JPS598386B2 - Method for manufacturing coke for blast furnaces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing blast furnace coke using a briquette blending method, and aims to stabilize coke quality and increase the blending ratio of briquette coal.

The briquette blending method, which has been adopted as a method for producing coke for blast furnaces, involves blending dense briquette coal with powdered coal that has a moisture content of 5% or more and charging it into a coke oven. Although it is possible to improve coke strength and use low-rank coal, the amount of briquette coal blended is currently limited to 30% at most.

The reason for this is that when charging raw materials mixed with briquette coal, pulverized coal and briquette coal are not charged in a uniform ratio when charging into a coke oven, and segregation always occurs.

Therefore, although theoretically the amount of briquette coal can be up to 50 to 60%, it is limited to about 30% in consideration of the segregation of briquette coal in the coke oven.

It should be noted that even when the blended amount of briquette coal is 30%, segregation actually occurs in the coke oven, and it is known that segregation of briquette coal at each location in the coke oven is approximately 10%. There is.

In order to prevent such segregation of briquette coal, various mixing methods have been studied, but the best method has not yet been established.

Preventing this segregation of briquette coal in the furnace not only stabilizes coke quality but also makes it possible to increase the blended amount of briquette coal to the theoretical 50-60%, which greatly improves the ratio of low-grade coal used. Establishment of technology to prevent the segregation of briquette coal is especially needed for the production of coke for blast furnaces.

In order to establish this technology, the inventors repeatedly investigated the segregation phenomenon of briquette coal in the furnace in the briquette blending method, and found that the cause of briquette segregation in the furnace is the angle of repose between powdered coal and briquette coal. Based on the knowledge that the angle of repose of pulverized coal is affected by the surface tension of adhering moisture, we developed a method for use in blast furnaces that reduces the angle of repose of pulverized coal and effectively prevents the segregation of molten coal in the furnace. Established a method for producing coke.

In other words, this invention reduces the surface tension of adhering moisture by adding and mixing oil or surfactant to powdered coal, and makes the angle of repose of powdered coal equal to or lower than that of molten coal. It is characterized by reducing the difference in angle of repose and preventing segregation of briquette coal in the furnace.

The experiments conducted by the inventors and their results will be described below.

The inventors manufactured a bulk density distribution measurement container with a size close to that of an actual furnace, mixed briquette coal in various proportions with various powdered coals with different moisture contents, and used this container for bulk density measurement. The charcoal was charged into a container from the top, and then the bulk density and blending ratio of briquette charcoal at each part of the container were measured.

As a result, the following was found.

That is, when the blending ratio of briquette coal is kept constant, as the moisture content of pulverized coal decreases, not only does the bulk density at each position in the furnace improve, but also the segregation of briquette coal tends to decrease.

This is particularly noticeable when the moisture content of the pulverized coal is 5% or less, and it is estimated that the effects of stabilizing coke quality and improving strength will be significant.

Further, when the water content of the powdered coal is set to 9.5% and the blending ratio of briquette coal is changed, the bulk density at each position in the furnace increases as the blending ratio of briquette coal increases.

However, this bulk density improvement effect is due to an increase in the blending ratio of high-density briquette coal, and the bulk density of pulverized coal actually decreases compared to when briquette coal is not blended. It was found that the segregation of briquette coal was amplified as the blending ratio of briquette coal increased.

This tendency was noticeable immediately below the charging port and between the charging ports, and was estimated to be a cause of variation in coke strength.

From the above results, if the moisture content of pulverized coal is suppressed to 5% or less, segregation of briquette coal is prevented, bulk density is improved, and coke quality is greatly improved.

However, reducing the moisture content of pulverized coal to 5% or less is difficult in actual operation because it generates a huge amount of dust during the transportation process of raw materials and during charging into a coke oven.

Therefore, the inventors investigated the cause of deflection of briquette coal when pulverized coal containing 5% or more water content was used, and found that it was due to the difference in the angle of repose between pulverized coal and briquette coal.

In this briquette coal blending method, the angle of repose of powdered coal and briquette coal is usually about 38 degrees when the former has a moisture content of 10%, and about 32 degrees for the latter. It has been found that it is necessary to suppress the difference in temperature to a maximum of 32 degrees.

It was also found that the angle of repose of pulverized coal is greatly influenced by the moisture content, and when the moisture content is 5% or less, it becomes smaller than the angle of repose of briquette coal.

Therefore, by making the angle of repose of pulverized coal equal to or less than the angle of repose of briquette coal, segregation of briquette coal in the furnace can be prevented.

As a method for reducing the angle of repose of the pulverized coal, the inventors have confirmed that a method of adding and mixing oils and surfactants to pulverized coal containing 5% or more water is effective.

In other words, oils and surfactants have the effect of reducing the capillary force caused by the surface tension of water that binds coal particles, and reduce the adhesion force between coal particles, so they reduce the fluidity of coal particles. This leads to a reduction in the angle of repose.

These effects vary depending on the type of oil or surfactant, the type of coking coal, and the water content, but the amount of oil or surfactant added is not particularly limited, but the former depends on the amount of powdered coal. It was also confirmed that 1% or less, and the latter 0.1% or less, is sufficient.

Note that oils in this invention include kerosene, A heavy oil,
Examples of surfactants include hydrophobic oils such as anthracene oil and creosote oil, and examples of surfactants include sulfonic acids such as sodium dodecylbenzenesulfonate, alkylbenzenes, and fluorocarbon compounds. Examples include those that significantly lower surface tension.

As described above, according to the method of the present invention, the angle of repose of the pulverized coal can be reduced by adding and mixing oils or surfactants to the pulverized coal containing 5% or more moisture, thereby reducing the in-furnace segregation of the briquette coal. can be prevented.

This prevention of segregation makes it possible to mix a large amount of briquette coal (50 to 60%), reduce variations in coke strength, and stabilize quality.

It is also expected to have the effect of reducing segregation of briquette coal during the transportation process before charging it into a coke oven, eliminating the need for segregation prevention equipment in conventional coal towers and coal loading cars.

Next, an example of an apparatus for carrying out the method of the invention will be explained based on the drawings.

The drawing is a flow sheet showing the equipment, 1 is a coking coal tank,
2 is a mixer, 3 is an additive tank for oils or surfactants,
4 is a mixer, 5 is a non-caking coal tank, 6 is a binder tank, 7 is a kneader, 8 is a molding machine, and 9 is a molded coal mixer.

That is, single coking coal is cut out from the coking coal tank 1, and blended coal 10 is obtained in the mixer 2.

Oil or surfactant 11 in the additive tank 3 is added to a portion of this blended coal, and the mixture is sufficiently mixed by a mixer 4 to form additive-mixed coal 12.

On the other hand, the remainder of the blended coal 10 is obtained by kneading the non-caking coal cut out from the non-caking coal tank 5 and the molding binder cut out from the binder tank 6 in a kneading machine 7. Molded coal 13 is obtained.

This briquette coal 13 and the additive-mixed coal 12 are mixed in a mixer 9 to form coke oven charged coal 14.

Examples of the present invention will be described below.

Example 1 Using the method shown in the drawings, a part of powdered coal adjusted to a particle size of 83% or less with the raw material properties and blending ratio shown in Table 1 was mixed with heavy oil A as the oil and dodecyl as the surfactant. The additive-mixed charcoal obtained by adding and mixing sodium benzenesulfonate, the non-caking coal and binder shown in Table 1 and the soft pitch shown in Table 1 are added to the remainder of the powdered charcoal, and the mixture is kneaded and molded using a molding machine. The briquettes produced in the above are mixed at a briquette ratio of 30%, the resulting briquette blend is charged into a coke oven, and blast furnace coke is produced by carbonization at a flue temperature of 1180°C for 24 hours. did.

The conditions for adding oils and surfactants at that time are shown in Table 2.
Table 3 shows the variation in the amount of briquette coal and the variation in coke strength in the coke oven.

In Table 3, the variation in the amount of briquette coal and the variation in coke strength are expressed as standard deviation values.

Table 3 also shows, as comparative examples, variations in the amount of briquette coal and variations in coke strength when no oil or surfactant is used for comparison with the method of the present invention.

In addition, the variation in the amount of briquette coal (δB) is calculated from the briquette content measured at each part of the bulk density measurement container with the size of an actual furnace described in the text, while the variation in coke strength (δC) is It is calculated from drum strength measurement results for samples at positions within the coke work that are thought to correspond to various parts of the coke oven.

From the results in Table 3, test boils 5 and 6 shown as comparative examples,
In the case of No. 7, the variation in strength of briquette coal and coke is smaller in Test A7, which has the lowest moisture content, than in Tests A5 and A6.

This indicates that reducing the moisture content of pulverized coal is effective in reducing variations in the amount of briquette coal and coke strength.

However, in the case of Test A7, the amount of dust was low due to the low moisture content, and stable operation was not possible.

On the other hand, in test plates 1, 2, 3, and 4 of the method of the present invention, even if the powder coal contained 9.5% moisture, which is the same as in test A5 of the comparative example, heavy oil A was 0.3% based on the amount of coal. It was confirmed that by adding only 0.5% and 0.02% and 0.03% of surfactant, respectively, the segregation of molded coal in the coke oven was reduced to about % or less in δB of Test A5. It was done.

In particular, test plates 2 and 4 with the addition of 0.5% heavy oil A and 0.03% surfactant were found to be more effective than test A7 with a water content of 4.8E3%.

Furthermore, due to the effect of halving the polarization of briquette coal, the variation in coke strength in the method of the present invention is reduced to 0.0 at δC compared to the comparative example.
It was confirmed that the reduction was 15 or more.

Incidentally, in the method of the present invention, as a matter of course, the generation of dust was not much different from that in the comparative example (Test A5), and there were no operational problems.

Example 2 Blast furnace coke was produced in the same manner as in Example 1, using powdered coal containing 9.5% moisture as in Example 1, and increasing the blending ratio of briquette coal to 40% and 50%. At that time, the variation in the amount of briquettes in the coke oven and the variation in coke strength of the resulting product were measured.

The results are shown in Table 4. Table 4 also shows the results obtained when heavy oil A and surfactant were not added, as in Example 1, for comparison with the method of the present invention.

It is clear from the results in Table 4 that in Tests JP6.10 and 13 shown as comparative examples and Test A5 of Example 1, as the blending ratio of briquette coal was increased to 30%, 40%, and 50%, While the variation in the amount of briquette coal in the coke oven and the variation in coke strength greatly increase, in the method of the present invention, as seen in Tests A8, 9, 11, and 12,
Both the dispersion of briquettes in the coke oven and the dispersion of coke strength are only slightly increased compared to Tests A2 and 4 of Example 1, where the blending ratio of briquette coal is 30%, resulting in stable quality. of coke was obtained.

As described above, according to the present invention, even if the blending ratio of briquette coal is increased to the theoretical 50%, the segregation of briquette coal in the coke oven is slight, and coke of stable quality can be obtained.

Therefore, the present invention has the extremely great effect of stabilizing the coke quality in the coke production method containing briquette coal and increasing the use of low-rank coal by blending a large amount of briquette coal.

[Brief explanation of drawings]

The drawing is a flow sheet showing an example of an apparatus for carrying out the method of this invention. In the figure 1... Caking coal tank, 2... Mixer,
3... Additive tank, 4... Mixer, 5...
...Non-caking coal tank, 6...Binder tank,
7... Kneading machine, 8... Molding machine, 9...
... Molded coal mixer, 10 ... Blended coal, 11
...Oils or surfactants, 12...
Additive mixed charcoal, 13... Molded coal, 14...
...Coke oven charging coal.

Claims (1)

[Claims] 1. In a method of manufacturing coke by blending briquette coal with pulverized coal containing 5% or more water, by adding oil or a surfactant to the pulverized coal in advance, segregation of the briquette coal in the furnace can be prevented. A method for producing coke for blast furnaces characterized by preventing.