JP4438532B2 - Coke and method for producing coke - Google Patents

Description

  The present invention relates to coke used for metallurgy and the like and a method for producing coke.

  Coke plays an important role in maintaining air permeability in the blast furnace, and high-quality coke is indispensable in order to achieve stable large pulverized coal blowing operation, high brewery operation, or low reducing material ratio operation. It is thought that there is. In particular, it is strongly desired to supply high-strength coke that suppresses the generation of powder in the blast furnace and large particle size coke that has a large void forming effect in the blast furnace.

  In order to produce such high-quality coke, there is a method for improving the properties of the blended coal charged into the coke oven, for example, average maximum reflectance (Ro) and maximum fluidity (MF). However, high quality coal with large Ro and MF is expensive, and it is difficult to produce high quality coke only by this method due to cost constraints.

  On the other hand, in order to significantly reduce the coke production cost, it is desirable to use non-slightly caking coal that is inexpensive but of low quality as coal for blending. Usually, when the blending amount of low-quality non-caking coal is increased, the coke strength is lowered, so development for avoiding the strength reduction is necessary.

  Thus, it is a big problem to produce high-quality coke while using cheap and low-quality coal blends. For this reason, a method for producing coke has been studied, and in particular, development regarding a coke quality control method by controlling a coal crushing method has been actively carried out.

  For example, after sieving the raw coal, pulverize those with a certain particle size or more, then re-sieve and remix those with a certain particle size or more, so that the overall particle size is increased A method of performing adjustment is known (see, for example, Patent Document 1 and Patent Document 2). In addition, a method is known in which a pulverized particle size target value is separately determined for coal rich in active components and coal not rich in active components (see, for example, Patent Document 3).

  The reason why the coke quality is improved by the above method is as follows. The strength or particle size of coke produced by carbonizing coal largely depends on the size and amount of defect structures such as cracks and pores formed during the coal carbonization process. In particular, cracks have a great influence on the physical properties of coke, and most of them have different properties such as a structure that shows soft melting and a structure that hardly shows soft melting during dry distillation mixed in coal. This occurs due to the difference in expansion and contraction behavior between the components. Therefore, in order to produce high quality coke, it is an effective means to suppress the occurrence of such cracks.

  In order to suppress crack initiation, in the coal carbonization process, a method of improving the fusing property between the softening melt and the structural component that hardly shows softening melting, the heat generated around the structural component showing little softening and melting. A method for suppressing the stress is conceivable. In the methods described in Patent Literature 1 to Patent Literature 3, the fusion property is improved by selectively reducing the particle size of coal particles having a low softening and melting property and containing a large amount of tissue components that hardly show softening and melting. The thermal stress generated due to the difference in expansion and contraction behavior is suppressed.

In either method, the generation of cracks that cause strength reduction and particle size reduction in the coking process of coal is suppressed, so there is no richness in coarse coal particles and active ingredients that are the source of cracks. The goal is to selectively reduce coal particles.
JP 58-162893 A Japanese Patent Laid-Open No. 4-309592 JP 56-32587 A

  By using the methods described in Patent Document 1, Patent Document 2, and Patent Document 3, coke having a quality equivalent to that of conventional products can be produced while using low-quality coal such as inexpensive non-coking coal. It became. However, at present, there is a demand for coke having higher strength and larger particle size and higher quality than before.

  Accordingly, an object of the present invention is to solve such problems of the prior art and provide a high-quality coke having a high strength and a large particle size and a method for producing a coke that can produce such a coke at a low cost. is there.

The features of the present invention for solving such problems are as follows.
( 1 ) Coal which is a coke raw material is adjusted so that the shape of the structure component which hardly shows softening and melting in the process of carbonization of coal in a coke oven is 0.58 or less in average flatness. Production method.
( 2 ) The method for producing coke according to ( 1 ), wherein the reflectance of coal is adjusted to 0.9 or more and 1.2 or less.
( 3 ) After classifying multiple types of coal, which are coke raw materials, into two or more groups according to the average flatness of the structural components that hardly show softening and melting during the coal carbonization process in the coke oven, The method for producing coke according to ( 1 ) or ( 2 ), wherein mixing is performed.
( 4 ) The additive particles added to the coal as the coke raw material are components that hardly show softening and melting in the coal dry distillation process in the coke oven, and hardly show softening and melting in the dry distillation process of coal derived from the coal. The method for producing coke according to any one of ( 1 ) to ( 3 ), wherein the shape of the tissue component and additive particles is adjusted so that the average flatness is 0.58 or less.

  According to the present invention, coke having a higher quality than that of conventionally manufactured coke can be produced. By using such high-quality coke in the blast furnace, sufficient air permeability is secured in the blast furnace, and stable operation of the blast furnace can be continued. In addition, while using a large amount of inexpensive non-coking coal, coke having a quality equivalent to that of conventionally manufactured coke can be produced, and the production cost of coke can be reduced.

  The present inventors pay attention to the shape control of the structural component that hardly shows softening and melting in the coal carbonization process, and the shape of the structural component that hardly shows softening and melting in the mixed coal by changing the mixing conditions and the grinding conditions. The present invention has been completed by newly discovering that coke quality is greatly improved by bringing a flat object closer to a true sphere.

  The reason for focusing on the shape of the tissue component, not the shape of the coal particles, is as follows. Coal particles include those composed of only a single structure and those composed of a plurality of tissue components. It is not the coal particles themselves but the tissue components that make up the coal particles that exhibit behavior as particles that hardly exhibit softening and melting in the actual carbonization process. Therefore, we thought that the structural components themselves should be managed in order to proceed with the crack suppression. Here, the structure | tissue component of coal represents fine structure components, such as vitrinite, semi-fujinit, and Fujinit observed with a microscope based on JISM8816. Among these, structures that hardly exhibit softening and melting include semi-fuji knit, fuji knit, and the like classified into the inert knit group.

  The influence of the shape of the structural component that hardly shows softening and melting of coal on coking can be considered from two viewpoints: the movement phenomenon behavior of the softened melt and the thermal stress generation behavior after resolidification. With regard to the former, the hydrodynamic interaction between the tissue component showing little softening melt and the softening melt differs depending on whether the shape of the tissue component showing little softening melt is flat or not. As the shape becomes flatter, the diffusion of the softened melt is hindered. As a result, the flatness of the tissue component shape deteriorates the fusion property with the softened melt. In the latter case, the flatter the shape of the tissue component that hardly shows softening and melting, the greater the stress intensity factor at the end point of the tissue component, so that stress concentration tends to occur. As a result, the probability of occurrence of cracks increases.

  Therefore, even when the sizes of the tissue components that hardly exhibit softening and melting are almost the same, the occurrence of defects occurring in the coking process can be suppressed by bringing the shape closer to a true sphere, thereby improving the coke quality.

  The structural component that hardly shows softening and melting in coal is a structural component in which the component that softens and melts at a temperature (coking temperature) when coal is carbonized using a coke oven or the like is about one third or less, One or two or more types selected from miclinit, sclerotite, Fujinit, and semi-Fujinit classified as inert knit in the fine tissue component group are targets (see JIS M 8816, etc.).

  As mentioned above, the shape of the tissue component that hardly shows softening and melting in the coal is made flat, and the shape of the tissue component that shows almost no softening and melting in the produced coke is flat. Approach to the true sphere and improve coke quality. On the other hand, if it is a tissue component that hardly shows softening and melting, even if it is not a coal-derived tissue component, the same effect can be obtained by bringing it closer to a true sphere. That is, when additive particles other than coal are added as a coke raw material, if the additive particles exhibit little softening and melting at the coking temperature, the shape of the additive particles is made closer to a sphere from a flat one. Even when coke is produced by adding it to the blended coal, the shape of the tissue component that hardly exhibits softening and melting in the produced coke approaches from a flat shape to a true sphere, and the coke quality is improved.

  As additive particles that hardly exhibit softening and melting at the coking temperature, it is desirable to use an inert material such as powdered coke, petroleum coke, anthracite, or sand. It is desirable that the inert material be added in an amount of 1 mass% to 10 mass%.

  As described above, it is desirable that the shape of the structure component and additive particles that hardly show softening and melting in coal is closer to the true sphere, but it is troublesome to quantify the three-dimensional shape when the shape distribution is large. Therefore, it is preferable to substitute a two-dimensional cross-sectional shape. In addition, the structural components that hardly show softening and melting in coal, and additive particles, although there are some changes in the surface state during the coal distillation process, the shape change is small, and there is almost no effect on the flatness, It is also possible to observe the shape of the component showing little softening and melting at the coking temperature at the stage of the coke produced. That is, the shape of the structural component that hardly shows softening and melting in coal and the shape of additive particles that show little softening and melting at the coking temperature, and the component that shows little softening and melting in the coal carbonization process are coke. The coke quality improves as it approaches a perfect circle from a flat one in any cross section.

  The degree to which the shape of the tissue component / additive particles that hardly show softening and melting approaches the true sphere or perfect circle is desirably quantified using the shape factor. The closer to the shape factor, the better. As the shape factor, there are three-dimensional shape factors such as length, flatness, Zingg index, Wandell sphericity, Aschenbrenner sphericity, etc. Is desirably quantified, and it is desirable to use flatness, roundness, circularity, etc. as a two-dimensional coefficient. The use of two-dimensional flatness as a coefficient indicating the shape is most effective for plate-like, piece-like, rod-like, needle-like, fiber-like, square-like shapes that have a great influence on the hydrodynamic interaction and stress intensity factor. It is optimal because it can be expressed with high sensitivity, and in order to sufficiently improve the strength of coke, it is desirable that the average flatness of tissue components and additive particles that hardly show softening and melting in the blended coal be 0.58 or less. . Further, it is particularly desirable that the aspect ratio is 0.53 or less. Alternatively, the number of tissue component / additive particles having an aspect ratio of 0.7 or more is desirably 25% or less of the total number of particles.

  On the other hand, when producing coke, it is desirable to adjust the reflectivity and maximum fluidity of the raw coal within a predetermined range. This is achieved by optimizing the coalification parameter (relevant to substrate strength) typified by reflectance and the caking parameter (relevant to particle adhesion) typified by maximum fluidity. This is because coke having the required strength can be produced. In general, coal with low flatness tends to be soft and have high reflectivity. When coke is produced using coal with low flatness as a raw material, coal with low fluidity and high reflectivity is the main component, and the coke strength decreases. May end up. Therefore, coke is produced by adjusting the average flatness of the structural component that hardly shows softening and melting of coal as a coke raw material to 0.58 or less, and adjusting the reflectance of coal to 0.9 or more and 1.2 or less. It is desirable. More desirably, it is 0.95 or more and 1.1 or less. Furthermore, it is desirable that the maximum fluidity (log MF) of coal be 2.08 or more. More desirably, it is 2.26 or more.

The shape factor of the coal-derived tissue component and additive particles that hardly show softening and melting at the coking temperature can be measured using, for example, a method according to the following steps (a) to (c). (A) Coal as raw coal and manufactured coke are filled with resin and photographed with a microscope capable of identifying the fine structure components. The additive particles are filled with resin in the same manner as coal and photographed with a microscope. (B) Using the image processing software, the tissue component is marked manually or automatically for the created micrograph, and a value necessary for calculating the shape factor is measured. (C) Shape factor, flatness = (long axis−short axis) / long axis, roundness = circumferential length ² / (4 × π × area), or circularity = (4 × π × area) / perimeter Obtained as a length of ² etc., and calculate the average value to obtain the average shape factor.

  Since the shape factor varies depending on the coal brand and type of additive, it is desirable to measure and quantify all the coal and additive particles used in coke production. For example, when the average flatness of coke raw material coal is measured for each type (brand) of coal using a mold adjusted in accordance with the microstructure and reflectance measurement method of JIS M 8816 coal, and used as a standard value This is effective when selecting coal brands.

  Similarly, it is desirable to measure and quantify the reflectance and maximum fluidity for all coal brands used in coke production. The reflectivity of coal (mixed coal) used in the present invention is calculated by calculating the reflectivity of each brand of coal measured according to JIS M 8816 as a weighted average with respect to the ratio of each brand in the blended coal. Yes, the maximum fluidity of coal (mixed coal) used in the present invention is obtained by weighting the logarithmic value of the maximum fluidity of each brand of coal measured according to JIS M 8801 with respect to the ratio of each brand in the blended coal. It is calculated as an average.

  In order to bring the shape of the structure component that hardly shows softening and melting at the coking temperature close to a perfect circle, (A) coal or additive particles whose shape of the structure component that shows little softening and melting at the coking temperature is close to a perfect circle It is desirable to use either or both of the two methods (A) and (B): (B) coal and additive particles are pulverized to reduce the particle size.

  In the method (A), an appropriate brand of coal or additive particles is selected and used as a coke raw material. Coal is selected as the coke raw material, with the average flatness of the tissue component that hardly shows softening and melting at the coking temperature being as close to a perfect circle as possible and having the lowest average flatness. Coal with a low average flatness tends to have a high reflectance and a high price. Therefore, if the average flatness is small and the average flatness is about the same, or if the average flatness is about the same, coal that has a reflectivity that has a predetermined reflectivity when blended with raw coal is coke. It is desirable to select it as a raw material. In order to produce coke having higher strength than before, the coke raw material coal has an average flatness of 0.58 or less in the shape of the structure component that hardly shows softening and melting in the coal carbonization process in the coke oven. It is desirable to adjust so that it becomes. At the same time, it is desirable to adjust the reflectance of coal to 0.9 or more and 1.2 or less. Coal raw material coal is blended so that the shape of the structural component that hardly shows softening and melting during the carbonization process of coal is 0.58 or less in average flatness, and the reflectance of coal is 0.9 or more and 1.2 or less. By doing so, it becomes possible to produce coke having higher strength and a larger average particle size by using conventional coke production technology in a coke oven. It is desirable that the ratio of the structural component that hardly shows softening and melting at the coking temperature in the coke raw material is about 50 mass% or less.

  In the method (B), the shape is brought close to a perfect circle by pulverization, and the degree of pulverization and the change in the shape vary depending on the structure of the structure, but the coal whose shape is greatly deviated from the perfect circle is selectively selected It is desirable to grind. Specifically, the coking coal is grouped in consideration of both its coking property and the shape of the structural component that hardly exhibits softening and melting, and is pulverized to a target particle size determined for each group, and then blended Etc. can be used. Alternatively, it is desirable to selectively pulverize additive particles whose shape is significantly different from a perfect circle.

  Therefore, after classifying multiple types of coal, which is a coke raw material, into two or more groups according to the average flatness of the structural components that hardly show softening and melting in the coal carbonization process in the coke oven, As described in (A), it is desirable to mix the coke raw material coal so that the shape of the tissue component that hardly shows softening and melting in the coal carbonization process is 0.58 or less in terms of average flatness. Furthermore, it is desirable to mix the coke raw material coal so that the reflectance of the coal is 0.9 or more and 1.2 or less. In addition, when additive particles are used as the coke raw material, the additive particles added to the coal as the coke raw material are components that hardly exhibit softening and melting in the coal carbonization process in the coke oven, and are derived from the coal. It is desirable to adjust the shape of the tissue component and additive particles that hardly show softening and melting in the dry distillation process so that the average aspect ratio is 0.58 or less.

  When the above method is used, the shape of the tissue component that hardly exhibits softening and melting in the coke is selectively close to a perfect circle, so that the coke quality is greatly improved as compared with the prior art.

  A test was conducted in which coal was carbonized to produce coke. The flatness of each coal (types A to J) and additive particles used in the test was measured. Coal (types A to J) was pulverized to a particle size of 3 mm or less and 80 mass%, and two types of powder coke (a, b) were used as additive particles. The average flatness is measured by first filling the coal and additive particles with resin, taking 50 photographs of each type of coal and additive particles using a polarizing microscope, and then processing the micrographs created. Semi-Fujinit, Fujinit, Miclinit, Sclerotinit, or powder coke particles, which are structural components that hardly show softening and melting in coal, were manually marked using software, and the average flatness was calculated. For coal, the reflectance (Ro), maximum fluidity (log MF), and total inert ratio (TI) were also measured in addition to the average flatness. The reflectivity is measured in accordance with JIS M 8816, the maximum fluidity is measured in accordance with JIS M 8801, and the total inert rate, which is the proportion of fine structure components that hardly show softening and melting in coal, is determined by JIS M 2 / 3SF + F + Mc + Sc + MM (SF, F, Mc, Sc, MM indicates volume% of each tissue. SF: Semi Fujinit, F: Fujinit, Mc: Miclinit, Sc: Scretinite, MM: Mineral ).

  Table 1 shows the measurement results of the coal properties of 10 types of coal of types A to J, and Table 2 shows the average flatness of the two types of powder coke (a, b). Table 1 reveals that the average flatness of semi-fujinit and Fujinite structures, which are structural components that hardly show softening and melting at the coking temperature, differ depending on the coal brand even when pulverized under the same conditions.

  Next, coal shown in Tables 1 and 2 and partly additive particles were blended, a dry distillation test was performed, and coke was produced. A dry distillation furnace capable of simulating an actual coke oven was used for the dry distillation test. Table 3 shows coal blending conditions (blendings 1 to 4). It adjusted so that Ro, logMF, and TI of the combination coal which mix | blended each coal (type AJ) became substantially constant after mixing | blending, and only the average flatness of a combination coal changed.

  Coal pulverization was performed under four conditions of pulverization 1, comparative pulverization 1, pulverization 2, and comparative pulverization 2 with the degree of pulverization varied depending on the type of coal. Table 4 shows coal pulverization conditions. In pulverization 1 and comparative pulverization 1 in Table 4, the coal indicated by 1 is a pulverization relaxation group, and after sieving with a 6 mm sieve, the sieving process was performed so that the top of the sieve was 6 mm or less and 100 mass%. The coal shown by 3 is a pulverization strengthening group, and after sieving with a 6 mm sieve, the sieving process was performed so that the top of the sieve was 3 mm or less and 100 mass%. Further, in pulverization 2 and comparative pulverization 2 in Table 4, the coal indicated by 1 is a pulverization relaxation group, and pulverization was performed so that the ratio of particles having a particle size of 6 mm or more was 10 mass% or less. The coal shown by 2 is usually a pulverization group, and was pulverized so that the ratio of particles having a particle size of 6 mm or more was 7 mass% or less. The coal shown by 3 is a pulverization strengthening group, and was pulverized so that the ratio of particles having a particle size of 6 mm or more was 4 mass% or less. Therefore, pulverization 1 classifies coal into two groups according to the average flatness of the tissue components that hardly show softening and melting at the coking temperature, strengthens the pulverization of coal with a high average flatness, and has a low average flatness This is a case where coal pulverization is relaxed and all coals of the pulverization strengthening group and the pulverization relaxation group are mixed. Crushing 2 classifies coal into three groups according to the average flatness of the tissue components that hardly show softening and melting at the coking temperature, strengthening the pulverization of coal with a relatively high average flatness, and relatively high average flatness This is the case when all the groups of coal are mixed by easing the low coal pulverization. Moreover, comparative grinding | pulverization 1 and 2 are the cases where it grind | pulverizes according to the kind of coal, without considering an average aspect ratio, and mixes the coal of all the groups.

  Further, for comparison, batch pulverization was performed in which all of the coal of blend 1 was pulverized after blending. In the case of batch pulverization, it is impossible to control the pulverization particle size for each coal brand.

  In addition, a test was also performed in the case where additive particles a and b were added in an external number of 3 mass% to the blended coal blended by performing the pulverization process of pulverization 2 under the conditions of formulation 1.

  Ingredients that produce coke using a raw material adjusted under the above blending conditions and pulverization conditions at a carbonization temperature of 900 degrees centigrade and a carbonization time of 15 hours, and show little softening and melting at the coking temperature of the produced coke. The average flatness, drum strength, and average particle diameter were measured. The average flatness of the component showing little softening and melting at the coking temperature was measured in the same manner as the average flatness of the tissue component showing little softening and melting in coal. The difference between the average flatness of components that show little softening and melting at the coking temperature in coke and the average flatness of components that show little softening and melting at the coking temperature at the blended coal stage is within the range of error. It was. Table 5 shows the influence of coal blending conditions and pulverization conditions on coke quality.

  Table 6 shows the average flatness, drum strength, and average particle diameter of the structural components that hardly show softening and melting at the coking temperature of the coke produced when additive particles a and b are added.

  As shown in Table 5, as compared with the cases of batch pulverization and comparative pulverizations 1 and 2 (Nos. 6 to 8), the pulverization 1 and 2 were performed by grouping according to the average flatness and changing the degree of pulverization treatment. In the case of (No. 1 to 5), it was found that the average flattening ratio was small, and the tissue component that hardly showed softening and melting at the coking temperature approached the true sphere. In addition, it was found that the lower the average flatness of the tissue component that hardly shows softening and melting at the coking temperature, the larger the drum strength and the average particle diameter, and the higher quality coke can be produced.

  In addition, as shown in Table 6, when additives having different average flatness ratios were added to the raw material coal, the one having a smaller average flatness ratio (No. 11) was softened and melted at the coking temperature in the coke. It was confirmed that the average flatness of the entire tissue component which is hardly shown was reduced and the coke quality was improved.

Claims (4)

A method for producing coke, characterized in that the coke raw material coal is adjusted so that the shape of a tissue component that hardly exhibits softening and melting in the process of carbonization in a coke oven is 0.58 or less in average flatness. The method for producing coke according to claim 1 , wherein the reflectance of coal is adjusted to 0.9 or more and 1.2 or less. Coke raw materials of multiple types are classified into two or more groups according to the average flatness of the tissue components that hardly show softening and melting during the carbonization process of coal in a coke oven, and are pulverized into groups and then mixed. The method for producing coke according to claim 1 or 2 , wherein: The additive particles added to the coal as the coke raw material are components that hardly show softening and melting in the coal dry distillation process in the coke oven, and the structural component that hardly shows softening and melting in the coal dry distillation process of the coal method for producing coke according to any one of claims 1 to 3 the shape of the additive particles and adjusting to 0.58 or less in average aspect ratio.