JP2016079387A - Method of producing blast furnace coke - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing blast furnace coke, in which a pellet is produced, the strength of whose pellet is not decreased even when the amount of a binder to be added, which binder is added when the pellet is produced, is made less than 18 mass% or more than 27 mass% and the blast furnace coke is produced by using the produced pellet.SOLUTION: A method of producing blast furnace coke comprises the steps of: adding a liquid bituminous material to fine-grained coal having 0.6 mm or smaller particle diameter so that the total of the content of the liquid bituminous material and that (including 0 mass%) of the surface water of the fine-grained coal becomes 7-40 mass% of the mass of the fine-grained coal as an outer number; adding superfine powder coal, which has the particle diameter equal to or smaller than 0.2 times of the average particle diameter of the fine-grained coal, to the liquid bituminous material-added fine-grained coal to obtain a mixture; pelletizing the mixture to obtain the pellet; blending the pellet with coarse-grained coal having the particle diameter larger than 0.6 mm to obtain a mixture; and charging the mixture into a coke oven to carbonize the mixture.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing blast furnace coke, and more particularly, to a method for producing blast furnace coke using granulated coal.

  In blast furnace operation, massive iron ore, powdered iron ore or agglomerates of iron dust are efficiently reduced by heating to produce pig iron and generate CO reducing gas and ensure the ventilation of the reducing gas. Coke is charged into the blast furnace as a spacer for this purpose.

  In order for the blast furnace coke to be fully effective as a spacer in the blast furnace, it has sufficient strength not to collapse due to impact during loading into the blast furnace or load loading of the charge in the blast furnace. Required. On the other hand, since high-quality strong caking coal as a raw material for coke is in a depleted state in terms of resources, many methods have been proposed for producing coke having the required strength using non-fine caking coal. .

  Technology to increase the charging density of the charging coal into the coke oven and technology to add a binder such as tar to the charging coal as a technology to produce coke with the necessary strength using non-slightly caking coal It has been known. As a combination of the two techniques, there is a forming coal blending method using a forming coal formed by adding a binder. However, in the method of blending coal, when a liquid binder such as tar is added in an amount of more than 10%, the strength of the produced coal is reduced, and molding becomes difficult due to deterioration of moldability. Therefore, it has been difficult to significantly increase the addition ratio of the liquid binder and improve the coke strength.

  Therefore, Patent Document 1 discloses a coke production technique that simultaneously achieves a high charging density and a large amount of binder addition.

  In Patent Document 1, 18 to 27 mass% of binder (water, liquid bituminous binder) is added to coal having a particle size of 0.6 mm or less, and granulated to produce pellets having a particle size of 8 to 50 mm. Then, the pellets are mixed with coarse coal having a particle size of more than 0.6 mm in an amount of 30% by mass or less, charged into a coke oven, and dry-distilled to produce coke. A technology that can produce high-quality blast furnace coke even if a large amount of caking coal is blended is disclosed.

  Since the coke strength is improved by the addition of the binder, a large amount of inexpensive non-coking coal can be used by increasing the addition of the binder under the same coke strength premise. However, since the binder is expensive, it is preferable that the addition amount of the binder can be freely changed according to the price of the inexpensive non-caking coal and the binder.

  The amount of the binder added is described in Patent Document 1 as follows. If the addition amount of the binder is less than the lower limit of 18% by mass, the amount of the binder that binds the coal particles is insufficient, making granulation difficult and maintaining the strength of the pellets. On the other hand, if the added amount of the binder exceeds the upper limit of 27% by mass, the added binder becomes excessive and the pellet is softened, the strength cannot be maintained, and the excess binder adheres to the pellet surface. It is said that the strength at which the sticking occurs cannot be maintained.

  That is, in the technique disclosed in Patent Document 1, the amount of binder added can be changed within the range of 18 to 27% by mass, but the amount of binder added in a wider range (less than 18% by mass or more than 27% by mass). Is difficult because the strength of the pellet cannot be maintained. However, when using non-slightly caking coal in the production of coke, depending on the price of non-slightly caking coal and binder, addition of binder while maintaining the strength of pellets in a wider range. It was desired to be able to change the amount.

  Furthermore, since pellets may be destroyed by impact in the process of conveyance to a coke oven, etc., it is required to produce strong pellets with a smaller additive amount or a larger additive amount. It was.

JP 2002-327181 A

  In view of the current state of the prior art described above, the present invention provides a pellet whose strength does not decrease even when the amount of binder added in the production of the pellet is less than 18% by mass or more than 27% by mass, and the pellet is used. An object is to provide a method for producing coke.

  Therefore, the present inventors diligently studied a method for solving the above problems. As a result, in addition to adding liquid bitumen, which is a liquid binder, to coal, adding ultrafine coal and granulating it has been found that the function of the binder can be dramatically increased and strong pellets can be obtained. did.

The present invention has been made based on the above findings, and the gist thereof is as follows.
(1) The total content of liquid bituminous matter and the surface moisture content (including 0% by mass) of fine bitumen in fine-grained coal having a particle size of 0.6 mm or less is smaller than the fine-grained coal. The liquid bitumen is added so that the external number becomes 7 to 40% by mass, and further, ultrafine coal having a particle size of 0.2 times or less the average particle size of the fine coal is added. A method for producing coke for a blast furnace, comprising blending the granulated pellets and coarse coal having a particle diameter of greater than 0.6 mm, charging the coke oven, and dry-distilling.
(2) The method for producing coke for blast furnace according to (1), wherein the ultrafine coal is added in an external number of 1 to 10% by mass with respect to the fine-grained coal.
(3) The total Y (mass%) of the liquid bitumen content and the surface moisture content (including 0 mass%) of the fine-grained coal and the ultrafine coal content X (mass%) are The method for producing coke for blast furnace according to (1) or (2), wherein the liquid bitumen and the ultrafine coal are added so as to satisfy the following formula (1).
(−6/4) × (X−1) + 13 ≦ Y ≦ (10/9) × (X−1) +30 (1)

  According to the present invention, it is possible to produce strong pellets even if the amount of binder added to the pellets for producing coke is wide, and even if a large amount of cheap non-caking coal is blended, it is good quality. Blast furnace coke can be produced.

It is a figure which shows the flow which mixes the pellet produced by adding ultrafine coal and coarse coal, and produces coke by dry distillation. It is a figure which shows the relationship between the content rate of a liquid binder, and the content rate of an ultrafine coal.

  Hereinafter, the method for producing coke for blast furnace of the present invention (hereinafter referred to as the production method of the present invention) will be described. In the following, the total content (mass%) of the surface moisture of the liquid bitumen and fine coal with respect to the fine-grained coal, and the content (mass%) of the ultrafine coal with respect to the fine-grained coal are as follows. Show.

  In the production of pellets for coke production (sometimes referred to as a granulated product), the present inventors have set a wide range (less than 18% by mass) of the amount of liquid binder (liquid bitumen and coal surface moisture) contained in coal. (Or more than 27% by mass), a method for producing strong pellets was studied.

  When the amount of the liquid binder is small relative to the coal, the crosslinking force between the coal particles to be granulated is weakened, making granulation difficult, and the pellet strength cannot be maintained. It was thought to increase the cross-linking power between the two.

  In addition, when the amount of liquid binder relative to coal is large, pellets are softened by excess liquid binder, the strength can not be maintained, and furthermore, the strength due to sticking of the pellets cannot be maintained by excess liquid binder, Considering adsorption or absorption of excess liquid binder.

  Then, when the means for that was investigated, the present inventors conceived adding ultra-fine coal in addition to a liquid binder to coal. That is, when the amount of the liquid binder is small, the finely pulverized coal fills the voids of the pellets, and the coal particles to be granulated are bonded by solid crosslinking force. When the amount of the liquid binder is large, the very finely pulverized coal However, it was thought that due to the large specific surface area of the ultrafine coal, a part of the liquid binder was adsorbed or absorbed, and excess liquid binder did not ooze out on the surface of the pellets.

  And the test which adds superfine coal in addition to a liquid binder to fine-grained coal was done. First, when the amount of the liquid binder is small, tar is added as a liquid binder so as to be 17.4% by mass with respect to fine-grained coal having a particle size of 0.6 mm or less, and further, the particle size is 0.06 mm. Test pellets 1 were prepared by adding 3% by mass of the following ultrafine coal, kneading and granulating. For comparison, tar was added as a liquid binder so as to be 17.4% by mass with respect to fine-grained coal, and kneaded and granulated to prepare test pellets 2.

  Next, assuming that the amount of the liquid binder is large, tar is added as a liquid binder so as to be 27.6% by mass with respect to fine coal having a particle size of 0.6 mm or less. Test pellets 3 were prepared by adding 1% by mass of ultrafine coal of 06 mm or less, kneading and granulating. For comparison, tar was added as a liquid binder to a fine coal having a particle size of 0.6 mm or less so as to be 27.6% by mass, kneaded and granulated to prepare a test pellet 4.

  As a result of this test, the test pellet 1 and the test pellet 3 became strong pellets and could be granulated with good granulation properties. On the other hand, the test pellet 2 and the test pellet 4 were not pelletized and could not be granulated. From this, the knowledge that pellets could be obtained with good granulation properties by adding ultrafine coal to the fine coal in addition to the liquid binder was obtained.

  And it tested about the addition amount of the liquid binder which can obtain a pellet with sufficient granulation property by adding ultrafine coal. This test is a test similar to the above, and for fine coal having a particle size of 0.6 mm or less, various addition amounts of tar are added as a liquid binder, and further, ultrafine coal is added, Test pellets were prepared by kneading and granulating.

  As a result of this test, it was found that when the addition amount of the liquid binder is 7 to 40% by mass, it is possible to obtain strong pellets with good granulation properties by adding ultrafine coal.

  The production method of the present invention has reached the invention described in the above (1) to (2) through the examination process as described above, and further describes necessary and preferable requirements for such the present invention. To do.

  The production method of the present invention increases the charging density and adds a large amount of non-slightly caking coal by blending pellets obtained by adding a liquid binder to fine-grained coal disclosed in Patent Document 1 into coarse-grained coal. In the technology that can be used for the above, a strong pellet can be produced even when the addition amount of the liquid binder is in a wide range by adding ultrafine coal when granulating the pellet. In the production of pellets, fine coal used for granulation, liquid binder to be added, ultrafine coal to be added, and the like are as follows.

(Coarse coal: particle size greater than 0.6 mm)
The coarse coal with which the pellets are blended is assumed to have a particle size of more than 0.6 mm. Coarse coal having a particle size of more than 0.6 mm is difficult to be taken into pellets, but can be used as a raw material for coke production as it is.

(Fine-grain coal: particle size 0.6mm or less)
Fine-grained coal that is granulated into pellets has a particle size of 0.6 mm or less. This is because coal particles having a particle size of more than 0.6 mm are difficult to be taken into the pellets. Moreover, it is ideal that the maximum particle size is 0.6 mm that the particle size is 0.6 mm or less. However, with an actual classifier, even if the classification point is set to 0.6 mm, particles having a particle size larger than 0.6 mm are mixed slightly, so the particle size of 0.6 mm or less in the present invention is the particle size. It shows that coal of 0.6 mm or less is 90% or more.

(Liquid binder: 7 to 40% by mass)
The liquid binder added at the time of pellet preparation contains a liquid bitumen. Liquid bitumen is coal-based binders such as coal tar, petroleum-based binders such as asphalt, and other bituminous binders. Further, the surface moisture of the fine-grained coal has a function of binding the coal particles and has a function as a binder, so that it is included in the addition amount of the liquid binder. Therefore, the sum of the surface moisture of the fine-grained coal and the liquid bitumen is used as a liquid binder, and the total amount is 7 to 40% by mass with respect to the fine-grained coal. When the surface moisture of coal is 0 mass%, a liquid bitumen is added so that it may become 7-40 mass% with respect to fine-grained coal.

  In addition, the surface moisture% of coal is calculated by subtracting the embraced moisture% of JIS-M8803 from the total moisture% of JIS-M8811. Ordinary coal handled at steelworks has a moisture content of around 2%.

  If the content of the liquid binder is less than 7% by mass with respect to the fine-grained coal, it becomes difficult to form pellets even if ultrafine coal is added. Moreover, if the content of the liquid binder exceeds 40% by mass with respect to the fine-grained coal, the binder is excessive and the pellet strength cannot be maintained.

(Particle size of ultrafine coal: 0.2 times or less the average particle size of fine coal)
When the particle size of the ultrafine coal to be added at the time of pellet production is more than 0.2 times the average particle size of the fine coal to be granulated, the coal particles to be granulated have solid cross-linking forces. The ability to bind and the ability to adsorb or absorb excess liquid binder is reduced. Therefore, the particle size of the ultrafine coal is 0.2 times or less the average particle size of the fine coal to be granulated. Moreover, when granulating fine coal having a particle size of 0.6 mm or less (for example, assuming an average particle size of 0.3 mm), ultrafine coal of 0.06 mm (0.3 mm × 0.2) or less is exemplified. The

(Content of ultrafine coal: 1-10% by mass with respect to fine-grained coal)
When the content of ultrafine coal added when making pellets is less than 1% by mass with respect to fine-grained coal, coal particles to be granulated are bonded together by a solid crosslinking force, and an excess liquid binder is adsorbed. Or the effect to absorb may not fully be exhibited. Moreover, when it is more than 10 mass%, it becomes an excessive quantity with respect to the space | gap of particle | grains, and the ultra fine coal which is not granulated may generate | occur | produce. Therefore, the content of ultrafine coal is preferably 1 to 10% by mass with respect to fine-grained coal.

(Relationship between liquid binder content and ultrafine coal content)
As shown in the examples described later, when a pellet was prepared in a combination of a liquid binder having various contents and ultrafine coal, the content Y (% by mass) of the liquid binder and the ultrafine coal It has been found that it is preferable to add liquid bitumen and ultrafine coal so that the content X (mass%) satisfies the following formula (1).
(−6/4) × (X−1) + 13 ≦ Y ≦ (10/9) × (X−1) +30 (1)

  In FIG. 2, the relationship between the content rate of a liquid binder and the content rate of pulverized coal is shown. The line A shown in FIG. 2 is Y = (− 6/4) × (X−1) +13, and the line B is Y = (10/9) × (X−1) +30. When the content X (mass%) of the ultrafine coal is a variable and the content Y (mass%) of the liquid binder is greater than or equal to the left side of the formula (1), it is difficult to generate dust during pellet transportation ( (Hereinafter referred to as “non-dusting”), and if it is less than the right side of the formula (1), it is difficult to adhere to the chute of the conveyor belt or the conveyor connecting portion when pellets are conveyed ( (Hereinafter referred to as “non-adhesiveness”) can be further improved.

(Pellet particle size: 8-50 mm)
The pellets to be granulated may have reduced strength when the particle size exceeds 50 mm, and when the particle size is less than 8 mm, the bulk density when mixed with coarse coal having a particle size exceeding 0.6 mm. May decrease. Therefore, it is preferable to granulate the pellet in the range of 8 to 50 mm in particle size.

(Non-slightly caking coal content: 65% by mass or less)
If the blending ratio of non-finely caking coal in the coal charged into the blast furnace is more than 65% by mass, the coke strength may be lowered. Therefore, it is preferable to make the compounding ratio of the non-slightly caking coal in the coal charged into the blast furnace be 65% by mass or less. Moreover, a non-fine caking coal can be contained in 1 or 2 or more of fine-grained coal, coarse-grained coal, and ultra-fine coal.

Next, the flow for implementing the manufacturing method of this invention is demonstrated concretely using a flowchart.
(Coke production flow)
FIG. 1 shows a flow in which pellets prepared by adding ultrafine coal and coarse coal are mixed and subjected to dry distillation to produce coke.

  Various brands of coal are placed in the coal yard 1. From this coal yard 1, coal is transported to the mixing / blending facility 2. In the mixing / blending facility 2, coal is blended and mixed so that the blended coal has a predetermined blending ratio. From this mixing and blending equipment 2, the blended charcoal is conveyed to the pulverizer 3. In the pulverizer 3, the pulverization is usually performed so that the blended coal has a particle size of 3 mm or less and 70 to 90%. In addition, you may perform the process of a grinding | pulverization before the process of mixing and a mixing | blending of coal.

  The pulverized blended coal is conveyed from the pulverizer 3 to the drying / classifying machine 4. In the drying / classifying machine 4, while drying the blended coal, coarse coal having a particle size of more than 0.6 mm (hereinafter also referred to as “+0.6 mm”) and a particle size of 0.6 mm or less (hereinafter, “−”). It is classified into fine-grained coal (sometimes called “0.6 mm”). In addition, you may perform drying and a classification using a separate dryer and a classifier. Then, +0.6 mm of coarse coal is transported from the drying / classifier 4 to the mixing facility 8.

  A part of the fine-grained coal of −0.6 mm or a part of the coal placed in the coal yard 1 is conveyed to the ultrafine coal production pulverizer 5. In the ultrafine coal production pulverizer 5, at least one of -0.6 mm fine coal and coal in the coal yard 1 is pulverized to become ultrafine coal. Ultrafine coal is manufactured by adjusting the operating conditions (rotation speed, etc.) of the pulverizer so that the target particle size is 70% or more. This is because when the target particle size is less than 70%, the particle size becomes coarse, and it has been experimentally confirmed that the effect expected of ultrafine coal cannot be sufficiently exhibited. As the ultrafine coal production pulverizer 5, a pulverizer such as a ball mill or a roller press can be used.

  Ultra fine coal is put into ultra fine coal hopper 6 and a predetermined amount is put into dry granulation equipment (kneader and granulator) 7. However, for example, a wind classifier such as a cyclone may be provided between the ultrafine coal production pulverizer 5 and the ultrafine coal pulverizer 6 so that the coal having a target particle size or more is returned to the ultrafine coal production pulverizer 5.

  Also, -0.6 mm fine-grained coal is conveyed from the drying / classifying machine 4 to the dry granulation equipment 7. In the dry granulation facility 7, a liquid binder (liquid bitumen) is dropped or sprayed on fine-coal and ultrafine coal of -0.6 mm, and kneaded and granulated to create pellets. The granulation method is not particularly limited, and examples thereof include rolling granulation and fluidized bed granulation.

  The pellets are transported from the dry granulation equipment 7 to the mixing equipment 8. In the mixing facility 8, pellets and coarse coal of +0.6 mm are mixed to obtain pellet-blending charging coal. From the mixing facility 8, the pellet-blended charging coal is charged into the coke oven 9 and dry-distilled to produce blast furnace coke. In addition, you may supply a pellet to + 0.6mm coarse-grained coal on a belt conveyor, without installing the mixing equipment 8. FIG.

  As described above, according to the production method of the present invention, it is possible to increase the amount of inexpensive non-slightly caking coal depending on the amount of liquid binder added to the coal. The amount of binder and non-slightly caking coal can be freely changed according to the balance between the price and the strength of coke obtained.

  For example, even if you want to add a large amount (40% by mass) of a liquid binder based on the price and strength of coke, by adding ultrafine coal to the liquid binder (liquid bitumen), granulation is good. Pellets can be obtained. In addition, based on price and strength of coke, even when a small amount (7% by mass) of liquid binder is to be added, by adding ultrafine coal to the liquid binder (liquid bitumen), the granulation property is good. Pellets can be obtained.

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on these one example conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

  Tar and ultrafine coal as liquid bitumen were added to the fine coal having a particle size of 0.6 mm or less, respectively, in the addition amounts shown in Table 1, and kneaded and granulated. Moreover, the fine-grained coal was pulverized so that the particle size was 0.6 mm or less, and the ultrafine coal was pulverized so that the particle size was 0.06 mm or less. Table 1 shows the surface moisture content of coal, tar content, ultrafine coal content, granulation properties, non-adhesiveness, and non-dusting properties. In Table 1, “%” indicates “% by mass”.

  The granulation property is good when the amount of 0.6 mm or less after granulation is 10% or less of the input amount and the ratio of the particle size of 8 to 50 mm of the pellet is 80% or more, and the amount of 0.6 mm or less More than 10% and 30% or less, or the case where the ratio of the pellet particle size of 8 to 50 mm is less than 80% and 50% or more, it was evaluated that granulation was possible, and other than that, granulation was impossible. In Table 1, good granulation: 、, possible granulation: 、, no granulation: indicated by ×.

  In Table 1, non-adhesiveness is ◎ when there is no adhesion of pellets to the transport device, ◯ when there is almost no adhesion, and × when there is no adhesion. However, the case where there is not at all is indicated as ◎, the case where there is almost none is indicated as ○, and the case where it is present is indicated as ×.

  Granulation No. Since 1-23a is granulated by adding ultrafine coal to fine-grained coal, a strong pellet can be obtained even when the liquid binder is added in the range of 7.0-38.0%. Good granulation.

  In contrast, granulation no. Nos. 24 and 25 are granulated by adding 17.4% and 17.5% of liquid binder without adding ultrafine coal to fine-grained coal. The cross-linking force between the particles becomes weak and granulation is impossible. Granulation No. No. 28 does not add ultrafine coal to fine-grained coal, and granulates with the amount of liquid binder being 27.6%, so pellets are softened by excess liquid binder and cannot be granulated. ing.

  Granulation No. In Nos. 26 and 27, granulation is possible without adding ultrafine coal to fine-grained coal, and the amount of liquid binder added is 18.2% or 24.5%. However, strong pellets were not obtained. In contrast, granulation no. In Nos. 12 and 13, granulated by adding ultrafine coal to fine-grained coal and setting the amount of liquid binder to 18.2% or 24.5%, respectively, so that a strong pellet is obtained. The granulation is good.

  Granulation No. In 3a and 5a, there was almost no dust generation of the pellets during conveyance, and the non-dust generation property was good (good). Granulation No. 1 to 3, 4, 5, and 6 to 23a, the relationship between the content of the liquid binder and the content of the ultrafine coal satisfies the relationship of the above formula (1). There was no dust generation and the non-dust generation was ◎ (very good).

  Granulation No. In 22a and 23a, there was almost no adhesion of pellets to the conveying device, and non-adhesion was good (good). Granulation No. 1 to 22 and 23, since the relationship between the content of the liquid binder and the content of the ultrafine coal satisfies the relationship of the above formula (1), the adhesion of the pellets to the transport device There was no non-adhesiveness, and it was ◎ (very good).

  As described above, in addition to the fine coal, in addition to the liquid binder, by adding ultrafine coal, granulation is improved, and pellets that do not decrease in strength can be obtained, using the pellets, Coke can be produced.

  According to the present invention, a strong pellet can be produced even if the amount of binder contained in the pellet for coke production is wide, and even if a large amount of inexpensive non-coking coal is blended, a good quality blast furnace Coke can be produced. Therefore, the present invention has high industrial applicability.

A Line indicating non-dusting boundary B Line indicating non-adhesive boundary

Claims (3)

  The total of the content of liquid bitumen and the content of surface moisture of the fine coal (including 0% by mass) in fine coal with a particle size of 0.6 mm or less is the outer number of fine coal A pellet obtained by adding a liquid bitumen so as to be 7 to 40% by mass and further granulating by adding ultrafine coal having a particle size of 0.2 times or less the average particle size of the fine coal And a coarse coal having a particle size of more than 0.6 mm, charged in a coke oven and dry-distilled, and a method for producing coke for blast furnace.   2. The method for producing coke for blast furnace according to claim 1, wherein the ultrafine coal is added in an external number of 1 to 10 mass% with respect to the fine-grained coal. The total Y (mass%) of the liquid bitumen content and the surface moisture content (including 0 mass%) of the fine-grained coal and the ultrafine coal content X (mass%) are the following (1 The method for producing coke for a blast furnace according to claim 1 or 2, wherein the liquid bitumen and the ultrafine coal are added so as to satisfy the formula.
(−6/4) × (X−1) + 13 ≦ Y ≦ (10/9) × (X−1) +30 (1)

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