JP5786810B2 - Blast furnace operation method - Google Patents

Description

  In the present invention, when ore is charged from the top of a blast furnace furnace, a small particle size coke and a large particle size coke are mixed with the ore to form a coke-ore mixed layer in the furnace, thereby aeration of the softening cohesive zone. The present invention relates to a method for operating a blast furnace capable of improving the efficiency and the reduction efficiency, and performing stable and highly efficient blast furnace operation.

  In blast furnace operation, coke as a reducing material and fuel, and sintered ore, pellets, lump ore, etc. as iron sources (hereinafter these iron sources are collectively referred to as “ores”) are generally used in the blast furnace. It is inserted so that it may become a mutual layer. On the other hand, heated air is blown from the tuyeres at the bottom of the furnace, and the coke before the tuyere is combusted and consumed by the heated air, and reducing gas is generated. Along with this, the ore descends in the furnace, is heated and reduced by the high-temperature reducing gas rising from the lower part of the furnace, softens and melts to become pig iron. Pig iron drops inside the furnace, accumulates in the lower part of the furnace, and is periodically taken out from the tap.

  In order to operate the blast furnace stably and with high efficiency, it is necessary to improve the air permeability and reduction efficiency in the furnace. In the furnace, the region having the greatest ventilation resistance is a region from when the ore starts to soften and melt to when it drops (hereinafter, this region is referred to as a “softening zone”). This is because the ore softens and melts in this softening zone and fuses each other to form a fused layer, which narrows the space through which gas can pass and greatly increases the resistance to gas flow in the furnace. It is to do. In the softening zone, the reaction of reducing the ore, which is iron oxide, to pig iron, which is a metal, proceeds rapidly, and governs the reduction efficiency in the furnace. Therefore, in order to improve the air permeability and reduction efficiency in the furnace, it is important to keep the properties of the softened cohesive zone that govern the air permeability and reduction efficiency in the furnace.

  As a method for improving the air permeability of the softened cohesive zone and improving the reduction efficiency of the ore, the ore and coke are mixed and charged into the furnace, and the coke-ore mixed layer (hereinafter simply referred to as “mixed layer”). Technology) is also being developed.

In this technique, in the softening and cohesive zone in which the airflow resistance is greatly increased, coke that is not softened and melted is mixed in the ore to prevent the ore from being fused together and improve the air permeability. In addition, coke is mixed in the vicinity of ore where CO ₂ gas generated by ore reduction exists at a high concentration, thereby promoting the coke solution loss reaction (C + CO ₂ → 2CO) and increasing the concentration of CO gas as the reducing gas. To improve the ore reduction efficiency.

  Furthermore, since coke in the mixed layer is consumed by a solution loss reaction prior to a single coke layer (hereinafter referred to as “coke slit”) that forms a separate layer from the mixed layer, the coke in the coke slit The deterioration due to the reaction (reaction deterioration of coke) is suppressed, and the air permeability of the coke slit is greatly improved. Further, when the FeO-based melt generated from the ore comes into contact with the coke in the mixed layer, the smelting reduction reaction (FeO + C → Fe + CO) is promoted and the reduction efficiency of the ore is improved.

  In order to maximize the effect of improving the air permeability in the softened cohesive zone, it is possible to prevent the ores from fusing together by providing a gap between the individual ores and improve the gas flow. It is desirable to mix diameter coke. On the other hand, in order to maximize the effect of improving the reduction efficiency of ore due to the formation of the mixed layer, it is desirable to mix coke having a small particle diameter from the viewpoint of promoting the reaction of coke in the mixed layer.

  Moreover, the air permeability improvement effect and the ore reduction efficiency improvement effect by mixed layer formation are so large that the amount of coke mixed is large. However, in actual blast furnace operation, when a large amount of coke is mixed and charged, the coke in the mixed layer, which has been reduced in particle size by the solution loss reaction or smelting reduction reaction, enters the coke slit in the dripping zone. This causes a problem that the average particle size of the coke is lowered, the air permeability and liquid permeability are deteriorated, and the pressure loss in the lower part of the blast furnace is increased. Therefore, the upper limit of the amount of coke to be mixed is the amount that can be consumed in the softened cohesive zone by solution loss reaction or smelting reduction (about 50 kg / pig iron, hereinafter, this unit is expressed as “kg / pt”). I was trying.

  As a technique for greatly increasing the amount of coke mixed in the mixed layer, for example, in Patent Document 1, when mixing 50 kg / pt or more of coke into ore, the particle size is 20 mm or less up to 50 kg / pt, and 50 kg For the coke mixed exceeding / pt, a blast furnace raw material charging method with a particle size of 30 mm or more has been proposed, and a coke mixing amount of 120 kg / pt has been achieved.

  In the method described in Patent Document 1, coke particles having a large particle size are mixed so that even if the coke particle size is somewhat reduced by reaction, the air permeability and liquid permeability of the coke slit are not hindered. The diameter can be secured, and it is considered effective in that the concern about the increase in pressure loss at the bottom of the blast furnace can be solved while increasing the amount of coke mixed.

  Patent Document 2 proposes a technique for forming a mixed layer by mixing coke having a small particle size and coke having a large particle size into ore. In this technique, large coke and granular coke are separated from raw coke by sieving to form medium coke, and the large coke and granular coke are mixed in ore to form a mixture. Is a raw material charging method for a blast furnace, characterized in that the blast furnace is charged alternately. The large coke contains 90% or more of a particle size of 65 mm or more, and the granular coke contains 90% or more of a particle size of less than 30 mm.

  However, the techniques described in Patent Documents 1 and 2 are both the segregation of coke size (when the coke mixed in the mixed layer has a particle size distribution, the coarser the coke size, the easier it is to reseparate and the segregation to the furnace center. ), A small particle size coke is disposed on the furnace wall side, and a large particle size coke is disposed on the furnace center side, thereby strengthening the central flow of the gas. Therefore, only the large particle size coke is present in the mixed layer on the furnace center side, and only the small particle size coke is present on the furnace wall side. Depending on the position in the radial direction, there is a possibility that it will not be sufficiently exerted.

JP-A-1-287212 Japanese Patent No. 2752502

Iron and steel Vol. 87 (2001) p350-p356

  The present invention has been made in view of such circumstances, and forms a mixed layer of coke and ore normally used in a blast furnace, and maximizes the effect of improving the air permeability and the reduction efficiency of ore in the softened cohesive zone. The purpose is to provide a method for operating a blast furnace that can be used to the fullest and can be operated stably and efficiently.

  As a result of repeated studies to solve the above problems, the present inventors have shared the function of improving the air permeability to coke with a large particle size and the effect of improving the reduction efficiency by forming a mixed layer to coke with a small particle size. The present inventors have found that coexistence of these cokes in a mixed layer of coke and ore can achieve both an effect of improving air permeability and an effect of improving reduction efficiency.

  In other words, the coke with a small particle size is preferentially assigned to the coke with a small particle size, such as a solution loss reaction or a smelting reduction reaction that brings about an effect of improving the reduction efficiency. By suppressing the reaction deterioration of the coke in the particle size and the coke in the coke slit and causing the coke having a large particle size to reach the lower part of the cohesive zone, the air permeability of the cohesive zone can be improved. Hereinafter, the coke having a large particle size and the coke having a small particle size, which are assigned functions, are referred to as a large coke and a small coke, respectively.

The present invention has been made on the basis of the above idea and the knowledge obtained therefrom, and the gist thereof is in the following blast furnace operating method.
That is, when charging ore and coke from the top of the blast furnace into the blast furnace so as to be in an alternating layer, the ore charging batch is divided into two, and the large charging coke is mixed in the first charging batch at 70 to 100 kg / pt. In the second charging batch, a small amount of coke is mixed at a maximum of 50 kg / pt, charged in the order of the first batch and the second batch, and the particle size of the large coke is 65 to 100 mm. The operation method is characterized in that the particle size is 15 to 35 mm .

In the operation method of the blast furnace of the present invention, the charging of the first batch and the second batch is performed so that the large coke and the small coke mixed in the batch coexist vertically in the furnace radial direction, It is desirable to do.

Here, “batch” means that each charge is divided into a plurality of times with respect to the charge of coke and ore.
As for the particle size, for example, “particle size of 15 to 35 mm” means that the sieve was screened with a sieve mesh having a mesh opening of 15 mm and the sieve mesh having a mesh opening of 35 mm. The particle size corresponding to the case under the sieve.

  According to the operation method of the blast furnace of the present invention, the effect of improving the air permeability by the formation of the mixed layer of coke and ore and the effect of improving the reduction efficiency of the ore can be maximized, and the air permeability and reduction efficiency of the lower part of the blast furnace can be improved. You can plan. As a result, it is possible to realize a blast furnace operation capable of operating stably and with high efficiency.

It is a figure which shows schematic structure of a load softening test apparatus. It is a figure which shows the relationship between the large block coke mixing ratio obtained by the test by a load softening test apparatus, and the high temperature ventilation resistance index KS. It is a figure which shows the relationship between the introduction gas temperature and an ore reduction rate in a reaction analysis simulator. It is a figure which shows the coke-ore mixed layer used for the reaction analysis simulator typically, (a) is the case where the small coke is arranged in the upper layer and the large coke is arranged in the lower layer, (b) is the small coke in the lower layer, large When the block coke is disposed in the upper layer, (c) is a case where the small block coke and the large block coke are uniformly mixed and disposed. It is a figure which illustrates the relationship between the reduction time obtained using the reaction analysis simulator, the coke gasification reaction rate, and the exhaust gas temperature. It is a figure which shows the influence of the mixing coke ratio on the gasification reaction rate of the small coke obtained using the reaction analysis simulator. It is a figure which shows the relationship between the large block coke reaction rate obtained using the reaction analysis simulator, and a large block coke representative particle size. It is the figure which piled up and showed the conditions of this invention on an example of the coke particle size distribution figure.

  First, in order to investigate the coke-ore mixing conditions that can maximize the effect of improving the air permeability by the formation of the mixed layer, the present inventors used a load softening test apparatus to determine the air permeability of the large coke-ore packed bed. We conducted a survey.

  FIG. 1 is a diagram showing a schematic configuration of a load softening test apparatus. As shown in FIG. 1, the load softening test apparatus includes a graphite crucible 2 in which a charge sample 3 is contained in a vertical electric furnace 1, and the load sample apparatus 3 in the crucible 2 is placed on an upper load control apparatus 6. The graphite heating element 5 is heated while applying a load, and the reducing gas 4 is introduced from the lower part of the furnace so that the reducing property of the charged bed and the reduction efficiency of the ore can be investigated. The graphite crucible 2 has an inner diameter of 72 mm and a rooster at the bottom.

  Using this load softening test apparatus, a charged sample simulating large coke and ore was charged into a graphite crucible to form a packed bed.

As the charged sample, pre-reduced sintered ore and coke were used. The pre-reduced sintered ore is a sinter with an average particle size of 9.0 mm, which is sized so that the particle size range is 8.0 to 10.0 mm, and CO and CO ₂ gas are each 8Nl at 1000 ° C. Liter) / min at a flow rate of 5 Nl / min for 1.75 hours. The coke is sized so that the particle size range is 16.0 to 19.0 mm, 25.4 to 31.7 mm, or 35.0 to 38.0 mm, and the average particle size is 17.5 mm, Three types of 28.5 mm and 36.5 mm were prepared. The “average particle diameter” refers to the intermediate diameter of the sieve openings (for example, in the case of 35.0 to 38.0 mm, (35.0 + 38.5) /2=36.5 mm).

  Table 1 shows the filling conditions of the charge sample. In the present invention, since the amount of coke to be mixed is easier to evaluate when converted to coke ratio (kg / pt), the amount of coke mixed with ore is expressed in the form of mixed coke ratio (kg / pt). In Test No. 1 to Test No. 12, the mixed coke ratio was 50, 75, 100 or 150 kg / pt, and the coke average particle size was divided by the ore average particle size (coke / ore). A packed bed of coke and pre-reduced sintered ore was formed as .17 or 4.05. Here, the filling amounts of coke and pre-reduced sintered ore are as shown in Table 1, and the column of “filled coke amount” is the amount of large coke mixed and charged in the packed bed. In test number 0, an ore single layer with a mixed coke ratio of 0 was formed. In all tests, the packed bed height was 300 mm.

In the test, the sample was heated in an N ₂ atmosphere, and after the sample temperature reached 800 ° C., 98 kPa imitating the average load of the actual furnace was applied from the upper part of the crucible. The main purpose of this test is to measure the airflow resistance of the packed bed from 1200 ° C to melting and dripping. In order to make the reduction rate at the beginning of ore fusion equal among the tests, the ore reduction rate in each test is the sample. The heating rate and the introduced gas composition were manipulated according to the change in the ore reduction rate so that the temperature would be 80% at 1200 ° C.

After the sample temperature reaches 1200 ° C., the gas flow rate control device 10 increases CO at 13.8 Nl / min, N ₂ : 16.2 Nl / min while increasing the temperature at a rate of 4.6 ° C./min. A CO / N ₂ mixed gas controlled at a flow rate of ₂ was introduced into the packed bed as a reducing gas 4 and heated to 1600 ° C. to melt or drop the ore. The dropped product was collected in the dropped sample tray 9.

In this test, a CO / N ₂ mixed gas was introduced so that the coke gasification reaction was only CO ₂ gas generated by reduction of ore in order to pay attention to the effect of improving the air permeability by mixing large coke.

Further, during the test, the composition (CO, CO ₂ ) of the exhaust gas 11 by the exhaust gas analyzer (infrared spectrometer) 12, the exhaust gas flow rate by the integrating flow meter, the ventilation resistance between the filling layers by the gas pressure measuring device 8, and by the displacement meter Each packed bed height was measured.

  FIG. 2 is a diagram showing the relationship between the mass coke mixing ratio obtained by the test using the load softening test apparatus and the high temperature ventilation resistance index KS. The vertical axis in the figure is the high temperature ventilation resistance index KS calculated by the following formulas (1) and (2) (for example, see Non-Patent Document 1), and the smaller the value, the better the breathability. Indicates. The “particle size ratio” shown in FIG. 2 means the (coke / ore) particle size ratio.

Here, KS is the high temperature ventilation resistance index, ΔP / ΔL is the ventilation resistance (Pa / m) of the whole packed bed, ρ _g is the gas density (kg / m ³ ), and μ _g is the gas viscosity (kg / m / s). , u _g is the gas superficial velocity (m / s), T is the sample temperature (° C.).

ΔP / ΔL is a value obtained by dividing the measured value by the gas pressure measuring device 8 by the sample height.
ρ _g (gas density) is calculated by dividing the gas density of CO and N ₂ according to the supply gas composition, and correcting the temperature and pressure.
mu _g (gas viscosity), the feed gas composition, temperature, and is calculated in consideration of the pressure.
u _g (gas superficial velocity) are those calculated by the temperature correction and pressure compensation of the gas flow.
T (sample temperature) is a value measured by the temperature measuring device 7.

  As shown in FIG. 2, by increasing the mass coke mixing ratio, the value of KS decreases and the air permeability of the packed bed is improved. (Coke / Ore) By mixing 75 kg / pt of large coke with a particle size ratio of 3.17, the value of KS becomes about 1/4 compared to when the mixed coke ratio is 0 (no mixing), and air permeability There has been a significant improvement. In addition, even in the case where the particle size ratio is 4.05, mixing 100 kg / pt of large coke makes it possible to improve the air permeability equivalent to the case of mixing 75 kg / pt of large coke having a particle size ratio of 3.17. was gotten.

  This air permeability improvement effect is as shown in the case where the (coke / ore) particle size ratio is 3.17, and the improvement range is reduced from around 75 kg / pt when the large coke mixing ratio is about 100 kg. Since the tendency to saturate is recognized when exceeding / pt, it can be judged that the upper limit of the mixing amount of the large coke responsible for improving air permeability is about 100 kg / pt.

  From the above test using the load softening test device, mixing large coke with a (Coke / Ore) particle size ratio of about 3 to 4 with about 70 kg / pt or more and about 100 kg / pt has a sufficient air permeability improvement effect. It can be concluded that it is obtained.

  In the operation method of the blast furnace of the present invention, the ore charging batch is divided into two and the first charging batch is mixed with 70 to 100 kg / pt of large coke in accordance with the results of the above test. is there.

  Next, the arrangement conditions of coke for effectively demonstrating the function sharing of small coke and large coke in the mixed layer were examined.

  In the mixed layer where small coke and large coke coexist, in order to maximize the air permeability improvement effect of the large coke, the small coke is preferentially gasified and the large coke reaction deteriorates. However, in order to do so, it is necessary to set appropriate conditions in consideration of not only the particle size ratio and mixing ratio of small coke and large coke but also the influence of the arrangement in the ore layer. is there.

  Therefore, using the reaction analysis simulator, the gasification reaction rate of small coke and large coke when the arrangement conditions of small coke and large coke are manipulated is evaluated, and the preferential reaction consumption and large mass of small coke are evaluated. The arrangement structure for coke reaction suppression was investigated.

  The reaction analysis simulator used for the evaluation is a general one with the function of analyzing the gas flow and reduction reaction, solution loss reaction, heat transfer behavior of the ore packed bed containing coke particles. , And the behavior of the mixed layer is analyzed in consideration of the generation and transfer of heat associated with the reaction after setting the geometrical arrangement of the mixed coke particles in the packed bed. It is an engineering general-purpose analysis method.

From the viewpoint that the gasification reaction of the mixed coke proceeds with the reduction of the ore, the introduced gas condition was set to CO / N ₂ = 39/61 mixed gas equivalent to Bosch gas.

  FIG. 3 is a diagram showing the relationship between the introduced gas temperature and the ore reduction rate in the reaction analysis simulator. As shown in FIG. 3, the introduction gas temperature was controlled according to the ore reduction rate, and the calculation was terminated when the ore reduction rate reached 90%.

  In addition, the calculation was performed assuming three types of packed beds assuming that the standard blast furnace operating condition is a superficial velocity of 41 m / min (converted to the standard state) and the amount of introduced gas.

  FIG. 4 is a diagram schematically showing a coke-ore mixing layer used in the reaction analysis simulator, where (a) shows a small coke placed in the upper layer and a large coke placed in the lower layer, and (b) shows the small coke. (C) is a case where small coke and large coke are uniformly mixed and arranged. FIG. 4 shows an ore packed bed containing coke particles. In (a), (b), and (c) of FIG. 4, ore is not present in a portion where no small or large coke is present. Filled.

  Here, the ore has a representative particle size of 20 mm and the composition is all FeO, the representative particle size of the small coke is 25 mm, and the mixing amount of the small coke is one-dimensional as described in Patent Document 1 described above. Based on the results of the blast furnace mathematical model, the coke solution loss reaction, the ore smelting reduction reaction, and the upper limit (50 kg / pt) that can be consumed by carburizing the hot metal, the particle size and quantity of the large coke are manipulated. The coke gasification reaction rate for each packed bed structure in the blast furnace solution loss reaction activation temperature range (1100 ° C. to 1300 ° C.) was calculated. In addition, since the method of arrange | positioning coke particle | grains to the ore layer space divided | segmented into the mesh has arbitraryity, multiple specific particle arrangements were set to the same conditions.

  FIG. 5 is a diagram illustrating the relationship between the reduction time, coke gasification reaction rate, and exhaust gas temperature obtained using a reaction analysis simulator. The mixed coke ratio is 120 kg / pt (small coke 50 kg / pt, large coke). 70 kg / pt) is a calculation example of a uniform mixed state (FIG. 4C) at a representative particle size of 75 mm of large coke. Paying attention to the reaction rate of coke shown on the vertical axis, it can be seen that the reaction rate of large coke is very small compared to the reaction rate of small coke, and the small coke is selectively consumed in the gasification reaction .

  FIG. 6 is a diagram showing the influence of the mixed coke ratio on the gasification reaction rate of small coke obtained using a reaction analysis simulator. In FIG. 6, the mixed coke ratio on the horizontal axis is displayed as “(small chunk + large chunk) coke mixing ratio” in comparison with the scale of the large chunk coke mixing ratio added to the upper side of the drawing. From the comparison of both scales, it can be seen that the small coke mixing ratio is 50 kg / pt.

  When small coke is placed on the upper part of the mixed layer (see FIG. 4 (a)), the small coke reaction rate tends to decrease as the coke mixing ratio (ie, mixed coke ratio) increases. Although shown, a high reaction rate is maintained as compared with the result of the lower arrangement (FIG. 4B) or the uniform mixing arrangement (FIG. 4C). From this result, it is understood that the effect as a reducing material can be maximized by arranging the small coke at the upper part of the mixed layer. In addition, the gasification reaction rate of small coke is high and the amount of reaction is large, which means that the effect of suppressing the deterioration of coke in the coke slit is also large, and in order to keep the coke slit healthy, it is small. It is desirable to place the mass coke at the top of the mixed layer.

FIG. 7 is a diagram showing the relationship between the large coke reaction rate and the large coke representative particle size obtained using the reaction analysis simulator.
By taking a large block coke representative particle size, it is possible to suppress its own gasification reaction. Furthermore, it can be seen that placing the large coke at the bottom of the mixed layer (see FIG. 4A) is effective in suppressing reaction deterioration of the large coke.

  From the above, placing the small coke at the top of the mixing layer and placing the large coke at the bottom of the mixing layer maximizes the reduction efficiency improvement effect of the small coke and at the same time The reaction deterioration of coke can be suppressed as much as possible, and the effect of improving air permeability by large coke can be maximized.

  In the blast furnace operating method of the present invention, the ore charging batch is divided into two, the first charging batch is mixed with large coke, the second charging batch is mixed with small coke, the first batch, The charging in the order of the second batch is based on the results of the test. By charging in this order, the small coke is placed at the top of the mixed layer and the large coke is placed at the bottom of the mixed layer, and the above-described reduction efficiency improvement effect and air permeability improvement effect are maximized. It becomes possible.

  Furthermore, in the method of operating a blast furnace according to the present invention, it is specified that a small amount of coke is mixed with the second charging batch at a maximum of 50 kg / pt. This is described in Patent Document 1 as described above. The upper limit is taken.

  The amount and particle size of coke that can be actually mixed are determined according to the coke particle size distribution in the actual blast furnace.

  FIG. 8 is a diagram in which the conditions of the present invention are superimposed on an example of a coke particle size distribution diagram. In the coke particle size distribution schematically shown by the broken line connecting the actual measurement points (circles) in the figure, the coke ratio is assumed to be 350 kg / pt (the coke in this case is mixed coke + slit coke). In addition, assuming that the ore average particle size is 20 mm, it is recognized from FIG. 2 that large coke having a particle size ratio of 3 to 4 is suitable for improving air permeability. The appropriate particle size of 60 to 80 mm (20 mm × 3 to 20 mm × 4).

  From FIG. 8, large coke can ensure approximately 100 kg / pt in a particle diameter range of 65 to 100 mm including most of the appropriate particle diameter, and the small coke depends on the particle size distribution of the charged coke. It can be considered that the upper limit of 50 kg / pt can be secured within a particle size range of 15 to 35 mm. That is, it is possible to extract the upper limit appropriate amount of mixed coke (100 kg / pt for large coke and 50 kg / pt for small coke) in an appropriate particle size range from coke normally used in the current blast furnace. I understand that.

In operation the method of the blast furnace of the present invention, the particle size of the large lump coke and 65～100Mm, to on purpose form of embodiment to 15~35mm the particle size of the small lump coke, as described above, respectively particle size By setting the amount within this range, it is possible to maximize the air permeability improvement effect and reduction efficiency improvement effect by mixing up to the upper limit appropriate amount for both large coke and small coke. . The particle size range may be satisfied by either one of the large coke and the small coke, and a corresponding effect can be expected.

  In the operation method of the blast furnace of the present invention, the charging of the first batch and the second batch is performed such that the large coke and the small coke mixed in the batch coexist in the radial direction of the furnace. Embodiments are desirable.

  By forming a mixed layer in which the small coke is at the top of the mixed layer and the large coke is at the bottom of the mixed layer, both the large coke and the small coke coexist, and the reduction efficiency improvement effect by the small coke is maximized. As shown in FIG. 6 and FIG. 7, the effect of improving the air permeability by the large coke can be maximized at the same time as shown in FIG. 6 and FIG. 7, but such a mixed layer is formed in the radial direction in the furnace. If it is possible, the effect can be exerted on the entire furnace.

  In order to form a mixed layer in which the small coke is at the top of the mixed layer and the large coke is at the bottom of the mixed layer, the small block coke and the large block coke are mixed into the ore batch divided into two parts, as described above. The ore batch mixed with the large coke may be charged first, and the ore batch mixed with the small coke may be charged later.

  In order to make small coke and large coke coexist in the radial direction of the furnace, it is conceivable to control the coke deposition position in the radial direction of the furnace by suppressing the segregation of coke grain size on the slope. For this purpose, for example, coke is separately charged first to form a flat in-furnace raw material distribution so that segregation of coke particle size on the slope does not occur as much as possible. The ore batch mixed with the small coke is finally charged so as to be uniform in the radial direction of the furnace.

  As described above, according to the operation method of the blast furnace of the present invention, the effect of improving the air permeability and the effect of improving the reduction efficiency of the ore by forming the mixed layer of coke and ore can be maximized. As a result, the air permeability and reduction efficiency of the lower part of the blast furnace can be improved, and the operation can be performed stably and with high reduction efficiency.

  In order to confirm the effect of the present invention, verification calculation was performed using a blast furnace total simulator that takes into account the reaction, flow, and heat transfer in the blast furnace.

As calculation conditions, assuming a blast furnace with an internal volume of 2700 m ³ , a conventional operation with a mixed coke ratio of 20 kg / pt (Comparative Example 1), a small coke (50 kg / pt) and a large coke (100 kg / pt) The operation to be mixed and charged in one ore batch (Comparative Example 2), and the small block coke (50 kg / pt) and the large block coke (100 kg / pt) were mixed in two ore divided batches. The operation (example of the present invention) was set so that lump coke was present in the upper part of the mixed layer and large coke was present in the lower part of the mixed layer.

  Further, in the calculation of Comparative Example 2 and the present invention example, all ores in the furnace are mixed with small coke and large coke so that the effect of improving the air permeability and reduction efficiency by forming the mixed layer is maximized. Assumed to form. It should be noted that the blast volume, oxygen enrichment rate, blast temperature, blast moisture, and pulverized coal injection volume are the common calculation preconditions, and the mass ratio of coke and ore is manipulated so that the hot metal temperature is the same in all calculation results. Calculated.

Table 2 shows the calculation results. In Table 2, the “gas utilization rate” is the CO gas utilization rate represented by the following formula (3), and it can be judged whether ore reduction efficiency is good.
CO gas utilization rate = {CO ₂ / (CO ₂ + CO)} × 100 (3)
The “PC ratio” is the amount of pulverized coal blown from the tuyere converted per ton of pig iron.

  In Comparative Example 2 and Example of the present invention in which the mixed coke ratio was increased to 150 kg / pt (small coke 50 kg / pt, large coke 100 kg / pt), the pressure loss was significantly reduced as compared with Comparative Example 1. It was seen. In the present invention example, not only the pressure loss was reduced, but also the gas utilization rate was greatly increased.

  As a result of the above-mentioned verification by the blast furnace total simulator, it was found that the operation method of the blast furnace of the present invention greatly contributes to the improvement of the air permeability in the furnace even in consideration of the possibility of the deterioration of the air permeability due to the reduction of the coke slit amount. It was. Moreover, it was confirmed that by forming a mixed layer of coke and ore in which small coke and large coke coexist, a great improvement effect can be obtained in both the air permeability in the furnace and the reduction efficiency of the ore.

  According to the method for operating a blast furnace of the present invention, by forming a mixed layer of coke and ore, it is possible to perform an operation that improves both the air permeability in the furnace and the reduction efficiency of the ore. Therefore, the present invention can be effectively used for blast furnace operation.

1: vertical electric furnace, 2: graphite crucible, 3: charge sample,
4: reducing gas, 5: graphite heating element, 6: load control device,
7: Temperature measuring device, 8: Gas pressure measuring device, 9: Drip sample pan,
10: Gas flow control device, 11: Exhaust gas, 12: Exhaust gas analyzer

Claims (2)

When charging ore and coke from the top of the blast furnace into the blast furnace so as to form alternate layers,
The ore charging batch is divided into two, and the first charging batch is mixed with 70-100 kg / pt of lump coke,
Mix a maximum of 50kg / pt of small coke into the second charging batch,
The first batch is charged in the order of the second batch ,
The particle size of the large coke is 65-100 mm,
A method for operating a blast furnace, wherein a particle size of the small coke is 15 to 35 mm . The charging of the first batch and the second batch is performed so that the large coke and the small coke mixed in the batch coexist vertically in the radial direction in the furnace. Blast furnace operation method.