JP5012138B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to improvement of furnace air permeability and hot metal components during blast furnace mass injection operation, and specifically suppresses an increase in blast furnace ventilation resistance, lowers the furnace gas temperature, The present invention relates to a blast furnace operation method that reduces the heat load of the hot metal and realizes reduction of the Si content and the S content in the hot metal.

  Conventionally, as the blast furnace charge, an ore charge as an iron source and coke as a reducing material are charged into the furnace from the top of the furnace, respectively. Ore charges are roughly classified into sintered ores, massive ores and pellets. The lump ore has a particle size that can be charged directly into the blast furnace, and the sintered ore and agglomerate the powdered ore by agglomeration and calcination to process it into a particle size that can be charged into the blast furnace. It is generally called agglomerate. These ore charges are selected according to the operating conditions of each blast furnace, but in general, sintered ore is processed such as blending raw ores and adjusting secondary raw materials so as to satisfy the required properties. Is used as the main iron source charge because the quality can be kept relatively constant.

  On the other hand, for reducing materials, instead of coke, pulverized coal, which is pulverized by low-cost coal, is blown from the tuyeres at the bottom of the blast furnace and used in recent years. As the number of coke increased significantly, the amount of coke used decreased gradually. In such pulverized coal injection operation, pulverized coal injected from the blast furnace tuyere instead of some coke burns in the blast furnace, and a high calorific value is obtained, so a large amount of high temperature reducing gas is generated. Thus, the furnace heat of the blast furnace can be increased, and an efficient reduction reaction of the ore charges can be advanced.

  In addition, when a large amount of pulverized coal is injected in the above pulverized coal injection operation, the heat flow ratio (ratio of the heat capacity of the solid to the heat capacity of the gas), which is an index of the heat reduction efficiency in the blast furnace block, decreases. Since the heating reduction margin is generated, the height position of the cohesive zone (the region from the start of softening and melting of the ore charge until the completion of dripping) increases in the furnace. When the height position of the cohesive zone rises, the furnace top gas temperature discharged from the upper part of the blast furnace rises, and there is a risk that the equipment may be damaged due to an increase in the heat load on the furnace top equipment.

Moreover, the Si content in hot metal increases with an increase in the amount of pulverized coal used. The reason for this is that a transfer reaction of Si into the hot metal represented by the following formulas (1) and (2) occurs. That is, at the tuyere tip raceway, as expressed by the equation (1), SiO ₂ in the pulverized coal is reduced by the red hot coke (C) to generate SiO gas, and the SiO gas and the molten iron are in contact with each other. Then, the reaction represented by the formula (2) is caused with C in the hot metal, and SiO is reduced and transferred to the hot metal as Si. When the height position of the cohesive zone rises, the dripping distance becomes longer and the contact frequency between the liquid hot metal particles and the SiO gas increases, so the frequency of occurrence of equation (2) increases and the Si content in the hot metal increases. Because it becomes a tendency.

SiO ₂ + C = SiO (g) + CO (g) (1)
SiO (g) + C = Si + CO (g) (2)
The increase in the Si content in the hot metal indicates that a large amount of heat is consumed to reduce SiO ₂ in the blast furnace, and the reducing material ratio (the amount of reducing material used per ton (t) of hot metal (kg )) Rises, that is, the operating cost deteriorates. In addition, the increase in the Si content in the hot metal leads to an increase in the amount of the desiliconizing agent and the dephosphorizing agent used in the hot metal pretreatment process, leading to an increase in the hot metal treatment cost. preferable. For the above reasons, in the operation of blowing a large amount of pulverized coal, it is important to prevent the rise of the furnace top gas temperature and to reduce the Si content in the hot metal in order to protect the furnace top equipment.

  Conventionally, as a technique for dealing with the above problems, from the viewpoint of suppressing an increase in the furnace top temperature, the methods described in Patent Document 1 and Patent Document 2 are known, and the viewpoint of reducing the Si content in hot metal Are known from the methods described in Patent Document 3, Patent Document 4 and Patent Document 5.

Patent Document 1 discloses a method of lowering the furnace top temperature by utilizing a decomposition reaction of crystal water by charging a high crystal water ore during a large amount of pulverized coal injection operation. However, in general, the high crystal water ore generates many pores when the crystal water is decomposed, so that the high temperature strength is weak, a large amount of powder is generated in the blast furnace, and the air permeability in the furnace is deteriorated. In recent years, the quality of iron ore has deteriorated and the SiO ₂ content in the ore has increased. Under such circumstances, increasing the charging amount of the high crystalline hydrous ore having a high SiO ₂ content not only increases the amount of slag in the furnace and deteriorates the air permeability of the blast furnace, but also increases the heat of slag formation and Due to the increase in the amount of heat required due to heat, the reducing material ratio increases, leading to an increase in operating costs.

Patent Document 2 discloses a method of controlling the amount of auxiliary raw materials such as dolomite by using the blast furnace top gas temperature as an index, and controlling the slag basicity, the MgO concentration, and the S content in the hot metal. . This method has a problem that the slag basicity is changed by charging an auxiliary material such as dolomite. The slag basicity is a numerical value divided by CaO mass% SiO ₂ mass% in the slag component, and affects the melting point, viscosity, desulfurization ability, etc. of the blast furnace slag.

  Therefore, slag basicity is designed from a comprehensive viewpoint including the stability of blast furnace operation and the cost of hot metal treatment. When the basicity fluctuates, the melting start temperature of the charged material changes in the blast furnace, so that the thickness of the fusion zone that causes the largest pressure loss in the furnace increases, and the furnace condition becomes unstable. In addition, the hot metal component may fluctuate, resulting in an increase in processing cost in the hot metal pretreatment process.

Therefore, it is preferable that the slag basicity keeps the design value in each blast furnace operation and does not vary as much as possible. If the basicity is to be kept constant when charging dolomite, etc., the amount of slag in the blast furnace is required because SiO ₂ source auxiliary materials such as serpentine and quartzite must be charged in accordance with the dolomite charging. Increases and the air permeability of the blast furnace deteriorates. In addition, when the blast furnace basicity is adjusted by adjusting the basicity of the sintered ore, it is necessary to reduce the CaO content in the sintered ore. As a result, the cost of the sintering operation increases.

  The invention described in Patent Document 3 is a method that can reduce the Si and S content in hot metal by mixing auxiliary materials such as dolomite, serpentine, and limestone in the coke layer around the furnace. Also in this method, the amount of slag tends to increase by adjusting the basicity as in the case of the above-described invention, which adversely affects the blast furnace condition.

  In addition, as a method for reducing the Si content in hot metal, Patent Document 4 discloses that a plurality of types of ores having different basicities are charged at different positions in the furnace radial direction, and the base of the charge in the furnace radial direction is used. A blast furnace operating method is disclosed in which the temperature distribution is controlled in correspondence with the radial furnace temperature distribution at the tuyere level to control the Si content in the hot metal. However, in this method, since the slagging agent is charged in the entire blast furnace radial direction, the slagging agent remains in the core coke, thereby deteriorating the breathability of the furnace core, and the slagging agent is added to the raceway. Since it is also supplied to other areas, the addition efficiency of the slagging agent is reduced.

And the method disclosed by patent document 5 blows in a stalking agent flux which consists of 1 or more types among FeO, CaO, and MgO with pulverized coal from a tuyere, and reduces the amount of generated SiO gas. This is a method of reducing the Si content in the hot metal by suppressing it. Since this method is a method of reducing the temperature before the tuyere, there is a risk of leading to a major accident such as cooling in the furnace. In addition, in order to prevent inactivation of the furnace core, it is necessary to simultaneously add SiO ₂ or the like, so that the amount of slag in the blast furnace increases, the air permeability in the furnace deteriorates, and the furnace condition tends to deteriorate. .

JP 2001-140007 (Claims, paragraphs [0009] and [0010]) Japanese Patent Laid-Open No. 61-261407 (Claims and upper left column, lines 5 to 15 on page 2) JP-A-5-311217 (Claims and paragraphs [0013] to [0015]) JP-A-58-0661204 (Claims and upper left column, pages 14 to 19 on page 2) JP 2003-183711 A (claims and paragraphs [0015] to [0018])

The above prior art has the following problems. That is, as a secondary raw material for reducing the Si content in the hot metal, raw materials containing a large amount of CaO or SiO ₂ components such as dolomite and serpentine, and carbonate-based materials that generate CO ₂ gas by thermal decomposition like magnesite There was a problem with using raw materials. When an auxiliary material containing a CaO or SiO ₂ component is used, the basicity of the blast furnace slag varies. Therefore, in order to readjust the basicity, it is necessary to add an additional raw material. As a result, the amount of blast furnace slag increases, the air permeability of the blast furnace deteriorates, and the furnace condition of the blast furnace becomes unstable.

Carbonate such as magnesite generates CO ₂ gas by thermal decomposition. In the upper part of the blast furnace, as indicated by the following formulas (3) and (4), the indirect reduction reaction of iron ore proceeds mainly by CO gas. Therefore, when CO ₂ gas is generated by thermal decomposition, the reducing ability of the gas is reduced, and the reduction reaction of iron ore is delayed. When the reduction reaction is delayed, the unreduced ore descends to the front of the tuyere and causes a direct reduction reaction represented by the following formula (5) before the tuyere. Since this reaction is a significant endothermic reaction, when the amount of direct reduction increases, the temperature in front of the tuyere decreases and the fluidity of the hot metal decreases, and the contact frequency between the tuyere and the hot metal increases, May cause tuyere damage.

3Fe ₂ O ₃ + CO → 2Fe ₃ O ₄ + CO ₂ (3)
Fe ₃ O ₄ + CO → 3FeO + CO ₂ (4)
FeO + C → Fe + CO (5)
As described above, the prior art has not been sufficient for the selection of the auxiliary material. As a result, the amount of slag in the blast furnace is increased, or CO ₂ gas is generated due to the thermal decomposition of the auxiliary material, resulting in a reduction in the reduction rate. It was easy to cause troubles in blast furnace operation.
The present invention has been made in order to solve the above-mentioned problems, and the problem is that a large amount of slag is generated without causing fluctuations in slag basicity in a blast furnace high-injection operation of pulverized coal. In spite of this, it is intended to provide a method for operating a blast furnace that can suppress the rise in the furnace top temperature and reduce the Si and S content in the hot metal. Another object of the present invention is to provide a method for operating a blast furnace that can protect the furnace top equipment and improve the hot metal treatment cost while suppressing deterioration of the air permeability of the blast furnace as a result of the above.

  In order to solve the above-mentioned problems, the present inventor studied an operation method capable of reducing the furnace top temperature while suppressing the deterioration of the air permeability of the blast furnace and reducing the Si content and the S content in the hot metal. The present invention was completed by obtaining the knowledge shown in (a) and (b).

  (A) The method of charging magnesium hydroxide ore from the top of the furnace is effective to lower the furnace top temperature while suppressing the deterioration of air permeability of the blast furnace and to reduce the Si content and S content in the hot metal. The reason is as follows.

1) Magnesium hydroxide ore is generally called brucite, the main mineral is Mg (OH) ₂ , MgO content is 50% by mass or more, and the slag basicity fluctuates even when charged in a blast furnace Therefore, it is not necessary to charge additional auxiliary materials for adjusting the basicity.

2) Magnesium hydroxide ore does not generate CO ₂ gas during the thermal decomposition process, so it does not affect the reduction reaction in the furnace, lowers the furnace top temperature, and lowers the Si content and S content in the hot metal. In that respect, it is superior to other by-products.

  Table 1 shows the decomposition reaction formula and endothermic reaction amount in the furnace of the main auxiliary materials used in the blast furnace.

From the same table, it can be seen that brucite has a large endothermic reaction amount per unit mass, so that the furnace top temperature can be lowered with a smaller charging amount than other auxiliary materials. In addition, since magnesium hydroxide ore does not generate CO ₂ gas during the thermal decomposition reaction, it is unlikely to hinder the indirect reduction reaction in the upper part of the blast furnace.

  (B) It is preferable to insert the magnesium hydroxide ore into the blast furnace interior at a position 0.4 to 1 times the furnace radius from the center of the furnace. The reason for this is that if the charging position is less than 0.4 times the furnace radius, unmelted auxiliary materials remain in the furnace core coke, the furnace core air permeability and liquid permeability deteriorate, and the raceway. This is because the effect of suppressing the generation of SiO gas and S gas that are frequently generated on the furnace wall side around the vicinity is reduced, and the effect of reducing the Si and S content in the hot metal is reduced.

  This invention is completed based on said knowledge, The summary exists in the operating method of the blast furnace shown to following (1)-(3).

  (1) The amount of pulverized coal injection is 100 kg or more per 1 ton (t) of hot metal (hereinafter also referred to as “100 kg / t-hot metal”), and the mass of ore in the ore charge is 30% by mass or less. In blast furnace operation, 5-30 kg / t-molten magnesium hydroxide ore is charged into the furnace from the top of the blast furnace furnace.

  (2) The magnesium hydroxide ore is a massive ore, and r is the radial distance in the furnace from the furnace center to the magnesium hydroxide ore charging position at the charge stock level, from the furnace center to the furnace wall. When the distance of R is R, the magnesium hydroxide ore is charged into the furnace so that the charging position satisfies the relationship represented by the following formula (1): ) Blast furnace operation method.

0.4 ≦ r / R ≦ 1 (1)
(3) the the SiO ₂ content to the said magnesium hydroxide ore with 4.5 mass% or more lump ore, wherein the mixing Sonyusu Turkey into the furnace from the blast furnace top (1) or (2 ) Blast furnace operation method.

  In the present invention, the “ore ore charge” means an iron source charge (main raw material) such as sintered ore, massive ore, pellets, briquettes and the like.

  In addition, the term “block ore” or “block ore” means an ore in which the ratio of the portion having a particle size of 5 mm or less is 20% by mass or less and the average particle size is 10 mm or more.

  According to the present invention, the rise in the furnace top temperature, which is a problem during a large amount of pulverized coal injection, is suppressed without causing fluctuations in the basicity of the blast furnace slag and without significantly increasing the amount of slag. Si and S content can be reduced. Furthermore, according to the present invention, as a result of the above, it is possible to realize the protection of the furnace top equipment and the improvement of the hot metal treatment cost while suppressing the deterioration of the air permeability of the blast furnace.

  As described above, in the blast furnace operation in which the pulverized coal injection amount is 100 (kg / t-molten metal) or more and the lump ore ratio in the ore charge is 30% by mass or less, A blast furnace operating method characterized in that a magnesium hydroxide ore of (kg / t-molten metal) is charged into the furnace from the top of the blast furnace furnace. The reason why the present invention is defined as described above and preferred embodiments will be described below.

1. Fig. 1 shows a blast furnace with a furnace volume of 2150 m ³ (the same applies below). The amount of pulverized coal injection is 130 kg / t-hot metal, and the feed ratio is around 1.9 t / d / m ^3. It is a figure which shows the relationship between the amount of blast furnace slag, and the change of pressure loss in a furnace at the time of operating on conditions with a sintered ore ratio of 80 mass% and a lump ore ratio of 20 mass%. The change in the pressure loss in the furnace on the vertical axis in the figure shows the amount of change from the value at the time of standard operation for the difference between the blowing pressure at the blast furnace tuyeres and the gas pressure at the top of the furnace, and the permeability of the packed bed in the furnace Represents changes. That is, the relationship between the blast furnace slag amount and the change in the furnace pressure loss is shown on the basis of the furnace pressure loss when the blast furnace slag amount is 275 (kg / t-molten metal). Therefore, an increase in the pressure loss change in the furnace means deterioration of the blast furnace air permeability with respect to the reference operation (that is, an increase in the blast furnace air resistance).

  As shown in the figure, when the amount of blast furnace slag increases, the amount of melt in the furnace increases, the gas flow path is narrowed, and air permeability deteriorates. In addition, since the amount of slag accumulated in the furnace between the tapping and the tapping increases, the buoyancy that the filling in the furnace receives from the tapping and tapping between the tapping and tapping increases. The porosity of the furnace filling decreases, resulting in fluctuations in gas flow and deterioration of air permeability.

  FIG. 2 is a diagram showing the relationship between the amount of auxiliary material charged and the change in the amount of blast furnace slag, obtained by blending calculation considering raw material components. The relationship in the figure shows a comparison of changes in the amount of blast furnace slag when each auxiliary material is charged so that the basicity of the blast furnace slag is constant. When dolomite or serpentine is charged, it is necessary to add other auxiliary materials to adjust the slag basicity. As a result, the total slag amount increases. On the other hand, since the magnesium hydroxide ore does not need to adjust the slag basicity when charging, the increase in the amount of slag is small.

  FIG. 3 shows the result of calculating the relationship between the charging amount of the auxiliary raw material and the amount of change in the blast furnace top gas temperature in consideration of the heat of reaction under the same operating conditions as shown in FIG. FIG. The temperature of the blast furnace top gas decreases due to the thermal decomposition of each auxiliary material, but the effect of lowering the blast furnace top temperature due to the thermal decomposition of the crystal water contained in the magnesium hydroxide ore is the effect of dolomite and serpentine Bigger than.

2. Appropriate range of magnesium hydroxide ore charge, pulverized coal injection amount and ratio of sintered ore It is appropriate that the magnesium hydroxide ore content in the furnace is 5-30 (kg / t-hot metal). is there.

FIG. 4 is a graph showing the relationship between the amount of magnesium hydroxide ore charged, the MgO content in the slag, and the change in furnace pressure loss when operating under the same operating conditions as shown in FIG. It is. The MgO content in the slag increases almost linearly as the amount of magnesium hydroxide ore is increased. In the range where the amount of magnesium hydroxide ore charged is within 30 (kg / t-molten metal), the amount of change in pressure loss in the furnace slightly increases due to the increase in the amount of slag as the magnesium hydroxide ore is charged (that is, the furnace The air permeability is slightly deteriorated), but the increase is small. Moreover, in order to obtain the charging effect of magnesium hydroxide ore, it is necessary to charge 5 kg / t or more from the relationship shown in FIG. 3 and FIGS. 5 and 6 described later.
On the other hand, when the amount of magnesium hydroxide ore is increased beyond 30 (kg / t-molten metal), the increase in the pressure loss change in the furnace becomes remarkable (that is, the deterioration of the air permeability in the furnace is remarkable). Becomes). This is because the melting point of the slag rises due to the increase in the MgO component in the slag, and the air permeability and liquid permeability in the blast furnace deteriorate due to the increase in the amount of residual slag in the furnace. According to the test conducted by the present inventor, if the MgO content in the slag is 10% by mass or less, the adverse effect due to the residual slag in the furnace is relatively small.

FIG. 5 shows the amount of charge when each of magnesium hydroxide ore, dolomite and serpentinite is charged as auxiliary materials when operating under the same conditions as those shown in FIG. It is a figure which shows the relationship with the change of Si content rate in hot metal. When magnesium hydroxide ore is charged, the activity of SiO _{2 in} the slag decreases, and as a result of suppressing the generation of SiO gas, the Si content in the hot metal decreases. Magnesium hydroxide ore has a large effect of reducing the Si content in the hot metal compared with other auxiliary materials even if the amount is the same.

  FIG. 6 shows the relationship between the amount of the auxiliary raw material charged and the change in the S content in the hot metal when operating under the same operating conditions as those shown in FIG. As seen in the figure, the introduction of the auxiliary material improves the absorption capacity of the S gas slag generated in front of the tuyere and decreases the S content in the hot metal. Magnesium hydroxide ore has a greater effect of reducing the S content in hot metal than other auxiliary materials.

  FIG. 7 shows the relationship between the charging amount of the auxiliary raw material and the change in pressure loss in the furnace when operated under the same operating conditions as those shown in FIG. Although the pressure drop change in the furnace increases with the increase in the amount of secondary raw material, the amount of increase in slag is smaller when magnesium hydroxide ore is charged than when dolomite or serpentine is charged. Therefore, the amount of increase in furnace pressure loss is small.

  The blast furnace operation method of the present invention is intended for blast furnace operation in which the pulverized coal injection amount is 100 (kg / t-molten metal) or more and the lump ore ratio is 30 mass% or less. In operations where the amount of pulverized coal injection is less than 100 (kg / t-molten metal), the furnace top gas temperature is low, the heat load on the furnace top equipment is small, and there is little need to lower the furnace top gas temperature. In addition, when the amount of pulverized coal injection is small, the operation of the blast furnace is stabilized and the furnace heat fluctuation is reduced, so that the Si content in the hot metal and the S content in the hot metal are easily stabilized at a low level. For the above reasons, the effect of applying the operation method of the present invention is small under the operation conditions where the amount of pulverized coal injection is less than 100 (kg / t-molten metal).

  Moreover, when the mass ore ratio exceeds 30 mass% and becomes high, the water | moisture content derived from an ore will increase and furnace top gas temperature will fall. In addition, when magnesium hydroxide ore is introduced in a state where the temperature inside the blast furnace is lowered due to an increase in the moisture in the ore, the temperature is further reduced, and the temperature rise and reduction of the iron ore is delayed, causing melting in the furnace. The deterioration of the blast furnace air permeability due to the enlargement of the banding and the fall of the unreduced ore before the blowing tuyere impedes the air permeability and liquid permeability and may cause tuyere damage. If a tuyere breaks down, the blast furnace must be stopped to replace the tuyere and the operating rate falls. As described above, when the lump ore ratio exceeds 30% by mass, the effect of applying the operation method of the present invention is reduced. Therefore, in the present invention, the lump ore ratio is set to 30% or less.

3. The position of the magnesium hydroxide ore entering the blast furnace interior The position of the magnesium hydroxide ore entering the blast furnace interior is 0.4 to 1 times the furnace radius from the center of the furnace, that is, the relationship expressed by the above formula (1) is satisfied. It is preferable to charge the position.

  The reason for this is that when the charging position is less than 0.4 times the furnace radius from the furnace center, unmelted auxiliary materials remain in the furnace core coke, and the air permeability and liquid permeability of the furnace core deteriorate. This is because the effect of suppressing the generation of SiO gas and S gas that are frequently generated on the furnace wall side around the vicinity of the raceway is reduced, and the effect of reducing the Si and S content in the hot metal is reduced.

  In order to further improve the air permeability in the furnace, the magnesium hydroxide ore to be charged is preferably a massive ore. In the present invention, the term “block ore” or “block ore” means an ore in which the ratio of the portion having a particle size of 5 mm or less is 20% by mass or less and the average particle size is 10 mm or more.

FIG. 8 is a diagram showing the relationship between the charging position of the auxiliary raw material in the furnace radial direction, the change in pressure loss in the furnace and the change in the Si content in the hot metal, and FIG. The relationship between the charging position and the change in furnace pressure loss is shown, and FIG. 5B shows the relationship between the charging position of the auxiliary material in the furnace radial direction and the change in the Si content in the hot metal. The result of the figure shows that the pressure loss in the furnace when the test was performed to change the charging position in the blast furnace under the condition that the charging amount of magnesium hydroxide ore was constant in a blast furnace with a furnace volume of 2150 m ³ . The change and the change of Si content in hot metal are shown.

  From the results shown in the figure, it can be confirmed that the pressure loss in the furnace increases as the charging position shifts to the center side, and the amount of decrease in the Si content in the hot metal also decreases. In particular, when the battery is inserted into a region on the center side within 0.4 times the furnace radius from the center, the amount of change in pressure loss in the furnace significantly increases. Therefore, it is preferable to insert the magnesium hydroxide ore into the furnace interior at a position 0.4 to 1 times the furnace radius from the furnace center, that is, at a position satisfying the relationship of the expression (1).

4). Mixing and charging with lump ore with SiO ₂ content of 4.5% by mass or more When magnesium hydroxide ore is mixed with lump ore with SiO ₂ content of 4.5% by mass or more and charged, Si in hot metal This is preferable because not only the increase in the content rate but also the deterioration of the blast furnace air permeability can be suppressed.

Among existing lump ores, most lump ores having a SiO ₂ content of 4.5% by mass or more exist as high crystal hydrous ores. High crystal hydrous iron ore is generally pulverized in the furnace due to cracking or strength reduction when the crystal water is released from the upper part of the blast furnace, and impairs the air permeability in the furnace. As a result, the reduction is delayed, and the unreduced FeO reacts with CaO or SiO ₂ to form a low melting point compound. When this low-melting-point compound is produced, the cohesive zone in the furnace is enlarged, and the lower part air permeability is deteriorated.

On the other hand, when magnesium hydroxide ore is mixed with high-crystal water block ore having a SiO ₂ content of 4.5% by mass or more and charged into the furnace, magnesium hydroxide is thermally decomposed. The produced MgO is dissolved in the unreduced FeO to form a high melting point compound. By producing this high melting point compound, softening and melting of the lump ore at a low temperature is prevented, and enlargement of the cohesive zone is prevented. Moreover, since the melting point of the lump ore is raised, it is possible to proceed the gas reduction up to the high temperature region at the bottom of the furnace. As a result, the ultimate reduction rate due to gas reduction is improved, and the ratio of the direct reduction reaction, that is, the endothermic reaction, occupying the reduction reaction in the furnace is reduced, so that the endothermic amount is reduced. In addition, since the melting point of MgO itself is very high, it is possible to maintain a relatively high interparticle porosity even in the fusion layer, and to ensure good air permeability even in the fusion zone having the lowest air permeability in the furnace. it can.

FIG. 9 shows the relationship between the use ratio of high-crystal water iron ore with a SiO ₂ content of 4.5% by mass or more and the change in pressure loss in the furnace. It is a figure shown in comparison with the case of use. From the results in the figure, it can be confirmed that when the magnesium hydroxide ore is mixed and used, the increase in pressure loss in the furnace is small. Therefore, it is preferable to use magnesium hydroxide ore because a large amount of massive iron ore having a SiO ₂ content of 4.5% by mass or more can be charged without deteriorating the blast furnace condition.

  In order to confirm the effect of the blast furnace operation method of the present invention, the following test operation was performed and the effect was confirmed.

1. Example 1
Furnace volume: 2150 m ³ , pulverized coal injection amount: 135 kg / t-hot metal, sintered ore ratio: 80 mass%, lump ore ratio: 20 mass%, tapping ratio: 1.92 t / d / m ³ A pilot operation was conducted in the blast furnace where the operation was conducted. Table 2 shows the test results such as the charging amount of the auxiliary raw materials as the test conditions, the slag amount change, the furnace pressure loss change, the furnace top temperature change, and the Si and S content in the hot metal.

  Test No. 1 is a test for an example of the present invention in which magnesium hydroxide ore is charged as an auxiliary material and satisfies the conditions specified in the present invention. Test No. 2 is dolomite as an auxiliary material, and the test number. 3 is a test for a comparative example in which serpentine is inserted as an auxiliary material. In each test, the charging amount of the secondary raw material was 15 (kg / t-hot metal), and the charging position in the blast furnace was 0.7 to 0.8 in the dimensionless position (r / R) in the radial direction of the furnace. The position of the range. In addition, magnesium hydroxide ore having a weighted average particle diameter of 14 mm and a ratio of 5 mm or less of 7% by mass was used.

  In Test No. 1, which is a test of the present invention example, the use of magnesium hydroxide ore decreases both the furnace top temperature, the Si content in the hot metal and the S content in the hot metal, thereby protecting the furnace top equipment and the hot metal treatment cost. It was possible to reduce. Moreover, although the pressure loss in the furnace slightly increased, the effect on the air permeability in the blast furnace was small.

  On the other hand, in Test No. 2 and Test No. 3 of the comparative example, although the amount of dolomite and serpentine is the same as that of Test No. 1 of the present invention example, the amount of increase in the amount of blast furnace slag is As a result, the pressure loss in the furnace increased significantly, and the effect on the deterioration of the air permeability in the furnace became large. In addition, the amount of decrease in the Si content in the hot metal and the S content in the hot metal was less than that in Test No. 1.

2. Example 2
Furnace volume: 2150 m ³ , pulverized coal injection amount: 100 kg / t-hot metal, sintered ore ratio: 75 mass%, lump ore ratio: 25 mass%, tapping ratio: 2.00 t / d / m ³ A pilot operation was conducted in the blast furnace where the operation was conducted. Table 3 shows the test conditions such as the charge amount of the auxiliary material and the use ratio of the high-crystal water ore, and the test results such as changes in the furnace pressure loss and changes in the Si and S contents in the hot metal.

Test No. 4 is a test for the example of the present invention that satisfies the conditions according to claim 3 in which magnesium hydroxide ore is charged as an auxiliary material in using the high crystalline hydrous ore. This is a test for a comparative example in which no auxiliary material was charged. As the high crystalline hydrous ore, the SiO ₂ content is 5.1 mass%, the weighted average particle diameter is 15 mm, and the ratio of 5 mm or less is 8 mass%. Used as a percentage. The magnesium hydroxide ore used had a weighted average particle diameter of 12 mm and a ratio of 5 mm or less of 8% by mass, and the charging amount was 15 (kg / t-hot metal). Further, the charging position of the magnesium hydroxide ore in the blast furnace was a dimensionless position (r / R) in the radial direction of the furnace, which was 0.6 to 0.7.

  In the test number 4 of the present invention example in which the magnesium hydroxide ore and the high crystal hydrous iron ore were mixed and charged, the increase in the pressure loss in the furnace was extremely small compared to the test number 5 of the comparative example, and the air permeability of the blast furnace High crystal hydrous ore could be used with almost no deterioration. Further, both the Si content in the hot metal and the S content in the hot metal decreased, and the total operating cost in the iron making and hot metal treatment processes could be reduced.

  According to the present invention, the rise in the top temperature of the blast furnace slag, which does not cause a fluctuation in blast furnace slag basicity and is accompanied by a significant increase in the amount of slag, is suppressed during the operation of injecting a large amount of pulverized coal. Medium Si and S content can be reduced. Therefore, the present invention provides a steelmaking and hot metal treatment process as a method of operating a blast furnace capable of protecting the furnace top equipment and improving the hot metal treatment cost while suppressing deterioration in blast furnace air permeability associated with a large amount of pulverized coal injection operation. The technology is widely applicable.

It is a figure which shows the relationship between the amount of blast furnace slag, and the change of furnace pressure loss. It is a figure which shows the relationship between the charging amount of an auxiliary material, and the change of the amount of blast furnace slag. It is a figure which shows the relationship between the charging amount of an auxiliary material, and the variation | change_quantity of blast furnace top gas temperature. It is a figure which shows the relationship of the charging amount of magnesium hydroxide ore, the relationship between the MgO content rate in slag, and the change of furnace pressure loss. It is a figure which shows the relationship between the charging amount of an auxiliary material, and the change of Si content rate in hot metal. It is a figure which shows the relationship between the charging amount of an auxiliary material, and the change of S content rate in hot metal. It is a figure which shows the relationship between the charging amount of an auxiliary material, and the change of the furnace pressure loss. It is a figure which shows the relationship between the radial charging position in the furnace of an auxiliary raw material, the change of the furnace pressure loss, and the change of Si content rate in a hot metal, The figure (a) is the radial charging position of the auxiliary raw material in the furnace. The relationship with the change in the furnace pressure loss is shown, and FIG. 4B shows the relationship between the charging position of the auxiliary material in the furnace radial direction and the change in the Si content in the hot metal. It is a figure which shows the relationship between the use ratio of a high-crystal water iron ore, and the change of the pressure loss in a furnace in the case of using a high-crystal water iron ore alone and the case of using a magnesium hydroxide ore mixed use.

Claims (3)

  In blast furnace operation in which the amount of pulverized coal injection is 100 kg or more per 1 ton (t) of hot metal and the mass of ore in the ore charge is 30% by mass or less, 5 to 30 kg of water per 1 ton (t) of hot metal A method of operating a blast furnace, characterized in that magnesium oxide ore is charged into the furnace from the top of the blast furnace. The magnesium hydroxide ore is a massive ore, and the distance from the center of the furnace to the charging position of the magnesium hydroxide ore at the stock level of the charge is r, and the distance from the furnace center to the furnace wall is The said magnesium hydroxide ore is charged in a furnace so that the charging position may satisfy the relationship represented by the following formula (1) when R is set. Blast furnace operation method.
0.4 ≦ r / R ≦ 1 (1) Blast furnace operation according to claim 1 or 2 SiO ₂ content to the said magnesium hydroxide ore with 4.5 mass% or more lump ore, wherein the mixing Sonyusu Turkey into the furnace from the blast furnace top Method.

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