JP2010106333A - Method for charging raw material into bell-less blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for charging a raw material, which uniformizes a distribution of coke in a diametric direction in a coke-mixed ore layer and shows an adequate mixability of the coke after the raw material has been charged into a furnace, when charging ore mixed with the coke into a bell-less blast furnace having a center-feed type apparatus for charging the raw material. <P>SOLUTION: When charging the raw material by alternately depositing a coke layer and the coke-mixed ore layer 12, this charging method includes: controlling a grain size of the coke mixed in the coke-mixed ore layer 12 to 0.2 times or larger than the grain size of a lump coke in the coke layer and to less than 1.3 times of the grain size of an ore 1; completing an operation of discharging the coke onto a belt conveyor 4 which supplies the raw material toward an upper bunker 7 from a raw material tank 3, in the timing of 0.5 with respect to the whole period needed to discharge the ore 1 onto the belt conveyor 4 to charge the ore 1 and the coke 2 in the upper bunker 7; charging the raw material in the upper bunker 7 into a lower bunker 8; and charging the raw material discharged from the lower bunker 8 into the blast furnace 9 through a slewing chute 10 so as to form the coke-mixed ore layer 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a raw material charging method for a bell-less blast furnace having a center-feed type bell-less furnace top charging device in which raw material bunkers are arranged in two stages at the top of the furnace, and in particular, coke formed by mixing coke in an ore layer. The present invention relates to a charging method in which a mixed ore layer and a coke layer of coke alone are alternately deposited.

  In blast furnace operation, ore and coke are usually charged in layers from the top of the furnace alternately, and the layer thickness distribution or particle size distribution of the ore layer and coke layer in the furnace radial direction is controlled. Thus, the gas flow distribution in the furnace is controlled.

  In recent years, from the viewpoint of environmental problems, development of a technology that can reduce the amount of coke used in a blast furnace as much as possible has been demanded. There are two methods for reducing the amount of coke charged: a method of increasing the amount of ore charged per charge, or a method of decreasing the amount of coke charged per charge. In this case, when the former is carried out, the ore layer thickness is increased, so the reducibility of the ore is deteriorated and the furnace heat is lowered due to the direct reaction of the unreduced ore in the lower part of the furnace, thereby deteriorating the furnace condition. On the other hand, if the latter is carried out, the coke layer thickness forming the coke slit in the cohesive zone becomes thin, so that the air permeability at the lower part of the furnace is deteriorated.

  Therefore, conventionally, in order to alleviate these effects, a method has been developed in which coke is mixed in advance in the ore layer (ore coke mixing charging) to improve the reducibility of the ore layer itself. For example, Patent Document 1 and Patent Document 2 propose a method of stabilizing the furnace condition by improving the air permeability and liquid permeability in the furnace by adopting a charging method for forming a coke mixed ore layer. is doing. These technologies are methods of alternately charging coke and mixing ore and coke, and reducing the coke particle size in the coke mixed ore layer and adjusting the particle size of ore and coke. In addition, in order to eliminate the charging segregation in the furnace radial direction due to the density difference and the particle size difference between the ore and coke by mixing and charging the auxiliary materials, to form the assumed gas flow distribution, and This is a method for improving the molten state of the ore.

  However, the above-mentioned ore coke mixing technology, which mixes coke with a reduced coke particle size, reacts in the region from the start of the ore melting until the ore starts dripping (ie, softening cohesive zone). It is considered that the effect of reducing the coke charging amount, that is, the reduction of the coke ratio is small.

  Also, bellless charging equipment is widely used as the raw material charging equipment for the blast furnace, and the bellless charging equipment includes a “parallel bunker type” in which a furnace bunker (hopper) is installed in parallel, and a raw material bunker. There is a “center feed type” installed in the upper and lower two stages. In general, the center-feed type bell-less charging device is structurally simple compared to the parallel bunker type device, so the capital investment is low, and the cost for charging the charged material into the furnace is low. There is an advantage that the distribution in the circumferential direction is small and the distribution can be made almost uniformly.

  On the other hand, if a raw material charging device equipped with a two-stage bunker at the top and bottom like the center-feed type bell-less device, the furnace height tends to be high, and the height of the device will be diverted for reasons such as diverting existing equipment. Therefore, it is necessary to increase the diameter of the upper and lower bunker bunkers to ensure the internal volume. However, by increasing the diameter of the upper and lower two-stage bunker, when the raw material is received into the upper bunker or when the raw material is charged from the upper bunker to the lower bunker, it is mixed in the ore layer in each bunker. Coke segregation occurs. When the mixed coke finally segregated in the lower bunker is charged into the furnace using a swivel chute, the coke mixing ratio increases from the beginning to the middle of the charging, and the coke mixing ratio decreases at the end. The discharge coke mixing ratio distribution is as follows.

When raw materials with such a discharge mixing ratio distribution are sequentially inserted from the center side of the blast furnace to the furnace wall direction using a swirl chute, the mixing ratio is large at the center and mixed between the middle part and the furnace wall part. It will be deposited at a low rate. As a result, the radial distribution of coke in the coke mixed ore layer becomes non-uniform and cannot be effectively used as mixed coke.
JP-A-8-283804 JP-A-10-183210

  In general, in order to achieve stable operation of the blast furnace, it is effective to maintain good air permeability in the furnace, particularly in the softening and fusion zone. And in order to keep the air permeability of the softened cohesive zone good, basically, the amount of ore charged at one time is reduced, the layer thickness of the softened cohesive zone is reduced, and simultaneously with the ore. It is known that ore coke mixing charging to charge a part of coke is effective.

  Here, the former is not desirable because it increases the coke ratio. On the other hand, in the latter ore coke mixing charging, by controlling the distribution of coke mixed in the ore layer appropriately, coke suppresses the softening shrinkage of the ore layer, especially in the cohesive zone, and thus has high ventilation resistance. It is effective in stabilizing the furnace condition by allowing gas to enter the softened cohesive zone and improving air permeability.

  However, since the ore coke mixing charging technology described in Patent Documents 1 and 2 promotes melting of the ore, it is considered that coke in the coke mixed ore layer disappears while descending the furnace, It is thought that the air permeability improvement at the cohesive zone is insufficient.

  In addition, in ore coke mixing charging, the mixing ratio distribution in the furnace inner diameter direction becomes non-uniform due to the discharge mixing ratio characteristics from the top bunker, or ore and coke charged simultaneously by mixing charging are charged. There is a risk that the segregation phenomenon will occur after entering and the mixing rate distribution in the furnace inner diameter direction becomes non-uniform so that the gas flow distribution becomes unstable and the furnace condition deteriorates.

  The center feed type raw material charging apparatus has a characteristic that the mixing amount becomes large in the initial stage of discharging in the distribution of the mixing amount discharged from the top bunker. Therefore, for example, when charging sequentially from the central part toward the peripheral part, after entering the furnace interior, it will be deposited with a large mixing amount in the central part and a small mixing amount in the middle part to the furnace wall part. The radial distribution of coke in the coke mixed ore layer becomes non-uniform.

  It has been found that coke in the coke mixed ore layer can effectively suppress local deterioration of airflow and is effective in improving air permeability by controlling the coke in a uniformly dispersed state without causing segregation to specific sites. Yes.

  Further, since coke in the coke mixed ore layer is expected to improve the air permeability in the cohesive zone, it is necessary that the coke does not disappear even in the cohesive zone. Therefore, it is considered effective to increase the amount of mixed coke and to increase the particle size. However, when a large amount or large particle size of coke is mixed in the ore layer, segregation occurs due to the difference in particle size, and the mixing rate distribution tends to be uneven. I think that. Furthermore, since the amount of segregation increases with the mixing amount, there is a problem that a uniform mixing rate distribution cannot be formed.

  Therefore, the object of the present invention is to solve such problems of the prior art, and when performing ore coke mixing charging in a bellless blast furnace having a center feed type raw material charging apparatus, In consideration of the segregation phenomenon after charging, a raw material charging method for a bellless blast furnace in which the radial distribution of coke in the coke mixed ore layer becomes uniform after mixing the raw material inside the furnace and the mixing property is good is provided. It is in.

The features of the present invention for solving such problems are as follows.
(1) In a bell-less blast furnace having a center-feed type bell-less furnace top charging device in which an upper bunker and a lower bunker are arranged in two stages, a raw material is charged from the top of the furnace and a coke layer and a coke mixed ore layer are formed. When charging raw materials that are alternately deposited,
The particle size of the coke mixed in the coke mixed ore layer is 0.2 times or more with respect to the particle size of the massive coke charged as the coke layer, and is 1.3 with respect to the particle size of the ore. Less than
In order to form the coke mixed ore layer, the timing for discharging the coke from the raw material tank to the belt conveyor that supplies the raw material toward the upper bunker is set to 0.5% with respect to the total time for discharging the ore to the belt conveyor. And the ore and coke are charged into the upper bunker, the raw material in the upper bunker is charged into the lower bunker, and the raw material discharged from the lower bunker is placed in the blast furnace through a swivel chute. A method for charging raw materials into a bell-less blast furnace, characterized by charging.
(2) The raw material to the bell-less blast furnace according to (1), wherein the amount of coke mixed in the coke mixed ore layer is 10 mass% or more with respect to the total amount of coke charged from the top of the furnace. The charging method.

  According to the present invention, in the ore coke mixing charging of the bellless blast furnace having the center feed type raw material charging device, the mixing amount of the mixed coke is determined in advance in consideration of the discharge characteristics of the mixed coke in the coke mixing ore layer. By controlling over time, it is possible to control the distribution of discharged mixture from the top bunker and to control the radial distribution of the mixed coke in the coke mixed ore layer after entering the furnace interior. As a result, the mixing property is improved and the air permeability of the lower part of the furnace is improved, so that a more efficient operation of the blast furnace becomes possible.

  FIG. 1 is a schematic view showing an embodiment of a method for charging a raw material into a bell-less blast furnace according to the present invention. The arrows in FIG. 1 indicate the tilting direction of the turning chute. A method of charging a raw material for a coke mixed ore layer into a center-feed type bellless furnace top charging device in which an upper bunker and a lower bunker are arranged in two upper and lower stages will be described with reference to FIG.

  Ore and coke are individually stored in the raw material tank 3 (3a, 3b). First, the ore 1 is discharged from the raw material tank 3 a, and the feeding to the surge hopper 5 is started using the belt conveyor 4. At the same time, the coke 2 is discharged from the raw material tank 3b, and feeding to the surge hopper 5 is started. At this time, the discharge amount of the ore 1 from the raw material tank 3a reaches 50% of the single discharge amount. By the end of the coke 2 discharge. That is, the raw material conveyed by the belt conveyor 4 is in the state of ore 1 and coke 2 in the first half and only the ore 1 in the second half. For this purpose, the timing for discharging the coke may be completed within 0.5 with respect to the total time for discharging the ore to the belt conveyor 4. The raw materials conveyed by the belt conveyor 4 are sequentially charged into the surge hopper 5. Next, the raw material is discharged from the lower part of the surge hopper 5 and fed sequentially to the upper bunker 7 and the lower bunker 8 via the charging conveyor 6. At this time, the ore 1 and the coke 2 are stored in the lower bunker 8 in a state where the ore and the coke are mixed under the influence of the discharge behavior determined by the deposition state and segregation state in the bunkers 7 and 8. .

  When charging into the blast furnace 9 from the lower bunker 8, the raw material is discharged from the lower part of the lower bunker 8. In that case, in the operation of starting the discharge of ore and coke from the raw material tanks 3a and 3b at the same time and ending the discharge at the same time, the raw material charged into the blast furnace 9 has a large mixing ratio of coke at the initial discharge, The distribution of the mixing ratio of the coke in the latter part of the discharge tends to be small. However, by adjusting the timing of discharging the ore and coke from the raw material tank 3 as described above, by setting the particle size so that the particle size distribution of the raw material in the upper bunker 7 and the lower bunker 8 is optimized, The change in the mixing ratio discharged from the lower bunker 8 can be controlled uniformly. As a result, when the raw material for the coke mixed ore layer is charged into the blast furnace 9 through the turning chute 10, the radial distribution of the coke in the coke mixed ore layer becomes uniform.

  In the present invention, the method for controlling the timing at which coke discharge is terminated is not limited to a specific method. For example, after starting the discharge of ore and coke at the same time, the discharge of a predetermined amount of coke may be completed until the discharge of ore is completed, and it may be controlled using a timer or various sensors. Moreover, about the time which discharge | releases the coke 2 from the raw material tank 3b, the discharge of the ore 1 from the raw material tank 3a should just be completed by 50% of one discharge | emission amount, and before starting discharge of an ore There is no problem even if the coke discharge is started. Even when the discharge of the coke 2 is after the start of the discharge of the ore, it is sufficient that the discharge of the coke 2 is completed before the discharge of the ore 1 reaches 50% of the discharge amount of one time.

  In addition to mixing the ore 1 and coke 2 in the surge hopper 5 through the surge hopper 5 with the raw material discharged onto the belt conveyor 4 as described above, the raw material tank 3b is moved to the downstream side of the surge hopper 5 and the coke 2 is discharged on the ore 1 on the belt conveyor 6 before being charged into the upper bunker 7, and the ore and coke are first discharged to the upper bunker 7. After charging ore, the raw material in the upper bunker 7 is charged into the lower bunker 8, and the raw material discharged from the lower bunker 8 is charged into the blast furnace 9 via the swivel chute 10. Thus, the coke mixed ore layer 12 can be formed. In this case, the timing at which the coke 2 is discharged on the belt conveyor 6 immediately before supplying the raw material to the upper bunker 7 is adjusted, and the coke is discharged only on the front half of the transported ore 1 and then the upper part. Ore 1 and coke 2 will be charged into the bunker 7.

  As a result of conducting a discharge test from the lower bunker 8 in order to investigate the optimum particle size of the coke to be mixed, the coke particle size (mixed coke particle size) mixed in the coke mixed ore layer is determined with respect to the ore particle size. It was found that the discharge from the lower bunker becomes uniform when the ratio is 1.3 times or less. As the particle size, the average particle size of ore and mixed coke may be used.

  In addition, while descending the inside of the blast furnace, the particle size of the coke gradually decreases due to the gasification reaction. At this time, the coke mixed in the coke mixed ore layer is more affected by the gasification reaction due to the larger specific surface area difference if the particle size difference from the coke is large. It is conceivable that the particle size is significantly reduced and the mixed coke disappears before reaching the lower end of the cohesive zone, and the air permeability improvement effect is diminished. Therefore, the optimum particle size was examined by an electric furnace experiment simulating the temperature rise pattern and gas composition in the blast furnace until the ore melts down. The results are shown in FIG. From the result of FIG. 2, when the coke particle size (mixed coke particle size) mixed in the coke mixed ore layer is too small, the coke disappears, and the coke particle size is 0.2 times or more than the particle size of the lump coke. Thus, it was found that the disappearance of coke mixed in the coke mixed ore layer can be suppressed. As the particle diameter, the average particle diameter of the lump coke and mixed coke may be used.

  The amount of coke mixed in the coke mixed ore layer is preferably 10 mass% or more with respect to the total amount of coke charged from the top of the furnace. When segregation does not become a problem, it is preferable that the amount of mixed coke is large so that coke does not disappear even in the cohesive zone.

  If the raw material charging method of the present invention is used, the mixing ratio of coke in the coke mixed ore layer becomes uniform, so that the tilt of the swivel chute moves from the center of the blast furnace toward the furnace wall as shown in FIG. The present invention can be applied to both the case of reverse tilting and the case of forward tilting moving from the furnace wall side of the blast furnace toward the furnace center.

  Using the same equipment as the apparatus shown in FIG. 1, the discharge mixing ratio distribution when the raw material was charged into the blast furnace was measured. FIG. 3 shows the discharge coke mixing ratio distribution from the lower bunker when the conventional technique is used (comparative example). In the prior art, the discharge of ore and coke from the raw material tanks 3a and 3b is started at the same time, the discharge is simultaneously ended, and a predetermined amount of ore and coke necessary for one charging is discharged to the belt conveyor 4. The ore and coke were mixed while being conveyed by the belt conveyor 4, the surge hopper 5, and the charging conveyor 6, and charged into the upper bunker 7 in a mixed state. Moreover, as an example of the present invention, the discharge rate from the raw material tank 3b is adjusted, and the timing for discharging the coke from the raw material tank 3b is the same as the ore, but the ore discharge amount from the raw material tank 3a FIG. 4 shows the distribution ratio of the discharged coke from the lower bunker when all the discharge of coke is completed when the amount is 25% of the amount required for one charge. Compared with the case of FIG. 3 of the comparative example, in FIG. 4 of the example of the present invention, it can be seen that the mixing ratio of coke to the blast furnace is substantially uniform over the entire discharge.

  Next, using the charging method of the comparative example and the example of the present invention, the operation of the blast furnace was carried out by ore coke mixing charging in which coke single charging and ore and coke mixing charging were alternately performed. Table 1 shows the measurement results of operating conditions, ventilation resistance index, gas utilization rate, and the like.

  After applying the raw material charging method of the present invention, the gas flow distribution was stabilized by homogenizing the radial distribution of coke in the coke mixed ore layer charged in the blast furnace. The index decreased and the gas utilization rate improved, and the ratio of reducing materials decreased. As a result, it was confirmed that the method of the present invention is effective as a stable operation technique for a blast furnace, and can also be used as an operation technique with a low reducing material ratio.

Schematic which shows one Embodiment of this invention. The graph which shows the relationship between the lump coke particle size ratio investigated by the electric furnace experiment, and the coke particle size ratio after reaction. The graph which shows the discharge coke mixing rate distribution from a lower bunker at the time of using a prior art. The graph which shows the discharge coke mixing rate distribution from a lower bunker at the time of using this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ore 2 Coke 3 (3a, 3b) Raw material tank 4 Belt conveyor 5 Surge hopper 6 Loading conveyor 7 Upper bunker 8 Lower bunker 9 Blast furnace 10 Swivel chute 11 Mixture of ore and coke 12 Coke mixed ore layer

Claims (2)

In a bell-less blast furnace with a center-feed type bell-less furnace top charging device in which an upper bunker and a lower bunker are arranged in two upper and lower stages, raw materials are charged from the top of the furnace and coke layers and coke mixed ore layers are alternately deposited. When performing raw material charging,
The particle size of the coke mixed in the coke mixed ore layer is 0.2 times or more with respect to the particle size of the massive coke charged as the coke layer, and is 1.3 with respect to the particle size of the ore. Less than
In order to form the coke mixed ore layer, the timing for discharging the coke from the raw material tank to the belt conveyor that supplies the raw material toward the upper bunker is set to 0.5% with respect to the total time for discharging the ore to the belt conveyor. And the ore and coke are charged into the upper bunker, the raw material in the upper bunker is charged into the lower bunker, and the raw material discharged from the lower bunker is placed in the blast furnace through a swivel chute. A method for charging raw materials into a bell-less blast furnace, characterized by charging.   The method for charging a raw material into a bell-less blast furnace according to claim 1, wherein the amount of coke mixed in the coke mixed ore layer is 10 mass% or more with respect to the total amount of coke charged from the top of the furnace. .

Images