Method for producing carbon iron composite

Abstract

To provide a method for producing ferrocoke by which high-strength ferrocoke can be produced even when a large amount of molding powder produced in a molding step is blended.SOLUTION: A method for producing carbon iron composite according to the present invention includes a molding step of molding a molding material with a double roll molding machine to produce a molded material, a separation step of separating the molded material into a molded material for carbonization and a molding powder, and a carbonization step of carbonizing the molded material for carbonization to produce carbon iron composite, wherein the molding material contains coal, an iron source material, a binder, and the molding powder, and in the molding step, a molding condition satisfies a condition based on a ratio of the molding powder in the molding material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing ferro-coke for metallurgy using an iron source material such as iron ore, coal, and briquettes as raw materials. [Background technology]

[0002] In order to efficiently operate a blast furnace, coal is carbonized in a coke oven to produce coke, and the coke is then charged into the blast furnace. The coke in the blast furnace serves various purposes, including as a spacer to improve ventilation within the furnace, as a reducing agent, and as a heat source. In recent years, a technique has been developed to obtain ferrocoke for metallurgy by mixing iron ore with coal in order to improve the reactivity of the coke (see, for example, Patent Document 1). Whether the ferrocoke raw material is rich in coal or rich in iron ore is determined arbitrarily depending on whether it is intended to replace coke or to be used as an iron source.

[0003] In the process of producing this ferro-coke, coal and iron ore need to be agglomerated in a molding machine. There are two types of agglomeration methods: one in which a binder is added to the raw materials and molding is performed at room temperature to about 250°C; and another in which the coal is softened and melted at a high temperature of 250°C or higher and molding is performed using the caking properties of the coal without adding a binder. Known examples of the former method include kneading coal, iron ore, and a binder in a kneading machine and then molding at room temperature (see, for example, Patent Document 2). Known examples of the latter method include mixing coal and iron ore, rapidly heating to 250°C or higher, and molding under pressure (see, for example, Patent Document 3). The agglomerated moldings are carbonized in a carbonization furnace to produce ferro-coke.

[0004] As another example of a method for producing ferro-coke, Patent Document 4 reports that powdered parts (hereinafter also referred to as briquetting powder), which are defective products rejected as finished products during briquetting, are blended in an amount of 3 to 15 mass% with respect to new raw materials. Furthermore, Patent Document 5 reports that when pulverized coal of 0.5 mm or less is hot briquetting, the linear pressure is changed depending on the maximum particle size, the apparent density and the porosity of the briquetting coal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-15700 A (Claims) [Patent Document 2] JP-A-64-81889 (page 2) [Patent Document 3] JP 2005-53986 A (Claim 3) [Patent Document 4] Patent No. 5365044 [Patent Document 5] Japanese Patent Application Publication No. 8-259951 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, the methods for producing ferro-coke described in Patent Documents 1 to 3 include a kneading process for kneading raw materials, a transporting process for transporting the mixed raw materials to a molding machine, a molding process for agglomerating the raw materials, and a subsequent process for carbonizing the agglomerated materials to obtain a ferro-coke product. In producing ferro-coke, the agglomerated materials must have high handling strength, and the strength of the carbonized ferro-coke product must also be high because it is fed into a blast furnace. However, the briquetting yield in the briquetting process is important in terms of production costs. However, since a considerable amount of defective powder (briquette powder) is generated during the briquetting and handling processes, there has been a recent demand for reducing the amount of new raw material used by reusing this powder.

[0007] In this regard, the method of Patent Document 4 allows for the blending of 3 to 15 mass% of molded powder, but when the blending amount exceeds 15 mass%, there is a problem that the dispersibility of the binder is hindered and the quality and strength are reduced. Also, in ferro-coke plants, there are cases where 30 mass% of molded powder is generated due to operational disturbances, etc., and a technology that can always reuse the entire amount depending on the amount generated has been desired. Furthermore, the method of Patent Document 5 can be applied to pulverized coal with a sieve top size of about 0.5 mm, but it is difficult to apply to molded powder of ferro-coke with a sieve top size of 10 mm or more.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing ferro-coke that can produce high-strength ferro-coke even when a large amount of molding powder generated in the molding step is blended with new raw materials. [Means for solving the problem]

[0009] The method for producing ferro-coke of the present invention includes a molding step of molding raw materials for molding using a double-roll molding machine to produce molded products, a separation step of separating the molded products into molded products for carbonization and molded powder, and a carbonization step of carbonizing the molded products for carbonization to produce ferro-coke, wherein the raw materials for molding contain coal, an iron source raw material, a binder, and the molded powder, and in the molding step, molding conditions satisfy conditions based on the ratio of molded powder in the raw materials for molding.

[0010] In the method for producing ferro-coke according to the present invention configured as described above, (1) The molding conditions are the linear pressure of a double roll molding machine; (2) The linear pressure is within a predetermined range based on the linear pressure under conditions in which molding powder is not included and the linear pressure increase rate per molding powder ratio. (3) The linear pressure satisfies the following formulas (1) and (2): 0.9{P0×(a×R+1)} <P<1.1{P0×(a×R+1)}···(1) 0 <R≦0.4···(2) where P is the linear pressure (tf / cm), P0 is the linear pressure (tf / cm) when the molding powder is 0% by mass, a is the constant 1.2 (-), R is the molding powder ratio (-), and the linear pressure P (tf / cm) = roll pressure (tf) / roll length (cm). (4) The molding powder ratio in the molding raw material is 0.2 or more; This is considered to be a more preferable solution. [Effects of the Invention]

[0011] According to the method for producing ferro coke of the present invention, by satisfying the molding conditions based on the molding powder ratio in the raw material for molding in the molding step, it is possible to produce high-strength ferro coke even when a large amount of molding powder is blended. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a flowchart showing an embodiment of a production flow in a method for producing ferro coke according to the present invention. [Figure 2] FIG. 1 is a schematic view showing one embodiment of a molding machine used in the method for producing ferro-coke of the present invention. [Figure 3] 10 is a graph showing an example of the relationship between particle sizes of new raw materials and molding powder and cumulative ratios. [Figure 4] 1 is a graph showing an example of the relationship between the linear pressure of the molding raw material and the I-shape strength of the molding when the molding powder ratio is 0, 0.2, 0.4, and 0.5. [Figure 5] 1 is a graph showing an example of the relationship between the molding powder ratio and the linear pressure of the molding material. DETAILED DESCRIPTION OF THE INVENTION

[0013] In the following detailed description, numerous specific details are set forth to illustrate embodiments of the present invention in order to provide a thorough understanding of the present invention. However, it will be apparent that one or more embodiments may be practiced without such specific details. Also, for the sake of clarity, the drawings may depict well-known structures and devices in simplified form.

[0014] <One embodiment of the production flow for the production of ferro coke of the present invention> (molding process) FIG. 1 is a flowchart showing one embodiment of a production flow in the method for producing ferro-coke of the present invention. In the example shown in FIG. 1, coal 1 and iron source raw material 2 are pulverized to a predetermined particle size or less in a pulverizer (not shown) and then blended in a predetermined ratio. For example, the coal and iron source raw material are pulverized to 3 mm or less. Then, for example, they are blended in a ratio of 60 to 90 mass % coal and 10 to 40 mass % iron source raw material. Iron ore is mainly used as the iron source raw material 2, but iron ore may be replaced by iron source raw materials by-produced in steelworks, such as blast furnace dust, converter dust, or rolling sludge. Furthermore, multiple brands of iron ore and coal may be combined. In this embodiment, iron ore is used as the iron source raw material 2.

[0015] The blended coal 1 and iron ore 2 are fed into a kneader 3. A binder is added to the kneader 3 from a binder tank 4. Commonly used binders include soft pitch (SOP), asphalt pitch (ASP), and ferrotar (a by-product produced during the carbonization process of ferro-coke), and one or more types can be used in combination. The binder is added from the binder tank 4 at the same time as the coal 1 and iron ore 2 are fed into the kneader 3, or during kneading. Through the above process, a mixed raw material for molding can be obtained.

[0016] The kneaded molding raw material is transferred via conveying equipment 5 to a double-roll molding machine 6, which is a high-pressure molding machine, and is subjected to high-pressure molding. Typical examples of the conveying equipment 5 include a belt conveyor, a flight conveyor, and a screw feeder. The double-roll molding machine 6 molds the kneaded molding raw material.

[0017] (separation process) The briquettes (briquettes) formed by the double roll molding machine 6 are separated into oversized charcoal 7 and undersized charcoal 8 through a sieve. The oversized charcoal 7 is used as a briquette for carbonization, and the undersized charcoal 8 is mixed with new raw materials as briquette powder and reused.

[0018] (carbonization process) The briquettes separated as the oversized particles 7 are supplied to a carbonization furnace 9, where they are carbonized to form ferro-coke. The briquetting yield is calculated by dividing the weight of the oversized particles 7 by the sum of the weights of the oversized particles 7 and the undersized particles 8. An example of the shape of the briquettes is an oval shape with a major axis of 25 mm, a minor axis of 18 mm, and a depth of 6 mm.

[0019] The strength quality of the molded product is evaluated by sampling (10) the molded product on the sieve 7 from the system discharge pipe and measuring the I-type strength of the molded product (11).

[0020] <Regarding the molding machine used in the method for producing ferro-coke of the present invention> In the present invention, a double-roll molding machine is used as the molding machine. In the double-roll molding machine, it is desirable to optimize the linear pressure and suppress the pressure deviation in the width direction according to the molding powder ratio in the molding raw material from the viewpoint of improving strength.

[0021] FIG. 2 is a schematic diagram showing a double-roll molding machine as one embodiment of a molding machine used in the ferro-coke manufacturing method of the present invention. In the example shown in FIG. 2, an adjusting gate 13 is provided between a double-roll molding machine 6, which is composed of a conveying roll 6-1 rotating counterclockwise and a fixed roll 6-2 rotating clockwise, and a raw material hopper 12, which stores the mixed raw material for molding. Specifically, the adjusting gate 13 is arranged so as to be able to rise and fall above a kiss portion K between the conveying roll 6-1 and the fixed roll 6-2 of the double-roll molding machine 6. The adjustment gate 13 is raised and lowered by using a power cylinder (not shown) to change the height of the adjusting gate 13 while the raw material is being transported. The adjusting gate 13 is made of a plate-shaped member formed across the entire width of the double-roll molding machine 6.

[0022] In this embodiment, the absolute value of the linear pressure can be controlled using the adjusting gate 13. When the gate position of the adjusting gate 13 is high, a large amount of raw material is supplied, increasing the linear pressure, whereas when the gate position of the adjusting gate 13 is lowered, a small amount of raw material is supplied, decreasing the linear pressure. Furthermore, the linear pressure can be reduced by increasing the roll length, and can be increased by shortening the roll length.

[0023] <Regarding the method for producing ferro-coke of the present invention> The method for producing ferro-coke of the present invention will be described below with reference to Figs. 3 to 5. Fig. 3 is a graph showing an example of the relationship between the particle sizes of the new raw material and the briquetting powder and the briquetting powder ratio. Fig. 4 is a graph showing an example of the relationship between the linear pressure of the briquetting raw material and the I-shape strength of the briquetting powder when the briquetting powder ratio is 0, 0.2, 0.4, and 0.5. Fig. 5 is a graph showing an example of the relationship between the briquetting powder ratio and the linear pressure.

[0024] Figure 3 shows the particle size distribution of the new raw materials (coal and iron source raw materials) and the shaped powder used to obtain the results in Figures 4 and 5. There are no particular restrictions on the size of the sieve used to separate the shaped powder, but a 16 mm sieve was used in this study.

[0025] In the example shown in Figure 4, the strength of the molded product was measured using an I-type drum testing device (a cylindrical device with an inner diameter of 130 mm and a diameter of 700 mm). The I-type strength was determined by the percentage of parts remaining 15 mm or larger after 30 revolutions at a rotation speed of 20 revolutions per minute. The linear pressure was calculated by dividing the pressure applied by the roll by the length of the roll. There is an optimum value (optimum linear pressure) for the linear pressure at which the I-type strength is maximized; insufficient linear pressure results in a decrease in strength due to insufficient molding, while excessive linear pressure causes cracks and a deterioration in strength. From the above, the inventors discovered that the optimum linear pressure changes depending on the molding powder ratio, which indicates the blending ratio of the molding powder.

[0026] From the results in Figure 5, it was found that the optimum linear pressure at which the I-type strength is maximized increases as the molding powder ratio increases (hereinafter referred to as P), compared to the optimum linear pressure (hereinafter referred to as P0) when no molding powder is contained (molding powder ratio 0 mass%). R The optimum linear pressure P at which the I-type strength is maximized isR It was found that the value of changes linearly with the molding powder ratio R(-), and the rate of change is the molding powder ratio R × 1.2. Furthermore, the linear pressure does not necessarily become the optimum linear pressure P R It is not necessary to set the optimum linear pressure P R 0.9P R ~1.1P R It was found that if the strength is within the range of , the I-type strength can be maintained within the appropriate range (specifically, the I-type strength is 85% or more).

[0027] From the above, in a preferred embodiment seen from FIGS. 3 to 5, the inventors have found that by setting the linear pressure of the double-roll molding machine within the range of the following formula (1), it is possible to produce high-strength ferro-coke even when a large amount of molding powder is mixed. 0.9{P0×(a×R+1)} <P<1.1{P0×(a×R+1)}···(1) 0 <R≦0.4···(2) Here, P: linear pressure (tf / cm), P0: linear pressure (tf / cm) when molding powder is 0% by mass, a: constant 1.2 (-), R: molding powder ratio (-), and linear pressure P (tf / cm) = roll pressure (tf) / roll length (cm). In the above formula (1), a is set to a constant of 1.2(-). This is because, although a is 1.2 in the embodiments described so far, if other conditions such as material composition change, it is believed that an optimal constant a other than 1.2 exists.

[0028] The reason why the optimum linear pressure changes depending on the molding powder ratio is presumably because the molding powder has been heated once in the kneader, causing the binder to volatilize compared to new raw materials, making it necessary to compensate for the binder deficiency with a higher linear pressure. Furthermore, when the molding powder ratio was 0.5, increasing the linear pressure did not restore the strength to the lower limit of 85%. Based on these facts, in the present invention, it was considered preferable to satisfy the following formula (2) in addition to the above formula (1). 0 <R≦0.4···(2)

[0029] Furthermore, from the viewpoint of increasing the yield by blending a large amount of the generated molding powder, it is preferable to set the molding powder ratio in the range of 0.2 to 0.4. If molding is performed at this molding powder ratio, it is found that the generated molding powder in this process is 20 to 40 mass %, and therefore the entire amount of molding powder can be utilized. [Industrial Applicability]

[0030] As described above, when using molding powder, the molding conditions must satisfy the conditions based on the molding powder ratio in the raw materials for molding, and preferably, molding is performed at an appropriate linear pressure estimated from equation (1) under the condition of equation (2), thereby ensuring the strength of the molding powder and making it possible to use it. As a result, raw materials are not wasted, and a manufacturing method for ferro-coke can be achieved that can reduce manufacturing costs, which is industrially useful. [Explanation of symbols]

[0031] 1. Coal 2. Iron ore 3. Mixing machine 4 binder tank 5. Conveying equipment 6 Double roll molding machine 6-1 Transport roll 6-2 Fixed roll 7 Sieve top 8 Under the sieve 9. Dry distillation furnace 10. Sampling 11 Strength evaluation 12 Raw material hopper 13 Adjustment gate K Kiss Club

Claims

1. A method for producing ferro coke, comprising: a molding step of molding a raw material for molding using a double roll molding machine to produce a molded product; a separation step of separating the molded product into a molded product for carbonization and a molded powder; and a carbonization step of carbonizing the molded product for carbonization to produce ferro coke, the molding raw material contains coal, an iron source raw material, a binder, and the molding powder; In the molding step, the molding conditions satisfy the conditions based on the molding powder ratio in the molding raw material. Ferro coke manufacturing method.

2. 2. The method for producing ferro-coke according to claim 1, wherein the molding condition is a linear pressure of a double-roll molding machine.

3. 3. The method for producing ferro-coke according to claim 2, wherein the linear pressure is within a predetermined range based on the linear pressure under conditions in which the molded powder is not included and the linear pressure increase rate per ratio of the molded powder.

4. The method for producing ferro-coke according to claim 2, wherein the linear pressure satisfies the following formulas (1) and (2): 0.9{P ０ ×(a×R+1)}<P<1.1{P ０ ×(a×R+1)}・・・(1) 0<R≦0.4 (2) where P is linear pressure (tf / cm), P ０ : Linear pressure (tf / cm) when molding powder is 0 mass%, a: Constant 1.2 (-), R: Molding powder ratio (-), and linear pressure P (tf / cm) = Roll pressure (tf) / Roll length (cm).

5. The method for producing ferro coke according to any one of claims 1 to 4, wherein the ratio of molded powder in the raw material for molding is 0.2 or more.

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