JP5549227B2 - Method for producing pre-reduced sintered ore and blast furnace operating method using the same - Google Patents

Description

  The present invention relates to a method for producing a pre-reduced sintered ore in which a high-temperature crushed sintered cake is pre-reduced with a high-temperature gas in a production process of iron ore sintered ore. Further, the present invention relates to a method for operating a blast furnace that uses this pre-reduced sintered ore and that can reduce the reducing material ratio and improve productivity.

1. Blast Furnace Method FIG. 1 is a schematic diagram showing a system configuration of a blast furnace method. In pig iron production, from the viewpoint of energy consumption, productivity and production scale, the so-called “blast furnace method” using a sintering machine, a coke oven and a blast furnace is widely used in Japan. As shown in FIG. 1, in the blast furnace method, first, a blended raw material in which fine iron ore as an iron source, limestone as a solvent, and fine coke as a heat source are mixed is baked by a great furnace type sintering machine. The sintered sintered cake is crushed and sized to produce a massive sintered ore. On the other hand, using a coke oven, caking coal is dry-distilled at 1050 ° C. in a room furnace to produce massive coke. And pig iron can be obtained through a reduction / melting reaction by charging sintered iron as an iron source and coke as a heat source and a reducing material into a blast furnace.

  Since productivity in blast furnace operation is largely controlled by the air permeability in the furnace, an iron source and a reducing material having a larger particle size and strength are desired so as not to lower the air permeability. Therefore, when using the powdered iron ore, it is not charged in the blast furnace as it is, but in order to agglomerate in advance, it is charged as a sintered ore after being subjected to a sintering treatment as described above.

  On the other hand, when using coal, instead of charging low-strength coal into the blast furnace as it is, in order to increase the strength in advance, it is subjected to dry distillation melting treatment as described above to be coke, and then charged as a reducing agent. ing.

  Of course, the processing of these iron sources and reducing materials requires large energy consumption and equipment. However, the entire iron making process including the blast furnace is widely recognized as the best pig iron production method because of its extremely low energy consumption and production cost.

  The reason why the blast furnace method is so efficient is that the logistics as processes are mutually complemented. For example, a coke cake produced in the coke production process is crushed to generate a lump and a powder. A lump is used in a blast furnace, and a powder is used as a sintered fuel. Further, dusts generated in the blast furnace and the coke oven are collected and used as a sintering raw material and a sintering fuel.

2. Technology for Counteracting the Blast Furnace Method Now, as a pig iron manufacturing technology against such a blast furnace method, natural gas is used as a reducing material, pellet ore and block iron ore are reduced in a shaft furnace, and the resulting reduced iron is briquetted at high temperature. There is a method of making HBI (hot briquette iron). This method is characterized in that coke is not used, and a raw material other than coke must be used as a raw material for forming voids for ensuring air permeability in the shaft furnace. Therefore, powdered iron ore cannot be used directly. Not only that, it is important to manage the state of reduced pulverization, where iron ore, whose strength has decreased during the reduction process, breaks down and generates powder, and it is difficult to use sintered ore with poor reduced pulverization properties. Has been. Of course, since it reduces only with natural gas, it is characterized by extremely large energy consumption.

  There is also a pig iron production method that uses coal as a reducing material. In this method, a mixed raw material of fine iron ore and coal is heated and reduced in a rotary kiln furnace or a rotary hearth furnace, and the resulting reduced iron is converted into briquette HBI at a high temperature. In this method, the iron ore is not reduced by the reducing gas that is vented into the furnace, but the reaction principle is to reduce the solid carbon derived from the added coal inside the high-temperature heating furnace. This method always requires solid carbon, and has low thermal efficiency. Therefore, the energy intensity and cost are high, and there are many problems as a method for mass production of pig iron.

  In addition, an iron source is charged into the melting furnace, pulverized coal and oxygen (air) are blown into a molten state, rapidly reduced to produce pig iron, and iron ore is produced with the reducing gas generated at that time. There is a method in which reduced iron is used as the iron source to be reduced and charged into the melting furnace. This method also uses powdered iron ore and coal directly and does not use coke, so it is difficult to ensure air permeability, and has not achieved more results than the blast furnace method in terms of energy intensity and cost.

3. In recent years, due to the global warming problem, there has been a demand for suppression of carbon dioxide generation, especially in the pig iron production process where a large amount of carbon dioxide is generated. Conventionally, energy consumption and manufacturing cost have been the basis of process adoption evaluation, but the concept of carbon dioxide generation is becoming more important.

Generally, iron oxide ore (main component Fe ₂ O ₃ ) is widely used as an iron source for pig iron production. As a material (reducing material) for deoxidizing (reducing) iron ore, coal, natural gas, or the like is used. In order to increase the reaction efficiency of reduction, it is not used directly, but processing of iron sources such as sintered ore, pellet ore, reduced iron, processing of reducing materials separated by dry distillation into coke and coke oven gas, and gas As a matter of course, a device for improving the efficiency by modifying the composition has been made.

  The elements constituting the reducing material are mainly C and H. Needless to say, if a reducing material having a low C component content and a high H component content is used, it is advantageous for suppressing the generation of carbon dioxide. In this respect, in order to suppress the generation of carbon dioxide gas, natural gas or coke oven gas having a high H component content is preferable as a reducing material, and use of coal, particularly coke mainly composed of carbon is not preferable. However, in the method of circulating the reducing gas in the furnace, in order to ensure productivity, reducing the amount of coke that is a ventilation spacer is accompanied by great difficulty in terms of ensuring this ventilation. .

  In addition, from the viewpoint of ensuring air permeability, it is strongly desired that the charge as the iron source is in a lump shape and not reduced powder.

  Based on the above concept, Patent Document 1 discloses a technique for reducing coke intensity by using coke as the main reducing material and using high-strength reduced iron HBI as part of the iron source.

  Non-Patent Document 1 discloses a technique for reducing the amount of coke used by blowing natural gas or coke oven gas into a blast furnace.

4). Problems of reduced iron HBI The method of using reduced iron HBI as an iron source for blast furnace operation is a technique that can reduce the amount of coke that is a reducing material in blast furnace operation. However, when producing reduced iron HBI, there is a problem that the reduction efficiency is lower than that of a blast furnace, the reducing material is consumed greatly, and the amount of carbon dioxide generated in the total production of pig iron is not suppressed. In this regard, Non-Patent Document 2 considers that it is advantageous to use prereduced iron (partially reduced iron) in a blast furnace rather than reduced iron with a high metalization rate.

JP 09-013109 A

Hiroo Nishio, Tsuneo Miyashita, Iron and Steel, Vol. 59 no. 12 P.M. 1506-1522 (1973) Kazuya Kunitomo, Masaaki Naito, Gakushin 54 Committee-2352 (2005.6.23)

  However, Non-Patent Document 2 is a paper intended to use a partially reduced ore obtained by reducing fine iron ore with natural gas, and does not mention the production of a pre-reduction briquette having a strength that can withstand blast furnace operation.

  In the case of pellet ore or block iron ore, there is little reduction pulverization, and it is possible to obtain a block preliminary reduction ore by sieve classification. However, when sintered ore is used as a target, there is a problem that the reduction powdering is intense and the yield is extremely low in order to obtain a massive preliminary reduced ore. For this reason, agglomeration of prereduced ore has become a major issue.

  Pellet or block iron ore has a low CaO content, and the constituent minerals are mainly hematite, magnetite, and silicate. On the other hand, the sintered ore has a high CaO content, and the constituent mineral is mainly calcium ferrite. Calcium ferrite, unlike silicates, has a high reducibility, but has the property of being easily reduced to powder. For this reason, a sintered cake is easy to reduce powder compared with a pellet ore and block iron ore.

Further, CO gas reduction is an exothermic reaction, whereas H ₂ gas reduction is an endothermic reaction. Therefore, when H ₂ rich gas obtained by reforming natural gas or coke oven gas is directly blown into the blast furnace, there is a problem that the temperature inside the blast furnace is lowered and the operation is deteriorated due to reaction inactivation.

  Coke oven gas is produced by coal carbonization, and is hardly used in the ironmaking process in the conventional blast furnace method, but is transported and used in heat treatment furnaces and power generation furnaces in nearby factories. For this reason, the use of coke oven gas requires a large-scale facility and is problematic. From this, it can be said that self-utilization of coke oven gas in the iron making process is a fundamental issue that cannot be avoided in improving the efficiency of the blast furnace method.

  The present invention has been made in view of this problem, and the problem is that the amount of coke used in the blast furnace can be reduced on the premise of the existing sintering machine-coke furnace-blast furnace process. An object of the present invention is to provide a method for producing a pre-reduced sintered ore to which coke oven gas can be applied. Another object of the present invention is to provide a method for operating a blast furnace in which the pre-reduced sintered ore produced by this method is used in a blast furnace, and the amount of coke used in the blast furnace can be reduced.

  The present inventors have studied to solve the above-mentioned problems, conducted experiments described below, and found that the above-described pre-reduction sintered ore can be produced by satisfying the following (a) to (c): Got.

(A) The crushed sintered cake is charged into a reduction furnace at 420 to 970 ° C.
(B) The reducing gas blown into the reducing furnace has an H ₂ gas concentration of 50% by volume or more and a temperature of 700 ° C. or more.
(C) The pre-reduction sintered cake obtained by reducing the sintered cake has a metallization rate of 25 to 60 mass%, and particles having a particle size of 5 to 50 mm occupy 50 mass% or more.

  The present invention has been completed on the basis of the above knowledge, and has the following (1) to (9) methods for producing a pre-reduced sintered ore and methods for operating a blast furnace.

(1) Charge the sinter cake crushed material from the top of the reduction furnace, discharge the pre-reduction sinter cake obtained by pre-reducing the sinter cake crushed material from the lower part of the reduction furnace, A method for obtaining a pre-reduced sintered ore having a particle diameter of 5 mm or more from a cake, wherein the sinter of the sintered cake is charged into the reduction furnace in a temperature range of 420 to 970 ° C., and the reduction furnace H ₂ gas having a concentration of 50% by volume or more and a temperature of 700 ° C. or more is blown as a reducing gas, and the pre-reduction sintered cake has a metallization rate of 25 to 60 mass% and a particle size of 5 to 50 mm. Is composed of 50 mass% or more, a method for producing a pre-reduction sintered ore.

(2) Using a Dwytroid type sintering facility, placing a burner on the upper part of the strand in the vicinity of the sintered cake discharge part of the sintering facility, and blowing a combustion gas from the burner, It heats, The manufacturing method of the pre-reduction sintered ore as described in said (1) characterized by the above-mentioned.

(3) The method for producing a pre-reduction sintered ore according to (2) above, wherein coke oven gas, natural gas, or exhaust gas from the reduction furnace is used as fuel for the burner.

(4) The reducing gas blown into the reducing furnace is characterized by reforming natural gas or coke oven gas so that the volume ratio of H ₂ to CO (H ₂ / CO) is 2.0 or more. The manufacturing method of the pre-reduction sintered ore as described in said (1)-(3).

(5) As described in (1) to (4) above, gas inlets and outlets are provided at the upper and lower parts of the reducing furnace, and the reducing gas blown into the reducing furnace is caused to flow from the upper part to the lower part of the reducing furnace. Manufacturing method of pre-reduction sintered ore.

(6) The method for producing a pre-reduction sintered ore according to any one of (1) to (5), wherein the reduction furnace is a horizontal rotary double cylindrical type and has a water seal.

(7) The method for producing a pre-reduced sintered ore as described in (1) to (6) above, wherein the CaO content of the sintered cake is 7.0 to 13.0 mass%.

(8) The preliminary reduction sintered cake according to any one of (1) to (7), wherein the preliminary reduction sintered cake is classified by sieving, and the sieving product is made into briquette type preliminary reduction sintered ore by a molding machine. A method for producing sintered ore.

(9) A blast furnace operating method in which the prereduced sintered ore produced by the method for producing a prereduced sintered ore according to the above (1) to (8) is used as a part of a blast furnace raw material.

  In the present invention and the present specification, the “sintered cake” refers to a large mass of a sintered product produced on a sintering machine and not subjected to a sieving treatment. “Sintered ore” refers to a charge of a blast furnace, and refers to a sintered cake that has been subjected to a treatment that can be charged into a blast furnace by sieving before being charged into the blast furnace, and a crushed product thereof. There is almost no difference in chemical composition between the sintered cake and the sintered ore. The “pre-reduction sintered cake” means a sintered cake that has been pre-reduced in a pre-reduction furnace and has not been subjected to sieving, and the “pre-reduction sintered ore” means a blast furnace. This refers to a pre-reduced sintered cake that has been subjected to a treatment that can be charged into the cake.

  In the present invention, the “metalization rate of sintered cake” is a value obtained by dividing mass% (metallic Fe%) of metallic iron contained in the sintered cake by mass% (T.Fe%) of total iron. Fe% / T.Fe%).

  In the following description, “mass%” representing a component composition of sintered ore or the like is also simply expressed as “%”.

  According to the method for producing a pre-reduction sintered ore of the present invention, it is possible to produce a pre-reduction sintered ore that can reduce the amount of coke used in the blast furnace. In addition, the coke oven gas can be self-utilized in the iron making process.

  According to the blast furnace operating method of the present invention, it is possible to reduce the amount of coke used and suppress the generation of carbon dioxide.

It is a schematic diagram which shows the system form of a blast furnace method. It is a block diagram of the blast furnace method system which can apply the manufacturing method of the preliminary reduction sintered ore of the present invention, and the blast furnace operating method. It is a schematic diagram of a sintering pot test apparatus. It is a figure which shows the time change of the temperature distribution of the whole raw material layer, The figure (a) shows the case where the 1st sintering method is applied, The figure (b) shows the case where the 2nd sintering method is applied. . It is the approximate curve processing result of the temperature distribution of the height direction of the measured raw material layer at the time of completion | finish of sintering. It is a figure which shows the time change of exhaust gas temperature. It is a schematic diagram of a reduction test apparatus. It is a figure which shows the change of the metalization rate of the sintered cake computed from the mass change in a reduction test. It is a particle size distribution of the sintered cake taken out after reducing for 30 minutes. It is the simulation result of the temperature and metallization rate of the sintered cake in the height direction of a prereduction furnace, The figure (a) shows the result of a cocurrent type, and the figure (b) shows the result of a countercurrent type. It is a schematic diagram of a double cylindrical shaft furnace. It is sectional drawing which shows the water seal structure of a double cylindrical shaft furnace. It is a figure which shows the relationship with the crushing strength of the metallization rate of a briquette and CaO content rate.

1. Overview The method of the present invention does not charge a blast furnace in a state where the entire amount of the produced sintered cake is produced as in the prior art. The final goal is to reduce the amount of coke, which is a reducing material, by processing in a furnace with a pre-reduction function to produce pre-reduced sintered ore and using it as part of the blast furnace raw material. Is. Below, the manufacturing method of the pre-reduction sintered ore of this invention is explained in full detail.

2. Configuration of Blast Furnace Method System FIG. 2 is a configuration diagram of a blast furnace method system to which the prereduction sintered ore manufacturing method and blast furnace operation method of the present invention can be applied. The blast furnace method system shown in FIG. 2 includes a dwelloid (DL) type sintering machine 1, a crushed material container 2, a preliminary reduction furnace 3, a sieve device 4, a molding machine 5, and a blast furnace 6.

  In the sintering machine 1, the blended raw material 11 is sintered to produce a sintered cake 12 and is crushed to produce a sintered cake crushed material 13. The crushed container 2 is a container for receiving the sinter cake crushed material 13 produced by the sintering machine 1 and also serves as a container for transporting the sinter cake crushed material 13 to the top of the preliminary reduction furnace 3. In the pre-reduction furnace 3, the sintered cake crushed material 13 is pre-reduced to produce a pre-reduction sintered cake 31.

  In the sieving device 4, the pre-reduction sintered cake 31 discharged from the pre-reduction furnace 3 is classified into a lump pre-reduction sintered ore 31a that is a sieving product and a powdery pre-reduction sintered cake 31b that is a sieving product. . The molding machine 5 agglomerates the powdery pre-reduction sintered cake 31b, which is a product under sieve, and forms a briquette-type pre-reduction sintered ore (hereinafter also referred to as “pre-reduction briquette”) 51. The blast furnace 6 is fed with massive prereduced sintered ore 31a, which is a product on the sieve of the sieving device 4, and a prereduced briquette 51 formed by the molding machine 5.

3. Sintered cake crushed material First, the sintered cake crushed material, which is a target for preliminary reduction, will be described. The sinter cake crushed material may be produced by the same method as that produced from a conventionally produced sintered cake. However, the temperature needs to be 420 to 970 ° C. when charging the preliminary reduction furnace.

3-1. Heating method of sintered cake crushed material 3-1-1. Gas to be used To bring the sinter cake crushed material into this temperature range, it is necessary to devise a thermally advantageous means such as increasing the ratio of fuel in the sintered raw material (blended raw material). However, since the sintered cake does not easily reach a high temperature when only the raw material is devised, a method of positively injecting high-temperature combustion gas from a burner into the sintering bed is an effective heating method. In this case, as the gas fuel used in the burner, use of a gas such as natural gas or coke oven gas having a high H ₂ / CO ratio (volume ratio of H ₂ and CO) reduces the amount of carbon dioxide generated. Is necessary. Of course, it is also possible to use the reducing gas discharged from the preliminary reduction furnace as the gas fuel.

3-1-2. Blowing position of gas The blowing position of the high-temperature combustion gas in the sintered layer is from the top of the sintered strand of the sintering machine 1 shown in FIG. 2 from FFP (Flame Front Point) to the discharge end. It is preferable to be between. By blowing high-temperature combustion gas at this position, the surface layer portion of the sintered cake that has been cooled to near normal temperature is heated to about 1200 ° C. again at the FFP point. FFP is a point where the temperature of exhaust gas rapidly rises. In the sintering machine 1 shown in FIG. 2, the length of all strands is 100%, the ignition start point 1a is at the 0% position, and the exhaust end 1b is 100%. If it is a position, it is located near 75%.

  Injecting high-temperature combustion gas in the portion where the fuel is present and burning in the raw material in the sintered layer (sintered cake) will reduce the oxygen concentration in the sintered layer suction air, Must be avoided.

3-2. Crushing of sintered cake The high-temperature sintered cake 12 conveyed to the discharge end 1b of the sintering machine 1 is discharged from the sintered cake discharge section by tilting the pallet at the discharge end 1b. By crushing with a mold crusher, a sinter cake 13 is produced. And the sintered cake crushing material 13 is conveyed by the crushing material container 2, and is charged into the furnace top of the preliminary reduction furnace 3 in the state of 420-970 degreeC.

4). Prereduction 4-1. Method and Effect of Prereduction in the Present Invention The prereduction furnace 3 has a structure in which the charge charged from the top of the furnace is unloaded by gravity and discharged from the lower part of the furnace. The pre-reduction furnace 3 may be located under the sintered cake discharge part like a sintering cooler (not shown), or may be installed separately from the sintering machine 1. When installing in the place away from the sintering machine 1, the sintered cake crushing material 13 should just be conveyed using a refractory container container.

The pre-reduction furnace 3 is charged with a crushed sintered cake 13 of 420 to 970 ° C. from the top of the furnace, and H ₂ gas having a concentration of 50% by volume or more and a temperature of 700 ° C. or more as a reducing material (reducing gas). It blows in from the gas inlet 3a provided in the side surface. In the pre-reduction furnace 3, a lump coke or a CO-rich gas is not used as a reducing material, and a reducing gas having an H ₂ concentration described later of 50 volume% or more is used. For this reason, when preliminary reduction is performed, a large amount of H ₂ O gas is generated, but the generation amount of CO gas and carbon dioxide gas is small, and the generation amount of carbon dioxide gas can be suppressed as a whole of the ironmaking process.

H ₂ gas is overwhelmingly smaller in molecular diameter than CO gas, and can easily penetrate into fine solid pores. Therefore, it has the characteristic that the reduction | restoration of iron oxide can be advanced in a short time. Therefore, when compared with a case where an equimolar amount of reducing gas is used, the H ₂ gas may have a shorter residence time in the furnace for achieving the target reduction rate than the CO-rich gas, and the volume of the preliminary reducing furnace is Even if it is small, it can fully function.

However, this is only under the same temperature condition. Since the reduction of iron oxide with H ₂ gas is an endothermic reaction, when H ₂ gas is used as the reducing gas, the temperature of the charge in the furnace decreases. On the other hand, since the reduction of iron oxide with CO gas is an exothermic reaction, when CO gas is used as the reducing gas, the temperature of the charge in the furnace tends to increase. Therefore, the reduction with H ₂ gas is actually slower than the reduction with CO gas.

Therefore, in the present invention, a high-temperature sintered cake crushed material of 420 to 970 ° C. is charged into the prereduction furnace so that the reaction temperature is ensured even when the temperature of the charged material is reduced by reduction with H ₂ gas. I have to. In this respect, it is greatly different from the conventional blast furnace method in which a normal temperature sintered ore is charged into the furnace.

4-2. Temperature range of the sinter cake crushed material The temperature of the sinter cake charged in the prereduction furnace reduces the volume of the prereduction furnace to reduce the installation space of the equipment as much as possible, and also improves the reduction rate. It is necessary to make it as high as possible.

  In the present invention, the lower limit temperature of the crushed sintered cake charged into the prereduction furnace is set to 420 ° C., because if it is lower than 420 ° C., the reduction reaction becomes too slow to exhibit the effect. Moreover, since the sinter cake crushed material contains calcium ferrite mineral, reduction powdering becomes intense. On the other hand, the reason why the upper limit temperature is set to 970 ° C. is that when the temperature exceeds 970 ° C., the charges tend to stick to each other and the unloading property in the prereduction furnace deteriorates.

4-3. Reducing gas conditions 4-3-1. Composition In the present invention, the composition condition of the reducing gas is such that the H ₂ concentration is 50% by volume or more. Therefore, in the prereduction furnace, the endothermic reaction is richer than the exothermic reaction. Under this condition, the reduction reaction rate is ensured by charging the above-mentioned 420 to 970 ° C. sintered cake crushed material. In this respect, it differs greatly from the conventional reduction furnace.

The reducing gas only needs to have an H ₂ concentration of 50% by volume or more. Such H ₂ rich gas can be obtained by reforming, for example, coke oven gas or natural gas containing CH ₄ with water vapor, combustion exhaust gas, air, oxygen or the like. Even if CO, CO ₂ , CH ₄ , N _2, or H ₂ O is mixed in the reducing gas, the reduction efficiency is deteriorated and the effect of the present invention is not hindered. By using the coke oven gas, the coke oven gas can be self-utilized in the iron making process, and the efficiency of the blast furnace method can be improved.

The gas composition preferably has a volume ratio of H ₂ to CO (H ₂ / CO) of 2.0 or more. By H ₂ / CO is between 2.0 or more H ₂ rich gas, as compared with H ₂ / CO of less than 2.0 significantly improves the reduction rate, further reducing the volume of the pre-reduction furnace can do.

4-3-2. Temperature The temperature of the reducing gas blown into the prereduction furnace is 700 ° C. or higher. If not 700 ° C. or higher, the endothermic reaction proceeds by H ₂ gas reduction of iron oxide, reduction efficiency is deteriorated is furnace temperature decreases.

4-3-3. As described above, the prereduction furnace has a structure in which a charge is charged from the top of the furnace, moved down by gravity, and discharged from the lower part of the furnace. Therefore, the pre-reduction furnace applied to the present invention may be a parallel flow type in which reducing gas is introduced into the furnace top and discharged from the furnace lower side wall or the furnace bottom, or conversely, the reducing gas is supplied from the furnace lower side wall or the furnace bottom. It is good also as a countercurrent type which blows in and discharges from a furnace top part. FIG. 2 shows a counterflow type prereduction furnace 3 having a gas inlet 3a on the side wall of the lower part of the furnace.

  As long as iron oxide can be reduced, the flow direction of the reducing gas is not specified. However, the cocurrent flow type is more effective than the counterflow type because the temperature of the charge is secured higher.

4-3-4. Pre-reduction furnace type As the pre-reduction furnace type, a shaft furnace type that discharges the charge from the bottom of the furnace is applicable. In addition to this, there can be applied a system in which a furnace bottom plate exists, this furnace bottom plate rotates horizontally together with the furnace wall, and the charged material is scraped out from the furnace lower side wall with a scraper or the like. Thus, no format is defined for the prereduction furnace.

  In the type in which the furnace wall and the hearth rotate horizontally, the rotating part needs to be sealed with the reducing gas to be blown, so a water seal system is adopted. Such a horizontal rotary type prereduction furnace having a double cylindrical furnace wall is effective for forming a moving bed having a low layer height and a large cross-sectional area as compared with an elongated shaft furnace. Moreover, since both sides of the double cylindrical furnace wall can be used as the reducing gas injection port, there is an advantage that the pre-reduced charge can be discharged stably. A preliminary reduction furnace having a double cylindrical furnace wall will be described later.

4-4. Effect of preliminary reduction Conventionally, in shaft furnaces such as blast furnaces, the high-temperature reducing gas introduced from the lower part of the furnace is heat-exchanged with the charge as it moves toward the upper part of the furnace, and the temperature is lowered. Then, it is discharged at a low temperature of 200 ° C. This is the reason why the normal temperature raw material charged from the top of the furnace unloads and moves toward the lower part of the furnace, and the counterflow type thermal efficiency in which the reducing gas flows in opposition thereto is good.

In the case of such a countercurrent type, there is always a temperature change from high temperature to low temperature in the shaft furnace height direction. It is a sintered ore that becomes a problem with such a temperature change. Conventionally, it is known that sintered ore expands and pulverizes vigorously when it is reduced from Fe ₂ O ₃ to Fe ₃ O ₄ at around 420 to 600 ° C. Since this reduced powdering is a major problem, sintered ore cannot be used in a shaft furnace.

  On the other hand, in the method of the present invention, since the high-temperature sintered cake crushed material of 420 to 970 ° C. is charged into the preliminary reduction furnace and the input reducing gas temperature is 700 ° C. or higher, sintering is performed in the shaft furnace. When the section of 420 to 600 ° C. where the reduction powdering of the cake becomes a problem is shortened and the sinter cake of the sintered cake to be charged is 600 ° C. or more, this reduction of reduction powdering does not occur. Therefore, even a sintered cake crushed material that is a sintered product of iron ore can be used.

  According to the method of the present invention, the pre-reduced sintered cake obtained by pre-reducing the crushed sintered cake has a particle size somewhat lower than that of the crushed sintered cake, but the sinter ore is powdered. There is no problem with conventional shaft furnaces.

Further, since the pre-reduction sintered cake discharged from the pre-reduction furnace is in a high temperature state immediately after the discharge, heat exchange is performed with N ₂ gas or the like as shown in FIG. 2, and the recovered thermal energy is generated. It can also be used for power generation in the machine 7.

5. Classification with sieve device 5-1. Method for Utilizing Product on Sieve The pre-reduction sintered cake cooled to room temperature is classified by the sieving device 4 with a particle size of about 5 mm as a boundary, as shown in FIG. The lump pre-reduction sintered ore 31a, which is a product on the sieve, has a particle size of 5 mm or more and can ensure the air permeability of the blast furnace, so that it is used as it is as a blast furnace raw material (pre-reduction sintered ore).

5-2. On the other hand, the powdery pre-reduction sintered cake 31b, which is the under-sieving product, may be reused by being blended in the sintering raw material as a sintered remineralized powder as in the prior art. However, it is not preferable to return the ore preliminarily reduced mineral powder to the sintering process in which oxidation treatment is performed in terms of production efficiency and suppression of carbon dioxide gas generation. The powdery pre-reduction sintered cake 31b is preferably briquetted by the molding machine 5 to be used as a pre-reduction briquette 51 so that it can be used in a blast furnace. The pre-reduction briquette 51 can be used as a blast furnace raw material (pre-reduction sintered ore) by setting the particle diameter to 5 mm or more.

  In the prior art, it has been difficult to compression-mold sintered briquettes into briquettes. However, the powdery pre-reduction sintered cake 31b contains 25-60% metallic iron and is easily reduced with a small particle size, so the content of metallic iron is higher than the average of the whole pre-reduced sintered cake. Therefore, the sufficiently reduced pre-reduction briquette 51 that can withstand use in a blast furnace can be manufactured.

  As a method for producing a high-strength pre-reduction briquette, it is preferable to apply the briquette curing technique described in Japanese Patent Application No. 2009-214259 filed by the present applicant. In this case, the pre-reduction briquette preferably has a CaO content of 7% or more and 13% or less as a sintered ore composition. The reason why the CaO content is preferably 7% or more is that, when hydrated as a method for improving the strength of reduced iron briquettes containing partially reduced iron, hydration and solidification develops when a CaO component is present, which is stronger. This is because it becomes a bond, and is effective for a raw material having a high CaO content such as sintered ore. The reason why the CaO content is preferably 13% or less is that when the CaO content is higher than 13%, the Fe grade is too low to be suitable as an iron source used in a blast furnace.

  Of course, in addition to this, HBI ore may be produced from a hot solid reduced iron discharged from a conventional reduction furnace using a hot forming machine. However, the hot forming process has many problems such as a large equipment size of the molding machine, a short roll life of the molding machine, and a large trouble compared with the cold forming process. Therefore, a cold forming process is preferable.

5-3. Effect of classification and briquetting in sieving equipment By using the pre-sintered bulk pre-reduced sintered ore produced in this way and the pre-reduced briquette as part of the blast furnace raw material, reduction in blast furnace operation While reducing load, generation | occurrence | production of the reduction | restoration powdering in a blast furnace can be suppressed, Therefore A coke ratio can be reduced.

  In addition, by using a powdered pre-reduction sintered cake having a high metallization rate in a blast furnace as a pre-reduction briquette, it is a powdered product compared with the case where it is returned to the sintering process in a powdery state. The amount of carbon dioxide generated as a whole process can be suppressed.

5-4. Reasons for defining the metallization rate of the pre-reduction sintered cake In the present invention, the reasons for defining the metallization rate of the pre-reduction sintered cake as 25 to 60% will be described. If the metallization rate of the bulk prereduced sintered ore and prereduction briquette, which is the product on the sieve, is less than 25%, the metallization rate is too low and the reduction effect of the reduction load in the blast furnace is small. This is because it is not worth applying. On the other hand, if the metallization rate of the pre-reduction sintered cake is higher than 60%, the amount of reducing gas required in the pre-reduction furnace becomes too large, causing a problem that the total energy consumption in the iron making process is greatly increased. .

The method of the present invention is a method for suppressing the amount of generated carbon dioxide gas by optimizing the reduction load balance between the preliminary reduction furnace and the blast furnace using the above-mentioned H ₂ gas. From this point, the metallization rate of the pre-reduction sintered cake needs to be 25 to 60%.

5-5. Reasons for defining the particle size of the pre-reduced sintered cake The particle size of the pre-reduced sintered cake will be described. A pre-reduction sintered cake having a strength that is too high or a pre-reduction sintered cake having a high content of coarse particles having a fixed particle size of 50 mm or more has many problems as unloading and discharge cutout in the pre-reduction furnace. On the other hand, because the strength is too low or the temperature of the prereduction furnace is low, the prereduction sintered cake is markedly reduced by powder in the prereduction furnace, and fine particles with a particle size of 5 mm or less are prereduction sintered. In the situation where the cake is the main component, the air permeability in the prereduction furnace is deteriorated, the gas flow in the furnace and the unloading are biased, and the prereduction furnace operation is hindered.

  From the above viewpoint, in the method of the present invention, the pre-reduction sintered cake is configured such that particles having a particle size of 5 to 50 mm occupy 50 mass% or more. The pre-reduction sintered cake having such a particle size can be obtained by controlling the strength of the sintered cake in the sintering machine or operating the pre-reduction furnace.

5-6. Effect of pre-reduced sinter produced by the method of the present invention The pre-reduced sinter produced by the method of the present invention is pre-reduced unlike ordinary sinter. Therefore, Fe ₂ O ₃ is not contained, and when used in a blast furnace, there is an advantage that air permeability can be improved without causing deterioration of air permeability due to reduced powdering. Due to this advantage, it is possible to offset the deterioration of the air permeability accompanying the reduction of the coke ratio, and it is possible to maintain good blast furnace operation.

  Further, by operating the blast furnace using the pre-reduced sintered ore produced by the method of the present invention as a part of the blast furnace raw material, the coke reducing material action and the ventilation space action in the blast furnace are secured, An excellent blast furnace method system that can achieve a reduction in the coke ratio and promote suppression of carbon dioxide generation can be constructed.

6). Element examination result performed in order to complete this invention In order to complete this invention, the element examination was performed about the sintering process and the preliminary reduction process as follows.

6-1. Examination of Sintering Process FIG. 3 is a schematic diagram of a sintering pot test apparatus. In the method of the present invention, it is necessary to produce a crushed sintered cake at 420 to 970 ° C. In general, as shown in FIG. 2, the sintered cake is continuously produced in large quantities by a DL type sintering machine. In the experiment for element examination conducted this time, the production of a high-temperature sintered cake was demonstrated using a sintering pot test apparatus shown in FIG. 3 widely used as a sintering simulator. The sintering pot testing apparatus includes a cylindrical container 14 having a diameter of 300 mm and a height of 500 mm, and an air box 15 provided at the lower part of the container 14. At the boundary between the container 14 and the wind box 15, a net-like grate and a bedding layer 16 are provided.

6-1-1. Experimental Method In this experiment, a raw material containing iron ore, limestone, fuel coke, and water in two mixing ratios (sintered cake A and sintered cake B) shown in Table 1 was used. .

First, an experiment using the blended raw material of the sintered cake A will be described. This blended raw material was mixed for 4 minutes with a rotary drum mixer having a diameter of 600 mm to produce a granulated raw material. This granulated raw material is charged into the cylindrical container 14 of the sintering pot test apparatus shown in FIG. In this state, exhaust gas is sucked by a blower (not shown) through the wind box 15 at a suction amount of 1 to ³ Nm ³ / min. A thermometer 17 is installed inside the wind box 15, and the temperature of the exhaust gas can be measured. In this experiment, the point in time when the temperature of the exhaust gas measured by the thermometer 17 is stable at around 60 ° C. and starts to rise rapidly to 400 ° C. is called FFP.

  An LPG-fired burner 18 is disposed above the sintering pot test apparatus, and high-temperature gas burned by the burner 18 is sprayed onto the surface of the raw material layer 19 made of the granulated raw material. This spraying of hot gas is called surface ignition in the sintering process. The surface reaction initiates the sintering reaction. Hereinafter, the raw material layer including the raw material layer that has changed to a sintered cake as the sintering reaction proceeds is referred to as a “raw material layer”.

  In this experiment, a normal manufacturing method (hereinafter referred to as “first sintering method”) and a manufacturing method for increasing the temperature of the sintered cake (hereinafter referred to as “second sintering method”), A sintered cake was produced.

  In the first sintering method, a sintered cake was manufactured with an ignition time of surface ignition of 1.0 minute. That is, the burner 18 was extinguished when 1.0 minute passed from the start of ignition, and thereafter, the air at normal temperature was sucked by the blower through the wind box 15 so as to pass through the raw material layer 19. Then, the temperature of the exhaust gas in the wind box 15 showed the maximum temperature, and the air was blown until 28 minutes passed from the start of ignition. After the blowing was stopped, the produced sintered cake was discharged from the container 14.

  On the other hand, in the second sintering method, in order to increase the temperature of the sintered cake, in addition to the surface ignition conditions of the first sintering method, from the start of ignition to 25 to 28 minutes immediately before stopping the blowing. The gas burned by the burner 18 for 3 minutes was blown onto the surface of the raw material layer 19 and subjected to final heat treatment.

  In the container 14, thermocouples 14 a were disposed at 80 mm, 240 mm, and 400 mm positions from the surface of the raw material layer 19. The temperature inside the raw material layer 19 was measured by these thermocouples 14a, and the temperature change during the sintering process was recorded.

6-1-2. Experimental Results FIG. 4 is a diagram showing the time change of the temperature distribution of the entire raw material layer. FIG. 4A shows the case where the first sintering method is applied, and FIG. 4B shows the second sintering method. The case where is applied is shown.

  Based on the temperature in the raw material layer 19 recorded using the thermocouple 14a, the temperature distribution of the entire raw material layer 19 was mathematically estimated by interpolation. The result is schematically shown in FIG. It can be seen that the temperature of the upper portion of the raw material layer 19 is increased by the final heat treatment.

  FIG. 5 shows an approximate curve processing result of the temperature distribution in the height direction of the measured raw material layer (sintered cake) at the end of sintering (28 minutes after the start of ignition). Table 2 shows the average temperature of the raw material layer 19 at the end of sintering in this experiment.

  The average temperature of the raw material layer 19 at the end of sintering, that is, the sintered cake, is 421 ° C. in the first sintering method and 822 ° C. in the second sintering method, and increases by 400 ° C. by the final heat treatment by the burner 18. I was able to.

  FIG. 6 is a diagram showing the time change of the exhaust gas temperature. From FIG. 6, in both the first sintering method and the second sintering method, a rapid increase in exhaust gas temperature occurred 23 minutes after the start of ignition. That is, FFP was 23 minutes from the start of ignition.

  Thus, just before the end of the sintering process, as a final heat treatment, if a high-temperature gas is supplied to the surface of the sintered cake using a combustion gas-fired burner, the temperature of the sintered cake can be easily raised by suction action. It was also found that the temperature could be controlled to the target value.

  Replacing the result of this experiment with the actual sintering machine shown in FIG. 2, the time from the start of ignition to the completion of combustion is 28 minutes. The horizontal movement speed of the pallet is 100% / 28 minutes, ie 3.6% / min. If the ignition start point is 0% position and the discharge end is 100% position, additional combustion for 3 minutes from the start of ignition to 25 minutes to 28 minutes is performed at the upper part of the sintered cake strand. It is performed at a position of 89 to 100% that is in the vicinity. What is necessary is just to arrange | position the burner used for final heat processing to the upper part of a strand so that this range may be covered. FFP, which was 23 minutes from the start of ignition, corresponds to the 82% position from 23 minutes ÷ 28 minutes≈0.82.

6-1-3. In the case of Sintered Cake B Using the blended raw material of Sintered Cake B shown in Table 1 as a blended raw material, an experiment using the same sintering pot test apparatus was performed. In this case, the ignition time was extended from 1 minute to 2 minutes for the sintered cake A to enhance the ignition, and the blending ratio of the powdered coke as the fuel was increased from 4.5% to 5.5%, Was reduced from 7.0% to 6.6%, and the input heat amount was increased as compared with the case of the sintered cake A.

  The results of the average sintered cake temperature at 28 minutes from the start of ignition in this experiment are shown in Table 2 together with the results of the sintered cake A. In the case of sintered cake B, the amount of heat input was increased, so that the first sintering method could be increased to 573 ° C., and the second sintering method could be increased to 971 ° C. by the final heat treatment.

6-2. Examination of Prereduction Process Next, in order to examine the prereduction process, a reduction experiment was performed using the combustion cake obtained by the above-described sintering simulation.

6-2-1. Experimental Method FIG. 7 is a schematic diagram of a reduction test apparatus. As shown in FIG. 7, the reduction test apparatus includes a cylindrical reaction tube container 32 and an electric heating furnace 33 surrounding it. The cylindrical reaction tube container 32 is regarded as a preliminary reduction furnace, and has a diameter of 74 mm. A gas having a composition (volume ratio) of H ₂ : CO: CO ₂ = 76: 21: 3 was used as the reducing gas, and the flow rate was 9.4 NL / min. As a sample, 500 g of the sintered cake obtained from the blended raw material of the sintered cake A by the second sintering method in the above-described sintering simulation was used.

  This sintered cake was charged into the cylindrical reaction tube container 32 at room temperature to form a sintered cake packed layer 34. The sintered cake in the cylindrical reaction tube container 32 was controlled by the electric heating furnace 33 so that the temperature became 900 ° C. Similarly, the reducing gas introduced into the cylindrical reaction tube container 32 was also heated to 900 ° C. The reducing gas is introduced from the lower part of the cylindrical reaction tube container 32, passes through the sintered cake packed bed 34 from the lower part to the upper part, and is discharged from the upper part of the cylindrical reaction tube container 32.

6-2-2. Experimental Results FIG. 8 is a diagram showing the change in the metalization rate of the sintered cake calculated from the change in mass in the reduction test. As shown in FIG. 8, the metallization rate reached 25% when 20 minutes passed from the start of reduction, and reached 60% when 30 minutes passed. Thus, if the reduction reaction is performed at a high temperature from the beginning, the sintered cake can be preliminarily reduced to a metalization rate of about 60% in an extremely short time of about 30 minutes.

  FIG. 9 is a particle size distribution of the sintered cake taken out after reduction for 30 minutes. Since the sintered cake is reduced at a high temperature, there is almost no reduction pulverization phenomenon even after reduction, and the grain size composition of the sintered cake after reduction is 5 to 50 mm, which is considered good in a blast furnace. It turns out that it is 50% or more. FIG. 9 also shows the results of a similar experiment performed using a sintered cake obtained from sintered cake A by the first sintering method.

  A similar experiment was performed using a sintered cake obtained from sintered cake B by the second sintering method. As a result, the metallization rate was 25% when the reduction time was 18 minutes, 60% when 27 minutes, and the particle size constitution was 61% when the particle size was 5 to 50 mm.

6-2-3. Preferable gas composition Furthermore, the same experiment was performed using the gas of the composition 1-10 shown in Table 3, and reducing time was 25 minutes. The conditions and results are shown in Table 3.

Table 3 shows the metallization rate after reduction for 25 minutes together with the gas composition. As can be seen from Table 3, the metallization rate tends to increase as the H ₂ concentration and the H ₂ / CO concentration ratio increase, except when the H ₂ concentration is 100% by volume (composition 1). Assuming that the residence time of the reduction furnace is 25 minutes, the metallization rate was 25% or more (compositions 1 to 9) when the H ₂ concentration was 50% by volume or more. Further, in a high case (compositions 2, 3, 4, 5 and 8) where the H ₂ / CO concentration ratio was 2.0 or more, a high metallization rate of 35% or more was shown. That is, the gas composition under these conditions is preferable because the production efficiency relating to the preliminary reduction is high.

6-3. Study on pre-reduction furnace 6-3-1. Simulation conditions Furthermore, in order to clarify the method of the prereduction furnace and the situation in the prereduction furnace, it was examined using a mathematical model simulation. Table 4 shows the specifications and operating conditions of the shaft furnace type prereduction furnace applied to the simulation.

6-3-2. FIG. 10 is a simulation result of the temperature and metallization rate of the sintered cake in the height direction of the prereduction furnace. FIG. 10 (a) shows the result of the parallel flow type, and FIG. 10 (b) shows the counter current type. Is the result of In the figure, only the reducing portion which is the upper half of the preliminary reduction furnace is shown.

  The sintered cake is charged from the top of the pre-reduction furnace, which is a shaft furnace, and the charged material descends due to gravity to form a moving layer that moves down. As described above, the co-current type is a type in which the flow direction of the reducing gas is the same as the moving direction of the sintered cake, that is, a type in which the gas is input from the top of the furnace and discharged from the lower part. The counter flow type is a type in which the flow direction of the reducing gas is opposite to the moving direction of the sintered cake, that is, a type in which the gas is input from the lower part and discharged from the top of the furnace.

  As shown in FIGS. 10 (a) and 10 (b), in both cases of the cocurrent type and the countercurrent type, if the length of the furnace is 8 m, the metallization rate of 60%, which is the target value, can be sufficiently achieved. .

  Furthermore, when this simulation result is examined, in the co-current shaft furnace, a metallization rate of 60% can be sufficiently achieved with a length of about 2.0 m. In the counter-flow shaft furnace, although the top of the furnace and the lower excavation part are necessary, the middle part of about 5 m is useless, so a length of about 3.0 m is considered sufficient.

  Further, in the case of the co-current shaft furnace shown in FIG. 10 (a), the sintered cake is heated at the top of the furnace with a gas of 960 ° C., and then endothermic by a reduction reaction. However, 800 ° C., which is the temperature at the time of charging, can be almost maintained, and it can be said that a good furnace temperature condition is maintained. Of course, since the lower heat preservation zone is unnecessary, the furnace length can be shortened.

  On the other hand, in the case of the countercurrent shaft furnace shown in FIG. 10 (b), although the sintering cake temperature is 800 ° C. at the top of the furnace, the temperature of the reducing gas rising from the lower part is reduced to about 600 ° C. By this endothermic reduction reaction with the reducing gas, the sintered cake is cooled to form a 600 ° C. heat preservation zone. Then, in the vicinity of the final waste portion, the heat is reduced by the input reducing gas at 960 ° C. Thus, since there is a useless 600 ° C. storage zone, the furnace length of this portion can be shortened.

  Based on the above results, the type of the shaft furnace used as the preliminary reduction furnace may be either a parallel flow type or a counter flow type. However, of these two types, the co-current type is more efficient and is preferred.

  The type of the pre-reduction furnace applied to the method of the present invention is not limited to the moving bed type, and may be a fixed bed type or a cross flow type, and is not particular about the type.

6-3-3. Double cylindrical shaft furnace However, in the type of furnace having a small cross-sectional area of the pencil cylinder, such as the shaft furnace shown in FIG. 2, the height of the packed bed formed by the charge is several meters as described above. And requires a large blowing pressure. In addition, the gas is supplied or discharged from the lower furnace wall, so that the gas at the lower part of the furnace hardly flows to the center of the furnace. Therefore, application of a double-cylinder type moving bed or the like that can increase the cross-sectional area of the furnace is the most preferable mode.

  FIG. 11 is a schematic diagram of a double cylindrical shaft furnace. As shown in FIG. 11, the double cylindrical shaft furnace 35 is the same as the cylindrical shaft furnace in that the sintered cake crushed material 13 is introduced from the top of the furnace. However, the diameter of the furnace is larger than that of the cylindrical shaft furnace, and the furnace wall of the inner wall 36 exists at the center of the outer wall 37 to constitute a double cylinder type. This type of furnace can solve the fundamental problem that the input gas from the furnace wall does not easily reach the center of the furnace when the furnace diameter is increased, and the blowing pressure can be reduced by increasing the cross-sectional area. .

  Further, the reducing gas can be introduced from gas inlets 36 a and 37 a provided on both the inner wall 36 and the outer wall 37. However, when the cross-sectional area increases, it becomes difficult to discharge the pre-reduction sintered cake 31 obtained by pre-reducing the sintered cake crushed material 13. In this case, it is possible to rotate the furnace wall or the bottom of the furnace and forcibly discharge it with a scraper or the like.

  FIG. 12 is a cross-sectional view showing a water seal structure of a double cylindrical shaft furnace. When the furnace wall or the like of the double cylindrical shaft furnace 35 is rotated, the atmosphere and the reducing gas need to be sealed. In this case, since the blowing pressure is about several hundreds of millimeters of water, a water seal structure 38 as shown in FIG. 12 can be applied to seal the atmosphere and the reducing gas. The water seal structure 38 has the following structure.

  The upper side includes an annular lid 38a covering the entire upper surface of the double cylindrical shaft furnace 35, and an annular inner water tank 38b and an outer water tank 38c, respectively. The double cylindrical shaft furnace 35 has an extension portion 36b and an extension portion 37b that extend the upper ends of the inner wall 36 and the outer wall 37 downward. The inner side surface of the lid 38a is connected to the inner side surface of the inner water tank 38b, and the extension portion 36b of the inner wall 36 is immersed in the water stored in the inner water tank 38b. The outer side surface of the lid 38a is connected to the outer side surface of the outer water tank 38c, and the extension portion 37b of the outer wall 37 is immersed in the water stored in the outer water tank 38c.

  The lower side includes an annular water tank 38d that covers the entire lower surface of the double cylindrical shaft furnace 35. The water tank 38d includes grooves on the inner peripheral side and the outer peripheral side. The lower end of the inner wall 36 is immersed in the water accommodated in the groove portion on the inner peripheral side, and the lower end of the outer wall 37 is immersed in the water accommodated in the groove portion on the outer peripheral side.

1. Briquette forming of powdered pre-reduction sintered cake Pre-reduction sintered cake obtained by pre-reducing the sinter cake crushed material in a reduction furnace is classified by sieve, and the powdered pre-reduction sintering which is the generated under-sieving product An example of briquetting using a cake will be described.

  A powdery pre-completely sintered cake having a particle size of −5 mm, which was produced from a sintered cake having a CaO component content of 7.0% and 13.0%, was used. Using a compression molding machine, a cylindrical briquette having a diameter of 28 mm and a length of 12 mm was produced from this powdery pre-reduction sintered cake, and after being immersed in water, it was left to dry to complete. The completed briquette was subjected to a compression test, and the crushing strength was measured.

  FIG. 13 is a graph showing the relationship between the briquette metallization rate and the crushing strength of the CaO content. From FIG. 13, when the metallization rate was 20% or more, the CaO content was 7% and 13%, both having a strength of 50 kgf / lump considered to be usable in the blast furnace. From this result, it was found that a powdery pre-reduction sintered cake of an under-sieving product that cannot be used in a blast furnace as it is can be made usable by performing a molding treatment.

2. Improvement effect by using pre-reduced sintered ore in blast furnace The improvement effect of using pre-reduced sintered ore manufactured by the method of the present invention in a blast furnace was examined by applying a blast furnace simulation model. As the pre-reduced sintered ore, a briquette made from a bulk pre-reduced sintered ore having a particle size of 5 mm as a sieve product and a powdery pre-reduced sintered cake having a particle size of -5 mm as a sieve product was used as a model. Table 5 shows the conditions of the blast furnace, pre-reduced sintered ore, raw material amount, and reducing material applied to the simulation. As a comparative example, a case where no pre-reduced sintered ore is used is shown as “conventional method”. Table 6 shows the compositions of the sintered cake and the pre-reduced sintered ore before the pre-reduction.

The results of the simulation are shown in Table 5 together with the conditions. As can be seen from Tables 5 and 6, when 432 kg / pt of pre-reduced sintered ore having a metallization rate of 40% and a CaO content of 9% is used, 432 kg / pt × 27.4% ≈118 kg / From pt, it was possible to reduce the blast furnace reducing load corresponding to about 118 kg / pt in terms of the amount of metallic iron, and to reduce the amount of coke coke consumed in the blast furnace from 360 kg / pt to 301 kg / pt. Moreover, the production amount of pig iron was increased from 2.10 (pt / D.m ³ ) to 2.34 (pt / D.m ³ ).

  Thus, the blast furnace operation method of the present invention is a method that can greatly improve the blast furnace operation, and an excellent pig iron manufacturing system can be constructed by applying this method.

  According to the method for producing a pre-reduction sintered ore of the present invention, it is possible to produce a pre-reduction sintered ore that can reduce the amount of coke used in the blast furnace. In addition, the coke oven gas can be self-utilized in the iron making process.

  According to the blast furnace operating method of the present invention, it is possible to construct an excellent pig iron production system that reduces the amount of coke used and reduces the amount of carbon dioxide emission.

1: sintering machine, 1a: ignition start point, 1b: discharge end, 11: compounding raw material,
12: Sintered cake, 13: Sintered cake, 14: Container, 14a: Thermocouple,
15: wind box, 16: flooring, 17: thermometer, 18: burner, 19: raw material layer,
2: container, 3: prereduction furnace, 3a: gas inlet, 31: prereduction sintered cake,
31a: massive prereduced sintered ore, 31b: powdery prereduced sintered cake,
32: Cylindrical reaction tube container, 33: Electric heating furnace, 34: Sintered cake packed bed,
35: Double cylindrical shaft furnace, 36: Inner wall, 36a: Gas inlet,
36b: Extension part, 37: Outer wall, 37a: Gas inlet, 37b: Extension part,
38: Water seal structure, 38a: Lid, 38b: Inner water tank, 38c: Outer water tank,
38d: water tank, 4: sieve device, 5: molding machine, 51: preliminary reduction briquette,
6: Blast furnace, 7: Generator

Claims (9)

The sintered cake crushed material is charged from the upper part of the reduction furnace, the pre-reduced sintered cake obtained by pre-reducing the sintered cake crushed material is discharged from the lower part of the reducing furnace, and the pre-reduced sintered cake is removed. A method for obtaining a pre-reduced sintered ore having a particle size of 5 mm or more,
The sinter of the sintered cake is charged into the reduction furnace in a temperature range of 420 to 970 ° C.,
H ₂ gas having a concentration of 50% by volume or more and a temperature of 700 ° C. or more was blown into the reduction furnace as a reducing gas,
A method for producing a pre-reduction sintered ore, characterized in that the pre-reduction sintered cake has a metallization rate of 25 to 60 mass% and particles having a particle size of 5 to 50 mm are composed of 50 mass% or more.
  Using a Dwytroid-type sintering facility, placing a burner on top of the strand in the vicinity of the sintered cake discharge part of the sintering facility, and heating the sintered cake by blowing combustion gas from the burner The manufacturing method of the pre-reduction sintered ore of Claim 1 characterized by these.   The method for producing a pre-reduced sintered ore according to claim 2, wherein coke oven gas, natural gas, or exhaust gas from the reduction furnace is used as fuel for the burner. As the reducing gas blown into the reducing furnace, according to claim 1 volume ratio of H ₂ and CO (H ₂ / CO) is such that 2.0 or more, which is characterized by reforming natural gas or coke oven gas The manufacturing method of the pre-reduction sintered ore in any one of Claims 3 thru | or 3.   5. The reserve according to claim 1, wherein gas inlets and outlets are provided at an upper part and a lower part of the reducing furnace, and a reducing gas blown into the reducing furnace is caused to flow from the upper part to the lower part of the reducing furnace. Manufacturing method of reduced sintered ore.   The method for producing a pre-reduction sintered ore according to any one of claims 1 to 5, wherein the reduction furnace is a horizontal rotary double cylinder type and has a water seal.   The method for producing a pre-reduced sintered ore according to any one of claims 1 to 6, wherein the CaO content of the sintered cake is 7.0 to 13.0 mass%.   The pre-reduction sintering cake according to any one of claims 1 to 7, wherein the pre-reduction sintered cake is classified by sieving, and the under-sieving product is made into briquette-type pre-reduction sintered ore by a molding machine. Production method of ore.   A blast furnace operating method in which the prereduced sintered ore produced by the method for producing a prereduced sintered ore according to any one of claims 1 to 8 is used as part of a blast furnace raw material.

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