Manufacturing method for ferrocoke molded products

Abstract

To provide a further simplified and easily controlled method for producing a molding for ferrocoke as means to improve a yield of the molding while ensuring the strength of the molding by inhibiting adherence of raw materials to roll cups.SOLUTION: A method for producing a molding in a method for producing ferrocoke by mixing and kneading coal and iron ore after pre-preparation such as crushing and drying, and dry distilling the molding obtained by molding, includes continuously spraying a hydrophilic liquid onto a molding machine when adding a binder to the coal and iron ore after pre-preparation and kneading, and then forming the kneaded raw materials using a double roll molding machine.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing ferrocoke briquettes by briquetting a mixture of coal and iron ore into briquettes in a method for producing ferrocoke obtained by carbonizing a mixture of coal and iron ore. [Background technology]

[0002] To operate blast furnaces efficiently, coke, which is produced by carbonizing coal in a coke oven, is charged into the furnace. The coke charged into the furnace serves the following roles: a spacer to improve ventilation inside the furnace, a reducing agent, and a heat source. In recent years, technology using ferro-coke has been developed to improve the reactivity of coke.

[0003] Ferro coke is produced by crushing and drying the primary raw materials, coal and iron, and mixing and kneading them in a kneader with a few mass percent of binder. The materials are then molded into compacts in a double-roll molding machine, which then carbonizes the compacts in a vertical furnace. During molding in the molding machine, the materials are compressed under high pressure to produce high-density compacts. However, depending on the operating conditions during production, broken raw materials may remain attached to the roll cup. As the amount of adhesion to the roll cup increases, the materials cannot enter those areas, resulting in the production of plate-shaped compacts. Compared to conventional rounded compacts, plate-shaped compacts are more prone to powdering after carbonization, making them unsuitable as blast furnace feedstock. Therefore, the yield of the compacts decreases due to the adhesion to the roll cup. Furthermore, it is not practical to completely remove such plate-shaped ferro coke before charging into the blast furnace, which would result in a deterioration in the overall quality of the ferro coke.

[0004] There are various possible reasons for adhesion to the roll cup, but because ferro-coke is molded at a high temperature of about 160°C, the binders, including soft pitch, are in a softened state, and the molding rolls themselves begin to heat up as molding continues. As a result, the raw materials are not cooled during compression molding, and the binder adheres to the roll cup, causing the molded product to crack and remain in the cup, which is thought to be the cause of the raw material adhesion.

[0005] To improve the releasability of the molding machine roll cup, a method of forming a thin film with good releasability on the surface of the molding machine (Patent Document 1) and a method of applying a lubricant such as wax (Patent Document 2) have been proposed. Also, when the cause of raw material adhesion is the temperature during molding, such as in the case of molded ferro-coke, a method of cooling by continuously blowing cold air onto the roll has been proposed (Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-259787 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-82650 [Patent Document 3] Patent No. 6151169 Summary of the Invention [Problem to be solved by the invention]

[0007] However, because ferro-coke is molded using high-pressure molding and uses highly abrasive iron ore, coating the molding machine surface as in Patent Document 1 quickly loses its effectiveness in improving mold release due to surface wear. Using a lubricant as in Patent Document 2 raises concerns about increased costs due to the use of special chemicals. Furthermore, the binder used, such as soft pitch, is lipophilic, so it wets well with the lubricant, making mold release difficult. Furthermore, the lubricant dissolves in the binder, potentially affecting the quality of the ferro-coke. Cooling using a refrigerant as in Patent Document 3 has a very narrow optimal temperature range of 70 to 80°C, making it difficult to control. Furthermore, as molding machines become larger, the amount of refrigerant required increases, and because only the surface can be cooled, the cooling efficiency decreases, making temperature control difficult.

[0008] The present invention has been made in view of the above circumstances, and aims to prevent the occurrence of adhesion of raw materials to roll cups when raw materials for molding are molded into molded products by a double-roll molding machine. The present invention also proposes a simpler and more easily controllable method for producing molded products for ferro-coke, as a means for improving the yield of molded products while ensuring the strength of the molded products by preventing the occurrence of adhesion of raw materials to the roll cups. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the method for producing ferro-coke briquettes of the present invention is a method for producing ferro-coke briquettes in a process in which coal and iron ore are subjected to preliminary preparation such as crushing and drying, and then the briquettes obtained by mixing, kneading, and molding are carbonized to produce ferro-coke, characterized in that a binder is added to the pre-prepared coal and iron ore and kneaded, and the kneaded raw materials are molded using a double-roll molding machine, and a hydrophilic liquid is continuously sprayed into the molding machine.

[0010] In the method for producing ferro coke briquettes according to the present invention configured as described above, (1) The hydrophilic liquid is water; (2) The amount of the hydrophilic liquid to be sprayed is such that the value of α in the following formula (1) is 15 to 580: W / L=α T / V (1) where W is the spray amount (mL / min), L is the roll width (m), T is the roll temperature (℃), V is the roll rotation speed (m / min), α is a constant (mL / ℃ / min 2 ), is, This is considered to be a more preferable solution. [Effects of the Invention]

[0011] According to the method for producing ferro coke briquettes of the present invention, adhesion of the raw material to the briquetting rolls can be suppressed and the amount of defective briquettes can be reduced, thereby realizing a reduction in the production costs of the ferro coke briquettes and ferro coke. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a molding machine used in the present invention. [Figure 2] FIG. 2 is a schematic diagram of a molding roll used in the present invention. [Figure 3] FIG. 2 is a diagram showing a schematic arrangement of a forming roll water sprinkler system used in the present invention. [Figure 4] 1 is a schematic diagram of an example of a sprinkler system used in the present invention. [Figure 5] 10 is a graph showing the relationship between the presence or absence of spraying of a hydrophilic liquid onto a forming roll and the amount of adhesion to the forming roll. [Figure 6] 1 is a graph showing the relationship between the presence or absence of water spraying and air cooling on the forming rolls and the yield of non-defective formed products. [Figure 7] 1 is a graph showing the relationship between the presence or absence of water spraying and air cooling on the forming roll and the amount of cooling on the forming roll. [Figure 8] 1 is a graph showing the relationship between the amount of water sprayed onto the molding roll and the yield improvement rate of the molded product. [Figure 9] 1 is a graph showing the relationship between the constant α and the yield improvement rate of the molded product. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] FIG. 1 shows a schematic diagram of the double-roll molding machine used in the present invention. The double-roll molding machine 1 has a pair of molding rolls 2 that rotate in opposite directions, and raw material 3 is supplied from above and molded. As shown in FIG. 2, multiple roll cups 4 are formed on the outer periphery of the molding rolls 2. The raw material 3 enters these cups and is pressed by the pair of molding rolls 2 to form a molded product 5. If the raw material 3 has poor releasability during this process, the molded product 5 will crack within the roll cups 4, leaving the compressed raw material 3 remaining. If molding continues without the raw material 3 being released from the mold, a plate-shaped molded product 5 will be produced, reducing the yield of the molded product 5. Therefore, it is necessary to improve the releasability of the raw material 3 to remove any adhesion.

[0015] The inventors have considered the use of a hydrophilic liquid, particularly water, as a release agent for the ferro-coke molded product 5 from the molding roll 2. Because water is hydrophilic, it does not wet well with the hydrophobic binder. Therefore, spraying water as a hydrophilic liquid onto the surface of the molding roll 2 (sprinkling) is expected to improve the release properties of the molded product 5. Furthermore, even if it is difficult to cool the mold to the optimum range described in Patent Document 3, the evaporation of water and heat conduction to the water can be expected to increase the viscosity of the binder, thereby providing the secondary effect of improving the release properties.

[0016] Figure 3 shows a schematic diagram of a double roll molding machine in which a water sprinkler system 11 is provided for each of the molding rolls 2. The water sprinkler system 11 can be installed anywhere as long as it can spray water onto the molding rolls 2, but as shown in Figure 3, it is preferable to install it on the side that does not face the other molding roll 2. In addition, it is difficult to install a molding roll 2 on the side that faces the other molding roll 2, and if water is sprayed directly onto the raw material 3 before molding, the moisture content of the raw material will increase, worsening moldability and raising concerns about a decrease in the quality of the molded product 5.

[0017] The molding rolls 2 are sprayed with water by the water spraying equipment 11, and then the raw material 3 is pressurized and molded while the roll cups 4 of the molding rolls 2 still retain water. After pressurization, the molded raw material 3 (molded product 5) leaves the roll cups 4 and falls downstream of the double roll molding machine 1. If the roll cups 4 retain water at this time, they will not wet well with the binder and will be easier to release from the mold, which is expected to result in improved quality and yield of the molded product 5.

[0018] If a large amount of water is used, the moisture content of the raw material 3 will increase, which is likely to deteriorate moldability. Therefore, it is desirable to spray the minimum amount of water (the amount of water sprayed as a hydrophilic liquid) necessary to improve mold releasability. Therefore, the amount of water sprayed should be uniform in the width direction, and as shown in Figure 3, it is preferable to spray water using a pipe 13 consisting of multiple mist sprinkler nozzles 12 arranged in a line. In this case, it is preferable to determine the distance L between adjacent mist sprinkler nozzles 12 based on the spray angle of the mist sprinkler nozzles 12 and the spray range estimated from the distance between the forming roll 2 and the mist sprinkler nozzles 12. As the mist sprinkler nozzle 12 for spraying water, a two-fluid mist sprinkler nozzle 12 that combines water and air to produce small droplets is preferable to a single-fluid nozzle that produces large droplets, because it can achieve a mold release agent effect with a minimum amount of water.

[0019] Furthermore, the amount of water sprayed is preferably controlled according to the temperature of the molding roll 2 and the rotation speed of the molding roll 2. The amount of water evaporated before reaching the raw material 3 varies depending on the temperature of the molding roll 2, while the time for spraying water varies depending on the rotation speed of the molding roll 2. Therefore, these two conditions must be taken into consideration when determining the amount of water sprayed, and it is preferable to control it using the following formula (1). Note that the amount of water sprayed W (amount of hydrophilic liquid sprayed W) is preferably adjusted so that the value of α shown in the following formula (1) is 15 to 580: W / L=α T / V (1) Where, W: water spray rate (mL / min), L: roll width (m), T: roll temperature (℃), V: roll rotation speed (m / min), α: constant (mL / ℃ / min 2 ), is. [Example]

[0020] In this example, the relationship between the presence or absence of spraying of a hydrophilic liquid onto the forming roll during forming and the adhesion of the raw material to the roll cup of the forming roll was determined. In addition, to evaluate the effect on the yield of the formed product, the degree of adhesion of the raw material to the forming roll during forming was measured for the raw material kneaded in the following manner, and the yield of non-defective formed products after forming.

[0021] First, a binder was added to a mixture of a blended coal consisting of two coal brands and iron ore, and the mixture was then kneaded and molded. The particle size of the coal was 2 mm or less, and the particle size of the iron ore was 3 mm or less in total. The ratios of coal and iron ore were 80.0 mass% and 20 mass%, respectively. Furthermore, soft pitch (SOP) and asphalt pitch (ASP) were added as binders at 5 mass% and 3.5 mass%, respectively, based on the raw material weight. The mixture was kneaded using a high-speed mixing machine while heating to 160°C. The kneaded raw materials were molded using a double-roll molding machine. A two-fluid spray nozzle for hydrophilic liquid and air and a compressed air pipe were installed on the side of the molding roll opposite the molding surface of the molding machine, and water spraying and air cooling were performed depending on the conditions. Water or ethanol was used as the hydrophilic liquid. The molding roll size was 650mmφ x 104mm, the rotation speed was 3.5 rpm, and the linear pressure was 2t / cm. The number of roll cups to which the raw material adhered during molding was counted to evaluate the effect of spraying water. In addition, the ratio of good molded products (without cracks or chips) after molding was measured to investigate the effect of spraying hydrophilic liquid.

[0022] Figure 5 shows the amount of adhesion to the molding roll, with the number of adhesions set to 1 when the hydrophilic liquid was not sprayed on the molding roll and air cooling was not performed. It was confirmed that spraying a hydrophilic liquid on the molding roll significantly reduced the amount of adhesion. In particular, the amount of adhesion was significantly reduced when water was sprayed as the hydrophilic liquid. This is thought to be because water is more hydrophilic than ethanol and has a lower affinity with pitch, which is the binder of the molded product, thereby further suppressing adhesion. The molding roll temperature during molding was a maximum of 88°C without spraying a hydrophilic liquid and a maximum of 82°C with water spraying. Although the temperature decreased when spraying water, it was confirmed that the effect of spraying water on reducing adhesion was obtained even at temperatures higher than the range described in Patent Document 3.

[0023] Figure 6 shows the results of measuring the yield of molded products. Measurements of the yield of non-defective products were conducted under four conditions: no water spray or air cooling, water spray only, air cooling only, and water spray and air cooling. The temperature drop caused by water spraying and air cooling on the forming rolls was defined as the roll cooling amount ΔT. Figure 7 shows the results of measuring the roll cooling amount ΔT under each of these four conditions. As shown in Figure 7, the cooling effect was highest under the condition where both air cooling and water spraying were performed, but the yield of non-defective products was highest under the condition where only water spraying was performed. These results also indicate that the water spray on the forming rolls is more effective as a release agent than as a cooling agent. This is presumably because, although the cooling capacity is increased by combining water spraying and air cooling, the air cooling blows away any water droplets remaining in the cup, reducing its effectiveness as a release agent and thereby reducing the yield improvement effect.

[0024] Next, an investigation was conducted into the optimal amount of water spray. The test conditions for Examples 1 to 3 in Table 1 below were used to evaluate the effect on yield by changing the amount of water sprayed. The results are shown in Figure 8. A comparison of Examples 1 and 2 reveals that the amount of water sprayed that maximizes yield decreases as the rotation speed of the forming roll increases. Meanwhile, a comparison of Examples 2 and 3 reveals that the amount of water sprayed that maximizes yield increases as the temperature of the forming roll increases. These results demonstrate that the optimal amount of water sprayed is affected by the temperature and rotation speed of the forming roll. Furthermore, Figure 9 shows the results of evaluating the yield measurement results for Examples 1 to 3 using the constant α in equation (1). It was confirmed that the yield improvement effect correlates with the value of α, and that by setting the value of α between 15 and 580, the yield improvement effect can be obtained.

[0025] [Table 1]

[0026] From the above results, it became clear that spraying water on the forming roll during forming can prevent adhesion more effectively than the cooling capacity, and it was confirmed that the yield improvement effect can be maximized by controlling the amount of water sprayed by the temperature and rotation speed of the forming roll. [Industrial Applicability]

[0027] In the method for producing ferro coke briquettes of the present invention, the adhesion of the raw material to the briquetting rolls is suppressed by continuously spraying a hydrophilic liquid onto the briquetting machine, which results in a reduction in the number of defective briquettes, thereby realizing a reduction in the production costs of the ferro coke briquettes and ferro coke, and is therefore industrially useful. [Explanation of symbols]

[0028] 1 Double roll molding machine 2. Forming roll 3 Raw materials 4 Roll Cups 5 Molded object 11 Watering equipment 12 Mist sprinkler nozzle 13 Pipe

Claims

1. A method for producing a briquette in a process for producing ferro-coke by pre-preparing coal and iron ore by crushing, drying, etc., mixing, kneading, and molding the resulting briquette, and then carbonizing the resulting briquette, the method comprising the steps of: adding a binder to the pre-prepared coal and iron ore, kneading the kneaded raw materials, and molding the kneaded raw materials using a double-roll molding machine; continuously spraying a hydrophilic liquid onto the surfaces of the molding rolls of the molding machine; and adjusting the amount W of spraying of the hydrophilic liquid so that the value of α shown in the following formula (1) is 15 to 580: W / L=α・T / V...(1) where W is the spray amount (mL / min), L is the roll width (m), T is the roll temperature (°C), V is the roll rotation speed (m / min), and α is a constant (mL / °C / min 2 ).

2. 2. The method for producing ferro-coke molded articles according to claim 1, wherein the hydrophilic liquid is water.

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