TWI482848B - Method for producing coke for metallurgy - Google Patents

Description

Method for producing metallurgical coke

The present invention relates to a method for producing high-strength metallurgical coke by adjusting the type and amount of coal contained in a mixed coal.

In order to produce pig iron by a blast furnace, firstly, it is required to be filled into layers by alternately loading iron ore and coke in a blast furnace, and blown in from a tuyere. The high temperature hot air heats the iron ore or coke, and the iron ore is reduced and melted by the CO gas mainly produced by the coke. In order to stably carry out the operation of such a blast furnace, it is effective to improve the air permeability and the liquid permeability in the furnace. Therefore, the use of metallurgical coke having excellent properties such as strength, particle size, and post-reaction strength is indispensable. Among them, the strength is considered to be a particularly important characteristic.

As described above, in order to improve the air permeability or the liquid permeability in a vertical furnace such as a blast furnace, it is effective to use high-strength metallurgical coke. The metallurgical coke is usually subjected to strength management by intensity measurement using a rotation strength test or the like specified by Japanese Industrial Standard (JIS) K 2151. Usually, coal is softened and melted by dry distillation, and bonded to each other to become coke. Therefore, the strength of coke is greatly affected by the softening and melting characteristics of coal, so The strength of high coke requires accurate evaluation of the softening and melting characteristics of coal. This softening and melting property is a property of softening and melting when heating coal, and can usually be evaluated by softening the fluidity, viscosity, adhesion, and expandability of the melt.

As a general method for measuring the softening and melting characteristics of coal, that is, the fluidity at the time of softening and melting of coal, a coal flowability test method by a Gieseler Plastometer method defined by JIS M 8801 can be cited. In the Gisele plastometer method, coal pulverized to 425 μm or less is added to a crucible, heated at a specific temperature increase rate, and a rotation speed of a stirring rod to which a specific torque is applied is read by a scale plate, and A method expressed by dial division per minute (ddpm).

Further, the coal is usually obtained by mixing an active ingredient which softens and melts upon heating with an inert component which does not soften and melt, and the inert component is subsequently passed through the active ingredient. Therefore, the coke strength is strongly influenced by the balance between the amount of the active ingredient and the amount of the inert component, and in particular, the state of the amount of the inert component is considered to be important.

As a general method of measuring the amount of the inert component, a method for measuring the fine structure of coal specified in JIS M 8816 can be mentioned. This method is a method in which coal pulverized to 850 μm or less is mixed with a thermoplastic or thermosetting adhesive to be briquettte, and the surface to be tested is polished, and then the optical property and the morphological property are identified using a microscope. The above method is a method in which the content ratio of each fine structure component in the sample is a percentage of the number of the components measured. The total inert amount (TI) was determined by the following formula (1) using the content of the fine structure component obtained by the above method.

Total inertia (%) = fusinite (%) + hard coal (micinite) (%) + (2 / 3) × half silk coal (%) + minerals (%) ... (1)

Here, the content is all vol.%.

Further, the content of the mineral can be determined by calculating the Parr formula described in JIS M 8816 based on the dry basis ash and the total sulfur content of the dry base.

The idea of blending coal for producing high-strength coke is to divide the constituent components of coal into two types: a fibrous portion (inert component) that does not soften and melt, and a softened and melted bonded portion (active component). The method of optimization is based on (Non-Patent Document 1). In addition, the above-mentioned idea of coal blending is generally developed, and a method of blending design according to two characteristics of coalification degree parameter and viscosity parameter is carried out.

Examples of the coalification degree parameter include a vitrinite average maximum reflectance (Ro) of JIS M 8816, a coal volatile component, and the like. In addition, examples of the viscosity parameter include a maximum fluidity (MF) or a CBI (Composition Balance Index) (for example, Non-Patent Document 2). In addition, the CBI is an index based on the following idea: there is an optimum amount of the binder component corresponding to the amount of the inert component contained in the coal blend, and the closer the ratio of the two components is to the optimum value, the more the coke strength becomes. high.

Further, Patent Document 1 reports that the average maximum reflectance (Ro) and the highest fluidity are considered in consideration of the correlation between the average maximum reflectance (Ro), the highest fluidity (MF), and the total inertia (TI). (MF) obtained when set to a specific value The coke strength exhibits an upwardly convex parabolic relationship according to the value of the total inertia (TI), and the amount of the inert component whose strength becomes extremely large changes depending on the maximum fluidity (MF).

Patent Document 2 reports a method of estimating coke strength based on various coking coal properties including maximum fluidity (MF) and total inertia (TI).

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2007-246593

[Patent Document 2] Japanese Patent Laid-Open No. 61-145288

[Non-patent literature]

[Non-Patent Document 1] "Flame Association" City, Vol.26, 1947, p.1-p.10

[Non-Patent Document 2] Schapiro et al., "Proc. Blast Furnace, Coke oven and Raw Materials", Vol. 20, 1961, p. 89 -p.112

[Non-Patent Document 3] "Fuel Association", Oyama et al., Vol.49, 1970, p.736-p.743

In the blast furnace operation, if low-strength metallurgical coke is used, the amount of powder generated in the blast furnace increases, resulting in an increase in pressure loss, resulting in destabilization of operation and localized concentration of gas in the furnace. The so-called worry of airflow unevenness (blow-by). In addition, in the production of coke for metallurgy, in order to obtain coke quality Stabilization and high strength are used, and coal blended with a plurality of varieties of coal in a specific ratio is used as a raw material.

As coal properties affecting coke quality, it is important to have an average maximum reflectance (Ro), a maximum fluidity (MF), and the like, and it is necessary to improve these characteristics in order to manufacture high-strength metallurgical coke. However, high-quality coal with a large average maximum reflectance (Ro) or a maximum fluidity (MF) is expensive, and simply increasing the blending rate of these high-quality coals is directly related to an increase in coke production costs, and thus is not the best policy.

Regarding the properties of the coal blend, the addition property of the single coal property constituting the coal blend and the simplicity of quality management are usually managed by the average quality of the coal blend. However, the degree of coke quality of the coal constituting the coal blending will affect the degree of coke, and which coal will effectively increase the coke strength, there are many unclear aspects, and there are examples in which the assumed strength cannot be obtained.

In particular, the effect of the total inert amount of coke in the coal has not been sufficiently studied, and a method for obtaining a high-strength metallurgical coke with respect to the effective utilization of coal having a small total inert amount is hardly found.

An object of the present invention is to provide a method for producing coke for metallurgy excellent in quality such as strength. In particular, the present invention provides a technique for producing high-strength coke by utilizing coal (low inert coal) having a small amount of an inert component which has been previously used as a raw material for coke production.

As an effective method for solving the above problems and for achieving the above object, a method for producing metallurgical coke is proposed in the present invention, which is characterized in that: In the method of producing a metallurgical coke by dry distillation of a coal containing a plurality of types of coal, the highest fluidity of 10% by mass or more and 75% by mass or less is used as the above-mentioned coal blending, and the maximum fluidity is 80 ddpm or more and 3000 ddpm or less. The low inert coal having a total inert amount of 3.5 vol.% or more and 11.7 vol.% or less.

In the present invention, it is considered that the following is a more preferable method for solving the above problems: (1) as the coal blending, a low inert coal blended with 20% by mass or more and 75% by mass or less is used; (2) The low inert coal has a maximum fluidity of 80 ddpm or more and less than 1000 ddpm, and a total inert amount of 3.5 vol.% or more and 11.7 vol.% or less; (3) an ash content of the low inert coal contained in the above coal blended coal. 4.8% by mass or more and 8.6% by mass or less; (4) The highest fluidity is a value measured by a coal flow test method by Gisele plastometer prescribed in JIS 8801; (5) the above total inertia It is a value determined by the following formula according to the method for measuring the fine structure of coal specified in JIS M8816: total inert amount (%) = silk coal (%) + hard coal (%) + (2/ 3) × half silk coal (%) + minerals (%)... (1)

Here, the content is all vol.%.

According to the present invention comprising the constitution as described above, it is possible to produce coke of higher quality (high strength) than the prior metallurgical coke. When such high-quality coke is used in a blast furnace, it contributes to improvement of the air permeability in a vertical furnace such as a blast furnace, and is effective for stable operation. Further, according to the present invention, it is possible to effectively utilize coal which has been previously used less and has a low content of inert components (total inert amount), that is, low inert coal, and can reduce the average maximum reflectance (Ro) which indicates the degree of coalification or The blending amount of high-priced coal having a high fluidity (MF) with high cohesiveness is shown, so that the manufacturing cost of coke can be reduced.

Figure 1 is a graph showing the relationship between the highest fluidity (MF) of Giselle and the total inertia (TI) of a single coal.

Fig. 2 is a photomicrograph of coke obtained by dry distillation.

The inventors and the like have conducted intensive studies on the relationship between various coal blending conditions and coke strength. As a result, it has been found that, according to the relationship between the maximum fluidity (MF) and the total inertia (TI) of the normal coal, when a coal having a small total inertia (TI), that is, a low inert coal having a small content of an inert component, is appropriately blended, The present invention has also been developed by unexpectedly greatly increasing the coke strength.

In the prior art, for example, in the method described in Non-Patent Document 2, the average maximum reflectance (Ro) indicating the degree of coalification is about 0.9 to 1.2, and the total inert component (hereinafter referred to as the total inert component). "Total inert amount" is 20 When vol.%~30vol.%, the coke strength becomes extremely large, the total inert amount is more or less than this range, and the coke strength is lowered, which is a common understanding. Further, the same tendency is also disclosed in Non-Patent Document 3, and it is reported that when the total inert amount is still 20 vol.% to 30 vol.%, the drum index of coke becomes extremely large. The above is also disclosed in Patent Document 1, but according to the disclosure, it is revealed that the coke strength becomes extremely large when the total inert amount is 31%. That is, the previous findings mean that it is difficult to obtain high-strength coke when blending coal having a small total inert amount.

However, the inventors have found that even if the coal having a low total inertia, that is, the low inert coal, is suitable for the maximum fluidity (MF) and the blending amount, not only the coke strength is not lowered, but also the usual blending. Compared to the increase in coke strength.

Fig. 1 is a graph showing the relationship between the maximum fluidity (logMF) of Gisele and the total inertia (TI) of various single coals (individual coals). As shown in the figure, generally, the maximum fluidity of coal having a small total inertia (TI) is large. However, in order to produce high-strength coke, it is important to strengthen the adhesion of the coal particles to each other without causing the connected pores accompanying the foaming. In this respect, when the maximum fluidity (MF) is large, the adhesiveness can be expected, but foaming is likely to occur, and the strength may be lowered due to the formation of the connected pores. Therefore, the idea of coal blending to date has been generally managed in such a manner that the maximum fluidity (MF) of the blended coal becomes appropriate.

However, in reality, there are coals having the same maximum fluidity (MF) and a different total inertia (TI). Since the coal is present as a solid in a softened molten state, the softened melt exhibits a physical property close to that of the slurry. behavior. That is, if the amount of the inert component is large in coal, the apparent viscosity in the softened molten state becomes large. In this respect, since the highest fluidity (MF) is considered to be an apparent viscosity, the coal with the larger total inertia (TI) in the coal with the highest fluidity (MF) level (the solid phase component is more), The smaller the viscosity of the liquid component present in the softened melt, the less the total inert amount, the greater the viscosity of the liquid component in the softened melt. It is considered that as the liquid component becomes lower in viscosity, the growth of the pores in the dry distillation is promoted to be one, and the more easily the pores are formed, the more easily the coke containing the coarse defects is formed.

In order to confirm the above, the inventors investigated the coke obtained from the previous coal blending (coal blending a) and the total inert content of 50% by mass in total of 3.5 vol.% or more and 11.7 vol.%. The microstructure of the coke obtained by mixing coal (mixed coal b) of low inert coal having a maximum fluidity (MF) of 80 ddpm or more and 3000 ddpm or less. Here, the quality of the coal blend a by the prior method is the average maximum reflectance (Ro) = 1.00%, the highest fluidity of the Giesel (logMF) = 2.5 logddpm, and the total inertia (TI) = 34 vol.%. The quality of a large amount of low inert coal blended b is the average maximum reflectance (Ro) = 1.00%, Gisele's highest fluidity (logMF) = 2.2 logddpm, and total inertia (TI) = 18 vol.%. A micrograph of coke obtained by dry distillation of the mixed coal under the same conditions is shown in Fig. 2 .

As can be seen from Fig. 2, in the blended coal b, the nearly round pores exist independently of the blended coal a, and in the blended coal b, the coke formation is more suppressed than the previous blended coke. It is also difficult to form a connecting vent. Thus, when a large amount of low inert coal is blended, a coke is formed which makes the microstructure different from the previous one, which is the previous Discovered by unknown discoverers and others. This suggests that the use of low inert coal is not based on the continuation of previous blending techniques, but rather on the basis of new blending, as compared to the generation of previously different microstructured coke.

In order to suppress the formation of the connected pores and to produce high-strength coke, it is generally considered to be effective in utilizing coal having a small total inert amount and a high viscosity of the liquid component in the softened melt, but the specific blending conditions are not taken for granted. Since it is difficult to imagine that there is a linear relationship between the total inertia (TI) and the amount of formation of the connected pores and the influence on the strength of the coke, the inventors and the like have conducted a large number of experiments to clarify the optimum coal trait conditions shown below. .

As can be understood from the above description, when the coke strength is increased by using low inert coal, it is possible to achieve good fusion of coal particles with each other and to have the highest fluidity (MF) to the extent that no pores are formed, and It is desirable to use a coal having a low total inertia (TI). It can be said that the range is preferably a maximum fluidity (MF) of 80 ddpm or more and 3000 ddpm or less, and a total inertia (TI) of 3.5 vol.% or more and 11.7 vol.% or less. .

Here, when the value of the highest fluidity (MF) of the low inert coal of Giselle is less than 80 ddpm, the lack of adhesion is caused. On the other hand, if the value exceeds 3000 ddpm, the connected pores are liable to be formed. The more desirable MF value is 80ddpm~1000ddpm, and more preferably 150ddpm~900ddpm.

Further, if the total inert amount (TI) of the low inert coal is less than 3.5 vol.%, the amount of inertness which contributes to the strength improvement as an aggregate is insufficient. On the other hand, if the total inertia (TI) of low inert coal exceeds 11.7 vol.%, it will be mourned. The cause of the use of low inert coal is the cause of the loss. A more desirable TI is about 4 vol.% to 10 vol.%.

In addition, if the blending ratio of such low inert coal is too small (<10% by mass), the effect is difficult to be expressed. Conversely, if too much (>75% by mass), the total inertia (TI) in the blended coal becomes too low. As a composite material composed of a structure derived from a molten component and a structure derived from an inert component, the properties are lost, and it is difficult to express strength. Therefore, the ideal blending ratio of the low inert coal is 10% by mass or more and 75% by mass or less. The amount is preferably from 20% by mass to about 75% by mass, more preferably from about 20% by mass to about 65% by mass.

Further, the ash in the above-mentioned inert coal is also a component which exists as a solid in a softened molten state, like the total inert structure. However, when compared with an inert component derived from carbon, ash tends to have a low volume ratio and further finely dispersed due to high density. Therefore, the degree of influence is small compared to the total inert amount (TI), but it is preferable that the ash content is also low, and the ash content is desirably 4.8% by mass or more and 8.6% by mass or less on the basis of the dry basis. The ash content is more preferably 5.0% by mass to 8.0% by mass.

Further, in the present invention, the blending amount of the low inert coal in the blended coal is recommended to be 10% by mass to 75% by mass, but as the rest of the coal, for example, the total inert amount is appropriately formulated to be not more than 3.5 vol.% or more. , 11.7 vol.% or less, and the highest fluidity of Giselle is not 80 logddpm or more, 300 logddpm or less of recalculated coking coal, weak coking coal, medium coking coal, low volatile coal Or ordinary coal such as non-coking coal or upgrading coal. General coal blending The amount is about 25% by mass to 90% by mass. In addition, the coal blend may be an additive including a binder material, an oil, a coke breeze, a petroleum coke, a resin, and a waste.

Further, as described above, in the present invention, it is effective to formulate a specific amount of low inert coal having the above conditions, that is, a specific maximum fluidity (MF) and a specific total inert amount (TI). Further, as the blended coal, in order to ensure a stable matrix strength, the average maximum reflectance (Ro) indicating the degree of coalification of the blended coal is preferably adjusted to about 0.95% to 1.20%.

[Example 1]

This example shows the test results when coke was dry-distilled to produce coke. In this test, a weighted average of the common maximum reflectance (Ro) of the blended coal as the usual strength-interminating factor and the common logarithm (logMF) of the Giselle's highest fluidity (MF) is prepared in a substantially fixed manner. Blended coal. The coal blend was prepared using Coal A to Coal P shown in Table 1. Further, the average maximum reflectance (Ro) was measured in accordance with JIS M8816, and the highest fluidity (MF) of Gisele was measured in accordance with JIS M8801, and the commonly used logarithm (logMF) is also shown in Table 1. Volatile components (VM) and ash (Ash) were measured in accordance with JIS M8812 and expressed as % dry basis. The total inertia (TI) is determined in accordance with JIS M8816 using the formula (1).

The dry distillation test uses an electric furnace that simulates the actual furnace. The pulverization conditions of the coal particles were set to 3 mm or less and 100%, and the filling conditions were such that the moisture content was 8% by mass, the bulk density was 750 kg/m ³ , and the dry distillation conditions were a dry distillation temperature of 1050 ° C and a dry distillation time of 6 hours. . The evaluation of the properties of the obtained coke was carried out using DI (150/15) in a ratio of 15 mm or more after 150 rotations as a drum as defined in JIS K2151. Further, coke CO intensity (Coke Strength after Reaction, CSR) and after the _second reaction is measured in accordance with ISO18894. The blending configuration of each coal blend (drying ratio of each coal (mass%)) and the results of the dry distillation test are shown in Table 2.

With the formulation of 20% by mass of the total inertia (TI) of 13.2 vol.% and more than the preferred range of coal I, 1-2, the highest fluidity (MF) of 20% by mass is formulated up to 10964 ddpm. Compared with the blending of 1-3 of coal J, the blending of 1-1 of coal with a maximum fluidity (MF: 447 ddpm) and a total inertia (TI: 6.7 vol.%) of 20% by mass is used for dry distillation. Coke, showing high strength.

For coal with average average reflectance (Ro) ratio of coal I (=0.77%), coal J (=0.79%), coal K (=0.76%) (Ro: 1.06%), coal M (Ro: 1.11%) The results of the blending were also compared. As a result, the highest fluidity of 20% by mass was formulated compared with the blending of 2-2 of coal L having a total inertia (TI) of up to 24.0 vol.%. The coke obtained by blending 2-1 with MF) and coal M having a low total inertia (TI) exhibits high strength. In the formulation of the confirmation of the coke strength In the case of high coal K and coal M with coal N and coal O with the highest fluidity (MF) and total inertia (TI), high-strength coke can also be produced (mixing 3-1, blending 4- 1).

According to the above test results, it is understood that the maximum fluidity (MF) of 20% by mass is set to be 80 ddpm or more, 3000 ddpm or less, and the total inertia (TI) is 3.5 vol.% or more and 11.7 vol.% or less. The blending of inert coal can produce high strength metallurgical coke.

Then, in order to confirm the influence of the blending ratio of the above-mentioned coal K and coal M in which the effect of improving the coke strength was found, the test was carried out by blending coal K with coal M at 40 mass%, 50 mass%, and 75 mass. %, 80% by mass of the blending 5-1, blending 5-2, blending 5-3, blending 5-4 coke strength for comparison. As a result, as shown in Table 2, those having a blending ratio of 40% by mass to 75% by mass of 5-1 to 5-3 (Examples 5 to 7) can produce high-strength coke. However, in the blending 5-4 (Comparative Example 4) in which the blending ratio of the coal K and the coal M was 80% by mass, it was found that the strength was greatly lowered. The reason for this is considered to be that the total inertia (TI) of the coal blend is lowered, so that the properties of the composite material composed of the structure derived from the molten component and the structure derived from the inert component are lost. In addition, when the total blending ratio of the coal K and the coal M is reduced, the strength is 84.5 in the example (mixing 5-5) when the blending ratio is 10% by mass, but the blending ratio is 8 mass%. (Assembling 5-6), the strength is reduced to 84.1.

Moreover, it is understood that 30% by mass of the coal having the highest fluidity (MF) of 836 ddpm and less than 1000 ddpm is formulated 10-1, and 35 mass% is contained. Coal P and 25% by mass of the highest fluidity (MF) and the total inertia (TI) of coal M, which are both low, have a high drum strength.

Further, as the coke strength, the same tendency is found for the strength index other than the drum strength (DI) (150/15), for example, the CO ₂ post-reaction strength (CSR). The reason for this is considered to be that the strength expression mechanism due to the difference in pore structure also acts, for example, on the strength after the CO ₂ reaction.

[Embodiment 2]

In Example 1, the experiment was carried out by unifying the average maximum reflectance (Ro) of the blended coal to 1.05. In general, the average maximum reflectance (Ro) of the blended coal can be said to affect the strength of the coke matrix portion, and it is clear in the present invention that it is independent of the formation of the connected pores. Therefore, the technique of the present invention can also be applied to coal blends having different average maximum reflectances (Ro).

In order to confirm the above, the blending ratio of each coal was changed in the same manner as in Example 1 to prepare different blended coals of Ro, and the strength of the coke obtained by dry distillation of the blended coal was evaluated. Table 3 shows the blending configuration of each blended coal (drying ratio of each coal (% by mass)) and the results of the dry distillation test. In the coal blended with a high maximum reflectance (Ro), the strength of the matrix portion is high, so the coke strength tends to be high, but the maximum fluidity (MF) is 80 ddpm or more, 3000 ddpm or less, and the total inertia (TI) is When the total blending ratio of K coal, M coal, and N coal in the range of 3.5 vol.% or more and 11.7 vol.% or less is too high or too low, the strength tends to decrease, and in the same manner as in the first embodiment, The blending ratio of the coal having a maximum fluidity (MF) of 80 ddpm or more and 3,000 ddpm or less and a total inertia (TI) of 3.5 vol.% or more and 11.7 vol.% or less is in a range of 10% by mass to 75% by mass. When the coal is subjected to dry distillation, coke having high strength can be obtained.

[Industrial availability]

The technique of the present invention is effective not only as a technique for producing coke for blast furnace as exemplified, but also as a method for producing coke for a vertical metallurgical furnace or coke for a combustion furnace.

Claims (6)

A method for producing a coke for metallurgy, characterized in that, in a method of producing a metallurgical coke by dry distillation of a coal containing a plurality of types of coal, the blended coal is used in an amount of 10% by mass or more and 75% by mass or less. The low inert coal having a maximum fluidity of 80 ddpm or more and 3000 ddpm or less and a total inertia of 3.5 vol.% or more and 11.7 vol.% or less. The method for producing a metallurgical coke according to the first aspect of the invention, wherein the low-inert coal blended with 20% by mass or more and 75% by mass or less is used as the coal blend. The method for producing metallurgical coke according to the first or second aspect of the invention, wherein the low inert coal has a maximum fluidity of 80 ddpm or more and less than 1000 ddpm, and the total inert amount is 3.5 vol.% or more. 11.7 vol.% or less. The method for producing a metallurgical coke according to the first or second aspect of the invention, wherein the low inert coal contained in the coal blend has an ash content of 4.8% by mass or more and 8.6% by mass or less. The method for producing a metallurgical coke according to the first or second aspect of the invention, wherein the highest fluidity is a value measured by a coal flow test method according to JIS 8801 by a Gisele plastometer method. . The method for producing a metallurgical coke according to the first or second aspect of the invention, wherein the total inert amount is determined by applying the following formula according to a method for measuring a fine microstructure component of coal specified in JIS M8816. Value: total inertia (%) = silk coal (%) + hard coal (%) + (2 / 3) × half wire Coal (%) + mineral (%)... (1) Here, the content is all vol.%.