JP5241105B2 - Coke manufacturing method and pig iron manufacturing method - Google Patents

Description

  The present invention relates to a method for producing coke using raw coal containing a large amount of low-coalizing and low-fluidity coal, and a method for producing pig iron using the production method.

  The blast furnace coke is preferably coke that has a predetermined strength and can ensure gas permeability during operation in the blast furnace. For producing such blast furnace coke, high-grade coal such as strongly caking coal is used, but the high-grade coal is gradually depleted. On the other hand, there are a large amount of low-grade coals such as weakly caking coal and non-caking coal.

  For this reason, various techniques for obtaining high-strength coke while reducing the amount of use of high-grade coal by blending low-grade coal with high-grade coal have been studied. For example, a method for reforming low-grade coal Are disclosed (Patent Documents 1 to 5, Non-Patent Document 1).

  In Patent Documents 1 and 2, a coal reformed product obtained by mixing pulverized coal and a solvent and heating in a hydrogen atmosphere at normal pressure or under pressure may be treated to volatilize 60 to 25%. It has been disclosed that a caking filler having a content and having a caking strength index of 90% or more is blended with weak caking coal or non-caking coal. In Patent Documents 3 and 4, brown coal or the like is mixed with a hydrogen-donating solvent to form a slurry, which is hydrogenated and liquefied using a catalyst at high temperature and high pressure, and finally refined SRC (solvent refined coal ) Is extracted and used as coking coal.

In recent years, there has been a demand for a method for producing high-strength coke while further increasing the blending ratio of low-grade coal to high-grade coal. Patent Document 5 discloses a method for producing blast furnace coke in which a heavy fraction in tar is added to and mixed with raw coal containing 0 to 60 wt% of non-slightly caking coal, followed by dry distillation.
Japanese Patent Laid-Open No. 51-107301 JP 51-107302 A JP-A-7-53965 JP-A-8-269459 JP-A-9-241653 Toru Nishi et al., “About using SRC as a raw material for coke”, Proceedings of the 72nd Coke Special Meeting, p. 46-p. 49 (1982)

  The present invention has been made in view of the above circumstances, and obtains high-strength coke while reducing the amount of valuable high-grade coal used as a coke production raw material and increasing the amount of inexpensive low-grade coal used. The purpose is to provide technology.

  The method for producing coke according to the present invention is a method for producing coke by dry distillation of raw coal, and in 100% by mass of the raw coal, high coal degree coal is 16% by mass or more, low coal degree and low fluidity. It contains at least 25% by mass of charcoal and coal containing substantially no ash (hereinafter sometimes referred to as “ashless charcoal”).

  In the present invention, if raw coal containing ashless coal is used, a large amount of low coal low flow coal is present in the raw coal (100% by mass of raw coal is low coal low fluid coal. Even if it is contained in an amount of 25% by mass or more, high strength coke can be obtained.

  Here, as a classification method of coal, focusing on its caking property, when classifying into anthracite, strong caking coal, caking coal, weak caking coal, non-caking coal, lignite, peat, etc. There are methods such as classification based on the degree of coalification and fluidity. Of the raw coal used in the method for producing coke of the present invention, blended coal excluding ashless coal is classified using the degree of coalification and fluidity (the ashless coal will be described later). In the present specification, high-coalized coal refers to coal having an average maximum reflectance ≧ 1.1. The low-coalizing and low-flowing coal refers to coal having an average maximum reflectance <1.1 and a Gieseler maximum fluidity (hereinafter sometimes referred to as “logMFD”) <2.5. In addition, the low coalification high fluidity coal mentioned later refers to coal of average maximum reflectivity <1.1 and logMFD ≧ 2.5.

  In this specification, the average maximum reflectance is the average maximum reflectance of vinylit measured by the method for measuring the reflectance of coal structure described in JIS M8816. The Gieseeller maximum fluidity (logMFD) is an index measured by the Gieseler plastometer method defined in JIS M8801.

  In the method for producing coke of the present invention, the coal substantially free of ash is extracted from coal having a carbon content (daf) of 60% or more and less than 95% using an organic solvent. It is preferable to use a soluble component obtained in this way.

  Carbon content (daf = dry ash free) refers to the carbon content (mass%) of organic matter (C, H, O, S, N) excluding coal moisture and ash, It can be measured according to JIS M8819.

  As the organic solvent, for example, an organic solvent mainly containing a bicyclic aromatic compound is preferably used.

  In the method for producing coke according to the present invention, it is preferable that the coal containing substantially no ash is contained in an amount of 1% by mass or more and less than 10% by mass in 100% by mass of the raw coal.

  In the method for producing coke of the present invention, it is preferable that the raw coal of the present invention further contains a low-coalification and high-fluidity coal.

  The present invention includes a method for producing pig iron using coke obtained by the above-described method for producing coke.

  According to the present invention, in coking coal including a high-grade high-coalizing coal that is a coke production raw material or a low-grade low-coalizing low-flowing coal, etc., Even if the blending ratio was increased, high strength coke was obtained by containing coal containing substantially no ash in the raw coal. For this reason, the method for producing coke of the present invention is in a situation where high grade high-coalification coal is depleted while low-grade low-coalification low-flow coal is available in large quantities, and the coke production raw material soars. Even in this case, it is possible to suppress an increase in coke production costs.

  Moreover, the obtained coke can be utilized suitably for manufacture of pig iron in a blast furnace.

(Coke production method)
The method for producing coke according to the present invention is a method for producing coke by dry distillation of raw coal, and in 100% by mass of the raw coal, high coal degree coal is 16% by mass or more, low coal degree and low fluidity. It contains at least 25% by mass of charcoal and at least coal containing substantially no ash. Hereinafter, the manufacturing method of the coke of this invention is demonstrated in detail.

  In order to reduce the production cost of coke, the highly coalized coal used in the present invention is blended in the raw coal to such an extent that the strength of the obtained coke can be kept high while keeping the amount used as low as possible. There is a need. For this reason, it is preferable that the mixture ratio of highly coalified degree coal is 16 mass% or more in 100 mass% of raw coal, and it is more preferable that it is 20 mass% or more. When the blending ratio of the high-rank coal used in the present invention is less than 16% by mass, the amount of high-grade coal used can be kept low, but the strength of the resulting coke may not be maintained high. In addition, although the upper limit of the blending ratio of highly coalified degree coal is not specifically limited, In order to prevent the increase in the manufacturing cost of coke, it is preferable to set it as 45 mass% or less.

  The low-coalification and low-flow coal used in the present invention is blended in a large amount in the raw coal, thereby reducing the amount of high-grade coal used and reducing the production cost of coke, while increasing the strength of the obtained coke. Need to be maintained. For this reason, the blending ratio of the low coal content low flow coal is preferably 25% by mass or more, more preferably 30% by mass or more, and 40% by mass or more in 100% by mass of the raw coal. More preferably, it is more preferable that it is 50 mass% or more, and it is especially preferable that it is 60 mass% or more. When the blending ratio of the low-coalizing and low-flowing coal is less than 25% by mass, high-strength coke can be obtained, but the blending ratio of the high-grade coal contained in the raw coal increases. The manufacturing cost cannot be effectively suppressed. The upper limit of the blending ratio of the low coalification low flowable coal is not particularly limited, but is preferably 65% by mass in order to maintain the strength of the obtained coke sufficiently high.

  As the ashless coal used in the present invention, a soluble component obtained by extraction from coal with an organic solvent is used. Here, as coal used as a starting material in order to manufacture ashless coal, if a soluble component can be obtained when extracted with an organic solvent, its carbon content (daf) .) Is not particularly limited, but the carbon content (daf) is preferably 60% or more and less than 95% (more preferably 60% or more and less than 85%). More specifically, as coal extracted with an organic solvent, the carbon content (daf) is 70% or more and less than 83% weakly caking coal, non-caking coal, and lignite, or these It is preferable to use a mixture of If ashless coal is obtained using coal having such a carbon content (daf) as a starting material, the production of coke is not affected by the problem of depletion of high-grade coal.

  The coal having a carbon content (daf) of 60% or more and less than 95% used as a starting material for producing ashless coal preferably has, for example, the following characteristics. That is, the volatile content is preferably 30% or more, more preferably 32% or more, preferably 40% or less, more preferably 36% or less. The average maximum reflectance is preferably 0.6 or more, more preferably 0.8 or more, preferably 1.0 or less, more preferably 0.9 or less. The total inert is preferably 5% or more, more preferably 15% or more, preferably 35% or less, more preferably 20% or less.

  In the present specification, the volatile content can be determined by a method defined in JIS M8812. Further, the total inert (TI) is calculated by the following formula using the ratio of semi-fujinite and the ratio of the microstructure component group (maceral group) in the analysis value of the coal microstructure component (maceral) of JIS M8816. be able to.

  In the formula, MM (mineral matter) means a mineral, A means ash (anhydrous base, measured by JIS M8812), and S means a total sulfur content (anhydrous base, measured by JIS M8813).

  As the organic solvent used for extracting ashless coal from coal, a solvent having high coal dissolving power is preferable, and specifically, an organic solvent mainly composed of a bicyclic aromatic compound approximate to a coal structural unit is used. preferable. Among organic solvents mainly composed of a bicyclic aromatic compound, organic solvents having a boiling point of 180 ° C. or higher and 330 ° C. or lower are preferable. When the boiling point is lower than 180 ° C., the recovery rate of the organic solvent evaporated and removed from the supernatant liquid (described later) obtained when extracting ashless coal from the coal using the organic solvent may decrease. On the other hand, when the boiling point exceeds 330 ° C., it is difficult to separate the coal and the organic solvent, and the recovery rate of the organic solvent may be lowered.

  Specific examples of the bicyclic aromatic compound used in the present invention include, for example, naphthalene (boiling point: 218 ° C); methylnaphthalene (boiling point: 241 to 242 ° C), dimethylnaphthalene (boiling point: 261 to 272 ° C), trimethylnaphthalene, and the like. And biphenyls having aliphatic side chains or aromatic substituents, or mixtures thereof.

  The method for producing ashless coal used in the present invention is not particularly limited. For example, the carbon content (daf) is 60% or more and less than 95% (more preferably 60% or more). (Less than 85%) coal and an organic solvent are mixed to prepare a slurry, the slurry is heated and aged to extract soluble components in the organic solvent, and then the slurry is concentrated with solid phase components concentrated The liquid is separated into a supernatant and a supernatant, and then the supernatant is filtered, and finally the organic solvent is removed by evaporation from the supernatant to obtain ashless coal.

  In addition, the ashless coal used by this invention does not need to be manufactured by heating coal at high temperature under high-pressure hydrogen, and performing hydrocracking.

  FIG. 1 is an explanatory view illustrating an apparatus and a process for producing ashless coal. In the tank 1, coal having a carbon content (daf) of 60% or more and less than 95% is mixed with an organic solvent to produce a slurry. The obtained slurry is supplied to an extraction tank 4 where an extraction process is performed by a pump 2. At that time, the slurry is heated to a predetermined temperature by the preheater 3. In the extraction tank 4, after the soluble component is extracted into the organic solvent while stirring the slurry with the stirrer 10, the obtained slurry is supplied to the gravity settling tank 5. In the gravity settling tank 5, gravity settling is performed to settle the solid phase component (arrow 11), and the slurry is separated into a liquid in which the solid phase component is concentrated and a supernatant liquid. The obtained supernatant is supplied to the filter unit 8, and the solid phase component concentrate settled in the gravity sedimentation tank 5 is collected in the solid phase component concentrate receiver 6. The supernatant liquid is filtered by the filter member 7 of the filter unit 8, and the obtained filtrate is recovered in a supernatant liquid receiver 9 that recovers the supernatant liquid. Next, ashless coal used in the present invention can be obtained by evaporating and removing the organic solvent from the collected supernatant. As a method for evaporating and removing the organic solvent from the supernatant, a general drying method such as a spray drying method, a distillation method, or a vacuum drying method can be applied.

  The coal concentration in the slurry in the step of producing the ashless coal used in the present invention is suitably 10% by mass or more and 35% by mass or less. Moreover, when extracting a soluble component in an organic solvent by heating and aging the slurry to solubilize the soluble component in coal, for example, the slurry is heated at 300 ° C. or higher and 420 ° C. or lower for 5 minutes or longer and 120 minutes. It is preferable to keep the minute or less. If the temperature condition for extraction is 300 ° C. or higher and 420 ° C. or lower, the bonds between the molecules constituting the coal are loosened to cause mild thermal decomposition, and the proportion of soluble components extracted from the coal increases. At this time, the mild pyrolysis of coal produces an aromatic-rich component mainly having an average boiling point (Tb50: 50% distillation temperature) of 200 to 300 ° C., which is effectively used as a part of the organic solvent. it can.

  In addition, when the temperature conditions of extraction are lower than 300 degreeC, weakening the coupling | bonding between the molecules which comprise coal will become inadequate, and the ratio of the soluble component which can be extracted from coal will fall. Moreover, when the temperature condition of extraction is higher than 420 ° C., the pyrolysis reaction of coal becomes active, and recombination of generated pyrolysis radicals occurs, so that the ratio of soluble components to be extracted also decreases.

  The temperature at which the obtained slurry is separated into a supernatant and a solid phase component concentrate by gravity sedimentation is preferably 300 ° C. or higher and 420 ° C. or lower. If it is less than 300 degreeC, a part of component which melt | dissolves in a liquid phase component may precipitate, and the yield of ashless coal may fall.

  The ashless coal used in the present invention is preferably coal containing no ash, but may be coal containing substantially no ash, and therefore may contain a small amount of ash. The content of ash contained in the ashless coal is preferably 5,000 ppm or less, more preferably 2,000 ppm or less, and even more preferably 1,000 ppm or less. In addition, ash is a residual inorganic substance when coal is ashed by heating at 815 ° C., and includes, for example, silicic acid, alumina, iron oxide, lime, magnesia, alkali metal, and the like.

  The ashless coal used in the present invention preferably has a Gieseler maximum fluidity (logMFD) of 4.5 (logddpm) or more, and more preferably 4.7 (logddpm) or more. Further, the total expansion rate is preferably 200% or more, and more preferably 250% or more. In this specification, the total expansion coefficient is a value measured according to the dilatometer method defined in JIS M8801.

  The blending ratio of ashless coal used in the present invention is not particularly limited as long as high-strength coke can be obtained even if the blending ratio of the low coalification low flowable coal in the raw coal is increased. However, 1 mass% or more is preferable in 100 mass% of raw coal, 3 mass% or more is more preferable, 5 mass% or more is more preferable, and less than 10 mass% is preferable. If the blending ratio of ashless coal is less than 1% by mass, high strength coke cannot be obtained. Moreover, when the mixture ratio of ashless coal is 10 mass% or more, the strength of the obtained coke tends to decrease.

  It is preferable that the raw coal used in the present invention further contains a low coalification high fluidity coal. This facilitates the production of high strength coke.

  The blending ratio of the low coalification high fluidity coal used in the present invention is 100 in total with the blending ratio of other blending coals (high coalization degree coal, low coalization degree low fluidity coal, ashless coal, etc.). If it is in the range which does not exceed mass%, it will not specifically limit. In addition, it is preferable to mix | blend a low coalification high fluidity coal so that raw coal may have the following characteristics. In other words, the Gieseler maximum fluidity (logMFD) of the raw coal is preferably 1.9 (logddpm) or more, more preferably 2.0 (logddpm) or more. The total expansion rate of the raw coal is preferably 75% or less. Coke having sufficient strength can be obtained by adjusting the maximum fluidity of the coking coal and the total expansion rate within an appropriate range.

  In this specification, the maximum flow rate and total expansion rate of coking coal are determined by the Gieseler plastometer method and dilatometer method specified in JIS M8801, and each blended coal contained in the coking coal (high coal conversion). This is a weighted average of measured values of low-coal, low-coalizing high-flowing coal, weakly caking coal, and ashless coal.

  The method for producing coke according to the present invention is characterized in that the above-mentioned raw coal is carbonized. In the present invention, the conditions for dry distillation are not particularly limited, and normal dry distillation conditions in coke production using a coke oven can be employed. For example, the temperature is preferably 950 ° C. or higher, more preferably 1000 ° C. or higher, preferably 1200 ° C. or lower, more preferably 1050 ° C. or lower, preferably 8 hours or longer, more preferably 10 hours or longer, preferably 24 It is carried out by dry distillation for a time or less, more preferably 20 hours or less.

(Manufacturing method of pig iron)
The present invention includes a pig iron manufacturing method characterized by using coke obtained by the coke manufacturing method of the present invention. The coke obtained by the method for producing coke of the present invention is excellent in strength, and can be suitably used for producing pig iron in a blast furnace. That is, if coke obtained by the production method of the present invention is used, gas permeability at the time of pig iron production in a blast furnace is improved. A known method may be used for producing pig iron in the blast furnace.For example, iron ore and coke are alternately laminated in a blast furnace in layers, and hot air from the bottom of the blast furnace, and if necessary, pulverized coal. The method of blowing is mentioned.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples, and all modifications and embodiments within the scope of the present invention do not depart from the spirit of the present invention. Included in the scope.

<Preparation of ashless coal>
As ashless coal to be added to the raw coal, a soluble component (ash content 600 ppm) extracted from Australian caking coal (carbon content (daf) 84%) using 1-methylnaphthalene was used. . In addition, the ashless coal was prepared by the following method using the apparatus of FIG.

  Australian caking coal (carbon content (daf) 84%) and 1-methylnaphthalene were mixed in tank 1 (Australian caking coal: 1-methyltaphthalene = 20% by mass: 80 mass%) slurry was prepared. The obtained slurry was heated to 370 ° C. by the preheater 3, and soluble components were extracted from the caking coal produced in Australia in the extraction tank 4. The slurry after the extraction treatment is supplied to the gravity sedimentation tank 5 at a flow rate of 15 kg / h, gravity sedimentation is performed, and the supernatant liquid and the solid phase component concentrate are separated. The supernatant liquid is filtered at a flow rate of 3 kg / h. The solid component concentrate was discharged from the bottom of the gravity sedimentation tank 5 to the solid component concentrate receiver 6 at a flow rate of 12 kg / h. The supernatant liquid was filtered by the filter unit 8 and then collected in the supernatant liquid receiver 9, and the organic solvent was removed by evaporation from the collected liquid by spray drying to obtain ashless charcoal (ash content: 600 ppm).

<Preparation of raw coal>
Using the obtained ashless coal, raw coal was prepared at a blending ratio shown in Table 1. Table 1 shows the Gieseler maximum fluidity (LogMFD) and the total expansion rate of the prepared raw coal.
(Examples 1-2, Comparative Examples 1-5)

<Manufacture of coke>
The prepared raw coal was filled into a can container having a width of 378 mm, a length of 121 mm, and a height of 114 mm so as to have a density of 720 kg / m ³ . 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 coking coal was carbonized. The dry distillation was performed at 1000 ° C. for 10 hours, and then 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 cooled retort, and a 189 mm portion of coke corresponding to half in the width direction was cut out. When double-sided heating is performed, the location that hits the center in the width direction is called the charcoal core, and the coke that is fired from the heating surface to the charcoal core is called the head, body, and tail from the location near the heating surface. It is known that a difference in strength occurs due to a difference in heating rate during heating of the 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. The sized coke after drying was blended according to the weight ratio of the head, body, and tail so that the total was 200 g, and used as a sample for strength measurement.

<Coke strength measurement>
Using the obtained strength measurement sample, the I-type strength was measured. As a device used for the type I strength test, a cylindrical container made of SUS material (length: 720 mm, circular bottom diameter: 132 mm) is used, and 200 g of the sample is put in this container, and rotated 20 times per minute. It was rotated at a speed for 30 minutes, and an impact due to a total of 600 rotational motions was applied. 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 intensity index (IDI) was calculated as follows, and the calculated results are shown in Table 1.
Type I strength index (IDI) = 100 × 9.5 mm Mass on sieve (unit: g) / 200 g

  In general, the rotational strength of coke is classified into one that evaluates volume fracture in which a coke lump is broken as a large lump and one that evaluates surface breakage due to surface wear, but is the type I used in the present invention. Intensity index (IDI) is interpreted as an index used to assess surface fracture.

  In the present invention, the strength of the obtained coke is preferably IDI of 80.5 or more.

  From the results of Table 1, ashless coal is added even for raw coal (Examples 1 and 2) in which the blending of high-coalizing coal is suppressed and the blending ratio of low-coalizing and low-flowing coal is increased. As a result, it was found that the maximum fluidity (LogMFD) and the total expansion coefficient showed appropriate values, and coke having sufficient strength (IDI of 80.5 or more) was obtained.

  In addition, the raw coal (Comparative Examples 1 and 2) in which the coalification degree coal, the low coality degree high fluidity coal, and the low coality degree low fluidity coal are blended in a balanced manner has an appropriate maximum fluidity (LogMFD, 1.9 logddpm or more) and a total expansion rate (75% or less), it can be seen that coke having a sufficient strength can be obtained without the addition of ashless coal.

  On the other hand, the maximum fluidity (LogMFD) is reduced in the raw coal (Comparative Example 3) to which ashless coal is not added while increasing the blending ratio of inexpensive low-coalizing low-fluidity coal. As a result, it was found that the strength of the obtained coke is greatly reduced.

  Moreover, in the raw coal which suppresses the blending of the high-coalizing coal and increases the blending ratio of the low-coalizing and low-flowing coal, the blending ratio of the ashless coal is too large as 10% by mass (Comparative Example 4). It has been found that the strength of the resulting coke decreases as the overall expansion rate increases.

  Furthermore, even if the blending ratio of ashless coal falls within an appropriate range, when the blending ratio of the high coal degree coal is low (Comparative Example 5), the total expansion rate becomes high, and the strength of the obtained coke. Was found to decrease.

  The present invention can be suitably applied to the production of coke and further to the production of pig iron in a blast furnace.

It is explanatory drawing which illustrates the apparatus and process which manufacture ashless coal used by this invention.

Explanation of symbols

1: tank, 2: pump, 3: preheater, 4: extraction tank, 5: gravity sedimentation tank, 6: solid phase component concentrate receiver, 7: filter member, 8: filter unit, 9: supernatant receiver 10: Stirrer, 13: Stirrer

Claims (4)

A method of producing coke by dry distillation of raw coal, in 100% by mass of the raw coal,
16% to 45% by mass of high-carbonized coal,
40 % by mass or more of low coal content low flowable coal,
Containing at least 1% by mass and less than 10% by mass of coal substantially free of ash,
As the coal substantially free of ash, a soluble component obtained by extracting from a coal having a carbon content (daf) of 60% or more and less than 95% using an organic solvent is used. Coke production method.   The method for producing coke according to claim 1, wherein an organic solvent containing a bicyclic aromatic compound as a main component is used as the organic solvent. The method for producing coke according to claim 1 or 2 , wherein the raw coal further contains low-coalification and high-fluidity coal. A method for producing pig iron, wherein coke obtained by the method for producing coke according to any one of claims 1 to 3 is used.

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