JP5817758B2 - Raw material charging device and raw material charging method to blast furnace using the raw material charging device - Google Patents

Description

  The present invention relates to a raw material charging apparatus having an upper bunker and a lower bunker connected by at least two ports, and a raw material charging method to a blast furnace using the same.

  In recent years, from the viewpoint of environmental problems, it has been required to reduce the amount of coke used in blast furnace operation. As a method for reducing the amount of coke used, first, two methods are conceivable: a method of increasing the amount of ore charged per charge and a method of decreasing the amount of coke charged per charge. However, if the former method is performed, the ore charged in the blast furnace becomes thicker, so the ore reducibility is reduced, and the furnace heat decreases due to the direct reaction of unreduced ore at the lower part of the blast furnace. The situation will worsen. On the other hand, if the latter method is carried out, the layer thickness of the coke charged in the blast furnace becomes thin in the cohesive zone (the region where the ores soften and fuse together), so the air permeability at the bottom of the blast furnace will deteriorate. .

  The technology to stabilize the blast furnace condition by maintaining good blast furnace permeability and liquid permeability is to charge coke into the blast furnace, and then charge the ore and coke at the same time to coke layer and coke in the blast furnace. Techniques for alternately forming mixed ore layers are known (see, for example, Patent Documents 1 and 2). However, in the techniques described in Patent Documents 1 and 2, since the particle size of coke charged simultaneously with the ore is reduced in order to promote the melting of the ore, the ore starts to melt and then drops. It is considered that coke disappears in the region (softened cohesive zone), the air permeability in the softened cohesive zone becomes insufficient, and the effect of reducing the amount of coke used is small.

  Therefore, in Patent Document 3, when the coke mixed ore layer is formed in the blast furnace, the coke particle size is set to 1.3 times or more than the ore particle size, and the upper portion disposed at the top of the bell-less blast furnace. After putting ore into the bunker, and then throwing in ore and coke, the raw material in the upper bunker is transferred into the lower bunker located below the upper bunker, and the raw material discharged from the lower bunker is turned into a swivel chute Is disclosed in which a coke mixed ore layer is formed in the blast furnace by charging the bellless blast furnace.

JP-A-8-283804 JP-A-10-183210 JP 2010-133008 A

  According to the technique disclosed in Patent Document 3, coke charged at the same time as the ore can be prevented from disappearing in the softening zone of the blast furnace. However, the radial distribution of the coke mixing ratio of the coke segregation caused by the particle size difference between the ore and the coke has not yet been made uniform. The change in the coke mixing rate with time is that the coke mixing rate increases from the beginning to the middle of the mixed raw material of ore and coke, and the coke mixing rate decreases at the end. When the mixed raw material is discharged from the lower bunker and charged into the blast furnace with the distribution of the coke mixing ratio over time, the effect of improving the air permeability at the bottom of the furnace cannot be expected so much in the region charged at the end of the discharge. . The coke mixing ratio is the ratio of coke out of the total amount of coke charged simultaneously with the ore.

  Further, in the technique disclosed in Patent Document 3, in order to prevent the distribution in the furnace of coke charged at the same time as the ore from becoming uneven in the radial direction of the blast furnace, on the furnace top conveyor of the raw material charging apparatus. The timing of supplying coke from the raw material tank is adjusted, but coke segregation occurs due to the difference in particle size between ore and coke. It is difficult to suppress the change in the discharge ratio over time.

  The present invention was made in view of the above problems, a raw material charging apparatus capable of forming a coke mixed ore layer in the blast furnace in which the distribution of coke in the furnace is uniform in the radial direction of the blast furnace, and It aims at providing the raw material charging method to the blast furnace using it.

The gist of the present invention for solving the above problems is as follows.
(1) A raw material charging apparatus for charging raw material into a blast furnace, comprising an upper bunker, an upper chute capable of tilting provided in the upper bunker, a lower bunker connected to the upper bunker through at least two ports, and A sieve provided in the upper bunker below the upper chute, the sieve having a sieve surface, a side wall, and an opening in a part of the side wall, and the sieve surface, A raw material charging apparatus characterized by being inclined with respect to a horizontal plane at an angle of repose of the raw material or more.
(2) A raw material charging method to a blast furnace using the raw material charging device described in (1) above, in which a raw material in a state where ore and coke are mixed is introduced into an upper bunker through an upper chute. In this case, the raw material is dropped toward the sieve, and the raw material that falls on the sieve surface is supplied to the main port through the opening, and the raw material that passes through the sieve surface is supplied to all ports including the main port. Then, the raw material is deposited on the upper bunker, the raw material of the upper bunker is transferred to the lower bunker with all the ports open, the raw material in the lower bunker is charged into the blast furnace, and coke mixing is performed. A raw material charging method for a blast furnace, wherein an ore layer is formed in the blast furnace.
(3) The blast furnace according to (2) above, wherein the amount of coke contained in the coke mixed ore layer is 10% by mass or more and 20% by mass or less of the total coke amount charged into the blast furnace. Raw material charging method.

  According to the present invention, when a raw material in a state where coke and ore are mixed is introduced into the upper bunker, segregation of coke due to a particle size difference from the ore is less likely to occur in the upper bunker or the lower bunker. The coke and ore can be discharged from the lower bunker and charged into the blast furnace while maintaining a constant mixing ratio of coke and ore. Therefore, a coke mixed ore layer in which the distribution of coke in the furnace is uniform in the radial direction of the blast furnace can be formed in the blast furnace.

It is explanatory drawing which shows a blast furnace and a raw material charging device. It is a top view which shows the positional relationship of the sieve shown in FIG. 1, and the raw material deposition part of a port. It is explanatory drawing which shows the state which has thrown in the coke to the upper bunker. It is explanatory drawing which shows the state which is transferring the coke of an upper bunker to a lower bunker. It is explanatory drawing which shows the state which has injected | thrown-in coke and an ore to an upper bunker. It is a top view which shows the positional relationship with the coke and ore which accumulate in the raw material deposition part of a sieve and a port in the state of FIG. It is explanatory drawing which shows the state which is transferring the coke and ore of an upper bunker to a lower bunker. It is a graph which shows the relationship between the discharge | emission mass ratio and coke mixing rate in an Example.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory view showing a blast furnace and a raw material charging apparatus. As shown in FIG. 1, a raw material charging device 4 for charging a raw material containing coke 2 and ore 3 into the blast furnace 1 is provided at the top of the blast furnace 1. The raw material charging device 4 includes an upper bunker 11, a tiltable and turnable upper chute 12 provided on the top of the upper bunker 11, a lower bunker 14 connected to the upper bunker 11 through four ports 13, and A sieve 15 is provided. In the raw material charging apparatus 4 of the present embodiment, the number of ports 13 that connect the upper bunker 11 and the lower bunker 14 is four, but the present invention is not limited to four ports, Two are enough. Each port 13 is provided with a gate 16 for opening and closing the port 13.

  The raw material which is the coke 2 and the ore 3 stored in the coke storage tank 22 and the ore storage tank 23 is supplied to the upper charging port of the raw material charging device 4 via the furnace top conveyor 21, and the upper chute 12 It is thrown into the bunker 11. Four ports 13 are arranged at the bottom of the upper bunker 11, and each port 13 is formed with an inverted truncated cone-shaped raw material deposition portion 5, and a lower bottom surface portion in the inverted truncated cone shape is opened. The lower bottom portion constitutes the port 13. The raw material charged into the upper bunker 11 is deposited on the raw material depositing portion 5 on each port 13 with the gate 16 closed. When the gate 16 is opened, the deposited material is transferred to the lower bunker 14 through the port 13. The raw material accumulation portion 5 is described by taking the right port 13 in FIG. 1 as an example. The horizontal surface at the upper end position of the right port 13 is a lower bottom surface portion, and the left port 13 from the upper portion of the right port 13 is An inverted frustoconical shape having a horizontal plane at the position where the inclined surface inclined to the provided side and the inclined surface inclined to the side on which the right port 13 is provided from the upper side of the left port 13 is the upper bottom surface portion This part.

  A raw material discharge port 17 for discharging the raw material transferred from the upper bunker 11 to the blast furnace 1 is disposed at the bottom of the lower bunker 14. The raw material discharge port 17 is also formed with a reverse frustum-shaped raw material deposition portion 9, and the lower bottom portion constitutes the raw material discharge port 17, and a gate 18 is provided in the same manner as the port 13. The raw material transferred from the upper bunker 11 is deposited on the raw material depositing portion 9 on the raw material outlet 17 with the gate 18 closed. When the gate 18 is opened, the deposited raw material is discharged from the raw material discharge port 17, and the raw material is charged into the blast furnace 1 from a turning chute 19 disposed below the lower bunker 14. The raw material accumulation portion 9 is an inverted frustoconical portion having a horizontal surface at the upper end position of the raw material discharge port 17 as a lower bottom surface portion and a horizontal surface at the upper end position of the inclined surface of the lower bunker 14 as an upper bottom surface portion. Say.

  As shown in FIG. 1, the sieve 15 is provided inside the upper bunker 11. FIG. 2 is a plan view showing the positional relationship between the sieve shown in FIG. 1 and the raw material depositing portion of the port. In order to distinguish each of the four ports 13, reference numerals 13a to 13d are assigned to the four ports 13, respectively. The sieve 15 is disposed below the upper chute 12 and above the ports 13a to 13d and between them.

  As shown in FIG. 2, as an example of the sieve 15, a plurality of rods are arranged in a plurality of intervals at the lower end portion of the side wall 15 b formed in a U-shape when viewed from above at intervals that serve as sieve meshes. A sieve 15 having a sieve surface 15a can be used. The sieve 15 shown in FIG. 2 has a form in which a plurality of bars are arranged perpendicular to the inclination direction of the sieve surface 15a, but is not limited to this form, and the direction of the plurality of bars is the same direction as the inclination direction. They may be arranged in a line, or a plurality of these bars may be crossed to form a mesh on the sieve surface 15a.

  The sieve 15 has a sieve surface 15a, a side wall 15b that protrudes upward from the periphery of the sieve surface 15a, and an opening 15c that is not formed with a side wall 15b at a part of the periphery, and is open. The sieving surface 15a is provided in the upper bunker 11 so as to incline more than the repose angle of the raw material with respect to the horizontal plane. Further, a side wall 15b is formed around the screen surface 15a other than the lower side of the screen, while a side wall is not formed at the lower end of the inclined surface, and the periphery of the side end becomes the opening 15c. ing. A main port 13a, which is one of the four ports 13, and a raw material deposition portion 5a are disposed at the tip of the sieving surface 15a in the downward direction of the sieving surface 15a. Below all the ports 13, sub-ports 13b to 13d other than the main port 13a and raw material deposition portions 5b to 5d are arranged.

  The sieve surface 15a is formed by arranging a plurality of rods at equal intervals in a direction perpendicular to the inclination direction, but the present invention is not limited to this form, and the intervals between the rods are not necessarily equal. However, it is preferable that the maximum value of the spacing (sieve) between the bars of the sieve 15 is less than the particle diameter of the coke 2 that has been sized to a predetermined particle size or more. However, in this embodiment, since the plurality of metal rods are arranged at equal intervals, all the meshes in the inclination direction are the same.

  Since the inclination angle of the sieving surface 15a is equal to or greater than the repose angle of the raw material, the raw material does not accumulate on the sieving surface 15a and falls down in the inclination direction. In addition, the side wall 15b prevents the raw material on the sieve surface 15a from falling in a direction other than the downward direction of the sieve surface 15a, and the side wall 15b has the raw material dropped on the sieve surface 15a beyond the side wall 15b. It is preferable to have a height high enough not to fall.

  Next, a method for alternately forming the coke layer 31 and the coke mixed ore layer 32 in the blast furnace 1 using the raw material charging device 4 having the above-described configuration will be described.

  First, a raw material charging method for forming the coke layer 31 will be described. FIG. 3 is an explanatory view showing a state in which coke is thrown into the upper bunker. The coke 2 is conveyed to the upper charging port of the raw material charging device 4 by the furnace top conveyor 21 and charged into the upper bunker 4 from the upper chute 12. At the time of this charging, as shown in FIG. 3, the coke 2 is charged after adjusting the angle of the upper chute 12 so as not to hit the sieve 15. The coke 2 is deposited on the raw material deposition portion 5 on each port 13.

  FIG. 4 is an explanatory view showing a state where the coke of the upper bunker is being transferred to the lower bunker. As shown in FIG. 4, the gate 16 is opened to open all of the ports 13, and the deposited coke 2 is transferred to the lower bunker 14 and deposited on the material deposition portion of the material discharge port 17. Thereafter, when the gate 18 of the raw material discharge port 17 disposed at the bottom of the lower bunker 14 is opened and the coke 2 transferred to the lower bunker 14 is charged into the blast furnace 1 from the turning chute 19, as shown in FIG. A coke layer 31 is formed inside the blast furnace 1.

  Following the formation of the coke layer 31, a raw material charging method for forming the coke mixed ore layer 32 on the coke layer 31 will be described. FIG. 5 is an explanatory view showing a state in which coke and ore are being charged into the upper bunker, and FIG. 6 shows a positional relationship between the sieve in that state and the coke and ore deposited on the raw material accumulation portion of the port. It is a top view.

  The inclination angle of the upper chute 12 is adjusted so that the raw material in which the coke 2 and the ore 3 are mixed falls from the upper chute 12 onto the sieve 15, and the raw material is supplied to the upper charging port of the raw material charging device 4. To the upper bunker 11 through the upper chute 12. As shown in FIG. 6, among the raw materials, the coke 2 and the ore 3 having a size less than the maximum value of the sieve mesh pass through the sieve surface 15a and a part of the raw material deposition portions 5a to 5d is included. While falling to the central portion 6 and then being distributed to the raw material accumulation portions 5a to 5d, the coke 2 and the ore 3 having a size larger than the maximum value of the sieve mesh roll down the sieve surface 15a to the main port. 13a is supplied to the raw material deposition portion.

  In normal blast furnace operation, the particle size of the ore 3 is smaller than the particle size of the coke 2, so the screen of the sieve 15 may be set to a value at which most of the ore 3 passes without passing the coke 2. Before the material is charged into the raw material charging device 4, the particle size of the ore 3 is made smaller than the maximum value of the mesh of the sieve 15, and the particle size of the coke 2 is set to the mesh of the sieve 15. It is preferable to make it larger than the maximum value. If it does so, the raw material which passes through the sieve surface 15a will more certainly be the ore 3 and the raw material which falls down the sieve surface 15a will be mainly the coke 2. For this reason, the coke mixed ore deposit layer 7 formed by mixing the coke 2 that has fallen through the sieve surface 15a and the ore 3 that has passed through the sieve surface 15a is formed in the raw material deposit portion 5a of the main port 13a, and the sub port 13b. The ore deposit layer 8 mainly composed of the ore 3 is formed in the ~ 13d raw material deposit portions 5b to 5d.

  FIG. 7 is an explanatory diagram showing a state in which coke and ore of the upper bunker are being transferred to the lower bunker. As shown in FIG. 7, when all the ports 13 are opened after the raw materials have been charged into the upper bunker 11, the raw materials for the coke mixed ore deposit layer 7 and the ore deposit layer 8 on the port 13 are converted into the lower bunker. 14, the coke mixed ore deposit layer 7 and the ore deposit layer 8 are formed in the lower bunker 14 while being separated when viewed from above and maintaining the positional relationship in the upper bunker 11. Thereafter, when the raw material discharge port 17 is opened and the coke 2 and the ore 3 transferred to the lower bunker 14 are charged into the blast furnace 1 from the turning chute 19, a coke mixed ore layer 32 is formed on the coke layer 31. .

  The amount of coke contained in the coke mixed ore layer 32 is preferably 10% by mass or more and 20% by mass or less of the total amount of coke charged into the blast furnace 1. This is because if the coke 2 mixed with the ore 3 is 10% or more with respect to the total amount of the coke 2 charged into the blast furnace 1, the amount of coke mixed with the coke mixed ore layer 32 is too small. This is because the coke 2 in the mixed ore layer 32 suppresses the possibility that all of the coke 2 will disappear due to the gasification reaction before reaching the cohesive zone, and the air permeability is easily improved. For example, after the raw material in a state where the coke 2 and the ore 3 are mixed is put into the upper bunker 11, the sieving by the sieve 15 is appropriately performed, and the coke 2 is easily distributed to the raw material accumulation portion 5a of the main port 13a. Therefore, the effect of charging the blast furnace while maintaining the mixing ratio of the coke 2 and the ore 3 constant is more easily achieved. In other words, when it exceeds 20 mass%, the coke 2 overflows from the main port 13a, and the possibility that the coke 2 flows into the adjacent sub ports 13b to 13d more than expected is increased.

  The coke 2 to be mixed with the ore 3 and put into the upper bunker 11 is preferably a lump coke having a particle size of 40 mm or more, but may be a small coke having a particle size of 20 to 40 mm. The lump coke having a particle size of 40 mm or more is lump coke on a sieve sieved at 40 mm, and the particle size of 20 to 40 mm is a lump coke on a sieve sieved at 20 mm and under a sieve sieved at 40 mm. is there. For example, when using coke with a particle size of 40 mm or more, the maximum value of the sieve mesh of the sieve 15 is set to less than 40 mm, and the ore under the sieve that has been pre-sieved with the ore 3 less than the maximum value of the sieve mesh is used. It is preferable to do. When small coke having a particle size of 20 to 40 mm or more is used, the maximum value of the sieve 15 is less than 20 mm, and the ore 3 has a particle size of less than the maximum value of the sieve 15 in advance. It is preferable to use a sieving ore. Further, the particle diameter of the ore 3 is preferably less than the minimum length of the sieve 15, but the sieve mesh length of the sieve 15 is 90% or more of the ore 3 of the raw material. It is sufficient if the dimensions are such that it can pass through. The coke 2 and the ore 3 are preferably presized, but in the normal operation of the blast furnace 1, the particle size of the ore 3 is smaller than the particle size of the coke 2. Does not pass and most of the ore 3 passes. For this reason, it is not necessary to pre-size the coke 2 and the ore 3.

  As described above, as shown in FIGS. 5 and 7, the coke mixed ore deposit layer 7 and the ore deposit layer 8 clearly separated by the upper bunker 11 are transferred to the lower bunker 14 while being clearly separated. Therefore, along the discharge direction (vertical direction) of the raw material at the raw material discharge port 17, the coke mixed ore deposit layer 7 and the ore deposit layer 8 are discharged from the raw material discharge port 17 at the same rate. . For this reason, the coke 2 and the ore 3 can be charged into the bell-less blast furnace 1 while the mixing rate of the coke 2 and the ore 3 is always kept constant while the raw material is discharged. Therefore, the coke mixed ore layer 32 in which the distribution of the coke 2 in the furnace is uniform in the radial direction of the blast furnace 1 can be formed in the blast furnace 1.

  As described in the above embodiment, using the raw material charging apparatus 4 shown in FIG. 1, after forming the [1] coke layer 31 in the blast furnace 1, [2] the coke mixed ore layer thereon 32, [3] A coke layer 31 is formed on the coke mixed ore layer 32 formed in [2], [1] and [2] are repeated, and the blast furnace 1 The raw material was charged to the blast furnace 1 and the blast furnace 1 was operated (invention example).

In the example of the present invention, the flow rate and pressure of the air fed into the inside from the blower tuyere of the blast furnace 1 were 7200 (Nm ³ / min) and 420 kPa, and the air blowing temperature was 1150 ° C. The hot metal temperature was 1511 ° C.

  On the other hand, using a conventional raw material charging device, that is, a raw material charging device having the same dimensions as the raw material charging device 4 and the upper bunker shown in FIG. After the coke layer 31 is formed, [2 ′] the upper chute 12 is swung as in the prior art, the coke 2 and the ore 3 are thrown into the upper bunker 11, and then transferred from the upper bunker 11 to the lower bunker 14. Then, a coke mixed ore layer 32 is formed on the coke layer 31. [3] On the coke mixed ore layer 32 formed by [2 ′], [1] the coke layer 31 is formed, 1] and [2 ′] were repeated, and the blast furnace 1 was operated in the same manner as the inventive example except that the raw material was charged into the blast furnace 1 (comparative example).

  The raw material containing the coke 2 and the ore 3 was the same in the inventive example and the comparative example, and the ratio of the coke 2 and the ore 3 charged into the raw material charging device was also the same. Table 1 shows the operating conditions and results of the blast furnace 1, the size of the raw material, and the length of the sieve mesh in the present invention example and the comparative example.

The ventilation resistance index K in Table 1 is represented by K = (P _blast ² −P ² ) / V ^1.7 × 100.
Where P _blast : blowing pressure (kPa),
P: furnace top pressure (kPa),
V: Air flow rate (Nm ³ / min).
The gas utilization rate is expressed by (CO ₂ gas composition in blast furnace gas (%) / (CO gas composition in blast furnace gas (%) + CO ₂ gas composition in blast furnace gas (%))).

  According to Table 1, in the comparative example, the ventilation resistance index was 2.35, and the gas utilization rate was 47.9%. On the other hand, in the example of the present invention, the airflow resistance index was 2.30 and the gas utilization rate was 48.5%, and both the coke ratio and the reducing material ratio were lower than in the comparative example. From this, it was confirmed that this invention is effective for the stable operation of a blast furnace, and can be used also as a low reduction material ratio operation technique.

  Moreover, the present inventors investigated the temporal change of the coke mixing ratio in the raw material discharged | emitted from the lower bunker of the raw material charging device of this invention example and a comparative example. The survey results are shown in FIG. As can be seen from the graph of FIG. 8, in the comparative example, although the coke mixing ratio in the raw material (ore) discharged from the lower bunker along with the ore is large at the initial stage of discharge, it decreases from the middle stage of discharge, and at the end stage of discharge. The coke mixing ratio is greatly reduced. On the other hand, in the example of the present invention, it is understood that the coke mixing ratio discharged from the lower bunker does not change greatly from the initial discharge to the final discharge.

  Therefore, after the present invention is applied to the blast furnace operation, the coke 2 is charged into the blast furnace 1 from the lower bunker 14 and the coke layer 31 is formed in the blast furnace 1, and then the upper portion where the sieve 15 is provided from the turning chute 19. By supplying the ore 3 and the coke 2 to the bunker 11, the coke mixed ore deposit layer 7 and the ore deposit layer 8 can be deposited in the lower bunker 14 in a clearly separated state. The segregation of the coke 2 due to the ash is less likely to occur in the upper bunker 11 and the lower bunker 14, and the coke 2 and the ore 3 are charged into the blast furnace 1 from the lower bunker 14 while keeping the mixing ratio of the coke 2 and the ore 3 constant at all times. And low-reducing material ratio operation becomes possible.

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Coke 3 Ore 4 Raw material charging device 5 Raw material deposition part 5a-5d Raw material deposition part 6 Center part 7 Coke mixed ore deposition layer (Ore deposition layer relatively containing coke 2)
8 Ore deposits (Ore deposits with ore 3 containing almost no coke 2)
9 Raw material accumulation part 11 Upper bunker 12 Upper chute 13 Port 13a Main port 13b to 13d Subport 14 Lower bunker 15 Sieve 15a Sieve surface 15b Side wall 15c Opening 16 Gate 17 Raw material discharge port 18 Gate 19 Turning chute 21 Furnace conveyor 22 Coke Storage tank 23 Ore storage tank 31 Coke layer 32 Coke mixed ore layer

Claims (3)

A raw material charging device for charging raw materials into a blast furnace,
Upper bunker,
A tiltable upper chute provided in the upper bunker,
A lower bunker connected to the upper bunker with at least two ports; and
A sieve provided in the upper bunker below the upper chute,
The sieve has a sieve surface, a side wall, and an opening in a part of the side wall,
The raw material charging apparatus, wherein the sieve surface is inclined with respect to a horizontal plane at an angle of repose of the raw material or more. A raw material charging method to a blast furnace using the raw material charging device according to claim 1,
When the raw material mixed with ore and coke is put into the upper bunker through the upper chute, the raw material is dropped toward the sieve,
The raw material that falls on the sieve surface is supplied to the main port through the opening, the raw material that passes through the sieve surface is supplied to all ports including the main port, and the raw material is deposited on the upper bunker,
With all the ports open, the raw material of the upper bunker is transferred to the lower bunker,
A raw material charging method into a blast furnace, wherein the raw material in the lower bunker is charged into a blast furnace, and a coke mixed ore layer is formed in the blast furnace.   The amount of coke contained in the coke mixed ore layer is set to 10% by mass or more and 20% by mass or less of the total amount of coke charged to the blast furnace. How to enter.

Images