ore while charging them simultaneously in order to yield three batches at the same time: a batch for regularly charged coke, a batch for mainly charging coke, and a batch for mixed charging.

[0008] Furthermore, in order to prevent the cohesive zone shape from becoming unstable during blast furnace operation, to prevent a reduction in the gas utilization rate near the central region, and to improve operation safety and thermal efficiency, JP S59-10402 B2 (PTL 3) discloses a method for charging blast furnace raw material into a blast furnace whereby all of the ore and all of the coke are charged into the furnace after being completely mixed.

CITATION LIST

Patent Literature

[0009] 

PTL 1: JP H3-211210 A

PTL 2: JP 2004-107794 A

PTL 3: JP S59-10402 B2

SUMMARY OF INVENTION

(Technical Problem)

[0010] In the disclosure in PTL 3, the representative mean particle size of coke is approximately 40 mm to 50 mm, and the mean particle size of ore is approximately 15 mm. The particle sizes thus greatly differ, and simply mixing the coke and ore may lead to problems such as a great reduction in the void ratio, worsening of gas permeability in the furnace, blowout of gas, and improper descent of blast furnace raw material.

[0011] One possible method for avoiding these problems is to form a layer of only coke near the center of the furnace shaft. With this method, a path for gas is ensured by the coke layer near the center of the furnace shaft, allowing for improvement of gas permeability.

[0012] When mixing a large amount of coke, however, in addition to small coke, bigger lump coke is also mixed in, causing the difference in particle size between the ore and the coke to increase further. Upon mixing particles of different particle size, it is known that the void ratio in the mixed layer reduces even further. Accordingly, when mixing a large amount of coke, gas permeability in the cohesive zone improves, yet worsening of gas permeability in the blast furnace lumpy zone is a concern.

[0013] The present invention has been developed in light of the above circumstances, and it is an object thereof to provide a method for charging blast furnace raw material into a blast furnace that ensures gas permeability in the blast furnace, stabilizes blast furnace operations, and improves thermal efficiency even when performing an operation to mix a large amount of coke.

(Solution to Problem)

[0014] Specifically, main features of the present invention are as follows.

(1) A method for charging blast furnace raw material including coke and ore material such as sintered ore, pellet, and lump ore into a blast furnace using at least three furnace top bunkers disposed at a top of the blast furnace, a collecting hopper disposed at an outlet of the furnace top bunkers to mix the raw material discharged from the furnace top bunkers and feed the raw material to a rotating chute, and the rotating chute, the method comprising:

classifying the coke into lump coke and small coke and filling separate ones of the furnace top bunkers with the lump coke and the small coke;

classifying the ore material into large ore material and small ore material and filling separate ones of the furnace top bunkers with the large ore material and the small ore material; and

subsequently simultaneously discharging the large ore material when discharging the lump coke and simultaneously discharging the small ore material when discharging the small coke.

(2) The method for charging blast furnace raw material into a blast furnace according to (1), wherein a particle size range of the small coke is 10 mm to 40 mm, and a particle size range of the small ore material is 3 mm to 20 mm.

(3) The method for charging blast furnace raw material into a blast furnace according to (1) or (2), wherein a particle size range of the lump coke is 30 mm to 75 mm, and a particle size range of the large ore material is 10 mm to 50 mm.

(4) The method for charging blast furnace raw material into a blast furnace according to any one of (1) to (3), wherein when classifying the ore material into the large ore material and the small ore material, a mass ratio of the large ore material to the small ore material is matched to a mass ratio of lump coke that, among the lump coke, is mixed with the ore material, to the small coke.

(5) The method for charging blast furnace raw material into a blast furnace according to any one of (1) to (4), wherein a ratio of a harmonic mean size of the small ore material to a harmonic mean size of the small coke and a ratio of a harmonic mean size of the large ore material to a harmonic mean size of the lump coke are each 0.1 or more.

(Advantageous Effect of Invention)

[0015] According to the present invention, when charging ore material and coke into a blast furnace, large ore material is simultaneously discharged when discharging lump coke, and small ore material is simultaneously discharged when discharging small coke. Therefore, gas permeability is improved dramatically at the bottom of the furnace, reducibility of ore is greatly improved, and even when performing an operation to mix a large amount of coke, the blast furnace can be operated stably.

BRIEF DESCRIPTION OF DRAWINGS

[0016] The present invention will be further described below with reference to the accompanying drawings, wherein:

FIG. 1 is a diagram illustrating an embodiment of a method according to the present invention for charging blast furnace raw material into a blast furnace;

FIG. 2 schematically illustrates a device for assessing a packed layer pressure drop;

FIG. 3(a) illustrates a particle size distribution for pre-classified ore and lump coke, and FIG. 3(b) illustrates a particle size distribution for pre-classified ore and small coke;

FIG. 4(a) illustrates a particle size distribution for large ore and lump coke, and FIG. 4(b) illustrates a particle size distribution for small ore and small coke;

FIG. 5(a) illustrates the pressure drop for the particle size distributions in FIG. 3(a) and FIG. 4(a), and FIG. 5(b) illustrates the pressure drop for the particle size distributions in FIG. 3(b) and FIG. 4(b);

FIG. 6 illustrates the result of assessing the effect of the void ratio on the packed layer pressure drop using an Ergun formula; and

FIG. 7 illustrates the result of geometrically calculating the proportion of large particles and the reduction in void ratio.

DESCRIPTION OF EMBODIMENTS

[0017] The following describes a representative embodiment of the present invention with reference to the drawings.

[0018] The specific way of charging ore material and coke into a blast furnace is described based on FIG. 1.

[0019] In the following explanation, it is assumed that lump coke is stored in a furnace top bunker 12a, that large ore material is stored in a furnace top bunker 12b, and that small coke and small ore material are mixed in advance and stored in a furnace top bunker 12c.

[0020] FIG. 1 illustrates the following: a blast furnace 10, furnace top bunkers 12a to 12c, flow regulating gates 13, a collecting hopper 14, a bell-less charging device 15, and a rotating chute 16. Furthermore, θ indicates the angle of the rotating chute with respect to a vertical direction. The coke used with the present invention is not particularly limited and may be any known coke for blast furnaces. The ore material is also not particularly limited, as long as the ore material is a regularly used ore for blast furnaces such as sintered ore, pellet, lump ore, and the like.

[0021] The order for charging blast furnace raw material from the furnace top bunkers is as follows. First, the rotating chute 16 is set to charge blast furnace raw material into the inner peripheral region of the blast furnace wall, and by charging only coke from the furnace top bunker 12a, into which lump coke has been charged, a central coke layer can be formed in the central portion of the blast furnace as necessary, and a peripheral coke layer can be formed in the inner peripheral region of the furnace wall.

[0022] In other words, with the rotating chute 16 set to charge blast furnace raw material into the central portion of the blast furnace or into the furnace wall region, the flow regulating gates 13 of the furnace top bunkers 12b and 12c are closed, the flow regulating gate 13 of only the furnace top bunker 12a is opened, and only the lump coke stored in the furnace top bunker 12a is fed to the rotating chute 16. In this way, a central coke layer can be formed in the central portion of the blast furnace, and a peripheral coke layer can be formed in the inner peripheral region of the furnace wall.

[0023] As described above, the coke is classified into lump coke and small coke, and separate furnace top bunkers are filled with the lump coke and the small coke. Furthermore, the ore material is classified into large ore material and small ore material, and separate furnace top bunkers are filled with the large ore material and the small ore material. In the present invention, large ore material is simultaneously discharged when discharging lump coke, and small coke and small ore material are simultaneously discharged.

[0024] In other words, when discharging lump coke from the furnace top bunker 12a, large ore material is simultaneously discharged from the furnace top bunker 12b, and furthermore, by discharging pre-mixed small coke and small ore material from the furnace top bunker 12c as appropriate, a good mixed layer with a low gas permeability resistance can be formed in the blast furnace lumpy zone.

[0025] As described above, when mixing a large amount of coke, by mixing lump coke in addition to small coke, the difference in particle size between the ore and the coke increases, and the void ratio of the mixed layer lowers. Therefore, gas permeability in the cohesive zone improves, yet gas permeability in the blast furnace lumpy zone deteriorates.

[0026] To address this problem, in the present invention, lump coke and large ore material are simultaneously discharged, whereas when discharging small coke, small ore material is simultaneously discharged, as described above. The reduction in the void ratio of the blast furnace lumpy zone is thus eliminated, and even when mixing a large amount of coke, gas permeability in the blast furnace can be ensured.

[0027] In this context, a mixed layer of lump coke and large ore material is referred to as a mixed layer L, and a mixed layer of small coke and small ore material is referred to as a mixed layer S. The effects of the present invention may be obtained when, in accordance with the allocation of blast furnace raw material during actual production, the mixed layer L and mixed layer S are layered alternately, one mixed layer S is layered on top of a plurality of mixed layers L, or conversely one mixed layer L is layered on top of a plurality of mixed layers S, or when a layer of only coke is formed between any of these layers. As described above, the central coke layer and peripheral coke layer may be formed together.

[0028] Next, the effects of the mixed layer L and mixed layer S are described based on an experiment to confirm the effects.

[0029] In the experiment, the device for assessing a packed layer pressure drop illustrated in FIG. 2 was used to measure the pressure drop of the ore coke packed layer before and after classification.

[0030] FIG. 3(a) illustrates a particle size distribution for pre-classified ore and lump coke, and FIG. 3(b) illustrates a particle size distribution for pre-classified ore and small coke. FIG. 4(a) illustrates a particle size distribution for large ore and lump coke, and FIG. 4(b) illustrates a particle size distribution for small ore and small coke.

[0031] Comparing FIG. 3(a) with FIG. 4(a) and FIG. 3(b) with FIG. 4(b), it is clear that the particle size distributions decrease when mixing large ore and lump coke and when mixing small ore and small coke.

[0032] Based on this result, it can be expected that the packed layer pressure drop due to a reduction in the void ratio caused by increased variation in particle width can be controlled.

[0033] Next, FIGS. 5(a) and 5(b) illustrate the results of measuring the pressure drop when filling the device for assessing a packed layer pressure drop illustrated in FIG. 2 with samples having the particle size distributions in FIG. 3(a), FIG. 3(b), FIG. 4(a), and FIG. 4(b). Ore with a mass of 1900 g was mixed with coke with a mass of 170 g, and the mixture was charged into cylindrical containers to yield the samples.

[0034] The results illustrated in FIG. 5(a) and FIG. 5(b) confirm that, as compared to the particle size distributions in FIG. 3(a) and FIG. 3(b), the packed layer pressure drop was reduced for the particle size distributions in FIG. 4(a) and FIG. 4(b). It is thus clear that setting the mixed layers of ore and coke to be a mixed layer of large ore and lump coke, i.e. the mixed layer L, and a mixed layer of small ore and small coke, i.e. the mixed layer S, allows for a reduction in the packed layer pressure drop.

[0035] The following summarizes the above experiment results and the results of a variety of other experiments on particle size of the ore material and the like.

[0036] First, the particle size range of the small coke is preferably 10 mm to 40 mm. On the other hand, the particle size range of the lump coke is preferably 30 mm to 75 mm. The reason is that upon deviating from the above particle size ranges, the effect of reducing the packed layer pressure drop lessens in every case. Note that as indicated above, the particle size ranges may overlap.

[0037] The particle size range of the small ore material is preferably 3 mm to 20 mm, and the particle size range of the large ore material is preferably 10 mm to 50 mm. The reason is that here as well, upon deviating from the above particle size ranges, the effect of reducing the packed layer pressure drop lessens in every case. Note that as indicated above, the particle size ranges of the ore material as well may overlap.

[0038] Furthermore, in the present invention, it was discovered that better gas permeability can be obtained by, when classifying the ore material into the large ore material and the small ore material, setting the classification point for the large ore material and small ore material so that the mass ratio thereof, i.e. (mass of large ore material / mass of small ore material) × 100 matches the mass ratio of lump coke that, among the lump coke charged into the blast furnace, is mixed with the ore material, to the small coke, i.e. (mass of lump coke mixed with ore material / mass of small coke) × 100. Note that in the present invention, "matching" preferably refers to a complete match, yet an error of approximately 5 % poses no problem whatsoever.

[0039] The inventors also assessed the effect of the void ratio on the packed layer pressure drop using the Ergun formula (Equation 1) shown below:


where ρ [kg/m³] is the density of fluid, µ [Poise] is the coefficient of viscosity of fluid, u [m/sec] is the mean flow velocity of fluid, Dp [m] is the average particle diameter, ε [-] is the void ratio, and Δp/L [Pa/m] is the packed layer pressure drop.

[0040] By simulating a blast furnace shaft, the physical properties were set to ρ [kg/m³] = 2.1, µ [Poise] = 2.23 × 10^-5, u [m/sec] = 0.85, and D_p [m] = 0.02.

[0041] FIG. 6 shows the measurement results.

[0042] From FIG. 6, it is clear that when the void ratio is in a region of 0.3 or less, the increase in pressure drop with respect to a reduction in void ratio grows larger, and that the effect of the void ratio on the pressure drop is salient in the region where the void ratio is 0.3 or less. Accordingly, in order to control a rise in the pressure drop, it is considered effective to maintain the void ratio at 0.3 or more.

[0043] On the other hand, FIG. 7 illustrates a conventional understanding of geometrically calculating the proportion of large particles and the reduction in void ratio. From FIG. 7, it is clear that when the particle size ratio is in a range of 0.2 to 0.1, the void ratio is greatly reduced. It is also clear that at a particle size ratio of 0.1, the void ratio becomes approximately 33 % when the proportion of large particles is near 65 %.

[0044] Accordingly, in the present invention, the ratio of the harmonic mean size of the small ore material to the harmonic mean size of the small coke and the ratio of the harmonic mean size of the large ore material to the harmonic mean size of the lump coke are each preferably 0.2 or more.

[0045] The actual coke ore mixed layer has a particle size distribution, and considering how the void ratio is further reduced, when the particle size ratio is 0.1, the void ratio may become less than 0.3.

[0046] Accordingly, the particle size ratio of ore and coke is preferably 0.1 or more and more preferably 0.2 or more for both the combination of large ore with lump coke and of small ore with small coke.

[0047] On the other hand, the particle size ratio is not particularly limited, yet preferably is approximately 0.2 to 0.75.

[0048] Next, the above-described mixed layers are formed sequentially inside the blast furnace from the bottom to the top.

[0049] Therefore, by injecting high-temperature gas having CO as the main constituent through a blast tube of a tuyere disposed in a basin at the bottom of the blast furnace, a gas flow that traverses the coke layers and rises is formed, and a gas flow that traverses the mixed layers and rises is also formed. The coke is combusted by the high-temperature gas injected through the blast tube, and the ore material is subjected to reductive dissolution.

[0050] In this way, the ore material at the bottom of the blast furnace dissolves, the coke and ore material charged into the blast furnace descend from the furnace top to the furnace bottom, and the ore material is reduced and rises in temperature.

[0051] Therefore, at the top of the melt layer, a cohesive zone in which the ore material is softened forms, and the ore material is reduced at the top of this cohesive zone.

[0052] At this time, at the bottom of the blast furnace in the mixed layers, the ore material and the coke are completely mixed, with coke penetrating between the ore materials. The gas permeability improves, and high-temperature gas passes directly between ore materials, allowing for improvement of heat-transfer properties without delay in heat transfer.

[0053] Additionally, at the bottom of the cohesive zone in the blast furnace, the area of contact between the ore material and the high-temperature gas expands, encouraging carburizing. In the cohesive zone, gas permeability and thermal conductivity can also be improved. Furthermore, at the top of the blast furnace as well, ore material and coke are provided near each other. Hence, due to a coupling reaction, which is a reciprocal activation phenomenon between a reduction reaction of the ore material and a gasification reaction (carbon solution loss reaction), reduction proceeds well without a reduction delay.

[0054] The reduction reaction at this time is represented by FeO + CO = Fe + CO₂.

[0055] The gasification reaction is represented by C + CO₂ = 2CO.

[0056] On the other hand, in the above-described conventional example in which ore and coke are stacked as layers, ore and coke are alternately charged into the blast furnace so that ore layers and coke layers are formed in the blast furnace. In this case, when injecting high-temperature gas having CO as the main constituent through the blast tube of the tuyere, at the bottom of the cohesive zone gas permeability is restricted by the reduction in the coke slit and the pressure drop increases, leading to the problem of a reduction in the area of contact between the ore and the high-temperature gas and restriction of carburizing.

[0057] At the top of the cohesive zone, a coke slit is formed, and heat is conducted to the ore mainly through this coke slit. Therefore, a delay in heat transfer occurs, causing insufficient heat transfer. Furthermore, since a coke layer with good gas permeability and an ore layer with poor gas permeability are stacked at the top of the blast furnace, not only does the rate of temperature increase drop, but also the reduction reaction alone occurs, so that the above coupling reaction cannot be expected. The problem of reduction delay thus occurs.

[0058] In the embodiment according to the present invention, however, ore layers and coke layers are formed after the above-described particle size adjustment, thereby allowing for uniform gas flow, a guarantee of good thermal conductivity, and stable improvement in gas permeability, thus resolving the problems in the above conventional example.

[0059] Note that conventionally, in order to produce 1 t of hot metal, the necessary amount of coke (kg), i.e. the coke ratio is 320 kg/t to 350 kg/t, yet by charging blast furnace raw material in accordance with the present invention, the coke ratio can be reduced to approximately 270 kg/t to 300 kg/t.

[0060] In the above embodiment, the case of control by reverse tilting control to tilt the rotating chute in the blast furnace successively from the shaft central portion towards the outer peripheral wall has been described, yet control is not limited in this way. Equivalent effects as in the above embodiment can also be obtained with so-called forward tilting control to tilt the rotating chute from the outer peripheral wall to the shaft central portion. In this case, coke and ore material are discharged from the three furnace top bunkers until the rotating chute moves to the shaft central portion by, as described above, discharging large ore material simultaneously with discharge of lump coke and discharging small ore material simultaneously when discharging small coke.

[0061] The case of three furnace top bunkers has been described above, yet separate furnace top bunkers may be filled with the lump coke, small coke, large ore material, and small ore material. Furthermore, a different furnace top bunker may be filled with lump coke that, among the lump coke, is not mixed with the ore material.

EXAMPLES

[0062] In order to prove the effects of the present invention, the laboratory device illustrated in FIG. 2 was used to simulate a blast furnace lumpy zone in a blast furnace, and the packed layer pressure drop was examined.

[0063] This laboratory device is a cylindrical stainless steel tube with a diameter of 10 cm, as illustrated in FIG. 2, and a predetermined volume of air can be blown in from the bottom. At the top and the bottom of the tube, openings for measuring the pressure inside the tube are provided and are connected to a pressure gauge by tubing.

[0064] The charged raw material used in the following examples is listed below.

coke	bulk density: 0.578 g/cm3
ore	bulk density: 1.835 g/cm3

In Comparative Example 1, the coke specific consumption of the coke mixture was 120 kg/t. In Inventive Example 1, with the same specifications, the ore was classified, and small ore and large ore were respectively mixed. In Inventive Example 2, the mixing quantity of coke was further increased to 200 kg/t-p. In Inventive Example 3, the particle size range of the small ore was reduced to further the improvement in gas permeability over Inventive Example 2. Note that in Inventive Example 1, the sample layers in FIG. 2 included the two layers of lump coke + ore (without classification) and small coke + ore (without classification), and in Inventive Examples 1, 2, and 3, the sample layers included the two layers of lump coke + large ore and small coke + small ore.

[0065] Additionally, the particle size ranges, mass ratios, and harmonic mean sizes of the coke and ore in these layers were all as listed in Table 1.

[0066] In each case, the result of measuring the packed layer pressure drop is listed in Table 1 for comparison.

[0067] In the present invention, before transport to a furnace top facility of the blast furnace, the particle size is preferably measured after discharge from an ore bin for storing ore near the ground and from a coke bin for storing coke.

[0068] A measurement frequency of approximately once per week is desirable, and measurement is preferably performed several times a day. Furthermore, as the mean size, the harmonic mean size indicated below is appropriate for assessing the pressure drop in the blast furnace. Here, the harmonic mean size: D_p is represented by Equation 2 below for a sample sorted into i portions:


where Dp [m] is the harmonic mean size of particles, w_i [-] is the mass ratio of each sieve opening, and d_pi [m] is the representative particle size of each sieve opening.

[Table 1]

	Comparative Example 1	Inventive Example 1	Inventive Example 2	Inventive Example 3
productivity (t/m3/day)	2.0	2.0	2.0	2.0
coke ratio (kg/t)	350	332	337	334
pulverized coal ratio (kg/t)	148	148	148	148
reducing agent ratio (kg/t)	498	480	485	482
gas utilization rate (%)	49.6	51.6	52.5	52.5
lump coke particle size range (mm)	30-75	30-75	30-75	30-75
large ore particle size range (mm)	3-50	20-50	20-50	15-40
small coke particle size range (mm)	10-40	10-40	10-40	10-30
small ore particle size range (mm) *1	-	3-20	3-20	5-15
mass ratio of large ore raw material to small ore raw material and (%)	-	50	70	70
mass ratio of lump coke to small coke (%)	50	50	70	70
harmonic mean size ratio of small ore to small coke	-	0.17	0.20	0.38
harmonic mean size ratio of large ore to lump coke	0.22	0.40	0.53	0.60
packed layer pressure drop: ΔP/V (kPa/(Nm3/min))	26.43	22.71	25.13	24.23

*1 non-classified materials are listed in the lump coke and large ore sections

[0069] Table 1 shows that by classifying the ore as listed in Inventive Example 1, the packed layer pressure drop can be sufficiently mitigated. Table 1 also shows that for Inventive Example 2, by increasing the ratio of large ore and decreasing the small ore, the mean particle size of the small ore decreased. Therefore, although the packed layer gas permeability resistance increased as compared to Inventive Example 1, a lower packed layer gas permeability resistance than Comparative Example 1 of 1000 Pa or more per 1 m was achieved. Furthermore, Table 1 shows that for Inventive Example 3, since the ratio of the large ore was the same as Inventive Example 2 yet the particle width of the small ore was reduced, the packed layer gas permeability resistance increased as compared to Inventive Example 1, yet a lower packed layer gas permeability resistance than Comparative Example 1 of 2000 Pa or more per 1 m was achieved.

[0070] Accordingly, it was proven that by simultaneously discharging the large ore material when discharging the lump coke and simultaneously discharging the small ore material when discharging the small coke, the gas permeability resistance can be reduced.

[0071] Note that in the above embodiment, 10 mm to 75 mm coke and 3 mm to 50 mm ore was used, yet as long as the combination of particle size ranges and the combination of mass ratios, as well as relationships such as the harmonic mean sizes, are satisfied in accordance with the present invention, the effects of the present invention can be obtained without any problem even if the values are changed as appropriate.

REFERENCE SIGNS LIST

[0072] 

10: Blast furnace

12a to 12c: Furnace top bunker

13: Flow regulating gate

14: Collecting hopper

15: Bell-less charging device

16: Rotating chute

Claims

1. A method for charging blast furnace raw material including coke and ore material such as sintered ore, pellet, and lump ore into a blast furnace using at least three furnace top bunkers disposed at a top of the blast furnace, a collecting hopper disposed at an outlet of the furnace top bunkers to mix the raw material discharged from the furnace top bunkers and feed the raw material to a rotating chute, and the rotating chute, the method comprising:

classifying the coke into lump coke and small coke and filling separate ones of the furnace top bunkers with the lump coke and the small coke;

classifying the ore material into large ore material and small ore material and filling separate ones of the furnace top bunkers with the large ore material and the small ore material; and

subsequently simultaneously discharging the large ore material when discharging the lump coke and simultaneously discharging the small ore material when discharging the small coke.

2. The method for charging blast furnace raw material into a blast furnace according to claim 1, wherein a particle size range of the small coke is 10 mm to 40 mm, and a particle size range of the small ore material is 3 mm to 20 mm.

3. The method for charging blast furnace raw material into a blast furnace according to claim 1 or 2, wherein a particle size range of the lump coke is 30 mm to 75 mm, and a particle size range of the large ore material is 10 mm to 50 mm.

4. The method for charging blast furnace raw material into a blast furnace according to any one of claims 1 to 3, wherein when classifying the ore material into the large ore material and the small ore material, a mass ratio of the large ore material to the small ore material is matched to a mass ratio of lump coke that, among the lump coke, is mixed with the ore material, to the small coke.

5. The method for charging blast furnace raw material into a blast furnace according to any one of claims 1 to 4, wherein a ratio of a harmonic mean size of the small ore material to a harmonic mean size of the small coke and a ratio of a harmonic mean size of the large ore material to a harmonic mean size of the lump coke are each 0.1 or more.

Drawing