JPH01136917A - Method for treating molten iron - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for pre-treating hot metal for converter refining, such as removing Si, removing P, and removing S.

(Prior Art) Conventionally, as a hot metal pretreatment method, for example, JP-A-57-1.
35604, JP-A No. 58-130208, etc. Various methods have been adopted, such as a treatment method in a hot metal conveying container such as a torpedo car, a hot metal pot, a treatment method in a cast bed trough, or a combination thereof, and each method has its own characteristics. Although it has the above problems, generally speaking, there are major problems such as a decrease in productivity and a decrease in hot metal saturation due to process division.

In order to solve this problem, it is important to shorten the treatment time as much as possible, and among the above methods, the method of direct continuous treatment in the cast bed trough and simultaneous slag removal treatment is effective, but it is difficult to remove the slag easily. However, in some cases, a considerable scale of slag drainage and conveying equipment is required, and the equipment cost for adding powder to the cast bed trough is high, and there are problems such as large iron loss in the slag. However, compared to other methods, it has not yet reached the point where it is economically viable.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems, and in order to reduce the drop in hot metal temperature, part of the treatment is carried out in the cast bed trough, making it economically viable as a whole process. The purpose of the present invention is to provide a method for pretreatment of bath iron.

(Means for Solving Problems) The gist of the present invention is (1) In the hot metal gutter of a blast furnace casthouse, one or more pieces are installed on top of the hot metal or immersed in the hot metal. De-sulfur is removed through a lance nozzle using a carrier gas containing 02 and having a gas-acidity ratio of 10 to 60% defined by the following formula.
1 so that the slag basicity after treatment with agent I is 0.5 or more.
5 to 25 KLi/ton per lance nozzle
The first step is to blow the hot metal into the hot metal, perform Si removal treatment so that the [s1] after treatment is 0.1% or less, and receive the hot metal along with the generated slag into a torpedo car or hot metal ladle through a tilting gutter, and then discharge the slag. Hot metal pretreatment method (2) characterized by comprising a step and a second step of blowing a dephosphorizing agent through a immersed lance nozzle with a carrier gas to dephosphorize. The first
Hot metal pretreatment method (3) after the second step, the hot metal is received in the converter charging ladle, and the dephosphorized slag is left in the torpedo car or swamp pig iron ladle and is received in the first step. The first method is characterized in that:
This is the hot metal pretreatment method described in item 1 or 2.

(Function) The inventors of the present invention have diligently carried out tests to remove Si, P, etc. from cast bed troughs, and as a result, have been able to clarify the following characteristics of advantages and disadvantages. That is, the method of removing Si in a cast bed using the blasting method or the injection method has the advantage of 1) higher Si removal efficiency than a batch treatment process such as the upward addition method of flux.

■The amount of P removed at the same time during desorption 81 is very high, and the burden of P removal in the next process can be reduced.

■The use of silver acid has a large effect on raising the temperature of hot metal, and the temperature of hot metal charged in the converter can be increased.

■It is possible to reduce forming when receiving the torpedo car or hot metal pot.

On the other hand, the drawbacks are: The loss of iron in the slag is large.

I understand.

In addition, the P removal method in the cast bed using the blasting method or the injection method has an advantage over batch processing processes such as P removal using the injection method in a torpedo car or pot. can be obtained.

■ The use of silver acid has a large effect of increasing the temperature of hot metal, and the temperature of hot metal charged into the converter can be increased.

On the other hand, the drawback is that ■ Large iron loss in slag.

■ The fluidity of the slag after treatment is poor, and forced slag drainage equipment is usually required.

I understand.

Therefore, it is possible to prevent the loss of iron in the slag, which is a drawback of the casting bed desiliconization method using the blasting method and the injection method, and to utilize the above advantages, and to planute,
In order to avoid the problems of slag in the castbed and loss of iron content in slag, which are the drawbacks of the casting bed dephosphorization method using the injection method, only the casting bed dephosphorization method using the blasting method or the injection method is used for refining on the cast bed. It was found that the most economical process is to carry out the deP treatment in a torpedo car or hot metal pot. Furthermore, in this process, the merits of the rise in temperature of hot metal during casthouse desorption 81 are fully enjoyed by gas-solid acid deSi removal, and in order to recover the iron content in the deSi slag, the deSi slag is transferred together with the hot metal through a tilting gutter to a torpedo car or hot metal. The most rational method is to receive the slag in a pot and discharge the slag from the container before deP treatment.

Furthermore, in this case, it is a two-step Si removal process including blasting or injection in the cast bed and treatment using falling energy from the tilting gutter to the torpedo car or hot metal gutter, and the Si removal efficiency is as high as that of each one-stage process. I also found it to be more expensive.

As shown in Figure 1, the temperature increase effect due to the use of silver acid is calculated as follows: gas acid ratio (%) = carrier gas 02 (KLi/t)
The relationship between X100 / (0□ (Kp/t) in the desiliconizing agent + 0x (Kg/l) of the carrier gas and hot metal temperature increase was obtained. In order to stably enjoy the effect of increasing the hot metal temperature, K is a gaseous acid. A high oxygen gas ratio of over 60% is required, but the reaction surface will be in a high oxygen potential state, resulting in a decrease in the Si removal efficiency.
As the gas flow rate increases, problems such as fluctuation of the hot water level and spitting become more obvious, so the upper limit of the gas-acidity rate is 6o.
% is reasonable.

In addition, in order to enjoy the benefits of reducing the burden of removing P in the next process,
As a result of examining the conditions for increasing the simultaneous dephosphorization amount during i treatment, it was found that the slag basicity and post-treatment [Si] value are important factors affecting dephosphorization. In other words, the relationship between the slag metal P distribution value (P)/(P) and basicity is shown in Figure 2 as (P)/[P] and after treatment [Si].
The relationship between the Si
] was found to need to be 0.1% or less. In addition, in order to efficiently remove Si to 0.1% after treatment, the basic unit of the desiliconizing agent added per lance nozzle must be 5 to 5 Kq/l. That is,
In order to stably secure the amount of Si removed, a minimum amount of 5 K9/t is required as the basic unit of the desilicon agent per lance nozzle, and as shown in Figure 4, the basic unit of desilicon If there are many units, the Si removal efficiency will decrease, so
The upper limit of the basic unit amount of the desiliconizing agent per lance nozzle is 25 kg/t.

Furthermore, when a plurality of lance nozzles are used, the spacing between the tuyeres has a large effect on the Si removal efficiency, and it is effective to space the tuyeres apart by about 1 am or more, as shown in FIG. Furthermore, a method for receiving de-Si slag and bath pig iron while leaving the slag after deP in the deP treatment container of a torpedo car or hot metal pot is known from Japanese Patent Publication No. 60-59962. After P, return P from the slag into the hot metal can be seen. When hot metal and slag that have been removed from Si by blasting or injection in the casthouse are received into a torpedo car or hot metal ladle in which slag remains after removal of Si, the removal of Si can be done by adjusting the CαO/SiO□ of the slag after removal of Si. The basicity of the mixed slag of slag and deP slag is higher than before, and after deSi [Si]
It has been found that by lowering the phosphor content to 0.10% or less, the return phosphorus from the dephosphorized slag can be reduced. That is, even greater economic effects can be obtained by combining the technique disclosed in Japanese Patent Publication No. 60-59962 with the Si removal treatment using a blasting method or an injection method in a cast bed.

(Example) The present invention will be explained based on examples.

The test results for the inventive example and the comparative example are shown in the first table.
Table treatment ml, 3, 4, 5, 7, 8, 9, treatment Na2,
6.10.

Treatment ml, 3,5. In the case of the present invention example of '7.8, a [Si] value of 0.1% or less and a slag basicity of 0.5 or more after the Si removal were obtained in all cases, and the amount of P removed during the removal of the Si was also large. In addition, the use of silver acid increases the temperature of the mortar after removing Si, and the consumption of the dephosphorizing agent in the next step of dephosphorization treatment is also low. In the case of treatment ugliness 9, the slag may be returned to the desiliconization treatment after dephosphorization, but in this case as well, the effect similar to that of the above-mentioned invention example is obtained, and the casting bed desiliconization treatment is carried out using the method of upward addition of the desiliconization agent (basicity 20), the return is 0.01O.
The effect was as small as about %. In the case of treatment m4, the distance between the lance tuyeres was small and the Si removal efficiency was slightly lower than that of other examples of the present invention, but the Si removal efficiency was higher than that of the comparative example.

On the other hand, in the case of treatment 2 in the comparative example, the iron oxide basic unit per lance tuyere is large, so the Si removal efficiency decreases, and after the treatment [Si]
Since the amount of P removed during desorption 81 is high,
The amount of P removed per unit is high.

In the case of treatment IVkL6, which is a comparative example of sprinkling, the gas-oxidation rate was as high as 62%, so during the Si removal treatment, the hot water level fluctuated, splashed, etc., making the test difficult.

Furthermore, in the case of Comparative Example N[110, the basicity of the slag after the Si removal treatment is low, so the amount of simultaneous dephosphorization during dephosphorization 81 is small, and therefore the basic unit of dephosphorization agent in the next step is large.

(Effects of the Invention) The present invention alleviates the drop in temperature of hot metal charged into a converter, which is a drawback of conventional bath pig iron pretreatment, and provides an overall cheaper treatment process, thereby making hot metal pretreatment more versatile. It became something.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the gas acid rate and the amount of increase in hot metal temperature regarding the effect of increasing hot metal salinity by using silver acid. Figure 2 shows the slag basicity (Cab/5i) after the Si removal treatment.
02) and the slag metal P distribution value. FIG. 3 is a diagram showing the relationship between [Si] after Si removal treatment and the slag metal P distribution value. FIG. 4 is a diagram showing the relationship between the unit of Si-removal agent per tuyere and the S'i removal rate per unit of Si-removal agent. FIG. 5 is a diagram showing the relationship between the lance tuyere spacing and the Si removal rate per unit unit of the Si removal agent. Fig. 1 Air acid rate (X) Fig. 2 Fig. 3 After treatment [Si desiliconizing agent consumption unit/tuyere (kg/l) Lance W” interval (m)

Claims (3)

[Claims] (1) In the hot metal trough of the blast furnace casthouse, an O_2-containing gas and a gaseous acid defined by the following formula are passed through one or more lance nozzles installed above the hot metal or immersed in the hot metal. DeSi is removed using a carrier gas with a ratio of 10 to 60%.
The agent is injected into the hot metal at a rate of 5 to 25 kg/ton per lance nozzle so that the slag basicity after treatment is 0.5 or more, and [Si] after treatment is 0.1% or less. The first step is to remove Si and receive the hot metal along with the generated slag into a torpedo car or hot metal ladle via a tilting gutter, and then discharge the slag, and the second step is to blow a deP agent with a carrier gas through a submerged lance nozzle to deP. A hot metal pretreatment method characterized by consisting of the steps gas-acidity ratio (%) = {carrier gas O_2 (Kg/t)}/
{O_2 minutes (Kg/t) in desiliconizing agent + carrier gas O_
2 (Kg/t)}×100 (2) A hot metal pretreatment method according to claim 1, characterized in that when using a plurality of lance nozzles, the lance nozzles are separated by 1.0 m or more. (3) After the second step, the hot metal is received in a converter charging pot,
Hot metal pretreatment method according to claim 1 or 2, characterized in that the dephosphorized slag is received in the first step while remaining in a torpedo car or a hot metal ladle.