JPH0465882B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for charging raw materials into a bellless blast furnace, and more specifically, the present invention relates to a method for charging raw materials into a bell-less blast furnace, and more specifically, the weight ratio of iron source to reducing agent in the radial direction within the furnace (hereinafter abbreviated as "O/C"). This relates to a raw material charging method aimed at improving distribution controllability. (Prior art) In blast furnace operation, the radial distribution of O/C, particle size, etc. of the charge at the top of the blast furnace is appropriately controlled, and the radial gas flow distribution and heat flow ratio distribution in the furnace are It is necessary to maintain the ore within a predetermined range and to stably reduce and dissolve the ore. A method of charging raw materials into a conventional bell-less blast furnace will be explained with reference to FIG. Figure 4 shows a schematic diagram of the raw material charging device at the top of the bellless blast furnace.
The raw material 3 transported to the top of the blast furnace 1 by the belt conveyor 2 is temporarily stored in the top bunker 6 through the upper gate valve 4 and the upper seal valve 5, and the charge in the blast furnace is unloaded. When a predetermined stock level 7 to be replenished is reached, the lower gate valve 8 and the lower seal valve 9 for adjusting the charge flow rate are opened, and the raw material in the furnace top bunker 6 is transferred to the distribution chute 10.
It is charged into the furnace through the . (Problems to be Solved by the Invention) However, in the conventional raw material charging method, the controllability of the O/C distribution in the radial direction was insufficient. In other words, the O/C distribution in the radial direction tends to fluctuate due to fluctuations in the amount of mixed layer formed when charging the iron source, fluctuations in the stacking angle of the raw material, fluctuations in the time taken to feed into the furnace, etc. . Each of them will be explained in detail below. Regarding fluctuations in the amount of mixed layer formed during iron source charging In the conventional raw material charging method, the tilting angle of the distribution chute (θ in Figure 4: the angle between the bottom of the distribution chute and the furnace axis of the blast furnace) The raw materials were sequentially charged from the wall of the furnace to the center of the furnace by decreasing the angle from a predetermined angle. Therefore, in most cases, the surface shape of the raw material after charging was V-shaped or M-shaped as shown in FIG. 4, and both of them formed slopes. Therefore, when the iron source is charged above the reducing agent layer, a part of the surface layer of the reducing agent layer near the iron source falling position is scraped off by the impact energy of the iron source and moves toward the center of the furnace. , a mixed layer of iron source and reducing agent is deposited over a wide area in the center of the furnace. Regarding the formation of a mixed layer in the bellless charging method, one of the present inventors has reported a study using a full-scale model ("Tetsu to Hagane" Vol. 71, 1985,
175 pages). An example of this mixed layer measurement is shown in FIG. In this measurement example, sintered ore is used as the iron source and coke is used as the reducing agent. In the figure, the broken line is the surface shape of the coke layer before charging the sintered ore.
The solid line shows the surface shape of the coke layer after charging the sintered ore. The coke that was present near the sintered ore falling position on the furnace wall has been moved to the vicinity of the center.
A monolayer of coke and a mixed layer of sinter and coke are formed over a wide area. If the coke layer forms a slope in this way, the surface shape of the coke layer will change when charging the sintered ore, and the O/C distribution in the radial direction will change depending on the surface shape of the raw material before and after charging the sintered ore. This is significantly different from the O/C distribution calculated from . Furthermore, the amount of mixed layer formed is influenced by not only controllable factors such as the distribution chute tilt angle schedule and charging amount, but also disturbance factors such as changes in the particle size composition of the raw material and changes in the surface shape of the coke layer due to changes in the gas flow distribution in the furnace. receive. Therefore, in the conventional bellless charging method that forms a slope, the radial O/
The controllability of C distribution was insufficient. Regarding fluctuations in the stacking angle of raw materials The second problem with the radial O/C distribution due to the formation of slopes is that the radial O/C distribution tends to fluctuate due to fluctuations in the stacking angle of the charged raw materials. be. In other words, when forming a slope,
Because the surface shape of the raw material changes easily due to fluctuations in the gas flow distribution in the furnace, the raw material was charged into the furnace using the same distribution chute tilt angle schedule and the same charging amount, that is, the same charging conditions. However, the O/C distribution in the radial direction is likely to fluctuate. Regarding variation in charging time in the furnace A third problem arises in the conventional charging method in which the distribution chute tilting angle is gradually decreased from large to small, regardless of whether or not a slope is formed. In other words, in the conventional charging method, the raw material is charged from the part where the raw material layer thickness increases per unit time is small, that is, the furnace wall, to the part where the raw material layer thickness increases per unit time, that is, the center part. is included. Therefore, if the outflow characteristics at the lower gate valve change due to changes in the moisture content of the raw material or changes in the particle size composition of the raw material, and the total charging time into the furnace changes, the raw material at the final stage of charging may The variation in the layer thickness of the raw material at the center, which is the internal insertion position, becomes extremely noticeable. In the conventional material charging method for bellless blast furnaces, in which the tilting angle of the distribution chute is gradually decreased from large to small both when charging the iron source and when charging the reducing agent, the O/C distribution in the radial direction is Controllability was insufficient. The present invention aims to solve the above-mentioned problems and provide a method for charging materials into a bellless blast furnace, which can improve the controllability of the radial O/C distribution in the furnace. (Means for Solving the Problems) The raw material charging method for a bell-less blast furnace according to the present invention includes tilting of the distribution chute in order to charge the iron source from the furnace wall toward the center of the furnace when charging the iron source. In addition, when charging the reducing agent, the tilting angle of the distribution chute is controlled so that the reducing agent is charged from the center of the furnace toward the furnace wall, and the deposition angle on the surface of the reducing agent after charging is controlled. The gist of this invention is to control at least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve so that the distribution chute does not exceed 20 degrees. In the present invention, the following method was adopted to solve the above-mentioned problems. That is, in order to prevent the variation in the amount of mixed layer formation, which is the first problem, it is necessary to create a condition in which the mixed layer itself is not formed, that is, a condition in which no slope is formed. According to research reports using the above-mentioned full-scale model, it is clear that when coke is charged onto a sintered ore layer, a mixed layer is hardly formed because the impact energy possessed by the coke is small. Therefore, it can be seen that in order to suppress the formation of a mixed layer, the deposition angle of the surface of the reducing agent layer at the time of charging the iron source can be well controlled. The present inventors manufactured a full-scale model outside the furnace, charged sinter with various coke layer deposition angles, and investigated the effect of the coke layer deposition angle on the amount of mixed layer formation. The results are shown in FIG. As a guideline for the amount of mixed layer formed, increase the thickness of the coke layer in the center (increase in the thickness of the single coke layer + 1/2
x increase in mixed layer thickness) was adopted. As is clear from the figure, the coke layer deposition angle reaches a boundary of 20 degrees, and when this is exceeded, the thickness of the coke layer in the center increases significantly due to sinter charging, but below that, it is practically ignored. It turned out that it is possible. To summarize the above results, in order to prevent fluctuations in the amount of mixed layer formation,
It can be seen that the deposition angle after charging the reducing agent should not exceed 20 degrees. In order to prevent fluctuations in the stacking angle of the raw material, which is the second problem, it is sufficient to prevent fluctuations in the gas flow distribution, but this is difficult in actual operation, and rather the gas flow distribution fluctuates. It is necessary to create conditions in which the stacking angle of the raw material does not change even when However, since the iron source has a high density and a small deposition angle in the furnace, it is not susceptible to fluctuations in the deposition angle due to changes in gas flow distribution, but the reducing agent has a low density,
Moreover, since the deposition angle in the furnace is large, the deposition angle tends to fluctuate due to fluctuations in gas flow distribution. Therefore, it is necessary to reduce the deposition angle after charging the reducing agent to prevent fluctuations in the deposition angle due to variations in gas flow distribution. In order to suppress the third problem, radial O/C distribution fluctuations due to fluctuations in the in-furnace loading time,
Areas with large increase in material layer thickness per unit time,
That is, the raw material may be charged from the center toward the area where the amount of increase in the raw material layer thickness per unit time is small, that is, toward the furnace wall. In particular, the moisture content of the reducing agent fluctuates more than the iron source, and the discharge time from the furnace top bunker, that is, the time it takes to enter the furnace, fluctuates significantly. Therefore, the reducing agent is charged from the center toward the furnace wall. It is necessary to do it. Based on the above considerations, in the present invention, when charging the reducing agent, the reducing agent is charged from the center of the furnace to the furnace wall, and the deposition angle on the surface of the raw material after charging is controlled.
By setting the angle to 20 degrees or less, the above-mentioned problems of the conventional method are solved. Of course, if similar measures are taken when charging the iron source, the effect will be even better, but even if it is applied only to the reducing agent as in the present invention, the effect is sufficient as described below. The configuration of the present invention will be explained based on FIG. Note that the same numbers in FIG. 1 as in FIG. 4 indicate the same or corresponding parts, and the explanation will be omitted. The raw material is transported to the top of the furnace by the belt conveyor 2, passes through the upper gate valve 4 and the upper seal valve 5, and is temporarily stored in the top bunker 6, and the charge in the blast furnace 1 is unloaded and needs to be replenished. When a predetermined stock level 7 is reached, the lower gate valve 8 and the lower seal valve 9 are opened, and the flow of charging into the furnace via the distribution chute 10 is the same as in the conventional method. First, in order to achieve the first condition of charging from the center of the furnace toward the wall of the furnace, a schedule is set in which the tilt angle of the distribution chute is gradually increased from small to large. The arrows shown in FIG. 1 indicate the movement of the distribution chute tilting angle. Next, in order to achieve the second condition of reducing the stacking angle after charging to 20 degrees or less, at least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve must be set. This allows one to be set arbitrarily. By doing so, the angle at which the reducing agent 11 is deposited in the furnace can be kept at 20 degrees or less, as shown in FIG. On the other hand, as in the conventional method, the iron source 12 is charged from the furnace wall toward the center by gradually reducing the tilt angle of the distribution chute 10 from large to small, as shown in FIG. The surface shape is V-shaped. Therefore, the O/C distribution in the radial direction is such that the O/C at the furnace center is low and the O/C at the furnace wall is high. In normal blast furnace operation, in order to ensure a central gas flow, a radial O/C distribution with a reduced O/C in the center is desired, and the present invention satisfies that purpose. In addition, in order to prevent the formation of an inert zone on the furnace wall and to ensure an appropriate flow of gas on the furnace wall, the distribution chute tilt angle should be adjusted so that the surface shape of the iron source is M-shaped. At least one of the number of turns in the tilting angle and the opening degree of the lower gate valve may be controlled. In the present invention, since the deposition angle of the reducing agent layer before charging the iron source is 20 degrees or less, control of the surface shape after charging the iron source is much easier than in the conventional method. In order to fully demonstrate the effects of the present invention, the stacking angle of the raw material after charging is actually measured using a profile meter 13 usually installed at the top of the blast furnace, and if the desired stacking angle is not obtained, At least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve is controlled, and measurement is performed using the profile meter 13, and the deposition angle of the raw material is adjusted to the desired value while checking the effect. It can also be controlled within a range. Furthermore, in order to improve the controllability of the raw material loading time into the furnace, it goes without saying that the amount of raw material deposited in the furnace top bunker may be measured by sounding 14 or the raw material charging time may be measured by acoustic methods, etc. stomach. By the way, although the method of the present invention employs a method of gradually increasing the tilt angle of the distribution chute, this method cannot be easily invented even by a person skilled in the art. In other words, in the conventional method of gradually decreasing the tilting angle of the distribution chute, the direction of the moment generated by the distribution chute load and the material load on the distribution chute is the same as the direction of the tilting of the distribution chute. The shaft torque applied to the tilting motor is small and therefore within the rated torque tolerance of the motor. In contrast, in the method of the present invention in which the tilting angle of the distribution chute is gradually increased, the direction of the moment generated by the distribution chute load and the load of the raw material on the distribution chute is opposite to the direction of the tilting of the distribution chute. It is. Therefore, since the shaft torque applied to the tilting motor is large and expected to exceed the rated torque of the motor, an invention such as the present invention in which the tilting angle of the distribution chute is gradually increased has not been made. However, in implementing the present invention, we actually measured the required torque of the motor shaft when the tilting angle of the distribution chute was gradually increased, and as shown in Figure 3, it was found that if the capacity of the conventional motor was increased by about 20%, it could be used regularly. It has been found that the tilting angle of the distribution chute can be gradually increased within the distribution chute tilting angle range. Therefore, the present invention in which the tilting angle of the distribution chute is gradually increased can be implemented with a small investment. (Function) When charging an iron source and a reducing agent into a bellless blast furnace, the present invention adjusts the tilt angle of the distribution chute so that the iron source is charged from the furnace wall toward the center of the furnace. In addition, when charging the reducing agent, the tilting angle of the distribution chute is controlled so that the reducing agent is charged from the center of the furnace toward the furnace wall, and the deposition angle on the surface of the reducing agent after charging is 20°. This control controls at least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve so as not to exceed the radial O/C distribution in the furnace. Can be controlled with precision. (Example) In order to confirm the effects of the present invention, a charge distribution test was conducted using the above-mentioned full-scale model outside the furnace. The iron source used in the test was sintered ore used in actual blast furnaces, and the reducing agent was coke. In addition, the raw material charging conditions in the test were the same as those in an actual blast furnace, except that there was no unloading and no air blowing, and the radial O/
C distribution was measured by solidifying the raw material after charging with epoxy resin and taking it out of the apparatus. By applying the present invention, the radial O/C distribution can be controlled with high precision. For example, the conventional charging method is
1 2 2 3 3 4 4 5 5 6 6
7 7), O(1 1 2 2 3 3 4 4
5 5 6 6 7 7). The numbers in parentheses indicate the magnitude and order of the tilting angle of the distribution chute, and the smaller the number, the larger the tilting angle of the distribution chute is set. The number of turns was 14. On the other hand, the charging method of the present invention for obtaining the same radial O/C distribution as the charging method described above has C(10 10 9 9
8 8 7 6 5 4 3 2 1 1),
O(1 1 1 1 2 2 2 2 3 3
3 3 4 5). A charging test was conducted by increasing the water content of the coke used under these conditions from 1.5% by weight to 6.5% by weight. In the conventional charging method, charging was not completed in 14 revolutions, but in approximately 6
Seconds exceeded. For this reason, at the tilt angle of 7 of the final distribution chute, extra coke was charged from the center to the center of the furnace, and the thickness of the coke layer in the center increased. In addition, the amount of increase in the thickness of the coke layer in the center due to the formation of a mixed layer after charging the sintered ore decreased slightly. As a comprehensive result, the O/C at the center of the furnace decreased from 1.2 to 0.9, as shown in the table below. In contrast, in the charging method according to the present invention, an increase in the amount of charged coke deposited due to an increase in coke moisture content is detected by a sounding installed in the furnace top bunker, and the same O/C ratio as before the increase in coke moisture is detected.
The opening of the lower gate valve was increased by 5% to obtain the distribution. As a result, the coke charging time can be kept almost the same at 106 seconds, the surface deposition angle after coke charging can be maintained below 20 degrees, and the coke layer in the center can be maintained by forming a mixed layer when charging sintered steel. The increase in layer thickness is
The coke moisture content was extremely suppressed to 10 mm, the same as before the increase. As a result of these, the central O/C is
1 and 1, the coke water content could be maintained almost the same as before the change, confirming the effectiveness of the present invention. As described above, the present invention is used to control the tilting angle of the distribution chute from small to large when charging the reducing agent, and to distribute the distribution so that the deposition angle on the surface after charging the reducing agent is 20 degrees or less. By controlling at least one of the tilting angle of the chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve, the controllability of the radial O/C distribution in the furnace can be improved.

[Table] (Effects of the Invention) As explained above, the present invention allows the iron source to move from the furnace wall toward the center of the furnace when charging the iron source and reducing agent to a bellless blast furnace. The tilt angle of the distribution chute is controlled to charge the reducing agent, and when charging the reducing agent, the tilt angle of the distribution chute is controlled so that the reducing agent is charged from the center of the furnace toward the furnace wall. The purpose is to control at least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve so that the deposition angle on the surface of the reducing agent does not exceed 20 degrees. The O/C distribution in the radial direction within the blast furnace can be precisely controlled, which has a great effect on stable operation of the blast furnace.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the method of the present invention, Fig. 2 is a relationship diagram between the coke layer deposition angle and the amount of increase in the thickness of the coke layer in the center of the furnace, and Fig. 3 is a diagram showing the relationship between the tilting angle of the distribution chute and the motor shaft torque. FIG. 4 is an explanatory diagram of the conventional method, and FIG. 5 is an explanatory diagram of the state of formation of a mixed layer in the conventional method. 1 is a blast furnace, 7 is a stock level, 8 is a lower gate valve, 10 is a distribution chute, 11 is a reducing agent, 12
is an iron source.

Claims (1)

[Claims] 1 When charging the iron source and reducing agent into a bell-less blast furnace, the tilting angle of the distribution chute is controlled so that the iron source is charged from the furnace wall toward the center of the furnace. When charging the reducing agent, the tilting angle of the distribution chute is controlled so that the reducing agent is charged from the center of the furnace toward the furnace wall, and the angle of accumulation on the surface of the reducing agent after charging does not exceed 20 degrees. A method for charging raw materials into a bellless blast furnace, comprising controlling at least one of the tilting angle of the distribution chute, the number of turns at each tilting angle, and the opening degree of the lower gate valve.