JP2019002011A - Method for manufacturing coke - Google Patents

Abstract

To provide a method for manufacturing high-strength coke by adding a caking agent, where the method maintains the high strength of coke and enlarges coke size even when a blending ratio of non or slightly caking coals is increased.SOLUTION: A method of the present invention is a method for manufacturing coke by charging blended coals comprising coals having highly volatile content in a coke oven and carbonization. The coals having highly volatile content used in the method comprises 30 mass% or more of volatile content and preferably has 50% or more of a caking index. According to the method, adding a caking agent in a liquid state to the coals having highly volatile content in such an amount that mass ratio of the added caking agent to the coals having highly volatile content is more than 5%, mixing, and blending the mixture to other material coals.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing coke used as an iron-making raw material, and more particularly to a method for producing high-strength coke by adding a caking additive to coal and subjecting it to dry distillation in a coke oven.

A method for producing a high-strength coke by adding a caking additive to raw coal is conventionally known, and the following known literatures are available.
Patent Document 1 discloses a method for producing high-strength coke by adjusting the binder addition ratio between pulverized coal and coarse coal according to the properties of pulverized coal and coarse coal.
Patent Document 2 discloses a method for producing high-strength coke by grouping raw coals according to properties and adding a binder having an optimum composition for each group.
Patent Document 3 discloses a method for producing high-strength coke while reducing expansion pressure by selectively adding, kneading, and molding a binder to high expansion pressure coal.
In the coke manufacturing method as described above, in order to further reduce the manufacturing cost, it is desired to further improve the blending ratio of the non-slightly caking coal.

  On the other hand, there is an increasing need for stabilization of blast furnace operation and reduction of coke usage in the blast furnace, and development of a method for improving not only the coke strength but also the coke particle size is required. As a method for improving the coke particle size, for example, there is a method of kneading coal with bituminous material as disclosed in Patent Document 4, but a method for further improving the coke particle size while increasing the blending ratio of non-slightly caking coal. Is required.

International Publication No. 2010/073535 Japanese Patent Laid-Open No. 2007-9016 JP 2011-26468 A Japanese Patent Laid-Open No. 6-264069

However, the conventional methods as described above do not show a method for producing coke that increases the blending ratio of non-slightly caking coal and maintains high strength and further improves the particle size.
Therefore, the present invention is a method for producing a high-strength coke by adding a caking agent, and even if the blending ratio of non-slightly caking coal is increased, high strength can be maintained and the coke particle size can be further improved. A method for producing coke is provided.

In general, non-finely caking coal has a high content of volatile matter (VM), and when the blending ratio of non-minor caking coal increases, the VM of the entire coal blend increases and the coke particle size decreases.
The reason why the coke particle size is lowered when the VM is high is that, generally, coal having a high VM has a large shrinkage rate after resolidification, and thus the strain becomes large. For this reason, the stress increases, cracks in the coke increase, and cracks reduce the particle size of the coke.
The present inventors have focused on coal with high VM (high VM coal) among non-slightly caking coals, and as a result of repeating various studies in order to solve the above-mentioned problems with blended coal containing high VM coal. In addition, it is possible to improve the coke particle size while maintaining the coke strength by selectively adding and mixing the binder to a certain ratio or more selectively only in the high VM coal in the blended coal. It has been found that there is a certain relationship between the amount of the caking additive added in a concentrated manner and the coke particle size of the resulting coke, and the effect of improving the coke particle size can be predicted to determine the amount of caking additive added.

The present invention has been made based on the above findings, and the gist thereof is as follows.
(1) In the method for producing coke, in which blended coal containing high volatile content coal is loaded into a coke oven and carbonized, the high volatile content coal contains 30% by mass or more of volatile matter. Production of coke characterized by adding more than 5% of liquid caking additive to volatile matter-containing coal in a mass ratio (external number) to the content of high-volatile matter-containing coal and blending with other raw coal Method.

(2) The average of coke produced without adding the binder to the blended coal containing the high volatile content coal in advance, after obtaining the effect of improving the coke particle size per added amount of the binder to the high volatile content coal. A target particle size improvement margin for obtaining a target average particle size is determined with respect to the particle size, the coke particle size improvement effect, the content of the high volatile content coal, and the binder for the high volatile content coal The coke production method according to (1) above, wherein the caking additive is added so that a coke particle size improvement allowance expressed by a product of the addition rate is equal to or greater than the target particle size improvement allowance.

(3) The coke production method according to (1) or (2) above, wherein the high volatile content coal has a cohesive strength index of 50% or more.

  According to the present invention, as a result, even if the use ratio of non-caking coal (high VM charcoal) is increased, the coke particle size can be improved while maintaining the coke strength at a certain level or higher.

It is a figure which shows the relationship between the caking additive addition rate at the time of carrying out dry distillation by adding caking additive to highly volatile content carbon, and the average particle size of the coke obtained.

The present inventor, in a method for producing coke in which coal blend containing high volatile content coal is loaded into a coke oven and dry distillation, intensively adding a caking additive to high volatile content coal and kneading it. It was found that coke strength and coke particle size can be improved by mixing with other raw coal and dry distillation.
First, experimental knowledge that is the basis of the present invention will be described. In addition, "%" showing the quantitative ratio of coal and a caking additive shows "mass%".

(Experiment 1)
Coal with different volatile content was used to produce coke by selectively adding a caking additive to the raw coal, and the effects on coke particle size and coke strength were investigated.
Three types of coal having the properties shown in Table 1 were prepared. The volatile content is a dry base value.
A caking additive was selectively concentrated and added to some of these coals, and mixed with other coals to obtain blended coals. The blending conditions and the binder addition conditions were as shown in Table 2.

Here, “base blend” indicates coal in which A coal, B coal, and C charcoal are blended in equal mass ratios, and “no caking additive added” means a brand of coal not containing caking additive. The mass ratio is indicated, and “selective concentrated addition of binder” indicates the brand of coal to which the binder is added and kneaded and the mass ratio of the coal and the binder.
Each mass ratio is indicated by an inner number. In the above conditions 2 to 5, the addition ratio of the binder to the coal to be added is 3.0 / 30.4 × 100 = 9.9% (outer number )

In conditions 2 to 5, after adding and kneading intensively to the coal intended for the binder, the coal without the binder added and the coal selectively added with the binder are mixed and dry-distilled in a test coke oven. did. Note that coal tar was used as the caking agent as a liquid. As a result, it is considered that the surface of the target coal particles is coated with a caking additive.
The coke after dry distillation was cooled in nitrogen and then measured for coke average particle size and coke strength DI.
Here, the average particle size of the coke is obtained by sieving with a plurality of meshes, measuring the mass for each particle size category of the mesh, and using the representative diameter of each particle size category (intermediate diameter of the upper and lower sieve meshes), A weighted average value was obtained based on the mass ratio of the particle size classification. Further, as the coke strength DI, a drum strength index DI ¹⁵⁰ ₁₅ (hereinafter sometimes simply referred to as “DI”) was measured.
The results are also shown in Table 2.

Condition 1 is an example without addition of a binder, Condition 2 is an example of concentrated addition of a binder to a part of the base formulation, and Conditions 3 to 5 are concentrated binders for A, B, and C charcoal respectively. An example of addition is shown.
With respect to the coke strength DI, the strength was improved in conditions 2 to 5 in which a caking additive was added compared to condition 1 in which the caking strength was not added.
On the other hand, the influence of the addition of the binder on the coke particle size is not uniform. Compared with condition 1, it is effective when added to all three types of coal or when added to A coal with the lowest VM. Even when added to B coal, which has a higher VM than coal A, the coke average particle size is hardly improved. On the other hand, under the condition 5 added to C charcoal having the highest VM, a result that the average particle size of coke was improved by about 3 mm was obtained.

From this result, it was confirmed that the coke average particle size is improved by adding and mixing the binder to a high VM coal having a certain value or more at a certain ratio in a concentrated manner.
High VM charcoal is the starting point for cracking of coke because the shrinkage rate after resolidification is large, but by covering the high VM charcoal with a binder, the viscosity of the structure around the high VM charcoal is improved. At the same time, as a result of the decrease in elasticity, the stress during contraction was relaxed, and it was thought that cracks were less likely to progress.

  In this experiment, an effect of improving the coke particle size by the concentrated addition of the caking additive to the high VM charcoal was recognized. Next, the conditions under which the effect was manifested were examined.

(Experiment 2)
First, the influence of the caking additive addition ratio was examined.
As shown in conditions 6 and 7 in Table 3, the above-mentioned A to C charcoal were used under the same blending conditions as in Experiment 1, and a new blended coal was produced by changing the addition rate of the caking additive to C charcoal. Coke was produced in the same manner as above, and the average coke particle size and coke strength DI were measured.
The results are also shown in Table 3. Table 3 also shows Conditions 1 and 5 of Experiment 1. In addition, the concentration addition rate of caking coal to object charcoal was shown by the outside number.

  As shown in Table 3, there was no change in the average coke particle size when the concentration ratio of the caking additive to C charcoal was 3%, but when the addition rate was 5.2%, the average coke particle size was improved by 1.7 mm. The result to be obtained. From this result, it was confirmed that when the addition ratio of caking coal to high VM coal exceeds 5%, the effect of improving the average coke particle size appears.

(Experiment 3)
Next, it investigated about the volatile content of coal from which the coke particle size improvement effect by concentrated addition of caking additive was acquired.
D charcoal having the properties shown in Table 4 was newly prepared, and the blending conditions and the binder addition conditions were as shown in Table 5. Here, “base blend 2” indicates coal in which A coal, B coal, and D coal are blended in equal mass ratios.
Coke was produced in the same manner using the blended coals of conditions 8 and 9, and the average coke particle size and coke strength DI were measured. The results are also shown in Table 5.

表５についても、それぞれの質量比率は内数で示しているが、上記条件９において、添加対象の石炭に対する粘結材の添加率は、３．０／３０．４×１００＝９．９％（外数）となる。

Also in Table 5, each mass ratio is indicated by an inner number. However, in the above condition 9, the addition ratio of the binder to the coal to be added is 3.0 / 30.4 × 100 = 9.9%. (Outside number).

  As shown in Table 5, under condition 9 in which a caking additive was concentratedly added to D charcoal having a volatile content of 30%, the coke strength was improved and the average coke particle size was improved by 2.5 mm. From the result of Condition 9 and the result of Condition 5 of Experiment 1, both coke strength and coke average particle size are improved by concentrated addition of caking coal to coal containing 30% or more of volatile matter in the raw coal. It was confirmed.

  Based on the above experiment, the present inventors further conducted various tests using various types of coal having different volatile contents, changing the target coal to which the binder is added and the binder addition rate. Add coke to concentrated high VM charcoal with a volatile content of 30% or more at an addition rate of more than 5% and mix with other raw coal to produce coke. Thus, it was confirmed that even if the blending ratio of non-slightly caking coal (high VM charcoal) was increased, coke with improved coke strength and coke average particle size could be produced.

  By this, for each combination of brand and blending amount of high-VM coal blended with raw coal and the binder to be concentrated and added to the coal, experimentally obtain the addition rate of the binder to obtain the target coke particle size. The actual amount of caking additive added can be determined, but in the combination of a predetermined brand of coal and caking additive, the effect of improving the coke particle size per caking additive addition is obtained in advance, and the target coke is obtained. It is preferable to be able to know in advance the amount of the caking additive added so as to obtain a particle size.

Therefore, when the relation between the addition rate of the binder and the average particle size of the coke was examined for various brands of coal, the addition rate of the binder to high VM coal having a volatile content of 30% or more was an external number of 15. In the range up to about%, it was experimentally found that the binder addition rate and the coke particle size have a linear relationship.
As an example, FIG. 1 shows the relationship between the caking additive addition rate and the average particle size of the coke obtained when caking additive is added to the C charcoal and D charcoal, respectively.

  As a result, the present inventor determined the combination of coal brand and caking material in advance by seeking the effect of improving the coke particle size per caking additive addition amount in each combination of various coal brands and caking material. It was found that the effect of improving the coke particle size can be predicted by the following procedure.

That is, if the average particle size Ia (mm) of coke produced from coal I, which is high VM coal, and the average particle size Ib (mm) of coke produced by adding caking agent J to coal I are investigated, The improvement effect E _IJ (mm /%) of the coke particle size per added amount of binder in the combination of coal I and binder J can be obtained from the following equation.
E _IJ = (Ib−Ia) / j

In addition, the average particle size improvement allowance E (mm) of coke obtained by dry distillation of coal blend containing coal% containing coal% and coal I containing ca% concentrated in coal I is calculated using E _IJ. It is calculated by the following formula using a weighted average of effects.
E = E _IJ × (i / 100) × ja

Based on the method of obtaining the average particle size improvement allowance E, an estimated value of the average particle size improvement allowance E was obtained for the conditions 5, 7, and 9 used in the previous experiment, and compared with the actually measured value obtained in the previous experiment.
First, conditions 7 and 5 using C charcoal were examined.
The average particle size Ia of coke that was carbonized with 100% C charcoal was 38 mm, and the average particle size Ib of coke that was carbonized by adding 6% caking additive J to C charcoal was 44 mm. In the combination of carbon charcoal and caking additive J, the coke particle size improvement effect E _IJ per caking additive addition amount is determined to be (44−38) / 6 = 1 mm /%.
In Table 3 above, in condition 5, 30.4% C charcoal is included in the blended coal, and 9.9% caking additive J is added to C charcoal. In this case, the average particle size improvement margin E of the coke obtained by carbonizing the blended coal is estimated to be 1 × (30.4 / 100) × 9.9 = 3.0 mm, and similarly for condition 7, it is estimated to be 1.7 mm. It was confirmed that both agreed with the measured values.

Similarly, the condition 9 using D charcoal was examined.
The average particle size Ia of coke dry-distilled with 100% D charcoal was 42 mm, and the average particle size Ib of coke dry-mixed with 7% caking additive J added to D charcoal was 47.5 mm. In combination with D carbon and caking J, coke particle sizes improvement _{E ij} per caking additive amount is calculated as (47.5-42) /7=0.79mm/%.
In Table 5, in condition 9, 30.4% of D charcoal is contained in the blended coal, and 9.9% of caking additive J is added to D charcoal. In this case, the particle size improvement margin E of the coke obtained by carbonizing the blended coal was estimated to be 0.79 × (30.4 / 100) × 9.9 = 2.4 mm, and it was recognized that it substantially coincided with the actual measurement value. .

Therefore, when a caking additive J is added to coal I in a concentrated composition containing coal I as high VM coal with a content i, the effect of improving the coke particle size per added amount of caking additive J to coal I in advance. E _IJ is obtained, and the target particle size corresponding to (M′−M) is obtained by setting M ′ as the average particle size of the target coke with respect to the average particle size M of the coke produced without adding the binder J to coal I. An improvement allowance is determined, and the viscosity is determined so that the value obtained from the product of the coke particle size improvement effect E _IJ and the addition rate ja of the binder J with respect to the coal i content i is equal to or greater than the target particle size improvement allowance (M′−M). By determining the addition rate ja of the binder J, the addition rate of the binder capable of achieving the target coke particle size can be determined in advance.

In addition, when a some high VM coal is included in blended coal, it can obtain _| require by calculating _| requiring each average particle size improvement effect _EIJ by the combination of coal I and caking additive _J , and adding it.
For example, the average particle size improvement allowance ΣE (total of the case where m% coal Im, n% coal In, ja% binder J is added to coal Im, and ka% ka binder K is added to coal In. mm) is an average particle size effect of improving the caking J for coal Im and E _IMJ, an average particle size effect of improving the caking K for coal in as E _InK, determined by the following equation.
ΣE = {E _ImJ × (m / 100) × ja} + {E _Ink × (n / 100) × ka}

The basic form of the present invention has been described above, but further, individual conditions and preferable conditions constituting the present invention will be described.
(Mixed coal)
As a part of the blended coal to be used, high VM coal with a VM of 30% by mass or more on a dry basis is used. The high VM charcoal may be a single brand or multiple brands. The blending ratio of the high VM charcoal is preferably 10% or more from the viewpoint that the effect of improving the average coke particle size is further exhibited, and is preferably 80% or less from the viewpoint of securing the coke strength.

In addition, as high VM charcoal which this invention makes object, having moderate caking property is important. This is because when the caking material to be coated improves not only the structure around the high VM charcoal particles but also the caking property in the vicinity of the surface of the high VM charcoal particles and the elasticity decreases, the stress relaxation effect is further promoted and cracks are generated. This is because it becomes more difficult to progress. In order to improve the caking property in the vicinity of the particle surface and reduce the elasticity by the caking material to be coated, it has been confirmed that the caking force index should be 50% or more.
Therefore, it is preferable that the caking force index of the high VM charcoal targeted by the present invention is 50% or more. Incidentally, the A to D charcoal used in the above test has a cohesive strength index of 50% or more.

  Here, the cohesive strength index is an index indicating the strength of coal tackiness, and is determined by the method described on page 255 of the coal utilization technical terminology (edited by the Japan Fuel Association, published in 1983 by Corona). Use measured value. Specifically, 9 g of 0.25 to 0.30 mm of powdered coke is mixed with 1 g of coal of 0.25 mm or less, dried in a magnetic crucible at 900 ° C. for 7 minutes, sieved at 0.42 mm, and remains on the sieve. The cohesive strength index can be measured by the method of displaying the percentage of weight.

  Other coal to be blended with the high-VM coal targeted by the present invention is not particularly limited, and is a coal for ordinary blended coal including strong caking coal (VM: 17% by mass or more and less than 30% by mass) ) Is used.

(Binder)
The caking additive added to the high VM coal is liquid at the operating temperature so that the surface of the target coal particles can be covered with the caking additive. Even if the binder is solid at room temperature, if it is heated to a liquid state, the effect can be exhibited by mixing with the target coal.
As the liquid binder, coal-based binders such as coal tar, petroleum-based binders such as asphalt, and other bituminous binders can be used. As the solid binder, coal pitch, heavy petroleum residue, asphalt pitch or the like can be used.

The operating temperature of the binder is exemplified by about 60 to 80 ° C. for the liquid binder and about 80 to 200 ° C. for the solid binder. Since the solid binder solidifies and aggregates as soon as the temperature is lowered, it is preferable to heat and stir with a high-speed stirring mixer.
The addition amount of the binder is more than 5% by mass (outside number) with respect to the high VM coal to be added. If it is 5% by mass or less, its action is not sufficient. The upper limit is preferably 15% or less from the viewpoint of improving the coke particle size. In order to further improve the coke strength, a larger amount may be added. However, if it exceeds 20% by mass, the coke strength may be adversely affected.

(Manufacturing process)
Basically, the present invention can be carried out in the following steps using a normal coke production technique.
Prepare coking coal pulverized after drying. High VM charcoal with a volatile content of 30% or more of the raw coal is put into a kneading and granulating facility, and a liquid binder is dropped or sprayed on the high VM charcoal to knead to prepare a kneaded product. . This kneaded product and other raw coal (coal for ordinary blended coal including strong caking coal) are transported to the blending facility, and the blended coal mixed and blended in the blending facility is charged into the coke oven. To produce blast furnace coke. In addition, you may supply kneaded material to the coke raw coal on a belt conveyor, without installing a mixing equipment.

Claims (3)

In a method for producing coke in which coal blend including high volatile content coal is loaded into a coke oven and dry-distilled,
The high volatile matter-containing coal contains 30% by mass or more of volatile matter, and the mass ratio (outside number) of the high-volatile matter-containing coal with a liquid caking additive to the content of the high-volatile matter-containing coal. The method for producing coke, characterized by adding more than 5%, kneading and blending with other raw coal.   For the average particle size of the coke produced without adding the binder to the blended coal containing the high volatile content coal, the effect of improving the coke particle size per added amount of the binder to the high volatile content coal was obtained in advance. The target particle size improvement margin for obtaining the target average particle size is determined, the coke particle size improvement effect, the content of the high volatile content coal, and the addition rate of the binder to the high volatile content coal The coke production method according to claim 1, wherein the caking additive is added so that a coke particle size improvement allowance represented by a product of the product is equal to or greater than the target particle size improvement allowance.   The method for producing coke according to claim 1 or 2, wherein the high volatile content coal has a cohesive strength index of 50% or more.

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