Method for producing modified tar, method for producing binder for ironmaking raw materials, method for producing molded bodies, and method for producing ferrocoke

Abstract

To provide a method for producing reformed tar, capable of being used as a binder at low cost, by reforming tar.SOLUTION: A method in an aspect of the present invention for producing a modified tar includes: a dry distillation step of obtaining ferro coke and tar through dry distillation of a molded mixture of coal, iron ore, and a binder for a ferrous raw material; and a distillation step of distilling the tar.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing modified tar, a method for producing a binder for iron-making raw materials, a method for producing a molded body, and a method for producing ferrocoke.

Background Art

[0002] In a blast furnace for producing pig iron by reducing iron ore, coke is used as a reducing agent and a heat source (fuel). In the operation of this blast furnace, there is a strong demand for reducing carbon dioxide emissions as a measure against global warming and for improving efficiency. As a measure for improving the efficiency of blast furnace operation from the aspect of production raw materials, it is known to use coke containing iron (ferrocoke). In a blast furnace, iron ore, which is an iron-making raw material, and ferrocoke are arranged so as to form alternating layers. By adopting such a layer structure, the air permeability in the furnace is ensured, and the reduction reaction efficiency of iron ore is improved.

[0003] When iron ore or ferrocoke does not have sufficient strength, significant destruction (pulverization) of iron ore or ferrocoke occurs during operation, and the above layer structure collapses, resulting in deterioration of the air permeability in the blast furnace. Therefore, high strength is required for ferrocoke. However, since there is not enough binding force between coal, which is a raw material for ferrocoke, and iron ore, a binder for iron-making raw materials is required to mold ferrocoke. As such a binder for iron-making raw materials, a method for producing a ferrocoke raw material molded product (molded body) using an organic binder having a softening point of 100°C or lower has been proposed (Japanese Patent Application Laid-Open No. 2008-56777).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The organic binders described in the above-mentioned publication are relatively expensive, which may increase the manufacturing costs of the molded articles and the ferrocoke produced from them. There is a need to manufacture high-strength molded articles and ferrocoke at a low cost by using inexpensive binders.

[0006] The present invention has been made based on the circumstances described above, and its object is to provide a method for producing modified tar that can be used as a binder at low cost by modifying tar, and a method for producing a binder for steelmaking raw materials that has high binding strength at low cost. Another object of the present invention is to provide a method for producing molded articles and ferrocoke that have high strength at low cost. [Means for solving the problem]

[0007] A method for producing modified tar, which is one aspect of the present invention made to solve the above problems, comprises a carbonization step of obtaining ferrocoke and tar by carbonization of a molded body of a mixture containing coal, iron ore, and a binder for ironmaking raw materials, and a distillation step of distilling the tar.

[0008] Another aspect of the present invention, which was made to solve the above problems, is a method for manufacturing a binder for ironmaking raw materials, comprising a first carbonization step of obtaining first ferrocoke and tar by carbonization of a first molded body of a mixture containing coal, iron ore and first binder for ironmaking raw materials, and a distillation step of obtaining second binder for ironmaking raw materials by distilling the tar.

[0009] A further embodiment of the present invention, made to solve the above problems, is a method for manufacturing a molded body, comprising a mixing step of obtaining a mixture by mixing coal, iron ore, and the above-mentioned second ironmaking raw material binder, and a molding step of molding the mixture into a second molded body.

[0010] A further embodiment of the present invention, which was made to solve the above problems, is a method for producing ferrocoke, comprising a second carbonization step of carbonizing the second molded body to obtain second ferrocoke. [Effects of the Invention]

[0011] The present invention provides a method for producing modified tar and a binder for steelmaking raw materials, which allows for the low-cost production of modified tar usable as a binder by distilling and modifying the tar obtained in the process of obtaining ferrocoke. Because this modified tar has strong binding properties, it can be particularly suitable for use as a binder for steelmaking raw materials. Furthermore, the present invention provides a method for producing molded articles and ferrocoke, which allows for the production of molded articles and ferrocoke with low manufacturing costs and high strength by using a binder for steelmaking raw materials obtained by modifying the tar obtained in the process of obtaining ferrocoke. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a flowchart showing the manufacturing methods for a binder (modified tar) for steelmaking raw materials, a molded body, and ferrocoke according to one embodiment of the present invention. [Modes for carrying out the invention]

[0013] One aspect of the present invention is a method for producing modified tar, comprising a carbonization step of obtaining ferrocoke and tar by carbonization of a molded body containing coal, iron ore, and a binder for ironmaking raw materials, and a distillation step of distilling the tar.

[0014] The modified tar obtained by this manufacturing method can be produced at low cost because it uses tar obtained in the process of manufacturing ferrocoke. Furthermore, because this modified tar is modified by distillation, it can be used as a binder with strong binding properties.

[0015] In the distillation process described above, it is preferable to adjust the viscosity of the resulting modified tar to between 5 mPa·s and 139 mPa·s. Doing so can further increase the binder strength of the modified tar.

[0016] In the above distillation step, it is preferable to distill the above tar at a temperature of 320°C or higher and 450°C or lower in terms of normal pressure. By doing so, the strength of the modified tar as a binder can be further enhanced.

[0017] Another aspect of the method for manufacturing a binder for iron-making raw materials according to the present invention includes a first carbonization step of obtaining first ferro-coke and tar by carbonizing a first molded body of a mixture containing coal, iron ore, and a first binder for iron-making raw materials, and a distillation step of distilling the above tar to obtain a second binder for iron-making raw materials.

[0018] Since the binder for iron-making raw materials obtained by the manufacturing method uses the tar obtained in the process of manufacturing ferro-coke, it can be manufactured at a low cost. Further, since the binder for iron-making raw materials is obtained by distilling and modifying the above tar, coal and iron ore can be bonded with high strength.

[0019] Another aspect of the method for manufacturing a molded body according to the present invention includes a mixing step of obtaining a mixture by mixing coal, iron ore, and the above second binder for iron-making raw materials, and a molding step of molding the above mixture into a second molded body.

[0020] Since the molded body obtained by the manufacturing method uses the above second binder for iron-making raw materials, coals, iron ores, and coal and iron ore are bonded at high density and high strength. Therefore, the molded body has high strength and excellent handling properties. Further, since the manufacturing method uses the above second binder for iron-making raw materials, the above second molded body can be manufactured at a low cost.

[0021] Another aspect of the method for manufacturing ferro-coke according to the present invention includes a second carbonization step of carbonizing the above second molded body to obtain second ferro-coke.

[0022] By carbonizing the second molded body, the fusion of coals, iron ores, and between coal and iron ore can be promoted, and a second ferro-coke with high density and high strength can be obtained. Since the destruction of this ferro-coke in the blast furnace is suppressed, efficient blast furnace operation can be performed by using the second ferro-coke. Further, since the second molded body is used in this production method, the second ferro-coke can be produced at low cost.

[0023] [Details of the mode for carrying out the invention] The present invention will be described in detail below.

[0024] <Method for producing a binder for iron-making raw materials> The method for producing the binder for iron-making raw materials includes a carbonization step S1 of obtaining first ferro-coke and tar by carbonizing a first molded body of a mixture containing coal, iron ore, and a first binder for iron-making raw materials, and a distillation step S2 of distilling the tar to obtain a second binder for iron-making raw materials (S1 and S2 in FIG. 1). The second binder for iron-making raw materials is a modified tar obtained by distilling the tar obtained in the process of producing the first ferro-coke.

[0025] That is, the method for producing the modified tar according to one aspect of the present invention includes a carbonization step of obtaining first ferro-coke and tar by carbonizing a first molded body of a mixture containing coal, iron ore, and a first binder for iron-making raw materials, and a distillation step of distilling the tar to obtain a modified tar. The carbonization step in the method for producing the modified tar corresponds to the carbonization step S1 of the method for producing the binder for iron-making raw materials, and the distillation step in the method for producing the modified tar corresponds to the distillation step S2 of the method for producing the binder for iron-making raw materials. The modified tar can be used as a binder having a strong binding force, and is particularly suitable as a binder for iron-making raw materials.

[0026] The modified tar can also be used as other binders other than the binder for iron-making raw materials. Further, the modified tar can also be used as a fuel, a pitch, a raw material for carbon materials, etc.

[0027] [First carbonization process] The method for carbonizing the first molded body is not particularly limited, and examples include a method in which the first molded body is continuously loaded from the top of a vertical shaft furnace and carbonized as it moves from top to bottom inside the furnace.

[0028] The lower limit of the heating temperature in the first carbonization process is preferably 600°C, and more preferably 700°C. On the other hand, the upper limit of the heating temperature in the first carbonization process is preferably 950°C, and more preferably 900°C. By setting the heating temperature above the lower limit, the softening of the first ironmaking raw material binder is promoted, and the strength of the first ferrocoke can be improved. By setting the heating temperature below the upper limit, an increase in manufacturing costs can be suppressed from the standpoint of the heat resistance of the furnace and fuel consumption.

[0029] The lower limit of the heating time in the carbonization process is preferably 5 minutes, and more preferably 10 minutes. On the other hand, the upper limit of the heating time in the heat treatment process is preferably 24 hours, and more preferably 16 hours. By setting the heating time to be above the lower limit, the melting of the coal is promoted and the strength of the first ferrocoke can be improved, and by setting the heating time to be below the upper limit, fuel consumption can be suppressed and the increase in manufacturing costs can be prevented.

[0030] While there are no particular limitations on the atmosphere used for carbonization, a non-oxidizing gas atmosphere, such as a nitrogen atmosphere, is preferred to prevent deterioration due to oxidation of the coal.

[0031] The above tar is obtained by cooling the gas (steam) generated during the carbonization of the first molded body.

[0032] [Distillation process] The method of distilling the above tar is not particularly limited; it may be atmospheric pressure distillation or reduced pressure distillation. The upper limit of the reduced pressure when performing reduced pressure distillation is not particularly limited; for example, it may be 70 mmHg or 60 mmHg. The lower limit of the reduced pressure when performing reduced pressure distillation is not particularly limited; if possible, it may be 2 mmHg.

[0033] When the above tar is distilled to remove the low-boiling point components, modified tar (a binder for ironmaking raw materials) is obtained as the residue.

[0034] In the above distillation process, it is preferable to distill the tar at a temperature of 320°C to 450°C in terms of atmospheric pressure. A lower limit of 330°C is more preferable for the lower limit of the temperature in terms of atmospheric pressure. A higher limit of 390°C is more preferable for the upper limit of the temperature in terms of atmospheric pressure. By using such a temperature range, the binder for the second ironmaking raw material can be easily made to have a suitable viscosity. Specifically, by setting the temperature in terms of atmospheric pressure above the lower limit, the resulting binder for the second ironmaking raw material (modified tar) becomes excessively low viscosity, which reduces the bonding force between the coal and the iron ore (the objects to be bound), thus suppressing a decrease in the strength of the second molded body described later. Also, by setting the temperature in terms of atmospheric pressure below the upper limit, the binder for the second ironmaking raw material becomes excessively high viscosity, which makes it difficult for it to penetrate between the coal and the iron ore, thus suppressing a decrease in the strength of the second molded body.

[0035] In the above distillation process, it is preferable to adjust the viscosity of the second ironmaking raw material binder (modified tar) obtained to 5 mPa·s or more and 139 mPa·s or less. The lower limit of the viscosity is preferably 10 Pa·s. The upper limit of the viscosity is preferably 100 Pa·s. By setting the viscosity above the lower limit, a decrease in the bonding force between the coal and the iron ore can be suppressed, and by setting the viscosity below the upper limit, it is possible to suppress the difficulty of penetration between the coal and the iron ore. Note that "viscosity" refers to the value of the viscosity at 150°C measured with a Brookfield viscometer according to industrial analysis (JIS M 8812).

[0036] <Method for manufacturing molded products> The method for manufacturing the molded body comprises a mixing step S3 to obtain a mixture by mixing coal, iron ore, and the above-mentioned binder for second-generation ironmaking raw materials, and a molding step S4 to mold the mixture into a second molded body (S3 and S4 in Figure 1).

[0037] (coal) The coal used is not particularly limited and can be any known coal, ranging from low-carbonized lignite with a carbon content (daf: dry ash free) of less than 78% to high-carbonized anthracite with a carbon content exceeding 91%. Among these, coal with a carbon content of 78% to 91% is preferred from the viewpoint of ensuring the strength of the second molded body. Examples of such coal include bituminous coal and sub-bituminous coal. Note that "carbon content" refers to the carbon content (mass %) relative to the organic matter (C, H, N, S, O) of the coal excluding moisture and ash, and is measured in accordance with JIS-M8819:1997.

[0038] Furthermore, from the viewpoint of suppressing the manufacturing cost of the second molded body, it is preferable that the coal includes low-grade coal such as sub-bituminous coal and lignite, as well as general coal, which are inexpensive but have low coking properties, and it is particularly preferable that it includes inferior coal. "Inferior coal" refers to coal with a carbon content of 85% by mass or less and a logarithmic value of maximum fluidity LogMF [logddpm] of 1 or less. Here, "maximum fluidity MF [ddpm]" means the value measured by the Gieseler plastometer method in accordance with JIS-M8801:2004.

[0039] The lower limit of the inferior coal content in the total coal is preferably 20% by mass, and more preferably 30% by mass. On the other hand, the upper limit of the inferior coal content in the total coal is preferably 60% by mass, and more preferably 50% by mass. By setting the inferior coal content in the total coal to be above the lower limit, the manufacturing cost of the second molded body can be reduced by using inferior coal, and by setting the inferior coal content in the total coal to be below the upper limit, the strength of the second molded body produced can be improved.

[0040] The above coal is in the form of finely ground particles. The upper limit of the particle size is preferably 4 mm, and more preferably 2 mm. By keeping the particle size of the coal below the above upper limit, the binder for ironmaking raw materials can be sufficiently filled between the coal particles, thereby improving the strength of the molded body. Note that "particle size" refers to the particle size that can be sieved through a metal mesh sieve as specified in JIS-Z8801-1:2006. For example, a particle size of 4 mm or less means the particle size that can be sieved through a sieve with a mesh opening of 4 mm in accordance with JIS Z 8801-1:2006.

[0041] The above coal may be dried by air drying or other means, or it may be used in a state that still contains moisture.

[0042] (Iron ore) The iron ores mentioned above are not particularly limited, and examples include hematite (Fe2O3), magnetite (Fe3O4), limonite (Fe2O3·nH2O), and iron oxyhydroxide (FeOOH). When using iron oxyhydroxide, it is preferable to dehydrate it beforehand to obtain iron oxide. These iron ores may be used individually or in combination of two or more types.

[0043] The iron ore described above is in the form of finely ground particles. The upper limit of the particle size at which 90% of the cumulative mass of these particles is obtained is preferably 250 μm, more preferably 200 μm, and even more preferably 150 μm. By keeping the particle size below the above upper limit, the stress acting at the interface of the iron ore can be suppressed, and the decrease in strength of the resulting second molded body can be prevented.

[0044] The lower limit of the iron ore content in the total mass of the above coal and iron ore is preferably 5% by mass, and more preferably 10% by mass. On the other hand, the upper limit of the iron ore content in the total mass of the above coal and iron ore is preferably 40% by mass, and more preferably 30% by mass. By setting the iron ore content in the total mass of the above coal and iron ore to be above the lower limit, the efficiency of blast furnace operation can be improved by the coexistence of the iron ore, and by setting it to be below the upper limit, the reactivity-enhancing effect of the iron ore can be prevented from reaching a plateau.

[0045] [Mixing process] In the mixing process, a mixture is obtained by mixing the above-mentioned coal, iron ore, and the above-mentioned binder for second-stage ironmaking raw materials. The above mixing is preferably carried out by heating. The heating temperature in the mixing is preferably in the temperature range in which the binder for second-stage ironmaking raw materials melts, for example, preferably between 80°C and 150°C. The atmosphere in the mixing is not particularly limited, and the mixing may be carried out in an inert atmosphere using nitrogen or the like, or in air. The means (apparatus) for mixing is not particularly limited, and existing means may be used for mixing.

[0046] The lower limit of the content of the second ironmaking raw material binder in the above mixture is preferably 1% by mass, and more preferably 3% by mass. On the other hand, the upper limit of the content of the second ironmaking raw material binder is preferably 15% by mass, and more preferably 12% by mass. By setting the content of the second ironmaking raw material binder to be above the lower limit, the second molded body can be made sufficiently strong and dense, and by setting the content of the second ironmaking raw material binder to be below the upper limit, the manufacturing cost of the second molded body can be suppressed.

[0047] [Molding process] In the molding process, a second molded body is obtained by molding the above mixture. The molding method is not particularly limited, and examples include using a twin-roll molding machine with flat rolls, a twin-roll molding machine with almond-shaped pockets, a single-screw press or roller-type molding machine, or an extrusion molding machine. Among these, it is preferable to use a twin-roll molding machine, which has high productivity.

[0048] The pressure used during molding by the molding machine is not particularly limited; for example, 3 t / cm² 2 5 t / cm² or more 2 The following is the result: By applying such pressure, the strength and density of the second molded body can be increased.

[0049] Furthermore, molding is preferably carried out by heating. The heating temperature during molding is preferably above the softening start temperature of the second ironmaking raw material binder, for example, 80°C to 150°C. By setting the heating temperature above the softening start temperature of the second ironmaking raw material binder, the second ironmaking raw material binder softens, promoting the densification and strength of the second molded body.

[0050] The shape of the second molded body is not particularly limited and can be, for example, briquette-shaped or pellet-shaped. The average volume of the second molded body can be, for example, 2 mL or more and 20 mL or less.

[0051] Since the second molded body is formed by molding the above mixture, carbonization of this second molded body strongly binds the iron ore particles together, the coal particles together, and the iron ore and coal particles together. Therefore, the strength of the second ferrocoke, which will be described later, can be improved. Furthermore, the modified tar, which is the binder for the ironmaking raw material of the second molded body, is inexpensive because it is produced from tar, a by-product of obtaining the first ferrocoke. Thus, by using the above second molded body, high-strength second ferrocoke can be produced at a low cost.

[0052] <Method for producing ferrocoke> The method for producing the ferrocoke includes a second carbonization step S5 in which the second molded body is carbonized to obtain a second ferrocoke (S5 in Figure 1).

[0053] [Carry distillation process] The method for carbonizing the second molded body is not particularly limited and can be the same as the procedure for the first carbonization step described above.

[0054] <Advantages> The modified tar can be produced at low cost because it is distilled from tar obtained as a by-product in the ferrocoke manufacturing process. Furthermore, because the modified tar can be used as a binder with strong binding properties, it is particularly suitable as a binder for steelmaking raw materials. The molded body can be manufactured at low cost, with high density and high strength because it uses the modified tar as a binder for steelmaking raw materials. The ferrocoke can be manufactured at low cost and with high strength because it is produced by carbonization of the molded body.

[0055] [Other embodiments] The embodiments described above should be considered in all respects as illustrative and not restrictive. The scope of the present invention is not limited to the configurations of the embodiments described above, but is indicated by the claims, and all modifications within the meaning and scope of the claims are intended to be included. [Examples]

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0057] Tar obtained during the ferrocoke manufacturing process was subjected to simple distillation under reduced pressure at a temperature equivalent to atmospheric pressure between 310°C and 450°C. This distillation removed low-boiling point components, yielding modified tars (binders for steelmaking raw materials) B1-B9 as distillation residues. The volatile content (VM) and 150°C viscosity of the recovered modified tars were measured. Table 1 shows the distillation conditions, volatile content, and 150°C viscosity. VM is defined as JIS M The measurements were taken in accordance with 8812:2004. Viscosity was measured in accordance with the measurement method using a single-cylindrical rotational viscometer as specified in JIS Z 8803:2011.

[0058] [Table 1]

[0059] Coal (100% particle size 1 mm or less), iron ore (100% particle size 0.25 mm or less), asphalt pitch (100% particle size 0.5 mm or less), and ironmaking raw material binders B1 to B9 were blended in a mass ratio of 64.8:27.8:3.0:4.5, respectively, and uniformly mixed at a temperature of 140°C to obtain a mixture. As a comparative test example, a comparative mixture was also prepared in which soft pitch (SOP) was mixed in place of the above ironmaking raw material binders. The components, content ratios, and mixing conditions of this comparative mixture, other than the ironmaking raw material binders, were the same as those of the above mixture.

[0060] The above comparative mixture and the above mixture were subjected to a temperature of 140°C at a rate of 3 t / cm². 3 By applying pressure, cylindrical molded bodies with a diameter of 30 mm and a height of 10 mm were obtained (Test Examples 1-10). A portion of each molded body from Test Examples 1-10 was heated to 900°C in a nitrogen atmosphere at 5°C / min, held at 900°C for one hour, and dried to obtain ferrocoke samples from Test Examples 1-10. The strength of these molded bodies and ferrocoke samples was evaluated by indirect tensile testing. In the above indirect tensile testing, pressure was gradually applied radially to the molded bodies and ferrocoke samples using a benchtop precision universal testing machine (Autograph AGS-X: Shimadzu Corporation), and the tensile stress (strength) was calculated from the pressure at the time the molded bodies and ferrocoke samples fractured using Equation 1 below.

[0061]

number

[0062] The molded bodies and ferrocoke samples obtained from the above comparative mixture are designated as Test Example 1, and the molded bodies and ferrocoke samples obtained from the above mixture are designated as Test Examples 2 to 10. The results of the above indirect tensile tests are shown in Table 2. For the strength evaluation of the molded bodies and ferrocoke samples in Test Examples 2 to 10, those with 90% or more of the strength of Test Example 1 were designated as "A," and those with less than 90% were designated as "C." In the overall evaluation, those with 90% or more of the strength of both the molded body and ferrocoke sample compared to Test Example 1 were designated as "A," those with 90% or more of the strength of the molded body compared to Test Example 1 but less than 90% of the strength of the ferrocoke sample were designated as "C," and those with less than 90% of the strength of the molded body compared to Test Example 1 but 90% or more of the strength of the ferrocoke sample were designated as "B."

[0063] [Table 2]

[0064] In Test Example 2, the molded body showed high strength, but the ferro-coke sample showed low strength. This is likely because the atmospheric pressure equivalent temperature in the distillation process was low, preventing sufficient 150°C viscosity from being obtained for the binder used for steelmaking raw materials. In Test Examples 9 and 10, the molded body showed low strength, but the ferro-coke sample showed high strength. This is likely because the atmospheric pressure equivalent temperature in the distillation process was high, resulting in excessive 150°C viscosity of the binder used for steelmaking raw materials. [Industrial applicability]

[0065] As described above, the modified tar and ironmaking raw material binder of the present invention can be obtained at low cost and can produce high-strength molded bodies and ferrocoke, making it suitable for efficient blast furnace operation.

Claims

1. A carbonization process to obtain ferrocoke and tar by carbonization of a molded body containing coal, iron ore, and a binder for ironmaking raw materials, A distillation process to obtain modified tar having a viscosity of 5 mPa·s or more and 139 mPa·s or less at 150°C, by distilling the above tar at a temperature equivalent to atmospheric pressure of 320°C or more and 450°C or less. A method for producing modified tar, comprising the following:

2. A first carbonization step to obtain first ferrocoke and tar by carbonization of a first molded body of a mixture containing coal, iron ore, and a binder for first ironmaking raw materials, A distillation process to obtain a binder for second-generation ironmaking raw materials, in which the above tar is distilled at a temperature equivalent to atmospheric pressure of 320°C to 450°C, and the viscosity at 150°C is 5 mPa·s to 139 mPa·s. A method for manufacturing a binder for ironmaking raw materials, comprising the features described above.

3. A mixing step of obtaining a mixture by mixing coal, iron ore, and a binder for second ironmaking raw materials obtained by the manufacturing method described in claim 2, A molding process for forming a second molded body by mixing the above ingredients. A method for manufacturing a molded article comprising the following:

4. A second carbonization step to obtain a second ferrocoke by carbonizing the second molded body obtained by the manufacturing method described in claim 3. A method for producing ferrocoke, comprising the following features.

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