JPH1036906A - Operation of vertical furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce molten iron at low cost and at low fuel ratio while keeping high combustion efficiency and avoiding the hanging by using dusts containing iron and/or iron scraps and small grain solid fuel in a vertical shaft furnace. SOLUTION: In this vertical furnace, the dust containing iron and/or the iron scraps are charged as iron source. In such a case, they are charged by dividing the furnace into a furnace peripheral part 8 and a furnace center part 9 and e.g. in order to avoid the hanging, the dusts containing iron charged into the furnace peripheral part 8 are mixed with the solid fuel and, at the same time, the small grain solid fuel is positively used. On the other hand, in order to keep a coke bed 10, the iron source having high metal ratio is charged in the center part 9 of the furnace and the solid fuel being the carburizing component is supplied and the large diameter coke is used. In this operational method, a stock level is changed according to the reducing ratio of iron source or the content of M.Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an iron source using dust containing iron and / or iron shavings and / or reduced iron (a lump ore with a small amount of impurities) as an iron source. The present invention relates to a method of operating a vertical furnace capable of continuously producing pig iron at a low fuel ratio.

[0002]

2. Description of the Related Art Various methods have been developed for producing pig iron from unreduced ore, but the blast furnace method is still mainstream even today. In this blast furnace method, the raw material charged from the furnace top is sufficiently preheated by the high-temperature gas flowing from bottom to top while descending,
Iron oxide is indirectly reduced by carbon monoxide (CO) at a rate of 60% or more. In the blast furnace method, in order to secure such an indirect reduction rate, a raceway space is provided in front of the tuyere,
Here, a reducing gas of η _CO (= CO ₂ / (CO + CO ₂ )) = 0 is produced. Further, in order to increase the temperature of the combustion gas that becomes the high-temperature gas, the blowing temperature is set to 1
000 ° C or higher.

[0003] However, in a melting furnace mainly using an iron source such as iron-containing dust and / or iron scrap, the necessity of producing a reducing gas at the tuyere is reduced, and therefore, coke in front of the tuyere is reduced. It is considered that the combustion of the fuel is efficiently used as a means for securing a heat source for heating or melting the raw fuel. For example, in the cupola method, which mainly dissolves iron sources such as iron shavings, foundry shavings, and pig iron, and does not require a reducing function, usually, raw fuel is mixed and charged, and η _CO =
Dissolution of the iron source is performed under the conditions of 40 to 50%.
In order to obtain such a gas composition, in the cupola method, a large-diameter coke for casting having a particle size of 100 to 150 mm is used, thereby suppressing a solution loss reaction after coke combustion. However, since large-diameter coke for casting is expensive, it is considered effective to use small-grain coke to reduce fuel cost. However, in this case, the solution loss reaction rate, which is an endothermic reaction, increases, and as a result, the combustion efficiency η _{CO of} coke decreases. As a result, the amount of heat of fusion decreases, and stable operation becomes difficult. On the other hand, there are few examples of the operation of vertical furnaces that require a reducing function for melting up to self-reducing ore and iron scrap as main raw materials. In such a vertical furnace, unlike the blast furnace, the raceway is not provided, and the operation is performed with the blowing temperature lowered to 600 ° C. or lower.

[0004] Goksel et al. (Transactions of the American
Foundrymen's Society Vol 85 AFSDes Plaines. III.
According to (1977). P.327-332), there is a report of a test using a hot-air cupola with a blast temperature of 450 ° C. and 5% by weight of C-containing pellets. There is no working example for the operation when a large amount of is blended.

Japanese Unexamined Patent Publication No. 1-501401 discloses a hot metal manufacturing apparatus comprising a blast furnace having a secondary tuyere and a hearth having a diameter larger than the diameter of the blast furnace and having a primary tuyere. Have been. In this furnace, only the iron source is charged from the top of the furnace, and the fuel is directly added to the fuel bed existing at the joint between the blast furnace and the hearth. Therefore,
Since the inside of the blast furnace is an ore layer without fuel, the solution loss reaction with solid fuel does not proceed,
The exhaust gas composition has a high value of CO ₂ / (CO + CO ₂ ), and efficient operation can be expected. In this furnace, the self-reducing iron lump serving as a main raw material reacts with bed coke in the hearth to generate smelting reduction, which is an endothermic reaction.
However, in the secondary tuyere, an exothermic reaction as shown in the following equation (2) occurs, and it is considered that this heat is directed to preheating, heating, or melting of the ore to obtain hot metal. CO + (1/2) O ₂ → CO ₂ +67590 kcal / kmolt · CO ・ ・ ・ (2) However, in this case, only the ore is charged without charging the fuel from the top of the blast furnace. When the continuous operation is performed for a long time, the bed coke is consumed for carburizing of the hot metal with the elapse of the operation time, which is not preferable. Further, as is apparent from the Fe— _CO equilibrium diagram, in an environment having a highly oxidized gas composition of η _CO ≧ 30% and an environment at a temperature of 1000 ° C. or more, the self-reducing ore containing C is not sufficient. Even so, the gas reduction from FeO to Fe is difficult to proceed, so that smelting reduction is inevitable in the lower part of the furnace, increasing the coke consumption in the coke bed, lowering the furnace heat, or causing poor ventilation due to the increase in the amount of melt. May be invited. Furthermore, when the ore is welded and melted in a high-temperature zone, it comes into contact with the furnace wall and becomes a deposit, which causes shelving.

[0006] In addition to these problems, the shape of the furnace is complicated, so that there is a problem in terms of cooling the furnace body when scaling up, and it is considered difficult to increase the size. On the other hand, the relationship between the addition position and the primary tuyere when fuel is added from the joint between the blast furnace and the hearth is described in the above-mentioned Japanese Patent Application Laid-Open No. 1-501401.
No specific reference is made in the official gazette. However, judging from FIG. 2 of the publication, the primary tuyere is installed in the middle of the adjacent fuel addition position. Hearth average diameter D ≧ 1.00m
In such a furnace, when the primary tuyere is located between the adjacent fuel addition positions, replenishment of the coke burned in the primary tuyere portion is performed with the charge immediately above. Therefore, in this case, the ore that has fallen from the upper part of the furnace is in a state of replacing the burned coke, and the added fuel is not considered to fall smoothly, and there is a high possibility that the operation will be disabled.

[0007]

Conventional melting furnace operations for iron sources have necessitated the use of expensive large diameter coke. On the other hand, Japanese Patent Publication No. 1-501401 proposes a melting furnace having a complicated furnace body structure, using small coke and using a large amount of self-reducing ore, and achieving high combustion efficiency η _CO . Aiming at operation, a technology aimed at reducing the fuel ratio was devised. However, there remain problems that hinder long-term stable operation, such as a problem that shelves are easily suspended in the furnace and a problem of consumption of a coke bed in the lower part of the furnace. In addition, there is a facility problem in scale-up. As described above, in the conventional technology for dissolving self-reducing ore and iron scraps, it has been considered that long-term stable operation toward a low fuel ratio is difficult if a large amount of small solid fuel is used. The problem to be solved in the present invention is
Even when a solid fuel having a smaller particle size than that of cast coke is used, it is an object to enable efficient operation without lowering the combustion efficiency η _CO of the solid fuel and avoiding hanging on the shelves.

[0008]

SUMMARY OF THE INVENTION The present invention provides an iron source which requires a reducing function, such as dust agglomerate, self-reducing agglomerate (C-containing agglomerate), reduced iron having a low metallization ratio, and the like. HBI, DRI, iron scrap, pig iron, return scrap, etc., one of the iron sources that only need melting function, and an iron source and solid fuel are charged into the vertical furnace and installed on the wall of the vertical furnace In the operation method of reducing and dissolving by blowing oxygen-containing gas at room temperature or 600 ° C or less from the tuyere, fine solid fuel can be used, and depending on the type of iron source,
Η _CO = (CO ₂ / (C
O + CO ₂ )) is controlled to efficiently reduce and dissolve the iron source at a low fuel ratio.

That is, iron sources that require a reducing function, such as dust agglomerates, self-reducing agglomerates (C-containing agglomerates), reduced iron with a low metallization rate, and HBI, DRI, iron shavings, molds Pig iron, return debris, etc.
The operating method of the vertical furnace of the present invention in which the iron source including any one of the iron sources having only the melting function and the solid fuel are charged into the vertical furnace has the following points. As a method of controlling the reaction and thermal efficiency, that is, the gas utilization rate η _CO , in the furnace, the charging height (stock level) of the vertical furnace with the charge consisting of an iron source and solid fuel is used.
Adjusting at least one of the height of the coke bed, the amount of air blown, the tuyere diameter, and the tuyere projecting position according to the particle size of the solid fuel.
Provide tuyeres with more than one stage, and change the blow ratio of each tuyere installed in the height direction according to the particle size of the solid fuel and the average metallization ratio of the iron source (average M.Fe / T.Fe) Thereby, the η _CO value suitable for the reductive dissolution of the iron source is controlled.

In addition, when charging the iron source and the solid fuel into the furnace from the upper part of the furnace, an iron source having a high metallization ratio is mixed with the solid fuel and charged into the furnace center of the vertical furnace, and the metal is charged. An iron source with a low conversion rate is mixed with a solid fuel and charged around the furnace of a vertical furnace.
At this time, the height of the coke bed at the lower part of the vertical furnace is adjusted to a predetermined height according to the particle size of the solid fuel composed of coke charged into the vertical furnace and the blowing conditions from the tuyere. Also,
When the solid fuel and the iron source are mixed and charged into the furnace center of the vertical furnace, the weight ratio of C contained in the solid fuel and Fe contained in the iron source is set to 0.01 to 0.05. . Further, the charging height (stock level) of the charge composed of the iron source and the solid fuel to be charged into the periphery of the furnace with respect to the furnace center of the vertical furnace is changed according to the average metallization rate of the iron source. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an apparatus and an operation method used in the present invention will be described. The reactor used in the present invention is shown in FIGS. 1 (b), (c)
1 shows the upper charging device of FIG. 1 (a). As shown in FIGS. 1A to 1C, the reactor used in the present invention has a bucket 1, a bell 2, a movable armor 3, and a charging guide 4 as a charging device. An exhaust gas pipe 6 is provided at an upper part, and a tuyere 7 is provided at a lower part. The charge is
It can be inserted into a central part 9 and a peripheral part 8 separately.
The coke bed 10 is formed at a lower portion of the furnace body with its height adjusted. The reactor has two or more tuyeres 7 in the height direction, and has a charging device at the furnace top that can be charged separately in the radial direction (FIGS. 1 (b) and 1 (c)). The air blowing conditions are room temperature air blowing or hot air blowing at 600 ° C. or less, and considering the enrichment of oxygen, the tuyere diameter is set so that a raceway is not formed at the tuyere tip. In addition, the secondary tuyere changes the projecting position in the furnace depending on the charged material.

The raw materials are iron sources with high metallization rates, such as iron shavings, pig iron, casting shavings, hot briquette iron (HBI) and reduced iron (DRI), dust agglomerates, self-reducing ores, oxidizing The main source is an iron source having a low metallization rate, such as reduced iron lump, and the fuel is mainly a solid fuel such as coke or anthracite. The charging method is the normal charging method in which the coke is charged to form a coke bed layer, and then the raw fuel is completely mixed or layered, and the new charging method in which the raw fuel is radially divided and charged. The method was adopted. The new charging method is divided into cases based on the average metallization rate (average M.Fe / T.Fe) obtained by weighting the metallization rates of the charged raw materials, and the average metallization rate (average M.Fe / T.Fe). ) With high reaction efficiency by mixing raw material with high average metallization ratio (average M.Fe / T.Fe) with fine-grain coke at the center side I do.

The operation of the reactor is controlled by adjusting the height of the coke bed, the stock level position, the charging division method according to the type of raw fuel, the secondary tuyere projecting position, and the like. The optimum height of the coke bed differs depending on whether the iron source is mainly dissolved or the iron source is reduced, and the upper end position of the coke bed is set at a position corresponding to the target η _CO . In the coke bed, the combustion reaction of coke and the solution loss reaction after combustion proceed. The reaction speed of both reactions is adjusted by the solid fuel particle size, the gas flow rate, and the blast temperature. In addition, the stock level position is related to the heating rate of the raw fuel,
In particular, since it affects the solution loss reaction rate of solid fuel, it is used as a control means for preventing the reaction efficiency from decreasing. For the radial charging method, the parts with high metallization rate and the parts with low metallization rate are separated, and the former is oriented to melting-oriented operations, aiming at the upper limit of the secondary combustion rate η _CO , Regarding the latter, reduction is emphasized, and the most efficient operation as a whole can be directed by controlling the secondary fuel rate required for reduction according to the average metallization rate and C content of the raw material. Dissolution-oriented parts with a high metallization rate
Aiming at the upper limit of the secondary combustion rate by using the secondary tuyere effectively and using secondary ventilation. In the case where the melting-oriented part is set to the center side in the radial division charging, setting the projecting position of the secondary tuyere to the boundary position between the center and the periphery of the furnace is most effective.

Next, a method for controlling the secondary fuel rate η _CO will be described. An example of the η _CO control method of the present invention is as follows. The outline of the control flow of η _CO in the furnace of the present invention will be described. The control of the present invention is summarized as follows.

The average metallization ratio (average M.Fe / T.Fe) is determined from the components and the amounts (use amounts) of the iron source charged into the vertical furnace. When aiming for more efficient operations, radial division charging is performed, but when applying this charging method,
The average metallization ratio is determined for the iron sources inserted into the center and the periphery.

The average metallization ratio of the charged iron source (average M.Fe
/T.Fe) and the C content in the iron source from the following equation (1) (FIG. 2).
Ref.) To determine the range of _ηCO levels suitable for operation. When applying the radial division charging method, an appropriate η _CO is specified for each of the center side and the peripheral side. 1.5 × C% ≦ η _CO −0.7 × (average M.Fe / T.Fe) ≦ 3.0 × C% (1) where C is C% contained in the iron source. 0% ≦ C% ≦ 2
0% η _CO : Gas utilization rate (%) (Average M.Fe / T.Fe): Average metallization rate (%) Metallization rate: Metallic iron in iron source (M.Fe) / Total in iron source Iron (T.Fe) Average metallization ratio: Metallization ratio of weighted average of several iron sources

Since the average gas velocity in the furnace (Nm / s) is determined by the operating conditions of the melting furnace (standard of tapping amount), the coke from the primary tuyere is determined from the data of FIG. Set the bed height.

Regarding the stock level, the following (3)
Based on the equation (see FIG. 4), the stock level (the height of the charging surface from the primary tuyere) H (m) corresponding to the target ηCO is specified and set. Equation (3) is an approximation line based on the least squares method, and although it may be somewhat different depending on the type of iron source and the metallization ratio, the stock level H (m) is set based on the target η _CO . H = −0.02775 η _CO +4.775 (3) When the radial division charging method is adopted, it is preferable to set the stock level separately for the center side and the peripheral side.

The fuel cost is shown above in addition to the furnace body heat dissipation (kcal / h) which is a characteristic of the furnace, the target tapping rate (t / d), the operating conditions including the iron source type and quality, and the like. Once the target η _CO is determined, the fuel cost (kg / t) level can be determined from the heat / material balance.
Fine adjustment of the next air volume and fine adjustment of the stock level will be carried out to maintain the target η _CO level. When the radial charging method is adopted, the fuel cost is set separately for the center side and the peripheral side and charged.

Hereinafter, the present invention will be described in more detail.
The reason why it is necessary to adjust and control the in-furnace ηCO in accordance with the average metallization ratio (M.Fe / T.Fe) of iron contained in the iron source when reducing and dissolving the iron source will be described. Scrap, pig iron, the casting scrap, HBI, metallization ratio as DRI, for example in the operation of dissolving more than 90% and high iron source, because it does not require the reducing function, high eta _CO conditions low fuel rate It is preferable in terms of directing the operation, and the target is an operation where η _CO > 80%. On the other hand, in the case of reducing and dissolving iron sources with a low metallization rate, such as dust agglomerates and self-reducing ores or partially oxidized reduced iron and reduced iron powder, the reduction proceeds by solid-gas reaction, It is preferable to produce a large amount of solid iron and then melt the iron in terms of operation stability and hot metal quality. For this purpose, thermodynamic (equilibrium) conditions for incorporating pure wustite (FeO) into iron are preferable. For example, in a temperature range of 1000 ° C. or higher, a gas condition of η _CO <about 30% is required. The iron source requiring this condition is wustite (FeO) with a metallization ratio of 0%.
And sinter ore, pellets, lump ore, etc., which are blast furnace charges.

On the other hand, in the case of agglomerate ore containing C, for example, self-reducing ore lump containing C or dust agglomerate containing C used in the present invention, the gas atmosphere outside the agglomerate is η _CO > About 3
At 0%, even if the reduction of FeO to iron does not progress equilibrium theory, the condition of η _CO <about 30% is formed inside the agglomerate due to the presence of C existing inside the agglomerate, It has been confirmed that the reduction to reduced iron proceeds. For example, in an operation in which 50% of self-reducing ore lump containing C = 12% is mixed and iron scrap is mixed in 50%, the furnace top η _CO = 50%
Even under moderate gas conditions, the operation was favorable, suggesting that the reduction was progressing moderately in the furnace. In this way, under conditions of heavy use of dust with a low metallization rate, where the reduction process of the iron source is emphasized, high η _CO cannot be expected, but the melting operation of iron scraps, which mainly dissolves the iron source, High η _CO operation can be _{aimed at the} operation using a large amount of iron source with high metallization rate or the small amount of use of dust with low metallization rate. That is, it is desirable to manage and control the η _CO level within a range that does not hinder the reduction reaction, according to the type of the iron source and the ratio of M.Fe / T.Fe.

Next, a method of controlling η _CO will be described. As a method of controlling η _CO , in the present invention, control of the charging height position (stock level) of the charging material, control of the coke bed height, etc., use of multistage tuyeres, radial charging of the charging material Admission was proposed. Below, regarding nuclear technology,
It will be described step by step. First, it is explained that changing the charging height (stock level) of the charged material consisting of an iron source and solid fuel in a vertical furnace is effective for η _CO control. Regarding the stock level, for example, in a cupola operation in which large-diameter casting coke is used and iron scrap and casting scrap are melted, usually, the height (H) from the lower tuyere to the stock level (H) / furnace diameter (D) ) = 4-5, but there is no study on the stock level for vertical furnaces that use fine-grain coke such as coke for blast furnaces and require a reduction function such as dust reduction. Therefore,
A stock level change test was conducted under the condition of using a large amount of iron shavings, and the relationship with the exhaust gas η _CO was arranged in FIG.

According to the test results using a vertical furnace having a hearth diameter D = 1.4 m, it is possible to maintain the exhaust gas η _CO > 70% as high as possible by setting H / D = 2.0 to a small value. It has been found that it is possible to reduce the exhaust gas η _CO by increasing. This is because, when the stock level is increased, the heat transfer from the gas to the raw fuel becomes better, and the preheating and heating of the solid fuel proceed from the upper part. As a result, the solution loss reaction region of the following equation (4) is formed at the upper part of the furnace. This suggests that the consumption of C increases as a result, and that ηCO decreases. C + CO ₂ = 2CO (4) As described above, the change of the stock level has a role of controlling the rate of temperature rise of the raw fuel in the furnace, and serves as a control means of the exhaust gas η _CO .

Next, it will be described that changing the height of the coke bed in the lower part of the vertical furnace, and that changing the air flow rate, tuyere diameter and tuyere protrusion position is effective for η _CO control. FIG. 3 shows experimental results obtained by an off-line simulator in which the coke bed height from the tuyere and the transition of η _CO at that location were investigated by changing the coke particle size and the air flow rate (gas flow rate). According to FIG. 3, the oxygen and enriched oxygen in the air sent from the tuyere burn with the coke by the reaction of the following formula (5) to produce CO ₂ and complete combustion at the site where O ₂ has disappeared. Leads to. This portion has the highest gas temperature. Above this portion, the solution reaction of the formula (4), which is an endothermic reaction, proceeds, so that η _CO decreases and the gas temperature also decreases. C + O ₂ → CO ₂ (5) When the coke particle size becomes smaller, the combustion rate of the equation (5) becomes faster, so that the maximum gas temperature (η _CO = 100 at O ₂ = 0%)
%) Is close to the tuyere. In addition, when the blowing rate is increased and the gas flow rate is increased, the flow rate of oxygen blown from the tuyere in the furnace increases, and the contact time with C near the tuyere becomes shorter. The reaction extends to the top of the furnace. Therefore, when the flow rate is increased at the same coke particle size, as shown in FIG. 3, η _CO in the furnace becomes higher as a whole as compared with the case where the flow rate is low. Protruding the primary tuyere into the furnace, or reducing the tuyere diameter and increasing the tuyere wind speed,
This corresponds to shortening the contact time between the blown oxygen and C, and has the same effect as increasing the flow velocity in the furnace. As described above, changing the height of the coke bed in the lower part of the vertical furnace, and further, changing the blowing amount, tuyere diameter, and tuyere protrusion position are effective means for controlling the in-furnace η _CO .

Next, the method of radially charging the charged material is effective means for η _CO control without reducing the combustion efficiency of the vertical furnace even when a small solid fuel is used. Explain that it is effective to install multiple multi-stage tuyeres in the furnace height direction on the shaft wall surface of the furnace by η _CO control. At the primary tuyere, the solid fuel is burned by the reaction represented by the equation (5), and then CO gas is generated by the solution loss reaction represented by the equation (4). On the other hand, in the secondary tuyere located above the primary tuyere, the CO gas rising from below is combusted by the reaction represented by the formula (2), and this exothermic reaction is used to generate the iron source. Preheat to achieve high η _CO and reduce fuel ratio. According to the experiment, under the condition of secondary air volume / primary air volume = 1/4,
It has been confirmed that η _CO can be improved by 15% or more, and upper-stage air blowing using multi-stage tuyere can be a means for controlling η _CO in the furnace.

However, the solution loss reaction represented by the formula (4) occurs in the secondary tuyere, and even if the ratio of the solution loss reaction is reduced as much as possible, and even if a small solid fuel is used, A method that aims to be able to operate without reducing the combustion efficiency of the vertical furnace is the radial division charging method of the charge. This charging method is a method of charging the iron source and the solid fuel on the furnace center side and the furnace peripheral side in different amounts. For example, the weight ratio of the iron source / solid fuel at the center of the furnace is increased, that is, the ratio of the solid fuel is reduced, the weight ratio of the iron source / solid fuel at the periphery of the furnace is reduced, and the fine solid fuel is shifted toward the periphery. As an example of a method of charging a large amount, the use of fine-grain coke with a large ventilation resistance at the periphery of the furnace enables the central flow of gas to be directed, and the periphery of the furnace where the gas flow rate decreases decreases the furnace periphery. The temperature is lower than the central part of the furnace, including the effect of water spray cooling, and the amount of solution loss reaction of coke in the peripheral part of the furnace can be suppressed. Further, although the amount of gas is large in the central part of the furnace, the amount of coke charged is small, so that the solution loss reaction amount of the equation (4) can be suppressed as compared with the ordinary mixed charging method or layered charging method. Thus, the method of radially charging the charge is an effective means for η _co control without reducing the combustion efficiency of the vertical furnace even when using small solid fuel.

Next, the reduction and melting method of the iron source employing the radial charging method is effective for the operation stability and low fuel ratio operation, and is efficient regardless of the type and the particle size of the iron source. An operation method for directing an efficient operation according to the fact that the operation can be directed and the properties of the iron source and the solid fuel will be described. Regarding the radial charging method, there is an appropriate charging method depending on the type of iron source. One is an example of increasing the η _CO in the furnace and aiming for efficient operation.This is a separation method using M.Fe / T.Fe of iron source, and the other is a separation method according to the particle size of the iron source. Is the law.

First, the metallization rate of the iron source (M.Fe / TF
Explain that the separation method according to e) contributes to stable operation and enables efficient operation. When there are several types of iron sources used for reduction melting and can be separated according to the size of M.Fe / T.Fe, preferably, an iron source having a high metallization rate, for example, pig iron (type pig), iron waste, casting waste , Reduced iron, HBI, DRI, etc. are charged into the center of the furnace and iron sources with low metallization rate (dust agglomerate, self-reducing ore, partially oxidized reduced iron, pellets) are placed around the furnace. To charge. This is a charging method in which the furnace center has a melting function and the furnace periphery has a reducing function.An iron source with a low metallization rate is charged in the furnace periphery, and a high metallization rate is charged in the furnace center. The reason for loading the iron source is to facilitate the control of the height of the coke bed in the center of the furnace, to secure the center gas flow, and to aim for a low fuel ratio operation.

In the case of directing this operation, the secondary tuyere has a structure in which the tuyere tip protrudes from the furnace wall to the inside of the furnace. Ideally, it is provided at the boundary of the furnace periphery. In addition, when the gas flow is the central flow and the reduction function of the iron source charged in the peripheral part of the furnace is emphasized, the solid fuel in the peripheral part is preferably fine, and the solid fuel in the central part is preferably large. The reason that the secondary tuyere is set at the boundary between the center and the periphery of the furnace is that the secondary blast is not used for burning solid fuel existing in the periphery, and the secondary blast is a CO gas of the formula (2). This is to make it work for combustion. Because the furnace center mainly has a melting function, it is
It is most efficient if the operation is performed with η _CO > 90% in the center of the furnace, and the solid fuel in the center of the furnace can be reduced to the lowest fuel ratio of about the carburized content. Therefore, a sudden change in the height of the coke bed can be suppressed, and the coke with the particle size maintained becomes the coke bed, so that a low fuel ratio operation that ensures ventilation and liquid permeability can be performed.

In this operation, the appropriate secondary air flow is determined by the height of the coke bed. As described above, the coke bed height varies depending on the coke particle size, the gas flow rate in the furnace, and the like. However, when the upper end of the coke bed is set at the optimum position (η _CO > 90%), the secondary blowing becomes unnecessary. . When η _{CO at the} upper end position of the coke bed is 90% or less, η _CO > 90% can be set by secondary blowing, and ideal operation can be performed with respect to the furnace center. Further, as for the coke in the central part of the furnace, even in the operation using fine-grain coke, as shown in FIG. 3, by setting the coke bed height lower than that when using large-grain coke, or by adjusting the blowing rate, η Theoretically, efficient operation can be achieved without changing _CO .

With respect to the upper end position of the coke bed, since the iron source is melted at this position, in the melting operation of iron scraps, the optimum position of the coke bed height is the position where the gas temperature is the highest, that is, 0 ₂ = 0. % In η _CO = 100%. In the test operation of the vertical furnace of performing a multistage blower at the secondary blast volume / primary blast volume = 1/4, the upper blowing, eta _CO is possible to improve more than 15% referring to this, eta _CO> When the operation is to be performed at 80%, the coke bed height may be set so that η _CO > 65% at the upper end position of the coke bed. On the other hand, in the surrounding area where an iron source having a low average metallization rate is charged, it is necessary to promote reduction at a position above the upper end of the coke bed, and η _CO is reduced when O ₂ = 0%.
= 100% as the lower limit position, the type of iron source and M.Fe
/ Set the coke bed height high according to T.Fe etc.
It is necessary to control η _CO at the upper end of the coke bed.

The coke bed height is set at a predetermined position at the start of operation. During operation, by charging coke from the top of the furnace corresponding to the coke consumption in the furnace,
The coke bed height can be maintained. When a large diameter coke of 80 mm is used, η _CO > 65% at the upper end of the coke bed during operation at a gas flow rate of 1 Nm / S in the furnace.
3, the height of the coke bed is suitably from 60 cm to 90 cm from the lower tuyere. In addition, when the operation is aimed at ηCO <30% at the upper end of the coke bed, when the large diameter coke of 80 mm is used, the primary wing is 130 cm or more from the primary tuyere and when the small blast furnace coke of 30 mm is used. 120c from mouth
m or more.

Next, it will be explained that the charging method of mixing an iron source with a low metallization rate with the solid fuel when charging the iron source with a low metallization rate around the furnace is efficient. If we can operate with a high η _CO , we can operate at a low fuel ratio, but we conducted an experiment to reduce an iron source with a low metallization rate that requires a reduction function under the condition of η _CO > 30%. Under conditions that do not mix with coke,
The reduction reaction from wustite in the iron source to iron does not proceed, and causes smelting reduction that adversely affects the operation at high temperatures. On the other hand, even if an iron source having a low metallization rate is mixed with coke and charged, there is at least a 20% or more reduction rate improvement effect as compared with the case where coke is not mixed.
The result of studying the offline simulator as shown in FIG. This suggests that in operations that charge iron sources with a low metallization rate, the charging method that mixes with solid fuel (coke) improves the reducibility of iron sources compared to operations that do not mix with solid fuel (coke). As a result, the amount of slag melt at the time of melting can be reduced, which also contributes to avoiding hanging on a shelf.

As a method of promoting the reduction of the iron source with a low metallization rate charged in the periphery of the furnace and increasing the reduction rate of the iron source before melting, as a method of encapsulating C in dust containing iron, It is effective to increase the amount of the interior C. The upper limit of the amount of interior C is
It is about 20% due to strength constraints. FIG. 2 shows an example of examining the average metallization rate of the iron source and the η _CO level at which the reduction and dissolution of the iron source can be performed without any trouble.
Although the η _CO level varies slightly depending on the amount, the operable η _CO level can be determined from the metallization ratio of the charged iron source. Generally, coke is used as the solid fuel, but carbonaceous materials such as anthracite can also be used.

Next, iron sources to be charged from the furnace top include dust agglomerate, self-reducing ore, lump reduced iron (HBI, DRI),
6 (a) to 6 (d) show typical examples of charging methods for charging iron source, foundry dust, pig iron (shaped pig), ore, pellets, reduced iron, and the like. 6 (a) and 6 (b) show an iron source having a high metallization rate, that is, pig iron, iron shavings, lump reduced iron, and large coke for replenishing the coke bed and carburizing at the center of the furnace. In this method, iron sources with low metallization rate (dust agglomerates, self-reducing ores, partially oxidized reduced iron, pellets) are mixed with small coke and charged around the furnace. It is most efficient in enabling operation with high combustion efficiency and aiming for a low fuel ratio. As for the partially oxidized lump reduced iron, as shown in FIG.
It is also possible to charge in the center of the furnace. As described above, the adoption of the radial charging method has enabled multifunctional operation according to the type and properties of the iron source.

Next, it will be described that it is effective to change the stock line in accordance with the portion of the raw fuel to be charged in the radial direction of the vertical furnace. For example, the reduction is not necessary scrap, pig iron, in the case of charged casting scrap or the like in the furnace center portion, eta _CO is as high as possible it is desirable, eta _CO> 70%
When the above is targeted, the stock level is suitably ((Height charged from primary tuyere) / (hearth diameter D)) <2.0.
When reducing and dissolving dust agglomerates, self-reducing ores, and reduced iron that require reduction, it is necessary to reduce η _CO . In this case, for example, if η _CO = 50% is targeted,
The stock level may be set to H / D = about 2.4. Thus, there is an appropriate value of the stock level in the radial direction according to the type of the iron source to be charged. Radially,
As a method of controlling the stock level, a dedicated charging device is required. For example, there is a charging device shown in FIG. In this device, the charging position of the charged material can be divided into a furnace central portion and a furnace peripheral portion in a furnace top radial direction. A charging guide is provided in this device, and each charged material is provided in the charging guide. This is a way to manage stock levels. Thus, at the charging site of the iron source that does not need to be reduced, the solution loss reaction of coke at the site above the coke bed can be suppressed, and more efficient operation can be performed.

Next, a control method for maintaining the coke bed height will be described. It is difficult to control the height of the coke bed because it is located in the lower center of the furnace, and if the coke ratio is not appropriate, the unreduced FeO melts and reduces at the lower part of the furnace and consumes the coke bed. This is because abnormal wear of the device is caused. In particular, if such coke is abnormally consumed in the lower center portion of the furnace, it will not only hinder the melting of the iron source, but also may cause an operation failure due to solidification of the slag or the like. Therefore, as described above, an iron source having a high metallization rate, that is, iron pig, iron waste, casting waste, etc., is mainly charged into the furnace center, so that the operation is less likely to cause smelting reduction in the furnace center. In addition, it suppresses abnormal consumption of the coke bed in the center of the furnace.
In order to minimize the solution loss reaction of coke, large-diameter coke is used by distinguishing the solid fuel charged in the furnace center from the solid fuel charged in the furnace periphery. This makes it possible to suppress abnormal wear of the coke bed in the central part of the furnace and to operate the furnace with a higher combustion efficiency η _{CO in the} lower part of the furnace.

The installation position of the upper tuyere has an appropriate position depending on the operating parameters such as the coke particle size and the air flow rate. However, basically, the η _CO level at the secondary tuyere is 65% < η _CO
<90% or so is a guide. In addition, the upper end position of the coke bed differs depending on the type of iron source to be charged. For the charging site of the iron source that does not require a reducing function, the coke combustion is controlled as much as possible below the secondary tuyere to minimize the coke combustion. Preferably, it is suppressed. On the other hand, at the charging site of the iron source requiring the reducing function, the upper end position of the coke bed is preferably higher than the secondary tuyere. This is because it is necessary to control η _CO at the upper end position of the coke bed by the ratio of M.Fe / T.Fe in the iron source. As a simple method of controlling or monitoring the height of the coke bed, there is a visual observation at a secondary tuyere. Observation at the secondary tuyere can at least determine that the molten portion of the iron source is present either above or below the secondary tuyere. In addition, as a method of measuring the height of the coke bed with high accuracy, the height can be determined by measuring the descending behavior of a vertical sonde or iron wires charged from the upper part of the furnace. In the case of a vertical sonde, the temperature in the furnace rises sharply to 1200 ° C. or higher, and when iron wires are used, the point at which the descent speed stops corresponds to the upper end of the coke bed.

Next, the iron source having a low metallization rate charged into the peripheral portion is mixed with the solid fuel and charged, and the coke charged into the peripheral portion of the furnace is made into small coke. It is explained that directing the charging method in which the ratio of iron source / solid fuel is changed in the radial direction of the furnace is effective for avoiding rack hanging. In general, when using a large amount of dust containing iron,
Deposits are easily generated on the furnace wall. For example, the reduction reaction slows down, and as a result, slag containing a large amount of FeO is generated, and this slag is cooled by smelting reduction, which is an endothermic reaction, and the case where the slag adheres to the furnace wall, a large amount of slag containing FeO In a case where the slag is blown up and adheres to the furnace wall at the lower part of the furnace, or unreduced FeO is melted at the upper part of the furnace due to the rising high temperature gas, and combined with or fused with the adjacent iron source, There are cases etc. that adhere to the furnace wall. In each case, near the furnace wall,
A large amount of slag melt is generated or liquefied by bonding or fusing with an adjacent iron source, which adheres to the furnace wall and becomes an adhered substance, which causes shelving.

Therefore, in order to avoid this hanging on the shelves, it is necessary to reduce the amount of melt generated around the furnace and to minimize the contact between adjacent iron sources. In order to reduce the amount of melt around the furnace, it is necessary to increase the reduction rate of the iron source. For this purpose, as described above, the iron source charged around the furnace is mixed with solid fuel. It is effective to charge them. As for the particle size of the solid fuel at this time, a smaller particle size is more preferable. This is because if coke of the same weight is charged, the number of charged small solid fuels is larger, and it is possible to sufficiently avoid contact between iron sources. In addition, as a small solid fuel here, for example, coke for blast furnace (particle size of 60 mm or less) or small coke for blast furnace with a particle size of about 30 mm is preferable.

It is also effective to make the weight of the solid fuel charged into the periphery of the furnace larger than the weight of the solid fuel charged into the center of the furnace. To do this, the weight ratio of iron source / solid fuel must be
Separate into the furnace center and the furnace periphery.Introduce a high metallization rate iron source in the furnace center to reduce the coke weight charged in the center and minimize the amount of coke charged in the periphery. Increase. The solid variable ratio charged to the periphery of the furnace slightly varies depending on the metallization ratio of the iron source to be charged, such as dust agglomerate, self-reducing ore, and reduced iron. For example, as a charging iron source, C is 1
In the case of using 75% of self-reducing ore lump containing 75% of reduced iron, 15% of reduced iron, and 10% of iron waste, the ratio of iron source to solid fuel excluding iron waste that does not require reduction is (self-reduction It has been confirmed by operation that shelving can be avoided under the condition of (soluble ore + reduced iron) / (solid fuel) ≦ 5. The condition is (weight of metal M.Fe in charged iron source) / solid fuel <
1.24. When an iron source having a low metallization rate is used, it is necessary to further increase the amount of solid fuel charged around the furnace. Conversely, when an iron source with a high metallization rate is used, the amount of solid fuel charged around the furnace can be reduced.

Next, an iron source having a low metallization rate and a solid fuel, such as small solid fuel, reduced iron, self-reducing ore, dust agglomerate, and the like, are charged into the periphery of the furnace, and the center of the furnace is charged. Iron scrap, foundry scrap,
In the case of charging a solid fuel and an iron source having a high metallization rate such as pig iron, the weight ratio of C contained in the solid fuel charged into the center of the furnace and Fe contained in the iron source is 0.01 ≦ C / Fe ≦
The fact that setting to 0.05 is effective will be described. If the iron source charged into the furnace center is iron scrap, casting scrap, or pig iron, it contains C except iron scrap, so basically only iron scrap should be replenished with the C required for carburization. In addition, it is sufficient to replenish the solid fuel that is partially consumed in the combustion of the coke bed. The amount of carburization of iron scrap in the furnace
4% by weight. In addition, a test result was obtained in which the coke bed consumption in the central part of the furnace was about 10 kg / t (corresponding to a rate of about 0.01). When iron scrap is used as the iron source to be charged into the center, the amount of coke charged is the largest. In this case, C / Fe = 0.02 to 0.0
4 is required, so that when the consumption of the coke bed is added, 0.03 ≦ C / Fe ≦ 0.05. In addition, the case where casting waste and pig iron are charged and iron waste is not charged as the iron source to be charged into the center is the case where the amount of coke charged is the smallest.In this case, the coke necessary for carburizing is used. Is not necessary, the solid fuel may be charged at a ratio of C / Fe = 0.01 corresponding to the coke bed consumption at the center of the furnace. Therefore, the weight ratio of C contained in the solid fuel charged into the center of the furnace to Fe contained in the iron source is set to 0.01 ≦ C / Fe ≦
The charging ratio of the solid fuel and the iron source may be determined as 0.05.

Regarding the charging method, for example, the weight ratio of the iron source / fixed fuel is changed for each charging by using an armor with a bell-type charging apparatus, and the first charging is performed at the center of the furnace. In addition, it has been confirmed that a predetermined charge can be obtained by charging the second charge to the periphery of the furnace. In addition, in the case of using a top-opening type charging device which is often found in a melting furnace such as a cupola, the charging device shown in FIGS. It is effective to classify and charge. In addition, as shown in FIG. 6 (d), the charging method is slightly complicated as shown in FIG. 6 (d), regardless of the metalization rate of the iron source. There is a method in which only the solid fuel is charged into the furnace wall, and an iron source and the solid fuel are mixed and charged inside the solid fuel. Specifically, one cycle is charged with three charges,
At the first charge, only solid fuel is charged in the vicinity of the furnace, at the second charge, the fuel is charged into the center of the furnace, and at the third charge, the iron source and the solid fuel are mixed and charged into the furnace periphery. By inserting, predetermined charging becomes possible.

Boundary position between the furnace center and the furnace periphery in the present invention
The equipment determines the metallization rate and coke particle size of the iron source,
Some extent in the furnace radial direction depending on the percentage of dust used
Move with. The boundary position ri between the furnace center and the furnace periphery
Once the amount of iron source and solid fuel to be charged into each part is determined,
It is obtained by the following equation (6). ri^Two= (Wm^(c)/ ρm^(c)+ Wc^(c)/ ρc^(c)) / ｛(Wm^(c)/ ρm^(c)+ Wc ^(c) / ρc^(c)) + (Wm^(p)/ ρm^(p)+ Wc^(p)/ ρc^(p))｝ (6) where ri is the dimensionless boundary radius (−) Wm between the center and the periphery of the furnace.^(c) : Weight of iron source charged in the center (kg / charge) Wc^(c) : Weight of solid fuel charged in the center (kg / charge) Wm^(p) : Weight of iron source to be charged in peripheral area (kg / charge) Wc^(p) : Weight of solid fuel charged in the surrounding area (kg / charge) ρm^(c) : Bulk density of iron source charged in the center (kg / m^Three) Ρc^(c) : Bulk density of solid fuel charged in the center (kg / m^Three) Ρm^(p) : Bulk density (kg / m^Three) Ρc^(p) : Bulk density (kg / m^ThreeNote that this ri is expressed by a dimensionless radius, and
When the lowering speed of the charge in the furnace and around the furnace is constant
The field position is shown. Adjust the boundary position indicated by this ri.
There are various possible charging methods for knotting,
Use armor even when using bell-type charging equipment
The center charge and the peripheral charge are alternated for each charge
When a mixed layer is formed by returning and charging
The predetermined boundary can be set.

[0045]

EXAMPLES The characteristics of the present invention will be described more specifically with reference to the following examples. 1.4 m hearth diameter, 6 primary tuyeres, 6 secondary tuyeres, the upper limit of the stock level is 5.0 m above the primary tuyeres, open-top type, moving bed type, two-stage tuyere structure Vertical furnace was used. As the charging device, a charging device capable of sorting charging positions in the furnace radial direction was used. Note that the composition of the furnace top exhaust gas is η _CO ^(TOP) = (CO ₂ ^(TOP) / (CO ^(TOP) + CO ₂
^(TOP) )). Further, among the operation parameters, the blast moisture was set to 15 g / Nm ³ , which is the atmospheric humidity, and the limestone basic unit charged from the furnace top was set to set the slag basicity to 1.0.
The iron source to be charged is a self-reducing ore lump (40 mm × 20 mm × 30 mm in size and a particle size of 3 mm) with a C (4 to 20%) interior.
agglomerate ore produced by mixing blast furnace secondary ash and coke powder with reduced iron powder having a diameter of not more than 2 mm), dust agglomerate mainly formed of blast furnace secondary ash, and agglomerated by mixing dust in an ironworks, It is Kirshredder scrap iron, which is a common waste in the city. As solid fuel, small coke for blast furnace with a particle size of about 30 mm and about 80 mm
Lump coke was used. Table 1 shows Examples and Table 2 shows Comparative Examples.

[0046]

[Table 1]

[Table 2]

Example 1 (a) and (b), Comparative Example 1
Is a self-reducing ore (T.Fe = 59.5%, M.Fe / T.Fe =
0.19): Dust agglomerate (T.Fe = 50.81%, M.Fe / T.Fe = 0.05)
7): Car shredder scrap iron (T.Fe = 90%, M.Fe / T.Fe = 0.9
9): Reduced iron lump (T.Fe = 87%, M.Fe / T.Fe = 0.80) = 50: 1
In the operation at 0:30:10, the average metallization rate of the charged iron source is 56%. In Examples 1 (a) and (b), self-reducing ore, dust agglomerate, reduced iron ingot, and small coke are mixed and charged in the peripheral portion, and car shredder scrap iron and carburizing in the central portion. Large coke was charged. Comparative Example 1 is a case in which the above-mentioned iron source and solid fuel were completely mixed and charged, but the in-furnace combustion efficiency was as low as η _CO = 20%, the molten iron temperature was low, and slag discharge was difficult. Whereas
In Examples 1 (a) and (b) employing the radial division charging method, the in-furnace combustion efficiency η _CO was high and the hot metal temperature was 1
The temperature rose to about 500 ° C, and stable operation became possible.
Example 1 (b) is an operation in which the large lump coke charged at the center is partially replaced with small lump coke, and the height level of the bed coke is changed to the vicinity where the gas combustion temperature becomes maximum. , That is, a position 40 cm from the lower tuyere, enables more efficient operation.

In Example 2 and Comparative Example 2, the dust agglomerate 20
Comparative Example 2 was a case where raw fuel was completely mixed and charged, while Example 2 (a) was an example in which the stock level was adjusted. It is. In Examples 2 (b) to 2 (d), 20% by weight of dust agglomerate and small coke were mixed and charged in the periphery, and 80% by weight of car shredder scrap and large coke for carburizing were charged in the center. In the charging example, in contrast to Example 2 (b), in the process of replacing large lump coke with small lump coke, Example 2 (c) protrudes the lower tuyere about 20 cm into the inside of the furnace and reduces the tuyere diameter to 50 mm. In Example 2 (c), the gas flow rate in the furnace was 0.8 m / s.
This is the case where the wind increased due to the rise. In Example 2, compared with Comparative Example 2, a large amount of small coke can be used, and efficient operation can be performed. Further, it is effective to change the stock level, the tuyere structure, and optimize the gas flow rate in the furnace, and the efficiency is higher than in the first embodiment.

In Example 3 and Comparative Example 3, the self-reducing ore lump (C
12%): Dust agglomerate (C4%): Car shredder scrap iron: Reduced iron (T.Fe = 87%, M.Fe / T.Fe = 0.80) = 50: 1
In the operation at 0:30:10, self-reducing ore, dust agglomerate, reduced iron and small coke are mixed and charged in the periphery, and car shredder scrap iron and carburized large ingot are placed in the center. Coke was charged. Average metallization rate of charged iron source is 5
6%, and the metallization rate of the iron source charged in the periphery was 29.
It corresponds to 6%. Comparative Example 3 is a case where the stock level was set in the normal operation state, that is, the case where the stock level was set to 4.2 m above the primary tuyere. In Example 3 (a), Equation (1) and FIG. 2 is an example in which the stock level is set to 3.2 m with the target of η _CO = 55%. In Example 3 (b), the equation (1) and FIG. In the example 3 (c), the primary air temperature was further reduced by 2 with reference to FIG.
Example 3 (d) is an example in which hot air of 00 ° C. is used and oxygen-enriched is 0%, and Example 3 (d) is an example in which only one-stage air blowing is used and air blowing temperature is 550 ° C., and Example 3 (e) is used. This is an example in which an iron source having an interior C of 20% is used as a self-reducing ore and the blowing conditions are changed. In Example 3 (f), when the type of the charged iron source is changed, the equation (1) This is an example in which η _CO is changed according to FIG. The operation of Example 3 was better than that of Comparative Example 3, and it was clarified that the efficiency was improved by controlling the stock level according to the iron source in the radial direction, changing the blast temperature, and the like.

Example 4 and Comparative Example 4 show a case in which 80% by weight of car shredder scrap iron, 20% by weight of pig iron and large lump coke were charged in the center, and small lump coke was charged in the periphery. Example 4 is a case where the stock level is set to 4.2 m, while Example 4 is an example in which the stock level is adjusted to enable a highly efficient operation.

Example 5 and Comparative Example 5 show a case where 80% by weight of car shredder scrap iron and large lump coke were charged in the center, and 20% by weight of dust lump ore and small lump coke were charged in the periphery. Comparative Example 5 is a case where the stock level is set to 4.2 m, while Example 5 is an example in which the stock level is adjusted to enable a highly efficient operation.

Example 6 (b) is a case in which 100% by weight of car shredder scrap iron and large coke were charged in the center portion, and small coke was charged in the peripheral portion. Example 6
Prior to (b), in an operation similar to the normal cupola operation, the iron source and coke were completely mixed and charged, the height of the coke bed was set to about 1 m above the primary tuyere, and the stock level was set to 4.
Considering the case of normal operation (Comparative Example 6) set at 2 m and operation with complete mixing, but considering that the average gas flow rate in the furnace was 0.7 m / s, η _{CO at the} upper end position of the coke bed was considered. = 80-90%, with the coke bed height set to 60 cm above the primary tuyere and the stock level set to 3.0 m.
(A)). In Comparative Example 6, η _CO could only be operated at a low level of about 20%, and the coke ratio had to be increased. In the case of Example 6 (a), even when a large amount of fine coke was used, η _CO = It was possible to operate at 50%, and it was confirmed that coke betting and stock level control were effective.
In addition, in Example 6 (b), it was confirmed that the higher efficiency η _CO (> 90%) can be achieved by the radial charging and the most efficient operation can be performed.

[0053]

As described above, the present invention is more efficient in an operation utilizing a new raw material charging method in a pig iron production method using iron-containing dust and / or iron scrap as a main raw material. The operation is proposed, and its development enables continuous operation, high combustion efficiency, and the use of inexpensive small solid fuel. Therefore, operation with high productivity and low fuel ratio is possible.

[Brief description of the drawings]

FIG. 1 (a) is an explanatory view showing an example of a reaction apparatus and a charging apparatus, FIG. 1 (b) is an explanatory view of an upper charging apparatus at the time of center charging, and FIG. It is explanatory drawing of the upper charging device at the time of peripheral part charging.

FIG. 2 is an explanatory diagram showing a relationship between an average metallization ratio of an iron source and an η _CO level at which reduction and dissolution of the iron source can be performed without any trouble.

FIG. 3A shows a gas flow rate in a furnace: 0.35 Nm /
FIG. 3B is a graph showing the relationship between the coke bed height and ηCO when the coke particle size changes, and FIG.
m, the relationship between the coke bed height and η _CO when the gas flow rate in the furnace changes, and FIG. 3 (c) shows the relationship between the coke bed height and η _CO when the gas flow rate in the furnace changes.

FIG. 4 is a relationship diagram between a stock level and η _CO .

FIG. 5 (a) is a diagram showing the relationship between furnace temperature and η _CO during coke mixing of iron-containing dust (self-reducing ore), and FIG. 5 (b) is a graph showing iron-containing dust. FIG. 4 is a diagram illustrating a relationship between a furnace temperature and a reduction rate with and without coke mixing of dust (self-reducing ore lump).

FIGS. 6A to 6C are explanatory diagrams each showing an example of a typical charging method.

[Explanation of symbols]

 Reference Signs List 1 bucket 2 bell 3 movable armor 4 charging guide 5 furnace body 6 exhaust gas pipe 7 tuyere 8 peripheral part 9 central part 10 coke bed

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuhiro Fukasawa 5-3 Tokai-cho, Tokai-shi, Aichi Prefecture Nippon Steel Corporation Nagoya Works (72) Inventor Teruhiko Kokubu 18-18 Fujine, Wagacho, Kitakami-shi, Iwate Prefecture 14 Iwate Steel Corporation (72) Inventor Nao Ohara 18-14 Fujine, Waga-cho, Kitakami City, Iwate Prefecture Iwate Steel Corporation (72) Inventor Koji Ohara 18-14, Fujine, Waga-machi, Kitakami City, Iwate Prefecture Iwate Steel Corporation

Claims (12)

[Claims] An iron source requiring reduction of dust agglomerate, self-reducing agglomerate (C-containing agglomerate), reduced iron having a low metallization rate, HBI (hot briquette reduced iron), DRI (Direct reduced iron), iron scrap, pig iron, return scrap, etc., and an iron source that only needs to be melted and a solid fuel charged into a vertical furnace and installed on the wall of the vertical furnace Normal temperature or 600 ° C from mouth
In the following operation method in which oxygen-containing gas is blown to reduce and dissolve, the average metallization rate of the iron source (average Metallic Fe / T
A method for operating a vertical furnace, characterized by controlling the exhaust gas η _CO of the vertical furnace to the optimum η _CO (gas utilization rate) for reduction and melting based on otal Fe). 2. An average metallization ratio of the iron source.
By determining the optimal η _CO (gas utilization rate) for reduction and dissolution based on the Fe / Total Fe, and adjusting the charging height of the charged material composed of the iron source and the solid fuel in the vertical furnace, The method for operating a vertical furnace according to claim 1, wherein ηCO is controlled. 3. An average metallization ratio of the iron source.
The optimum η _CO (gas utilization rate) for reduction and dissolution is calculated based on Fe / Total Fe), and the weight ratio of C contained in the iron source is determined by the following formula (1). 2. The method according to claim 1, wherein the charging height in the vertical furnace is adjusted for the charge comprising the iron source and the solid fuel for adjusting the charging height of the charge in the vertical furnace. 2. The method for operating a vertical furnace according to 2. 1.5 × C% ≦ ηCO−0.7 × (average M.Fe / T.Fe) ≦ 3.0 × C% (1) where C is C% contained in the iron source. And 0% ≦ C% ≦ 2
0% η _CO : Gas utilization rate (%) (Average M.Fe / T.Fe): Average metallization rate (%) Metallization rate: Metallic iron in iron source (M.Fe) / Total in iron source Iron (T.Fe) Average metallization ratio: Metallization ratio of weighted average of several iron sources 4. An iron source requiring reduction of dust agglomerate, self-reducing agglomerate (C-containing agglomerate), reduced iron having a low metallization rate, HBI (hot briquette reduced iron), DRI (Direct reduced iron), iron scrap, pig iron, return scrap, etc., and an iron source that only needs to be melted and a solid fuel charged into a vertical furnace and installed on the wall of the vertical furnace Normal temperature or 600 ° C from mouth
In the following operation method in which oxygen-containing gas is blown to reduce and dissolve, the average metallization rate of the iron source (average Metallic Fe / T
otal Fe) to determine the optimal η _CO (gas utilization rate) for reduction and dissolution, and control the η _CO by adjusting any of the coke bed height, tuyere diameter, and tuyere protrusion position A method for operating a vertical furnace, comprising: 5. An average metallization ratio of said iron source (average metallicity).
Calculate the optimal η _CO (gas utilization rate) for reduction and dissolution based on the following formula (1) based on Fe / Total Fe) and adjust any of the coke bed height, tuyere diameter, and tuyere protrusion position. The method for operating a vertical furnace according to claim 4, wherein the η _CO is controlled thereby. 1.5 × C% ≦ ηCO−0.7 × (average M.Fe / T.Fe) ≦ 3.0 × C% (1) where C is C% contained in the iron source. And 0% ≦ C% ≦ 2
0% η _CO : Gas utilization rate (%) (Average M.Fe / T.Fe): Average metallization rate (%) Metallization rate: Metallic iron in iron source (M.Fe) / Total in iron source Iron (T.Fe) Average metallization ratio: Metallization ratio of weighted average of several iron sources 6. The η _CO is controlled by adjusting any one of a height of a coke bed, a tuyere diameter, and a tuyere projecting position according to the particle size of the solid fuel. Item 4. The method for operating a vertical furnace according to Item 4. 7. The tuyere is provided at least at two positions in the furnace height direction, and the tuyere is provided in accordance with the particle size of the solid fuel and the average metallization ratio (average Metallic Fe / Total Fe) of the iron source. The method for operating a vertical furnace according to claim 2 or 4, wherein the blowing ratio of each tuyere provided in the height direction is adjusted. 8. Iron sources requiring reduction of dust agglomerate, self-reducing agglomerate (C-containing agglomerate), reduced iron having a low metallization rate, HBI (hot briquette reduced iron), DRI (Direct reduced iron), iron scrap, pig iron, return scrap, etc., and an iron source that only needs to be melted and a solid fuel charged into a vertical furnace and installed on the wall of the vertical furnace Normal temperature or 600 ° C from mouth
In the following operating method of blowing and reducing and dissolving oxygen-containing gas, an iron source with a high metallization rate is mixed with a solid fuel and charged into the furnace center of a vertical furnace, and an iron source with a low metallization rate is When mixed with solid fuel and charged into the periphery of a vertical furnace, the optimal η _CO (gas utilization rate) for reduction and dissolution based on the average metallization rate (average Metallic Fe / Total Fe) of the iron source And controlling the η _CO by adjusting the charging height of the charge comprising the iron source and the solid fuel in the vertical furnace. 9. An average metallization ratio of the iron source.
9. The method for operating a vertical furnace according to claim 8, wherein the following equation (1) is applied when obtaining the optimum η _CO (gas utilization rate) for reduction / dissolution based on Fe / Total Fe). 1.5 × C% ≦ η _CO −0.7 × (average M.Fe / T.Fe) ≦ 3.0 × C% (1) where C is C% contained in the iron source. 0% ≦ C% ≦ 2
0% η _CO : Gas utilization rate (%) (Average M.Fe / T.Fe): Average metallization rate (%) Metallization rate: Metallic iron in iron source (M.Fe) / Total in iron source Iron (T.Fe) Average metallization ratio: Metallization ratio of weighted average of several iron sources 10. The height of the coke bed at the lower part of the vertical furnace is adjusted to a predetermined height according to the particle size of the coke as the solid fuel and the blowing conditions from the tuyere. The method for operating a vertical furnace according to claim 7. 11. The iron source and the solid fuel are mixed, and the weight ratio of C contained in the solid fuel and Fe contained in the iron source in the charge to be charged into the furnace center of the vertical furnace is 0.01. The method for operating a vertical furnace according to claim 8, wherein the value is from 0.05 to 0.05. 12. The method according to claim 12, wherein the height of the periphery of the furnace with respect to the center of the furnace of the charge comprising the iron source and the solid fuel charged into the vertical furnace is adjusted according to the average metallization ratio of the iron source. The method for operating a vertical furnace according to claim 8, characterized in that: