RU2780654C1 - Method for operation of the blast furnace - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to a method for introducing iron ore and coal into a blast furnace. The method includes pulverization of coal to produce pulverized coal, pulverization of iron ore to produce pulverized iron ore and the introduction of pulverized coal and pulverized iron ore through a tuyere. At the same time, iron ore is introduced, which has losses during calcination greater than or equal to 9 wt. %, and less than or equal to 12 wt. %. The consumption when introducing pulverized coal is set to be greater than or equal to 150 kg/t of cast iron, and the consumption when introducing pulverized iron ore is set to be greater than or equal to 2.5 kg/t of cast iron and less than or equal to 50 kg/t of cast iron. Iron ore and coal are pulverized together.

EFFECT: invention provides an improvement in gas permeability in the lower part of the furnace by introducing pulverized iron ore from the tuyere.

2 cl, 15 dwg, 7 tbl

Description

FIELD OF TECHNOLOGY

[0001] The present invention relates to a method for operating a blast furnace.

BACKGROUND OF THE INVENTION

[0002] Typically, in a blast furnace, molten iron is produced by: alternately loading layers of coke and iron ore (iron ore, sintered iron ore, pellets, etc.) from the top of the furnace; and introducing pulverized coal together with hot air (air, oxygen) from the tuyere to reduce and melt iron ore. In order to carry out stable operations in such a blast furnace having a solid/gas countercurrent transfer layer, it is important to maintain favorable gas permeability inside the furnace, since a decrease in gas permeability prevents stable operation.

[0003] For example, coke plays the role of a spacer that provides gas permeability within the oven; thus, a certain amount of coke should be used. However, if the use of coke can be reduced and the gas permeability inside the furnace can be reduced, expensive coke can be replaced with inexpensive pulverized coal, whereby the amount of coke used (coke consumption) can be reduced.

In recent years, it has become common to carry out blast furnace operations in which pulverized coal is introduced from the blast furnace lance, the pulverized coal being used as a fuel to replace part of the coke (reducing agent). Recently, operations have been constantly performed to introduce highly crushed coal, while the amount of pulverized coal used is up to 150 kg/t of pig iron or more.

[0004] Herein, pulverized coal to be blown into a blast furnace contains ash at a content of about 10 wt.% (hereinafter simply referred to as "%"), ash consisting of 50-60% SiO ₂ , 20-30% Al ₂ O ₃ , as well as Fe ₂ O ₃ , CaO, etc., and mainly consisting of acidic components.

Thus, if the flow rate when the pulverized coal is introduced increases, then the acid slag produced from the ash in the pulverized coal increases, thereby increasing the viscosity and/or the melting point of the slag layer (commonly referred to as "bird's nest slag") that accumulates in the " bird's nest" inside the circulation zone. Accordingly, the amount of bird's nest slag (hanging) increases, resulting in a decrease in gas permeability at the bottom of the blast furnace (see FIG. 15).

[0005] Regarding the aforementioned decrease in gas permeability at the bottom of a blast furnace, Patent Document 1 discloses a method in which the productivity of a blast furnace is increased and coke consumption is reduced by using iron ore having a bound water content of greater than or equal to 2.0 wt%, as a raw material for the blast furnace process. Specifically, the method according to Patent Document 1 includes: reducing iron ore having a bound water content of greater than or equal to 2.0 mass% to have a reduction percentage greater than or equal to 30%, followed by charging and/or introducing iron ores into a blast furnace as raw material for the blast furnace process. The reduction of iron ore is carried out in a reducing atmosphere containing CO and/or H ₂ at a high temperature greater than or equal to 400°C.

[0006] In addition, Patent Document 2 discloses a method relating to a method for operating a blast furnace, a method specifically relating to slowing down the growth of Si in molten iron that has been produced. Specifically, the method described in Patent Document 2 includes: simultaneously introducing pulverized ore and pulverized coal from each tuyere, making the consumption of pulverized ore and pulverized coal equivalent to the consumption of ore and coke charged from the top of the blast furnace. In the method of Patent Document 2, it is considered that by introducing pulverized ore in addition to pulverized coal, the growth of Si is slowed down, and furthermore, due to the fact that the consumption of pulverized ore and pulverized coal when introduced is equivalent to the consumption of ore and coke loaded from upper part of the blast furnace, the distribution of the charged material in the furnace does not change, thereby facilitating the control of the distribution of the charged material. Moreover, it is reported that due to the injection by separation into separate tuyeres, the amount injected from each tuyere is small, and the effect that equipment problems are unlikely to occur can be achieved.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Unexamined Patent Application Application No. H09-165607

Patent Document 2: Japanese Unexamined Patent Application Application No. H04-002708

SUMMARY OF THE INVENTION

PROBLEMS SOLVED BY THE INVENTION

[0008] In the method according to Patent Document 1, the flow rate when non-dehydrated iron ore is introduced reaches 100 kg/t iron, and there is a significant temperature loss; thus, the amount of accumulated slag of the bird's nest (hanging) cannot decrease.

In addition, with regard to the method disclosed in Patent Document 2, the consumption when pulverized coal is introduced is already 0 to 40 kg/t iron, whereby the amount of bird's nest slag (hanging) cannot decrease. Moreover, the characteristics of the ore are not disclosed in Patent Document 2; thus, during the introduction, there is a possibility that the temperature of the molten iron in the blast furnace will decrease due to insufficient reduction of the ore, resulting in an additional increase in the consumption of coke. In addition, the method of the cited publication 2 is a method related to the reduction of Si in molten iron; thus, unlike the present invention, Patent Document 2 does not aim to improve the gas permeability in the bottom of the blast furnace.

[0009] The present invention has been made based on the above problems, and an object of the present invention is to provide a blast furnace operation method that can improve the gas permeability at the bottom of the blast furnace by introducing pulverized iron ore from a tuyere.

TROUBLESHOOTING TOOLS

[0010] In order to solve the above problems, the operation method of the blast furnace of the present invention includes the following technical steps.

Specifically, the operation method of the blast furnace of the present invention includes: pulverizing coal to produce pulverized coal and pulverizing iron ore to produce pulverized iron ore; and introducing pulverized coal and pulverized iron ore from the lance, characterized in that the iron ore ignition loss is greater than or equal to 9 wt% and less than or equal to 12 wt%, the pulverized coal injection rate is greater than or equal to 150 kg/t iron, and the consumption when introducing pulverized iron ore is greater than or equal to 2.5 kg/t iron and less than or equal to 50.0 kg/t iron.

[0011] It should be noted that iron ore and coal are preferably pulverized together.

EFFECTS OF THE INVENTION

[0012] According to the method of operating the blast furnace of the present invention, it is possible to improve the gas permeability in the bottom of the blast furnace by introducing pulverized iron ore from the tuyere.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a drawing schematically illustrating the processing carried out by a lance in the method of operating a blast furnace according to the present invention.

2 is a graph showing how the viscosity of a slag containing 15% Al ₂ O ₃ and 5% MgO and having a basicity of 1.2 changes according to the percentage of FeO.

3 is a graph showing how the viscosity of a slag containing 40 mol% SiO ₂ changes according to the concentration of Fe ₂ O ₃ mol%.

4 is a graph showing the relationship between loss on ignition of coal used for pulverized coal and the Hardgrove index.

Fig. 5 is a graph showing the relationship between specific surface area and loss on ignition of coal used for pulverized coal.

Fig. 6 is a graph showing the relationship between the flow rate when pulverized iron ore is introduced and the amount of pressure loss change in the blast furnace.

Fig. 7 is a graph showing the result of using a real blast furnace to investigate the relationship between the flow rate when pulverized iron ore is introduced and the amount of pressure loss change in the blast furnace.

Fig. 8 is a block diagram showing the operation method of the present invention.

Fig. 9 is a block diagram showing a procedure for calculating the amount of pressure loss change in a blast furnace.

10A to 10H are graphs showing each physical property value obtained in the step of calculating the amount of pressure loss change in the blast furnace.

11 is a drawing showing a torque meter used in measuring slag viscosity.

12 is a graph showing the temperature dependence of viscosity in a slag with a basicity of 0.6.

13 is a graph showing the temperature dependence of viscosity in a slag with a basicity of 1.0.

Fig. 14 is a graph showing the relationship between slag basicity and viscosity in the case where the flux consumption is 20 kg/t iron.

Fig. 15 is a drawing schematically illustrating the processing carried out by a tuyere in a conventional blast furnace operation.

DESCRIPTION OF EMBODIMENTS

[0014] Hereinafter, embodiments of the method for operating the blast furnace 1 according to the present invention will be described in detail based on the drawings.

As shown in fig. 1, the operation method of the blast furnace 1 includes: pulverizing coal to produce pulverized coal and pulverizing iron ore to produce pulverized iron ore; and introducing pulverized coal and pulverized iron ore from the lance 2, characterized in that the iron ore ignition loss is greater than or equal to 9 wt.% and less than or equal to 12 wt.%, the pulverized coal injection rate is greater than or equal to 150 kg/t iron , and the consumption when introducing pulverized iron ore is greater than or equal to 2.5 kg/t iron and less than or equal to 50.0 kg/t iron ("kg/t iron", as above, means mass (kg) per ton of molten iron ; the same applies below).

[0015] In particular, with respect to the blast furnace 1 for which the operation method of the present invention is carried out, coke and iron ore raw materials (iron ore, sintered iron ore, pellets, etc.) are alternately charged in layers from the top of the furnace, pulverized coal is introduced together with hot air (air, oxygen) from the tuyere 2, and molten pig iron is obtained by reduction and melting of iron ore. In order to carry out stable operations using the blast furnace 1 having the solid/gas countercurrent transfer layer, it is important to favorably maintain the gas permeability inside the furnace, since the decrease in gas permeability prevents stable operations. The coke plays the role of a spacer, which ensures gas permeability inside the furnace; however, if the gas permeability inside the furnace can be made favorable, expensive coke can be replaced with inexpensive pulverized coal, whereby the amount of coke used (coke consumption) can be reduced.

[0016] In the operation method of the present invention as described above, pulverized coal being coal that has been ground and pulverized iron ore being iron ore that has been ground are introduced from the tuyere 2.

For example, pulverized coal has a maximum particle size of less than or equal to 1000 μm and an average particle size of 50 μm, and is introduced into the blast furnace 1 at a rate greater than or equal to 150 kg/t of pig iron. In other words, the operation method of the present invention is directed to high pulverized coal consumption operations, and is a method whose purpose is to improve gas permeability inside the furnace in high pulverized coal consumption operations and reduce coke consumption in blast furnace 1 operations (mass (kg) of coke required to produce 1 ton of molten iron).

[0017] In addition, pulverized coal contains ash with a content of about 10 wt.% (hereinafter simply referred to as "%"), and the ash consists of 50-60% SiO ₂ , 20-30% Al ₂ O ₃ and also Fe ₂ O ₃ , CaO, etc., mainly consists of acid components.

Thus, when the pulverized coal injection rate becomes high, the acidic slag produced from the pulverized coal increases, thereby increasing the viscosity and/or the melting point of the slag layer (commonly referred to as "bird's nest slag 4") that accumulates in the interior of the zone. circulation (which is the bird's nest area 3) as shown in FIG. 1, whereby the gas permeability decreases (pressure loss increases). As a result, the gas permeability in the lower part of the blast furnace 1 is reduced.

[0018] In addition, the method of operation of the present invention includes the introduction of iron ore from tuyere 2 in addition to pulverized coal. Such introduction of iron ore is already known from Japanese Unexamined Patent Application No. 05-214414 and the like. For example, as shown in FIG. 2 and the like, it is reported that when iron ore (Fe ₂ O ₃ ) is injected from a lance, for example, while reaching the bird's nest area, 10% to 40% is Fe ₃ O ₄ to FeO while part of the iron ore is reduced to metallic iron, and that when iron ore and coal are pulverized at the same time, coal and iron ore are close to each other and the reduction percentage is increased. In addition, figures 2 and 3 show that, as a rule, the viscosity decreases when the iron oxide(s) component(s) (FeO, Fe2O3) is/are added to the acid slag.

[0019] In other words, as can be seen from the above figure 2 and the like, when coal and iron ore are introduced together from the tuyere, a part of the iron ore is reduced in the circulation zone, resulting in the reduced and pulverized iron ore entering the bird's nest slag within the circulation zone. As a result, the viscosity of the slag decreases due to the iron oxide component(s) of the reduced and pulverized iron ore, and the bird's nest slag becomes prone to dripping. Accordingly, it is believed that an effect can be obtained in which the amount of slag that accumulates in the bird's nest is reduced, resulting in a decrease in slag retention, thereby improving gas permeability at the bottom of the furnace (reducing pressure loss at the bottom of the furnace).

[0020] However, in a case in which the iron oxide contained in the pulverized iron ore reacts with the coke in the furnace, it will lead to a direct reduction reaction (for example, FeO+C→Fe+CO). Because this reaction is accompanied by significant heat absorption, it is possible to lower the temperature of the molten iron, which causes the molten iron to cool. In other words, pulverized iron ore cannot be over-introduced with the mere intention of making the gas permeability favorable.

Thus, in the operation method of the blast furnace 1 of the present invention, the characteristics of the iron ore and the injection rate are adjusted to appropriate conditions so as to both improve the gas permeability and prevent cooling.

[0021] The characteristics of the iron ore as a raw material for the pulverized iron ore in the operation method of the present invention, as well as the consumption when the pulverized iron ore is introduced, will be described next.

Pulverized iron ore is obtained by grinding iron ore. Iron ore, which is a raw material for pulverized iron ore, has a loss on ignition greater than or equal to 9 wt.% and less than or equal to 12 wt.%. Loss on ignition (LOI, loss on ignition,) in iron ore is a measure measured in accordance with JIS M8850; in the case of iron ore, the WFP indicates mainly the content of bound water.

[0022] Thus, the control of loss on ignition (LOI) of iron ore aims to make the grinding characteristic of pulverized iron ore equivalent to the grinding characteristic of coal for pulverized coal, thereby making the iron ore easy to grind (easily finely ground), whereby the particle size and iron ore and coal in the case of grinding is the same. HGI (Hardgrove Index, Hardgrove Grindability Index) is an index expressing the grindability characteristic shown in the Grindability Strength Test of Coal (JIS M8801). Grinding characteristics of various types of iron ore are determined in accordance with the procedure for testing coal for grinding according to the Hardgrove method; determining the relationship between grinding performance and loss on ignition (LOI) results in a relationship such as the relationship shown in FIG.

[0023] As shown in FIG. 4, when the loss on ignition (LOI) of the iron ore is high, the HGI of the iron ore also becomes high, whereby the iron ore is easier to grind (easier to make fine).

In this document, the HGI of the coal used as the pulverized coal for the blast furnace 1 is usually 40 to 90. The HGI of the coal is set to greater than or equal to 40 because when the HGI falls below 40, the pulverizing performance deteriorates and the particle size increases, in as a result, equipment wear, etc. may occur. In addition, the HGI of the coal is set to less than or equal to 90, because when the HGI exceeds 90, the coal that is too finely ground may cause clogging of the pipe.

[0024] In the case where the loss on ignition is greater than or equal to 9 wt.% and less than or equal to 12 wt.%, the HGI of iron ore becomes 40-90, similar to the HGI of coal for pulverized coal, and the particle size of pulverized iron ore, when the iron ore is pulverized, it becomes similar to the particle size of pulverized coal (the maximum particle size is less than or equal to 1000 µm, the average particle size is 50 µm), which can prevent equipment wear and transport pipe rupture.

In addition, as shown in FIG. 5, the loss on ignition (LOI) of iron ore and the specific surface area (BET method) are positively correlated: when the loss on ignition increases, the specific surface area also increases.Pulverized iron ore (iron ore) having a high specific surface area reacts more easily in the circulation zone, thereby also allowing the reduction percentage of pulverized iron ore to be improved.

[0025] In connection with the above, at the time when the pulverized iron ore enters the bird's nest slag 4 in the inside of the circulation zone, the accumulation of the bird's nest slag 4 can be reduced by lowering the viscosity of the bird's nest slag 4. As a result, the pressure loss in the blast furnace 1 is reduced, so that the gas permeability in the lower part of the blast furnace 1 can be favorable.

It should be noted that in the case where the loss on ignition (LOI) of the iron ore is less than 9% by mass, pulverization is difficult due to the use of low HGI iron ore as the raw material. As a result, the particle size of the pulverized iron ore increases, and significant wear and tear of the equipment may occur, possibly leading to malfunctions such as rupture of transport pipes, leading to termination of use. Moreover, the iron ore, in which the loss on ignition (LOI) is low, has a low specific surface area, whereby the percentage of reduction in the circulation zone decreases during injection from tuyere 2. Thus, there is increased heat absorption due to the direct reduction reaction with coke in the core of the furnace in the inner part of the circulation zone, which helps to reduce the temperature of the molten iron (reduction of heat in the furnace). As a result, the pressure loss, on the contrary, increases, as a result of which it may not be possible to obtain an effect by introducing pulverized iron ore.

[0026] In addition, with regard to the case in which the loss on ignition (LOI) of iron ore exceeds 12 mass%, iron ore having such a loss on ignition does not exist; thus, the case when the SPP exceeds 12 wt.% is excluded.

The following describes the flow rate when introducing pulverized iron ore.

Using the calculation method from Fig. 9 described below, the relationship between the flow rate when pulverized iron ore was introduced and the pressure loss reduction amount was calculated. The calculation results are shown in Fig.6. With an increase in consumption with the introduction of pulverized iron ore, the viscosity of the bird's nest slag 4 decreases, and the linear flow rate of the drops increases, resulting in a decrease in the hanging of the slag (the amount of accumulation of slag decreases). As a result, the amount of pressure loss reduction increases. However, when the flow rate upon introduction of pulverized iron ore becomes greater than or equal to 20 kg/t iron, the amount of slag in the bird's nest area increases, thereby reducing the pressure loss reduction amount due to the influence of the slag temperature decrease. It should be noted that when the flow rate when introducing pulverized iron ore is increased to more than 50 kg/t iron, the pressure loss will exceed the condition in which the flow rate when introducing pulverized iron ore is 0 kg/t iron (basic), so that the effect will be lost. .

[0027] It should be noted that the results in Fig. 6 described above were calculated in accordance with the calculation methodology disclosed in Fig. 9, but when tests are carried out using an actual blast furnace, results similar to those shown in Fig. 7 are obtained. .

As shown in FIG. 7, when the operations were carried out according to the procedure described in FIG. how the pressure loss was reduced to that shown in FIG. 6 when the injection rate was 2.5 kg/t iron. This is believed to be due to the injection rate being low when the injection was carried out at 1.3 kg/t iron, and the pulverized iron ore could not be distributed equally among the tuyeres 2, the number of which was 25 in the circumferential direction. , which led to an imbalance in the circumferential balance and thus prevented the effect of improving the gas permeability from being obtained. Accordingly, in the operation method of the present invention, the lower limit of the flow rate when introducing pulverized iron ore, in which the effect of the present invention is exhibited, was set to be greater than or equal to 2.5 kg/t iron.

[0028] In addition, in the case where the injection rate of pulverized iron ore exceeds 50 kg/t iron, the sensible heat of injection (heat absorption amount) increases, whereby the temperature (T) of the bird's nest slag is lowered. In addition, the amount (W) of the inflowing slag is also increased, whereby the pressure loss is increased above the base before injection.

It should be noted that pulverized iron ore as described above means iron ore subjected to pulverization (pulverization) processing with a roller crusher, ball mill or the like, and means that the iron ore has been ground to equal to or less than 1000 µm . Moreover, pulverized coal means coal subjected to pulverization (pulverization) processing by the same roller crusher, ball mill or the like, and means that the coal has been ground to equal to or less than 1000 µm.

EXAMPLES

[0029] Hereinafter, the effects of the operation method of the blast furnace 1 of the present invention are described in detail by way of comparative examples and examples.

First, the change in the amount of reduction in pressure loss with respect to the flow rate with the introduction of pulverized iron ore was determined in accordance with the calculation method disclosed in Fig.9. It should be noted that the "pressure loss reduction amount" means the extent to which the pressure loss has been reduced from that before administration; for example, "increasing the pressure loss reduction amount" means reducing the pressure loss, and "decreasing the pressure loss reduction amount" means increasing the pressure loss. On the other hand, "pressure loss change amount" means the extent to which the pressure loss has increased or decreased from that before administration. "Increase in pressure loss change amount" means an increase in pressure loss, while "decrease in pressure loss change amount" means, as written, that the pressure loss has decreased.

[0030] In addition, hereinafter, the results of the method of operation of the present invention are described using the symbols defined as shown in Table 1.

[0031] Table 1

Name of indicator Unit Description Formula(s) µ mPa s Viscosity of bird's nest slag (one) u m/s Linear flow rate of slag droplets from a bird's nest (12) h - Hang (Fig. 10G) (2), (3) S m ² Cross-sectional area of compacted layer (2) W kg/t pig iron Amount of bird's nest slag (Fig. 10C) being shoulder slag+pulverized coal slag+pulverized iron ore (2) ∆P kPa Pressure loss (3) L m bird's nest height (3) k1 - Factor (150) (3) k2 - Factor (1.75) (3) Ɛ - Share of voids (3) _dW m Average compacted bed size (3) V Nm ³ /min Gas volume (3) _g Pass Gas viscosity (3) _ρg kg / m ³ Gas density (3)

[0032] First, the upper injection rate limit (upper injection limit) of pulverized iron ore from tuyere 2 will be described. slag 4 bird's nest) depending on the consumption during the introduction of pulverized iron ore. This calculation method was performed based on the mathematical model disclosed in "Iron and Steel, Xiao et al., Vol. 78, 1992, page 1,230." The results of the calculation are shown in Fig. 10A, and the coefficients for the calculation are shown in Table 2.

[0033] Table 2

Name of indicator Unit Numerical value Air consumption Nm ³ /min 7600 Oxygen volume Nm ³ /min 550 Blast temperature °C 1180 Humidity g/Nm ³ ten Number of lances number 40 Consumption when introducing pulverized coal kg/t pig iron 215 Average particle size of pulverized coal micron fifty Consumption when introducing pulverized iron ore kg/t pig iron 0-50 Average particle size of pulverized coal micron fifty

[0034] At this time, based on the premise that only molten iron ore contributes to lowering the viscosity of the bird's nest slag 4, the ratio between molten iron ore (flux) and unmolten iron ore was determined from the injection rate and the percentage of pulverized iron ore melted. The ratio between molten iron ore and unmolten iron ore thus determined is shown in FIG. 10b.

In addition, based on the premise that the entire amount of the introduced pulverized iron ore must be added to the slag output of the bird's nest slag 4, the relationship between the injection rate of the pulverized iron ore and the amount of the bird's nest slag 4 (w) was determined. The relationship thus determined is shown in FIG. 10C. It should be noted that with respect to the components of the slag 4 of the bird's nest, based on the examination of the samples, it was calculated that the ratio of the components of the slag of the shoulders to the components of the slag in the pulverized coal of the dust was 0.18:1.00. Moreover, with respect to the components and the amount of the bird's nest slag 4 in the state in which the injection rate was 0, calculations were made on the assumption that the basicity (C/S) was constant at 0.75 and the amount of bird's nest slag was 64 kg/t pig iron. It should be noted that the basicity (C/S) is the ratio of CaO (wt.%) to SiO ₂ (wt.%) contained in the slag.

[0035] Moreover, based on the premise that the introduced pulverized iron ore is directly reduced by the entire amount of coke, the heat absorption amount (part of the absorbed heat) of the reduction reaction was subtracted from the boundary temperature of the circulation zone (bird's nest temperature 3), and the dependence between the flow rate at the introduction of pulverized iron ore and the temperature of the slag 4 bird's nest. The dependence thus determined is shown in FIG. 10D.

Next, the viscosity (µ) of the 4 bird's nest slag was determined. The temperature dependence of the viscosity of the slag 4 bird's nest at each flow rate of the slag was determined by experiment.

[0036] Using the temperature variation of the bird's nest 3 (bird's nest slag temperature 4) in FIG. 10D, the viscosity (µ) of the bird's nest slag 4 was determined from the experimental values (described in detail below). It should be noted that the value at which the flow rate when introducing pulverized iron ore was 0 was calculated using the viscosity estimation formula described in "Iron and Steel, Sugiyama et al., Vol. 73, 1987, page 2,044".

The relationship between the injection rate of pulverized iron ore and the viscosity (µ) of the bird's nest slag 4 determined by the above procedure is shown in FIG. 10E.

[0037] Moreover, with respect to the linear flow rate of slag droplets (µ), based on the relational expression described in "Materials and Processes, Kato et al., Vol. 28, 2015, S25", the relationship between the flow rate when introducing dust iron ore and linear drip rate. The relationship thus determined is shown in FIG. 10F.

In addition, with regard to the delay (h), based on the relational expression described in "Materials and Processes, Kato et al., Vol. 28, 2015, S25", the relationship between the flow rate when introducing pulverized iron ore and the delay (h ). The relationship thus determined is shown in FIG. 10G.

[0038] At this time, assuming that the cross-sectional area of the compacted layer is 6.67 m ² (constant), the values in FIG. 10C were used for the amount of slag (W).

Finally, the relationship between the flow rate when pulverized iron ore was introduced and the pressure loss reduction amount (pressure loss change amount) was determined. The pressure loss was calculated based on the calculation formula described in "Iron and Steel, Fukutake et al., Vol. 66, 1980, page 1,974". It should be noted that the calculation coefficients are as shown in Table 3. The thus determined relationship between the flow rate of the introduction of pulverized iron ore and the amount of pressure loss change is shown in FIG. 10H.

[0039] Table 3

Name of indicator Unit Meaning Consumption when introducing pulverized coal kg/t pig iron 215 Consumption when introducing pulverized iron ore kg/t pig iron 0-50 V: Volume of gas in the shoulders Nm ³ /min 11340 oven temperature °C 1180 Furnace pressure kPa 420 S: Cross-sectional area of the densified layer m ² 6.67 L: Bird's nest height m 7.5 ρ _g : Gas density kg / m ³ 0.641 µ _g : Gas viscosity Pass 0.00000627 Ɛ: Void fraction of compacted bed - 0.29 d _W : Average coke size m 0.023

[0040] It should be noted that the "volume of gas in the shoulders" in Table 3 is a calculated value of the total volume of gas formed before the lance due to, for example, combustion of coke in front of the tuyere due to blast: air blown from the lance, oxygen for enrichment of the blast with oxygen, moisture content in the blast, etc.; and combustion of additional fuel such as pulverized coal and is indicated in Nm ³ /min. A method for calculating this volume of gas in the shoulders, for example, is described in "Iron and Steel, Vol. 48 (1962), No. 12, page 1,606".

[0041] As shown in FIG. 10H, when the introduction of pulverized iron ore is increased, the viscosity of the bird's nest slag 4 decreases, and the pressure loss reduction amount increases (pressure loss decreases). However, if the flow rate when introducing pulverized iron ore is set to be greater than or equal to 20 kg/t iron due to the effect of reducing the amount of slag in the bird's nest area and lowering the temperature of the bird's nest slag 4, the pressure loss reduction amount decreases (pressure loss increases). If the injection rate of pulverized iron ore is increased to more than 50 kg/t iron, the pressure loss is increased by an excess of this, when the injection rate of pulverized iron ore is 0 kg/t iron, whereby the effect of introducing pulverized iron ore is lost.

[0042] Incidentally, in order to derive the viscosity of the bird's nest slag 4 from the bird's nest temperature 3 described above, it is preferable to conduct a preliminary experiment to understand how the flow rate of the molten iron ore mixture (flux), the temperature of the slag, and/or the like . affect the viscosity of the slag.

With respect to the preliminary experiment described above, as a preliminary preparation, a torque meter 5 such as shown in FIG. 11 is prepared, and the ceramic anti-oxidation paste is applied to the pure iron crucible 7 and the pure iron rotor 6 of the torque meter 5. In addition, the pure iron rotor 6 of the torque meter 5 is adjusted using correction fluid JS1000, and the relationship between rotation speed and torque is determined. When such a correction is carried out, a primary regression equation is obtained, in which y=ax+b is obtained, allowing the rotor coefficient (K0) to be determined. It should be noted that the definition can be carried out as follows:

rotor factor: K0=[standard viscosity (mPa s)]/[regression factor b].

[0043] When the rotation ratio is obtained in this way, the reactant (slag-containing flux) mixed in a predetermined formulation (the formulation is shown in the following Table 4) is loaded into the pure iron crucible 7. The pure iron crucible 7 containing the reagent is then heated to a predetermined temperature using an electric furnace to melt the reagent. The heating temperature is 1300°C, 1350°C, 1400°C, 1450°C and 1500°C. The rotor (pure iron rotor 6) attached to the torque meter 5 is inserted into the center of the molten slag, and the rotation of the rotor starts. When the change in the detected torque becomes 0.1%/min, the viscosity is considered to have stabilized, the measurement is continued for 1 minute after the viscosity stabilizes, and the values obtained during the 1 minute interval are considered to be the torque measurement values. After the measurement, the rotation is stopped and the experiment is terminated. It should be noted that cases in which the viscosity did not stabilize were excluded from the data.

[0044] The measurement values for 1 minute in which the torque stabilized as described above are taken as the measurement values of the torque (torque (%)). The resulting torque (%) is substituted into the following equation:

viscosity ƞ (mPa s)=torque (%)xK0÷rotation speed (rpm), and

slag viscosities ƞ (mPa s) are determined, for which flux costs differ. Flux viscosities ƞ (mPa s) determined in this way are shown in Table 4.

[0045] Table 4

- Flux consumption _SiO2 CaO _{Al2O3 _} MgO Fe ₃ O ₄ Total C/S kg/t pig iron % % % % % % - one 5.0 46.9 28.1 15.0 5.0 5.0 100 0.60 2 10.0 43.7 26.3 15.0 5.0 10.0 100 0.60 3 20.0 37.5 22.5 15.0 5.0 20.0 100 0.60 four 30.0 31.2 18.8 15.0 5.0 30.0 100 0.60 5 5.0 37.5 37.5 15.0 5.0 5.0 100 1.00 6 10.0 35.0 35.0 15.0 5.0 10.0 100 1.00 7 20.0 30.0 30.0 15.0 5.0 20.0 100 1.00 eight 30.0 25.0 25.0 15.0 5.0 30.0 100 1.00

[0046] Thus, the change in the viscosity of the bird's nest slag 4 (µ) with respect to the flow rate when pulverized iron ore was introduced was determined in the case in which the basicity of the slag C/S was 0.6, and in the case in which the basicity C/ S was 1.0 in a temperature dependent manner. Collectively, the obtained results of the temperature dependence of each of the thus obtained slag viscosities (µ) are shown in FIGS. 12 and 13.

Each viscosity was determined from the relational expression in FIG. 10D, wherein the relationship between basicity and viscosity of the slag was determined as an exponential function. As one example, the relationship between slag basicity and viscosity organized based on the case in which the flux consumption was 20 kg/t iron is shown in FIG. From the relational expression in FIG. 14, it is possible to determine the viscosity at a basicity of 0.75.

[0047] In accordance with the viscosity calculation procedure described above, when the relationship between the injection rate and the viscosity of pulverized iron ore is plotted, the relationship shown in FIG. 10E is obtained.

According to the relationship shown in FIG. 10E obtained from the above procedure, or in other words, the relationship shown in FIG. pressure is negative) when the consumption during the introduction of pulverized iron ore is greater than or equal to 0 kg/t of pig iron and less than or equal to 50 kg/t of pig iron; thus, it is possible to determine the upper limit of the flow rate when introducing pulverized iron ore.

[0048] It should be noted that the details of the above calculation methodology can be summarized in Table 5.

[0049] Table 5

Name of indicator Content Notes (A) Method for calculating the melting ratio of powdered iron ore In accordance with this model, the recovery percentage, the melt percentage, and the temperature at the boundary of the circulation zone (bird's nest temperature) were calculated (FIG. 10A).
Molten iron ore helps reduce the viscosity of the bird's nest as a flux material.
Unmelted iron ore does not contribute to reducing the viscosity of the slag (Fig. 10B) Iron and Steel, Xiao et al., Vol. 78, 1992, page 1,230 (B) Slag viscosity calculation method The components of the slag are calculated from the percentage of melt, calculated on the basis of a mathematical model of the circulation zone.
The components are an average load of bird's nest slag and molten iron ore (flux). It should be noted that with regard to the slag components of the bird's nest, based on the examination of the samples, it was calculated that the ratio of the slag components in the shoulders to the slag components in the pulverized coal accumulated to 0.17 : 1.00. Based on this, the amount of bird's nest slag was considered to be 64 kg/t iron.
With regard to the temperature of the slag, the temperature at which the heat absorption due to the direct reduction reaction with coke resulting from the introduction of iron ore was subtracted from the temperature of the boundary of the circulation zone (bird's nest area) determined using the mathematical model of the circulation zone, was considered the temperature of the slag ( Fig.10D). The experiment was built according to the Arrhenius equation, and the viscosity of the slag was calculated based on the temperature at which the heat absorption of the slag from arbitrary components was taken into account (Fig. 10E). Fig.11-14 (C) Method for calculating the linear drip rate

Used in FIG. 10F.

Materials and Processes, Kato et al., Vol. 28, 2015, S25 (D) Delay amount calculation method Used in FIG. 10G.

Materials and Processes, Kato et al., Vol. 28, 2015, S25 (E) Pressure loss calculation method Used in Fig. 10H.

Iron and Steel, Fukutake et al., Vol. 66, 1980, page 1,974

[0050] On the other hand, the lower limit of the flow rate when introducing pulverized iron ore can be obtained from an experiment using a real blast furnace (real device test).

The blast furnace 1 used in the actual testing of the device was a real furnace with a volume of 2112 m ³ with a capacity of 1.8 t/m ³ /day. The test operation was carried out for a period of five days while changing the amount of iron ore in the pulverized iron ore introduced into the blast furnace 1 in the following order: 0.0 kg/t iron-1.3 kg/t iron, 2.5 kg/t t of pig iron-5.0 kg/t of pig iron.

[0051] It should be noted that the pulverized iron ore introduced into the actual furnace has a composition as shown in Table 6.

[0052] Table 6

- Fetot _SiO2 CaO RFP HGI wt% wt% wt% wt% - Powdered iron ore 58.5 5.0 0.03 11.1 42.9

[0053] It should be noted that the above-described pulverized iron ore was ground by carrying out processing such as that shown in Fig.8.

The test results of the real device are shown in Table 7 below.

[0054] Table 7

Experiment # Introduction Constituent features, execution conditions Explanation A1 B1 C1 Reducing agent Grade Pulverized coal consumption (PC rate)
Range per point: greater than or equal to 150 kg/t pig iron RFP
Range per point: 9.0-12.0 wt.% Consumption when introducing pulverized iron ore
Range per point: 2.5-50.0 kg/t pig iron Pulverized Coal Consumption (PC) Coke Consumption(CR) Reductant consumption (RAR) Pressure loss (kg/t pig iron) Fitness (% by weight) Fitness (kg/t pig iron) Fitness (kg/t pig iron) (kg/t pig iron) (kg/t pig iron) (kPa)

RAR=PC+CR "good" was chosen for the values in which the pressure loss was lower than the baseline.

EXAMPLES

one 208 good 11.1 good 2.5 M 208 316 524 -1.72 good Permeability resistance
the lower part has decreased over the base 2 208 good 11.1 good 5.0 M 208 316 524 -3.33 good “

COMPARATIVE EXAMPLES

3 208 good - - 0.0 L 208 316 524 0.00 - the foundation four 208 good 11.1 good 1.3 L 208 316 524 0.73 bad Pressure loss increased due to circumferential imbalance.

[0055] Looking at Table 7, the consumption of pulverized coal (consumption when introducing pulverized coal) and in the examples and comparative examples is 208 kg/t iron (satisfies the condition greater than or equal to 150 kg/t iron), and the loss on ignition (LOI) coal, which is a raw material for pulverized coal, is 11.1 wt.% (satisfies the condition of 9.0 wt.% -12.0 wt.%). Moreover, the consumption of the reducing agent (the sum of the consumption of pulverized coal and the consumption of coke) is 524 kg/t pig iron for both examples and comparative examples.

[0056] Operations were carried out while performing the introduction of pulverized iron ore under such conditions for the consumption of pulverized coal, loss on ignition, and consumption of the reducing agent, and the determination was carried out with respect to the manner in which the pressure loss changed from that before the introduction. The measurement results are shown in Table 7.

As shown in Table 7, in the examples, the consumption rate when introducing pulverized iron ore was 2.5 kg/t iron and 5.0 kg/t iron, and the consumption when introducing pulverized coal in the comparative examples was 0.0 kg/t iron and 1 .3 kg/t pig iron.

[0057] With regard to the examples and comparative examples described above, with respect to the examples, the pressure loss change amounts were -1.72 kPa and -3.33 kPa; thus, it can be understood that the pressure loss was lower compared to that before the introduction, and the gas permeability was favorable. In contrast, with respect to the Comparative Examples, the pressure loss change amounts were 0.00 kPa and 0.73 kPa; thus, the pressure loss was the same as before the injection, or was greater than that before the injection, while the gas permeability did not improve.

From the foregoing, it can be concluded that the gas permeability improvement effect can be obtained in the case in which the consumption rate when introducing pulverized iron ore is greater than or equal to 2.5 kg/t iron.

[0058] Comprehensively inferring from the results of the above examples and comparative examples, it can be concluded that by pulverizing coal to obtain pulverized coal and pulverizing iron ore to obtain pulverized iron ore; and introducing pulverized coal and pulverized iron ore from the tuyere 2, while the loss on ignition of iron ore was greater than or equal to 9 wt.% and less than or equal to 12 wt.%, the consumption when introducing pulverized coal is greater than or equal to 150 kg/t of pig iron, and the consumption when introducing pulverized iron ore is greater than or equal to 2.5 kg/t iron and less than or equal to 50.0 kg/t iron, it is possible to improve the gas permeability in the bottom of the blast furnace 1 by introducing pulverized iron ore from the lance 2.

[0059] It should be noted that the embodiments disclosed herein should be considered examples in all respects and should not be construed as limiting. In particular, in the embodiments disclosed herein, indicators that are not clearly disclosed, for example, operating conditions, working conditions, various parameters, as well as dimensions, weights and volumes of structures, do not fall outside the ranges related to the general execution by a person skilled in the art. in the art, and values that can be easily estimated by one of skill in the art have been used.

EXPLANATION OF REFERENCE SYMBOLS

[0060]

1 Domna

2 lance

3 Bird nest area

4 Bird's Nest Slag

5 Torque meter

6 Pure iron rotor

7 Pure iron crucible

Claims (7)

1. A method for introducing iron ore and coal into a blast furnace, including: pulverizing coal to obtain pulverized coal, and pulverizing iron ore to obtain pulverized iron ore; and introduction of pulverized coal and pulverized iron ore through a tuyere, characterized in that introducing iron ore having loss on ignition greater than or equal to 9 wt.% and less than or equal to 12 wt.%, the flow rate when introducing pulverized coal is set to be greater than or equal to 150 kg/t of pig iron, and the flow rate when introducing pulverized iron ore is set to be greater than or equal to 2.5 kg/t of pig iron and less than or equal to 50 kg/t of pig iron. 2. Method according to claim 1, characterized in that iron ore and coal are pulverized together.

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