JPH0765089B2 - Smelting reduction method and smelting reduction furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a smelting reduction method and a smelting reduction furnace for directly producing molten steel from a converter or iron ore, and more particularly to improving the efficiency of utilization of secondary combustion heat.

[Conventional technology]

Conventionally, in a converter, a top-blowing method in which oxygen is blown from a top-blowing lance or a bottom-blowing method in which oxygen is blown from tuyere provided at the bottom of the furnace has been used.

[Problems to be solved by the invention]

However, in the conventional converter using the top-blown method or the bottom-blown method, it is difficult to efficiently recover the heat of reaction when the CO gas is secondarily combusted in the furnace. .

This is because CO gas generated by primary combustion C + O → CO during blowing in the converter reacts with oxygen above the iron bath level. However, if the furnace body is used as the heat transfer medium for the heat generated by this secondary combustion, the upper part of the furnace will be extremely worn, especially (CO ₂ + H ₂ O) / (CO + CO ₂ + H This tendency increases as the secondary combustion ratio represented by ( ₂ + H ₂ O) increases, and thus it was impractical to use the furnace body as the heat medium for the secondary combustion heat. The iron bath surface is hereinafter referred to as a bath surface.
The reference bath surface position is based on the nominal capacity of the bath surface Akito.

Even in a conventional converter using a top-blowing lance, a considerable part of the heat of secondary combustion is recovered in the iron bath due to the slag and the iron bath splash generated by the oxygen jet from the top-blowing lance. However, since gas expansion occurs at the tip of the lance nozzle and considerable gas energy is consumed to dent the bath surface, the amount of splash generated is limited, and the secondary combustion ratio is high. Becomes 0.
When it was 3 or more, the heat-adsorption efficiency decreased, and the secondary combustion heat was largely removed by the cooling water for cooling the lance, resulting in insufficient heat recovery.

Therefore, even if a lance or a bottom blowing tuyere was provided for the purpose of generating splash, sufficient improvement could not be obtained. That is, the bottom blowing tuyere consumes most of the energy of the gas in order to separate the iron bath, so the amount of splash produced is limited, and the high heat deposition to the iron bath is also limited.

The present invention has been made to solve the above problems, and provides a smelting reduction method and a smelting reduction furnace that can heat secondary combustion heat to an iron bath with high efficiency by increasing the amount of splash generation. It is intended to be provided.

[Means for solving problems]

The smelting reduction method according to the present invention, in relation to the distance from the center position of the outlet of the tuyere to the position where the centerline of the tuyere intersects the bath surface, produces a splash with a high efficiency in a specific range of distance. It was made based on the knowledge that it is possible to blow gas by maintaining the condition below the bath surface of the converter or smelting reduction furnace and from the side wall of the furnace near the bath surface. The feature is that the bath water is splashed.

Where D: tuyere outlet immersion depth Θ; tuyere angle to the furnace side wall d ₀ ; tuyere inner diameter Further, the smelting reduction furnace according to the present invention is under the bath surface of the converter or the smelting reduction furnace, and It is characterized in that a splash generating tuyere is provided upward on a nearby furnace side wall at a position where the following conditions can be set.

[Work]

In the present invention, the gas energy of the blown gas is effectively utilized for splash generation by operating under the above conditions and performing the splash, and by providing the tuyere at a position where the above operating conditions can be set. can do. That is, when the distance L is smaller than d ₀ , the distance L is too short, the energy of the blowing gas on the bath surface is large, and therefore the splash becomes a very fine mist, and the mass of the generated splash is light, Most of the droplets are carried out of the furnace due to the gas flow, and the heat deposition efficiency on the iron bath deteriorates. Conversely, the distance L is
In the case of 100d ₀ or more, the distance L is too long, and most of the energy of the blowing gas for splash generation is used to raise the bath surface, so the amount of splash generation is drastically reduced, and the amount of splash generated Since the diameter is too large, the surface area per unit weight of the splash is reduced and the heat receiving efficiency is reduced, so that the heat transfer efficiency to the iron bath is deteriorated.

〔Example〕

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, in which 1 is a converter, 2 is an iron bath in the converter 1, 3 is tuyere provided on the side wall of the door 1 of the converter, 4 Is a slag layer formed on the bath surface of the iron bath 2, and 5 is a secondary combustion zone formed above the bath surface of the iron bath 2.

The tuyere 3 is under the bath surface of the iron bath 2 as shown in the partial detailed view of FIG. It is provided so as to satisfy the condition of. Here, D represents the depth from the bath surface 2a of the iron bath 2 to the blowhole center position 7 of the tuyere 3, that is, the tuyere outlet immersion depth, Θ is the tuyere angle with respect to the furnace side wall, and d ₀ is the wing The inner diameter of the mouth 3.

Under the condition of the above formula (1), D / cos Θ is from the center position 7 of the outlet of the tuyere 3 to the position 9 where the center line 8 of the tuyere 3 intersects with the bath surface 2a.
The inventor of the present invention has found that a good splash can be obtained by providing the tuyere 3 so that the distance L can be expressed by the condition (1).

That is, the angle Θ of the tuyere 3 and the tuyere outlet immersion depth D were variously changed under a constant amount of gas and gas pressure, and the amount of slag and iron bath splash generated was investigated. The following characteristics of the amount of splash production were obtained. Figure 3 is on the horizontal axis
D / d ₀ cos Θ is taken and the vertical axis is the weight of the splash W (ton / H)
The iron bath is limited to showing weight W ₀ (ton) taking the ratio of the Supuratsushiyu generation amount represents the Supuratsushiyu generation amount in the range A shown by oblique lines.

As shown in FIG. 3, a good splash is generated when D / d ₀ cos Θ is in the range of 1 to 100. When D / d ₀ cos Θ1, that is, when the distance L is Ld ₈ , the energy of the blown gas on the bath surface 2 is large, and very fine mist-like droplets with a particle size of 0.1 mm or less are generated. Since the weight is light and most of the droplets are carried out of the furnace by the gas flow, the amount of splash generated that is effective for heat exchange is small. On the other hand, when D / d ₀ cos Θ ≧ 100, that is, when the distance L is L ≧ 100d ₀ , most of the energy of the blown gas is used to raise the bath surface 2a, and the amount of splash generation is drastically reduced. . Further, the diameter of the generated splash is considerably large, and the surface area per unit weight of the splash is also reduced. Therefore, if the bath surface position, which rises with the progress of smelting, exceeds the above condition, the bath surface position is naturally lowered to lower the bath surface position.

However, D / d ₀ cos Θ is in the range of 1 to 100, that is, the distance L
In the range of d ₀ <L <100d ₀ , the energy loss required to generate the splash of the blown gas is small, the amount of splash generated is large, and the particle size is the surface area that can efficiently promote heat exchange. It also becomes large enough to move and fall against the gas flow. Since the splash having a large particle size and a large amount can be blown into the secondary combustion zone, the secondary combustion heat can be transferred to the iron bath 2 by using the splash as a heat medium.

In addition, in the smelting reduction method, the amount of splash generated naturally changes when the gas flow rate is changed.
In the range of / min / ton It is necessary to That is, by blowing not only the gas but also the powder from the tuyere, the heat exchange efficiency can be further enhanced. This is because the kinetic energy of the powder is large, the flow velocity of the splash is high, the heat exchange is smoothly performed, and the amount of the splash generated is larger than that of the gas alone.

〔The invention's effect〕

This invention, as described above, the converter or the smelting reduction furnace, the energy of the blowing gas on the bath surface is large, the mass of the splash generated is light, most of the droplets are taken out of the furnace by the gas flow, Operate under optimal conditions that can eliminate the deterioration of heat transfer efficiency to the iron bath, and
By providing the tuyere at a position where the operating condition where the splash generation is optimum can be set, it is possible to blow the splashes having a relatively large particle size in the optimum range and a large amount of generation into the secondary combustion zone. The heat of secondary combustion can be recovered in the iron bath with high efficiency. Therefore, coal basic unit (kg / ton
(Iron) can be greatly reduced and damage to the furnace refractory due to secondary combustion can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a partial detailed view showing a tuyere portion of the above embodiment, and FIG. 3 is a splash generation amount characteristic diagram. 1 ... Converter, 2 ... Iron bath, 2a ... Bath surface, 3 ... Tuyere, 5
...... Secondary combustion zone.

Claims (2)

[Claims] 1. A converter or smelting reduction furnace that forms a secondary combustion zone in which CO gas emitted from a bath is burned on the bath, below the bath surface and from a furnace side wall near the bath surface. Where D is the tuyere outlet immersion depth Θ is the tuyere angle with respect to the furnace side wall d _{0 is the} tuyere inner diameter
A smelting reduction method characterized by splashing molten metal. 2. In a converter or smelting reduction furnace that forms a secondary combustion zone in which CO gas emitted from the bath is burned on the bath, splash-forming tuyere under the bath surface and on the side wall of the furnace near the bath surface. To Here, D is the soaking depth of the tuyere outlet Θ; Tuyere angle to the furnace side wall d ₀ ; Tuyere inner diameter The smelting reduction furnace is installed upward at a position that satisfies the conditions.