JP5974759B2 - Blast furnace raw material charging method - Google Patents

Description

  The present invention relates to a method for charging coke and ore, which are blast furnace raw materials, into a bellless blast furnace, and more particularly, to a method for charging a blast furnace raw material into a bellless blast furnace from two upper and lower bunkers arranged at the top of the bellless blast furnace.

Coke and ore, which are blast furnace raw materials, are generally charged alternately into a bellless blast furnace from a raw material charging apparatus provided at the top of the bellless blast furnace. In this case, in recent years, from the viewpoint of environmental problems, it has been required to operate the blast furnace while reducing the amount of coke used in the blast furnace as much as possible.
There are two methods for reducing the amount of coke used in the blast furnace: 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 carried out, the ore charged in the blast furnace becomes thicker, so the ore reducibility is reduced and the furnace heat lowers due to the direct reaction of unreduced ore at the bottom of the blast furnace. The situation will worsen. On the other hand, when the latter method is carried out, the layer thickness of the coke charged in the blast furnace becomes thin at the cohesive zone (the region where the ores soften and fuse together), so that the air permeability at the lower part of the blast furnace is deteriorated.

The technology to stabilize the blast furnace condition by maintaining the air permeability and liquid permeability of the blast furnace well, after charging coke into the blast furnace, charging ore and coke at the same time and mixing the coke layer and coke into the blast furnace. Techniques for alternately forming 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 at the same time as the ore is made small in order to promote the melting of the ore, the ore starts to melt until it 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 charged, that is, the effect of reducing the coke ratio with respect to the ore is small.

  Therefore, when forming the coke mixed ore layer in the bellless blast furnace, the coke particle size should be 1.3 times or more than the ore particle size, and the ore is put into the upper bunker located at the top of the bellless blast furnace. Then, after ore and coke are introduced, the raw material in the upper bunker is transferred into the lower bunker located at the lower part of the upper bunker, and the raw material discharged from the lower bunker is transferred to the bell-less blast furnace through the swivel chute. Patent Document 3 discloses a technique for charging and forming a coke mixed ore layer in a blast furnace.

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

According to the technique disclosed in Patent Document 3, the coke charged simultaneously with the ore is prevented from disappearing in the softening cohesive zone of the blast furnace, and the coke caused by the difference in particle size between the ore and the coke is suppressed. The effect of segregation on the coke mixing ratio is somewhat improved, but the radial distribution has not been made uniform.
That is, the coke mixing ratio increases from the initial charging stage to the middle stage, and changes with time such that the coke mixing ratio decreases at the end stage. When the raw material is charged into the blast furnace through the swirl chute with such a discharge mixture ratio distribution, an improvement effect of air permeability cannot be expected in the lower part of the furnace in the region charged at the end of discharge.

  In addition, in the technique described 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 has been made in view of such problems, and among the upper and lower bunkers arranged at the top of the bellless blast furnace, ore and coke are charged into the bellless blast furnace from the lower bunker and placed in the blast furnace. An object of the present invention is to provide a blast furnace raw material charging method capable of charging a blast furnace raw material into a bell-less blast furnace while maintaining a substantially constant mixing ratio of ore and coke when forming a coke mixed ore layer.

In order to achieve the above object, according to the present invention, an upper bunker and a lower bunker connected by a plurality of three or more ports are arranged at the top of a bell-less blast furnace, and raw materials in the upper bunker are placed in the plurality of ports. It is transferred to the lower bunker via the port by opening and closing the blast furnace, and the blast furnace raw material charged into the upper bunker is charged into the bell-less blast furnace from the lower bunker through a turning chute, and the coke layer and the coke mixed ore are alternately placed. A method of charging a blast furnace raw material to be formed, in a state in which coke is left on one or two of the plurality of ports when the coke put into the upper bunker is transferred to the lower bunker. after transporting the coke to the lower bunker, coke layer is formed in the blast furnace was charged into the blast furnace, one or two ports of the plurality of ports After putting ore into the upper bunker with coke left on the top, the coke and ore are transferred to the lower bunker with all of the ports open, then charged into the blast furnace and mixed with coke. An ore layer is formed in a blast furnace.

  According to the present invention, when the coke put into the upper bunker is transferred to the lower bunker, a part of the coke remains in the upper bunker, and when the ore put into the upper bunker is transferred to the lower bunker, it is put into the upper bunker. The ore and coke remaining in the upper bunker are transferred to the lower bunker from separate raw material discharge ports. As a result, the ore charged in the upper bunker and the coke remaining in the upper bunker can be transferred separately to the lower bunker, and when the ore and coke are charged into the bell-less blast furnace from the lower bunker, Since it is in a mixed state, the ore and coke are charged into the bell-less blast furnace from the lower bunker among the upper and lower two-stage bunker arranged at the top of the bell-less blast furnace and the ore and coke are formed in the blast furnace. The blast furnace raw material can be charged into the bell-less blast furnace while maintaining the coke mixing ratio almost constant.

It is a figure which shows the furnace top part of the bell-less blast furnace to which this invention is applied. It is a figure which shows the state of a raw material charging device when a coke is thrown into the upper bunker among the upper and lower two-stage bunker arranged at the top of the bellless blast furnace. It is a figure which shows the state of a raw material charging device when coke is transferred from an upper bunker to a lower bunker with one of a plurality of raw material discharge ports formed in the upper bunker closed. It is a figure which shows the state of a raw material charging device when an ore is thrown into an upper bunker. It is a figure which shows the state of a raw material charging device when ore is transferred from an upper bunker to a lower bunker with all the raw material discharge ports opened. It is a figure which shows typically the discharge ratio of the ore and coke discharged | emitted from a lower bunker. It is a figure which shows the time change of the coke mixing rate in the ore discharged | emitted from a lower bunker.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The top of the bellless blast furnace to which the present invention is applied is shown in FIG. As shown in FIG. 1, the bell-less blast furnace 1 includes a raw material charging device 4 for charging coke 2 and ore 3 as blast furnace raw materials into the blast furnace. The raw material charging apparatus 4 has an upper bunker 5 and a lower bunker 6, and these bunker 5 and 6 are arranged at the top of the bellless blast furnace 1.

Further, the blast furnace raw material stored in the raw material tanks 7 and 8 is supplied to the upper charging port of the raw material charging device 4 via the furnace top conveyor 9, and from a turning chute 10 disposed on the top of the upper bunker 5. It is thrown into the upper bunker 5.
The raw material charging device 4 is provided with a plurality (for example, four) of raw material discharge ports 51 for transferring the blast furnace raw material charged into the upper bunker 5 to the lower bunker 6. The material discharge port 51 has a plurality of gates 52 that open and close the material discharge port 51.

On the other hand, a raw material discharge port 61 for discharging the blast furnace raw material transferred from the upper bunker 5 is disposed at the bottom of the lower bunker 6. The material discharge port 61 has a gate 62 that opens and closes the material discharge port 61.
The blast furnace raw material discharged from the raw material discharge port 61 of the lower bunker 6 is charged into the bell-less blast furnace 1 from the turning chute 11 disposed below the lower bunker 6.

  When the coke layer 12 shown in FIG. 1 is formed in the raw material charging portion of the bell-less blast furnace 1 using such a raw material charging device 4 and the coke mixed ore layer 13 is formed on the coke layer 12, first, The coke 2 stored in the raw material tank 7 is conveyed to the upper charging port of the raw material charging device 4 by the furnace top conveyor 9, and charged into the upper bunker 5 from the turning chute 10. The state of the raw material charging apparatus 4 at this time is shown in FIG.

Next, the coke 2 is transferred from the upper bunker 5 to the lower bunker 6 with one of the plurality of raw material discharge ports 51 closed and the remaining raw material discharge ports 51 opened. The state of the raw material charging apparatus 4 at this time is shown in FIG.
Next, the raw material discharge port 61 disposed at the bottom of the lower bunker 6 is opened, the coke 2 transferred to the lower bunker 6 is charged into the bell-less blast furnace 1 from the turning chute 11, and a coke layer is formed. The ore 3 stored in the raw material tank 8 is conveyed to the upper charging port of the raw material charging device 4 by the furnace top conveyor 9. Then, the transported ore 3 is thrown into the upper bunker 5 from the turning chute 10 . The state of the raw material charging apparatus 4 at this time is shown in FIG.

Next, all the raw material discharge ports 51 are opened, and the ore 3 and the coke 2 in the upper bunker 5 are transferred to the lower bunker 6. The state of the raw material charging apparatus 4 at this time is shown in FIG.
Thereafter, the raw material discharge port 61 disposed at the bottom of the lower bunker 6 is opened, and the ore 3 and the coke 2 transferred to the lower bunker 6 are charged into the bellless blast furnace 1 from the turning chute 11 and the coke mixed ore layer is formed. Form.

  In addition, when the coke 2 thrown into the upper bunker 5 is transferred to the lower bunker 6, the amount of the coke 2 left on the port may be set to 10% or more with respect to the amount of the coke 2 thrown into the upper bunker 5. preferable. This is because when the amount of coke 2 left on the port is less than 10% of the amount of coke 2 charged into the upper bunker 5, the amount of coke mixed with the ore layer is less than 10%. This is because all the coke in the mixed ore layer disappears by the gasification reaction before reaching the cohesive zone, and the effect of improving air permeability cannot be expected.

In order to leave coke on at least one of a plurality of ports, as described above, when transferring the coke 2 from the upper bunker 5 to the lower bunker 6, one port is closed and the other There is a method of opening a port, but when the amount of coke mixed with ore is relatively small, the time during which one port is opened may be adjusted to adjust the amount of coke left on the port. If the amount of ore mixed coke is relatively large, the two ports may be closed and the other ports opened to transfer the coke, leaving the coke on the two ports.
As described above, when the ore and coke in the raw material charging apparatus 4 are stacked as shown in FIGS. 4 and 5, the coke 2 and the ore 3 of the lower bunker 6 are, for example, as shown in FIG. It is discharged from the lower bunker 6 at a discharge rate and charged into the bellless blast furnace 1.

  Therefore, in one embodiment of the present invention, the ore 3 charged in the upper bunker 5 and the coke 2 remaining in the upper bunker 5 are transferred from separate ports to the lower bunker 6 and separated from the upper side. Ore 3 and coke 2 can be deposited in the lower bunker 6, and when the lower bunker 6 is charged into the bell-less blast furnace 1, the ore 3 and coke 2 are discharged in the order shown in FIG. When the ore 3 and the coke 2 are charged into the bell-less blast furnace 1 from the raw material charging device 4 arranged at the top of the bell-less blast furnace 1 to form the coke mixed ore layer 13 in the blast furnace, the ores 3 and coke 2 The blast furnace raw material can be charged into the bell-less blast furnace 1 while keeping the mixing ratio substantially constant.

  The inventors investigated the temporal change in the coke mixing ratio in the ore discharged from the lower bunker. The survey results are shown in FIG. FIG. 7 (a) shows the temporal change in the coke mixing ratio in the ore discharged from the lower bunker when ore and coke are simultaneously charged into the upper bunker, and FIG. 7 (b) is a case where the present invention is applied. Shows the change over time of the coke mixing ratio in the ore discharged from the lower bunker.

When ore and coke are introduced into the upper bunker at the same time, the mixing ratio of coke in the ore discharged from the lower bunker with the ore is large in the early stage of discharge, but decreases from the middle stage of discharge, and in the ore at the end stage of discharge. It can be seen from FIG. 7A that the coke mixing ratio is greatly reduced.
On the other hand, when this invention is applied, it turns out from FIG.7 (b) that the coke mixing rate in the ore discharged | emitted from a lower bunker does not change a lot from the discharge | emission initial stage to the discharge | emission final stage.

Therefore, as in the above-described embodiment of the present invention, when the coke 2 charged into the upper bunker 5 is transferred to the lower bunker 6, the coke is transferred to the lower bunker with one of the plurality of raw material discharge ports 51 closed. When the ore 3 transferred to the upper bunker 5 is transferred to the lower bunker 6, the ore 3 is transferred to the lower bunker 6 with all of the raw material discharge ports 51 being opened. When the ores 3 and coke 2 are charged into the bellless blast furnace 1 to form the coke mixed ore layer 13 in the blast furnace, the raw material of the blast furnace is charged into the bellless blast furnace 1 while keeping the mixing ratio of the ore 3 and coke 2 substantially constant. can do.
Table 1 shows the results of measuring the ventilation resistance index and gas utilization rate of the blast furnace when coke and ore are charged into the bell-less blast furnace by the conventional method and when charged by the method of the present invention.

  When coke and ore were charged into the bell-less blast furnace by the conventional method, as shown in Table 1, the ventilation resistance index was 2.35, and the gas utilization rate was 47.9%. On the other hand, when coke and ore are charged into the bell-less blast furnace according to the method of the present invention, the airflow resistance index is 2.30 and the gas utilization rate is 48.5%, and the coke ratio and reducing material ratio are conventionally The value was lower than the method. From this, it was confirmed that the method of the present invention is effective for the stable operation of the blast furnace and can be used as an operation technique with a low reducing material ratio.

  In the embodiment of the present invention, the coke 2 is transferred to the lower bunker 6 with one of the plurality of raw material discharge ports 51 formed in the upper bunker 5 closed. The coke 2 may be transferred to the lower bunker 6 with at least one of them closed. Moreover, the number of the raw material discharge ports 51 is not limited to four, and may be two or three or more.

DESCRIPTION OF SYMBOLS 1 ... Bell-less blast furnace 2 ... Coke 3 ... Ore 4 ... Raw material charging device 5 ... Upper bunker 6 ... Lower bunker 7, 8 ... Raw material tank 9 ... Furnace top conveyor 10, 11 ... Swivel chute 12 ... Coke layer 13 ... Coke mixed ore Layer 51, 61 ... Raw material discharge port 52, 62 ... Gate

Claims (1)

An upper bunker and a lower bunker connected by a plurality of three or more ports are arranged at the top of the bell-less blast furnace, and the raw material in the upper bunker is opened and closed to the lower bunker via the ports. A blast furnace raw material charging method in which a blast furnace raw material transferred to the upper bunker is charged into a bell-less blast furnace through a turning chute from the lower bunker to alternately form a coke layer and a coke mixed ore,
A blast furnace after transferring the coke to the lower bunker with coke left on one or two of the plurality of ports when transferring the coke charged to the upper bunker to the lower bunker; To form a coke layer in the blast furnace,
Transfer coke and ore to the lower bunker with all of the ports open after putting ore into the upper bunker with coke left on one or two of the ports And then charging the blast furnace with a blast furnace raw material by forming a coke mixed ore layer in the blast furnace.

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