JPH0452205A - Method for desulfurizing molten iron in casting floor in blast furnace - Google Patents

Abstract

PURPOSE:To effectively execute desulfurization in a low cost by submerging an injection lance into molten iron in a pretreating reaction vessel at downstream side from a skimmer in casting floor toward the downstream side and reciprocatively moving the injection lance to width direction while injecting CaO series desulfurizing agent together with carrier gas. CONSTITUTION:The molten iron 12 tapped from a blast furnace is guided to a pre-treating reaction vessel 2 through the skimmer 14 together with slag 10. Into the molten iron 12 in the reaction vessel 2, while blowing the CaO series desulfurizing agent carried with inert gas through an injection lance 6 toward the downstream thereof, the injection lance is reciprocatively moved to the width direction. Therefore, as the slag 10 produced in the reaction vessel 2 is floated up and piled only at the downstream side from the lance 6, the slag is dropped with a slag-off machine 20 and is discharged into a slag pan 24 through a chute 22 without interrupting desulfurizing reaction with the lance 6.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is applied to a blast furnace cast bed in which a pretreatment reaction tank is installed downstream of the skimmer of the blast furnace cast bed, and a CaO-based desulfurization agent is injected into hot metal for desulfurization. This invention relates to a method for desulfurizing hot metal.

<Prior art> Desulfurization of hot metal is generally carried out in a mixed pig iron furnace or ladle, and desulfurization agents include CaC0, Cab, CaCz, and Can-based desulfurization agents, as well as NazCOy, inert gas, and carrier gas. As a method, there is a method of blowing hot metal through a lance while stirring it. However, since the desulfurization reaction is both a reduction reaction and an endothermic reaction, even if a desulfurization agent such as soda ash or lime is injected into the pig iron mixer car, the temperature of the hot metal is low and the desulfurization reaction does not proceed easily. There are limits to desulfurization treatment. For the above reasons, it goes without saying that it is most desirable to perform the desulfurization treatment during the process of flowing down the tap culvert, which is the highest temperature period immediately after the iron is tapped from the blast furnace.

From this point of view, many conventional techniques have been disclosed in which desulfurization treatment is performed immediately after the iron is tapped into the cast bed of a blast furnace. For example, JP-A-51
-105913, JP-A No. 52-42411, JP-A-59-143010, and JP-A-62-42010. A brief explanation of these conventional techniques will be given below.

(a) Japanese Unexamined Patent Publication No. 51-105913 This invention has an inlet at one end, an outlet at the other end, and a series of circular horizontal cross sections arranged in a row with some overlap. A rotating shaft located at the center of each single circular part of the cocoon-shaped processing tank is provided, and a stirring mechanism having a plurality of stirring rods fixed to the rotating shaft via an arm is provided. This is a continuous desulfurization method for molten metal, in which the rotating direction is the same and the upper end of the stirring rod is always positioned below the static surface of the molten metal in a processing tank.

Although this invention seems to have a stirring effect, it is thought that running costs are relatively high due to wear and tear on large ml products.

(bl Japanese Patent Publication No. 52-42411) This invention involves continuously pouring hot metal from a tap runner or a hot metal ladle into a desulfurization tank that has a gas-injected porous plug for stirring the hot metal at the bottom and a heating electrode. This continuous desulfurization method for hot metal is characterized by performing electric arc heating while stirring and using a mixture of blast furnace slag and fluorite or CaO-based synthetic slag as a desulfurization agent.

In this method, the molten pig iron is heated with a heating electrode, and inert gas is injected through a porous plug at the bottom for stirring, so the reaction efficiency is thought to increase, but the equipment cost is high and the There are problems with space, etc., and it is thought that the cost will be high.

(C) Japanese Unexamined Patent Publication No. 59-143010 This invention divides hot metal that is continuously flowing down in a hot metal gutter in the middle of the flow system of the hot metal to create a dispersed flow with a head difference and flow on the downstream side. A falling flow toward the system is generated, and powder and granular additives for pre-treatment of the hot metal are conveyed by high-speed airflow to the entrained flow area that is generated on the surface of the hot metal in the downstream flow system as a result of this dispersed falling flow. This is a method for continuous preliminary treatment of hot metal, which comprises accelerating charging by means of projection.

This invention also seems to be able to desulfurize at a relatively low cost because the hot metal is divided into streams and the hot metal is stirred using a head, and the pneumatic desulfurization agent is jetted into this stirring flow, but it is not suitable for blast furnace casthouses. There is a problem in that a large space is required for dividing the flow.

(c) Japanese Patent Publication No. 62-42010 This invention is a hot metal sluice refining method in which a wide slag channel is formed in the molten metal sluice, and an injection lance is inserted into the molten metal channel to inject a refining agent together with a carrier gas.

In this invention, when a slag with a low melting point, such as a desiliconizing agent, is turned into sludge, the desulfurization efficiency is good, but with a solid desulfurization flux such as CaO, desulfurization does not proceed due to the rate-limiting reaction at the solid-liquid reaction interface. If Car' is added to the solid desulfurization flux and mixed with the liquefied slag, desulfurization will proceed. However, in the injection treatment in the flow-through system of hot metal, CaO-based flux is used instead of low-melting-point slag such as CaFz, so there is a problem that the slag accumulates in the hot metal troughs, making it difficult for the reaction to proceed.

As mentioned above, conventional methods for continuous desulfurization treatment in blast furnace casthouses include methods such as injection in the flow or projection blasting from the surface of the hot metal, but both require a large space. Alternatively, there are problems such as requiring expensive equipment.

Furthermore, regarding desulfurization agents, in addition to a mixture of CaO-based synthetic slag and fluorite, soda ash (NatCOi), and other B
Some contain halogen compounds such as aC1z, but Ca
Desulfurization agents other than O-based desulfurization agents are not suitable for use as cement or roadbed materials in terms of quality, and have to be disposed of as industrial waste at great expense.

Regarding CaO-based desulfurization agents, in steel plants,
It is possible to reuse it as a sintering raw material, but in this case as well, Na
, Ba, F, etc. cannot be reused. Therefore, CaO-based desulfurization agents are the only desulfurization agents that can be reused as sintering raw materials, but the use of CaO-based desulfurization agents has the following problems.

In other words, when desulfurization is performed continuously with a CaO-based desulfurization agent, the reaction is CaO+S→CaS+O.
Since the single substance has poor wettability, dispersion is insufficient in a shallow reaction tank of a molten iron bath, resulting in a problem that the desulfurization reaction does not proceed. Providing a deep bath reaction tank such as a pig iron mixer in a blast furnace casthouse requires a huge amount of capital in terms of equipment and also requires a large space.

<Problems to be solved by the invention> Is the purpose of Kinoi '91 to improve the blast furnace casthouse? It is an object of the present invention to solve the problems of the above-mentioned conventional techniques of pre-treatment of hot metal using a RuruCan-based desulfurization agent, and to provide a method for desulfurizing hot metal that can efficiently desulfurize at low cost.

<Means to Solve the Problem> The present inventor has improved the desulfurization capacity (S) by changing the relationship between the flow direction of hot metal and the blowing direction regarding the injection of CaO-based desulfurization agent using an injection lance in the pretreatment reaction tank.
(S) was investigated. Here, [S]: S in hot metal, (
S) S in the varnish slag, that is, the desulfurization agent injected from the injection lance 6 in the hot metal flow direction 4 in the pretreatment reaction tank 2 like a third leap, is deposited on the downstream side of the reaction tank 2. Therefore, we investigated the desulfurization ability of the reaction tank along with the desulfurization agent injection time, and found that when CaO-based desulfurization agent is injected with the lance fixed, the flow of hot metal gets blocked by the desulfurization agent accumulated in reaction tank 2, and the flow of hot metal is inhibited. As shown in Figure 5, the reaction efficiency decreases after 30 minutes. On the contrary,
It has been found that desulfurization ability can be maintained at a high level by periodically moving the lance and changing the injection point while performing injection.

The present invention has been made based on the above findings, and the gist thereof is as follows.

The present invention provides a method for desulfurizing hot metal in a blast furnace castbed, in which a pretreatment reaction tank is provided downstream of the skimmer of the blast furnace casthouse, and a CaO-based desulfurization agent is added to the hot metal in the pretreatment reaction tank to desulfurize the hot metal. An injection lance is immersed in hot metal in a pretreatment reaction tank to a predetermined depth toward the downstream side in the flow direction of the hot metal, and while a CaO-based desulfurization agent is injected from the lance together with a carrier gas, the tip of the lance is immersed in the pretreatment reaction tank. This is a method for desulfurizing hot metal in a blast furnace casthouse, which is characterized by reciprocating movement in the width direction of a treatment reaction tank.

Further, in the present invention, instead of reciprocating the tip of the injection lance in the width direction of the pretreatment reaction tank, the injection lance can be reciprocated in parallel to the flow direction of the hot metal in the pretreatment reaction tank.

Furthermore, in the present invention, the tip of the injection lance may be reciprocated in the width direction of the pretreatment reaction tank and may also be reciprocated in the hot metal flow direction.

Next, the configuration and operation of the present invention will be explained in detail based on the drawings.

Hot metal 1 tapped from the blast furnace as shown in Figures 1 and 2
The slag 10 flows down through a tapping sakaki (not shown) and reaches the skimmer 14, and the hot metal 12 passing through the lower end of the skimmer damper 16 is introduced into the pretreatment reaction tank 2. The hot metal 12 in the reaction tank 2 is injected with a CaO-based desulfurization agent pneumatically supplied with an inert gas by an injection lance 6.

The desulfurizing agent is blown from the lance 6 toward the hot metal 12 downstream of the lance 6. Therefore, the slag 10 generated in the reaction tank 2 is floated and deposited only downstream of the lance 6, so it can be discharged into the slag pot 24 via the scraping chute 22 by the slag remover 8120 without interrupting the desulfurization reaction by the lance 6. I can do it.

In addition, in FIGS. 1 and 2, the skimmer J4 and the reaction tank 2 are equipped with a splash cover 26 and a tool 1', respectively.
The hot metal 12 that has been covered for two days and desulfurized in the reaction tank 2 is discharged from the pre-treated pig iron outlet 8.

What is important here is that the injection lance 6 is immersed in the hot metal I2 in the pretreatment reaction tank 2 to a predetermined depth toward the downstream side in the hot metal flow direction 4, and the lance 6 is The CaO-based desulfurization agent is injected together with a carrier gas, and then the lance 6 is reciprocated in a fan shape so that its tip part rotates horizontally within the width of the reaction tank 2. Such reciprocating motion allows the desulfurizing agent to be uniformly dispersed in the hot metal, improving desulfurizing efficiency and eliminating the desulfurizing agent from stagnation in the reaction tank.

It is preferable to move the lance 6 at a constant speed during injection so that the fan-shaped reciprocating movement of the lance 6 forms an angle α with the hot metal flow direction 4 within 45 degrees. This is because if the temperature exceeds 45 degrees, the desulfurizing agent collides with the wall surface of the reaction tank 2, which may cause local melting loss of the inner wall refractories. Note that the lance 6 is not limited to the one that reciprocates in the width direction in a fan shape, but the same effect can be obtained even if the lance 6 is made to reciprocate linearly in the width direction of the reaction tank 2.

On the other hand, instead of reciprocating the lance 6 in the width direction in a fan shape or in a straight line in the reaction tank 2, as shown in the fourth example, the lance 6 is moved in a straight line parallel to the hot metal flow direction 4 within the length of the reaction tank 2. More preferably, while injecting the desulfurization agent from the lance 6, the lance 6 is rotated horizontally within a 45 degree angle with the hot metal flow direction 4, and parallel to the hot metal flow direction 4. Each of them is reciprocated at a constant speed.

Note that if the lengthwise range in which the lance 6 is reciprocated in a straight line parallel to the hot metal flow direction 4 is too close to the upstream side of the reaction tank 2, the lance 6 will be affected by the inflow of hot metal 12 and the life of the lance 6 will be shortened. If the length of the reaction tank 2 is L, the desulfurization agent will collide with the side wall of the reaction tank 2, causing local damage to the wall and reducing the desulfurization efficiency. It is preferable to have a range of L/4 before and after the center.

<Example> In the same pretreatment reaction tank provided downstream of the skimmer of the blast furnace casthouse, the reaction tank was immersed toward the downstream side in the flow direction of hot metal, and CaO-based desulfurization agent was injected using the lance shown in Table 1. Desulfurization treatment experiments of hot metal were conducted using the method of the present invention and the conventional method under the following conditions. The results are shown in Table 1 for comparison.

As is clear from Table 1, the examples of the present invention exhibit superior desulfurization ability compared to the conventional examples.

<Effects of the Invention> As is clear from the above embodiments, the present invention rotates the desulfurizing agent using an injection lance in a direction parallel to the hot metal flow within a certain angular range from the center line of the reactor at a constant angular velocity or in the width direction. Blast furnace casthouse Excellent desulfurization performance can be achieved in a limited space at a low equipment cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of the device according to the present invention, FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing the movement of the lance parallel to the flow direction of hot metal according to the present invention;
FIG. 5 is a diagram showing the relationship between the injection time of CaO-based desulfurization agent and the desulfurization ability. 2... Pre-treatment reaction tank, 6... Injection rack 8... Discharge port, I2... i capacity pig iron, 16... skin damper, 22... chute, 2G... spranschkaher 4... hot metal flow direction, 10... slag, I4... skimmer, 20... Sludge remover, 24...Slag pot, 28...Hood.

Claims (1)

[Scope of Claims] 1. Desulfurization of hot metal in the blast furnace casthouse, in which a pretreatment reaction tank is provided downstream of the skimmer of the blast furnace casthouse, and a CaO-based desulfurization agent is added to the hot metal in the pretreatment reaction tank to desulfurize the hot metal. In the method, an injection lance is immersed into the hot metal in the pretreatment reaction tank to a predetermined depth toward the downstream side in the flow direction of the hot metal, and while a CaO-based desulfurization agent is injected from the lance together with a carrier gas, the tip of the lance is 1. A method for desulfurizing hot metal in a blast furnace casthouse, comprising reciprocating a part in the width direction of the pretreatment reaction layer. 2. The blast furnace according to claim 1, characterized in that instead of reciprocating the tip of the injection lance in the width direction of the pretreatment reaction tank, the injection lance is reciprocated in parallel to the flow direction of the hot metal in the pretreatment reaction layer. A method for desulfurizing hot metal in a cast bed. 3. The method for desulfurizing hot metal in a blast furnace casthouse according to claim 1, wherein the tip of the injection lance is reciprocated in the width direction of the pretreatment reaction tank and reciprocated in the flow direction of the hot metal.