JP7444147B2 - Granulated iron production equipment and granulated iron manufacturing method - Google Patents

Description

The present invention relates to a technology for manufacturing granular iron, that is, a technology for manufacturing granular iron (granular iron material) by cooling and solidifying molten iron such as hot metal or molten steel in a droplet state.

Granular iron is a granular iron material obtained by cooling and solidifying molten iron such as hot metal or molten steel dispersed in droplets, and its average particle size is about several mm to several tens of mm. In an integrated steelworks that manufactures steel, when problems occur in the processes below steelmaking and the processing of hot metal tapped from the blast furnace is delayed, resulting in surplus hot metal, this surplus blast furnace hot metal (1200 to 1500 It is possible to make granular pig iron by cooling and solidifying molten pig iron (which is liquid at a high temperature of about 30°F (℃)) into droplets of several mm to several tens of mm, and then storing this granular pig iron as an iron source for cast iron. It is being said.
When turning hot metal into granular pig iron, the hot metal is transported in a hot metal pot or torpedo car to a granular pig iron manufacturing facility, and in this granular pig iron manufacturing facility, for example, the hot metal flows out from a tundish and collides with a refractory receiving plate. The granulated pig iron is made into droplets by cooling the droplets.

As a method for obtaining granular pig iron from hot metal, Patent Document 1 discloses that a flow of hot metal is applied to a fixed plate to decompose it into droplets, and the droplets are allowed to fall into a puddle of water in a cooling water tank to cool and solidify. An apparatus for producing pig iron is disclosed. Droplets of hot metal fall inside a funnel-shaped cylinder placed in a cooling water tank and are cooled by the cooling water, and the granulated pig iron produced by this cooling is discharged from the bottom end of the funnel-shaped cylinder and transported by a conveyor. It is carried out outside the cooling water tank.
In addition, Patent Document 2 discloses that a flow of hot metal is applied to a plurality of inclined surface plates arranged in a stepped manner to form droplets, and the droplets are dropped into a puddle of a cooling water tank to be cooled and solidified to produce granulated pig iron. An apparatus for manufacturing is disclosed.

When obtaining granular pig iron from hot metal, if the granular pig iron particle size (droplet particle size) is too large, sufficient cooling will not be possible, and the granular iron will fuse together in the cooling water. If contained, it may cause a steam explosion. Therefore, in order to cool the granular pig iron stably, it is important not to make the granular pig iron particle size too large (the average particle size should be approximately 15 to 20 mm or less).
Regarding the method of adjusting the grain size of granular pig iron, Patent Document 1 states, ``It is generally said that if the height of the ladle 1 on the fixed plate 7 is increased, the decomposition of the flow 8 will progress and fine granular metal will be produced.'' (Page 2, column 3, lines 7-9), and in Patent Document 2, ``The particle size of this granular pig iron can be reduced by increasing the free fall energy.'' (Paragraph 0020) ), and the diameter of the granular pig iron is adjusted according to the height from the fixed plate or inclined surface plate where the hot metal flows to the hot metal discharge port (tundish nozzle, etc.) of the container (tundish, etc.) that stores the hot metal. It has been shown that it can be done.

Special Publication No. 52-20948 Japanese Patent Application Publication No. 5-154607

The present inventors have developed a granular pig iron manufacturing equipment according to Patent Document 1, in which hot metal is discharged from a nozzle of a tundish and flows down, and the hot metal collides with a fixed plate (hot metal receiving plate) below to form droplets. A production test of granular pig iron was conducted using a test facility in which the droplets were dropped into cooling water in a cooling water tank, cooled, and recovered as granular pig iron. At that time, the height of the tundish nozzle relative to the fixed plate (hot metal receiving plate) was adjusted so that the diameter of the pig iron particles was approximately 8 to 25 mm (average approximately 15 mm). For a while after starting the production test, we were able to stably obtain granular pig iron within the target particle size range, but when we continued testing with the same tundish, the granular pig iron particle size gradually became unstable. As a result, there were cases where abnormally large pig iron particles with a particle diameter of about 100 mm and abnormally small pig iron particles with a particle diameter of 3 mm or less were mixed together.

It is conceivable to use a belt conveyor equipped with a mesh-like belt that can drain the water as an unloading device for discharging the granular pig iron from the cooling water tank, but if the particle size of the granular pig iron obtained is too small, Since the granular pig iron passes through the mesh-like belt, the recovery yield of the granular pig pig will be reduced. On the other hand, if the particle size of the obtained granular pig iron is too large (for example, a particle size of 100 mm or more), as mentioned above, it cannot be cooled sufficiently in the cooling water tank, and the granular iron will fuse together in the cooling water. If cooling water is included during this process, there is a risk of a steam explosion.
However, in Patent Documents 1 and 2, there is no knowledge about the above-mentioned phenomenon in which the particle diameter of granular pig iron becomes unstable when granular pig iron is manufactured continuously, and of course there is no knowledge regarding the phenomenon in which the particle size of granular pig iron becomes unstable as described above. There is no disclosure.

Therefore, an object of the present invention is to provide an apparatus and method for producing granulated iron that can solve the problems of the prior art as described above and stably and continuously produce granulated iron having an appropriate particle size over a long period of time. It is about providing.

In order to solve the above problems, the present inventors first investigated the cause of the phenomenon in which the particle size of granulated iron gradually becomes unstable when granulated iron is continuously produced in one facility, and As a result, it was found that the reason why the particle size becomes unstable is that the nozzle that discharges molten iron from the tundish becomes worn out and the nozzle diameter increases (expands). Here, wear of the nozzle due to use is unavoidable, and therefore, when the iron grain size becomes unstable, it is necessary to replace the tundish to solve this problem. However, with this type of countermeasure, it is necessary to replace the tundish at relatively short intervals, and maintenance costs for the replaced tundish and equipment downtime occur due to replacement, so the processing efficiency of molten iron that occurs due to trouble etc. becomes lower. Therefore, as a result of further investigation into countermeasures for destabilizing the iron particle size, we found that even if the nozzle diameter increases to a certain extent due to nozzle wear, the iron particle size will not become unstable for a certain period of time. The conditions that allow iron production to continue exist, and it is possible to continue using the same tundish by initializing the equipment configuration or operating conditions to meet those conditions, or by changing operating conditions during operation. It has been found that the production of granulated iron can be continued for a considerable period of time without causing instability of the granulated iron particle size.

但し Ｉ：衝突レイノルズ数［－］
Re：レイノルズ数［－］
We：ウェーバー数［－］
ｄ：ノズル（２）から吐出されて流下する溶鉄の液柱が溶銑受け盤（３）に衝突する際の液柱径［mm］
ｖ：ノズル（２）から吐出されて流下する溶鉄の液柱が溶銑受け盤（３）に衝突する際の衝突流速［m/s］
ρ：溶鉄の密度［kg/ m^３］
μ：溶鉄の粘度［mPa・s］
σ：溶鉄の表面張力［mN/m］
ｇ：重力加速度［m/s^２］
ｄ_０：ノズル（２）のノズル口径［mm］
ｖ_０：ノズル（２）からの溶鉄の吐出速度［m/s］
ｈ_ｄ：ノズル（２）の先端から溶鉄受け盤（３）の上面までの垂直方向距離［mm］ The present invention has been made based on the above knowledge and has the following gist.
[1] A tundish (1) equipped with a nozzle (2) for discharging the contained molten iron,
a molten iron receiving plate (3) that collides a liquid column of molten iron discharged from a nozzle (2) of the tundish (1) and flowing down;
A granule equipped with a cooling water tank (4) disposed below the molten iron receiving plate (3) and cooling droplets of molten iron that collide with the molten iron receiving plate (3) and are scattered around it by falling into the cooling water. Iron manufacturing equipment,
The nozzle diameter d ₀ of the nozzle (2) and the discharge speed of molten iron from the nozzle (2) are adjusted so that the collision Reynolds number I defined by the following equations (1) to (5) satisfies 3000≦I≦7500. v ₀ and the vertical distance h _d from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3), and the nozzle diameter is set to the nozzle diameter at the discharge speed v ₀ and the vertical distance h _d . ) (However, the nozzle diameter when nozzle (2) reaches its service limit due to expansion of the nozzle diameter due to nozzle wear), the impact Reynolds number I satisfies 3000≦I≦7500. Granular iron manufacturing equipment characterized by:

However, I: Collision Reynolds number [-]
Re: Reynolds number [-]
We: Weber number [-]
d: Diameter of the liquid column when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the hot metal receiving plate (3) [mm]
v: Collision flow velocity when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the molten metal receiving plate (3) [m/s]
ρ: Density of molten iron [kg/ ^m3 ]
μ: Viscosity of molten iron [mPa・s]
σ: Surface tension of molten iron [mN/m]
g: Gravitational acceleration [m/s ² ]
d ₀ : Nozzle diameter of nozzle (2) [mm]
v ₀ : Discharge speed of molten iron from nozzle (2) [m/s]
h _d : Vertical distance from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3) [mm]

[2] In the granular iron production equipment of [1] above, the nozzle diameter of the nozzle (2) at its usage limit (however, the nozzle diameter when the nozzle (2) reaches its usage limit due to expansion of the nozzle diameter due to nozzle wear) ) is within the range of nozzle diameter d ₀ +5 mm to nozzle diameter d ₀ +30 mm.
[3] In the granular iron manufacturing apparatus of [1] or [2] above, the planar shape of the molten iron receiving plate (3) is circular, and the outer diameter D [mm] of the circular molten iron receiving plate (3) is , characterized in that the diameter d [mm] of the liquid column of molten iron discharged from the nozzle (2) and flowing down when it collides with the molten iron receiving plate (3) satisfies 1≦D/d≦7. Granular pig iron manufacturing equipment.

[4] In the granular iron manufacturing apparatus according to any one of [1] to [3] above, a partition cylinder (5) with open upper and lower ends is arranged in the cooling water tank (4), and the partition cylinder (5) is ) is a cooling area (A) that receives and cools droplets of molten iron falling from above,
A granulated iron manufacturing apparatus characterized in that a cooling water supply pipe (6) is provided for introducing cooling water supplied from the outside of a cooling water tank (4) into a cooling area (A).
[5] In the granulated iron production apparatus of [4] above, a carry-out conveyor (7) for carrying out the granulated iron produced by cooling the molten iron droplets in the cooling area (A) to the outside of the cooling water tank (4). Equipped with
By locating the conveyance start end of the carry-out conveyor (7) below the lower end of the partition cylinder (5), the granulated iron that has fallen from the lower end of the partition cylinder (5) is transferred to the cooling water tank (4) by the carry-out conveyor (7). A granular iron manufacturing device characterized in that it is transported outside.

[6] In the granular iron manufacturing apparatus according to [4] or [5] above, cooling water is introduced into the partition cylinder (5) in a direction eccentric to the cylinder core, so that the cooling area ( A) The cooling water supply pipe (6) is connected to the partition cylinder (5), or the end of the cooling water supply pipe (6) is connected to the partition cylinder (5) so that a swirling flow of cooling water is generated. Granular iron manufacturing equipment characterized by being placed in.
[7] In the granular iron manufacturing apparatus according to any one of [4] to [6] above, the entire partition cylinder (5) or the lower part is configured in a funnel shape, and a cooling water supply pipe ( 6) is connected thereto, or the end of the cooling water supply pipe (6) is disposed within the funnel-shaped part thereof.

但し Ｉ：衝突レイノルズ数［－］
Re：レイノルズ数［－］
We：ウェーバー数［－］
ｄ：ノズル（２）から吐出されて流下する溶鉄の液柱が溶銑受け盤（３）に衝突する際の液柱径［mm］
ｖ：ノズル（２）から吐出されて流下する溶鉄の液柱が溶銑受け盤（３）に衝突する際の衝突流速［m/s］
ρ：溶鉄の密度［kg/ m^３］
μ：溶鉄の粘度［mPa・s］
σ：溶鉄の表面張力［mN/m］
ｇ：重力加速度［m/s^２］
ｄ_０：ノズル（２）のノズル口径［mm］
ｖ_０：ノズル（２）からの溶鉄の吐出速度［m/s］
ｈ_ｄ：ノズル（２）の先端から溶鉄受け盤（３）の上面までの垂直方向距離［mm］ [8] A tundish (1) equipped with a nozzle (2) for discharging the contained molten iron;
a molten iron receiving plate (3) that collides a liquid column of molten iron discharged from a nozzle (2) of the tundish (1) and flowing down;
A device comprising a cooling water tank (4) disposed below the molten iron receiving plate (3) and cooling droplets of molten iron that collide with the molten iron receiving plate (3) and scatter around it by falling into the cooling water. A method for producing granulated iron using
The nozzle diameter d ₀ of the nozzle (2) and the discharge speed of molten iron from the nozzle (2) are adjusted so that the collision Reynolds number I defined by the following equations (1) to (5) satisfies 3000≦I≦7500. v ₀ and the vertical distance h _d from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3), and the nozzle aperture at the discharge speed v ₀ and the vertical distance h _d is the same as that of the nozzle (2). ) (However, the nozzle diameter when nozzle (2) reaches its service limit due to expansion of the nozzle diameter due to nozzle wear), the impact Reynolds number I satisfies 3000≦I≦7500. A method for producing granular iron characterized by:

However, I: Collision Reynolds number [-]
Re: Reynolds number [-]
We: Weber number [-]
d: Diameter of the liquid column when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the hot metal receiving plate (3) [mm]
v: Collision flow velocity when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the molten metal receiving plate (3) [m/s]
ρ: Density of molten iron [kg/ ^m3 ]
μ: Viscosity of molten iron [mPa・s]
σ: Surface tension of molten iron [mN/m]
g: Gravitational acceleration [m/s ² ]
d ₀ : Nozzle diameter of nozzle (2) [mm]
v ₀ : Discharge speed of molten iron from nozzle (2) [m/s]
h _d : Vertical distance from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3) [mm]

[9] In the method for producing granulated iron in [8] above, the nozzle diameter of the nozzle (2) at its service limit (however, the nozzle diameter when the nozzle (2) reaches its service limit due to expansion of the nozzle diameter due to nozzle wear) ) is within the range of nozzle diameter d ₀ +5 mm to nozzle diameter d ₀ +30 mm.

但し Ｉ：衝突レイノルズ数［－］
Re：レイノルズ数［－］
We：ウェーバー数［－］
ｄ：ノズル（２）から吐出されて流下する溶鉄の液柱が溶銑受け盤（３）に衝突する際の液柱径［mm］
ｖ：ノズル（２）から吐出されて流下する溶鉄の液柱が溶銑受け盤（３）に衝突する際の衝突流速［m/s］
ρ：溶鉄の密度［kg/ m^３］
μ：溶鉄の粘度［mPa・s］
σ：溶鉄の表面張力［mN/m］
ｇ：重力加速度［m/s^２］
ｄ_０：ノズル（２）のノズル口径［mm］
ｖ_０：ノズル（２）からの溶鉄の吐出速度［m/s］
ｈ_ｄ：ノズル（２）の先端から溶鉄受け盤（３）の上面までの垂直方向距離［mm］ [10] A tundish (1) equipped with a nozzle (2) for discharging the contained molten iron;
a molten iron receiving plate (3) that collides a liquid column of molten iron discharged from a nozzle (2) of the tundish (1) and flowing down;
A device comprising a cooling water tank (4) disposed below the molten iron receiving plate (3) and cooling droplets of molten iron that collide with the molten iron receiving plate (3) and scatter around it by falling into the cooling water. A method for producing granulated iron using
The nozzle diameter d ₀ of the nozzle (2) and the discharge speed of molten iron from the nozzle (2) are adjusted so that the collision Reynolds number I defined by the following equations (1) to (5) satisfies 3000≦I≦7500. v ₀ and a vertical distance h _d from the tip of the nozzle (2) to the top surface of the molten iron receiver (3) to start producing granulated iron;
After starting the production of granulated iron, the collision Reynolds number I is maintained to satisfy 3000≦I≦7500 until the nozzle (2) reaches its usable limit due to expansion of the nozzle diameter due to nozzle wear. A method for producing granulated iron, characterized in that the discharge speed v ₀ and/or the vertical distance h _d are adjusted.

However, I: Collision Reynolds number [-]
Re: Reynolds number [-]
We: Weber number [-]
d: Diameter of the liquid column when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the hot metal receiving plate (3) [mm]
v: Collision flow velocity when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the molten metal receiving plate (3) [m/s]
ρ: Density of molten iron [kg/ ^m3 ]
μ: Viscosity of molten iron [mPa・s]
σ: Surface tension of molten iron [mN/m]
g: Gravitational acceleration [m/s ² ]
d ₀ : Nozzle diameter of nozzle (2) [mm]
v ₀ : Discharge speed of molten iron from nozzle (2) [m/s]
h _d : Vertical distance from the tip of the nozzle (2) to the top of the molten iron receiving plate (3) [mm]

[11] In the method for producing granulated iron according to [10] above, the nozzle diameter when the nozzle (2) reaches its usable limit due to expansion of the nozzle diameter due to nozzle wear is between nozzle diameter d ₀ +5 mm and nozzle diameter d ₀ +30 mm. A method for producing granulated iron, characterized by being within a range.
[12] In the method for producing granulated iron according to any one of [8] to [11] above, the planar shape of the molten iron receiving plate (3) is circular, and the outer diameter D of the circular molten iron receiving plate (3) is mm] and the liquid column diameter d [mm] when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the molten iron receiving plate (3) satisfy 1≦D/d≦7. A method for producing granular iron characterized by:

[13] In the method for producing granulated iron according to any one of [8] to [12] above, a partition cylinder (5) with open upper and lower ends is placed in the cooling water tank (4), and the partition cylinder (5) is ) is a cooling area (A) that receives and cools droplets of molten iron falling from above,
A method for manufacturing granulated iron, characterized in that cooling water supplied from outside of a cooling water tank (4) is introduced into a cooling area (A) through a cooling water supply pipe (6).
[14] In the method for producing granulated iron according to [13] above, a carry-out conveyor (7) for carrying out the granulated iron produced by cooling the droplets of molten iron in the cooling area (A) out of the cooling water tank (4). Equipped with
By locating the conveyance start end of the carry-out conveyor (7) below the lower end of the partition cylinder (5), the iron granules that have fallen from the lower end of the partition cylinder (5) are transferred to the cooling water tank (4) by the carry-out conveyor (7). A method for producing granulated iron characterized by transporting it outside.

[15] In the method for producing granulated iron according to [13] or [14] above, cooling water is introduced into the partition cylinder (5) in a direction eccentric to the cylinder core through the cooling water supply pipe (6). A method for producing granulated iron, characterized in that a swirling flow of cooling water is generated in the cooling region (A).
[16] In the method for producing granulated iron according to any one of [13] to [15] above, the entire partition cylinder (5) or the lower part is configured in a funnel shape, and a cooling water supply pipe ( 6) A method for producing granulated iron characterized by introducing cooling water through the method.

According to the present invention, granulated iron having an appropriate particle size can be produced stably and continuously over a long period of time. That is, when the same tundish is continued to be used, it is possible to prevent the particle size of the iron granules from becoming unstable, and to continue to stably produce iron particles having an appropriate particle size. This makes it possible to extend the tundish replacement cycle, suppressing tundish maintenance costs and equipment downtime associated with replacement, and increasing molten iron processing efficiency.

An explanatory diagram that schematically shows an embodiment of the granulated iron production apparatus of the present invention and the granulated iron production method of the present invention using this apparatus, and shows the entire apparatus in a longitudinal section. A plan view of the partition cylinder arranged in the cooling water tank in the embodiment of FIG. A vertical cross-sectional view of the partition cylinder arranged in the cooling water tank in the embodiment of FIG. This diagram schematically shows the state (behavior) when molten iron (liquid column) collides with the center of the top surface of the molten iron receiving plate, scatters around it, and turns into droplets. 4(b) is an explanatory diagram showing the molten iron receiving plate in a longitudinal cross-sectional state, and FIG. 4(b) is an explanatory diagram showing the state of molten iron colliding with the top surface of the molten iron receiving plate. An explanatory diagram showing the experimental method of a water model experiment to investigate the situation in which molten iron umbrellas and droplets are generated when molten iron collides with the top surface of a molten iron receiving plate. A photograph taken of the situation in which molten iron (water) umbrellas and droplets are generated in the water model experiment shown in Figure 5. These are the test results obtained in a water model experiment to investigate the situation when a liquid column of molten iron discharged from a nozzle collides with a molten iron receiving plate. Graph showing the relationship between d ₀ and nozzle discharge speed v ₀ An explanatory diagram schematically showing the mode of the molten iron (water) umbrella formed in the water model experiment in Figure 7. An explanatory diagram schematically showing a vertical cross section of a molten iron granulation mechanism comprising a tundish, a nozzle, and a molten iron receiving plate used in the present invention. 7 is a graph showing the relationship between the formation of an appropriate molten iron (water) umbrella, the impact Reynolds number I, and the nozzle diameter d ₀ , which is a test result obtained in a water model experiment similar to that shown in FIG. This figure shows other embodiments of the granulated iron production apparatus of the present invention and the granulated iron production method of the present invention using this apparatus, and shows several methods of supplying cooling water to the inside of the partition cylinder using the cooling water supply pipe. An explanatory diagram showing an example of this

1 to 3 schematically show an embodiment of the granulated iron production apparatus of the present invention and the granulated iron production method of the present invention using this apparatus, and FIG. 1 shows a longitudinal section of the entire apparatus. FIG. 2 is a plan view of a partition cylinder arranged in a cooling water tank, and FIG. 3 is a longitudinal sectional view of the partition cylinder.
This granular iron production equipment is a device that produces granular iron (granular iron material) by cooling and solidifying molten iron such as hot metal or molten steel into droplets. A tundish 1 (such as a molten pig iron bucket) equipped with a nozzle 2 for discharging molten iron, a molten iron receiving plate ₃ that collides with a liquid column of molten iron discharged from the nozzle 2 of this tundish 1 and flowing down, and a cooling water w. A cooling water tank 4 that accommodates molten iron x, which is disposed below the molten iron receiving plate 3, and cools droplets of molten iron It is equipped with

The molten iron receiving plate 3 is made of a disc-shaped refractory, and is supported by a component of the cooling water tank 4 (in this embodiment, a partition cylinder 5 to be described later) via a support.
The granulated iron manufacturing apparatus of the present embodiment further includes a partition cylinder 5 that partitions a part of the cooling water tank 4 to form a cooling area A, and a partition cylinder 5 that forms a cooling area A by cooling droplets of molten iron x. The apparatus is equipped with a conveyor 7 for carrying out the granulated iron _xg to the outside of the cooling water tank 4, and details of the structure of the granulated iron manufacturing apparatus including these will be described in detail later.

The molten iron x is transported to the granulated iron production apparatus in a molten iron transport container 10 (for example, a torpedo, a hot metal pot, etc.), and is poured into the tundish 1 via a gutter 11 or the like. At this time, the amount of molten iron x flowing in from the molten iron transport container 10 is controlled so that the molten metal level in the tundish 1 is at a constant level.
The molten iron x in the tundish 1 is discharged from the nozzle 2 and flows down (free fall), and the liquid column _xc of the molten iron collides with the molten iron receiving plate 3 and scatters as droplets around the tundish. The droplets of the molten iron x fall into the cooling water w stored in the cooling water tank 4, are cooled and solidified, and become granular iron x _g (granular iron material). This granulated iron x _g is carried out of the tank by a carrying-out conveyor 7 and recovered.

The present inventors have discovered the following facts regarding the state (behavior) when molten iron x (liquid column x _c ) collides with the center of the upper surface of molten iron receiving plate 3, scatters around it, and turns into droplets. I found out. FIG. 4 schematically shows the state (behavior) of the molten iron x at that time, and FIG. b) is an explanatory diagram showing how the molten iron x collides with the upper surface of the molten iron receiving plate 3.
As shown in FIG. 4, the molten iron x (liquid column x _c ) that collided with the molten iron receiving plate 3 flows concentrically around the collision position on the upper surface of the molten iron receiving plate and spreads, forming a liquid film that covers the molten iron receiving plate 3. It forms a molten iron umbrella that spreads like an umbrella. When this molten iron umbrella leaves a certain distance from the collision position, the liquid film gradually becomes unstable and becomes droplets (granulation), which fall into the cooling water tank 4 in the form of droplets. The size of the droplet at this time (droplet diameter) is the grain size of the granular pig iron.

The size of the granulated iron obtained by turning the molten iron x into droplets as described above and cooling and solidifying them with cooling water is usually the maximum particle size (the method for measuring the maximum particle size is as described in the example). is preferably 50 mm or less, particularly preferably 35 mm or less. Further, the average particle size (the method for measuring the average particle size is as described in the examples) is preferably about 8 to 20 mm, particularly preferably about 12 to 16 mm. Optimize the size of the droplets of molten iron x by setting the height from the molten iron receiving plate 3 to the nozzle 2 of the tundish 1 so that granulated iron x _g with such particle size and particle size can be obtained. become
However, as described above, if the production of granulated iron is continued for a certain period of time in the same equipment, the grain size of the granulated iron gradually becomes unstable, and abnormally large granulated iron and abnormally small granulated iron begin to coexist. The present inventors investigated the causes and countermeasures for this phenomenon in which the grain size of granulated iron becomes unstable.

The present inventors conducted a water model experiment using water instead of molten iron, which is difficult to handle due to its high temperature of 1000° C. or more, and investigated the situation in which molten iron umbrellas and droplets are generated.
In this experiment, as shown in Fig. 5, a water model experimental device was constructed in which the nozzle 2, the molten iron receiving plate 3, and the vertical distance _hd from the tip (lower end) of the nozzle 2 to the top surface of the molten iron receiving plate were set to the same scale as the actual machine. The nozzle diameter d ₀ of the tip (lower end) of the nozzle 2 (hereinafter simply referred to as "nozzle diameter d ₀ ") and the discharge speed v ₀ of the molten iron x from the nozzle 2 (hereinafter simply referred to as "nozzle discharge speed v ₀ ") ) was changed and the situation in which molten iron umbrellas and droplets were generated was observed.

FIG. 6 is a photograph taken of the situation in which a molten iron (water) umbrella and droplets are generated in the water model experiment of FIG. As shown in FIG. 6(a), at a nozzle discharge speed v ₀ within a certain range, after a molten iron (water) umbrella with a stable liquid film is formed, droplets of uniform particle size are formed. It is scattered all over the place. On the other hand, as shown in Fig. 6(b), when the nozzle discharge speed v ₀ is low, a molten iron (water) umbrella is formed, but the liquid film at the periphery of the molten iron (water) umbrella fluctuates. , a liquid film is not formed partially, and the droplets scatter as large droplets, resulting in non-uniform droplet sizes. In addition, as shown in Fig. 6(c), when the nozzle discharge speed _v0 is high, a liquid film is not formed immediately after impact on the upper surface of the molten iron receiving plate 3, and the droplets become a mixture of large and small particles. The droplets will scatter and the size of the droplets will be non-uniform.
From the above results, the present inventors have found that droplets with uniform particle size can be formed when a molten iron (water) umbrella having a stable liquid film can be formed.

FIG. 7 shows the relationship between whether or not an appropriate molten iron (water) umbrella can be formed in a water model experiment, and the nozzle diameter d ₀ and nozzle discharge speed v ₀ . Here, FIGS. 8(a) to 8(c) schematically show the aspects of the molten iron (water) umbrella formed in this water model experiment, but whether or not the molten iron (water) umbrella was properly formed is Judgment was made by visual inspection based on the following criteria.
○: As shown in Figure 8(a), when the molten iron (water) umbrella is viewed from above, a liquid film is stably formed in a circular shape as shown by the imaginary line in the figure (the outline of the liquid film is clear). ), the peripheral edge of the liquid film has turned into droplets.
△: As shown in Fig. 8(b), when the molten iron (water) umbrella is viewed from above, the liquid film has a nearly circular shape, and the periphery has turned into droplets, but as shown by the imaginary line in the figure. Fluctuations occur at the peripheral edge of the liquid film, making the contour shape unstable, and as a result, the size of the droplets becomes somewhat non-uniform, with some of the droplets becoming large.
×: As shown in Figure 8 (c1), when the molten iron (water) umbrella is viewed from above, a clear liquid film is not formed and the droplets are a mixture of large and small particles and are scattered. The texture becomes uneven. Alternatively, as shown in FIG. 8(c2), the molten iron (water) umbrella falls without turning into droplets.

According to FIG. 7, the range of the nozzle discharge speed v ₀ that can form an appropriate molten iron (water) umbrella with a stable liquid film becomes narrower toward the upper limit as the nozzle diameter d ₀ becomes larger. This is because as the nozzle diameter _d0 increases, the flow rate increases, and the kinetic energy when it collides with the top surface of the molten iron receiving plate 3 increases, and immediately after the collision, droplets containing a mixture of large and small particles are scattered. This is because an appropriate molten iron (water) umbrella cannot be formed.
Based on the above results, the present inventors believe that if the same tundish is continued to be used, the phenomenon in which the particle size of iron particles becomes unstable is due to the progress of wear and tear on the nozzle 2, which increases the nozzle aperture _d0 , and the proper molten iron ( It is assumed that this is because the umbrella (water) is no longer formed.

Therefore, in order to apply the conditions under which a molten iron (water) umbrella with a stable liquid film obtained in the water model experiment can be formed to an actual molten iron manufacturing equipment, we investigated the viscosity, surface tension, and inertial force. Relatedly, we focused on the collision Reynolds number, which is a dimensionless number related to the collision of a liquid column with an object.
FIG. 9 schematically shows a vertical cross section of the molten iron granulation mechanism consisting of the tundish 1, nozzle 2, and molten iron receiving plate 3. It is schematically shown that the column _xc collides with the molten iron receiving plate 3, becomes a liquid film on the upper surface of the molten iron receiving plate, and then turns into droplets.
In FIG. 9, _d0 is the nozzle diameter [mm] of the nozzle 2, _v0 is the discharge velocity [m/s] (discharge flow velocity) of the molten iron x from the nozzle 2, and _hd is the distance from the tip of the nozzle 2 to the molten iron receiving plate 3. Vertical distance to the top surface [mm] (molten iron falling height), D is the outer diameter of the disc-shaped molten iron receiving plate 3 [mm], h is the height of the liquid level in the tundish 1, and d is from the nozzle 2. The liquid column diameter [mm] when the liquid column x _c of molten iron x discharged and flowing down collides with the hot metal receiving plate 3, v is the liquid column x _c of molten iron x discharged from the nozzle 2 and flowing down the hot metal receiving plate 3. It is the collision flow velocity [m/s] when colliding with 3. In addition, Table 1 shows the physical property values of molten iron (hot metal) and water.

The collision Reynolds number I is determined by the diameter and velocity of the molten iron flow (liquid column x _c ) at the position where the molten iron flow (liquid column x _c ) discharged from the nozzle 2 collides with the upper surface of the molten iron receiving plate 3, and the viscosity of the molten iron. It is a dimensionless number related to the collision of liquid (molten iron), which is given by density and surface tension, and is affected by the viscosity and surface tension of molten iron, and the inertial force acting on the discharged molten iron flow. This is an indicator of how easily a liquid film is formed during a collision. The collision Reynolds number I is calculated by the following equation (1), which is a relational expression between the Weber number We, which is a dimensionless quantity in fluid dynamics, and the Reynolds number Re.
The Weber number is a dimensionless quantity that expresses the similarity law for the dynamic behavior of phenomena involving surface tension, such as droplets and bubbles, and is a parameter that governs the shape and deformation behavior of droplets and bubbles. Calculated from formula (2). Here, the representative length is the diameter of the liquid column when the liquid column _xc of the molten iron collides with the molten iron receiving plate 3.
Furthermore, the Reynolds number is a dimensionless quantity that represents the ratio of the viscous force and inertial force of the flow, represents a dynamically similar flow state, and is calculated from the following equation (3). Here, the representative length is the diameter of the liquid column when the liquid column _xc of the molten iron collides with the molten iron receiving plate 3.
Equations (4) and (5) below indicate that the liquid column _xc of molten iron discharged from nozzle 2 of tundish 1 and flowing down is a vertical distance hd from the tip (lower end) of nozzle 2 _to the molten iron receiving plate below. 3 is a calculation formula for the liquid column diameter d derived from the law of conservation of energy, and a calculation formula for the collision flow velocity v derived from the law of constant volume.

但し Ｉ：衝突レイノルズ数［－］
Re：レイノルズ数［－］
We：ウェーバー数［－］
ｄ：ノズル２から吐出されて流下する溶鉄の液柱が溶銑受け盤３に衝突する際の液柱径［mm］
ｖ：ノズル２から吐出されて流下する溶鉄の液柱が溶銑受け盤３に衝突する際の衝突流速［m/s］
ρ：溶鉄の密度［kg/ m^３］
μ：溶鉄の粘度［mPa・s］
σ：溶鉄の表面張力［mN/m］
ｇ：重力加速度［m/s^２］
ｄ_０：ノズル２のノズル口径［mm］
ｖ_０：ノズル２からの溶鉄の吐出速度［m/s］
ｈ_ｄ：ノズル２の先端から溶鉄受け盤３の上面までの垂直方向距離［mm］

However, I: Collision Reynolds number [-]
Re: Reynolds number [-]
We: Weber number [-]
d: Diameter of the liquid column when the liquid column of molten iron discharged from the nozzle 2 and flowing down collides with the hot metal receiving plate 3 [mm]
v: Collision flow velocity when the liquid column of molten iron discharged from the nozzle 2 and flowing down collides with the molten metal receiving plate 3 [m/s]
ρ: Density of molten iron [kg/ ^m3 ]
μ: Viscosity of molten iron [mPa・s]
σ: Surface tension of molten iron [mN/m]
g: Gravitational acceleration [m/s ² ]
d ₀ : Nozzle diameter of nozzle 2 [mm]
v ₀ : Discharge speed of molten iron from nozzle 2 [m/s]
h _d : Vertical distance from the tip of nozzle 2 to the top surface of molten iron receiving plate 3 [mm]

FIG. 10 shows the relationship between the formation of an appropriate molten iron (water) umbrella in a water model experiment, the collision Reynolds number I, and the nozzle diameter d ₀ . Here, whether the molten iron (water) umbrella was properly formed was determined using the same criteria as in FIG. 7.
According to FIG. 10, it can be seen that in order to form an appropriate molten iron (water) umbrella with a stable liquid film, the collision Reynolds number I should be set to 3000≦I≦7500, regardless of the nozzle diameter _d0 . . Note that the collision Reynolds number I is determined by taking into account the variations in the factors that determine the collision Reynolds number I, such as the discharging velocity v ₀ of molten iron from the nozzle 2 and the variation in control accuracy of the height h of the molten metal in the tundish 1. may be in a narrower range than 3000≦I≦7500.

Here, from the above-mentioned equations (1) to (5), the factors that determine the collision Reynolds number I in the molten iron granulation mechanism as shown in _FIG . There is a discharge speed v ₀ of the molten iron x from the molten iron x, and a vertical distance h _d from the tip of the nozzle 2 to the upper surface of the molten iron receiving plate 3. Note that the discharge speed v ₀ of the molten iron x from the nozzle 2 can be adjusted by changing the height h of the molten metal level in the tundish 1 shown in FIG.
As mentioned earlier, when the production of granulated iron is continued for a certain period of time, the grain size of granulated iron becomes unstable because the nozzle diameter d ₀ increases due to wear and tear on the nozzle 2, and the impact Reynolds number I is outside the range of 3000≦I≦7500.

Therefore, in the first embodiment of the present invention, the nozzle diameter d ₀ of the nozzle 2 is set such that even if the nozzle diameter d ₀ increases to some extent due to wear and tear of the nozzle 2, the collision Reynolds number I falls within 3000≦I≦7500. The discharge speed v ₀ of the molten iron x from the nozzle 2 and the vertical distance h _d from the tip of the nozzle 2 to the upper surface of the molten iron receiving plate 3 are set.
It is known from experience that the nozzle diameter d ₀ of the nozzle 2 provided in a typical tundish 1 increases by about 1 mm per 300 tons of molten iron discharged due to nozzle wear. The usage limit is determined by considering the equipment specifications of the entire granular pig iron manufacturing equipment, such as the thickness of the heat-resistant material at the nozzle diameter of nozzle 2 and the upper limit of the amount of molten iron that can be processed based on the cooling capacity of the granular iron manufacturing equipment. It can be decided. For example, cases where nozzle 2 reaches its usable limit due to expansion of the nozzle diameter due to nozzle wear include (i) when the thickness of the heat-resistant material at the nozzle diameter decreases and the nozzle itself becomes unusable; (ii) when the nozzle itself becomes unusable; itself can be used, but if the amount of molten iron discharged increases due to the enlargement of the nozzle diameter and exceeds the cooling capacity of the granular iron manufacturing equipment, (iii) suppressing the increase in the amount of molten iron discharged due to the enlargement of the nozzle diameter. If you take measures to adjust the hot water level h of the tundish 1 (lower the hot water level height) to ensure stable operation, the adjustment allowance will reach its limit, etc. The usage limit of the nozzle 2 is determined by these circumstances.

Therefore, in the first embodiment of the present invention, the nozzle diameter d ₀ of the nozzle 2, the discharge speed v ₀ of the molten iron x from the nozzle 2, and the nozzle The vertical distance h _d from the tip of the nozzle 2 to the top surface of the molten iron receiving plate 3 is determined, and the nozzle diameter at the discharge speed v ₀ and the vertical distance h _d is the nozzle diameter at the usage limit of the nozzle 2 (however, The nozzle diameter is set so that the collision Reynolds number I satisfies 3000≦I≦7500 (the nozzle diameter when the nozzle 2 reaches its usable limit due to enlargement of the nozzle diameter due to nozzle wear).

On the other hand, in the second embodiment of the present invention, even if the nozzle diameter d ₀ increases to some extent due to wear and tear on the nozzle 2, the discharge velocity v ₀ or / and to adjust (change) the vertical distance h _d .
That is, the nozzle diameter d ₀ of the nozzle 2, the discharge speed v ₀ of the molten iron x from the nozzle 2, and the distance from the tip of the nozzle 2 to the upper surface of the molten iron receiving plate 3 are adjusted such that the collision Reynolds number I satisfies 3000≦I≦7500. The collision _Reynolds The discharge speed v ₀ and/or the vertical distance h _d are adjusted (changed) so that the number I satisfies 3000≦I≦7500. More specifically, as the nozzle diameter d ₀ increases due to wear and tear on the nozzle ₂ , the collision Reynolds number I increases. Reduce distance h _d .

As described above, the discharge speed v ₀ of the molten iron x from the nozzle 2 can be adjusted by changing the height h of the molten metal level in the tundish 1 shown in FIG. Therefore, when adjusting (reducing) the discharge speed v ₀ , the molten metal level height h in the tundish 1 may be reduced by adjusting the amount of molten iron flowing in from the molten iron transport container 10 . Further, in order to reduce the vertical distance _hd , for example, the height of the molten iron receiving plate 3 may be increased by making the molten iron receiving plate 3 have a height-adjustable structure. Further, by using these in combination, both the discharge speed v ₀ and the vertical distance h _d may be changed (reduced).

Here, the nozzle aperture of the nozzle 2 at its usable limit (however, the nozzle aperture at the time when the nozzle 2 reaches its usable limit due to expansion of the nozzle aperture due to nozzle wear) is usually the nozzle aperture in view of the above-mentioned circumstances. It is often within the range of about aperture d ₀ (initial nozzle aperture) + 5 mm to nozzle aperture d ₀ (initial nozzle aperture) + 30 mm. Therefore, the nozzle diameter at the usage limit of the nozzle 2 is determined as, for example, "nozzle diameter d ₀ + 10 mm" or "nozzle diameter d ₀ + 20 mm", and the above-mentioned first embodiment and second embodiment of the present invention All you have to do is carry out the following.
As mentioned above, it is known that the degree of enlargement of the nozzle diameter due to nozzle wear is approximately 1 mm per 300 tons of molten iron discharge, but tests have shown that the degree of expansion of the nozzle diameter due to molten iron discharge and nozzle wear is The relationship between the nozzle diameter and the enlargement may also be investigated.

Although the planar shape of the molten iron receiving plate 3 is arbitrary, in order to stably form a circular liquid film as shown in FIG. 8(a), it is circular (disc-shaped) as in this embodiment. It is preferable.
There is no particular limit to the size of the molten iron receiving plate 3, but the size of the molten iron receiving plate 3 is large relative to the diameter d of the liquid column when the molten iron liquid column _xc discharged from the nozzle 2 and flowing down collides with the molten iron receiving plate 3. If the outer diameter D is too large, the rate at which the liquid film spreads becomes unstable due to the influence of viscous resistance, which may adversely affect the formation of molten iron umbrellas and droplets. For this reason, the outer diameter of the molten iron receiving plate 3 was set as D [mm], and the liquid column diameter when the molten iron liquid column _xc discharged from the nozzle 2 and flowing down collides with the molten iron receiving plate 3 was set as d [mm]. In this case, the upper limit of D/d is preferably about 7.0. On the other hand, if the liquid column diameter d is larger than the outer diameter D of the molten iron receiving plate 3, the peripheral portion of the liquid column _xc will not collide with the molten iron receiving plate 3 and will not become droplets, so D/d will be 1.0 or more. It is preferable that

Next, details of the iron granule manufacturing apparatus and manufacturing method of the embodiment shown in FIGS. 1 to 3 will be described.
The nozzle 2 included in the tundish 1 has a substantially cylindrical shape, and is provided at the bottom of the tundish 1 in this embodiment, but may be provided at the lower side of the tundish 1, for example.
In the cooling water tank 4 of this embodiment, a partition cylinder 5 with open upper and lower ends is disposed, and the inside of the partition cylinder 5 is a cooling area that receives droplets of molten iron x falling from above and cools the partition cylinder 5. A, and cooling water supplied from the outside of the cooling water tank 4 is introduced into the cooling area A (inside the partition cylinder 5) through the cooling water supply pipe 6.

The reason why the cooling area A is provided in the cooling water tank 4 by the partition cylinder 5 is that (i) the droplets of molten iron x are efficiently cooled by introducing the cooling water into this area in a concentrated manner; (ii) By generating granular iron x _g within the partition cylinder 5 and discharging the granular iron x _g downward from the opening at the lower end of the partition cylinder 5, the granular iron x _g is collected in one place. This is to achieve the two effects of making it easier to collect and collect. Furthermore, by forming the partition cylinder 5 into a specific shape as described below, a swirling upward flow of cooling water is generated in the cooling area A (inside the partition cylinder 5) as described later, and the powdered iron The effect of increasing the cooling efficiency of _g is also obtained.

The partition cylindrical body 5 has a funnel-shaped (cone-shaped) structure in which the upper and lower ends are open (in the figure, 50 is an opening at the upper end, 51 is an opening at the lower end), and a cooling water tank is formed. 4 through a support member (not shown). The angle of inclination θ (see FIG. 3) of the funnel-shaped (cone-shaped) inclined surface of the partition cylinder 5 from the horizontal is preferably about 40 to 60 degrees from the viewpoint of preventing granular iron from accumulating.
One or more cooling water supply pipes 6 are connected to the partition cylinder 5, and cooling water is introduced into the cooling area A (inside the partition cylinder 5) from outside the cooling water tank 4, but in this embodiment In this case, cooling water supply pipes 6 are connected to a plurality of positions spaced apart in the circumferential direction and the vertical direction of the partition cylinder 5, respectively, and the cooling area portion A (of the partition cylinder 5) is connected from the plurality of cooling water supply pipes 6. Cooling water is introduced to the inside (inside).

By supplying cooling water from the cooling water supply pipe 6 into the funnel-shaped partition cylinder 5 in this way, the cooling water tends to flow toward the upper end opening 50 side of the partition cylinder 5, which has a large opening area, and the cooling water When the cooling water flow discharged from the supply pipe 6 hits the inner inclined surface of the partition cylinder 5, it tends to swirl upward, so that an upward swirling flow of cooling water is generated within the partition cylinder 5. This eliminates water stagnation in the cooling area A (inside the partition cylinder 5), and the cooling water flow becomes a countercurrent to the granulated iron x _g (solidifying molten iron droplets) falling from above. , the cooling efficiency of x _g of granulated iron is increased. Further, by connecting a cooling water supply pipe 6 to the lower side of the partition cylinder 5 and introducing cooling water from this cooling water supply pipe 6, a larger upward flow of cooling water can be formed.

Further, as shown in FIG. 2, each cooling water supply pipe 6 is connected to the partition cylinder 5 so as to introduce cooling water into the partition cylinder 5 in a direction eccentric to the cylinder core. As a result, a swirling flow of cooling water can be more effectively generated in the cooling area A, so that the cooling efficiency of the granulated iron can be further improved.
Note that only the lower part of the partition cylinder 5 may be configured in a funnel shape (cone shape), and the cooling water supply pipe 6 is connected to the funnel shape in the same manner as in this embodiment, so that the cooling water is supplied. It may also be introduced.

Furthermore, the cooling water supply pipe 6 is not connected to the partition cylinder 5, but has its end disposed within the partition cylinder 5, as shown in FIGS. 12(a) to 12(d), for example. You can do it like this.
Therefore, the cooling water supply pipe 6 can be provided to the partition cylinder 5 as shown in (i) and/or (ii) below.
(i) The cooling water supply pipe 6 is arranged so that the cooling water is introduced into the partition cylinder 5 in a direction eccentric to the cylinder core, thereby generating a swirling flow of the cooling water in the cooling area A. It is connected to the partition cylinder 5 or the end of the cooling water supply pipe 6 is disposed within the partition cylinder 5 .
(ii) The whole or lower part of the partition cylinder 5 is configured in a funnel shape, and the cooling water supply pipe 6 is connected to the funnel-shaped part, or the end of the cooling water supply pipe 6 is arranged in the funnel-shaped part. be done.

A drain port 8 is provided at the bottom of the cooling water tank 4, and an amount of cooling water corresponding to the amount of cooling water supplied by the cooling water supply pipe 6 is supplied to the drain port so that the cooling water level in the cooling water tank 4 is constant. Water is drained from 8. In addition, when cooling water is circulated inside and outside the cooling water tank 4, the temperature rises due to cooling of the molten iron in the cooling water tank 4 (e.g., 65°C or higher), and the cooling water drained from the drain port 8 flows into the cooling system. After being cooled (for example, to about 30 to 35° C.), the water is introduced into the cooling area A of the cooling water tank 4 from the cooling water supply pipe 6.

The cooling water tank 4 is provided with a conveyor 7 for transporting granulated iron produced by cooling droplets of molten iron in the cooling area A to the outside of the cooling water tank 4 . This carry-out conveyor 7 is installed in the cooling water tank 4 in an inclined state so that the transport start end 70 is located below the lower end of the partition cylinder 5 and the transport terminal end 71 is located outside the cooling water tank 4. ing.
The granulated iron generated in the cooling area section A is collected by a funnel-shaped (cone-shaped) partition cylinder 5, falls from the lower end opening 51 of the partition cylinder 5, is placed on the conveyance start end 70 of the carry-out conveyor 7, and continues as it is. It is continuously carried out of the tank by a carrying-out conveyor 7.
Note that the delivery conveyor 7 is preferably equipped with a mesh-like conveyor belt that can drain water.

In this embodiment, the molten iron receiving plate 3 is supported by the partition cylinder 5 via the support 9, and is disposed below the nozzle 2 of the tundish 1.
Here, in the second embodiment of the present invention, in order to adjust (change) the vertical distance _hd from the tip of the nozzle 2 to the upper surface of the molten iron receiving plate 3, the height of the molten iron receiving plate 3 is changed during operation. If it is necessary to change the height of the molten iron receiving plate 3, the height of the molten iron receiving plate 3 can be adjusted by, for example, making the support 9 supporting the molten iron receiving plate 3 expandable and retractable.
In addition, as a granular iron manufacturing apparatus, the cooling water supply pipe 6 is connected to the cooling water tank 4 itself without installing a partition cylinder in the cooling water tank 4, or the end of the cooling water supply pipe 6 is connected to the cooling water tank 4. It may be arranged within 4. In this case, the entire or lower portion of the cooling water tank 4 may be constructed in the shape of a funnel (cone shape), and a discharge pipe for sucking and discharging the granulated iron together with the cooling water may be connected to the bottom thereof.

[Example 1]
Using the granular iron manufacturing apparatus of the present invention as shown in FIG. 1, granular pig iron was manufactured according to the first embodiment of the present invention under the conditions shown in Tables 2 and 3. Regarding the usage limit of the nozzle, based on the upper limit of the amount of molten iron that can be processed based on the cooling capacity of the granular iron production equipment, the nozzle diameter of nozzle 2 becomes nozzle diameter d ₀ (initial nozzle diameter) + 20 mm due to nozzle wear. did. That is, as an example of the present invention, the nozzle diameter d ₀ of the nozzle 2, the discharge speed v ₀ of the molten iron from the nozzle 2, and the molten iron receiving from the tip of the nozzle 2 are adjusted such that the collision Reynolds number I satisfies 3000≦I≦7500. Configure the vertical distance h _d to the top surface of the board 3, and set the nozzle diameter at the discharge speed v ₀ and the vertical distance h _d to the nozzle diameter at the limit of use of the nozzle 2 (that is, the nozzle diameter due to nozzle wear). Granular pig iron is manufactured under the condition that the collision Reynolds number I satisfies 3000≦I≦7500, when the nozzle diameter when the nozzle 2 reaches its usage limit due to diameter expansion = nozzle diameter d ₀ (initial nozzle diameter) + 20 mm) went.
On the other hand, as a comparative example, granular pig iron was produced under the condition that the collision Reynolds number I at the nozzle diameter d ₀ or the collision Reynolds number I at the nozzle diameter at the limit of use of nozzle 2 did not satisfy 3000≦I≦7500, respectively. went.

Among the produced granular pig iron, the particle size of the product (granular pig iron) obtained by charging when the nozzle 2 reached its usage limit was measured, and the average particle size and maximum particle size of the granular pig pig were determined. The results are also shown in Tables 2 and 3.
To measure the particle size of granular pig iron and calculate the average particle size and maximum particle size, use the test sieve described in JIS Z8801-1 "Test sieve: Metal mesh sieve" or JIS Z8801-2 "Test sieve: Metal plate sieve". The measurement was carried out in accordance with JIS M8706 "Iron ore and reduced iron - Measuring method of particle size distribution by sieving".
In addition, in this example, the amount of hot metal per charge is 300 tons, and as a rule of thumb, it is thought that the nozzle diameter will expand by about 1 mm for each charge due to nozzle wear, so assuming this, after 5 charges and 10 The collision Reynolds number after charging was calculated.

According to Tables 2 and 3, in Comparative Examples 1 to 14, either or both of the collision Reynolds number I at the nozzle diameter d ₀ and the collision Reynolds number I at the nozzle diameter at the limit of nozzle usage is 3000. Since ≦I≦7500 is not satisfied, the maximum particle size of all the granular pig iron obtained by charging at the nozzle usage limit exceeds 50 mm. Furthermore, in Comparative Examples 8 to 10 in which the collision Reynolds number I at the nozzle diameter d ₀ exceeds 7500, the average particle diameter also exceeds 20 mm. On the other hand, in Invention Examples 1 to 13, the granular pig iron obtained by charging at the nozzle usage limit all have an average particle size of 20 mm or less, and a maximum particle size of 35 mm or less.

[Example 2]
Using the granular iron manufacturing apparatus of the present invention as shown in FIG. 1, granular pig iron was manufactured according to the second embodiment of the present invention under the conditions shown in Tables 4 and 5. That is, as an example of the present invention, the nozzle diameter d ₀ of the nozzle 2, the discharge speed v ₀ of the molten iron from the nozzle 2, and the molten iron receiving from the tip of the nozzle 2 are adjusted such that the collision Reynolds number I satisfies 3000≦I≦7500. The vertical distance h _d to the top surface of the plate 3 (molten iron falling height h _d to the molten iron receiving plate) was configured as shown in Table 4, and production of granular pig iron was started. , until the nozzle 2 reaches its usage limit due to expansion of the nozzle diameter due to nozzle wear (as in Example 1, the time when the nozzle diameter of nozzle 2 becomes nozzle diameter d ₀ (initial nozzle diameter) + 20 mm due to nozzle wear). The granular pig iron was manufactured while adjusting the molten iron falling height _hd as shown in Table 5 so that the collision Reynolds number I satisfied 3000≦I≦7500. Specifically, the molten iron falling height _hd , which was initially 1000 mm, was changed to 737 mm after 5 charges, 524 mm after 10 charges, and then further changed to 206 mm. Note that the molten iron falling height _hd was adjusted by changing the height of the molten iron receiving plate 3 whose height is adjustable.
On the other hand, as a comparative example, the nozzle diameter d ₀ of the nozzle 2, the discharge speed v ₀ of the molten iron from the nozzle 2, and the molten iron receiving plate from the tip of the nozzle 2 are set such that the collision Reynolds number I satisfies 3000≦I≦7500. The vertical distance h _d to the upper surface of 3 (the falling height h _d of the molten iron to the molten iron receiving plate) was configured as shown in Table 4, and the production of granulated iron was started. Granular pig iron production continued under the same conditions.

Among the manufactured granular iron, the particle size of the product (granular pig iron) obtained by charging when the nozzle 2 reached its usage limit was measured using the same method as [Example 1], and the average particle size of the granular pig iron was determined. The diameter and maximum particle size were determined. The results are also shown in Table 5.
Note that the method for calculating the collision Reynolds number after 5 charges and after 10 charges is the same as in [Example 1].
According to Table 5, in the comparative example, the impact Reynolds number I after 5 charges no longer satisfies 3000≦I≦7500, and the granulated pig iron obtained by charging when nozzle 2 reaches its usage limit has a maximum particle size. Exceeds 50mm. On the other hand, in the invention example, since the collision Reynolds number I is maintained at 3000≦I≦7500, the granular pig iron obtained by charging when the nozzle 2 reaches its usage limit has an average particle size of 20 mm or less and a maximum The particle size is 50 mm or less (35 mm or less).

[Example 3]
Using the granular iron manufacturing apparatus of the present invention as shown in FIG. 1, granular pig iron was manufactured according to the second embodiment of the present invention under the conditions shown in Tables 6 and 7. That is, as an example of the present invention, the nozzle diameter d ₀ of the nozzle 2, the discharge speed v ₀ of the molten iron from the nozzle 2, and the molten iron receiving from the tip of the nozzle 2 are adjusted such that the collision Reynolds number I satisfies 3000≦I≦7500. The vertical distance h _d to the top surface of the plate 3 (molten iron falling height h _d to the molten iron receiving plate) is configured as shown in Table 6, and the production of granular pig iron is started. , until the nozzle 2 reaches its usage limit due to expansion of the nozzle diameter due to nozzle wear (as in Example 1, the time when the nozzle diameter of nozzle 2 becomes nozzle diameter d ₀ (initial nozzle diameter) + 20 mm due to nozzle wear). As shown in Table 7, the granular pig iron was produced while adjusting the discharge speed v ₀ of the molten iron from the nozzle 2 so that the collision Reynolds number I satisfied 3000≦I≦7500. Specifically, the discharge speed _v0 of molten iron from the nozzle 2, which was initially 3.6 m/s, was reduced to 3.4 m/s after 5 charges and 10 charges by lowering the height h of the molten metal surface in the tundish 1. It was later changed to 3.2 m/s, and then further changed to 2.9 m/s.
On the other hand, as a comparative example, the nozzle diameter d ₀ of the nozzle 2, the discharge speed v ₀ of the molten iron from the nozzle 2, and the molten iron receiving plate from the tip of the nozzle 2 are set such that the collision Reynolds number I satisfies 3000≦I≦7500. The vertical distance h _d to the top surface of 3 (the falling height h _d of molten iron to the molten iron receiving plate) was configured as shown in Table 6, and the production of granulated iron was started. Granular pig iron production continued under the same conditions.

Among the manufactured granular iron, the particle size of the product (granular pig iron) obtained by charging when the nozzle 2 reached its usage limit was measured using the same method as [Example 1], and the average particle size of the granular pig iron was determined. The diameter and maximum particle size were determined. The results are also shown in Table 7.
Note that the method for calculating the collision Reynolds number after 5 charges and after 10 charges is the same as in [Example 1].
According to Table 7, in the comparative example, the impact Reynolds number I after 5 charges no longer satisfies 3000≦I≦7500, and the granulated pig iron obtained by charging when nozzle 2 reaches its usage limit has a maximum particle size. Exceeds 50mm. On the other hand, in the invention example, since the impact Reynolds number I is maintained at 3000≦I≦7500, the granular pig iron obtained by charging when the nozzle 2 reaches its usage limit has an average particle size of 20 mm or less, and a maximum particle size of 20 mm or less. The diameter is 50 mm or less.

1 Tundish 2 Nozzle 3 Molten iron receiving plate 4 Cooling water tank 5 Partition tube 6 Cooling water supply pipe 7 Unloading conveyor 8 Drain port 9 Support 10 Molten iron transport container 11 Gutter 50 Upper end opening 51 Lower end opening 70 Conveyance start end 71 Conveyance end A Cooling area x Molten iron x _C liquid column x _G grain iron w Cooling water

Claims (16)

a tundish (1) equipped with a nozzle (2) for discharging the contained molten iron;
a molten iron receiving plate (3) that collides a liquid column of molten iron discharged from a nozzle (2) of the tundish (1) and flowing down;
A granule equipped with a cooling water tank (4) disposed below the molten iron receiving plate (3) and cooling droplets of molten iron that collide with the molten iron receiving plate (3) and are scattered around it by falling into the cooling water. Iron manufacturing equipment,
The nozzle diameter d ₀ of the nozzle (2) and the discharge speed of molten iron from the nozzle (2) are adjusted so that the collision Reynolds number I defined by the following equations (1) to (5) satisfies 3000≦I≦7500. v ₀ and the vertical distance h _d from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3), and the nozzle diameter is set to the nozzle diameter at the discharge speed v ₀ and the vertical distance h _d . ) (However, the nozzle diameter when nozzle (2) reaches its service limit due to expansion of the nozzle diameter due to nozzle wear), the impact Reynolds number I satisfies 3000≦I≦7500. Granular iron manufacturing equipment characterized by:

However, I: Collision Reynolds number [-]
Re: Reynolds number [-]
We: Weber number [-]
d: Diameter of the liquid column when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the hot metal receiving plate (3) [mm]
v: Collision flow velocity when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the molten metal receiving plate (3) [m/s]
ρ: Density of molten iron [kg/ ^m3 ]
μ: Viscosity of molten iron [mPa・s]
σ: Surface tension of molten iron [mN/m]
g: Gravitational acceleration [m/s ² ]
d ₀ : Nozzle diameter of nozzle (2) [mm]
v ₀ : Discharge speed of molten iron from nozzle (2) [m/s]
h _d : Vertical distance from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3) [mm] The nozzle diameter of the nozzle (2) at its usage limit (however, the nozzle diameter when the nozzle (2) reaches its usage limit due to expansion of the nozzle diameter due to nozzle wear) is from nozzle diameter d ₀ + 5 mm to nozzle diameter d ₀ + 30 mm. The granulated iron manufacturing apparatus according to claim 1, wherein the iron granule production apparatus is within the range of . The planar shape of the molten iron receiving plate (3) is circular, and the outer diameter D [mm] of the circular molten iron receiving plate (3) and the liquid column of molten iron discharged from the nozzle (2) and flowing down are the molten iron receiving plate. The granular pig iron manufacturing apparatus according to claim 1 or 2, characterized in that the diameter d [mm] of the liquid column when it collides with the disk (3) satisfies 1≦D/d≦7. A cooling area section in which a partition cylinder (5) with open upper and lower ends is arranged in a cooling water tank (4), and the inside of the partition cylinder (5) is cooled by receiving droplets of molten iron falling from above. (A) and
The granules according to any one of claims 1 to 3, further comprising a cooling water supply pipe (6) for introducing cooling water supplied from the outside of the cooling water tank (4) into the cooling area (A). Iron manufacturing equipment. Equipped with a carry-out conveyor (7) for carrying out granulated iron produced by cooling droplets of molten iron in the cooling area (A) to the outside of the cooling water tank (4),
By locating the conveyance start end of the carry-out conveyor (7) below the lower end of the partition cylinder (5), the granulated iron that has fallen from the lower end of the partition cylinder (5) is transferred to the cooling water tank (4) by the carry-out conveyor (7). 5. The granulated iron manufacturing apparatus according to claim 4, wherein the granulated iron manufacturing apparatus is adapted to be carried outside. The cooling water supply pipe ( 6) is connected to the partition cylinder (5), or the end of the cooling water supply pipe (6) is arranged in the partition cylinder (5). Iron manufacturing equipment. The entire or lower part of the partition cylinder (5) is configured in the shape of a funnel, and the cooling water supply pipe (6) is connected to the funnel-shaped part, or the end of the cooling water supply pipe (6) is connected to the funnel-shaped part. The granulated iron manufacturing apparatus according to any one of claims 4 to 6, characterized in that a part is arranged. a tundish (1) equipped with a nozzle (2) for discharging the contained molten iron;
a molten iron receiving plate (3) that collides a liquid column of molten iron discharged from a nozzle (2) of the tundish (1) and flowing down;
A device comprising a cooling water tank (4) disposed below the molten iron receiving plate (3) and cooling droplets of molten iron that collide with the molten iron receiving plate (3) and scatter around it by falling into the cooling water. A method for producing granulated iron using
The nozzle diameter d ₀ of the nozzle (2) and the discharge speed of molten iron from the nozzle (2) are adjusted so that the collision Reynolds number I defined by the following equations (1) to (5) satisfies 3000≦I≦7500. v ₀ and the vertical distance h _d from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3), and the nozzle aperture at the discharge speed v ₀ and the vertical distance h _d is the same as that of the nozzle (2). ) (However, the nozzle diameter when nozzle (2) reaches its service limit due to expansion of the nozzle diameter due to nozzle wear), the impact Reynolds number I satisfies 3000≦I≦7500. A method for producing granular iron characterized by:

However, I: Collision Reynolds number [-]
Re: Reynolds number [-]
We: Weber number [-]
d: Diameter of the liquid column when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the hot metal receiving plate (3) [mm]
v: Collision flow velocity when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the molten metal receiving plate (3) [m/s]
ρ: Density of molten iron [kg/ ^m3 ]
μ: Viscosity of molten iron [mPa・s]
σ: Surface tension of molten iron [mN/m]
g: Gravitational acceleration [m/s ² ]
d ₀ : Nozzle diameter of nozzle (2) [mm]
v ₀ : Discharge speed of molten iron from nozzle (2) [m/s]
h _d : Vertical distance from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3) [mm] The nozzle diameter of the nozzle (2) at its usage limit (however, the nozzle diameter when the nozzle (2) reaches its usage limit due to expansion of the nozzle diameter due to nozzle wear) is from nozzle diameter d ₀ + 5 mm to nozzle diameter d ₀ + 30 mm. The method for producing granulated iron according to claim 8, wherein the granulated iron is within the range of . a tundish (1) equipped with a nozzle (2) for discharging the contained molten iron;
a molten iron receiving plate (3) that collides a liquid column of molten iron discharged from a nozzle (2) of the tundish (1) and flowing down;
A device comprising a cooling water tank (4) disposed below the molten iron receiving plate (3) and cooling droplets of molten iron that collide with the molten iron receiving plate (3) and scatter around it by falling into the cooling water. A method for producing granulated iron using
The nozzle diameter d ₀ of the nozzle (2) and the discharge speed of molten iron from the nozzle (2) are adjusted so that the collision Reynolds number I defined by the following equations (1) to (5) satisfies 3000≦I≦7500. v ₀ and a vertical distance h _d from the tip of the nozzle (2) to the top surface of the molten iron receiver (3) to start producing granulated iron;
After starting the production of granulated iron, the collision Reynolds number I is maintained to satisfy 3000≦I≦7500 until the nozzle (2) reaches its usable limit due to expansion of the nozzle diameter due to nozzle wear. A method for producing granulated iron, characterized in that the discharge speed v ₀ and/or the vertical distance h _d are adjusted.

However, I: Collision Reynolds number [-]
Re: Reynolds number [-]
We: Weber number [-]
d: Diameter of the liquid column when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the hot metal receiving plate (3) [mm]
v: Collision flow velocity when the liquid column of molten iron discharged from the nozzle (2) and flowing down collides with the molten metal receiving plate (3) [m/s]
ρ: Density of molten iron [kg/ ^m3 ]
μ: Viscosity of molten iron [mPa・s]
σ: Surface tension of molten iron [mN/m]
g: Gravitational acceleration [m/s ² ]
d ₀ : Nozzle diameter of nozzle (2) [mm]
v ₀ : Discharge speed of molten iron from nozzle (2) [m/s]
h _d : Vertical distance from the tip of the nozzle (2) to the top surface of the molten iron receiving plate (3) [mm] According to claim 10, the nozzle diameter when the nozzle (2) reaches its usable limit due to enlargement of the nozzle diameter due to nozzle wear is within the range of nozzle diameter d ₀ +5 mm to nozzle diameter d ₀ +30 mm. Granular iron manufacturing method. The planar shape of the molten iron receiving plate (3) is circular, and the outer diameter D [mm] of the circular molten iron receiving plate (3) and the liquid column of molten iron discharged from the nozzle (2) and flowing down are the molten iron receiving plate. The method for producing granulated iron according to any one of claims 8 to 11, characterized in that the liquid column diameter d [mm] when colliding with the plate (3) satisfies 1≦D/d≦7. A cooling area section in which a partition cylinder (5) with open upper and lower ends is arranged in a cooling water tank (4), and the inside of this partition cylinder (5) is cooled by receiving droplets of molten iron falling from above. (A) and
Granulated iron according to any one of claims 8 to 12, characterized in that cooling water supplied from outside of the cooling water tank (4) is introduced into the cooling area (A) through a cooling water supply pipe (6). Production method. Equipped with a carry-out conveyor (7) for carrying out granulated iron produced by cooling droplets of molten iron in the cooling area (A) to the outside of the cooling water tank (4),
By locating the conveyance start end of the carry-out conveyor (7) below the lower end of the partition cylinder (5), the iron granules that have fallen from the lower end of the partition cylinder (5) are transferred to the cooling water tank (4) by the carry-out conveyor (7). The method for manufacturing granulated iron according to claim 13, characterized in that the iron granules are transported outside. By introducing the cooling water into the partition cylinder (5) in a direction eccentric to the cylinder core through the cooling water supply pipe (6), a swirling flow of the cooling water is generated in the cooling area (A). The method for producing granulated iron according to claim 13 or 14, characterized in that: Any one of claims 13 to 15, characterized in that the entire or lower portion of the partition cylinder (5) is configured in a funnel shape, and cooling water is introduced into the funnel-shaped portion through a cooling water supply pipe (6). Granular iron production method described in.

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