JP6065510B2 - Method of blending coke raw material for blast furnace - Google Patents

Description

  The present invention relates to an improvement in coke strength of a blast furnace coke raw material and a technique for expanding the coke particle size.

Various cokes such as blast furnace coke are pulverized and blended with many brands of coal (coking coal) and then charged into the coke oven. The charged coal mixture is coke by being carbonized in the furnace. Coke particle size and coke strength are known as quality control items that are particularly important in the production of coke.
Maintaining the coke grain size and coke strength at a certain level or more is indispensable for ensuring the air permeability of the blast furnace and realizing stable operation.

  Various techniques for enlarging the coke particle size have been proposed so far, and Patent Document 1 obtains the relationship between the particle size of the inert substance and the particle size of the coke obtained using the added amount as a variable. A method for producing a coke particle size is proposed.

  In Patent Document 2, attention is paid to the fact that the influence on the coke particle size and coke strength differs depending on the type and particle size of the low-shrinkage carbonaceous material, and the type and particle size of the low-shrinkage material so that the target coke strength and particle size are obtained. A method of adjusting is proposed. In Patent Document 3, the coke shrinkage is measured from the amount of shrinkage from the resolidification temperature to the heating temperature by heating to a heating temperature exceeding the resolidification temperature of the raw coal blend, and the coke particle size is estimated from this measured value. A method of adjusting the blending ratio of each coal in the blended coal has been proposed so that the estimated value is equal to or larger than the target coke particle size. In Patent Document 4, after blended coal is dried and further preheated, a mixture of pulverized coal and coarse coal at a temperature of 150 to 300 ° C. is added to any one of heavy tar fraction, soft pitch, and petroleum pitch. A method has been proposed in which a caking material consisting of seeds or two or more kinds is added to the mixture of the pulverized coal and the coarse coal so that the resolidification temperature of the mixture is 460 ° C. or more, and the coke strength and the coke particle size are increased. Yes.

Japanese Patent Laid-Open No. 11-181439 JP 2011-26514 A JP-A-2005-232349 JP 2008-120973 A

  However, in the method of Patent Document 1, it is necessary to compensate for a decrease in coke strength due to the addition of an inert substance with an expensive binder. In the method of Patent Document 2, the reduction in coke strength due to the addition of low-shrinkage carbonaceous material must be compensated for by a method such as a caking additive or charging bulk density improvement. The method of Patent Document 3 is a method for adjusting the blending ratio of each simple coal within a limited range of coal types, and with this method, it was difficult to sufficiently expand the coke particle size. . In the method of Patent Document 4, it is necessary to add an expensive binder to increase the coke particle size, and the coke particle size cannot be sufficiently increased. Then, an object of this invention is to provide the compounding method of the coke for blast furnaces which makes the coke particle size expansion and the improvement of coke strength compatible.

In order to solve the above-mentioned problems, the blending method of the blast furnace coke raw material according to the present invention is a non-slightly caking coal having a resolidification temperature of 470 ° C. or less according to the Gisela plastometer method defined in JIS M8801, and resolidification In a blending method of coke raw material for blast furnace including a low shrinkage carbonaceous material having a shrinkage rate of 10.5% or less when heated from a temperature to 1000 ° C., the following formulas (1) to ( 4 ) are satisfied: It is characterized by blending coke raw materials for blast furnace.
X mass% ≥ 70 mass% ... (1)
SV × BD ≧ 1.2 (2)
DI ¹⁵⁰ ₁₅ > DI ¹⁵⁰ _15base (3)
DI ¹⁵⁰ ₆ > DI ¹⁵⁰ ₆ base (4)
However, X mass% is a blending ratio of non-slightly caking coal and low shrinkage carbonaceous material, and the balance is caking coal. SV is the expansion specific volume at the time of coal softening, BD is the bulk density of the coal at the time of charging into the coke oven, DI ¹⁵⁰ _15base contains X mass% of non-slightly caking coal, and low shrinkage coal Is the coke strength of the reference coke not containing the material, DI ¹⁵⁰ ₁₅ is the coke strength of the blast furnace coke containing the low shrinkage carbon material, and DI ¹⁵⁰ ₁₅ is the coke strength of the blast furnace coke containing the low shrinkage carbon material. Oh Ri, DI ^0.99 ₆ base is a non-microporous viscosity coals include X mass%, and a surface-breaking strength of the reference coke containing no low shrink carbonaceous material, the high furnace DI ^0.99 _6, including a low shrinkage carbonaceous material Ru surface fracture strength der of use coke.

  ADVANTAGE OF THE INVENTION According to this invention, the compounding method of the coke for blast furnaces which can make the coke particle size expansion and the improvement of coke strength compatible can be provided.

Void filling degree during coal softening (-) to indicate a relationship between the surface fracture strength DI ^0.99 _6. The temperature and the volume change at the time of dry distillation of caking coal and non-slightly caking coal are shown typically. The relationship between the blending ratio of non-slightly caking coal and the volume fracture powder coke amount DI ¹⁵⁰ _6-15 generated by shrinkage after _{resolidification} is shown.

Even if a large amount of non-slightly caking coal is blended, the present inventor has reduced a part of non-slightly caking coal under the condition that the degree of void filling SV × BD (−) during coal softening is a predetermined value or more. It has been found that the coke strength can be improved and the coke particle size can be increased by switching to the contracted carbonaceous material. Here, the coke strength DI ¹⁵⁰ ₁₅ as a management index can be obtained from the following calculation formula when the surface fracture strength is DI ¹⁵⁰ ₆ and the volume fracture powder coke amount is DI ¹⁵⁰ _6-15 . The “coke strength” used in the following description means “coke strength DI ¹⁵⁰ ₁₅ as a management index” unless otherwise specified.
(Equation 1)
_DI ¹⁵⁰ ₁₅ = DI ¹⁵⁰ ₆ -DI ¹⁵⁰ _6-15 (1)

  The non-slightly caking coal in the present invention is a coal having a resolidification temperature of 470 ° C. or less according to the key celler plastometer method defined in JISM8001. Non-slightly caking coal has the characteristics that extensibility is not excellent and shrinkage rate is large. Non-slightly caking coal is inexpensive, has a high volatile content, and is not excellent in expansibility. Therefore, coal particles cannot be sufficiently bonded to each other when coal is melted, and tends to be low strength coke.

The graph in FIG. 1 shows the degree of void filling SV × BD (−) and the surface fracture strength when coal is softened when coal containing 50% non-caking coal (the remaining 50% is caking coal) is used. The relationship with DI ¹⁵⁰ ₆ is shown, with the horizontal axis representing the degree of void filling (−) and the vertical axis representing the surface fracture strength DI ¹⁵⁰ ₆ . From the figure, the surface breaking strength DI ¹⁵⁰ ₆ is improved until the void filling degree (−) reaches 1.2, and when the void filling degree (−) exceeds 1.2, the surface breaking strength DI ¹⁵⁰ ₆ is improved. You can see that it is getting smaller. Here, SV (cm ³ / g) is an expansion specific volume (Specific dilatation Volume), and BD (g / cm ³ ) is a charged bulk density (Bulk Density). The void filling degree SV × BD, which is the product of the charged bulk density BD (g / cm ³ ) and the expansion specific volume SV (cm ³ / g), is a dimensionless number, so to speak, indicates the degree of void filling due to the expansion of coal particles. It is a parameter and shows the adhesion between coal particles.

  Under the condition that SV × BD is lower than 1, voids between coal particles existing at the time of charging cannot be filled due to expansion of coal, and voids between coal particles remain as defects, resulting in low-strength coke. It has been known. In addition, when SV × BD ≧ 1, voids between coal particles existing at the time of charging are completely filled by the expansion of coal, and it is considered that there is no defect and the strength is constant. However, in an actual coke oven, since the charging bulk density and the properties of coal vary, it has been found that the surface strength of coke can be sufficiently improved by setting SV × BD ≧ 1.2. Incidentally, it has also been confirmed that even under the condition where a large amount of non-slightly caking coal is blended, the value of the surface fracture strength of coke is low, but the same tendency is exhibited.

Here, the expansion specific volume is calculated from, for example, the expansion rate b (%) measured by JISM8801 dilatometer as described in Nippon Steel Technical Report No. 384 (2006) p.43.
(Equation 2)
Expansion specific volume (cm ³ / g) = Coal volume at maximum expansion (cm ³ ) / Coal charge to dilatometer (g) = 0.96π (1 + b / 100) / Coil charge to dilatometer Receipt amount (g) (2)
Can be derived using the following formula.

As described above, even when 50% non-finely caking coal is blended, a sufficient surface for use in a blast furnace can be obtained by setting the degree of void filling SV × BD (−) during coal softening to 1.2 or more. It is possible to produce coke with a breaking strength DI ¹⁵⁰ ₆ . By the way, as a method of setting the void filling degree SV × BD (−) during coal softening to 1.2 or more, adjusting the blended coal blended with the coke raw material, SCOPE21 (Super Coke Oven for Productivity and Environmental enhancement toward the 21st century) and other methods such as rapid heat treatment of coal, addition of binders such as tar, etc., to control the expansion specific volume (cm ³ / g) to a desired value, or DAPS (Dry-cleaned and Agglomerated Precompaction It can be ensured by controlling the charging bulk density (g / cm ³ ) to a desired value by using preheating charcoal charging such as System) or stamping. That is, various methods including a known method can be used in order to increase the void filling degree (−) to 1.2 or more.

However, even when the degree of void filling SV × BD (−) during softening of coal is 1.2 or more, if a large amount of non-slightly caking coal is blended in the coke raw material (70% by mass or more), the shrinkage rate is reduced. Due to the large size, there is a problem that a large number of large cracks in the order of cm are generated at the time of shrinkage, resulting in a decrease in coke strength and a decrease in coke particle size due to an increase in the volume fracture powder coke amount DI ¹⁵⁰ _6-15 .

  The fact that the shrinkage rate increases when non-slightly caking coal is blended in a large amount (70% or more) in the coke raw material will be described with reference to FIG. FIG. 2 schematically shows changes in temperature and volume when caking coal and non-slightly caking coal are each carbonized, with the horizontal axis representing temperature and the vertical axis representing volume change. As shown in FIG. 2, caking coal starts expanding at about 400 ° C., and the softened and melted coal resolidifies at about 500 ° C. and contracts to about 1000 ° C. On the other hand, the non-slightly caking coal starts expanding at a temperature lower than that of the caking coal, and the softened and melted coal is re-solidified at a temperature lower than 470 ° C. and contracts to about 1000 ° C. That is, the non-slightly caking coal has a lower resolidification temperature than that of the caking coal, so that the shrinkage rate is relatively large.

Moreover, the graph of FIG. 3 has shown the relationship between the mixture ratio of non-slightly caking coal, and the volume fracture | rupture powder coke amount which arises by shrinkage | contraction after resolidification, a horizontal axis | shaft is a mixture ratio, and a vertical axis | shaft is volume fracture powder. It represents the amount of coke. Here, the volume fracture occurs with a large crack on the order of cm that can be observed with the naked eye as a base point. Large cracks on the order of centimeters that cause volume fracture are generated by thermal stresses generated by non-uniform shrinkage of the entire coke. That is, when the blending ratio of non-slightly caking coal increases, the shrinkage rate increases, and the non-uniform shrinkage of the entire coke also increases, so the volume fracture powder coke amount DI ¹⁵⁰ _6-15 increases. Therefore, when the surface fracture strength DI ¹⁵⁰ ₆ is constant, there is a problem in that the coke strength DI ¹⁵⁰ ₁₅ is reduced due to the increase in the volume fracture powder coke amount DI ¹⁵⁰ _6-15 , thereby causing a reduction in the coke particle size. .

Therefore, in order to reduce the volume fracture powder coke amount DI ¹⁵⁰ _6-15 and expand the coke particle size, it has been newly found that these can be achieved by appropriately adding a low shrinkage carbonaceous material. Invented the invention.

  Low shrinkage carbonaceous materials are known as additives that increase the coke particle size. Here, the low shrinkage carbon material is a carbon material having a shrinkage rate of 10.5% or less from the resolidification temperature to 1000 ° C., and the measurement method is as described in Patent Document 3. , Heating to a temperature T (° C.) above the coal resolidification temperature, and dividing the volume difference or length difference between the resolidification temperature and temperature T by the volume or length at the resolidification temperature It is set as the shrinkage rate at the temperature T of the coke produced | generated from coal. The details of the method for measuring the coke shrinkage rate are described in Patent Document 3 and will be omitted. Low shrinkage carbonaceous materials include petroleum coke, anthracite, semi-anthracite, and powdered coke.

On the other hand, low-shrinkage carbonaceous material and coal having a higher shrinkage rate than low-shrinkage carbonaceous material (a blended coal of caking coal and non-slightly caking coal, with a blending ratio of non-slightly caking coal less than 70% by mass) When the coke raw material blended with carbon was subjected to dry distillation, the volume fracture powder coke amount DI ¹⁵⁰ _6-15 hardly changed, but there was a problem that the surface fracture strength DI ¹⁵⁰ ₆ decreased. The reason why the surface fracture strength DI ¹⁵⁰ ₆ is decreased is considered to be that a small crack of the order of mm is generated around the low-shrinkage carbonaceous material due to the stress due to the unevenness of the shrinkage between the coal particles locally. .

However, as a result of the study by the present inventors, if the blending ratio of the non-slightly caking coal is 70% by mass or more, the volume of the non-slightly caking coal may be transferred to the low shrinkage carbonaceous material. It has been newly found that the amount of broken powder coke DI ¹⁵⁰ _6-15 can be reduced.

For blended coal whose blending ratio of non-slightly caking coal is 70% by mass or more, the volume fracture powder coke amount DI ¹⁵⁰ _6-15 is reduced by transferring a part of the non-slightly caking coal to a low shrinkage carbonaceous material. We can guess as follows.

When a low shrinkage carbonaceous material is added as a coke raw material, in addition to a reduction in the shrinkage ratio of the weighted average due to the addition of the low shrinkage carbonaceous material, a matrix due to the fact that small cracks on the order of mm are likely to be generated around the low shrinkage carbonaceous material. As the shrinkage rate decreases, the occurrence of large cracks is suppressed. Thereby, it is thought that the volume fracture powder coke amount DI ¹⁵⁰ _6-15 can be reduced.

However, since the coke strength is obtained as a value obtained by subtracting the volume fracture powder coke amount DI ¹⁵⁰ _6-15 from the surface fracture strength DI ¹⁵⁰ _{6 as} shown by the above-described formula (1), For the blended coal with a ratio of 70% by mass or more, the change in the surface fracture strength DI ¹⁵⁰ ₆ when a part of the non-slightly caking coal is transferred to the low-shrinkage coal is also related to the coke strength. As an important factor.

When the low shrinkage carbonaceous material is blended, if the surface fracture strength DI ¹⁵⁰ ₆ also increases, the coke strength increases. However, when the low shrinkage carbonaceous material is blended, if the surface fracture strength DI ¹⁵⁰ ₆ decreases, the amount added should be appropriately _{adjusted so that} the effect of reducing the volume fracture powder coke amount DI ¹⁵⁰ _6-15 is greater. It is important to set.

First, a low shrinkage carbonaceous material, shrinkage than the low shrinkage carbonaceous material is high coal (coking coal, non-fine caking) by dry distillation of the coke raw material blended with a surface fracture strength DI ^0.99 ₆ increases The case will be described. Examples of such a low shrinkage carbon material include petroleum coke (shrinkage rate: 9.8%) and semi-anthracite (shrinkage rate: 9.8%).

The reason why the surface fracture strength DI ¹⁵⁰ ₆ is increased when these low shrinkage carbonaceous materials are blended is that the surface fracture strength DI ¹⁵⁰ ₆ is determined only by the degree of void filling SV × BD (−) during coal softening described above. This is considered to be due to the influence of small cracks on the order of mm that can be seen with a microscope and the angular ridges of the coke mass. That is, as described above, small cracks in the order of mm, which cause surface destruction, are generated not from the shrinkage of the entire coke but from the stress due to the unevenness of the shrinkage between the coal particles, Angular ridges are generated by volume fracture due to large cracks on the order of cm. The angular edge of the coke mass for easy fracture, surface fracture strength DI ^0.99 ₆ and edges often decreases. Therefore, by adding a low shrinkage carbonaceous material above the coking, since the small cracks mm order is generated around the surface fracture strength DI ^0.99 ₆ coke is reduced by this phenomenon.

On the other hand, there is a correlation between the ridges which angular surface destruction of the coke, generally, edge of angular of coke is surface-breaking strength DI ^0.99 ₆ as increases decreases. In the present embodiment, the non-slightly caking coal and the low shrinkage carbonaceous material are blended in a large amount (70% by mass or more), and in the state where the low shrinkage carbonaceous material is not added, the volume fracture powder coke amount DI ¹⁵⁰ _{6− Although 15} is large, volume fracture is suppressed by adding a low shrinkage carbonaceous material to a coke raw material. Accordingly, since the generation of the angular edges are suppressed, the probability of surface fracture strength DI ^0.99 ₆ is increased becomes high. Increase in the surface fracture strength ^{DI 0.99} ₆ is, when exceeded decrement of surface fracture strength ^{DI 0.99} ₆ by small cracks, surface fracture strength ^{DI 0.99} ₆ with the expansion of the coke particle size is thought to be improved.

As described above, the content of the aforementioned low shrinkage carbonaceous material and non-slightly caking coal is X mass% (X mass% ≧ 70 mass%) (hereinafter sometimes referred to as the first condition), expansion specific volume (cm ^3). / G) and the filling density (g / cm ³ ) multiplied by the void filling degree (−) is 1.2 or more (hereinafter sometimes referred to as the second condition), and By adding the low-shrinkage carbon material in an addition amount that exhibits the effect of suppressing the volume fracture and the effect of increasing the surface fracture strength DI ¹⁵⁰ ₆ , the coke strength can be made higher than the reference coke strength. Here, the standard coke strength is coke strength when all of the low shrinkage carbonaceous materials are transferred to non-slightly caking coal. In addition, the coke particle size can be increased.

When the low shrinkage carbonaceous material is petroleum coke (shrinkage ratio: 9.8%), semi-anthracite coal (shrinkage ratio: 9.8%), the lower limit value of the addition amount is the volume fracture inhibiting effect and the surface fracture strength DI ¹⁵⁰ ₆ It is the minimum addition amount in which the increase effect is manifested. Specifically, 2% by mass can be exemplified. The upper limit of the addition amount, if satisfy the above first and second conditions, to confirm that express volume destruction suppressing effect and surface fracture strength DI ^0.99 ₆ increasing effect due to the addition of low profile carbonaceous material Therefore, it is not specified from this viewpoint.

In addition, in this application, with respect to the coal mixture of caking coal and non-slightly caking coal, the coal blend which changed a part of non-caking coal to the low shrinkage carbon material is made into object. Further, the upper limit of the blending ratio of the low shrinkage carbonaceous material is determined by the upper limit of the amount of the low shrinkage carbonaceous material, and specifically, the expansion specific volume (cm ³ / g) and the charging bulk density (g / The degree of void filling (−) multiplied by cm ³ ) is determined at a blending ratio satisfying 1.2 or more. Incidentally, when the low-shrinkage carbon material is petroleum coke or semi-anthracite, about 35% by mass can be exemplified.

Next, low-shrinkage coal and coal having a higher shrinkage rate than low-shrinkage coal (a mixture of caking coal and non-caking coal, with a blending ratio of non-caking coal of 70% by mass or more) The low-shrinkage carbon material in which the surface fracture strength DI ¹⁵⁰ ₆ is reduced by dry-distilling the coke raw material blended with the above will be described. An example of such a low shrinkage carbonaceous material is powder coke (shrinkage rate: 0.1%).

Even in the case of a low-shrinkage carbonaceous material such as powdered coke, it is necessary to add powdered coke so as to satisfy the first and second conditions. However, in the case of coke breeze, even if the first and second conditions are satisfied, the surface fracture strength reduction may exceed the volume fracture suppression effect, so the third condition may not be satisfied. . That is, in the case of powder coke, the coke strength may not be higher than the reference coke strength only by satisfying the first and second conditions. For example, when the addition amount exceeds 10% by mass, the coke strength of powder coke having a shrinkage rate of about 0.1% may be lower than the reference coke strength. That is, although the addition amount of the powder coke varies depending on the blending of coal, if it exceeds 10% by mass, the coke strength becomes lower than the reference coke strength even if the void filling degree (−) is 1.2 or more. There is a case. This is because low shrinkage carbonaceous materials such as powdered coke, which have a large difference in shrinkage ratio between caking coal and non-slightly caking coal, have small cracks on the order of mm when dry-distilled compared to other low shrinkage carbonaceous materials. This is probably because the surface breaking strength DI ¹⁵⁰ ₆ is greatly reduced.

Incidentally, by adding 0.05 mass% or more of powder coke, the effect of suppressing volume fracture is exhibited, and the effect of reducing the volume fracture powder coke amount DI ¹⁵⁰ _6-15 than the amount of decrease in the surface fracture strength DI ¹⁵⁰ ₆ is achieved. Is bigger. Therefore, when using powder coke as the second low-shrinkage carbon material, in addition to the first and second conditions, the strength DI when the low-shrinkage carbon material is added to the reference coke strength DI ¹⁵⁰ _15base. ^It is necessary to determine the blending ratio so that ¹⁵⁰ ₁₅ becomes high. On the other hand, when the amount of coke breeze is too large, although expressing the volume fracture inhibiting effect, since the direction of reduction of surface fracture strength DI ^0.99 ₆ increases, occurs when the coke strength is lowered. Therefore, it is important to set the addition amount so that the reduction effect of the volume fracture powder coke amount DI ¹⁵⁰ _6-15 is larger than the reduction amount of the surface fracture strength DI ¹⁵⁰ ₆ . Specifically, the amount of powdered coke added may be 0.05% by mass to 10% by mass, although it varies depending on the blending of coal.

  In addition, when using mixed low-shrinkage carbonaceous materials such as low-shrinkage carbonaceous materials such as petroleum coke and semi-anthracite and low-shrinkage carbonaceous materials having a smaller shrinkage rate such as powdered coke, the respective low-shrinkage carbonaceous materials The range of the content of the mixed low-shrinkage carbonaceous material can be set by determining the range of the content of the additive based on the respective standards and weighted averaging them. For example, the range of low shrinkage carbonaceous materials such as petroleum coke and semi-anthracite is X1 to Y1, the range of low shrinkage carbonaceous materials such as powder coke is X2 to Y2, and the low shrinkage of petroleum coke and semi-anthracite When the addition amount of carbon material is x% and the addition amount of low shrinkage carbon material such as coke breeze is y%, the lower limit value of the addition amount of mixed low shrinkage carbon material is (X1 × x + X2 × y) / (x + y) The upper limit value is (Y1 × x + Y2 × y) / (x + y).

The present invention will be described more specifically with reference to examples. Table 1 shows the properties (ash content, volatile content, resolidification temperature, shrinkage rate, and pulverized particle size) of caking coal, non-slightly caking coal, and low-shrinkage charcoal as coke raw materials used in this example. .
Table 2 shows that the coke raw materials of Example 1, Comparative Examples 1 to 5, and Reference Examples 1 to 2 were dry-distilled in a test coke oven, and the expansion specific volume (cm ³ / g) and charging bulk density (g / cm ³ ), void filling degree (−), surface fracture strength DI ¹⁵⁰ ₆ , volume fracture strength DI ¹⁵⁰ _6-15 , coke strength DI ¹⁵⁰ ₁₅ , and average coke particle size (mm). SV (cm ³ / g) represents the expansion specific volume (cm ³ / g), BD (g / cm ³ ) represents the charged bulk density (g / cm ³ ), and SV × BD (− ) Represents the void filling degree (-). The average coke particle size in the test coke oven was obtained by taking a 2m-high shutter once for coke after dry distillation, measuring the particle size distribution, collecting a sample for drum test, and + 25mm after drum 30 impact Average coke particle size.

Comparative Example 1 is a coke raw material containing 20% by mass of coal A (caking coal) and 80% by mass of coal B (non-minor caking coal). This is a coke raw material obtained by transferring caking coal) to petroleum coke by 15% by mass. The charging bulk density (g / cm ³ ) of Comparative Example 1 and Example 1 was both 0.80 (g / cm ³ ). By comparing and comparing Comparative Example 1 and Example 1, part of B coal (non-slightly caking coal) is transferred to petroleum coke (low shrinkage carbonaceous material), so that volume fracture is greatly suppressed, and surface fracture strength. DI ¹⁵⁰ ₆ improved. As a result, the coke strength DI ¹⁵⁰ _{15 as} a management index was improved. Moreover, since the coke raw material of Example 1 was added with petroleum coke having a low shrinkage rate, the average coke particle size was expanded. The effect of expanding the coke particle diameter by charging petroleum coke was also observed in Comparative Examples 2 and 3 and Reference Examples 1 and 2. The coke strength DI ¹⁵⁰ _{15 of} Comparative Examples 1 and 2 and Reference Example 1 is the reference coke strength.

Comparative Example 2 is a coke raw material having a void filling degree (-) lower than that of Comparative Example 1. Comparative Example 3 is a coke raw material in which the B coal (non-slightly caking coal) of Comparative Example 2 is transferred to petroleum coke by 15% by mass. In Comparative Example 3, since the void filling degree (−) was less than 1.2, the surface fracture strength DI ¹⁵⁰ ₆ was not improved although there was a volume fracture suppression effect by petroleum coke. Therefore, the coke strength DI ¹⁵⁰ ₁₅ that is a management index was not improved.

Reference Example 1 is a coke raw material containing 50% by mass of coal A (caking coal) and 50% by mass of coal B (non-caking coal). Reference Example 2 is a coke raw material obtained by transferring B coal (non-slightly caking coal) of Reference Example 1 to petroleum coke by 15% by mass. The charging bulk density (g / cm ³ ) of Reference Example 1 and Reference Example 2 was both 0.80 (g / cm ³ ).
In Reference Example 1, since the blending amount of the non-slightly caking coal was too small, volume fracture did not easily occur in the first place, and no effect of suppressing volume fracture by adding petroleum coke was observed. Therefore, surface breakage occurring around the petroleum coke, will exceed the effect of improving surface fracture strength DI ^0.99 ₆ by inhibiting volume fracture, surface fracture strength DI ^0.99 ₆ is lowered. As a result, the coke strength DI ¹⁵⁰ _15, which is a management index, decreased.

Table 3 shows the expansion specific volume (cm ³ / g), charging bulk density (g / cm ³ ), voids for a plurality of coke raw materials with different transfer rates from B coal (non-slightly caking coal) to petroleum coke. degree of filling (-), the surface fracture strength ^{DI 0.99} _6, volume breaking strength ^DI _{0.99 6-15,} coke strength ^DI _{0.99 15,} a measurement result of measuring the average coke particle size (mm).
Referring to Table 3, as shown in Examples 2 and 1, when the degree of void filling (-) is 1.2 or more, increase the transfer rate from non-slightly caking coal to petroleum coke. As a result, the effect of suppressing volume fracture was increased and the surface fracture strength DI ¹⁵⁰ ₆ was improved. As a result, the coke strength DI ¹⁵⁰ _{15 as} a management index was improved. On the other hand, as shown in Comparative Example 4, when the transfer rate from non-slightly caking coal to petroleum coke becomes too high, the degree of void filling (−) decreases to less than 1.2, and the surface fracture strength DI ¹⁵⁰ ₆ is Remarkably reduced. As a result, the coke strength DI ¹⁵⁰ _15, which is a management index, decreased.

Table 4 shows the expansion specific volume (cm ³ / g), charging bulk density (g / cm ³ ), degree of void filling (−), surface fracture strength DI for a plurality of coke raw materials with different types of low shrinkage carbonaceous materials. It is the measurement result which measured ¹⁵⁰ ₆ , volume fracture strength DI ¹⁵⁰ _6-15 , coke strength DI ¹⁵⁰ ₁₅ , and average coke particle size (mm).
As shown in Examples 1, 3 to 5, and Reference Example 3 , the content of B charcoal (non-slightly caking coal) and low shrinkage carbonaceous material is 70% by mass or more, and the degree of void filling (−) is 1. In the case of .2 or more, it was found that the addition of the low shrinkage carbon material improves the coke strength DI ¹⁵⁰ ₁₅ as a management index. However, as shown in Comparative Example 5, when the content of the coke powder having an extremely small shrinkage rate exceeds 10% by mass, the coke as a management index even if the void filling degree (−) is 1.2 or more. It turned out that intensity falls.

Table 5 shows the expansion specific volume (cm ³ / g), charging bulk density (g / cm ³ ), degree of void filling (−), etc. for coke raw materials including two types of low shrinkage carbon materials having different shrinkage rates. surface fracture strength ^{DI 0.99} _6, volume breaking strength ^DI _{0.99 6-15,} coke strength ^DI _{0.99 15,} a measurement result of measuring the average coke particle size (mm).
Since the mixed low shrinkage carbonaceous materials according to Examples 7 and 8 are within the range of the upper and lower limits of the addition rate, the coke strength DI ¹⁵⁰ ₁₅ as a management index is improved.

Claims (3)

Non-slightly caking coal whose re-solidification temperature is 470 ° C or less according to JISM8801 and low shrinkage whose shrinkage is 10.5% or less when heated from the re-solidification temperature to 1000 ° C. In the blending method of coke raw material for blast furnace including carbonaceous material,
A method for blending a blast furnace coke raw material, wherein the coke raw material for a blast furnace is blended so as to satisfy the following formulas (1) to ( 4 ).
X mass% ≥ 70 mass% ... (1)
SV × BD ≧ 1.2 (2)
DI ¹⁵⁰ ₁₅ > DI ¹⁵⁰ ₁₅ base (3)
DI ¹⁵⁰ ₆ > DI ¹⁵⁰ ₆ base (4)
However, X mass% is a blending ratio of non-slightly caking coal and low shrinkage carbonaceous material, and the balance is caking coal. SV is the expansion specific volume at the time of coal softening, BD is the bulk density of the coal at the time of charging in the coke oven, DI ¹⁵⁰ ₁₅ base contains X mass% of non-finely caking coal, and low shrinkage a coke strength criteria coke containing no carbonaceous material, DI ^0.99 ₁₅ may Ri coke strength der of the high furnace coke comprising low shrinkage carbonaceous material, DI ¹⁵⁰ ₆ base is a non-microporous viscosity coals include X mass% and a surface-breaking strength of the reference coke containing no low shrink carbonaceous material, DI ^0.99 ₆ is Ru surface fracture strength der of the high furnace coke comprising low shrinkage carbonaceous material. Furthermore, the Σ shrinkage | contraction rate which is a weighted average of the shrinkage rate of the blast furnace coke raw material satisfies following formula (5), The blending method of the blast furnace coke raw material of Claim 1 characterized by the above-mentioned.
ΣShrinkage ≦ 15.279% (5) The blast furnace coke raw material blending method according to claim 1 or 2 , wherein the low shrinkage carbonaceous material is petroleum coke, anthracite, semi-anthracite or powdered coke.