JP6623629B2 - Manufacturing method of coke for blast furnace - Google Patents

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, in order to efficiently heat and reduce lump iron ore, agglomerates of powdered iron ore or ironmaking dust, and to produce pig iron, generate CO reducing gas and secure ventilation of reducing gas. Coke is charged into the blast furnace as a spacer for the blast furnace.

  In order for coke for blast furnaces to be sufficiently effective as a spacer in a blast furnace, it must have sufficient strength so that it does not collapse due to the impact of charging into the blast furnace or the load of the load in the blast furnace. Required. On the other hand, high-quality strong caking coal as a raw material for coke is in a resource-depleted state, and therefore, many methods for producing coke having the necessary strength using non-fine caking coal have been proposed. .

  Technology to produce coke with the required strength using non-coking coal, technology to increase the charging density of the charged coal into the coke oven, and technology to add a binder such as tar to the charged coal It has been known. As a combination of the two technologies, there is a forming coal blending method using a forming coal formed by adding a binder. However, in the forming coal blending method, if a liquid binder such as tar is added in an amount of more than 10%, the strength of the manufactured forming coal is reduced, and molding is difficult due to deterioration of moldability. For this reason, it has been difficult to significantly increase the proportion of the liquid binder to be added and to 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.

  Patent Literature 1 discloses that a binder (water, liquid bituminous binder) is added to coal having a particle size of 0.6 mm or less in an amount of 18 to 27% by mass and granulated to produce pellets having a particle size of 8 to 50 mm. Then, the pellets are mixed with coarse-grained 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 carbonized to produce coke. There is disclosed a technique capable of producing high-quality blast furnace coke even when a large amount of caking coal is blended.

  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 binder addition under the same coke strength. However, since the binder is expensive, it is preferable that the amount of the binder to be added can be freely changed according to the price of the inexpensive non-finely caking coal and the binder.

  Patent Literature 1 describes the amount of the binder to be added as follows. If the amount of the binder added is less than the lower limit of 18% by mass, the amount of the binder that binds the coal particles becomes insufficient, making it difficult to granulate and maintaining the strength of the pellets. If the amount of the binder exceeds 27% by mass, which is the upper limit, the amount of the added binder is excessive and the pellets are softened, the strength cannot be maintained, and the excess binder adheres to the pellet surface. It is said that the strength at which the pieces are fixed cannot be maintained.

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

  Furthermore, since pellets may be broken by impact in the process of transportation to a coke oven, it is required to produce strong pellets with a smaller amount of the binder or with a larger amount of the binder. I was

JP 2002-327181 A

  In view of the above-mentioned state of the art, the present invention provides a pellet whose strength is not reduced even when the amount of a binder added in the production of pellets is less than 18% by mass or more than 27% by mass, and using the pellets It is an object of the present invention to provide a method for producing coke.

  Then, the present inventors diligently studied a method for solving the above problem. As a result, we found that by adding superfine coal in addition to the liquid bituminous material that is a liquid binder to the coal and granulating, the function of the binder was dramatically increased and strong pellets were obtained. did.

The present invention has been made based on the above findings, and the gist thereof is as follows.
(1) The sum of the content of liquid bitumen and the content (including 0% by mass) of the surface moisture of the fine coal in the fine coal having a particle size of 0.6 mm or less is smaller than that of the fine coal. Liquid bitumen is added so as to be 7 to 40% by mass, and the ultrafine coal having a particle size of 0.2 times or less the average particle size of the fine coal is added to the fine coal. Blast furnace characterized by blending pellets obtained by adding 1 to 10% by mass as an external number with respect to the above and granulated coal having a particle size of more than 0.6 mm, charging the coke oven and carbonizing. Production method for coke .
(2 ) The sum Y (mass%) of the content of the liquid bitumen and the content of the surface moisture (including 0 mass%) of the fine coal and the content X (mass%) of the ultrafine coal are: The method for producing coke for blast furnace according to (1) , wherein the liquid bituminous substance and the ultrafine coal are added so as to satisfy the following equation (1). (−6/4) × (X−1) + 13 ≦ Y ≦ (10/9) × (X−1) +30 (1)

  According to the present invention, even if the addition amount of the binder to be contained in the pellets for producing coke is wide, it is possible to produce strong pellets, and even if a large amount of inexpensive non-coking coal is blended, good quality can be obtained. Blast furnace coke can be manufactured.

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

  Hereinafter, the method for producing blast furnace coke of the present invention (hereinafter, referred to as the method of the present invention) will be described. In the following, the total content (% by mass) of the surface moisture of the liquid bituminous substance and the fine coal with respect to the fine coal, and the content (% by mass) of the ultrafine coal with respect to the fine coal are represented by the following external numbers. Shown.

  In the production of pellets (sometimes referred to as granules) for coke production, the present inventors increased the amount of liquid binder (liquid bitumen and surface moisture of coal) contained in coal over a wide range (less than 18% by mass). Or more than 27% by mass), a method capable of producing a strong pellet was examined.

  When the amount of the liquid binder with respect to the coal is small, the crosslinking force between the coal particles to be granulated is weakened, and granulation becomes difficult, and the strength of the pellets cannot be maintained. The idea was to increase the bridging power between them.

  Further, when the amount of the liquid binder with respect to the coal is large, the pellets are softened by the excessive liquid binder, the strength cannot be maintained, and further, the strength due to the sticking of the pellets due to the excessive liquid binder cannot be maintained. The idea was to adsorb or absorb excess liquid binder.

  Then, when investigating the means for that, the present inventors conceived to add ultrafine coal to coal in addition to the liquid binder. That is, when the amount of the liquid binder is small, the ultrafine coal fills the voids of the pellets and bonds the coal particles to be granulated by solid crosslinking force, and when the amount of the liquid binder is large, the ultrafine coal However, it was considered that due to the large specific surface area of the ultrafine coal, a part of the liquid binder was adsorbed or absorbed, and the excess liquid binder was not exuded on the surface of the pellet.

  Then, a test was conducted in which ultrafine coal was added to fine coal in addition to the liquid binder. First, as a case where the amount of the liquid binder is small, tar is added as a liquid binder to a fine coal having a particle size of 0.6 mm or less so as to be 17.4% by mass. Test pellets 1 were prepared by adding 3% by mass of the following ultrafine coal, kneading and granulating. For comparison, a test pellet 2 was prepared by adding tar as a liquid binder so as to be 17.4% by mass with respect to the fine coal, kneading and granulating.

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

  As a result of this test, the test pellets 1 and 3 became strong pellets, and were able to be granulated with good granulation properties. On the other hand, the test pellets 2 and 4 did not become pellets and could not be granulated. Thus, it has been found that pellets can be obtained with good granulation properties by adding ultrafine coal to the fine binder in addition to the liquid binder.

  Then, a test was performed on the amount of liquid binder that can obtain pellets with good granulation properties by adding ultrafine coal. This test is a test similar to the above, to fine coal having a particle size of 0.6 mm or less, various 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 amount of the liquid binder to be added is 7 to 40% by mass, by adding ultrafine coal, it is possible to obtain strong pellets with good granulation properties.

  The production method of the present invention is the one described above (1) to (2) through the above-described examination process, and further describes necessary and preferable requirements of the present invention. I do.

  The manufacturing method of the present invention increases the charging density and mixes a large amount of non-fine caking coal by blending coarse coal with pellets obtained by adding a liquid binder to fine coal disclosed in Patent Document 1. In the technology which can be used for the above-mentioned method, by adding ultrafine coal when granulating into pellets, it is possible to produce strong pellets even if the amount of the liquid binder to be added is wide. In the production of the pellets, the fine coal used for granulation, the liquid binder to be added, the ultrafine coal to be added, and the like are as follows.

(Coarse coal: particle size more than 0.6mm)
The coarse coal into which the pellets are blended has 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.

(Fine-grained coal: particle size 0.6 mm 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 diameter of more than 0.6 mm are difficult to be taken into pellets. In addition, it is ideal that the maximum particle diameter is 0.6 mm when the particle diameter is 0.6 mm or less. However, even if the classification point is set to 0.6 mm by an actual classifier, particles having a particle size larger than 0.6 mm are slightly mixed. It indicates 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 forming the pellet contains a liquid bitumen. The liquid bitumen is a coal-based binder such as coal tar, a petroleum-based binder such as asphalt, and other bituminous binders. In addition, the surface moisture of the fine coal has a function of binding the coal particles and has a function as a binder, and thus is included in the amount of the liquid binder to be added. Therefore, the sum of the surface moisture of the fine coal and the liquid bitumen is used as the liquid binder, and the total amount is 7 to 40% by mass based on the fine coal. When the surface moisture of the coal is 0% by mass, the liquid bitumen is added so as to be 7 to 40% by mass with respect to the fine coal.

  The surface moisture percentage of coal is calculated by subtracting the contained moisture percentage of JIS-M8803 from the total moisture percentage of JIS-M8811. The normal storage of coal in a steel mill is about 2%.

  If the content of the liquid binder is less than 7% by mass based on the fine coal, it is difficult to form pellets even if ultrafine coal is added. Further, when the content of the liquid binder is more than 40% by mass with respect to the fine coal, the binder is excessive and the strength of the pellet 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 added at the time of pellet making is more than 0.2 times the average particle size of the fine coal to be granulated, the solid crosslinking force between the coal particles to be granulated. The ability to bind and 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. Further, 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), an ultrafine coal having a particle size of 0.06 mm (0.3 mm × 0.2) or less is exemplified. You.

(Content of ultrafine coal: 1 to 10% by mass based on fine coal)
If the content of ultrafine coal added at the time of pellet preparation is less than 1% by mass with respect to the fine coal, the coal particles to be granulated are bonded to each other by solid bridging force, and excess liquid binder is adsorbed. Alternatively, the effect of absorbing may not be sufficiently exhibited. On the other hand, if it exceeds 10% by mass, the amount becomes excessive with respect to the voids of the particles, and unpulverized ultrafine coal may be generated. Therefore, the content of the ultrafine coal is preferably 1 to 10% by mass based on the fine coal.

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

  FIG. 2 shows the relationship between the content of the liquid binder and the content of the fine coal. 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 Y (mass%) of the liquid binder is set to be equal to or more than the left side of the equation (1) while the content X (mass%) of the ultrafine coal is used as a variable, the property of hardly generating dust during the transportation of the pellets ( (Hereinafter referred to as "non-dusting"), and if the ratio is equal to or less than the right-hand side of the expression (1), the property that the pellet hardly adheres to a conveyor belt or a chute at a connecting portion of the conveyor at the time of transporting the pellets. Hereinafter, “non-adhesiveness”) can be further improved.

(Pellet particle size: 8 to 50 mm)
If the particle size exceeds 50 mm, the strength may be reduced. If 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 be reduced. May decrease. Therefore, it is preferable that the pellets are granulated to have a particle size of 8 to 50 mm.

(Blending ratio of non-slightly caking coal: 65% by mass or less)
If the blending ratio of the non-fine caking coal in the coal charged into the blast furnace is more than 65% by mass, the coke strength may decrease. Therefore, it is preferable that the blending ratio of the non-fine caking coal in the coal charged into the blast furnace is 65% by mass or less. Further, the non-fine caking coal can be contained in one or more of fine coal, coarse coal and ultrafine coal.

Next, a flow for carrying out the manufacturing method of the present invention will be specifically described with reference to a flow chart.
(Coke production flow)
FIG. 1 shows a flow in which pellets prepared by adding ultrafine coal and coarse coal are mixed and carbonized to produce coke.

  In the coal yard 1, various brands of coal are placed. From this coal yard 1, the coal is transported to a mixing and blending facility 2. In the mixing / blending equipment 2, the coal is blended and blended so that the blended coal has a predetermined blending ratio. From this mixing / blending equipment 2, the blended coal is transported to a crusher 3. In the pulverizer 3, the pulverized coal is usually pulverized so that a particle size of 3 mm or less becomes 70 to 90% of coal blend. Note that a pulverizing step may be performed before the coal mixing and blending step.

  From the pulverizer 3, the pulverized coal blend is conveyed to the dryer / classifier 4. In the drying and classifying machine 4, while drying the blended coal, coarse coal having a particle size of more than 0.6 mm (hereinafter sometimes referred to as “+0.6 mm”) and particle size of 0.6 mm or less (hereinafter, “− 0.6 mm "). In addition, you may perform drying and classification using a separate dryer and a classifier. Then, the coarse coal of +0.6 mm is conveyed from the drying / classifying machine 4 to the mixing equipment 8.

  A part of the fine coal of −0.6 mm or a part of the coal placed in the coal yard 1 is transported to the ultrafine coal production and pulverizer 5. In the ultrafine coal production and pulverizer 5, at least one of -0.6 mm fine coal and coal in the coal yard 1 is pulverized into ultrafine coal. The ultrafine coal is manufactured by adjusting the operating conditions (such as the number of revolutions) of the pulverizer so that the target particle size is contained at 70% or more. This is because it has been experimentally confirmed that if the target particle size is less than 70%, the particle size becomes coarse, and the effect expected from ultrafine coal cannot be sufficiently exhibited. A crusher such as a ball mill or a roller press can be used as the crusher 5 for producing ultrafine coal.

  The ultrafine coal is put into the ultrafine coal hopper 6 and a predetermined amount into the dry granulation equipment (kneader and granulator) 7. However, for example, an air classifier such as a cyclone may be provided between the ultrafine coal production crusher 5 and the ultrafine coal hopper 6, and coal having a target particle size or more may be returned to the ultrafine coal production crusher 5.

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

  The pellets are conveyed from the dry granulation equipment 7 to the mixing equipment 8. In the mixing equipment 8, the pellets and the coarse coal of +0.6 mm are mixed to form a pellet blended coal. From the mixing equipment 8, the pellet-blended coal is charged into the coke oven 9 and carbonized to produce blast furnace coke. The pellets may be supplied to the +0.6 mm coarse coal on the belt conveyor without installing the mixing equipment 8.

  As described above, according to the method of the present invention, it is possible to increase the amount of inexpensive non-fine caking coal used in accordance with the amount of the liquid binder to be added to coal. The amount of binder and non-coking coal used can be freely changed in accordance with the balance between the price and the strength of the obtained coke.

  For example, even when it is desired to add a large amount (40% by mass) of a liquid binder based on the price and the strength of coke, by adding ultrafine coal to the liquid binder (liquid bituminous material), good granulation properties can be obtained. Pellets can be obtained. In addition, even when it is desired to add a small amount (7% by mass) of a liquid binder based on the price and the strength of coke, the granulation property is improved by adding the ultrafine coal to the liquid binder (liquid bituminous material). Pellets can be obtained.

  Next, an example of the present invention will be described. The conditions in the example are one condition example adopted for confirming the operability and the effect of the present invention. It is not limited. The present invention can employ 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 fine coal having a particle size of 0.6 mm or less in the amounts shown in Table 1, respectively, and kneaded and granulated. The fine coal was pulverized so as to have a particle diameter of 0.6 mm or less, and the ultrafine coal was pulverized so as to have a particle diameter of 0.06 mm or less. Table 1 shows the content of surface water, the content of tar, the content of ultra-fine coal, granulation, non-adhesion, and non-dusting of coal. In Table 1, “%” indicates “% by mass”.

  The granulation 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 pellets having a particle size of 8 to 50 mm is 80% or more. When the ratio was more than 10% and 30% or less, or when the ratio of the particle size of the pellets was 8 to 50 mm was less than 80% and 50% or more, granulation was possible, and the other cases were evaluated as granulation impossible. In Table 1, good granulation: ◎, good granulation: ○, bad granulation: ×.

  In Table 1, non-adhesiveness is indicated by ◎ when there is no sticking of pellets to the transfer device, を when almost no sticking of the pellets, and x when there is no sticking. However, 場合 indicates that there was no sample, ○ indicates that there was no sample, and X indicates that there was one.

  Granulation No. In Nos. 1 to 23a, ultrafine coal is added to fine coal and granulation is performed, so that a strong pellet can be obtained even if the liquid binder is added in the range of 7.0 to 38.0%. Good granulation.

  On the other hand, granulation No. Nos. 24 and 25 do not add ultrafine coal to the fine coal, and perform granulation with the added amounts of the liquid binder of 17.4% and 17.5%. The cross-linking force between the particles becomes weak, and granulation is impossible. Granulation No. No. 28 does not add ultrafine coal to the fine coal, and performs granulation with the amount of the liquid binder being 27.6%. Therefore, the pellets are softened by the excess liquid binder, and granulation is impossible. ing.

  Granulation No. Nos. 26 and 27 do not add ultrafine coal to the fine coal but perform granulation with the added amount of liquid binder of 18.2% or 24.5%, respectively, so that granulation is possible. However, strong pellets were not obtained. On the other hand, granulation No. In Nos. 12 and 13, fine powder coal was added to ultrafine coal, and the amount of liquid binder added was 18.2% or 24.5%, respectively, and granulation was performed, so that strong pellets were obtained. And granulation is good.

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

  Granulation No. In Nos. 22a and 23a, the pellets hardly adhered to the transfer device, and the non-adhesiveness was ○ (good). Granulation No. In Nos. 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-described formula (1), the adhesion of the pellets to the transport device is not satisfied. There was no adhesion and the non-adhesion was ◎ (very good).

  As described above, to the fine coal, in addition to the liquid binder, by adding ultrafine coal, granulation properties are improved, it is possible to obtain a pellet that does not decrease the strength, using the pellet, Coke can be produced.

  According to the present invention, even if the amount of binder to be contained in the pellets for coke production is wide range, it is possible to produce strong pellets, and even if a large amount of inexpensive non-coking coal is blended, a good blast furnace For producing coke. Therefore, the present invention has high industrial applicability.

A Line indicating a non-dusting boundary B Line indicating a non-adhering boundary

Claims (2)

In the fine coal having a particle size of 0.6 mm or less, the sum of the content of the liquid bitumen and the content of the surface moisture (including 0% by mass) of the fine coal is an external number with respect to the fine coal. The liquid bitumen is added so as to be 7 to 40% by mass, and the ultrafine coal having a particle size of 0.2 times or less the average particle size of the fine coal is added to the fine coal. A blast furnace coke characterized in that pellets added and granulated by adding 1 to 10% by mass as an outer number and coarse coal having a particle size of more than 0.6 mm are blended, charged into a coke oven and carbonized. Production method. The sum Y (% by mass) of the content of the liquid bitumen and the content (including 0% by mass) of the surface moisture of the fine coal and the content X (% by mass) of the ultrafine coal are as follows: The method for producing coke for a blast furnace according to claim 1, wherein the liquid bituminous substance and the ultrafine coal are added so as to satisfy the formula (1).
(−6/4) × (X−1) + 13 ≦ Y ≦ (10/9) × (X−1) +30 (1)

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