COAL BLEND

A coal-blended material is obtained by mixing an ashless coal that is a solvent extract of a coal, and a steam coal, in a weight ratio of from 1:1 to 1:5 without heating. The mixed coal after the mixing has a Gieseler fluidity of 1.0 (Log ddpm) or more and an average maximum reflectance of 0.75 (%) or higher.

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Description
TECHNICAL FIELD

The present invention relates to a coal-blended material obtained by mixing ashless coal that is a solvent extract of coal, and steam coal.

BACKGROUND ART

In the production of steel using a blast furnace, coke obtained by carbonizing raw material coal under heating is used as a reducing agent. To produce coke having high quality, blended coal for coke containing heavy caking coal having high caking property as a main raw material is necessary. However, there is a concern that the heavy caking coal will be difficult to be available in future and the price thereof will rise quickly.

In view of the above, it is required to suppress the amount of heavy caking coal used and reduce the cost of a coke raw material by using low rank raw materials (non-caking coal, weak caking coal and steam coal) as a coke raw material.

Patent Document 1 discloses a method for producing raw material coal for producing coke, by heating a mixed coal containing low rank coal and ashless coal that does not substantially contain ash components (hyper-coal) at a softening temperature of the ashless coal or higher. Where the raw material coal for producing coke is used as a coke raw material, the amount of heavy caking coal used in the production of coke can be suppressed.

Prior Art Document Patent Document

Patent Document 1: JP-A-2009-215454

SUMMARY OF THE INVENTION Problem that the Invention is to Solve

When low rank raw material having low caking property is simply blended with blended coal for coke, the caking property of the blended coal for coke is deteriorated, and coke strength is also deteriorated. Therefore, it is controlled in a usual operation such that negative influence by the blend of low rank raw material is controlled by increasing high rank raw material coal blended so that the representative properties (volatile content, average maximum reflectance and Gieseler fluidity) required in the blended coke for coke fall within proper ranges. However, in this method, it is necessary to increase the amount of expensive heavy caking coal used with increasing the amount of low rank raw material used, and the cost of coke raw material cannot be reduced.

Petroleum type caking material practically used has high compensation effect of caking property, but has a restriction in the amount of production. Furthermore, it has high sulfur content and remains in coke. Where sulfur content in iron ore and coke is increased, there is a problem that the residual sulfur content in molten iron is also increased, and as a result, the load to a desulfurization treatment process is increased. To avoid this problem, the upper limit is set to the sulfur content input in a blast furnace. Furthermore, it is known that sulfur deteriorates properties of iron. In view of those facts, it is considered that the limit of the amount of the petroleum type caking material blended with the blended coal for coke is several %. Thus, the compensation of caking property has the limit, and it is not easy to increase the amount of low rank raw material blended with the blended coal for coke.

An object of the present invention is to provide a coal-blended material that can reduce the cost of coke raw material.

Means for Solving the Problems

A coal-blended material in the present invention is obtained by mixing an ashless coal that is a solvent extract of a coal, and a steam coal, in a weight ratio of from 1:1 to 1:5 without heating, in which a mixed coal after the mixing has a Gieseler fluidity of 1.0 (Log ddpm) or more and an average maximum reflectance of 0.75 (%) or higher.

Advantageous Effects of the Invention

According to the coal-blended material of the present invention, the cost of coke raw material can be reduced.

BRIEF DESCRIPTION OF THE DRAWING

[FIG. 1] This is a schematic view of an ashless coal production equipment.

 MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention is described below by reference to the drawing.

(Constitution of Coal-Blended Material)

The coal-blended material according to the embodiment of the present invention is obtained by mixing ashless coal in which coal is used as a raw material, and steam coal, in a weight ratio of from 1:1 to 1:5 without heating. The ashless coal is a solvent extract of coal and is one obtained by extracting a coal component that is soluble in a solvent from a slurry obtained by mixing and heating coal and a solvent.

(Steam Coal)

Steam coal used in the coal-blended material of the present embodiment is bituminous coal, subbituminous coal and brown coal, classified into coal rank of C to F2 in Table 1. That is, the steam coal of the present embodiment is coal having a calorific value (dry ash free base) (kcal/kg) of 5800 or more and less than 8400.

TABLE 1 Classification Calorific value Classification by (Dry ash-free Fuel by caking Classification Classification coal rank Rank base) kcal/kg ratio property by cokability by use Anthracite A1 — 4.0 or Non-caking — For general and blast A2 more coal furnace sintering Bituminous B1 8,400 or more 1.5 or Caking coal Heavy caking Raw material coal more coal coal for coke B2 1.5 or Medium caking more coal C 8,100 or more and — Weak caking Raw material coal less than 8,400 coal for cokeand PCI Subbituminous D 7,800 or more and — For boiler and coal less than 8,100 electric power E 7,300 or more and — Non-caking Non-caking less than 7,800 coal coal Brown coal F1 6,800 or more and — For electric power less than 7,300 F2 5,800 or more and — less than 6,800

The calorific value (dry ash free base) (kcal/kg) defined in Japanese Industrial Standards (JIS M 1002:1978) is calculated by the following formula.


Calorific value (corrected dry ash free base)=Calorific value/(100−1.08×ash content−water content)×100

The fuel ratio is a value obtained by dividing fixed carbon by a volatile content. When steam coal is heated to high temperature in an inert gas such as nitrogen, a side chain part and/or bridge part of a polymer matrix constituting the steam coal are cut by thermal decomposition, and low boiling components such as low molecular weight hydrocarbon, CO, H2, and the like are generated and are discharged to the outside of steam coal particles in the form of a gas. Those low boiling components such as low molecular weight hydrocarbon, CO, H2, and the like, which are discharged to the outside of steam coal particles in the form of a gas, are called a volatile content (VM) of steam coal, and the volatile content is represented by dry-base. The fixed carbon means a non-volatile component of carbons contained in steam coal.

Steam coal that is bituminous coal, subbituminous coal or brown coal and has a calorific value (dry ash free base) (kcal/kg) of 5800 or more and less than 8400, is raw material coal for coke and PCI (pulverized coal injection to a blast furnace), and is coal for boiler and electric power. Caking property thereof is inferior to that of bituminous coal belonging to coal rank of B1 and B2 in Table 1, that is, heavy caking coal and medium caking coal that are raw materials for coke.

(Ashless Coal)

The ashless coal used in the coal-blended material of the present embodiment is one obtained by extracting a coal component that is soluble in a solvent from a slurry obtained by mixing and heating coal and a solvent, and has an ash content of 5 wt % or less and preferably 3 wt % or less. The “ash content” used herein means a residual inorganic material when coal has been heated at 815° C. and ashed, and the inorganic material includes silicic acid, alumina, iron oxide, lime, magnesia, an alkali metal, and the like. The ashless coal is completely free from water content.

The ashless coal is excellent in fluidity and expansibility and shows high effect as a caking material. Preferred ashless coal is one having maximum fluidity (log MF) confirmed by a Gieseler fluidity test by Gieseler plastometer method defined in JIS M8801 of 4.78 (Log ddpm) or more. Furthermore, one having a solidification temperature exceeding 450° C. is also preferred as the ashless coal.

Coal as a raw material of the ashless coal is not particularly limited. Bituminous coal having high extraction rate may be used and a lower rank coal (subbituminous coal or brown coal) that is less expensive may be used. Therefore, in the present embodiment, steam coal is used as a raw material of ashless coal. By producing ashless coal with steam coal as a raw material, utilization of steam coal in the production of a coal-blended material is expanded. Furthermore, by using steam coal as a raw material of ashless coal, a process of from the production of ashless coal to the production of a coal-blended material can be integratedly performed such that ashless coal is produced in a production area of steam coal and a coal-blended material is produced with the ashless coal and the steam coal.

(Production Method of Ashless Coal)

A production method of ashless coal is described here. An ashless coal production equipment 100 used in the production method of ashless coal includes a coal hopper 1, a solvent tank 2, a slurry preparation tank 3, a transport pump 4, a preheater 5, an extraction tank 6, a gravitational settling tank 7, and solvent separators 8 and 9, from the upstream side of a production process, in this order, as illustrated in FIG. 1.

The production method of ashless coal includes an extraction step, a separation step and an ashless coal acquirement step. Each step is described below. In the present embodiment, steam coal is used as a raw material of ashless coal.

(Extraction Step)

The extraction step is a step of heating a slurry obtained by mixing coal and a solvent and extracting a coal component that is soluble in a solvent (dissolving in a solvent). This extraction step is performed in the slurry preparation tank 3, the preheater 5 and the extraction tank 6 in FIG. 1.

Coal as a raw material is introduced into the slurry preparation tank 3 from the coal hopper 1, and a solvent is introduced into the slurry preparation tank 3 from the solvent tank 2. The coal and solvent introduced into the slurry preparation tank 3 are mixed by a stirrer 3a, thereby preparing a slurry containing the coal and the solvent. The slurry prepared in the slurry preparation tank 3 is fed to the preheater 5 by means of the transport pump 4, and heated to a predetermined temperature. Thereafter, the slurry is fed to the extraction tank 6 and maintained at a predetermined temperature while stirring with a stirrer 6a, thereby performing extraction. An aromatic solvent (hydrogen donating or non-hydrogen donating solvent) can be preferably used as the solvent for extracting a coal component that is soluble in a solvent.

(Separation Step)

The separation step is a step of separating the slurry obtained in the extraction step into a solution in which a coal component that is soluble in a solvent has been dissolved and a solid content-concentrated liquid (solvent-insoluble component-concentrated liquid) in which a coal component that is insoluble in a solvent (solvent-insoluble component such as ash component) has been concentrated, by, for example, a gravitational settling method. This separation step is performed in the gravitational settling tank 7 in FIG. 1. The slurry obtained in the extraction step is separated into a supernatant liquid as a solution and a solid content-concentrated liquid by gravity in the gravitational settling tank 7. The supernatant liquid in the upper part of the gravitational settling tank 7 is transferred to a solvent separator 8, and the solid content-concentrated liquid settled in the lower part of the gravitational settling tank 7 is transferred to a solvent separator 9.

(Ashless Coal Acquirement Step)

The ashless coal acquirement step is a step of obtaining ashless coal (HPC) by evaporation-separating the solvent from the solution (supernatant liquid) separated in the separation step. This ashless coal acquirement step is performed in the solvent separator 8 in FIG. 1. The solution separated in the gravitational settling tank 7 is fed to the solvent separator 8, and the solvent is evaporation-separated from the supernatant liquid in the solvent separator 8.

A method for separating the solvent from the solution (supernatant liquid) can use a common method such as a distillation method or an evaporation method. Ashless coal (HPC) that does not substantially contain an ash component can be obtained by separating the solvent from the supernatant liquid.

The ashless coal does not almost contain an ash component, is completely free from water content, and shows calorific value higher than that of raw material coal.

Furthermore, softening and melting properties (fluidity) that are particularly important quality as a raw material of coke for making iron are greatly improved, and even though raw material coal does not have softening and melting properties, the ashless coal (HPC) obtained have good softening and melting properties.

The solvent is separated from the solid content-concentrated liquid separated in the gravitational settling tank 7, in the solvent separator 9, thereby by-product coal in which solvent-insoluble components containing ash components and the like have been concentrated (also called RC, residual coal) can be obtained.

(Coal-Blended Material)

The coal-blended material of the present embodiment is described below. The low rank raw materials (non-caking coal, weak caking coal and steam coal) including the above -described steam coal have caking property inferior to that of heavy caking coal and medium caking coal that are raw material coals for coke. Therefore, in the case where low rank raw material is used as a coke raw material, the representative properties (volatile content, average maximum reflectance and Gieseler fluidity) required in a blended coal for coke are required to be within proper ranges by increasing blending proportion of heavy caking coal in the blended coal for coke. In other words, the amount of expensive heavy caking coal used must be increased with increasing the amount of low rank raw materials used in the blended coal for coke. Therefore, the cost for a coke raw material cannot be reduced.

It is conducted in the coke production to compensate caking property by using a petroleum type caking material practically used. However, the petroleum type caking material has high sulfur content, remains in coke, and increases sulfur content contained in coke. On the other hand, the sulfur content input in a blast furnace is limited. Therefore, it is considered that the limit of the amount of the petroleum type caking material blended with the blended coal for coke is several %. For this reason, it is not easy to increase the amount of low rank raw materials blended with the blended coal for coke.

In view of the above, the coal-blended material of the present embodiment is obtained by mixing ashless coal and steam coal in a weight ratio of from 1:1 to 1:5 and more preferably in a weight ratio of from 1:3 to 1:5, without heating. By mixing the ashless coal and steam coal in such a weight ratio without heating, Gieseler fluidity of a mixed coal after mixing is 1.0 (Log ddpm) or more and more preferably 1.5 (Log ddpm) or more. Furthermore, the average maximum reflectance of the mixed coal is 0.75 (%) or more. Each of the Gieseler fluidity and average maximum reflectance of the mixed coal means a value obtained by weight-averaging numerical values of ashless coal and steam coal contained in the mixed coal. The Gieseler fluidity of the mixed coal is preferably less than 4.0 (Log ddpm) and more preferably less than 3.8 (Log ddpm). The average maximum reflectance of the mixed coal is preferably less than 1.2 (%) and more preferably less than 1.0 (%). By this, the properties of the coal-blended material obtained are equivalent to the properties of general heavy caking coal (general heavy caking) or medium caking coal belonging to ranks B to D in Table 2.

TABLE 2 Average Volatile maximum Gieseler content reflectance fluidity VM Ro log MF Classification Rank Type % % Log ddpm Heavy caking A LV 17-20 1.3-1.6 0.8-2.5 coal B General 20-27 1.0-1.3 1.5-4.0 heavy caking Medium caking C High fluidity 26-33 0.8-1.0 3.0-4.0 coal D General 20-27 0.9-1.3 1.5-3.0 medium caking Slightly weak E Medium VM About 25 About 1.0 1.0-1.5 caking coal F High VM 33-38 About 0.7 1.5-2.5 G Low VM 15-20 1.2-1.7 2.0 or less

Properties of general heavy caking coal (general heavy caking) or medium caking coal are that a volatile content is from 20 to 33 (mass %), an average maximum reflectance is from 0.8 to 1.3 (%) and Gieseler fluidity is from 1.5 to 4.0 (Log ddpm). The average maximum reflectance (%) is calculated based on the formula defined in Japanese Industrial Standards (JIS M 8816:1992).

As described above, the ashless coal is excellent in fluidity and expansibility, and shows high effect as a caking material. For this reason, mixed coal having caking properties comparable to those of heavy caking coal having good quality can be obtained by mixing the ashless coal and steam coal without heating. When the ashless coal and steam coal are mixed in a weight ratio of from 1:1 to 1:5 without heating, Gieseler fluidity of the mixed coal after the mixing is 1.0 (Log ddpm) or more and the average maximum reflectance is 0.75 (%) or more. By this, a coal-blended material having properties equivalent to those of general heavy caking coal (general heavy caking) or medium caking coal can be obtained. By using the coal-blended material as a coke raw material in place of heavy caking coal, the amount of heavy caking coal used in the coke production can be reduced, and the amount of steam coal contained in a blended coal for coke can be increased. Furthermore, the ashless coal has a sulfur content comparable to that of steam coal. Therefore, there is no limitation by sulfur content in the amount of the ashless coal blended with the blended coal for coke. As a result, by using the coal-blended material obtained by mixing ashless coal and steam coal without heating, as a coke raw material, the amount of low rank raw material that can be blended with the blended coal for coke can be increased. By this, the cost of a coke raw material can be reduced. Mixing of ashless coal and steam coal is performed without applying heat from the outside by heating means. There may be the case that coal itself to be blended has heat, and in such a case, the temperature during mixing can be about lower than 100° C., lower than 60° C. or the like.

The ashless coal and steam coal have been coarsely ground during mixing or before mixing. The coarse grinding used herein means grinding to obtain a particle diameter of 20 mm or less. The ashless coal and steam coal may be simultaneously introduced into a grinder and mixed without heating while coarsely grinding, and may be separately introduced into grinders, coarsely ground, and then introduced into a coal mixer so as to have an appropriate mixing ratio, followed by mixing without heating. In the case where the ashless coal and steam coal are simultaneously introduced into a grinder and are mixed while coarsely grinding, both are further uniformly mixed, and as a result, the ashless coal is easy to adhere to the circumference of particles of the steam coal. In the case of verifying a particle diameter of coal as to, for example, whether or not the particle diameter of coal is 20 mm or less, a screening test defined in, for example, JIS A 1102 is used.

The ashless coal tends to be easily ground as compared with steam coal. Finely ground coal generally tends to cause dust generation. Furthermore, in finely ground coal, low temperature oxidation is generally easy to proceed. Therefore, there is a concern of spontaneous combustion by generation of heat by oxidation. Therefore, by coarsely grinding the ashless coal and steam coal, those are uniformly mixed during mixing, and the ashless coal adheres to the circumference of particles of the steam coal. By this, dust generation and low temperature oxidation are suppressed, and as a result, a coal-blended material can be stored and transported in a stable manner. Furthermore, by that the ashless coal having high caking property adheres to the circumference of particles of the steam coal having low caking property, the caking effect by the ashless coal is enhanced, and as a result, the caking property of the coal-blended material can be increased.

When used as a raw material coal for coke, the coal-blended material is ground into a particle size of general blended coal for coke (the proportion of particles having a particle size of 3 mm or less is about 80 wt % of the whole) by a grinder accompanying with a coke furnace.

As described above, coal as a raw material of ashless coal is steam coal. By using a coal-blended material obtained by mixing ashless coal in which steam coal is a raw material and steam coal without heating, as a coke raw material, the amount of the steam coal contained in the blended coal for coke is further increased. Therefore, the cost of a coke raw material can be further reduced. Furthermore, a process of from the production of ashless coal to the production of a coal-blended material is integratedly performed such that ashless coal is produced in a production area of steam coal and a coal-blended material is produced with the ashless coal and the steam coal, thereby transport cost and the like can be suppressed. As a result, the production cost can be reduced.

In the case of integratedly performing a process of from the production of ashless coal to the production of a coal-blended material in the production area of steam coal, it is preferred that by-product coal obtained as a by-product in the production of ashless coal is used as a fuel of a local electric power plant or a fuel in an ashless coal production process. By effectively utilizing the by-product coal that is a by-product as a fuel, the production cost of ashless coal or even the production cost of a coal-blended material can be decreased.

(Evaluation of Mixing Ratio)

Mixing ratio (weight ratio) between ashless coal and steam coal was evaluated from properties of a coal-blended material expected in the case of mixing at least one kind of representative four kinds of steam coals A, B, C, and D and ashless coal without heating. The properties of the coal-blended material aim at the properties of heavy caking coal (general heavy caking) or medium caking coal (properties of ranks B to D) in Table 2, and were set such that Gieseler fluidity is 1.0 (Log ddpm) or more and an average maximum reflectance is 0.75 (%) or more.

The ashless coal produced and steam coal were transported from a coal yard or a silo, simultaneously introduced into a grinder, and mixed in a state of an ordinary temperature (about 25° C.) without heating while coarsely grinding such that a particle size is 20 mm or less. Alternatively, the ashless coal and steam coal were separately introduced into the respective grinders, and ground such that a particle size is 20 mm or less, and they were then introduced into a coal mixer in a proper mixing ratio, followed by mixing without heating. Representative analytical values (volatile content, average maximum reflectance and Gieseler fluidity) as raw material coal for coke, expected in the case of mixing at least one kind of the representative four kinds of steam coals A, B, C, and D and ashless coal without heating were calculated, and the mixing ratio satisfying the aimed properties was evaluated. Properties of the ashless coal and four kinds of steam coals A, B, C, and D are shown in Table 3.

TABLE 3 Volatile Average maximum Gieseler content reflectance fluidity VM Ro log MF Brand % % Log ddpm Caking Ashless 43.2 0.9 6.0 material coal Steam coal A 32.0 0.7 0.6 B 28.5 0.9 0.3 C 34.1 0.7 1.3 D 25.3 0.9 0.6

The ashless coal and steam coal A were mixed without heating while changing the mixing ratio (weight ratio) by 6 stages between 1:1 and 1:20, and properties were evaluated. The results are shown in Table 4.

TABLE 4 Average Gieseler Volatile maximum fluidity Mixing ratio content reflectance log MF Ashless Steam VM Ro Log Eval- No. coal coal A % % ddpm uation Invention 1 1 37.6 0.8 3.3 Good Example Comparative 1 3 34.8 0.7 2.0 Poor Example 1 5 33.9 0.7 1.5 Poor 1 8 33.2 0.7 1.2 Poor 1 10 33.0 0.7 1.1 Poor 1 20 32.5 0.7 0.9 Poor

When the mixing ratio (weight ratio) is 1:1, the average maximum reflectance and Gieseler fluidity were within the target ranges, but the volatile content was higher than 33% that is the upper limit of the target range. When the mixing ratio (weight ratio) is from 1:3 to 1:5, the Gieseler fluidity was within the target range, but the volatile content was higher than 33% that is the upper limit of the target range, and the average maximum reflectance was lower than 0.8% that is the lower limit of the target range. When the mixing ratio (weight ratio) is 1:8, the volatile content was higher than 33% that is the upper limit of the target range, and the average maximum reflectance and Gieseler fluidity were lower than the lower limits of the target ranges. When the mixing ratio (weight ratio) is from 1:10 to 1:20, the volatile content was within the target range, but the average maximum reflectance and Gieseler fluidity were lower than the lower limits of the target ranges. From the above, it was judged that the mixing ratio (weight ratio) of 1:1 is good.

Next, the ashless coal and steam coal B were mixed without heating while changing the mixing ratio (weight ratio) by 6 stages between 1:1 and 1:20, and properties were evaluated. The results are shown in Table 5.

TABLE 5 Average Gieseler Volatile maximum fluidity Mixing ratio content reflectance log MF Ashless Steam VM Ro Log Eval- No. coal coal B % % ddpm uation Invention 1 1 35.9 0.9 3.2 Good Example 1 3 32.2 0.9 1.7 Optimum 1 5 31.0 0.9 1.3 Good Compar- 1 8 30.1 0.9 0.9 Poor ative 1 10 29.8 0.9 0.8 Poor Example 1 20 29.2 0.9 0.6 Poor

When the mixing ratio (weight ratio) is 1:1, the average maximum reflectance and Gieseler fluidity were within the target ranges, but the volatile content was higher than 33% that is the upper limit of the target range. When the mixing ratio (weight ratio) is 1:3, the volatile content, average maximum reflectance and Gieseler fluidity were all within the target ranges. When the mixing ratio (weight ratio) is from 1:5 to 1:20, the volatile content and average maximum reflectance were within the target ranges, but the Gieseler fluidity were lower than 1.5 (Log ddpm) that is the lower limit of the target range. However, when the mixing ratio (weight ratio) is 1:5, the Gieseler fluidity was 1.0 (Log ddpm) or more. From the above, it was judged that the mixing ratio (weight ratio) of 1:3 is optimum and the mixing ratios (weight ratios) of 1:1 and 1:5 are good.

Next, the ashless coal and steam coal C were mixed without heating while changing the mixing ratio (weight ratio) by 6 stages between 1:1 and 1:20, and properties were evaluated. The results are shown in Table 6.

TABLE 6 Average Gieseler Volatile maximum fluidity Mixing ratio content reflectance log MF Ashless Steam VM Ro Log Eval- No. coal coal C % % ddpm uation Invention 1 1 38.7 0.82 3.6 Good Example 1 3 36.4 0.77 2.4 Good 1 5 35.6 0.75 2.1 Good Comparative 1 8 35.1 0.74 1.8 Poor Example 1 10 34.9 0.74 1.7 Poor 1 20 34.5 0.73 1.5 Poor

When the mixing ratio (weight ratio) is 1:1, the average maximum reflectance and Gieseler fluidity were within the target ranges, but the volatile content was higher than 33% that is the upper limit of the target range. When the mixing ratio (weight ratio) is from 1:3 to 1:20, the Gieseler fluidity was within the target range, but the volatile content was higher than 33% that is the upper limit of the target range, and the average maximum reflectance was lower than 0.8% that is the lower limit of the target range. However, when the mixing ratio (weight ratio) is 1:3 or 1:5, the average maximum reflectance was 0.75 (%) or higher. From the above, it was judged that the mixing ratios (weight ratios) of from 1:1 to 1:5 are good.

Next, the ashless coal and steam coal D were mixed without heating while changing the mixing ratio (weight ratio) by 6 stages between 1:1 and 1:20, and properties were evaluated. The results are shown in Table 7.

TABLE 7 Average Gieseler Volatile maximum fluidity Mixing ratio content reflectance log MF Ashless Steam VM Ro Log Eval- No. coal coal D % % ddpm uation Invention 1 1 34.3 0.9 3.3 Optimum Example 1 3 29.8 0.9 2.0 Optimum 1 5 28.3 0.9 1.5 Optimum 1 8 27.3 0.9 1.2 Good 1 10 26.9 0.9 1.1 Good Compar- 1 20 26.2 0.9 0.9 Poor ative Example

When the mixing ratio (weight ratio) is 1:1, the average maximum reflectance and Gieseler fluidity were within the target ranges, but the volatile content was higher than 33% that is the upper limit of the target range. When the mixing ratio (weight ratio) is from 1:3 to 1:5, the volatile content, average maximum reflectance and Gieseler fluidity were all within the target ranges. When the mixing ratio (weight ratio) is from 1:8 to 1:20, the volatile content and average maximum reflectance were within the target ranges, but the Gieseler fluidity was lower than 1.5 (Log ddpm) that is the lower limit of the target range. However, when the mixing ratio (weight ratio) is 1:8 or 1:10, the Gieseler fluidity was 1.0 (Log ddpm) or more. From the above, it was judged that the mixing ratios (weight ratios) of from 1:1 to 1:5 are optimum and the mixing ratios weight ratios) of 1:8 and 1:10 are good.

From the above, it was judged that the mixing ratio between ashless coal and steam coal in which properties are equivalent to those of general heavy caking coal (general heavy caking) or medium caking coal is a weight ratio of from 1:1 to 1:5, and more preferably a weight ratio of from 1:3 to 1:5.

The above evaluation is conducted so that the weight of steam coal is larger than that of ashless coal. In the case where the weight of ashless coal is larger than that of steam coal, the Gieseler fluidity and volatile content are increased and are excessive, and the properties greatly deviate from the target properties. Therefore, the effect as a coal-blended material cannot be expected.

(Effect)

As described above, in the present embodiment, a coal-blended material is obtained by mixing ashless coal and steam coal in a weight ratio of from 1:1 to 1:5 without heating. The ashless coal is excellent in fluidity and expansibility, and shows high effect as a caking material. For this reason, mixed coal having caking properties comparable to those of heavy caking coal having good quality can be obtained by mixing the ashless coal and steam coal without heating. When the ashless coal and steam coal are mixed in a weight ratio of from 1:1 to 1:5 without heating, Gieseler fluidity of the mixed coal after the mixing is 1.0 (Log ddpm) or more and the average maximum reflectance is 0.75 (%) or more. By this, a coal-blended material having properties equivalent to those of general heavy caking coal or medium caking coal can be obtained. By using the coal-blended material as a coke raw material in place of heavy caking coal, the amount of heavy caking coal used in the coke production can be reduced, and the amount of steam coal contained in a blended coal for coke can be increased. Specifically, the amount of the coal-blended material blended with a blended coal for coke is suitably from 10 mass % to 50 mass %, and preferably suitably from 20 mass % to 30 mass %, based on the whole blended coal for coke. In the case where ashless coal is used alone as an additive, it was necessary to adjust the proper amount thereof depending on properties of the blended coal. However, the coal-blended material of the present invention is one where proper amounts of ashless coal and steam coal are previously blended, and therefore, it can be easily added to and blended with the blended coal for coke in a proper amount. Furthermore, the ashless coal has a sulfur content comparable to that of steam coal. Therefore, there is no limitation by sulfur content in the amount of the ashless coal blended with the blended coal for coke. As a result, by using the coal-blended material obtained by mixing ashless coal and steam coal without heating, as a coke raw material, the amount of low rank raw material that can be blended with the blended coal for coke can be increased. By this, the cost of a coke raw material can be reduced.

Ashless coal and steam coal have been coarsely ground. The ashless coal tends to be easily ground as compared with steam coal. Finely ground coal generally tends to cause dust generation. Furthermore, in finely ground coal, low temperature oxidation is generally easy to proceed. Therefore, there is a concern of spontaneous combustion by generation of heat by oxidation. Therefore, by coarsely grinding ashless coal and steam coal, those are uniformly mixed during mixing, and the ashless coal adheres to the circumference of particles of steam coal. By this, dust generation and low temperature oxidation are suppressed, and as a result, a coal-blended material can be stored and transported in a stable manner. Furthermore, by that the ashless coal having high caking property adheres to the circumference of particles of steam coal having low caking property, the caking effect by the ashless coal is enhanced, and as a result, the caking property of the coal-blended material can be increased.

Furthermore, coal as a raw material of ashless coal is steam coal. By using a coal-blended material obtained by mixing ashless coal in which steam coal is a raw material and steam coal without heating, as a coke raw material, the amount of the steam coal contained in the blended coal for coke is further increased. Therefore, the cost of a coke raw material can be further reduced. Furthermore, a process of from the production of ashless coal to the production of coal-blended material is integratedly performed such that ashless coal is produced in a production area of steam coal and a coal-blended material is produced with the ashless coal and the steam coal, thereby transport cost and the like can be suppressed. As a result, the production cost can be reduced.

Modification Example of Present Embodiment

The embodiment of the present invention is described above. However, it merely exemplifies a specific example and does not particularly limit the present invention, and the design of specific constitution and the like can be appropriately changed. Furthermore, the action and effect described in the embodiment of the present invention merely enumerate the most preferred action and effect resulting from the present invention, and the action and effect by the present invention are not limited to those described in the embodiment of the present invention.

The present application is based on a Japanese patent application filed on Mar. 31, 2014 (Application No. 2014-072439), the contents thereof being incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The coal-blended material of the present invention is useful as raw material coal for coke production, and can be produced inexpensively.

DESCRIPTION OF REFERENCE NUMERALS

  • 1 Coal hopper
  • 2 Solvent tank
  • 3 Slurry preparation tank
  • 3a Stirrer
  • 4 Transport pump
  • 5 Preheater
  • 6 Extraction tank
  • 6a Stirrer
  • 7 Gravitational settling tank
  • 8, 9 Solvent separator
  • 100 Ashless coal production equipment

Claims

1. A coal-blended material, obtained by a process comprising mixing an ashless coal that is a solvent extract of a coal, and a steam coal, in a weight ratio of from 1:1 to 1:5 without heating, thereby obtaining a mixed coal,

wherein the mixed coal has a Gieseler fluidity of 1.0 (Log ddpm) or more and an average maximum reflectance of 0.75 (%) or higher.

2. The coal-blended material according to claim 1, wherein the ashless coal and the steam coal are coarsely ground.

3. The coal-blended material according to claim 1, wherein the coal that is a raw material of the ashless coal is a steam coal.

4. The coal-blended material according to claim 2, wherein the coal that is a raw material of the ashless coal is a steam coal.

Patent History
Publication number: 20170096603
Type: Application
Filed: Mar 19, 2015
Publication Date: Apr 6, 2017
Applicant: KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.) (Kobe-shi)
Inventors: Takahiro SHISHIDO (Hyogo), Maki HAMAGUCHI (Hyogo), Naoki KIKUCHI (Hyogo)
Application Number: 15/127,900
Classifications
International Classification: C10B 57/04 (20060101); C10L 9/02 (20060101); C10L 5/04 (20060101);