JP6007958B2 - Coke production method - Google Patents

Description

  The present invention relates to a method for producing coke, and in particular, a coking coal obtained by adding a caking filler and blending inferior coal is charged into a coke oven together with pulverized coal obtained by pulverizing another blended coal. The present invention relates to a method for producing coke that is carbonized.

  In blast furnace operation, the coke is required to have a required strength in order to ensure air permeability in the furnace. On the other hand, high-quality strong caking coal as a raw material for coke is exhausted in terms of resources, and many methods for producing coke having the necessary strength using inferior quality coal have been proposed. As one of them, there is a method of blending inferior coal to form coal, mixing the coal and pulverized coal prepared by pulverizing another blended coal, and charging the mixture into a coke oven.

  FIG. 1 shows a processing flow when coke is produced by mixing coal and pulverized coal and dry-distilling in a coke oven. In this production method, blended coal A containing at least inferior coal is prepared, pulverized with a pulverizer, a caking filler is added to the pulverized blended coal, kneaded with a kneader, and then molded with a molding machine. And form charcoal. On the other hand, after pulverizing another blended coal B into pulverized coal, for example, both are mixed at a ratio of 70 to 90% by mass of pulverized coal and 10 to 30% by mass of molded coal, charged into a coke oven, and subjected to dry distillation. , To produce coke.

  In this production method, coke strength is improved because coal blended with inferior coal is formed into coal with high apparent density. Moreover, by mixing the coal coal having a high apparent density with the coal coal having a low charge bulk density, the overall bulk density is improved, and the coke quality is improved as compared with the case where only the coal powder is used.

  In such a method using coal, in order to further increase the amount of inferior coal in the coal, even if the amount of inferior coal increases, it will be possible to produce coke with high cold strength. It is necessary. In the production of coke using the above-described coal, methods for producing coke having high strength are disclosed in Patent Documents 1, 2, and 3.

  In Patent Literature 1, when estimating the coke strength of the coking coal part and the pulverized coal part, respectively, when estimating the coke strength from the weight ratio at the time of coking of both, the particle size, true specific gravity, volatile matter of the raw material used for the coking coal, Estimating the coke strength of the coal-forming part from the expansion rate, the density of the coal-forming, and the dry distillation conditions, and estimating the coal-coal part in the same way, it is possible to more appropriately adjust the blending of the raw coal to obtain high-strength coke A method that can be performed is disclosed.

  Patent Document 2 discloses a high-strength coke that is produced by forming a coking coal produced by molding a low-quality coke raw material into a raw coal, adjusting the particle size of the forming coal, and producing coke having higher strength than before. A manufacturing method is disclosed.

  In addition, as a method of pulverizing and agglomerating coal, Patent Document 3 discloses that coal having a cohesive strength index of less than 80 is pulverized to 3 mm or less to 70 mass% or more and 100 mass% or less, and having a cohesive strength index of 80 or more. A method is described in which coal is pulverized to 2 mm or less and 90% by mass or more, and these coals are blended to agglomerate, and only the agglomerated coal is dry-distilled to obtain high strength molded coke.

Japanese Patent Application Laid-Open No. 60-174951 JP 2008-120898 A JP 2002-121568 A

  When coke is produced by charging cast coal mixed with inferior coal into coke oven together with pulverized coal, coke strength is estimated by the method disclosed in Patent Document 1, and the coal raw material to be used is adjusted. Even if the particle size of the coal is adjusted by the method disclosed in the above, the coke strength may be lowered depending on the proportion of the inferior quality coal and sufficient strength may not be obtained.

  In addition, the method disclosed in Patent Document 3 makes coal particles specially fine, and leads to generation of dust due to an increase in required electric energy and an increase in fine powder. In addition, this method agglomerates all the coal and charges it in a coke oven, shortens the carbonization time using heat transfer through the gaps between the agglomerated coals. There is no particular knowledge about the use of a large amount of inferior coal when mixing and dry distillation.

  The present inventors consider that the strength of coke produced using coal and pulverized coal depends on the strength of coke in the portion derived from coal (coal coal part) when the same coal powder is used. The relationship between the blending amount of inferior coal and the pulverized particle size of coal in coking coal and the coke strength of the forming coal was investigated. As a result, in the case of coal, regardless of the blending amount of inferior coal, when the coal has a large pulverized particle size, the strength of the coking coal coke is low. Moreover, when the pulverization particle size of coal was large, the strength of the formed coal portion coke decreased with an increase in the blending amount of inferior coal.

  About this, ΣTD (weighted average total expansion coefficient obtained by weighted average of the total expansion coefficient of coal to be blended) that is an index of blending amount of inferior coal, and RD (crushed coal blend) that is an index of coal pulverization particle size When the blended coal with a ΣTD of less than 40% and an RD of less than 75% is used, it is impossible to obtain a sufficient coking strength of the coke part. However, even if the RD less than 75% is used, if the coal char less than ΣTD 40% can be used, it will lead to suppression of the required electric energy and the generation of dust due to the fine powder at a low cost.

  Therefore, the present invention is a method for producing coke in which coal is charged into a coke oven together with pulverized coal and dry-distilled, and even if the amount of inferior coal blended with the coal is increased, the coal particles are made particularly fine. It is another object of the present invention to provide a method that can stably produce coke with high strength at a low cost.

  The coal formed using a blended coal having a ΣTD of less than 40% and an RD of less than 75% has a coarse inert because the raw coal is coarse. Furthermore, the present inventors have found that there are local voids around coarse coal particles. On the other hand, when the blending amount of inferior coal is large, since the swelling of coal after dry distillation is not sufficient, the present inventors have generated carbon cracks due to coarse inerting when carbonizing such cast coal. In addition, it was considered that due to the expansion of coal, local voids in the coal coal were not filled, and the strength of the coal portion coke was lowered.

  Therefore, the present inventors have tried to increase the coke strength of the coal forming part without increasing the coal particle size even if the blending amount of inferior coal is increased. It was found that the adhesion between the coals was strengthened by expanding and filling the local voids in the coal.

The gist of the present invention made through such examination is as follows.
(1) After pulverizing blended coal for at least including inferior charcoal, adding a caking filler to the blended coal after pulverization and kneading, molding with a molding machine to form coal, In the method for producing coke, which is charged into a coke oven together with pulverized coal prepared by pulverizing another blended coal for pulverized coal and dry-distilled,
When the weighted average total expansion coefficient obtained by weighted averaging the total expansion coefficient of the blended coal is ΣTD, and the ratio of the coal particles having a particle size of 3 mm or less after pulverization of the blended coal is RD,
As a coal blend for coal, ΣTD is 3% or more and less than 40%, and RD is less than 75% by mass,
Furthermore, the method for producing coke is characterized in that it uses molded charcoal that is added and molded so that the caking filler is 9 to 17% by mass with respect to blended charcoal for molding charcoal.

  ADVANTAGE OF THE INVENTION According to this invention, in the manufacturing method of the coke which charges a coking coal with a pulverized coal in a coke oven, and dry-distills, coal inferior to a forming coal can be used in a larger quantity.

It is a figure which shows the processing flow at the time of mixing coking coal and pulverized coal, and dry-distilling with a coke oven, and manufacturing coke. Changes the weighted average total expansion coefficient ΣTD, which is a weighted average of the ratio RD of coal particles with a particle size of 3 mm or less after pulverization of the coal for coal casting and the total expansion of the coal blended with the coal for coal casting It is a figure which shows the relationship between (SIGMA) TD and the coke intensity | strength DI of a forming coal part for every RD. It is a figure which shows the tomographic image obtained by imaging the coal char before and behind carbonization by X-ray CT. (1) is a tomographic image of coal after carbonization, and (2) is a tomographic image of coal after carbonization. Relationship between ΣTD and coke strength DI of coal-forming part when weighted-average total expansion coefficient ΣTD, which is a weighted average of coal expansion blending ratio and total expansion coefficient of coal blended in coal for coal casting, is changed FIG.

  First, the present inventors made coals with different coal blends and pulverized particle sizes, and investigated changes in the coke strength of the coals. Hereinafter, the weighted average total expansion coefficient obtained by weighted average of the total expansion coefficient of coal blended with the coal mixture for coal casting is ΣTD, and the ratio of coal particles having a particle size of 3 mm or less after pulverizing the coal blend for coal molding Is described as RD.

  As a blended coal for forming coal, prepare a mixture of inferior quality coal with respect to strong caking coal, pulverize each so that RD becomes 60% and 90%, and use the blended coal A charcoal was produced. The coal is wrapped in paper so that it can be taken out and evaluated independently after dry distillation. = 10%) at a constant blending amount, and the mixed raw material was subjected to dry distillation to produce coke. The obtained coke is in the form of being separated from the coke consisting of the surrounding powdered coal part due to the presence of inert paper around the coke consisting of the coal forming part. Can be taken out. The strength was measured for the coke of the formed coal portion thus obtained.

The coke strength of the cast charcoal part was obtained by actually measuring the coke percentage DI ¹⁵⁰ ₁₅ on a 15 mm sieve after rotating the coke 150 times with a drum tester described in JIS K2151 as in the case of ordinary coke. Hereinafter, the coke strength DI ¹⁵⁰ ₁₅ will be described simply as the coke strength DI.

  ΣTD was determined, and the coking strength coke strength DI was organized for each RD in relation to ΣTD. The results are shown in FIG.

  From FIG. 2, regardless of the value of ΣTD, in the coal using the same blended coal, when the RD is large, the coal-forming portion coke strength DI is improved. Further, when the RD was 90%, a coking coal coke having the same level of coking strength coke strength DI was obtained regardless of ΣTD. On the other hand, when the RD was 60%, the coking strength coke strength DI of the formed coal portion decreased with the decrease of ΣTD.

  Thus, as the RD is increased, that is, the pulverized particle size of the coal for forming coal is made finer, the strength of the forming coal portion increases. However, if the particle size is made fine, it leads to generation of dust due to an increase in required electric energy and an increase in fine powder. Therefore, it is desirable that a desired coke strength can be obtained even in a region where the particle size is coarse.

  On the other hand, even if RD is 60%, if ΣTD is 40% or more, the coke strength DI exceeds 80%. However, in order to increase ΣTD, it is necessary to reduce the proportion of inferior coal in the formed coal part, and a large amount of inferior coal cannot be used.

  However, it was found that when the ΣTD is less than 40%, the coke strength of the formed coal portion is greatly reduced when the RD is less than 75%.

  Therefore, X-ray CT observation was performed in order to examine the change in the coal before and after dry distillation with RD of less than 75% and ΣTD of less than 40%. FIG. 3 shows a tomographic image obtained by imaging the charcoal with X-ray CT. (1) is a tomographic image of coal after carbonization, and (2) is a tomographic image of coal after carbonization. In the image, the higher the density, the more white the color, and the lower the density, the darker the image. In the coal before dry distillation, there are black low density portions which are voids around coarse coal particles. Moreover, the black part which is a coarse pore exists in the coal after dry distillation.

  Based on this observation result, the relationship between the coking strength coke strengths DI, RD, and ΣTD in FIG. 2 is considered as follows.

  When RD is less than 75%, coarse pulverization causes coarse inerts to remain in the coal, and after dry distillation, due to the difference in shrinkage from the surroundings, Cracks occur. Further, the presence of coarse coal particles in the coal forms local voids around the particles. When the ΣTD of the coal forming part is low, since the expansibility of the coal around the void is insufficient, coarse pores and connected pores are generated after dry distillation. As a result, cracks due to coarse inert stripping and cracks in the inert occur. As a result, the strength of the coking coal coke is reduced.

  On the other hand, when ΣTD is 40% or more, the swollen coal in the coal is sufficient, and even if there are voids in the coal, the free expansion of the voids can be suppressed during dry distillation. The required coke strength of the coal-forming part can be obtained.

  Then, even if it is a case where the blending coal for coal molding with ΣTD of less than 40% is used, if ΣTD swells to the same level as or more than the coal of coal blending for coal molding with 40% coal, Therefore, it is considered that the required coking strength of coke is obtained.

  That is, the present inventors expand the coal in the coal by further adjusting the amount of the caking filler added to the coal mixture of the coal forming portion even when the coal particle size of the coal portion is coarse. The effect of voids around coarse particles can be reduced. Therefore, 3% of asphalt pitch (hereinafter referred to as ASP) and 7% of tar are added as a caking filler for blended coals having different RDs of 60% (that is, caking filler) 10% was added as a total) to produce coal, and the coal strength coke strength DI was measured.

  And (SIGMA) TD was calculated | required and the relationship between coking strength Coke strength DI and (SIGMA) TD was arranged. The results are shown in FIG. FIG. 4 also shows the relationship between the coke strength DI and ΣTD of the formed coal obtained by adding 7% tar alone as the caking filler, with the RD shown in FIG. 2 being 60%. Also shown.

  As a result, in the coal using the same blended coal, when the addition amount of the caking filler was increased from 7% to 10%, the coal coke strength DI was improved.

The examination results are summarized as follows.
When using a coal blend with a coal casting part with an RD of less than 75% and a ΣTD of less than 40%, if the amount of caking filler added to the coal mixture of the coal part is adjusted, the coke strength of the coal part DI can be adjusted.

  The present invention has reached the invention described in the above (1) through the examination process as described above, and the necessary and preferred requirements will be further described in order.

[Powdered coal]
In the present invention, coking coal is mixed with powdered coal obtained by pulverizing blended coal, charged into a coke oven, and dry-distilled to produce coke. Examples of the mixing ratio of pulverized coal and cast coal include pulverized coal of 70 to 90 mass% and molded coal of 10 to 30 mass%. The coal powder is not limited, but a normal blended coal containing strong caking coal (weighted average total expansion coefficient ΣTD = 50-100% of coal, weighted average volatile content quantification ΣVM = 26-29 dry% of coal) 3 mm or less Is obtained by pulverizing the ratio to a particle size of 60% to 95%.

[Forming charcoal]
Formed charcoal is manufactured by pulverizing blended charcoal as a raw material, adding a caking filler to this, kneading, and molding this kneaded product into a predetermined shape with a briquette machine or the like. Examples of molding conditions include a size range of 4 cc to 125 cc and a density range of 1.1 to 1.2 g / cm ³ .

  In recent years, the compounding quantity of inferior quality coal is increasing, and it is preferable to mix 40-70 mass% of inferior quality charcoal in a molding charcoal. By intensively blending the inferior coal with the coal, even if a large amount of the inferior coal is used, coke having the strength required for use in the blast furnace can be produced. Here, inferior coal has a low degree of coalification (average maximum reflectivity of vitrinite is 0.85% or less) and has poor caking or no caking (maximum fluidity 2.5 (log) (Ddpm)) hereinafter) refers to coal.

[Weighted average expansion coefficient of coal blended coal]
In order to increase the blending amount of inferior coal, ΣTD is set to less than 40%. The lower limit value of ΣTD is not particularly limited, and includes 0%. The total expansion coefficient TD of coal is measured by an expansibility test method (dilatometer method) described in JIS M8801. Many things have already been investigated for the total expansion rate TD of coal, and if the blending of coal constituting the coal is determined, the total expansion amount TD of simple coal corresponding to the blending amount (mass ratio) is added. The weighted average expansion coefficient ΣTD obtained by taking the average can be known.

  In the expansibility test method described in JIS M8801, the charcoal is charged into a reaction tube, a piston is placed on the top of the reaction tube, the container is heated, and the rising amount of the upper end of the molded product is set to the amount of the piston. It is read from the displacement amount, the fraction of the displacement amount of the piston with respect to the initial length of the molded product is obtained, and this fraction is taken as the total expansion rate.

[Crushing particle size of coal blended with coal]
Coal coal is produced by pulverizing blended coal as a raw material. The finer the coal blended with the coal, the more the inert present in the coal is crushed. Since inert has a low volatile content, the shrinkage rate during dry distillation is different from other softening and melting structures. Due to the difference, stress is generated at the interface between the two structures, and cracks are generated in or around the inert. By crushing the inert, the occurrence of such cracks is suppressed, and the strength of the formed charcoal portion is improved.

  However, if the particle size is made finer, it leads to generation of dust due to an increase in required electric energy and an increase in fine powder. Therefore, as described above, RD is made less than 75%. The lower limit of RD is not particularly limited, but RD is exemplified by 50% or more in consideration of operational problems such as clogging of the apparatus.

[Caking filler]
As the caking filler, both petroleum caking materials (tar, pitch, etc.) and coal caking materials can be used. It has been found that the caking filler needs to be added in an amount of 9% by mass or more with respect to the blended coal of the forming coal portion in order to obtain the necessary forming coal portion coke strength DI. On the other hand, when the compounding ratio of the caking filler exceeds 17% by mass, the porosity of coke obtained is increased by blending a large amount of caking filler with a high volatile content, and the coking strength coke strength DI is reversed. Therefore, the effect of adding a large amount of the caking filler is not obtained, and the production cost is increased. Therefore, the upper limit is set to 17% by mass.

  In addition, although the relation of ΣTD, RD and caking filler to the coking strength of the coking coal is confirmed to be effective even when the type of coal used and the apparent density of the coal are different, the coal used When the seeds and the molding conditions of the charcoal change, it is necessary to examine the relationship as shown in FIG. 4 in advance and select the amount of the caking filler that can obtain the target coking strength coke strength DI. preferable.

  Although the embodiments of the present invention have been described above, the feasibility and effects of the present invention will be further described with reference to examples.

  As shown in Table 2, blended coals 1 and 2 blended so that ΣTD is less than 40% using five types of simple coal (A coal to E coal) having different total expansion amounts TD shown in Table 1. Got ready.

After the blended coal 1 was pulverized to a particle size of RD 60% or 70%, 7-19% by mass of a caking filler was added and molded by a briquette machine, and the density was 1.12 g / cm ³ . 3, 6 and the charcoal of Comparative Examples 1 and 2 were obtained. This caking filler is composed of 7% by mass tar and 0-12% by mass ASP. Further, after the blended charcoal 2 was pulverized to a particle size of RD 60%, 9% by mass or 12% by mass of the above-mentioned caking filler was added, and molding charcoal was obtained under the same conditions as in Examples 1-3. 4 and 5.

  Table 3 shows the blending ratio of the caking filler with respect to ΣTD, RD of the coal for forming coal, and the blended coal for forming coal. Next, with respect to 80% by mass of pulverized coal under the conditions shown in Table 4, 20% by mass of coking coal shown in Table 3 is mixed, charged into a coke oven and dry-distilled, and coke strength DI of the coking coal part DI. I investigated.

  The results are shown in Table 5. In Examples 1-6, although ΣTD of coal for forming coal is less than 40% and RD is less than 75%, since caking filler is added in an amount of 9 to 17% by mass, sufficient coke strength is obtained. Has been obtained. Examples 4 and 5 are examples in which the value of ΣTD of coal for forming coal was increased as compared with Examples 1 and 2, respectively, and high coke strength was obtained. Example 6 is an example in which the value of RD was increased as compared with Example 1, and high coke strength was obtained. On the other hand, Comparative Examples 1 and 2 are those obtained by adding 7% by mass or 19% by mass of a caking filler to the blended coal for forming coal, and are outside the scope of the present invention, so that sufficient coke strength is obtained. It was not obtained.

  As described above, even if a large amount of inferior coal is contained in the coal, the coke having a sufficient coke strength can be obtained by producing the coal using the blended coal to which the caking filler is added.

  ADVANTAGE OF THE INVENTION According to this invention, in the manufacturing method of the coke which charges a coking coal with a pulverized coal in a coke oven, and dry-distills, coal inferior to a forming coal can be used in a larger quantity. Therefore, the present invention has high industrial applicability.

Claims (1)

After pulverizing blended coal for molding coal containing at least inferior coal, kneading and adding a caking filler to the blended coal after pulverization, molding with a molding machine to form coal, this coal for powder coal In a method for producing coke, which is charged into a coke oven together with pulverized coal prepared by pulverizing another blended coal of carbon dioxide and dry-distilled,
When the weighted average total expansion coefficient obtained by weighted averaging the total expansion coefficient of the blended coal is ΣTD, and the ratio of the coal particles having a particle size of 3 mm or less after pulverization of the blended coal is RD,
As a coal blend for coal, ΣTD is 3% or more and less than 40%, and RD is less than 75% by mass,
Furthermore, the method for producing coke is characterized in that it uses molded charcoal that is added and molded so that the caking filler is 9 to 17% by mass with respect to blended charcoal for molding charcoal.