JPH0776370B2 - Blast furnace operation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for operating a blast furnace in which a branch pipe air flow control valve and a branch pipe air flow meter are provided for each blast branch pipe.

(Prior Art) In order to stabilize the operation of the blast furnace, it is necessary to make the gas distribution in the furnace circumferentially uniform. For that purpose, it is necessary to make the air permeability in the circumferential direction of the furnace uniform and the air flow from each tuyere uniform.

However, in general, air is blown into the furnace of a blast furnace by sending cold air from a blower to a hot air stove, and sending cool air from the tuyeres through the air blow pipes through the hot air pipes with 1000 to 1200 ° C. and without hot air pipes and annular pipes. However, since the annular tube and the hot-air stove are usually connected by a single hot-air tube, even if the air permeability in the circumferential direction in the furnace is uniform, the tuyere near the connecting part of the hot-air tube and the far away tuyere Then, the amount of air blown into the furnace varies. Such non-uniformity of the air flow from each tuyere on the blast furnace blast equipment is caused by changing the diameter of each tuyere and the setting of the valve opening of the branch air flow control valve provided on the blast branch pipe (Japanese Patent Publication No. 53-13325). No. 60-114511). In addition, the annular tube of the blast furnace was divided into multiple parts, and each of the divided annular tubes was connected with a hot air tube, a hot air oven, and a blower, and an independent air blowing system was installed for each annular tube (Japanese Patent Publication No. 48-39122). Alternatively, the blast branch pipe group is divided into multiple blast branch pipe groups along the blast furnace circumferential direction, this blast branch pipe group is connected to the distribution pipes provided for each blast branch pipe group, and each distribution pipe is looped through a communication pipe. It can also be solved by connecting to a pipe and installing a flow control valve in each communication pipe (Japanese Patent Publication No. 57-52923). Incidentally, if the air permeability in the circumferential direction in the furnace is uniform, in the blast furnace that is configured so that the amount of air blown from each tuyere is uniform as described above and that a branch pipe airflow meter is provided for each blown branch pipe, The branch pipe air volumes measured by the branch pipe airflow meters show the air permeability in the furnace circumferential direction, and the branch pipe airflow groups measured by the branch pipe airflow meter group show the air permeability in the furnace circumferential direction.

On the other hand, the non-uniformity of air permeability in the circumferential direction of the furnace is caused by coke, ore particle size segregation, non-uniformity of raw fuel properties, deterioration of profile due to damage to the furnace body, and the like.

(Problems to be solved by the invention) By the way, such non-uniformity of air permeability in the circumferential direction of the furnace is
It can be solved by controlling the distribution of the charge from the top of the furnace, but it takes several days to determine the effect after the charge distribution has been taken. That is, the charge distribution control cannot immediately eliminate the non-uniformity of air permeability in the circumferential direction of the furnace.

The present invention utilizes immediate improvement characteristics of in-furnace air permeability in front of a specific tuyere, which is a new finding in a blast furnace in which a branching airflow control valve and a branching airflow meter are provided for each of the above blasting branch pipes. Thus, the present invention provides a method for operating a blast furnace in which the non-uniformity of air permeability in the circumferential direction of the furnace can be promptly made uniform to stably maintain the operation of the blast furnace.

(Means for Solving Problems) The gist of the present invention is as follows.

In a blast furnace equipped with a branch pipe air flow control valve and a branch pipe air flow meter for each blast branch pipe connected to the tuyere, the air flow rate of the branch pipe air flow meter group under the set valve opening of the branch pipe air flow control valve group is periodically detected. , Each blast branch pipe has an air volume that is less than the set air volume.The air flow rate control valve of the blast branch pipe has a valve opening that is smaller than the set valve opening, and the air volume has been reduced to connect to a blast tube that has a smaller air volume than the set air volume. The method for operating a blast furnace is characterized by improving the air permeability in the furnace before the tuyere and returning the valve opening of the branch pipe air flow control valve to the set valve opening.

The inventors of the present invention have shown that, as shown in FIG. 1, a single hot air tube 7 is connected to the annular tube 6, and 27 air blowers connected to 27 tuyere 1 provided at equal intervals in the furnace circumferential direction. Each branch pipe 2 is provided with a branch pipe air flow rate control valve 3 and a branch pipe air flow meter 4 having the valve opening-flow rate ratio characteristics shown in FIG. 2. If the in-furnace air permeability in front of each tuyere 1 is uniform, each branch pipe air flow rate is increased. In the blast furnace 5 in which the diameter of each tuyere 1 is adjusted so that the amount of air blown from each tuyere 1 is uniform under the same opening degree of the control valve 3, all the branch pipe air volume control valves 3 are opened. While the air is being blown at full opening (valve opening 100%), the valve opening of one branch pipe air flow control valve 3 is decreased (valve opening 30%) as shown in Fig. 3 to decrease the valve opening. The amount of branch air of the blown branch pipe 2 (the amount of air blown from the tuyere 1 connected to the operated blower branch pipe 2 into the furnace) was measured by the branch pipe air flow meter 4 installed in the blower branch pipe 2. By the way After the operation of decreasing the valve opening of the pipe air volume control valve 3, the branch pipe air volume temporarily decreases, but thereafter the branch pipe air volume increases, that is, the valve opening of the branch pipe air volume control valve 3 decreases and the amount of air blown from the tuyere 1 It was found that the air permeability in the furnace before the tuyere 1 was improved immediately within a few hours by decreasing

Although the mechanism by which the air permeability in the furnace in front of the tuyere 1 is immediately improved by reducing the valve opening of the branch pipe air flow control valve 3 to reduce the air flow from the tuyere 1, is not clear, It is considered that this is because when the branch air volume and the tuyere air flow rate decrease, the tuyere tip wind speed decreases and the coke powder ratio in the raceway decreases. The set valve opening of the branch pipe air flow control valve group is
A single hot air pipe is connected to the annular pipe, and if the air permeability in the circumferential direction in the furnace is uniform, under equal valve opening of each branch pipe air flow control valve,
In a blast furnace in which the diameter of each tuyere is adjusted so that the amount of air blown from each tuyere is uniform, for example, fully open, that is, valve opening 100
%. If the air permeability in the circumferential direction in the furnace is uniform,
In the blast furnace 5 in which the valve opening of each branch pipe air flow control valve is set so that the air flow from each tuyere is uniform, the valve opening is set as described above.

In addition, by having a ventilation system proposed in Japanese Patent Publication No. 48-39122 or Japanese Patent Publication No. 57-52923, it eliminates the unevenness of the amount of air blown from each tuyere on the ventilation equipment, and In a blast furnace in which a branch pipe air flow control valve and a branch pipe air flow meter are provided for each connected blower branch pipe, for example, it is fully opened, that is, the valve opening is 100%.

Further, as the set air flow rate of the blower branch pipe, for example, a total average air flow rate of the blast furnace divided by the number of tuyere of the blast furnace, or [(1-α) × logical average air flow rate] (where α <1,
α is determined according to the reduced air flow rate from the logical average air flow rate that can maintain stable operation of the blast furnace).

(Example) Hereinafter, the blast furnace operating method of the present invention will be described in detail based on an example.

As shown in FIG. 1, a single hot air tube 7 is connected to the annular tube 6, and for each of the 27 blower branch tubes 2 connected to the 27 tuyeres 1 provided at equal intervals in the furnace circumferential direction, The branch pipe air volume control valve 3 and the branch pipe air flow meter 4 having the valve opening-flow rate ratio characteristics shown in FIG.
The total air flow rate in which the diameter of each tuyere 1 is adjusted so that the air flow rate from each tuyere 1 is uniform when the air flow rate of each tributary airflow control valve 3 is uniform, for example, fully open (100% valve opening). 4050 (Nm ³ / min)
In the blast furnace 5 having a [logical average air flow rate of 150 (Nm ³ / min)], for example, circumferential branch pipe air flow control valve opening distributions in FIGS. 4 and 6 (hereinafter, abbreviated as circumferential valve opening distributions) As described above, each branch pipe air flow control valve 3 has a uniform set valve opening, that is, fully opened (valve opening 100
%), The branch air flow rate (Nm ³ /
min) is periodically detected, for example, every 20 minutes, and a branch pipe air flow distribution in the circumferential direction as shown in FIGS. 5 and 7 (hereinafter abbreviated as circumferential branch pipe air flow distribution) is detected.

In the distribution diagrams shown in FIGS. 4 to 7 and FIGS. 8 to 13, which will be described later, 1 to 27 indicate the tuyere and blast branch pipe numbers of the blast furnace 5 in the circumferential direction. In the circumferential valve opening distribution charts in Figures 4, 6, 8, 10, and 12, 0, 50, and 100 indicate the valve opening (%), and the circumferences in Figures 5, 7, 9, 11, and 13 In the directional branch airflow distribution map, 100, 150, 200 indicate the branch airflow (Nm ³ / min).

Further, in the embodiment described in detail below, the set air volume is [(1
−α) × logical average air volume], and α = 0.
03 is adopted. In addition, the air volume of each blast branch pipe is [(1 ± α)
X logical average air volume], it is judged that the circumferential branch pipe air volume is uniform and the air permeability in the furnace circumferential direction is uniform.

Now, as shown in the circumferential valve opening distribution in FIG. 4, all branch pipe air flow control valves 3 have a uniform set valve opening, and in the circumferential branch pipe air flow distribution in FIG. 5, the circumferential branch pipe air amounts are uniform. The same setting valve as in Fig. 4 was used due to disturbances such as coke, ore particle size segregation, non-uniformity of raw fuel properties, deterioration of profile due to damage to the furnace body, etc. Under the opening distribution (see FIG. 6), the air volume of the branch pipes 2 and tuyere 1 of Nos. 2 to 9 is smaller than the set air volume as in the circumferential branch pipe air volume distribution of FIG. As described above, when the unevenness of the circumferential branch pipe airflow is detected and the unevenness of the air permeability in the circumferential direction of the furnace is detected, the valve opening degree of the branch pipe airflow control valve 3 of the blower branch pipes No. 2 to 9 is changed. As shown in FIG.
The air volume of the blast branch pipe 2 and the tuyere 1 is further reduced as shown in FIG. 9 as compared with FIG. Due to the operation of decreasing the valve opening of the branch pipe air volume control valve 3 of the blower branch pipe 2 of No. 2 to 9 from the set valve opening
Due to the decrease in the amount of air blown from the No. 2 to 9 blast branch pipes 2 and the tuyere 1, the in-furnace air permeability in front of the No. 2 to 9 tuyere 1 is improved,
Under the same valve opening distribution as in Fig. 8 (see Fig. 10), as shown in Fig. 9 to Fig. 11, the blower branch pipes 2 and tuyeres 1 of Nos. 2 to 9 have the set air volume and the theoretical average air volume of 150. Recovers to (Nm ³ / min) once.

In this way, the blower branch pipes No. 2 to 9 and the tuyere 1 are fed into the furnace by the operation of decreasing the valve opening degree of the branch pipe air volume control valve 3 of the blower branch pipes No. 2 to 9 No.2 due to the reduction of air volume
No.2 to 9 blows as shown in Fig. 9 to Fig. 11 under the same valve opening distribution as Fig. 8 (see Fig. 10) with improved air permeability in front of tuyere 1 When the air volume of the branch pipe 2 and the tuyere 1 once recovered toward the set air volume and the theoretical average air volume of 150 (Nm ³ / min),
As shown in FIG. 12, the branch pipe air flow control valve 3 of the blower branch pipes No. 2 to 9
The valve opening of is returned to the set valve opening, that is, fully opened, and then the branch pipe airflow meter (group 4) detects the branch pipe airflow (Nm ³ / min) to detect the branch pipe airflow distribution in the circumferential direction. Based on this branch airflow distribution,
By judging the uniformity of air permeability in the circumferential direction of the furnace, the uniformity of air flow in the circumferential branch pipe is ensured as shown in the distribution of air flow in the circumferential direction of the branch pipe in Fig. 13. Until it is determined that there is a set air flow, the branch air flow control valve 3 of the blower branch pipe 2
The operation of decreasing the valve opening from the set valve opening or the operation of returning to the set valve opening is repeatedly performed.

If the uniformity of the circumferential branch pipe air flow is ensured as in the circumferential branch pipe air flow distribution in Fig. 13, and the air permeability in the circumferential direction of the furnace is also ensured, the total branch pipe air flow control is performed as shown in Fig. 12. Set the valve opening of valve 3 (The air is blown while the valve is fully opened, and the branch pipe airflow meter (Nm ³ / min) is periodically detected by the branch pipe airflow meter 4 group to detect the branch pipe airflow distribution in the circumferential direction. To do.

Next, the specific implementation results will be described. When the valve opening of the total branch air flow control valve 3 is under the set valve opening (fully open = valve opening 100%), the branch pipe air flow meter (Nm ³ / min) every 20 min to detect the distribution flow amount of the branch pipe in the circumferential direction. The distribution flow amount of the branch pipe in the circumferential direction was uniform as shown in Fig. 5, and the air permeability in the circumferential direction of the furnace was uniform. Fig. 8 shows the valve opening of the branch pipe air volume control valve 3 of the blower branch pipes No. 2 to 9 in which the air volume is reduced from the set air volume when it is detected that the air flow is uneven as shown in Fig. 7. As shown in Fig.8 and 10, the ventilation is continued with the valve opening distribution shown in Figs.8 and 10, and the valve opening decreasing operation is performed through the branch pipe air volume distribution shown in Fig.9. After hours, 11th
When the branch pipe air flow distribution shown in the figure is reached, as shown in FIG. 12, when the valve opening of the branch pipe air flow control valve 3 of the blower branch pipes No. 2 to 9 is returned to the set valve opening, as shown in FIG. It was possible to make the distribution of the branch pipe air flow in the circumferential direction uniform and to make the air permeability in the circumferential direction in the furnace uniform. That is, after the non-uniformity of the air permeability in the circumferential direction in the furnace was detected, the air permeability in the circumferential direction in the furnace could be immediately made uniform in a short time of 6 hours.

(Effects of the Invention) As described in detail above, according to the blast furnace operating method of the present invention,
The unevenness of the air permeability in the circumferential direction in the furnace can be promptly made uniform, and the blast furnace operation can be stably maintained.

[Brief description of drawings]

FIGS. 1 to 3 (a) and (b) are explanatory views of the immediately effective improvement characteristics of the in-furnace air permeability before the specific tuyere due to the reduction of the air flow rate of the specific tuyere, which is the basis of the method of the present invention, and 4 to 13 The figure is an explanatory view of an embodiment of the blast furnace operating method of the present invention. 1 …… Tuyere 2 …… Blast branch pipe 3 …… Branch pipe air flow control valve 4 …… Branch pipe air flow meter 5 …… Blast furnace 6 …… Annular pipe 7 …… Hot air pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-61-295309 (JP, A) JP-A-51-24515 (JP, A) JP-A-54-110906 (JP, A) JP-A-49- 91906 (JP, A)

Claims (1)

[Claims] 1. In a blast furnace in which a branch pipe air flow control valve and a branch pipe air flow meter are provided for each blast branch pipe connected to a tuyere, the air flow rate of the branch pipe air flow meter group under the set valve opening of the branch pipe air flow control valve group is set. Detected periodically, the air volume has decreased from the set air volume evenly for each blast branch pipe.The valve opening of the tributary air flow control valve of the blast tributary is reduced below the set valve opening, and the blast volume is reduced to decrease the air volume below the set air volume. A method for operating a blast furnace, characterized in that the air permeability in the furnace before the tuyere connected to the blower branch pipe is improved, and the valve opening of the branch pipe air flow control valve is returned to the set valve opening.