JP2006336094A - Apparatus and method for charging raw material into blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for charging raw material into a blast furnace with which "coke/ore" layer thickness ratio only in a limited range at a furnace center part is kept to be large and also, the coke grain diameter charged in the furnace center part can be made coarse. <P>SOLUTION: The apparatus is installed at a furnace top part for charging the raw material into the blast furnace. The apparatus provided with: furnace top bunkers having discharging holes at a position eccentric to the center axis; a swinging chute for charging the raw material discharged from the furnace top bunkers; and a center coke exclusive chute for charging the coke into the area near the furnace axis, is used. It is preferable to provide ≥3 sets of the furnace bunkers and a guide means for charging the raw material from the upper part of the discharging hole to the furnace top bunker. Further, as regards the grain diameter of the charging material charged into the blast furnace from the furnace top bunker, a large amount of fine grain is charged at the initial stage of the discharge and a large amount of coarse grain is charged at the latter stage of the discharge. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a blast furnace raw material charging apparatus for charging raw materials such as ore and coke into a blast furnace and a blast furnace raw material charging method using this apparatus.

The ventilation and liquid permeability of the blast furnace core and hearth have a significant impact on stable blast furnace operation. The core and hearth are formed of a coke packed bed, and the core and hearth coke are composed of coke charged in a narrow range (dimensionalless radius 0 to 0.2) around the furnace axis. It is known that In recent years, operations that lower the coke ratio and the reducing material ratio are directed, and the reaction load of coke tends to increase, and a technique for supplying healthy coke to the furnace core and hearth is required. At this time, distribution control of the charge charged from the furnace top is an important operating factor. Coke reacts with CO ₂ in the furnace and deteriorates. This CO ₂ is produced when a raw material such as sintered ore or iron ore (hereinafter referred to as “ore”) is reduced with CO gas. Therefore, in order to reduce the amount of coke reaction at the center of the furnace and prevent the deterioration of coke, the amount of coke at that location is made larger than the amount of ore, that is, at the center of the furnace, the layer thickness ratio of coke to ore A certain “coke / ore” needs to be large. In view of this, a technology for charging coke into the center of the blast furnace has been developed, controlling the charging method when charging coke into the center of the furnace via a dedicated chute, and preventing ore flow into the center. Thus, a technique for increasing the “coke / ore” in the center is known (for example, see Patent Document 1). By using a dedicated chute, it becomes easy to charge coke into the center of the blast furnace.

  On the other hand, it is possible to charge coke near the furnace axis without using a dedicated chute, even if a swiveling chute is used. In some cases, only concentric charging can be performed. As shown in FIG. 12 (a), the coke charged from the rotating chute 1 falls as shown by the drop trajectory 5, and becomes a coke accumulation shape 7 having a top at a position displaced from the furnace axis. Further, even if the fall main flow coincides with the furnace axis, the fall region is wider than that through the dedicated chute, so it may be difficult to form a coke accumulation state similar to the dedicated chute (FIG. 12B). reference.). As shown in FIG. 12C, the coke charged from the dedicated chute falls as indicated by a coke dropping locus 6 from the dedicated chute to form a coke accumulation shape 8. In the coke charging to the center portion by the turning chute as shown in FIG. 12B, compared to the charging by the dedicated chute shown in FIG. The coke / ore layer thickness ratio tends to increase. This causes an excessive central gas flow and increases the number of sites with low reduction efficiency, which is not preferable particularly in an operation with a low reducing material ratio.

  On the other hand, in order to maintain good ventilation and liquid permeability of the furnace core and hearth, it is desirable to increase the coke particle size of the part, that is, to increase the coarse particle ratio of the particles constituting the packed bed. The charge charged in the furnace by the swivel chute has a characteristic that coarse particles segregate to the lower part of the slope, that is, to the center due to the classification effect when the slope is constructed from the drop position toward the furnace center. It is reasonable in the sense of coarsening the coke of the part.

Moreover, in order to effectively supply coarse-grained coke to the furnace center, it is more effective to use the time-dependent change in the particle size at the time of charging the furnace interior charge in addition to the aforementioned classification effect in the furnace. It is. In the bell-less charging device, a predetermined amount of the charged material is stored in the furnace top bunker, and is charged into the furnace through a turning chute at a predetermined timing and within a predetermined time. Within this charging time, the tilt angle of the swivel chute is changed over time. Generally, at the initial stage of charging, the tilting angle is such that the charge falls to the periphery, and in the latter stage, the charge falls from the middle to the center. Insert at a tilting angle. Therefore, in order to charge the coarse particle charge to the furnace center side, it is desirable that the coarse particle is discharged at a later stage when discharging the charge from the furnace top bunker. Although the discharge characteristics from the bunker differ depending on the shape of the top bunker and the method of depositing the charge in the bunker, according to the results of investigating the change over time in the particle size during discharge in several types of bunker, A furnace top bunker that is of a parallel arrangement type, whose discharge port does not coincide with the bunker central axis (off-center type), and that has a mechanism for depositing charges in the bunker with the furnace axis as the top, It has a characteristic that fine particles are discharged at an early stage and coarse particles are discharged at a later stage (see, for example, Non-Patent Document 1). In this way, if the arrangement and shape of the furnace bunker are selected, it is possible to set an advantageous condition for depositing coarse coke at the center portion by charging with a turning chute.
JP 2001-323305 A Journal of the Japan Institute of Metals vol.31, p330-332 (1992)

  As described above, when a bell-less charging apparatus having a turning chute is used, it is possible to relatively easily increase the ratio of coarse particles of coke in the furnace core and hearth. However, when coke is charged directly into the center using a turning chute, there is a problem that an excessive reduction in the coke / ore layer thickness ratio tends to occur near the center as described above.

  On the other hand, in the coke charging method to the furnace center via the chute for exclusive use of coke charging, the central coke stacking shape is compact without spreading greatly in the radial direction of the furnace, but the charged material is directly in the dropping position. Therefore, the supply of coarse coke to the center due to the above classification effect cannot be expected. As a countermeasure against this, there is a method in which the pre-sieving of coke charged through a special chute is strengthened and only coarse particles are selectively charged into the center of the furnace. Problems such as clogging of the coke in the special chute due to the coarsening of the material occur.

  Accordingly, an object of the present invention is to solve such problems of the prior art, to keep a large “coke / ore” layer thickness ratio only in a limited area of the furnace center, and to coke charged into the furnace center. An object of the present invention is to provide a blast furnace raw material charging apparatus and a blast furnace raw material charging method capable of coarsening the particle size.

The features of the present invention for solving such problems are as follows.
(1) An apparatus installed at the top of the furnace for charging raw materials into the blast furnace, the furnace top bunker having an outlet at a position eccentric to the central axis, and discharged from the furnace top bunker A blast furnace raw material charging apparatus comprising a turning chute for charging a raw material into a blast furnace and a central coke dedicated chute for charging coke in a region near the furnace shaft.
(2) The blast furnace raw material charging apparatus according to (1), which has three or more furnace top bunker.
(3) The blast furnace raw material charging apparatus according to (1) or (2), characterized in that the furnace top bunker has guide means for charging the raw material from above the discharge port.
(4) When the raw material is charged using the blast furnace raw material charging apparatus described in any one of (1) to (3), the particle size of the charged material charged into the blast furnace from the top bunker However, the blast furnace raw material charging method is characterized in that the raw material is charged so that there are many fine grains in the early stage of discharge and more coarse grains in the later stage of discharge.

  According to the present invention, the “coke / ore” layer thickness ratio of the furnace center can be increased only in the vicinity of the furnace shaft, and the coke grain size can be coarsened. Maintains good reducibility and stabilizes blast furnace operation.

  The present inventors conducted an experiment using a reduced model and studied a furnace top charging device for a blast furnace raw material suitable for solving the above-described problems. The scale of the apparatus is 1/10 of the actual machine (corresponding to a furnace diameter of 11.4 m), and has a turning chute and a chute for supplying coke to the center (hereinafter referred to as “dedicated chute”). The furnace top bunker and the arrangement of the bunker have a discharge port at the central axis position, a type in which the central axis is arranged on the furnace axis (vertical type), and a bunker that has a discharge port at a position eccentric to the central axis. A type (parallel + off-center type) in which a discharge port is arranged at a position eccentric with respect to the furnace axis is used. In addition, when using either furnace top bunker, the raw material was charged into the bunker from the upper position of the discharge port. Deposition in the furnace when crushed coke is charged with a specified bell-less pattern (depending on the condition, a dedicated chute for central charging is used) using a sample prepared to correspond to the particle size distribution of the actual machine (25 mm to 80 mm) The shape and radial particle size distribution were measured. FIG. 1 shows the apparatus and coke deposit shape under each experimental condition. FIG. 1A shows the result of charging coke using only the turning chute 1 in a vertical bunker device, and FIG. 1B shows the turning chute 1 for charging the coke into the furnace center with the vertical bunker device. As a result of carrying out using both dedicated chutes 2, FIG. 1 (c) shows a parallel + off-center type bunker device, and as a result of charging coke using only the turning chute 1, FIG. 1 (d) shows parallel + off. This is the result of coke charging into the furnace center using both the turning chute 1 and the dedicated chute 2 with a center-type bunker device. The coke layer thickness at the furnace shaft was the same under each condition. The position of the turning chute in FIG. 1 indicates the tilting position at the end of charging in each condition. When the dedicated chute is not used (FIGS. 1A and 1C), the turning chute directly from the turning chute to the furnace shaft. When the dedicated chute is used while the coke is dropped and deposited (FIGS. 1B and 1D), the coke dropping position from the turning chute 1 in the final turning is the position from the furnace axis to the middle part. Yes, coke is deposited from the drop position to the center by flowing in the furnace, and the coke is charged by the dedicated chute 2 thereon. The behavior of these cokes is shown in FIG. 1 by a broken line 5 (coke dropping trajectory from the turning chute) and an arrow. 7 is a coke accumulation shape formed by charging with a swirl chute, and 8 is a coke accumulation shape formed by charging with a dedicated chute. According to FIG. 1, when coke is supplied to the furnace center using only the turning chute 1, the coke layer has a wider coke layer near the center than when the dedicated chute 2 is used even if the coke layer thickness of the furnace shaft is the same. It can be seen that the thickness increases. When the dedicated chute 2 is used, the coke layer thickness increases in the range of approximately 0 to 0.2 with a dimensionless radius, whereas when only the turning chute 1 is used, the dimensionless radius is approximately 0 to 0. When the coke layer thickness is large in the range of .3 and only the swivel chute 1 is used, the coke layer thickness is wider than the above-described core coke supply region (range of 0 to 0.2 in dimensionless radius). However, when only the turning chute 1 is used, not only a remarkable effect on the core control can be expected, but also a negative effect of expanding a region where the reduction efficiency is low is generated. Therefore, it is desirable to use a dedicated chute as shown in FIGS. 1B and 1D from the viewpoint of the deposited shape.

  Next, the particle size distribution in the radial direction under each condition of FIGS. 1 (a) to 1 (d) is shown in FIGS. In FIG. 2, when the coke particle size in the center is compared, the cases of a and b in the vertical bunker (FIGS. 1A and 1B) are small, and in comparison with this, the parallel + off-center type (FIG. 1 ( In the cases of c) and c) and d) of c) and (d), both values were large. Here, FIG. 3 shows a change in the particle size at the time of coke discharge from each furnace top bunker in FIG. The result of FIG. 2 reflects this, and in order to supply coarse coke to the central part, it is desirable to use a parallel + off-center type in which coarse particles are discharged in the latter period. The reason why the conditions shown in FIGS. 1C and 1D gave the same particle size distribution is as follows. In FIG. 2d, the charging by the turning chute does not reach the furnace shaft shape, and a segregation effect occurs in the process in which the coke flows into the shaft core portion from the dropping position. Combined with this, the effect of coke with an average particle size staying on the furnace shaft as it is by charging with a special chute (see Fig. 4), resulting in coarse coke from the swiveling chute shown in Fig. 1 (c). It is thought that it became equivalent to the conditions charged on the upper side, that is, on the condition that there is no particle segregation on the slope.

  Table 1 is obtained by arranging the above examination results. In other words, in order to increase the coke particle size while suppressing excessive coke deposition in the center, which causes the furnace to expand in the radial direction, in addition to the furnace top bunker having an outlet at an eccentric position with respect to the center axis. It can be seen that a charging device having a dedicated chute for supplying coke to the furnace center is optimal.

  The parallel + off-center type bunker has a device characteristic that it does not fall on the furnace shaft when the charge is guided to the turning chute. Accordingly, as shown in FIG. 5, the position where the charge falls on the chute 1 differs depending on the direction of the turning chute 1, and the pop-out speed, that is, the drop behavior varies due to the difference in the sliding distance on the chute. Is. This promotes circumferential deviation and may cause instability in blast furnace operation. As a countermeasure, by setting the number of parallel + off-center type bunkers to at least three, the deviation can be dispersed. Therefore, the number of parallel + off-center bunker is preferably 3 or more.

  From the above, as shown in FIG. 6, the furnace top bunker having the swivel chute 1, the discharge port at a position eccentric with respect to the central axis, and the three or more bunker 3, and the coke are removed from the furnace. Regarding a condition in which a blast furnace raw material charging device having a dedicated chute 2 for supplying to a shaft portion enlarges the “coke / ore” in the center only in the vicinity of the furnace shaft portion and increases the coke particle size in the portion. It was concluded that it was particularly suitable.

  Moreover, in the blast furnace raw material charging apparatus of the present invention, it is desirable that the furnace top bunker has guide means for charging the raw material from above the discharge port of the furnace top bunker. When charging the raw material into the furnace top bunker, it is desirable to deposit the charge in the bunker so as to form a mountain shape having an apex at the top of the discharge port. It can be made the above shape by charging the raw material into the bunker from the top, but in order to more reliably form a mountain shape having a vertex at the top of the discharge port, the upper part of the discharge port using guide means etc. It is desirable that the raw material is reliably charged at the position. By inserting the raw material in the bunker so as to have a mountain shape having an apex at the top of the discharge port, it is possible to reliably discharge the raw material of fine particles in the early stage and coarse particles in the later stage.

  A means as shown in FIG. 7 can be used as a guide means or the like for charging the raw material into a chevron shape having an apex at the top of the discharge port in the furnace top bunker. FIG. 7A shows the case where the chute 10 for raw material charging is installed in the furnace top bunker 3, and FIG. 7B shows the case where the repulsion plate 11 serving as guide means is installed. Due to the rolling of the charged raw material, fine particles tend to be distributed in the upper part of the discharge port and coarse particles are distributed in a portion far from the discharge port. Furthermore, a classification device can also be used when charging the raw material into the furnace top bunker. FIG. 7C shows a case where the wire classifier 12 is installed.

  Therefore, when charging the raw material using the blast furnace raw material charging apparatus described above, the particle size of the charge charged into the blast furnace from the furnace top bunker is large in the initial stage of discharge, and the discharge By using the blast furnace raw material charging method in which the raw material is charged so that coarse grains increase in the latter stage, the “coke / ore” layer thickness ratio in only a limited area of the furnace center is kept large, and the furnace center The coke particle diameter charged into the part can be coarsened.

  When refurbishing the blast furnace, the top of the furnace is a parallel + off-center type, and has a discharge port at a position eccentric to the central axis, where the central axis is parallel to the furnace axis and not aligned with the furnace axis. A blast furnace raw material charging device having three furnace top bunkers arranged in parallel, a swivel chute, and a dedicated chute for charging coke into the furnace core was installed. The shape of deposition in the furnace and the particle size distribution in the radial direction of the coke at the time of charging the furnace into the furnace before firing were measured. These results were compared with the case of using a vertical furnace top bunker and a bell-less charging device having a turning chute without the special chute previously measured. The results are shown in FIGS. FIG. 8 (a) shows the in-furnace deposition shape in the case of a vertical bunker blast furnace raw material charging apparatus, and FIG. 8 (b) shows a blast furnace having three parallel + off-center type top furnace bunkers and a dedicated chute. FIG. 9 shows the particle size distributions a and b of FIGS. 8A and 8B. As shown in Figs. 8 and 9, the results obtained in the model experiment have been reproduced, confirming the effectiveness of the blast furnace raw material charging equipment with three parallel + off-center type top furnace bunker and dedicated chute. did it.

  Furthermore, the distribution of gas in the upper part of the furnace at the time of operation when using a blast furnace raw material charging device having three furnace bunker of parallel + off-center type and a dedicated chute and a blast furnace raw material charging device having a vertical bunker A comparison was made. The results are shown in FIG. 10. When a blast furnace raw material charging apparatus having three furnace bunker of parallel + off-center type and a dedicated chute is used (reducing material ratio 490 kg / t), a vertical bunker is used. Compared with a (reducing material ratio 510 kg / t) when using the blast furnace raw material charging device, the area where the gas utilization rate is low is small, and excessive gas flow in the vicinity of the center can be suppressed. Can be done. Further, FIG. 11 shows the ventilation resistance at the bottom of the furnace when using a blast furnace raw material charging apparatus having three parallel + off-center type top bunker and dedicated chute when the coke ratio is 380 kg / t. The comparison between the index (a) and the ventilation resistance index (b) at the bottom of the furnace when using a blast furnace raw material charging apparatus having a vertical bunker is shown. According to FIG. 11, the ventilation resistance at the lower part of the furnace is also lower when using the blast furnace raw material charging apparatus having three furnace top bunker of parallel + off-center type and dedicated chute (a), It was possible to contribute to stable operation through improving the core and hearth ventilation.

Device outline and coke deposit shape in 1/10 model. The graph which shows the radial direction coke particle size distribution in a 1/10 model. The graph which shows the time-dependent change of the particle size at the time of the coke discharge | emission from a furnace top bunker. The graph which shows the radial direction particle size distribution at the time of coke charging with a turning chute and a special chute. Schematic which shows the influence which a parallel + off-center type furnace top bunker has on charging deviation. Schematic which shows one Embodiment of the blast furnace raw material charging device of this invention. (A) Chute, (b) Rebound plate, (c) Classifier installed in the top bunker. Schematics showing the coke deposit shape ((a) conventional example, (b) example of the present invention). The graph which shows the coke particle size distribution of radial direction (a conventional example, b this invention example). The graph which shows the gas utilization factor distribution of a radial direction (a conventional example, b this invention example). The graph which shows a furnace lower part ventilation resistance index (a conventional example, b this invention example). Schematic which shows the coke pile shape at the time of performing center part coke charging with a turning chute and a special chute.

Explanation of symbols

1 Rotating chute 2 Choke for central coke charging 3 Furnace top bunker (parallel + off-center type)
4 Furnace top bunker (vertical type)
5 Coke fall trajectory from swiveling chute 6 Coke fall trajectory from special chute 7 Coke accumulation shape formed by charging with swivel chute 8 Coke accumulation shape formed by charging with special chute 10 Chute 11 Rebound plate 12 Classifier

Claims (4)

  A device installed at the top of the furnace for charging the raw material into the blast furnace, the furnace top bunker having an outlet at a position eccentric to the central axis, and the raw material discharged from the furnace bunker in the blast furnace A blast furnace raw material charging apparatus, comprising: a swivel chute charged to the furnace and a central coke dedicated chute for charging coke in a region near the furnace axis.   The blast furnace raw material charging apparatus according to claim 1, comprising three or more furnace top bunker.   The blast furnace raw material charging apparatus according to claim 1 or 2, further comprising guide means for charging the raw material from above the discharge port of the furnace top bunker.   When the raw material is charged using the blast furnace raw material charging device according to any one of claims 1 to 3, the particle size of the charged material charged into the blast furnace from the top bunker A blast furnace raw material charging method, characterized in that raw materials are charged so that there are many fine grains in the early stage and coarse grains in the later stage of discharge.

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