Method for producing ferrocoke raw material

Abstract

To provide an efficient and novel method for producing a ferrocoke raw material that takes into consideration an improvement in a molding yield in a molding step for agglomerating raw materials.SOLUTION: A method for producing a ferrocoke raw material of the present invention comprises kneading a molding raw material containing coal, an iron source raw material, and a binder, transporting the kneaded molding raw material to a double roll molding machine, and carbonizing a molded product agglomerated by the double roll molding machine to produce ferrocoke, wherein the kneaded molding raw material is transported to the double roll molding machine using a vibration conveyor. In a preferred example, a vibration feeder is used as the vibration conveyor to transport the kneaded molding raw material, and a variation Isp in a particle size distribution of the kneaded molding raw material supplied to the double roll molding machine is 200 or more and 600 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing ferro-coke raw material in a process for producing ferro-coke for metallurgy from an iron source raw material such as iron ore and coal 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. [Prior art documents] [Patent documents]

[0004] [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] JP 2009-235222 A (Claim 4) Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, the production of ferro-coke involves a mixing process for mixing raw materials, a transport process for transporting the mixed raw materials to a molding machine, a molding process for agglomerating the agglomerates, and a subsequent process for carbonizing the agglomerates to obtain a ferro-coke product. In producing ferro-coke, the agglomerates 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, while Patent Documents 1 to 3 discuss the briquetting temperature, the types of raw materials used, and auxiliary materials, they do not consider the briquetting yield.

[0006] Patent Document 4 proposes blending a powdery portion into the raw material at a predetermined ratio and using a double-roll molding machine to improve molding yield. However, powdery portions are defective products that are rejected as finished products during molding, and it is desirable to prevent their generation. Furthermore, although the technology described in Patent Document 4 is a technology for improving molding yield, it was unable to improve the molding yield of molded products at a level that has been highly demanded in recent years.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to propose a new and efficient method for producing ferro-coke raw materials, which takes into consideration an improvement in the briquetting yield in the briquetting step of agglomerating raw materials. [Means for solving the problem]

[0008] The inventors discovered that the particle size of the test raw material has a large effect on the performance of a double-roll molding machine, and that a broader particle size distribution increases the amount of material filled into the cup and improves molding yield. This led them to come up with the idea of ​​broadening the particle size distribution of the raw material supplied to the molding machine in advance.

[0009] The method for producing a ferro-coke raw material of the present invention is characterized in that, when a briquetting raw material containing coal, an iron source raw material, and a binder is mixed and kneaded, the mixed briquetting raw material is transported to a double-roll molding machine, and the briquettes formed by the double-roll molding machine are carbonized to produce ferro-coke, the mixed briquetting raw material is transported to the double-roll molding machine using a vibrating conveyor.

[0010] In the method for producing a ferro coke raw material of the present invention configured as described above, (1) Using a vibrating feeder as the vibrating conveyor, and conveying the kneaded molding raw material by the vibrating feeder; (2) The particle size distribution variation Isp (defined by the following formula 1) of the kneaded molding material supplied to the double roll molding machine is 200 or more and 600 or less:

[0011]

number

[0012] In this study, 1 kg of powder sample after stirring was collected and sieved using sieves with openings of 0.074, 0.15, 0.25, 0.5, 1.0, 2.0, and 3.0 mm in order of decreasing size, and the weight percentage of each particle size was measured. The representative particle size (di) between the sieve openings in particle size analysis was calculated using the geometric mean of the larger and smaller openings. For particles 0.074 mm or smaller, the representative particle size (di) was set to 0.037 mm (1 / 2 of 0.074 mm), and for particles 3 mm or larger, the representative particle size (di) was set to 3.9 mm (the geometric mean of 3 mm and 5 mm). [Effects of the Invention]

[0013] According to the method for producing ferro-coke of the present invention, by selecting and using a vibratory conveyor from among various conveying devices, which can broaden the particle size distribution of raw materials including a binder during the conveying process, it is possible to improve the yield of compacts formed by a double-roll compactor. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a flowchart showing one embodiment of a method for producing ferro coke, including a method for producing a ferro coke raw material of the present invention. [Figure 2] 1 is a graph showing the influence of a production method on a briquetting yield in a production method for a ferro-coke raw material of the present invention. [Figure 3] 1 is a graph showing the influence of a production method on the variation in particle size distribution (Isp) in a production method for a ferro-coke raw material of the present invention. [Figure 4] 1 is a graph showing the effect of the variation in particle size distribution (Isp) on the briquetting yield in the method for producing a ferro-coke raw material of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes in detail the embodiments of the present invention. Note that the following embodiments are intended to exemplify devices and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to that described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope defined in the claims.

[0016] <One embodiment of the method for producing ferro coke raw material of the present invention> FIG. 1 is a flowchart showing one embodiment of a method for producing ferro-coke, including the method for producing ferro-coke raw material of the present invention. In the example shown in FIG. 1, coal 1 and iron-source raw material 2 are crushed to a predetermined particle size or less in a crusher (not shown) and then blended in a predetermined ratio. For example, the coal is crushed to 3 mm or less, and the iron-source raw material is crushed to 0.5 mm or less. Then, the coal and iron-source raw material are blended in a ratio of, for example, 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 material by-products in steelworks, such as blast furnace dust, converter dust, and 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.

[0017] The blended coal 1 and iron ore 2 are fed into the kneader 3. A binder is added to the kneader 3 from a binder tank 4. Commonly used binders include SOP (soft pitch), ASP (asphalt pitch), 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.

[0018] 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 then molded under high pressure. As the conveying equipment 5, a belt conveyor, a flight conveyor, a screw feeder, or the like is generally used. The double-roll molding machine 6 molds the kneaded molding raw material.

[0019] The briquettes (briquettes) formed by the double roll molding machine 6 are separated into an oversize fraction 7 and an undersize fraction 8 through a sieve with a mesh size of 12 mm, and the briquettes separated as the oversize fraction 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 oversize fraction 7 by the sum of the weights of the oversize fraction 7 and the undersize fraction 8 when the briquettes are passed through a sieve with a mesh size of 12 mm. 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.

[0020] In a double-roll molding machine, the more raw material is filled into the cup, the better the moldability. Therefore, a broader particle size distribution is preferable. Therefore, the inventors came up with the idea of ​​using a vibrating conveyor, preferably a vibrating feeder, as the conveying equipment 5 before loading the raw material into the molding rolls of the double-roll molding machine 6, rather than the general conveying equipment described above. In other words, by conveying the raw material for molding using a vibrating feeder, the raw material for molding is granulated before molding in the double-roll molding machine 6, broadening the particle size distribution and improving moldability. [Example]

[0021] According to the ferro-coke manufacturing method shown in FIG. 1 , the raw materials for molding were transported to a double-roll molding machine 6 using a commonly used belt conveyor and screw conveyor as the transport equipment 5, and the vibrating feeder of the present invention, to produce molded products. Here, the belt conveyor, screw conveyor, and vibrating feeder do not require any special structures, and commercially available products can be used. Then, for each example, the molded product yield obtained by the double-roll molding machine 6 was calculated. Furthermore, for each example, the variation in particle size distribution (Isp) was calculated, and further, the relationship between the variation in particle size distribution (Isp) and the molded product yield was calculated. The results are shown below.

[0022] Figure 2 is a graph showing the influence of the production method on the briquetting yield in the ferro-coke raw material production method of the present invention. Figure 2 shows the briquetting yield of the briquettes when using each method (belt conveyor, screw conveyor, and vibrating feeder). In the test, Blend 2 of the raw material blends shown in Table 1 below was used for transport using each equipment, and the transported raw materials were then briquetted using a double-roll compactor. The briquetting yield of the briquettes for each equipment was determined. For raw materials containing no binder (Breakdown 1 in Table 1), the briquetting yield was constant regardless of the transporting equipment. However, for raw materials containing a binder, the briquetting yield dramatically improved when using a vibrating feeder, as shown in Figure 2. The briquetting yield peaked at around 85% when using a vibrating feeder. It is believed that this is due to the burrs (approximately 15%) that formed during briquetting.

[0023] [Table 1]

[0024] Figure 3 is a graph showing the influence of the manufacturing method on the variation in particle size distribution (Isp) in the manufacturing method of the ferro-coke raw material of the present invention. In the example of Figure 3, the raw material for briquetting was sampled before and after conveyance, and the variation in particle size distribution (Isp) was evaluated using the following formula (1), and the relationship with the briquetting yield was investigated. The particle size distribution was measured using sieve meshes of 2.5 / 1.5 / 0.75 / 0.375 / 0.2 / 0.112 / 0.074. The results of Figure 3 confirmed that the variation in particle size distribution (Isp) increased when a vibrating feeder was used.

[0025]

number

[0026] In this study, 1 kg of powder sample after stirring was collected and sieved using sieves with openings of 0.074, 0.15, 0.25, 0.5, 1.0, 2.0, and 3.0 mm in order of decreasing size, and the weight percentage of each particle size was measured. The representative particle size (di) between the sieve openings in particle size analysis was calculated using the geometric mean of the larger and smaller openings. For particles 0.074 mm or smaller, the representative particle size (di) was set to 0.037 mm (1 / 2 of 0.074 mm), and for particles 3 mm or larger, the representative particle size (di) was set to 3.9 mm (the geometric mean of 3 mm and 5 mm).

[0027] Next, the frequency of the vibrating feeder was changed from 42 to 60 Hz, and the feed rate of the raw material was changed from 8 to 25.5 t / h by adjusting the opening of the cut gate installed at the outlet of the vibrating feeder.

[0028] In general, granulation is promoted with an increase in frequency and a decrease in cut-out amount, and the variation in particle size distribution increases. Figure 4 shows the relationship between the variation in particle size distribution (Isp) and molding yield. We confirmed that the molding yield of the molded product tends to improve as the variation in particle size distribution increases. The molding yield improved rapidly when Isp was between 200 and 600, but deteriorated when it exceeded 600. This is thought to be because when a large amount of raw material is filled into the cup of the double-roll molding machine, it becomes difficult for the initial voids inside to disappear through molding, and voids remain. From the above, it was found that in the present invention, it is preferable to control Isp to 200 to 600. [Industrial Applicability]

[0029] According to the present invention, by using a vibrating feeder as a conveying equipment, the molding yield can be improved and molding can be performed efficiently. As a result, raw materials are not wasted and manufacturing costs can be reduced. [Explanation of symbols]

[0030] 1. Coal 2. Iron ore 3. Mixing machine 4 binder tank 5. Conveying equipment 6 Double roll molding machine 7 Sieve top 8 Under the sieve 9. Dry distillation furnace

Claims

1. A method for producing a ferro-coke raw material, comprising: kneading a raw material for briquetting, the raw material for briquetting comprising coal, an iron source raw material, and a binder; transporting the kneaded raw material for briquetting to a double-roll molding machine; and carbonizing the briquettes formed by the double-roll molding machine to produce ferro-coke, the method comprising: transporting the kneaded raw material for briquetting to the double-roll molding machine using a vibrating conveyor.

2. 2. The method for producing ferro-coke raw material according to claim 1, wherein a vibrating feeder is used as the vibrating conveying machine, and the kneaded raw material to be molded is conveyed by the vibrating feeder.

3. 3. The method for producing a ferro-coke raw material according to claim 1 or 2, characterized in that the particle size distribution variation Isp (defined by the following formula 1) of the mixed raw material to be supplied to the double-roll molding machine is 200 or more and 600 or less: [Equation 1] where Dp is the harmonic mean diameter (mm), di is the representative particle size between sieve openings in particle size analysis (mm), and wi is the weight ratio (wt%) of particles having a representative particle size of di in particle size analysis.

Images