JP2005068474A - Method and system for blowing pulverized fine coal into blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably perform blowing of pulverized fine coal by resolving a problem in the blowing of the pulverized fine coal with a simpler procedure. <P>SOLUTION: A system for blowing the pulverized fine coal is provided with a control unit 7 for adjusting moisture content in the pulverized fine coal by adjusting the temperature of carrying gas. The control unit 7, concretely, adjusts the temperature of the carrying gas based on HGI and VM value in the characteristics of the coal having high correlation with the moisture content in the pulverized fine coal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for injecting pulverized coal into a blast furnace and a system for injecting pulverized coal into a blast furnace.

The operation of injecting pulverized coal into the blast furnace is frequently used because the amount of coke charged into the blast furnace can be reduced. In recent years, the operation of blowing pulverized coal into the blast furnace has been carried out on a large scale, and a problem that is particularly problematic in the operation of blowing pulverized coal is a method of blowing pulverized coal that can achieve stable blowing.
In the operation of injecting pulverized coal into the blast furnace, the coal is crushed and supplied to the blast furnace as pulverized coal, and various varieties (brands) are used as the coal. However, since the crushing conditions differ depending on the coal varieties, there is a problem in that stable blowing during pulverized coal blowing is hindered. For example, there is a problem that the pulverized coal supply pipe is clogged.

Japanese Patent Application Laid-Open No. H10-228707 discloses a technique that can solve such a problem.
When pulverized coal having different hardness (HGI (Hard Glove Grindability Index)) is pulverized at the same time, the particle size of the pulverized coal depends on the blending ratio of hard pulverized coal (HGI ≦ 50) and soft pulverized coal (HGI ≧ 70). In contrast, when the blending ratio of the soft pulverized coal is increased, the particle size of the pulverized coal is reduced, which causes clogging of the pulverized coal supply piping to the blast furnace air tuyeres. For this reason, there arises a problem that the pulverized coal supply pipe is blocked only by managing the particle sizes of a plurality of types of pulverized coal having different hardness only by the combustibility of the pulverized coal.

With respect to such a problem, in Patent Document 1, when a plurality of types of pulverized coal having different hardnesses are used at the same time, the pulverized coal supply pipe is prevented from being blocked without impairing the combustibility of the pulverized coal in the blast furnace. A blast furnace pulverized coal injection method is proposed.
In the pulverized coal blowing operation method of the blast furnace, when simultaneously blowing a plurality of types of pulverized coal having different hardness together with hot air from the blower tuyere, the plurality of types of pulverized coal having different hardnesses are simultaneously 200 mesh or less from 65% to 65%- By crushing and maintaining the particle size to 75%, blockage of the pulverized coal supply piping to the blower tuyere is prevented.

  That is, if the pulverized coal is too small in particle size, the flowability is deteriorated and the supply piping to the blast furnace tuyere is clogged. Further, when pulverized coals having different hardnesses are simultaneously pulverized, the soft pulverized coal is excessively pulverized and the particle size becomes too small. Therefore, in Patent Document 1, since there is a correlation between the pulverized coal particle size and the collector differential pressure, the pulverized coal particle size after pulverization is estimated from the collector differential pressure. The crusher is controlled so that the charcoal particle size does not become too small.

Patent Document 2 also proposes a method for injecting pulverized coal into a blast furnace.
Coal contains, in addition to carbon, which is the main component, ash composed of volatile components and oxides that volatilize when heated. Here, the volatile matter of coal greatly depends on the particle size at the time of crushing. That is, the strength of coal indicated by a hard clove index (HGI) or the like mainly changes depending on the volatile content in the coal. This indicates that coal with less volatile content has lower strength and is easily crushed. From these characteristics, when pulverized under the same rolling force, the smaller the volatile content, the smaller the particle size. Become.

As a result, when coal with a small amount of volatile matter is pulverized coal and blown into the blast furnace, blow-through in the injection tank and blockage in the transport piping are likely to occur. In particular, pulverized coal composed of particles having a volatile content of less than 30% by mass has a markedly reduced transport property.
Therefore, in Patent Document 2, 5 to 60% by mass of pulverized coal is a particle having a particle diameter of 1 to 20 μm and pulverized powder to a blast furnace using pulverized coal containing 1 to 8% by mass of water. Proposes a charcoal blowing method.

Further, in Patent Document 2, it is proposed that pulverized coal is regarded as a combination of coal types, and that 10 to 90% by mass in the pulverized coal is preferably composed of coal containing 30 to 50% by mass of volatile matter. doing.
Patent Document 3 also proposes a method for producing pulverized coal for in-reactor blowing.
In the method for producing pulverized coal for in-reactor blowing, in the production of pulverized coal for in-blast furnace blowing, the particle size distribution of the pulverized coal to be injected is controlled by using the pulverization characteristics of the coal used for producing the pulverized coal as a parameter. The crushing force applied to the coal is adjusted in the production apparatus.
JP-A-9-143519 JP 2001-271105 A JP 2002-194408 A

In the techniques of Patent Documents 1 to 3, the problem of blowing pulverized coal is solved by adjusting the particle size of coal supplied as pulverized coal. For this reason, in the techniques of Patent Documents 1 to 3, it is necessary to adjust crushing with a crusher every time the coal type changes.
However, when trying to produce pulverized coal using a wide variety of inexpensive coal, it is difficult to adjust crushing with a crusher each time. For this reason, when using a wide variety of inexpensive coals, it becomes impossible to stabilize the injection and perform the operation of injecting pulverized coal into the blast furnace.
Therefore, the present invention has been made in view of such a situation, and can solve the above-described problem of pulverized coal injection by a simpler procedure and can stably perform the injection. The purpose is to provide a pulverized coal injection method and a pulverized coal injection system to a blast furnace.

In the blast furnace pulverized coal blowing operation method according to the first aspect of the invention, the moisture content of the pulverized coal is adjusted by adjusting the temperature of the carrier gas.
The blowing of pulverized coal depends on the moisture content of the pulverized coal. Using such a relationship, the moisture content of the pulverized coal is adjusted by adjusting the temperature of the carrier gas, and the blowing state of the pulverized coal is adjusted.
A blast furnace pulverized coal injection operation method according to claim 2 is the blast furnace pulverized coal injection operation method according to claim 1, wherein the pulverized coal is controlled by adjusting a moisture content of the pulverized coal. The moisture content of is set to a predetermined amount or less.
The blast furnace pulverized coal injection operation method according to claim 3 is the blast furnace pulverized coal injection operation method according to claim 2, wherein the moisture content of the pulverized coal is 4% or less. It is characterized by.

A blast furnace pulverized coal blowing operation method according to the invention described in claim 4 is the blast furnace pulverized coal blowing operation method according to any one of claims 1 to 3, wherein The temperature of the carrier gas is adjusted based on the properties of the coal having a high correlation.
A blast furnace pulverized coal injection operation method according to the invention described in claim 5 is the blast furnace pulverized coal injection operation method according to claim 4, wherein the property of the coal is a hard glove pulverization index (HGI). is there.
A blast furnace pulverized coal injection operation method according to the invention described in claim 6 is the blast furnace pulverized coal injection operation method according to claim 4, wherein the property of the coal is a VM (Volatile Matter) value.
Moreover, the pulverized coal injection system to the blast furnace according to the invention of claim 7 includes a pulverized coal-containing water content adjusting means for adjusting the moisture content of the pulverized coal by adjusting the temperature of the carrier gas.

  According to the present invention, the blowing state of pulverized coal can be adjusted only by adjusting the temperature of the carrier gas of pulverized coal. Thereby, the problem on pulverized coal blowing can be solved by a simpler procedure, and the blowing can be stabilized.

The best mode for carrying out the present invention will be described in detail with reference to the drawings.
The embodiment is a pulverized coal blowing system to which the present invention is applied. FIG. 1 shows the configuration of the pulverized coal blowing system.
In the pulverized coal blowing system, coal that has been conveyed by the conveyor 1, the mill feed bin 2, and the conveyor 3 is input to the crushing mill 4.
The crushing mill 4 crushes the input coal. This crushing mill 4 has a crushing performance of 60 t / hr, for example. Hot air is sent to the exit side of the pulverizing mill 4, that is, a portion where the pulverized coal is present, and the pulverized coal is conveyed to the pulverized coal blowing unit 10 via the piping system 5 by airflow transportation using the carrier gas. The carrier gas is generated in the hot air generator 6.
The hot air generating furnace 6 is fed with C (coke oven) gas and combustion air, and thereby burns. Then, N ₂ gas is fed into the hot air generating furnace 5.

The flow rate of C gas to the hot air generating furnace 6 is controlled by the control unit 7. Further, the combustion air and N ₂ gas are usually set to a constant flow rate. In some cases, the flow rate of the N ₂ gas is increased to suppress the temperature rise of the hot air generating furnace 5. Further, various exhaust gases or inert gases may be used instead of N ₂ .
The control unit 7 adjusts the water content of the pulverized coal generated by the pulverization mill 4. Specifically, the control unit 7 adjusts the flow rate of the C gas based on the hard glove grindability index (HGI) and the VM (Volatile Matter) value of coal, and controls the temperature of the hot air sent to the crushing mill 4. ing.

Here, the VM value is a value indicating a volatile component or a volatile component in the coal properties. The VM value and HGI have a high correlation with the moisture content of the coal, and the control unit 7 controls the temperature of the hot air fed into the pulverizing mill 4 by adjusting the flow rate of C gas using these values as an index. . Thereby, the control part 7 is adjusting the water content of the pulverized coal produced | generated with the grinding | pulverization mill 4. FIG.
Note that the temperature at the inlet of the bag filter 11 described later is sampled, and the control unit 7 controls the temperature of the hot air based on the sampling result.

The pulverized mill 4 is supplied with hot air whose temperature is controlled by the control unit 7 as described above. The pulverized coal generated by the pulverized mill 4 is pulverized coal via the piping system 5 using the hot air as a carrier gas. It is sent to the blowing unit 10.
In the pulverized coal blowing section 10, the pulverized coal that has been transferred to the transfer gas is sent to the bag filter 11. The bag filter 11 collects pulverized coal and exhausts hot air through the chimney. The pulverized coal collected by the bag filter 11 is sifted through a screen 12 to remove a rough portion and is put into a hopper 13.

The pulverized coal charged into the hopper 13 is supplied to the injection tank 15 via the intermediate tank 14. The injection tank 15 is pressurized, and the pulverized coal is blown into the blast furnace 18 through the tuyere 16 and the pipe line 17 due to the differential pressure between the injection tank 15 and the blast furnace 18.
Here, the hopper 13 is at atmospheric pressure, and the intermediate tank 14 pressurizes the pulverized coal supplied from the hopper 13 and sends it to the injection tank 15.
Further, when there is no accumulated amount of pulverized coal in the hopper 13, the entire pressure in the intermediate tank 14 is the same as the pressure in the injection tank 15 in order not to stop the blowing of pulverized coal from the injection tank 15. By making it into (pressurized state), the pulverized coal in the intermediate tank 14 is continuously blown into the pipe line 17 through the injection tank 15.

Next, temperature control of the hot air by the control unit 7 will be specifically described.
FIG. 2 shows the relationship between the moisture percentage of pulverized coal and the average blowing speed when being blown into the blast furnace 18. That is, FIG. 2 shows the influence of the moisture% of the pulverized coal on the conveyance of the pulverized coal. In addition, as shown in FIG. 2, the result is acquired about the brands X and Y of two coals.
In the brand Y, when the moisture% becomes larger than 4%, the average blowing speed is greatly reduced. This is presumably because the line (pipe 16 or the like) is clogged when the moisture percentage of the brand Y is greater than 4%.

In brand X, even if the moisture percentage is increased to around 8%, there is no significant change in the average blowing rate. However, although not shown in the figure, when the moisture percentage is higher than 8%, the average blowing speed is greatly reduced. This is presumably because in the case of the brand X, the line (the pipe line 16 or the like) is clogged when the moisture percentage becomes larger than 8%.
Next, the relationship between the VM value and HGI having a high correlation with the moisture content of coal and the transportability of pulverized coal will be considered. The following table shows the relationship between the VM value and HGI and the transportability of pulverized coal.

In this table, the relationship between the brands A to J of coal having various VM values and HGI and the transportability is shown. Here, ◯ in the transportability column indicates that the transportability is good, Δ indicates that the transportability is not very good, and x indicates that the transportability is not good.
As can be seen from this table, in the brands A, D, E, F, G, H, I, and J having a VM value of about 20 or more, or HGI of about 80 or less, the transportability is good. ing. This is considered that the line (pipe line 16 and the like) is not clogged with coal having a VM value of around 20 or more, or HGI of around 80 or less.
Further, FIG. 3 shows the relationship between the average VM value and the blowing index. The blowing index is a value obtained by dividing the actual blowing amount by the set blowing amount. Therefore, the case where the blowing index is small means that blowing is difficult.

As shown in FIG. 3, when the average VM value is less than about 20 (%), the blowing index is greatly reduced, that is, it becomes difficult to blow.
FIG. 4 shows the relationship between the average VM value of the coal used during operation ((B) in the figure) and the number of times of blockage of the blowing operation ((B) in the figure). Here, the horizontal axis indicates the time, for example, the result of sampling a period of 2 years.
As shown in FIG. 4, when the average VM value becomes less than about 20%, the number of line blockages increases. Such results qualitatively show the same results as in the above table and FIG.
As described above, when the moisture percentage of coal is increased to some extent, the average blowing speed is greatly reduced, that is, it becomes difficult to blow or the transportability is deteriorated. Since the VM value and HGI have a high correlation with the moisture content of coal, as can be seen from Table 1, FIG. 3 and FIG. To come.

  For this reason, the control unit 7 adjusts the supply amount of the C gas based on the VM value and the HGI, and adjusts the temperature of the hot air. Specifically, when the VM value is less than 20 (%) or the HGI is greater than 80, the control unit 7 increases the temperature of the hot air by increasing the supply amount of C gas. At this time, the control unit 7 increases the temperature of the hot air based on the VM value that is less than 20 (%) or the HGI that is greater than 80. Thereby, in the pulverized coal blowing system, the moisture content of the pulverized coal is reduced, making it easy to blow or improving the transportability.

Thus, in the pulverized coal blowing system, the temperature of the hot air (carrier gas) is adjusted to adjust the moisture content of the pulverized coal to facilitate blowing or improve the transportability.
Conventionally, in order to improve transportability, it has been difficult to control the crushing diameter in response to changes in coal properties. On the other hand, when the present invention is applied, it is easy to blow or to improve transportability simply by adjusting the temperature of the hot air (carrier gas) based on the moisture content of the pulverized coal. Or it can be said that the improvement of transportability is realized.

Also, focusing on the fact that the VM value and HGI, which are the properties of coal, have a high correlation with the moisture content of pulverized coal, the temperature of hot air (carrier gas) is adjusted based on the VM value and HGI. Even if the type of coal is changed, the temperature of hot air (carrier gas) can be easily adjusted according to the moisture content of the pulverized coal by referring to the VM value and HGI which are the properties of the coal. .
Furthermore, it is difficult to control the pulverization mill so that the particle size of the pulverized coal becomes a desired value, but it is easy to adjust the temperature of the hot air (carrier gas) from the hot air generating furnace 6. From such a thing, blowing property or conveyance property can be improved quickly and reliably.
The embodiment of the present invention has been described above. However, the present invention is not limited to being realized as the above-described embodiment.
That is, in the above-described embodiment, the case where the property of coal having a high correlation with the moisture content of pulverized coal is a VM value or HGI has been described. However, it goes without saying that the present invention is not limited to this.

Moreover, in the above-described embodiment, the case where one kind of coal is changed to pulverized coal has been described. However, it goes without saying that the present invention is not limited to this. For example, when producing pulverized coal from two or more brands of coal, refer to the value of the VM value or HGI of those coals with the smallest VM value or the largest HGI, and determine the temperature of the hot air. adjust.
Moreover, in above-mentioned embodiment, it utilizes that the VM value and HGI which are the characteristics of coal have a high correlation with the moisture content of pulverized coal, and hot air (carrier gas) based on the VM VM value and HGI. This explains the case where the temperature is adjusted. However, it goes without saying that the present invention is not limited to this. That is, the moisture content of pulverized coal may be directly detected, and the temperature of the hot air (carrier gas) may be adjusted based on the moisture content. In this case, as can be seen from the results of FIG. 2, the temperature of the hot air (carrier gas) is adjusted so that the moisture content of the pulverized coal is at least 4% or less.

It is a figure which shows the structure of the pulverized coal blowing system of embodiment of this invention. It is a characteristic view which shows the relationship between the water | moisture content of pulverized coal, and an average blowing speed. It is a characteristic view which shows the relationship between an average VM value and a blowing index. It is a characteristic view which shows the relationship between an average VM value and the number of line blockages.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,3 Conveyor 2 Mill feed bin 4 Crushing mill 5 Piping system 6 Hot-air generating furnace 10 Pulverized coal blowing part 11 Bag filter 12 Screen 13 Hopper 14 Intermediate tank 15 Injection tank 16 Tuna 17 Pipe line 18 Blast furnace

Claims (7)

Crushing coal to produce pulverized coal, conveying the pulverized coal with a carrier gas, and a blast furnace pulverized coal blowing operation method for blowing the pulverized coal from a blast furnace tuyere,
A method for injecting pulverized coal into a blast furnace, wherein the moisture content of the pulverized coal is adjusted by adjusting the temperature of the carrier gas.   2. The method for injecting pulverized coal into a blast furnace according to claim 1, wherein the moisture content of the pulverized coal is adjusted so that the moisture content of the pulverized coal is not more than a predetermined amount.   The method for injecting pulverized coal into a blast furnace according to claim 2, wherein the moisture content of the pulverized coal is 4% or less.   The blast furnace blast coal injection operation according to any one of claims 1 to 3, wherein the temperature of the carrier gas is adjusted based on the property of the coal having a high correlation with the moisture content of the pulverized coal. Method.   The method for injecting pulverized coal into a blast furnace according to claim 4, wherein the property of the coal is a hard globe grindability index (HGI).   The pulverized coal blowing operation method for a blast furnace according to claim 4, wherein the property of the coal is a VM (Volatile Matter) value. A pulverized coal blowing system for a blast furnace that pulverizes coal to produce pulverized coal, conveys the pulverized coal with a carrier gas, and blows the pulverized coal from a blast furnace tuyere,
A pulverized coal blowing system for a blast furnace, comprising a pulverized coal-containing water content adjusting means for adjusting the moisture content of the pulverized coal by adjusting the temperature of the carrier gas.

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