KR20150021543A - Coke and method for producing same - Google Patents

Abstract

The coke according to the present invention is characterized in that 2 to 8% of the unburned coal is mixed with coal to carry out the distillation, and the maximum flow MF value (log (ddpm)) of the mixture of coal and unburned coal is 1.8 to 3.0 . The addition ratio is suppressed to 8% or less while replenishing the cohesion by the ash tundish, and the degree of fluidity is secured by the coal as a whole to prevent the volume destruction by the ash tundish and the development inhibition of the crystal, Respectively.

Description

TECHNICAL FIELD [0001] The present invention relates to a coke-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coke used in blast furnace steel making and a method for producing the coke, and more particularly to a coke blended with an ashless coal obtained by extracting coal with a solvent.

Coke used in the blast furnace steel requires various properties such as the size and distribution of the lumps necessary for ensuring a certain mechanical strength, reactivity, apparent density, and further air permeability, which are not easily collapsed in the blast furnace. The raw materials of coke suitable for these properties are generally called "coking coal" and tough coal, which is coal having a high quality in a certain range of the degree of cohesion, fluidity or coalification, and which is expensive compared to general fuel coal for boilers, is used. Such tough coal is melted and softened at around 400 캜 to form a viscous liquid to be fused and expanded by containing gas so that gaps between coal particles are effectively filled and adhesion between particles is further promoted to produce strong coke . In recent years, however, attempts have been made to use less expensive and lower quality coal as a raw material for coke in the background of persecution of resources and price hike. For example, technology for developing more low- .

Low-grade coals such as non-coking coals have lower fluidity and lower cohesiveness than coarse coal, thereby inhibiting adhesion between coal particles and increasing the defect density, thereby lowering the strength of the coke. Therefore, in order to compensate for the degree of cohesion, there is disclosed a technique of coke added with asphalt pitch (ASP) which is a petroleum-derived point filling material and asphalt (hypercall, HPC) composed of a soluble component obtained by extracting coal with an organic solvent. In particular, various techniques have been developed for effective use of low-grade carbon. For example, Patent Document 1 discloses a technique of adding coke to a coal containing low-grade carbon added with an unburned coal, and when coke is added in an amount of 5 to 10%, particularly high-strength coke is obtained.

Japanese Patent Application Laid-Open No. 2009-221361

Since the fly ash has a higher fluidity than the coking coal (unmodified coal), the coke is added to the fly ash more, so that even if a lot of low carbon is compounded, it becomes a high strength structure. However, the coke used in the blast furnace is required to have not only strength but also large and uniform particles. However, when a large amount of unburnt carbon is added to the coke, there is a tendency that the coke is produced by mixing small particles. Therefore, the above-described Patent Document 1 has room for improvement.

Further, it is generally believed that the coke has a variation in quality (strength, particle size, porosity, etc.) due to the structural problems of the coke oven. Since the coke furnace is heated from the furnace wall side, the temperature of the central portion is low and the effective heating time in the course of the drying is shortened. Further, since a pressure distribution is generated in the height direction of the coke oven, a large load is applied to the lower portion of the coke oven, so that coking coal or the like (charged charcoal) hardly expands and freely expands at the upper portion. As a result, depending on the position in the interior of the coke oven, the quality of the resulting coke is varied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a coke having uniform quality with sufficient strength and large grain size while suppressing the mixing of coarse coal and a method for producing the coke.

DISCLOSURE OF THE INVENTION In order to solve the above problems, the inventors of the present invention have found that coke has a particle size reduced by volumetric fracture, and as a result of verifying the mechanism of occurrence of volumetric fracture, I did. Therefore, the inventors of the present invention have decided to optimize the addition amount of the ashless coal and ensure the degree of fluidity as a whole by coal.

That is, the coke according to the present invention is a coal coke obtained by carbonizing a coal mixture obtained by mixing coal with 2 to 8% of ashless coal constituted of a component soluble in coal and having a maximum flow MF value (log (ddpm ) Is 1.8 to 3.0.

As described above, the addition of an ash-free coal having higher fluidity than coal (coking coal) enhances the strength of the coke by supplementing the required degree of cohesion required for coke formation. In addition, the ash coal flows at a lower temperature than coal, It is possible to uniformize the quality of the coke and to improve the uniformity of the amount of the unburned coal and the average maximum degree of fluidity in the entire coal mixture as the charging coal By setting it to an appropriate range, the particle diameter of the coke can be increased.

Further, a method for producing a coke according to the present invention is characterized by comprising a mixing step of mixing 2 to 8% of unburned coal with coal to obtain a coal mixture having a maximum flow MF value (log (ddpm)) of 1.8 to 3.0, To carry out the carburizing process for carburizing the coal mixture.

By performing such a procedure, the coke production method is characterized in that, in the mixing step, the raw coal is selected based on the average value of the maximum flowability that can be calculated in advance, mixed with the ashless coal, mixed, And a uniformly large particle size coke can be produced.

According to the coke of the present invention, sufficient strength and particle size can be obtained while suppressing the cost of raw materials. Further, according to the method for producing coke according to the present invention, it is possible to manufacture the ashless coal from low-grade coal, for example, so that the cost of the raw material can be reduced and the coke having sufficient strength and particle size can be produced in the coke oven Can be uniformly manufactured regardless of the position of the substrate.

BEST MODE FOR CARRYING OUT THE INVENTION The coke of the present invention and its production method will be described in detail.

〔cokes〕

The coke according to the present invention is intended to be charged into a blast furnace for the production of pig iron, and is obtained by carbonizing a coal mixture in which coal ash is blended, under the general conditions as described later. Hereinafter, coal and ashless coal, which are raw materials of coke, will be described.

(Coal)

As described later, the coal is applied on one or two or more species having an average MF value within a predetermined range on average with an unburned coal. Particularly, in the case of applying low-grade carbon which is classified as weak coking coal or non-coking coking coal, which is difficult to make with coke raw materials alone, tungsten coal or semi-tough coal generally used as coke raw materials are used in combination. The low-grade coal generally refers to coal having a maximum flow MF value (log (ddpm)) of 2.0 or less and an average maximum reflectance Ro value of 1.1 or less. The maximum flow MF value is the heat flux, and the average maximum reflectance Ro value is the degree of coalification. In the coke of the present invention, depending on the characteristics of each coal, weak coking coal or non-coking coal can be blended up to 50% as dry coal at a blending ratio including ash trough. Coal may be dry coal by air drying or the like, but it may be mixed with non-coal and dry coal in a state containing water.

It is preferable that the coal is finely pulverized granular phase. Specifically, it is preferable that 80% or more of the coal is a granular particle having a diameter of 3 mm or less. In the present specification, the diameter of the particles means the maximum length of the particles, and 80% or more of the particles having a diameter of 3 mm or less means that when coal is impregnated with a sieve having a size of 3 mm, 80% It means to pass. Further, for example, coal having a grain size of 3 mm or less refers to a powder or granules in which a crushed coal after crushing is crushed with a sieve body having a scale of 3 mm or less (metal netting, Standard No. JIS Z 8801-1 (2006) . Such coal is described in detail in the production process, but it may be pulverized in advance or it may be pulverized while being mixed with the non-coal.

(Non-coking coal: 2-8%)

Unburi charcoal is a kind of reformed coal modified for effective use of coal as a resource and developed for high efficiency utilization as fuel. The unburned coal is a reformed coal obtained by removing ash and inferior coal components from coal as much as possible and extracting the coal with a solvent having high affinity with the coal to obtain an extract liquid separated from insoluble components such as ash, And removing the solvent by a distillation method or an evaporation method. Such an ashless carbon can be produced by a known method (for example, see Japanese Patent No. 4045229). Therefore, the ashless coal contains substantially ash-soluble organic matter which is soluble in the solvent and does not substantially contain ash, and structurally, the condensed aromatic ring is formed from a relatively low molecular weight component of the 2,3- Molecular weight component of < / RTI > Since the ash-free coal is dehydrated in the form of a mixture (slurry) of coal and a solvent before extraction and separation, the water content is reduced to about 0.2 to 3% by mass and the heat generation amount is sufficient. Therefore, the ashless coal exhibits high fluidity under heating, and generally melts at 200 to 300 캜 (softening and melting property) irrespective of the quality of the coal as the raw material. In the present invention, the quality of the coal used as the raw material of the ashless coal is irrelevant. In order to increase the strength of the coke, the ashless coal is preferably as small as possible, and more specifically, it is preferable to set the diameter (maximum length) to 1 mm or less.

As described above, the ashless coal has a high volatile content, is excellent in heat fluidity, and has a high degree of cohesion, so that it is possible to supplement the integrity of low-grade coal such as weak coking coal and non-coking coal. Since the unburned coal begins to flow at a lower temperature than the coking coal, it is added to and dispersed in the coal to uniformly bind the coal particles uniformly in the coke oven, including the center portion having a slow temperature rise. In addition, since the non-flammable carbon is higher than the expansive coke, the particles of the ash carbon are expanded in the lower part of the coke furnace where a large load is applied to fill the space between the coal particles and at the same time, . As a result, generation of defects such as adhesion failure (macroscopic cracking) or excessive expansion part (coarse pore) between coal particles, which can be a starting point of destruction of coke, is reduced, Can be suppressed. The addition ratio (blending ratio) of the ashless coal is less than 2% in the mixture with the coal (coal mixture, charged charcoal), the necessary degree of cohesion when the low-grade coal is blended, but the above-mentioned effect is not sufficiently obtained. Therefore, it is preferable that the rate of addition is 2% or more and 3% or more.

On the other hand, since the unburned coal is often produced by modifying low-cost low-cost carbon, the coke (carbon) produced by the coking coal having such a low degree of coalification has a higher degree of crystallinity than the carbon derived from the coarse coal, (An enlarged carbon nanotube structure and a small thickness). In addition, as the ashless coal becomes larger, the continuous phase of the ashless coal in the coke becomes larger, and when it becomes excessive, the continuous phase itself becomes the starting point of the fracture. In addition to this volume fracture, there is surface breakage in the fracture of the coke, and in the drum strength (DI), which is mainly used as an index of strength of the coke, volume fracture is hard to occur. When a large amount of ash tin is added, the grain size of the coke is hardly increased and the strength is rather lowered, and when the addition ratio exceeds 8%, this tendency becomes remarkable. Therefore, it is preferable that the addition ratio is 8% or less and 6% or less. As described above, in the coke of the present invention, the addition rate of ashless coal is suppressed to a certain level or less, and the strength is ensured to some extent by the inherent integrity of the raw coal (coal).

(Maximum flow MF value (log (ddpm)): 1.8 to 3.0)

When the maximum flow MF value is less than 1.8, the degree of fluidity is insufficient and the strength of the resulting coke is lowered in the mixture of coal and non-coal (coal mixture). In detail, when the maximum flow MF value is less than 1.8, a lot of low-grade coal having low fluidity and extensibility is mixed, and such coal particles are difficult to bond with other coal particles in the course of the drying process. Therefore, the maximum flow MF value of the mixture of coal and non-coal is set to be 1.8 or more, preferably 2.0 or more. When the MF value of the maximum flow rate is 1.8 or more, expandability is easily ensured. Since the coal particles expand due to the gas contained in the carbonization process, the gap between the coal particles is effectively filled, the adhesion between the particles is further promoted, . On the other hand, when the maximum flow MF value exceeds 3.0, there is a fear that the fluidity becomes excessive and air bubbles are generated in the coke. Therefore, the maximum flow MF value of the mixture of coal and non-ferrous carbon should be 3.0 or less, preferably 2.6 or less. The maximum flow MF value of a mixture of coal and non-ferrous carbon can be measured by Kisler plastometry based on JIS M8801 with the value measured for the mixture. However, in the case where the maximum flow MF value of each of various coal and non-ferrous coal is known, it may be calculated approximately by multiplying it by the compounding ratio (mass% / (100%)).

Further, when the average maximum reflectance Ro value is low, the mixture of coal and non-ferrous carbon has a low degree of coalification, so that expansion or fusion of particles of coal or non-coal is insufficient during the carbonization process or the strength of the coke substrate is low It is difficult to obtain high strength coke. The mixture of coal and ashless coal preferably has an average maximum reflectance Ro value of 0.95 or more, more preferably 1.0 or more. On the other hand, if the average maximum reflectance Ro value is large, the quality of the coke will not be deteriorated. However, the maximum reflectance Ro value increases due to the increase of high-quality coals such as coarse coal, and the coarse coal has high expandability. , Not only the cost of the raw material is increased but also the expansion pressure becomes excessive and the risk of damages to the coke oven may be increased. Concretely, the mixture of coal and non-ferrous carbon preferably has an average maximum reflectance Ro value of 1.3 or less, more preferably 1.2 or less.

[Production method of coke]

The method for producing coke according to the present invention carries out a mixing step of mixing unburned coal with coal and a carbonizing step of carbonizing the coal or the like. Each step will be described below.

(Mixing process)

In the mixing process, a coal mixture is obtained by mixing coal and non-coal. The maximum flow MF value of the blend and coal mixture is as described above. At this time, it is preferable to crush them simultaneously. As described above, when coal is pulverized into granules having a diameter of 3 mm or less, the unburnt carbon is simultaneously pulverized into granules having a diameter of 1 mm or less. For example, coal and unburned coal are introduced into a known mixer through a hopper, and the mixture is pulverized while stirring in a conventional manner, whereby the secondary particles of the ashless coal are easily pulverized and the coal is pulverized into granular particles. The procedure and the method of mixing are not particularly specified, and for example, the previously pulverized ashless coal and coal may be mixed.

(Carrying process)

In the present invention, the conditions of the dry distillation are not particularly limited, but the ordinary dry conditions in the production of coke using the coke oven can be adopted. For example, in the case of charging the coal mixture . At this time, by charging the coal mixture at a sufficiently high filling density, a high strength coke is obtained, and it is preferable that the filling density is 730 kg / m 3 or more. Particularly, a coal mixture having a low degree of fluidity in the entire mixture can be supplemented to some extent by the lack of strength due to low fluidity by increasing the filling density. Specifically, the coal mixture having a MF value of 2.0 or less has a filling density Lt; 3 > kg / m < 3 > The carbonization condition is preferably 950 DEG C or higher, more preferably 1000 DEG C or higher, preferably 1200 DEG C or lower, more preferably 1050 DEG C or lower, preferably 8 hours or higher, more preferably 10 Hour, preferably not more than 24 hours, more preferably not more than 20 hours.

Example

Next, the coke of the present invention and the production method thereof will be specifically described with reference to examples and comparative examples.

[Production of coke]

(Manufacture of non-coated carbon)

First, ashless coal was produced by the following method as a hypercoke continuous production facility (Bench Scale Unit).

(Manufactured by Nippon Steel Chemical Co., Ltd.) of 5 kg (in terms of dry coal) of this raw material coal and 4 times (20 kg) of 1-methylnaphthalene (manufactured by Shin-Nitetsu Chemical Co., Ltd.) Were mixed to prepare a slurry. The slurry was pressurized at 1.2 MPa by introducing nitrogen and subjected to extraction treatment at 370 占 폚 for 1 hour in a 30 liter internal volume autoclave. This slurry was separated into a supernatant and a solid concentrate in the gravity sedimentation under the same temperature and pressure, and the solvent was separated and recovered from the supernatant by distillation to obtain 2.7 kg of ashless coal. The ashed coal thus obtained had an ash content of 0.9% by mass. The maximum flow MF value (log (ddpm)) and the average maximum reflectance Ro value were as shown in Table 1. The ashless coal was pulverized so that its 100% (all) grain size (maximum length) was 3 mm or less.

(Mixing process)

The ashless coal and various coals having the characteristics shown in Table 1 were respectively adjusted to moisture of 7.5% by mass and mixed in the formulations shown in Table 2 on the basis of dry coal. The maximum flow MF value (log (ddpm)) of the coal and non-coal as shown in Table 1 was measured by a Kisler plastometer method based on JIS M8801. The average maximum reflectance Ro value was measured based on JIS M8816. Further, for the mixture, the maximum flow MF value and the average maximum reflectance Ro value were calculated from the mixing ratios of various coal and non-ferrous materials, and are shown in Table 2. The coal was pulverized so that 100% of the coal had a particle diameter of 3 mm or less.

(Carrying process)

The above-mentioned mixture (charged charcoal) was arranged in a forced retort, and the retort was subjected to vibration, adjusted to the packing density shown in Table 2, put in a double-side heating type electric furnace, and dried in a nitrogen stream to prepare a sample . The carbonization conditions were heated to 3 ° C / min and heated at 1000 ° C for 20 minutes. Thereafter, the retort was removed from the electric furnace and allowed to stand in natural cooling. In addition, as the evaluation standard, the sample (No. 20) was produced from the coal having the highest flow MF value without adding the non-coking coal and without adding the unburned coal.

〔evaluation〕

(burglar)

As the strength of the coke, the drum strength index DI ¹⁵⁰ ₁₅ is shown in Table 2. Specifically, according to JIS K2151, the sample was sieved with a sieve having a size of 15 mm after rotating the drum for 150 times, and the weight ratio remained was calculated. The acceptance standard of strength is DI ¹⁵⁰ ₁₅ : 84.8% or more. The coke strength was measured using a sample after the particle size distribution was measured by a method described later.

(Average particle diameter)

The coke was dropped by a shutter device twice and impacted by a drum tester 30 times. With respect to the coke subjected to the impact, the particle size distribution was measured using a square graduated body having one side of 100, 75, 50, 38, 25 and 15 mm, and the average particle size was calculated by the following formula (1). None of the samples had a coke having a square scale of 100 mm on one side. Table 2 shows the calculated average particle diameters. The acceptance criteria shall be an average particle size of 45.0 mm or more.

M _{75 -100} : Coke weight on 75 mm body

M _{50 -75} : Coke weight on the body of 75 mm to 50 mm body

M _{38 -50} : Coke weight on 50 mm to 38 mm body weight

M _{25 -38} : Coke weight of 38 mm to 25 mm body weight

M _{15 -25} : Coke weight of 25 mm to 15 mm body weight

M _{15 <} : Coke weight of 15 mm

M _ALL : total sum of coke weight after sieving (= M _{75 -100} + M _{50 -75} + M _{38 -50} + M _{25 -38} + M _{15 -25} + M _{15 <}

As shown in Table 2, Samples Nos. 1, 2, 16, and 17 in which coking coal was added without adding unburnt carbon had insufficient strength and an insufficient average particle size due to a large amount of small coke. Samples Nos. 3 and 4, in which the addition ratio of ashless coal was insufficient, similarly had insufficient strength and average particle size.

On the other hand, Samples Nos. 5 to 13, 18 and 19, in which the addition ratio of ashless carbon and the MF value of the mixture were in the range of the present invention, were lower than those of Sample No. 20, Of coke. Particularly, Sample Nos. 8 to 11 and 19 having an addition ratio of ashless coal of 4 to 6% were coke having a particle size as large as that of Sample No. 20. In addition, Sample Nos. 16 to 19 had a relatively low degree of flow of the mixture because of the relatively large amount of non-coking coal having a low fluidity, but the addition of ash carbon and the filling density of the mixture were increased, , 19, coke of sufficient strength and particle size. On the other hand, the samples Nos. 14 and 15, in which the addition ratio of the unscented coal was excessive, were insufficient in strength and particle size even when the degree of flow of the mixture was equal to or higher than that of the samples Nos. 5 to 13.

Although the present invention has been described in detail with reference to the preferred embodiments thereof, the scope of the present invention should be broadly interpreted based on the description of the claims . It goes without saying that the contents of the present invention can be widely modified or changed on the basis of the above description.

Claims (2)

A coke obtained by carbonizing a coal mixture obtained by mixing coal with 2 to 8% of ash tin, which is composed of a component soluble in coal,
Wherein the coal mixture has a maximum flow MF value (log (ddpm)) of 1.8 to 3.0. A mixing step of mixing 2 to 8% of ash tundish with coal to obtain a coal mixture having a maximum flow MF value (log (ddpm)) of 1.8 to 3.0,
Wherein the coal mixture is dry-distilled.