JP2006089773A - Method for charging raw material into blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish a method for charging a raw material into a blast furnace, which secures a stable central flow operation even when having employed an ore blended with a pellet as ore to be charged, and can continue an operation of a low coke ratio and/or a high tapping ratio while maintaining a stable furnace condition. <P>SOLUTION: This charging method comprises the steps of: charging coke by using a chute 2 for charging coke only into an axial core part, so that the ratio of the coke can be increased in the axial core part, and simultaneously by using a bell type charging device 3 so that a coke layer C2 can form a heap having a peak P at a position closer to the axial core part than a furnace wall; and then charging the ore onto the coke layer C2 at two divisional times, wherein the ratio of the pellet blended in ore O1 to be charged at first is controlled so as to be lower than the average ratio of the pellet blended in the whole ore. Thereby, it is inhibited that one part of the coke layer C2 is carried away to the axial core side by the charged ore, and the pellet consequently intrudes into a coke-packed part CP formed around the axial core part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a raw material charging technique that can contribute to the stabilization and efficiency of blast furnace operation, and more particularly, to an improvement in a coke shaft core charging (or coke center charging) technique developed by the present applicant.

  The present applicant has established a coke shaft core charging technique for improving so-called stabilization or reliability of the central flow operation in order to realize stabilization and efficiency improvement of the blast furnace operation (see, for example, Patent Document 1). An improved technology that can reliably demonstrate the effect of the coke shaft charging operation under the coke ratio operation has been completed (see Patent Document 2).

  The invention described in Patent Document 2 described above includes: “coke shaft core charging means for intensively charging coke into the shaft core portion of the blast furnace; and peripheral charging means for charging coke and ore to the peripheral edge side of the blast furnace. In the method for charging coke and ore into the blast furnace provided, the coke ratio of the blast furnace shaft core portion is increased by the coke shaft core charging means, and 0.02R-0 from the furnace wall by the peripheral charging means. .6R (where R is the radius of the blast furnace), the ore charging position at least in the initial stage of the ore charging is set to the peripheral edge of the coke layer charged in a mountain shape so as to have a peak height. By setting to the centrifugal side with respect to the peak position by the charging means, the high ground portion including at least the summit portion of the mountain-shaped charging coke layer is destroyed, and is configured to be pushed to the blast furnace shaft core portion side. Special Raw material charging method to the blast furnace to be. ", Which is a.

  According to the present invention, the O / C of the shaft core portion is lowered and the O / C of the furnace wall portion is raised, and the O / C is smoothed in the middle portion thereof, and the change is gentle. Since the O / C does not suddenly increase or decrease, the rising gas in the furnace concentrates on the shaft core, and stable central flow operation can be continued. Operations began to take place.

  However, when an ore containing a large amount of pellets is used as the charging ore, the ore collapses the high altitude part including at least the summit of the mountain-shaped charging coke layer and flows to the blast furnace shaft core side, and the blast furnace shaft core part When forming a coke filling part around, it turned out that a pellet mixes in a coke filling part and the porosity of a coke filling part falls (after-mentioned). For this reason, if an ore containing a large amount of pellets is used as the charging ore, and if the coke ratio is further reduced or the feed ratio is increased from the current level, the ventilation resistance around the shaft core portion is increased and stable. As a result, there is a possibility that the central flow operation cannot be maintained, and there is room for improvement.

  In addition, in order to improve the air permeability of the blast furnace when the pellet mixing ratio is high, as a method not using the coke shaft core charging technique, “Ore containing pellets is divided into several times and charged near the furnace wall. In the blast furnace operation method, the ore mainly composed of pellets is charged as the first ore dump after the coke dump, and the ore mainly composed of sintered ore and / or lump as the subsequent other ore dumps. ”Is disclosed (refer to Patent Document 3).

  In this method, as the first ore dump after the coke dump, the ore mainly composed of pellets is charged, so that the coke layer is destroyed and the inclination angle becomes small, and the dumped pellets directly above the coke layer are mainly used. Therefore, the ore layer formed by the subsequent ore dump is formed in a state of being deposited on the furnace wall, and the thickness of the ore layer in the center is thin. Therefore, the central flow operation is possible, and the air permeability of the blast furnace is improved when the pellet mixing ratio is high (see the second column, right column, lines 1 to 17 of Patent Document 3).

However, even in this method, as the first ore dump after the coke dump, when the ore mainly composed of pellets is charged, the coke layer is destroyed and flows into the furnace center together with a small amount of pellets. Since a mixed layer of pellets and coke having a low porosity is formed over the region (see Patent Document 3, page 2, right column, lines 4 to 6), in operation with a low coke ratio and / or a high output ratio, There is a high possibility that the airflow resistance in the middle to the central region will increase and stable central flow operation cannot be maintained.
JP-A-64-65207 Japanese Examined Patent Publication No. 6-27283 Japanese Patent Publication No. 61-12967

  Therefore, the present invention can ensure stable central flow operation even when using ore containing pellets as charging ore, and maintain low coke ratio and / or high coke ratio operation while maintaining stable furnace conditions. The purpose is to establish a method for charging raw materials into a blast furnace.

  In the conventional blast furnace core operation using the raw material charging method described in Patent Document 2, in order to grasp the state of mixing of the pellets into the above-mentioned coke packed bed, the present inventors have changed the raw material deposition layer from the top of the blast furnace furnace. Sampling was performed.

  Specifically, as shown in the longitudinal sectional view explaining the raw material charging situation at the top of the blast furnace furnace in FIG. 1, in accordance with the raw material charging method described in Patent Document 2, C1 ↓ C2 ↓ CCC1 ↓ O1 ↓ A sample deposition layer was sampled from the raw material deposition layer charged with CCC2 ↓ O2 ↓ as one cycle using the sampling jig and sampling method described in Japanese Patent No. 3358955. Here, C1 ↓ and C2 ↓ are coke charging to the peripheral part, CCC1 ↓ and CCC2 ↓ are coke charging to the shaft core part (here, CCC is an abbreviation of Center-Charged Coke), O1 ↓ and O2 ↓ Indicates ore charging, and O1 ↓ and O2 ↓ have the same pellet blending ratio.

  The sampling position of the sample deposit layer in the blast furnace radial direction is 0.5 R (where R is the blast furnace radius) from the furnace wall, and the ore layer O1 and the coke layer C2 are sampled together after the ore charging O1 ↓. A sample deposition layer was obtained. Here, a symbol without ↓ (for example, O1) means a deposited layer formed by raw material charging (for example, O1 ↓), and so on.

  FIG. 2A shows the stacked state of the sample deposition layers collected. From the figure, it is clear that a mixed layer M of coke and ore exists between the ore layer O1 and the coke layer C2.

  On the longitudinal cross-sectional photograph of this sample deposition layer, it is discriminated whether it is coke, pellets, ore other than pellets (sintered or massive ore) or voids, and after marking each separately, sample deposition The entire longitudinal section of the layer is divided into 10 sections along a straight line parallel to the stock line (upper surface of the ore layer O1), and the area ratio of each material and void is measured for each section by image analysis. The ratio and porosity were determined.

  FIG. 2B shows changes in the ore ratio in the total raw material, the pellet concentration in the ore, and the porosity in the height direction of the sample deposition layer. In the figure, the height of the sample deposition layer is indicated by a dimensionless height H which is dimensionless with respect to the total height h of the sample deposition layer, and the position where H = 0 is the lower surface of the coke layer C2. The position of H = 1.0 corresponds to the upper surface of the ore layer O1.

  And from the change of the ore ratio in all the raw materials in the height direction, the range of H = 0 to about 0.5 is the coke layer C2, and the range of H = about 0.5 to about 0.8 is the mixed layer M, H. = A range of about 0.8 to 1.0 is determined as the ore layer O1.

  From the figure, the pellet concentration in the ore maintains a value close to 30% by mass, which is the pellet content in the ore, in the ore layer O1 (H> 0.8), but enters the mixed layer M. And once in the vicinity of the boundary (H = 0.8 to 0.7), and further down, beyond the mixed layer M and into the coke layer C2 (H = 0.7 to 0.3) You can see that it is rising rapidly. Moreover, it can be clearly seen that the porosity of the mixed layer M is significantly lower than that of the ore layer O1 and the coke layer C2.

  It can be explained that such a phenomenon is caused by a physical property peculiar to pellets different from other ores. That is, since the pellets are spherical and have a high apparent density, only the pellets are likely to be selectively separated from the charged ore O1 when the ore O1 ↓ is put on the coke layer C2. Then, the separated pellets fall deeply into the large voids of the coke layer C2 composed of coke having a larger particle size than the ore (submerge), thereby selectively mixing the pellets into the coke layer C2. Is considered to occur.

  Based on the above knowledge, we believe that the above problem can be solved by reducing the amount of pellets in the ore charged directly above the coke layer so that the pellets are not mixed into the coke layer as much as possible. It came to be completed.

  The present invention relates to a coke into a blast furnace provided with coke shaft core charging means for intensively charging coke into the shaft core part of the blast furnace and peripheral charging means for charging coke and ore to the peripheral edge side of the blast furnace. In addition, when charging the ore containing the pellets, the coke ratio of the blast furnace shaft core is increased by the coke shaft core charging means, and 0.02R to 0.6R from the furnace wall by the peripheral charging means. The coke layer is charged in a mountain shape so that it has a peak height at the position (where R is the blast furnace radius), and then the ore is divided into multiple times on the coke layer and charged by the peripheral charging means. However, by setting the pellet blending ratio in the ore of the first charging among the plurality of ore chargings lower than the average pellet blending ratio in the entire charging ore, Part of the layer is a blast furnace shaft Is pushed to the parts side pellets coke packed portion formed around the blast furnace axis unit is summarized in that it made be configured to prevent the contamination.

  In the above, it is more desirable that at least the input position of the ore for the initial charge is set on the centrifugal side with respect to the peak position of the coke layer.

  According to the present invention, the mixing ratio of the pellets in the coke packed portion (at least the first charging ore on the coke layer is made lower than the average mixing ratio of the pellets in the total charging ore ( (Snipping) can be suppressed, the air permeability of the blast furnace core to the middle can be kept high, and stable central flow operation can be continued. For this reason, the furnace condition is stabilized, low coke ratio and / or high output ratio operation is achieved, and economical blast furnace operation can be realized.

Embodiment
Hereinafter, the present invention will be described in more detail with reference to the longitudinal sectional view for explaining the raw material charging state at the top of the blast furnace furnace of FIG. In the following description, only the bell charging type blast furnace will be described, but the present invention is not limited to this, and can naturally be applied to a bellless charging type blast furnace.

  As shown in FIG. 1, the blast furnace 1 according to the present embodiment includes a shaft core portion dedicated chute 2 as coke shaft core charging means for intensively charging coke into the shaft core portion of the blast furnace, coke and ore. Is provided with a bell type charging device 3 composed of a combination of a bell 3a and an armor plate 3b as peripheral charging means for charging the blast furnace to the peripheral edge side of the blast furnace.

  First, the coke layer is formed by dividing the coke charging into two times of C1 ↓ C2 ↓ using the bell system charging device 3 (a combination of the bell 3a and the armor plate 3b). Specifically, for example, after operating the armor plate 3b to form a coke layer thickness as a base by charging a coke layer in a mountain shape so as to have a peak height near the furnace wall at C1 ↓, The setting of the plate 3b is changed, and in C2 ↓, the coke layer is charged in a mountain shape so as to have a peak height at a position P closer to the blast furnace axis than C1 ↓.

  The peak position P of C2 ↓ is recommended to be 0.02R to 0.6R (where R is the blast furnace radius) from the furnace wall. When it is smaller than 0.02R, the coke layer on the furnace wall side becomes relatively thick. As a result, the ore layer on the furnace wall side becomes relatively thin and a part of the rising gas flow drifts to the furnace wall side, resulting in a large amount of heat dissipation. This is because when it is larger than 0.6R, the coke in the high altitude portion is broken to form a coke filling portion, and the effect of making the layer thickness of the coke layer as uniform as possible is not sufficiently exhibited (Patent Document 2). (Refer to the third line from the bottom of the left column on page 3 to the eighth line from the top of the right column).

  Next, the ore layer is formed. The ore layer is formed by dividing the ore charging into a plurality of times, for example, two times of O1 ↓ O2 ↓. Specifically, after the coke layers C1 and C2 are formed, the shaft core portion dedicated chute 2 and the bell system charging device 3 are alternately used to charge the shaft core portion with the coke charging CCC1 ↓, The charging is performed in the order of ore charging O1 ↓ to the peripheral portion, coke charging CCC2 ↓ to the shaft core portion, and ore charging O2 ↓ to the peripheral portion. Thus, by performing ore charging to the peripheral portion after the coke charging to the shaft core portion, the shaft core charging coke CCC1, CCC2 is not divided by the ore layer, and the coke layer C1, C2 and the shaft core portion charging coke CCC1, CCC2 are continuous, and a complete coke column can be formed in the shaft core portion.

  In the above ore charging, among the charging ores divided multiple times (in this example, twice), the pellet mixing ratio in the first charging ore O1 is based on the average pellet mixing ratio in all charging ores (O1 + O2). Also keep it low.

  By charging the ore on the mountain-shaped coke layer C2, a part of the mountain-shaped coke layer C2 is washed away to the blast furnace shaft core portion, and is deposited around the blast furnace shaft core portion to form a coke filling portion CP. The At this time, the pellet mixing ratio in the first charging ore O1 is set lower than the average pellet mixing ratio in the total charging ore (O1 + O2) (that is, the sintered ore or ingot ore in the first charging ore O1). Unlike the spherical pellets, the sinter or block ore having an angular shape preferentially cross-links to the entrance of the cavity of the coke filling part CP and closes the cavity. Therefore, coupled with the effect of reducing the number of pellets originally present in O1, the probability that the pellets fall into the voids of the coke filling portion CP is reduced, and mixing of the pellets into the coke filling portion CP is effectively suppressed. It will be. In order to surely obtain the effect of suppressing mixing of pellets, the pellet mixing ratio in O1 is preferably 70% or less of the average pellet mixing ratio in all charged ores (O1 + O2), and 40% or less. Is more preferable.

  In the first ore charging O1 ↓, it is more desirable to adjust the armor plate 3b and set the input position of O1 ↓ to the centrifugal side rather than the peak position P of the coke layer C2.

  As a result, the high altitude portion including at least the summit portion of the mountain-shaped coke layer C2 can be destroyed, and a larger amount of coke can be swept away to the blast furnace shaft core portion side. Therefore, the coke filling portion CP around the blast furnace shaft core portion Formation can be performed more reliably. In addition, what is necessary is just to adjust the specific injection | throwing-in position of O1 ↓ suitably in consideration of the charging amount (namely, division | segmentation number of ore charging) of O1 ↓, a pellet compounding rate, etc.

[Modification]
In the above embodiment, the bell type charging device comprising a combination of a bell and an armor plate is exemplified as the peripheral portion charging means, and the shaft core portion dedicated chute is exemplified as the coke shaft core charging means. In the blast furnace having the charging device, a turning chute may be used to serve as the peripheral portion charging means and the coke shaft core charging means.

  Moreover, although the example which divided | segmented ore charging into 2 times was shown in the said embodiment, you may divide into 3 or more times. However, as the number of divisions increases, the charging sequence becomes complicated and troubles are likely to occur, so about twice is recommended.

  In the above embodiment, the example in which the ore charging is divided into two times and the pellet mixing ratio in the first charging ore is set lower than the average pellet mixing ratio in the entire charging ore is shown. When the input is divided into three or more times, for example, when the input is divided into three times, the average pellets in the total charged ore is the pellet content in at least the first charge ore (first time only or first time + second time). You may make it lower than a mixture rate.

  In the above embodiment, the ore charge is divided into two times, and the input position of the initial charge ore is set to the centrifugal side from the peak position of the coke layer formed immediately before. When the input is divided into three or more times, for example, when divided into three times, at least the first charging ore (first time only, or first time + second time) the input position of the peak of the coke layer formed immediately before You may make it set to the centrifugal side rather than a position.

  Moreover, in the said embodiment, although the ore charge was divided into 2 times and the pellet mixing rate of the initial charging was shown lower than the average pellet mixing rate in all the charging ores, the ore charging was 3 Divide the number of times into at least the first ore charge (for example, only the first ore charge, the first + second ore charge), and the pellet content is lower than the average pellet content in all ores. May be.

  In the above embodiment, the ore charging is divided into two times, and the pellet mixing ratio in the first charging ore is set lower than the average pellet mixing ratio in the entire charging ore, and the initial charging ore is charged. Although the example in which the position is set to the centrifugal side from the peak position of the coke layer formed immediately before is shown, when ore charging is divided into three times or more, for example, when divided into three times, at least the first time The pellet content in the charged ore (first time only, or first time + second time) is set lower than the average pellet content in all the charged ores, and at least the first time ore (first time only, or first time + first time) You may make it set the injection | throwing-in position of 2 times to the centrifuge side rather than the peak position of the coke layer formed immediately before.

  Moreover, although the example which divided | segmented the coke charging into 2 times was shown in the said embodiment, you may charge in 1 time or may be divided into 3 times or more. However, if the charging is performed once, the thickness of the coke layer is likely to be uneven, and if the number of divisions is increased, the charging sequence becomes complicated and troubles are likely to occur as in the above ore charging. The degree is recommended.

In order to confirm the effect of the present invention, the shaft core charging shown in FIG. 1 is performed in a blast furnace having an internal volume of 4500 m ³ , a coke ratio of 340 kg / thm, and a pulverized coal injection ratio of 170 kg / thm. The conventional operation in which the pellet mixing ratios of O1 ↓ and O2 ↓ are equal is carried out as a comparative example, and then the pellet mixing ratio of O1 ↓ is sequentially maintained while maintaining the average pellet mixing ratio in all the charged ores (O1 + O2). The reduced operation was carried out as an example of the present invention. In addition, the pellet mixture rate in all the charging ores (O1 + O2) was 30 mass%, the sintered ore mixture rate was 45 mass%, and the lump ore mixture rate was 25 mass%.

  3 and 4 show the operation results.

FIG. 3 shows the relationship between the ratio IP _O1 of the pellet blending ratio in _O1 with respect to the average pellet blending ratio in all the charged ores (O1 + O2) and the gas utilization ratio η _CO . The plot of IP _O1 = 100% corresponds to the conventional example, and the plots of IP _O1 = 67% and 38% correspond to the example of the present invention. As is apparent from the figure, the gas utilization rate η _CO increases as IP _O1 is reduced (decrease in the pellet content in O1), and by the application of the method of the present invention, pellets are mixed into the coke packed portion. As a result, the central flow is secured and the gas flow in the furnace is improved. As a result, it can be assumed that the gas utilization rate has increased.

FIG. 4 shows a comparison of the daily solution loss / carbon fluctuation amount σ _SLC in the comparative example and the example of the present invention (IP _O1 = 67%). Here, intraday solution loss / carbon fluctuation amount σ _SLC indicates the degree of fluctuation of solution loss / carbon amount over time, and one day (24 points) of time average data of solution loss / carbon amount. This is the standard deviation obtained from the data. From the figure, σ _SLC decreased by approximately 12% from 4.1 kg / thm to 3.6 kg / thm by applying the method of the present invention, indicating that the operation was further stabilized by improving the gas flow in the furnace. ing.

Next, in order to understand the situation inside the blast furnace during the blast furnace operation, a simulation calculation was performed in consideration of heat transfer and gas flow in the furnace. As a target of the simulation calculation, the comparative example shown in FIG. 4 and the example of the present invention (IP _O1 = 67%) were selected.

FIG. 5 shows a comparison between the in-furnace temperature distribution and the total blast furnace pressure loss (= tuyere pressure-furnace top pressure) in the comparative example and the present invention example (IP _O1 = 67%). In the figure, the black-painted portion indicates a softened cohesive zone. Compared to the comparative example of (a), the present invention example of (b) has a thinner softened cohesive zone near the shaft core part, and the total pressure loss of the blast furnace from 187.4 kPa to 182.6 kPa is about 2. It was confirmed that the gas permeability in the furnace was improved and the gas flow in the furnace was improved by the present invention.

It is a longitudinal cross-sectional view explaining the raw material charging condition in a blast furnace top part. (A) is a longitudinal cross-sectional view showing the stacked state of the sample deposit layer, (b) is a graph showing the change in the ore ratio in the total raw material, the pellet concentration in the ore, and the porosity in the height direction of the sample deposit layer. It is. The proportion IP _O1 pellet blending ratio of O1 in respect to the average pellet blending ratio of the total charge in the ore is a graph showing the relationship between gas utilization ratio eta _CO. It is a graph which compares and shows _intraday solution loss and carbon fluctuation amount (sigma) _SLC in a comparative example and the example of this invention. It is a graph which compares and shows the furnace temperature distribution and blast furnace total pressure loss in a comparative example and the example of this invention.

Explanation of symbols

1: Blast furnace 2: Coke shaft core charging means (shaft for exclusive use of shaft core portion charging)
3: Peripheral charging means (bell type charging device)
3a: Bell 3b: Armor plate O1 ↓, O2 ↓: Ore charging C1 ↓, C2 ↓: Coke charging CCC1 ↓, CCC2 ↓: Coke charging O1, O2 to shaft core O1, O2: Ore layer C1 , C2: Coke layers CCC1, CCC2: Shaft core charging coke CP: Coke filling portion P: Peak position of coke layer C2

Claims (2)

Coke and pellets into a blast furnace comprising coke shaft core charging means for intensively charging coke into the shaft core part of the blast furnace and peripheral charging means for charging coke and ore to the peripheral edge side of the blast furnace. In charging ore containing
While increasing the coke ratio of the blast furnace shaft core portion by the coke shaft core charging means, the peripheral height charging means increases the peak height at a position of 0.02R to 0.6R (where R is the blast furnace radius). The coke layer is charged in a mountain shape so that the ore is divided into a plurality of times and charged by the peripheral charging means on the coke layer. By making the pellet mixing ratio in the charged ore lower than the average pellet mixing ratio in the entire charged ore, a part of the mountain-shaped charging coke layer is pushed to the blast furnace shaft core side, and the blast furnace A raw material charging method into a blast furnace, characterized in that it is configured to suppress mixing of pellets into a coke filling part formed around a shaft core part. The method for charging raw materials into a blast furnace according to claim 1, wherein at least a charging position of the ore for the initial charging is set on a centrifugal side with respect to a peak position of the coke layer.

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