TWI504738B - Coke and its manufacturing method - Google Patents

Description

Coke and its manufacturing method

The present invention relates to coke used in blast furnace iron making and a method for producing the same, and more particularly to coke having ashless coal obtained by solvent extraction and treatment of coal.

In order to ensure a certain mechanical strength, reactivity, apparent density, and air permeability which are not easily crushed in the blast furnace, coke used in the blast furnace method is required to have various characteristics such as the size and distribution of the necessary bulk. The raw material of coke suitable for these characteristics is generally referred to as raw material carbon, and is a strongly cemented coal of coal which is high in quality in a certain range of viscosity, fluidity or coalification, and which is more expensive than general boiler fuel coal. This kind of strongly cemented coal softens and melts at 400 °C to form a viscous liquid and melts, and expands due to the inclusion of gas, so it can effectively fill the gap between the coal particles and promote the adhesion between the particles. Can produce strong coke. However, in recent years, due to the persecution of resources and high prices, various technologies have been developed, that is, attempts have been made to use cheaper and lower quality coal as raw materials for coke. For example, in the case of strong cemented coal blending, A lot of low-rank coal technology.

Low-order coal such as non-micro-coalized coal, due to strong fluidity The cemented coal is low and has poor cohesiveness, so that the adhesion between the coal particles is hindered, and the defect density is increased to lower the strength of the coke. Therefore, in order to fill the cohesiveness, a technique of adding coke with petroleum-derived binder (ASP) and coke-free coal (super-coal coal; HPC) composed of soluble components of coal extracted by an organic solvent is disclosed. . In particular, ashless coal has been developed as a technique for the effective utilization of low rank coal. For example, Patent Document 1 discloses a technique of adding coke-free coal coke to coal containing low rank coal, and high strength coke can be obtained when 5 to 10% of ashless coal is added.

[Advanced technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-221361

Since the fluidity of the ashless coal system is higher than that of the raw coal (unmodified coal), coke can be a high-strength structure by adding more ashless coal even if more low-rank coal is blended. However, coke used in blast furnaces is not only strength but also requires equal particle size. However, when coke is added with more ashless coal, it tends to mix smaller particles of coke. Therefore, the aforementioned Patent Document 1 still needs improvement.

In addition, it is generally considered that the quality (strength, particle size, porosity, etc.) of coke is uneven due to problems in the structure of the coke oven. by Since the coke oven heats from the furnace wall side, the temperature at the center portion is low, and the effective heating time in the dry distillation process becomes short. Further, since the coke oven has a pressure distribution in the height direction, a large load is applied to the lower portion of the coke oven, so that the raw coal or the like (loaded with coal) is less likely to expand, and is free to expand at the upper portion. As a result, the quality of the produced coke is uneven due to the position of the inside of the coke oven.

The present invention has been developed in view of the aforementioned problems. It is an object of the invention to provide a coke which is capable of suppressing the blending of strongly cemented coal and having uniform properties of large particles and having sufficient strength, and a method for producing the same.

In order to solve the above problems, the present inventors have found that coke is reduced in size by volume destruction, and the structure in which volume destruction occurs is examined, and it is thought that volume destruction is caused by adding a large amount of ashless coal. Therefore, the inventors have optimized the amount of ash-free coal to be added, and the fluidity of the whole is ensured by the coal.

That is, the coke of the present invention is characterized in that a mixture of 2 to 8% of an ashless coal composed of a component soluble in coal and a coal mixture of coal is subjected to dry distillation, and the maximum fluidity of the coal mixture is MF. The value (log(ddpm)) is 1.8 to 3.0.

In this way, by adding ashless coal with higher fluidity than coal (raw coal), the necessary cohesiveness for coke formation is filled, the strength of coke is increased, and in the dry distillation process, the ashless coal is at a lower temperature than coal. Flowing and uniformly coal particles in a coke oven, and filling with high expansion The space between the coal particles is filled, so that the quality of the coke can be equalized, and the coke can be increased by setting the amount of the ashless coal and the average maximum fluidity of the coal mixture charged in the coal to an appropriate range. Particle size.

Moreover, the method for producing the coke of the present invention is carried out without 2 to 8% of ash coal is mixed with coal as a mixing process for a coal mixture having a maximum fluidity MF value (log (ddpm)) of 1.8 to 3.0; and a dry distillation process in which the aforementioned coal mixture is subjected to dry distillation.

By performing this sequence, the coke manufacturing method is The mixing process selects the raw coal according to the average value of the highest fluidity that can be calculated in advance, mixes and mixes with the ashless coal, and performs dry distillation in the dry distillation process, thereby producing coke having sufficient strength and equal large particles.

According to the coke of the present invention, both the raw material cost and the sufficient strength and particle diameter can be suppressed. Moreover, according to the method for producing coke according to the present invention, ash-free coal can be produced from, for example, low-rank coal, and the raw material cost can be reduced, and the production can be uniformly performed without being affected by the position of the inside of the coke oven by a simple production method. Coke with sufficient strength and particle size.

The coke of the present invention and a method for producing the same will be described in detail.

[Coke]

The coke system of the present invention is used for the production of pig iron into the blast furnace. The general conditions described are obtained by dry distillation of a coal mixture of coal mixed ashless coal. Hereinafter, coal and ashless coal which are raw materials for coke will be described.

(coal)

As described later, the coal system is applied to one or two or more types of the highest fluidity MF value in a predetermined range in the average of the ashless coal. In particular, in the case of low-order coal classified as weakly cohesive coal or non-micro-coalized coal, which is not easily used as a coke raw material, it is used as a coke raw material, and a commonly used strongly cemented coal, quasi-strongly bonded coal, etc. . Further, the so-called low rank coal generally refers to coal having a maximum fluidity MF value (log (ddpm)) of 2.0 or less and an average maximum reflectance Ro value of 1.1 or less. The highest fluidity MF value shows thermal fluidity, and the average maximum reflectance Ro value shows the degree of coalification. In the coke of the present invention, although the coal is different according to the coal, the weakly coalified coal, the non-micro-cohesive coal and the like also contain the mixing ratio of the ashless coal, and the maximum blending of the dry coal is about 50%. Coal can be made into dry coal by air drying, etc., but it can also be mixed with dry coal and dry distillation in the state containing water.

The coal is preferably pulverized into fine granules. Specifically, it is preferable that 80% or more of the coal is granules having a particle diameter of 3 mm or less. The particle diameter referred to in the present specification means the maximum length of the particles, and 80% or more of the particles having a particle diameter of 3 mm or less means that when the coal is poured into a sieve having a mesh size of 3 mm, 80% or more passes through the mesh. Further, for example, coal having a particle diameter of 3 mm or less means that the pulverized coal after pulverization is sieved by a sieve having a mesh size of 3 mm or less (metal mesh sieve; specification number JIS Z 8801-1 (2006)). Powder, granules, etc. dropped under the sieve at the time of selection. Such coal is described in detail in the production method, and may be pulverized in advance or may be mixed with ashless coal and pulverized.

(2~8% without ash)

The ashless coal is developed as a modified coal for use as a fuel for efficient use as a resource. The ashless coal is a modified coal which removes ash and insoluble coal components as much as possible from coal, and extracts the coal from a solvent having high affinity with coal to obtain an extract separated from insoluble components such as ash. Further, the extract is prepared by removing a solvent by a distillation method, an evaporation method, or the like. Such an ashless coal system can be produced by a known method (for example, refer to Japanese Patent No. 4045229). Therefore, the ashless coal is substantially free of ash and contains a large amount of organic matter having a softening meltability which is soluble in a solvent, and has a structure having a lower molecular weight component from the 2, 3 ring of the aromatic ring and 5 to 6 ring. A broad molecular weight distribution of the high molecular weight components on the left and right. In addition, since the ashless coal is dehydrated in the state of a mixture (slurry) of coal and solvent before extraction and separation, the water content is reduced to about 0.2 to 3% by mass, and the amount of heat is sufficient. Therefore, the ashless coal exhibits high fluidity under heating and is not affected by the grade of the coal of the raw material, and is generally melted at 200 to 300 ° C (having softening meltability). In the present invention, coal as a raw material for ashless coal is not limited to its quality. Further, in order to increase the strength of the coke, the ashless coal is preferably as small as possible, and specifically, the particle diameter (maximum length) is preferably 1 mm or less.

Thus, the ashless coal system contains a large amount of volatiles, which is excellent. Good thermal fluidity and high adhesion make it possible to fill the adhesion of low-rank coal such as weakly coalified or non-bonded coal. Further, since the raw coal is started to flow at a lower temperature than the raw coal, by adding and dispersing it in the coal, the coal particles in the coke oven in the dry distillation process can uniformly equalize the coal particles in the center portion including the temperature rise. Directly combined. Moreover, since the ashless coal is also more expandable than the raw coal, even in the lower portion of the coke oven where a large load is applied, the particles of the ashless coal expand, filling the voids between the coal particles and simultaneously expanding Pressure is generated to allow other coal particles to combine. As a result, it is possible to reduce the occurrence of defects such as defective defects (large cracks) and excessive expansion portions (coarse pores) between the coal particles which may be the starting point of the destruction of the coke, and it is possible to suppress the furnace width and the height direction of the coke oven. The quality caused by the etc. is uneven. When the addition ratio (mixing ratio) of ashless coal is less than 2% of the mixture with coal (coal mixture and coal), the adhesiveness required for the preparation of low rank coal, the aforementioned effects, etc. cannot be sufficiently obtained. . Therefore, the addition rate of ashless coal is 2% or more, and 3% or more is preferable.

In addition, since most of the ashless coal is cheap low-grade coal Since it is manufactured by upgrading, the carbon produced by the coal having a low degree of coalification is less developed than the carbon produced by the strongly cemented coal having a high degree of coalification. The diffusion and thickness of the plain mesh surface are small. Further, as the ashless coal becomes more and the continuous phase of the coke-free ashless coal becomes large, when it becomes too large, the continuous phase itself becomes a starting point of destruction. Furthermore, in addition to this volume destruction, there is surface damage in the destruction of coke, and the cylinder index (drum index) is mainly used as the strength index of coke. ; DI), it is not easy to show volume damage. When a large amount of ashless coal is added, the particle size of the coke is not easily increased, but a strong decrease is caused. When the addition rate exceeds 8%, this tendency becomes remarkable. Therefore, the addition rate of ashless coal is set to 8% or less, and preferably 6% or less. As described above, the coke of the present invention is suppressed to a certain value or less by the addition rate of the ash-free coal, and the strength is ensured by the original cohesiveness of the raw coal (coal).

(Maximum fluidity MF value (log(ddpm)): 1.8~3.0)

The mixture of coal and ashless coal (coal mixture) is such that when the maximum fluidity MF value is less than 1.8, the fluidity will be insufficient and the strength of the coke obtained will be low. In detail, when the maximum fluidity MF value is less than 1.8, the formulation of low-order coal having low fluidity and low expansion is increased, and such coal particles are not easily combined with other dry distillation processes in the dry distillation process. Therefore, the maximum fluidity MF value of the mixture of coal and ashless coal is set to 1.8 or more, and desirably 2.0 or more. In addition, when the maximum fluidity MF value is 1.8 or more, it is easy to ensure the expandability, and since the coal particles are expanded by the gas in the carbonization process, the gap between the coal particles can be effectively buried, and the adhesion between the particles can be further promoted. Produces strong coke. In addition, when the maximum fluidity MF value exceeds 3.0, the fluidity becomes excessive and there is a possibility that bubbles are generated in the coke. Therefore, the maximum fluidity MF value of the mixture of coal and ashless coal is set to 3.0 or less, preferably 2.6 or less. The maximum fluidity MF value of the mixture of coal and ashless coal is taken as the value measured for the mixture, and can be measured by the Gieseler Plastometer according to JIS M8801. However, the maximum fluidity MF value of each type of coal and ashless coal In the known case, the sum may be multiplied by the blending ratio (% by mass/(100%)) to calculate an approximate value.

Also, when the average of the mixture of coal and ashless coal is the largest When the incident rate Ro is small and the degree of coalification is low, the expansion and fusion of coal, ashless coal particles are insufficient in the dry distillation process, or the strength of the coke base is low, and high strength coke cannot be obtained. The average maximum reflectance Ro of the mixture of coal and ashless coal is preferably 0.95 or more, more preferably 1.0 or more. In addition, even if the average maximum reflectance Ro value is too large, the quality of the coke is not lowered, but since the maximum reflectance Ro value is increased according to the increase of the high-order coal of the strongly cemented coal, the strongly cemented coal Since the expansion property is also high, when the raw material coal is excessively mixed, not only the raw material cost becomes high, but also the expansion pressure is excessive and the consumption of the coke oven becomes sharp. Specifically, the average maximum reflectance Ro of the mixture of coal and ashless coal is preferably 1.3 or less, more preferably 1.2 or less.

(Manufacturing method of coke)

The coke production method of the present invention is a mixing process for coal mixed ashless coal and a dry distillation process for dry distillation of the coal. The following is a description of each process.

(mixed process)

The mixing process is to mix coal with ashless coal to obtain a coal mixture. The highest fluidity MF values for blending and coal blends are as described above. Also, at this time, it is preferable to pulverize these at the same time. Because the pulverization of coal is less ashless Since the coal is inferior, when 80% or more is pulverized into pellets having a particle diameter of 3 mm or less, the ash-free coal is also pulverized into pellets having a particle diameter of 1 mm or less. For example, coal and ash-free coal are separately supplied from a supply hopper to a conventional pulverizer, and stirred by a general method while being pulverized, whereby secondary particles of ashless coal are easily pulverized, and coal is pulverized into pellets. Further, the order, method, and the like of the mixing are not particularly limited. For example, the ash-free coal that has been previously pulverized may be mixed with coal.

(dry distillation process)

In the present invention, the conditions of the dry distillation are not particularly limited, and general dry distillation conditions using coke from a coke oven can be employed. For example, the coal mixture can be charged into a chamber furnace having a capacity of about 30 tons, and then subjected to dry distillation. At this time, by increasing the packing density of the coal mixture and then charging it, it is possible to obtain high-strength coke, and it is preferable to form a filling density of 730 kg/m ³ or more. In particular, a coal mixture having a low fluidity of the entire mixture can fill a certain degree of insufficient strength due to low fluidity by increasing the packing density. Specifically, a coal mixture having a maximum fluidity MF value of less than 2.0 is prepared. A filling density of 750 kg/m ³ or more is preferred. The dry distillation conditions are preferably 950 ° C or higher, more preferably 1000 ° C or higher, and still more preferably 1200 ° C or lower, more preferably 1050 ° C or lower, and more preferably 8 hours or longer, more preferably 10 hours or longer, and ideally 24 hours. Hereinafter, it is more preferably 20 hours or less.

[Examples]

Next, the coke of the present invention and a method for producing the same will be specifically described by way of examples and comparative examples.

(production of coke)

(Manufacture of ashless coal)

First, ashless coal was produced by the following method in a Bench Scale Unit.

The bituminous coal produced in Australia was used as a raw material coal, and 5 kg (calculated as dry coal) of the raw coal was mixed with 1-methyl naphthalene (manufactured by Nippon Steel Chemical Co., Ltd.) as a solvent in four times (20 kg) to prepare a slurry. The slurry was introduced into a nitrogen gas, pressurized to 1.2 MPa, and subjected to extraction treatment at 370 ° C for 1 hour in a batch type high pressure micro-disinfector having an internal volume of 30 L. The slurry was separated into a supernatant liquid and a solid fraction concentrate in a gravity settling tank maintained at the same temperature and pressure, and the solvent was separated and distilled from the supernatant liquid to obtain 2.7 kg of ashless coal. The obtained ashless coal system had an ash content of 0.9% by mass, a maximum fluidity MF value (log (ddpm)), and an average maximum reflectance Ro value as shown in Table 1. This ash-free coal is pulverized to have a particle diameter (maximum length) of 100% (all) of 3 mm or less.

(mixed process)

Each of the coals having the characteristics of the ashless coal and the characteristics shown in Table 1 was adjusted to 7.5% by mass of water, and mixed by the mixing ratio shown in Table 2 on the basis of dry coal. Furthermore, the highest fluidity MF value (log(ddpm)) of coal and ashless coal shown in Table 1 is based on JIS M8801 by Kjeldahl method. (Gieseler Plastometer) was measured. The average maximum reflectance Ro value was measured in accordance with JIS M8816. Further, regarding the mixture, the highest fluidity MF value and the average maximum reflectance Ro value were calculated from the respective mixing ratios of various coals and ashless coals, and are shown in Table 2. Further, the coal is mixed and pulverized into 100% of which is 3 mm or less in particle diameter.

(dry distillation process)

The mixture (loaded into coal) was placed in a steel distiller, and the distiller was vibrated to adjust the packing density shown in Table 2, and then placed in a double-sided heating type electric furnace, and the mixture was flowed in a nitrogen stream. The sample was prepared by dry distillation. The dry distillation conditions were carried out at a temperature of 3 ° C/min and heated at 1000 ° C for 20 minutes. Then, the distiller was taken out from the electric furnace and naturally allowed to cool. In addition, as a criterion for evaluation, no non-coarse coal was blended and no ashless coal was added, and a sample (No. 20) was prepared from coal having a high fluidity MF value.

[Evaluation]

(strength)

Table 2 shows the cylinder index index DI ¹⁵⁰ ₁₅ as the strength of coke. Specifically, the sample was rotated 150 times on the drum according to JIS K2151, and then sieved with a mesh of 15 mm to calculate the remaining weight ratio. The acceptable standard of strength is set to DI ¹⁵⁰ ₁₅ : 84.8% or more. Further, the coke strength was measured by using a sample after measuring the particle size distribution by a method described later.

(The average particle size)

The coke was dropped twice with the door stopper device, and the impact of the rotation was applied 30 times with the roller tester. For the coke to which the impact was applied, a sieve having a mesh size of 100, 75, 50, 38, 25, and 15 mm square was used, and the particle size distribution was measured, and the average particle diameter was calculated by the following formula (1). Furthermore, none of the samples did not become coke on a 100 mm square mesh screen. The calculated average particle diameter is shown in Table 2. The pass criteria are made to have an average particle diameter of 45.0 mm or more.

Average particle diameter (mm) = (87.5 × M _75-100 + 62.5 × M _50-75 + 44.0 × M _38-50 + 31.5 × M _25-38 + 20.0 × M _15-25 + 7.5 × M _{15 <} ) / M _ALL . . . (1)

M _75-100 : coke weight on a 75mm sieve

M _50-75 : Coke weight from a 75mm sieve to a 50mm sieve

M _38-50 : coke weight down to a 38mm sieve from a 50mm sieve

M _25-38 : coke weight down to a 25mm sieve from a 38mm sieve

M _15-25 : Coke weight from a 25mm sieve to a 15mm sieve

Coke weight under M _15< :15mm sieve

M _ALL : sum of weights of coke after screening (=M _75-100 +M _50-75 +M _38-50 +M _25-38 +M _15-25 +M _15< )

As shown in Table 2, it is known that no ashless coal is added and the blending is not The No.1, 2, 16, and 17 samples of the cemented coal were insufficient in strength, and the coke was small in particle size and the average particle diameter was insufficient. Similarly, Sample Nos. 3 and 4 in which the addition rate of ashless coal was insufficient were insufficient in strength and average particle diameter.

In contrast, the addition rate of ashless coal and the highest of the mixture The sample Nos. 5 to 13, 18, and 19 having a fluidity MF value in the range of the present invention have a fluidity lower than that of the sample No. 20, but are coke having a sufficient strength and particle diameter. In particular, sample No. 8 to 11, 19 in which the addition rate of ashless coal was 4 to 6% was a coke having a large particle diameter similar to that of sample No. 20. Further, in the sample Nos. 16 to 19, since a large amount of non-bonded coal having a low fluidity was blended, the fluidity of the mixture was also low, but the sample No. 18 in which the ashless coal was added and the packing density of the mixture was increased and the dry distillation was carried out was carried out. 19, which becomes coke with sufficient strength and particle size. Further, in Sample Nos. 14 and 15 in which the addition rate of ash-free coal was excessive, even if the fluidity of the mixture was the same as or higher than that of Sample Nos. 5 to 13, the strength and the particle size were insufficient.

The present invention has been described in detail above with reference to the embodiments and examples. However, the scope of the present invention is not limited to the foregoing, and the scope of the claims is broadly construed in accordance with the description in the claims. Further, the content of the present invention can be widely changed and changed in accordance with the above description.

Claims (2)

A coke which is a coke formed by mixing a mixture of 2 to 8% of ashless coal composed of coal and a coal mixture of coal and a coal mixture of coal, characterized in that the coal mixture is the highest fluidity MF The value (log(ddpm)) is 1.8 to 3.0, and the average maximum reflectance value is 0.95 to 1.3. A method for producing coke is carried out by mixing 2 to 8% of ashless coal with coal to form a coal mixture having a maximum fluidity MF value (log (ddpm)) of 1.8 to 3.0 and an average maximum reflectance value of 0.95 to 1.3. a mixing process; and a carbonization process in which the coal mixture is filled to a packing density of 730 kg/m ³ or more and then subjected to dry distillation.