JP2596556B2 - Method for refining molten metal and injection lance used in the method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a refining technique for molten metal represented by hot metal, and particularly to a technique for desiliconization, dephosphorization, desulfurization, etc. performed prior to refining in a converter or the like. The present invention relates to a molten metal refining technique including hot metal pre-refining. More specifically, the present invention relates to a method for refining molten metal that succeeds in achieving a reduction in refining agent basic unit and an improvement in yield while increasing the reaction efficiency between a molten metal and a refining agent, and an injection lance used in the refining method. is there.

[Prior art] Various methods have been developed and put into practical use today as preliminary refining techniques performed prior to converter refining and the like. After that, it can be divided into a batch type refining method in a hot metal pot or a mixed iron wheel.

For example, pre-refining in a cast iron hot metal gutter is performed by using a hot metal transfer flow from a blast furnace to a hot metal ladle, etc., and the processing time is shorter than the refining process in the hot metal ladle, etc., and time loss and thermal loss It has been evaluated mainly for its desiliconization process, and has achieved results mainly in desiliconization. As such hot metal gutter refining, conventionally, a refining agent is injected into the surface of hot metal flowing through a hot metal gutter, and hot metal falls at a step portion of the hot metal gutter from a tap hole to a falling gutter, hot metal falls at a step portion of a hot metal gutter, and furthermore, is poured. A method that promotes the reaction by increasing the chance of contact between the refining agent and the hot metal by using the stirring power when the hot metal falls from the gutter to the hot metal ladle (or hot metal wheel) (the so-called upper price method) was generally used. . However, the reaction efficiency is not always satisfactory, and not only declination, which has conventionally been the center of hot metal gutter refining, but also the dephosphorization effect and desulfurization effect, and the improvement of the reaction efficiency itself in hot metal gutter refining, etc. As a result of the request,
An injection method in which a refractory lance is immersed in hot metal in a hot metal gutter and a refining agent is blown by a carrier gas has been proposed, and a method combining the above-mentioned overhead method and the injection method has been proposed.

In addition, as a preliminary refining in a hot metal ladle or a mixed iron wheel, a lance (injection lance) made of refractory is immersed in hot metal in a hot metal ladle or the like as in the hot metal gutter injection method described above.
An injection method for refining by blowing a refining agent with a carrier gas is widely used.

By performing such hot metal pretreatment, the refining load in the steelmaking process, which is a subsequent process, is reduced, and it is possible to reduce steelmaking costs and improve productivity.
Preliminary refining, especially in a cast iron hot metal gutter, plays an important role in reducing the total cost of ironmaking and steelmaking. On the other hand, also in the secondary refining, the gas blown by the refractory lance and the refining agent blown together with the gas make it easy to obtain a refining effect near a limit value thermodynamically required.

[Problems to be Solved by the Invention] As a preliminary refining method in a hot metal gutter or a hot metal ladle, and a secondary refining method in a molten steel ladle, an injection method is widely used. The method involves blowing a powdery refining agent with a carrier gas through a nozzle hole at the lower end of a lance that is inserted substantially vertically into the hot metal as shown in Fig. 3, and then bringing it into contact with the hot metal to generate a refining reaction. The carrier gas containing the powdery refining agent forms bubbles and rises near the lance. If the flow rate of the carrier gas is too small compared to the amount of the refining agent blown, a situation occurs in which the nozzle portion of the lance tip is clogged with hot metal or slag, and the continuous blowing process is hindered. On the other hand, if the flow rate of the carrier gas is excessive, the diameter of the carrier gas bubble which is entrapped into the molten iron by entraining the powdered refining agent increases, causing a so-called blow-through phenomenon. Insufficient contact of the refining agent leads to a reduction in reaction efficiency. That is, in the injection method, the carrier gas flow rate must be properly adjusted in order to maintain the solid-gas ratio (powder refining agent weight / carrier gas weight) within an appropriate range. When the amount is small, the nozzle blockage tends to occur, and when the amount is large, the blow-by phenomenon tends to occur, and it is difficult to obtain high reaction efficiency. As a result, it has been pointed out that the reaction efficiency cannot be sufficiently increased, the powdery refining agent basic unit increases, and the yield decreases. A similar problem occurs not only in the hot metal pretreatment method but also in the secondary refining of molten steel.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a hot metal refining technique capable of securing high reaction efficiency regardless of the amount of powdered refining agent to be injected.

Means for Solving the Problems According to the method of the present invention which has attained the above object, an injection lance is inserted into a molten metal, and a powdery refining agent is blown by a carrier gas, whereby the powdery refining agent is introduced into the molten metal. Forming a carrier gas bubble containing the gas, and performing refining of the molten metal by contact with the molten metal while floating the gas, the collision with the carrier gas bubble above the refining agent blowing nozzle hole of the lance, and The present invention has an essential point in that an auxiliary nozzle hole for gas injection for forming a gas jet flow for making finer particles is provided for refining.

In such a refining method, the gas from the auxiliary nozzle hole for gas jet flow formation is mixed with a solid-gas-liquid mixture formed by blowing a powdery refining agent and a carrier gas into a molten metal from a refining agent blowing nozzle hole. As the gas jet stream formed by the blowing is collided, the floating bubbles in the molten metal are fragmented to improve the contact between the powdered refining agent and the molten metal, and also blown into the molten metal together with the carrier gas. Since the powdery refining agent is widely and finely dispersed in the molten metal by the gas jet stream blown from the gas jet stream forming auxiliary nozzle hole, the refining effect is improved by these actions.

Further, the injection lance provided by the present invention is provided with a gas jet flow forming gas blowing auxiliary nozzle above the refining agent blowing nozzle hole, and in a preferred embodiment, these are provided by the same number, and It is recommended to provide the gas jet stream forming refining agent blowing nozzle holes and the individual gas blowing auxiliary nozzle holes in correspondence with each other.

[Action] The basic idea for improving the smelting reaction efficiency lies in how to increase the contact efficiency between the smelting agent and the hot metal.
This concept is also applied to the injection method. The contact efficiency in the injection method is that the carrier gas bubbles are blown around the refining agent,
It can be said that it is determined by how to expand the contact area between the carrier gas bubbles containing the refining agent and the hot metal, in other words, how to widely and finely disperse the carrier gas bubbles into the hot metal. That is, the reaction efficiency decreases when the carrier gas flow rate is increased under the problem of preventing nozzle clogging at the time of injecting a small amount of refining agent or increasing the amount of refining agent injected. This is considered to be because the bubble diameter of the contained carrier gas becomes large and does not widely disperse in the hot metal. However, in order to prevent nozzle clogging and to blow a large amount of refining agent, it is necessary to supply a considerable amount of carrier gas.In order to further increase productivity, the amount of refining agent used must be increased to some extent. As a result, the supply amount of the carrier gas further increases, the bubble diameter naturally increases, and fine dispersion in the hot metal becomes more and more difficult.

Therefore, the present inventors repeated various studies on means for reducing the bubble diameter, and variously changed the design of the lance shape, particularly the shape of the carrier gas blowout hole. Since the gas passage section must have a fine structure, it tends to be clogged by the refining agent powder or the like contained in the carrier gas, and stable blowing cannot be continued. Therefore, the policy was changed, and as a result of repeated studies in the direction of miniaturizing bubbles once formed in the hot metal,
The method of the present invention shown in the above configuration has been completed.

That is, in the present invention, in the lance for blowing the refining agent, a gas channel is formed separately from the refining agent blowing channel, and an auxiliary nozzle hole serving as an outlet of the gas channel is formed in the refining agent blowing nozzle. The reaction efficiency was successfully improved by forming it above and including the hole. In other words, the refining agent blowing nozzle holes are blown with a carrier gas containing the refining agent as usual, forming bubbles and trying to float in the hot metal. Only a gas containing no refining agent is blown from a separately provided gas blowing auxiliary nozzle, and a gas jet stream formed thereby collides with the floating bubbles. The buoyant bubbles are crushed and fragmented by the collision force of the gas jet flow or the stirring force by the gas jet flow, and are widely and finely dispersed in the molten metal, so that the refining agent and the hot metal contained in the reduced bubbles are removed. The contact area increases, and high reaction efficiency can be obtained.

Furthermore, when the refining agent that jumps out of the bubbles when the bubbles are destroyed comes into direct contact with the molten metal, higher reaction efficiency can be obtained.

As described above, in the present invention, air bubbles are divided by a gas flow separate from the refining agent blowing gas flow, so that a problem such as blockage of the nozzle portion occurs without changing the structure of the refining agent blowing nozzle portion. A desired amount of refining agent, in particular a carrier gas, can be applied without the need.

Since the gas blowing auxiliary nozzle for gas bubble fragmentation exhibits the above-described function, it is closer to the refining agent blowing nozzle hole than to the refining agent blowing nozzle hole. In particular, the blowing direction is the refining agent blowing direction (or the refining agent blowing area).
Setting towards is recommended as one of the most preferred embodiments.

On the other hand, it is conceivable to replace this auxiliary nozzle with a lance separate from the injection lance, but in this case, multiple lances are inserted into the hot metal, and the insertion position and height of the fragmentation gas are separately controlled. Therefore, the operation becomes complicated and there is a practical problem. On the other hand, in the present invention, since the refining agent injection nozzle hole and the gas injection auxiliary nozzle hole are formed in one lance, the operation of raising and lowering the lance is easy, and the carrier gas bubbles containing the refining agent are as described above. Since the gas is formed at a position near the refining agent injection nozzle hole, the gas bubbles can be effectively divided by discharging the gas jet stream from the auxiliary nozzle hole provided in the same lance. However, as understood from the above description, when the blowing directions of the refining agent blowing nozzle hole and the gas blowing auxiliary nozzle hole are largely different in the circumferential direction around the lance axis, the gas jet flow is suitable for the floating bubbles. Since the collision hardly occurs, it is desirable that the positions formed in the circumferential direction be approximately the same. Therefore, the number of auxiliary nozzle holes for gas injection is preferably at least the same as or greater than the number of nozzle holes for refining agent injection. In the case where the number of the nozzles exceeds the same number, it is desirable to design the auxiliary nozzles for gas injection so that the respective injection directions correspond to either the refining agent or the injection direction.

Further, the method of the present invention can be applied to all types of refining of hot metal in a cast iron hot metal gutter, a hot metal ladle, a mixed iron wheel, a molten steel ladle, etc. There is no limitation on the application, and the injection method is used. Any refining method can be adopted. It goes without saying that the refining reaction can be applied not only to desiliconization, dephosphorization and desulfurization but also to other refining reactions.
Note that the present invention does not particularly limit the carrier gas and the auxiliary gas, and N ₂ , Ar,
A gas such as air or O ₂ can be appropriately used. Also,
The carrier gas and the auxiliary gas can also be different in gas type.

Embodiment FIG. 1 is a sectional explanatory view showing an embodiment of the present invention, and FIG.
FIG. 1 is a sectional view taken along the line II-II in FIG. 1, and an injection lance 5 is inserted substantially vertically into a hot metal bath 2 in a desiliconized refractory 1. The lance 5 is formed with a desiliconizing agent flow path 4 at an axial center position and four auxiliary gas flow paths 7 around the same at circumferentially equal intervals. The lower end portion is connected to a refining agent blowing nozzle 10 formed at equal intervals in the circumferential direction, and the upstream side of the desiliconizing agent flow path 4 is connected to a tank 9 for storing the desilicifying agent 8. carrier gas supply pipe to the line l ₁ connecting the 9 and demi珪剤channel 4
l ₂ is inserted. On the other hand, the downstream side of the auxiliary gas passage 7
The auxiliary nozzles 11 are connected to four auxiliary nozzle holes 11 opened at positions corresponding to the opening position of the refining agent blowing nozzle when viewed in the circumferential direction of the lance, and their upstream sides are connected to the auxiliary gas supply main pipes 12, respectively.

According to the embodiment performed using the injection mechanism having the above-described configuration, the desiliconizing agent 8 conveyed from the tank 9 by the carrier gas G is blown into the hot metal from the blowing nozzle 10 to form relatively large bubbles. To float in the hot metal. On the other hand, the auxiliary gas Ga that has passed through the auxiliary gas flow path 7 is jetted from the auxiliary nozzle into the hot metal as a jet flow, and the above-mentioned floating bubbles are subdivided by the jet flow and become fine bubbles. And disperse in the hot metal. Thus, the desiliconizing agent contained in the air bubbles is also uniformly dispersed in the hot metal, and the following desiliconization reaction sufficiently proceeds with an increase in the contact area.

2FeO + Si → SiO ₂ + 2Fe The utilization efficiency of the desiliconizing agent is increased, and the slag 3 remains unreacted.
As a result, the amount of desiliconizer per unit can be reduced.

According to the desiliconization method of the above example, a desiliconization agent composed of a fine ore and a mill scale mixture was blown in with a carrier gas (air) (air supply amount: 250 to 300 Nm ³ / hr) to perform a desiliconization treatment. The auxiliary gas injection rate was 150 Nm ³ / hr, and the results shown in Table 1 were obtained as compared with the conventional method without auxiliary gas injection.

As shown in Table 1, the desiliconization oxygen efficiency when the desiliconization unit rate was set to 50 kg / t was significantly increased as compared with the conventional method. From these results, it was confirmed that even if the [Si]% level in the hot metal was considerably increased, desiliconization could be performed without deteriorating the reaction efficiency.

FIG. 4 shows an example in which the present invention is implemented when desiliconization is performed in a mixed-iron car. The injection lance is inserted in the hot metal in the mixed iron wheel. The lance has two refining agent injection nozzles formed axially symmetrically with each other. The auxiliary nozzle is formed above the refining agent injection nozzle at a position corresponding to the refining agent injection nozzle.

The same desiliconizing agent and carrier gas (air flow rate 20
0-400Nm ³ / hr), auxiliary gas (air flow 100-200Nm ³ / hr)
Was used to perform a desiliconization treatment. Bubbles formed by the blowing from the refining agent blowing nozzle are subdivided by the auxiliary gas jet stream, the desiliconizing agent is evenly dispersed in the hot metal, and the utilization efficiency of the desiliconizing agent increases. The results shown were obtained.

In the case of a mixed iron wheel, by blowing the gas blown from the auxiliary nozzle to a deep position in the molten iron bath, the stirring power is greatly increased, and the desiliconization efficiency can be increased.

[Effects of the Invention] The present invention is configured as described above, and can perform refining without reducing the reaction efficiency even when the refining agent basic unit increases, and can operate according to the refining load. became. Further, with the improvement of the reaction efficiency, when the refining load is the same, the refining agent basic unit can be reduced, and the processing cost and the steel making cost can be reduced. In addition, it is possible to prevent occurrence of a situation such as blockage of the refining agent blowing nozzle.

[Brief description of the drawings]

1 is a cross-sectional explanatory view showing one embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, FIG. 3 is an explanatory view showing a conventional injection method, and FIG. It is an explanatory view showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Desiliconized refractory, 2 ... Hot metal bath 3 ... Slag 4, ... Desiliconizer channel 5 ... Lance, 6 ... Bubbles 7 ... Auxiliary gas channel, 8 ... Desiliconizer 9 …… Tank, 10… Desilicant injection nozzle, 11 …… Auxiliary nozzle

Claims (5)

(57) [Claims] An injection lance is inserted into a molten metal, and a powdery refining agent is blown by a carrier gas to form carrier gas bubbles containing the powdery refining agent in the molten metal. In refining the molten metal by contact, above the refining agent blowing nozzle hole of the injection lance, an auxiliary nozzle hole for gas blowing for forming a gas jet stream for colliding with the carrier gas bubble to make it finer. A method for refining molten metal, comprising: 2. A solid-gas-liquid mixed system formed by blowing a powdery refining agent and a carrier gas into a molten metal from a refining agent blowing nozzle hole provided in the injection lance, and provided in parallel with the injection lance. A method for refining a molten metal, comprising forming finely divided floating bubbles in a molten metal and refining the gas by blowing and impinging gas from an auxiliary nozzle hole for gas injection for forming a gas jet flow. 3. A gas refining agent, which is blown into a molten metal together with a carrier gas from a refining agent blowing nozzle hole provided in an injection lance, into a gas jet flow forming gas provided in the injection lance. A method for refining a molten metal, which comprises finely dispersing and floating the molten metal in a molten metal by blowing gas from an auxiliary nozzle hole. 4. A refining agent blowing nozzle hole for injecting a powdery refining agent into a molten metal by a carrier gas, wherein a gas jet stream is applied to a carrier gas bubble floating in the molten metal containing the powdery refining agent. An injection lance, wherein an auxiliary nozzle hole for gas injection for forming a gas jet for injecting a gas for causing the gas to collide is provided above the refining agent injection nozzle hole. 5. A gas jet stream forming gas nozzle having at least as many refining agent blowing nozzle holes and at least as many or more gas jet stream forming gas nozzles as nozzles. 5. The injection lance according to claim 4, wherein the gas blowing direction of the auxiliary nozzle hole for injection is formed so as to correspond to the refining agent blowing direction of each refining agent blowing nozzle hole.