DESCRIPTION
COKE AND METHOD FOR MANUFACTURING THE SAME
TECHNICAL FIELD
[0001] The present invention relates to a coke and
a method for manufacturing the same.
BACKGROUND ART
[0002] In production of pig iron in a blast furnace, iron ore (mainly, sintered ore) and a blast furnace coke having a mean particle diameter of 4 0 mm to 6 0 mm are charged into the blast furnace in a layered form via the furnace top, and hot air is sent in via a tuyere provided in a lower part of the blast furnace. The iron ore and the blast furnace coke gradually descend inside the blast furnace.
[0003] Sending the hot air causes a thermal reserve zone at about 1000°C to be present at the position of a shaft part inside the blast furnace. Consequently, in the thermal reserve zone, gasification reaction "C (coke) + CO2 = 2CO" of the coke descending in the blast furnace occurs. That is, CO is produced in the thermal reserve zone. On the other hand, the iron ore is heated while descending the blast furnace, and is reduced by a reduction gas constituted of CO which has been produced in the thermal reserve zone.
[0004] However, when a temperature of the thermal reserve zone, namely, a coke gasification temperature
is too high, it become difficult for the iron ore to be reduced.
[0005] For example, in reduction reaction of iron ore, as a reaction temperature gets higher, a reduction equilibrium gas composition shifts to a high CO concentration side. Specifically, as the reaction temperature gets higher, it becomes difficult for the reduction reaction to proceed unless CO with higher concentration is supplied.
[0006] Further, when the temperature of the thermal reserve zone is about 1100°C or higher, a molten liquid begins to be generated on a surface portion of the iron ore, which makes it difficult for the reduction gas to permeate to the inside of the iron ore. Consequently, it becomes difficult for the reduction reaction of the iron ore to proceed, and the efficiency of reduction decreases.
[0007] Accordingly, techniques to facilitate the reduction reaction of the iron ore by lowering the temperature of the thermal reserve zone (coke gasification temperature) are considered. As one of such techniques, there is a technique to maintain the temperature of the thermal reserve zone at 900°C to 950°C using a highly reactive blast furnace coke.
[0008] However, the blast furnace coke has a nature that its strength decreases as its reactivity is increased. In the blast furnace coke, a function to secure air permeability within the blast furnace is needed besides production of the reduction gas. When
the strength is low, however, the blast furnace coke pulverizes and the air permeability decreases, and the reduction efficiency decreases.
[0009] On the other hand, there is a technique to use a small coke having a mean particle diameter of 3 8 mm or less in mixture with the iron ore, besides the blast furnace coke having a mean particle diameter of about 40 mm to about 60 mm to be charged in a layered form together with the iron ore, and a highly reactive coke is used as the small coke. However, even such a small coke is needed to have strength to the degree that the air permeability is not limited.
[0010] However, in conventional methods for manufacturing a highly reactive small coke, it is difficult to obtain sufficient reactivity when it is attempted to secure a certain degree of strength.
CITATION LIST PATENT LITERATURE
Patent Document 1: Japanese Laid-open Patent Publication No. 2001-187887
Patent Document 2: Japanese Laid-open Patent Publication No. 2002-105458
Patent Document 3: Japanese Laid-open Patent Publication No. 2003-268381
Patent Document 4: Japanese Laid-open Patent Publication No. 2004-224844
Patent Document 5: Japanese Laid-open Patent
Publication No. 2001-348576
Patent Document 6: Japanese Laid-open Patent Publication No. 2004-035752
Patent Document 7: Japanese Laid-open Patent Publication No. H06-313171
Patent Document 8: Japanese Laid-open Patent Publication No. 2006-233071
Patent Document 9: Japanese Laid-open Patent Publication No. 2005-232348
SUMMARY OF THE INVENTION
TECHNICAL PROBLEM
[0012] It is an object of the present invention to
provide a coke capable of achieving high reactivity
while securing strength and a method for
manufacturing the same.
SOLUTION TO PROBLEM
[0013] The present inventors have conducted extensive studies on factors affecting reactivity of cokes.
[0014] As a result, the inventors have found that the diameter of pores existing in a coke largely affect its reactivity, and the larger the total volume of pores having a diameter of 1 urn to 10 µm per gram in the coke, the more the reactivity improves.
[0015] The present inventors have further conducted extensive studies on a method for increasing the
total volume of the pores having a diameter of 1 µm to 10 µm while securing a certain degree of strength. [0016] As a result, the inventors have found that four types of coal which differ in combination of the range of volatile matter content and the range of total dilatation may be blended appropriately to obtain coal blends, and carbonization of these coal blends may be performed.
[0017] The present invention is made in view of these findings, and the spirit thereof is as follows. [0018] A method for manufacturing a coke according to the present invention includes: obtaining a coal blend by blending at least two of first coal having a volatile matter content less than 3 0%, second coal having a volatile matter content of 30% or more and a total dilatation of 60% or more, third coal having a volatile matter content of 30% or more and 42% or less and a total dilatation less than 60%, and fourth coal having a volatile matter content more than 42% and a total dilatation less than 60%; and performing carbonization of the coal blend, in which in the obtaining the coal blend, the total ratio of the second coal and the third coal in the coal blend is 80 mass% or more, the ratio of the second coal in the coal blend is 20 mass% or more, the ratio of the fourth coal in the coal blend is 5 mass% or less, and the remaining portion of the coal blend is the first coal . [0019] A coke according to the present invention
includes pores having a diameter of 1 urn or more and 10 urn or less in a total volume per gram of 25 mm3/g or more, and a drum strength index DI15015 of the coke is 7 0 or higher.
ADVANTAGEOUS EFFECTS OF INVENTION
[0020] According to the present invention, high reactivity of a coke can be obtained while securing high strength of the coke.
BRIEF DESCRIPTION OF DRAWINGS
[0021] Fig. 1 is a graph illustrating a relation between a total volume of all pores per gram and a gasification reactivity;
Fig. 2 is a graph illustrating a relation between a total volume of pores having a diameter of 1 µm to 10 µm per gram and a gasification reactivity; and
Fig. 3 is a chart illustrating groups to which various coal belong.
DESCRIPTION OF EMBODIMENTS
[0022] As described above, the present inventors have found that the diameter of pores existing in a coke largely affect its reactivity, and the larger the total volume of pores having a diameter of 1 µm to 10 µm per gram in the coke, the more the reactivity improves. This finding will be described. [0023] The present inventors evaluated gasification reactivity of 11 types of cokes which differ in total
volume of all pores per gram and/or total volume of pores having a diameter of 1 µm to 10 µm per gram. In the evaluation, reactivity index CRI is measured. Specifically, sieved coke samples having a particle diameter of 19 mm ± 1 mm were charged at a weight of 200 g into a reactor, and a weight reduction ratio (percentage) after allowing reaction for two hours at
1100°C in a CO2 atmosphere was measured. Further, the total volume of pores of the coke was measured while changing a pressure condition depending on the pore diameter (the diameter of pores) measured using a mercury porosimeter. For the 11 types of cokes described above, there were obtained the relation between the total volume of all pores per gram and the gasification reactivity, and the relation between the total volume of the pores having a diameter of 1 µm to 10 µm per gram and the gasification reactivity. Results thereof are shown in Fig. 1 and Fig. 2. Fig. 1 is a graph illustrating the relation between the total volume of all pores per gram and the gasification reactivity. Further, Fig. 2 is a graph illustrating the relation between the total volume of the pores having a diameter of 1 µm to 10 µm per gram and the gasification reactivity.
[0024] As illustrated in Fig. 1, there was found no correlation between the total volume of all pores per gram and the reactivity index CRI. On the other hand, as illustrated in Fig. 2, the larger the total volume of the pores having a diameter of 1 µm to 10
urn per gram, the larger the reactivity index CRI became. Further, from the results shown in Fig. 2 , it was found that the reactivity index CRI becomes 5 0 or more when the total volume of the pores having a diameter of 1 urn to 10 urn per gram is equal to or more than 2 5 mm3/g. Moreover, it was also found that the reactivity index CRI becomes 5 5 or higher when the total volume of the pores having a diameter of 1 urn to 10 µm per gram is equal to or more than 30 mm3/g.
[0025] Reasons for that the pores having a diameter of 1 µm to 10 µm are effective for gasification reaction of a coke include following three reasons ( i) to ( iii) .
[0026] Reason (i) In gasification reaction of a coke, the mean free path of CO2, which reacts with the coke, is 0.1 urn to 1 urn. Accordingly, it is difficult for CO2 to enter pores having a diameter less than 1 urn. Thus, the pores having a diameter less than 0.1 urn do not contribute much to the gasification reactivity of the coke.
[0027] Reason (ii) CO2 can easily enter pores having a diameter of 1 urn to 10 urn in a coke. Further, since the diameter of the pores is relatively small, there is a high probability that CO2 comes in contact with inner surfaces of the pores. In other words, the reaction surface area is large. Accordingly, the pores having a diameter of 1 urn to 10 µm can contribute easily to improvement of the gasificat ion
reactivity of the coke.
[0028] Reason (iii) In pores having a diameter of 10 µm or more, there is a low probability that CO2 comes in contact with inner surfaces of the pores as compared to the pores having a diameter of 1 µm to 10 pm. That is, the reaction surface area is small. Accordingly, the pores having a diameter of 10 µm or more do not contribute much to the gasification reactivity of the coke.
[0029] From these reasons, high reactivity can be obtained with a coke in which numerous pores having a diameter of 1 µm to 10 µm exist. When the total volume of the pores having a diameter of 1 µm to 10 µm per gram is 25 mm3/g or more, sufficient gasification reactivity (reactivity index CRI of 5 0 or higher) can be obtained. Furthermore, when the total volume of the pores having a diameter of 1 µm to 10 µm per gram is 30 mm3/g or more, higher gasification reactivity (reactivity index CRI of 5 5 or higher) can be obtained.
[0030] Therefore, in the present invention, the total volume of pores having a diameter of 1 µm to 10 µm per gram in a coke is 25 mm3/g or more, and it is preferably 3 0 mm3/g or more.
[0031] Further, as described above, for a coke to be mixed with iron ore such as sintered ore and charged into the blast furnace, strength as high as that of a coke having a particle diameter of about 40 mm to about 60 mm to be charged in a layered form
together with the iron ore is not needed. However, if the strength of the coke to be mixed with iron ore and charged into the blast furnace is too low, for example, if the drum strength index DI15015 is lower than 70, destruction and pulverization of the coke may occur, leading to decrease in air permeability and reduction efficiency.
[0032] Therefore, in the present invention, the drum strength index DI15015 of the coke to be mixed with iron ore and charged into the blast furnace is 70 or higher. In addition, it is preferred that the particle diameter of such coke be 3 8 mm or less, for example. The specific surface area of the coke becomes smaller as the particle diameter becomes larger, and when the particle diameter of such coke is more than 38 mm, the specific surface area becomes too small and the reaction area is insufficient, by which it is difficult to obtain high reactivity. [0033] Furthermore, in the present invention, it is preferred that one or two of Ca compound and Fe compound be contained in the coke, and that the content be 0.5 mass% to 10 mass% in total with reference to the mass of a coal blend used for manufacturing the coke. When the coke contains them, higher gasification reactivity can be obtained. In addition, the content of 0.5 mass% to 10 mass% with reference to the mass of a coal blend is equivalent to the content of about 0.7 mass% to about 14 mass% with reference to the mass of the coke.
[0034] The Ca compound and the Fe compound function as a catalyst in gasification reaction of the coke. When an appropriate amount of Ca compound and/or Fe compound is contained in the coke of the present invention, the reactivity of the coke improves dramatically due to the synergistic operation of pores having an appropriate volume and the catalysts. This point has been confirmed experimentally by the present inventors, as will be described later. [0 035] Such synergistic operation can be described as follows. Specifically, since the numerous pores having a diameter of 1 jam to 10 pm exist in the coke, there exist many air paths reaching the catalysts existing inside the coke from the surface, and the gasification reaction determines the diffusion rate of CO2 entering via the surface. Consequently, the catalysts existing inside the coke becomes able to function sufficiently. In conventional cokes, it is difficult for CO2 entering via the surface to enter the inside even when catalysts are contained. Also, there also exist catalysts which do not easily contribute to the gasification reaction.
[0036] Further, when the content of one or two of Ca compound and Fe compound is less than 0.5 mass% in total, the aforementioned synergistic operation is not easily exhibited. On the other hand, when the content is more than 10 mass% in total, the aforementioned synergistic operation and effect merely saturate. Therefore, it is preferred that the
content of the one or two of Ca compound and Fe compound be 0.5 mass% to 10 mass% in total with reference to the mass of a coal blend used for manufacturing the coke.
[0037] In addition, the Ca compound and the Fe compound can be contained in powder form in the coke.
[0038] Further, the Ca compound and the Fe compound may exist also in the inside of the coke, and may exist only in a surface or the vicinity of the surface of the coke. In either case, the aforementioned synergistic operation is obtained, and high catalyst addition effect can be obtained as compared to conventional cokes. Particularly when the Ca compound and the Fe compound exist also in the inside of the coke, the difference in catalyst addition effect compared to conventional cokes is large. This is because in conventional cokes, catalysts which are not able to contribute to the gasification reaction are contained more in the case where catalysts exist also in the inside than in the case where catalysts exist only in a surface or the vicinity of the surface.
[0039] Next, a method for manufacturing the above-described coke will be described.
[004 0] As described above, the present inventors have found that use of appropriately blended four types of coal which differ in combination of the range of volatile matter content and the range of total dilatation allows to increase the total volume
of pores having a diameter of 1 urn to 10 urn while securing a certain degree of strength. This finding will be described.
[0041] The present inventors examined process of generation of pores in various coal, and organized examination results based on the volatile matter content affecting generation of pores and the total dilatation affecting strength. In this organization, as illustrated in Fig. 3, the coal is categorized into group A, group B, group C, and group D based on the ranges of the volatile matter content and the ranges of the total dilatation. Here, the total dilatation is the sum of contraction and dilatation measured by the dilatation measuring method (dilatometer method) described in JIS M8801. Further, the group A is a group to which coal (first coal) having a volatile matter content VM(%) less than 30% belongs. The group B is a group to which coal (second coal) having a volatile matter content VM(%) of 30% or more and a total dilatation TD(%) of 60% or more belongs. The group C is a group to which coal (third coal) having a volatile matter content VM(%) of 30% or more and 42% or less and a total dilatation TD{%) less than 60% belongs. The group D is a group to which coal (fourth coal) having a volatile matter content VM(%) of 42% or more and a total dilatation TD(%) less than 60% belongs. [0042] As a result of the organization described above, the following findings are obtained.
[0043] (1) The pores in a coke are formed by that the volatile matter in coal escapes during carbonization of the coal. In coal belonging to the group A having the volatile matter content VM(%) less than 30% in coal, there is a small amount of volatile matter to escape during carbonization. Thus, the pores are not easily formed, and the total volume of the pores having a diameter of 1 urn to 10 urn existing in the coke becomes small.
[0044] (2) In coal belonging to the group B, C, or D (having the volatile matter content VM(%) of 30% or more), there is a large amount of volatile matter to escape during carbonization. Thus, the pores are easily formed, and the total volume of the pores having a diameter of 1 µm to 10 µm existing in the coke becomes large.
[0045] (3) In coal belonging to the group B having the total dilatation TD(%) of 60% or more among coals belonging to the group B, C, or D, coal particles easily adhere to each other in the process of expansion after softening and melting which occur during carbonization. Accordingly, in the coal belonging to the group B, appropriate formation of pores is possible, and high strength can be obtained easily.
[0046] (4) In coal belonging to the group C having the total dilatation TD(%) less than 60% and the volatile matter content VM(%) of 42% or less among coals belonging to the group B, C, or D, there is a
relatively small amount of caking components, and the coal particles do not easily adhere to each other in the process of expansion after softening and melting. Accordingly, in coal belonging to the group C, appropriate formation of pores is possible, but strength as high as that of coal belonging to the group B cannot be obtained easily.
[0047] (5) In coal belonging to the group D having the total dilatation TD(%) less than 60% and the volatile matter content VM(%) more than 42% among coals belonging to the group B, C, or D, there is a less amount of caking components than in the coal belonging to the group C, and the content of oxygen, which decreases the caking property during softening and melting, is high. Accordingly, with the coal belonging to the group D, strength to be obtained becomes low.
[0048] In the present invention, based on these five findings, coal is categorized into the above-described four types (group A, group B, group C, and group D), and carbonization of a coal blend made by blending these types of coal as follows is performed.
The total ratio of coal belonging to the group B or the group C in the coal blend is 80 mass% or more.
The total ratio of coal belonging to the group B in the coal blend is 20 mass% or more.
The total ratio of coal belonging to the group D in the coal blend is 5 mass% or less.
The remaining portion of the coal blend is coal
belonging to the group A.
[0049] These coals can be blended in the form of powder, for example. It is preferred that the mean particle diameter of the powder be 1 mm to 2 mm, for example. Further, the minimum value and the maximum value of the particle diameter are not particularly-limited, but it is preferred that the ratio of powder having a particle diameter of 3 mm or less be about 70 mass% to about 85 mass%, for example.
[0050] By using such a coal blend, the total volume of the pores having a diameter of 1 urn to 10 urn per gram in the coke can be 25 mm3/g or more, while obtaining strength of the drum strength index DI15015 of 70 or higher. That is, high gasification property can be obtained while maintaining high strength.
[0051] When the total ratio of coal belonging to the group B or the group C in the coal blend is less than 80 mass%, the total volume of the pores having a diameter of 1 µm to 10 µm per gram is 25 mm3/g or less, and the high gasification reactivity cannot be improved. Therefore, the total ratio of coal belonging to the group B or the group C in the coal blend is set to 80 mass% or more. It should be noted that the coal blend may be constituted of coal belonging to the group B or the group C. In other words, it is possible that coal belonging to the group A and coal belonging to the group D are not contained in the coal blend.
[0052] When the ratio of coal belonging to the
group D in the coal blend is more than 5 mass%, the caking property during softening and melting is low, and it is not possible to secure strength of the drum strength index DI15015 of 70 or higher. Therefore, the ratio of coal belonging to the group D in the coal blend is set to 5 mass% or less.
[0053] When the ratio of coal belonging to the group B in the coal blend is less than 20 mass%, the total dilatation TD(%) becomes low, and high strength cannot be obtained. Therefore, the ratio of coal belonging to the group B in the coal blend is 20 mass% or more. Even when the coal blend is constituted of coals belonging to the group B or the group C, strength of the drum strength index DI15015 of 70 or higher can be secured since the ratio of coal belonging to the group B in the coal blend is 20 mass% or more.
[0054] When the ratio of coal belonging to the group B in the coal blend is 20 mass% or more, the total ratio of coals belonging to the group B or the group C may be 80 mass%, and the ratio of coal belonging to the group A may be 20 mass%, for example. With such a coal blend, high gasification reactivity can be obtained compared to conventional cokes.
[0055] Further, as described above, it is preferred that the coke contain one or two of Ca compound and Fe compound. It is preferred that the content be 0.5 mass% to 10 mass% with reference to the mass of the
coal blend (about 0.7 mass% to about 14 mass% with reference to the mass of the coke). By catalytic operation of the Ca compound and the Fe compound, the gasification reactivity improves. Further, the degree of improvement in gasification reactivity by the Ca compound and the Fe compound is large compared to conventional cokes. Such a coke can be manufactured by performing carbonization of, for example, a mixture of a coal blend obtained by blending powder of coal and powder of one or two of Ca compound and Fe compound. At this time, the total mass of the Ca compound and the Fe compound with respect to the total mass of the coal blend is set to 0.5% to 10%.
EXAMPLE
[0056] There were prepared four types of coal a,
coal b, coal c, and coal d listed in Table 1. The
coal a, the coal b, the coal c, and the coal d belong
to the group A, the group B, the group C, and the
group D, respectively.
[0057] [Table 1]
(Table Removed)
[0058] Then these four types of coal a, coal b, coal c, and coal d were blended in ratios listed in Table 2 , thereby obtaining coal blends. Here, a Ca
compound and/or an Fe compound was/were added to the coal blend in the examples No. 5, No. 6, and No. 7. In Table 2, the ratios of the Ca compound and the Fe compound (additives) are expressed by numerical values with respect to the total mass of the coal blend.
[0059] [Table 2]
(Table Removed)
[0060] Next, carbonization of the coal blends (containing additives as necessary) was performed to manufacture cokes. Thereafter, the total volume of pores having a diameter of 1 urn to 10 µm per gram, the reactivity index CRI, and the drum strength index DI15015 of each coke were measured. The total volume of pores was measured using a mercury porosimeter. In measurement of the reactivity index CRI, a sieved coke sample having a particle diameter of 19 mm ± 1 mm was charged at a weight of 200 g into a reactor, and a weight reduction ratio (percentage) after
allowing reaction for two hours at 1100°C in a CO2 atmosphere was measured. Results thereof are listed
in Table 3.
[0061] [Table 3]
(Table Removed)
[0062] As listed in Table 3, in the examples No. 1 to No. 7, the total volume of the pores having a diameter of 1 µm to 10 µm per gram was 25 mm3/g or more, the reactivity index CRI was 50 or more, and the drum strength index DI15015 was 70 or more. That is, high gasification reactivity was obtained while maintaining strength.
[0063] Further, the examples No. 5 to No. 7 are ones obtained by adding the powder of Ca compound and/or Fe compound to the example No. 2. Thus, gasification reactivity higher than that of the example No. 2 was obtained in the examples No. 5 to No. 7 .
[0064] On the other hand, in the comparative example No. 8, since the total ratio of the coal b belonging to the group B and the coal c belonging to the group C was less than 80 mass%, the total volume of the pores having a diameter of 1 µm to 10 µm per
gram was less than 25 mm3/g. Accordingly, the reactivity index CRI was less than 50.
[0065] Further, in the comparative example 9, since the ratio of the coal b was less than 20 mass%, the drum strength index DI15015 was less than 70.
[0066] Moreover, in the comparative example 10, since the ratio of the coal d belonging to the group D contained in the coal blend was more than 5 mass%, the drum strength index DI150i5 was less than 70.
[0067] It should be noted that Patent Document 7 describes a method for manufacturing cokes from mixtures of five types of coal (coal B, coal C, coal D, coal E, and coal F), two types of inert matters (inert matter A and inert matter B), and a caking additive as "example 1". When these items are categorized into the above-described groups A to D, results are as listed in Table 4 . Incidentally, Patent Document 7 does not describe the total dilatation, and thus the total dilatation TD is estimated from the publicly known correlation between the maximum fluidity and the total dilatation using the maximum fluidity (MF) described in Patent Document 7. Further, since there are described two "coal C" in the table in paragraph 0024, the lower "coal C" is assumed as "coal D".
[0068] [Table 4]
(Table Removed)
[0069] As shown in Table 4 , in the coal blend of the "example 1" in Patent Document 7 , the ratio of coal belonging to the group A is 60 mass% in total, the ratio of coal belonging to the group B is 10 mass%, the ratio of coal belonging to the group C is 25 mass% in total, and the ratio of coal belonging to the group D is 0 mass%. Further, the caking additive not belonging to any of the group A to group D is also included. That is, in the coal blend of the "example 1" in Patent Document 7, similarly to the aforementioned comparative example No. 8, the total ratio of the coal belonging to the group B and the group C is less than 80 mass%. Furthermore, similarly to the comparative example No. 9, the ratio of the coal belonging to the group B is less than 20 mass%. Accordingly, the strength thereof becomes insufficient.
[0070] Note that the conditions of these experimental examples are examples employed for recognizing the applicability and effect of the present invention, and the present invention is not
limited thereto. The present invention may employ various conditions without departing from the spirit of the invention, as long as the object of the present invention is achieved.
INDUSTRIAL APPLICABILITY
[0071] The present invention may be used in, for example, coke manufacturing industry and steel industry.

CLAIMS
1. A method for manufacturing a coke,
comprising:
obtaining a coal blend by blending at least two of
first coal having a volatile matter content less than 30%,
second coal having a volatile matter content of 30% or more and a total dilatation of 60% or more,
third coal having a volatile matter content of 30% or more and 42% or less and a total dilatation less than 60%, and
fourth coal having a volatile matter content more than 42% and a total dilatation less than 60%; and
performing carbonization of the coal blend, wherein in the obtaining the coal blend,
the total ratio of the second coal and the third coal in the coal blend is 80 mass% or more,
the ratio of the second coal in the coal blend is 20 mass% or more,
the ratio of the fourth coal in the coal blend is 5 mass% or less, and
the remaining portion of the coal blend is the first coal.
2. The method for manufacturing a coke according
to claim 1, further compris ing, before the performing
the carbonization, adding to the coal blend one or
two of calcium compound and iron compound in the ratio of 0.5 mass% or more with respect to the coal blend.
3. The method for manufacturing a coke according to claim 1, wherein coal in powder form having a mean particle diameter of 1 mm or more and 2 mm or less is used as the first, the second, the third, and the fourth coal.
4. The method for manufacturing a coke according to claim 2, wherein coal in powder form having a mean particle diameter of 1 mm or more and 2 mm or less is used as the first, the second, the third, and the fourth coal.
5. A coke, comprising:
pores having a diameter of 1 µm or more and 10 urn or less in a total volume per gram of 25 mm3/g or more, and
a drum strength index DI15015 of the coke is 70 or higher.
6. The coke according to claim 5, wherein the
total volume per gram is 30 mm3/g or more.
7 . The coke according to claim 5, containing one or two of calcium compound and iron compound in a ratio of 0.7 mass% or more.
8. The coke according to claim 6, containing one or two of calcium compound and iron compound in a ratio of 0.7 mass% or more.
9. The coke according to claim 5, wherein a mean particle diameter of the coke is 38 mm or less.
10. The coke according to claim 6, wherein a mean particle diameter of the coke is 38 mm or less.
11. The coke according to claim 7 , wherein a mean particle diameter of the coke is 38 mm or less.
12. The coke according to claim 8, wherein a mean particle diameter of the coke is 38 mm or less.