Manufacturing method of coal cake, manufacturing method of metallurgical coke, and strength improving material for coal cake

Abstract

The present invention provides a method for producing a coal cake capable of improving the strength of the coal cake without using a caking binder. The method for producing a coal cake according to the present invention is a method for producing a coal cake in a stamp charge type coke oven, and is characterized in that cellulose fibers having an average fiber length of 1.0 mm or more and 3.0 mm or less are blended and mixed with a powdered coal cake raw material, and the resulting cellulose fiber mixed raw material is stamped to obtain a coal cake.

Description

[Technical field]

[0001] The present invention relates to a method for producing a coal cake, a method for producing a metallurgical coke, and a strength improving agent for a coal cake. [Background technology]

[0002] Currently, in the production of pig iron using a blast furnace, coke produced by carbonizing coal in a coke oven is used as a reducing agent for iron ore and to ensure gas permeability inside the blast furnace. It is known that high-strength coke is preferable for efficient operation of the blast furnace. This is because if coke is powdered in the blast furnace, the resulting powder will deteriorate the gas permeability of the blast furnace, making it impossible to operate the blast furnace efficiently.

[0003] It is known that increasing the bulk density of the coal charged into the coke oven is an effective way to produce high-strength coke, and for this purpose, stamp-charge coke ovens are used. In the typical coke ovens currently used in Japan (hereinafter referred to as "top-charge coke ovens"), the coal, which is the raw material for coke, is charged by gravity from the top of the coke oven carbonization chamber, and the bulk density of the gravity-charged coal is 700-800 kg-dry / m 3 It is.

[0004] On the other hand, in the stamp charge type coke oven, the coal is compacted by a stamping device arranged on the side of the coke oven carbonization chamber before being charged into the coke oven, and the bulk density is 1000 kg-dry / m 3 After being processed into the above coal cakes, they are mechanically charged into the coke oven chamber from the side. By using a stamp charge coke oven, the density of the coke raw material can be increased before carbonization as described above, and higher strength coke can be produced than with a top charge coke oven.

[0005] As mentioned above, stamp-charge coke ovens are superior to top-charge coke ovens in terms of coke strength. However, if the strength of the coal cake produced by stamping is low, it may cause operational troubles such as the coal cake collapsing during charging into the coke oven carbonization chamber. Therefore, technology to produce high-strength coal cakes is required for stable operation of stamp-charge coke ovens.

[0006] It is also known that the strength of the coal cake is greatly affected by the moisture content of the coal, and in stamp charge coke ovens, the moisture content of the coal is generally adjusted to 10 to 12 mass%. However, if the moisture content of the coal cake is high, the carbonization time increases accordingly, and productivity decreases. Therefore, in order to improve the productivity of stamp charge coke ovens, there is a demand for technological development that can manufacture coal cakes with sufficient strength for operation while maintaining a low coal moisture content.

[0007] To date, the use of caking binders has been considered for the above-mentioned purpose. For example, Patent Document 1 reports a method in which caking coal is heated to 300 to 500°C and the coal in a softened and molten state is used as a binder for the coal cake. In addition, Non-Patent Document 1 reports that by adding pitch with a softening point of 80°C as a binder to the raw material, the strength of the coal cake is increased, and a coal cake with sufficient strength can be produced even under conditions where the coal moisture content is lower than usual. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 7-109467 [Non-patent literature]

[0009] [Non-Patent Document 1] SH Krishnan, et al., "Application of Binder in Stamp Charge Coke Making", ISIJ International, 44(2004), 1150. Summary of the Invention [Problem to be solved by the invention]

[0010] In the method using a caking binder described in Patent Document 1 and Non-Patent Document 1, the caking raw material adheres to the belt conveyor and stamping device during the process of transporting the coke raw material containing the caking binder and during the process of compacting the raw material with a stamping device. Therefore, the device needs to be cleaned frequently, resulting in a problem of reduced productivity.

[0011] An object of the present invention is to provide a method for producing a coal cake that can improve the strength of the coal cake without using a caking binder. [Means for solving the problem]

[0012] The inventors conducted extensive research to solve the above problems, and obtained experimental results showing that the strength of the coal cake is improved by mixing cellulose fiber with the coke raw material. Based on the empirical knowledge that cellulose fiber does not adhere to the equipment, unlike caking binders, the inventors found that cellulose fiber may be suitable as a binder for stamp-charge coke ovens. In addition, using cellulose fiber, which is a wood-derived biomass, as a binder, rather than a binder derived from fossil fuels, also meets the social demand for carbon-neutral steelmaking.

[0013] The inventors further investigated the relationship between each analytical value of cellulose fiber and the strength of coal cake, and found that the average fiber length of pulp has a significant effect on the strength of coal cake, thereby completing the present invention.

[0014] That is, the gist and configuration of the present invention are as follows. [1] A method for producing coal cake in a stamp charge coke oven, comprising the steps of: A method for producing coal cake, comprising: blending and mixing cellulose fibers having an average fiber length of 1.0 mm or more and 3.0 mm or less with a powdered coal cake raw material; and stamping the resulting cellulose fiber mixed raw material to obtain a coal cake.

[0015] [2] The method for producing a coal cake described in [1] above, wherein the blending ratio of the cellulose fiber is 2.0 mass% or less relative to 100 mass% of the raw materials of the coal cake.

[0016] [3] A method for producing metallurgical coke, comprising carbonizing a coal cake produced by the method according to [1] or [2] above in a coke oven to obtain coke.

[0017] [4] A strength improving material for coal cake used in stamp charge coke ovens, characterized in that it is a cellulose fiber with an average fiber length of 1.0 mm or more and 3.0 mm or less. Effect of the Invention

[0018] According to the present invention, it is possible to provide a method for producing a coal cake that can improve the strength of the coal cake without using a caking binder. Also, according to the present invention, it is possible to produce a coal cake that has sufficient strength for operation while keeping the coal moisture at a low level. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing the relationship between the average fiber length of cellulose fibers and the strength of a coal cake. [Diagram 2] FIG. 1 is a diagram showing the relationship between the blending ratio of cellulose fiber and the strength of coal cake. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The method for producing a coal cake according to the present invention is a method for producing a coal cake in a stamp charge type coke oven, and is characterized in that cellulose fibers having an average fiber length of 1.0 mm to 3.0 mm are blended and mixed with a powdered coal cake raw material, and the resulting cellulose fiber mixed raw material is stamped to obtain a coal cake.

[0021] First, cellulose fibers having an average fiber length of 1.0 mm or more and 3.0 mm or less are blended and mixed with a powdered coal cake raw material to obtain a cellulose fiber mixed raw material.

[0022] [Ingredients for coal cake] As the raw material for the coal cake, a powdered blended coal consisting mainly of raw coal generally used for coke production may be used. In addition to raw coal, non- or slightly caking coal, biomass, charcoal obtained by heating biomass, and other raw materials mainly composed of carbon may be used as long as the quality of the coke obtained by carbonizing the coal cake is not an issue.

[0023] The above raw material may be crushed using a hammer crusher or the like to a particle size of -3 mm, 70 to 100 mass% (crushed so that the proportion of particles with a particle size of 3 mm or less is 70 to 100 mass%), as is conventionally done in the operation of stamp charge coke ovens, and used as the raw material for the coal cake.

[0024] The moisture content of the coal cake raw material can be adjusted before and after the above-mentioned crushing treatment by drying using a coal moisture adjustment facility, spraying water from a nozzle, etc. The target value of the moisture content of the coal cake raw material is preferably 10 to 12 mass% for the purpose of increasing the strength of the coal cake, but for the purpose of improving productivity, the moisture content may be reduced within a range in which the strength of the coal cake does not become an issue.

[0025] [Cellulose fiber] In the present invention, cellulose fibers having a certain average fiber length or more are blended, mixed, and dispersed into the raw material of the coal cake to form a network in which the cellulose fibers are intertwined with each other to produce a cellulose fiber mixed raw material, which allows the production of a coal cake with higher strength.

[0026] The larger the average fiber length of the cellulose fibers, the more the cellulose fibers come into contact with each other, and a cellulose fiber network is formed throughout the entire coal cake. In order to improve the strength of the coal cake, it is necessary to make the average fiber length of the cellulose fibers 1.0 mm or more. The average fiber length of the cellulose fibers is preferably larger in terms of improving the strength of the coal cake, and the upper limit of the average fiber length of the cellulose fibers is not limited for the purpose of improving the strength of the coal cake. However, the average fiber length of cellulose fibers produced from raw materials derived from coniferous trees, which are generally known to have a large fiber length, is about 3.0 mm or less. Therefore, in the method for producing a coal cake according to the present invention, the average fiber length of the cellulose fibers is set to 3.0 mm or less. The average fiber length of the cellulose fibers is preferably 1.5 mm or more and 3.0 mm or less, and more preferably 1.8 mm or more and 3.0 mm or less.

[0027] In this specification, the term "cellulose fiber" refers to a fibrous material obtained from a cellulose raw material of normal origin. The cellulose raw material is preferably pulp, more preferably wood-derived pulp. Examples of wood-derived pulp include pulp derived from broadleaf trees and pulp derived from softwood trees.

[0028] Wood-derived pulp can be prepared by known methods, including, for example, a method involving a chemical pulping process (cooking process). The chemical pulping process (cooking process) dissolves and removes lignin, a coloring substance, and by combining this with an oxygen delignification process and a bleaching process, a pulp with a high degree of whiteness can be obtained. Although such oxygen delignification and bleaching processes are not necessary for this application, there is no problem if they are performed. In other words, a normal pulp manufacturing process can be applied.

[0029] Chemical pulping methods (cooking methods) include, for example, sulfite cooking, kraft cooking, soda-quinone cooking, and organosolv cooking, with kraft cooking being preferred from an environmental and economical standpoint. The "kraft cooking" method uses alkaline chemicals such as sodium hydroxide, potassium hydroxide, and sodium carbonate in combination with chemicals containing sulfur such as sodium sulfide and sodium sulfite, and can use quinone-based cooking aids, polysulfides, and other additives.

[0030] In the method for preparing pulp, the pulp obtained by cooking can be subjected to oxygen delignification. As the oxygen delignification method used in the present invention, a known medium consistency method or high consistency method can be directly applied. When using the medium consistency method, the pulp consistency is preferably set to 8 to 15 mass%, and when using the high consistency method, the pulp consistency is preferably set to 20 to 35 mass%. As the alkali in the oxygen delignification treatment, sodium hydroxide or potassium hydroxide can be used, and as the oxygen gas, oxygen from the cryogenic separation method, oxygen separated by the pressure swing adsorption (PSA) method, oxygen separated by the vacuum swing adsorption (VSA) method, etc. can be used.

[0031] The reaction conditions for the oxygen delignification treatment are not particularly limited. For example, the oxygen pressure is 3 to 9 kg / cm 2 The alkali addition rate may be 0.5 to 4 mass%, the temperature may be 80 to 140° C., and the treatment time may be 20 to 180 minutes. Other conditions may be those known in the art. In the present invention, the oxygen delignification treatment may be carried out multiple times.

[0032] The pulp that has been subjected to the oxygen delignification treatment may then be sent to a washing step, for example, and after washing, may be subjected to a bleaching treatment as described below.

[0033] In the preparation of pulp, in addition to chemical pulping (cooking) and oxygen delignification, a bleaching treatment can also be carried out, which results in a pulp with a higher brightness. Examples of bleaching treatment methods include chlorine treatment (C), chlorine dioxide bleaching (D), alkaline extraction (E), hypochlorite bleaching (H), hydrogen peroxide bleaching (P), alkaline hydrogen peroxide treatment stage (Ep), alkaline hydrogen peroxide-oxygen treatment stage (Eop), ozone treatment (Z), chelate treatment (Q), and combinations of two or more of these treatments, on pulp that has been delignified by any conventional method. Examples of combinations (sequences) of two or more treatments include DE / PD, C / DEHD, ZEDP, Z / D-Ep-D, Z / D-Ep-DP, D-Ep-D, D-Ep-DP, D-Ep-PD, Z-Eop-DD, Z / D-Eop-D, and Z / D-Eop-DED (the " / " in the sequence means that the treatments before and after the " / " are performed consecutively without washing). The bleaching treatment is not limited to the above examples, and may be a commonly used method. Pulp that has been bleached is usually in a fluid state (fluid pulp).

[0034] The moisture content of the above-mentioned pulp is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, for example, when a pulp sheet is subjected to a crushing treatment. Furthermore, in order to prevent the raw material fibers from being shortened before and after the crushing of the cellulose fibers of the present invention, the moisture content is more preferably 30% by mass or more, and particularly preferably 40% by mass or more. The moisture content of the pulp is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less. By adjusting the moisture content of the pulp within this range, the cellulose fibers in the crushing treatment can be easily adjusted.

[0035] When the cellulose fibers are prepared by subjecting the pulp sheet to a beating treatment in water without subjecting it to a crushing treatment, the moisture content of the pulp is not particularly limited and can be selected appropriately.

[0036] The average fiber length of cellulose fibers can be determined by an image analysis type fiber analyzer such as a fractionator manufactured by Valmet or an L&W Fiber Tester Plus manufactured by ABB. Specifically, for example, 300 ml of an aqueous dispersion diluted to contain 0.1 g of solid cellulose fibers is subjected to an image analysis type fiber analyzer (product name: L&W Fiber Tester Plus, manufactured by ABB), and measurement is performed for 300 seconds to determine the length-weighted fiber length (n=2). At that time, the measurement is performed after setting the Max value of Fines Limit to 0.2 and the Min value of Length class 1 to 0.2 on the Sample type screen that determines the measurement conditions.

[0037] In the present invention, a high-strength coal cake can be produced by stamping and compacting the cellulose fiber mixed raw material obtained by blending cellulose fiber with the powdered coal cake raw material.

[0038] Regarding the blending ratio of cellulose fiber to the raw material of coal cake, as shown in the examples described later, the strength of the coal cake is improved as the blending ratio of cellulose fiber is higher. Since the relationship between the blending ratio of cellulose fiber and the strength of the coal cake is linear, the upper limit of the blending ratio is not limited from the viewpoint of the strength of the coal cake. However, if a biomass raw material such as cellulose fiber is blended and mixed with the raw material of the coal cake to make a coal cake, and the obtained coal cake is used for coke production, the strength of the coke obtained after carbonization decreases. Therefore, it is preferable that the blending ratio of cellulose fiber is 2.0 mass% or less with respect to 100 mass% of the raw material of the coal cake, as a range in which the adverse effect on the coke strength is minor and the effect on the blast furnace operation can be ignored. In addition, blending cellulose fiber at a ratio of 2.0 mass% or less means blending so that the dry mass of the cellulose fiber is 2.0 mass% or less when the total dry mass of the raw materials (coal, coal carbonization product, other carbon materials, etc., excluding cellulose fiber) used in the production of the coal cake is 100 mass%. The blending ratio of cellulose fibers is more preferably 1.5% by mass or less, and even more preferably 1.0% by mass or less.

[0039] On the other hand, even when the blending ratio of cellulose fibers is small, the effect of improving the strength of the coal cake corresponding to the blending ratio is exhibited, so that the lower limit of the blending ratio is not particularly limited. However, from the viewpoint of producing a coal cake with higher strength and preventing the collapse of the coal cake, the blending ratio of cellulose fibers is preferably 0.01 mass% or more, more preferably 0.02 mass% or more, and even more preferably 0.05 mass% or more.

[0040] In addition, coal cake raw materials and cellulose fibers generally contain a certain amount of moisture. Therefore, the blending ratio of cellulose fibers is calculated by measuring the moisture content of the coal cake raw materials and cellulose fibers in advance and using the dry mass (mass excluding moisture). The moisture content of cellulose fibers is calculated from the weight loss of the sample when heated and dried at 107°C for 1 hour using the air drying loss measurement method specified in JIS M 8812. In addition, although this method is a moisture quantification method for coals, the moisture content of coal cake raw materials and cellulose fibers containing raw materials other than coal may also be measured using the same method.

[0041] The method of mixing the raw coal cake and the cellulose fiber is not particularly limited, and may be a mixer generally used for mixing coal in a coke plant. In order to mix a large amount of raw coal cake and the cellulose fiber in a short time and increase productivity, a method of using a mixer with chopper blades such as PAM Apex Mixer (manufactured by Pacific Machinery Works, Ltd.) can also be exemplified.

[0042] When producing a coal cake from the cellulose fiber mixed raw material prepared as described above, a stamping device that compacts the cellulose fiber mixed raw material by impact of a falling weight may be used. In this case, when cellulose fibers having an average fiber length of 1.0 mm or more and 3.0 mm or less are blended, a coal cake having higher strength can be produced than when no cellulose fibers are blended. As a result, the coal cake is less likely to collapse, and the coke oven can be operated stably. In addition, even under operating conditions where the coal moisture is low and the coal cake is usually frequently collapsed, when the cellulose fibers are blended, the strength of the coal cake can be maintained within a range that does not cause operational problems. The effect of blending cellulose fibers on the strength of the coal cake will be explained in more detail in the following examples.

[0043] (Metallurgical coke manufacturing method) Next, a method for producing metallurgical coke according to the present invention will be described. The method for producing metallurgical coke according to the present invention is characterized in that the coal cake produced by the above-mentioned method for producing coal cake according to the present invention is carbonized in a coke oven to obtain coke.

[0044] The coal cake produced by the above-mentioned method for producing a coal cake according to the present invention is mechanically charged from the side of the coke oven carbonization chamber. At this time, the coal cake is subjected to the impact of its own weight and the vibration of the charging machine. If the strength of the coal cake is low, an operational problem may occur in which the coal cake collapses during charging. In the method for producing a coal cake according to the present invention, cellulose fiber is used as a binder, which improves the strength of the coal cake and suppresses the collapse of the coal cake.

[0045] There are no particular restrictions on the conditions for carbonizing the coal cake. The coal cake can be carbonized at a temperature of about 900°C or higher using a general stamp charge coke oven.

[0046] (Strength improving material for coal cake) Next, the strength improving material for coal cake according to the present invention will be described. The strength improving material for coal cake according to the present invention is a strength improving material for coal cake used in stamp charge type coke ovens, and is characterized by being made of cellulose fibers having an average fiber length of 1.0 mm or more and 3.0 mm or less.

[0047] The cellulose fiber may be the cellulose fiber used in the method for producing a coal cake according to the present invention described above. The requirements for the cellulose fiber may be the same as those for the cellulose fiber used in the method for producing a coal cake.

[0048] As described above, a high-strength coal cake can be manufactured by mixing cellulose fibers having an average fiber length of 1.0 mm to 3.0 mm as a binder with the raw material of the coal cake and stamping the resulting cellulose fiber mixed raw material. As a result, when the resulting coal cake is carbonized in a coke oven to produce coke, the collapse of the coal cake can be suppressed, and the operation of the coke oven can be stably performed. EXAMPLES

[0049] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the examples and can be modified as desired without departing from the gist of the present invention.

[0050] First, cellulose fibers to be used in the production of coal cake were produced as follows.

[0051] <Production Example 1> A pulp sheet (brightness 47.2%, solid content 53% by mass / moisture content 47% by mass) obtained by subjecting unbleached pulp derived from hardwood to oxygen delignification treatment was dispersed in water to obtain a 4% by mass aqueous dispersion. The aqueous dispersion obtained was then treated with a single disc refiner (product name: 14-inch Lab Refiner (manufactured by Aikawa Iron Works Co., Ltd.), clearance 0.15 mm), and beaten until the Canadian standard freeness (csf) was 0 ml. The beaten aqueous dispersion was then adjusted with a centrifugal dehydrator so that the solid content was 16% by mass, and cellulose fiber A with an average fiber length of 0.76 mm was obtained.

[0052] <Production Example 2> Beating was continued until the csf became 400 ml, and the resulting aqueous dispersion was adjusted to have a solid content of 22 mass %, and the same procedures as in Production Example 1 were repeated to obtain cellulose fibers B having an average fiber length of 0.93 mm.

[0053] <Production Example 3> Cellulose fiber C having an average fiber length of 1.03 mm was obtained in the same manner as in Production Example 1, except that a pulp sheet (brightness 38.0%, solids content 46% by mass / moisture content 54% by mass) obtained by subjecting unbleached pulp derived from coniferous wood to oxygen delignification treatment was used.

[0054] <Production Example 4> An unbleached pulp sheet (brightness 22.8%, solid content 45% by mass / moisture content 55% by mass) derived from coniferous trees was dispersed in water to obtain a 3% by mass aqueous dispersion, which was then processed with a single disc refiner (product name: 14-inch Lab Refiner (manufactured by Aikawa Iron Works Co., Ltd.), clearance 0.15 mm) and beaten until the Canadian Standard Freeness (csf) was 0 ml. The resulting aqueous dispersion was then adjusted with a centrifugal dehydrator to a solid content of 12% by mass, to obtain cellulose fiber D with an average fiber length of 1.08 mm.

[0055] <Production Example 5> Unbleached pulp derived from coniferous trees was subjected to oxygen delignification to obtain a pulp sheet (brightness 38.0%, solids content 46% by mass / moisture content 54% by mass), and water was added to the pulp sheet to obtain a wet sheet-like material with a solids content of 20% by mass. The obtained wet sheet-like material was treated with a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.), clearance 0.15 mm) and beaten until the Canadian Standard Freeness (csf) reached 400 ml, obtaining cellulose fiber E with an average fiber length of 1.63 mm.

[0056] <Production Example 6> Beating was continued until the csf became 400 ml, and the obtained aqueous dispersion was adjusted to have a solid content of 20 mass %, and the same procedure as in Production Example 4 was repeated to obtain cellulose fibers F having an average fiber length of 1.95 mm.

[0057] <Production Example 7> Cellulose fiber G having an average fiber length of 1.98 mm was obtained in the same manner as in Production Example 2, except that a pulp sheet (brightness 38.0%, solids content 46% by mass / moisture content 54% by mass) obtained by subjecting unbleached pulp derived from coniferous trees to oxygen delignification treatment was used.

[0058] <Production Example 8> A bleached pulp sheet (brightness 85%, solid content 85% by mass / moisture content 15% by mass) derived from coniferous trees was treated with a defibrator (product name: ATOMZ M4-300, manufactured by Ishikawa Soken Co., Ltd., screen diameter φ25 mm) to obtain a coarsely pulverized material. The obtained coarsely pulverized material was further treated with a defibrator (product name: ATOMZ M4-300, manufactured by Ishikawa Soken Co., Ltd., screen diameter φ4.5 mm) to obtain cellulose fibers H with an average fiber length of 1.81 mm.

[0059] <Production Example 9> An unbleached pulp sheet (brightness 22.8%, solid content 45% by mass / moisture content 55% by mass) derived from coniferous trees was dispersed in water to obtain a 3% by mass aqueous dispersion, which was then treated with a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.), clearance 0.1 mm) and beaten until the Canadian Standard Freeness (csf) was 695 ml. The aqueous dispersion thus obtained was then adjusted with a centrifugal dehydrator so that the solid content was 30% by mass, to obtain a wet sheet-like material. The obtained wet sheet-like material was crushed by treating it with the aforementioned single disc refiner (clearance 3.95 mm) to obtain cellulose fiber I having an average fiber length of 2.06 mm.

[0060] <Production Example 10> An unbleached pulp sheet derived from coniferous trees (brightness 22.8%, solid content 45% by mass / moisture content 55% by mass) was dispersed in water to obtain a 3% by mass aqueous dispersion. The obtained aqueous dispersion was adjusted in a centrifugal dehydrator so that the solid content was 35% by mass, and a wet sheet-like material was obtained. The obtained wet sheet-like material was disintegrated by processing with a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.), clearance 3.95 mm) to obtain cellulose fiber J with an average fiber length of 2.08 mm.

[0061] <Production Example 11> An unbleached pulp sheet derived from coniferous trees (brightness 22.8%, solids 45% by mass / moisture content 55% by mass) was crushed by processing it with a single disc refiner (product name: BR-300CB Lab Refiner (manufactured by Kumagai Riki Kogyo), clearance 2.5 mm) to obtain cellulose fiber K with an average fiber length of 2.15 mm.

[0062] <Production Example 12> Cellulose fibers L having an average fiber length of 2.15 mm were obtained in the same manner as in Production Example 11, except that an FM mixer (product name: FM-150, manufactured by Nippon Coke and Engineering Co., Ltd., rotation speed: 2750 rpm / 30 minutes) was used instead of the single disc refiner.

[0063] The characteristics of the cellulose fibers produced as described above are shown in Table 1.

[0064] [Table 1]

[0065] Example 1 In Example 1, cellulose fibers having various fiber lengths were used to produce coal cakes according to the method for producing a coal cake according to the present invention, and their strengths were evaluated.

[0066] As the coal cake raw material, a blended coal in which raw coal was blended so that the weighted average of the coal rank (Ro) was 0.92 was pulverized to a particle size of -3 mm (100 mass%) and used. The cellulose fiber shown in Table 1 was blended and mixed with the above-mentioned coal cake raw material at the blending ratio shown in Table 2 to obtain a cellulose fiber mixed raw material. The moisture content of the obtained cellulose fiber mixed raw material was measured, and a calculated amount of water was added so that the moisture content was 10 mass%, which is a general condition in a stamp charge type coke oven.

[0067] The cellulose fiber mixed raw material whose moisture content was adjusted by the above procedure was used to manufacture a coal cake in the following procedure. First, about 200 g of the cellulose fiber mixed raw material was charged into a metal mold with an inner diameter of 10 cm and a height of 20 cm, and a rammer with a mass of 9 kg was dropped 10 times from a height of 30 cm from the surface of the sample, so that the charged cellulose fiber mixed raw material was compacted by the impact. The above operation from charging the coal to dropping the rammer was repeated 10 times to manufacture a coal cake with a diameter of 10 cm, a height of 20 cm, and a mass of about 2 kg. After that, the mold was gently removed from the coal cake, and the strength of the coal cake was measured. The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The obtained results are shown in Table 2.

[0068] [Table 2]

[0069] Table 2 shows the strength of coal cake when cellulose fibers with different average fiber lengths are blended and mixed into the coal cake raw material. The coal cake strength (uniaxial compressive strength) varies greatly depending on the type and particle size of the coal cake raw material used. Therefore, when evaluating the effect of blending cellulose fibers on the coal cake strength, it is better to evaluate each coal cake raw material in terms of the strength ratio to the standard, which is the uniaxial compressive strength of a coal cake produced under conditions of a moisture content of 10 mass% and no blending of cellulose fibers, which are general conditions in stamp charge coke ovens.

[0070] If the strength ratio is less than 1.0, the strength of the coal cake is lower than that under general operating conditions, and it can be considered that the condition is prone to problems such as the collapse of the coal cake. On the other hand, if the strength ratio exceeds 1.0, the strength of the coal cake is higher than that under general operating conditions, and it can be considered that the condition is desirable for stable operation in which the collapse of the coal cake is unlikely to occur. From this perspective, under the conditions in which the cellulose fibers A and B, which are comparative examples, are blended, the strength ratio to the standard is less than 1.0, and the strength of the coal cake is reduced by blending the cellulose fibers. On the other hand, when the cellulose fibers C to G, which are examples of the invention, are blended, the strength ratio to the standard is all more than 1.0, and it can be said that the condition is desirable for stable operation in which the collapse of the coal cake is unlikely to occur.

[0071] The relationship between the average fiber length of cellulose fibers and the strength of the coal cake (strength ratio) is shown in Figure 1. As is clear from Figure 1, the relationship between the average fiber length and the strength of the coal cake (strength ratio) is clear, and the strength of the coal cake can be improved by blending and mixing long cellulose fibers with an average fiber length of 1.0 mm or more.

[0072] Example 2 As Example 2, the blending ratio of the cellulose fiber F was changed, and coal cakes were produced by the production method according to this embodiment, and their strength was evaluated.

[0073] For the coal cake raw material, a blended coal in which the weighted average of the coal rank (Ro) of raw coal was 0.93 was pulverized to a particle size of -3 mm (100 mass%) and used. Cellulose fiber F was blended and mixed with the above coal cake raw material at the blending ratio shown in Table 3 to obtain a cellulose fiber mixed raw material. The moisture content of the above cellulose fiber mixed raw material was measured, and a calculated amount of water was added so that the moisture content was 10 mass%, which is a general condition for stamp charge type coke ovens. A coal cake was manufactured using the cellulose fiber mixed raw material whose moisture content was adjusted by the above procedure in the same manner as in Example 1, and its strength was measured. The obtained results are shown in Table 3.

[0074] [Table 3]

[0075] As shown in Table 3, the coal cake strength increases linearly with an increase in the blending ratio of cellulose fiber F, and a higher blending ratio of cellulose fiber is preferable for the purpose of improving the coal cake strength. On the other hand, as described above, if the blending ratio of cellulose fiber is too high, the strength of the coke obtained by carbonizing the coal cake decreases. Therefore, when implementing the present invention, it is preferable to determine the optimal blending ratio of cellulose fiber through a prior experiment in light of the standards for coal cake strength and coke strength at each plant.

[0076] The relationship between the blending ratio of cellulose fiber and the strength of the coal cake (strength ratio) is shown in Figure 2. As is clear from Figure 2, the relationship between the blending ratio of cellulose and the strength of the coal cake is clear, and the strength of the coal cake can be improved by blending cellulose fiber into the coal cake raw material.

[0077] Example 3 In Example 3, the effect of blending cellulose fiber on the strength of the coal cake was investigated under conditions in which the moisture content of the coal cake raw material was 7% by mass, which is lower than the general stamp charge operating conditions in which the moisture content of the coal cake raw material was 10% by mass. To this end, a coal cake was manufactured by the manufacturing method of the coal cake according to the present invention, and its strength was evaluated.

[0078] As the coal cake raw material, the raw coal was blended so that the weighted average of the coal rank (Ro) was 0.94, and the blended coal was pulverized to a particle size of -3 mm (100 mass%) and used. The cellulose fiber shown in Table 1 was blended and mixed with the above-mentioned coal cake raw material at the blending ratio shown in Table 4 to obtain a cellulose fiber mixed raw material. The moisture content of the obtained cellulose fiber mixed raw material was measured, and a calculated amount of water was added so that the moisture content was 10 mass%, which is a general condition in a stamp charge type coke oven, or 7 mass%, which is a condition with a lower moisture content than usual. Using the cellulose fiber mixed raw material whose moisture content was adjusted by the above-mentioned procedure, a coal cake was manufactured in the same manner as in Example 1, and its strength was measured. The obtained results are shown in Table 4.

[0079] [Table 4]

[0080] Table 4 shows the effect of blending cellulose fiber on the strength of the coal cake when the moisture content of the coal cake raw material is lower than the general conditions in the stamp charge coke oven. As shown as a reference example in Table 4, when the moisture content of the coal cake raw material is reduced from 10 mass% to 7 mass%, the strength ratio of the coal cake to the standard falls to 0.45. Under these conditions, the coal cake frequently collapses, making it difficult to produce coke stably. Also, in Table 4, the strength of the coal cake when cellulose fiber B is blended is shown as a comparative example, and the strength is about the same as when cellulose fiber B is not blended. On the other hand, in the invention example, it can be seen that by blending cellulose fibers H to L, the strength ratio is higher than the standard even under the condition that the moisture content of the coal cake raw material is 7 mass%. As described above, the blending of cellulose fiber can reduce the moisture content of the coal cake while maintaining the strength of the coal cake, thereby improving the productivity of the coke. [Industrial Applicability]

[0081] According to the present invention, it is possible to provide a method for producing a coal cake that can improve the strength of the coal cake without using a caking binder.

Claims

1. A method for producing a coal cake in a stamp charge coke oven, comprising the steps of: A method for producing a coal cake, comprising: blending and mixing cellulose fibers having an average fiber length of 1.0 mm or more and 3.0 mm or less with a powdered coal cake raw material; and stamping the resulting cellulose fiber mixed raw material to obtain a coal cake.

2. The method for producing a coal cake according to claim 1 , wherein a blending ratio of the cellulose fiber is 2.0 mass% or less with respect to 100 mass% of the raw materials of the coal cake.

3. A method for producing metallurgical coke, comprising carbonizing the coal cake produced by the method according to claim 1 or 2 in a coke oven to obtain coke.

4. A strength improving material for coal cake used in stamp charge type coke ovens, characterized by being cellulose fibers having an average fiber length of 1.0 mm or more and 3.0 mm or less.