JP6590007B2 - Steelmaking coke blending coal, ironmaking coke forming coal, ironmaking coke and method for producing ironmaking coke forming coal - Google Patents

Description

  The present invention relates to a blended coal for iron making coke, a forming coal for iron making coke, an iron making coke, and a method for producing a forming coal for iron making coke.

  In the production of iron coke produced by carbonizing coal, cracks are generated when the thermal stress generated by the shrinkage after resolidification of semi-coke produced during the coal carbonization process exceeds the substrate strength. The particle size (coke particle size) of the iron coke to be determined is determined. Therefore, in order to increase the particle size of the iron coke, it is necessary to reduce the thermal stress or increase the substrate strength.

  In order to lower the thermal stress, methods are known in which the coke oven wall temperature is lowered, the operating rate of the coke oven is lowered, or powder coke is added. However, there is a problem that a decrease in the furnace wall temperature and a reduction in the operating rate of the coke oven cause a decrease in productivity, and the addition of powdered coke or the like causes a decrease in strength. Moreover, in order to increase the substrate strength, it is necessary to add expensive caking coal to the raw material coal, but there is a concern that the clearance with the furnace wall will be narrowed due to an increase in the expansion pressure of the coal. Decrease in performance and cost increase become problems. The clearance with the furnace wall is the distance between the coke cake and the furnace wall after coal dry distillation. The larger the clearance, the better the extrudability of the coke cake.

  In response to such problems, efforts have been made in the past to increase the particle size of iron coke and improve the strength of iron coke. For example, Patent Document 1 discloses a technique in which carbon long fibers are added to coal blend and dry-distilled, thereby improving the coke particle size without impairing the coke strength. Patent Document 2 discloses a technique for adding carbon short fibers to coal blend and dry distillation, thereby improving the cold strength of coke.

  Furthermore, Patent Document 3 discloses a technique in which a fiber containing keratin is added to blended coal, and this is converted into carbon fiber during the production of coke. As a result, it is said that coke having a high strength and a large particle size can be produced while increasing the clearance with the furnace wall of the coke oven.

JP-A-4-258690 JP-A-2-235990 JP 2012-158636 A International Publication No. 2009/069641 JP 2003-96466 A

  Patent Document 1 discloses that the strength of iron coke is maintained when iron coke is produced by adding carbon long fibers to the blended coal at an addition rate of 1%. However, since carbon fiber does not soften and melt during dry distillation, when 1% is added to blended coal by a normal method, it is presumed that the strength of iron-coke is reduced because coal and carbon fiber are not fused. That is, the technique disclosed in Patent Document 1 is considered to be a special case in which carbon fibers are dispersed and added as much as possible. Since long carbon fibers are generally manufactured by bundling single fibers (filaments) with an adhesive or the like, it is difficult to separate them one by one, and the carbon fibers are added to the blended coal as a bundle. In this case, as described above, there has been a problem that the quality of the steelmaking coke is inevitably deteriorated.

  On the other hand, Patent Document 2 discloses adding a carbon short fiber. Carbon short fibers are usually produced by cutting carbon long fibers produced by spinning and firing. The shape of the short carbon fiber is almost straight and short and is treated at a high temperature, so that the surface is inactive, and the carbon fiber is easily removed from the steelmaking coke. For this reason, there existed a subject that the intensity | strength improvement width | variety of iron-making coke was small and the particle size of steel-making coke was enlarged, and expansion of clearance could not be expected very much. In addition, the carbon fiber has to be manufactured by spinning a raw material and then performing a heat treatment at a high temperature, which makes it difficult to obtain the carbon fiber.

  Further, Patent Document 3 discloses that a fiber containing keratin is added to blended coal. However, since bird wings and / or feathers, which are raw materials for keratin, are natural products, depending on the type and route of acquisition. However, since the dispersibility of the fibers is reduced, the strength of the steelmaking coke obtained is reduced, the particle size is reduced, and the clearance between the coke cake and the furnace wall is reduced. The present invention has been made in view of such problems of the prior art, and its purpose is to add easily available fibers when manufacturing steelmaking coke by adding fibers to blended coal as an additive. An object of the present invention is to provide a blended coal for iron making coke that can be used to produce high-strength coke, a forming coal for iron making coke, a manufacturing method for iron making coke produced using these, and a forming coal for iron making coke.

The features of the present invention that solve such problems are as follows.
(1) A coal blend for iron-making coke, to which cellulose nanofibers having a number average fiber diameter in the range of 2 nm to 300 nm are added.
(2) A coal blend for iron-making coke, to which cellulose nanofibers having a number average fiber diameter of 2 nm or more and 20 nm or less are added.
(3) The blended carbon for iron making coke according to (1) or (2), wherein the cellulose nanofiber has a carboxyl group of 0.1 mmol / g or more.
(4) Steelmaking coke obtained by dry-distilling the steelmaking coke blended coal according to any one of (1) to (3).
(5) A coal char for iron-making coke, in which cellulose nanofibers having a number average fiber diameter in the range of 2 nm to 300 nm are mixed.
(6) A coal char for iron-making coke, in which cellulose nanofibers having a number average fiber diameter of 2 nm or more and 20 nm or less are mixed.
(7) The cellulose nanofiber is a coal for iron-making coke according to (5) or (6), which has a carboxyl group of 0.1 mmol / g or more.
(8) Steelmaking coke obtained by dry distillation of the coal for ironmaking coke according to any one of (5) to (7).
(9) Iron-manufactured coke, in which a carbon nanofiber having a number average fiber diameter in a range of 2 nm or more and 300 nm or less dispersed in a solvent is used as a binder, and the binder and coal are mixed and molded to produce a molded coal. Of manufacturing coal for coal.
(10) Iron-manufactured coke, in which a carbon nanofiber having a number average fiber diameter in a range of 2 nm to 20 nm dispersed in a solvent is used as a binder, and the binder and coal are mixed and molded to produce a molded coal. Of manufacturing coal for coal.
(11) The method for producing a coal for iron-making coke according to (9) or (10), wherein the cellulose nanofiber has a carboxyl group of 0.1 mmol / g or more.

  Since the easily available cellulose nanofiber is added to the iron-making coke blended coal and iron-making coke coal blend of the present invention, the production of the iron-making coke blending coal and the iron-making coke coal becomes easy. Moreover, high strength steel-manufactured coke can be produced by using blended coal for iron-making coke to which cellulose nanofibers are added and coal-forming coal for iron-making coke.

It is a TEM photograph of cellulose nanofiber. It is a graph which shows the drum strength of a coke, an average particle diameter, and the clearance with a furnace wall. It is a graph which shows the relationship between the mixing amount of a binder, and the relative intensity | strength of the iron-making coke manufactured from the forming charcoal with which the said binder was mixed. It is a graph which shows the relationship between the addition amount of a cellulose nanofiber, and the crushing strength of a molding. It is a graph which shows the relationship between the kind of binder, and the crushing strength of the iron-making coke obtained by dry-distilling a molding. It is a graph which shows the relationship between the quantity of the carboxyl group contained in a cellulose nanofiber, and the crushing strength of a molding. It is a graph which shows the relationship between the quantity of the carboxyl group contained in a cellulose nanofiber, and the crushing strength of the iron-making coke obtained by dry-distilling a molding.

  The present inventors use carbon nanofibers having a number average fiber diameter in the range of 2 nm or more and 300 nm or less as the fibers to be added to the coal blend, thereby carbonizing the blended coal to which the cellulose nanofibers are added. The present invention was completed by finding that the strength of the manufactured iron-making coke can be increased, the particle size can be increased, and the clearance between the coke cake and the furnace wall can be increased. Hereinafter, the present invention will be described through embodiments of the invention. In the present embodiment, the iron making coke is coke used in the iron making process and is mainly coke charged into a blast furnace.

  FIG. 1 is a TEM photograph of cellulose nanofibers. The fibers added to the blended coal according to this embodiment are cellulose nanofibers having a number average fiber diameter of 2 nm to 300 nm as shown in FIG. In recent years, cellulose nanofibers have been attracting attention as a new lightweight and high-strength material, and application development for functional materials such as deodorizers and reinforcing materials for resin composite materials is being promoted. In the present embodiment, the cellulose nanofiber added to the blended coal is a cellulose nanofiber obtained by defusing a cellulose fiber constituting a plant by mechanical defibration such as a water jet method, or chemical such as hydrolysis by cellulase. Cellulose nanofibers obtained by defibrating cellulose fibers constituting plants by treatment. Since these cellulose nanofibers are obtained from various plants, they can be obtained easily and in large quantities compared to carbon fibers and keratin. Cellulose fibers are obtained from raw materials containing cellulose, such as plants, mechanical pulp, chemical pulp, pulps that are processed products thereof, and paper.

  Recently, as disclosed in Patent Document 4, an oxidizing agent is allowed to act on cellulose fibers in the presence of a 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) catalyst. Thus, it is possible to produce cellulose nanofibers in which microfibrils, which are the smallest unit of cellulose fibers, are defibrated and dispersed in water. Cellulose nanofibers obtained by defusing cellulose fibers constituting plants by such TEMPO catalytic oxidation treatment can also be suitably used as cellulose nanofibers added to blended coal.

  Cellulose nanofibers are either defibrated and dispersed in water, the one dispersed in water is replaced with an organic solvent such as tar, or the water and organic solvent are removed and dried. It may be added to the blended coal. However, in order to disperse cellulose nanofibers on the surface of the blended coal, spray the cellulose nanofibers dispersed in water or an organic solvent toward the blended coal, and add the cellulose nanofibers to the blended coal. It is preferable. When the cellulose nanofibers dispersed in water are sprayed and added to the blended coal, the blended coal may be conditioned thereafter. By conditioning the blended coal, the moisture brought into the coke oven along with the cellulose nanofibers can be reduced, so the amount of heat and the carbonization time required for removing the moisture in the coke oven can be saved.

  When iron-mixed coke is produced by dry distillation of blended coal to which cellulose nanofibers are added, the strength of the produced steel-making coke increases and the particle size increases, and the clearance between the coke cake and the furnace wall increases. And the extrudability from the furnace of iron-making coke improves by the expansion of the clearance between a coke cake and a furnace wall. Although these factors are not clear, since cellulose nanofibers are dispersed and added to the surface of blended coal, the fine carbon fibers produced from cellulose nanofibers and softened and melted coal contact and adhere to each other, and The effect of suppressing the crack growth of coke cake by carbon fiber is expressed, which increases the clearance between the coke cake and the furnace wall, and increases the strength of iron-making coke produced by pulverizing the coke cake. It is thought that the particle size of the coke has increased.

  By adding cellulose nanofibers to the coal blend, the strength of iron coke produced by dry distillation of the coal blend can be increased, but cellulose nanofiber blended with TEMPO catalytic oxidation treatment is blended. When added to charcoal, the strength of iron-made coke can be further increased as compared with the case where cellulose nanofibers produced by mechanical defibration are added.

  The number average fiber diameter of the cellulose nanofiber produced by mechanical defibration is 20 nm or more and 300 nm or less. On the other hand, the number average fiber diameter of cellulose nanofibers produced by fibrillation by TEMPO catalytic oxidation treatment is 2 nm to 20 nm, and the number average fiber diameter of cellulose nanofibers produced by TEMPO catalytic oxidation treatment is mechanical It becomes smaller than the cellulose nanofiber manufactured by the regular defibration. In addition, the number average fiber diameter of the cellulose nanofiber is TEM observed using a TEM observation sample prepared by casting a 0.0001 to 0.1% by mass cellulose nanofiber solution, and a plurality of cellulose nanofibers observed. You may calculate by averaging the fiber diameter of a fiber.

  The fact that the number average fiber diameter of the cellulose nanofibers is small means that the cellulose nanofibers are defibrated and dispersed. Therefore, it can be said that the cellulose nanofiber manufactured by fibrillation by TEMPO catalytic oxidation treatment is more highly dispersed than the cellulose nanofiber manufactured by mechanical defibration.

  When cellulose nanofibers thus highly dispersed are added to the carbon surface, the effect of suppressing crack propagation by fine carbon fibers generated from cellulose nanofibers is enhanced. On the other hand, when low-dispersion cellulose nanofibers are added to the carbon surface, the cellulose nanofibers agglomerate with each other and the contact / adhesion between the fine carbon fibers produced from the cellulose nanofibers and the softened and melted coal deteriorates. As a result, the number of fine carbon fibers that escape from steelmaking coke increases. For this reason, the crack growth suppression effect by fine carbon fibers is low, and compared with the case where cellulose nanofibers are not added, the iron coke particle size and iron coke strength are improved, and the clearance between the coke cake and the furnace wall is expanded, The particle size of the iron coke and the strength of the iron coke were not improved and the clearance between the coke cake and the furnace wall did not increase as compared with the case where cellulose nanofibers produced by fibrillation by TEMPO catalytic oxidation were added.

  The amount of cellulose nanofiber added to the blended coal is preferably within the range of 0.01% by mass to 3.00% by mass of the outer frame with respect to the blended coal mass. More preferably, it is in the range of 0.10% by mass or more and 1.00% by mass or less with respect to the mass of charcoal. If the amount of cellulose nanofiber added is less than 0.01% by mass with respect to the blended coal mass, the iron coke particle size and iron coke strength are not improved, and the clearance between the coke cake and the furnace wall cannot be increased. On the other hand, even if the addition amount of cellulose nanofibers is more than 3.00% by mass with respect to the blended coal mass, no further improvement in steelmaking coke strength is seen, and the production of ironmaking coke by adding cellulose nanofibers is not observed. This is not preferable because the cost increases. As described above, since the effect of improving the performance of coke by adding highly dispersed cellulose nanofibers is high, the added amount of highly dispersed cellulose nanofibers is more than the added amount of lowly dispersed cellulose nanofibers. May be less.

  The coke cake after dry-blending the blended charcoal added with cellulose nanofibers in the range of 0.01% to 3.00% by weight with respect to the blended coal mass is stable without collapsing in the carbonization chamber. Was. This is because the fine carbon fibers produced from cellulose nanofibers cross-linked inside the coke cake, and the progress of cracks that occurred in the coke cake was suppressed, which enabled the clearance between the coke cake and the furnace wall to be expanded. It is done.

  The cellulose nanofibers defibrated by the TEMPO catalytic oxidation treatment have a carboxyl group. As the cellulose nanofibers added to the blended charcoal, it is preferable to use cellulose nanofibers having a carboxyl group of 0.1 mmol / g or more, more preferably cellulose nanofibers having a carboxyl group of 0.3 mmol / g or more. preferable. By adding cellulose nanofibers having a carboxyl group of 0.1 mmol / g or more to the blended coal, the strength of iron-made coke produced using the blended coal is improved.

  In addition, in this embodiment, although the example which adds a cellulose nanofiber to the coal mix used as the raw material of iron-making coke was shown, it is not restricted to this. For example, cellulose nanofibers dispersed in a solvent may be used as a binder for forming coal for iron-making coke. Thereby, the intensity | strength of the iron-making coke manufactured using the said steel-making coal is improved.

  Moreover, in this embodiment, although the example which adds a cellulose nanofiber to blended charcoal was shown, you may add a cellulose nanofiber to the raw material which mixed blended charcoal and cast charcoal. Moreover, it is a case where the raw material which mixed coal and combination charcoal is used, Comprising: The quantity which exists in the range of 0.01 mass% or more and 3.00 or less of the mass sum of coal formation and combination coal as a binder of coal formation When the cellulose nanofibers are mixed with the formed charcoal, it is not necessary to add the cellulose nanofibers to the raw material.

  Next, Example 1 which added the cellulose nanofiber to the charcoal and manufactured iron-made coke using the charcoal will be described. In this example, cellulose nanofibers (CNF (A)) that have been defibrated by TEMPO catalytic oxidation treatment and dispersed in water as a solvent, and defibrated by a water jet method that is mechanical defibration, Cellulose nanofiber (CNF (B)) dispersed in a certain water was used. CNF (A) is CNF (number average fiber diameter 3 nm, number average fiber length 500 nm) obtained by TEMPO oxidation of pulp. CNF (B) is BiNFi-s (registered trademark) product number WMa-1002 (number average fiber diameter of 20 nm to 50 nm, number average fiber length of several μm) manufactured by Sugino Machine Co., Ltd. For the production of iron coke, blended coal having a vitrinite average maximum reflectance of 1.02%, a Gieseler maximum fluidity of 196 ddpm, and a total inert amount of 31.1% by volume was used.

  The TEMPO catalytic oxidation treatment was performed as follows. Bleached pulp obtained by bleaching wood-derived chemical pulp as a raw material containing cellulose (dry weight 1.0 g) is washed with distilled water and 0.01 M hydrochloric acid, and then 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) Suspended in 100 mL of an aqueous solution containing 0.0156 g and 0.10 g of sodium bromide. The TEMPO catalyzed oxidation reaction was started by adding an aqueous sodium hypochlorite solution. The amount of sodium hypochlorite was 10.0 mmol to obtain cellulose nanofibers. This reaction was performed for 3 hours with stirring at room temperature. The TEMPO catalytic oxidation reaction proceeds under alkaline conditions, but the pH of the reaction solution decreases due to the formation of carboxyl groups, so the aqueous solution of sodium hydroxide was added to maintain the pH at 9.8 to 10.2. . After completion of the reaction, ethanol was added and the precipitate was collected using a centrifuge. The precipitate was washed with distilled water and the chemical solution was removed to obtain CNF (A).

The amount of CNF (A) or CNF (B) added to the blended coal mass was 1.00 mass%, and the blended coal to which these were added was dry-distilled in a test coke oven to produce iron-made coke. CNF (A) was added to the blended coal in a state of being dispersed in water so that the concentration was 1% by mass and CNF (B) was 2% by mass. Carbonization is obtained by charging a test furnace with a furnace wall temperature of 1050 ° C. and charging 16 kg (anhydrous base) of coal blended in a carbonization can (width 360 mm × depth 270 mm × height 400 mm) for 4 hours. The coke was fire extinguished in a nitrogen stream. The strength of the manufactured iron-making coke, the average particle size of the iron-making coke, and the clearance between the coke cake after the carbonization and the coke oven were measured, and the effect of adding CNF (A) or CNF (B) was confirmed. The strength of the iron-made coke was measured by the drum strength (DI ¹⁵⁰ ₁₅ ) defined in JIS K2151. The drum strength (DI ¹⁵⁰ ₁₅ ) was measured by putting iron coke into a rotating drum of a test facility specified in JIS K2151, rotating 150 rpm at 15 rpm, and sieving with a 15 mm sieve. The strength is defined by the mass ratio of iron coke having a particle diameter of 15 mm or more. In addition, the average particle diameter of iron-made coke is the average value calculated | required from the mass ratio of each particle size by sifting manufactured coke. The clearance between the coke cake and the coke oven was measured by the method described in Patent Document 5.

FIG. 2 is a graph showing the drum strength, average particle diameter, and clearance between the coke cake and the furnace wall of the iron coke. FIG. 2 (a) shows the drum strength (DI ¹⁵⁰ ₁₅ ), FIG. 2 (b) shows the average particle size (mm), and FIG. 2 (c) shows the clearance (mm) between the coke cake and the furnace wall. ). As shown in FIGS. 2 (a), (b), and (c), by adding cellulose nanofibers to the blended charcoal in either CNF (A) or CNF (B), the drum strength ( DI ¹⁵⁰ ₁₅ ) increased, the average particle size of the iron-made coke increased, and the clearance between the coke cake and the furnace wall increased. In this way, by adding cellulose nanofibers to the coal mix and producing the iron coke by dry distillation of the coal mix, the strength and average particle size of the iron coke can be improved, and the clearance between the coke cake and the furnace wall can be improved. It was confirmed that it could be expanded. And the extrudability of coke can be improved by expanding the clearance between the coke cake and the furnace wall in this way. Table 1 shows values of the drum strength (DI ¹⁵⁰ ₁₅ ), the average particle diameter of the iron coke, and the clearance of the iron coke in FIGS. 2 (a), 2 (b), and 2 (c).

Further, when compared with CNF (A) and CNF (B), the drum strength of steel coke is higher when CNF (A) with high dispersion is added than when CNF (B) with low dispersion is added (DI ¹⁵⁰ ₁₅ ). The average particle size of steel coke increased, and the clearance between the coke cake and the furnace wall increased. Thus, by adding cellulose nanofibers defibrated by TEMPO catalytic oxidation treatment in which the number average fiber diameter of cellulose nanofibers is 20 nm or less to blended coal, the blended coal is dry-distilled to produce iron coke. It was confirmed that the strength and average particle size of the iron-made coke could be further improved and the clearance between the coke cake and the furnace wall could be further expanded. In addition, even when the number average fiber diameter is large, if the cellulose nanofiber having a fiber diameter of 50 nm or less is contained in the added cellulose nanofiber, the effect of improving the strength and average particle diameter of the iron-making coke and the effect of expanding the clearance are obtained. can get. However, when the number average fiber diameter of the cellulose nanofibers to be added exceeds 300 nm, the content of fibers having a fiber diameter of 50 nm or less is extremely reduced. Therefore, the upper limit of the number average fiber diameter of the cellulose nanofibers to be added is set to 300 nm or less.

  Next, Example 2 in which cellulose nanofibers are used as a binder for forming charcoal will be described. In this example, the properties of CNF (A) and CNF (BNF) used in Example 1 were applied to coking coal having a vitrinite average maximum reflectance of 0.99%, a Gieseler maximum fluidity of 2 to 8 ddpm, and a total inert amount of 38% by volume. ) Or a mixture in which soft pitch (SOP), which is a conventional binder, is mixed, is formed into cylindrical shaped charcoal having a diameter of 10 mm and a height of 12 mm at a molding pressure of 30 MPa, and the produced charcoal is put into the powdered coke. Then, the temperature was raised to 900 ° C. at a temperature rising rate of 3 ° C./min, the temperature was maintained for 0.5 h, dry distillation was performed, and cooling was performed in a nitrogen atmosphere to produce iron-made coke.

  The strength of the iron coke produced in this way was evaluated by the amount of indentation until the type D conical indenter was broken using a durometer. About 3 specimens were measured per level, and the average value was taken as the measurement result, and the ratio of the strength of each steelmaking coke to the case where no binder was added was calculated as the relative strength. FIG. 3 is a graph showing the relationship between the mixing amount of the binder and the relative strength of the iron-making coke produced from the coal coal mixed with the binder. In FIG. 3, the horizontal axis represents the amount of binder mixed (outer frame mass%) with respect to the mass of raw coal serving as the raw material for the formed coal, and the vertical axis represents the relative strength (−) of the steelmaking coke. Moreover, the profile shown by the circle plot shows the relative strength when CNF (A) is used as the binder, and the profile shown by the triangle plot shows the relative strength when CNF (B) is used as the binder, The profile shown by the square plot shows the relative strength when SOP is used as the binder.

  As shown in FIG. 3, when using a highly dispersed CNF (A) defibrated and manufactured by TEMPO catalytic oxidation treatment as a binder, compared to using a soft pitch (SOP) as a conventional binder The relative strength of coke increased. Specifically, the strength of steelmaking coke produced using molded charcoal formed by mixing and molding CNF (A), which is 0.5% by mass with respect to the mass of raw coal as a binder, is SOP, which is a conventional binder. It became about 1.3 times the strength of the iron-making coke produced using the same amount. In addition, the strength of iron coke produced using cast charcoal formed by mixing and molding CNF (A), which is 1.0% by mass with respect to the raw coal mass, is the same as that of SOP, which is a conventional binder. It was about 2.4 times the strength of the steel coke produced using the same.

  On the other hand, the strength of steelmaking coke produced using coking charcoal formed by mixing CNF (B) as a binder was less effective than the case of mixing CNF (A). It became higher than the intensity | strength of the iron-making coke manufactured using the same amount of SOP.

  From these things, compared with the case where SOP is used as a binder for coal, the strength of iron coke produced by dry distillation of the coal is increased by using cellulose nanofiber as the binder for coal. It was confirmed. Moreover, if the intensity | strength of iron-making coke becomes high, the average particle diameter of iron-making coke will also become large. From these results, it can be said that by using cellulose nanofibers as a binder for the coal, the strength of the iron-making coke produced using the coal-forming can be increased, and the particle size of the iron-making coke can be increased.

  CNF (A) is added to the blended coal for coke production (Vitrinite average maximum reflectance 1.02%, Gieseller maximum fluidity 163ddpm) with a predetermined amount of CNF (A) and kneaded, 44mm x 44mm x 13mm (one side) The charcoal was produced using a double roll molding machine having a Macek mold. The produced coking coal is buried in powdered coke, heated to 900 ° C at a heating rate of 3 ° C / min, maintained at that temperature for 0.5 h, dry-distilled, and cooled in a nitrogen atmosphere to produce iron coke. Manufactured. The crushing strength of coking coal and iron coke is obtained by applying pressure at a pressure rate of 1 mm / min using an autograph crushing strength measuring machine (AGS-X) manufactured by Shimadzu Corporation, and measuring about 3 specimens per level. The average value was taken as the measurement result.

  FIG. 4 is a graph showing the relationship between the amount of cellulose nanofiber added and the crushing strength of the molded product. In FIG. 4, the horizontal axis represents the amount of CNF (A) added (dry—outer frame mass%), and the vertical axis represents the crushing strength (kN / piece) of the molded product. As shown in FIG. 4, when the amount of CNF (A) added was increased, the crushing strength of the molded product formed by adding CNF (A) was also improved. From this result, it was confirmed that when the amount of CNF (A) added was increased, the strength of the molded product produced by adding CNF (A) was also increased.

  FIG. 5 is a graph showing the relationship between the type of binder and the crushing strength of iron-made coke obtained by dry distillation of a molded product. In FIG. 5, the horizontal axis indicates the type of binder. The vertical axis represents the crushing strength (kN / piece) of the iron-made coke. “SOP + tar pitch” on the horizontal axis is iron-making coke obtained from formed coal produced by adding 3% by mass of SOP in the outer frame and 6% by mass of tar pitch to the coal as a binder. “CNF” is iron-making coke obtained from formed coal produced by adding 0.5% by mass of CNF (A) to the coal as a binder with an outer frame. As shown in FIG. 5, although the amount of binder added to coal is smaller in CNF (A), the crushing strength of iron coke produced from a molded product using CNF (A) as a binder is SOP. And the crushing strength of iron coke produced from coking coal using tar pitch as a binder. From this result, it was confirmed that high strength steel-making coke can be produced by using CNF (A) as a binder.

  In Examples 1 to 3, the strength of iron coke was improved by adding TEMPO-oxidized CNF (A), so the effect of the degree of oxidation of CNF on the molded product and coke strength was confirmed. The oxidation method was the same as in Example 1, and CNF (A) with different degrees of oxidation was produced by changing the amount of sodium hypochlorite added to 1 to 15 mmol. The degree of oxidation was evaluated by measuring the amount of carboxyl groups contained in CNF. In addition, the quantity of the carboxyl group contained in CNF was measured by the following method described in Patent Document 4.

  First, 60 ml of a 0.5 to 1.0 mass% slurry was prepared from an oxidized cellulose sample whose dry weight was precisely weighed, adjusted to pH 2.5 with a 0.1 M hydrochloric acid aqueous solution, and then 0.05 M water A sodium oxide aqueous solution is dropped and the electrical conductivity is measured. The measurement is continued until the pH is 11. And the amount of functional groups is determined using the following formula (1) from sodium hydroxide (V) consumed in the neutralization step of the weak acid whose electrical conductivity changes slowly. This amount of functional groups is the amount of carboxyl groups.

  Functional group amount (mmol / g) = V (ml) × 0.05 / mass of cellulose (g) (1)

  Manufacture of the forming coal and the forming coke which is the carbonized product thereof was carried out in the same manner as in Example 2. Note that SOP and tar pitch are not used as the binder, and CNF (A) having a different degree of oxidation is added to the mass of the blended coal by adding 0.5% by mass of the outer frame, respectively, to produce a molded coal. Steelmaking coke was produced using charcoal. The strength of the cast charcoal and the cast coke was measured using a Shimadzu autograph crushing strength measuring machine (AGS-X) at a pressurization speed of 1 mm / min in the column height direction of the molded product. Was the crushing strength (N / piece). About 3 samples were measured per level, and the average value was taken as the measurement result.

  FIG. 6 is a graph showing the relationship between the amount of carboxyl groups contained in cellulose nanofibers and the crushing strength of the molded product. In FIG. 6, the horizontal axis represents the amount of carboxyl groups contained in CNF (mmol / g), and the vertical axis represents the crushing strength (kN / piece) of the molded product. Moreover, FIG. 7 is a graph which shows the relationship between the quantity of the carboxyl group contained in a cellulose nanofiber, and the crushing strength of the iron-making coke obtained by dry-distilling a molding. In FIG. 7, the horizontal axis represents the amount of carboxyl groups contained in CNF (mmol / g), and the vertical axis represents the crushing strength (kN / piece) of iron coke. 6 and 7, the point where the amount of carboxyl group is 0 is the crushing strength of a molded product and iron coke formed without adding CNF (A).

  As shown in FIGS. 6 and 7, when CNF (A) having a carboxyl group of 0.1 mmol / g or more is added to the raw coal, a molded product produced using the raw coal and the molded product are used. The strength of the manufactured steel coke was improved. Moreover, when CNF (A) having a carboxyl group of 0.3 mmol / g or more is added to the raw coal, the strength of the molded product produced using the raw coal and the iron coke produced using the molded product is increased. Further improved. From this result, it is preferable to use CNF oxidized to have a carboxyl group of 0.1 mmol / g or more, and more preferable to use CNF oxidized to have a carboxyl group of 0.3 mmol / g or more. I understand that. Carboxyl groups have a negative charge and repel each other by this negative charge. It is considered that CNF containing a large amount of carboxyl groups has a large repulsive force due to a negative charge, and the fibers are easily defibrated, and the improved dispersion of CNF contributed to the improvement of the strength of the molded product and iron coke. In addition, if the oxidation of cellulose proceeds too much, the fibrous structure of CNF cannot be maintained, and the effect of CNF addition is reduced. For this reason, it is preferable that the quantity of the carboxyl group contained in CNF is 3.0 mmol / g or less.

Claims (8)

A coal blend for iron-making coke, to which cellulose nanofibers having a number average fiber diameter in the range of 2 nm or more and 20 nm or less are added in an outer frame of 1.00 mass% or more and 3.00 mass% or less .   The said carbon nanofiber is a coal mixture for iron-making coke of Claim 1 which has a carboxyl group of 0.1 mmol / g or more. The iron-making coke formed by dry-distilling the coal-mixing coal for iron-making cokes of Claim 1 or Claim 2 . A coal for steelmaking coke, in which cellulose nanofibers having a number average fiber diameter in the range of 2 nm or more and 20 nm or less are mixed in the outer frame by 0.5 mass% or more and 3.00 mass% or less . The said carbon nanofiber is a coal charcoal for iron-making coke of Claim 4 which has a carboxyl group of 0.1 mmol / g or more. The iron-making coke formed by dry-distilling the coal for iron-making coke of Claim 4 or Claim 5 . Cellulose nanofibers having a number average fiber diameter in a range of 2 nm or more and 20 nm or less dispersed in a solvent are used as a binder,
The manufacturing method of the forming coal for iron-making cokes which mixes the said binder and coal of 0.5 mass% or more and 3.00 mass% or less with an outer frame, and manufactures forming coal by shaping | molding. The said cellulose nanofiber is a manufacturing method of the coal charcoal for iron-making cokes of Claim 7 which has a carboxyl group of 0.1 mmol / g or more.