Method for producing pig iron

Abstract

To provide a method for producing pig iron, which can effectively reduce the amount of CO2 to be discharged without affecting the strength and yield of coke.SOLUTION: A method for producing pig iron according to the present invention includes a step of alternately stacking an ore layer containing an ore raw material and a coke layer containing coke in a blast furnace, a step of blowing hot air and auxiliary fuel into the blast furnace from a tuyere, and a step of heating, reducing, and melting the ore raw material, and includes a step of mixing an aggregate containing a biomass molded body obtained by heat-treating and molding woody biomass and / or herbaceous biomass with the ore layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing pig iron. [Background technology]

[0002] In recent years, methods have been proposed for substituting a portion of the coal used in pig iron production with woody biomass in order to reduce CO2 emissions during pig iron production. Specifically, Patent Document 1 describes a method in which dried woody biomass is pulverized and then molded together with coal to form molded bodies, the molded bodies are charged into a coke oven together with the coal, and the coke produced by carbonization is charged into a blast furnace. Furthermore, Patent Document 2 describes a method for producing blast furnace coke in which char recovered from pyrolysis of woody biomass is added to a coal blend for coke production and carbonized in a coke oven. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-17528 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-77086 Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the methods described in Patent Documents 1 and 2, woody biomass after drying or pyrolysis does not have caking properties, and the oxygen-containing functional groups of dried woody biomass inhibit the caking properties of the surrounding raw coal, resulting in reduced coke strength. Furthermore, the density of woody biomass after drying or pyrolysis is lower than that of coal, which reduces the charging density of coal in the coke oven and reduces coke strength. Furthermore, woody biomass after drying or pyrolysis contains more volatile components than coal, resulting in reduced coke yield. For this reason, the methods described in Patent Documents 1 and 2 require a limited blending ratio of woody biomass, limiting their effectiveness in reducing CO2 emissions.

[0005] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a method for producing pig iron that can effectively reduce CO2 emissions without affecting the strength or yield of coke. [Means for solving the problem]

[0006] The method for producing pig iron according to the present invention includes the steps of alternately stacking ore layers containing ore raw materials and coke layers containing coke in a blast furnace, blowing hot air and auxiliary fuel into the blast furnace from tuyere nozzles, and heating, reducing, and melting the ore raw materials, and further includes the step of mixing aggregate including biomass molded bodies obtained by heat-treating and molding woody biomass and / or herbaceous biomass into the ore layers.

[0007] It is preferable that the amount of the biomass shaped bodies charged is 5 kg or more per ton of pig iron, and the ratio of the average particle size of the biomass shaped bodies to the average particle size of the raw ore is 0.25 or more.

[0008] The apparent density of the biomass molded body is 0.8 g / cm 3 It would be better if it was more than that.

[0009] The biomass molded body preferably has a post-reaction strength CSR of 45% or more.

[0010] The heat treatment is preferably carried out at a temperature of 400° C. or higher.

[0011] The molding is preferably carried out using a continuous pressure molding machine. [Effects of the Invention]

[0012] According to the method for producing pig iron of the present invention, CO2 emissions can be effectively reduced without affecting the strength or yield of coke. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a blast furnace to which a method for producing pig iron according to one embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a method for producing pig iron according to one embodiment of the present invention will be described with reference to the drawings.

[0015] [Blast furnace configuration] First, with reference to FIG. 1, the configuration of a blast furnace to which a method for producing pig iron according to one embodiment of the present invention is applied will be described.

[0016] Fig. 1 is a schematic diagram showing the configuration of a blast furnace to which a pig iron manufacturing method according to one embodiment of the present invention is applied. As shown in Fig. 1, in a blast furnace 1 to which a pig iron manufacturing method according to one embodiment of the present invention is applied, an ore layer 2 containing raw ore materials such as sintered ore, pellets, and lump ore and a coke layer 3 containing coke are alternately layered, and hot air and auxiliary fuel are blown into the blast furnace 1 from tuyere 4 provided at the bottom of the blast furnace 1 to heat, reduce, and melt the raw ore materials to produce pig iron.

[0017] [Method for producing pig iron] Next, a method for producing pig iron according to one embodiment of the present invention will be described in detail.

[0018] In one embodiment of the method for producing pig iron, when raw ore is charged into a blast furnace, aggregate including biomass briquettes, which are formed by heat-treating and molding woody biomass and / or herbaceous biomass, such as sawmill waste, thinned wood, and agricultural residue, is mixed into the ore layer. Conventionally, to improve permeability in the blast furnace, particularly in the high-temperature region where the ore layer softens and melts, small and medium-sized coke, which has a smaller particle size than the coke forming the coke layer, has been mixed into the ore layer as aggregate. In contrast, in one embodiment of the method for producing pig iron, biomass briquettes are mixed into the ore layer instead of small and medium-sized coke, thereby effectively reducing CO2 emissions. Furthermore, since woody biomass and / or herbaceous biomass is heat-treated without using a coke oven and then the molded biomass briquettes are mixed into the ore layer, CO2 emissions can be effectively reduced without affecting the strength or yield of the coke.

[0019] The amount of biomass briquettes charged should be 5 kg or more per ton of pig iron, and the ratio of the average particle size of the biomass briquettes to the average particle size of the raw ore should be 0.25 or more. By charging 5 kg or more of biomass briquettes per ton of pig iron, more than 10% of the small and medium-sized lump coke can be replaced, effectively reducing CO2 emissions. Furthermore, by setting the ratio of the average particle size of the biomass briquettes to the average particle size of the raw ore to 0.25 or more, excessive particle size differences between the raw ore and the biomass briquettes can be suppressed. As a result, excessive segregation of the biomass briquettes due to particle size differences during the process of transporting, mixing, and charging the raw ore and the biomass briquettes into the blast furnace can be suppressed, and the biomass briquettes can be uniformly distributed within the ore layer.

[0020] The apparent density of the biomass molded body is 0.8 g / cm 3 This can prevent an excessive difference in density between the raw ore and the biomass shaped bodies. As a result, excessive segregation of the biomass shaped bodies due to the difference in density during the process of transporting, mixing, and charging the raw ore and the biomass shaped bodies into the blast furnace can be prevented, and the biomass shaped bodies can be uniformly distributed in the ore layer.

[0021] Furthermore, it is desirable for the biomass briquette's post-reaction strength (CSR) to be 45% or higher. This prevents excessive deterioration and pulverization of the biomass briquette due to the reducing atmosphere in the blast furnace, and allows it to maintain its aggregate effect even in the high-temperature range inside the blast furnace where the ore layer softens and melts, improving breathability. The post-reaction strength (CSR) can be measured by reacting 200g of coke with a particle size of 19-21mm in a CO2 atmosphere at 1100°C for 2 hours, then conducting a rotational strength test (30 revolutions, 20 rpm) using an I-type drum at room temperature, and determining the mass fraction of the sieved size when sieved through a 9.52mm sieve.

[0022] Furthermore, it is advisable to heat treat woody biomass and / or herbaceous biomass at a temperature of 400°C or higher. This removes volatile components such as gas and tar, and prevents the strength of the molded biomass from decreasing due to the volatilization of gas and tar when the molded body is charged into a blast furnace. It also prevents the adverse effects of the generated tar on the gas purification equipment of the blast furnace.

[0023] Furthermore, biomass molded bodies can be produced by pressure molding using a continuous pressure molding machine such as an extruder or a double roll molding machine (briquette machine), which allows for the production of biomass molded bodies with high production efficiency. [Example]

[0024] Table 1 shows the results of investigating charging segregation when coke and 10 mass% of the biomass briquettes of the present invention were mixed and charged using a charging test machine simulating the inside of a blast furnace. As shown in Table 1, when the ratio of the average particle size of the biomass briquettes to the average particle size of the sintered ore was 0.10, the biomass briquettes were relatively small, so segregation of the biomass briquettes during charging was significant, making it difficult to control the charging distribution. In contrast, when the average particle size ratio was 0.25, the biomass briquettes segregated slightly during charging, but control of the charging distribution was generally possible. Furthermore, when the average particle size ratio was 0.50 or more, control of the charging distribution of the biomass briquettes was generally possible. This confirmed that it is effective to set the ratio of the average particle size of the biomass briquettes to the average particle size of the raw ore to 0.25 or more.

[0025] [Table 1]

[0026] Table 2 shows the results of investigating the segregation of the biomass shaped body when the apparent density of the biomass shaped body was changed using the same charging tester as above. As shown in Table 2, when the apparent density of the biomass shaped body was 0.6 g / cm 3 In the case of , the biomass molded bodies were relatively light, so segregation of the biomass molded bodies was large during charging, making it difficult to control the charging distribution. 3 In the case of , the biomass molded bodies segregated slightly during charging, but it was generally possible to control the charging distribution. 3 In the above cases, it was possible to control the distribution of the biomass shaped bodies. From this, it was found that the apparent density of the biomass shaped bodies was 0.8 g / cm 3 It was confirmed that the above is sufficient.

[0027] [Table 2]

[0028] Table 3 shows the results of an investigation into the relationship between the post-reaction strength (CSR%) of biomass shaped bodies and the air permeability resistance in the lumpy zone of the blast furnace shaft. As shown in Table 3, when the post-reaction strength of the biomass shaped bodies was 35%, the biomass shaped bodies were severely pulverized by gasification, and the air permeability and liquid permeability inside the blast furnace deteriorated. In contrast, when the post-reaction strength was 45%, the biomass shaped bodies were pulverized by gasification, but if the amount was small, the impact on the air permeability and liquid permeability inside the blast furnace was limited. Furthermore, when the post-reaction strength was 55% or higher, the biomass shaped bodies were slightly pulverized by gasification, but were generally usable. This confirmed that a post-reaction strength CSR of 45% or higher is desirable for biomass shaped bodies.

[0029] [Table 3]

[0030] Table 4 shows the results of an investigation into the relationship between the heat treatment temperature of agricultural residue biomass and the amount of volatile matter (VM) remaining after heat treatment. As shown in Table 4, when the heat treatment temperature was 300°C, the amount of volatile matter remaining after heat treatment was high, and tar adhesion to the inside of the blast furnace and the blast furnace exhaust gas treatment equipment became a problem. In contrast, when the heat treatment temperature was 400°C, the amount of volatile matter remaining after heat treatment was high, but if it was small, it could be used in a limited manner. Furthermore, when the heat treatment temperature was 600°C or higher, the amount of volatile matter remaining was low and it could be used in the blast furnace. From these results, it was confirmed that heat treatment of woody biomass and / or herbaceous biomass should be performed at a temperature of 400°C or higher.

[0031] [Table 4]

[0032] Although the present invention has been described above as an embodiment, the present invention is not limited to the descriptions and drawings that form part of the disclosure of the present invention. In other words, other embodiments, examples, and operational techniques that can be made by those skilled in the art based on the present invention are all included in the scope of the present invention. [Explanation of symbols]

[0033] 1 blast furnace 2 Ore Layers 3 Coke layer 4 Tuyere

Claims

1. A method for producing pig iron, comprising the steps of alternately stacking ore layers containing an ore raw material and coke layers containing coke in a blast furnace, blowing hot air and auxiliary fuel into the blast furnace from tuyere nozzles, and heating, reducing, and melting the ore raw material, A method for producing pig iron, comprising a step of mixing aggregate containing biomass molded bodies obtained by heat-treating and molding woody biomass and / or herbaceous biomass with the ore layer.

2. 2. The method for producing pig iron according to claim 1, wherein the amount of the biomass shaped bodies charged is 5 kg or more per ton of pig iron, and the ratio of the average particle size of the biomass shaped bodies to the average particle size of the raw ore is 0.25 or more.

3. The apparent density of the biomass molded body is 0.8 g / cm ３ The method for producing pig iron according to claim 1.

4. The method for producing pig iron according to claim 1, wherein the biomass molded body has a post-reaction strength CSR of 45% or more.

5. The method for producing pig iron according to claim 1, wherein the heat treatment is carried out at a temperature of 400°C or higher.

6. The method for producing pig iron according to claim 1, wherein the molding is carried out using a continuous pressure molding machine.

Images