JP6447614B2 - Raw material charging method to blast furnace - Google Patents

Description

  The present invention relates to a method for charging a raw material into a blast furnace, and particularly relates to a method for charging a raw material in which ore and coke having a small particle diameter are mixed in advance.

  In blast furnaces that produce pig iron (also referred to as “melting furnaces”), iron ore that is a raw material (hereinafter, also simply referred to as “ore”) and coke that is a reducing material are layered alternately. Charged from the top of the furnace, an ore layer and a coke layer are formed in the blast furnace. And the gas flow in a furnace is controlled by adjusting the distribution after the deposition of the ore layer and the coke layer of the furnace radial direction (furnace diameter direction) in the schematic longitudinal cross-sectional view of the blast furnace shown in FIG. In order to maintain stable operation of the blast furnace, it is important to ensure good air permeability in the blast furnace and to stabilize the flow of high-temperature air supplied into the blast furnace from a hole called tuyere at the bottom of the furnace. is there.

  The air permeability in the blast furnace is affected by the properties and particle size of the ore and coke to be charged, but in addition to this, it depends on the charging method of the charge from the top of the furnace and the distribution of the charge in the furnace. Is also greatly affected.

  As one of the methods for improving the air permeability in the blast furnace, Non-Patent Document 1 discloses a raw material ("mixed raw material") obtained by previously mixing ore and a small particle size coke (referred to as "small medium mass coke"). ) And coke having a large particle size (large coke) are alternately charged, and a coke mixed ore layer made of mixed raw material and a coke layer made of large coke are formed into layers. Yes. In Non-Patent Document 2, an operation is performed in which the blending amount of the small medium lump coke to the mixed raw material is 28 kg / t-pig. It has been reported that the operation of 30 kg / t-pig is carried out, thereby improving the air permeability of the lower part of the furnace and improving the reduction efficiency. In addition, "kg / t-pig" means the mixing amount of small and medium lump coke mixed when producing per ton of hot metal.

  The ore charged in the blast furnace is heated and reduced as it descends in the furnace and is fused together to form a layer called a fused layer. Since the fusion layer has a low ratio of voids in the layer, the gas permeability is remarkably lowered. However, an improvement in the permeability is recognized in the fusion layer containing coke. This is considered to be due to the coke mixed in the coke mixed ore layer serving as a gas path instead of the ore in which the porosity is significantly reduced due to fusion / shrinkage in the fusion layer.

  Further, when the coke mixed ore layer and the coke layer are formed in layers, it is expected that the reduction efficiency is improved by lowering the gasification start temperature in addition to the improvement of the air permeability of the fusion layer described above. This is based on the principle that the reduction equilibrium point of FeO—Fe can be controlled by lowering the gasification start temperature of coke and lowering the heat storage zone temperature.

  To summarize the above, by charging a raw material mixed in advance with ore and small coke coke and mixing the small medium coke into the ore layer (hereinafter also referred to as “mixed charging”), ( Advantages such as 1) improvement in air permeability in the lower furnace cohesive zone and (2) improvement in reduction efficiency can be expected.

  In order to maximize the effect of the mixed charging, it is important to charge a necessary amount of a charging material composed of ore and coke having different particle diameters and densities. However, since the charge is granular, segregation (separation) between coke and ore due to particle size difference or density difference is basically an inevitable problem. For this reason, a method of controlling the distribution of the charge according to the property / grain size of the charge or the charging method has been proposed.

  For example, Patent Document 1 discloses a bell-less blast furnace in which the turning speed of a turning chute when mixing ore and coke is mixed is lower than the turning speed when at least one of ore and coke is charged separately. A raw material charging method has been proposed. According to the method described in Patent Literature 1, the turning surface of the turning chute at the time of simultaneous charging of ore and coke is set to be lower than the turning speed at the time of charging ore and coke alone, so that the deposition surface It is said that segregation of coke in can be suppressed, that is, a coke mixed ore layer can be formed in a state where separation of coke and ore is suppressed. As shown in FIG. 2, the bell-less blast furnace 1 refers to a blast furnace having a swivel chute 11 inside the furnace top portion for flowing ore and coke cut out from the furnace top bunker 10 into the furnace. The turning chute 11 is configured to turn in the circumferential direction of the furnace with the furnace center as an axis, and to tilt in the radial direction of the furnace with a pin 12 that fixes the turning chute 11 as an axis.

  On the other hand, according to the result of a numerical calculation method called Discrete Element Method (DEM) described in Non-Patent Document 4, when particles having different particle sizes simulating ores flow down on a turning chute, It is known that particles on the large particle size side float and segregate from particles on the small particle size side. In other words, when ore and small coke coke are charged simultaneously through a swivel chute, small medium coke that has a larger particle size and lower density than ore shows a more prominent segregation tendency on the swirl chute. Therefore, even if the method described in Patent Document 1 is adopted, it is considered difficult to uniformly charge small and medium-sized coke in the furnace radial direction.

  By the way, when forming a coke mixed ore layer, it is reported by patent document 2 that the average reduction rate of an ore improves by segregating, that is, unevenly distributing the small and medium lump coke on the upper part of a coke mixed ore layer. . This is because when comparing the lower part and the upper part of the coke mixed ore layer, the upper part has a lower reduction rate than the lower part. It is thought that it is based on improving the reduction rate of the coke mixed ore layer upper part by raising.

  Patent Document 2 describes a method of segregating coke on the upper part of a coke mixed ore layer. “A segregation control plate or the like is installed in the upper part of the furnace top bunker, and the mixed raw material charged in the furnace top bunker is `` It only has to be charged while forming a raw material flow that falls near the center axis of the blast furnace close to the discharge port '', but this method alone is insufficient to obtain the desired segregation state. We have confirmed that this is the case. In this method, it is necessary to install a segregation control plate in the upper part of the furnace top bunker.

JP 2012-36425 A JP 2012-188744 A

Shimomura et al., Iron and Steel, vo.62 (1976), No.11, S404 Okuda et al., Iron and Steel, vol. 70 (1984), No. 4, S102 Anan et al., CAMP-ISIJ, vol.12 (1999), No.1, p.234 H. Mio et al., ISIJ International, 49 (2009), p.479 Shimizu, etc., iron and steel, vol. 73 (1987), No. 12, S754

  As described above, it is known that it is effective to segregate coke on the upper part of the coke mixed ore layer, but when ore and small coke are charged at the same time, the particle size is smaller than that of the ore. Large and low density small coke has a tendency to segregate even on the swivel chute, and the actual situation is that segregation of coke on the upper part of the coke mixed ore layer has not been sufficiently implemented.

  The present invention has been made in view of such circumstances. The purpose of the present invention is to charge a coke mixing ratio in the furnace radial direction when charging a mixed raw material obtained by mixing ore and small ingot coke into a blast furnace. It is intended to provide a raw material charging method to a blast furnace in which small and medium lump coke can be further present in the upper part of the coke mixed ore layer in the thickness direction of the coke mixed ore layer.

The gist of the present invention for solving the above problems is as follows.
[1] The ratio of the average particle size of the mixed small ore coke to the average particle size of the iron ore to be mixed (small) A method of charging a raw material into a blast furnace, characterized in that the average particle size of medium coke / average particle size of iron ore is in the range of 0.8 to 1.2.
[2] When each position in the furnace radial direction in the furnace is indicated by a dimensionless radius obtained by dividing the distance from the furnace center to each position by the furnace diameter (radius), the position of the mixed raw material on the furnace center side is not indicated. The mixed raw material is charged with the position of the dimensional radius 0.12 to the position of 0.25, the furnace wall side position of the mixed raw material as a range from the position of the dimensionless radius 0.80, The raw material charging method to the blast furnace as described in [1] above.
[3] The raw material charging method to the blast furnace according to [1] or [2] above, wherein the iron ore is sintered ore.

  According to the present invention, in the blast furnace, the mixing ratio distribution of the small and medium-sized coke in the coke mixed ore layer is appropriately maintained, thereby achieving improvement in the air permeability and reduction efficiency of the blast furnace.

It is a schematic longitudinal cross-sectional view of a blast furnace. It is a schematic longitudinal cross-sectional view of the furnace top part of a bell-less blast furnace. It is the schematic which shows the accumulation cross section of the charge in a blast furnace top part. It is a figure which shows the model of the calculation area | region used by this invention. It is a figure which shows an example of the calculation result of the deposit shape of a coke mixed ore layer by a discrete element method. It is a perspective view of the small and medium lump coke of the cross-section of the coke mixed ore layer when the particle size ratio is 1.9 and 0.5. When the particle size ratio is 1.9,1.2,0.8,0.5 a diagram showing the distribution of the mixing ratio _{X k} of the layer thickness direction. When the particle size ratio is 1.9,1.2,0.8,0.5 a diagram showing a deviation σ of the mixing ratio _{X k} of the layer thickness direction. When the particle size ratio is 1.9,1.2,0.8,0.5 a diagram showing the distribution of the mixing ratio _{X k} in the furnace radial direction. When the particle size ratio is 1.9,1.2,0.8,0.5 a diagram showing a deviation σ of the mixing ratio _{X k} distribution in the furnace radial direction. It is a figure which shows typically the raw material charging range at the time of calculating | requiring the relationship between deviation (sigma) of the mixing rate _Xk of a furnace radial direction, and raw material charging range. In case where the particle diameter ratio of 1.2, a diagram showing the investigation results of the relationship between the deviation σ and the raw material charging range of the mixing ratio X _k of the furnace radial direction. It is the schematic of a load softening test apparatus. It is a figure which shows the measurement result of the pressure loss of the fuse | melted sample in case the particle size ratio is 1.9, 1.2, 0.8, 0.5.

  Hereinafter, the present invention will be described in detail. The present invention has been made based on a numerical simulation called a discrete element method. The calculation method called Discrete Element Method is also called the name of Discrete Element Method. In the present invention, these are representatively called the discrete element method.

  The present invention simulates the discharge and deposition of iron ore (ore) and coke from the swirling chute at the top of the blast furnace by this discrete element method, and the mixing state of small and medium mass coke in the coke mixed ore layer in the actual furnace. Simulate. According to the discrete element method, the charged ore and coke are configured as spherical or non-spherical particles, and equations of motion are constructed for individual components (particles), by contact between particles or between particles and walls. By taking the interaction force into account, the velocity and position of each particle are sequentially calculated.

  Hereinafter, simulation results by the discrete element method will be described.

First, a model simulating the top of the furnace where the charge was deposited was created. FIG. 3 shows a charge cross-section at the top of the blast furnace. As shown in FIG. 3, the charge to the blast furnace is usually divided into four times, each of the mixed raw material in which the ore and small medium coke are mixed in advance and the large coke coke twice. It is inserted. This series of charging divided into four times is called one charge. In FIG. 3, the layer indicated by reference numeral C ₁ is a coke layer formed by charging the first large block coke, and the layer indicated by reference numeral C ₂ is formed by charging the second large block coke. , and the coke mixed ore layer formed by charging the mixed material layer th one indicated by reference numeral O _1, coke mixed ore layer indicated by reference numeral O ₂ is formed by loading of the second mixed feed Is a layer. The small coke in this specification is a coke having a size passing through a sieving machine having an opening size of 40 mm, and even a spindle type coke having a major axis exceeding 40 mm has a sieve size having an opening size of 40 mm. As long as it passes through the divider, it is defined as a small coke.

  The charging of the mixed raw material and the large coke is called one batch, and the charging per charge is composed of two batches of the mixed raw material and the large coke. Therefore, in estimating the mixing ratio distribution when small coke coke mixed in the coke mixed ore layer is deposited on the upper part of the furnace, calculation is performed only for batches of mixed raw materials mixed with small coke coke. Can be done.

  FIG. 4 shows a calculation domain model used in the present invention. Normally, in the bell-less blast furnace 1, charges such as ore and coke are charged and stored in a furnace bunker 10 installed at the top of the blast furnace, and when charging these charges, The lower gate is opened and the charge is discharged from the furnace top bunker 10. The charge discharged from the furnace top bunker 10 flows down the inside of the turning chute 11 turning at a rotational speed of about 8 to 10 rpm, and is discharged to the furnace top. 4A is a schematic longitudinal sectional view of the top of the bell-less blast furnace, FIG. 4B is a deposition cross-section of the charge at the top of the blast furnace, and FIG. 4C is a calculation by a discrete element method. It is a figure which shows an area | region.

In the discrete element method employed in the present invention, the calculation load increases as the number of particles to be calculated increases, and the time required for the simulation increases. Therefore, in the present invention, the discharge of the particles from the lower part of the furnace top bunker 10 and the flow of the discharged particles on the swirl chute 11 are not considered, and the movement of the swirl chute 11 between the furnace center and the furnace wall (hereinafter, Only the discharge of particles from the tip of the tilting swivel chute 11 is considered. In addition, since the calculation for the region covering the entire circumference of the furnace top similarly increases the calculation load, as shown in FIG. 4C, the width is 10D _p (D _p ; The calculation is performed on a rectangular area of the average particle size of the coke).

  In addition, as described above, since only the coke mixed ore layer in which small coke coke is mixed needs to be calculated, a bottom surface shape simulating the shape of the coke layer is prepared, and the ore and small medium coke are loaded thereon. Enter. Small medium-sized coke and ore (FIG. 4 is an example using sintered ore as the ore) are simultaneously discharged and deposited from the particle discharge unit 13 (tip of the swirl chute 11) shown in FIG. The mixing amount of the small medium mass coke to the coke mixed ore layer was set to 60 kg / t-pig.

An example of the calculation result of the deposited shape of the coke mixed ore layer by the discrete element method is shown in FIG. After calculating the deposit shape of the coke mixed ore layer by the discrete element method, sampling is performed after dividing the region in the furnace radial direction and the layer thickness direction shown in FIG. 5, and the mixing ratio X _k (kg / T-pig) was calculated. The definition of the mixing ratio _Xk is as shown in the following equation (1). The mass of the equation (1) may be expressed as “kg”. In the equation (1), 1.6 is multiplied as a correction coefficient in order to convert from ore mass to pig iron mass.

X _k = [(Coke mass at sampling position) / (Ore mass at sampling position)] × 1.6 × 1000 (1)
The ratio of the average particle size of small coke coke to the average particle size of iron ore in the mixed raw material (average medium particle size of small coke coke / average particle size of iron ore) was variously changed to deposit the coke mixed ore layer The state was calculated. In addition, the particle size in this invention points out an average particle size. Next, after calculating the mixing rate X _k for each position in the furnace radial direction and the layer thickness direction, the deviation σ of the mixing rate X _k was calculated for each of the furnace radial direction and the layer thickness direction. The smaller the deviation σ, the smaller is the segregation of small coke in the coke mixed ore layer, and the better the mixing is.

  Fig. 6 shows the mixing of coke in the case where the ratio of the particle size of small coke coke to the particle size of iron ore (average particle size of small coke coke / average particle size of iron ore) is 1.9 and 0.5. A perspective view of a small medium mass coke in the cross section of the ore layer is shown. As shown in FIG. 6, when the ratio (average particle size of small coke coke / average particle size of iron ore) is 1.9, small coke coke segregates in the lower part in the layer thickness direction, while It can be seen that when the (average particle size of small coke coke / average particle size of iron ore) is 0.5, the small medium coke is dispersed substantially uniformly in the layer thickness direction. Hereinafter, the ratio of the particle size of the small medium lump coke to the particle size of the iron ore (the average particle size of the small medium lump coke / the average particle size of the iron ore) is also simply referred to as “particle size ratio”.

Further, in FIG. 7, in the case where the particle diameter ratio of 1.9,1.2,0.8,0.5, showing the distribution of the mixing ratio _{X k} of the layer thickness direction. As is clear from FIG. 7, when the particle size ratio is 0.8, the small medium coke is substantially uniformly dispersed in the layer thickness direction, but when the particle size ratio is smaller than 0.8, the layer It was found that the small coke coke segregates on the upper side in the thickness direction, and conversely, when the particle size ratio is larger than 0.8, the small coke coke tends to segregate on the lower side in the layer thickness direction. . In addition, the vertical axis | shaft of FIG. 7 is displayed by the non-dimensional numerical value which remove | divided the layer height of the sampling position by the furnace diameter (radius).

  That is, from FIG. 6 and FIG. 7, it was found that as the particle size ratio decreased, the dispersibility of the small medium coke in the layer was improved, and the small medium coke was also distributed on the surface layer side of the deposition slope. .

8, in the case where the particle diameter ratio of 1.9,1.2,0.8,0.5, showing a deviation σ of the mixing ratio _{X k} of the layer thickness direction. As shown in FIG. 8, it can be seen that the deviation σ in the layer thickness direction decreases as the particle size ratio decreases, and the mixing property improves.

Next, in FIG. 9, in the case where the particle diameter ratio of 1.9,1.2,0.8,0.5, showing the distribution of the mixing ratio _{X k} in the furnace radial direction. The horizontal axis in FIG. 9 represents a non-dimensional value obtained by dividing the distance from the furnace center to the position of each sampling point in the furnace radial direction by the furnace diameter (radius), that is, “non-dimensional radius”. . As shown in FIG. 9, it can be seen that the small coke coke tends to segregate on the furnace center side and the furnace wall side in each particle size ratio.

Moreover, it can be seen from FIG. 9 that there is a region where small and medium-sized coke and ore are distributed at a certain ratio in the furnace radial direction. Such regions are mixing ratio _{X k} elementary, middle lump coke 20 and 100 kg / t-pig, i.e., deviation σ is 40 kg / t-pig following areas.

10, in the case where the particle diameter ratio of 1.9,1.2,0.8,0.5, showing a deviation σ of the mixing ratio _{X k} in the furnace radial direction. FIG. 10 shows an area _where the deviation σ of the mixing ratio Xk is 40 kg / t-pig or less, which is a condition in which the small medium coke and the ore are distributed at a certain ratio, obtained from FIG. Thus, when the particle size ratio is in the range of 0.8 to 1.2, it can be expected that the mixing ratio is more uniform in the furnace radial direction.

Furthermore, the case of changing the charging range of the mixed raw material in which the small coke coke and iron ore are mixed into the furnace in the radial direction of the furnace is simulated by the discrete element method, and the small radial coke in the radial direction of the furnace is simulated. The mixing rate X _k and the deviation σ of the mixing rate X _k were calculated.

The distribution of the charge accumulated in the blast furnace and the gas flow velocity in the blast furnace are often handled by dividing the deposition region into three equal parts in the center, middle, and peripheral areas in the cross-sectional area in the radial direction of the furnace. When the furnace diameter (radius) is R ₀ , the furnace wall side corresponds to the peripheral part rather than the distance of about 0.80 × R ₀ . In this region, the ore layer is thin and the coke layer that serves as a gas path is often thick. For this reason, the region closer to the furnace wall than 0.80 × R ₀ is sufficient in both reducing property and air permeability, so that the effect obtained by mixing charging is small. Therefore, in this simulation, as shown in FIG. 11, a distance of 0.80 × R ₀ from the furnace center and a position away from the furnace wall side was set as the raw material charging end point position. Under these conditions, the ratio of the charging range of the mixed raw material into the furnace with respect to the furnace diameter R ₀ was changed in the range of 40% to 70%. That is, when the ratio of the charging range of the mixed raw material into the furnace with respect to the furnace diameter R ₀ is 40%, when each position in the furnace is displayed with a dimensionless radius, the position from the dimensionless radius of 0.40 When the mixed raw material is charged in the range up to the position of the dimension radius 0.80 and the ratio of the charging range of the mixed raw material into the furnace with respect to the furnace diameter R ₀ is 70%, the position of the dimensionless radius 0.10 To the range of a dimensionless radius of 0.80.

In FIG. 12, the horizontal axis is the ratio of the charging range of the mixed raw material into the furnace with respect to the furnace diameter R ₀ , and the vertical axis is the deviation σ of the mixing ratio X _{k in} the furnace radial direction. It shows the investigation results of the relationship between the deviation σ and the raw material charging range of X _k. FIG. 12 shows the calculation result when the particle size ratio is 1.2. However, the present inventors have shown that when the particle size ratio is 0.8 to 1.2, FIG. The same trend has been confirmed.

As is clear from FIG. 12, when the ratio of the charging range of the mixed raw material into the furnace with respect to the furnace diameter R ₀ is less than 55% (that is, charging starts from the position of the dimensionless radius 0.25), the mixing is performed. the deviation σ rate X _k increases with the decrease in the ratio of the raw material charging range, mixing deteriorates. This is because when the ratio of the raw material charging range decreases, the amount of the mixed raw material charged to the same falling surface increases, and the mixed coke in the raw material segregates due to the steep slope of the mixed raw material deposition surface. It is because it ends up. On the other hand, when the ratio of the charging range of the mixed raw material into the furnace with respect to the furnace diameter R ₀ is 55% or more, the variation of the deviation σ is small, and the mixing property is less affected by the charging range. Recognize.

  On the other hand, as shown in FIG. 1, there is a region called a core in the lower portion of the blast furnace where the coke descending speed is very slow compared to other regions. In general, a decrease in air permeability in the furnace core hinders stable operation due to unsatisfactory descending of the charge and the accompanying fluctuations in furnace heat, so lump coke is charged in the center of the blast furnace to ensure air permeability. The According to Non-Patent Document 5, it is understood that the core is composed of coke charged in a dimensionless radius from a position of 0 to a position of 0.12 (that is, a charging range of 68% or more). Therefore, it is not preferable from the viewpoint of ensuring air permeability to insert small coke having a small particle diameter in the region.

From this result, when charging the mixed raw material of small coke coke and iron ore, the range from the position of dimensionless radius 0.12 to the position of 0.25 is loaded at the top of the furnace as shown in FIG. It is possible to minimize the deviation σ of the mixing ratio X _k of the small and medium-sized coke by charging the mixed raw material in the range up to the position of the dimensionless radius 0.80 as the starting position of the charging. all right. That is, in order to minimize deviation σ of the mixing ratio X _k elementary, middle lump coke, the furnace center side position of the mixed material and the position of 0.25 from the position of the dimensionless radius 0.12, furnace mixed material It is preferable that the wall side position is in a range up to a position having a dimensionless radius of 0.80. Ratio furnace diameter _{R 0} of the raw material charging range in this case is 55 to 68%.

  The present invention was made on the basis of the simulation results obtained by the discrete element method described above. The mixed raw material obtained by previously mixing iron ore and small medium coke and large coke are alternately loaded in the blast furnace. In the operation of forming a coke mixed ore layer made of mixed raw material and a coke layer made of large block coke in a layered manner, the average particle size of small medium block coke mixed with the mixed raw material and the average particle size of iron ore It is essential that the ratio of (average particle size of small coke / average particle size of iron ore) be in the range of 0.8 to 1.2. At that time, the mixed raw material is charged in the range up to the position of the dimensionless radius 0.80, with the position of the dimensionless radius 0.12 to 0.25 as the starting position, and as the iron ore It is preferable to use a commonly used sintered ore.

  According to the present invention having this configuration, in the blast furnace, the mixing ratio distribution of the small and medium-sized coke in the coke mixed ore layer is appropriately maintained, thereby achieving improvement in air permeability and reduction efficiency of the blast furnace.

  In order to confirm the validity of the simulation results by the discrete element method, a load softening test was performed on a sample in which sintered ore was used as iron ore, and small and medium-sized coke was mixed in the sintered ore. The ventilation resistance was evaluated.

In FIG. 13, the schematic of a load softening test apparatus is shown. The load softening test apparatus 21 includes a plurality of heating furnaces 22, and heats a sample 24 such as ore in an atmosphere heated by the heating furnace 22 (N ₂ —CO—CO ₂ atmosphere). This is an apparatus that can apply a load via the loader 23 and determine the pressure loss of the sample 24 when the load is applied. Reference numeral 25 in FIG. 13 is a gas mixer, and 26 is a gas analyzer. The load softening test device 21 is used for evaluating the high-temperature properties of ores.

  In the test, sample 24 was obtained by changing the particle size ratio of the small ingot coke and the ore under various conditions under the condition where the mixing amount of the small ingot coke in the coke mixed ore layer corresponds to 60 kg / t-pig. Then, the airflow resistance of the softened / fused sample 24 was evaluated. Specifically, a mixed raw material obtained by mixing small medium-sized coke and sintered ore is filled in a graphite crucible having a diameter of 50 mm, and this crucible is left in the load softening test apparatus 21 to simulate the inside of a blast furnace. Under these conditions (temperature pattern, composition of gas reacted with the sample, load applied to the sample), the pressure loss of the sample 24 simulating the coke mixed ore layer was measured.

  FIG. 14 shows the measurement results of the pressure loss of the molten sample 24 when the particle size ratio is 1.9, 1.2, 0.8, and 0.5. It was found that when the particle size ratio is in the range of 0.8 to 1.2, the ventilation resistance remains low, and the ventilation resistance is effective. This result was in good agreement with the result of the simulation by the discrete element method. That is, it was confirmed that the result of the simulation by the discrete element method is appropriate.

In this example, a blast furnace with an internal volume of 5000 m ³ was used, and coke and mixed raw materials were alternately charged into the blast furnace using a turning chute. In addition, the mixed raw material used by the present Example used the sintered ore whose iron content is 58 mass% as an ore raw material, and used the lump ore whose iron content is 60 mass%. Coke containing 88% by mass of fixed carbon was used.

  In the test, the air permeability of the blast furnace when the particle size ratio of the small medium coke and the ore was varied under the condition that the mixing amount of the small medium coke in the coke mixed ore layer was 60 kg / t-pig. evaluated.

  The air permeability of the blast furnace was evaluated by the airflow resistance index obtained by the following equation (2).

Ventilation resistance index = (P _B ² −P _T ² ) / V ^1.7 × 100 (2)
In the formula (2), P _B is the blowing pressure (kPa), _PT is the furnace top pressure (kPa), and V is the blowing amount (Nm ³ / min). The larger the required airflow resistance index, the higher the pressure loss in the furnace and the worse the air permeability, and the lower the airflow resistance index, the better the air permeability in the furnace.

  In Table 1, the charging range of the mixed raw material in which the ore and the small ingot coke are mixed is defined as the range from the position of the dimensionless radius 0.20 to the position of the dimensionless radius 0.80. The results of the investigation of the airflow resistance index when the particle size ratio (small medium mass coke particle size / ore particle size) is changed in the range of 0.5 to 1.9 are shown. In Table 1, the coke ratio and the pulverized coal ratio represent the amounts of coke and pulverized coal used to produce per ton of pig iron.

  As shown in Table 1, in the range of the present invention, the airflow resistance index is low, and by applying the present invention, the mixing ratio distribution of the small and medium mass coke of the coke mixed ore layer is appropriately maintained, and thereby the blast furnace It was confirmed that the air permeability and the reduction efficiency were improved.

  Also, in Table 2, when the particle size ratio between small coke coke and ore (small medium coke particle size / ore particle size) is 1.0 and 1.2, the ore and small medium coke are The examination result of the ventilation resistance index when changing the charging range of the mixed raw material mixed is shown.

  As shown in Table 2, the mixed raw material charging range is a dimensionless radius compared to the case where the charging range of the mixed raw material is from the position of dimensionless radius 0.35 to the position of dimensionless radius 0.80. It was confirmed that the ventilation resistance index of the blast furnace was kept at a lower level when the position was from 0.12 or 0.25 to 0.80.

1 Bellless Blast Furnace 10 Furnace Bunker 11 Swivel Chute 12 Pin 13 Particle Discharge Part 21 Load Softening Test Device 22 Heating Furnace 23 Loader 24 Sample 25 Gas Mixer 26 Gas Analyzer

Claims (2)

In charging the blast furnace with a mixed raw material that is premixed with iron ore and small coke,
The ratio of the average particle size of the mixed small ingot coke and the average particle size of the iron ore to be mixed (average small particle size coke / average particle size of iron ore) in the range of 0.8 to 1.2 And
In addition, when each position in the furnace radial direction in the furnace is displayed with a dimensionless radius obtained by dividing the distance from the furnace center to each position by the furnace diameter (radius), the position of the mixed raw material on the furnace center side is dimensionless. A blast furnace in which the mixed raw material is charged in a range from a position of a radius of 0.12 to a position of 0.25, a position of the mixed raw material on the furnace wall side to a position of a dimensionless radius of 0.80. Raw material charging method. The method for charging a raw material into a blast furnace according to claim 1, wherein the iron ore is sintered ore.