JP5440077B2 - Raw material charging method for bell-less blast furnace - Google Patents

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. 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, the ore coke mixing charging technique described in Patent Documents 1 and 2 is considered to cause coke to disappear because the coke has a small particle size and further promotes melting of the ore. Insufficient breathability improvement in

  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, a segregation phenomenon due to a particle size difference occurs, and therefore the mixing rate distribution tends to be non-uniform. 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 coke mixed in the coke mixed ore layer is 1.3 times or more the particle size of the ore,
In order to form the coke mixed ore layer, ore is charged into the upper bunker, and then the ore and coke are charged, and then the raw material in the upper bunker is charged into the lower bunker, A raw material charging method for a bell-less blast furnace, wherein the raw material discharged from a lower bunker is charged into a blast furnace through a turning chute.
(2) The timing of 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 or later with respect to the total time of discharging the ore to the belt conveyor, The raw material charging method to the bell-less blast furnace as described in (1).
(3) The bellless according to (1) or (2), 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. Raw material charging method to blast furnace.

  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.

Schematic which shows one Embodiment of this invention. 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. The graph which shows the relationship between the furnace top bunker discharge ratio and furnace top bunker discharge mass ratio of each raw material tank discharge part.

  In the present invention, the coke in the coke mixed ore layer formed by mixing ore and coke does not disappear even in the cohesive zone, so that the air permeability in the cohesive zone is improved. A large coke having a particle size of 1.3 times or more the particle size of the ore is used. As the particle size, the average particle size of ore and coke may be used.

  However, when coke having a particle size larger than that of the ore is mixed and used as described above, a segregation phenomenon occurs, so that the mixing rate distribution tends to be non-uniform. In the present invention, when charging the raw material for the coke mixed ore layer into the center feed type bellless furnace top charging device in which the upper bunker and the lower bunker are arranged in two upper and lower stages, the ore is first charged, By charging ore and coke, the radial distribution of the mixed coke in the coke mixed ore layer after entering the furnace interior can be controlled. For this purpose, the ore is first discharged from the ore raw material tank to the belt conveyor that supplies the raw material from the raw material tank to the upper bunker, and the coke is discharged from the coke raw material tank after a predetermined time has elapsed after starting the ore discharge. To do. Then, the raw material on the belt conveyor is supplied to 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 charged into the blast furnace through the turning chute. The turning chute usually charges the raw material into the blast furnace while turning the turning chute while tilting. The raw material transported on the belt conveyor is normally supplied to the upper bunker via a surge hopper in the middle, and the raw materials are mixed appropriately, but the raw material first charged in the upper bunker The raw material for the coke mixed ore layer may be charged into the upper bunker so that the state becomes only the ore. When there is no surge hopper, the raw material is charged directly into the upper bunker from the belt conveyor, but the raw material may be charged in the same manner as described above. When using the center-feed type bellless furnace top charging equipment arranged in two stages in this way, if the ore is first charged into the upper bunker to form a coke mixed ore layer, It is possible to adjust the change with time of the coke mixing ratio in the raw material discharged into the factory.

  To discharge the ore to the belt conveyor that supplies the raw material from the raw material tank to the upper bunker, control the timing of discharging the raw material from the raw material tank to the belt conveyor that supplies the raw material from the raw material tank to the upper bunker. Can be used. In actual operation, if the timing of discharging the coke from the coke raw material tank to the belt conveyor is 0.5 or later with respect to the total time of discharging the ore from the ore raw material tank to the belt conveyor, the ore is first put in the upper bunker. Can only be charged.

  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. This is because when the segregation does not become a problem, the coke does not disappear even in the cohesive zone, so that the blended amount of the mixed coke is preferably large.

  FIG. 1 is a schematic view showing an embodiment of the raw material charging method of the present invention. The arrows in FIG. 1 indicate the tilting direction of the turning chute. The ore 1 and the coke 2 are individually stored in the raw material tank 3 (3a, 3b).

  First, only the ore 1 is discharged from the raw material tank 3 a, and feeding to the surge hopper 5 is started using the belt conveyor 4. Thereafter, for example, when the discharge amount of the ore 1 from the raw material tank 3a becomes 50% or more of the single discharge amount, the coke 2 is discharged from the raw material tank 3b and the feeding to the surge hopper 5 is started. . The coke 2 can be discharged from the raw material tank 3b when the discharge of the ore 1 from the raw material tank 3a is almost completed. FIG. 1 shows a case where the discharge of coke is started after the entire amount of ore is discharged. Regardless of the timing at which the discharge of the coke 2 is started, it is only necessary that the leading portion of the raw material fed to the surge hopper 5 is only ore. 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. Here, the ore stored at the bottom of the surge hopper 5 is discharged first, and then the ore and coke mixture 11 is discharged. In addition, since the raw material is not stored in the upper bunker 7 and the lower bunker 8, the ore is basically stored at the bottom in the upper bunker 7 and the lower bunker 8, but the amount thereof is reduced. The remaining ore is stored as a mixture of ore and coke by the transit process or segregation in the bunker.

  When charging from the lower bunker 8 into the blast furnace 9, the raw material is discharged from the lower part of the lower bunker 8. That is, the ore stored at the bottom of the lower bunker 8 is discharged first, and thereafter, the charging is mixed. As a result, the emission mixture ratio distribution is such that the mixing ratio is low at the beginning of discharge, the mixing ratio is high at the middle stage of discharging, and the mixing ratio is low at the end of discharging. When the raw material is charged into the blast furnace 9 through the swirl chute 10 with such a discharge mixing ratio distribution, a segregation phenomenon occurs on the deposited surface after the charging, that is, the mixed coke charged in the middle discharge period. When a part flows into the central portion, the coke radial distribution in the coke mixed ore layer 12 becomes uniform.

  In the present invention, the method for controlling the timing of starting the discharge of the coke 2 from the raw material tank 3b is not limited to a specific method. The coke 2 may be discharged after the ore 1 has been discharged from the raw material tank 3a by a predetermined amount, and may be controlled using a timer or various sensors. Further, regarding the timing of discharging the coke 2 from the raw material tank 3b, it is preferable that the discharge of the ore 1 is preferably completed by 50% or more, and there is no problem even if the discharge of the coke is started after the discharge of the ore is completed. . That is, if the upper bunker 7 is initially charged with only ore and subsequently the mixture of ore and coke is charged, the effect of the present invention can be obtained.

The reason why it is preferable to discharge the coke 2 from the raw material tank 3b when the discharge of the ore 1 is 50% or more is as follows. Divide the discharge timing of the raw material discharged from the raw material tank into the following four areas (I to IV), and how much is discharged according to the discharge timing from the top bunker (lower bunker) FIG. 4 shows the results of measurement in each region.
Area I: Raw material discharged at a time of 0 to 25% of the total discharge time of the raw material tank II: Raw material area III discharged at a time of 25 to 50% of the entire discharge time of the raw material tank : Raw material area discharged at a time of 50 to 75% of the whole discharge time of the raw material tank IV: Raw material discharged at a time of 75 to 100% of the whole discharge time of the raw material tank

  In FIG. 4, each point on the graph represents measurement data in the case of a raw material at a raw material tank discharge time of 25%, a raw material at a raw material tank discharge time of 50%, and a raw material at a raw material tank discharge time of 75%. Further, the horizontal axis represents the furnace top bunker discharge mass ratio (discharge time from the furnace top bunker), and the vertical axis represents the discharge ratio from the furnace top bunker at each discharge time from the raw material tank. According to FIG. 4, in the initial stage of discharge near the furnace top bunker discharge mass ratio of 0, region I (raw material tank discharge time 0-25% raw material) and region II (raw material tank discharge time 25-50% raw material) are large. Since it is a part, what is first discharged from the top bunker is considered to be mainly composed of the one discharged from the raw material tank at less than 50%. Therefore, in order to reduce the coke mixing ratio when being discharged from the top of the furnace bunker, it is preferable to discharge the coke 2 from the raw material tank 3b when the ore discharge from the raw material tank has been completed by 50% or more. It will be.

  When the coke mixed ore layer is formed as a reverse tilt moving from the center of the blast furnace toward the furnace wall, the swirling chute is tilted, and the raw material with a low coke mixing ratio is charged near the center of the blast furnace as described above. The mixing ratio of coke is averaged by rolling of coarse coke charged in the center portion in the furnace radial direction. Even when the tilt of the swivel chute is a forward tilt that moves from the furnace wall direction to the center of the blast furnace, after rolling the coarse coke charged in the center of the furnace radial direction to the vicinity of the furnace center, A raw material with a low coke mixing ratio is charged, and the coke mixing ratio is averaged. Considering the stability of the deposited shape after charging, it is preferable to use reverse tilting.

  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. 2 shows the distribution ratio of the mixed coke discharged from the lower bunker when using the prior art (comparative example). In the prior art, the ore and coke are simultaneously discharged from the raw material tanks 3a and 3b, and the ore and coke are mixed while being conveyed by the belt conveyor 4, the surge hopper 5, and the charging conveyor 6, and the upper bunker is mixed. 7 was charged. In addition, as Example 1 of the present invention, FIG. 3 shows the discharge coke mixing ratio distribution from the lower bunker when the time for discharging the coke from the raw material tank 3b is performed after all the discharge of ore from the raw material tank 3a is completed. . Compared with the case of FIG. 2 of the comparative example, it can be seen that the mixing ratio of coke at the initial stage of charging into the blast furnace is lowered in FIG.

  Next, using the charging method of Comparative Example and Invention Example 1, the operation of the blast furnace was performed by ore coke mixing charging in which coke single charging and ore and coke mixing charging were alternately performed. Further, as Example 2 of the present invention, the coke discharge from the raw material tank 3b is started by using a charging method in which the discharge of ore from the raw material tank 3a is completed by 50%. The blast furnace was operated by mixing ore coke mixing with alternating mixing of coke and coke. 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.

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 coke mixed in the coke mixed ore layer is 1.3 times or more the particle size of the ore,
In order to form the coke mixed ore layer , the ore is discharged from a raw material tank to a belt conveyor that supplies the raw material toward the upper bunker, and then the coke is discharged to load the ore into the upper bunker. and, after charged with ore and coke was subsequently charged with raw materials in said upper bunker in said lower bunker, you charged into the blast furnace via the swivel chute raw material discharged from the bunker lower portion a raw material charging method to the base Ruresu blast furnace,
A method of charging a raw material into a bell-less blast furnace, characterized in that the timing of discharging the coke to the belt conveyor is 0.5 or more with respect to the total time of discharging the ore to the belt conveyor . 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. .

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