JP5438277B2 - Coke manufacturing method and pig iron manufacturing method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for producing raw coke for producing coke, a method for producing coke, and a method for producing pig iron using coke for realizing high strength coke desired in blast furnace iron making.

  Coke used for iron making is required to have high strength in order to ensure air permeability in the blast furnace. It is generally said that coke is produced by dry distillation of coal and it is better to use strong caking coal with a high carbon content in order to achieve its high strength. Coal with a high rate is expensive, and it is desirable to reduce its usage. If non-caking coal or slightly caking coal is used in combination, the amount of coal with a high carbon content can be reduced, but the reduction in coke strength associated with the reduction in the amount of use must be considered.

  It is known that means for reducing the moisture content of coal and mechanically compacting the coal charged in the coke oven can increase the coal filling density in the coke oven and increase the strength of the coke. However, when the reduction of the moisture content is adopted, there is a problem that the fine powder of coal is likely to be scattered, and one of the operations for compacting is complicated.

  Another technique for obtaining high-strength coke is disclosed in Patent Document 1. In this technology, asphalt, asphalt pitch, coal liquefaction residue, caking filler such as solvent-generated coal are impregnated on the surface of fine-grained carbon material that is not soft and meltable, and mixed with coal to dry distillation. To do.

  The applicant has already filed a patent application relating to high-strength coke, and the contents thereof are disclosed in Patent Documents 2 and 3. Patent Document 2 discloses coal containing substantially no ash to 100 parts by mass of coal containing coal having a carbon content of 85% or more and 91% or less and coal having a carbon content of 60% or more and less than 85%. It discloses that what contains 1 mass part or less is used as coal for coke manufacture. On the other hand, patent document 3 discloses adding 1 mass part or less of coal which does not contain ash substantially with respect to 100 mass parts of coking coal for coke manufacture.

As described above, obtaining high-strength coke while reducing the use amount of coal having a high carbon content such as strongly caking coal is a problem in coke production. For the purpose of solving this problem, asphalt pitch, coal tar, Or caking fillers such as ashless charcoal are used, but due to the complex action of caking fillers, the use of high carbon content coal is reduced (other than high carbon content charcoal) Coexistence of high-coal strength and coke strength is difficult.
JP 2001-40363 A JP 2007-23190 A JP 2007-246684 A

  In view of the above circumstances, an object of the present invention is to provide a method for producing a raw coke for producing coke, which is also suitable for blending with coal having a high carbon content to produce high strength coke.

  The method for producing coking coal for producing coke according to the present invention includes 1.0 part by mass of ashless coal and inferior coal 2 having a carbon content (daf) of 78.0% or more and less than 88.0%. It has the process of heating the mixed coal which consists of 0.0 mass part or more and 20.0 mass parts or less above the softening temperature of ashless coal.

  In the present invention, “ashless coal” refers to coal having an ash content, which is a residual inorganic substance when heated and incinerated by heating at 815 ° C., at 5000 ppm or less (mass basis) in the ashless coal before heating. In addition, “poor quality coal” has a carbon content (daf) as defined above of 78.0% or more and 88.88, regardless of whether it falls under bituminous coal or subbituminous coal. It means less than 0% coal.

  The method for producing coke according to the present invention is a method for producing coke by carbonizing a blended coal in which two or more types of coal are blended, wherein the blended coal is a method for producing coking coal for coke production according to the present invention. It contains 20 mass% or more of the obtained first raw coal and second raw coal having a carbon content (daf) of 85.0% or more and 91.0% or less. The blended coal is preferably composed of only the first raw coal and the second raw coal.

  Moreover, the manufacturing method of pig iron which concerns on this invention uses the coke obtained by the manufacturing method of the coke which concerns on this invention.

  The coking coal (first coking coal) obtained by the method for producing coking coal for coke production according to the present invention is a mixture of a predetermined amount of ashless coal and inferior coal heated to a temperature above the softening temperature of ashless coal. Therefore, even if coke is produced by blending the first raw coal while suppressing the amount of coal (second raw coal) having a high carbon content, high strength coke can be obtained.

(Method for producing raw coal for coke production)
The method for producing coking coal for producing coke according to the present invention comprises 1.0 part by mass of ashless coal, and an inferior quality having a predetermined amount of carbon content (daf) of 78.0% or more and less than 88.0%. It has the process of heating the mixed coal which consists of charcoal above the softening temperature of ashless coal.

  Ashless coal is coal having an ash content of 5000 ppm or less (mass basis, the same applies hereinafter), and the ash content is preferably 2000 ppm or less. Here, “ash” means a residual inorganic substance when coal is incinerated by heating at 815 ° C., and the inorganic substance is silicic acid, alumina, iron oxide, lime, magnesia, alkali metal, and the like.

  Suitable ashless coal has a maximum fluidity (log MF) of 3.0 (logddpm) or more, which is confirmed by a Gieseler flowability test by the Gieseler plastometer method specified in JIS M8801. A solidification temperature exceeding 450 ° C. is also suitable as ashless coal.

  In order to increase the surface area of the inferior coal covered with the ashless coal, the ashless coal preferably has a particle size smaller than that of the inferior coal. The particle size of the preferred ashless coal is 0.5 mm or less, more preferably 0.3 mm or less, and still more preferably 0.2 mm or less. This particle size is determined by whether or not it can pass through a predetermined sieve sieve. For example, the particle size of ashless coal that passes through a sieve having an aperture of 0.5 mm is 0.5 mm or less. In order to adjust the particle size of the ashless charcoal, a known crusher such as a hammer mill, a jaw crusher, or a jet mill may be used.

  As a method for obtaining ashless coal, a known method for producing ashless coal may be employed. For example, extraction of coal components with an organic solvent corresponds to the production of ashless coal.

  Coal used in the production of ashless coal is not particularly limited, such as bituminous coal, subbituminous coal, lignite, and the carbon content is not particularly limited. In other words, coal having a carbon content (daf) of 60.0% or more and less than 95.0% may be used. However, coal with a high caking carbon content is a problem of depletion. Therefore, it is preferable to use coal having a carbon content (daf) of 60.0% or more and less than 88.0%, and a carbon content (daf) of 70.0% or more. More preferably, less than 85.0% coal is used.

  In order to efficiently extract the coal component, it is appropriate to pulverize the coal to 5 mm or less in advance.

  Organic solvents used in the production of ashless charcoal include aromatic aromatic compounds such as benzene, toluene, xylene; naphthalene, methylnaphthalene, dimethylnaphthalene, trimethylnaphthalene, biphenyl, aliphatic side chain or biphenyl having an aromatic substituent One or more organic solvents such as bicyclic aromatic compounds; tricyclic aromatic compounds; and the like can be used. However, when an aromatic compound is used, the extraction rate of the coal component is low, and when the extraction temperature is increased to increase the extraction rate, the pressure for setting the temperature may be high. Moreover, when using a tricyclic aromatic compound, since there exists a general tendency for the boiling point of the said compound to be high, the organic solvent separation from coal may become difficult. Therefore, it is preferable to use a bicyclic aromatic compound. More suitable bicyclic aromatic compounds are those having a boiling point of 180 ° C to 330 ° C.

  If a hydrogen-donating solvent such as tetralin, which is known to be used in coal liquefaction methods, is used, coal can be solubilized or liquefied to achieve a high extraction rate of coal components. The hydrogen atom of the organic solvent may move to the constituent molecules of coal. Therefore, it is preferable to extract a coal component by selecting a non-hydrogen-donating organic solvent instead of a hydrogen-donating organic solvent.

  In the extraction of coal components with an organic solvent, coal and organic solvents are mixed to prepare a slurry and the coal components are extracted. After that, the organic solvent is removed from the liquid portion such as the supernatant of the slurry, and ashless coal is obtained. can get.

  It is appropriate that the coal concentration in the slurry is 10 to 35% by mass, and the coal component may be extracted by heating the slurry. For example, the slurry is held at 300 to 420 ° C. for 5 to 120 minutes. If the temperature is lower than 300 ° C, the bond between coal constituent molecules cannot be weakened sufficiently, so that the extraction rate of the coal component is low, and if the temperature is higher than 420 ° C, the pyrolysis radical generated by the pyrolysis reaction of coal. Will recombine with the coal, so the extraction rate of the coal component will also be low. On the other hand, at a temperature of 300 to 420 ° C., the coal component molecules loosen and mild thermal decomposition occurs, so that a high extraction rate of the coal component is achieved. Further, the pressure in the extraction is adjusted so that the organic solvent does not reach the boiling point, and is usually 0.8 to 2.5 MPa, and the atmosphere during the extraction is an inert gas (for example, nitrogen) atmosphere Good to be.

  After the extraction of the coal component, it is necessary to separate the extracted coal from the organic solvent before removing the organic solvent. In this separation, a known separation method may be employed. The known separation methods include, for example, a sedimentation method and a filtration method. Since the filtration amount of the filtration filter is limited in the filtration method, a sedimentation method may be employed to separate a large amount of coal. Is preferred. In addition, in order to avoid precipitation of the coal component in an organic solvent, it is suitable to set the temperature of the removal of coal from a slurry to the same temperature as at the time of extraction, and the same applies to the pressure.

  FIG. 1 is a diagram for explaining an example of an apparatus for producing ashless coal. In the tank 1, coal and an organic solvent are mixed to form a slurry. The slurry is sent out by the pump 2, heated to a predetermined temperature while passing through the preheater 3, and then supplied to the extraction tank 4. . In the extraction tank 4, while the slurry is stirred by the stirrer 10, the coal component is extracted into the organic solvent, and then the slurry is supplied to the gravity settling tank 5. In the gravity sedimentation tank 5, the coal after the components are extracted settles in the direction of the arrow 11, and the supernatant liquid in the gravity sedimentation tank 5 is supplied to the filter unit 8, while the sediment is supplied to the sediment receiver 6. Collected. The supernatant liquid is filtered by a filter member 7 provided in the filter unit 8, and the filtrate is collected in a supernatant liquid receiver 9. Next, ashless coal is obtained by evaporating and removing the organic solvent from the collected filtrate. As a method for evaporating and removing the organic solvent, a general drying method such as a spray drying method, a distillation method, or a vacuum drying method may be applied.

  Various standardizations have been tried for the classification criteria of coal, the judgment criteria as coke coking coal, and the structure and composition of the coal, but there are no standards yet. Therefore, in this specification, coal having a carbon content (daf) of less than 88.0% is defined as inferior coal. Many non-minor cohesive coals and caking coals belong to the inferior coals, and inferior coals often reduce coke strength, thus avoiding large amounts of use in coke production. Since the content (daf) is less expensive than coal with 88.0% or more, it is desired to use a large amount. In the present invention, the carbon content (daf) of the inferior quality coal has a lower limit, and the lower limit is 78.0%. The carbon content (daf) of the inferior coal in the present invention is preferably 82.0% or more and 87.0% or less. Carbon content (daf = dry ash free), which is a standard for classification of coal, refers to the organic content (mass%) excluding moisture and ash content of coal, according to JIS M8819. Can be measured.

  The inferior charcoal is desirably fine, and the inferior charcoal may be refined using a known crusher such as a hammer mill, a jaw crusher, or a jet mill. If inferior coal with a particle size of more than 2 mm is used, the proportion of the inside of the ashless coal that does not have the same contact as the inferior coal surface in contact with the ashless coal is increased, and the caking property improving effect imparted from the ashless coal is ineffective. Since it may become sufficient, it is preferable that the particle size of inferior coal is 2 mm or less, and 1 mm or less is more preferable. This particle size is determined by whether or not it can pass through a predetermined sieve sieve. For example, the particle size of what passes through a sieve having an opening of 2 mm is 2 mm or less.

  The inferior coal has a carbon content (daf) of 78.0% or more and less than 88.0%. Coal with a carbon content of 88.0% or more is not required to be treated with ashless coal because it usually has sufficient tackiness for coke production unless it has a particularly high degree of coalification. If coal having a carbon content of 88.0% or more is treated with ashless coal, the coke strength may be reduced. Therefore, the method according to the present invention is applied to coal having a carbon content of 88.0% or more. It is not necessary to perform the same heat treatment. On the other hand, coal having a carbon content of less than 78.0% inevitably has a high crosslink density due to oxygen-containing functional groups, and therefore the coal having a carbon content of less than 78.0% is used in the method for producing raw coal for producing coke according to the present invention. High-strength coke cannot be produced using Coal having a carbon content of less than 78.0% corresponds to lignite, and is not usually used as coking coal for coke production.

  In order to obtain mixed coal, a predetermined amount of ashless coal and inferior coal is blended and uniformly mixed using a known device such as a mixer. The blending ratio at this time is 1.0 part by mass of ashless coal and 2.0 parts by mass or less and 20.0 parts by mass or less of poor quality coal. Setting the inferior quality to less than 2.0 parts by mass is inappropriate from the viewpoints of economy that ashless coal is more expensive than inferior quality and coke strength. Moreover, it is not preferable to use more than 20.0 parts by mass of inferior coal because the caking supplement effect of ashless coal becomes insufficient. A more preferable blending ratio of inferior quality coal to 1.0 part by mass of ashless coal is 5 parts by mass or more and 10 parts by mass or less.

  The optimization of the mixing ratio of ashless coal and inferior coal is determined according to the properties of the inferior coal. In other words, when using inferior coal with a relatively low degree of coalification, the blending ratio of ashless coal should be high, and inferior coal with a relatively high degree of coalification having properties close to caking coal. When using, it is good to make the mixture ratio of ashless coal low.

  In the heating of mixed coal, the heat melting property and caking property of ashless coal are transferred to inferior coal. For that purpose, the temperature of the ashless coal is heated to the softening temperature (usually 300 ° C.) or higher. As a result, the liquefied ashless coal becomes easily compatible with the inferior quality coal, and further, the constituent molecules of the ashless coal and the inferior quality coal are activated, and the interaction between the molecules becomes stronger. The softening start temperature of ashless charcoal is the softening start temperature measured by the Gieseller fluidity test, and the temperature of the ashless charcoal set by heating is preferably higher than the softening start temperature, and 20 times higher than the softening start temperature. A temperature higher by at least ° C is preferred. On the other hand, the upper limit of the temperature of the heated ashless coal is preferably 400 ° C. or lower, and more preferably 380 ° C. or lower. Heating to a temperature exceeding 400 ° C. is not preferable because there is a decrease in the caking property of the raw coal due to the progress of the coking reaction.

  By heating the mixed coal, the raw coal according to the present invention suitable for coke production can be produced. The mechanism by which the raw coal is obtained by heating the mixed coal is as follows. First, the ashless coal melted by heating penetrates into the inferior coal and imparts tackiness to the inferior coal, and second, the ashless coal itself It is presumed that the inferior coal particles are bonded together, and thirdly, volatile components such as aromatic compounds generated from ashless coal heated to the softening temperature or more penetrate into the inferior coal and improve the adhesion of the inferior coal. ing. Actually, the first to third phenomena are considered to proceed simultaneously.

  The heating time above the softening temperature of ashless coal may be within 30 minutes, and may be within 10 minutes, because prolonged heating may cause a reduction in the cohesiveness of the raw coal. In order to produce homogeneous coke-producing raw coal, it is preferable to use a known mixer and kneader equipped with a heating mechanism and heat while continuing mixing of the mixed coal.

(Coke production method)
In coke production, coking coal obtained by the method for producing coking coal for coke production according to the present invention (hereinafter, the coking coal may be referred to as “first coking coal”) and the carbon content (d. a.f.) of 85.0% or more and 91.0% or less, preferably 88.0% or more and 91.0% or less (hereinafter, the coal may be referred to as “second raw coal”). ) And carbonizing this blended coal can produce high-strength coke. In the preparation of the blended coal, it is preferable to use a coal whose carbon content is higher than the inferior coal used in the production of the first raw coal as the second raw coal, and the blended coal has a carbon content (d. a.f.) may contain less than 85.0% of coal, but is preferably composed of only the first raw coal and the second raw coal. In these productions, the first raw coal may be molded and / or pulverized before blending, and the particle size may be adjusted after molding and / or pulverization.

  By making the first raw coal 20% by mass or more in the total amount of blended coal, coke having high strength can be produced. If it is the amount range of this 1st raw coal, coke with especially high intensity | strength is realizable by fine adjustment of the usage-amount of the said raw coal. On the other hand, the upper limit of the first coking coal is not particularly limited, but depending on the coke production conditions, blended coal (various coals used at the time of blending) and the like, if the first coking coal is excessive, the coke strength may decrease. The upper limit of the first raw coal is preferably 50% by mass.

  When the coal blend is dry-distilled, softening / melting, re-solidification, and coking of the coal blend occurs. Conditions for this carbonization are not particularly limited, and normal carbonization conditions using a coke oven can be adopted. The temperature condition is, for example, 950 ° C. or more and 1200 ° C. or less, more preferably 1000 ° C. or more and 1050 ° C. or less, and the dry distillation time is, for example, 8 hours or more and 24 hours or less, more preferably 10 hours or more and 20 hours or less.

  The obtained coke can be used for the production of pig iron as conventionally known. Since the said coke is excellent in intensity | strength, it is used suitably also for pig iron manufacture in a blast furnace. And since the intensity | strength of coke is high, the outstanding air permeability in a blast furnace is realizable. The pig iron production method in the blast furnace may be a known method. For example, iron ore and coke are alternately laminated in layers in the blast furnace, hot air from the bottom of the blast furnace, and if necessary, pulverized coal. Can be mentioned.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. Any of these may be included in the technical scope of the present invention.

(Ashless coal)
A slurry was prepared by mixing 5 kg of bituminous coal (carbon content (daf) 83.2%) and 20 kg of 1-methylnaphthalene (manufactured by Nippon Steel Chemical Co., Ltd.) which is a bicyclic aromatic compound. The slurry was treated under conditions of 1.2 MPa, 370 ° C., and 1 hour in a nitrogen purged autoclave with an internal volume of 30 L, and bituminous coal components were extracted with bicyclic aromatic compounds. The slurry is separated into a supernatant and a solid concentrate in a gravity settling tank at the same temperature and pressure as this extraction, and then the bicyclic aromatic compound is separated and recovered from the supernatant by distillation. What remained was obtained as ashless coal. The ashless coal had a yield of 2.7 kg and an ash content of 900 ppm. Moreover, the softening start temperature by the Guesser fluidity | liquidity test of ashless coal was 305 degreeC, and the maximum fluidity was 4.7 (logddpm).

(Coking coal for coke production)
A coal mixture was prepared by blending ashless coal having a particle size of 0.3 mm or less and any of the coals shown in Table 1 below having a particle size of 1 mm or less (see Table 2 below for the blend ratio of the coal mixture). This mixed charcoal was charged in a mixer having a heating mechanism and mixed, and heated at 350 ° C. for 10 minutes to obtain raw coal for coke production. No. 2 shown in Table 2 below. For 9 and 11, the mixed coal was not heated. No. For 10 and 12, use of ashless coal and heating were omitted.

(Coke)
Coke was obtained by dry-distilling a mixture of Russian strong caking coal (carbon content (daf) 90.6%) and the above-mentioned raw coal for producing coke (mixed coal) as follows. No. shown in Table 2 below. For 10 and 12, ashless coal was also blended in the blended coal preparation.

  The above blended charcoal was filled into a can container having a size of 378 mm width × 121 mm length × 114 mm height. Four of these cans are placed in a steel retort (size: width 380 mm × length 430 mm × height 350 mm), and the retort is placed in a double-sided heating electric furnace that can heat the cans in the width direction. The coal blend was dry-distilled. The dry distillation conditions were 1000 ° C. and 10 hours, and the retort was taken out of the electric furnace and allowed to cool naturally over about 16 hours.

  Four can containers were taken out from the retort after natural cooling, and a 189 mm portion of coke corresponding to half in the width direction was cut out. When performing double-sided heating, the place that hits the middle in the width direction is called a charcoal core, and the calcined coke from the heating surface to the charcoal core is called the head, body, tail from the place close to the heating surface, It is known that a difference in strength occurs due to a difference in heating rate during heating of the head, body, and tail. For this reason, the coke head, body, and tail of the 189mm portion corresponding to half of the width direction are cut into approximately cuboids (one side: approximately 20mm ± 1mm) from each part divided into approximately 60mm and sized. Got coke. The sized coke was washed with distilled water to remove fine coke powder adhering during sizing (at the time of cutting), and dried with a dryer at 150 ° C. ± 2 ° C.

(Coke strength)
The type I strength was measured using the washed and dried coke as a sample for strength measurement. The apparatus used for the I-type strength test is a cylindrical container (length: 720 mm, circular bottom diameter: 132 mm) made of SUS material. In this container, 200 g of a strength measurement sample is placed, and 20 minutes per minute. Impacts from a total of 600 rotational motions were applied to the sample at a rotational speed of 1 time. The rotation of the cylinder was performed such that a rotation axis was provided at a position of 360 mm corresponding to the middle of the cylinder length of 720 mm, and the cylinder was rotated around the rotation axis so that the bottom surface of the cylinder drawn a circle with a diameter of 720 mm. After applying an impact by the specified 600 rotations, a sample was taken out from the cylindrical container, and divided by a 9.5 mm sieve to measure the mass on the sieve. At this time, the mass caught on the sieve was also measured on the sieve and the mass was measured. The type I strength index was calculated as follows.
Type I strength index DI ⁶⁰⁰ _9.5 = 100 × 9.5 mm Mass on sieve (unit: g) / 200 g

  Table 2 below shows the results including coke strength.

From Table 2, the following can be confirmed.
(1) No. From the results of 1 to 6, in the production of raw coal, it is suitable to improve the coke strength that the carbon content of 78.0% or more and less than 88.0% is used as inferior coal.
(2) No. From the results of 2, 9, and 10, in the production of raw coal, it is suitable to improve coke strength by mixing and heating ashless coal and inferior coal. No. The same applies to the results of 3, 11, and 12.
(3) No. From the result of 14-17, in manufacture of raw material coal, it is suitable for coke strength improvement to use inferior quality coal 2.0 mass part or more and 20.0 mass part or less with respect to 1.0 mass part of ashless coal. That.
(4) No. About 8, the mass ratio of the strong caking coal used by coke manufacture was high coke strength, although it was less than 50.

It is a figure for demonstrating an example of the apparatus for manufacturing ashless charcoal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tank 2 Pump 3 Preheater 4 Extraction tank 5 Gravity sedimentation tank 6 Sediment receiver 7 Filter member 8 Filter unit 9 Supernatant receiver 10 Stirrer

Claims (2)

A method for producing coke by carbonizing a blended coal containing two or more types of coal,
The blended charcoal is 20 wt% or more and 55 wt% or less of the first raw coal, and the carbon content (daf) is 8 8 . 0% or more and 91.0% or less of the second coking coal 45% by mass or more ,
The first coking coal is a compounding ratio,
For 1.0 mass part of ashless coal,
A mixed coal comprising 2.0 mass parts or more and 20.0 mass parts or less of inferior coal having a carbon content (daf) of 78.0% or more and less than 88.0% is used as a softening temperature of ashless coal. A method for producing coke, which is a raw coal obtained by heating as described above. The manufacturing method of pig iron using the coke obtained by the manufacturing method of Claim 1 .

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