JP2007262520A - Method for charging raw material into blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for charging a raw material into a blast furnace so that fine grains in the raw material may not be charged onto the central part or peripheral part of the furnace and deposit there, even when the grain sizes of the raw material discharged from a hopper at the furnace top fluctuate. <P>SOLUTION: When charging one batch of the raw material 5 into the blast furnace with the use of a slewing chute 1 in a bell-less type charging device provided at the furnace top, this charging method comprises the steps of: adjusting a tilt angle θ of the slewing chute so that the tip of the slewing chute directs at a central position (S) in a radially middle part of the blast furnace, and starting charging of the raw material; then, continually charging the raw material 5 gradually toward the furnace center while changing the tilt angle so that the tip of the slewing chute sequentially directs at the central part of the furnace; subsequently, charging the raw material 5 gradually toward the peripheral part of the furnace while changing the tilt angle so that the tip of the slewing chute directs at the periphery of the furnace; and changing the tilt angle so that the tip of the slewing chute directs at the furnace center again, and finishing the charge at a central position (F) in the middle part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a raw material charging method for a blast furnace, and more particularly to a technique for ensuring both air permeability in a furnace and improving gas utilization in a blast furnace equipped with a bell-less charging device at the top of the furnace.

  In the blast furnace for producing hot metal, granular coke as raw materials and iron ore containing sintered ore are alternately charged from the top of the furnace, and their alternate layers are formed in the upper part of the furnace. The raw material charging apparatus is roughly classified into a bell type charging apparatus and a bellless type charging apparatus. Of these, the bell-type charging device has a structure in which a furnace center axis is apex at the top of the furnace, and a bell-shaped member with a bowl-like shape is installed so that it can be raised and lowered, and the peripheral edge of the bell is held by a partition called a cone. It has become. Then, a space called a bell hopper is formed by the bell and the cone, and a raw material for one batch (one charge) forming the alternate layers is supplied to the space from above, and temporarily stored. At the same time, the bell is moved downward at a predetermined timing, and the raw material slides down to the inside of the furnace top through a gap formed between the bell and the cone. At that time, the raw material is first deposited on the periphery of the top of the furnace, and then sequentially flows into the center of the furnace. In this state, the raw material is always charged at a fixed position around the furnace, so a tiltable repulsion plate called a movable armor is installed on the furnace wall, and the inclination angle is changed to appropriately change the raw material. By changing the contact position to the furnace center side, the raw material dropping position is changed in the radial direction. However, since the raw material slides down from the whole circumference of the bell at the same time and there is no time to change the position of the movable armor, the raw material charging position is limited compared to the bellless type charging device described later. Become.

  On the other hand, the bell-less charging device opens the gate at the bottom of the hopper with raw materials such as iron ore and coke (may be mixed and charged) stored in the hopper installed at the top of the furnace. It is a device that drops and deposits on the surface, controls the discharge time of the raw material by adjusting the opening of the gate, and the discharged raw material is called a charging chute or a turning chute and is centered on the furnace center axis The raw material is charged into the top of the blast furnace through a chute that can change the tilt angle of the chute while rotating. Therefore, this type of charging device can charge the raw material for an arbitrary number of rotations at an arbitrary tilt angle of the charging chute, so that an arbitrary amount of raw material can be charged to an arbitrary location in the blast furnace top radius direction. It has the advantage of being able to.

  By the way, in the blast furnace, the reducing gas generated by burning the coke by the air blown from the lower part of the packed bed formed by the raw material charged from the top of the furnace flows upward toward the top of the furnace. Since the temperature and ore are reduced, it is necessary to form an appropriate gas flow uniformly in the circumferential direction of the furnace and in the radial direction of the furnace. Therefore, it is important to appropriately distribute the particle size configuration of the raw material charged in the furnace radial direction. In this respect, the bell-less charging device is considered an effective device.

  However, since the bellless type charging device deposits the raw material sequentially discharged from the hopper as it is on the furnace top through the charging chute, if the particle size of the raw material discharged from the hopper fluctuates with time, the deposition at the top of the furnace is performed as it is. This will affect the state (radial particle size distribution). FIG. 3 shows the change in the particle size of the raw material discharged from the vertical two-stage hopper over time. The two data illustrated in FIG. 3 show extreme examples of the change in particle size over time, but the raw material particle size may become coarser or finer, especially at the beginning of discharge. , You can see that it is widely dispersed. Also, at the end of discharge, small particles tend to be discharged. As a result, as in the prior art, first, the tip of the swivel chute 1 is directed to the furnace wall 3 and the direction of the tip is changed in the direction of the furnace center 4 by sequentially reducing the tilt angle, and one batch of the raw material 5 is added. When continuously charged, as shown in FIG. 2, the particle size of the raw material 5 charged in the periphery of the furnace becomes fine, becomes coarse and unstable, and becomes fine in the center of the furnace. Therefore, the gas flow distribution in the radial direction in the furnace tends not to be in a desirable state, as will be described later.

That is, in order to continue the blast furnace operation stably and efficiently, it is necessary to appropriately control the gas flow distribution in the furnace. The shape of this appropriate gas flow distribution varies depending on the operating conditions of the blast furnace, etc., but in general, a strong gas flow is formed in the center of the furnace, while protecting the furnace wall in the furnace periphery. It is said that it is desirable that a suitable amount of gas flow be formed. Therefore, when the raw material discharged from the charging chute is charged to the furnace center or the peripheral part of the furnace, if the particle size of the raw material is too small or is likely to fluctuate, stable raw material charging cannot be performed and an appropriate gas is supplied. Not only is it difficult to form a flow distribution, but it also makes it difficult to continue efficient blast furnace operation.
JP 2005-264295 A

  In view of such circumstances, the present invention provides a raw material charge for a blast furnace in which fine raw materials are not charged and deposited in the furnace central part and the furnace peripheral part even if the raw material discharged from the furnace top hopper varies in particle size. The purpose is to provide an entry method.

  The inventor has intensively studied to achieve the above object, and the results have been embodied in the present invention. The present invention uses a swirl chute of a bell-less type charging device provided at the top of the furnace, and when charging one batch of raw material into the blast furnace, first, the tip of the swirl chute is intermediate in the radial direction of the blast furnace. After the tilt angle of the swivel chute is adjusted so as to face the central position of the part, the charging of the raw material is started, and then the tilt angle is changed so that the tip of the swirl chute is sequentially directed toward the furnace center. The furnace center is continuously charged, and the tilt angle is changed so that the tip of the swivel chute is directed toward the furnace periphery, and the furnace chute is charged to the furnace periphery. Is a raw material charging method for a blast furnace, wherein the tilt angle is changed so as to be directed toward the center of the intermediate portion, and charging is terminated at the center position of the intermediate portion. In this case, the raw material is preferably iron ore containing coke or sintered ore.

  According to the present invention, it is possible to make the particle size of the raw material charged in the furnace central part and the furnace peripheral part relatively large and stable, thereby achieving stabilization of blast furnace operation.

  Hereinafter, the best embodiment of the present invention will be described based on the background of the invention.

  First, the inventor makes the gas flow distribution in the radial direction in the furnace appropriate for stable operation of the blast furnace based on the change with time of the particle size when cutting out one batch of raw material from the hopper of FIG. Therefore, we examined what kind of charging method should be used. As a result, the raw material with unstable particle size initially cut out from the hopper and the fine raw material at the end of cutting are charged in the middle part in the radial direction of the furnace, and the raw material at the intermediate time of cutting with relatively coarse particle size is used. I thought that it would be good to put it in the periphery or center of the furnace. That is, as schematically shown in FIG. 1, when charging the batch 5 of raw material 5 into the blast furnace using the swivel chute 1, first, the tip of the swirl chute 1 is the center of the intermediate portion in the radial direction of the blast furnace. The charging of the raw material 5 is started after adjusting the tilt angle (the angle from the horizontal, symbol: θ) of the swivel chute 1 so as to face the position (indicated by symbol: S). Thereafter, the tilt angle is changed so that the tip of the swivel chute 1 is directed toward the furnace center 4 sequentially, and charging into the furnace center is continuously performed. Then, the tilt angle is changed so that the tip of the swivel chute 1 is directed toward the furnace periphery, and charging is performed up to the furnace peripheral part. The tilt angle is changed so as to face in the center direction, and the charging is terminated at the center position of the intermediate portion (indicated by symbol F).

  And in order to confirm this, it tried using the mixture of a sintered ore, a lump iron ore, and iron scrap as a raw material with an actual blast furnace. The hopper provided at the top of the blast furnace has two upper and lower portions, and the tilt angle of the turning chute is changed by changing the notch corresponding to each tilt angle as shown in Table 1. . The larger the notch number, the smaller the tilt angle (θ) of the turning chute and the closer to the furnace center. In Table 1, the number of notches is shown as 25. In the present invention, it is not necessary to use all of them, and they may be selected as appropriate. This is because it is not necessary to continuously change the magnitude of the tilt angle of the turning chute, and if it is changed step by step, the charging purpose can be achieved.

  First, in the conventional charging (see FIG. 2), one batch of raw material is charged from the furnace periphery (symbol: G) to the furnace center (symbol: C) while the swiveling chute is rotated 19 times. It was. In the meantime, the tilt angle of the turning chute is changed. As shown in Table 2, the change uses 7 to 20 notches step by step.

In contrast to this conventional method, Table 2 also shows notch changes adopted in the trial. From Table 2, it is clear that the above idea is feasible. As a result of actual trials, the blast furnace was able to operate smoothly with stable furnace conditions. Further, the CO ₂ concentration of the gas measured by the sensor provided in the furnace top, was estimated radial distribution of the gas flow, it was confirmed that becomes a desired distribution profile. Therefore, the inventor made the above-described charging method the present invention.

  In the present invention, it is preferable to use iron ore or coke as a raw material. The so-called “mixed charging” in which these are mixed can be carried out, but the charging is easier if the shape and size of the raw materials are similar. The iron ore means a material that becomes a so-called “iron source”, and refers to a massive iron ore, sintered ore or iron scrap, and a mixture of two or more thereof. Further, as a hopper incidental to the bell-less type charging device, there are two types of upper and lower ones (referred to as a vertical two-stage type) or a plurality of hoppers arranged in one stage. It doesn't matter if it is a hopper.

The operation of a 4000 m ² class blast furnace with an internal volume of 4000 m equipped with a bellless type charging device having a vertical two-stage hopper and a turning chute at the top of the furnace was performed. The main operating conditions of the blast furnace are an output ratio of 2.3 and a coke ratio of 420 kg / t. During the operation, the raw materials were alternately charged with the above iron ore and coke batch by batch.

  First, the raw materials are charged by the conventional method shown in Table 2 above, and the operation is performed for 2 weeks, which is used as a comparative example. The charging method according to the present invention was carried out by the method shown in Table 2 at the same time and operated for 2 weeks. This operation is taken as an example.

The results of these operations were evaluated by the gas flow distribution in the radial direction in the furnace. In other words, the gas sampler is pushed horizontally from the furnace wall near the top of the blast furnace shaft, the gas in the furnace is sampled at a predetermined position in the radial direction of the furnace, and the obtained samples are analyzed by a gas chromatograph. The CO concentration and CO ₂ concentration were measured. And based on this measured value, a gas usage rate is calculated by the following formula, and the distribution of the gas usage rate in the furnace is evaluated. This is because the larger the gas utilization rate, the smaller the gas flow rate in the furnace, which means that the chemical reaction between the gas and the raw material (iron ore, coke, etc.) proceeds. In addition, a low gas utilization rate means a high gas flow rate and good ventilation.

Gas utilization factor _{(η CO) = 100 × [} (CO 2 vo%) / ((COvol%) + (CO 2 vol%))
FIG. 4 shows the gas utilization rate distribution in the radial direction of the furnace in the comparative example and the example described above. FIG. 4 clearly shows that in the embodiment according to the present invention, a sufficiently strong central gas flow is formed in the vicinity of the furnace center (near 0 on the horizontal axis) with a small gas utilization factor. In addition, a slightly stronger gas flow is also seen in the furnace peripheral part (near 1 on the horizontal axis) compared to the furnace intermediate part. That is, in the practice of the present invention, the blast furnace is operated with the desired gas flow distribution as described above.

  On the other hand, the result of the comparative example shows that the gas utilization rate in the furnace center is relatively large, and the air permeability in the furnace center is poor compared to the example. Moreover, it was judged that the air permeability was too good in the furnace peripheral portion, and the operation was unstable in air permeability as compared with the examples as a whole.

It is a longitudinal cross-sectional view of the furnace which illustrates typically the raw material charging method of the blast furnace which concerns on this invention. It is a longitudinal cross-sectional view of the furnace which illustrates the raw material charging method of the conventional blast furnace typically. It is a figure which shows the time-dependent change of the raw material particle size shown when a raw material is cut out from a furnace top hopper. It is the figure which compared the gas utilization factor distribution in the radial direction of a blast furnace with the case where this invention is applied, and the case where the conventional charging method is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turning chute 2 Arrow which shows moving direction of turning chute 3 Furnace wall 4 Furnace center axis 5 Raw material layer

Claims (2)

When charging a batch of raw material into a blast furnace using a swivel chute of a bell-less charging device provided at the top of the furnace,
First, the raw material charging is started after adjusting the tilt angle of the swivel chute so that the tip of the swivel chute is directed to the center position of the intermediate portion in the radial direction of the blast furnace. The tilt angle was changed so that the tip was sequentially directed toward the furnace center, and the charging was continuously performed in the furnace center. Subsequently, the tilt angle was changed so that the tip of the swivel chute was directed toward the furnace periphery. The charging is performed up to the furnace periphery, the tilt angle is changed so that the tip of the turning chute is directed toward the center of the intermediate portion, and the charging is terminated at the center position of the intermediate portion. Raw material charging method for blast furnace.   The blast furnace raw material charging method according to claim 1, wherein the raw material is iron ore containing coke or sintered ore.

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