EP4628601A1

EP4628601A1 - Slag modification method and slag modification device

Info

Publication number: EP4628601A1
Application number: EP24766719.9A
Authority: EP
Inventors: Yusuke Kato; Katsunori Takahashi
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2023-03-07
Filing date: 2024-01-30
Publication date: 2025-10-08
Also published as: KR20250129061A; JP7522983B1; EP4628601A4; CN120712365A; JPWO2024185344A1

Abstract

A slag modification method including: a slag flow forming step of causing slag in a molten state to flow down so as to form a slag flow (5); and an injection step of injecting a gas flow from an injection portion of a nozzle (3) and blowing the gas flow onto the slag flow, wherein when a flow rate of the slag flow is Qs (t/s), a flow rate of the gas flow is Qg (m³/s), a flow velocity of the gas flow is V (m/s), a distance in a vertical direction between the flow-down portion and the injection portion is y1 (m), and a length in the vertical direction of the injection portion is y2 (m),

640000 \leq Qg \div Qs \times V^{2}

and

7000 \leq V^{2} \times y 2 \times \{{(y 2 + 0.009)}^{- 0.25} + {(y 1 + y 2 + 0.009)}^{- 0.25}\}

are satisfied.

Description

TECHNICAL FIELD

The present disclosure relates to a slag modification method and a slag modification apparatus.

BACKGROUND

Decarburized slag produced by decarburization blowing is sometimes used as road base material. Because decarburized slag contains a large amount of calcium oxide, if it is left unmodified, it has the nature of expanding when coming into contact with water. When decarburized slag is used as road base material, the expansion of the decarburized slag may cause deformation of a road surface, for example. Accordingly, when decarburized slag is used as road base material, modification processing is applied to reduce the expansion of the decarburized slag. One example of such expansion reduction processing is to oxidize the decarburized slag to thereby reduce the expansion of the decarburized slag.
Patent Literature (PTL) 1 describes a slag material production method. In this slag material production method, air is blown from a nozzle onto the steelmaking slag in a molten state, so as to blow the steelmaking slag into slag droplets, and by causing the slag droplets to collide with a slope that is inclined to become higher as it is away from the nozzle, the slag droplets are made into lumpy slag material. This lumpy slag material is subsequently crushed. In PTL 1, the process of blowing steelmaking slag into slag droplets is called "air granulation." In this air granulation process, FeO contained in the steelmaking slag is oxidized to Fe₂O₃ by oxygen in the air. This Fe₂O₃ produces 2CaO·Fe₂O₃, which reduces calcium oxide in the steelmaking slag, thereby preventing the expansion of the slag material.
Patent Literature (PTL) 2 describes a converter slag product production method. In this production method, a modifier that immobilizes CaO is fed into converter slag in a molten state, and the converter slag is oxidized at least once by blowing gas containing oxygen onto the converter slag in a molten state and granulating the slag to a grain size of 10 mm or less. This ensures that the composition of the final product satisfies a predetermined relationship in terms of mass%. The method according to PTL 2 requires a certain amount of gaseous energy to granulate the slag to 10 mm or less. PTL 2 describes that the square product of the amount of gas per ton of slag (m³/t) and the flow velocity (m/s) at a section of the blow nozzle is to be 64,000 or more from behind the molten slag flowing down from a slag pot.

CITATION LIST

Patent Literatures

PTL 1: JP 2017-081814 A
PTL 2: JP 2003-155511 A

SUMMARY

(Technical Problem)

In the conventional methods as described in PTL 1 and PTL 2, slag in a molten state is caused to flow down from a spout so as to form a slag flow, and a gas flow containing oxygen is injected from an injection orifice of a nozzle so that this gas flow is blown onto the slag flow. Such conventional methods have the problem that the slag falls without becoming droplets, even when the flow velocity and the flow rate of the gas flow are sufficient. The slag that falls without becoming droplets is not sufficiently oxidized, and thus becomes unmodified slag wherein expansion is not adequately reduced. It is therefore desirable to reduce the amount of slag that falls without becoming droplets when slag is modified by air granulation.
The present disclosure has been made in view of the above circumstances and aims to provide a slag modification method and a slag modification apparatus by which the amount of slag that falls without becoming droplets is reduced when slag is modified by air granulation.

(Solution to Problem)

A slag modification method according to the present disclosure designed to achieve the aforementioned objective includes:

a slag flow forming step of causing slag in a molten state to flow down from a flow-down portion so as to form a slag flow; and
an injection step of injecting a gas flow containing oxygen from an injection portion of a nozzle and blowing the gas flow onto the slag flow, wherein
when a flow rate of the slag flow is Qs (t/s), a flow rate of the gas flow is Qg (m³/s), a flow velocity of the gas flow in the nozzle is V (m/s), a distance in a vertical direction between the flow-down portion and the injection portion is y1 (m), and a length in the vertical direction of the injection portion is y2 (m), the following Formula (1) and Formula (2) are satisfied $640000 \leq Qg \div Qs \times V^{2}$ $7000 \leq V^{2} \times y 2 \times \{{(y 2 + 0.009)}^{- 0.25} + {(y 1 + y 2 + 0.009)}^{- 0.25}\}$

A slag modification apparatus according to the present disclosure designed to achieve the aforementioned objective includes:

a flow-down portion configured to cause slag in a molten state to flow down so as to form a slag flow; and
a nozzle configured to inject a gas flow containing oxygen from an injection portion and blow the gas flow onto the slag flow, wherein
when a flow rate of the slag flow is Qs (t/s), a flow rate of the gas flow is Qg (m³/s), a flow velocity of the gas flow in the nozzle is V (m/s), a distance in a vertical direction between the flow-down portion and the injection portion is y1 (m), and a length in the vertical direction of the injection portion is y2 (m), the aforementioned Formula (1) and Formula (2) are satisfied.

According to the above configuration, the slag modification method and the slag modification apparatus by which the amount of slag that falls without becoming droplets is reduced when slag is modified by air granulation can be provided.

(Advantageous Effect)

According to the present disclosure, the slag modification method and the slag modification apparatus by which the amount of slag that falls without becoming droplets is reduced when slag is modified by air granulation can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a view illustrating a slag modification apparatus and its mode of use according to an embodiment of the present disclosure;
FIG. 2 is a view illustrating positions and a positional relationship between a flume and a nozzle; and
FIG. 3 is a view illustrating positions, sizes, and a positional relationship between the flume, a slag flow, and the nozzle.

DETAILED DESCRIPTION

Based on the drawings, a slag modification method and a slag modification apparatus 100 (refer to FIG. 1) according to an embodiment of the present disclosure will be described.

(First Embodiment)

FIG. 1 illustrates the slag modification apparatus 100 (hereinafter referred to as the modification apparatus 100) according to the present embodiment. The modification apparatus 100 includes a flume 1 having a flume tip 11 serving as a spout through which slag in a molten state is caused to flow down so as to form a slag flow 5, and a nozzle 3 that injects a gas flow containing oxygen and blows the gas flow onto the slag flow 5. Here, the spout is an example of a flow-down portion, which is a section through which the slag in a molten state is caused to flow down. The flow-down portion is not limited to the spout, and its shape is also not limited to a hole surrounded on all sides or the like.
The slag modification method according to the present embodiment is implemented by the modification apparatus 100 in an example. That is, the modification apparatus 100 can implement the slag modification method that includes a slag flow forming step and an injection step. The slag flow forming step causes slag in a molten state to flow down from the flume tip 11 of the flume 1 so as to form the slag flow 5. The injection step injects a gas flow containing oxygen from an injection orifice 30 of the nozzle 3 and blowing the gas flow onto the slag flow 5. Here, the injection orifice 30 is an example of an injection portion, which is a section from which the gas flow containing oxygen is injected. The injection portion is not limited to the injection orifice 30, and its shape is also not limited to a hole surrounded on all sides or the like.
The modification of slag in the present embodiment refers to immobilizing calcium oxide in the slag as 2CaO·Fe₂O₃ and subsequently preventing the expansion of the slag caused by calcium oxide when the slag comes into contact with water.
In the slag modification method according to the present embodiment, it is assumed that a flow rate of the slag flow 5 (refer to FIG. 1) is Qs (t/s), a flow rate of the gas flow is Qg (m³/s), and a flow velocity of the gas flow in the nozzle 3 is V (m/s). As illustrated in FIG. 2, the distance in a vertical direction between the flume tip 11, which serves as a spout for causing the slag in a molten state to flow down so as to form the slag flow 5, and the injection orifice 30 is distance y1 (m). A length in the vertical direction of the injection orifice 30 is y2 (m). In this case, the following Formula (1) and Formula (2) are satisfied.
$640000 \leq Qg \div Qs \times V^{2}$ $7000 \leq V^{2} \times y 2 \times \{{(y 2 + 0.009)}^{- 0.25} + {(y 1 + y 2 + 0.009)}^{- 0.25}\}$
That is, in the modification apparatus 100 of FIG. 1, the flow rate Qs of the slag flow 5, the flow rate Qg of the gas flow, and the flow velocity V of the gas flow in the nozzle 3 are controlled to satisfy Formula (1), in order to implement the slag modification method according to the present embodiment. Along with that, the distance y1 (refer to FIG. 2) between the flume tip 11 and the injection orifice 30 and the length y2 (refer to FIG. 2) in the vertical direction of the injection orifice 30 are set to satisfy Formula (2).
According to the slag modification method according to the present embodiment, the amount of slag that falls without becoming droplets can be reduced when slag is modified by air granulation.
The modification apparatus 100 and the slag modification method according to the present embodiment will be described in detail below.
As illustrated in FIG. 1, in addition to the flume 1 and the nozzles 3 described above, the modification apparatus 100 further includes a slag pot 2 that stores slag in a molten state and that supplies the slag to the flume 1, a gas supply device 4 that supplies gas to the nozzles 3, and a solidification table 9.
The flume 1 is placed below an upper surface of the slag pot 2. The nozzle 3 is placed below the slag pot 2 and the flume 1. Slag stored in the slag pot 2 flows down from the slag pot 2 to the flume 1, and then from the flume 1 to the front of the injection orifice 30 as the slag flow 5.
The slag is, for example, steelmaking slag in a molten state generated in a steelmaking plant, especially converter slag in a molten state generated in a converter. The slag contains iron components, such as iron or iron oxide, and calcium oxide.
The slag pot 2 is a container for storing slag in a molten state. The slag pot 2 may be, for example, a bottomed tubular container with a bottom portion and side walls, and an upper end side open to the outside. The slag stored in the slag pot 2 is supplied from the slag pot 2 to the flume 1 by, for example, tilting the slag pot 2 so that the slag is poured from the slag pot 2 into the flume 1.
The flume 1 is a channel-like supply member that causes the slag in a molten state supplied from the slag pot 2 to flow down to a position in front of the injection orifice 30 of the nozzle 3. Here, the front of the injection orifice 30 is the front in an outflow direction of the gas flow. Hereafter, the same direction as the front in the outflow direction of the gas flow may simply be referred to as the front.
The flume 1 is placed on an upper side in the vertical direction of the nozzle 3, which will be described later. The flume 1 is arranged so that it extends along the outflow direction of the gas flow injected from the nozzle 3, for example, in a top view (viewed from the upper side in the vertical direction). The flume 1 may be placed so as to overlap the nozzle 3 in a top view. In the following, a case in which the flume 1 is placed so as to overlap the nozzles 3 in a top view will be illustrated as an example.
The flume 1 is shaped such that its width narrows as it extends from the slag pot 2 toward the injection orifice 30 in a top view or a front view (viewed from the front side). FIG. 3 illustrates a front view of the flume 1, the injection orifice 30, and the slag flow 5.
As illustrated in FIG. 1 and FIG. 3, the flume 1 guides the slag in a molten state from the slag pot 2 toward the injection orifice 30. The flume 1 may be provided, at the bottom, for example, with a convex groove-shaped portion as a flow path to guide the slag.
As illustrated in FIG. 3, the width W1 in a horizontal direction of the flume tip 11, which is an end portion of the flume 1 near the injection orifice 30, may be wider or narrower than the width W2 of the injection orifice 30 in a top view or a front view. In FIG. 3, a case in which the width W1 and the width W2 are the same length is illustrated as an example. The flume tip 11 is located on a lower side in the vertical direction than a receiving portion 12, which is another end portion of the flume 1 near the slag pot 2.
The slag in a molten state supplied from the slag pot 2 to the flume 1 illustrated in FIG. 1 flows down as the slag flow 5 in front of the injection orifice 30 of the nozzle 3, which will be described later, as illustrated in FIG. 1 and FIG. 3. In the present embodiment, the flow rate Qs of the slag flow 5 is a mass flow rate of the slag flowing down from the flume 1.
As illustrated in FIG. 1, the nozzle 3 is a gas flow supply mechanism that injects a gas flow, such as air, that contains oxygen, from the injection orifice 30. A gas supply device 4, such as a fan, a blower, or a compressor, is connected to the nozzle 3 via a gas supply path 40, such as a duct. The nozzle 3 injects a gas supplied from the gas supply device 4 from the injection orifice 30. The flow rate, the pressure, and the flow velocity of the gas flow injected from the injection orifice 30 can be controlled by adjusting the output of the gas supply device 4 or by providing an adjustment valve in the gas supply path 40 and adjusting the aperture. The output of the gas supply device 4 can be adjusted, for example, by adjusting a rotational speed of the fan, the blower, or the compressor.
In the present embodiment, the flow rate Qg of the gas flow is a volumetric flow rate of the gas flowing through the nozzle 3 when being subjected to normal conversion (when converted to 0 °C and 1 atmosphere).
In the present embodiment, the flow velocity V of the gas flow in the nozzle 3 is a value obtained by dividing the flow rate Qg by an opening area (m²) of the injection orifice 30.
The nozzles 3 may be placed along the horizontal direction, for example. The injection orifice 30 may inject a gas flow along the horizontal direction. The outflow direction of the gas flow from the injection orifice 30 may be inclined with respect to the horizontal direction. The outflow direction of the gas flow from the injection orifice 30 may be a direction that allows slag to be scattered in the horizontal direction (a direction away from the nozzle 3, in front of the nozzle 3). The outflow direction of the gas flow from the injection orifice 30 is preferably along the horizontal direction or inclined upward in the vertical direction at an angle of 20 degrees or less with respect to the horizontal direction. Here, the outflow direction of the gas flow from the injection orifice 30 refers to a direction of flow of part of the gas flow injected from the injection orifice 30 that has the fastest flow velocity.
The shape of the opening of the injection orifice 30 is not particularly limited and may be polygonal, such as rectangular, or circular in a front view. As illustrated in FIG. 3, the injection orifice 30 may have a rectangular shape wherein the horizontal direction is the longitudinal direction, an oval shape, or an elliptical shape in the front view, for example. In a case in which the injection orifice 30 has a rectangular shape, the corners may be chamfered.
The injection orifice 30 may have a rectangular shape in a front view wherein preferably the horizontal direction is the longitudinal direction. This can reduce energy consumption when slag is subjected to air granulation.
The width W2 in the horizontal direction of the injection orifice 30 may be the same length as the width W1 in the horizontal direction of the flume tip 11. This can reduce energy consumption when slag is subjected to air granulation.
In the present embodiment, the length Y2 in the vertical direction of the injection orifice 30 (refer to FIG. 2 and FIG. 3) is the maximum length (maximum width) of the injection orifice 30 in a direction along the vertical direction.
As illustrated in FIG. 1, the injection orifice 30 and the flume 1 may be placed so as to overlap in a top view. For example, the injection orifice 30 may be placed 0 cm to 15 cm (10 cm in an example) behind the flume tip 11 in the top view.
As illustrated in FIG. 2 and FIG. 3, the distance y1 in the vertical direction between the flume tip 11 serving as a spout and the injection orifice 30 is a distance in the vertical direction between the flume tip 11 and an upper end portion of the injection orifice 30.
As illustrated in FIG. 1, the gas flow injected from the injection orifice 30 of the nozzle 3 collides with the slag flow 5 flowing down in front of the injection orifice 30, thereby dispersing the slag flow 5 into droplets 50 so that they scatter (fly). At this time, iron components of the slag are oxidized through gas-liquid or solid-gas contact with the gas flow. With the oxidation of the iron components, calcium oxide in the slag is immobilized as 2CaO·Fe₂O₃. The calcium oxide in the slag is converted to 2CaO·Fe₂O₃, which prevents the expansion of the slag caused by calcium oxide when the slag subsequently comes into contact with water.
For example, in a case in which a gas flow is injected along the horizontal direction from the injection orifice 30 of the nozzle 3 and collides with the slag flow 5, the slag is dispersed into droplets 50 of 10 mm or less (approximately a few mm) and scattered in front of the nozzle 3. At this time, the dispersed slag is scattered upward in a convex arc in the vertical direction. The droplets 50 then fall and accumulate on the solidification table 9. The accumulated slag 59 that falls and accumulates on the solidification table 9 after being scattered in front of the nozzle 3 is slag that has undergone modification and reduction in expansion.
Here, the installation height, that is, the distance from the ground 90, of the nozzle 3 and the injection orifice 30 is not particularly limited. It is, however, preferable that the injection orifice 30 be at an appropriate height with respect to the ground 90, as illustrated in FIG. 2, so that the gas flow injected from the injection orifice 30 is not slowed down by contact with the ground 90. For example, the height of the injection orifice 30 from the ground 90 is 1.5 times to 4 times, preferably 2 times to 3.5 times, the length Y2.
In the slag modification method according to the present embodiment, the distance y1 and the length y2 of the modification apparatus 100 are set to satisfy the aforementioned Formula (1) and Formula (2). Furthermore, by controlling the flow rate Qs, the flow rate Qg, and the flow velocity V (m/s), the amount of slag that falls without becoming droplets 50 can be reduced when slag is modified by air granulation. By reducing the amount of slag that falls without becoming droplets 50, the amount of unmodified slag in the slag after modification can be reduced, and the expansion of the slag after the modification can be sufficiently reduced.

(Modified First Embodiment)

In the above embodiment, as illustrated in FIG. 1, a case in which the modification apparatus 100 includes the flume 1 and in which the flume tip 11 of the flume 1 serves as a spout that forms a slag flow 5 is described. In the modification apparatus 100 and the slag modification method according to the present embodiment, however, the flume 1 is not essential. In the modification apparatus 100 and the slag modification method according to the present embodiment, the slag flow 5 may be formed by letting the slag flow down from the slag pot 2. In this case, the distance in the vertical direction between a spout portion 21 in the slag pot 2 from which the slag flows down and the injection orifice 30 corresponds to the distance y1.

EXAMPLES

In the following, the slag modification method and the slag modification apparatus 100 according to the present embodiment will be described based on Examples.

(Example 1)

Air granulation according to Example 1 was performed, and the state of the air granulation of slag was evaluated as follows.
For the air granulation, the aforementioned modification apparatus 100 of FIG. 1 was used. As the slag, converter slag generated in a converter was used. Air was used as a gas injected from the injection orifice 30 of the nozzle 3.
The width in the horizontal direction of the spout portion 21 in the slag pot 2 was 0.80 m. The slag was in a molten state at 1550 °C to 1700 °C in the slag pot 2.
The flume 1 was used to form a slag flow 5. The flume 1 and the nozzle 3 were placed so as to overlap each other in a top view. The nozzle 3 was placed to extend in the horizontal direction so that the direction of a gas flow injected from the injection orifice 30 was along the horizontal direction. The width W2 in the horizontal direction of the injection orifice 30 of the nozzle 3 (refer to FIG. 3) was 0.60 m. The width W1 in the horizontal direction of the flume tip 11 (refer to FIG. 3) was 0.60 m, which was the same as the width W2 in the horizontal direction of the injection orifice 30 of the nozzle 3. The injection orifice 30 was placed at a height of 1.00 m from the ground 90.
The injection orifice 30 was placed 0.3 m away from the slag flow 5 in the horizontal direction.
The distance y1 in the vertical direction between the flume tip 11 and the injection orifice 30 (refer to FIG. 2 and FIG. 3) in the modification apparatus 100 was set to the value presented in Table 1

[Table 1]

Table 1

	Qs (t/s)	Qg (m³/s)	V (m/s)	y1 (m)	y2 (m)	State of air granulation
Example 1	0.100	21.6	90	0.30	0.40	Good
Example 2	0.150	21.6	90	0.30	0.40	Good
Example 3	0.150	28.8	120	0.50	0.40	Good
Example 4	0.050	15.0	125	0.40	0.30	Good
Example 5	0.167	13.0	93	0.05	0.35	Extremely good
Example 6	0.067	6.8	85	0.05	0.40	Extremely good
Comparative Example 1	0.150	21.6	90	1.50	0.40	Poor
Comparative Example 2	0.100	21.6	90	0.30	0.20	Poor
Comparative Example 3	0.100	15.6	130	0.90	0.20	Poor
Comparative Example 4	0.150	16.8	70	0.02	0.40	Poor

The shape of the opening of the injection orifice 30 was rectangular in a front view (refer to FIG. 3). The length y2 in the vertical direction of the injection orifice 30 (refer to FIG. 2 and FIG. 3) was set to the value presented in Table 1. In the present Example, the injection orifice 30 has a rectangular shape. The length y2 therefore corresponds to the width in the vertical direction of the injection orifice 30.
The following procedure was used for air granulation. First, the slag pot 2 was tilted, slag was poured over the flume 1, and the slag in a molten state was fallen from the flume tip 11 so as to form a slag flow 5. At this time, the outflow velocity of the slag from the slag pot 2 (which was the same as the flow rate Qs of the slag flow 5) was controlled to be 0.150 t/s or less. Table 1 also presents the actual flow rate Qs (t/s) of the slag flow 5.
The slag flow 5 was caused to collide with the gas flow injected from the injection orifice 30, so that the slag was air-granulated, and the state of the air granulation was evaluated. Table 1 presents the flow rate Qg (m³/s) and the flow velocity V (m/s) of the gas flow, together with the evaluation result of the air granulation.
The state of the air granulation was observed by visual observation from the side of the nozzle 3 in the horizontal direction. The state of the air granulation was evaluated as good when the air-granulated slag was scattered as droplets 50 in front of the nozzle 3 and there was no slag that passed in front of the nozzle 3 and subsequently fell. When the state of the air granulation was good, especially when there was no excessive air granulation of slag, it was evaluated as extremely good. When the state could not be evaluated as good, it was evaluated as poor. In the present Example, "there was no slag that passed in front of the nozzle 3 and subsequently fell" means that no slag fell within a radius of 0.6 m from the injection orifice 30 in a top view. Similarly, "there was no excessive air granulation of slag" means that no slag fell within a radius of more than 30 m from the injection orifice 30 in the top view.
The air granulation according to Example 1 was evaluated as good, as presented in Table 1.

(Example 2)

In Example 2, the flow rate Qs was changed to the value presented in Table 1, while other conditions remained the same as Example 1, and the state of air granulation of slag was evaluated. The air granulation according to Example 2 was evaluated as good, as presented in Table 1.

(Example 3)

In Example 3, the flow rate Qs, the flow rate Qg, the flow velocity V, and the distance y1 were changed to the values presented in Table 1, while other conditions remained the same as Example 1, and the state of air granulation was evaluated. The air granulation according to Example 3 was evaluated as good, as presented in Table 1.

(Example 4)

In Example 4, the flow rate Qs, the flow rate Qg, the flow velocity V, the distance y1, and the length y2 were changed to the values presented in Table 1, and the state of air granulation was evaluated. The air granulation according to Example 4 was evaluated as good, as presented in Table 1.

(Example 5)

In Example 5, the flow rate Qs, the flow rate Qg, the flow velocity V, the distance y1, and the length y2 were changed to the values presented in Table 1, and the state of air granulation was evaluated. The air granulation according to Example 5 was evaluated as extremely good, as presented in Table 1.

(Example 6)

In Example 6, the flow rate Qs, the flow rate Qg, the flow velocity V, and the distance y1 were changed to the values presented in Table 1, while other conditions remained the same as Example 1, and the state of air granulation was evaluated. The air granulation according to Example 6 was evaluated as extremely good, as presented in Table 1.
Under the conditions of Example 5 and Example 6, one factor is thought to be that the distance y1 was made smaller so that the falling speed of the slag flow 5 reaching the front of the nozzle 3 did not become too fast, resulting in extremely good air granulation. In detail, it is thought that the slag had enough time to receive kinetic energy of the gas flow injected from the nozzle 3, which allowed the slag to receive sufficient kinetic energy of the gas flow injected from the nozzle 3.

(Comparative Example 1)

In Comparative Example 1, the flow rate Qs, the flow rate Qg, the flow velocity V, and the distance y1 were changed to the values presented in Table 1, and a slag flow 5 was formed by letting slag flow down directly from the slag pot 2 without using a flume 1. Other conditions remained the same as Example 1, and the state of air granulation was evaluated. The air granulation according to Comparative Example 1 was evaluated as poor, as presented in Table 1.
Under the conditions of the present Comparative Example, one factor is thought to be that the distance y1 was made larger so that the falling speed of the slag flow 5 reaching the front of the nozzle 3 became too fast, resulting in poor air granulation. In detail, under the conditions of the present Comparative Example, the falling speed of the slag flow 5 is considered to have become too fast. It is therefore thought that the slag did not have time to receive kinetic energy of the gas flow injected from the nozzle 3 and could not receive sufficient kinetic energy. It is considered that this prevented the slag from being dispersed sufficiently, resulting in poor air granulation.

(Comparative Example 2)

In Comparative Example 2, the length y2 was changed to the value presented in Table 1, and the width W2 in the horizontal direction of the injection orifice 30 was changed to 1.20 m. Other conditions remained the same as Example 1, and the state of air granulation of slag was evaluated. The air granulation according to Comparative Example 2 was evaluated as poor, as presented in Table 1.

(Comparative Example 3)

In Comparative Example 3, the flow rate Qg, the flow velocity V, the distance y1, and the length y2 were changed to the values presented in Table 1, while other conditions remained the same as Example 1, and the state of air granulation was evaluated. The air granulation according to Comparative Example 3 was evaluated as poor, as presented in Table 1.
Under the conditions of Comparative Example 2 and Comparative Example 3, one factor is thought to be that the length y2 became too small and the slag could not receive sufficient kinetic energy of the gas flow injected from the nozzle 3, resulting in poor air granulation. In addition, under the conditions of Comparative Example 2 and Comparative Example 3, it is considered that the length y2 became too small and the time for the slag flow 5 to pass in front of the injection orifice 30 became too short, and the slag could not have enough time to receive kinetic energy of the gas flow injected from the nozzle 3. It is considered that this prevented the slag from being dispersed sufficiently, resulting in poor air granulation.

(Comparative Example 4)

In Comparative Example 4, the flow rate Qs, the flow rate Qg, the flow velocity V, and the distance y1 were changed to the values presented in Table 1, while other conditions remained the same as Example 1, and the state of air granulation of slag was evaluated. The air granulation according to Comparative Example 4 was evaluated as poor, as presented in Table 1.
Under the conditions of the present Comparative Example, one factor is thought to be that kinetic energy (density of energy that the slag flow 5 received from the gas flow) became smaller because the flow velocity V became smaller and the flow rate Qs became larger. That is, when the gas flow collided with the slag flow 5, the kinetic energy of the gas flow received by the slag per unit area of a surface of the slag flow 5 became relatively small, resulting in poor air granulation.
From the above results of Examples and Comparative Examples, it is considered that kinetic energy of the gas flow injected from the nozzle 3 (wherein the flow rate Qg and the flow velocity V are parameters) is closely related to whether air granulation can be appropriately performed in the slag modification method according to the present embodiment. It is also considered that the processing amount of slag to be air-granulated (wherein the flow rate Qs is a parameter) is closely related.
From the above results of Examples and Comparative Examples, it is considered preferable for the distance y1 to be more than 0 m and less than 1.5 m. When the distance y1 is within this range, the state of air granulation can be expected to be good.
It is considered more preferable for the distance y1 to be more than 0 m and less than 0.3 m. When the distance y1 is within this range, the state of air granulation can be expected to be good.
It is also considered that the time for which slag can receive kinetic energy of the gas flow injected from the nozzle 3 (wherein the distance y1 and the length y2 are parameters) is closely related to whether air granulation can be appropriately performed in the slag modification method according to the present embodiment. It is also considered that the density of energy that the slag flow 5 receives from the gas flow (wherein the flow velocity V is a parameter) is closely related.
Based on the findings thus obtained from Examples and Comparative Examples on the above, the relationship among the flow rate Qs, the flow rate Qg, the flow velocity V, the distance y1, and the length y2 was studied, and the aforementioned Formula (1) and Formula (2) were derived as empirical formulas.
Table 2 presents results of obtaining values of the right-hand sides of Formula (1) and Formula (2) for the aforementioned conditions of air granulation in Examples and Comparative Examples. As presented in Table 1 and Table 2, it can be seen that in order to achieve good air granulation, the conditions of air granulation are to satisfy Formula (1) and Formula (2).

[Table 2]

Table 2

	Value of right-hand side of Formula (1)	Value of right-hand side of Formula (2)
Example 1	1749600	7876
Example 2	1166400	7876
Example 3	2764800	12718
Example 4	4687500	11395
Example 5	673275	7696
Example 6	733284	7125
Comparative Example 1	1166400	5680
Comparative Example 2	1749600	4091
Comparative Example 3	2636400	6755
Comparative Example 4	548800	7171

As described above, the slag modification method and the slag modification apparatus 100 by which the amount of slag that falls without becoming droplets 50 is reduced when slag is modified by air granulation can be provided.
The embodiment disclosed herein is an example. The embodiment according to the present disclosure is not limited to this and may be modified as appropriate without departing from the objective of the present disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure can be applied to the slag modification method and the slag modification apparatus 100.

REFERENCE SIGNS LIST

1: Flume
100: Modification apparatus
11: Flume tip

12: Receiving portion
2: Slag pot
21: Spout portion
3: Nozzle
30: Injection orifice
4: Gas supply device
40: Gas supply path
5: Slag flow
50: Droplet
59: Accumulated slag
9: Solidification table
90: Ground
y1: Distance
y2: Length
W1: Width
W2: Width

Claims

A slag modification method comprising:
a slag flow forming step of causing slag in a molten state to flow down from a flow-down portion so as to form a slag flow; and

an injection step of injecting a gas flow containing oxygen from an injection portion of a nozzle and blowing the gas flow onto the slag flow, wherein

when a flow rate of the slag flow is Qs (t/s), a flow rate of the gas flow is Qg (m³/s), a flow velocity of the gas flow in the nozzle is V (m/s), a distance in a vertical direction between the flow-down portion and the injection portion is y1 (m), and a length in the vertical direction of the injection portion is y2 (m), the following Formula (1) and Formula (2) are satisfied $640000 \leq Qg \div Qs \times V^{2}$ $7000 \leq V^{2} \times y 2 \times \{{(y 2 + 0.009)}^{- 0.25} + {(y 1 + y 2 + 0.009)}^{- 0.25}\}$
The slag modification method according to claim 1, wherein y1 is more than 0 m and less than 1.5 m.
The slag modification method according to claim 2, wherein y1 is less than 0.3 m.
A slag modification apparatus comprising:
a flow-down portion configured to cause slag in a molten state to flow down so as to form a slag flow; and

a nozzle configured to inject a gas flow containing oxygen from an injection portion and blow the gas flow onto the slag flow, wherein

when a flow rate of the slag flow is Qs (t/s), a flow rate of the gas flow is Qg (m³/s), a flow velocity of the gas flow in the nozzle is V (m/s), a distance in a vertical direction between the flow-down portion and the injection portion is y1 (m), and a length in the vertical direction of the injection portion is y2 (m), the following Formula (1) and Formula (2) are satisfied $640000 \leq Qg \div Qs \times V^{2}$ $7000 \leq V^{2} \times y 2 \times \{{(y 2 + 0.009)}^{- 0.25} + {(y 1 + y 2 + 0.009)}^{- 0.25}\}$
The slag modification apparatus according to claim 4, wherein y1 is more than 0 m and less than 1.5 m.
The slag modification apparatus according to claim 5, wherein y1 is less than 0.3 m.