JP3498969B2 - Raw material charging method for bellless blast furnace - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging a raw material into a blast furnace suitable for a large blast furnace having a large internal volume, and more particularly, to pulverized coal together with hot air from a blowing tuyere. The present invention relates to a method for securing a central flow by adjusting the state of lamination of raw materials (ore and coke) in reducing the total amount of coke charged into a furnace by blowing water. 2. Description of the Related Art Although the tapping amount of a blast furnace has increased remarkably due to the increase in the size of the blast furnace, it is important to stabilize the operation of the blast furnace in order to take advantage of the increase in the size of the blast furnace. Particularly in large blast furnaces, the output of tapping is greatly reduced due to the deterioration of the furnace conditions, which has a great effect on the next process. For this reason, various operating conditions must be controlled when operating the blast furnace, but various factors are intricately intertwined in controlling the distribution of ore and coke at the top of the blast furnace.
The main factors are as follows. (1) Physical properties of raw materials (ore, coke)-density, particle size, internal friction coefficient, etc. (2) Raw material charging speed (3) Charging conditions-layer ratio of ore to coke, stock line level ( 4) Tilt angle of swirl chute (5) Charging sequence (6) Furnace gas flow [0003] The distribution of ore and coke is determined when the raw material is charged through the swirl chute in a bellless blast furnace, but the fuel ratio What is important for reduction and operational stability is the distribution of the ore layer and coke layer in the furnace in the radial direction of the blast furnace. In other words, the concept of charge distribution control in blast furnace operation has been to optimize the radial distribution of the ratio of the amount of ore to the amount of coke (Ore / Coke). In order to efficiently heat and reduce ore charged in a blast furnace with a high-temperature reducing gas rising in the furnace, it is necessary to uniformly supply the ore with a reducing gas. It is difficult to make them uniform because of the influence of the characteristics and the deposition characteristics. If the rising reducing gas loses its balance, local drift will occur, and shelves and slips will occur frequently, deteriorating the furnace condition. For this reason, it has become common to concentrate a part of the reducing gas flow in the furnace center instead of dispersing the furnace gas evenly. For example, Japanese Patent Publication No. 64-9373 discloses that the charging of coke in each charge is divided into at least two series with time, and 92 to 98.5% by weight of the total charge of coke of the charge is charged to a previously charged ore layer. In the final charging system, 8 to 1.5% by weight of the total coke charge of the charge is intensively charged into the center of the furnace, so that (Ore / Coke) in the center of the furnace is charged. A method is disclosed in which the deposition is performed so that the ratio is substantially smaller than the (Ore / Coke) ratio at a portion other than the center of the furnace. Japanese Patent Application Laid-Open No. Hei 3-232912 discloses a method of charging coke in a bellless blast furnace in which 15 to 20% by weight of the total charge is charged into the center of the furnace. Conventionally, in a blast furnace, coke is used as a reducing agent and a part of a heat source. However, in order to reduce the amount of coke that requires the use of expensive coking coal, oil is blown from a blowing tuyere and blown from the bottom of the furnace. A method of supplying reducing agent and heat was established to improve the operation of the blast furnace. Due to the subsequent rise in oil prices, a method has been adopted in which pulverized coal is blown from the tuyere with hot air. The stabilization of the blast furnace operation and the effect of increasing the production of pulverized coal have been demonstrated, and recently, as much as 180 kg of pulverized coal has been injected per ton of pig iron. [0007] As disclosed in the above publication, when charging coke into a blast furnace, coke of a fixed ratio with respect to the total charge of coke is concentrated in the center of the furnace. In such a method, when the total amount of coke charged decreases due to the injection of a large amount of pulverized coal, the amount of coke charged into the center of the furnace also decreases proportionally. At the same time, a decrease in the total coke charge increases the (Ore / Coke) ratio, which also increases the amount of ore flowing into the furnace center. However, there is a problem in that the desired effect of improving the air permeability by concentrating the gas in the center of the furnace cannot be obtained. The present invention has been made in view of such circumstances, and it is possible to increase the amount of pulverized coal blown together with hot air from a blast furnace tuyere to reduce the total amount of coke charged into the blast furnace. It is an object of the present invention to provide a method for charging a raw material into a blast furnace, which can ensure air permeability in the center of the furnace. According to the inventor's experience of operating a bellless blast furnace, the ratio of the amount of ore (Ore) to the amount of coke (Ore) relative to the amount of coke (Coke) is measured when pulverized coal is not blown from the tuyere. O
In the blast furnace operation of (re / Coke) = 3.3, the coke of the charge is charged so as to cover the entire ore layer of the previous charge, and then charged into the center of the furnace before the ore of the next charge is charged. It is known that if the coke amount is controlled in the range of 2.0 to 3.0 tons per charge, the hearth is activated, and the hearth does not have a hardly permeable layer, and the gas permeability and liquid permeability are improved. The inventor first activates the hearth using a scale model of a blast furnace when the ratio of ore amount to coke amount (Ore / Coke) = 3.3 when pulverized coal is not injected from the blast tuyere. The ratio of the ore layer to the coke layer at the center of the furnace when the raw materials were charged under the possible charging conditions was measured. Next, pulverized coal is blown from the blast tuyere using the scale model to reduce the amount of coke charged into the furnace, and therefore, even during operations where the ratio of ore amount to coke amount (Ore / Coke) increases. As described above, in the case where pulverized coal is not blown from the tuyere, the ratio of the amount of ore to the amount of coke (Ore / Cok
e) The amount of coke charged into the center where the ratio of the ore layer to the coke layer at the center of the furnace required to activate the hearth to the same extent as when the hearth was activated at 3.3 was obtained. As a result of conducting experiments to determine the present invention, the present invention has been accomplished,
The gist of the present invention is as follows. The present invention relates to a method for charging a raw material into a bellless blast furnace in which ore and coke are charged alternately. In the method, coke (Coke) charged into the furnace by blowing pulverized coal together with hot air from a blowing tuyere. Ore (Ore)
In the operation to reduce the total amount of coke charged into the furnace by increasing re / Coke), after charging the coke of the charge so as to cover the entire ore layer of the previous charge,
Before charging the ore of the next charge, a constant amount of coke of 2.5 to 3.0 tons per charge is concentrated and charged into the center of the furnace via the swirling chute to reduce the ore layer thickness ratio in the center. This is a method for charging a raw material into a bellless blast furnace, characterized in that the ore of the next charge is charged to 0.15 or less, and the ore of the next charge is continuously charged over the entire surrounding area. FIG. 1 is a schematic explanatory view showing a furnace top charging apparatus for a blast furnace according to the present invention. As shown in the figure, when charging the raw material into the bellless blast furnace 14 in which the ore and the coke are charged alternately, pulverized coal is blown together with hot air from a blowing tuyere (not shown) provided at the lower part of the furnace. Decrease total coke charge. Ore layer A with pre-charged coke layer B
To cover all. Thereafter, before charging the ore of the next charge, the swirling chute 16 is overrun above the lower limit of the inclination angle and 2.5 to 3.0 tons of coke C per charge is concentrated in the center of the furnace. , subsequently charged while controlling the ore the inclination angle of the turning chute 16 follows charged to peripheral regions of the coke C. By doing so, the ore layer A has a layer of coke C at the center, so that air permeability at the center of the furnace can be ensured. In order to supply coke C only to the central part of the furnace, as described above, the inclination angle is overrun to the lower limit or more, and the turning chute 16 is formed into a body. It can be dropped to the center of the furnace. However, the charging direction vector of coke C from the top bunker 10 is not always constant. That is, since the vector is not always directed to the center and varies, and the vector is oriented in a specific direction due to the characteristics of the arrangement of the furnace top bunker 10, it does not always fall exactly only at the center of the furnace. For example, coke C from furnace top bunker 10
When the coke C is dropped into the furnace by the opening operation of the flow rate adjusting gate 12, the coke C may be scattered and dispersed in the falling process as shown by the dotted arrow (b) and may not drop and accumulate at the center of the furnace. Therefore, in the present invention, it is preferable that coke C is accumulated and charged in the center of the furnace by using the turning chute 16 by the following operation. As shown in FIG. 1, prior to charging the coke C in the furnace top bunker 10 into the center of the blast furnace 14, the swing chute 16 is tilted by a tilt motor controlled by a tilt position control device 30.
Driven by 31. At this time, when the tilt angle detector 32 detects the specified position (a), the tilt position control device 30 gives a stop command to the tilt motor 31 to stop the tilt. This tilting regulation position (a) is a position where the lower end position of the tip of the revolving chute 16 is beyond the center line of the cross section of the furnace and is largely overrun from the conventional operation position. Operate. Next, the turning motor 34 of the turning chute 16 is turned at high speed by the turning position control device 33. The present invention operates at about 120% of the conventional operating speed, which is the limit of high speed. At this stage, the coke C starts to fall as the flow control gate 12 is opened by the flow control gate control device 36, and the coke C turns the funnel-shaped turning chute 16 as it falls into the furnace. The trajectory is used as a guide to locally accumulate and deposit at the center of the furnace. Turning direction of the turning shoe <br/> DOO 16 may be reversed in forward. The furnace top sequence control device 37 controls a series of controls including the above-described tilt position control device 30, turning position control device 33, flow rate adjustment gate control device 36, and others. FIG. 3 shows that the ratio of the amount of ore to the amount of coke charged into the blast furnace (Ore / Coke) is set to 3.3, and the ratio of the ore layer thickness at the center to the coke layer when pulverized coal is not injected from the blast tuyere. It shows the relationship with the furnace bottom temperature (° C.). Although the lower limit of the temperature control value of the hearth bottom is 180 ° C., the temperature of the hearth bottom is maintained at 180 ° C. or more from the lower limit of the temperature control shown in FIG. That is, it is understood that the central ore layer thickness ratio should be set to 0.15 or less in order to make the hearth activated. FIG. 2 shows the relationship between the amount of coke charged in the center of the furnace as described above (t / charge) and the ore layer thickness ratio in the center of the furnace, based on the ratio of the amount of ore to the amount of coke (Ore / Cok).
The figure shows the case where e) is changed in six levels from 3.3 to 5.3. It is needless to say that pulverized coal is blown from the tuyere at the five levels except for the ratio (Ore / Coke) = 3.3. From FIG. 2, in order to secure the ratio of the ore layer thickness in the central part to the coke amount of 0.15 or less, the amount of coke charged into the central part of the furnace is 2.5 until the ratio of the ore amount to the coke amount (Ore / Coke) is 4.1. t / charge, 3.0 after 4.1
This indicates that t / charge is required. This reduces the amount of coke charged centrally in the furnace in the present invention.
The reason is that the range is 2.5 to 3.0 t / charge. Next, an embodiment of the present invention will be described. In bell-less blast furnace 14 in furnace capacity 3363M ^3, when the Dezukuhi 2.1, the position where the lower end portion exceeds the furnace section center line of the swivel chute 16 as shown in FIG. 1, the inclination of approximately 12 ° to the vertical While rotating at an angle and at a high speed, 3.0 tons of coke C per charge was charged into the center of the furnace. The amount of raw material charged per cycle was 75.5 tons of ore forming ore layer A and lump ore.
15.5 tons and 18.3 tons of coke forming the coke layer B were used. The coke ratio in this case was 390 kg / t.pig, and pulverized coal of 130 kg / t.pig was blown from the tuyere. The ratio of the amount of ore to the amount of coke (Ore / Coke) is 4.27. The ratio of the ore layer thickness at the center of the furnace to the coke layer =
0.142, which made it possible to improve the permeability of the reducing gas to the charge in the center of the furnace and the liquid permeability of the melt, so that the temperature of the bottom of the furnace changed to a temperature control lower limit of 180 ° C or more. . As a result, the activation of the hearth was maintained, and a stable operation of the blast furnace was able to be performed despite the reduced amount of coke charged into the furnace due to the pulverized coal injection from the blow tuyere. As described above, according to the present invention, when charging coke in the central portion of the blast furnace and charging the coke, the charging amount is set to a constant weight% of the total charging amount of the coke. Instead of
By setting the charge to 2.5 to 3.0 t / charge irrespective of the total charge of coke, the charge (Ore / C
At the time of oke) increase, a large amount of coke is selectively introduced into the furnace center, so that the air permeability is improved by promoting the center gas flow, and as a result, the hearth can be activated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view showing a furnace top charging apparatus for a blast furnace according to the present invention. [Figure 2] The ratio of the amount of ore to the amount of coke (Ore / Coke) is 3.
4 is a graph showing the relationship between the amount of coke charged into the furnace center (t / charge) and the ore layer thickness ratio at the center of the furnace when the range is changed from 3 to 5.5. Fig. 3 Ratio of ore amount to coke amount charged to blast furnace
FIG. 6 is a graph showing the relationship between the ratio of the central ore layer to the coke layer and the furnace bottom temperature (° C.) when (Ore / Coke) is set to 3.3 and pulverized coal is not blown from the tuyere. [Description of Signs] 10 Furnace top bunker 12 Flow rate adjusting gate 14 Blast furnace 16 Swing chute 22 Collective hopper 30 Tilt position control device 31 Tilt motor 32 Tilt angle detector 33 Swivel position control device 34 Swivel motor 35 Swing angle detector 36 Flow rate adjustment Gate control device 37 Furnace top sequence control device

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-2-228408 (JP, A)                 JP-A-64-65207 (JP, A)                 JP-A-4-6206 (JP, A)                 JP-A-3-232912 (JP, A)                 JP-A-64-65218 (JP, A)

Claims (1)

(57) [Claims 1] In a method of charging raw materials into a bellless blast furnace in which ore and coke are charged alternately, pulverized coal is blown together with hot air from a blowing tuyere into the furnace. In the operation of increasing the ratio of the amount of ore (Ore) to the amount of coke (Coke) to be charged (Ore / Coke) and reducing the total amount of coke charged into the furnace, After charging so as to cover the entire ore layer, a certain amount of coke of 2.5 to 3.0 tons per charge is concentrated at the center of the furnace via a swirling chute before charging the ore of the next charge. A method for charging raw materials into a bellless blast furnace, characterized in that the ore layer thickness ratio of the central ore is adjusted to 0.15 or less and the ore of the next charge is continuously charged over the entire peripheral area.