JP2005307303A - Method for operating blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace by which the aggravation of gas permeability at the lower part of the furnace generated at blowing time of a large quantity of fine powdery coals can effectively be eliminated. <P>SOLUTION: When the blast furnace is operated by injecting the fine powdery coals from a tuyere 2 in the blast furnace 1, material under state of mixing slag-making agent and the fine powdery coal is injected into the blast furnace 1 from the tuyere 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a blast furnace operating method for improving deterioration of air permeability in the lower part of a furnace due to a large amount of pulverized coal.

  Pulverized coal injection into blast furnaces is carried out in many blast furnaces for the purpose of reducing costs by reducing the coke ratio. In recent years, blast furnaces that perform a large amount of pulverized coal injection exceeding 200 kg / thm of pulverized coal per ton of hot metal are also seen. .

However, as the amount of pulverized coal is increased, coke pulverization at the bottom of the furnace is promoted, and the generated powder accumulates in the furnace core, resulting in significant deterioration in air permeability, making it difficult to maintain stable operation. is there. Furthermore, the growth of the raceway shell is pointed out as a factor that deteriorates the furnace bottom air permeability in the operation of blowing pulverized coal. In this raceway shell, the ash content mainly composed of SiO ₂ —Al ₂ O ₃ produced by the combustion of pulverized coal in the raceway becomes a high melting point slag and adheres to the end of the raceway, and a poorly vented layer is formed. Caused by forming. The deterioration of the air permeability due to the raceway shell is not a problem when the ratio of the pulverized coal per ton of hot metal is about 100 kg / thm, but becomes remarkable when the ratio is 150 kg / thm or more.

  In order to suppress the formation and growth of this raceway shell, the CaO content is supplied from the tuyere and assimilated with the high melting point slag derived from the ash content of the pulverized coal, as shown in the state diagram of FIG. It is considered effective to lower the melting point of the way shell to melt and remove it.

  Conventionally, as a method for supplying CaO from a tuyere, for example, pulverized coal blowing or flux blowing considering an ash composition has been proposed.

For example, in Patent Document 1, in a large quantity of pulverized coal injection operation of 100 kg / thm or more per ton of molten iron, the average value of (CaO + MgO) / SiO ₂ exceeds 0.3 as the component composition of ash, and the volatile content Has disclosed a technique of blowing pulverized coal whose content is 20% or more.

  In Patent Document 2, fine dolomite, serpentine, olivine, limestone, etc. are blown as a high basicity fine powder solvent, and the basicity when the basic medium solvent and the ash content in pulverized coal are mixed is 0. The technique which makes it in the range of 0.5-1.3 is disclosed.

  In Patent Document 3, by blowing it as a powdery orienting agent such as fine dolomite, serpentinite, olivine, limestone, etc. with a particle size of 1 mm or more and 2 mm or less, it is possible to reach the end of the raceway without scattering to the outside of the raceway. A technique for reaching and effectively melting and removing the shell formed at the end of the raceway is disclosed.

  In the above-mentioned Patent Document 1, pulverized coal is used, and in the above-mentioned Patent Document 2, it is desirable to use a medium solvent having a particle size of 200 mesh or less. However, in such a fine powder, it was blown from the tuyere. Most of the powder follows the gas flow and scatters outside the raceway and is not effectively used for assimilation with the raceway shell. Therefore, if it is attempted to obtain an effect by blowing a large amount, there is a concern that the combustibility of pulverized coal deteriorates, coke pulverization is further promoted, and accumulation of powder leads to deterioration of air permeability.

On the other hand, in Patent Document 3, by using a powder having a particle size of 1 mm or more and 2 mm or less as a slagging agent, it is effectively assimilated with the raceway shell without following the gas flow and scattering. Although it is said that it is used, in practice, in order to more effectively reach the edge of the raceway with the anti-fake agent, an anti-fouling agent of more than 2 mm is preferable. However, if the particle size exceeds 2 mm in the technique disclosed in Patent Document 3, the slag-forming agent reaches the raceway shell much lower than the flame temperature before the temperature is raised to the melting temperature, and the slag-making agent Is still unsatisfactory because it accumulates in the raceway shell as it is unmelted, resulting in poor air permeability. Therefore, there is a demand for a technique that can effectively eliminate the deterioration of air permeability in the lower part of the furnace that occurs when a large amount of pulverized coal is blown.
JP 2002-206106 A Japanese Patent Publication No. 6-89382 JP 2002-302708 A

  This invention is made | formed in view of this situation, Comprising: It aims at providing the blast furnace operating method which can eliminate effectively the deterioration of the air permeability of the lower part of a furnace generate | occur | produced at the time of a large amount of pulverized coal blowing.

  In order to solve the above problems, the present invention is a blast furnace operating method in which pulverized coal is blown from the tuyere of the blast furnace, and the blast furnace is blown into the blast furnace from the tuyere in a mixed state. Provide blast furnace operation method.

  In the blast furnace operation method according to the present invention, the blast furnace operation method is characterized in that the slagging agent and pulverized coal are mixed so that the slagging agent can be melted by combustion heat of the pulverized coal. I will provide a.

  Furthermore, the present invention provides the blast furnace operating method according to any one of the above, wherein the particle size of the slagging agent reaches a residence time and a melting temperature until the slagging agent is blown into the tuyere and reaches the end of the raceway. Provided is a method for operating a blast furnace, characterized in that the time is equal to or less than the same particle size.

  From the standpoint of staying in the raceway and causing assimilation with the raceway shell, the blowing agent to be blown in is preferably coarse particles that reach the raceway shell without being scattered following the gas flow. An excessively coarse grain-forming agent reaches the raceway shell before melting and causes deterioration of air permeability, so that there is a limit to the particle size of the molding agent to be blown.

  In the method of individually blowing pulverized coal and the slagging agent as in Patent Document 3, the slagging agent is heated to the melting temperature when the particle size of the slagging agent exceeds 2 mm as shown by the wavy line in FIG. Since the raceway shell is reached before, the particle size of the slagging agent is limited to 2 mm. On the other hand, in the present invention, since the pouring agent and pulverized coal are mixed and blown into the blast furnace from the tuyere, the pouring agent is exposed to a high temperature atmosphere by the combustion heat of the pulverized coal immediately after being blown. . For this reason, compared to the case of single blowing, the slagging agent is effectively heated and melts easily, so that a coarser slagging agent can be used, and the loss due to scattering of the stalking agent is further increased. It can be effectively reduced. Therefore, it is possible to effectively improve the deterioration of the air permeability in the lower part of the furnace that occurs when a large amount of pulverized coal is blown.

ただし、
ρ_ｆ：ガス密度（ｋｇ／ｍ_３)
Ｃ_Ｄ：抵抗係数(−)
Ｕ_ｆ：ガス速度(ｍ／ｓ)
ｔ：時間（ｓ）
ρ_ｐ：粒子密度（ｋｇ／ｍ_３）
ｄ_ｐ：粒子径（ｍ）
Ｃ_ｃ：カニンガムの補正係数(―)
上記（１）式を数値計算により解くと、粒子速度と経過時間の関係が得られる。これを積分することで粒子の移動距離と時間の関係が得られる。 The reason will be described below.
The slagging agent supplied to the wing is accelerated following the hot gas blown into the blast furnace. Here, the velocity U _p of the particles following the gas is expressed by the following equation (1).

However,
ρ _f : gas density (kg / m ₃ )
C _D : Resistance coefficient (−)
U _f : Gas velocity (m / s)
t: Time (s)
ρ _p : Particle density (kg / m ₃ )
d _p : particle diameter (m)
C _c : Cunningham correction coefficient (-)
When the above equation (1) is solved by numerical calculation, the relationship between particle velocity and elapsed time is obtained. By integrating this, the relationship between the moving distance of the particles and time can be obtained.

ただし、
Ｄ_ｔ：羽口内径（ｍ）
Ｌ：ランス先端から羽日先までの距離(ｍ)
また、上記（２）式のＲＦは、以下の（３）式で表される。

ただし、
ρ_ｆ０：標準状態におけるボッシュガス密度（ｋｇ／ｍ^３）
Ｖ_ｆ：ボッシュガス量（Ｎｍ^３／s）
Ｔ_ｆｔ：羽口先ガス温度（℃）
Ｐ_０：大気圧(ｋｇ／ｃｍ^２)
ｇ：重力加速度（ｍ／ｓ^２）
Ｓ：羽口断面積（ｍ^２）
Ｔ_０：大気温度(℃)
Ｐ：送風圧力（ｋｇ／ｃｍ^２）
ｄ_ｐｔ：羽口前コークス粒度（ｍ）
ρ_ｐｔ:羽口前コークス密度（ｋｇ／ｍ^３） Here, the moving distance D of the faux agent particles blown into the blades is from the tip of the lance to the end of the raceway and is expressed by the following equation (2).

However,
D _t : inner diameter of tuyere (m)
L: Distance from the tip of the lance to the wing tip (m)
Further, the RF of the above formula (2) is represented by the following formula (3).

However,
ρ _f0 : Bosch gas density in standard state (kg / m ³ )
V _f : Bosch gas amount (Nm ³ / s)
T _ft : tuyere gas temperature (° C)
P ₀ : Atmospheric pressure (kg / cm ² )
g: Gravity acceleration (m / s ² )
S: tuyere cross-sectional area (m ² )
T ₀ : Atmospheric temperature (° C)
P: Air blowing pressure (kg / cm ² )
d _pt : Coal particle size in front of tuyere (m)
ρ _pt : coke density in front of tuyere (kg / m ³ )

  From these calculation results, it is possible to obtain the relationship between the residence time and the particle size from when the western additive shown in FIG. 1 is blown to the end of the raceway.

ただし、
ｃ_ｐ：粒子比熱（ｋＪ／ｋｇ／℃）
Ｖ：粒子体積（ｍ^３）
Ｔ_ｐ：粒子温度(℃)
Ａ：粒子表面積（ｍ^２）
Ｔ_ｆ：ガス温度（℃）
ｈ：熱伝達係数
ここで、ガス温度Ｔ_ｆは後述の図２で示され、上記（４）式の熱伝達係数ｈは以下の（５）式で表される。

ただし、
μ：ガス粘度(ｋｇ・ｓ／ｍ^３)
λ_ｆ：ガス熱伝導度（Ｗ／ｍ／℃） Further, the slagging agent blown from the lance simultaneously with the pulverized coal is heated by an external heat supply by the combustion heat of the pulverized coal immediately after being blown. In this case, the heat transfer mode of the particles is heat transfer, and the rate of temperature rise is expressed by the following equation (4).

However,
c _p : Particle specific heat (kJ / kg / ° C.)
V: Particle volume (m ³ )
T _p : Particle temperature (° C)
A: Particle surface area (m ² )
T _f : gas temperature (° C.)
h: Heat transfer coefficient Here, the gas temperature T _f is shown in FIG. 2 to be described later, and the heat transfer coefficient h in the above equation (4) is expressed by the following equation (5).

However,
μ: Gas viscosity (kg · s / m ³ )
λ _f : gas thermal conductivity (W / m / ° C.)

Substituting the physical property values of the glaze-forming agent particles into the above formula (4), the relationship between the time until the glaze-making agent particles reach the melting temperature and the particle size as shown in FIG. In order for the blown-in molding agent to melt at the end of the raceway, it is necessary to reach the melting temperature within the residence time. In the example of FIG. 1 showing a typical example, the maximum particle size is 3 mm. In other words, if the particle size of the glaze-making agent is equal to or less than the particle size at which the residence time from when the glaze-making agent is blown into the tuyere to reach the end of the raceway and the time to reach the melting temperature are equal to or less, the melt will be melted within the residence time. . The flow rate at which the residence time and the time to reach the melting temperature are equal is the maximum particle size of the slagging agent, and the following equation (6) is obtained from the relationship between the maximum particle size obtained under various conditions and the residence time. It is done.
^{_{d MAX = 0.0135t r 0.496 ‥‥ (}} 6)
However,
d _MAX =: Maximum particle size (m)
_tr : Residence time (s)
By applying the present invention, in the typical example shown in FIG. 1, the maximum particle size is 3 mm, and it is possible to use a coarser grain forming agent than the conventional one. Of course, it is possible to increase the maximum particle size by making the raceway have a longer residence time.

  On the other hand, from the viewpoint of meltability, a finer particle size is preferable, but as described above, the particle size of the blown particles is limited from the powder transport surface. That is, the smaller the particle size, the worse the transportability. As a result, it was found that when the particle size exceeds 2 mm, there is not much problem in transportability. Therefore, it is considered that the particle size of the slagging agent is preferably 2 mm or more.

  From the above, in the present invention, in order to melt and remove the raceway shell that is generated when a large amount of pulverized coal is blown, the slagging agent and pulverized coal are mixed in order to effectively eliminate the problem of air permeability in the lower part of the furnace. In the state, it was blown into the blast furnace from the tuyere so that the heat of combustion of the pulverized coal could be melted, so that a coarser particle-forming material could be applied. That is, as shown in FIG. 2, the gas temperature until reaching the tip of the tuyere is higher in the present invention than in the prior art, and the present invention facilitates melting of the coarse-grained slagging agent. At this time, the particle size of the slagging agent needs to be equal to or less than the particle size at which the residence time from when blown into the tuyere to reach the end of the raceway and the time to reach the melting temperature are equal, and transportability is good. It is also necessary that the particle size be large. From such a viewpoint, the preferable particle size of the slagging agent is more than 2 mm and 3 mm or less.

  According to the present invention, since the mixture of the coal making agent and the pulverized coal is blown into the blast furnace from the tuyere, it can be melted by the combustion heat of the pulverized coal even if the particle size of the coal making agent is somewhat large, It is possible to effectively supply the faux agent in a state where the glaze is melted to the end of the raceway. For this reason, the growth suppression and melting / removal of the raceway shell are promoted, and the deterioration of the furnace bottom air permeability can be effectively eliminated, and a good state can be maintained.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 3 is a schematic configuration diagram showing equipment for carrying out the blast furnace operating method according to the present embodiment. In the figure, reference numeral 1 denotes a blast furnace, and a tuyere 2 is provided at the bottom of the blast furnace 1. A blow pipe 3 for blowing hot air 4 is connected to the tuyere 2. A blow lance 5 is connected to the blow pipe 3, and to this blow lance 5, a fouling agent and pulverized coal are supplied from a fouling agent blowing facility 10 and a pulverized coal blowing facility 20. .

  The antifouling agent blowing facility 10 includes an antimony agent hopper 11 for storing an antimony agent, a pressure-increasing / decreasing pressure switching hopper 12 provided downstream thereof, a blowing hopper 13 provided further downstream thereof, and a blowing hopper. 13, an air feed pipe 14 for air-feeding the fouling agent, a cutout amount adjusting feeder 15 provided in the air feed pipe 14, a distributor 16 for distributing the fouling agent particles flowing through the air feed pipe 14, and a distribution And an air supply pipe 17 extending from the vessel 16 to the lance 5.

  On the other hand, the pulverized coal blowing facility 20 includes a pulverized coal hopper 21 for storing pulverized coal, a pressure-increasing / decreasing pressure switching hopper 22 provided on the downstream side thereof, a blowing hopper 23 provided on the further downstream side, and a blowing hopper 23. The air feed pipe 24 for transporting the pulverized coal from the air, the cutout amount adjusting feeder 25 provided in the air feed pipe 24, the distributor 26 for distributing the pulverized coal flowing through the air feed pipe 24, and the distributor 26 It has an air supply pipe 27 that reaches the supply pipe 17. In other words, the pulverized coal that has been fed through the pneumatic piping 27 joins the fretting agent that is fed through the pneumatic piping 17 at the junction 28.

  That is, in such a facility, the fossilizing agent and the pulverized coal merge at the confluence point 28 in the air feed pipe 17 and are jetted from the blow lance 5 to the blow pipe 3 in a mixed state. 4 is blown from the tuyere 2 into the blast furnace 1.

  In this way, the mixture is injected from the tuyere 2 into the blast furnace 1 in a state where the coal-forming agent and the pulverized coal are mixed, so that the coal-forming agent is exposed to a high temperature atmosphere by the combustion heat of the pulverized coal immediately after being injected. For this reason, compared with the case of single blowing, since the temperature-raising agent is effectively heated and melts easily, a coarse-grained weight-making agent such as more than 2 mm and 3 mm or less can be used. Loss due to scattering can be reduced more effectively. Therefore, it is possible to effectively improve the deterioration of the air permeability at the bottom of the blast furnace 1 that occurs when a large amount of pulverized coal is blown.

  The blowing amount of the slagging agent shows an effective action for lowering the melting point depending on the blowing amount to a certain extent, but if it is blown too much, the slag increases and accumulates to cause deterioration of air permeability. Therefore, it is desirable that the amount of blowing agent is not more than the amount of slag generated from pulverized coal.

Examples of the present invention will be described below.
[Test 1]
Using the coke packed bed type test combustion furnace shown in FIG. 4 simulating a blast furnace, the influence of the particle size of the blown glaze agent on the pressure loss in the furnace was evaluated. In FIG. 4, a coke packed bed 32 is formed in the pulverized coal combustion furnace 31, and tuyere 33 is provided in the lower part of the pulverized coal combustion furnace 31. A blow pipe 34 is connected to the tuyere 33, and hot air 35 is blown into the pulverized coal combustion furnace 31 from the tuyere 33 through the blow pipe 34. A coke cutting hopper 36 is provided above the pulverized coal combustion furnace 31, and coke is supplied into the pulverized coal combustion furnace 31 from there. In addition, blow lances 37 and 38 are connected to the blow pipe 35. In the case of the present invention, the blow lances 37 and 38 are supplied from the slagging agent cutting hopper 39 and the pulverized coal cutting hopper 40 through the air feed pipes 41 and 42, respectively. In the case of the conventional example, the air feeding pipe 41 is connected to the air blowing lance 37 and the air feeding pipe 42 is blown into the lance. 38, the slagging agent and pulverized coal were jetted separately. In the above coke packed bed type test combustion furnace, hot air 35 adjusted to have the same components as the blast furnace was blown into the pulverized coal combustion furnace 31 to burn the coke therein.

In this test, limestone was used as a slagging agent, and the pressure loss in the furnace and the yield in the furnace were measured by changing the particle size. The main test conditions are as follows.
・ Hot air blowing rate: 350 Nm ³ / hr
・ Blower temperature: 1200 ℃
・ Blowing oxygen concentration: 24 vol%
・ Pulverized coal injection amount: 65 kg / hr (equivalent to 200 kg / thm in blast furnace operation)
・ Limestone blowing rate: 1kg / hr (equivalent to 3kg / thm in blast furnace operation)

  FIG. 5 shows the relationship between the particle size of the slagging agent, the pressure loss in the furnace, and the yield in the furnace. The yield of the glaze-making agent in the furnace increases with the particle size regardless of the present invention example and the conventional example, and becomes approximately 1 at 3 mm. On the other hand, in the conventional example, when the particle size becomes 2 mm or more in the conventional example, the pressure loss in the furnace reaches the raceway shell before the smelting agent melts despite the high yield, and thus starts to increase due to accumulation. However, in the example of the present invention, the pressure loss in the furnace decreases to a particle size of 3 mm and increases when the particle size is more than that. From this, it was confirmed that in the present invention, it was possible to blow in with a particle size that yielded a high yield, and the slagging agent could be used very efficiently for the suppression of the growth of the raceway shell, and for the melting and removal.

  Next, in the case of jetting from the blowing lance 37 in a state where the coal making agent and pulverized coal are mixed according to the present invention, the particle size of the iron making agent is changed, and the pressure loss in the furnace with respect to the elapsed time after the start of limestone blowing is changed. The increase was determined. The particle size of limestone was more than 2 mm and less than 3 mm in condition 1, less than 1 mm in condition 2, more than 5 mm in condition 3, and 1 mm or more and 2 mm or less in condition 4.

  FIG. 6 shows the test results. From the figure, the increase in the pressure loss in the furnace with respect to the elapsed time after the start of limestone blowing is small when the limestone particle size is greater than 2 mm and less than 3 mm, but larger when condition 2 is less than 1 mm. In the case of condition 3 exceeding 5 mm, it was further increased. In the case of the condition 4 of 1 mm or more and 2 mm or less, the increase amount in the furnace pressure loss is small, but the effect is small. From this, when the particle size of limestone is 1 mm or more and 3 mm or less, the limestone mixed and mixed with pulverized coal reaches the raceway shell without being scattered, and is assimilated with the raceway shell by melting, The growth suppression and melting / removal of the raceway shell were promoted, and the effect could be estimated to be maximized when blown at a particle size of more than 2 mm and not more than 3 mm.

[Test 2]
In a blast furnace in which pulverized coal was being blown from the tuyere at a pulverized coal ratio of 200 kg / thm, the ratio of limestone was blown into the blast furnace from the tuyere at 3 kg / thm. At this time, as shown in Table 1, Example 1 in which limestone and pulverized coal were blown in a mixed state in accordance with the present invention with a limestone particle size of 2.2 mm, and the limestone particle size of 1.8 mm and 2. The transition of the pressure loss in the furnace was grasped for Comparative Examples 1 and 2 in which limestone and pulverized coal were blown separately. The result is shown in FIG. When limestone blowing was started from time t1, the pressure loss in the furnace gradually decreased and became stable. When the limestone blowing was stopped at time t2, the pressure loss in the furnace rose again and returned to the same level as before the limestone blowing start. Reduction of furnace pressure loss at this time, as shown in Table 1, while the present invention Example 1 was 0.12 kgf / cm ^2, Comparative Example 1, 0.10kgf / cm ^2, Comparative Example 2 Then, it was only a small amount of decline. from this result,
Inventive Example 1 is estimated that the effect of improving the furnace bottom air permeability at the time of blowing a large amount of pulverized coal is larger than Comparative Examples 1 and 2, effectively suppressing the growth of the raceway shell and promoting the melting / removal. did it.

The relationship between the particle size of the glaze-making agent and the temperature rise time, and the relationship between the particle size of the glaze-making agent and the residence time from when the glaze-making agent is blown into the tuyere until it reaches the end of the raceway are shown in the present invention. Graph showing comparison with technology. The graph which shows the relationship between the particle movement distance near a tuyere and gas temperature. The schematic block diagram which shows the installation for enforcing the blast furnace operating method which concerns on one Embodiment of this invention. The schematic block diagram which shows the coke packed bed type | mold test combustion furnace which simulated the blast furnace. The coke packed bed type test combustion furnace is a graph showing the relationship between the particle size of the slagging agent, the pressure loss in the furnace and the yield in the furnace in comparison with the present invention example and the conventional example. The coke packed bed type test combustion furnace is a graph showing the transition of the pressure loss in the furnace after the start of blowing the molding agent, by comparing the particle sizes of the various molding agents. The graph which shows the transition of the pressure loss in a furnace by comparing with the example of this invention and a comparative example. The ternary phase diagram showing the low melting point of the raceway shell by supplying CaO.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Blast furnace 2 ... Tuyere 3 ... Blow pipe 4 ... Hot air 5 ... Blowing lance 10 ... Slagging agent blowing equipment 11 ... Slagging agent hopper 12 ... Pressurization switching pressure hopper 13 ... Blowing hopper 14 …… Pneumatic feed pipe 15 …… Cutting amount adjusting feeder 16 …… Distributor 17 …… Pneumatic feed pipe 20 …… Pulverized coal blowing equipment 21 …… Pulverized coal hopper 22 …… Pressure and pressure switching hopper 23 …… Blowing hopper 24 …… Pneumatic feed pipe 25 …… Cutting amount adjustment feeder 26 …… Distributor 27 …… Pneumatic feed pipe 28 …… Confluence

Claims (3)

  A blast furnace operating method in which pulverized coal is blown from a tuyere of a blast furnace, the blast furnace being blown into the blast furnace from a tuyere in a state where a coal-forming agent and pulverized coal are mixed.   The blast furnace operating method according to claim 1, wherein the slagging agent and pulverized coal are mixed so that the slagging agent can be melted by the heat of combustion of the pulverized coal. The particle size of the faux agent is equal to or less than a particle size in which the residence time from when the faux agent is blown into the tuyere to reach the end of the raceway is equal to the time to reach the melting temperature. A blast furnace operating method according to claim 1 or claim 2.

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